[coordination] Ticket 1 — subordinate_status: give the Lead a global picture #205

Problem

coder-lead supervises N coder-repo instances through agent_supervision (#183) — the Overseer moved up a level, which is the design. But the Lead is not yet as capable as the thing it replaces.

The hardcoded Overseer (routes/coding.ts ~1085) opens by building a global picture — for every repo: is a session live, what did it last print, what are its instructions — then answers from it in one model call, or delegates. That answering half is what makes it an overseer.

list_subordinates returns {instanceId, name, status}, and status is agent_instances.status — the subscription lifecycle (active|paused|canceled), permanently "active" whether a subordinate is idle, mid-run, or on fire. So the Lead must delegate a run (durable workflow + full LLM loop) to learn anything.

This is a wrong field on a read path, not a missing abstraction.

Decision: compose, do not unify

Rejected: widening agent_loop_runs with a kind discriminator so pipeline/apply/browse/coding runs share one table.

• "Idle" and "stuck" are not rows. Idle is the absence of a row; stuck is a derivation over timestamps + runner liveness. A resolver is needed either way — the composition is irreducible, the table merge is not. That inverts the build order.
• Four lifecycle records, not three. A human-driven coding session writes only coding_sessions — and that is the Lead's main case. A kind over the three named tables misses the row it most needs.
• A kind enum is a second closed enum, in D1 where it is harder to change, while [coordination][deferred] Retire the workflow closed enum → declarative behavior #160 is retiring the first.
• Measured cost. The one partial unification already done (delegateToPilot writing a loop row) shipped two stranded-row bugs, both memorialised in coding-session.ts:122 and :158. Unifying adds ~5 open and ~20 terminal sites, and a stranded row is permanent data — unlike a read bug, which a redeploy fixes.
• It fails the docs' own test (coordination-primitives.md: "Build the abstraction when the fix you'd make anyway can be made through it"). The fix you'd make anyway is a status read, and it cannot be made through the unified table — it would be blocked behind five write-path conversions before producing one correct answer.

The staged gate for revisiting: a second consumer needs cross-instance run pagination that an in-memory merge cannot serve, and the reader is measured as the bottleneck. A read-only SQL VIEW union is the correct intermediate, and probably the terminal state.

The rule this must not break

Connectors read generic platform tables or a declared per-instance setting — never a domain store. Precedent: lib/connectors/repo-local.ts:35-51 stays generic by reading config.settings["repo_path"] rather than importing coding-store. lib/delegation.ts:8-27: "Generic so the board card doesn't have to be re-shaped per target kind."

The domain writes into a generic record; the supervisor reads platform records. A first attempt made lib/connectors/supervision.ts import coding-store/coding-timeline — reverted in 3f14bd3, because that is exactly the coupling migration 0063 says was removed.

The enabler

capabilities.boardColumns is already a declared, per-agent status vocabulary ({id,title,statuses[]}), resolved by boardConfigForInstance (lib/board.ts:33). A supervisor normalises any subordinate's free-text status through the subordinate's own declaration — no new declaration surface, and a third-party agent with columns "Triage / Cooking / Shipped" works on day one.

Two vocabularies, handled differently — this distinction is the design:

• instance_runtime_tasks.status is free text → bucketed through the subordinate's declared columns; output carries both the raw status and that agent's own columnTitle.
• agent_loop_runs.status is a closed platform enum → passed through verbatim, never bucketed.

Scope

1. columnForStatus in lib/agent-capabilities.ts. The rule exists twice already, both outside the API and both also matching column.id === status: store/console/src/tabs/BoardTab.tsx:636 and workers/mcp/src/instance-tools/shared.ts:87. Point the MCP copy at the new canonical one.
2. lib/instance-work.ts (new) — recentWorkForInstances / recentRunsForInstances. One D1 statement each, a UNION ALL of one indexed branch per subordinate (a flat IN (…) ORDER BY … LIMIT n lets one busy subordinate crowd out eleven). Must filter hidden = 0 (0019) or cleared cards resurface. Guard the empty-id case — an empty UNION ALL is a syntax error and a Lead with no links is reachable.
3. lib/subordinate-observation.ts (new) — pure, no D1. Bucketing, staleness, and the 16 000-char cap (the ceiling the Overseer itself uses).
4. lib/agent-loop-store.ts — last_progress_at, written by recordIteration via a defaulted arg so AgentLoopWorkflow starts reporting progress with no change. check_delegation improves for free.
5. lib/connectors/supervision.ts — add subordinate_status (read); rename list_subordinates' misleading status → subscription; intersect any instanceId argument with the graph.
6. agent-think.ts — add to READ_ONLY_TOOLS, or the cross-round dedup refuses the Lead's second observation in a turn.
7. Migration 0067 — the column, plus json_set on the coder-lead template's declared tools. No per-instance backfill: agentCapabilities resolves from agents.config at read time, so every subscribed Lead picks it up.

Read-only feature: it writes nothing, so no row can be stranded by it.

Acceptance

Ask the Lead "what is each of your agents doing right now?" — it answers from one subordinate_status call with zero delegate_goal calls.

Depth is deliberately outcomes + progress (objective, running/needs-you/done, step 4/10, quiet-for-N-min, outcome text), not raw terminal. The honest equivalent of the Overseer's terminal tail is deferred to #207.