72020b1901
Implements the walking skeleton from the roadmap: agents connect to one HTTP
endpoint and Nexus aggregates upstream MCP servers behind it with namespaced
tools. Written in Go (single static binary), no external services required.
What works end-to-end (verified live + hermetic e2e tests):
- MCP protocol layer: JSON-RPC 2.0 + initialize/tools.list/tools.call
(internal/mcp), with stdio (subprocess) and Streamable HTTP client
transports, and a reusable stream transport for in-process wiring.
- Router + Dynamic Tool Registry: connects/initializes upstreams in parallel,
loads tools, namespaces them as {namespace}.{tool}, dispatches tools/call to
the owning upstream; refreshes on list_changed. A failed upstream stays
not-ready without taking down the gateway (data plane stays up).
- Gateway: single MCP endpoint (POST /mcp) that is an MCP server to agents,
plus /healthz and a minimal /metrics exposition.
- CLI (cmd/nexus): `serve`, `connect` (stdio<->HTTP bridge for local agents),
`demo-mcp` (built-in zero-dep demo server: echo/add/now), `version`.
- Config: declarative YAML with env expansion + validation.
- Store: persistence interfaces + in-memory impl (SQLite lands later).
Foundations for later phases: domain types (ARCHITECTURE §7), two-plane
split, event-driven refresh seam.
Tooling: Makefile (build/test/vet/fmt with version ldflags), config.example
.yaml. GOPATH moved to /go so it doesn't collide with the module root at /root;
.gitignore whitelist extended to track Go sources while ignoring build output.
Tests: unit (registry/namespacing) + full e2e (client -> demo server over
pipes -> router -> HTTP gateway: initialize, aggregated tools/list, tool-call
routing, unknown-tool error). go vet + gofmt clean.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
20 lines
798 B
Go
20 lines
798 B
Go
package mcp
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import "context"
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// Transport is a bidirectional MCP channel to a single peer. Implementations
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// correlate requests with responses internally so callers see simple
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// request/response semantics.
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//
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// Call returns the response Message (which may itself carry a JSON-RPC error in
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// Message.Error); the returned error is reserved for transport-level failures
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// (process died, connection refused, context cancelled, malformed frame).
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type Transport interface {
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Call(ctx context.Context, method string, params any) (*Message, error)
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Notify(ctx context.Context, method string, params any) error
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// SetNotificationHandler registers a handler for peer-initiated
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// notifications/requests (e.g. tools/list_changed). May be nil.
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SetNotificationHandler(func(*Message))
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Close() error
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}
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