# Changelog — einherjar/mcp

All notable changes to this module are documented here.
Format follows [Keep a Changelog](https://keepachangelog.com/en/1.1.0/).
This module adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).

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## [0.1.1] — 2026-05-29

Patch release. Two changes to `cmd/server` make the binary cleaner to run behind a unix socket on a reverse-proxied host, plus two repository-hygiene changes that follow from the same deployment exercise.

### Added

- **Systemd socket activation** in `cmd/server`. The binary inherits the listener from `LISTEN_FDS` via `github.com/coreos/go-systemd/v22/activation` when present, falling back transparently to TCP `-addr` binding otherwise. Startup log records `"mode":"socket-activated"` or `"mode":"tcp"`. Same binary, no flag or env var to toggle.

### Changed

- **Health probe path** moved from `/healthz` to `<path>/healthz` (default `/mcp/healthz`). Lets a reverse proxy expose the entire MCP service through one location prefix. v0.1.0 consumers hitting the old `/healthz` route receive 404; update to `/mcp/healthz` (or whatever path matches your `-path` flag).
- **`README.md` deployment section** rewritten to be hosting-agnostic. Points at the `Dockerfile` and systemd socket activation as supported binary modes without prescribing one operator's setup. Adds the SSE-buffering caveat once: any reverse proxy must disable response buffering on the `/mcp` location, otherwise Server-Sent Events get batched and streamable MCP sessions break.
- **`/deploy/`** is now `.gitignored`. Local deployment artefacts (systemd units, reverse-proxy templates, per-release scripts) are operator-specific by design and live outside the public repository. The `Dockerfile` at the module root remains the only portable, public-facing build artefact.

### Dependencies

- **Added:** `github.com/coreos/go-systemd/v22 v22.7.0` — used by `cmd/server` to detect and use a systemd-passed listener.

### Upgrade notes

| If you… | Action |
|---|---|
| Consume the MCP service from an MCP client (Claude, Cursor, Zed, etc.) | None — `/mcp` is unchanged |
| Monitor the service via the healthz probe | Update the probe URL from `/healthz` to `/mcp/healthz` |
| Run the binary directly (no reverse proxy) | None — `-addr` TCP binding still works the same way |
| Run the binary under systemd with a socket unit | The same binary now picks up the inherited listener automatically |

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## [0.1.0] — 2026-05-29

Initial release. The `mcp` module hosts the **Einherjar Model Context Protocol server** — a remote, streamable-HTTP service that teaches AI assistants about every other module of the framework.

### Added

#### Server (`cmd/server`)

- Streamable-HTTP MCP server built on `github.com/modelcontextprotocol/go-sdk` v1.0.0
- Listen address and HTTP path configurable via `EINHERJAR_MCP_ADDR` (default `:8080`) and `EINHERJAR_MCP_PATH` (default `/mcp`)
- `/healthz` liveness endpoint
- Embedded framework index loaded once at startup; in-memory for the lifetime of the process

#### Indexer (`cmd/indexer`)

- Walks an Einherjar repository checkout and produces `data/index.json`
- For each sibling module captures: import path, Go version, README (full + extracted tagline), CHANGELOG, root `doc.go` package comment, sub-package doc comments, every exported symbol (type/interface/func/method/const/var) with signature + godoc, ADRs, README code-fence examples, dependency edges from `go.mod`, and the contents of `compliance_test.go` (interface assertions + structural test names)
- Appends a synthetic `wire` module documenting canonical Einherjar application wiring conventions

#### Tools (10)

- `list_modules` — enumerate every Einherjar module with purpose and sub-packages
- `get_module` — package doc, dependencies, sub-packages, key symbols, ADRs, compliance counts; optional embedded README
- `search_symbols` — full-text search across name, doc, sub-package, module
- `get_symbol` — full signature, doc, and source location for one symbol
- `list_adrs` — list architectural decision records, optionally filtered by module
- `get_adr` — fetch one ADR's markdown body
- `get_example` — canonical usage snippets extracted from module READMEs and the `wire` conventions
- `get_compliance` — interface assertions and structural test names from a module's `compliance_test.go`
- `get_changelog` — full CHANGELOG.md markdown for one module
- `validate_snippet` — pattern-match a Go snippet against framework conventions; returns findings with severity, hint, and line

#### Validation rules (8)

- `launcher.missing-run`, `launcher.no-components`, `launcher.run-error-discarded`
- `logz.direct-env-read`
- `web.server-not-appended`
- `wire.hook-bad-signature`, `wire.hook-outside-beforestart`, `wire.route-specific-after-param`

#### Synthetic `wire` module

- Authored in `internal/index/builtins/README.md`; participates in `list_modules`, `get_module`, and `get_example` exactly like a real module
- Sections: project layout, `Run()` shape, feature hook shape, route ordering, authorization, middleware helpers, adapters at the wire boundary, migrations and seeds
- All examples use einherjar import paths

#### Packaging

- Multi-stage `Dockerfile` that builds from the einherjar repository root (`docker build -f mcp/Dockerfile .`) so the indexer can walk every sibling module at image-build time
- Distroless runtime image; static binary; non-root user