Adaptive Subagent Routing

FIRST: Decompose Before Acting

Do NOT start working on the task directly. Before reading files or making edits, decompose the task into subtasks and delegate each one to the cheapest sufficient model via the Agent tool. The only exception is if the entire task is under ~100 tokens of output (a one-liner fix).

Quick Decision (apply to EVERY delegation)

Default: Haiku. Escalate only with reason.

1. Is this a mechanical lookup? (find files, grep for a string, list structure, check if something exists) → Haiku
2. Does it require comprehension or writing? (implement, refactor, test, debug, fix, analyze code, explain logic, summarize complex systems) → Sonnet
3. Is it architectural, security-sensitive, or ambiguous? → Opus

Haiku boundary: Haiku can find things and format things. It cannot understand or reason about code. If the task requires reading code and making a judgment, that's Sonnet.

If unsure between two tiers, pick the cheaper one. Escalate after failure, not before.

Before each delegation, output Routing to {Model}: {brief reason} on its own line. When handling work inline, output Staying on {Model}: {brief reason} instead.

When to Delegate vs Handle Inline

Always delegate to a cheaper tier — the 3x–15x cost savings always outweigh subagent overhead.

Skip delegation only when:

• The output is under ~100 tokens (one-liner answers, quick fixes already in context)
• The overhead of spawning a subagent exceeds the work itself
• The subtask needs the same model tier you're already on and context is already available

Routing Rules

Haiku (1x)	Sonnet (3x)	Opus (15x)
File search, grep, glob	Implementation, bug fix	Architecture, migration
Format/lint existing text	Refactor (< 10 files)	Security review
Check if file/string exists	Test writing	Ambiguous/conflicting scope
List files, directory structure	Debugging with stack traces	Multi-system design
Literal string replacements	Code generation (< 500 lines)	Performance analysis
	Summarize/analyze code logic
	Rename across multiple files
	Code review, explain code

Escalate +1 tier: ambiguous requirements, public-facing output, security-sensitive, production-critical, or 2 consecutive failures. Downgrade: after planning completes, or remaining work is formatting/summarization.

Cost Ratios

Model	Relative Cost	Pricing
Haiku (1x)	Baseline	~$1/M input, $5/M output
Sonnet (3x)	3x Haiku	~$3/M input, $15/M output
Opus (15x)	15x Haiku	~$15/M input, $75/M output

A 10-delegation task routed to Haiku instead of Opus saves ~93% on those calls.

Per-Subtask Routing

When a request involves multiple steps:

1. Decompose first. Break the request into a todo list of subtasks.
2. Route each subtask independently. Most items are cheaper than the overall task.
3. Downgrade after planning. If Opus produces a plan, implementation goes to Sonnet. Lookups and cleanup go to Haiku.

Example — "design and implement a caching layer":

• Plan the architecture → Opus
• Search for existing cache usage → Haiku
• Implement the cache module → Sonnet
• Write tests → Sonnet
• Update internal dev notes → Haiku
• Write public API docs → Sonnet (escalated: public-facing)

Delegation

Choose agent type by task and model by complexity independently.

Agent Type	Use When	Tools Available
Explore	Search, grep, read-only exploration	Read, Glob, Grep (no Edit/Write)
general-purpose	Implementation, edits, multi-step work	All tools
Plan	Architecture design, implementation planning	Read, Glob, Grep (no Edit/Write)

Combine freely — Explore + haiku for file lookups, general-purpose + sonnet for implementation, Explore + sonnet for complex investigation, Plan + sonnet for straightforward design.

Agent(subagent_type: "Explore", model: "haiku", description: "...", prompt: "...")
Agent(subagent_type: "general-purpose", model: "sonnet", description: "...", prompt: "...")
Agent(subagent_type: "Explore", model: "sonnet", description: "...", prompt: "...")
Agent(subagent_type: "Plan", model: "sonnet", description: "...", prompt: "...")

Keep prompts scoped: relevant files, constraints, expected output format. The description parameter is required — use a short 3-5 word summary.

Expected Output Formats

Tier	Expected Output
Haiku	File paths, grep results, existence checks, formatted text
Sonnet	Code diffs, implementation files, test files, error analysis
Opus	Numbered plan steps, architecture decisions with rationale, risk assessment

Parallel Fan-Out

When a request contains independent subtasks, launch multiple subagents in a single message.

Before splitting, build a dependency graph. Does any subtask need another's output, or do they modify the same file? If yes, run them sequentially.

Pattern	Parallel?	Why
Separate files, separate concerns	Yes	No shared state
Research + unrelated implementation	Yes	Read-only doesn't conflict with writes
Implementation + its tests	No	Tests depend on the implementation
Feature + docs describing that feature	No	Docs need to reflect what was built
Two features touching different modules	Yes	Independent code paths
Refactor + anything in same files	No	Refactor changes the baseline

After all phases return, review outputs for conflicts before applying.

User Overrides

If the user says any of the following, respect it for the current request:

• "no routing" / "don't delegate" — handle everything inline on the current model.
• "use Opus" / "use Sonnet" / "use Haiku" — force that tier for all delegations.

Log the override with Override: {what the user requested} and resume normal routing on the next request.

Routing Log

After each routing decision, append a line to routing.log in the project root using the Bash tool:

echo "{model} | {agent_type or inline} | {estimated savings vs Opus, e.g. ~93%} | {brief task description}" >> routing.log

Log every Routing to and Staying on decision.

Guardrails

• Max 2 retries per subagent, then escalate or ask the user.
• Max 5 sequential delegations per user request. No limit on parallel.
• Always review subagent outputs before applying — check for conflicts, hallucinated paths, and incomplete work.
• Do NOT modify project files: Never write routing rules to CLAUDE.md. Never add hooks to settings.json. This skill is loaded automatically by the plugin.