Subagent Spawn

/subagent-spawn — G7 Spawn Payload Helper

Constructs a typed spawn payload conforming to plugin/schemas/spawn-payload.schema.json for a chosen role. Used internally by orchestrator skills (/develop, /feature-design, /team-bugfix); also available standalone for power users building custom workflows.

When to use

• Inside a custom orchestrator skill where you need a standardized G7 spawn payload
• When debugging a subagent spawn — build the payload manually, inspect it before invoking
• When testing a single agent role against a small task without the full workflow overhead

Not for: routine agent invocation (use the orchestrator skill); bypassing role-selection-table (use the table directly).

Invocation

/subagent-spawn --role frontend-engineer --task "implement OAuth2 login form per src/auth/spec.md"
/subagent-spawn --role security-engineer --task "audit src/api/auth.ts" --max-tokens 30000
/subagent-spawn --role db-engineer --task "design schema migration" --stack postgres

Arguments

Behavior

1. Validate --role against plugin/agents/<name>.md. If not found, error with full list.
2. Look up agent frontmatter (tools, max_output_tokens, maxTurns, disallowedTools) for default budget values.
3. Generate trace_id: format wf-<YYYYMMDD>-<random6>-spawn-<seq> (per spawn-payload.schema.json pattern).
4. Construct G7 payload:

{
  "trace_id": "wf-20260427-abc123-spawn-001",
  "parent_trace_id": null,
  "subagent_role": "<role>",
  "goal": "<task>",
  "constraints": [],
  "state_slice": {},
  "allowed_tools": [<from agent frontmatter tools field>],
  "budget": {
    "max_input_tokens": <flag or default>,
    "max_output_tokens": <flag or agent frontmatter>,
    "max_tool_calls": <flag>,
    "max_turns": <flag or agent frontmatter>,
    "timeout_ms": <flag>,
    "retry_budget": 1
  },
  "untrusted_inputs": []
}

5. Validate the payload against plugin/schemas/spawn-payload.schema.json (best-effort; warn if validator unavailable).
6. Return the payload as JSON for the orchestrator to wrap in an Agent(...) call:

{
  "agent_call": "Agent({subagent_type: '<role>', name: '<role>-<seq>', prompt: '<task brief with G7 payload embedded>'})",
  "spawn_payload": <json>,
  "validation": "ok | warnings: [<list>]"
}

Hard rules

• Role lookup is strict — only the 26 plugin-shipped agents (plugin/agents/<name>.md) plus built-in Claude Code agents (Explore, Plan, general-purpose) are valid subagent_role values per team-protocols/role-selection-table.md
• Budget defaults from agent frontmatter — never invent budgets; use the role-type table values per glossary §3
• Untrusted inputs flagged — if the orchestrator passes any L0/L2/L4/tool/subagent content to populate state_slice, populate untrusted_inputs with wrapped: true per untrusted-content-wrapping.md rule
• No actual spawn here — this skill BUILDS the payload; the orchestrator INVOKES Agent(...) separately. Single-responsibility
• parent_trace_id for nested spawns — if THIS spawn is being initiated from inside another subagent (rather than the main thread), the orchestrator MUST set parent_trace_id to the parent's trace_id. Omit or set to null for top-level spawns. The subagent-depth-guard.py hook (v0.1.7) walks this chain to enforce userConfig.subagent_max_depth (default 3); a missing parent_trace_id on a nested spawn defeats depth tracking and the hook may underreport the actual depth.

Failure modes

• Invalid role: error with full list of 26 valid agent names + 3 built-in agents
• --task too short or too long: reject with the schema's minLength/maxLength bounds (10–1000 chars)
• Budget conflicts with agent frontmatter caps: if --max-tokens exceeds 200000 or --max-output exceeds agent's documented cap, reject with explanation
• Role exists but tools: field empty: warn; suggest reviewing agent frontmatter

Memory writes

This skill is read-only — no memory writes. The orchestrator that subsequently invokes Agent(...) is responsible for recording the spawn via subagent-start-budget.py hook.

Integration

• Reads: plugin/agents/<role>.md frontmatter for defaults
• Validates against: plugin/schemas/spawn-payload.schema.json (G7), team-protocols/role-selection-table.md
• Rules: subagent-isolation (delegation patterns + bounded recursion + Phase 4 #4 depth guard), untrusted-content-wrapping (G1 on untrusted_inputs field)
• Hooks: subagent-start-budget (token cap), subagent-depth-guard (max recursion depth via parent_trace_id chain, v0.1.7), subagent-stop-learnings (return-contract validation + chain closure)
• Used by: /feature-design, /develop, /team-bugfix, /refactor, /migrate orchestrators; available standalone
• Companion: /context-load (constructs state_slice content for the spawn payload)