fix: validate workspace drafts and reconcile models

frontend/src/shell/SteerInput.test.tsx

@@ -181,6 +181,56 @@ test("footer limits model choices to the selected workspace policy", async () =>
   await waitFor(() => expect(selector).not.toHaveTextContent("DeepSeek V4 Pro"));
 });
 
+test("switching workspaces replaces an out-of-policy model before session creation", async () => {
+  let body: unknown;
+  localStorage.setItem("thothii.workspace-registry.v1.preferences", JSON.stringify({
+    workspaceId: "research", provider: "deepseek", model: "deepseek-v4-pro", thinking: "medium",
+  }));
+  const revision = (id: string) => ({
+    id, commit: "a".repeat(40), blob: "b".repeat(40), snapshotPath: "/snapshot", state: "operational" as const,
+  });
+  server.use(
+    http.get("http://localhost:8787/settings", () => HttpResponse.json({
+      workspace: "research", provider: "deepseek", model: "deepseek-v4-pro", thinking: "medium",
+    })),
+    http.get("http://localhost:8787/workspaces", () => HttpResponse.json([
+      { id: "research", name: "research", file: "research.yaml", displayName: "Research", revision: revision("research") },
+      { id: "psd-clinical", name: "psd-clinical", file: "psd-clinical.yaml", displayName: "PSD Clinical", revision: revision("psd-clinical") },
+    ])),
+    http.get("http://localhost:8787/workspaces/research", () => HttpResponse.json({
+      workspace: { workspace: { id: "research" }, llm_policy: { allowed: ["deepseek/deepseek-v4-pro"] } },
+      revision: revision("research"),
+    })),
+    http.get("http://localhost:8787/workspaces/psd-clinical", () => HttpResponse.json({
+      workspace: { workspace: { id: "psd-clinical" }, llm_policy: { default: "zai/glm-5.2", allowed: ["zai/glm-5.2"] } },
+      revision: revision("psd-clinical"),
+    })),
+    http.get("http://localhost:8787/models", () => HttpResponse.json({ models: [
+      { provider: "zai", id: "glm-5.2", name: "GLM-5.2", reasoning: true },
+      { provider: "deepseek", id: "deepseek-v4-pro", name: "DeepSeek V4 Pro", reasoning: true },
+    ] })),
+    http.post("http://localhost:8787/sessions", async ({ request }) => {
+      body = await request.json();
+      return HttpResponse.json({ id: "s1" });
+    }),
+  );
+  const client = new QueryClient({ defaultOptions: { queries: { retry: false } } });
+  render(<QueryClientProvider client={client}><ComposerFooter /><SteerInput sessionId={null} /></QueryClientProvider>);
+
+  const workspaceSelector = await screen.findByRole("combobox", { name: "Workspace" });
+  await waitFor(() => expect(workspaceSelector).toHaveTextContent("psd-clinical"));
+  await userEvent.selectOptions(workspaceSelector, "psd-clinical");
+  await waitFor(() => expect(screen.getByRole("combobox", { name: "Model" })).toHaveValue("glm-5.2"));
+  expect(screen.getByRole("combobox", { name: "Model" })).not.toHaveTextContent("DeepSeek V4 Pro");
+
+  await userEvent.type(screen.getByRole("textbox", { name: /new question/i }), "q");
+  await userEvent.click(screen.getByRole("button", { name: /send/i }));
+
+  await waitFor(() => expect(body).toEqual({
+    question: "q", workspaceId: "psd-clinical", provider: "zai", model: "glm-5.2", thinking: "medium",
+  }));
+});
+
 test("pulses the stop dot only while the harness is working", () => {
   const { rerender } = render(<SteerInput sessionId="s1" working />);
   const dot = () =>

frontend/src/shell/SteerInput.tsx

@@ -189,6 +189,27 @@ export function ComposerFooter() {
     ? models.filter((candidate) => allowedModels.includes(`${candidate.provider}/${candidate.id}`))
     : models;
 
+  useEffect(() => {
+    if (!allowedModels?.length) return;
+    const selected = preferences.provider && preferences.model
+      ? `${preferences.provider}/${preferences.model}`
+      : undefined;
+    if (selected && allowedModels.some((allowed) => allowed === selected)) return;
+    const replacement = workspaceRecord?.workspace.llm_policy.default
+      && allowedModels.includes(workspaceRecord.workspace.llm_policy.default)
+      ? workspaceRecord.workspace.llm_policy.default
+      : allowedModels[0];
+    const separator = replacement.indexOf("/");
+    if (separator <= 0 || separator === replacement.length - 1) return;
+    const next = {
+      ...preferences,
+      provider: replacement.slice(0, separator),
+      model: replacement.slice(separator + 1),
+    };
+    workspacePreferences.save(next);
+    setPreferences(next);
+  }, [allowedModels, preferences, workspaceRecord]);
+
   function update(patch: WorkspacePreference) {
     const next = workspacePreferences.save({ ...preferences, ...patch });
     setPreferences(next);
@@ -200,6 +221,7 @@ export function ComposerFooter() {
   }
 
   const knownModel = policyModels.some((m) => m.id === model);
+  const showModelFallback = !allowedModels && !knownModel;
   const contextPct = tokenUsage && tokenUsage.contextWindow > 0
     ? tokenUsage.totalTokens / tokenUsage.contextWindow
     : 0;
@@ -232,7 +254,7 @@ export function ComposerFooter() {
             <option value={model}>{model || "— model —"}</option>
           ) : (
             <>
-              {!knownModel && <option value={model}>{model || "— model —"}</option>}
+              {showModelFallback && <option value={model}>{model || "— model —"}</option>}
               {policyModels.map((m) => (
                 <option key={`${m.provider}/${m.id}`} value={m.id}>
                   {m.name}