v10.1.0 — MCP server v1 + UDS transport

Highlights

This release ships two major new capabilities and folds in the explain=true query parameter from the previous cycle:

• MCP server v1 (agent-brain-mcp) — new stdio Model Context Protocol server with 7 tools, 5 read-only resources, 6 prompts. Wire it into Claude Desktop / Code via mcpServers. Backend selector (--backend {auto,uds,http}), version-compat check at startup, exhaustive HTTP→MCP error code mapping, notifications/cancelled propagation.
• Unix-domain-socket transport (agent-brain-uds) — new client-only package with adversarial permission validator (rejects symlinks, group/world bits, cross-UID, parent dir != 0700, malformed pointer files). Server-side dual-bind via uvicorn runs HTTP and AF_UNIX on a shared loop with automatic chmod 0o600 and long-path pointer-file fallback.
• CLI --transport {auto,http,uds} — every CLI command resolves through open_client(ctx). auto tries UDS first and falls back to HTTP loudly.
• GET /health/config — new endpoint exposing storage backend, vector/BM25/graph enable flags, embedding + rerank model names, watcher state. Powers the MCP corpus://config resource.
• explain=true query parameter — opt-in structured explanation block on every POST /query result with per-mode fusion breakdown, matched BM25 terms, graph path, and signed rerank movement.
• Import-linter contracts — 3 layering rules enforced by task check:layering.

Packages published

Package	First release
agent-brain-rag (server)	continuing
agent-brain-cli	continuing
agent-brain-uds	NEW
agent-brain-mcp	NEW

Roadmap

v1 deliberately defers several capabilities so each can land with its own design doc — see docs/roadmaps/mcp/ and the issues filed against this milestone:

• MCP v2 — resource subscriptions + deferred URI schemes + Streamable HTTP + 9 remaining tools
• MCP v3 — CLI-via-MCP + framework integration matrix
• MCP v4 — OAuth 2.1 for remote Agent Brain

Documentation

• USER_GUIDE: new "Choosing a Transport (HTTP vs UDS)" and "Using Agent Brain via MCP" sections
• Full CHANGELOG entry in docs/CHANGELOG.md
• Design plan at docs/plans/2026-05-28-mcp-uds-transport-design.md

Closes #159. PR #185.

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