fix(tui): reject an unconfigured /workflow model alias

An alias the engine cannot resolve falls back to the session model when the
subagent spawns, so accepting one reported a routing that never happened.
Check it against the configured models and show an error instead.

Author: elkaix

apps/pythinker-code/src/tui/commands/dynamic-workflow.ts

@@ -129,6 +129,13 @@ function handleModelSubcommand(host: SlashCommandHost, input: string): boolean {
     host.showStatus('Dynamic Workflow subagents now use this session model.');
     return true;
   }
+  // An alias the engine cannot resolve falls back to the session model at spawn
+  // time, so accepting one here would report a routing that never happens.
+  const configured = host.state.appState.availableModels;
+  if (Object.keys(configured).length > 0 && !Object.hasOwn(configured, value)) {
+    host.showError(`Unknown model: ${value}. Run /model to see the configured aliases.`);
+    return true;
+  }
   host.setAppState({ dynamicWorkflowModel: value });
   host.showStatus(`Dynamic Workflow subagents will use ${value}.`);
   return true;

apps/pythinker-code/test/tui/commands/dynamic-workflow.test.ts

@@ -22,6 +22,7 @@ function makeHost(
     hasSession?: boolean;
     permissionMode?: 'manual' | 'auto' | 'yolo';
     dynamicWorkflowMode?: boolean;
+    availableModels?: Record<string, unknown>;
   } = {},
 ) {
   const session = {
@@ -35,6 +36,9 @@ function makeHost(
         model: overrides.model ?? 'pythinker-model',
         permissionMode: overrides.permissionMode ?? 'auto',
         dynamicWorkflowMode: overrides.dynamicWorkflowMode ?? false,
+        availableModels: overrides.availableModels ?? {
+          'deepseek-v4': { provider: 'deepseek', model: 'deepseek-v4' },
+        },
       },
       theme: currentTheme,
       transcriptContainer: { addChild: vi.fn() },
@@ -365,6 +369,18 @@ describe('handleDynamicWorkflowCommand', () => {
     expect(host.sendNormalUserInput).not.toHaveBeenCalled();
   });
 
+  it('rejects a model alias that is not configured', async () => {
+    const { host } = makeHost({ permissionMode: 'auto' });
+
+    await handleDynamicWorkflowCommand(host, 'model not-a-real-alias');
+
+    expect(host.showError).toHaveBeenCalledWith(
+      expect.stringContaining('Unknown model: not-a-real-alias'),
+    );
+    expect(host.state.appState.dynamicWorkflowModel).toBeUndefined();
+    expect(host.sendNormalUserInput).not.toHaveBeenCalled();
+  });
+
   it('asks the task to route subagents to the configured model', async () => {
     const { host } = makeHost({ permissionMode: 'auto' });