For agents & LLMs

The undo button
for AI.

Agents act. Sometimes they act badly. Fast captures state before every run so "undo the last 47 tool calls" is a real, reliable operation — not a prayer.

Checkpoints

Capture the whole
moment.

Files, conversation state, and tool state — versioned together in one structured checkpoint, automatically, before an agent touches anything.

Rollbacks

Diff-aware, precise,
reversible.

Roll back exactly what an agent changed and nothing else. Structured diffs mean you can review before you revert — and revert the revert.

Agent API

Checkpoint, diff, and rollback verbs with idempotency keys, dry-run flags, and machine-readable errors.

Explore the API →

Integrations

MCP server, LangChain, Cursor and more — Fast plugs into the tools your agents already run on.

See integrations →

Docs

Precise docs written for machine readers as much as human ones.

Read the docs →