One durable memory across supported coding agents.
Your Markdown vault is canonical. DuckDB is the replaceable retrieval cache.

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A cairn marks a trail for whoever comes next. agentcairn does that for coding agents: it captures durable context from the tools you use, stores it as inspectable Markdown with provenance, and recalls only the most relevant pieces when another agent needs them.

Proof you can inspect

The memory is not hidden behind an admin console or a hosted database. The separate agentcairn-obsidian companion reads the same Markdown files as the agents and exposes provenance, currency, importance, supersession, and related: links.

_{A real agentcairn vault in Obsidian. The list is a view over the files—not a second memory store.}

Dogfood snapshot · 2026-07-15. Across 417 local recalls, the maintainer's vault returned context about 262× smaller than loading the full vault each time—an estimated 136.6M tokens of full-vault context avoided in aggregate. Token counts use approximately four characters per token. This is not billed-token savings, and agentcairn sends no telemetry.

Install

The shortest path is a first-class plugin. It bundles the MCP server, the memory skill, and the host-specific ambient hooks—no separate agentcairn package install. The plugin launches through uvx, so install uv first if uvx --version is not already available.

Claude Code

claude plugin marketplace add ccf/agentcairn
claude plugin install agentcairn@agentcairn

Claude Code gets per-turn project-scoped recall, session/compaction capture, and the /agentcairn:recall, /agentcairn:remember, /agentcairn:memory, /agentcairn:savings, and /agentcairn:ingest commands.

Codex

codex plugin marketplace add ccf/agentcairn
codex plugin add agentcairn@agentcairn

Codex gets the bundled MCP tools and memory skill, live-verified SessionStart recall, and SessionEnd capture with cairn sweep as the out-of-band backstop.

Agent-assisted setup

Already use skills.sh or a find-skills workflow? Install the public setup assistant:

npx skills add ccf/agentcairn --skill agentcairn-setup -g

Then ask your agent: Use $agentcairn-setup to preview, install, and verify AgentCairn for this coding agent.

This installs setup guidance only—not the AgentCairn runtime, MCP server, plugin, or hooks. The assistant delegates those changes to AgentCairn's preview-first native installer and verifies the resulting integration. The Claude Code and Codex plugin commands above remain the shortest path.

The default vault is ~/agentcairn and is created on first use. A new empty vault has nothing useful to recall yet, so prove the whole loop explicitly:

You   → Remember this durable fact: staging deploys use blue-green.
Agent → written and indexed
You   → Recall the staging deploy strategy.
Agent → staging deploys use blue-green.  ↳ <memory permalink>

remember writes the Markdown note and index entry together, so immediate recall is part of the contract. The first local run may download and warm the configured embedding/reranking models.

The contract

How it works

• Capture: host hooks improve immediacy; cairn sweep reads supported transcript stores out-of-band as the durable backstop. AgentCairn redacts recognized credentials, deduplicates, importance-gates, and distills before its automated plaintext writes.
• Reconcile: the first read transactionally brings the vault-scoped index in sync with Markdown. A failed rebuild preserves the last good cache and the durable files remain untouched.
• Recall: BM25 and semantic vectors are fused with Reciprocal Rank Fusion, then optionally reranked. Model/provider failures visibly fall back to BM25 with diagnostics instead of returning incompatible vectors.
• Remember: the MCP tool atomically writes a Markdown note and updates the index under one writer lock, making a successful save immediately recallable.

Designed for trust

• Local by default. FastEmbed runs locally, the MCP server uses stdio, there is no required daemon or external database, and there is no telemetry.
• Plain boundaries. The synced vault contains Markdown; by default, the rebuildable .duckdb index stays outside it. Vault symlinks that escape the configured root are rejected.
• Time-aware corrections. valid_from, valid_until, and superseded_by keep old evidence visible while making current facts rank first.
• Deterministic graph. [[wikilinks]] and optional cairn link neighbors create an Obsidian-native graph without asking an LLM to invent entities.
• Project-aware recall. The current project is boosted by default; cross-project results remain available and are labeled. Automatic recall is project-scoped unless you explicitly opt into all projects.

Agents supported

Every host resolves the same configured vault. cairn install previews detected hosts without writing. MCP configuration writes are backup-first and preserve unrelated servers; plugin-host installs delegate to the host's own CLI.

Codex SessionStart was verified live end-to-end with agentcairn 0.24.2 / plugin 0.1.2. The installed SessionEnd command dispatch and detached sweep pass exact handler probes; cairn sweep remains the out-of-band capture backstop. See the OpenCode integration and Hermes integration for their native lifecycle details.

Using it directly

The plugin is the easiest route, but agentcairn is also a standalone CLI and on-demand MCP server. Standalone installs require Python 3.11+.

uv tool install agentcairn

cairn init ~/agentcairn
cairn sweep --vault ~/agentcairn
cairn recall "how did we fix the auth bug?" --vault ~/agentcairn
cairn doctor --vault ~/agentcairn

Bring Claude Code's memory with you

Claude Code's auto-memory can seed the shared vault without changing its source files. The command previews only the current repository by default; add --apply to write the redacted notes and refresh the index.