feat(mcp): initial implementation — MCP server, framework indexer, 10 tools, 8 validation rules (v0.1.0)
Introduces code.nochebuena.dev/einherjar/mcp — the Einherjar Model Context Protocol
server. A remote, streamable-HTTP service that teaches AI assistants about every
other module of the framework: which package exposes which type, what each module
guarantees through its compliance tests, the canonical wiring shape for a service,
and whether a Go snippet follows the conventions. Indexes the framework on disk at
build time and ships a self-contained binary via go:embed; imports nothing from
other einherjar/* modules at compile time.
server (cmd/server):
- Streamable-HTTP MCP server built on github.com/modelcontextprotocol/go-sdk v1.0.0
- mcp.NewServer + mcp.NewStreamableHTTPHandler, served via net/http on EINHERJAR_MCP_ADDR
(default :8080) and EINHERJAR_MCP_PATH (default /mcp)
- /healthz liveness endpoint; structured JSON logging via log/slog
- Loads the embedded data/index.json once at startup; in-memory for the process lifetime
indexer (cmd/indexer):
- Walks an Einherjar repository checkout (default ../), parses every sibling
module's go.mod, README.md, CHANGELOG.md, docs/adr/ADR-*.md, doc.go package
comments, every exported type/interface/func/method/const/var (via go/doc on
go/parser ASTs), and compliance_test.go
- Captures module dependency edges by regex over each go.mod's require lines
(einherjar/* paths only; self-reference filtered)
- Appends a synthetic "wire" module documenting canonical application wiring
conventions, authored at internal/index/builtins/README.md and embedded via
go:embed; participates in list_modules / get_module / get_example like a real module
internal/index:
- Schema einherjar.mcp/index/v1; types: Index, Module, SubPackage, Symbol, ADR,
Example, Compliance, InterfaceAssert, ComplianceTest
- Build(repoRoot) → *Index walks the repo; BuildBuiltins() returns the synthetic
wire module from the embedded markdown
- Load([]byte) → *Index validates the schema version on read
- FindModule, SearchSymbols helpers used by tools
internal/tools (10 tools):
- list_modules — enumerate every module with purpose + sub-packages
- get_module — package doc, dependencies, sub-packages, key symbols, ADRs,
compliance counts; optional embedded README
- search_symbols — full-text across name, doc, sub-package, module; filterable by
module and kind
- get_symbol — full signature, doc comment, source file:line for one symbol
- list_adrs — list ADRs across the framework or within one module
- get_adr — fetch one ADR's markdown body
- get_example — canonical usage snippets extracted from module READMEs and from
the synthetic wire conventions
- get_compliance — interface assertions (var _ Iface = impl) 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
internal/rules (8 rules, registered via init() against a single registered slice):
- launcher.missing-run — launcher constructed but Run() never called
- launcher.no-components — launcher.New() called without any .Append(...)
- launcher.run-error-discarded — lc.Run() invoked as an ExprStmt (return ignored)
- logz.direct-env-read — os.Getenv("EINHERJAR_LOG_*") bypassing logz config
- web.server-not-appended — web/server constructed but not added to the launcher
- wire.hook-bad-signature — with<Feature>(...) first param is not launcher.Launcher
- wire.hook-outside-beforestart — repo/service/handler construction or route
registration at the top level of a hook (outside lc.BeforeStart)
- wire.route-specific-after-param — /users/{id} registered before a sibling
/users/me of the same length and method (chi would shadow the literal route)
Synthetic wire module (internal/index/builtins/README.md):
- Project layout (cmd/<app>/main.go + internal/wire/*.go + per-feature domain dirs)
- Canonical Run() shape: config → logger → infra (db, cache, pool, mc, srv) → cross-
cutting (validator, permission provider) → launcher.New → lc.Append(infra...) →
withMigrations / withSuperAdminSeed / withHealth / withFeature hooks → return lc.Run()
- Canonical with<Feature> hook shape: signature (launcher.Launcher first, server.Server
second, deps last), single lc.BeforeStart closure containing all construction +
route registration
- chi route ordering, srv.With(authz(...)) authorization, middleware helpers
(authz / skipPublicPaths / skipMethodPath), tokenSignerAdapter pattern showing
that the framework exposes Signer.Sign as a primitive and the application owns
the access/refresh response shape
Packaging:
- Multi-stage Dockerfile that builds from the einherjar repository root
(docker build -f mcp/Dockerfile .) so cmd/indexer can walk every sibling module
at image-build time; runtime layer is gcr.io/distroless/static-debian12:nonroot
- 86-byte placeholder data/index.json committed once with `git add -f`; subsequent
indexer runs overwrite it locally but the file is .gitignored
- .gitea/CODEOWNERS and pull_request_template.md mirror the sibling layout
Design notes:
- mcp depends on nothing in einherjar/* — it reads the framework via the filesystem
at index time. This keeps mcp outside the framework dependency graph and lets it
index any version of einherjar without versioning itself in lock-step.
- All structured-output tool responses initialise empty slices ([]Type{}) rather
than relying on Go's nil-marshals-to-null default, so the SDK's JSON-schema
output validator never rejects a tools/call result.
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CHANGELOG.md
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# Changelog — einherjar/mcp
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All notable changes to this module are documented here.
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Format follows [Keep a Changelog](https://keepachangelog.com/en/1.1.0/).
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This module adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
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---
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## [0.1.0] — 2026-05-29
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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.
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### Added
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#### Server (`cmd/server`)
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- Streamable-HTTP MCP server built on `github.com/modelcontextprotocol/go-sdk` v1.0.0
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- Listen address and HTTP path configurable via `EINHERJAR_MCP_ADDR` (default `:8080`) and `EINHERJAR_MCP_PATH` (default `/mcp`)
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- `/healthz` liveness endpoint
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- Embedded framework index loaded once at startup; in-memory for the lifetime of the process
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#### Indexer (`cmd/indexer`)
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- Walks an Einherjar repository checkout and produces `data/index.json`
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- 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)
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- Appends a synthetic `wire` module documenting canonical Einherjar application wiring conventions
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#### Tools (10)
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- `list_modules` — enumerate every Einherjar module with purpose and sub-packages
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- `get_module` — package doc, dependencies, sub-packages, key symbols, ADRs, compliance counts; optional embedded README
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- `search_symbols` — full-text search across name, doc, sub-package, module
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- `get_symbol` — full signature, doc, and source location for one symbol
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- `list_adrs` — list architectural decision records, optionally filtered by module
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- `get_adr` — fetch one ADR's markdown body
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- `get_example` — canonical usage snippets extracted from module READMEs and the `wire` conventions
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- `get_compliance` — interface assertions and structural test names from a module's `compliance_test.go`
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- `get_changelog` — full CHANGELOG.md markdown for one module
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- `validate_snippet` — pattern-match a Go snippet against framework conventions; returns findings with severity, hint, and line
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#### Validation rules (8)
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- `launcher.missing-run`, `launcher.no-components`, `launcher.run-error-discarded`
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- `logz.direct-env-read`
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- `web.server-not-appended`
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- `wire.hook-bad-signature`, `wire.hook-outside-beforestart`, `wire.route-specific-after-param`
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#### Synthetic `wire` module
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- Authored in `internal/index/builtins/README.md`; participates in `list_modules`, `get_module`, and `get_example` exactly like a real module
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- Sections: project layout, `Run()` shape, feature hook shape, route ordering, authorization, middleware helpers, adapters at the wire boundary, migrations and seeds
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- All examples use einherjar import paths
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#### Packaging
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- 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
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- Distroless runtime image; static binary; non-root user
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