Claude Co-work Substrate Memory

Beta — stdio transport unverified in the Co-work sandbox. The plugin format is verified against Anthropic's cached Co-work authoring skill, but its stdio MCP execution environment in Co-work's VM sandbox is not verified. A human must install the .plugin, open a Co-work session, and confirm substrate_status returns before support is claimed.

Substrate Memory gives Claude Co-work seven MCP tools for searching and recording organizational memory. Capture is skill-driven: the bundled skill directs Claude to search prior work before answering, remember durable user facts and decisions, and sync at natural session boundaries. Hooks are a best-effort bonus only and may never fire in Co-work.

Install

1. Package the repository as a .plugin file as described in docs/packaging.md.

2. Install the .plugin file in Claude Co-work.

3. Set the environment variables below in the process that launches Co-work.

4. Start a session and run substrate_status.

Related MCP server: Cornerstone MCP Server

Configuration

Set these secrets in the process environment only:

SUBSTRATE_API_URL=https://api.substrate.example
SUBSTRATE_API_KEY=...

SUBSTRATE_API_KEY is never written to a config file. Host config files are world-readable plaintext. SUBSTRATE_PYTHON optionally overrides the python executable used for the stdio server.

Sandbox consequences and mitigations:

1. A loopback http://127.0.0.1 Substrate URL may not resolve from the Co-work sandbox; use an HTTPS URL.

2. python may not be on the sandbox PATH; set SUBSTRATE_PYTHON to an available executable.

3. .mcp.json also supports an {"type":"http","url":...} transport as an alternative when a hosted MCP endpoint is available.

Tools

• substrate_search — search cited organizational memory cards.

• substrate_read — read a wiki page by path.

• substrate_query — ask for a cited synthesis.

• substrate_ingest — submit text for ingestion.

• substrate_remember — record a durable fact, decision, or preference.

• substrate_sync — flush the durable local spool.

• substrate_status — report content-free configuration and delivery status.

Privacy boundary

The plugin reads API credentials from the process environment only, redacts captured text before persistence or transfer, and emits content-free operational diagnostics. It does not read Co-work transcripts; hook events contain only a session boundary signal. Report vulnerabilities through GitHub private security advisories.

See BOUNDARY.md and SECURITY.md for the public commitment and security policy.

Repository map

• skills/ — the primary Co-work capture instructions and tool reference.

• src/claude_cowork_memory/ — Co-work runtime, MCP server, hook, and CLI.

• src/substrate_capture/ — frozen shared client, redaction, spool, event, and MCP core.

• hooks/ — best-effort Stop and SessionEnd integration.

• tests/ — core and plugin contract tests.

• docs/packaging.md — .plugin creation instructions.

MIT © 2026 Sightline Technologies Inc.