Mastra Showcase — Parity Notes

This document tracks progress toward feature parity with the LangGraph Python showcase and the rationale for every LangGraph demo that has NOT (yet) been ported to Mastra.

Ported in this PR

• prebuilt-sidebar, prebuilt-popup — pre-built chat surfaces
• chat-slots, chat-customization-css — chat customization
• headless-simple — custom chat UI via useAgent
• frontend-tools, frontend-tools-async — useFrontendTool sync/async
• hitl-in-chat, hitl-in-app — both human-in-the-loop patterns
• tool-rendering-default-catchall, tool-rendering-custom-catchall — catch-all tool rendering variants
• agentic-chat-reasoning, reasoning-default-render — reasoning slot customization (see reasoning caveat under "Architectural limitations")
• readonly-state-agent-context — useAgentContext read-only context
• agent-config — config-object forwarding (adapted to useAgentContext)
• cli-start — manifest-only npx degit entry for the Mastra starter
• declarative-gen-ui — A2UI dynamic-schema catalog via the existing generate_a2ui tool on the shared Mastra agent
• a2ui-fixed-schema — A2UI fixed-schema flight card catalog via the same generate_a2ui tool
• headless-complete — full chat-from-scratch on useAgent with a dedicated headlessCompleteAgent (weather + stock backend tools, frontend highlight_note component) and manual composition via useRenderToolCall / useRenderActivityMessage / useRenderCustomMessages. Routes through the shared /api/copilotkit runtime; the langgraph-python reference's MCP Apps "sketch a diagram" suggestion is dropped because Mastra skips mcp-apps (see below).
• auth — Bearer-token gate enforced by the V2 runtime's onRequest hook (wired via createCopilotRuntimeHandler from @copilotkit/runtime/v2). Starts authenticated to avoid the initial /info 401 crash; a local ChatErrorBoundary auto-resets when auth flips.

Skipped / Deferred

Each entry below documents one LangGraph-Python demo that was not ported in this PR and the reason.

gen-ui-interrupt

Requires LangGraph's interrupt() primitive so the frontend can "resume" a paused graph via useInterrupt. Mastra doesn't expose an equivalent interrupt/resume lifecycle through the AG-UI adapter yet. The hitl-in-chat port already covers the same user-visible UX using useHumanInTheLoop, so this demo was skipped to avoid misleading the feature matrix.

interrupt-headless

Same reason as gen-ui-interrupt — requires LangGraph interrupt lifecycle.

mcp-apps

Requires an MCP client to be wired into the agent's tool surface. Mastra's MCP story is still evolving and there's no established pattern for shipping an MCP-backed demo inside the Mastra showcase.

byoc-hashbrown

Large BYOC demo using @hashbrownai/react for structured streaming. The langgraph-python implementation is ~9 files and depends on strict hashbrown schema alignment. Deferred pending a dedicated pass.

byoc-json-render

BYOC demo using @json-render/react. Large surface area (~10 files). Deferred pending a dedicated pass.

open-gen-ui, open-gen-ui-advanced

The open generative UI demos ship their own iframe sandbox, frontend function injection, and a bespoke /api/copilotkit-ogui route. Non-trivial port. Deferred.

multimodal

Requires a vision-capable runtime and a dedicated /api/copilotkit-multimodal route with attachment handling. Deferred.

voice

Requires a voice-capable runtime at /api/copilotkit-voice plus a bundled sample-audio asset. Deferred.

beautiful-chat

Canonical polished starter — ~9 files including charts, hooks, and a dedicated /api/copilotkit-beautiful-chat route. Deferred pending a dedicated pass.

tool-rendering-reasoning-chain — architectural skip

Requires a dedicated agent that emits sequential tool calls with AG-UI REASONINGMESSAGE* events interleaved. The @ag-ui/mastra adapter (see node_modules/@ag-ui/mastra) does not currently emit any REASONING_MESSAGE_START | CONTENT | END events — a repository grep for those constants returns zero matches. Until the Mastra AG-UI bridge grows reasoning-event support, this demo cannot be ported without a cosmetic facade that fabricates reasoning tokens. Skipped as a truthful architectural limitation rather than a cosmetic stub.

Architectural limitations

• Reasoning events are not emitted by @ag-ui/mastra. The two reasoning demos (agentic-chat-reasoning, reasoning-default-render) ship the slot-override wiring so the UI shape is correct, but the @ag-ui/mastra adapter does not emit AG-UI REASONING_MESSAGE_START | CONTENT | END events — the slot will therefore never receive tokens in practice. These demos are kept in-tree for shape/compile coverage and so the slot-override pattern is visible to showcase readers, but operators should treat them as cosmetic until the Mastra AG-UI bridge grows reasoning support. tool-rendering-reasoning-chain is fully skipped for the same reason (see "Skipped / Deferred" above).

Compatibility notes

• Agent aliasing: All ported demos currently route to the shared weatherAgent via the demo-alias list in src/app/api/copilotkit/route.ts. Each alias gets a dedicated resourceId so working-memory buckets don't cross-contaminate. Full per-demo agent specialization is a follow-up.

• Agent config forwarding: The LangGraph reference uses provider properties passed to a dedicated route that rebuilds the system prompt per turn. The Mastra port uses useAgentContext instead — functionally equivalent from the user's perspective but a different wiring pattern.