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AG2 Parity Notes

showcase/integrations/ag2/PARITY_NOTES.md

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AG2 Parity Notes

Status of AG2 showcase demos relative to the langgraph-python canonical set.

Ported

Batch 1 — Frontend variants over the shared ConversableAgent

These demos reuse the existing src/agents/agent.py (one ConversableAgent wrapped with AGUIStream). The runtime route registers each agent name, all pointing to the same HTTP backend.

  • prebuilt-sidebar — <CopilotSidebar /> docked layout
  • prebuilt-popup — <CopilotPopup /> floating launcher
  • chat-slots — slot-overridden <CopilotChat /> (welcomeScreen, disclaimer, assistantMessage)
  • chat-customization-css — scoped CSS theming of built-in classes
  • headless-simple — bespoke chat built on useAgent / useComponent
  • readonly-state-agent-context — useAgentContext read-only context
  • reasoning-default — built-in CopilotChatReasoningMessage (no custom slot)
  • tool-rendering-default-catchall — useDefaultRenderTool() (built-in card)
  • tool-rendering-custom-catchall — single branded wildcard renderer
  • frontend-tools — useFrontendTool with sync handler (change_background)
  • frontend-tools-async — useFrontendTool with async handler (notes-card)
  • hitl-in-app — async useFrontendTool + app-level modal (approval-dialog)

Previously ported (kept)

  • agentic-chat, hitl-in-chat, tool-rendering, gen-ui-tool-based, gen-ui-agent, shared-state-streaming

Batch 3 — Headless complete + manifest-only entries

  • cli-start — informational manifest entry (copy-paste starter command).
  • gen-ui-tool-based — already shipped; manifest entry added.
  • headless-complete — TRULY headless chat re-composed from low-level hooks (useRenderToolCall, useRenderActivityMessage, useRenderCustomMessages). Backend: dedicated AG2 ConversableAgent (agents/headless_complete.py) mounted at /headless-complete/ with get_weather + get_stock_price tools; highlight_note is registered on the frontend via useComponent.

Batch 4 — A2UI / OGUI / MCP + reasoning ports (this batch)

Each demo gets its own AG2 sub-app mounted at a named path, plus (where required) its own dedicated /api/copilotkit-* runtime route so the runtime middleware config doesn't leak into other cells.

  • declarative-gen-ui — A2UI Dynamic Schema. Backend (src/agents/a2ui_dynamic.py) owns the generate_a2ui tool, which invokes a secondary OpenAI client bound to render_a2ui and returns an a2ui_operations container. Runtime route at api/copilotkit-declarative-gen-ui/route.ts with a2ui.injectA2UITool: false.
  • a2ui-fixed-schema — A2UI Fixed Schema. Backend (src/agents/a2ui_fixed.py) ships flight_schema.json and exposes a display_flight(origin, destination, airline, price) tool that emits a2ui_operations directly. Runtime route at api/copilotkit-a2ui-fixed-schema/route.ts with a2ui.injectA2UITool: false.
  • mcp-apps — Backend (src/agents/mcp_apps_agent.py) is a no-tools ConversableAgent; the runtime route at api/copilotkit-mcp-apps/route.ts configures mcpApps.servers pointing at the public Excalidraw MCP server, and the runtime middleware injects MCP tools at request time.
  • open-gen-ui, open-gen-ui-advanced — Backends are no-tools ConversableAgents (src/agents/open_gen_ui_agent.py and src/agents/open_gen_ui_advanced_agent.py). Shared runtime route at api/copilotkit-ogui/route.ts enables openGenerativeUI: { agents: [...] } so the runtime middleware converts streamed generateSandboxedUi tool calls into open-generative-ui activity events.
  • reasoning-custom, tool-rendering-reasoning-chain — Frontend ports of the LangGraph reasoning cells. The custom reasoningMessage slot is wired exactly as in the canonical reference. The tool chain (tool-rendering-reasoning-chain backend at src/agents/tool_rendering_reasoning_chain.py, mounted at /tool-rendering-reasoning-chain/) still exercises end-to-end. Reasoning channel does NOT light up — confirmed framework-bridge limitation, not a fixture bug. See the dedicated section below.

Batch 2 — Dedicated AG2 sub-apps

These demos own their own ConversableAgent(s) plus FastAPI sub-app mounted at a named path (agent_server.py mounts each one before the catch-all /). The Next.js runtime points an HttpAgent at the matching path so each demo gets its own ContextVariables-backed state slot, isolated from the shared default agent.

  • shared-state-read-write — bidirectional shared state via AG2 ContextVariables + ReplyResult. Agent calls get_current_preferences to read UI-written prefs and set_notes to write back.
  • subagents — supervisor ConversableAgent that delegates to three sub-ConversableAgents (research/writing/critique) exposed as tools; each delegation appends to delegations in shared state for the live log UI.

Deferred (require per-demo agent specialization)

AG2's AG-UI integration mounts a single AGUIStream over one ConversableAgent at the FastAPI root. Achieving per-demo specialized behavior (tailored system prompts, dedicated tool sets, backend-owned A2UI tools, MCP integration, vision input, structured-output BYOC, etc.) requires adding additional Python agent modules AND either (a) mounting each as its own ASGI app at a distinct path and pointing a dedicated HttpAgent({ url }) at it from a per-demo Next.js runtime route, or (b) adopting AG2's GroupChat to host multiple specialized agents behind a single stream with router logic. Both approaches are feasible but represent a distinct engineering investment and are not a pure port of the langgraph-python cell.

The following demos fall into that bucket and are deferred, not strictly "missing primitive" skips:

  • agent-config — needs the agent to re-materialize system prompt from forwardedProps on every turn (AG2 ConversableAgent supports this but a dedicated runtime wiring is required).
  • auth — pure runtime onRequest hook demo; dedicated /api/copilotkit-auth route; agent stays unchanged. Straightforward but requires a new route.
  • byoc-hashbrown, byoc-json-render — streaming structured-output BYOC with Zod-validated catalogs; each has its own runtime route, catalog, renderer, and supporting components.
  • multimodal — vision-capable AG2 agent + dedicated /api/copilotkit-multimodal.
  • voice — frontend voice STT; needs dedicated /api/copilotkit-voice and the lazy-init agent shape from langgraph-python.

Shipped — wave 2 follow-up

  • beautiful-chat — simplified port: combines A2UI Dynamic + Open Generative UI on a dedicated runtime (/api/copilotkit-beautiful-chat). MCP Apps is intentionally out-of-scope (covered separately by /demos/mcp-apps); the canonical reference's app-mode toggle / todos canvas is also not ported. Frontend reuses the catalog from /demos/declarative-gen-ui to avoid duplication.
  • hitl-in-chat-booking — manifest alias to the existing hitl-in-chat cell. The langgraph reference itself aliases the booking variant to the same /demos/hitl-in-chat route; AG2's useHumanInTheLoop surface (TimePickerCard) is functionally equivalent for the booking flow. NOT a missing-primitive case — the earlier "skipped" entry was incorrect (it conflated hitl-in-chat-booking with the useInterrupt-driven flow, which it isn't).

Skipped (missing primitive)

  • gen-ui-interrupt — requires a LangGraph-style interrupt() that round-trips a resumable graph pause through the event stream. AG2's human_input_mode is a synchronous request/reply; it does not resume the same run from a persisted checkpoint. Marked as not_supported_features in manifest.yaml; the route renders a stub page pointing at hitl-in-chat / hitl-in-app.
  • interrupt-headless — same underlying primitive as gen-ui-interrupt. Marked not_supported_features; stub page points at hitl-in-app / frontend-tools-async.

Reasoning channel — framework-bridge limitation (verified)

Applies to reasoning-custom, tool-rendering-reasoning-chain, and reasoning-default. The custom/built-in reasoningMessage slot is wired correctly, but the AG-UI reasoning channel never lights up because AG2's AGUIStream bridge cannot emit REASONING_MESSAGE_* events — it has no reasoning data to emit. This is the same class of gap as pydantic-ai, not a fixture or wiring bug. Do NOT attempt to fix it by hacking the aimock fixtures.

Verified against ag2==0.13.3 / autogen 0.13.3 (the version pinned by requirements.txt, ag2[openai,ag-ui]>=0.9.0).

What AGUIStream actually emits

autogen.ag_ui.adapter (the AGUIStream / run_stream implementation) imports and emits only this fixed set of AG-UI event types:

  • RUN_STARTED, RUN_FINISHED, RUN_ERROR
  • STATE_SNAPSHOT
  • TEXT_MESSAGE_START / _CONTENT / _END / _CHUNK
  • TOOL_CALL_START / _ARGS / _CHUNK / _END / _RESULT

There is no REASONING_MESSAGE_* import and no THINKING_* import anywhere in the adapter. So the question "does it emit REASONING_MESSAGE_*, THINKING_*, or nothing?" resolves to nothing — the reasoning channel is entirely absent from the bridge. (Note: even if it emitted THINKING_*, that would be a dead end — @ag-ui/client 0.0.52 drops THINKING_*; only REASONING_MESSAGE_* with role:"reasoning" reaches the UI.)

Why a custom-synth interceptor is NOT feasible

The agno / claude-sdk-python pattern (synthesize REASONING_MESSAGE_* from the model's native reasoning channel — agno reads RunContentEvent.reasoning_content; claude-sdk-python reads Anthropic's Messages-API thinking_delta, never chat-completions delta.reasoning_content) cannot be applied here, because the reasoning data never survives into any layer the bridge can see:

  1. AGUIStream exposes an event_interceptors hook, but interceptors receive ServiceResponse objects (autogen.agentchat.remote.protocol). ServiceResponse has exactly four fields — message, context, input_required, streaming_text — and no reasoning field.
  2. Upstream of that, AgentService (agent_service.py) builds its streaming text from an AsyncIOQueueStream whose send() only captures StreamEvent.content.content (visible text). The final reply comes from a_generate_oai_reply, which returns a plain OAI message (content + tool_calls).
  3. Upstream of that, autogen's OpenAI chat-completions client (autogen/oai/client.py) reads only choice.delta.content and choice.delta.tool_calls from each streaming chunk. choice.delta.reasoning_content is never read in the chat-completions path — it is silently dropped at ingestion. (Only the separate responses_v2 / Responses-API client surfaces reasoning via response.reasoning, and that path does not flow through AGUIStream either.)

Empirical confirmation: an OpenAI-compatible endpoint that streams delta.reasoning_content (exactly the channel aimock's reasoning fixture field drives) + delta.content, driven through a real ConversableAgent + AGUIStream, produces:

RUN_STARTED: 1
TEXT_MESSAGE_START: 1
TEXT_MESSAGE_CONTENT: 3
TEXT_MESSAGE_END: 1
RUN_FINISHED: 1
REASONING_MESSAGE_START: 0   ← reasoning channel never fires

and the assembled reply is just the visible string — the reasoning_content is gone. There is therefore no reasoning data for a custom interceptor to synthesize from; manufacturing reasoning text would be a demo fabrication, which we explicitly do not do.

What a real fix requires (upstream, in AG2)

A genuine fix must add reasoning support inside autogen itself, end to end:

  1. autogen/oai/client.py streaming consumer must read choice.delta.reasoning_content and accumulate it alongside content.
  2. A reasoning carrier must be threaded through StreamEvent → AsyncIOQueueStream → AgentService, and ServiceResponse must gain a reasoning field (or a dedicated streaming reasoning chunk type).
  3. autogen/ag_ui/adapter.py::run_stream must import and emit REASONING_MESSAGE_START / _CONTENT / _END (role "reasoning") when reasoning deltas arrive — analogous to its existing TEXT_MESSAGE_* handling.

Until AG2 ships that, the showcase reasoning slot for AG2 demos will render empty/skeletal. The cells remain valuable for exercising the slot plumbing and (for tool-rendering-reasoning-chain) the multi-tool chain.