odu: the MCP agent face — drive CI from a coding agent (juspay/odu#3, consumed here)

[srid]

odu: the MCP agent face — drive CI from a coding agent

This PR adds odu's agent face and consumes it in kolu, so a coding agent (Claude Code, Codex, opencode, Gemini CLI) drives kolu's CI with structured calls instead of scraping the terminal — the live-service dividend justci's batch shape couldn't deliver (juspay/justci#22 built an MCP mode and reverted it because process-compose auto-ran every recipe on launch; a runner that owns the DAG as idle state has that separation by construction).

odu side — juspay/odu#3 ✅ merged

odu mcp — an MCP stdio server on the SDK's low-level Server:

• Tools: run (start a background run and attach) · get_nodes · tail_log (live stream, or the durable per-SHA log) · rerun_node (the only mutation) · wait_for_settle (fail-fast — returns the instant a node goes red, not just on full settle).
• Resources: odu://nodes + odu://log/{node} subscribable, with notifications/resources/updated — the live-push ceiling; wait_for_settle is the floor for hosts that don't wake the model on a notification.
• In-band (dials .ci/odu.sock), predetermines no host (pool lease / hosts.json stays the coordinator's job), no new authz (single-operator, same ssh trust as the CLI).
• apm.yml declares the MCP server (the nix-chrome-devtools-mcp pattern) + ships the odu-mcp launcher (nix run github:juspay/odu -- mcp; ODU_FLAKE=.#odu to use a repo's own pinned odu).

It went through the full /be-review gauntlet: codex ⇄ Claude consensus (2 rounds, 7 findings fixed — a wait_for_settle false-green, a startRun hang/exit race, a durable-log path traversal, an unbounded readFileSync, MCP request-cancellation, subscribe-URI validation, a test temp-dir leak); lowy ⇄ hickey consensus (3 fixes — drive the verdict off the STATUS_META/summarize receptacles, share the node-row projection); code-police clean. A follow-up rigor/fallback audit found no stupid fallbacks. odu-on-odu CI green on both platforms.

kolu side — this PR (the consumption)

• npins pins odu → master (aa0af7c, the merge commit); nix run .#odu -- mcp works through kolu's flake re-export (validated — see Evidence).
• apm depends on juspay/odu, deploying the odu-mcp launcher and registering the odu MCP server in .mcp.json, .codex/config.toml, and opencode.json.
• Atlas note mini-ci-vs-justci.mdx updated as-built (MCP face shipped; status / roadmap / ledger / D2; @kolu/surface-mcp considered and rejected by a Lowy+Hickey pass — consumer-local odu mcp). Changelog entry under Added.

Dogfood

The MCP-capable odu runs kolu's own CI: a full two-platform run via ci/pu/run.sh (26/26 green), and an agent-driven linux run through this very MCP server (run → wait_for_settle → green in ~9 min).

🤖 Generated with Claude Code

[srid]

Evidence

odu mcp served through kolu's flake re-export (nix run .#odu -- mcp) — the agent face this PR adds, speaking MCP over stdio:

$ nix run .#odu -- mcp        # in-band; dials .ci/odu.sock

→ initialize
    server: odu v0.1.0   capabilities: tools, resources
→ tools/list
    run              Start a CI run the agent can then watch and drive.
    get_nodes        Snapshot the live pipeline: every node's id, status, exit code and duration in one structured frame.
    tail_log         One node's output so far (the buffered snapshot — replays a node that already finished).
    rerun_node       Reset a node and its transitive dependents on the live DAG and reschedule them — the only mutation, no new run process.
    wait_for_settle  Block until the run settles, or — fail-fast (default) — the instant a node goes red, so you can drill into a failure without waiting for the slow lanes.
→ resources/list:           odu://nodes
→ resources/templates/list: odu://log/{node}

This is the same odu kolu's CI runs (the npins pin), now also drivable by an agent. The end-to-end loop — run → wait_for_settle (fail-fast) → tail_log the red node → rerun_node → wait_for_settle — is covered by 61 unit tests over the real unix-socket transport in juspay/odu#3, and the MCP-capable odu is what posts this repo's checks (odu-on-odu CI green there).