Cost-Tier Routing

The main context runs on opus. Every Read, Grep, Glob, and Edit invoked at this tier bills at opus rates. Most operations don't need opus reasoning — they need a model that can run a command and report a result. This skill is the dispatch gate that stops opus from doing work haiku or sonnet would complete just as correctly for a fraction of the cost.

The three tiers

The dispatch decision (run this first, every turn)

Before reaching for any tool, run this classifier against the incoming request:

1. Is the work entirely read / search / location? → scout. Dispatch haiku-scout. Never call Read / Grep / Glob in the main context.
2. Is the change scope AND the design already decided? → coder. Dispatch sonnet-coder with a precise brief.
3. Is the user asking "should we", "why", "what are the tradeoffs", "design X"? → architect. Stay in-context (you ARE opus) or dispatch with model: "opus".
4. Mixed? → split. Scout first to gather facts, then re-classify the next step. Never bundle scout work into an architect dispatch.

Tool split (CodeGraph first, Memtrace for heavy hits). Use CodeGraph (codegraph_explore / codegraph CLI) for symbol lookup, file reads, callers/callees, and ordinary blast radius. Reserve Memtrace (and cortex) for git history/evolution, recall_decision, cross-repo/API topology, risky blast radius (get_impact), PR review evidence, and dead code/complexity, because Memtrace costs quota. If ~/.claude/state/memtrace-quota.json says blocked with a future until, never call Memtrace; use CodeGraph until that time.

If the answer to #1 is yes and you find yourself reaching for Read / Grep / Glob in the main context anyway — STOP. That is the violation this skill exists to prevent.

Dispatch templates

See PROMPTS.md for the canonical brief for each tier. Use them verbatim — every field is load-bearing.

Worked examples

See EXAMPLES.md for ~15 classifications across the boundary cases (multi-file search, bug fixes with unknown root cause, "small" edits that hide design questions).

Enforcement

The companion PreToolUse hook (hooks/pre-tool-use-cost-check.sh) warns when Read / Grep / Glob fires in the main context. Register it in ~/.claude/settings.json (see EXAMPLES.md § Installing the hook).

• Default mode: warn (writes to stderr, the call proceeds).
• COST_ROUTING_BLOCK=1 upgrades the warning to a hard deny — useful for sessions where you want zero tolerance.
• COST_ROUTING_BYPASS=1 silences the hook for legitimate one-shot inspection (a single Read of a file the user pasted a path to).

The hook cannot perfectly distinguish "top level opus" from "inside a subagent" — Claude Code does not currently expose that bit to hooks. It warns on every Read / Grep / Glob; you teach yourself to recognize the warning as "I'm probably in opus, should I have dispatched?"

When NOT to dispatch

• The entire task is one unattended CLI command (gh pr view, docker ps). Use Bash directly — wrapping a one-shot command in an agent is pure overhead.
• The user pasted a single file path and asked for a single fact. Read it directly; dispatch overhead exceeds the saved tokens.
• The work is genuinely ambiguous design that needs opus reasoning. Don't dispatch yourself to yourself.

Common failure modes

• Tier creep — classifying a multi-file search as "design work" because it touches many files. Multi-file search is still scout.
• Dispatch without `model:` — calling Agent with subagent_type: "general-purpose" and no model: parameter inherits the parent tier (opus → opus). Always pin the model.
• Skipping the classifier — jumping to Read on instinct. The classifier IS the skill; running it costs two seconds and saves the budget every time.
• Bundling tiers — handing scout work to a coder dispatch ("find the file, then edit it"). The coder agent will burn sonnet tokens doing scout work. Split: scout reports the path; coder edits at that path.