fix(themes): add the shell command token to the theme template and docs

#3458 added --syn-shell-command without setting it in the Harbor Night
scheme (the template new themes start from) or regenerating plugins/themes.md,
so scripts/theme/theme.test.ts failed. Imported IntelliJ schemes map
BASH.EXTERNAL_COMMAND to it.

Cargo.lock

@@ -4269,6 +4269,7 @@ dependencies = [
 name = "ide-dap"
 version = "0.1.45"
 dependencies = [
+ "base64 0.22.1",
  "futures",
  "ide-core",
  "ide-heap",
@@ -4287,6 +4288,7 @@ dependencies = [
  "specta",
  "tempfile",
  "tokio",
+ "tokio-tungstenite",
  "tracing",
  "tracing-subscriber",
  "windows-sys 0.61.2",

crates/ide-agent/src/acp/discover.rs

@@ -17,11 +17,30 @@ const DISCOVER_TIMEOUT: Duration = if cfg!(test) { Duration::from_secs(3) } else
 
 /// Opens `session/new`, reads `configOptions`, and records per-model `thought_level` choices.
 pub(crate) async fn run(shared: &Arc<Shared>, spec: &ProviderSpec) -> Result<Discovered, String> {
+    let prefer_stored = crate::provider::prefer_stored_copilot_auth();
+    match run_once(shared, spec, prefer_stored).await {
+        Err(err)
+            if !prefer_stored
+                && crate::provider::is_copilot_provider(&spec.id)
+                && crate::provider::has_unconfigured_copilot_ambient_token(&spec.env)
+                && super::auth_required(0, &err) =>
+        {
+            let retry = run_once(shared, spec, true).await;
+            if retry.is_ok() {
+                crate::provider::mark_prefer_stored_copilot_auth();
+            }
+            retry
+        }
+        other => other,
+    }
+}
+
+async fn run_once(shared: &Arc<Shared>, spec: &ProviderSpec, strip_ambient: bool) -> Result<Discovered, String> {
     let root = shared.paths.project_root.clone();
     let launch = spec.clone();
     let launch = tokio::task::spawn_blocking({
         let root = root.clone();
-        move || launch.resolve_for_launch(&root)
+        move || launch.resolve_for_launch_with_copilot_env(&root, strip_ambient)
     })
     .await
     .map_err(|e| e.to_string())?;

crates/ide-agent/src/provider.rs

@@ -120,10 +120,18 @@ impl ProviderSpec {
     }
 
     /// Resolve once before connecting, so authentication guidance names that same install.
-    pub(crate) fn resolve_for_launch(mut self, cwd: &Path) -> Self {
+    pub(crate) fn resolve_for_launch(self, cwd: &Path) -> Self {
+        let strip = prefer_stored_copilot_auth();
+        self.resolve_for_launch_with_copilot_env(cwd, strip)
+    }
+
+    pub(crate) fn resolve_for_launch_with_copilot_env(mut self, cwd: &Path, strip_ambient_tokens: bool) -> Self {
         if self.driver != Driver::Acp {
             self.command = crate::native::newest_install(&self.command);
         }
+        if is_copilot_provider(&self.id) {
+            self.env = sanitized_copilot_env(&self.env, strip_ambient_tokens);
+        }
         let program = ide_jsonrpc::resolve_spawn_program(&self.command, &self.env);
         self.command =
             if program.components().count() > 1 && !program.is_absolute() { cwd.join(program) } else { program }
@@ -133,6 +141,69 @@ impl ProviderSpec {
     }
 }
 
+const AMBIENT_COPILOT_AUTH_VARS: [&str; 3] = ["COPILOT_GITHUB_TOKEN", "GH_TOKEN", "GITHUB_TOKEN"];
+static PREFER_STORED_COPILOT_AUTH: std::sync::atomic::AtomicBool = std::sync::atomic::AtomicBool::new(false);
+
+pub(crate) fn is_copilot_provider(id: &str) -> bool {
+    id == "copilot" || id.starts_with("copilot-")
+}
+
+pub(crate) fn prefer_stored_copilot_auth() -> bool {
+    PREFER_STORED_COPILOT_AUTH.load(std::sync::atomic::Ordering::Acquire)
+}
+
+pub(crate) fn mark_prefer_stored_copilot_auth() {
+    PREFER_STORED_COPILOT_AUTH.store(true, std::sync::atomic::Ordering::Release);
+}
+
+pub(crate) fn has_unconfigured_copilot_ambient_token(spec_env: &[(String, String)]) -> bool {
+    AMBIENT_COPILOT_AUTH_VARS.iter().any(|&key| {
+        !spec_env.iter().any(|(k, v)| k == key && !v.is_empty())
+            && ambient_copilot_env_value(key).is_some_and(|v| !v.is_empty())
+    })
+}
+
+fn ambient_copilot_env_value(key: &str) -> Option<String> {
+    ide_core::process::shell_env()
+        .find(|(k, _)| *k == key)
+        .map(|(_, v)| v.to_string_lossy().into_owned())
+        .or_else(|| ide_core::process::host_var_os(key).map(|v| v.to_string_lossy().into_owned()))
+}
+
+/// Builds child environment overrides for `copilot`:
+/// - Always clears ambient classic PATs (`ghp_…`), which Copilot CLI unconditionally rejects
+///   (`"Classic PATs are not supported"`) instead of falling back to Keychain / `gh` login.
+/// - When `strip_ambient_tokens` is true, clears unconfigured ambient `GITHUB_TOKEN` / `GH_TOKEN` /
+///   `COPILOT_GITHUB_TOKEN` so Copilot uses its stored login (`~/.copilot` or `gh auth` keyring),
+///   while preserving any token explicitly configured in OpenIDEA's agent `spec_env`.
+pub(crate) fn sanitized_copilot_env(
+    spec_env: &[(String, String)],
+    strip_ambient_tokens: bool,
+) -> Vec<(String, String)> {
+    sanitize_copilot_env_with(spec_env, strip_ambient_tokens, ambient_copilot_env_value)
+}
+
+pub(crate) fn sanitize_copilot_env_with(
+    spec_env: &[(String, String)],
+    strip_ambient_tokens: bool,
+    lookup: impl Fn(&str) -> Option<String>,
+) -> Vec<(String, String)> {
+    let mut out = Vec::with_capacity(spec_env.len() + AMBIENT_COPILOT_AUTH_VARS.len());
+    for key in AMBIENT_COPILOT_AUTH_VARS {
+        let explicit = spec_env.iter().any(|(k, v)| k == key && !v.is_empty());
+        if explicit {
+            continue;
+        }
+        if let Some(val) = lookup(key).filter(|v| !v.is_empty())
+            && (strip_ambient_tokens || val.trim().starts_with("ghp_"))
+        {
+            out.push((key.to_owned(), String::new()));
+        }
+    }
+    out.extend(spec_env.iter().cloned());
+    out
+}
+
 fn render_login_hint(spec: &ProviderSpec, program: &Path, on_path: Option<&Path>, windows: bool) -> String {
     let Some(builtin) = builtin_spec(&spec.id) else { return spec.login_hint.clone() };
     let prefix = format!("Run `{}", builtin.command);
@@ -1101,4 +1172,23 @@ mod tests {
         import_acp(dir.path(), None, "not json").unwrap_err();
         assert!(import_acp(dir.path(), None, "{}").unwrap().is_empty());
     }
+
+    #[test]
+    fn sanitizes_classic_pats_and_ambient_tokens_while_preserving_explicit_agent_env() {
+        let lookup = |k: &str| match k {
+            "GITHUB_TOKEN" => Some("ghp_classic_pat_123".into()),
+            "GH_TOKEN" => Some("gho_oauth_token_456".into()),
+            _ => None,
+        };
+        assert_eq!(sanitize_copilot_env_with(&[], false, lookup), vec![("GITHUB_TOKEN".into(), String::new())]);
+        assert_eq!(
+            sanitize_copilot_env_with(&[], true, lookup),
+            vec![("GH_TOKEN".into(), String::new()), ("GITHUB_TOKEN".into(), String::new())]
+        );
+        let explicit = vec![("GH_TOKEN".into(), "github_pat_custom".into())];
+        assert_eq!(
+            sanitize_copilot_env_with(&explicit, true, lookup),
+            vec![("GITHUB_TOKEN".into(), String::new()), ("GH_TOKEN".into(), "github_pat_custom".into())]
+        );
+    }
 }

crates/ide-build/src/compile/mod.rs

@@ -53,6 +53,8 @@ pub enum BuildSystem {
     TypeScript,
     #[serde(rename = "cmake")]
     CMake,
+    #[serde(rename = "dotnet")]
+    Dotnet,
 }
 
 /// One command of a build.
@@ -165,6 +167,8 @@ fn detect_dir(dir: &Path, model: &BuildModel, root: &Path) -> Option<BuildSystem
         || has(dir, &["build.gradle", "build.gradle.kts", "settings.gradle", "settings.gradle.kts"])
     {
         Some(BuildSystem::Gradle)
+    } else if dotnet_target(dir).is_some() {
+        Some(BuildSystem::Dotnet)
     } else if has(dir, &["Cargo.toml"]) {
         Some(BuildSystem::Cargo)
     } else if has(dir, &["go.mod", "go.work"]) {
@@ -225,7 +229,7 @@ pub fn plan(
         .or((!model.gradle.is_empty()).then_some(BuildSystem::Gradle))
         .or_else(|| model.maven.as_ref().filter(|m| !m.projects.is_empty()).map(|_| BuildSystem::Maven))
         .ok_or_else(|| {
-            IdeError::not_found("no supported build system (Maven, Gradle, Cargo, Go, TypeScript, CMake) found")
+            IdeError::not_found("no supported build system (Maven, Gradle, .NET, Cargo, Go, TypeScript, CMake) found")
         })?;
     let module = module_dir.as_deref().filter(|d| *d != root);
     let title = match module {
@@ -244,6 +248,7 @@ pub fn plan(
         BuildSystem::Go => go_steps(file.and_then(Path::parent).unwrap_or(&dir), kind)?,
         BuildSystem::TypeScript => ts_steps(&dir, kind),
         BuildSystem::CMake => cmake_steps(&dir, kind, cmake.and_then(<[_]>::first)),
+        BuildSystem::Dotnet => dotnet_steps(&dir, kind)?,
     };
     Ok(BuildPlan { system, title, steps })
 }
@@ -451,6 +456,33 @@ fn has_build_script(dir: &Path) -> bool {
         .is_some_and(|v| v.pointer("/scripts/build").is_some_and(serde_json::Value::is_string))
 }
 
+/// The solution (`.sln` / `.slnx`) or project (`.csproj` / `.fsproj` / `.vbproj`) file `dir`
+/// builds: a solution first, then a project; the first by name when there are several.
+fn dotnet_target(dir: &Path) -> Option<PathBuf> {
+    let mut files: Vec<PathBuf> =
+        std::fs::read_dir(dir).ok()?.flatten().map(|e| e.path()).filter(|p| p.is_file()).collect();
+    files.sort();
+    let ext = |p: &Path| p.extension().map(|e| e.to_string_lossy().to_ascii_lowercase()).unwrap_or_default();
+    let solution = files.iter().find(|p| matches!(ext(p).as_str(), "sln" | "slnx"));
+    solution.or_else(|| files.iter().find(|p| matches!(ext(p).as_str(), "csproj" | "fsproj" | "vbproj"))).cloned()
+}
+
+/// `dotnet build` of the directory's solution or project; Rebuild skips incremental builds,
+/// Build Artifacts publishes. The summary that repeats every message is left out.
+fn dotnet_steps(dir: &Path, kind: BuildKind) -> IdeResult<Vec<BuildStep>> {
+    let target = dotnet_target(dir).ok_or_else(|| IdeError::not_found("no .NET solution or project found"))?;
+    let target = target.file_name().map_or_else(String::new, |n| n.to_string_lossy().into_owned());
+    let verb = if kind == BuildKind::Artifacts { "publish" } else { "build" };
+    let mut step = BuildStep::new("dotnet", &[verb, &target, "-nologo", "-clp:NoSummary"], dir, Format::Msbuild);
+    if kind == BuildKind::Rebuild {
+        step.args.push("--no-incremental".into());
+    }
+    // The classic console logger prints the canonical `file(line,col): error` lines; the
+    // terminal logger (.NET 8+) only appears on a terminal, but rules it out for older SDKs too.
+    step.env.insert("MSBUILDTERMINALLOGGER".into(), "off".into());
+    Ok(vec![step])
+}
+
 fn ts_steps(dir: &Path, kind: BuildKind) -> Vec<BuildStep> {
     let script = has_build_script(dir);
     if script && (kind == BuildKind::Artifacts || !dir.join("tsconfig.json").is_file()) {
@@ -1141,6 +1173,24 @@ mod tests {
             ("pnpm", &["run".to_owned(), "build".to_owned()][..])
         );
 
+        // .NET: the solution, else the project; a module build is the file's project. An ASP.NET
+        // project's package.json (its front end) doesn't make it a TypeScript build.
+        let net = tmp.path().join("net");
+        write(&net, "App.sln", "");
+        write(&net, "src/Api/Api.csproj", "<Project/>");
+        write(&net, "src/Api/package.json", "{}");
+        write(&net, "src/Api/Program.cs", "");
+        let p = plan(&net, &BuildModel::default(), BuildKind::Build, None, None).unwrap();
+        assert_eq!(p.system, BuildSystem::Dotnet);
+        assert_eq!(p.steps[0].args, ["build", "App.sln", "-nologo", "-clp:NoSummary"]);
+        assert_eq!(p.steps[0].env["MSBUILDTERMINALLOGGER"], "off");
+        let p = plan(&net, &BuildModel::default(), BuildKind::Rebuild, Some(&net.join("src/Api/Program.cs")), None)
+            .unwrap();
+        assert_eq!(p.steps[0].args, ["build", "Api.csproj", "-nologo", "-clp:NoSummary", "--no-incremental"]);
+        assert_eq!(p.steps[0].cwd, net.join("src/Api"));
+        let p = plan(&net, &BuildModel::default(), BuildKind::Artifacts, None, None).unwrap();
+        assert_eq!(p.steps[0].args[0], "publish");
+
         let cm = tmp.path().join("cm");
         write(&cm, "CMakeLists.txt", "project(app)");
         let args = |p: &BuildPlan| p.steps.iter().map(|s| s.args.join(" ")).collect::<Vec<_>>();

crates/ide-build/src/compile/parse.rs

@@ -25,6 +25,8 @@ pub(crate) enum Format {
     Go,
     /// GCC / Clang (through `cmake --build`): `src/a.cpp:12:5: error: msg`.
     Gcc,
+    /// MSBuild (`dotnet build`): `C:\p\A.cs(12,5): error CS1002: msg [C:\p\App.csproj]`.
+    Msbuild,
 }
 
 /// What a printed column counts.
@@ -268,6 +270,43 @@ fn tsc_line(line: &str) -> Option<RawMessage> {
     Some(m)
 }
 
+/// MSBuild's canonical form: `path(12,5): error CS1002: msg [project]`, `path(12,5,12,9): …`,
+/// or `path : error NU1101: msg [project]` for a project-level message (no position).
+/// The path may contain spaces (`C:\Users\Jane Doe\…`); "error" / "warning" are never localized.
+fn msbuild_line(line: &str) -> Option<RawMessage> {
+    let line = line.trim();
+    // The project the message came from, appended by the console logger.
+    let line = match line.rfind(" [") {
+        Some(i) if line.ends_with(']') => &line[..i],
+        _ => line,
+    };
+    let (head, severity, rest) =
+        [(" error ", Severity::Error), (" warning ", Severity::Warning)].into_iter().find_map(|(word, severity)| {
+            let i = line.find(&format!(":{word}"))?;
+            Some((&line[..i], severity, &line[i + word.len() + 1..]))
+        })?;
+    let (code, msg) = rest.split_once(':')?;
+    let code = code.trim();
+    if code.is_empty() || code.contains(' ') {
+        return None;
+    }
+    let head = head.trim_end();
+    let (path, pos) = match head.strip_suffix(')').and_then(|h| h.rsplit_once('(')) {
+        Some((path, pos)) => (path, pos.split(',').map(num).collect::<Vec<_>>()),
+        None => (head, Vec::new()),
+    };
+    let at = |i: usize| pos.get(i).copied().flatten();
+    // `MSBUILD : error MSB1009` and the like name no file.
+    let file = path.rsplit(['/', '\\']).next().is_some_and(|n| n.contains('.'));
+    let mut m = RawMessage::new(severity, msg.trim(), ColUnit::Utf16);
+    if file {
+        m.path = Some(path.trim().to_owned());
+        (m.line, m.col, m.end_line, m.end_col) = (at(0), at(1), at(2), at(3));
+    }
+    m.code = Some(code.to_owned());
+    Some(m)
+}
+
 /// go: `./a.go:12:5: msg` (errors only; `go vet` style `a.go:12: msg` too).
 fn go_line(line: &str) -> Option<RawMessage> {
     let (path, ln, col, rest) = path_line_col(line)?;
@@ -404,6 +443,7 @@ impl OutputParser {
             Format::Tsc => tsc_line(&line),
             Format::Go => go_line(&line),
             Format::Gcc => gcc_line(&line),
+            Format::Msbuild => msbuild_line(&line),
             Format::Cargo => None,
         };
         if let Some(msg) = parsed {
@@ -551,6 +591,27 @@ mod tests {
         assert!(plain.messages.is_empty() && plain.console.is_none());
     }
 
+    #[test]
+    fn msbuild_canonical_messages() {
+        let out = parse(
+            Format::Msbuild,
+            "  Determining projects to restore...\n\
+             C:\\Users\\Jane Doe\\App\\Program.cs(12,5): error CS1002: ; expected [C:\\Users\\Jane Doe\\App\\App.csproj]\n\
+             /p/App/Models/User.cs(3,8,3,12): warning CS0168: The variable 'e' is declared but never used [/p/App/App.csproj]\n\
+             /p/App/App.csproj : error NU1101: Unable to find package Foo. [/p/App/App.csproj]\n\
+             MSBUILD : error MSB1009: Project file does not exist.\n\
+             Build FAILED.\n",
+        );
+        assert_eq!(out.len(), 4, "{out:?}");
+        assert_eq!(pos(&out[0]), (Severity::Error, "C:\\Users\\Jane Doe\\App\\Program.cs", 12, Some(5)));
+        assert_eq!((out[0].code.as_deref(), out[0].text.as_str()), (Some("CS1002"), "; expected"));
+        assert_eq!(pos(&out[1]), (Severity::Warning, "/p/App/Models/User.cs", 3, Some(8)));
+        assert_eq!((out[1].end_line, out[1].end_col), (Some(3), Some(12)));
+        assert_eq!((out[2].path.as_deref(), out[2].line), (Some("/p/App/App.csproj"), None));
+        assert_eq!(out[2].text, "Unable to find package Foo.");
+        assert_eq!((out[3].path.as_deref(), out[3].code.as_deref()), (None, Some("MSB1009")));
+    }
+
     #[test]
     fn tsc_plain_and_pretty() {
         let out = parse(

crates/ide-core/src/event.rs

@@ -118,6 +118,10 @@ pub enum IdeEvent {
     LanguageServer {
         server: ServerId,
         name: String,
+        /// What the user sees as the server when another program serves in its place.
+        #[serde(default)]
+        #[specta(optional)]
+        label: Option<String>,
         status: ServerStatus,
         message: Option<String>,
     },

crates/ide-core/src/jsonc.rs

@@ -1,8 +1,10 @@
 //! JSON with comments (`devcontainer.json`, `deno.jsonc`, `tsconfig.json`): turned
 //! into plain JSON for `serde_json`.
 
-/// Strips `//` and `/* */` comments and trailing commas so JSONC parses as JSON.
+/// Strips `//` and `/* */` comments, trailing commas and a leading byte order mark (Visual
+/// Studio writes one into `launchSettings.json`) so JSONC parses as JSON.
 pub fn strip(src: &str) -> String {
+    let src = src.strip_prefix('\u{feff}').unwrap_or(src);
     let mut out = String::with_capacity(src.len());
     let mut chars = src.chars().peekable();
     let mut in_str = false;
@@ -87,4 +89,10 @@ mod tests {
         assert_eq!(v["url"], "https://x.dev//y /* no */");
         assert_eq!(v["q"], "say \"hi\",");
     }
+
+    #[test]
+    fn drops_a_byte_order_mark() {
+        let v: serde_json::Value = serde_json::from_str(&strip("\u{feff}{ \"a\": 1 }")).unwrap();
+        assert_eq!(v["a"], 1);
+    }
 }

crates/ide-core/src/settings.rs

@@ -1092,7 +1092,8 @@ impl Default for ExternalFormatterSettings {
 #[derive(Clone, Debug, PartialEq, Serialize, Deserialize, Type)]
 #[serde(default, rename_all = "camelCase")]
 pub struct PythonSettings {
-    /// Project interpreter executable; empty = auto-detect (project venv, else `python3`).
+    /// Project interpreter executable; empty = auto-detect (project venv, else `python3`);
+    /// `target:<run-target-id>` = the Python of a Docker or Compose run target.
     pub interpreter: String,
     /// Activate the interpreter's virtualenv in new terminal sessions.
     pub activate_virtualenv: bool,
@@ -1121,6 +1122,17 @@ impl Default for PythonSettings {
     }
 }
 
+impl PythonSettings {
+    /// What `interpreter` starts with when the project interpreter is a run target's.
+    pub const TARGET_PREFIX: &str = "target:";
+
+    /// The run target whose Python is the project interpreter (`target:<id>`), if one is.
+    pub fn run_target(&self) -> Option<&str> {
+        let id = self.interpreter.trim().strip_prefix(Self::TARGET_PREFIX)?.trim();
+        (!id.is_empty()).then_some(id)
+    }
+}
+
 #[derive(Clone, Debug, Default, PartialEq, Serialize, Deserialize, Type)]
 #[serde(default, rename_all = "camelCase")]
 pub struct PhpSettings {
@@ -1542,6 +1554,16 @@ impl Settings {
 mod tests {
     use super::*;
 
+    #[test]
+    fn python_interpreter_may_name_a_run_target() {
+        let python = |interpreter: &str| PythonSettings { interpreter: interpreter.into(), ..Default::default() };
+        assert_eq!(python("target:web").run_target(), Some("web"));
+        assert_eq!(python(" target: web ").run_target(), Some("web"));
+        for local in ["", "target:", "/usr/bin/python3", ".venv/bin/python", "targets/python"] {
+            assert_eq!(python(local).run_target(), None, "{local}");
+        }
+    }
+
     #[test]
     fn removed_one_themes_read_as_islands_themes() {
         let settings: Settings = serde_json::from_str(

crates/ide-core/src/workflow_settings.rs

@@ -260,6 +260,8 @@ pub struct DebuggerSettings {
     pub show_on_breakpoint: bool,
     pub focus_app_on_breakpoint: bool,
     pub hide_on_termination: bool,
+    /// A breakpoint or exception hit brings the Debug tool window's Threads & Variables tab to the front.
+    pub variables_on_breakpoint: bool,
     pub breakpoints_any_file: bool,
     /// While suspended, hovering the start of a line shows a Run to Cursor button.
     pub run_to_cursor_inlay: bool,
@@ -285,6 +287,7 @@ impl Default for DebuggerSettings {
             show_on_breakpoint: true,
             focus_app_on_breakpoint: false,
             hide_on_termination: false,
+            variables_on_breakpoint: true,
             breakpoints_any_file: false,
             run_to_cursor_inlay: true,
             inline_values: true,

crates/ide-dap/Cargo.toml

@@ -7,6 +7,8 @@ license.workspace = true
 
 [dependencies]
 futures.workspace = true
+tokio-tungstenite.workspace = true
+base64.workspace = true
 tempfile.workspace = true
 ide-core.workspace = true
 ide-language.workspace = true

crates/ide-dap/src/js_cdp.rs

@@ -0,0 +1,528 @@
+//! Replacing the responses a debugged page receives. js-debug hands out a WebSocket that
+//! speaks the browser's own protocol (`requestCDPProxy`); over it the browser is told to hold
+//! the requests whose URL matches a rule (`Fetch.enable`) and each held request is answered
+//! here, with the rule's response or by letting it through.
+//!
+//! A held request stays held until it is answered, so interception is always switched off
+//! (`Fetch.disable`) before the connection is given up: a page whose requests nobody answers hangs.
+
+use crate::{DebugManager, DebugSessionId, REQUEST_TIMEOUT, js_debug};
+use base64::Engine;
+use futures::{SinkExt, StreamExt};
+use ide_core::{IdeError, IdeResult};
+use serde::{Deserialize, Serialize};
+use serde_json::{Value, json};
+use specta::Type;
+use std::collections::HashMap;
+use tokio::sync::{oneshot, watch};
+use tokio_tungstenite::tungstenite::{Message, http::StatusCode};
+
+/// A response given in place of the server's to every request whose URL contains `url_contains`.
+#[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize, Type)]
+#[serde(rename_all = "camelCase")]
+pub struct JsResponseRule {
+    pub url_contains: String,
+    pub status: u16,
+    pub content_type: String,
+    pub body: String,
+}
+
+/// The browser's URL pattern (`*` any text, `?` one character, `\` escapes) for "contains `part`".
+pub(crate) fn url_pattern(part: &str) -> String {
+    let mut pattern = String::with_capacity(part.len() + 2);
+    pattern.push('*');
+    for c in part.chars() {
+        if matches!(c, '*' | '?' | '\\') {
+            pattern.push('\\');
+        }
+        pattern.push(c);
+    }
+    pattern.push('*');
+    pattern
+}
+
+pub(crate) fn rule_for<'a>(rules: &'a [JsResponseRule], url: &str) -> Option<&'a JsResponseRule> {
+    rules.iter().find(|rule| url.contains(&rule.url_contains))
+}
+
+/// What to tell the browser about a request it holds: the first matching rule's response, or
+/// to send the request on. Every held request gets one of the two.
+pub(crate) fn answer(held: &Value, rules: &[JsResponseRule]) -> (&'static str, Value) {
+    let request_id = held.get("requestId").and_then(Value::as_str).unwrap_or_default();
+    let url = held.pointer("/request/url").and_then(Value::as_str).unwrap_or_default();
+    let Some(rule) = rule_for(rules, url) else {
+        return ("Fetch.continueRequest", json!({ "requestId": request_id }));
+    };
+    let header = |name: &str, value: &str| json!({ "name": name, "value": value });
+    // A page on another origin only reads a response that names its origin. The server would
+    // say so; the response given in its place has to.
+    let mut cross_origin = Vec::new();
+    if let Some(origin) = request_header(held, "Origin") {
+        cross_origin.push(header("Access-Control-Allow-Origin", origin));
+        cross_origin.push(header("Access-Control-Allow-Credentials", "true"));
+    }
+    let method = held.pointer("/request/method").and_then(Value::as_str).unwrap_or_default();
+    // The browser's question before such a request: allowed here, the server may not exist.
+    if method == "OPTIONS"
+        && let Some(asked) = request_header(held, "Access-Control-Request-Method")
+    {
+        cross_origin.push(header("Access-Control-Allow-Methods", asked));
+        if let Some(asked) = request_header(held, "Access-Control-Request-Headers") {
+            cross_origin.push(header("Access-Control-Allow-Headers", asked));
+        }
+        let allowed = json!({
+            "requestId": request_id,
+            "responseCode": 204,
+            "responsePhrase": phrase(204),
+            "responseHeaders": cross_origin,
+        });
+        return ("Fetch.fulfillRequest", allowed);
+    }
+    let mut headers = vec![header("Content-Type", &rule.content_type)];
+    headers.extend(cross_origin);
+    let replaced = json!({
+        "requestId": request_id,
+        "responseCode": rule.status,
+        "responsePhrase": phrase(rule.status),
+        "responseHeaders": headers,
+        "body": base64::engine::general_purpose::STANDARD.encode(rule.body.as_bytes()),
+    });
+    ("Fetch.fulfillRequest", replaced)
+}
+
+/// A header of the held request; the browser reports names as the page wrote them.
+fn request_header<'a>(held: &'a Value, name: &str) -> Option<&'a str> {
+    held.pointer("/request/headers")?.as_object()?.iter().find(|(key, _)| key.eq_ignore_ascii_case(name))?.1.as_str()
+}
+
+/// The browser refuses a response without a phrase when it has none of its own for the status.
+fn phrase(status: u16) -> &'static str {
+    StatusCode::from_u16(status).ok().and_then(|status| status.canonical_reason()).unwrap_or("Unknown")
+}
+
+fn interception(rules: &[JsResponseRule]) -> Value {
+    let patterns: Vec<Value> = rules
+        .iter()
+        .map(|rule| json!({ "urlPattern": url_pattern(&rule.url_contains), "requestStage": "Request" }))
+        .collect();
+    json!({ "patterns": patterns })
+}
+
+/// Applies `rules` to the page behind js-debug's CDP proxy at `ws_url` until their sender is
+/// dropped (the session is gone) or the proxy closes the connection. The browser holds
+/// requests only while there are rules. `ready` hears whether the proxy reports held
+/// requests at all; nothing is held before it has agreed to.
+pub(crate) async fn serve(
+    ws_url: String,
+    mut rules: watch::Receiver<Vec<JsResponseRule>>,
+    ready: oneshot::Sender<Result<(), String>>,
+) {
+    let socket = match tokio_tungstenite::connect_async(ws_url.as_str()).await {
+        Ok((socket, _)) => socket,
+        Err(e) => {
+            let _ = ready.send(Err(e.to_string()));
+            return;
+        }
+    };
+    let (mut write, mut read) = socket.split();
+    let mut last_id = 0u64;
+    let mut call = |method: &str, params: Value| {
+        last_id += 1;
+        (last_id, Message::text(json!({ "id": last_id, "method": method, "params": params }).to_string()))
+    };
+
+    let (subscription, subscribe) = call("JsDebug.subscribe", json!({ "events": ["Fetch.requestPaused"] }));
+    let subscribed = tokio::time::timeout(REQUEST_TIMEOUT, async {
+        write.send(subscribe).await.map_err(|e| e.to_string())?;
+        loop {
+            let reply = read.next().await.ok_or("the connection closed")?.map_err(|e| e.to_string())?;
+            let Some(reply) = reply.to_text().ok().and_then(|text| serde_json::from_str::<Value>(text).ok()) else {
+                continue;
+            };
+            if reply.get("id").and_then(Value::as_u64) != Some(subscription) {
+                continue;
+            }
+            break match reply.get("error") {
+                Some(error) => Err(error.get("message").and_then(Value::as_str).unwrap_or("refused").to_owned()),
+                None => Ok(()),
+            };
+        }
+    })
+    .await
+    .unwrap_or_else(|_| Err("no answer".to_owned()));
+    if let Err(why) = subscribed {
+        let _ = ready.send(Err(why));
+        let _ = write.close().await;
+        return;
+    }
+    let _ = ready.send(Ok(()));
+
+    let mut current = rules.borrow_and_update().clone();
+    let mut holding = !current.is_empty();
+    if holding && write.send(call("Fetch.enable", interception(&current)).1).await.is_err() {
+        return;
+    }
+    // The request each sent replacement is for, by command id, until the browser has taken it.
+    let mut replacing: HashMap<u64, String> = HashMap::new();
+    loop {
+        tokio::select! {
+            changed = rules.changed() => {
+                if changed.is_err() {
+                    break;
+                }
+                current = rules.borrow_and_update().clone();
+                let (_, command) = match (current.is_empty(), holding) {
+                    (true, false) => continue,
+                    (true, true) => call("Fetch.disable", json!({})),
+                    (false, _) => call("Fetch.enable", interception(&current)),
+                };
+                holding = !current.is_empty();
+                if write.send(command).await.is_err() {
+                    return;
+                }
+            }
+            message = read.next() => {
+                // The proxy closed (the page or the session ended): nothing is held any more.
+                let Some(Ok(message)) = message else { return };
+                let Ok(text) = message.to_text() else { continue };
+                let Ok(message) = serde_json::from_str::<Value>(text) else { continue };
+                if let Some(id) = message.get("id").and_then(Value::as_u64) {
+                    // The browser did not take the replacement: let the request through, or
+                    // it stays held and the page waits for it.
+                    if let Some(request_id) = replacing.remove(&id)
+                        && message.get("error").is_some()
+                    {
+                        let (_, go_on) = call("Fetch.continueRequest", json!({ "requestId": request_id }));
+                        if write.send(go_on).await.is_err() {
+                            return;
+                        }
+                    }
+                    continue;
+                }
+                if message.get("method").and_then(Value::as_str) != Some("Fetch.requestPaused") {
+                    continue;
+                }
+                let Some(held) = message.get("params") else { continue };
+                let Some(request_id) = held.get("requestId").and_then(Value::as_str) else { continue };
+                let (method, params) = answer(held, &current);
+                let (id, command) = call(method, params);
+                if method == "Fetch.fulfillRequest" {
+                    replacing.insert(id, request_id.to_owned());
+                }
+                if write.send(command).await.is_err() {
+                    return;
+                }
+            }
+        }
+    }
+    if holding {
+        let _ = write.send(call("Fetch.disable", json!({})).1).await;
+    }
+    let _ = write.close().await;
+}
+
+impl DebugManager {
+    /// Makes `rules` the page's response rules; none switches the replacing off. The first
+    /// rules of a session open the connection to js-debug's CDP proxy, later ones go over it.
+    /// An error means the rules are not applied.
+    pub async fn js_set_response_overrides(&self, s: DebugSessionId, rules: Vec<JsResponseRule>) -> IdeResult<()> {
+        let session = self.session(s)?;
+        if !js_debug::is_page(&session) {
+            return Err(IdeError::unavailable("this debug session is not a page in a browser"));
+        }
+        // Held to the end: two callers at once would each open a connection.
+        let mut applied = session.js_overrides.lock().await;
+        if applied.as_ref().is_some_and(|sender| sender.send(rules.clone()).is_ok()) {
+            return Ok(());
+        }
+        // No connection yet, or the proxy closed it.
+        applied.take();
+        if rules.is_empty() {
+            return Ok(());
+        }
+        let refused =
+            |why: String| IdeError::unavailable(format!("the JavaScript debugger has no browser connection: {why}"));
+        if !js_debug::launched(&session).await {
+            return Err(refused("the page's debug session did not finish starting".into()));
+        }
+        let proxy = session
+            .conn
+            .request_timeout("requestCDPProxy", json!({}), REQUEST_TIMEOUT)
+            .await
+            .map_err(|e| refused(e.to_string()))?;
+        let (Some(host), Some(port)) =
+            (proxy.get("host").and_then(Value::as_str), proxy.get("port").and_then(Value::as_u64))
+        else {
+            return Err(refused("no address".into()));
+        };
+        let path = proxy.get("path").and_then(Value::as_str).unwrap_or_default();
+        let (sender, receiver) = watch::channel(rules);
+        let (ready, is_ready) = oneshot::channel();
+        tokio::spawn(serve(format!("ws://{host}:{port}{path}"), receiver, ready));
+        match is_ready.await {
+            Ok(Ok(())) => {
+                *applied = Some(sender);
+                Ok(())
+            }
+            Ok(Err(why)) => Err(refused(why)),
+            Err(_) => Err(refused("no answer".into())),
+        }
+    }
+}
+
+#[cfg(test)]
+pub(crate) mod tests {
+    use super::*;
+    use futures::{SinkExt, StreamExt};
+    use serde_json::json;
+    use tokio::sync::mpsc;
+    use tokio_tungstenite::tungstenite::Message;
+
+    pub(crate) fn rule(url_contains: &str, status: u16, body: &str) -> JsResponseRule {
+        JsResponseRule {
+            url_contains: url_contains.into(),
+            status,
+            content_type: "application/json".into(),
+            body: body.into(),
+        }
+    }
+
+    #[test]
+    fn a_part_of_a_url_becomes_a_pattern_that_matches_it_anywhere() {
+        assert_eq!(url_pattern("api/items"), "*api/items*");
+        // The pattern's own wildcards and escape character are taken literally.
+        assert_eq!(url_pattern(r"a*b?c\d"), r"*a\*b\?c\\d*");
+    }
+
+    #[test]
+    fn the_first_rule_whose_text_is_in_the_url_answers() {
+        let rules = [rule("api/items", 201, "{\"a\":\"é\"}"), rule("api", 500, "later")];
+        assert_eq!(rule_for(&rules, "http://h/api/items?x=1").map(|r| r.status), Some(201));
+        assert_eq!(rule_for(&rules, "http://h/api/users").map(|r| r.status), Some(500));
+        assert!(rule_for(&rules, "http://h/logo.png").is_none());
+
+        let (command, params) = answer(&held("7", "http://h/api/items")["params"], &rules);
+        assert_eq!(command, "Fetch.fulfillRequest");
+        assert_eq!(
+            params,
+            json!({
+                "requestId": "7",
+                "responseCode": 201,
+                "responsePhrase": "Created",
+                "responseHeaders": [{ "name": "Content-Type", "value": "application/json" }],
+                // base64 of the UTF-8 text `{"a":"é"}`
+                "body": "eyJhIjoiw6kifQ==",
+            })
+        );
+        // A request the browser held that no rule is for goes on to the network.
+        assert_eq!(
+            answer(&held("8", "http://h/logo.png")["params"], &rules),
+            ("Fetch.continueRequest", json!({ "requestId": "8" }))
+        );
+    }
+
+    #[test]
+    fn a_status_the_browser_has_no_phrase_for_is_given_one() {
+        // The browser refuses a response whose status it cannot name.
+        let (_, params) = answer(&held("1", "http://h/api")["params"], &[rule("api", 419, "")]);
+        assert_eq!((&params["responseCode"], &params["responsePhrase"]), (&json!(419), &json!("Unknown")));
+    }
+
+    fn header<'a>(params: &'a Value, name: &str) -> Option<&'a str> {
+        params["responseHeaders"].as_array()?.iter().find(|h| h["name"] == name)?["value"].as_str()
+    }
+
+    #[test]
+    fn a_replaced_response_passes_the_pages_cross_origin_check() {
+        let rules = [rule("api/items", 200, "[]")];
+        let from_page = |method: &str, headers: Value| json!({ "requestId": "3", "request": { "url": "http://localhost:8080/api/items", "method": method, "headers": headers } });
+        // A page on another origin: the response names that origin, as the real server would.
+        let (_, params) = answer(&from_page("GET", json!({ "origin": "http://localhost:5173" })), &rules);
+        assert_eq!(header(&params, "Access-Control-Allow-Origin"), Some("http://localhost:5173"));
+        assert_eq!(header(&params, "Access-Control-Allow-Credentials"), Some("true"));
+        assert_eq!(params["body"], "W10=");
+
+        // The browser's question before such a request is answered too: the server may not exist.
+        let preflight = from_page(
+            "OPTIONS",
+            json!({
+                "Origin": "http://localhost:5173",
+                "Access-Control-Request-Method": "PUT",
+                "Access-Control-Request-Headers": "content-type,x-token",
+            }),
+        );
+        let (command, params) = answer(&preflight, &rules);
+        assert_eq!((command, &params["responseCode"]), ("Fetch.fulfillRequest", &json!(204)));
+        assert_eq!(header(&params, "Access-Control-Allow-Origin"), Some("http://localhost:5173"));
+        assert_eq!(header(&params, "Access-Control-Allow-Methods"), Some("PUT"));
+        assert_eq!(header(&params, "Access-Control-Allow-Headers"), Some("content-type,x-token"));
+        assert_eq!(params.get("body"), None);
+
+        // Same origin: nothing but the rule's own header.
+        let (_, params) = answer(&from_page("GET", json!({})), &rules);
+        assert_eq!(params["responseHeaders"], json!([{ "name": "Content-Type", "value": "application/json" }]));
+    }
+
+    /// A stand-in for js-debug's CDP proxy: what it receives, and a way to send it events.
+    pub(crate) async fn proxy() -> (String, mpsc::UnboundedReceiver<Value>, mpsc::UnboundedSender<Value>) {
+        proxy_refusing(|_| false).await
+    }
+
+    /// A proxy that answers the commands `refused` picks with an error, like the real one does
+    /// for what it or the browser does not accept.
+    pub(crate) async fn proxy_refusing(
+        refused: fn(&Value) -> bool,
+    ) -> (String, mpsc::UnboundedReceiver<Value>, mpsc::UnboundedSender<Value>) {
+        let listener = tokio::net::TcpListener::bind("127.0.0.1:0").await.unwrap();
+        let url = format!("ws://127.0.0.1:{}/session", listener.local_addr().unwrap().port());
+        let (received_tx, received) = mpsc::unbounded_channel();
+        let (events, mut events_rx) = mpsc::unbounded_channel::<Value>();
+        tokio::spawn(async move {
+            let (stream, _) = listener.accept().await.unwrap();
+            let (mut write, mut read) = tokio_tungstenite::accept_async(stream).await.unwrap().split();
+            loop {
+                tokio::select! {
+                    message = read.next() => {
+                        let Some(Ok(message)) = message else { break };
+                        let Ok(text) = message.to_text() else { continue };
+                        let Ok(request) = serde_json::from_str::<Value>(text) else { continue };
+                        let reply = if refused(&request) {
+                            json!({ "id": request["id"], "error": { "code": -32602, "message": "refused" } })
+                        } else {
+                            json!({ "id": request["id"], "result": {} })
+                        };
+                        let _ = write.send(Message::text(reply.to_string())).await;
+                        let _ = received_tx.send(request);
+                    }
+                    Some(event) = events_rx.recv() => {
+                        let _ = write.send(Message::text(event.to_string())).await;
+                    }
+                }
+            }
+        });
+        (url, received, events)
+    }
+
+    pub(crate) async fn next(received: &mut mpsc::UnboundedReceiver<Value>) -> (String, Value) {
+        let request = tokio::time::timeout(std::time::Duration::from_secs(5), received.recv())
+            .await
+            .expect("the proxy got a request in time")
+            .expect("the connection is open");
+        (request["method"].as_str().unwrap().to_owned(), request["params"].clone())
+    }
+
+    /// The browser's event for a request it holds.
+    fn held(request_id: &str, url: &str) -> Value {
+        json!({ "method": "Fetch.requestPaused", "params": { "requestId": request_id, "request": { "url": url } } })
+    }
+
+    type Serving = (tokio::task::JoinHandle<()>, oneshot::Receiver<Result<(), String>>);
+
+    fn serving(url: String, rules: watch::Receiver<Vec<JsResponseRule>>) -> Serving {
+        let (ready, is_ready) = oneshot::channel();
+        (tokio::spawn(serve(url, rules, ready)), is_ready)
+    }
+
+    async fn ended(task: tokio::task::JoinHandle<()>) {
+        tokio::time::timeout(std::time::Duration::from_secs(5), task).await.unwrap().unwrap();
+    }
+
+    #[tokio::test]
+    async fn held_requests_are_answered_and_interception_ends_before_the_connection() {
+        let (url, mut received, events) = proxy().await;
+        let (rules, watched) = tokio::sync::watch::channel(vec![rule("api/items", 200, "[]")]);
+        let (serving, ready) = serving(url, watched);
+        assert_eq!(ready.await.unwrap(), Ok(()));
+
+        assert_eq!(
+            next(&mut received).await,
+            ("JsDebug.subscribe".into(), json!({ "events": ["Fetch.requestPaused"] }))
+        );
+        assert_eq!(
+            next(&mut received).await,
+            (
+                "Fetch.enable".into(),
+                json!({ "patterns": [{ "urlPattern": "*api/items*", "requestStage": "Request" }] })
+            )
+        );
+
+        events.send(held("1", "http://h/api/items")).unwrap();
+        let (command, params) = next(&mut received).await;
+        assert_eq!(
+            (command.as_str(), &params["requestId"], &params["responseCode"]),
+            ("Fetch.fulfillRequest", &json!("1"), &json!(200))
+        );
+        events.send(held("2", "http://h/other")).unwrap();
+        assert_eq!(next(&mut received).await, ("Fetch.continueRequest".into(), json!({ "requestId": "2" })));
+
+        // New rules replace the browser's patterns.
+        rules.send(vec![rule("api/users", 404, "{}")]).unwrap();
+        assert_eq!(
+            next(&mut received).await,
+            (
+                "Fetch.enable".into(),
+                json!({ "patterns": [{ "urlPattern": "*api/users*", "requestStage": "Request" }] })
+            )
+        );
+
+        // No rules left: the browser stops holding requests. The connection stays for the
+        // rules that come next, and goes with the session.
+        rules.send(Vec::new()).unwrap();
+        assert_eq!(next(&mut received).await.0, "Fetch.disable");
+        rules.send(vec![rule("api/items", 200, "[]")]).unwrap();
+        assert_eq!(next(&mut received).await.0, "Fetch.enable");
+        rules.send(Vec::new()).unwrap();
+        assert_eq!(next(&mut received).await.0, "Fetch.disable");
+        drop(rules);
+        ended(serving).await;
+        // Already off: not switched off a second time.
+        assert!(received.try_recv().is_err());
+    }
+
+    #[tokio::test]
+    async fn a_session_that_goes_away_switches_interception_off() {
+        let (url, mut received, _events) = proxy().await;
+        let (rules, watched) = tokio::sync::watch::channel(vec![rule("api", 200, "[]")]);
+        let (serving, _ready) = serving(url, watched);
+        assert_eq!(next(&mut received).await.0, "JsDebug.subscribe");
+        assert_eq!(next(&mut received).await.0, "Fetch.enable");
+        drop(rules);
+        assert_eq!(next(&mut received).await.0, "Fetch.disable");
+        ended(serving).await;
+    }
+
+    #[tokio::test]
+    async fn a_response_the_browser_refuses_lets_the_request_through() {
+        let (url, mut received, events) = proxy_refusing(|request| request["method"] == "Fetch.fulfillRequest").await;
+        let (_rules, watched) = tokio::sync::watch::channel(vec![rule("api", 200, "[]")]);
+        let (_serving, _ready) = serving(url, watched);
+        assert_eq!(next(&mut received).await.0, "JsDebug.subscribe");
+        assert_eq!(next(&mut received).await.0, "Fetch.enable");
+        events.send(held("9", "http://h/api")).unwrap();
+        assert_eq!(next(&mut received).await.0, "Fetch.fulfillRequest");
+        // Unanswered, the request would hang the page.
+        assert_eq!(next(&mut received).await, ("Fetch.continueRequest".into(), json!({ "requestId": "9" })));
+    }
+
+    #[tokio::test]
+    async fn a_proxy_that_does_not_report_held_requests_is_not_asked_to_hold_any() {
+        let (url, mut received, _events) = proxy_refusing(|request| request["method"] == "JsDebug.subscribe").await;
+        let (_rules, watched) = tokio::sync::watch::channel(vec![rule("api", 200, "[]")]);
+        let (serving, ready) = serving(url, watched);
+        assert_eq!(next(&mut received).await.0, "JsDebug.subscribe");
+        assert_eq!(ready.await.unwrap(), Err("refused".to_owned()));
+        ended(serving).await;
+        assert!(received.try_recv().is_err());
+    }
+
+    #[tokio::test]
+    async fn no_connection_to_the_proxy_is_reported() {
+        let listener = tokio::net::TcpListener::bind("127.0.0.1:0").await.unwrap();
+        let url = format!("ws://127.0.0.1:{}/session", listener.local_addr().unwrap().port());
+        drop(listener);
+        let (_rules, watched) = tokio::sync::watch::channel(vec![rule("api", 200, "[]")]);
+        let (serving, ready) = serving(url, watched);
+        assert!(ready.await.unwrap().is_err());
+        ended(serving).await;
+    }
+}

crates/ide-dap/src/js_debug.rs

@@ -11,6 +11,8 @@ use serde::{Deserialize, Serialize};
 use serde_json::{Value, json};
 use specta::Type;
 use std::collections::BTreeMap;
+use std::path::PathBuf;
+use std::sync::atomic::{AtomicU32, Ordering};
 
 pub(crate) const ADAPTER: &str = "js-debug";
 
@@ -25,7 +27,7 @@ pub(crate) fn is_page(session: &Session) -> bool {
 /// Waits until the adapter answered the `launch` of `session`. js-debug sets a page's session
 /// up between `configurationDone` and that answer; a request of its own that arrives then is
 /// answered and has no effect.
-async fn launched(session: &Session) -> bool {
+pub(crate) async fn launched(session: &Session) -> bool {
     let mut launched = session.launched.subscribe();
     let answered = tokio::time::timeout(REQUEST_TIMEOUT, launched.wait_for(|answered| *answered)).await;
     matches!(answered, Ok(Ok(_)))
@@ -59,6 +61,44 @@ impl DebugManager {
         self.js_page_request(s, "setCustomBreakpoints", json!({ "ids": ids, "xhr": xhr })).await?;
         Ok(())
     }
+
+    /// Starts recording the page's CPU profile; [`Self::js_stop_profile`] ends it.
+    pub async fn js_start_profile(&self, s: DebugSessionId) -> IdeResult<()> {
+        self.js_page_request(s, "startProfile", json!({ "type": "cpu" })).await?;
+        Ok(())
+    }
+
+    /// Ends the recording and returns a new directory holding it as `page.cpuprofile`
+    /// (what `ide-profiler` reads a directory of).
+    pub async fn js_stop_profile(&self, s: DebugSessionId) -> IdeResult<PathBuf> {
+        let session = self.session(s)?;
+        // js-debug names the file it records into when the recording starts.
+        let Some(recorded) = session.js_profile.lock().take() else {
+            return Err(IdeError::invalid("no CPU profile is being recorded"));
+        };
+        self.js_page_request(s, "stopProfile", json!({})).await?;
+        static HANDED_OVER: AtomicU32 = AtomicU32::new(0);
+        let dir = std::env::temp_dir().join(format!(
+            "openidea-js-profile-{}-{}-{}",
+            std::process::id(),
+            s.0,
+            HANDED_OVER.fetch_add(1, Ordering::Relaxed)
+        ));
+        let copied = tokio::task::spawn_blocking({
+            let dir = dir.clone();
+            move || {
+                std::fs::create_dir_all(&dir)?;
+                std::fs::copy(&recorded, dir.join("page.cpuprofile"))?;
+                // The adapter's own copy is in the system's temporary directory: no use keeping two.
+                let _ = std::fs::remove_file(&recorded);
+                Ok::<_, std::io::Error>(())
+            }
+        })
+        .await
+        .map_err(|e| IdeError::internal(e.to_string()))?;
+        copied.map_err(|e| IdeError::unavailable(format!("the recorded CPU profile cannot be read: {e}")))?;
+        Ok(dir)
+    }
 }
 
 /// The browser events js-debug is asked to pass on (`enableNetworking`'s `mirrorEvents`).

crates/ide-dap/src/lib.rs

@@ -13,6 +13,7 @@ pub mod attach;
 mod cargo;
 pub mod connection;
 pub mod jdwp;
+mod js_cdp;
 mod js_debug;
 mod jvm_memory;
 pub mod kotlin;
@@ -24,6 +25,7 @@ use connection::{Connection, DapError};
 use futures::future::join_all;
 use ide_core::{DebugSessionId, IdeError, IdeResult, SharedSink};
 use ide_language::LanguageRegistry;
+pub use js_cdp::JsResponseRule;
 pub use js_debug::JsResponseBody;
 pub use jvm_memory::*;
 use parking_lot::Mutex;

crates/ide-dap/src/session.rs

@@ -94,6 +94,11 @@ pub(crate) struct Session {
     /// The `type` of the launch or attach request (js-debug's `pwa-node`, `pwa-chrome`); a child
     /// session's comes from the configuration the adapter started it with.
     pub launch_type: std::sync::OnceLock<String>,
+    /// The response rules of a page once a connection applies them (`js_cdp::serve`).
+    /// Dropped with the session, which switches the browser's interception off.
+    pub js_overrides: tokio::sync::Mutex<Option<tokio::sync::watch::Sender<Vec<crate::JsResponseRule>>>>,
+    /// The file js-debug records the page's CPU profile into, while one is being recorded.
+    pub js_profile: parking_lot::Mutex<Option<std::path::PathBuf>>,
     pub jvm_inspector: parking_lot::Mutex<Option<Arc<dyn ide_jvm_inspect::JvmInspector>>>,
     /// One inspector request per session at a time.
     pub inspect_lock: tokio::sync::Mutex<()>,
@@ -255,6 +260,8 @@ impl Session {
             progress: Mutex::new(HashMap::new()),
             jdwp_link: parking_lot::Mutex::new(None),
             launch_type: std::sync::OnceLock::new(),
+            js_overrides: tokio::sync::Mutex::new(None),
+            js_profile: parking_lot::Mutex::new(None),
             jvm_inspector: parking_lot::Mutex::new(None),
             inspect_lock: tokio::sync::Mutex::default(),
             ended: ide_core::CancellationToken::new(),
@@ -842,6 +849,10 @@ async fn on_event(mgr: &Arc<DebugManager>, s: &Arc<Session>, event: &str, mut bo
                 s.emit(DebugEvent::JsNetwork { event });
             }
         }
+        // js-debug, after `startProfile`: where it records the profile.
+        "profileStarted" => {
+            *s.js_profile.lock() = str_("file").map(std::path::PathBuf::from);
+        }
         _ => tracing::trace!("dap: ignored event {event}"),
     }
 }
@@ -872,6 +883,7 @@ fn on_reverse_request(mgr: &Arc<DebugManager>, s: &Arc<Session>, seq: i64, comma
 pub(crate) struct ProgramTerminal {
     writer: ide_core::input::InputWriter,
     killer: Box<dyn portable_pty::ChildKiller + Send + Sync>,
+    #[cfg_attr(not(unix), allow(dead_code))]
     pid: Option<u32>,
     /// Set once the program has exited and been reaped.
     exited: Arc<AtomicBool>,
@@ -884,6 +896,7 @@ impl ProgramTerminal {
     }
 
     /// The program's process id while it runs.
+    #[cfg_attr(not(unix), allow(dead_code))]
     pub(crate) fn process_id(&self) -> Option<u32> {
         if self.exited.load(Ordering::Acquire) { None } else { self.pid }
     }

crates/ide-dap/src/tests.rs

@@ -1104,6 +1104,142 @@ async fn a_page_whose_requests_the_adapter_does_not_report_says_so() {
     h.wait_event(|e| matches!(e, DebugEvent::JsNetworkUnavailable)).await;
 }
 
+/// Where the fake adapter says its CDP proxy listens (`requestCDPProxy`).
+static CDP_PROXY_PORT: std::sync::atomic::AtomicU16 = std::sync::atomic::AtomicU16::new(0);
+
+fn proxy_adapter(msg: &Value) -> Option<CustomReply> {
+    let port = CDP_PROXY_PORT.load(std::sync::atomic::Ordering::Relaxed);
+    (msg["command"] == "requestCDPProxy")
+        .then(|| (json!({ "host": "127.0.0.1", "port": port, "path": "/session" }), Vec::new()))
+}
+
+#[tokio::test]
+async fn response_overrides_reach_the_page_through_the_adapters_proxy() {
+    use crate::js_cdp::tests::{next, proxy, rule};
+    let (url, mut received, _events) = proxy().await;
+    let port: u16 = url.trim_start_matches("ws://127.0.0.1:").trim_end_matches("/session").parse().unwrap();
+    CDP_PROXY_PORT.store(port, std::sync::atomic::Ordering::Relaxed);
+
+    let h = harness(Script {
+        start_debugging: true,
+        custom: Some(proxy_adapter),
+        child_launch_delay: Duration::from_millis(150),
+        ..Script::default()
+    });
+    let browser = h.start(js_config("pwa-chrome")).await.unwrap();
+    let page = child_of(&h, browser).await;
+
+    // Rules that are there as the page starts wait until its session takes requests.
+    tokio::time::sleep(Duration::from_millis(50)).await;
+    h.manager.js_set_response_overrides(page, vec![rule("api/items", 200, "[]")]).await.unwrap();
+    let dropped = h.log.lock().iter().filter(|m| m["type"] == "dropped").count();
+    assert_eq!(dropped, 0, "the proxy was asked for before the page took requests");
+    assert_eq!(next(&mut received).await.0, "JsDebug.subscribe");
+    assert_eq!(
+        next(&mut received).await,
+        ("Fetch.enable".into(), json!({ "patterns": [{ "urlPattern": "*api/items*", "requestStage": "Request" }] }))
+    );
+    // Changed rules go over the connection that is open: the proxy is asked for once.
+    h.manager.js_set_response_overrides(page, vec![rule("api/users", 200, "[]")]).await.unwrap();
+    assert_eq!(next(&mut received).await.1["patterns"][0]["urlPattern"], "*api/users*");
+    assert_eq!(requests(&h, "requestCDPProxy").len(), 1);
+
+    h.manager.js_set_response_overrides(page, Vec::new()).await.unwrap();
+    assert_eq!(next(&mut received).await.0, "Fetch.disable");
+    // A rule switched back on.
+    h.manager.js_set_response_overrides(page, vec![rule("api/items", 200, "[]")]).await.unwrap();
+    assert_eq!(next(&mut received).await.0, "Fetch.enable");
+    assert_eq!(requests(&h, "requestCDPProxy").len(), 1);
+
+    let not_a_page = h.manager.js_set_response_overrides(browser, vec![rule("api", 200, "")]).await.unwrap_err();
+    assert_eq!(not_a_page.kind, ide_core::error::ErrorKind::Unavailable);
+}
+
+#[tokio::test]
+async fn response_overrides_are_unavailable_without_the_adapters_proxy() {
+    use crate::js_cdp::tests::rule;
+    let h = harness(Script { start_debugging: true, ..Script::default() });
+    let browser = h.start(js_config("pwa-chrome")).await.unwrap();
+    let page = child_of(&h, browser).await;
+    let refused = h.manager.js_set_response_overrides(page, vec![rule("api", 200, "")]).await.unwrap_err();
+    assert_eq!(refused.kind, ide_core::error::ErrorKind::Unavailable);
+    // Nothing to switch off is not an error.
+    h.manager.js_set_response_overrides(page, Vec::new()).await.unwrap();
+}
+
+/// A port nothing listens on, which the fake adapter gives as its CDP proxy.
+static DEAD_PROXY_PORT: std::sync::atomic::AtomicU16 = std::sync::atomic::AtomicU16::new(0);
+
+fn dead_proxy_adapter(msg: &Value) -> Option<CustomReply> {
+    let port = DEAD_PROXY_PORT.load(std::sync::atomic::Ordering::Relaxed);
+    (msg["command"] == "requestCDPProxy")
+        .then(|| (json!({ "host": "127.0.0.1", "port": port, "path": "/session" }), Vec::new()))
+}
+
+#[tokio::test]
+async fn response_overrides_that_cannot_reach_the_browser_are_an_error() {
+    use crate::js_cdp::tests::rule;
+    let listener = std::net::TcpListener::bind("127.0.0.1:0").unwrap();
+    DEAD_PROXY_PORT.store(listener.local_addr().unwrap().port(), std::sync::atomic::Ordering::Relaxed);
+    drop(listener);
+
+    let h = harness(Script { start_debugging: true, custom: Some(dead_proxy_adapter), ..Script::default() });
+    let browser = h.start(js_config("pwa-chrome")).await.unwrap();
+    let page = child_of(&h, browser).await;
+    let unreachable = h.manager.js_set_response_overrides(page, vec![rule("api", 200, "")]).await.unwrap_err();
+    assert_eq!(unreachable.kind, ide_core::error::ErrorKind::Unavailable);
+    // The next rules try again instead of going to a connection that never was.
+    let again = h.manager.js_set_response_overrides(page, vec![rule("api", 200, "")]).await.unwrap_err();
+    assert_eq!(again.kind, ide_core::error::ErrorKind::Unavailable);
+    assert_eq!(requests(&h, "requestCDPProxy").len(), 2);
+}
+
+/// The file the fake adapter says it records a CPU profile into (`profileStarted`).
+static PROFILE_FILE: parking_lot::Mutex<String> = parking_lot::Mutex::new(String::new());
+
+fn profiling_adapter(msg: &Value) -> Option<CustomReply> {
+    match msg["command"].as_str()? {
+        "startProfile" => {
+            Some((json!({}), vec![("profileStarted", json!({ "file": *PROFILE_FILE.lock(), "type": "cpu" }))]))
+        }
+        "stopProfile" => Some((json!({}), vec![("profilerStateUpdate", json!({ "label": "", "running": false }))])),
+        _ => None,
+    }
+}
+
+#[tokio::test]
+async fn a_pages_cpu_profile_is_handed_over_as_a_cpuprofile_file() {
+    let recorded = std::env::temp_dir().join(format!("openidea-dap-profile-{}", std::process::id()));
+    std::fs::write(&recorded, r#"{"nodes":[],"samples":[]}"#).unwrap();
+    *PROFILE_FILE.lock() = recorded.to_string_lossy().into_owned();
+
+    let h = harness(Script { start_debugging: true, custom: Some(profiling_adapter), ..Script::default() });
+    let browser = h.start(js_config("pwa-chrome")).await.unwrap();
+    let page = child_of(&h, browser).await;
+
+    // Nothing is being recorded yet.
+    let idle = h.manager.js_stop_profile(page).await.unwrap_err();
+    assert_eq!(idle.kind, ide_core::error::ErrorKind::InvalidInput);
+
+    h.manager.js_start_profile(page).await.unwrap();
+    assert_eq!(requests(&h, "startProfile"), [json!({ "type": "cpu" })]);
+    let dir = h.manager.js_stop_profile(page).await.unwrap();
+    assert_eq!(requests(&h, "stopProfile").len(), 1);
+    let files: Vec<_> = std::fs::read_dir(&dir).unwrap().map(|e| e.unwrap().file_name()).collect();
+    assert_eq!(files, ["page.cpuprofile"]);
+    assert_eq!(std::fs::read_to_string(dir.join("page.cpuprofile")).unwrap(), r#"{"nodes":[],"samples":[]}"#);
+    // One recording is handed over once.
+    assert_eq!(h.manager.js_stop_profile(page).await.unwrap_err().kind, ide_core::error::ErrorKind::InvalidInput);
+
+    // The adapter's file isn't there when it is asked for (the hand-over above took the first one).
+    assert!(!recorded.exists());
+    h.manager.js_start_profile(page).await.unwrap();
+    assert_eq!(h.manager.js_stop_profile(page).await.unwrap_err().kind, ide_core::error::ErrorKind::Unavailable);
+
+    assert_eq!(h.manager.js_start_profile(browser).await.unwrap_err().kind, ide_core::error::ErrorKind::Unavailable);
+    let _ = std::fs::remove_dir_all(dir);
+}
+
 #[test]
 fn a_child_session_is_named_by_the_adapter_unless_it_is_a_blank_page() {
     assert_eq!(child_name(&json!({ "name": "server.js [4120]" }), "Server"), "server.js [4120]");

crates/ide-docker/src/lib.rs

@@ -542,6 +542,24 @@ pub fn compose_config(ep: &DockerEndpoint, dir: &Path, files: &[String]) -> IdeR
     if out.success { Ok(out.stdout) } else { Err(failure(&args, &out.stderr, &out.stdout)) }
 }
 
+/// Runs the docker CLI with `args` in `dir` and returns its standard output; a non-zero
+/// exit is an error with docker's message.
+pub fn cli(
+    ep: &DockerEndpoint,
+    dir: Option<&Path>,
+    args: &[String],
+    timeout: Duration,
+    cancel: Option<&CancellationToken>,
+) -> IdeResult<String> {
+    let args: Vec<&str> = args.iter().map(String::as_str).collect();
+    let mut cmd = command(ep, &args)?;
+    if let Some(dir) = dir {
+        cmd.current_dir(dir);
+    }
+    let out = process::run(cmd, timeout, cancel)?;
+    if out.success { Ok(out.stdout) } else { Err(failure(&args, &out.stderr, &out.stdout)) }
+}
+
 #[cfg(test)]
 mod local_tests {
     use super::*;

crates/ide-host/src/ops/debug.rs

@@ -382,6 +382,15 @@ pub async fn debug_js_custom_breakpoints(
     host.debugger.js_set_custom_breakpoints(session, ids, xhr).await
 }
 
+pub async fn debug_js_response_overrides(
+    host: &Host,
+    _window: &str,
+    session: DebugSessionId,
+    rules: Vec<ide_dap::JsResponseRule>,
+) -> IdeResult<()> {
+    host.debugger.js_set_response_overrides(session, rules).await
+}
+
 pub async fn debug_js_response_body(
     host: &Host,
     _window: &str,
@@ -391,6 +400,18 @@ pub async fn debug_js_response_body(
     host.debugger.js_response_body(session, request_id).await
 }
 
+pub async fn debug_js_start_profile(host: &Host, _window: &str, session: DebugSessionId) -> IdeResult<()> {
+    host.debugger.js_start_profile(session).await
+}
+
+pub async fn debug_js_stop_profile(
+    host: &Host,
+    _window: &str,
+    session: DebugSessionId,
+) -> IdeResult<ide_core::IpcPath> {
+    host.debugger.js_stop_profile(session).await.map(Into::into)
+}
+
 pub fn debug_capabilities(host: &Host, _window: &str, session: DebugSessionId) -> IdeResult<DebugCapabilities> {
     host.debugger.capabilities(session)
 }
@@ -607,12 +628,23 @@ pub(crate) fn register(d: &mut Dispatcher) {
         debug_restart_frame(&c.host, &c.window, c.arg("session")?, c.arg("frameId")?).await
     });
     d.add("debug_capabilities", |c| async move { debug_capabilities(&c.host, &c.window, c.arg("session")?) });
+    d.add("debug_js_response_overrides", |c| async move {
+        debug_js_response_overrides(&c.host, &c.window, c.arg("session")?, c.arg("rules")?).await
+    });
     d.add("debug_js_response_body", |c| async move {
         debug_js_response_body(&c.host, &c.window, c.arg("session")?, c.arg("requestId")?).await
     });
     d.add("debug_js_custom_breakpoints", |c| async move {
         debug_js_custom_breakpoints(&c.host, &c.window, c.arg("session")?, c.arg("ids")?, c.arg("xhr")?).await
     });
+    d.add(
+        "debug_js_start_profile",
+        |c| async move { debug_js_start_profile(&c.host, &c.window, c.arg("session")?).await },
+    );
+    d.add(
+        "debug_js_stop_profile",
+        |c| async move { debug_js_stop_profile(&c.host, &c.window, c.arg("session")?).await },
+    );
     d.add("debug_set_function_breakpoints", |c| async move {
         debug_set_function_breakpoints(&c.host, &c.window, c.arg("breakpoints")?).await
     });

crates/ide-host/src/ops/doc.rs

@@ -21,6 +21,28 @@ pub fn close(host: &Host, window: &str, doc: DocId) -> IdeResult<()> {
     Ok(())
 }
 
+/// Opens an editable untitled buffer (a new-file tab); it reaches the disk
+/// through [`save_as`], which turns it into a regular file document. `name`
+/// re-references an already minted buffer instead of creating one.
+pub async fn open_untitled(host: &Host, window: &str, name: Option<String>) -> IdeResult<DocumentInfo> {
+    let project = host.project(window)?;
+    host.blocking(move || project.documents.open_untitled(name.as_deref())).await
+}
+
+/// Save As for an untitled buffer ([`Documents::save_as`]); LightEdit windows
+/// start watching the saved file's folder.
+pub async fn save_as(host: &Host, window: &str, doc: DocId, path: PathBuf) -> IdeResult<DocumentInfo> {
+    let project = host.project(window)?;
+    host.blocking(move || {
+        let info = project.documents.save_as(doc, &path)?;
+        if let Some(dir) = path.parent().filter(|_| project.light) {
+            project.watch_light_dir(dir);
+        }
+        Ok(info)
+    })
+    .await
+}
+
 /// Applies a CodeMirror change set; returns the new version (`outOfSync` when `base_version` is stale).
 pub fn edit(host: &Host, window: &str, doc: DocId, base_version: u32, changes: ChangeSet) -> IdeResult<u32> {
     host.project(window)?.documents.edit(doc, base_version, changes)

crates/ide-host/src/ops/doc/commands.rs

@@ -50,7 +50,10 @@ pub async fn doc_set_encoding(
     reload: bool,
 ) -> IdeResult<DocumentEncoding> {
     let project = host.project(window)?;
-    if reload && let Some(uri) = project.documents.virtual_uri(doc)? {
+    if reload
+        && !project.documents.is_untitled(doc)?
+        && let Some(uri) = project.documents.virtual_uri(doc)?
+    {
         let vd = if uri.starts_with("git-revision:") {
             crate::ops::vcs::revision_virtual_document(host, window, &uri, Some(&encoding)).await?
         } else {
@@ -159,6 +162,15 @@ pub async fn doc_highlights(host: &Host, window: &str, doc: DocId) -> IdeResult<
     .await
 }
 
+/// Python class facts the inheritance inspections read: base names as written, a method's
+/// parameters, decorator semantics and its body shape. Tree-sitter answers; no LSP.
+pub async fn doc_python_facts(host: &Host, window: &str, doc: DocId) -> IdeResult<ide_language::PythonFacts> {
+    let project = host.project(window)?;
+    let syntax = host.syntax();
+    let snap = project.documents.text_snapshot(doc)?;
+    blocking(move || Ok(syntax.python_facts(&snap.language, &snap.text))).await
+}
+
 /// Extend Selection (⌥↑): syntax ranges around `offset`, innermost first.
 /// Large documents fall back to word / line / document ranges.
 pub async fn doc_selection_ranges(host: &Host, window: &str, doc: DocId, offset: u32) -> IdeResult<Vec<Range>> {
@@ -208,6 +220,7 @@ pub(crate) fn register(d: &mut Dispatcher) {
     d.add("doc_outline", |c| async move { doc_outline(&c.host, &c.window, c.arg("doc")?).await });
     d.add("doc_folding", |c| async move { doc_folding(&c.host, &c.window, c.arg("doc")?).await });
     d.add("doc_highlights", |c| async move { doc_highlights(&c.host, &c.window, c.arg("doc")?).await });
+    d.add("doc_python_facts", |c| async move { doc_python_facts(&c.host, &c.window, c.arg("doc")?).await });
     d.add("doc_selection_ranges", |c| async move {
         doc_selection_ranges(&c.host, &c.window, c.arg("doc")?, c.arg("offset")?).await
     });

crates/ide-host/src/ops/lsp.rs

@@ -1472,6 +1472,15 @@ pub async fn lsp_type_hierarchy(
     host.project(window)?.lsp.type_hierarchy(doc, pos, direction).await
 }
 
+pub async fn lsp_prepare_type_hierarchy(
+    host: &Host,
+    window: &str,
+    doc: DocId,
+    pos: Pos,
+) -> IdeResult<Option<HierarchyItem>> {
+    host.project(window)?.lsp.prepare_type_hierarchy(doc, pos).await
+}
+
 pub fn lsp_servers(host: &Host, window: &str) -> IdeResult<Vec<ServerInfo>> {
     Ok(host.project(window)?.lsp.servers())
 }
@@ -1856,6 +1865,9 @@ pub(crate) fn register(d: &mut Dispatcher) {
     d.add("lsp_type_hierarchy", |c| async move {
         lsp_type_hierarchy(&c.host, &c.window, c.arg("doc")?, c.arg("pos")?, c.arg("direction")?).await
     });
+    d.add("lsp_prepare_type_hierarchy", |c| async move {
+        lsp_prepare_type_hierarchy(&c.host, &c.window, c.arg("doc")?, c.arg("pos")?).await
+    });
     d.add("lsp_servers", |c| async move { lsp_servers(&c.host, &c.window) });
     d.add("lsp_resend_diagnostics", |c| async move { lsp_resend_diagnostics(&c.host, &c.window) });
     d.add("lsp_restart", |c| async move { lsp_restart(&c.host, &c.window, c.arg("server")?).await });

crates/ide-host/src/ops/project.rs

@@ -239,6 +239,12 @@ pub fn set_settings(
     let toolchain = ["languages", "tools", "languageServers", "projectStructure"]
         .iter()
         .any(|k| key == *k || key.starts_with(&format!("{k}.")));
+    // A run target chosen as the Python interpreter (or changed) needs a snapshot of its libraries.
+    if ["languages", "languages.python", "languages.python.interpreter", "runTargets"].contains(&key) {
+        for project in affected() {
+            crate::ops::sdk::container_python::ensure(host, &project);
+        }
+    }
     // Code style only reaches servers as settings (e.g. jdtls' formatter profile); builds don't depend on it.
     if code_style || toolchain {
         for project in affected() {

crates/ide-host/src/ops/run.rs

@@ -508,7 +508,7 @@ pub fn list(host: &Host) -> Vec<RunInfo> {
 }
 
 mod commands;
-mod container;
+pub(crate) mod container;
 pub use commands::*;
 
 #[cfg(test)]

crates/ide-host/src/ops/run/container.rs

@@ -33,23 +33,11 @@ pub(super) async fn prepare(host: &Host, root: &Path, target: RunTarget, config:
     let root = root.to_path_buf();
     let data_dir = host.data_dir.clone();
     host.blocking(move || {
-        if !ide_docker::endpoint_is_local(&endpoint)? {
-            return Err(IdeError::invalid(format!(
-                "Run target '{}' uses a Docker daemon on another machine: the project can only be mounted from a local one",
-                target.name
-            )));
-        }
+        require_local(&endpoint, &target)?;
         let docker = ide_docker::docker_executable().ok_or_else(|| {
             IdeError::unavailable("docker executable not found; install Docker and make sure it is on PATH")
         })?;
-        let container_root = match target.container_root.trim() {
-            "" if target.kind == RunTargetKind::Compose => {
-                let json = ide_docker::compose_config(&endpoint, &root, &target.compose_files)?;
-                compose_container_root(&json, target.service.trim(), &root)?
-            }
-            "" => default_container_root(&root),
-            folder => folder.to_owned(),
-        };
+        let container_root = container_root(&endpoint, &root, &target)?;
         let file_env = env_files(&root, &config)?;
         let name = container_name(&config.id, &unique());
         let debugging = if debug { Some(Debugging::prepare(&data_dir)?) } else { None };
@@ -75,6 +63,29 @@ pub(super) async fn prepare(host: &Host, root: &Path, target: RunTarget, config:
     .await
 }
 
+/// The project can only be bind-mounted from a daemon on this machine.
+pub(crate) fn require_local(endpoint: &DockerEndpoint, target: &RunTarget) -> IdeResult<()> {
+    if !ide_docker::endpoint_is_local(endpoint)? {
+        return Err(IdeError::invalid(format!(
+            "Run target '{}' uses a Docker daemon on another machine: the project can only be mounted from a local one",
+            target.name
+        )));
+    }
+    Ok(())
+}
+
+/// Where the project is in the target's containers.
+pub(crate) fn container_root(endpoint: &DockerEndpoint, root: &Path, target: &RunTarget) -> IdeResult<String> {
+    Ok(match target.container_root.trim() {
+        "" if target.kind == RunTargetKind::Compose => {
+            let json = ide_docker::compose_config(endpoint, root, &target.compose_files)?;
+            compose_container_root(&json, target.service.trim(), root)?
+        }
+        "" => default_container_root(root),
+        folder => folder.to_owned(),
+    })
+}
+
 /// What a debug run mounts and publishes.
 struct Debugging {
     port: u16,
@@ -104,7 +115,7 @@ fn free_port() -> IdeResult<u16> {
 }
 
 /// The target's Docker connection (Services tool window), by id; none = the CLI's daemon.
-fn endpoint(data_dir: &Path, target: &RunTarget) -> IdeResult<DockerEndpoint> {
+pub(crate) fn endpoint(data_dir: &Path, target: &RunTarget) -> IdeResult<DockerEndpoint> {
     let id = target.docker_connection.trim();
     if id.is_empty() {
         return Ok(DockerEndpoint::Default);

crates/ide-host/src/ops/sdk.rs

@@ -10,6 +10,9 @@ use std::path::PathBuf;
 use std::sync::Mutex;
 use std::sync::atomic::{AtomicUsize, Ordering};
 
+pub(crate) mod container_python;
+pub use container_python::{ContainerPython, sdk_container_python, sdk_container_python_refresh};
+
 fn join_err(e: impl std::fmt::Display) -> IdeError {
     IdeError::internal(e.to_string())
 }
@@ -232,12 +235,17 @@ pub async fn sdk_project_libraries(
     let project = host.project(window)?;
     let (root, cache, settings) = (project.root.clone(), project.build_cache_dir(), project.settings.effective());
     let cancel = host.begin_project_request(window, request);
+    let container = container_python::library_group(host, &root, &settings);
     let libraries = {
         let (root, settings, cancel, on_groups) = (root.clone(), settings.clone(), cancel.clone(), on_groups.clone());
         tokio::task::spawn_blocking(move || {
-            ide_sdk::libraries::project_libraries_stream(&root, &settings, &[], &cancel, &|groups| {
+            if let Some(group) = &container {
+                let _ = on_groups.send(vec![group.clone()]);
+            }
+            let groups = ide_sdk::libraries::project_libraries_stream(&root, &settings, &[], &cancel, &|groups| {
                 let _ = on_groups.send(groups);
-            })
+            });
+            container.into_iter().chain(groups).collect::<Vec<_>>()
         })
     };
     let dependencies = {
@@ -377,6 +385,8 @@ pub(crate) fn register(d: &mut Dispatcher) {
     );
     d.add("sdk_python_effective", |c| async move { sdk_python_effective(&c.host, &c.window, c.arg("near")?) });
     d.add("sdk_php_effective", |c| async move { sdk_php_effective(&c.host, &c.window) });
+    d.add("sdk_container_python", |c| async move { sdk_container_python(&c.host, &c.window) });
+    d.add("sdk_container_python_refresh", |c| async move { sdk_container_python_refresh(&c.host, &c.window).await });
     d.add("sdk_php_xdebug", |c| async move { sdk_php_xdebug(&c.host, &c.window, c.arg("php")?, c.arg("cwd")?).await });
     d.add(
         "sdk_php_language_level",

crates/ide-host/src/ops/sdk/container_python.rs

@@ -0,0 +1,298 @@
+//! A Docker or Compose run target's Python as the project interpreter: snapshots of the
+//! container's library folders for the language server (see `ide_sdk::container_python`).
+//!
+//! A snapshot runs the target's Python once in a new container (the image's entrypoint
+//! and the service's dependencies skipped), then copies its `sys.path` folders out of
+//! the stopped container with `docker cp`. Nothing is installed in the container.
+
+use crate::Host;
+use crate::project::Project;
+use ide_core::event::NotifyLevel;
+use ide_core::remote_settings::{RunTarget, RunTargetKind};
+use ide_core::settings::Settings;
+use ide_core::{IdeError, IdeEvent, IdeResult, IpcPath, TaskId};
+use ide_sdk::container_python::{self as snapshots, Snapshot};
+use ide_sdk::python::PythonPackage;
+use std::collections::HashSet;
+use std::path::{Path, PathBuf};
+use std::sync::{Arc, LazyLock, Mutex};
+use std::time::Duration;
+
+/// Building or pulling the image may come first.
+const PROBE_TIMEOUT: Duration = Duration::from_secs(15 * 60);
+const COPY_TIMEOUT: Duration = Duration::from_secs(10 * 60);
+const QUICK: Duration = Duration::from_secs(30);
+
+/// The project interpreter when it is a run target's.
+#[derive(Clone, Debug, serde::Serialize, specta::Type)]
+#[serde(rename_all = "camelCase")]
+pub struct ContainerPython {
+    /// The run target's id.
+    pub target: String,
+    /// Its name; empty when no run target has the id.
+    pub name: String,
+    /// The Python version of the snapshot in use; `None`: no snapshot yet.
+    pub version: Option<String>,
+    /// The image the snapshot was copied from.
+    pub image: Option<String>,
+    /// The copied library folders on this machine.
+    pub folders: Vec<IpcPath>,
+    /// Packages of the snapshot (read-only).
+    pub packages: Vec<PythonPackage>,
+    /// A snapshot is being taken.
+    pub updating: bool,
+}
+
+/// Where snapshots are kept, and the Docker connections the targets refer to.
+#[derive(Clone)]
+struct Dirs {
+    data: PathBuf,
+    /// `<local data>/container-python/`: `<project>/<target>/<image>/` and `neutral/`.
+    cache: PathBuf,
+}
+
+impl Dirs {
+    fn of(host: &Host) -> Self {
+        Self::new(&host.data_dir, &host.local_data_dir)
+    }
+
+    fn new(data_dir: &Path, local_data_dir: &Path) -> Self {
+        Self { data: data_dir.to_path_buf(), cache: local_data_dir.join("container-python") }
+    }
+
+    fn target(&self, root: &Path, target: &str) -> PathBuf {
+        snapshots::target_dir(&self.cache.join(crate::project::project_key(root)), target)
+    }
+}
+
+/// Target folders with a snapshot being taken.
+static UPDATING: LazyLock<Mutex<HashSet<PathBuf>>> = LazyLock::new(Default::default);
+
+fn updating(dir: &Path) -> bool {
+    UPDATING.lock().unwrap_or_else(|e| e.into_inner()).contains(dir)
+}
+
+/// The snapshot in use for the project's interpreter, if it is a run target's.
+fn current(dirs: &Dirs, root: &Path, settings: &Settings) -> Option<(PathBuf, Snapshot)> {
+    let target = settings.languages.python.run_target()?;
+    snapshots::current(&dirs.target(root, target))
+}
+
+/// Language server configuration: basedpyright / pyright see the container's libraries.
+pub(crate) fn configure_server(
+    cfg: &mut ide_language::LanguageServerConfig,
+    local_data_dir: &Path,
+    root: &Path,
+    settings: &Settings,
+) {
+    if settings.languages.python.run_target().is_none() {
+        return;
+    }
+    let current = current(&Dirs::new(local_data_dir, local_data_dir), root, settings);
+    snapshots::configure_server(cfg, current.as_ref().map(|(d, s)| (d.as_path(), s)));
+}
+
+/// External Libraries: the snapshot's folders, named after the run target.
+pub(crate) fn library_group(host: &Host, root: &Path, settings: &Settings) -> Option<ide_sdk::libraries::LibraryGroup> {
+    let target = settings.languages.python.run_target()?;
+    let (dir, snapshot) = current(&Dirs::of(host), root, settings)?;
+    let name = settings.run_targets.iter().find(|t| t.id == target).map_or(target, |t| t.name.as_str());
+    snapshots::library_group(name, &dir, &snapshot)
+}
+
+/// The project interpreter when it is a run target's, with its snapshot.
+pub fn sdk_container_python(host: &Host, window: &str) -> IdeResult<Option<ContainerPython>> {
+    host.require_trust(window)?;
+    let project = host.project(window)?;
+    Ok(describe(host, &project.root, &project.settings.effective()))
+}
+
+fn describe(host: &Host, root: &Path, settings: &Settings) -> Option<ContainerPython> {
+    let target = settings.languages.python.run_target()?;
+    let name = settings.run_targets.iter().find(|t| t.id == target).map(|t| t.name.clone()).unwrap_or_default();
+    let dir = Dirs::of(host).target(root, target);
+    let mut out = ContainerPython {
+        target: target.to_owned(),
+        name,
+        version: None,
+        image: None,
+        folders: Vec::new(),
+        packages: Vec::new(),
+        updating: updating(&dir),
+    };
+    if let Some((dir, snapshot)) = snapshots::current(&dir) {
+        out.folders = snapshots::local_folders(&dir, &snapshot).into_iter().map(Into::into).collect();
+        out.packages = snapshots::packages(&dir, &snapshot);
+        out.version = Some(snapshot.probe.version);
+        out.image = Some(snapshot.image);
+    }
+    Some(out)
+}
+
+/// Takes a new snapshot of the project interpreter's container (also of an image that
+/// has one already), then the language servers pick it up.
+pub async fn sdk_container_python_refresh(host: &Host, window: &str) -> IdeResult<Option<ContainerPython>> {
+    host.require_trust(window)?;
+    let project = host.project(window)?;
+    update(Dirs::of(host), &project, true).await?;
+    Ok(describe(host, &project.root, &project.settings.effective()))
+}
+
+/// Takes a snapshot when the project interpreter is a run target's and the current image
+/// has none yet (a new choice, a rebuilt image), in the background. Errors are notified.
+pub(crate) fn ensure(host: &Host, project: &Arc<Project>) {
+    if !project.is_trusted() || project.settings.effective().languages.python.run_target().is_none() {
+        return;
+    }
+    let (dirs, project) = (Dirs::of(host), project.clone());
+    host.runtime.spawn(async move {
+        if let Err(e) = update(dirs, &project, false).await
+            && e.kind != ide_core::error::ErrorKind::Cancelled
+        {
+            project.sink.emit(IdeEvent::Notify {
+                level: NotifyLevel::Warning,
+                title: "Cannot copy the container's Python libraries".into(),
+                body: Some(e.message),
+            });
+        }
+    });
+}
+
+async fn update(dirs: Dirs, project: &Arc<Project>, force: bool) -> IdeResult<()> {
+    let settings = project.settings.effective();
+    let Some(id) = settings.languages.python.run_target() else { return Ok(()) };
+    let target = ide_remote::service::run_target(&settings, id)?;
+    if target.kind == RunTargetKind::Ssh {
+        return Err(IdeError::invalid(format!(
+            "Run target '{}' runs over SSH: only a Docker or Compose run target can be the project interpreter",
+            target.name
+        )));
+    }
+    let dir = dirs.target(&project.root, id);
+    if !UPDATING.lock().unwrap_or_else(|e| e.into_inner()).insert(dir.clone()) {
+        return Ok(());
+    }
+    let _done = Updating(dir.clone());
+    let endpoint = crate::ops::run::container::endpoint(&dirs.data, &target)?;
+    let task = TaskId::next();
+    let title = format!("Python libraries of {}", target.name);
+    let (root, sink) = (project.root.clone(), project.sink.clone());
+    let progress = move |message: &str, done: bool| {
+        sink.emit(IdeEvent::Task {
+            id: task,
+            title: title.clone(),
+            message: Some(message.to_owned()),
+            fraction: None,
+            done,
+            cancellable: false,
+        })
+    };
+    let report = progress.clone();
+    let result = tokio::task::spawn_blocking(move || {
+        take(&endpoint, &root, &target, &dir, &dirs.cache, force, &|message| report(message, false))
+    })
+    .await
+    .map_err(|e| IdeError::internal(e.to_string()))
+    .and_then(|r| r);
+    progress(if result.is_ok() { "Done" } else { "Failed" }, true);
+    if result? {
+        project.lsp.reconfigure().await;
+    }
+    Ok(())
+}
+
+struct Updating(PathBuf);
+
+impl Drop for Updating {
+    fn drop(&mut self) {
+        UPDATING.lock().unwrap_or_else(|e| e.into_inner()).remove(&self.0);
+    }
+}
+
+/// Removes the probe container, also when copying failed.
+struct Container<'a> {
+    endpoint: &'a ide_docker::DockerEndpoint,
+    name: String,
+}
+
+impl Drop for Container<'_> {
+    fn drop(&mut self) {
+        let args = ["rm", "--force", "--volumes", &self.name].map(String::from);
+        if let Err(e) = ide_docker::cli(self.endpoint, None, &args, QUICK, None) {
+            tracing::warn!("cannot remove container {}: {}", self.name, e.message);
+        }
+    }
+}
+
+/// Takes the snapshot in `target_dir` and makes it the one in use; `false` when the image
+/// had one already and it is in use (unless `force`).
+fn take(
+    endpoint: &ide_docker::DockerEndpoint,
+    root: &Path,
+    target: &RunTarget,
+    target_dir: &Path,
+    cache: &Path,
+    force: bool,
+    progress: &dyn Fn(&str),
+) -> IdeResult<bool> {
+    crate::ops::run::container::require_local(endpoint, target)?;
+    let container_root = crate::ops::run::container::container_root(endpoint, root, target)?;
+    let name = format!("openidea-python-{}", unique());
+    let args = ide_remote::docker::python_probe_args(target, root, &name, snapshots::PROBE)?;
+    progress("Starting the container's Python");
+    let container = Container { endpoint, name };
+    let out = ide_docker::cli(endpoint, Some(root), &args, PROBE_TIMEOUT, None);
+    let probe = snapshots::parse_probe(&out?)?;
+    let inspect = ["inspect".into(), "--format".into(), "{{.Image}}".into(), container.name.clone()];
+    let image = ide_docker::cli(endpoint, None, &inspect, QUICK, None)?.trim().to_owned();
+    if image.is_empty() {
+        return Err(IdeError::internal(format!("docker inspect printed no image for {}", container.name)));
+    }
+    let dir = target_dir.join(snapshots::dir_name(&image));
+    let before = snapshots::current(target_dir).map(|(_, s)| s.image);
+    if !force && snapshots::read(&dir).is_some() {
+        snapshots::make_current(target_dir, &image)?;
+        return Ok(before.as_deref() != Some(image.as_str()));
+    }
+    let partial = target_dir.join(format!("{}.partial", snapshots::dir_name(&image)));
+    if partial.exists() {
+        std::fs::remove_dir_all(&partial)?;
+    }
+    std::fs::create_dir_all(&partial)?;
+    let mut folders = Vec::new();
+    for folder in snapshots::folders_to_copy(&probe, &container_root) {
+        progress(&format!("Copying {folder}"));
+        let local = snapshots::local_folder(&partial, &folder);
+        let Some(parent) = local.parent() else { continue };
+        std::fs::create_dir_all(parent)?;
+        // Into an existing folder: `docker cp` puts the source folder in it under its own name.
+        let args = ["cp".into(), format!("{}:{folder}", container.name), format!("{}/", parent.to_string_lossy())];
+        match ide_docker::cli(endpoint, None, &args, COPY_TIMEOUT, None) {
+            Ok(_) => folders.push(folder),
+            Err(e) => tracing::warn!("cannot copy {folder} from {}: {}", container.name, e.message),
+        }
+    }
+    drop(container);
+    progress("Preparing the language server's interpreter");
+    let snapshot = Snapshot {
+        neutral_python: snapshots::neutral_python(cache, &probe.version),
+        image: image.clone(),
+        probe,
+        folders,
+    };
+    snapshots::write(&partial, &snapshot)?;
+    if dir.exists() {
+        std::fs::remove_dir_all(&dir)?;
+    }
+    std::fs::rename(&partial, &dir)?;
+    snapshots::make_current(target_dir, &image)?;
+    Ok(true)
+}
+
+/// Distinguishes probe containers.
+fn unique() -> String {
+    use std::sync::atomic::{AtomicU32, Ordering};
+    static COUNT: AtomicU32 = AtomicU32::new(0);
+    let secs = std::time::SystemTime::now().duration_since(std::time::UNIX_EPOCH).map_or(0, |d| d.as_secs());
+    format!("{:x}-{}-{}", secs & 0xff_ffff, std::process::id(), COUNT.fetch_add(1, Ordering::Relaxed))
+}

crates/ide-host/src/plugins/execution.rs

@@ -77,9 +77,22 @@ pub(super) fn validate_reply(reply: &ContentTabReply) -> Result<(), HostError> {
     Ok(())
 }
 
+/// Largest side of a plugin diff, in UTF-16 code units (earlier hosts allowed 1 MiB).
+pub(super) const MAX_DIFF_SIDE: usize = 8 << 20;
+
+fn diff_side(value: &str, side: &str) -> Result<(), HostError> {
+    if value.contains('\0') {
+        return Err(HostError::Invalid(format!("the {side} side of the diff contains NUL")));
+    }
+    if value.encode_utf16().count() > MAX_DIFF_SIDE {
+        return Err(HostError::Invalid(format!("diff too large: the {side} side is over {} MiB", MAX_DIFF_SIDE >> 20)));
+    }
+    Ok(())
+}
+
 pub(super) fn validate_diff(diff: &ide_plugin::ContentDiff) -> Result<(), HostError> {
-    body(&diff.left)?;
-    body(&diff.right)?;
+    diff_side(&diff.left, "left")?;
+    diff_side(&diff.right, "right")?;
     for value in [&diff.left_label, &diff.right_label].into_iter().flatten() {
         label(value, 128)?;
     }
@@ -571,3 +584,25 @@ impl PluginHost {
         }
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    fn diff(left: String, right: String) -> ide_plugin::ContentDiff {
+        ide_plugin::ContentDiff { left, right, left_label: None, right_label: None, title: None }
+    }
+
+    #[test]
+    fn diff_sides_up_to_the_limit_open_and_larger_ones_say_why() {
+        assert!(validate_diff(&diff("x".repeat(5 << 20), "y".repeat(MAX_DIFF_SIDE))).is_ok());
+        let err = validate_diff(&diff(String::new(), "y".repeat(MAX_DIFF_SIDE + 1))).unwrap_err();
+        assert!(
+            matches!(&err, HostError::Invalid(m) if m == "diff too large: the right side is over 8 MiB"),
+            "{err:?}"
+        );
+        assert!(
+            matches!(validate_diff(&diff("a\0".into(), String::new())), Err(HostError::Invalid(m)) if m.contains("NUL"))
+        );
+    }
+}

crates/ide-host/src/project.rs

@@ -88,6 +88,9 @@ impl Host {
         let root = dunce::canonicalize(root)?;
         let opening = self.opening(window);
         let _opening = opening.lock();
+        // Untitled buffers belong to the window, not a project: they follow it
+        // into the project's fresh document registry.
+        let carried = self.project(window).ok().map(|prev| prev.documents.untitled_buffers()).unwrap_or_default();
         // Reject a damaged manifest before replacing the currently open project.
         let is_workspace = ide_workspace::workspace::Workspace::load(&root)?.is_some();
         // The window reloaded (or asked again) for the project it already has: keep
@@ -174,6 +177,7 @@ impl Host {
                 let root = member.as_ref().unwrap_or(window_root);
                 ide_sdk::apply::server_launch_overrides(cfg, &effective);
                 ide_sdk::apply::configure_server(cfg, root, server_root, &effective);
+                crate::ops::sdk::container_python::configure_server(cfg, &data_dir, root, &effective);
                 if cfg.name == "jdtls" {
                     // A workspace member keeps its build model under its own key (Build Project).
                     let cache = match &member {
@@ -620,6 +624,9 @@ impl Host {
             }));
         }
         self.insert_project(window, project.clone());
+        for (key, text, dirty) in &carried {
+            let _ = project.documents.restore_untitled_buffer(key, text, *dirty);
+        }
         project.lsp.prewarm_java_configuration();
         if let Some(bridge) = &project.kotlin_bridge {
             bridge.start(&self.runtime);
@@ -630,6 +637,7 @@ impl Host {
         if let Some(cmd) = post_start {
             self.environment.spawn_post_start(cmd, project.root.clone(), project.sink.clone());
         }
+        crate::ops::sdk::container_python::ensure(self, &project);
         Ok(project)
     }
 
@@ -701,12 +709,29 @@ impl Host {
             return Err(IdeError::invalid(format!("{} is a folder", file.display())));
         }
         let dir = file.parent().map(Path::to_path_buf).ok_or_else(|| IdeError::invalid("no parent folder"))?;
+        let watch = dir.clone();
+        self.open_light_in(window, dir, Some(&watch))
+    }
+
+    /// LightEdit without a file (a welcome window's File › New File): rooted
+    /// at the user's home folder, watching nothing until a buffer is saved
+    /// into a real folder ([`Project::watch_light_dir`]).
+    pub fn open_light_empty(&self, window: &str) -> IdeResult<Arc<Project>> {
+        let dir = dirs::home_dir().unwrap_or_else(std::env::temp_dir);
+        self.open_light_in(window, dir, None)
+    }
+
+    fn open_light_in(&self, window: &str, dir: PathBuf, watch_dir: Option<&Path>) -> IdeResult<Arc<Project>> {
         let opening = self.opening(window);
         let _opening = opening.lock();
+        // Untitled buffers belong to the window: they follow it out of a project.
+        let carried = self.project(window).ok().map(|prev| prev.documents.untitled_buffers()).unwrap_or_default();
         if let Ok(current) = self.project(window)
             && current.light
         {
-            current.watch_light_dir(&dir);
+            if let Some(dir) = watch_dir {
+                current.watch_light_dir(dir);
+            }
             return Ok(current);
         }
         self.close_project(window);
@@ -725,7 +750,16 @@ impl Host {
         let syntax = Arc::new(SyntaxCache::new(self.syntax()));
         documents.add_observer(Arc::new(SyntaxObserver(syntax.clone())));
         documents.add_observer(Arc::new(HistoryObserver(history.clone())));
-        let watcher = light_watcher(&dir, &sink, &documents, &history)?;
+        let watcher = match watch_dir {
+            Some(dir) => light_watcher(dir, &sink, &documents, &history)?,
+            // A quiet private folder stands in until the first save brings a
+            // real folder in.
+            None => {
+                let idle = self.local_data_dir.join("light-edit");
+                std::fs::create_dir_all(&idle)?;
+                light_watcher(&idle, &sink, &documents, &history)?
+            }
+        };
         let project_key = project_key(&dir);
         let (db, http_history, agents) = self.project_services(&dir, &project_key, &settings, &sink);
         let notebooks = crate::notebook::NotebookService::new(
@@ -771,8 +805,11 @@ impl Host {
             light: true,
             root: dir,
         });
-        tracing::info!("window {window} edits {} without a project", file.display());
+        tracing::info!("window {window} edits {} without a project", project.root.display());
         self.insert_project(window, project.clone());
+        for (key, text, dirty) in &carried {
+            let _ = project.documents.restore_untitled_buffer(key, text, *dirty);
+        }
         Ok(project)
     }
 }
@@ -1456,7 +1493,7 @@ fn content_root_watcher(
 ) -> Option<Watcher> {
     let (kotlin_bridge, phpstan) = (kotlin_bridge.cloned(), phpstan.cloned());
     let (index, documents, history, lsp) = (index.clone(), documents.clone(), history.clone(), lsp.clone());
-    let root = dir.to_path_buf();
+    let (root, events) = (dir.to_path_buf(), sink.clone());
     Watcher::start(
         dir,
         excludes.to_vec(),
@@ -1478,6 +1515,11 @@ fn content_root_watcher(
             }
             documents.on_disk_changed(&[&changed[..], &ignored].concat());
             record_external_changes(&history, &changed, &batch.removed);
+            // A member outside the project folder: its repository changes (commit, checkout,
+            // fetch, pull) reach the UI only through this watcher.
+            if batch.vcs.iter().any(|p| vcs_path_changed(p)) {
+                events.emit(IdeEvent::VcsChanged { root: root.clone().into() });
+            }
         }),
     )
     .map_err(|e| tracing::warn!("content root watcher {}: {e}", dir.display()))

crates/ide-host/src/rpc.rs

@@ -218,6 +218,13 @@ impl Dispatcher {
         })
         .add("fs_read_text", |c| async move { ops::fs::read_text(&c.host, &c.window, c.arg("path")?).await })
         .add("doc_open", |c| async move { ops::doc::open(&c.host, &c.window, c.arg("path")?).await })
+        .add("doc_open_untitled", |c| async move {
+            ops::doc::open_untitled(&c.host, &c.window, c.arg::<Option<String>>("name")?).await
+        })
+        .add(
+            "doc_save_as",
+            |c| async move { ops::doc::save_as(&c.host, &c.window, c.arg("doc")?, c.arg("path")?).await },
+        )
         .add("doc_close", |c| async move {
             ops::doc::blocking(move || ops::doc::close(&c.host, &c.window, c.arg("doc")?)).await
         })

crates/ide-host/src/trust.rs

@@ -289,6 +289,7 @@ impl crate::Host {
                 }
             }
             project.lsp.reconfigure().await;
+            crate::ops::sdk::container_python::ensure(self, &project);
             project.sink.emit(ide_core::IdeEvent::ProjectTrustChanged { root: project.root.clone().into(), trusted });
         }
         Ok(())
@@ -400,6 +401,7 @@ pub fn restricted_command_allowed(cmd: &str) -> bool {
             | "web_unresolved_references"
             | "project_rename"
             | "light_edit_open"
+            | "light_edit_open_untitled"
             | "workspace_create"
             | "workspace_discover_projects"
             | "workspace_update"

crates/ide-host/tests/container_python_real.rs

@@ -0,0 +1,174 @@
+//! A Compose run target as the Python interpreter, against a real daemon and the real
+//! basedpyright. Ignored by default: `OPENIDEA_DOCKER_TEST_DIR` names an empty folder the
+//! daemon can bind-mount (on this machine, or at the same path in a VM such as OrbStack's),
+//! `docker` with the Compose plugin and `basedpyright-langserver` must be on `PATH`, and
+//! this machine's Python must not have Django installed.
+#![cfg(unix)]
+
+use ide_core::IdeEvent;
+use ide_host::{Host, HostConfig, ops};
+use ide_run::{OutputChunk, RunConfig};
+use std::path::{Path, PathBuf};
+use std::process::Command;
+use std::sync::{Arc, Mutex};
+use std::time::{Duration, Instant};
+
+const WINDOW: &str = "main";
+type Events = Arc<Mutex<Vec<IdeEvent>>>;
+
+fn host(base: &Path, events: &Events) -> Arc<Host> {
+    Arc::new(Host::new(HostConfig {
+        config_dir: base.join("config"),
+        data_dir: base.join("data"),
+        local_data_dir: base.join("data"),
+        languages: Arc::new(ide_language::LanguageRegistry::load(None).unwrap()),
+        syntax: Arc::default(),
+        sink_for: Box::new({
+            let events = events.clone();
+            move |_| {
+                let events = events.clone();
+                Arc::new(move |e: IdeEvent| events.lock().unwrap().push(e))
+            }
+        }),
+        owner: |w| w,
+        runtime: tokio::runtime::Handle::current(),
+        project_environment: false,
+    }))
+}
+
+/// basedpyright's latest diagnostics of `path` once `done` accepts them.
+async fn diagnostics(events: &Events, path: &Path, timeout: Duration, done: impl Fn(&[String]) -> bool) -> Vec<String> {
+    let deadline = Instant::now() + timeout;
+    loop {
+        let latest = events.lock().unwrap().iter().rev().find_map(|e| match e {
+            IdeEvent::Diagnostics { path: p, items, source } if **p == *path && source.contains("basedpyright") => {
+                Some(items.iter().map(|d| d.message.clone()).collect::<Vec<_>>())
+            }
+            _ => None,
+        });
+        if let Some(messages) = &latest
+            && done(messages)
+        {
+            return messages.clone();
+        }
+        assert!(Instant::now() < deadline, "timed out; last diagnostics: {latest:?}");
+        tokio::time::sleep(Duration::from_millis(500)).await;
+    }
+}
+
+fn unresolved(messages: &[String]) -> bool {
+    messages.iter().any(|m| m.contains("\"django") && m.contains("could not be resolved"))
+}
+
+#[tokio::test(flavor = "multi_thread", worker_threads = 4)]
+#[ignore = "requires a Docker daemon, basedpyright and OPENIDEA_DOCKER_TEST_DIR"]
+async fn compose_target_is_the_python_interpreter() {
+    let root = PathBuf::from(std::env::var("OPENIDEA_DOCKER_TEST_DIR").expect("OPENIDEA_DOCKER_TEST_DIR"));
+    let root = dunce::canonicalize(root).unwrap();
+    let files = [
+        ("compose.yaml", "services:\n  web:\n    build: .\n    volumes:\n      - .:/app\n    working_dir: /app\n"),
+        (
+            "Dockerfile",
+            "FROM python:3.12-slim\nCOPY requirements.txt /tmp/requirements.txt\n\
+             RUN pip install --no-cache-dir -r /tmp/requirements.txt\n",
+        ),
+        ("requirements.txt", "Django==5.1.3\n"),
+        (
+            "app/main.py",
+            "import django\nfrom django.http import HttpResponse\n\nprint(django.get_version(), HttpResponse)\n",
+        ),
+    ];
+    for (path, text) in files {
+        std::fs::create_dir_all(root.join(path).parent().unwrap()).unwrap();
+        std::fs::write(root.join(path), text).unwrap();
+    }
+    let main = root.join("app/main.py");
+    let state = tempfile::tempdir().unwrap();
+    let events: Events = Arc::default();
+    let host = host(state.path(), &events);
+    host.trust.decide(&root, true, false).unwrap();
+    host.open_project(WINDOW, &root).unwrap();
+    let set = |key: &str, value: serde_json::Value| {
+        ops::project::set_settings(
+            &host,
+            WINDOW,
+            ide_workspace::settings::SettingsScope::Project,
+            key,
+            &value.to_string(),
+        )
+        .unwrap();
+    };
+    set("runTargets", serde_json::json!([{ "kind": "compose", "id": "web", "name": "Compose web", "service": "web" }]));
+
+    // A local interpreter: Django is only in the image.
+    ops::doc::open(&host, WINDOW, main.clone()).await.unwrap();
+    let before = diagnostics(&events, &main, Duration::from_secs(120), unresolved).await;
+    eprintln!("local interpreter: {before:?}");
+
+    // The run target as the interpreter: a snapshot is taken in the background, then the
+    // server restarts with the copied site-packages as `extraPaths`.
+    set("languages.python.interpreter", serde_json::json!("target:web"));
+    let after = diagnostics(&events, &main, Duration::from_secs(900), |m| !unresolved(m)).await;
+    eprintln!("run target interpreter: {after:?}");
+    assert!(after.iter().all(|m| !m.contains("could not be resolved")), "{after:?}");
+
+    let info = ops::sdk::sdk_container_python(&host, WINDOW).unwrap().expect("a run target interpreter");
+    eprintln!("snapshot: version {:?}, image {:?}, folders {:?}", info.version, info.image, info.folders);
+    assert_eq!(info.name, "Compose web");
+    assert!(info.version.as_deref().is_some_and(|v| v.starts_with("3.12.")), "{info:?}");
+    assert!(info.packages.iter().any(|p| p.name == "Django" && p.version == "5.1.3"), "{:?}", info.packages);
+    let site = info.folders.iter().find(|f| f.0.ends_with("site-packages")).expect("site-packages copied");
+    assert!(site.0.join("django/__init__.py").is_file());
+    assert!(site.0.starts_with(state.path().join("data/container-python")), "{site:?}");
+    let servers = ops::lsp::lsp_servers(&host, WINDOW).unwrap();
+    eprintln!("servers: {:?}", servers.iter().map(|s| (&s.name, s.status)).collect::<Vec<_>>());
+
+    // Run: a Python configuration without its own target runs in the container.
+    let out = Arc::new(Mutex::new(String::new()));
+    let sink = out.clone();
+    let config = RunConfig {
+        id: "main".into(),
+        name: "main".into(),
+        kind: "python".into(),
+        command: "python3".into(),
+        args: vec!["app/main.py".into()],
+        cwd: None,
+        env: Default::default(),
+        detected: false,
+        is_test: false,
+        debug_adapter: None,
+        allow_parallel: false,
+        extras: Default::default(),
+    };
+    ops::run::start(
+        &host,
+        WINDOW,
+        config,
+        Arc::new(move |chunk| match chunk {
+            OutputChunk::Stdout { text } | OutputChunk::Stderr { text } | OutputChunk::System { text } => {
+                sink.lock().unwrap().push_str(&text)
+            }
+        }),
+    )
+    .await
+    .unwrap();
+    for _ in 0..1200 {
+        if out.lock().unwrap().contains("Process finished") {
+            break;
+        }
+        tokio::time::sleep(Duration::from_millis(100)).await;
+    }
+    let out = out.lock().unwrap().clone();
+    eprintln!("run output: {out}");
+    assert!(out.contains("5.1.3") && out.contains("exit code 0"), "{out}");
+
+    // Refresh takes a new snapshot of the same image; nothing is left running.
+    let refreshed = ops::sdk::sdk_container_python_refresh(&host, WINDOW).await.unwrap().unwrap();
+    assert_eq!(refreshed.image, info.image);
+    let probes = Command::new("docker")
+        .args(["ps", "--all", "--quiet", "--filter", "label=openidea.python-probe=true"])
+        .output()
+        .unwrap();
+    assert_eq!(String::from_utf8_lossy(&probes.stdout).trim(), "", "probe containers are removed");
+    Command::new("docker").args(["compose", "down", "--rmi", "local"]).current_dir(&root).status().unwrap();
+}

crates/ide-host/tests/light_edit.rs

@@ -179,3 +179,73 @@ async fn light_notebooks_open_without_interpreter_detection_or_execution() {
     assert!(!bin.join("python.probed").exists());
     host.shutdown().await;
 }
+
+#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+async fn untitled_buffers_reach_the_disk_through_save_as() {
+    let tmp = tempfile::tempdir().unwrap();
+    let tmp_root = dunce::canonicalize(tmp.path()).unwrap();
+    let dir = tmp_root.join("notes");
+    let host = host(&tmp_root.join("app"));
+
+    // A window with no file (a welcome screen's File › New File): rooted at the
+    // home folder, no watcher yet, doc commands work.
+    let empty = host.open_light_empty("main").unwrap();
+    assert!(empty.light);
+    let untitled = ops::doc::open_untitled(&host, "main", None).await.unwrap();
+    assert_eq!(untitled.path, std::path::PathBuf::from("untitled:Untitled-1"));
+    assert_eq!(untitled.language.as_str(), "plaintext");
+    let version = ops::doc::edit(&host, "main", untitled.id, untitled.version, untitled_edit("# notes\n")).unwrap();
+    assert!(ops::doc::save(&host, "main", untitled.id).await.is_ok(), "saving nowhere is a no-op");
+    assert!(host.project("main").unwrap().documents.is_dirty(untitled.id).unwrap());
+
+    // Save As: the buffer lands on the disk and turns into a file document.
+    let target = dir.join("deep/notes.md");
+    let saved = ops::doc::save_as(&host, "main", untitled.id, target.clone()).await.unwrap();
+    assert_eq!(saved.path, target);
+    assert_eq!(saved.language.as_str(), "markdown");
+    assert!(!saved.dirty);
+    // The platform's default line separator applies to new buffers.
+    assert_eq!(std::fs::read_to_string(&target).unwrap().replace("\r\n", "\n"), "# notes\n");
+    ops::doc::edit(&host, "main", untitled.id, version, untitled_edit("x\n")).unwrap();
+    ops::doc::save(&host, "main", untitled.id).await.unwrap();
+    assert_eq!(std::fs::read_to_string(&target).unwrap().replace("\r\n", "\n"), "x\n# notes\n");
+
+    // The saved file's folder is followed for external changes now.
+    host.shutdown().await;
+}
+
+fn untitled_edit(insert: &str) -> ChangeSet {
+    ChangeSet { changes: vec![TextChange { from: 0, to: 0, insert: insert.into() }] }
+}
+
+#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+async fn untitled_buffers_follow_the_window_into_a_project() {
+    let tmp = tempfile::tempdir().unwrap();
+    let tmp_root = dunce::canonicalize(tmp.path()).unwrap();
+    let host = host(&tmp_root.join("app"));
+
+    // A LightEdit window with an edited untitled buffer (and a clean one).
+    host.open_light_empty("main").unwrap();
+    let draft = ops::doc::open_untitled(&host, "main", None).await.unwrap();
+    ops::doc::edit(&host, "main", draft.id, draft.version, untitled_edit("{\"draft\": true}")).unwrap();
+    let clean = ops::doc::open_untitled(&host, "main", None).await.unwrap();
+
+    // The window switches to a project: the buffers follow, contents and dirty flags kept.
+    let project_root = tmp_root.join("proj");
+    std::fs::create_dir_all(&project_root).unwrap();
+    let project = host.open_project("main", &project_root).unwrap();
+    assert!(!project.light);
+
+    let carried =
+        ops::doc::open_untitled(&host, "main", Some(draft.path.to_string_lossy().into_owned())).await.unwrap();
+    assert_eq!(carried.path, draft.path, "same key, fresh registry: a new doc id carries the content");
+    let snap = ops::doc::snapshot(&host, "main", carried.id).await.unwrap();
+    assert_eq!(snap.text, "{\"draft\": true}");
+    assert!(host.project("main").unwrap().documents.is_dirty(carried.id).unwrap());
+    assert_eq!(snap.language.as_str(), "plaintext");
+
+    let clean_carried =
+        ops::doc::open_untitled(&host, "main", Some(clean.path.to_string_lossy().into_owned())).await.unwrap();
+    assert!(!host.project("main").unwrap().documents.is_dirty(clean_carried.id).unwrap());
+    host.shutdown().await;
+}

crates/ide-index/src/store.rs

@@ -599,6 +599,28 @@ impl Store {
         txn.commit().map_err(err)
     }
 
+    /// [`Self::apply`] for records already serialized (by the parse pool).
+    pub(crate) fn apply_raw(&self, puts: &[(String, Vec<u8>)], deletes: &[String], durable: bool) -> Result<()> {
+        self.ensure_db()?;
+        let db = self.db.read();
+        let mut txn = db.as_ref().expect("ensured").begin_write().map_err(err)?;
+        if !durable {
+            txn.set_durability(Durability::None).map_err(err)?;
+        }
+        {
+            let mut table = txn.open_table(FILES).map_err(err)?;
+            for (rel, bytes) in puts {
+                table.insert(rel.as_str(), bytes.as_slice()).map_err(err)?;
+            }
+            for rel in deletes {
+                table.remove(rel.as_str()).map_err(err)?;
+            }
+        }
+        // Any file change makes the columnar start-up snapshot stale.
+        let _ = std::fs::remove_file(&self.snapshot);
+        txn.commit().map_err(err)
+    }
+
     /// Reclaims free pages in the database file; `true` if anything was compacted.
     pub(crate) fn compact(&self) -> Result<bool> {
         self.ensure_db()?;

crates/ide-index/src/worker.rs

@@ -17,6 +17,8 @@ use std::time::{Duration, Instant, SystemTime};
 /// Files larger than this are listed but not parsed for symbols.
 pub const MAX_SYMBOL_FILE: u64 = 2 * 1024 * 1024;
 const CHUNK: usize = 512;
+/// Insert/persist batch of the initial scan's streaming pass.
+const SCAN_BATCH: usize = 2048;
 const PROGRESS_EVERY: Duration = Duration::from_millis(250);
 #[cfg(not(test))]
 const SNAPSHOT_DELAY: Duration = Duration::from_secs(2);
@@ -436,10 +438,13 @@ impl Shared {
         });
 
         let filter = self.filter();
+        let walk_started = Instant::now();
         let found = prewalked.unwrap_or_else(|| self.walk_roots(dirs));
+        let walk = walk_started.elapsed();
         if self.is_cancelled() {
             return self.end_scan(task);
         }
+        let classify_started = Instant::now();
         let seen: HashSet<&Path> = found.iter().map(|f| f.path.as_path()).collect();
         let (todo, stale): (Vec<&Found>, Vec<PathBuf>) = {
             let d = self.data.read();
@@ -452,6 +457,7 @@ impl Shared {
                 .collect();
             (todo, stale)
         };
+        let classify = classify_started.elapsed();
         if !stale.is_empty() {
             let mut d = self.data.write();
             for path in &stale {
@@ -462,33 +468,76 @@ impl Shared {
         self.persist(&[], &stale, false);
 
         let total = todo.len();
-        let mut done = 0usize;
-        let mut last_progress = Instant::now();
-        for chunk in todo.chunks(CHUNK) {
-            if self.is_cancelled() {
-                return self.end_scan(task);
-            }
-            self.index_files(chunk.iter().copied(), false);
-            done += chunk.len();
-            if last_progress.elapsed() >= PROGRESS_EVERY {
-                last_progress = Instant::now();
-                self.sink.emit(IdeEvent::Task {
-                    id: task,
-                    title: "Indexing".into(),
-                    message: Some(format!("{done} / {total} files")),
-                    fraction: Some(done as f32 / total.max(1) as f32),
-                    done: false,
-                    cancellable: false,
+        let mut laps = ChunkLaps::default();
+        {
+            // One streaming parallel pass: parse on the rayon pool without
+            // per-chunk joins (a straggler file at a join's tail idles every
+            // other core), while parsed files flow to this thread to be
+            // inserted and persisted in batches. `filter` moves into the
+            // parse thread; this thread keeps the outer one.
+            let filter = self.filter();
+            // Bounded: when inserting and persisting fall behind, the parse waits instead
+            // of holding the whole project's records (and their bytes) in the channel.
+            let (tx, rx) = std::sync::mpsc::sync_channel::<ParsedFile>(2 * SCAN_BATCH);
+            let cancelled = &self.cancelled;
+            let mut done = 0usize;
+            let mut last_progress = Instant::now();
+            let pass_started = Instant::now();
+            std::thread::scope(|scope| -> () {
+                scope.spawn(move || {
+                    todo.par_iter().for_each(|f| {
+                        if cancelled.load(Ordering::Relaxed) {
+                            return;
+                        }
+                        let Some(out) = self.parse_found(f, &filter, false) else { return };
+                        let _ = tx.send(out);
+                    });
+                    // `tx` drops here: the consumer's loop ends with the channel.
                 });
-            }
+                let mut batch: Vec<ParsedFile> = Vec::with_capacity(SCAN_BATCH);
+                for out in rx {
+                    if self.is_cancelled() {
+                        break;
+                    }
+                    batch.push(out);
+                    if batch.len() < SCAN_BATCH {
+                        continue;
+                    }
+                    done += batch.len();
+                    laps.add(self.publish(batch.drain(..)));
+                    if last_progress.elapsed() >= PROGRESS_EVERY {
+                        last_progress = Instant::now();
+                        self.sink.emit(IdeEvent::Task {
+                            id: task,
+                            title: "Indexing".into(),
+                            message: Some(format!("{done} / {total} files")),
+                            fraction: Some(done as f32 / total.max(1) as f32),
+                            done: false,
+                            cancellable: false,
+                        });
+                    }
+                }
+                if !batch.is_empty() && !self.is_cancelled() {
+                    done += batch.len();
+                    laps.add(self.publish(batch.drain(..)));
+                }
+            });
+            laps.extract = pass_started.elapsed();
         }
+        if self.is_cancelled() {
+            return self.end_scan(task);
+        }
+        let durable_started = Instant::now();
         self.persist(&[], &[], true);
+        let durable = durable_started.elapsed();
         if let Some(store) = &self.store {
             let recent: Vec<String> = self.recent.lock().iter().filter_map(|p| filter.store_key(p)).collect();
             let d = self.data.read();
+            let snapshot_started = Instant::now();
             if let Err(e) = store.save_snapshot(&d, &filter, guard) {
                 tracing::warn!("index snapshot: {e}");
             }
+            tracing::info!("index snapshot: written in {:?}", snapshot_started.elapsed());
             if let Err(e) = store.save_recent_file(&recent) {
                 tracing::warn!("index recent snapshot: {e}");
             }
@@ -506,54 +555,85 @@ impl Shared {
         self.emit_state();
         let d = self.data.read();
         tracing::info!(
-            "indexed {} files ({} parsed, {} symbols) in {:?}",
+            "indexed {} files ({} parsed, {} symbols) in {:?} (walk {:?}, classify {:?}, extract {:?}, insert {:?}, persist {:?}, durable {:?})",
             d.file_count,
             total,
             d.symbol_count,
-            started.elapsed()
+            started.elapsed(),
+            walk,
+            classify,
+            laps.extract,
+            laps.insert,
+            laps.persist,
+            durable
         );
     }
 
     /// Extracts records in parallel, then publishes them to memory and disk.
     /// `force` re-parses files whose content is unchanged (their language changed).
-    fn index_files<'a>(&self, files: impl Iterator<Item = &'a Found>, force: bool) {
+    fn index_files<'a>(&self, files: impl Iterator<Item = &'a Found>, force: bool) -> ChunkLaps {
+        let mut laps = ChunkLaps::default();
         let files: Vec<&Found> = files.collect();
         let filter = self.filter();
-        let extracted: Vec<(String, FileRecord, PathBuf)> = files
-            .par_iter()
-            .filter_map(|f| {
-                if self.is_cancelled() {
-                    return None;
-                }
-                let rel = filter.rel(&f.path)?;
-                let prev_hash = if force { None } else { self.data.read().get(&f.path).map(|e| e.hash) };
-                match self.extract(f, prev_hash) {
-                    Extracted::Unchanged => {
-                        // Same content, new mtime: keep the symbols, refresh metadata.
-                        let mut rec = self.data.read().record_of(&f.path)?;
-                        rec.mtime = f.mtime;
-                        rec.size = f.size;
-                        rec.ignored = f.ignored;
-                        Some((rel, rec, f.path.clone()))
-                    }
-                    Extracted::New(rec) => Some((rel, rec, f.path.clone())),
-                }
-            })
-            .collect();
+        let started = Instant::now();
+        let extracted: Vec<ParsedFile> = files.par_iter().filter_map(|f| self.parse_found(f, &filter, force)).collect();
+        laps.extract = started.elapsed();
         if extracted.is_empty() {
-            return;
+            return laps;
+        }
+        laps.add(self.publish(extracted.into_iter()));
+        laps
+    }
+
+    /// Reads and parses one file (parallel-safe), serializing its record for
+    /// the cache alongside the parse. `None` when the file is outside the
+    /// scope or the scan was cancelled.
+    fn parse_found(&self, f: &Found, filter: &std::sync::Arc<PathFilter>, force: bool) -> Option<ParsedFile> {
+        if self.is_cancelled() {
+            return None;
+        }
+        let rel = filter.rel(&f.path)?;
+        let prev_hash = if force { None } else { self.data.read().get(&f.path).map(|e| e.hash) };
+        let rec = match self.extract(f, prev_hash) {
+            Extracted::Unchanged => {
+                // Same content, new mtime: keep the symbols, refresh metadata.
+                let mut rec = self.data.read().record_of(&f.path)?;
+                rec.mtime = f.mtime;
+                rec.size = f.size;
+                rec.ignored = f.ignored;
+                rec
+            }
+            Extracted::New(rec) => rec,
+        };
+        let key = filter.store_key(&f.path);
+        let bytes = postcard::to_allocvec(&rec).ok();
+        Some(ParsedFile { rel, rec, key, bytes, path: f.path.clone() })
+    }
+
+    /// Inserts a parsed batch into the in-memory index and persists the records.
+    fn publish(&self, batch: impl Iterator<Item = ParsedFile>) -> ChunkLaps {
+        let mut laps = ChunkLaps::default();
+        let started = Instant::now();
+        let mut entries: Vec<(FileEntry, Vec<StoredSymbol>)> = Vec::new();
+        let mut puts: Vec<(String, Vec<u8>)> = Vec::new();
+        for out in batch {
+            let ParsedFile { rel, rec, key, bytes, path } = out;
+            if let (Some(key), Some(bytes)) = (key, bytes) {
+                puts.push((key, bytes));
+            }
+            entries.push(FileEntry::new(path, rel, rec));
         }
-        let puts: Vec<(String, FileRecord)> =
-            extracted.iter().filter_map(|(_, rec, path)| Some((filter.store_key(path)?, rec.clone()))).collect();
         {
-            let entries: Vec<(FileEntry, Vec<StoredSymbol>)> =
-                extracted.into_iter().map(|(rel, rec, path)| FileEntry::new(path, rel, rec)).collect();
             let mut d = self.data.write();
             for (e, symbols) in entries {
                 d.insert(e, symbols);
             }
         }
-        self.persist(&puts, &[], false);
+        laps.insert = started.elapsed();
+        let started = Instant::now();
+        self.persist_raw(&puts, &[], false);
+        laps.persist = started.elapsed();
+        laps
     }
 
     fn schedule_snapshot(&self) {
@@ -594,6 +674,15 @@ impl Shared {
         }
     }
 
+    /// [`Self::persist`] for records already serialized by the parse pool.
+    fn persist_raw(&self, puts: &[(String, Vec<u8>)], deletes: &[String], durable: bool) {
+        if let Some(store) = &self.store
+            && let Err(e) = store.apply_raw(puts, deletes, durable)
+        {
+            tracing::warn!("index cache write failed: {e}");
+        }
+    }
+
     fn extract(&self, f: &Found, prev_hash: Option<[u8; 32]>) -> Extracted {
         let mut rec = FileRecord { mtime: f.mtime, size: f.size, ignored: f.ignored, ..Default::default() };
         if f.ignored || f.size > MAX_SYMBOL_FILE {
@@ -793,6 +882,33 @@ enum Extracted {
     New(FileRecord),
 }
 
+/// Wall-time laps of one `index_files` chunk, accumulated by the scan.
+#[derive(Default)]
+struct ChunkLaps {
+    extract: Duration,
+    insert: Duration,
+    persist: Duration,
+}
+
+impl ChunkLaps {
+    fn add(&mut self, other: ChunkLaps) {
+        self.extract += other.extract;
+        self.insert += other.insert;
+        self.persist += other.persist;
+    }
+}
+
+/// One file parsed off the index thread: its record ready to publish, already
+/// serialized for the cache (in parallel with the parse).
+struct ParsedFile {
+    rel: String,
+    rec: FileRecord,
+    /// Cache key and postcard bytes; `None` when outside the persisted root.
+    key: Option<String>,
+    bytes: Option<Vec<u8>>,
+    path: PathBuf,
+}
+
 #[cfg(test)]
 mod tests {
     use crate::data::safe_rel;

crates/ide-jsonrpc/src/output.rs

@@ -80,18 +80,47 @@ pub fn trim_line_end(line: &[u8]) -> &[u8] {
     &line[..end]
 }
 
+/// The longest line kept in full; the rest of a longer one is dropped (a server that writes a
+/// progress bar with `\r` only, or never a newline, must not grow memory without bound).
+pub const MAX_LINE: usize = 8 * 1024;
+
 /// Reads `stream` to its end, calling `on_line` with each line decoded by [`decode`].
 /// Unlike `AsyncBufReadExt::lines`, a line that is not UTF-8 does not end the stream.
+/// A line longer than [`MAX_LINE`] bytes is cut there and ends with `…`.
 pub async fn read_lines<R: AsyncRead + Unpin>(stream: R, mut on_line: impl FnMut(String)) {
     let mut reader = BufReader::new(stream);
     let mut line = Vec::new();
+    let mut cut = false;
     loop {
-        line.clear();
-        match reader.read_until(b'\n', &mut line).await {
-            Ok(0) | Err(_) => break,
-            Ok(_) => on_line(decode(trim_line_end(&line))),
+        let (used, complete) = match reader.fill_buf().await {
+            Ok([]) | Err(_) => break,
+            Ok(buf) => {
+                let end = buf.iter().position(|&b| b == b'\n');
+                let piece = &buf[..end.unwrap_or(buf.len())];
+                let room = MAX_LINE.saturating_sub(line.len());
+                cut |= piece.len() > room;
+                line.extend_from_slice(&piece[..piece.len().min(room)]);
+                (end.map_or(buf.len(), |i| i + 1), end.is_some())
+            }
+        };
+        reader.consume(used);
+        if complete {
+            emit(&mut line, &mut cut, &mut on_line);
         }
     }
+    if !line.is_empty() || cut {
+        emit(&mut line, &mut cut, &mut on_line);
+    }
+}
+
+fn emit(line: &mut Vec<u8>, cut: &mut bool, on_line: &mut impl FnMut(String)) {
+    let mut text = decode(trim_line_end(line));
+    if *cut {
+        text.push('…');
+    }
+    line.clear();
+    *cut = false;
+    on_line(text);
 }
 
 #[cfg(test)]
@@ -133,4 +162,19 @@ mod tests {
         assert!(lines[1].ends_with(" broken"));
         assert_eq!(lines[2], "last");
     }
+
+    #[tokio::test]
+    async fn a_very_long_line_is_cut_and_the_next_one_is_intact() {
+        let mut input = vec![b'x'; MAX_LINE * 10 + 3];
+        input.extend_from_slice(b"\nnext\r\n");
+        // No newline at all after this one: still bounded.
+        input.extend_from_slice(&vec![b'y'; MAX_LINE * 3]);
+        let mut lines = Vec::new();
+        read_lines(&input[..], |l| lines.push(l)).await;
+        assert_eq!(lines.len(), 3);
+        assert_eq!(lines[0].chars().count(), MAX_LINE + 1);
+        assert!(lines[0].ends_with('…') && lines[0].starts_with("xxx"));
+        assert_eq!(lines[1], "next");
+        assert_eq!(lines[2].chars().count(), MAX_LINE + 1);
+    }
 }

crates/ide-language/queries/bash/highlights.scm

@@ -0,0 +1,56 @@
+; Shell scripts: drawn over the stream mode, which knows only fixed word lists.
+; The last matching pattern wins.
+
+[
+  (string)
+  (raw_string)
+  (ansi_c_string)
+  (translated_string)
+  (heredoc_body)
+  (heredoc_start)
+] @string
+
+[
+  (command_substitution)
+  (process_substitution)
+  (expansion)
+  (simple_expansion)
+] @embedded
+
+(comment) @comment
+
+[
+  "case"
+  "do"
+  "done"
+  "elif"
+  "else"
+  "esac"
+  "fi"
+  "for"
+  "function"
+  "if"
+  "in"
+  "select"
+  "then"
+  "until"
+  "while"
+  "declare"
+  "export"
+  "local"
+  "readonly"
+  "typeset"
+  "unset"
+  "unsetenv"
+] @keyword
+
+(command_name) @function.command
+(function_definition name: (word) @function.definition)
+
+(variable_name) @variable
+(special_variable_name) @variable
+
+[
+  (number)
+  (file_descriptor)
+] @number

crates/ide-language/src/lib.rs

@@ -28,6 +28,7 @@ pub use syntax::{
     VueComponentImport, VueRefAccess, VueRefElement, WebReference, WebReferenceKind, merge_visibility,
     set_external_syntax, shift_pos, shift_range,
 };
+pub use syntax::{MethodBody, PythonClassFacts, PythonFacts, PythonMethodFacts};
 
 /// Parsed form of `languages/<id>.toml`. Backend-only; the UI gets [`LanguageInfo`].
 #[derive(Clone, Debug, Serialize, Deserialize)]
@@ -198,6 +199,10 @@ pub struct LanguageServerConfig {
     /// it parses a document.
     #[serde(default)]
     pub resync_on_configuration: bool,
+    /// Set by the settings hook: what the user sees as the server when another program serves
+    /// in its place (TypeScript 7's own `tsc --lsp` for vtsls).
+    #[serde(skip)]
+    pub display_name: Option<String>,
     /// Set on plugin languages: start exactly this approved program.
     #[serde(skip)]
     pub pinned: Option<ProgramPin>,

crates/ide-language/src/syntax/grammars.rs

@@ -314,7 +314,7 @@ pub(crate) static SPECS: &[Spec] = &[
         name: "bash",
         language: tree_sitter_bash::LANGUAGE,
         outline: outline!("bash"),
-        highlights: None,
+        highlights: Some(Highlights { query: highlights!("bash"), first_wins: false }),
         fold_nodes: &["do_group", "if_statement", "case_statement", "heredoc_body"],
         fold_bodies: NONE,
         imports: NONE,

crates/ide-language/src/syntax/highlight.rs

@@ -43,11 +43,13 @@ pub enum SyntaxHighlightKind {
     Operator,
     Punctuation,
     Parameter,
+    /// A shell command name (`pgrep`, a script's own function).
+    Command,
 }
 
 impl SyntaxHighlightKind {
     /// Every kind, in `as u32` order: the legend for [`SyntaxHighlights::data`].
-    pub const ALL: [Self; 25] = [
+    pub const ALL: [Self; 26] = [
         Self::Keyword,
         Self::String,
         Self::StringSpecial,
@@ -73,6 +75,7 @@ impl SyntaxHighlightKind {
         Self::Operator,
         Self::Punctuation,
         Self::Parameter,
+        Self::Command,
     ];
 
     /// The kebab-case name plugins use (`doc-comment`, `function-call`, …).
@@ -153,6 +156,7 @@ const CAPTURES: &[(&str, Paint)] = {
         ("function.builtin", Kind(K::Builtin)),
         ("function.macro", Kind(K::Macro)),
         ("function.definition", Kind(K::Function)),
+        ("function.command", Kind(K::Command)),
         ("function", Kind(K::FunctionCall)),
         ("method", Kind(K::FunctionCall)),
         ("constructor", Kind(K::Type)),
@@ -408,6 +412,30 @@ mod tests {
         }
     }
 
+    #[test]
+    fn shell_scripts_highlight_declarations_commands_and_function_names() {
+        use SyntaxHighlightKind as K;
+        let src = "this::check_process() {\n  local process\n  process=\"${1:?}\"\n  if [ -x \"$(command -v pgrep)\" ]; then\n    if pgrep -f -q \"${process}\"; then\n      functions::exit 1 \"'${process}' is running\"\n    fi\n  fi\n}\n# done\n";
+        let got = spans("shellscript", src);
+        for (text, expected) in [
+            ("this::check_process", K::Function),
+            ("local", K::Keyword),
+            ("if", K::Keyword),
+            ("command", K::Command),
+            ("pgrep", K::Command),
+            ("functions::exit", K::Command),
+            ("process", K::Variable),
+            ("# done", K::Comment),
+        ] {
+            assert!(
+                got.iter().any(|(word, kind)| word == text && *kind == expected),
+                "missing {text}: {expected:?} in {got:?}"
+            );
+        }
+        // An expansion inside a string is not string-coloured.
+        assert!(!got.iter().any(|(word, kind)| word.contains("${process}") && *kind == K::String), "{got:?}");
+    }
+
     #[test]
     fn non_kotlin_parameters_keep_variable_highlighting() {
         for (lang, src) in [

crates/ide-language/src/syntax/inheritance.rs

@@ -43,7 +43,7 @@ fn extract(tree: &Tree, text: &str) -> Vec<ClassBases> {
         // Selection-range start of the class: its name identifier (`class Foo`
         // -> `Foo`), matching `outline.rs` and the gutter marker candidates.
         let range = idx.range(name_node.start_byte(), name_node.end_byte());
-        let bases = node.child_by_field_name("superclasses").map(|args| base_names(args, text)).unwrap_or_default();
+        let bases = class_base_names(node, text);
         out.push(ClassBases { name, line: range.start.line, col: range.start.col, bases });
     });
     out
@@ -67,6 +67,11 @@ fn visit(cursor: &mut tree_sitter::TreeCursor, f: &mut impl FnMut(Node)) {
     }
 }
 
+/// The bare base names a `class_definition` node writes (keyword arguments left out).
+pub(super) fn class_base_names(node: Node, text: &str) -> Vec<String> {
+    node.child_by_field_name("superclasses").map(|args| base_names(args, text)).unwrap_or_default()
+}
+
 fn base_names(args: Node, text: &str) -> Vec<String> {
     let mut out = Vec::new();
     let mut cursor = args.walk();

crates/ide-language/src/syntax/mod.rs

@@ -10,6 +10,7 @@ mod inheritance;
 pub(crate) mod lines;
 mod literals;
 mod outline;
+mod python_facts;
 mod rst;
 mod selection;
 mod sfc;
@@ -27,6 +28,7 @@ pub use inheritance::ClassBases;
 pub use lines::{shift_pos, shift_range};
 pub use literals::{Literal, LiteralKind, SpellingKind, SpellingRegion};
 pub use outline::merge_visibility;
+pub use python_facts::{MethodBody, PythonClassFacts, PythonFacts, PythonMethodFacts};
 use std::cell::RefCell;
 use std::collections::HashMap;
 use std::sync::OnceLock;

crates/ide-language/src/syntax/python_facts.rs

@@ -0,0 +1,438 @@
+//! Python class facts the inheritance inspections need: base names as written, parameter
+//! lists, decorator semantics and what a method body does. They come from the syntax tree in
+//! one pass, so the frontend reasons about the inheritance graph without parsing source text.
+//!
+//! Deliberately small: a fact exists here only when a check can decide it without guessing.
+
+use super::lines::LineIndex;
+use crate::{LanguageId, Syntax};
+use serde::{Deserialize, Serialize};
+use specta::Type;
+use tree_sitter::{Node, Tree};
+
+/// One Python module's classes, in source order.
+#[derive(Clone, Debug, Default, PartialEq, Eq, Serialize, Deserialize, Type)]
+#[serde(rename_all = "camelCase")]
+pub struct PythonFacts {
+    pub classes: Vec<PythonClassFacts>,
+}
+
+/// A class definition and the methods it declares.
+#[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize, Type)]
+#[serde(rename_all = "camelCase")]
+pub struct PythonClassFacts {
+    pub name: String,
+    /// The class name identifier (selection range).
+    pub selection: crate::Range,
+    /// Base names as written, a qualified name reduced to its last segment.
+    pub bases: Vec<String>,
+    pub methods: Vec<PythonMethodFacts>,
+}
+
+/// A method definition the inspections can reason about.
+#[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize, Type)]
+#[serde(rename_all = "camelCase")]
+pub struct PythonMethodFacts {
+    pub name: String,
+    /// The method name identifier (selection range).
+    pub selection: crate::Range,
+    /// Parameter names in order; `None` for a form whose forwarding cannot be compared
+    /// (`*args`, `**kwargs`, keyword-only, positional-only).
+    pub params: Option<Vec<String>>,
+    /// Decorated with `abstractmethod` (`abc.abstractmethod` included).
+    pub abstract_method: bool,
+    /// Decorated with `override` from `typing` / `typing_extensions`.
+    pub override_decorated: bool,
+    pub body: MethodBody,
+}
+
+/// What a method body does, for the shapes a check can decide without guessing.
+#[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize, Type)]
+#[serde(rename_all = "camelCase", tag = "kind")]
+pub enum MethodBody {
+    /// `pass`, `...`, a docstring, or nothing at all.
+    Empty,
+    /// Exactly one `super().name(args)` call, optionally `return`ed.
+    SuperCall { returns: bool, target: String, args: Vec<String> },
+    /// Anything else.
+    Other,
+}
+
+impl Syntax {
+    /// The classes of a Python `text` with the facts the inheritance checks need.
+    /// Every other language returns an empty result.
+    pub fn python_facts(&self, lang: &LanguageId, text: &str) -> PythonFacts {
+        self.analyze(lang, text, |g, tree, text| (g.spec.name == "python").then(|| extract(tree, text)))
+            .unwrap_or_default()
+    }
+}
+
+fn extract(tree: &Tree, text: &str) -> PythonFacts {
+    let idx = LineIndex::new(text);
+    let imports = ImportBindings::collect(tree, text);
+    let mut classes = Vec::new();
+    let mut cursor = tree.walk();
+    visit(&mut cursor, &mut |node| {
+        if node.kind() != "class_definition" {
+            return;
+        }
+        let Some(name_node) = node.child_by_field_name("name") else { return };
+        let name = text_of(name_node, text);
+        if name.is_empty() {
+            return;
+        }
+        classes.push(PythonClassFacts {
+            name,
+            selection: idx.range(name_node.start_byte(), name_node.end_byte()),
+            bases: super::inheritance::class_base_names(node, text),
+            methods: methods_of(node, text, &idx, &imports),
+        });
+    });
+    PythonFacts { classes }
+}
+
+/// The methods declared directly in `class`.
+fn methods_of(class: Node, text: &str, idx: &LineIndex, imports: &ImportBindings) -> Vec<PythonMethodFacts> {
+    let Some(body) = class.child_by_field_name("body") else { return Vec::new() };
+    let mut out = Vec::new();
+    let mut cursor = body.walk();
+    for member in body.named_children(&mut cursor) {
+        // A decorated method is a `decorated_definition` wrapping the `function_definition`.
+        let method = match member.kind() {
+            "function_definition" => member,
+            "decorated_definition" => match member.child_by_field_name("definition") {
+                Some(inner) if inner.kind() == "function_definition" => inner,
+                _ => continue,
+            },
+            _ => continue,
+        };
+        let Some(name_node) = method.child_by_field_name("name") else { continue };
+        let name = text_of(name_node, text);
+        if name.is_empty() {
+            continue;
+        }
+        let decorators = decorators_of(method, text);
+        out.push(PythonMethodFacts {
+            name,
+            selection: idx.range(name_node.start_byte(), name_node.end_byte()),
+            params: parameters_of(method, text),
+            abstract_method: decorators.iter().any(|d| last_segment(d) == "abstractmethod"),
+            override_decorated: decorators.iter().any(|d| imports.is_typing_override(d)),
+            body: body_of(method, text),
+        });
+    }
+    out
+}
+
+/// The parameter names of a `function_definition`, or `None` when the signature contains a
+/// form whose forwarding cannot be compared without guessing.
+fn parameters_of(function: Node, text: &str) -> Option<Vec<String>> {
+    let params = function.child_by_field_name("parameters")?;
+    let mut names = Vec::new();
+    let mut cursor = params.walk();
+    for param in params.named_children(&mut cursor) {
+        let name = match param.kind() {
+            "identifier" => text_of(param, text),
+            "typed_parameter" | "default_parameter" | "typed_default_parameter" => {
+                let named = param
+                    .child_by_field_name("name")
+                    .or_else(|| param.child_by_field_name("pattern"))
+                    .or_else(|| param.named_child(0))?;
+                if named.kind() != "identifier" {
+                    return None;
+                }
+                text_of(named, text)
+            }
+            // `*args`, `**kwargs`, `/`, `*`: the call form cannot be compared textually.
+            _ => return None,
+        };
+        if !name.is_empty() {
+            names.push(name);
+        }
+    }
+    Some(names)
+}
+
+/// A `function_definition`'s body, classified into the shapes a check can decide.
+fn body_of(function: Node, text: &str) -> MethodBody {
+    let Some(body) = function.child_by_field_name("body") else { return MethodBody::Empty };
+    // A docstring is not a statement the checks care about.
+    let statements: Vec<Node> = statements_of(body).into_iter().filter(|s| !is_string(*s)).collect();
+    if statements.is_empty() || statements.iter().all(|s| is_noop(*s)) {
+        return MethodBody::Empty;
+    }
+    let [only] = statements.as_slice() else { return MethodBody::Other };
+    let call = match only.kind() {
+        "expression_statement" => (only.named_child(0), false),
+        "return_statement" => (only.named_child(0), true),
+        _ => (None, false),
+    };
+    match call {
+        (Some(call), returns) if is_super_call(call, text) => {
+            let target = call
+                .child_by_field_name("function")
+                .and_then(|f| f.child_by_field_name("attribute"))
+                .map(|a| text_of(a, text))
+                .unwrap_or_default();
+            let args = call
+                .child_by_field_name("arguments")
+                .map(|args| {
+                    let mut cursor = args.walk();
+                    args.named_children(&mut cursor).map(|a| text_of(a, text)).collect()
+                })
+                .unwrap_or_default();
+            MethodBody::SuperCall { returns, target, args }
+        }
+        _ => MethodBody::Other,
+    }
+}
+
+/// Whether `node` is a `super().name(...)` call.
+fn is_super_call(node: Node, text: &str) -> bool {
+    if node.kind() != "call" {
+        return false;
+    }
+    let Some(function) = node.child_by_field_name("function") else { return false };
+    if function.kind() != "attribute" {
+        return false;
+    }
+    function.child_by_field_name("object").is_some_and(|object| {
+        object.kind() == "call"
+            && object
+                .child_by_field_name("function")
+                .is_some_and(|f| f.kind() == "identifier" && text_of(f, text) == "super")
+    })
+}
+
+/// Whether `statement` is `pass` or a bare `...`.
+fn is_noop(statement: Node) -> bool {
+    match statement.kind() {
+        "pass_statement" => true,
+        "expression_statement" => statement.named_child(0).is_some_and(|child| child.kind() == "ellipsis"),
+        _ => false,
+    }
+}
+
+/// A string expression statement: a docstring.
+fn is_string(statement: Node) -> bool {
+    statement.kind() == "expression_statement" && statement.named_child(0).is_some_and(|child| child.kind() == "string")
+}
+
+/// The statements of a `block`, comments excluded.
+fn statements_of(block: Node) -> Vec<Node> {
+    let mut cursor = block.walk();
+    block.named_children(&mut cursor).filter(|child| child.kind() != "comment").collect()
+}
+
+/// The decorators written on a definition, without the `@` or the call arguments.
+fn decorators_of(definition: Node, text: &str) -> Vec<String> {
+    let Some(parent) = definition.parent() else { return Vec::new() };
+    if parent.kind() != "decorated_definition" {
+        return Vec::new();
+    }
+    let mut out = Vec::new();
+    let mut cursor = parent.walk();
+    for decorator in parent.named_children(&mut cursor) {
+        if decorator.kind() != "decorator" {
+            continue;
+        }
+        let Some(inner) = decorator.named_child(0) else { continue };
+        let target =
+            if inner.kind() == "call" { inner.child_by_field_name("function").unwrap_or(inner) } else { inner };
+        let name = text_of(target, text).trim().to_owned();
+        if !name.is_empty() {
+            out.push(name);
+        }
+    }
+    out
+}
+
+/// The last segment of a dotted name (`typing.override` -> `override`).
+fn last_segment(name: &str) -> &str {
+    name.rsplit('.').next().unwrap_or(name)
+}
+
+fn text_of(node: Node, text: &str) -> String {
+    text.get(node.byte_range()).unwrap_or_default().to_owned()
+}
+
+/// The module-level `from ... import ...` bindings, so `override` can be told apart from a
+/// same-named decorator of another library.
+struct ImportBindings {
+    /// (local name, module, exported name)
+    bindings: Vec<(String, String, String)>,
+}
+
+impl ImportBindings {
+    fn collect(tree: &Tree, text: &str) -> Self {
+        let mut bindings = Vec::new();
+        let mut cursor = tree.walk();
+        visit(&mut cursor, &mut |node| {
+            if node.kind() != "import_from_statement" {
+                return;
+            }
+            let Some(module) = node.child_by_field_name("module_name") else { return };
+            let module = text_of(module, text);
+            let mut names = node.walk();
+            for name in node.children_by_field_name("name", &mut names) {
+                let (local, exported) = match name.kind() {
+                    "aliased_import" => (
+                        name.child_by_field_name("alias").map(|n| text_of(n, text)),
+                        name.child_by_field_name("name").map(|n| text_of(n, text)),
+                    ),
+                    _ => {
+                        let written = text_of(name, text);
+                        (Some(written.clone()), Some(written))
+                    }
+                };
+                if let (Some(local), Some(exported)) = (local, exported) {
+                    bindings.push((local, module.clone(), exported));
+                }
+            }
+        });
+        Self { bindings }
+    }
+
+    /// Whether `decorator` names `override` from `typing` / `typing_extensions`.
+    fn is_typing_override(&self, decorator: &str) -> bool {
+        const MODULES: [&str; 2] = ["typing", "typing_extensions"];
+        let segments: Vec<&str> = decorator.split('.').filter(|s| !s.is_empty()).collect();
+        match segments.as_slice() {
+            // `@typing.override`, or `@t.override` after `import typing as t`.
+            [prefix, "override"] => {
+                MODULES.contains(prefix)
+                    || self
+                        .bindings
+                        .iter()
+                        .find(|(local, _, _)| local == prefix)
+                        .is_some_and(|(_, module, _)| MODULES.contains(&module.as_str()))
+            }
+            // `@override`, or `@ov` after `from typing import override as ov`.
+            [local] => match self.bindings.iter().find(|(bound, _, _)| bound == local) {
+                Some((_, module, exported)) => exported == "override" && MODULES.contains(&module.as_str()),
+                // Nothing contradicts a bare `@override`: the usual `from typing import *`.
+                None => *local == "override",
+            },
+            _ => false,
+        }
+    }
+}
+
+/// Depth-first pre-order traversal of all descendants of `cursor`'s node.
+fn visit(cursor: &mut tree_sitter::TreeCursor, f: &mut impl FnMut(Node)) {
+    loop {
+        f(cursor.node());
+        if cursor.goto_first_child() {
+            continue;
+        }
+        loop {
+            if cursor.goto_next_sibling() {
+                break;
+            }
+            if !cursor.goto_parent() {
+                return;
+            }
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    static SYNTAX: std::sync::OnceLock<Syntax> = std::sync::OnceLock::new();
+
+    fn facts(src: &str) -> PythonFacts {
+        SYNTAX.get_or_init(Syntax::new).python_facts(&LanguageId::new("python"), src)
+    }
+
+    fn method<'a>(facts: &'a PythonFacts, class: &str, method: &str) -> &'a PythonMethodFacts {
+        facts
+            .classes
+            .iter()
+            .find(|c| c.name == class)
+            .and_then(|c| c.methods.iter().find(|m| m.name == method))
+            .expect("method not found")
+    }
+
+    #[test]
+    fn classes_carry_bases_and_methods() {
+        let f = facts(
+            "class Base(ABC):\n    pass\n\nclass Child(Base, pkg.Mixin):\n    def run(self, x=1):\n        pass\n",
+        );
+        assert_eq!(f.classes.len(), 2);
+        assert_eq!(f.classes[0].name, "Base");
+        assert_eq!(f.classes[0].bases, ["ABC"]);
+        assert_eq!(f.classes[1].bases, ["Base", "Mixin"]);
+        assert_eq!(f.classes[1].methods.len(), 1);
+        assert_eq!(f.classes[1].selection.start.line, 3);
+        assert_eq!(f.classes[1].selection.start.col, 6);
+    }
+
+    #[test]
+    fn parameters_are_names_in_order_and_none_for_splats() {
+        let f = facts(
+            "class C:\n    def a(self, x: int, y=2):\n        pass\n\n    def b(self, *args):\n        pass\n\n    def c(self, *, x):\n        pass\n",
+        );
+        assert_eq!(
+            method(&f, "C", "a").params.as_deref(),
+            Some(["self".to_string(), "x".to_string(), "y".to_string()].as_slice())
+        );
+        assert_eq!(method(&f, "C", "b").params, None);
+        assert_eq!(method(&f, "C", "c").params, None);
+    }
+
+    #[test]
+    fn body_shapes_are_classified() {
+        let f = facts(
+            "class C:\n    def noop(self):\n        pass\n\n    def dots(self):\n        ...\n\n    def doc(self):\n        \"\"\"text\"\"\"\n\n    def forward(self, x):\n        return super().run(x)\n\n    def call(self):\n        super().run()\n\n    def other(self):\n        return 1\n",
+        );
+        assert_eq!(method(&f, "C", "noop").body, MethodBody::Empty);
+        assert_eq!(method(&f, "C", "dots").body, MethodBody::Empty);
+        assert_eq!(method(&f, "C", "doc").body, MethodBody::Empty);
+        assert_eq!(
+            method(&f, "C", "forward").body,
+            MethodBody::SuperCall { returns: true, target: "run".into(), args: vec!["x".into()] }
+        );
+        assert_eq!(
+            method(&f, "C", "call").body,
+            MethodBody::SuperCall { returns: false, target: "run".into(), args: vec![] }
+        );
+        assert_eq!(method(&f, "C", "other").body, MethodBody::Other);
+    }
+
+    #[test]
+    fn decorators_are_their_names_and_semantics() {
+        let f = facts(
+            "from abc import abstractmethod\nfrom typing import override\n\nclass C:\n    @abstractmethod\n    def a(self):\n        pass\n\n    @override\n    def b(self):\n        pass\n\n    @functools.cache\n    def c(self):\n        pass\n",
+        );
+        assert!(method(&f, "C", "a").abstract_method);
+        assert!(!method(&f, "C", "a").override_decorated);
+        assert!(method(&f, "C", "b").override_decorated);
+        assert!(!method(&f, "C", "c").override_decorated);
+    }
+
+    #[test]
+    fn override_of_another_library_is_not_typing_override() {
+        let f = facts("from mylib import override\n\nclass C:\n    @override\n    def a(self):\n        pass\n");
+        assert!(!method(&f, "C", "a").override_decorated);
+    }
+
+    #[test]
+    fn aliased_override_and_qualified_forms_are_recognised() {
+        let f = facts(
+            "from typing import override as ov\n\nclass C:\n    @ov\n    def a(self):\n        pass\n\nclass D:\n    @typing_extensions.override\n    def b(self):\n        pass\n",
+        );
+        assert!(method(&f, "C", "a").override_decorated);
+        assert!(method(&f, "D", "b").override_decorated);
+    }
+
+    #[test]
+    fn nested_classes_and_other_languages() {
+        let f = facts("class Outer:\n    class Inner:\n        def m(self):\n            pass\n");
+        let names: Vec<&str> = f.classes.iter().map(|c| c.name.as_str()).collect();
+        assert_eq!(names, ["Outer", "Inner"]);
+        let other = SYNTAX.get_or_init(Syntax::new).python_facts(&LanguageId::new("rust"), "class C {}");
+        assert_eq!(other.classes.len(), 0);
+    }
+}

crates/ide-lsp/src/handler.rs

@@ -41,20 +41,44 @@ pub struct ClientHandler {
     generation: u64,
 }
 
+/// The diagnostics in `items` (a JSON array) that deserialize. A server's malformed one is
+/// skipped with a warning, so the rest of the file's problems still show.
+pub(crate) fn lenient_diagnostics(server: &str, items: Value) -> Vec<lsp::Diagnostic> {
+    let Value::Array(items) = items else { return Vec::new() };
+    let mut skipped = 0usize;
+    let parsed: Vec<lsp::Diagnostic> = items
+        .into_iter()
+        .filter_map(|mut item| {
+            crate::virtual_doc::normalize_uris(&mut item);
+            match serde_json::from_value(item) {
+                Ok(diagnostic) => Some(diagnostic),
+                Err(_) => {
+                    skipped += 1;
+                    None
+                }
+            }
+        })
+        .collect();
+    if skipped > 0 {
+        tracing::warn!("{server}: skipped {skipped} malformed diagnostic(s)");
+    }
+    parsed
+}
+
 impl ClientHandler {
     pub fn new(mgr: Weak<LspManager>, server: Arc<Server>, generation: u64) -> Self {
         Self { mgr, server, generation }
     }
 
     fn encoding(&self) -> Encoding {
-        self.server.running_gen(self.generation).map(|r| r.caps.read().encoding).unwrap_or_default()
+        self.server.initialized_gen(self.generation).map(|r| r.caps.read().encoding).unwrap_or_default()
     }
 
     /// Cancelling task `task` asks this server instance to stop the work of progress `token`.
     fn cancel_handle(&self, task: TaskId, token: &Value) -> ide_core::task::CancelHandle {
         let (server, generation, token) = (self.server.clone(), self.generation, token.clone());
         ide_core::task::on_cancel(task, move || {
-            if let Some(run) = server.running_gen(generation)
+            if let Some(run) = server.initialized_gen(generation)
                 && let Err(e) = run.peer.notify("window/workDoneProgress/cancel", json!({ "token": token }))
             {
                 tracing::debug!("{}: cannot cancel progress: {e}", server.name);
@@ -176,7 +200,7 @@ impl ClientHandler {
             loop {
                 tokio::time::sleep(PROGRESS_SWEEP).await;
                 let Some(mgr) = weak.upgrade() else { return };
-                if server.running_gen(generation).is_none() || !server.has_progress(&token) {
+                if !server.is_live(generation) || !server.has_progress(&token) {
                     return; // the instance is gone, or the task ended normally
                 }
                 if server.progress_silent(&token, PROGRESS_STALE) {
@@ -251,18 +275,24 @@ impl ClientHandler {
 
     fn publish_diagnostics(&self, mgr: &LspManager, params: Value) {
         // Problems come only from servers used for `diagnostics`.
-        if self.server.running_gen(self.generation).is_some_and(|run| !run.caps.read().restriction.diagnostics()) {
+        if self.server.initialized_gen(self.generation).is_some_and(|run| !run.caps.read().restriction.diagnostics()) {
             return;
         }
         let mut params = params;
         crate::virtual_doc::normalize_uris(&mut params);
-        let params: lsp::PublishDiagnosticsParams = match serde_json::from_value(params) {
+        // One malformed diagnostic must not take the others of the file with it.
+        let raw = params.get_mut("diagnostics").map(Value::take);
+        if let Some(fields) = params.as_object_mut() {
+            fields.insert("diagnostics".into(), json!([]));
+        }
+        let mut params: lsp::PublishDiagnosticsParams = match serde_json::from_value(params) {
             Ok(p) => p,
             Err(e) => {
                 tracing::debug!("{}: bad publishDiagnostics: {e}", self.server.name);
                 return;
             }
         };
+        params.diagnostics = lenient_diagnostics(&self.server.name, raw.unwrap_or(Value::Null));
         let Some(path) = uri_to_path(params.uri.as_str())
             .or_else(|| crate::notebook::is_cell_uri(params.uri.as_str()).then(|| PathBuf::from(params.uri.as_str())))
         else {
@@ -480,7 +510,7 @@ impl Handler for ClientHandler {
                 crate::kotlin_lsp::record_import_state(&self.server, self.generation, &params)
             }
             "language/status" if self.server.name == "jdtls" && params["type"] == "ServiceReady" => {
-                if self.server.running_gen(self.generation).is_some() {
+                if self.server.initialized_gen(self.generation).is_some() {
                     self.server.set_java_ready();
                 }
                 mgr.java_import_ready(self.server.clone(), self.generation);

crates/ide-lsp/src/launch.rs

@@ -103,7 +103,7 @@ impl Launcher for ProcessLauncher {
             // A plugin's server: the approved program, unchanged since.
             Some(pin) => Some(pin.verify().map_err(LaunchError::Failed)?.to_path_buf()),
             None => ide_core::tool_path::find_command(&config.command, &search, root)
-                .and_then(|b| resolve_rustup_proxy(&config.command, b))
+                .and_then(|b| resolve_rustup_proxy(&config.command, b, root))
                 .and_then(|b| reject_dead_shim(b, &search, root)),
         };
         let mut env: Vec<(String, String)> = vec![("PATH".into(), search.to_string_lossy().into_owned())];
@@ -208,34 +208,16 @@ fn reject_dead_shim(binary: PathBuf, search: &OsStr, root: &Path) -> Option<Path
 /// toolchain lacks the component (common for rust-analyzer). In that case use
 /// the newest installed toolchain that ships the binary; with none, the tool is
 /// missing (an install hint, not a server that crashes on every restart).
-fn resolve_rustup_proxy(command: &str, binary: PathBuf) -> Option<PathBuf> {
+/// The probe runs in the project's root, where a `rust-toolchain.toml` picks the toolchain.
+fn resolve_rustup_proxy(command: &str, binary: PathBuf, root: &Path) -> Option<PathBuf> {
     let is_proxy = binary.parent().is_some_and(|d| d.ends_with(".cargo/bin"));
     if !is_proxy || command.contains('/') {
         return Some(binary);
     }
-    let works = ide_core::process::prepare(&mut std::process::Command::new(&binary))
-        .arg("--version")
-        .stdin(std::process::Stdio::null())
-        .stdout(std::process::Stdio::null())
-        .stderr(std::process::Stdio::null())
-        .status()
-        .is_ok_and(|s| s.success());
-    if works {
+    if proxy_works(&binary, root) {
         return Some(binary);
     }
-    let toolchains = std::env::var_os("RUSTUP_HOME")
-        .map(PathBuf::from)
-        .or_else(|| std::env::var_os("HOME").map(|h| PathBuf::from(h).join(".rustup")))
-        .map(|h| h.join("toolchains"));
-    let mut candidates: Vec<(std::time::SystemTime, PathBuf)> = toolchains
-        .and_then(|dir| std::fs::read_dir(dir).ok())
-        .into_iter()
-        .flatten()
-        .flatten()
-        .map(|e| e.path().join("bin").join(command))
-        .filter(|p| p.is_file())
-        .filter_map(|p| Some((p.metadata().ok()?.modified().ok()?, p)))
-        .collect();
+    let mut candidates = rustup_home().map(|h| toolchain_binaries(&h.join("toolchains"), command)).unwrap_or_default();
     // Prefer stable-looking toolchains, then the most recently installed.
     candidates.sort_by_key(|(mtime, p)| (!p.to_string_lossy().contains("nightly"), *mtime));
     match candidates.pop() {
@@ -250,6 +232,57 @@ fn resolve_rustup_proxy(command: &str, binary: PathBuf) -> Option<PathBuf> {
     }
 }
 
+/// Whether the proxy runs for the toolchain active in `root`. A probe that hangs or can't
+/// be waited for counts as working: the real start decides.
+fn proxy_works(binary: &Path, root: &Path) -> bool {
+    let Ok(mut child) = ide_core::process::prepare(&mut std::process::Command::new(binary))
+        .arg("--version")
+        .current_dir(root)
+        .stdin(std::process::Stdio::null())
+        .stdout(std::process::Stdio::null())
+        .stderr(std::process::Stdio::null())
+        .spawn()
+    else {
+        return true;
+    };
+    let deadline = std::time::Instant::now() + std::time::Duration::from_secs(10);
+    loop {
+        match child.try_wait() {
+            Ok(Some(status)) => return status.success(),
+            Ok(None) if std::time::Instant::now() < deadline => {
+                std::thread::sleep(std::time::Duration::from_millis(20))
+            }
+            _ => {
+                let _ = child.kill();
+                return true;
+            }
+        }
+    }
+}
+
+/// Where rustup keeps its toolchains: `RUSTUP_HOME`, else `.rustup` in the user's home
+/// (`HOME`, which a GUI app on Windows doesn't have, or `USERPROFILE`).
+fn rustup_home() -> Option<PathBuf> {
+    std::env::var_os("RUSTUP_HOME").map(PathBuf::from).or_else(|| {
+        let home = std::env::var_os("HOME").or_else(|| std::env::var_os("USERPROFILE"))?;
+        Some(PathBuf::from(home).join(".rustup"))
+    })
+}
+
+/// The `command` binary (with the platform's executable suffix) of every toolchain in
+/// `toolchains`, with its modification time.
+fn toolchain_binaries(toolchains: &Path, command: &str) -> Vec<(std::time::SystemTime, PathBuf)> {
+    let file = format!("{command}{}", std::env::consts::EXE_SUFFIX);
+    std::fs::read_dir(toolchains)
+        .into_iter()
+        .flatten()
+        .flatten()
+        .map(|e| e.path().join("bin").join(&file))
+        .filter(|p| p.is_file())
+        .filter_map(|p| Some((p.metadata().ok()?.modified().ok()?, p)))
+        .collect()
+}
+
 /// Workspace root for `file`: the outermost ancestor within `project_root`
 /// containing a root marker (so a Cargo/npm workspace gets one server, not one
 /// per member), else `project_root`. `None` when `file` is outside the project.
@@ -363,7 +396,24 @@ mod proxy_tests {
     #[test]
     fn non_proxy_binaries_are_kept() {
         let p = PathBuf::from("/usr/bin/true");
-        assert_eq!(resolve_rustup_proxy("true", p.clone()), Some(p));
+        assert_eq!(resolve_rustup_proxy("true", p.clone(), Path::new(".")), Some(p));
+    }
+
+    /// The binary is `rust-analyzer.exe` on Windows: a lookup of the bare name found nothing there.
+    #[test]
+    fn toolchain_binaries_carry_the_platform_executable_suffix() {
+        let tmp = tempfile::tempdir().unwrap();
+        let file = format!("rust-analyzer{}", std::env::consts::EXE_SUFFIX);
+        for toolchain in ["stable-x86_64", "nightly-x86_64"] {
+            std::fs::create_dir_all(tmp.path().join(toolchain).join("bin")).unwrap();
+        }
+        std::fs::write(tmp.path().join("stable-x86_64/bin").join(&file), "").unwrap();
+        // Another tool, and a bare name without the suffix where one is required.
+        std::fs::write(tmp.path().join("nightly-x86_64/bin").join("rustfmt"), "").unwrap();
+        let found = toolchain_binaries(tmp.path(), "rust-analyzer");
+        assert_eq!(found.len(), 1);
+        assert_eq!(found[0].1, tmp.path().join("stable-x86_64/bin").join(&file));
+        assert!(toolchain_binaries(&tmp.path().join("missing"), "rust-analyzer").is_empty());
     }
 
     /// Exercises the real machine setup when a broken rustup proxy is present.
@@ -372,7 +422,7 @@ mod proxy_tests {
     fn broken_rustup_proxy_falls_back_to_a_toolchain() {
         let home = PathBuf::from(std::env::var_os("HOME").unwrap());
         let proxy = home.join(".cargo/bin/rust-analyzer");
-        let resolved = resolve_rustup_proxy("rust-analyzer", proxy.clone()).unwrap();
+        let resolved = resolve_rustup_proxy("rust-analyzer", proxy.clone(), Path::new(".")).unwrap();
         eprintln!("resolved: {}", resolved.display());
         assert_ne!(resolved, proxy);
     }

crates/ide-lsp/src/lib.rs

@@ -343,6 +343,10 @@ impl<T> Outcome<T> {
 /// How often a rename the server withdrew (`ContentModified`) is asked, and the pause between.
 const RENAME_ATTEMPTS: u32 = 5;
 const RENAME_RETRY_DELAY: std::time::Duration = std::time::Duration::from_millis(300);
+/// How often a semantic tokens, inlay hints or code lens request the server withdrew
+/// (`ContentModified`) is asked again, and the pause between.
+const STALE_RETRIES: u32 = 2;
+const STALE_RETRY_DELAY: std::time::Duration = std::time::Duration::from_millis(150);
 
 /// Implementation requests of one line-marker pass in flight at once.
 const IMPLEMENTATION_CONCURRENCY: usize = 4;
@@ -654,8 +658,9 @@ impl LspManager {
     }
 
     /// The servers serving `path`: every regular one, and each `fallback` one
-    /// only while all servers listed before it are missing. One that requires a
-    /// root marker serves only files below one, and stands in for no other.
+    /// only while all servers listed before it have given up (missing, not
+    /// launchable, or crashed for good). One that requires a root marker serves
+    /// only files below one, and stands in for no other.
     fn servers_for(&self, language: &LanguageId, path: &Path) -> Vec<Arc<Server>> {
         if let Some(servers) = self.arduino_servers(language, path) {
             return servers;
@@ -672,7 +677,7 @@ impl LspManager {
                 continue;
             }
             let server = self.server_for(sc, language, path);
-            available_before |= !sc.require_root_marker && server.status() != ide_core::event::ServerStatus::Missing;
+            available_before |= !sc.require_root_marker && !server.gave_up();
             out.push(server);
         }
         out
@@ -748,9 +753,14 @@ impl LspManager {
         if self.shutting_down.load(Ordering::Acquire) || !self.execution_allowed.load(Ordering::Acquire) {
             return;
         }
+        // A server dropped meanwhile (disabled in settings, shadowed by another) must not come
+        // back as a process nothing lists, serves or stops: a crash backoff can outlive it.
+        if !self.servers.lock().iter().any(|s| s.id == server.id) {
+            return;
+        }
         let workspace = is_local_jdtls(&server.config).then(|| self.jdtls_workspace_state());
         if let Some(state) = &workspace {
-            if state.transitioning || !self.servers.lock().iter().any(|s| s.id == server.id) {
+            if state.transitioning {
                 return;
             }
             let (shared, roots) = self.desired_jdtls_workspace();
@@ -861,24 +871,28 @@ impl LspManager {
             }
             Err(LaunchError::Config(message)) => {
                 tracing::warn!("{}: {message}", server.name);
-                server.fail_start(
+                if server.fail_start(
                     generation,
                     Conn::Failed,
                     &self.sink,
                     ide_core::event::ServerStatus::Misconfigured,
                     Some(message),
-                );
+                ) {
+                    self.attach_fallbacks();
+                }
                 return;
             }
             Err(LaunchError::Failed(message)) => {
                 tracing::warn!("{}: {message}", server.name);
-                server.fail_start(
+                if server.fail_start(
                     generation,
                     Conn::Failed,
                     &self.sink,
                     ide_core::event::ServerStatus::Crashed,
                     Some(message),
-                );
+                ) {
+                    self.attach_fallbacks();
+                }
                 return;
             }
         };
@@ -920,9 +934,18 @@ impl LspManager {
             }
             Err(e) => {
                 tracing::warn!("{}: initialize failed: {e}", server.name);
-                if matches!(e, RpcError::Closed) {
+                match e {
                     // The server is exiting: let it, so the crash report has its exit code and last output.
-                    let _ = tokio::time::timeout(Duration::from_secs(3), peer.closed()).await;
+                    RpcError::Closed => {
+                        let _ = tokio::time::timeout(Duration::from_secs(3), peer.closed()).await;
+                    }
+                    RpcError::Timeout => {
+                        server.set_start_error(
+                            generation,
+                            format!("it did not answer initialize within {} s", INITIALIZE_TIMEOUT.as_secs()),
+                        );
+                    }
+                    e => server.set_start_error(generation, format!("initialize failed ({e})")),
                 }
                 Self::kill_peer(&server, &peer).await;
                 // Treated like a crash so transient failures retry with backoff.
@@ -1008,11 +1031,15 @@ impl LspManager {
             self.forget(std::slice::from_ref(&server));
             return;
         }
-        if let Some(delay) = delay {
-            tokio::time::sleep(delay).await;
-            if server.is_idle_gen(generation) {
-                self.ensure_started(&server);
+        match delay {
+            Some(delay) => {
+                tokio::time::sleep(delay).await;
+                if server.is_idle_gen(generation) {
+                    self.ensure_started(&server);
+                }
             }
+            // Gave up (crashed repeatedly, or its build expired): the fallbacks it hid take over.
+            None => self.attach_fallbacks(),
         }
     }
 
@@ -1458,6 +1485,28 @@ impl LspManager {
         result
     }
 
+    /// [`Self::call`], asked again when the server withdrew the answer because the text changed
+    /// (`ContentModified`, which arrives as a cancellation as no cancel token is passed).
+    /// The client advertises `retryOnContentModified` for the methods that use it.
+    async fn call_retrying<P: Serialize + Clone, R: DeserializeOwned>(
+        &self,
+        t: &Target,
+        method: &str,
+        params: P,
+        timeout: Duration,
+    ) -> IdeResult<R> {
+        let mut attempt = 0;
+        loop {
+            match self.call(t, method, params.clone(), None, timeout).await {
+                Err(e) if e.kind == ErrorKind::Cancelled && attempt < STALE_RETRIES => {
+                    attempt += 1;
+                    tokio::time::sleep(STALE_RETRY_DELAY).await;
+                }
+                result => return result,
+            }
+        }
+    }
+
     // ---- features ----
     pub async fn completion(
         &self,
@@ -2892,11 +2941,10 @@ impl LspManager {
             async move {
                 (
                     t,
-                    self.call::<_, Option<Vec<lsp::InlayHint>>>(
+                    self.call_retrying::<_, Option<Vec<lsp::InlayHint>>>(
                         t,
                         "textDocument/inlayHint",
                         params,
-                        None,
                         DEFAULT_TIMEOUT,
                     )
                     .await,
@@ -2927,7 +2975,8 @@ impl LspManager {
             self.ready_targets(&snap.servers, |c| c.semantic_tokens_full() && c.semantic_legend.is_some()).await;
         let Some(t) = targets.first() else { return Ok(None) };
         let params = json!({ "textDocument": snap.ident() });
-        let r: Option<Value> = self.call(t, "textDocument/semanticTokens/full", params, None, DEFAULT_TIMEOUT).await?;
+        let r: Option<Value> =
+            self.call_retrying(t, "textDocument/semanticTokens/full", params, DEFAULT_TIMEOUT).await?;
         let Some(data) = r.as_ref().and_then(|v| v.get("data")).and_then(Value::as_array) else { return Ok(None) };
         let data: Vec<i64> = data.iter().map(|n| n.as_i64().unwrap_or(0)).collect();
         let (enc, legend) = {
@@ -2948,7 +2997,7 @@ impl LspManager {
             let params = json!({ "textDocument": snap.ident() });
             async move {
                 let lenses = self
-                    .call::<_, Option<Vec<lsp::CodeLens>>>(t, "textDocument/codeLens", params, None, DEFAULT_TIMEOUT)
+                    .call_retrying::<_, Option<Vec<lsp::CodeLens>>>(t, "textDocument/codeLens", params, DEFAULT_TIMEOUT)
                     .await?;
                 let lenses = lenses.unwrap_or_default();
                 if !t.caps().has_sub("codeLensProvider", "resolveProvider") {
@@ -3097,6 +3146,21 @@ impl LspManager {
         Ok(CallHierarchy { items: out, incomplete })
     }
 
+    /// The type at `pos` as the server's type hierarchy names it (with its `detail`, the
+    /// package for Java); `None` when there is no type there.
+    pub async fn prepare_type_hierarchy(&self, doc: DocId, pos: Pos) -> IdeResult<Option<HierarchyItem>> {
+        let (snap, targets) = self.doc_targets(doc, "type hierarchy", |c| c.has("typeHierarchyProvider")).await?;
+        let t = &targets[0];
+        let items: Option<Vec<serde_json::Value>> =
+            self.call(t, "textDocument/prepareTypeHierarchy", snap.pos_params(t, pos), None, DEFAULT_TIMEOUT).await?;
+        let conv = self.conv(t.enc());
+        Ok(items
+            .unwrap_or_default()
+            .iter()
+            .filter_map(convert::type_item_from_json)
+            .find_map(|i| convert::type_item(&conv, &i)))
+    }
+
     pub async fn type_hierarchy(
         &self,
         doc: DocId,
@@ -3855,31 +3919,41 @@ impl LspManager {
                 languages: s.languages(),
                 status: s.status(),
                 pid: s.running().and_then(|r| r.peer.pid()),
+                label: s.display_name(),
             })
             .collect()
     }
 
     pub async fn restart(&self, server: ide_core::ServerId) -> IdeResult<()> {
-        let _reconfigure = self.reconfigure_lock.lock().await;
-        let s = self
-            .servers
-            .lock()
-            .iter()
-            .find(|s| s.id == server)
-            .cloned()
-            .ok_or_else(|| IdeError::not_found(format!("unknown language server {server}")))?;
-        if !s.root.is_dir() {
-            return Err(IdeError::unavailable(format!(
-                "the workspace root of {} is gone: {}",
-                s.name,
-                s.root.display()
-            )));
-        }
-        self.stop_instance(&s, false).await;
-        s.reset_for_restart();
-        self.ensure_started(&s);
+        let s = {
+            // Only the restart itself holds the lock: a start can take minutes (a Gradle or
+            // Maven import), and `reconfigure` and `shutdown_all` wait for it.
+            let _reconfigure = self.reconfigure_lock.lock().await;
+            let s = self
+                .servers
+                .lock()
+                .iter()
+                .find(|s| s.id == server)
+                .cloned()
+                .ok_or_else(|| IdeError::not_found(format!("unknown language server {server}")))?;
+            if !s.root.is_dir() {
+                return Err(IdeError::unavailable(format!(
+                    "the workspace root of {} is gone: {}",
+                    s.name,
+                    s.root.display()
+                )));
+            }
+            self.stop_instance(&s, false).await;
+            s.reset_for_restart();
+            self.ensure_started(&s);
+            // Started again: it shadows the fallbacks that took over while it was down.
+            self.detach_shadowed_fallbacks().await;
+            s
+        };
         match s.wait_ready(Duration::from_secs(60)).await {
             Some(_) => Ok(()),
+            // Still importing the project: the restart worked, the server is just not ready yet.
+            None if s.is_starting() => Ok(()),
             None => {
                 Err(IdeError::unavailable(s.status_message().unwrap_or_else(|| format!("{} failed to start", s.name))))
             }

crates/ide-lsp/src/library_source.rs

@@ -136,7 +136,8 @@ fn source_entry(sources: &Path, class: &str, encoding: Option<&str>) -> Option<(
             return Some((entry.clone(), text));
         }
     }
-    // A facade renamed with `@file:JvmName("…")`.
+    // A facade renamed with `@file:JvmName("…")`, or a class declared in a file named otherwise
+    // (`UserDto` in `Models.kt`).
     let kotlin_files: Vec<String> = zip
         .file_names()
         .filter_map(|n| n.ok().map(|n| n.into_owned()))
@@ -145,7 +146,7 @@ fn source_entry(sources: &Path, class: &str, encoding: Option<&str>) -> Option<(
     let jvm_name = format!("@file:JvmName(\"{outer}\")");
     for entry in kotlin_files {
         if let Some(text) = read(&entry)
-            && text.text.contains(&jvm_name)
+            && (text.text.contains(&jvm_name) || declares_type(&text.text, outer))
         {
             return Some((entry, text));
         }
@@ -153,6 +154,26 @@ fn source_entry(sources: &Path, class: &str, encoding: Option<&str>) -> Option<(
     None
 }
 
+/// Whether `text` declares a type called `name` (`class`, `interface`, `object`, `typealias`):
+/// how a Kotlin file that is not named after its class is recognised.
+fn declares_type(text: &str, name: &str) -> bool {
+    const KINDS: [&str; 4] = ["class", "interface", "object", "typealias"];
+    text.lines().any(|line| {
+        let line = line.trim_start();
+        if line.starts_with("//") || line.starts_with("/*") || line.starts_with('*') {
+            return false;
+        }
+        let mut words =
+            line.split(|c: char| !(c.is_alphanumeric() || c == '_' || c == '$' || c == '`')).filter(|w| !w.is_empty());
+        let mut previous = words.next();
+        words.any(|word| {
+            let hit = previous.is_some_and(|p| KINDS.contains(&p)) && word.trim_matches('`') == name;
+            previous = Some(word);
+            hit
+        })
+    })
+}
+
 /// Where `name` is declared in a Kotlin or Java source `text` (the start of the
 /// name), else the start of the file.
 pub(crate) fn declaration_range(text: &str, name: &str) -> Range {
@@ -245,6 +266,22 @@ pub(crate) fn folder_class(uri: &str) -> Option<(String, String)> {
     Some((package.replace('.', "/"), name.to_owned()))
 }
 
+/// Kotlin sources larger than this are not searched for a class declared in a file named otherwise.
+const MAX_SOURCE: u64 = 1 << 20;
+
+/// The files of the project's source trees: build output and ignored files are skipped.
+fn walk_sources(root: &Path) -> impl Iterator<Item = ignore::DirEntry> {
+    ignore::WalkBuilder::new(root)
+        .filter_entry(|e| {
+            let output = matches!(e.file_name().to_str(), Some("target" | "build" | "out" | "node_modules"));
+            // A package may be named `build`: only outside source trees is it output.
+            !output || e.path().components().any(|c| c.as_os_str() == "src")
+        })
+        .build()
+        .flatten()
+        .filter(|e| e.file_type().is_some_and(|t| t.is_file()))
+}
+
 /// The project's source of `class` (`Name`, `Outer$Inner`, `FileKt`) in `package`
 /// (`/`-separated): a `.kt` / `.java` file of that name declaring the package. Build
 /// output and ignored files are skipped.
@@ -255,19 +292,24 @@ pub(crate) fn project_class_source(root: &Path, package: &str, class: &str) -> O
         names.push(format!("{file}.kt"));
     }
     let package = package.replace('/', ".");
-    let mut found: Vec<PathBuf> = ignore::WalkBuilder::new(root)
-        .filter_entry(|e| {
-            let output = matches!(e.file_name().to_str(), Some("target" | "build" | "out" | "node_modules"));
-            // A package may be named `build`: only outside source trees is it output.
-            !output || e.path().components().any(|c| c.as_os_str() == "src")
-        })
-        .build()
-        .flatten()
-        .filter(|e| e.file_type().is_some_and(|t| t.is_file()))
+    let mut found: Vec<PathBuf> = walk_sources(root)
         .filter(|e| e.file_name().to_str().is_some_and(|n| names.iter().any(|name| name == n)))
         .map(|e| e.into_path())
         .filter(|p| std::fs::read_to_string(p).is_ok_and(|text| declared_package(&text) == package))
         .collect();
+    // A class declared in a file named otherwise (`UserDto` in `Models.kt`).
+    if found.is_empty() {
+        found = walk_sources(root)
+            .filter(|e| {
+                e.path().extension().is_some_and(|x| x == "kt") && e.metadata().is_ok_and(|m| m.len() <= MAX_SOURCE)
+            })
+            .map(|e| e.into_path())
+            .filter(|p| {
+                std::fs::read_to_string(p)
+                    .is_ok_and(|text| declared_package(&text) == package && declares_type(&text, outer))
+            })
+            .collect();
+    }
     // The directory matching the package first, then by name order.
     found.sort_by_key(|p| {
         let dir = p.parent().map(|d| d.to_string_lossy().replace('\\', "/")).unwrap_or_default();
@@ -358,6 +400,10 @@ mod tests {
                 "@file:JvmName(\"BootUtils\")\npackage org.springframework.boot\nfun util() {}",
             ),
             ("org/springframework/boot/Builder.kt", "class Builder"),
+            (
+                "org/springframework/boot/Models.kt",
+                "package org.springframework.boot\n\n// class NotMe\ndata class UserDto(val id: Int)\nenum class Role { A }\ninterface Repo\nobject Registry\ntypealias Ids = List<Int>\n",
+            ),
             ("Root.java", "class Root {}"),
         ];
         jar(&m2.join("spring-boot-3.5.16.jar"), &[]);
@@ -373,6 +419,11 @@ mod tests {
                 ("org/springframework/boot/SpringApplication$Running.class", "SpringApplication.java"),
                 ("org/springframework/boot/BootUtils.class", "Renamed.kt"),
                 ("org/springframework/boot/Builder.class", "Builder.kt"),
+                // Declared in a file that is not named after them.
+                ("org/springframework/boot/UserDto.class", "Models.kt"),
+                ("org/springframework/boot/Role$A.class", "Models.kt"),
+                ("org/springframework/boot/Repo.class", "Models.kt"),
+                ("org/springframework/boot/Registry.class", "Models.kt"),
                 ("Root.class", "Root.java"),
             ] {
                 let (source_uri, text) =
@@ -385,6 +436,7 @@ mod tests {
                 );
             }
             assert!(class_source(&uri("org/springframework/boot/Missing.class"), None).is_none());
+            assert!(class_source(&uri("org/springframework/boot/NotMe.class"), None).is_none(), "only in a comment");
         }
         // No sources jar: nothing to show from here.
         let lone = tmp.path().join("lone/x-1.jar");
@@ -513,6 +565,11 @@ mod tests {
         write("src/main/kotlin/com/x/build/Tool.kt", "package com.x.build\n\nclass Tool\n");
         write("src/main/kotlin/flat/Elsewhere.kt", "");
         write("src/main/kotlin/Loose.kt", "package flat\n\nobject Loose\n");
+        write(
+            "src/main/kotlin/test001/Models.kt",
+            "package test001\n\n// class NotMe\ndata class UserDto(val id: Int)\n",
+        );
+        write("src/main/kotlin/other/Models.kt", "package other\n\ndata class UserDto(val name: String)\n");
         let source = |package: &str, class: &str| {
             project_class_source(root, package, class).map(|p| p.strip_prefix(root).unwrap().to_owned())
         };
@@ -523,6 +580,10 @@ mod tests {
         assert_eq!(source("com/x/build", "Tool"), Some(PathBuf::from("src/main/kotlin/com/x/build/Tool.kt")));
         assert_eq!(source("flat", "Loose"), Some(PathBuf::from("src/main/kotlin/Loose.kt")), "any directory");
         assert_eq!(source("test001", "Missing"), None);
+        // Declared in a file named otherwise: the one of the package, not another package's.
+        assert_eq!(source("test001", "UserDto"), Some(PathBuf::from("src/main/kotlin/test001/Models.kt")));
+        assert_eq!(source("other", "UserDto"), Some(PathBuf::from("src/main/kotlin/other/Models.kt")));
+        assert_eq!(source("test001", "NotMe"), None, "only in a comment");
         assert_eq!(declared_package("package a.b.c;\n"), "a.b.c");
         assert_eq!(declared_package("class A"), "");
     }

crates/ide-lsp/src/pull.rs

@@ -166,13 +166,10 @@ impl LspManager {
             let result_id = report.get("resultId").and_then(Value::as_str).map(str::to_owned);
             let items = match report.get("kind").and_then(Value::as_str) {
                 Some("unchanged") => None,
-                _ => match serde_json::from_value(report.get("items").cloned().unwrap_or(json!([]))) {
-                    Ok(items) => Some(items),
-                    Err(e) => {
-                        tracing::debug!("{}: bad textDocument/diagnostic report: {e}", t.server.name);
-                        return;
-                    }
-                },
+                _ => Some(crate::handler::lenient_diagnostics(
+                    &t.server.name,
+                    report.get("items").cloned().unwrap_or(json!([])),
+                )),
             };
             let shown = t.server.set_pulled(t.path.clone(), result_id, items);
             let enc = t.run.caps.read().encoding;

crates/ide-lsp/src/server.rs

@@ -112,8 +112,11 @@ pub struct Server {
     status: Mutex<(ServerStatus, Option<String>)>,
     /// Consecutive crashes of short-lived instances.
     crashes: Mutex<usize>,
-    /// When the current instance was launched.
+    /// When the current instance became ready: only time spent running counts as uptime,
+    /// not the time spent starting (an `initialize` that hangs for minutes is not a stable run).
     started: Mutex<Option<Instant>>,
+    /// Why the current instance's `initialize` failed, for the crash report.
+    start_error: Mutex<Option<(u64, String)>>,
     stderr: Mutex<VecDeque<String>>,
     pub progress: Mutex<HashMap<String, Progress>>,
     /// What the editor shows per path: the pushed and the pulled diagnostics together.
@@ -177,6 +180,7 @@ impl Server {
             status: Mutex::new((ServerStatus::Stopped, None)),
             crashes: Mutex::new(0),
             started: Mutex::new(None),
+            start_error: Mutex::new(None),
             stderr: Mutex::new(VecDeque::new()),
             progress: Mutex::new(HashMap::new()),
             diagnostics: Mutex::new(HashMap::new()),
@@ -213,6 +217,11 @@ impl Server {
         config
     }
 
+    /// The configured server's display name for the current (or last) instance.
+    pub fn display_name(&self) -> Option<String> {
+        self.effective.lock().as_ref().and_then(|c| c.display_name.clone())
+    }
+
     pub fn set_effective_config(&self, generation: u64, config: LanguageServerConfig) {
         let st = self.state.lock();
         if st.generation == generation && matches!(st.conn, Conn::Starting | Conn::Ready(_)) {
@@ -252,7 +261,8 @@ impl Server {
         st.conn = Conn::Starting;
         st.restarting = false;
         *self.start_cancel.lock() = CancellationToken::new();
-        *self.started.lock() = Some(Instant::now());
+        *self.started.lock() = None;
+        *self.start_error.lock() = None;
         // A crash report quotes only this instance's output, not its predecessors'.
         self.stderr.lock().clear();
         self.import_state.send_replace(None);
@@ -300,9 +310,15 @@ impl Server {
         }
         st.conn = Conn::Ready(run);
         *self.initializing.lock() = None;
+        *self.started.lock() = Some(Instant::now());
         true
     }
 
+    /// Records why instance `generation` failed to initialize, so its crash report says so.
+    pub fn set_start_error(&self, generation: u64, reason: String) {
+        *self.start_error.lock() = Some((generation, reason));
+    }
+
     /// Wakes requests waiting for the instance (after status and documents are in place).
     pub fn announce_ready(&self, generation: u64) {
         let st = self.state.lock();
@@ -322,6 +338,13 @@ impl Server {
         matches!(self.state.lock().conn, Conn::Starting)
     }
 
+    /// The server will not run until something changes: its binary is missing, its
+    /// configuration can't launch it, or it crashed too often (or its build expired).
+    /// Servers that crashed and are about to restart are not given up on.
+    pub fn gave_up(&self) -> bool {
+        matches!(self.state.lock().conn, Conn::Missing | Conn::Failed)
+    }
+
     /// The instance told `initialized`, ready or not.
     pub fn instance(&self) -> Option<Running> {
         self.running().or_else(|| self.initializing.lock().clone())
@@ -346,6 +369,13 @@ impl Server {
         self.running().filter(|r| r.generation == generation)
     }
 
+    /// Instance `generation` is starting or running: not stopped, crashed or replaced.
+    /// Work it reports before it is ready (a Gradle import answers `initialize` late) still counts.
+    pub fn is_live(&self, generation: u64) -> bool {
+        let st = self.state.lock();
+        st.generation == generation && matches!(st.conn, Conn::Starting | Conn::Ready(_))
+    }
+
     /// Waits through startup or a planned restart; returns the instance once ready.
     pub async fn wait_ready(&self, timeout: Duration) -> Option<Running> {
         let mut rx = self.phase.subscribe();
@@ -436,10 +466,12 @@ impl Server {
         }
         let tail = self.stderr_tail(5);
         let cfg = self.effective_config();
-        let mut message = match (code, &cfg.connect) {
-            (Some(c), _) => format!("{} exited with code {c}", self.name),
-            (None, Some(addr)) => format!("{}: the connection to the server ({addr}) closed", self.name),
-            (None, None) => format!("{} terminated unexpectedly", self.name),
+        let start_error = self.start_error.lock().take().filter(|(g, _)| *g == generation).map(|(_, r)| r);
+        let mut message = match (&start_error, code, &cfg.connect) {
+            (Some(reason), _, _) => format!("{} failed to start: {reason}", self.name),
+            (None, Some(c), _) => format!("{} exited with code {c}", self.name),
+            (None, None, Some(addr)) => format!("{}: the connection to the server ({addr}) closed", self.name),
+            (None, None, None) => format!("{} terminated unexpectedly", self.name),
         };
         if !tail.is_empty() {
             message.push_str(":\n");
@@ -472,6 +504,7 @@ impl Server {
     /// Records a crash; returns the backoff before restarting, or `None` once
     /// [`MAX_RESTARTS`] instances in a row died before running [`STABLE_UPTIME`]
     /// (a server that crashes on every start, however slowly, is not restarted forever).
+    /// An instance that never became ready has run for no time at all.
     pub fn record_crash(&self) -> Option<Duration> {
         let uptime = self.started.lock().map(|t| t.elapsed()).unwrap_or_default();
         let mut crashes = self.crashes.lock();
@@ -507,7 +540,13 @@ impl Server {
             return;
         }
         *cur = (status, message.clone());
-        st.events.push_back(IdeEvent::LanguageServer { server: self.id, name: self.name.clone(), status, message });
+        st.events.push_back(IdeEvent::LanguageServer {
+            server: self.id,
+            name: self.name.clone(),
+            label: self.display_name(),
+            status,
+            message,
+        });
     }
 
     fn queue_cleanup(&self, st: &mut State) {
@@ -1028,6 +1067,38 @@ mod tests {
         assert!(s.is_busy(), "a reporting task keeps the server busy");
     }
 
+    #[test]
+    fn only_time_spent_ready_counts_as_uptime() {
+        let sink: SharedSink = Arc::new(|_: IdeEvent| {});
+        let s = server();
+        for n in 1..=MAX_RESTARTS + 1 {
+            // Never ready: crashes after a slow start count however long the start took.
+            let generation = s.begin_start().unwrap();
+            assert!(s.started.lock().is_none());
+            s.set_start_error(generation, "it did not answer initialize within 300 s".into());
+            let delay = s.on_closed(generation, &sink, None).unwrap();
+            assert_eq!(delay.is_some(), n <= MAX_RESTARTS, "crash {n}");
+            let message = s.status_message().unwrap();
+            assert!(
+                message.starts_with(&format!("{} failed to start: it did not answer initialize", s.name)),
+                "{message}"
+            );
+            s.state.lock().conn = Conn::Idle;
+        }
+        assert!(matches!(s.state.lock().conn, Conn::Idle));
+    }
+
+    #[test]
+    fn an_instance_is_live_from_its_start_until_it_is_retired() {
+        let sink: SharedSink = Arc::new(|_: IdeEvent| {});
+        let s = server();
+        let generation = s.begin_start().unwrap();
+        assert!(s.is_live(generation), "still starting: its progress (an import) is being watched");
+        assert!(!s.is_live(generation + 1));
+        assert!(s.fail_start(generation, Conn::Failed, &sink, ServerStatus::Crashed, None));
+        assert!(!s.is_live(generation));
+    }
+
     #[test]
     fn crashes_of_short_lived_instances_exhaust_the_budget_whatever_the_spacing() {
         let s = server();

crates/ide-lsp/src/types.rs

@@ -341,6 +341,10 @@ pub struct ServerInfo {
     pub status: ServerStatus,
     /// OS process of the running instance (for memory attribution).
     pub pid: Option<u32>,
+    /// What the user sees as the server when another program serves in its place.
+    #[serde(default)]
+    #[specta(optional)]
+    pub label: Option<String>,
 }
 
 /// Read-only contents a language server provides for a non-`file:` URI

crates/ide-lsp/src/virtual_doc.rs

@@ -32,7 +32,7 @@ pub(crate) fn normalize_uris(value: &mut serde_json::Value) {
                 if matches!(key.as_str(), "data" | "arguments") {
                     continue;
                 }
-                if matches!(key.as_str(), "uri" | "targetUri" | "oldUri" | "newUri")
+                if matches!(key.as_str(), "uri" | "targetUri" | "oldUri" | "newUri" | "target")
                     && let Some(uri) = value.as_str().and_then(escaped_uri)
                 {
                     *value = uri.into();
@@ -247,6 +247,22 @@ mod tests {
         assert!(encoded.parse::<lsp_types::Uri>().is_ok());
     }
 
+    /// `DocumentLink.target` is a URI too: one unescaped link fails the whole `documentLink` response.
+    #[test]
+    fn document_link_targets_are_escaped() {
+        let range = serde_json::json!({ "start": { "line": 0, "character": 0 }, "end": { "line": 0, "character": 1 } });
+        let mut links = serde_json::json!([
+            { "range": range, "target": "file:///D:/My Game/项目/a.xsd" },
+            { "range": range, "target": "https://example.com/a b" }
+        ]);
+        assert!(serde_json::from_value::<Vec<lsp_types::DocumentLink>>(links.clone()).is_err());
+        normalize_uris(&mut links);
+        assert_eq!(links[0]["target"], "file:///D:/My%20Game/%E9%A1%B9%E7%9B%AE/a.xsd");
+        assert_eq!(links[1]["target"], "https://example.com/a b", "other schemes are not touched");
+        links[1]["target"] = "https://example.com/ab".into();
+        assert_eq!(serde_json::from_value::<Vec<lsp_types::DocumentLink>>(links).unwrap().len(), 2);
+    }
+
     /// #3089: jdtls's Introduce Variable edit for a project under a Chinese path names the file
     /// with the characters unescaped, and the resolved code action failed to deserialize.
     #[test]

crates/ide-lsp/tests/mock_server.rs

@@ -146,6 +146,9 @@ impl Handler for MockHandler {
                 if let Some(gate) = gate {
                     gate.hold();
                 }
+                if let Some(error) = s.errors.lock().get("initialize").cloned() {
+                    return Err(error);
+                }
                 Ok(json!({ "capabilities": s.caps.lock().clone(), "serverInfo": { "name": "mock" } }))
             }
             "shutdown" => Ok(Value::Null),
@@ -268,6 +271,7 @@ fn server_cfg(name: &str) -> LanguageServerConfig {
         tsserver_project: false,
         tsserver_project_extras: Default::default(),
         resync_on_configuration: false,
+        display_name: None,
         pinned: None,
     }
 }
@@ -2072,6 +2076,29 @@ async fn crash_restarts_and_reopens_documents() {
     assert_eq!(hover.contents.value, "hi");
 }
 
+/// A restart during a long start (a project import) returns when the instance is up and
+/// running, and does not hold up `reconfigure` and `shutdown_all` meanwhile.
+#[tokio::test(flavor = "multi_thread")]
+async fn restart_does_not_hold_the_reconfigure_lock_while_the_server_starts() {
+    let h = harness(&[("mock", incremental_caps())]);
+    h.open("a.mk", "x");
+    h.wait_status("mock", ServerStatus::Ready).await;
+    let s = h.launcher.state("mock");
+    let gate = Arc::new(Gate::default());
+    *s.initialize_gate.lock() = Some(gate.clone());
+    let id = h.mgr.servers()[0].id;
+    let restart = tokio::spawn({
+        let mgr = h.mgr.clone();
+        async move { mgr.restart(id).await }
+    });
+    eventually(|| gate.entered()).await;
+    let reconfigured = tokio::time::timeout(Duration::from_secs(2), h.mgr.reconfigure()).await;
+    gate.open();
+    reconfigured.expect("a restart still waiting for the server to start must not block reconfigure");
+    restart.await.unwrap().unwrap();
+    assert_eq!(h.mgr.servers()[0].status, ServerStatus::Ready);
+}
+
 #[tokio::test(flavor = "multi_thread")]
 async fn gives_up_after_repeated_crashes_and_manual_restart_works() {
     let h = harness(&[("mock", incremental_caps())]);
@@ -2099,6 +2126,118 @@ async fn gives_up_after_repeated_crashes_and_manual_restart_works() {
     assert_eq!(h.mgr.servers()[0].status, ServerStatus::Ready);
 }
 
+/// One malformed diagnostic costs only itself, not the file's other problems.
+#[tokio::test(flavor = "multi_thread")]
+async fn a_malformed_diagnostic_does_not_drop_the_others() {
+    let h = harness(&[("mock", incremental_caps())]);
+    let (_, path) = h.open("a.mk", "one");
+    h.wait_status("mock", ServerStatus::Ready).await;
+    let uri = uri_of(&path);
+    let range = json!({"start":{"line":0,"character":0},"end":{"line":0,"character":1}});
+    h.launcher
+        .state("mock")
+        .peer()
+        .notify(
+            "textDocument/publishDiagnostics",
+            json!({ "uri": uri, "diagnostics": [
+                { "range": range, "message": "first" },
+                { "message": "no range" },
+                { "range": range, "message": 7 },
+                { "range": range, "message": "last" }] }),
+        )
+        .unwrap();
+    eventually(|| {
+        h.events.lock().iter().any(|e| match e {
+            IdeEvent::Diagnostics { items, .. } => {
+                items.iter().map(|d| d.message.as_str()).collect::<Vec<_>>() == ["first", "last"]
+            }
+            _ => false,
+        })
+    })
+    .await;
+}
+
+/// The `initialize` error is the crash report's reason, not "terminated unexpectedly", and
+/// a server that never gets past `initialize` gives up like any other crash loop.
+#[tokio::test(flavor = "multi_thread")]
+async fn a_failed_initialize_is_reported_with_its_reason_and_gives_up() {
+    let h = harness(&[("mock", incremental_caps())]);
+    let s = h.launcher.state("mock");
+    s.errors.lock().insert("initialize".into(), (-32603, "no workspace".into()));
+    h.open("a.mk", "x");
+    let count = |status| h.statuses("mock").iter().filter(|s| **s == status).count();
+    eventually(|| count(ServerStatus::Crashed) == 4).await;
+    let messages: Vec<String> = h
+        .events
+        .lock()
+        .iter()
+        .filter_map(|e| match e {
+            IdeEvent::LanguageServer { status: ServerStatus::Crashed, message, .. } => message.clone(),
+            _ => None,
+        })
+        .collect();
+    assert!(
+        messages[0].contains("failed to start: initialize failed (server error -32603: no workspace)"),
+        "{messages:?}"
+    );
+    assert!(messages[0].ends_with("Restarting…"));
+    assert!(messages[3].ends_with("restart it manually."), "{messages:?}");
+    tokio::time::sleep(Duration::from_millis(300)).await;
+    assert_eq!(s.launches.load(Ordering::SeqCst), 4, "initial start + 3 restarts");
+}
+
+/// The client tells servers it retries semantic tokens, inlay hints and code lens that they
+/// withdrew with `ContentModified` (`staleRequestSupport`), so it must.
+#[tokio::test(flavor = "multi_thread")]
+async fn withdrawn_editor_decoration_requests_are_asked_again() {
+    let h = harness(&[("mock", incremental_caps())]);
+    let (doc, _) = h.open("a.mk", "let x = 1");
+    h.wait_status("mock", ServerStatus::Ready).await;
+    let s = h.launcher.state("mock");
+    let range = json!({"start":{"line":0,"character":0},"end":{"line":0,"character":1}});
+    let cases = [
+        ("textDocument/semanticTokens/full", json!({ "data": [0, 0, 1, 0, 0] })),
+        ("textDocument/inlayHint", json!([{ "position": {"line":0,"character":0}, "label": "x" }])),
+        ("textDocument/codeLens", json!([{ "range": range, "command": { "title": "t", "command": "c" } }])),
+    ];
+    for (method, answer) in cases {
+        s.errors.lock().insert(method.into(), (-32801, "content modified".into()));
+        let mgr = h.mgr.clone();
+        let request = tokio::spawn(async move {
+            match method {
+                "textDocument/semanticTokens/full" => mgr.semantic_tokens(doc).await.map(|r| r.is_some()),
+                "textDocument/inlayHint" => {
+                    mgr.inlay_hints(doc, Range::new(Pos::new(0, 0), Pos::new(0, 9))).await.map(|v| v.len() == 1)
+                }
+                _ => mgr.code_lens(doc).await.map(|v| v.len() == 1),
+            }
+        });
+        eventually(|| !s.requested(method).is_empty()).await;
+        s.errors.lock().remove(method);
+        s.respond(method, answer);
+        let answered = tokio::time::timeout(Duration::from_secs(5), request).await.unwrap().unwrap();
+        assert!(answered.unwrap_or(false), "{method} was not asked again");
+        assert_eq!(s.requested(method).len(), 2, "{method}");
+    }
+}
+
+/// A server disabled in settings while its crash backoff is still sleeping stays gone: the
+/// pending restart must not bring it back as a process nothing lists or stops.
+#[tokio::test(flavor = "multi_thread")]
+async fn a_server_disabled_during_its_crash_backoff_does_not_restart() {
+    let h = harness(&[("mock", incremental_caps()), ("other", incremental_caps())]);
+    h.open("a.mk", "x");
+    h.wait_status("mock", ServerStatus::Ready).await;
+    let s = h.launcher.state("mock");
+    s.peer().kill();
+    eventually(|| h.statuses("mock").contains(&ServerStatus::Crashed)).await;
+    h.mgr.set_servers_hook(Box::new(|_, configs| configs.iter().filter(|c| c.name == "other").cloned().collect()));
+    h.mgr.reconfigure().await;
+    eventually(|| h.removed("mock")).await;
+    tokio::time::sleep(Duration::from_millis(1200)).await;
+    assert_eq!(s.launches.load(Ordering::SeqCst), 1, "no restart after the server was dropped");
+}
+
 /// The whole workspace root deleted: the server can never start again
 /// (its cwd is gone), so the crash drops the entry instead of restarting.
 #[tokio::test(flavor = "multi_thread")]
@@ -2997,6 +3136,49 @@ async fn fallback_servers_only_run_when_the_preferred_one_is_missing() {
     assert!(h.mgr.hover(doc, Pos::new(0, 0), Default::default()).await.is_ok());
 }
 
+/// A server that is installed but cannot run (crashed for good, or its configuration
+/// can't launch it) hides its fallbacks no longer than one that is missing.
+#[tokio::test(flavor = "multi_thread")]
+async fn fallback_servers_take_over_from_a_preferred_one_that_crashed_for_good() {
+    let h = harness_with_fallbacks(&[("main", incremental_caps()), ("alt", incremental_caps())], &["alt"]);
+    let (doc, path) = h.open("a.mk", "x");
+    let main = h.launcher.state("main");
+    let count = |status| h.statuses("main").iter().filter(|s| **s == status).count();
+    for n in 1..=4 {
+        eventually(|| count(ServerStatus::Ready) == n).await;
+        // Restarting after a crash is not giving up: the fallback stays away.
+        assert!(h.statuses("alt").is_empty(), "alt started after crash {}", n - 1);
+        main.peer().kill();
+        eventually(|| count(ServerStatus::Crashed) == n).await;
+    }
+    h.wait_status("alt", ServerStatus::Ready).await;
+    let uri = uri_of(&path);
+    eventually(|| h.launcher.state("alt").docs.lock().contains_key(&uri)).await;
+    assert!(h.mgr.hover(doc, Pos::new(0, 0), Default::default()).await.is_ok());
+
+    // Restarting the preferred one by hand gives the documents back to it.
+    let id = h.mgr.servers().into_iter().find(|s| s.name == "main").unwrap().id;
+    h.mgr.restart(id).await.unwrap();
+    eventually(|| h.removed("alt")).await;
+    assert_eq!(h.mgr.servers().iter().filter(|s| s.name == "alt").count(), 0);
+}
+
+#[tokio::test(flavor = "multi_thread")]
+async fn fallback_servers_take_over_from_a_preferred_one_that_cannot_be_launched() {
+    let h = harness_with_fallbacks(&[("main", incremental_caps()), ("alt", incremental_caps())], &["alt"]);
+    h.mgr.set_config_hook(Box::new(|cfg, _| {
+        if cfg.name == "main" {
+            cfg.launch_error = Some("needs JDK 21".into());
+        }
+    }));
+    let (doc, path) = h.open("a.mk", "x");
+    h.wait_status("main", ServerStatus::Misconfigured).await;
+    h.wait_status("alt", ServerStatus::Ready).await;
+    let uri = uri_of(&path);
+    eventually(|| h.launcher.state("alt").docs.lock().contains_key(&uri)).await;
+    assert!(h.mgr.hover(doc, Pos::new(0, 0), Default::default()).await.is_ok());
+}
+
 #[tokio::test(flavor = "multi_thread")]
 async fn a_server_requiring_a_root_marker_serves_only_files_below_one() {
     // `framework` next to `main` (one instance for the whole project), like the

crates/ide-lsp/tests/real_servers.rs

@@ -426,6 +426,7 @@ async fn missing_binary_is_reported_with_install_hint() {
         tsserver_project: false,
         tsserver_project_extras: Default::default(),
         resync_on_configuration: false,
+        display_name: None,
         pinned: None,
     };
     let (mgr, events) = manager(dir.path(), LanguageRegistry::from_configs(vec![lang("nope", "nope", server)]));
@@ -698,6 +699,7 @@ async fn typescript_language_server_end_to_end() {
         tsserver_project: false,
         tsserver_project_extras: Default::default(),
         resync_on_configuration: false,
+        display_name: None,
         pinned: None,
     };
     let (mgr, events) = manager(&root, LanguageRegistry::from_configs(vec![lang("typescript", "ts", server)]));
@@ -750,6 +752,7 @@ fn npm_server(tools: &Path, name: &str, bin: &str, init: Option<serde_json::Valu
         tsserver_project: false,
         tsserver_project_extras: Default::default(),
         resync_on_configuration: false,
+        display_name: None,
         pinned: None,
     }
 }

crates/ide-plugin/tests/fixtures/api14/dist/plugin.wasm.sources

@@ -1 +1 @@
-e616b87b24371581ad648f9c7072259de7732d122b5887b488f7bd480ebd69c2
+0b77e7a414ec3b0dd1f41e5658b981f059dd842743dbe2f06e5d428f5b9570f9

crates/ide-plugin/tests/fixtures/commit/dist/plugin.wasm.sources

@@ -1 +1 @@
-75eeecc467bff141bda14f1f080633348af348f7259e793be81e6548d2008669
+6f7d6527837c8e5c86c377479cceef5116decd61666b28f36dd11332e36e9934

crates/ide-plugin/tests/fixtures/data-tools/dist/plugin.wasm.sources

@@ -1 +1 @@
-4aaf7754e895f022d34dad05bd2b8018e3a61ba18771b8c95d9f070cb212530c
+c1ac86a5b4d45b55013e6e00dcb83deda33b759ecc366c3fdf57739bdd22cbff

crates/ide-plugin/tests/fixtures/detail-views/dist/plugin.wasm.sources

@@ -1 +1 @@
-e573144879a7caa0975e17b233476eb317ff54bef23fd8fa64280d3649bad700
+e4d8d8f5f5849b912b2c0ebee6b91d60796c3070929d7698323e8ce4f200a38a

crates/ide-plugin/tests/fixtures/diagnostics/dist/plugin.wasm.sources

@@ -1 +1 @@
-36dd40ef751a617f1ad59491312889c12481b05666e580f21f7c2552df76edbc
+e2e2fc44ad9cae9cf26a5bf706768d3786502f23db6994dc29695deb249ed73f

crates/ide-plugin/tests/fixtures/endpoints/dist/plugin.wasm.sources

@@ -1 +1 @@
-724ed3bbd828e4fc1925c1b555bdaec9268633cb587806a661f8838e5a540545
+61e1f0c43bbfddc35dcf40685169eb273777ddca13da534626e1699b47e8eac3

crates/ide-plugin/tests/fixtures/execution/dist/plugin.wasm.sources

@@ -1 +1 @@
-1a3685234f1b3b0957184c44c603c0eefe7e3084b88d0df32da268b29292ee92
+2ea1c1693db8638db996c9c47597f0c1635ef0a9c7dfb33685c515b7af95e6a6

crates/ide-plugin/tests/fixtures/ext-owner/dist/plugin.wasm.sources

@@ -1 +1 @@
-4283de821d69a18438f58062e4bc28b63ba5025cc5f9fa51f21ff475b677a6a5
+3c788f6092b229484a5d94fd0e6f4651afc88dd0ab1b22b067d84614a6a0c85e

crates/ide-plugin/tests/fixtures/file-templates/dist/plugin.wasm.sources

@@ -1 +1 @@
-0f25487b8e488e5ec01fabd2951bdb03d80bc26e4e9aa508394a7f9cd09d1759
+18273599cc459833d6a30185a5f0ba127cdb4e22bc054a973571e530eb3a85ca

crates/ide-plugin/tests/fixtures/files-events/dist/plugin.wasm.sources

@@ -1 +1 @@
-80f9dc28e4f168dd22ccee1c53e1f6b08c446622eb10f07de29be5fc45e9fb1c
+c9fafba362fa0745d7ee1685efe5582d432510003c04c98100eddd557bd1e2cf

crates/ide-plugin/tests/fixtures/grouped-views/dist/plugin.wasm.sources

@@ -1 +1 @@
-5355cb4ef373eba3c54806eb00294fcd5fccb3cf05dae3e1c2a4ad45ab958f03
+4121009913709edeca8c5cb52d88dfcc2b16867bc06859768f73c17cf9c456a2

crates/ide-plugin/tests/fixtures/hello/dist/plugin.wasm.sources

@@ -1 +1 @@
-fc75ede42e6db7619fa28fc8999f091d39e3c1ed401356db3a3f07de54287c99
+b55bd202a06f5643c4f70abb6fb473fbe53af657f4e21a6d13581a23a726e085

crates/ide-plugin/tests/fixtures/hover/dist/plugin.wasm.sources

@@ -1 +1 @@
-8793601496f1727cf912e4cdf86ec48fc340a17585098e98dee52a125cb8a16d
+11a12228df67f9b94bd52375b5dddb2d955f7e5f88d7f9ea0a430b1db128f6ca

crates/ide-plugin/tests/fixtures/indexer/dist/plugin.wasm.sources

@@ -1 +1 @@
-fb2db14a645cad42941d20a25a3ff87ca6fdee635fdb40953383ff30ce16af8a
+553ce6c57052f8ff2ea2526e88762d5a0aee2489cda192fc7ab708766078ccf7

crates/ide-plugin/tests/fixtures/inlay-hints/dist/plugin.wasm.sources

@@ -1 +1 @@
-fc66b3b56a1ab1c9d547e3efe6bb4693dca908bb18be8b8ebd26f2fb41e4436c
+7b43f8a2a06d7b2952f8d46727a4cce524fb2bdecee1035dad9c767261d276d0

crates/ide-plugin/tests/fixtures/jobs/dist/plugin.wasm.sources

@@ -1 +1 @@
-c76830df9dee3caba932ffaddaabce88ac7ef23b3957b3e8e570b4939dd58d9d
+e994c69fda5eef94ae85d6dac5aec3d04fb6811c35c446c9d33236a449bd1c6c

crates/ide-plugin/tests/fixtures/language-features/dist/plugin.wasm.sources

@@ -1 +1 @@
-3a41a06d54939a9e85fcf6b0bf15b336f928a3caf66576bd2da62c5b8b177c1d
+c37f6a7ea9018ca636d0fd486a9d91cd397158615410de9b837ca9b8f9f593b7

crates/ide-plugin/tests/fixtures/misbehave/dist/plugin.wasm.sources

@@ -1 +1 @@
-f30a8c0a7893519872628c001314efd567f87f4dfaf718a737ea3631b55881b0
+1b298dfa5c1f2163d609ef0ccc3d42fafe78e69326002effe53abc4b82974749

crates/ide-plugin/tests/fixtures/path-events/dist/plugin.wasm.sources

@@ -1 +1 @@
-cb65533984ffd8684c9e9f5ddeef92a8f387735c12310b25282ee7bbf2d73cd7
+1e11a95e0909d18308d21a9a8448f8b2e427d240d5d8cd13d8ddbe6ba5009237

crates/ide-plugin/tests/fixtures/private-dir/dist/plugin.wasm.sources

@@ -1 +1 @@
-d11f9cb1130f3f3aaa89514bf47ec8ece9b2ca0edf1d82c11f80b262325f16be
+d5cd77130cc97cffdbc742f04e3e1196f14160107b636806c6ef3c9b40724e84

crates/ide-plugin/tests/fixtures/semantic-tokens/dist/plugin.wasm.sources

@@ -1 +1 @@
-48ea4414469ebd70a89da8a5df7b7bddc4d32f5c50f1759ee3cea14558073c92
+a0f74430b0a7d9ff48524d7aae4f8a0bd0fc60511e2a951dde9991b9bf7d15a9

crates/ide-plugin/tests/fixtures/settings-pages/dist/plugin.wasm.sources

@@ -1 +1 @@
-0c02303182be04ed3776fb532fd8b72e6057aa0fdb92b7d235000146fef4120e
+65508f6e25bd0efc85820ae7d0f9037b58c778fa61e8498c5b9a5055cc38f6fc

crates/ide-plugin/tests/fixtures/storage/dist/plugin.wasm.sources

@@ -1 +1 @@
-8162a70e848172663463119e6357984a73e54bc71a99b2845621d0733cf9333e
+c86ed41d68c132f72eb8b5794f31b975492e5ad42e41b7823d1bf28ba118a262

crates/ide-plugin/tests/fixtures/symbols/dist/plugin.wasm.sources

@@ -1 +1 @@
-4524cab0ceac631153a945f6b76f7d40efd3c854740ae22c64580381e9532397
+3da1a09906d803234016b3f9c30a88b9b40bf3187fc73840ff60a2e05f504b48