fix: prevent permission reply from silently escalating "once" to "always"

Remove allow_always from the fallback chain when the user replies "once",
aligning with the ACP spec which says "map by option kind first" with no
fallback for allow_once. Also fix Inspector to use rawSend, revert
hydration guard to accept empty configOptions, and handle respondPermission
errors by rejecting the pending promise.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

docs/inspector.mdx

@@ -34,6 +34,7 @@ console.log(url);
 - Event JSON inspector
 - Prompt testing
 - Request/response debugging
+- Interactive permission prompts (approve, always-allow, or reject tool-use requests)
 - Process management (create, stop, kill, delete, view logs)
 - Interactive PTY terminal for tty processes
 - One-shot command execution

frontend/packages/inspector/src/App.tsx

@@ -870,7 +870,7 @@ export default function App() {
       // Apply mode if selected
       if (!skipPostCreateConfig && config.agentMode) {
         try {
-          await session.send("session/set_mode", { modeId: config.agentMode });
+          await session.rawSend("session/set_mode", { modeId: config.agentMode });
         } catch {
           // Mode application is best-effort
         }
@@ -886,7 +886,7 @@ export default function App() {
               (opt) => opt.category === "model" && opt.type === "select" && typeof opt.id === "string"
             );
             if (modelOption && config.model !== modelOption.currentValue) {
-              await session.send("session/set_config_option", {
+              await session.rawSend("session/set_config_option", {
                 optionId: modelOption.id,
                 value: config.model,
               });
@@ -1241,7 +1241,6 @@ export default function App() {
         }));
         const title = params?.toolCall?.title ?? params?.toolCall?.toolCallId ?? "Permission request";
         const resolved = resolvedPermissions.get(permissionId);
-        const isPending = pendingPermissionIds.has(permissionId);
         entries.push({
           id: event.id,
           eventId: event.id,
@@ -1252,7 +1251,7 @@ export default function App() {
             title,
             description: params?.toolCall?.description,
             options,
-            resolved: resolved != null || !isPending,
+            resolved: resolved != null || sdkPermissionId == null,
             selectedOptionId: resolved,
           },
         });
@@ -1288,7 +1287,7 @@ export default function App() {
     }
 
     return entries;
-  }, [events, pendingPermissionIds, resolvedPermissions]);
+  }, [events, resolvedPermissions]);
 
   useEffect(() => {
     return () => {

sdks/typescript/src/client.ts

@@ -1262,7 +1262,7 @@ export class SandboxAgent {
   }
 
   private async hydrateSessionConfigOptions(sessionId: string, snapshot: SessionRecord): Promise<SessionRecord> {
-    if (snapshot.configOptions !== undefined && snapshot.configOptions.length > 0) {
+    if (snapshot.configOptions !== undefined) {
       return snapshot;
     }
 
@@ -1440,7 +1440,14 @@ export class SandboxAgent {
       throw new Error(`permission '${permissionId}' not found`);
     }
 
-    const response = permissionReplyToResponse(permissionId, pending.request, reply);
+    let response: RequestPermissionResponse;
+    try {
+      response = permissionReplyToResponse(permissionId, pending.request, reply);
+    } catch (error) {
+      pending.reject(error instanceof Error ? error : new Error(String(error)));
+      this.pendingPermissionRequests.delete(permissionId);
+      throw error;
+    }
     this.resolvePendingPermission(permissionId, response);
   }
 
@@ -2704,7 +2711,7 @@ function permissionReplyToResponse(
 ): RequestPermissionResponse {
   const preferredKinds: PermissionOptionKind[] =
     reply === "once"
-      ? ["allow_once", "allow_always"]
+      ? ["allow_once"]
       : reply === "always"
         ? ["allow_always", "allow_once"]
         : ["reject_once", "reject_always"];

sdks/typescript/tests/integration.test.ts

@@ -512,7 +512,7 @@ describe("Integration: TypeScript SDK flat session API", () => {
 
     const session = await sdk.createSession({ agent: "mock" });
 
-    await expect(session.send("session/cancel")).rejects.toThrow(
+    await expect(session.rawSend("session/cancel")).rejects.toThrow(
       "Use destroySession(sessionId) instead.",
     );
     await expect(sdk.rawSendSessionMethod(session.id, "session/cancel", {})).rejects.toThrow(