diff --git a/backend/__tests__/unit/routes/agentBinding.phase2.test.js b/backend/__tests__/unit/routes/agentBinding.phase2.test.js
index d7a8d225bb..6b257568e2 100644
--- a/backend/__tests__/unit/routes/agentBinding.phase2.test.js
+++ b/backend/__tests__/unit/routes/agentBinding.phase2.test.js
@@ -154,6 +154,54 @@ describe('placement request', () => {
     expect(res.status).toBe(403);
   });
 
+  // C14 rehearsal follow-up (sprint-review on #2365): "On my computer" with
+  // the name of the person's hosted agent stamped a placement the daemon's
+  // runtime-token mint then refused, so the page said "requested" and nothing
+  // ran. Refused up front with the mint's own code, and nothing is stamped.
+  describe('an agent Commonly runs in-process cannot be placed on a machine', () => {
+    const runInProcess = (config) => AgentInstallation.updateOne(
+      { agentName: 'wren-test', instanceId: 'default' },
+      { $set: { config } },
+    );
+
+    it.each([
+      ['hosted on the native engine', { runtime: { runtimeType: 'hosted' }, hosted: { engine: 'native' } }],
+      ['native', { runtime: { runtimeType: 'native' } }],
+    ])('%s: 409 in_process_agent_no_token, and no request is stamped', async (_label, config) => {
+      await runInProcess(config);
+      const res = await requestPlacement('machine-a');
+      expect(res.status).toBe(409);
+      expect(res.body.code).toBe('in_process_agent_no_token');
+      expect(res.body.message).toMatch(/^wren-test is your hosted agent/);
+      const identity = await User.findById(bot._id).lean();
+      expect(identity.botMetadata.requestedMachineId ?? null).toBeNull();
+      const seenByA = await assigned(DAEMON_A);
+      expect(seenByA.body.agents).toEqual([]);
+    });
+
+    it('a request stamped before the check can still be withdrawn', async () => {
+      await User.updateOne({ _id: bot._id }, { $set: { 'botMetadata.requestedMachineId': 'machine-a' } });
+      await runInProcess({ runtime: { runtimeType: 'native' } });
+      const res = await requestPlacement(null);
+      expect(res.status).toBe(200);
+      const identity = await User.findById(bot._id).lean();
+      expect(identity.botMetadata.requestedMachineId).toBeNull();
+    });
+
+    it('ownership is checked first: another user learns nothing about how it runs', async () => {
+      await runInProcess({ runtime: { runtimeType: 'native' } });
+      global.__CALLER_ID = String(new mongoose.Types.ObjectId());
+      const res = await requestPlacement('machine-a');
+      expect(res.status).toBe(403);
+      expect(res.body.code).not.toBe('in_process_agent_no_token');
+    });
+
+    it('an agent the person runs themself is still placed', async () => {
+      const res = await requestPlacement('machine-a');
+      expect(res.status).toBe(200);
+    });
+  });
+
   it('409s when the agent is bound to a different machine', async () => {
     await User.updateOne({ _id: bot._id }, { $set: { 'botMetadata.machineId': 'machine-b' } });
     const res = await requestPlacement('machine-a');
diff --git a/backend/routes/agentBinding.ts b/backend/routes/agentBinding.ts
index 866ec33902..f7ecfa6aa0 100644
--- a/backend/routes/agentBinding.ts
+++ b/backend/routes/agentBinding.ts
@@ -29,6 +29,7 @@ const User = require('../models/User');
 const {
   getRuntimeTokenHashesForAgent,
   revokeRuntimeTokensForAgent,
+  runsInProcess,
 } = require('./registry/tokens');
 
 const router = express.Router();
@@ -216,6 +217,20 @@ router.post('/request', bindingRateLimit, auth, async (req: express.Request & {
       });
     }
 
+    // An agent Commonly runs in-process (the person's hosted agent) can't also
+    // run on a machine: its daemon would be refused at the runtime-token mint,
+    // so the page said "requested" and nothing ever ran. Refused here, with the
+    // mint's code, after the ownership check so another user's agent never
+    // reveals how it runs. Withdrawing (machineId: null) stays allowed, so a
+    // request stamped before this check can still be cleared.
+    if (requestedMachineId && await runsInProcess(null, { agentName, instanceId })) {
+      return res.status(409).json({
+        code: 'in_process_agent_no_token',
+        message: `${agentName} is your hosted agent, and Commonly runs it, so it can't also run on your computer. `
+          + 'Choose a different name for an agent you run yourself.',
+      });
+    }
+
     if (requestedMachineId) {
       // eslint-disable-next-line @typescript-eslint/no-require-imports
       const Machine = require('../models/Machine');
diff --git a/backend/routes/registry/tokens.ts b/backend/routes/registry/tokens.ts
index f0373e9617..39562953a0 100644
--- a/backend/routes/registry/tokens.ts
+++ b/backend/routes/registry/tokens.ts
@@ -433,6 +433,7 @@ module.exports = {
   revokeRuntimeTokensAfterLastUninstall,
   issueRuntimeTokenForAgent,
   InProcessAgentTokenRefused,
+  runsInProcess,
   issueRuntimeTokenForInstallation,
   issueUserTokenForInstallation,
 };
diff --git a/frontend/src/v2/__tests__/V2AgentBYOMachine.test.tsx b/frontend/src/v2/__tests__/V2AgentBYOMachine.test.tsx
index 53b4a548ad..41b4537c93 100644
--- a/frontend/src/v2/__tests__/V2AgentBYOMachine.test.tsx
+++ b/frontend/src/v2/__tests__/V2AgentBYOMachine.test.tsx
@@ -323,4 +323,39 @@ describe('BYO on-my-computer mode', () => {
     // route), so this asserts the exclusion is real rather than an empty set.
     expect(container.querySelectorAll('.v2-rail__account .v2-avatar').length).toBe(1);
   });
+
+  // The placement route refuses an agent Commonly runs in-process (the
+  // person's hosted agent) with in_process_agent_no_token. The page says so
+  // in plain words and shows no "waiting for your computer" result. Matched on
+  // the words both the server's message and the page's own copy for that code
+  // share, so it holds whichever one renders.
+  test("placing the person's hosted agent on a computer is refused in plain words", async () => {
+    mockGet();
+    axios.post.mockImplementation((url) => {
+      if (url === '/api/registry/install') {
+        return Promise.reject({ response: { status: 400, data: { error: 'Agent already installed in this pod' } } });
+      }
+      if (url === '/api/agent-binding/request') {
+        return Promise.reject({
+          response: {
+            status: 409,
+            data: {
+              code: 'in_process_agent_no_token',
+              message: "sam-hosted is your hosted agent, and Commonly runs it, so it can't also run on your computer. Choose a different name for an agent you run yourself.",
+            },
+          },
+        });
+      }
+      return Promise.resolve({ data: {} });
+    });
+    renderPage();
+    await waitFor(() => expect(screen.getByTestId('byo-mode-machine')).toBeInTheDocument());
+    fireEvent.click(screen.getByTestId('byo-mode-machine'));
+    fireEvent.change(screen.getByPlaceholderText('my-mcp-agent'), { target: { value: 'sam-hosted' } });
+    fireEvent.click(screen.getByText('Add to this computer'));
+
+    expect(await screen.findByText(/sam-hosted is your hosted agent/)).toBeInTheDocument();
+    expect(screen.queryByTestId('byo-machine-result')).toBeNull();
+    expect(screen.queryByText(/has no runtime token/)).toBeNull();
+  });
 });