# Ledger

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**Status:** SHIPPED, v0.5.6 on PyPI — https://pypi.org/project/arcaeon-ledger/
**Install:** `pip install arcaeon-ledger`
**Non-proofs:**
- truncation-without-witness
- truth of content
- authorship
- default verify() still tolerates unchained rows before the first chained row (adoption-on-existing-log design) — pass strict=True to reject any unchained row, including a fabricated legacy prepend (0.5.4)
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Observability tools show you what your agent did. Ledger lets you prove it.

Every action an AI agent takes is hash-chained to the one before it. Edit a row, delete one, or reorder history, and every later link breaks — verification names the exact line. You own a portable audit trail you can prove wasn't altered, and you can replay the exact state that produced a bad output.

- Open-source core, free to self-host. Zero dependencies.
- Hosted collection, long retention, and compliance export: coming.
- Status: SHIPPED — v0.5.6 on PyPI. `pip install arcaeon-ledger` then `python -m arcaeon_ledger.selftest` to check the guarantees yourself.

Contact: hello@arcaeon.io

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