Crew Contract — Main–Sub Delegation (主-子分工)

The main agent conducts — it doesn't play every instrument. The general division of labor for any substantial work, adapted from the "Astra + Luna" orchestrator pattern. The main agent keeps the goal, constraints, evidence and final judgment; bounded subagents do noisy execution; an independent reviewer checks material changes before anything is called done. Applies to engineering, research, writing, data, ops — anything. Project-specific processes plug in from their own docs; this skill is the method layer.

When to use

• The owner invokes it: "用主-子分工", "main-sub", "delegate this", "让子代理做".
• Any work that materially benefits from decomposition, independent contexts, parallel work, or independent review.
• Multi-component / cross-cutting / risky work where evidence and a review gate matter.

Do not use for simple questions, single small edits, or quick lookups — keep those in the main thread. Never create agents just to satisfy a template; use only the roles that improve the task, and scale to the job (explorer + worker may be enough; add tester/reviewer when risk warrants). Never switch the main model merely to activate this mode. Owner instructions always take precedence over this method.

Intent-driven guidance (defaults, not a rulebook)

This skill states intent and defaults — the dispatcher sizes effort, review and budget to the task's actual goal, and states a reason when deviating from a default. Only the invariants are non-negotiable: separation of duties (no self-review), evidence over self-report, fail-closed scope, agents don't commit, owner's permission/cost boundaries.

Defaults (adjust when the task clearly calls for it — note why):

• Small, local, sequential work: stay in the main thread; no subagents.
• Every brief carries BUDGET + STOP (see template): attempts/time ceiling + what to do when exceeded.
• At least one independent-context check before anything is called done; skip only for low-risk changes that were directly verified — and say so.
• Review depth scales with risk: separate context → evidence-anchored findings → cross-model / ground-truth when value warrants.
• Effort scales with task shape: one narrow child for a small lookup; several for genuinely independent streams — count coordination cost first (see "Orchestration signals").
• Handing work down fits by shape — clarity × verifiability × blast radius — not by a fixed list of cases (see "Handing work down (intent-driven)").

Roles

• The main agent owns: interpreting the real goal and authorization boundary; architecture, decomposition and ordering; non-overlapping ownership; resolving conflicting findings; integration; final inspection; all user-facing claims.
• The reviewer must be a separate context from whoever produced the work (self-review doesn't count). Material changes only — correctness, regressions, security and permission issues, data integrity, race conditions, compatibility, missing high-value tests; not style. Invoke it for high-risk, cross-cutting, security- or data-sensitive, non-obvious changes; skip it when the change is low-risk and directly verified.
• Review independence is layered — the owner's model policy always wins, and independence is never claimed as achieved (see "Unresolved limits"). When the available models span ≥2 families: high-risk or unanchorable review MUST go to a cross-family reviewer. When only one family is available: fall back to evidence-anchored review + position swapping (AB/BA) + long-CoT review + low-confidence escalation to human, and declare residual family-bias in the delivery. Supporting evidence map: references/evidence-index.md.
• Review protocol checklist (use what the risk justifies): deterministic/ground-truth checks first; per-dimension rubric scored independently; position swap on comparisons; reviewers recompute verifiable facts (hashes, counts) instead of restating them; human-labeled golden set to calibrate rubrics before trusting an LLM judge at scale.
• Role constraints: the explorer reports uncertainty or conflicting evidence and does not redesign; the worker follows existing project patterns and avoids unrelated refactors; the tester edits tests only when asked; the reviewer edits nothing.

Delegation contract (every brief)

Every dispatched task states:

1. one concrete objective;
2. exact scope / owned files;
3. necessary context only (children cannot ask questions — briefs must be self-contained);
4. constraints + forbidden scope expansion;
5. required deliverable;
6. acceptance evidence.

Subagents return conclusions, paths/symbols, commands + results, risks, blockers — no raw log dumps. Bulk or mechanical deliverables: write the artifact to a file, return a one-line status. Inline findings: keep the summary to ~1–2k tokens (prompt convention — there is no hard harness clamp; never promise one).

Ambiguity contract (return block, not a pause): every child's deliverable opens with assumptions[] / needs_input[] / default_if_forced / blocking_level (low|high). Depth-1 children cannot pause mid-run and wait — this block is a structured RETURN, aligning vocabulary (not mechanism) with A2A input-required. On needs_input, the main agent closes the loop: clarify with the owner when blocking_level is high, then narrow re-dispatch; when low, proceed with default_if_forced and record it.

Copy-paste template with per-role quick fills: references/child-brief-template.md. Read it when drafting any dispatch.

Model selection (route card)

No model names are hardcoded in this skill (grep-enforced). When work enters orchestrated mode, settle routes up front:

1. Candidate set = intersection of what the runtime can actually use (its provider registry / model list) and the owner's current model policy. Fewer than three qualify → present exactly those plus free-text; NEVER pad the list with policy-external models.
2. Ask once per slot — execution slot (all explorer/researcher/worker/tester children share one route) and reviewer slot (independent review). Criteria, not names: execution = cheapest adequate + cache affinity (see "Cost discipline"); reviewer = the layered independence criterion under "Roles".
3. Skip the prompt when the work stays in the main thread, the owner already named models, or a recent route card still matches current config — say which applies.
4. Provider changes are the owner's call: confirm explicitly, never pick a provider yourself (invariant).
5. Emit a route card (slot / model / provider / basis / effective time), then re-verify it immediately before dispatch — config can drift between asking and fanning out.

Execution pattern

1. Decide: main-thread-only or orchestrated.
2. Read-only exploration/research first when the surface is uncertain (parallel where truly independent).
3. Main decides direction; assign each writable area to ONE worker at a time.
4. Implement (bounded workers).
5. Verify with the smallest decisive test/reproduction. Verification priority: deterministic checks (tests, hashes, compilers, exact match) > weak-verifier ensembles > LLM judges; treat the LLM judge as a scarce budget — verification compute should stay below generation compute, and calibrate a judge before trusting it.
6. Independent review for material/risky changes; resolve findings; re-run affected checks.
7. Main inspects the final diff/artifact, then claims completion. Agents don't commit — the main reviews and commits.

Serialize any stage that depends on earlier evidence; parallelize only genuinely independent work.

Truncation & recovery

A child can be cut off (iteration cap, timeout) before its final write. Recovery order:

1. Inventory the disk first — with SAVE-EARLY the artifact usually exists and only the tail is missing; never assume nothing landed.
2. Prefer "artifact + one narrow re-dispatch" (or main-thread assembly) over re-sending the whole task.
3. Log the cut-off as a real event: fail-stop without durable resume is a known limit (below) — repeated cut-offs are evidence for changing budgets/staging, not for blind retries.

Manifest checkpoint protocol (optional — not the default): enable only when replay is likely — ≥3 slices, multi-child relay, or a prior cut-off / expected timeout. Otherwise SAVE-EARLY + narrow re-dispatch is enough (a single-slice task gets nearly all the benefit from SAVE-EARLY alone). When enabled: one task-level manifest (slice list + per-slice status/complete markers + artifact paths + next action); a resuming child reads the manifest first and works only unfinished slices. Rules: slices idempotent; artifacts append-only; resume points fall on slice boundaries.

Live steering may exist in some surfaces; treat it as best-effort, never as the correctness mechanism.

Failure and scope handling

• A subagent hitting an architectural decision, schema/API change, new dependency, security-sensitive choice, unclear requirement, or overlapping ownership must stop and report — not expand scope.
• On failure: inspect why; narrow, retry, reassign, or handle it in the main thread. Never silently ignore.
• Never claim delegated work finished unless it actually ran and its result was checked.
• Before finishing: every required agent has completed or explicitly failed; nothing required is still running.

Orchestration signals (when it pays)

Orchestration pays when the work is parallelizable, bounded, and verifiable: streams can run independently; each stream can be pinned down without asking questions (children can't ask); each has a check (test, ground truth, source, artifact) someone else can apply. It degrades on strictly sequential work (controlled study across 180 agent configurations: -39% to -70%), shared-file/state coupling, ambiguous requirements, or tiny tasks; coordination overhead grows with dependencies and tool count. Cost is ~15x chat tokens — the task's value must cover it. Signals, not gates: run ONE bounded child first, extend only if it clearly pays.

Admission gate: open subagents only when ≥2 of these hold — (a) genuinely parallelizable/decomposable; (b) does not fit one context window; (c) task value covers orchestration cost. Record a one-line written justification on the route card (the format is checkable; the judgment stays with the main agent).

Cost discipline (why not everything)

Orchestration is not free: the main stays in the loop for the whole task, and every subagent carries and re-reads its own context. Parallelism trades tokens for latency. So: keep agent count proportional to genuinely independent work; avoid duplicate scans; ask for short reports (raw logs pasted into the main thread get re-read every turn); skip the reviewer for low-risk changes; don't orchestrate small tasks at all.

Cost levers in order — cache hit rate → model routing → effort level. Children share the parent's prompt cache only with byte-identical prefixes, same model, same effort; switch models at compaction moments (the cache miss is already being paid there). Cheap execution tiers do not cancel orchestration overhead.

Handing work down (intent-driven)

Defaults, not rules — the main agent sizes each hand-down to the task in front of it.

Fit by shape, not by case. Judge fit by clarity × verifiability × blast radius (how far a mistake reaches × how reversible it is): clear + mechanically checkable + low blast radius → a good default for handing work to a cheaper executor; fuzzy, novel, or high-risk → keep it on the main line or with a stronger model. Complexity matters less than ambiguity: a long but crisp checklist suits a cheap executor; a short, vague judgment call does not. If the work cuts into clear steps with a check between each → hand the steps down; if every step's judgment feeds the next → keep it up here.

Calibrate verification to what the task can prove. Prefer deterministic checks (tests, grep gates, hashes, read-backs) over LLM review; review depth is a budget, spent where the task can't check itself. Borderline "does this need a review?" calls can go to a fast local typed-decision gate (choice/score) for a quick suggestion — it suggests, the main line decides. Output nothing can check must be reviewed or re-run; unverified output never gets laundered into a conclusion (an extension of "evidence over self-report"). Confidence in handed-down work comes from checkability, not from model tier.

Class patterns accumulate. When the same shape of task shows up again, add a line to references/class-playbook.md: shape → who ran it → which verification actually caught a problem → review verdict. Learned from real work, not legislated up front; keep the lines short. Whoever runs the work adds the line; mark a line stale when the tooling or models it names change.

Unresolved limits (mitigation only — never report as solved)

• No durable resume. A cut-off child is rescued by hand or restarted; mitigations: SAVE-EARLY artifacts, staged tasks, narrow re-dispatch, optional manifest protocol (above).
• Reviewer independence is partial. A clean context removes identity-visibility bias; a same-family reviewer still shares model blind spots — the layered criterion (Roles) mitigates but does not eliminate this; when only one family is available, declare residual family-bias in the delivery.
• Children cannot ask questions (depth 1). Handle with self-contained briefs + the ambiguity contract (explicit assumptions / needs_input return block); residual loss is inherent.
• Evidence-strength gaps (2026-09-20 evidence review, section 7): long-context degradation and code-review corpora at summary level only; no direct "cheap executor + expensive judge" study found (a 2026-05 formalization of cheap-reward + expensive-verifier is the closest — see evidence index); most conclusions are cross-source mapping inferences, empirical n=1; multi-turn finding from simulated sessions (external-validity limits).

Reporting rule: present these as open, mitigations in progress — never as resolved.

Theory basis

• Context hygiene is the primary value of subagents (not specialization): verbose output and intermediate reasoning die in the child context; the main thread keeps the goal, constraints, evidence, judgment.
• Separation of duties: explore / implement / verify / review are distinct roles; the generator and the verifier always work in different contexts.
• Non-overlapping ownership: one writer per area; prevents merge chaos.
• Evidence over self-report: child summaries are claims; the main checks artifacts, diffs, commands, hashes.
• Fail-closed scope: silent scope expansion is the failure mode this method exists to prevent.
• Evidence anchors (see references/evidence-index.md for the full rule → source map): parallelizable tasks +81% vs strictly sequential -39–70%; uncoordinated parallel error amplification 17.2x → 4.4x with an orchestrator (Google agent-scaling study); multi-agent ≈15x chat tokens (Anthropic); 41–86.7% failure across 7 SOTA multi-agent systems, 14 failure modes (MAST, arXiv:2503.13657); clean-context reviewers and conflicting-assumption risk (Cognition); weak-verifier ensembles close the generation–verification gap (Weaver). Reviewer family-bias 3.4–8.4pp even without self-review (arXiv:2508.06709, arXiv:2609.17857); context rot persists under perfect retrieval, 13.9–85% drop (arXiv:2510.05381); subagent clarification is a known platform gap (upstream not-planned); per-role model binding is standard in mainstream frameworks.

Harness-specific dispatch mechanics (Hermes example): references/hermes-mechanics.md.

Instances (non-exhaustive)

• Case/fixture production: frozen-artifact review with author/reviewer/oracle context isolation — this skill supplies the division of labor, the project supplies its process.
• Software development: two-stage review pipelines; cheap CLI worker lanes with a supervising main agent.
• Handovers: evidence-bearing work receipts between agents or sessions.

Provenance & changelog

Adapted from the "Astra + Luna" orchestrator (execution roles at high effort + a strong, low-effort, read-only reviewer) and the sub-agent pattern literature. Method validation report and sources referenced in references/evidence-index.md.

• v1.4.0 (2026-09-23) — hand-down guidance (shape-based delegation fit, verification calibration with typed-decision gates, class playbook); intent-driven, no new mandates.
• v1.3.1 (2026-09-23) — renamed conductor → crew-contract (marketplace name-uniqueness; method layer unchanged).
• v1.3.0 (2026-09-23) — model-agnostic route selection (route card + candidate-intersection rule); layered review-independence criterion + review protocol checklist; admission gate + cache-ordered cost levers; ambiguity contract (needs_input return block); optional manifest checkpoint protocol; verification priority; no hardcoded model routes (grep-enforced).
• v1.2.0 (2026-09-21) — intent-driven defaults, orchestration signals, truncation recovery, unresolved-limits discipline, evidence anchors.