Summary

The write path is built around a habit rather than a request: the capture tool is meant to fire at the end of every substantive exchange, unasked.

Capturing a turn carries the vendor's instruction to call it without being asked at the close of each exchange, on the argument that an uncaptured turn is lost to every other agent you work with tomorrow; the single-observation tool is the exception for a stated rule or a correction, not the default. Reading splits the same way — the question tool synthesises an answer with citations, while the export hands over everything and is flagged as potentially large. The third graph projection has no equivalent in the other two: it compares your self-image against the system's observation rather than returning either one.

What it is

A client for Polarity's Cosmos — a personal knowledge graph that any MCP-capable client writes observations into and reads context out of, so the memory follows you between Claude, Cursor, Codex and the rest rather than being rebuilt inside each one. A location layer sits alongside it for place-anchored notes and check-ins.

What you get

Writes at three levels of granularity: polarity_capture_turn for a whole user and assistant exchange, which Cosmos runs its own extractor over, polarity_observe for one durable fact, and the wrappers polarity_record_event and polarity_record_preference.
polarity_ask puts a natural-language question over the graph and returns a synthesised answer with the node and edge ids it drew on.
polarity_get_graph switches between three projections: the user's self-graph, the system's view of them, and the synchronisation between the two.
polarity_export produces the full graph — nodes, edges and counts — as JSON you can take with you.
A location layer: polarity_dump ties a short message to a waypoint, polarity_checkin records presence and triggers co-presence detection against other users' recent check-ins, and polarity_declare states future presence within a time window.
polarity_whoami as a cheap connectivity check that also reports which user and account this key resolves to.

Requirements

A Cosmos account and a per-user key. On macOS an install script does the whole job — it registers the server, wires the common clients, and stores the key in the system keychain, either through a one-shot deep link from the web console or by provisioning a key you already hold; a CI environment can supply the key through the environment instead. On Linux and Windows the same script installs the server path only. Read the script before running it if the extras matter to you: on macOS it also installs a background sync app that can feed iMessage, browser history, calendar, Claude Desktop transcripts and shell history into the graph, and iMessage access needs Full Disk Access granted to whatever runs it.

Setup effort

One command plus a key — curl -fsSL https://mcp.polarity-lab.com/install.sh | sh, then supply credentials