LayerMap

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LayerMap tells your coding agent what calls a function and what changing it affects, up to the HTTP routes, in one call. With at most 15 requests, agents found 97.9% of affected endpoints with LayerMap vs 58.8% without; with no limit, Claude Code cost 32% less (benchmark).

Resolved by each language's compiler or type checker, not guessed from names by tree-sitter: calls through interfaces, base classes, templates and decorators link as the compiler links them, for TypeScript, JavaScript, Go, Python and Java.

_{A real Claude Code session on Miniflux, replayed: one map call finds every endpoint, then the agent confirms them in source.}

A layered map of your codebase for coding agents. LayerMap gives Claude Code, Codex, DeepSeek
Harness and other MCP clients three read-only tools that answer, in one call, what an agent otherwise works out with
dozens of searches:

• What calls this, and what does changing it affect? Callers traced up to 8 levels, to the
  HTTP routes, handlers, jobs and commands they start from.
• What does it call? Callees down to 8 levels.
• What is here? Modules, each file's declarations, and every usage of a symbol.

It maps TypeScript, JavaScript, Go, Python and Java with each language's own compiler, so calls
through interfaces, base classes, templates and decorators resolve as the compiler resolves them,
including the ones text search misses.

Example

In Miniflux, one call on Storage.MarkFeedAsRead finds all four
ways a request reaches it, each with its route:

DECLARATION internal/storage/entry.go: Storage.MarkFeedAsRead m656-680 exported
  ← called by internal/api/feed.go: handler.markFeedAsRead m140-155 @149
  ← called by internal/fever/handler.go: handler.handleWriteFeeds m492-519 @508
  ← called by internal/googlereader/handler.go: handler.markAllAsReadHandler m1261-1338 @1311
  ← called by internal/ui/feed_mark_as_read.go: handler.markFeedAsRead m14-30 @24
[1] internal/api/feed.go: handler.markFeedAsRead m140-155
  ← used as value by internal/api/api.go: Serve f25-84 @61 "PUT /v1/feeds/{feedID}/mark-all-as-read"
[1] internal/googlereader/handler.go: handler.markAllAsReadHandler m1261-1338
  ← used as value by internal/googlereader/handler.go: Serve f44-64 @62 "POST /reader/api/0/mark-all-as-read"
[1] internal/ui/feed_mark_as_read.go: handler.markFeedAsRead m14-30
  ← used as value by internal/ui/ui.go: Serve f18-180 @77 "POST /feed/{feedID}/mark-all-as-read"
… (the Fever API, then on down to main.go: main)

m and f mark methods and functions with their lines; @ is the line of the call, and the quoted
route is what it is registered under: the HTTP method and the full path, with the /v1 prefix its
subrouter adds. In Java, Python and TypeScript the route shows on the handler itself, as in
@GetMapping("/{id}") route "GET /api/tasks/{id}".

Results

Impact questions ("which HTTP endpoints does changing this affect?") on public Go, Python and Java
projects, graded blind against truth sets cross-checked with each language's own toolchain:

With a tight budget, the map finds far more of the affected code, at about 24% more tokens. With
no limit, both agents find nearly everything either way. Claude Code costs a third less with the
map. Codex's current defaults already search lean, so the map no longer saves it tokens; at
reasoning effort max, in the first round, it saved 55%. Agents with the map explore more widely,
which takes longer. These are small samples on tasks written by LayerMap's authors.
The report has the
setup, the published tasks and the limitations.

How LayerMap differs

Other tools give agents part of this. LayerMap combines compiler accuracy with whole-chain traces
in one local map:

Another tool fits better if you need:

• more languages, since tree-sitter graphs cover 30 or more;
• Windows;
• renaming and refactoring, from language servers;
• search by meaning, from embedding search;
• search across many repositories, with Sourcegraph.

Install

Claude Code

/plugin marketplace add coffeecoproject/layermap
/plugin install layermap@layermap

Codex

codex plugin marketplace add coffeecoproject/layermap
codex plugin add layermap@layermap

DeepSeek Harness

npx layermap setup dsh

This adds LayerMap to every dsh profile. Each session maps the project dsh was started in, and
npx layermap remove dsh undoes it.

In every agent, start a new session in a Git repository and ask as usual. LayerMap tells the agent
when the map helps. On first launch, npx downloads the pinned layermap package from npm.

Claude Code asks once before each map tool runs in a project. Choose "don't ask again", or run
npx layermap allow claude to allow the plugin's read-only tools everywhere.

Without plugins: run npx layermap setup claude or npx layermap setup codex. Setup does three
things:

• registers the server;
• lets its read-only tools run without a prompt;
• adds one marked sentence to the agent's instructions file.

Use --scope project to set it up for a whole team, and npx layermap remove … to undo it. For any
other MCP client, run npx -y layermap mcp as a stdio server in the repository.

Requirements:

• Node.js 22.22 or later.
• macOS or Linux (x64 or arm64).
• A Git repository.
• For Java projects, a JDK 21 or later.

How it works

The first call in a repository builds its map: seconds for a small project, a few minutes for a
large one. Later calls re-analyze only what changed, so the map always matches the working tree.

Maps stay in your user cache (~/Library/Caches/layermap, ~/.cache/layermap or
LAYERMAP_CACHE), never in the repository. LayerMap runs entirely on your machine and sends
nothing anywhere (privacy,
security).

The same from the command line:

npx layermap explore src/api/users.ts --name createUser --direction INCOMING --depth 8
npx layermap search "invoice total"
npx layermap refs src/billing/tax.ts calculateTax

FAQ

How long does the first map take? On a recent Mac:

• Miniflux (400 Go files): about 3 s.
• Polar's server (1,900 Python files): about a minute.
• Conductor (1,500 Java and 1,300 TypeScript files): under two minutes.

What can't it see? Calls the compiler cannot resolve statically: dependency injection, unknown
framework routing, reflection and computed names. The tools say where a trace stops, and a missing
relationship does not prove absence.

Windows? Not yet.

How do I remove it?

• Claude Code: /plugin uninstall layermap@layermap.
• Codex: codex plugin remove layermap@layermap.
• Then delete the cache directory.

Development

You need pnpm, Go 1.24 and a JDK 21+. A missing toolchain leaves its language unanalyzed.

Run pnpm install. On the first install pnpm asks which dependencies may run build scripts; allow
esbuild only, since the SQLite package ships prebuilt binaries:

pnpm approve-builds esbuild '!@photostructure/sqlite'

Then run pnpm test, pnpm typecheck or pnpm lint.

pnpm package builds the npm package.

License

Apache-2.0. See LICENSE and
NOTICE.