One memory across your coding agents. Plain Markdown under your control.

The contract

The files are canonical. The index is replaceable.

Six differentiators

How it works

New in v0.25

Claude learned it once. Bring it to every supported agent.

See exactly what is imported and how history is preserved

Survives uninstall

Delete the index. Reindex. Everything's back.

Benchmarks measured

Quickstart

# Claude Code plugin (recommended)
claude plugin marketplace add ccf/agentcairn
claude plugin install agentcairn@agentcairn

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

# ...or use it directly — standalone CLI + MCP server
uv tool install agentcairn          # installs the cairn + agentcairn commands
uvx agentcairn                      # ...or run the MCP server ephemerally
cairn install cursor                # wire the server into another host
cairn recall "how did we fix auth?"  # hybrid recall
cairn savings                       # context recall has saved you
cairn doctor                        # health-check the index

Use it in any MCP host

First-class in Claude Code, Codex, OpenCode, Hermes, and Antigravity. Portable everywhere else.

Claude Code, Codex, and Antigravity get a first-class plugin — a bundled MCP server, a memory skill, and (on Claude Code and Codex) ambient session hooks (recall at session start, capture at session end). Antigravity has no plugin hooks, so capture runs out-of-band via cairn sweep. Every other MCP host gets the same recall/search/remember tools via the portable server; cairn install wires it in non-destructively (your other servers are preserved, the original backed up to <config>.bak). Hermes Agent gets a native agentcairn MemoryProvider, and the agentcairn-obsidian plugin lets you read and navigate that memory inside Obsidian. Every host resolves the same configured vault (default ~/agentcairn).

Swipe to compare every host →

cairn install                 # detect installed agents + preview (writes nothing)
cairn install codex           # install the Codex plugin (shells to `codex plugin …`)
cairn install cursor          # write MCP config for an MCP host
cairn install --all           # configure every detected agent

Plugin hosts (Claude Code, Codex, Antigravity) install via the host's own CLI — the MCP server is bundled in the plugin. MCP configuration is merged using each host's native schema, non-destructively, idempotently, and backup-first. Ambient recall-at-start + capture-at-end is fully wired on Claude Code and Codex; Codex SessionStart recall is verified live, and capture also runs out-of-band via `cairn sweep`. Antigravity has no recognized plugin hooks — capture runs out-of-band via `cairn sweep` (◐). `agy plugin install` takes a local directory (not a git repo), so install with `cairn install antigravity --source <plugin dir>`; it also removes any stale mcp_config.json entry. Cursor has no plugin hooks either — `cairn sweep` ingests sessions out-of-band from Cursor's global `state.vscdb` SQLite store (`cursorDiskKV` user bubbles); Cursor remains an MCP host (not a plugin host), but `cairn install cursor` also installs the `using-agentcairn-memory` skill to `~/.cursor/skills/` alongside writing `~/.cursor/mcp.json`. Hermes gets in-process recall and capture through its native MemoryProvider lifecycle, but the current agentcairn package requires a Hermes environment running Python 3.12 or newer; see the Hermes guide.

Because the vault is plain Markdown, you can read what every agent remembers in Obsidian: the agentcairn-obsidian plugin (on the community store) adds a vault-native Memory view — a filterable list with provenance and currency, plus a d3-force memory graph of related: links, colored by project and sized by importance.

Trust & security