diff --git a/docs/api-reference.md b/docs/api-reference.md
index 00e64663..38441dfd 100644
--- a/docs/api-reference.md
+++ b/docs/api-reference.md
@@ -1185,10 +1185,10 @@ Closing the session detaches. The foreign session keeps running, and only Codema
 wrapper and its grouped `codeman-view-<id>` session go, so `DELETE` removes nothing that
 belongs to someone else. Codeman did not start this agent, so these refuse an adopted
 session: respawn, Ralph (its config and the `fix-plan/write`, `fix-plan/read` and
-`ralph-prompt/write` file routes), auto-clear, auto-compact, auto-resume, custom model
-endpoints, prompt uploads and the image watcher. `stop` waits are a 400, and so are
-`blocked` waits unless Codeman reads that CLI's dialogs off its screen (codex), the git
-routes answer `unsupported` with `reason: "adopted"`, and
+`ralph-prompt/write` file routes), one-shot `POST .../run`, auto-clear, auto-compact,
+auto-resume, custom model endpoints, prompt uploads and the image watcher. `stop` waits
+are a 400, and so are `blocked` waits unless Codeman reads that CLI's dialogs off its
+screen (codex), the git routes answer `unsupported` with `reason: "adopted"`, and
 `last-response` answers empty, since Codeman knows no transcript for it. Its `paneExit`
 stays absent, because the pane holds a `tmux attach` and not the agent. Reboot restore
 does not rebuild one. A wrapper that cannot start answers `OPERATION_FAILED` and leaves
diff --git a/docs/architecture-invariants.md b/docs/architecture-invariants.md
index 90238859..dcc39f7b 100644
--- a/docs/architecture-invariants.md
+++ b/docs/architecture-invariants.md
@@ -109,7 +109,7 @@ Input arriving during a wake is buffered: a chunk over 4 KB is dropped whole, ne
 
 **No workspace.** ⚠️ An adopted session keeps its connection on `adopt.remote`/`adopt.docker`, so `session.remote` and `session.docker` are undefined, and its `workingDir` is the neutral `/tmp`. Code that branches on those two reads an in-container or over-ssh adoption as a local session working in `/tmp`. So anything that treats `workingDir` as the session's workspace must also test `session.isAdopted` (`adopt` on a pure view): uploads, the upload GC, git status, git fetch and its scheduler, the image watcher, Read My Mind's git signals, the Discord folder, `last-response`, guarded input and Ralph's `@fix_plan.md` and `@ralph_prompt.md` routes all do. The file surfaces (Files panel, File Viewer and its edit mode) still treat `/tmp` as the workspace, which is harmless: it is world-writable anyway, and adoption is admin-only in multi-user mode. A wrapper reports `statusLineExporter: 'remote'`, which is also what keeps keep-warm off it.
 
-**Lifecycle.** `paneExitApplies` is false for a wrapper, so an attach that ended is never `paneExit` and the sweep never closes the tab. Boot recovery re-attaches a dead wrapper, which prints that the session is gone and exits. Reboot restore refuses one, since all Codeman ever had was an attach command. ⚠️ A wrapper that cannot start fails the start, and selecting the tab tries it again (`_failAdoptedStart()`). It never takes the direct-PTY fallback, which would run a new local `claude --dangerously-skip-permissions` or a server-account shell in `/tmp` under the foreign session's name.
+**Lifecycle.** `paneExitApplies` is false for a wrapper, so an attach that ended is never `paneExit` and the sweep never closes the tab. Boot recovery re-attaches a dead wrapper, which prints that the session is gone and exits. Reboot restore refuses one, since all Codeman ever had was an attach command. ⚠️ A wrapper that cannot start fails the start, and selecting the tab tries it again (`_failAdoptedStart()`). It never takes the direct-PTY fallback, which would run a new local `claude --dangerously-skip-permissions` or a server-account shell in `/tmp` under the foreign session's name, and `runPrompt()` refuses it for the same reason.
 
 ### Docker cases
 
diff --git a/src/session.ts b/src/session.ts
index 5bc1176c..c08a069e 100644
--- a/src/session.ts
+++ b/src/session.ts
@@ -4581,6 +4581,8 @@ export class Session extends EventEmitter {
     prompt: string,
     options?: { model?: string; onProgress?: (info: { tokens?: number; status?: string }) => void }
   ): Promise<{ result: string; cost: number }> {
+    // ⚠️ A one-shot `claude -p` is a new local process in `/tmp`, never the agent in that pane.
+    if (this._adopt) throw new Error('One-shot prompts are not available for adopted sessions');
     if (this.guardedInputHeld) {
       this._guardedInputRevision++;
       throw new Error('Guarded submission in progress');
diff --git a/src/web/routes/session-routes.ts b/src/web/routes/session-routes.ts
index ca0b86ca..1838e40c 100644
--- a/src/web/routes/session-routes.ts
+++ b/src/web/routes/session-routes.ts
@@ -2070,6 +2070,15 @@ export function registerSessionRoutes(
     const { prompt } = parseBody(RunPromptSchema, req.body);
     const session = findSessionOrFail(ctx, id, req);
 
+    // Its own check: `runPrompt` starts a new local claude, and the answer has to say so
+    // here rather than as a `session:error` after a success.
+    if (session.isAdopted) {
+      return createErrorResponse(
+        ApiErrorCode.INVALID_INPUT,
+        'One-shot prompts are not available for adopted sessions: Codeman did not start this agent'
+      );
+    }
+
     if (session.isBusy()) {
       return createErrorResponse(ApiErrorCode.SESSION_BUSY, 'Session is busy');
     }
diff --git a/test/foreign-adoption-guards.test.ts b/test/foreign-adoption-guards.test.ts
index bed71d24..2e5605aa 100644
--- a/test/foreign-adoption-guards.test.ts
+++ b/test/foreign-adoption-guards.test.ts
@@ -251,4 +251,10 @@ describe('the direct-PTY fallback', () => {
     await expect(s[start]()).rejects.toThrow(/tmux/);
     expect(ptySpawn).not.toHaveBeenCalled();
   });
+
+  it('refuses a one-shot prompt, a new local claude rather than the agent in that pane', async () => {
+    const { s } = session('claude', { adopt });
+    await expect(s.runPrompt('hello')).rejects.toThrow(/adopted/i);
+    expect(ptySpawn).not.toHaveBeenCalled();
+  });
 });
diff --git a/test/routes/foreign-adoption-routes.test.ts b/test/routes/foreign-adoption-routes.test.ts
index 7ca8c0a2..4ba4aec7 100644
--- a/test/routes/foreign-adoption-routes.test.ts
+++ b/test/routes/foreign-adoption-routes.test.ts
@@ -82,6 +82,27 @@ describe('adopted sessions refuse every auto-op that drives the pane', () => {
     });
   }
 
+  it('refuses a one-shot prompt, which would start a new local claude in /tmp', async () => {
+    const h = await createRouteTestHarness(registerSessionRoutes, { sessionId: SID });
+    (h.ctx._session as unknown as { isAdopted: boolean }).isAdopted = true;
+    const res = await h.app.inject({
+      method: 'POST',
+      url: `/api/sessions/${SID}/run`,
+      payload: { prompt: 'hello' },
+    });
+    expect(res.json().success).toBe(false);
+    expect(res.json().error).toMatch(/adopted/i);
+    expect(h.ctx._session.runPrompt).not.toHaveBeenCalled();
+    await h.app.close();
+  });
+
+  it('still runs a one-shot prompt on a session Codeman started', async () => {
+    const h = await createRouteTestHarness(registerSessionRoutes, { sessionId: SID });
+    await h.app.inject({ method: 'POST', url: `/api/sessions/${SID}/run`, payload: { prompt: 'hello' } });
+    expect(h.ctx._session.runPrompt).toHaveBeenCalledWith('hello');
+    await h.app.close();
+  });
+
   it('refuses respawn, for a harder reason: it kills and restarts the pane', async () => {
     const h = await createRouteTestHarness(registerRespawnRoutes, { sessionId: SID });
     (h.ctx._session as unknown as { isAdopted: boolean }).isAdopted = true;