feat(agents): environment variables for built-in agents (#1157)

Settings › Tools › Agents › Built-in has an Environment variables field under the executable. They are saved in the agent's file like a command override, and the agent starts with them on top of the shell environment, replacing variables of the same name. Changing the command or the environment keeps the other; a file left with only the built-in's values is removed.

Closes #1133

src/features/agents/BuiltinAgents.tsx

@@ -93,6 +93,14 @@ function Details({
     onChanged?.();
     return command === agent.defaultProgram ? "" : (command ?? "");
   });
+  const envBase = formatEnv(agent.env);
+  const env = form.useExternal(`agents.${agent.id}.env`, envBase, async (draft) => {
+    const parsed = parseEnv(draft);
+    await backend.setEnv(agent.id, parsed);
+    await refresh();
+    onChanged?.();
+    return formatEnv(parsed);
+  });
   const [error, setError] = useState<string | null>(null);
   // An edit can have been staged by a previous page instance. Its Apply callback
   // refreshes that instance; the mounted one follows the newly applied value too.
@@ -174,6 +182,26 @@ function Details({
           )}
         </p>
       )}
+      {agent.commandReadOnlyReason !== "registry" && agent.commandReadOnlyReason !== "customAgent" && (
+        <>
+          <label className={styles.label} htmlFor={`agent-env-${agent.id}`}>
+            <T>Environment variables</T>
+          </label>
+          <div className={styles.controls}>
+            <Input
+              id={`agent-env-${agent.id}`}
+              mono
+              value={env.value}
+              disabled={env.saving}
+              placeholder="NAME=value; OTHER=value"
+              onChange={(e) => env.set(e.target.value)}
+            />
+          </div>
+          <p className={styles.hint}>
+            <T>Passed to the agent process, replacing variables of the same name. Changes apply to new sessions.</T>
+          </p>
+        </>
+      )}
       {agent.loginHint && (
         <>
           <h4 className={styles.section}>
@@ -193,6 +221,25 @@ function Details({
   );
 }
 
+/** `NAME=value` pairs separated by `;` or new lines. */
+function parseEnv(text: string): Record<string, string> {
+  const env: Record<string, string> = {};
+  for (const raw of text.split(/[;\n]/)) {
+    const pair = raw.trim();
+    if (!pair) continue;
+    const eq = pair.indexOf("=");
+    const key = eq < 0 ? "" : pair.slice(0, eq).trim();
+    if (!/^[A-Za-z_][A-Za-z0-9_]*$/.test(key)) throw new Error(tx`Expected NAME=value: ${pair}`);
+    env[key] = pair.slice(eq + 1).trim();
+  }
+  return env;
+}
+
+const formatEnv = (env: Record<string, string>) =>
+  Object.entries(env)
+    .map(([k, v]) => `${k}=${v}`)
+    .join("; ");
+
 /** Login hints are plain text with optional backtick-delimited command spans. */
 function LoginHint({ text }: { text: string }) {
   const translate = useTx();

src/features/agents/agentRegistry.test.tsx

@@ -145,6 +145,7 @@ describe("agent picker", () => {
     commandEditable: true,
     commandReadOnlyReason: null,
     installed: true,
+    env: {},
     config: [],
     commands: [],
     ...p,
@@ -312,6 +313,11 @@ class FakeCommands implements CommandsBackend {
   saved: [string, string | null][] = [];
   providers = vi.fn(async () => this.list);
   chooseExecutable = vi.fn(async () => "/chosen/agent");
+  savedEnv: [string, Record<string, string>][] = [];
+  async setEnv(id: string, env: Record<string, string>) {
+    this.savedEnv.push([id, env]);
+    this.list = this.list.map((p) => (p.id === id ? { ...p, env } : p));
+  }
   async set(id: string, command: string | null) {
     this.saved.push([id, command]);
     // What the agent list shows after the override takes effect.
@@ -341,6 +347,7 @@ const claudeProvider = (command: string): AgentProvider => ({
   commandEditable: true,
   commandReadOnlyReason: null,
   installed: true,
+  env: {},
   config: [],
   commands: [],
   source: { kind: "builtin" },
@@ -436,6 +443,23 @@ describe("Built-in executable overrides", () => {
     } else expect(screen.queryByRole("dialog")).toBeNull();
   });
 
+  it("writes the agent's environment variables on Apply and shows them again", async () => {
+    const commands = new FakeCommands();
+    commands.list = [claudeProvider("claude")];
+    await openCommands(commands);
+    const env = () => screen.getByRole("textbox", { name: "Environment variables" });
+    fireEvent.change(env(), { target: { value: "CLAUDE_CODE_ENTRYPOINT=openidea; HTTPS_PROXY=http://proxy:8080" } });
+    expect(commands.savedEnv).toEqual([]);
+    await act(async () => fireEvent.click(apply()));
+    expect(commands.savedEnv).toEqual([
+      ["claude", { CLAUDE_CODE_ENTRYPOINT: "openidea", HTTPS_PROXY: "http://proxy:8080" }],
+    ]);
+    expect(env()).toHaveValue("CLAUDE_CODE_ENTRYPOINT=openidea; HTTPS_PROXY=http://proxy:8080");
+    fireEvent.change(env(), { target: { value: "" } });
+    await act(async () => fireEvent.click(apply()));
+    expect(commands.savedEnv.at(-1)).toEqual(["claude", {}]);
+  });
+
   it("Cancel discards command edits without writing", async () => {
     const commands = new FakeCommands();
     commands.list = [

src/features/agents/composerCommands.test.tsx

@@ -50,6 +50,7 @@ const claude: AgentProvider = {
   commandOverridden: false,
   commandEditable: true,
   commandReadOnlyReason: null,
+  env: {},
   // Offered by the agent's last session in this project.
   commands: [command("compact", "Free up context")],
 };

src/features/agents/registry.ts

@@ -22,6 +22,7 @@ export interface RegistryBackend {
 export interface CommandsBackend {
   providers(): Promise<AgentProvider[]>;
   set(id: string, command: string | null): Promise<void>;
+  setEnv(id: string, env: Record<string, string>): Promise<void>;
   chooseExecutable(title: string, current?: string): Promise<string | null>;
 }
 
@@ -47,6 +48,9 @@ export const tauriCommands: CommandsBackend = {
   set: async (id, command) => {
     await call(commands.agentSetCommand(id, command));
   },
+  setEnv: async (id, env) => {
+    await call(commands.agentSetEnv(id, env));
+  },
 };
 
 export const DISTRIBUTION_LABEL: Record<RegistryDistribution, string> = {