fix(terminal): write process input off the UI thread (#2183)

A child that stopped reading its input could freeze the whole window, because terminal input was written synchronously on the UI thread. Terminal, Run and debug stdin now share a per-session ordered writer queue bounded to 4 MiB and 1,024 writes. An overflow rejects the whole write and shows an error; closing or killing a session discards pending input without waiting for the child, and an explicit stdin EOF drains accepted writes first.

Refs #2160

src/features/run/store.ts

@@ -1257,7 +1257,7 @@ export async function sendStdin(sessionId: string, text: string): Promise<void>
   } catch (e) {
     enqueue(sessionId, {
       kind: "system",
-      text: tx`Cannot write to stdin: ${e instanceof Error ? e.message : String(e)}\n`,
+      text: tx`Cannot write to stdin: ${e instanceof Error ? tx(e.message) : String(e)}\n`,
     });
   }
 }
@@ -1266,7 +1266,12 @@ export async function sendStdin(sessionId: string, text: string): Promise<void>
 export function writeTerminal(sessionId: string, data: string) {
   const session = getSession(sessionId);
   if (!session || session.runId === null || session.status !== "running") return;
-  void call(commands.runStdin(session.runId, data)).catch(() => undefined);
+  void call(commands.runStdin(session.runId, data)).catch((e) => {
+    enqueue(sessionId, {
+      kind: "system",
+      text: tx`Cannot write to stdin: ${e instanceof Error ? tx(e.message) : String(e)}\n`,
+    });
+  });
 }
 
 /** The terminal console's size in cells; the process's terminal follows it. */

src/features/terminal/session.test.ts

@@ -16,6 +16,7 @@ const ipc = vi.hoisted(() => ({
     termKill: vi.fn(),
     termResize: vi.fn(),
     termIsBusy: vi.fn(),
+    termWrite: vi.fn(),
   },
 }));
 const workbench = vi.hoisted(() => ({
@@ -122,6 +123,27 @@ describe("resolveStartCwd", () => {
 describe("terminal start directory fallback", () => {
   beforeEach(() => vi.clearAllMocks());
 
+  it("shows rejected terminal input instead of silently discarding it", async () => {
+    ipc.commands.termSpawn.mockResolvedValue({ id: 9, title: "zsh" });
+    ipc.commands.termWrite.mockRejectedValueOnce(new Error("input queue full"));
+    const session = new TerminalSession({
+      key: "s-input-error",
+      cwd: "/repo",
+      onChange: () => undefined,
+      onFocus: () => undefined,
+    });
+    await session.start();
+    session.input("paste");
+    await vi.waitFor(() =>
+      expect(workbench.notify).toHaveBeenCalledWith({
+        level: "error",
+        title: "Cannot write to terminal",
+        body: "input queue full",
+      }),
+    );
+    session.dispose();
+  });
+
   it("spawns a restored session in the project root when its saved directory is gone", async () => {
     ipc.commands.fsEntryKind.mockRejectedValue(new Error("gone"));
     ipc.commands.termSpawn.mockResolvedValue({ id: 7, title: "zsh" });

src/features/terminal/session.ts

@@ -9,6 +9,7 @@ import { SearchAddon, type ISearchOptions } from "@xterm/addon-search";
 import "@xterm/xterm/css/xterm.css";
 import { Channel } from "@tauri-apps/api/core";
 import { call, commands, isTauri, type TerminalId } from "@/platform/ipc";
+import { tx } from "@/platform/i18n";
 import { editorService, notifications, registerFontZoomSurface } from "@/workbench/contributions";
 import { fitScheduler, settledResize } from "./fit";
 import { installTerminalDrop } from "./drop";
@@ -658,14 +659,20 @@ export class TerminalSession {
       this.pendingInput += data;
       return;
     }
-    void commands.termWrite(this.ptyId, data);
+    void call(commands.termWrite(this.ptyId, data)).catch((error) => {
+      notifications().notify({
+        level: "error",
+        title: tx("Cannot write to terminal"),
+        body: error instanceof Error ? tx(error.message) : String(error),
+      });
+    });
   }
 
   /** Sends keystrokes buffered while the PTY was starting. */
   private flushPendingInput() {
     const queued = this.pendingInput;
     this.pendingInput = "";
-    if (queued && this.ptyId !== null) void commands.termWrite(this.ptyId, queued);
+    if (queued && this.ptyId !== null) this.input(queued);
   }
 
   /** Writes input immediately (shortcuts translated outside xterm). */