fix(exec): explain Session workspace mismatches instead of suggesting a retry

packages/code-sdk-python/README.md

@@ -40,14 +40,26 @@ async def main() -> None:
     # Same Session, next Turn.
     turn = await thread.run("Now list its top-level directories.")
 
-    # Persist thread.id and continue later.
-    later = client.resume_thread(thread.id)
+    # Persist thread.id and continue later, in the same workspace.
+    later = client.resume_thread(thread.id, ThreadOptions(cwd="."))
     print((await later.run("What did I ask first?")).final_response)
 
 
 asyncio.run(main())
 ```
 
+### Resuming a Session
+
+A Session belongs to the workspace it was created in. Pass the same `cwd` to `resume_thread()`;
+when `cwd` is omitted, the current working directory is used. A different workspace fails with
+`MCodeRunError` ("Session ... belongs to workspace ..."), and retrying does not help.
+
+```python
+thread = client.start_thread(ThreadOptions(cwd="/path/to/project"))
+await thread.run("...")
+later = client.resume_thread(thread.id, ThreadOptions(cwd="/path/to/project"))
+```
+
 ### Streaming
 
 ```python

packages/code-sdk-python/src/minimax_code/client.py

@@ -33,7 +33,12 @@ def start_thread(self, options: ThreadOptions | None = None) -> Thread:
         return Thread(self._host, options, None)
 
     def resume_thread(self, thread_id: str, options: ThreadOptions | None = None) -> Thread:
-        """Continues an existing Session, for example one persisted from ``thread.id``."""
+        """Continues an existing Session, for example one persisted from ``thread.id``.
+
+        Pass the same ``ThreadOptions.cwd`` the Session was created with. When ``cwd`` is omitted
+        the current working directory is used, and the CLI rejects a Session whose workspace
+        differs (``MCodeRunError`` with "belongs to workspace ...").
+        """
         if not isinstance(thread_id, str) or not thread_id.strip():
             raise MCodeInvocationError("resume_thread requires a non-empty Session id.")
         options = options or ThreadOptions()

packages/code-sdk-python/src/minimax_code/sync.py

@@ -48,6 +48,8 @@ def start_thread(self, options: ThreadOptions | None = None) -> SyncThread:
         return SyncThread(self._loop, self._client.start_thread(options))
 
     def resume_thread(self, thread_id: str, options: ThreadOptions | None = None) -> SyncThread:
+        """Continues an existing Session; pass the ``cwd`` it was created with (see
+        ``MCode.resume_thread``)."""
         return SyncThread(self._loop, self._client.resume_thread(thread_id, options))
 
     def close(self) -> None:

packages/tui/src/headless/error-presentation.ts

@@ -20,6 +20,7 @@ export function formatTuiExecFailure(error: TuiExecError): string {
   }
   if (error.kind === 'runtime') {
     if (isOutputLimitExhaustedFailure(error.message)) return OUTPUT_LIMIT_EXHAUSTED_GUIDANCE;
+    if (!error.retryable) return asSentence(`The run failed: ${tuiErrorDiagnostic(error)}`);
     return `The run failed: ${tuiErrorDiagnostic(error)}. Retry after the connection recovers.`;
   }
   return `MCode encountered an internal error: ${tuiErrorDiagnostic(error)}. Retry; if it keeps happening, report it through an available support channel.`;
@@ -43,5 +44,10 @@ export function formatTuiExecResultFailure(result: ExecResult): string {
   }
   if (isOutputLimitExhaustedFailure(result.error?.message)) return OUTPUT_LIMIT_EXHAUSTED_GUIDANCE;
   const reason = result.error?.message ? `: ${tuiErrorDiagnostic(result.error.message)}` : '';
+  if (result.error?.retryable === false) return asSentence(`The run failed${reason}`);
   return `The run failed${reason}. Retry after the connection recovers.`;
 }
+
+function asSentence(value: string): string {
+  return /[.!?…]$/u.test(value) ? value : `${value}.`;
+}

packages/tui/src/headless/exit-policy.ts

@@ -18,11 +18,16 @@ export type TuiExecErrorKind = keyof Pick<
   'invocation' | 'config' | 'runtime' | 'internal' | 'cancelled' | 'brokenPipe'
 >;
 
+export interface TuiExecErrorOptions extends ErrorOptions {
+  /** Defaults to true for runtime errors. Set false when retrying cannot succeed. */
+  readonly retryable?: boolean;
+}
+
 export class TuiExecError extends TuiFailure {
   constructor(
     public readonly kind: TuiExecErrorKind,
     message: string,
-    options?: ErrorOptions,
+    options?: TuiExecErrorOptions,
   ) {
     super(kind, message, {
       code: `exec.${kind}`,

packages/tui/src/headless/runner.ts

@@ -898,7 +898,8 @@ async function resolveSession(
     if (!session) {
       throw new TuiExecError(
         "runtime",
-        `No active Session exists for workspace ${input.workspaceDir}.`,
+        `No active Session exists for workspace ${input.workspaceDir}; omit --continue to start a new Session.`,
+        { retryable: false },
       );
     }
     assertSessionUsable(session, input.workspaceDir);
@@ -946,16 +947,23 @@ function assertSessionUsable(session: TuiSession, workspaceDir: string): void {
   if (session.archived) {
     throw new TuiExecError(
       "runtime",
-      `Session is archived: ${session.sessionId}`,
+      `Session ${session.sessionId} is archived; unarchive it in MCode or start a new Session.`,
+      { retryable: false },
     );
   }
-  if (
-    !session.workspaceDir ||
-    !sameWorkspace(session.workspaceDir, workspaceDir)
-  ) {
+  if (!session.workspaceDir) {
     throw new TuiExecError(
       "runtime",
-      `Session workspace does not match --cwd: ${session.sessionId}`,
+      `Session ${session.sessionId} has no recorded workspace and cannot be continued.`,
+      { retryable: false },
+    );
+  }
+  if (!sameWorkspace(session.workspaceDir, workspaceDir)) {
+    // Retrying cannot succeed: a Session only continues in the workspace it was created in.
+    throw new TuiExecError(
+      "runtime",
+      `Session ${session.sessionId} belongs to workspace ${session.workspaceDir}, not --cwd ${workspaceDir}; rerun with --cwd ${session.workspaceDir}.`,
+      { retryable: false },
     );
   }
 }

packages/tui/test/unit/headless-runner.test.ts

@@ -5,6 +5,7 @@ import { join } from 'node:path';
 
 import { describe, expect, it, vi } from 'vitest';
 
+import { formatTuiExecResultFailure } from '../../src/headless/error-presentation.js';
 import { runTuiExec } from '../../src/headless/runner.js';
 import type { TuiMessage, TuiStreamEvent } from '../../src/runtime/stream-events.js';
 
@@ -1316,3 +1317,55 @@ describe('runTuiExec', () => {
     expect(runtime.sendMessage).not.toHaveBeenCalled();
   });
 });
+
+describe('runTuiExec Session guidance', () => {
+  async function run(input: { sessionId?: string; continueSession?: boolean }, runtime: ReturnType<typeof runtimeWith>) {
+    const stderr = vi.fn();
+    const code = await runTuiExec(
+      { prompt: 'Fix it', workspaceDir: '/tmp/workspace', version: '0.1.0', ...input },
+      { runtime, stdout: vi.fn(), stderr, shutdown: async () => undefined },
+    );
+    return { code, stderr: stderr.mock.calls.map(([line]) => line).join('') };
+  }
+
+  it('names the Session workspace on a --cwd mismatch instead of suggesting a retry', async () => {
+    const runtime = runtimeWith();
+    runtime.getSession.mockResolvedValue({ sessionId: 'session-1', workspaceDir: '/tmp/other', archived: false } as never);
+
+    const { code, stderr } = await run({ sessionId: 'session-1' }, runtime);
+
+    expect(code).toBe(4);
+    expect(stderr).toBe(
+      'mcode exec failed: The run failed: Session session-1 belongs to workspace /tmp/other, not --cwd /tmp/workspace; rerun with --cwd /tmp/other.\n',
+    );
+    expect(runtime.sendMessage).not.toHaveBeenCalled();
+  });
+
+  it('does not suggest a retry for archived Sessions or a missing --continue target', async () => {
+    const archived = runtimeWith();
+    archived.getSession.mockResolvedValue({ sessionId: 'session-1', workspaceDir: '/tmp/workspace', archived: true } as never);
+    const missing = runtimeWith();
+
+    const results = [await run({ sessionId: 'session-1' }, archived), await run({ continueSession: true }, missing)];
+
+    expect(results.map((result) => result.code)).toEqual([4, 4]);
+    expect(results[0]?.stderr).toBe(
+      'mcode exec failed: The run failed: Session session-1 is archived; unarchive it in MCode or start a new Session.\n',
+    );
+    expect(results[1]?.stderr).toBe(
+      'mcode exec failed: The run failed: No active Session exists for workspace /tmp/workspace; omit --continue to start a new Session.\n',
+    );
+    for (const result of results) expect(result.stderr).not.toContain('Retry');
+  });
+
+  it('keeps the retry hint only for retryable failed results', () => {
+    const failed = (retryable: boolean | undefined) => formatTuiExecResultFailure({
+      status: 'failed',
+      error: { category: 'runtime', message: 'Upstream disconnected', ...(retryable === undefined ? {} : { retryable }) },
+    } as never);
+
+    expect(failed(true)).toBe('The run failed: Upstream disconnected. Retry after the connection recovers.');
+    expect(failed(undefined)).toBe('The run failed: Upstream disconnected. Retry after the connection recovers.');
+    expect(failed(false)).toBe('The run failed: Upstream disconnected.');
+  });
+});