fix: gate direct session creation by workspace policy

frontend/src/api/sessions.ts

@@ -1,6 +1,10 @@
 import { apiFetch } from "./client";
 import { getSettings } from "./settings";
-import { workspacePolicyGate, workspacePreferences, type WorkspacePreference } from "../workspaces/drafts";
+import { getWorkspace, listWorkspaces } from "./workspaces";
+import {
+  WORKSPACE_POLICY_ERROR, WORKSPACE_SUMMARY_ERROR, WorkspaceSelectionError, workspacePolicyGate,
+  workspacePreferences, type WorkspacePreference,
+} from "../workspaces/drafts";
 import type {
   Principal, ResumeSessionResult, SessionScope, SessionSummary, SessionDocument, UiResponse,
 } from "./types";
@@ -22,9 +26,83 @@ async function selectedPreferences(): Promise<WorkspacePreference> {
   });
 }
 
+function reconcileWorkspacePolicy(preferences: WorkspacePreference, allowed: readonly string[], defaultModel?: string) {
+  if (allowed.length === 0) throw new WorkspaceSelectionError(WORKSPACE_POLICY_ERROR);
+  const selected = preferences.provider && preferences.model
+    ? `${preferences.provider}/${preferences.model}`
+    : undefined;
+  if (selected && allowed.includes(selected)) return preferences;
+  const replacement = defaultModel && allowed.includes(defaultModel) ? defaultModel : allowed[0];
+  const separator = replacement.indexOf("/");
+  if (separator <= 0 || separator === replacement.length - 1) {
+    throw new WorkspaceSelectionError(WORKSPACE_POLICY_ERROR);
+  }
+  return workspacePreferences.save({
+    ...preferences,
+    provider: replacement.slice(0, separator),
+    model: replacement.slice(separator + 1),
+  });
+}
+
+async function ensureWorkspaceSelectionPolicy(): Promise<WorkspacePreference> {
+  while (true) {
+    const preferences = workspacePreferences.load();
+    const workspaceId = preferences.workspaceId;
+    if (!workspaceId) return preferences;
+    workspacePolicyGate.beginSummary(workspaceId);
+    let workspace;
+    try {
+      workspace = (await listWorkspaces()).find((candidate) => candidate.id === workspaceId);
+    } catch {
+      if (workspacePreferences.load().workspaceId !== workspaceId) continue;
+      workspacePolicyGate.rejectSummary(workspaceId);
+      throw new WorkspaceSelectionError(WORKSPACE_SUMMARY_ERROR);
+    }
+    if (workspacePreferences.load().workspaceId !== workspaceId) continue;
+    if (!workspace?.revision) {
+      workspacePolicyGate.allowLegacy(workspaceId);
+      return workspacePreferences.load();
+    }
+    workspacePolicyGate.select(workspaceId);
+    const outcome = await Promise.race([
+      getWorkspace(workspaceId).then(
+        (record) => ({ kind: "record" as const, record }),
+        () => ({ kind: "error" as const }),
+      ),
+      workspacePolicyGate.waitForCurrent(() => workspacePreferences.load()).then(
+        (selection) => ({ kind: "selection" as const, selection }),
+      ),
+    ]);
+    if (outcome.kind === "selection") {
+      if (outcome.selection.workspaceId !== workspaceId) continue;
+      return outcome.selection;
+    }
+    if (outcome.kind === "error") {
+      if (workspacePreferences.load().workspaceId !== workspaceId) continue;
+      workspacePolicyGate.reject(workspaceId);
+      throw new WorkspaceSelectionError(WORKSPACE_POLICY_ERROR);
+    }
+    const { record } = outcome;
+    if (workspacePreferences.load().workspaceId !== workspaceId) continue;
+    let selection: WorkspacePreference;
+    try {
+      selection = reconcileWorkspacePolicy(
+        preferences,
+        record.workspace.llm_policy.allowed,
+        record.workspace.llm_policy.default,
+      );
+    } catch (error) {
+      workspacePolicyGate.reject(workspaceId);
+      throw error;
+    }
+    workspacePolicyGate.resolve(workspaceId);
+    if (workspacePreferences.load().workspaceId === workspaceId) return selection;
+  }
+}
+
 export async function createSession(i: NewSessionInput) {
   await selectedPreferences();
-  const selection = await workspacePolicyGate.waitForCurrent(() => workspacePreferences.load());
+  const selection = await ensureWorkspaceSelectionPolicy();
   return apiFetch<{ id: string }>("/sessions", {
     method: "POST",
     body: JSON.stringify({ ...i, ...selection }),