Subagents offload context-expensive read-only work. The caller receives a digest, not the full trace. Subagents cannot modify state — they research, analyze, and summarize.

When to Delegate

See contract § Subagent Delegation Protocol for authoritative triggers.

Summary:

Trigger	Threshold
Uncertain scope	Assess with cheap ops first → convert to defined
Content to read	>250KB of files to READ (not search scope)
Processing depth	>2 intermediate tool calls whose outputs aren't needed in final delivery

Clarification on 250KB:

•Applies to Read operations (full content enters context)
•Does NOT apply to Grep (only matches enter context)
•Typical sequence: search (cheap) → identify matches → measure size of files to read → apply threshold

Keep Inline When

•Task requires user interaction mid-execution
•Result interpretation needs full conversation history
•Content to read ≤250KB and processing depth ≤2 steps

Delegation Protocol

1. Assess Scope (if uncertain)

bash

# Check total size of files to READ (not search)
stat --printf="%s\n" src/api/*.py | awk '{sum+=$1} END {print sum}'

2. Generate Brief

code

MODE: SUBAGENT
GOAL: {{objective}}
CONTEXT: {{what caller already knows — no pre-analysis required}}
SCOPE: {{files, directories, or boundaries}}

Brief principles:

•Write from existing knowledge only — if investigation is needed to specify the goal, that IS the delegated work
•Vague goals are valid when they reflect genuine uncertainty
•Subagent has the contract — don't repeat rules in the brief

3. Dispatch

Use Task tool. Subagent inherits contract but operates in Subagent Mode (read-only, no gates, compressed output).

For the Subagent

When receiving a MODE: SUBAGENT brief:

•Review ~/.claude/AGENT_TOOLS.md — MCP servers often provide efficient alternatives to manual tool chains
•Work within scope, abort if insufficient
•Return structured output (see below)

4. Review Output

code

RESULT: [success | partial | blocked | failed]
SUMMARY: [what was found/analyzed]
CONCERNS: [issues for caller review]
BLOCKERS: [if not success — what prevented completion]
DETAILED RESPONSE: [findings]

Review: Verify result addresses goal intent. Address concerns before proceeding.

5. Integrate

•Success: Use digest, continue main task
•Partial: Complete inline or re-delegate with narrower scope
•Blocked/Failed: Surface to user or try alternative approach

Common Delegation Patterns

Pattern	Goal Template
Find definition	"Find where {{symbol}} is defined and its signature"
Analyze dependencies	"List what {{module}} imports and what imports it"
Explore area	"Understand how {{area}} works" (vague is OK)
Search and summarize	"Find all {{pattern}} and summarize their purposes"
Architecture survey	"Identify the main components and their relationships in {{area}}"

Anti-Patterns

Don't delegate:

•State-modifying operations (subagents are read-only)
•Decisions requiring user input
•The debugging hypothesis loop (requires iterative testing with full context)

Exception — debugging research IS delegatable:

•"Find all call sites of function X"
•"Find working analogues for this pattern"
•"Check if error handling exists for case Y"

These support Bug Qualification / Pattern Analysis phases without owning the hypothesis loop.

Parallel Delegation

Independent research tasks can run simultaneously:

•Identify independent subtasks
•Generate briefs for each
•Dispatch in parallel (multiple Task tool calls)
•Await all results
•Integrate digests

Dependency awareness: If task B depends on task A's output, dispatch sequentially.