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Overview

Conversational apps treat each user line as a new flow run with the same session id. CrewAI adds helpers for message history, optional intent routing, deferred tracing, structured turn streaming, and a local flow.chat() REPL.

Turn APIs

Use flow.handle_turn(message, session_id=...) for every user message from REST, WebSocket, tests, and custom UIs. Use flow.chat() when you want a local terminal chat loop for a conversational Flow. Flow.kickoff() does not accept user_message= or session_id= keyword arguments. For conversational flows, handle_turn() stores the pending message and calls kickoff(inputs={"id": session_id}) internally after resetting per-turn execution state. handle_turn(), stream_turn(), and chat() raise ValueError unless conversational mode is enabled. Applying @ConversationConfig(...) enables it automatically; otherwise set conversational = True.

Quick start

Streaming a turn

Use stream_turn() when a UI or runtime needs structured events for one chat turn. It returns a stream session with ordered frames for Flow routing, LLM chunks, tool activity, and conversation messages.
For the full frame contract and channel list, see Streaming Runtime Contract.

Turn lifecycle

Each handle_turn runs this pipeline:
  1. Turn setup — stores the pending user message, resolves the session id, resets per-turn execution tracking, and calls kickoff(inputs={"id": session_id}).
  2. State restore — if inputs["id"] exists and @persist is configured, loads the latest snapshot.
  3. FlowStarted — emitted on the first deferred session turn only.
  4. Pending turn hydration — appends the user message to state.messages, sets current_user_message / last_user_message, and optionally classifies when intents / default_intents + intent_llm are set.
  5. Graph execution — user-defined @start methods (if any) → route_conversation (the built-in start/router) → the selected @listen handler. route_conversation also calls the overridable conversation_start() helper.
  6. End of run — per-turn flow_finished and trace finalization are skipped when deferral is enabled; nested Agent.kickoff() / crews do not close the parent batch either.
Handlers should call append_assistant_message(reply) when the visible reply is not the return value, or when you trim history. A public string return is also recorded as assistant and included in the @persist snapshot, so a fresh Flow instance restores it. The user line is already stored by handle_turn — do not append it again in handlers.

Configuration overview

Decorating a Flow subclass with ConversationConfig both attaches the chat defaults and enables conversational mode. See the full field reference below. Override pre-classification per turn with handle_turn(..., intents=..., intent_llm=...).

Lower-level ChatState helpers

ChatState, the legacy ConversationalConfig, and crewai.flow.conversation helpers are still importable for advanced orchestration, tests, or custom wrappers. They are separate from the ConversationState / ConversationConfig API and do not add user_message= or session_id= keyword arguments to Flow.kickoff().
ConversationalInputs is a TypedDict for conventional kickoff(inputs={...}) keys: id, user_message, last_intent. ConversationState stores messages as ConversationMessage objects and additionally provides current_user_message, ended, events, and agent_threads. Use conversation_messages when passing its canonical history to an LLM.

Flow conversational API

handle_turn parameters

kickoff parameters

Flow.kickoff() accepts inputs, input_files, from_checkpoint, and restore_from_state_id. Pass inputs={"id": session_id} when you need raw flow execution, but use handle_turn() when the call represents a chat message.

Instance attributes

Methods and properties

Module helpers (crewai.flow.conversation)

Importable from crewai.flow.conversation for tests or custom orchestration. These helpers use the legacy ConversationalConfig shape; prepare_conversational_turn() also clears last_intent, unlike handle_turn(), which preserves it as router context.

Intent routing patterns

A. Pre-classify via ConversationConfig (simplest)

Set default_intents and intent_llm. Each handle_turn() pre-classifies the current message. A non-empty result returned by a custom route_turn() takes precedence; otherwise route_conversation uses the current turn’s classified intent.

B. Classify inside route_turn (richer prompts)

Set default_intents=None so handle_turn() only appends the user message. In route_turn(), call classify_intent with a custom prompt or descriptions:
Use @listen("RESEARCH") (or similar) for steps that run Agent.kickoff() with tools — not bare LLM.call() — when you need web research or multi-step tool use.

When the flow finishes but the user keeps chatting

Each handle_turn() completes one graph run, and the conversation continues with another handle_turn() using the same session_id. With the default deferred trace lifecycle, that run emits conversation_turn_completed, while FlowFinished is emitted once when finalize_session_traces() closes the session. @persist restores messages, flags, and context. Persist pattern: prefer @persist on a single terminal step (for example finalize) rather than on the whole Flow class. Class-level persist saves after every method; load_state uses the latest row, which may be a mid-run snapshot (for example right after bootstrap) and miss handler updates from the same turn. Do not use @human_feedback for follow-up chat lines unless a human must approve a specific step output before it is shown.

Conversational Flow

Opt into the conversational chat graph by setting conversational = True on a Flow subclass or applying @ConversationConfig(...). The base Flow then supplies route_conversation as the built-in start/router plus the converse_turn and end_conversation listeners. The deprecated answer_from_history_turn listener remains available for compatibility. The framework manages state.messages, can drive a router LLM, and keeps the trace batch open across turns. You write the custom routes; the framework owns the rest. Use this when you want a multi-turn chat with a router and per-route handlers without wiring the lifecycle yourself. Use Flow[ChatState] (the lower-level pattern above) when you need full control.

Quick example

For a local terminal chat, use chat():
chat() wraps handle_turn() in a REPL, exits on exit / quit, skips blank lines by default, and calls finalize_session_traces() when the session ends.

ConversationConfig

Class decorator that attaches per-class chat defaults.
answer_from_history_prompt, answer_from_history_llm, and the answer_from_history route are deprecated and will be removed in a future release. They duplicate converse, add an eligibility LLM call, and are bypassed when the normal auto-router returns a route. Existing configurations continue to work and emit DeprecationWarning.
With no custom routes, turns fall through to converse. With custom routes and a conversation/router LLM, the framework synthesizes a default RouterConfig; provide one explicitly only to customize its prompt, route list, descriptions, or fallback behavior. Setting default_intents uses the legacy pre-classification path instead. If no conversation LLM is configured, the built-in converse_turn returns a configuration placeholder rather than generating an answer.

RouterConfig and the auto-built route catalog

The router prompt that gets sent to the LLM is built automatically. For each route the framework picks a description with this precedence:
  1. RouterConfig.route_descriptions[label] — explicit override.
  2. Flow.builtin_route_descriptions[label] — framework-canned text for converse, end, and the deprecated answer_from_history compatibility route (phrased for the router LLM).
  3. The method’s declared description (used by declarative flows and DSL projections).
  4. First non-empty line of the @listen(label) handler’s docstring.
  5. Empty (the route is listed without a description).
So in practice, adding a new route is @listen("X") + a one-line docstring:

Naming handlers

The string in @listen("…") is a router route label (an event name), not the Python method name. Route labels and method completion events share one trigger namespace, so naming a handler the same as its route causes the handler to re-trigger itself in a loop. Use a different method name — the docs examples use a handle_* prefix:
Do not mirror the route label on the method:
…and the router LLM sees:
RouterConfig.prompt is for domain framing (assistant persona, business rules, voice). The route catalog is auto-built — don’t list routes in prompt; they’ll drift the moment you add a handler.

Built-in routes

You can override any of these by defining a same-named handler in your subclass.

handle_turn() semantics

flow.handle_turn(message) runs one turn:
  1. Resets per-execution tracking (_completed_methods, _method_outputs) so the graph re-runs — without this, repeated kickoff calls on the same flow instance would short-circuit on turn 2+ because Flow.kickoff_async treats inputs={"id": ...} as a checkpoint restore.
  2. Appends the user message to state.messages, sets current_user_message / last_user_message. last_intent is preserved from the prior turn so the router LLM can use it as a signal.
  3. Runs user-defined @start methods (if any), then route_conversation as the built-in start/router, then the chosen @listen handler. route_conversation invokes the overridable conversation_start() helper.
  4. The router stores its decision in state.last_intent (visible to the next turn’s router context).
  5. If your handler returned a string and didn’t already call append_assistant_message, handle_turn appends it for you and persists the updated state.messages so @persist restore includes the assistant turn.
Call handle_turn() for chat messages. Calling kickoff(inputs={"id": ...}) directly runs the flow graph without applying the conversational turn wrapper.

chat() for local REPLs

flow.chat() is the batteries-included terminal wrapper around handle_turn():
It handles the common local loop:
  1. Prompts for a user message.
  2. Stops on exit / quit, EOFError, or KeyboardInterrupt.
  3. Calls handle_turn(message, session_id=...).
  4. Prints the assistant result.
  5. Finalizes deferred session traces in a finally block.
chat(defer_trace_finalization=True) temporarily enables the instance deferral flag for the REPL and restores its prior value on exit. Customize the terminal behavior with injectable I/O:
For web apps, background workers, tests, and custom transports, keep using handle_turn() directly.

Custom router behavior

To run side effects (event bus setup, telemetry) on every routing decision, override route_turn:
To bypass the LLM router entirely and pick a route programmatically, return a non-empty string from route_turn. A falsy return does not invoke _route_with_config() from your override; routing falls through to this turn’s pre-classified intent, then the deprecated answer_from_history compatibility path when configured, and finally converse. A previous turn’s last_intent is available in router context but is never replayed as a fallback.

append_assistant_message and append_agent_result

Inside a @listen(label) handler, choose:
  • self.append_assistant_message(text) — adds a user-visible assistant turn to state.messages. The next turn’s converse_turn sees it.
  • self.append_agent_result(agent_name, result, visibility="private") — records a structured event in state.events and a thread in state.agent_threads[agent_name]. Public visibility also calls append_assistant_message for you. Use private results for scratch work that shouldn’t pollute the canonical history.
ConversationConfig.visible_agent_outputs can promote specific agents’ private results to public globally ("all", or a list of agent names).

Declaring a conversational flow in JSON/YAML

A declarative Flow can be conversational too. Add a top-level conversational block and declare your own routes as methods that listen to a route label:
Declaring the block is the opt-in — enabled defaults to true. Set enabled: false to keep the configuration while turning chat off. This also disables built-in method synthesis, so the declaration must provide a normal non-conversational graph. Three things are supplied for you: Declarative llm, router.llm, and intent_llm fields accept either a model id or a configuration mapping such as {model: openai/gpt-4o-mini, max_tokens: 512}. The conversational block also supports default_intents, visible_agent_outputs, defer_trace_finalization, and the RouterConfig fields shown above. Deprecated answer_from_history_prompt / answer_from_history_llm declarations remain accepted for compatibility. Run it from Python with the same turn APIs as a class-based conversational Flow:

Naming routes

Route labels and method names share one trigger namespace, so a handler must not be named after the route it listens to — create_video listening to create_video is rejected when the flow is built. Use a handle_* prefix.

What a declaration cannot express

crewai run opens the chat TUI for a declarative conversational flow — the same one a Python conversational Flow gets. A chat loop needs a terminal, so a headless run exits non-zero with guidance instead of running a single turn; drive it from Python there with handle_turn() or stream_turn(). A declarative method with a human_feedback: block (Python: @human_feedback) runs on a terminal REPL, because the runtime collects feedback with a blocking prompt the TUI cannot service. --inputs is not accepted for a conversational flow — each turn’s input is the message you type — and resuming a session by id is not wired into the CLI yet; use flow.handle_turn(message, session_id=...) from Python for that.

Tracing across turns

With defer_trace_finalization=True (default in ConversationConfig):
  • One trace batch for the whole chat session.
  • flow_started on the first turn only; flow_finished once in finalize_session_traces().
  • Per-turn kickoff does not print “Trace batch finalized”.
  • Nested work (Agent.kickoff(), crews, Exa tools) appends to the parent batch; inner AgentExecutor flows do not close the session batch early.
flow.chat() calls finalize_session_traces() for you. When you own the loop with handle_turn(), call finalize_session_traces() when the session ends. suppress_flow_events=True hides Rich console panels and suppresses method execution events. Flow start/finish events still emit, so the outer Flow lifecycle remains traceable, but individual method spans are omitted.

Conversational Flow trace lifecycle

The conversational Flow uses the same tracing lifecycle: defer_trace_finalization defaults to True, so each handle_turn() keeps the session trace open. Deferred turns also suppress per-turn flow_failed; on a turn error or session abort, finalize the session explicitly. This closes the batch with the session-level FlowFinished event rather than a per-turn FlowFailed event. Always wrap your REPL/loop in try/finally and call flow.finalize_session_traces() on exit. Without it, the trace batch stays open and the final conversation may never export.

Streaming

For conversational UIs, use stream_turn() and iterate its ordered StreamFrame objects:
For a non-conversational Flow, setting stream = True makes kickoff() return a StreamSession. Do not set flow.stream = True when using handle_turn(); stream_turn() owns the conversational streaming lifecycle.

Imports

See also