pi
Facts
- Openness
- Open source
- Licence
- MIT
- Language
- TypeScript
- Pinned version
a13d35a(2026-10-01)- Topics checked
- 31 of 33
- Kind of agent
- Coding
What it does notably well
- Checkpoints and rewind
The session is an append-only tree: /tree and branch() only move a leaf pointer and never delete entries, an abandoned branch can be summarized into the branch entered, and…
- Code mode
Nested tool calls run through the session's own tool pipeline (ctx.executeTool to runToolCall with tool_call and tool_result hooks, validation, events with parentToolCallId), so…
A fresh worker and QuickJS wasm VM per run, killed with terminate() when the script settles, times out or is aborted, so even a microtask-spinning script cannot hold the host.
The tool description lists callable tools by namespace inside a token budget (default 3000 estimated tokens) and leaves deferred tools unlisted; scripts find them with…
- Compaction
Compaction is installed as a first-class step of the kernel's turn-preparation lifecycle: AgentSession fills agent.prepareNextTurnWithContext so that…
Summarization is failure-closed: getSummarizationFailure() turns an error or length stopReason into a failure (compaction.ts:585-593), and both summary calls throw on it and on a…
See how pi does on each topic
The topic-by-topic verdicts, the code lines and a side-by-side comparison are in the app. Sign in with Google; new accounts are approved by hand.
Independent analysis, not affiliated with pi.