co-mono/packages/coding-agent/docs/session.md

Session File Format

Sessions are stored as JSONL (JSON Lines) files. Each line is a JSON object with a type field.

File Location

~/.pi/agent/sessions/--<path>--/<timestamp>_<uuid>.jsonl

Where <path> is the working directory with / replaced by -.

Type Definitions

• src/session-manager.ts - Session entry types (SessionHeader, SessionMessageEntry, etc.)
• packages/agent/src/types.ts - AppMessage, Attachment, ThinkingLevel
• packages/ai/src/types.ts - UserMessage, AssistantMessage, ToolResultMessage, Usage, ToolCall

Entry Types

SessionHeader

First line of the file. Defines session metadata.

{"type":"session","id":"uuid","timestamp":"2024-12-03T14:00:00.000Z","cwd":"/path/to/project","provider":"anthropic","modelId":"claude-sonnet-4-5","thinkingLevel":"off"}

For branched sessions, includes the source session path:

{"type":"session","id":"uuid","timestamp":"2024-12-03T14:00:00.000Z","cwd":"/path/to/project","provider":"anthropic","modelId":"claude-sonnet-4-5","thinkingLevel":"off","branchedFrom":"/path/to/original/session.jsonl"}

SessionMessageEntry

A message in the conversation. The message field contains an AppMessage (see rpc.md).

{"type":"message","timestamp":"2024-12-03T14:00:01.000Z","message":{"role":"user","content":"Hello","timestamp":1733234567890}}
{"type":"message","timestamp":"2024-12-03T14:00:02.000Z","message":{"role":"assistant","content":[{"type":"text","text":"Hi!"}],"api":"anthropic-messages","provider":"anthropic","model":"claude-sonnet-4-5","usage":{...},"stopReason":"stop","timestamp":1733234567891}}
{"type":"message","timestamp":"2024-12-03T14:00:03.000Z","message":{"role":"toolResult","toolCallId":"call_123","toolName":"bash","content":[{"type":"text","text":"output"}],"isError":false,"timestamp":1733234567900}}

ModelChangeEntry

Emitted when the user switches models mid-session.

{"type":"model_change","timestamp":"2024-12-03T14:05:00.000Z","provider":"openai","modelId":"gpt-4o"}

ThinkingLevelChangeEntry

Emitted when the user changes the thinking/reasoning level.

{"type":"thinking_level_change","timestamp":"2024-12-03T14:06:00.000Z","thinkingLevel":"high"}

Parsing Example

import { readFileSync } from "fs";

const lines = readFileSync("session.jsonl", "utf8").trim().split("\n");

for (const line of lines) {
  const entry = JSON.parse(line);
  
  switch (entry.type) {
    case "session":
      console.log(`Session: ${entry.id}, Model: ${entry.provider}/${entry.modelId}`);
      break;
    case "message":
      console.log(`${entry.message.role}: ${JSON.stringify(entry.message.content)}`);
      break;
    case "model_change":
      console.log(`Switched to: ${entry.provider}/${entry.modelId}`);
      break;
    case "thinking_level_change":
      console.log(`Thinking: ${entry.thinkingLevel}`);
      break;
  }
}