swarm: atomic multi-agent batch engine

This skill is the low-level execution engine for parallel multi-agent sweeps. A single Swarm is an atomic execution unit: 1 Swarm = 1 concurrent batch of M read-only Interns (subagent_batch). Swarm does not define multi-round state machines. Caller skills (audit, init, ssot, auto) orchestrate N rounds of Swarms with custom M counts.

Specifications and constraints

• Worker role: Intern. The infra2 SDK LlmSettings role small gives its model and reasoning effort. subagent-worker --check-models prints them.
• Batch size (M): Default 10 tasks per swarm batch. PROVIDER_CONCURRENCY in subagent-worker sets how many requests run at once; the rest run in waves. Custom M specified by caller skill (e.g. M=4 in init/ssot, M=3 in auto).
• Tool profile: Strictly read-only tools or prompt-injected source code via subagent_batch.
• Output contract:
  • Dense, structured ASD-STE100 technical findings.
  • Length: 500 to 1200 tokens per Intern.
  • Anchors required: Every finding must cite exact file anchors (file#Lxx-Lyy) and reproducible counterexamples.
  • Zero conversational filler. Start line 1 with the single line-1 JSON verdict contract defined in workspace-iac/bin/subagent-worker ({"subject": "claim" | "code", "verdict": "holds" | "breaks" | "unknown", "anchors": [...], "unverified": [...]}). Do not restate or invent a secondary format.

Atomic invocation protocol

To execute 1 Swarm, the orchestrator invokes subagent_batch with M tasks:

1. Prepare task array with M distinct task objects: [{"id": "...", "prompt": "..."}].
2. Pass target files via context_files: [{"path": "...", "start_line": 1, "end_line": 120}] (and optional cwd) so the worker reads disk once without duplicating code in tool-call JSON.
3. Call subagent_batch.
4. Reduce outputs: Full output persists to ~/.local/state/subagent-worker/runs/<call_id>.md; inline return folds evidence-free holds tasks (unverified: []) and expands breaks, unknown, non-empty unverified, unparsed, PARTIAL, or FAILED tasks into SwarmResult.
5. Return SwarmResult to the calling skill for the next state transition.

Execution discipline

• Physical exit codes required: Cite actual commands and exit codes. A score or claim without a physical command is invalid.
• Call deadline: A call ends within 110 s. A batch with more tasks than the concurrency limit gets that time once per wave, up to 600 s. A task may use the time left in its batch, less one wave per wave of queued tasks; 50 s of silence still ends it. A task cut by the deadline is FAILED (no text) or PARTIAL (text so far). A provider filter or a provider fault inside the answer is PARTIAL too. The first output line gives the counts. Worker log: ~/.local/state/subagent-worker/worker.log.