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docs/en/learn/flowstate-chat-history.mdx
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docs/en/learn/flowstate-chat-history.mdx
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---
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title: "Flowstate Chat History"
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description: "Build a stateful chat workflow that keeps context compact, persistent, and production-friendly."
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icon: "comments"
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mode: "wide"
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---
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## Overview
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This guide shows a practical pattern for managing LLM chat history with Flow state:
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- Keep recent turns in a sliding window
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- Summarize older turns into a compact running summary
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- Persist state automatically with `@persist()`
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- Keep optional long-term recall using Flow memory
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## Why this pattern works
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Naively appending every message to prompts causes token bloat and unstable behavior over long sessions. A better approach is:
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1. Keep only the most recent turns in `state.messages`
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2. Move older turns into `state.running_summary`
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3. Build prompts from `running_summary + recent messages`
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## Prerequisites
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1. CrewAI installed and configured
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2. API key configured for your model provider
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3. Basic familiarity with Flow decorators (`@start`, `@listen`)
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## Step 1: Define typed chat state
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```python Code
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from typing import Dict, List
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from pydantic import BaseModel, Field
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class ChatSessionState(BaseModel):
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session_id: str = "demo-session"
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running_summary: str = ""
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messages: List[Dict[str, str]] = Field(default_factory=list)
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max_recent_messages: int = 8
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last_user_message: str = ""
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assistant_reply: str = ""
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turn_count: int = 0
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```
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## Step 2: Build the Flow
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```python Code
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from crewai.flow.flow import Flow, start, listen
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from crewai.flow.persistence import persist
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from litellm import completion
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@persist()
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class ChatHistoryFlow(Flow[ChatSessionState]):
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model = "gpt-4o-mini"
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@start()
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def capture_user_message(self):
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self.state.last_user_message = self.state.last_user_message.strip()
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self.state.messages.append(
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{"role": "user", "content": self.state.last_user_message}
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)
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self.state.turn_count += 1
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return self.state.last_user_message
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@listen(capture_user_message)
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def compact_old_history(self, _):
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if len(self.state.messages) <= self.state.max_recent_messages:
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return "no_compaction"
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overflow = self.state.messages[:-self.state.max_recent_messages]
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self.state.messages = self.state.messages[-self.state.max_recent_messages :]
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overflow_text = "\n".join(
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f"{m['role']}: {m['content']}" for m in overflow
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)
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summary_prompt = [
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{
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"role": "system",
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"content": "Summarize old chat turns into short bullet points. Preserve facts, constraints, and decisions.",
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},
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{
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"role": "user",
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"content": (
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f"Existing summary:\n{self.state.running_summary or '(empty)'}\n\n"
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f"New old turns:\n{overflow_text}"
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),
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},
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]
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summary_response = completion(model=self.model, messages=summary_prompt)
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self.state.running_summary = summary_response["choices"][0]["message"]["content"]
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return "compacted"
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@listen(compact_old_history)
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def generate_reply(self, _):
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system_context = (
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"You are a helpful assistant.\n"
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f"Conversation summary so far:\n{self.state.running_summary or '(none)'}"
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)
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response = completion(
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model=self.model,
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messages=[{"role": "system", "content": system_context}, *self.state.messages],
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)
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answer = response["choices"][0]["message"]["content"]
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self.state.assistant_reply = answer
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self.state.messages.append({"role": "assistant", "content": answer})
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# Optional: store key turns in long-term memory for later recall
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self.remember(
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f"Session {self.state.session_id} turn {self.state.turn_count}: "
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f"user={self.state.last_user_message} assistant={answer}",
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scope=f"/chat/{self.state.session_id}",
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)
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return answer
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```
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## Step 3: Run it
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```python Code
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flow = ChatHistoryFlow()
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first = flow.kickoff(
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inputs={
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"session_id": "customer-42",
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"last_user_message": "I need help choosing a pricing plan for a 10-person team.",
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}
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)
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print("Assistant:", first)
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second = flow.kickoff(
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inputs={
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"last_user_message": "We also need SSO and audit logs. What do you recommend now?",
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}
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)
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print("Assistant:", second)
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print("Turns:", flow.state.turn_count)
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print("Recent messages:", len(flow.state.messages))
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```
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## Expected output (shape)
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```text Output
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Assistant: ...initial recommendation...
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Assistant: ...updated recommendation with SSO and audit-log requirements...
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Turns: 2
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Recent messages: 4
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```
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## Troubleshooting
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- If replies ignore earlier context:
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increase `max_recent_messages` and ensure `running_summary` is included in the system context.
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- If prompts become too large:
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lower `max_recent_messages` and summarize more aggressively.
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- If sessions collide:
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provide a stable `session_id` and isolate memory scope with `/chat/{session_id}`.
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## Next steps
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- Add tool calls for account lookup or product catalog retrieval
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- Route to human review for high-risk decisions
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- Add structured output to capture recommendations in machine-readable JSON
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