CrewAI (Crews) — Parity Notes vs LangGraph Python

This document tracks which LangGraph-Python demos have been ported to CrewAI Crews, which have been intentionally skipped, and why.

Architecture

Unlike LangGraph-Python, where each demo can point at its own graph (langgraph.json maps agent names → graph modules), CrewAI Crews in this showcase uses a single shared LatestAiDevelopment crew registered at the FastAPI agent server (src/agent_server.py) and fronted by ag_ui_crewai.endpoint.add_crewai_crew_fastapi_endpoint.

The Next.js CopilotKit runtime registers multiple agent names but they all resolve to the same underlying crew via HttpAgent. This is an intentional constraint of the CrewAI runtime primitive — a crew is a pre-assembled set of agents + tasks, not a graph whose nodes are swappable per request.

Ported demos therefore fall into three categories:

1. Frontend-first demos — use useFrontendTool, useRenderTool, useAgentContext, useConfigureSuggestions, useComponent, useHumanInTheLoop, slot overrides, CSS theming, or chrome variants. These run against the shared crew without any backend change.
2. Backend-tool demos — rely on the tools already registered on the shared crew (get_weather, search_flights, query_data, schedule_meeting, generate_a2ui). These are ported verbatim.
3. Runtime-layer demos — exercise features of the Next.js CopilotKit runtime (auth via onRequest, voice via TranscriptionService, multimodal attachments). The shared crew is reused; per-demo behavior lives entirely in the runtime route module.

Ported demos (Wave 1 — 18 demos)

Demo	Kind	Notes
prebuilt-sidebar	Chrome	<CopilotSidebar /> against shared crew
prebuilt-popup	Chrome	<CopilotPopup /> against shared crew
chat-slots	Chrome	Slot overrides on <CopilotChat />
chat-customization-css	Chrome	CSS custom-properties theming
headless-simple	Chrome / Headless	useAgent + useComponent
headless-complete	Chrome / Headless	Full headless implementation
reasoning-custom	Reasoning	Uses the shared crew; reasoning tokens if model emits
reasoning-default	Reasoning	Default CopilotChatReasoningMessage
tool-rendering-default-catchall	Rendering	Out-of-the-box default renderer
tool-rendering-custom-catchall	Rendering	Custom wildcard renderer
tool-rendering-reasoning-chain	Rendering	Sequential tool calls + reasoning
frontend-tools	Frontend tools	useFrontendTool for background change
frontend-tools-async	Frontend tools	Async useFrontendTool handler
hitl-in-app	HITL	useFrontendTool + app-level modal
readonly-state-agent-context	Context	useAgentContext
agent-config	Context	Typed config object via useAgentContext (see Wave 2)
open-gen-ui	Generative UI	Fully open-ended gen UI, frontend-only
open-gen-ui-advanced	Generative UI	Sandbox functions inside iframe

Ported demos (Wave 2 — this PR)

Demo	Kind	Notes
auth	Runtime	Bearer-token gate via V2 onRequest hook
voice	Runtime	TranscriptionServiceOpenAI mounted on per-demo runtime
multimodal	Runtime	Image + PDF uploads via AttachmentsConfig

Wave 2 fix: agent-config backend wiring

Wave 1 shipped agent-config with the frontend forwarding tone/expertise/responseLength via <CopilotKitProvider properties>, but the CrewAI side ignored them: the upstream ag_ui_crewai.endpoint.crewai_prepare_inputs helper threads only state / messages / tools into ChatWithCrewFlow and drops forwardedProps on the floor.

Wave 2 fixes this end-to-end with a small FastAPI middleware in src/agent_server.py (ForwardedPropsMiddleware) that:

1. Intercepts POSTs to the crew endpoint.
2. Parses the JSON body and checks for forwardedProps.tone / expertise / responseLength.
3. When present, composes a plain-English style guide (_build_agent_config_guidance) matching the three-axis rulebook used by the LangGraph-Python reference (agent_config_agent.py).
4. Splices the guidance + raw enums into state.inputs.
5. Replays the rewritten body into the ASGI receive queue so the downstream ag_ui_crewai handler sees the mutated body verbatim.

The middleware only mutates bodies that carry agent-config props, so every other demo's request bytes pass through byte-identical. The crew chat flow already appends state["inputs"] to its system prompt (system_message += "\n\nCurrent inputs: " + json.dumps(inputs)) — which means the agent now sees the style rules on every turn and the response style changes as the user flips the selectors.

Skipped demos — architectural reasons

gen-ui-interrupt — skipped

Uses LangGraph's native interrupt() primitive and the v1 useLangGraphInterrupt hook, which depend on graph-level state suspension and a resume endpoint that LangGraph Platform exposes. CrewAI has no equivalent primitive exposed over AG-UI today — a crew task cannot be paused and resumed with out-of-band user input mid-execution. The existing hitl demo (which this showcase keeps as hitl-in-chat) covers the human-in-the-loop UX via useHumanInTheLoop, which is a frontend-tool round-trip and works across runtimes.

interrupt-headless — skipped

Same reason as gen-ui-interrupt — LangGraph-interrupt-specific.

mcp-apps — skipped

Requires LangGraph MCPAppsMiddleware and create_agent + MCP SSE client wiring at the graph level. CrewAI's tool registration is a Pydantic-schema BaseTool list on Agent, not an MCP client multiplexer. No equivalent primitive in ag-ui-crewai at the time of writing; porting would require first-class MCP support in CrewAI upstream.

Ported demos (Wave 3 — this update)

Five demos that previously required dedicated per-demo backend work have all been shipped in this wave. Each runs against its own CrewAI crew mounted at a distinct path on the FastAPI agent server (src/agent_server.py), leaving the shared LatestAiDevelopment crew on / untouched. The Next.js side uses per-demo runtime routes with HttpAgent URLs pointing at the dedicated backend paths.

Demo	Kind	Crew module	Backend path
declarative-gen-ui	A2UI Dynamic	agents/declarative_gen_ui.py	/declarative-gen-ui
a2ui-fixed-schema	A2UI Fixed	agents/a2ui_fixed.py	/a2ui-fixed-schema
byoc-hashbrown	BYOC JSON	agents/byoc_hashbrown_agent.py	/byoc-hashbrown
byoc-json-render	BYOC JSON	agents/byoc_json_render_agent.py	/byoc-json-render
beautiful-chat	Flagship	agents/beautiful_chat.py	/beautiful-chat

Wave 3 implementation notes

System-prompt control. ag-ui-crewai.crews.ChatWithCrewFlow runs crewai.cli.crew_chat.build_system_message(crew_chat_inputs) on construction, which wraps any crew description in fixed "CrewAI platform" boilerplate that instructs the LLM to introduce itself and ask for clarifying inputs. For the A2UI demos we use _chat_flow_helpers.preseed_system_prompt to install a tuned crew_description into _CREW_INPUTS_CACHE (also skipping the secondary AI description calls). For BYOC demos that must emit pure JSON, we additionally patch ChatWithCrewFlow.__init__ via _chat_flow_helpers.install_custom_system_message so our full system prompt replaces the composed one, fully bypassing the CrewAI platform wrapper.

BYOC wire format. Both BYOC demos emit the schema shape directly (NOT the XML-style <ui>...</ui> DSL used internally by hashbrown when hashbrown itself drives the LLM). Hashbrown's useJsonParser(content, kit.schema) consumes the schema shape at runtime; the XML DSL is the authoring syntax that hashbrown compiles into that schema when its own LLM adapters are wired up.

byoc-json-render frontend hardening (from PR #4271). Two fixes are rolled into the ported frontend:

1. registry.tsx forwards children through the MetricCard wrapper so multi-component dashboards (a MetricCard with a nested BarChart) render as a wrapped block rather than dropping the chart.
2. json-render-renderer.tsx wraps <Renderer /> in <JSONUIProvider> so the StateProvider / VisibilityProvider / ActionProvider / ValidationProvider contexts the ElementRenderer requires are available — without this wrap, clicking a suggestion crashes with "useVisibility must be used within a VisibilityProvider".

beautiful-chat deviations. Two deviations from the LangGraph reference, both rooted in the CrewAI / ag-ui-crewai primitive set:

1. No MCP Apps leg. ag-ui-crewai has no MCP SSE multiplexer; CrewAI crews use Pydantic BaseTool lists. The Excalidraw MCP suggestion pill is removed from hooks/use-example-suggestions.tsx. The rest of the cell (A2UI fixed + dynamic, Open Generative UI, shared-state todos via a manage_todos tool) ports cleanly.
2. Simplified shared-state todos. LangGraph's manage_todos returns a Command(update={...}) that patches graph state; CrewAI has no equivalent primitive. The CrewAI ManageTodosTool returns the new list as a JSON tool result which the frontend consumes via its existing useCoAgent wiring.

cli-start — not a page-level demo

Manifest-only entry describing the npx copilotkit@latest init command. Already covered implicitly by the root manifest.

Summary counts

• Total LangGraph-Python demos: 37
• Existing CrewAI-Crews demos (pre-parity): 10
• Wave 1 ports (PR #4262 first push): 18
• Wave 2 ports: 3 (auth, voice, multimodal)
• Wave 2 backend fix: agent-config now end-to-end
• Wave 3 ports (this update): 5 (declarative-gen-ui, a2ui-fixed-schema, byoc-hashbrown, byoc-json-render, beautiful-chat)
• Skipped (architectural): 3 (gen-ui-interrupt, interrupt-headless, mcp-apps)
• Not applicable: cli-start

Only the three architectural-skips remain out of the LangGraph-Python demo set.

Reasoning demos — framework-bridge limitation (no REASONING_MESSAGE_*)

Affected cells

• reasoning-custom
• reasoning-default
• tool-rendering-reasoning-chain

All three are registered in src/app/api/copilotkit/route.ts as agent names that resolve to the shared LatestAiDevelopment crew via HttpAgent pointed at / (the FastAPI add_crewai_crew_fastapi_endpoint mount). There is no dedicated reasoning agent module — these cells reuse the shared crew, exactly like the other frontend-first ports.

The Wave-1 table above lists these as ported with the caveat "reasoning tokens if model emits." That caveat is structurally incorrect: the CrewAI AG-UI bridge cannot emit reasoning to AG-UI at all, regardless of model. This section documents why and what a real fix requires.

What backs the reasoning cells

The frontend is correct and matches the LangGraph-Python gold standard: tool-rendering-reasoning-chain/page.tsx (and the reasoning-* pages) wire a reasoningMessage slot that renders the custom ReasoningBlock. That slot only paints when the agent streams AG-UI REASONING_MESSAGE_* events with role: "reasoning". The demo is built right — the events never arrive.

Why the bridge can't emit REASONING_MESSAGE_* (or anything reasoning)

The request flows entirely through ag-ui-crewai (pinned >=0.2.0,<0.3.0; verified against the installed 0.2.0):

1. ag_ui_crewai.crews.ChatWithCrewFlow.chat() runs the chat LLM via litellm.acompletion(model=self.crew.chat_llm, ..., stream=True). The shared crew's chat_llm is gpt-4o (src/agents/crew.py), a non-reasoning chat-completions model that emits no reasoning_content in the first place.
2. The stream is consumed by ag_ui_crewai.sdk.copilotkit_stream → _copilotkit_stream_custom_stream_wrapper. That loop reads only chunk.choices[0].delta.content (→ TEXT_MESSAGE_CHUNK) and chunk.choices[0].delta.tool_calls (→ TOOL_CALL_CHUNK). It never inspects delta.reasoning_content.
3. The bridge's entire event vocabulary (ag_ui_crewai/events.py) is four bridged types — TextMessageChunkEvent, ToolCallChunkEvent, CustomEvent, StateSnapshotEvent. The FastAPI endpoint (ag_ui_crewai/endpoint.py) registers AG-UI forwarding listeners for exactly those four. There is no reasoning event in the bridge — not REASONING_MESSAGE_* (the channel @ag-ui/client renders), and not THINKING_* (which @ag-ui/client drops anyway). Nothing reasoning-shaped is produced or forwarded.

So even pointing the crew at a reasoning-capable model would not light up the slot: the bridge discards reasoning_content before it can become an AG-UI event.

Why the agno / claude-sdk-python custom-synth pattern does NOT port here

Other non-Responses-API integrations (agno/src/agent_server.py, claude-sdk-python/src/agents/reasoning_agent.py) DO emit REASONING_MESSAGE_*. Their PRIMARY path reads the model's native reasoning channel — agno reads RunContentEvent.reasoning_content; claude-sdk-python reads Anthropic's Messages-API thinking_delta — and re-emits it as reasoning-role events. Only as a FALLBACK (when no native reasoning channel is present) do they buffer the assistant text, parse a <reasoning>…</reasoning> span, and re-emit that. Both paths work there because those integrations own their entire agent-server endpoint — they hand-write the async generator that yields the AG-UI event stream, so they control native-channel forwarding, buffering, and emission.

crewai-crews owns no such loop. The whole request lifecycle — the litellm stream, the chunk→event translation, the crewai event bus, the SSE encoder, kickoff/teardown — lives inside add_crewai_crew_fastapi_endpoint. The showcase's only sanctioned extension points are preseeding the system prompt (_chat_flow_helpers.preseed_system_prompt) and monkey-patching ChatWithCrewFlow.__init__ (install_custom_system_message). Neither touches the streaming path. Synthesizing reasoning would require forking or monkey-patching copilotkit_stream itself — the chunk-by-chunk heart of the bridge that never buffers a full assistant message — which is a framework fork, brittle across ag-ui-crewai releases, and exactly the kind of demo-hack this repo prohibits. There is no clean, supported synth seam for crewai-crews.

What a real fix requires (upstream ag-ui-crewai)

A first-class fix belongs in the bridge, not the showcase:

1. Add a BridgedReasoningMessageChunkEvent (mapping to AG-UI REASONING_MESSAGE_*, role: "reasoning") to ag_ui_crewai/events.py, and register a forwarding listener in endpoint.py.
2. In copilotkit_stream._copilotkit_stream_custom_stream_wrapper, read chunk.choices[0].delta.reasoning_content (the litellm chat-completions reasoning field) and emit the new reasoning chunk event, mirroring the existing content / tool_calls handling.
3. Point the reasoning cells' crew at a reasoning-capable chat-completions model whose litellm adapter populates reasoning_content (e.g. a DeepSeek-R1-class or o-series-via-litellm model), or wire a dedicated reasoning crew on its own mount the way Wave 3 added dedicated crews.

Until ag-ui-crewai surfaces reasoning, the three reasoning cells render the assistant answer and any tool cards correctly, but the reasoningMessage slot stays empty — the chain-of-thought channel is a bridge-level dead end on CrewAI today. The cells are intentionally left in place (frontend is parity-correct) rather than weakened or removed.