A persistent, Git-versioned map of your entire codebase — written by your coding agent, governed by a local MCP server. Agents read it once and know the system, instead of re-reading the repo on every task.

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Build large systems without losing the plot. In Codex, Claude Code, Cursor, OpenCode, and similar agents, your agent starts every task already knowing the whole system: what each file is for, what it depends on, and what must not break. It stops searching and re-reading the codebase for every request. People who are not professional developers can keep iterating on their own systems; professional developers can hand the whole system to an agent and keep their attention on architecture and design.

Take over an existing system in one step. Point the agent at an existing codebase of up to about 500,000 lines and ask it to build the index. It reports how well it knows each area, then picks up development from there. The practical limit is the size of the index, not the line count: a 700,000-line commercial system is developed this way today, with an index of about 300K tokens.

Change people, agents, or conversations without starting over. The index lives in the repository next to the code and is versioned by Git. When a project changes hands, switches agents, or opens a new conversation, one read of the index picks up where things left off.

After the first index, maintenance is automatic. The MCP server detects code changes and issues the entries that need updating. The agent fills them in as it finishes each task, so the index matches the current code and you never stop to maintain it.

One line per file, written by the model from the actual source. This is a real entry from this repository's own index:

atomic.go[CG9L]: F:Provides durable replace CAS, create CAS, atomic writes, and no-clobber recovery moves | R:code:internal/fs/atomic_exchange_linux.go,code:internal/fs/atomic_exchange_windows.go,code:internal/fs/lock.go | A:AtomicWrite,AtomicWriteCAS,AtomicCreateCAS,AtomicMoveCAS | S:Native publication never degrades to an overwriting rename; on a race, unsafe type, or unverifiable bytes, preserve third-party state