Genkit for Dart 0.16.1

Apply the Dart 3.13 prompt first. These rules cover Genkit for Dart 0.16.1 and the Shelf, middleware, session-store, MCP, and experimental A2UI integrations shipped with its release tag.

Version and runtime scope

• Lock genkit and its companion packages in pubspec.lock, and review each resolved version on upgrade: genkit_shelf, genkit_middleware, genkit_google_cloud, genkit_mcp, genkit_a2ui, and schemantic are versioned independently of the core package, so upgrading genkit doesn't move them. These rules compose with the Dart 3.13 baseline; the package declares Dart >=3.10.0 <4.0.0.
• Treat the Genkit Dart SDK's Preview status and A2UI's experimental status as compatibility boundaries; verify tools, transports, serializers, and provider behavior against the exact locked packages before upgrading.
• Accept the context parameter in custom AgentTransport.getSnapshot and abort overrides and forward it, just as turns, polling, and store notifications do; a dropped context makes a context-scoped store such as FirestoreSessionStore with snapshotPathPrefix fall back to the shared global prefix instead of the tenant's.
• Use ActionType.tool and /tool.v2/<name> for the multipart tool contract; allowlist action types and names even though ActionType permits arbitrary string values.

Shelf endpoints and authenticated context

• Expose an explicit action allowlist through reviewed Shelf routes; startFlowServer binds InternetAddress.anyIPv4 on port 3400 by default despite printing a localhost URL, and plain flow/action entries receive no