Model Routing

Model routing

run.sh reads three optional env vars and threads them into each claude invocation as --model. All default to unset, in which case the CLI default model is used (behaviour unchanged from a bare run).

The three knobs

• CLAUDE_PLANNER_MODEL — reserved for /spec workflows that draft PROMPT.md up front. Not read by the current run.sh loop, but claimed here so future planner passes bind to it.
• CLAUDE_EXECUTOR_MODEL — used on the "do the next step" call. This is the workhorse; it runs on every iteration. Pick something cheap and fast.
• CLAUDE_JUDGE_MODEL — used on the /verify call. Runs once per iteration to adversarially check the executor's diff. Pick a frontier model — a weak judge is worse than no judge.

Recommended shape

planner  = frontier   (Opus-class, runs once at /spec time)
executor = cheap-fast (Haiku-class, runs every turn)
judge    = frontier   (Opus-class, runs every turn but on a small diff)

Example

export CLAUDE_PLANNER_MODEL="claude-opus-4-7"
export CLAUDE_EXECUTOR_MODEL="claude-haiku-4-7"
export CLAUDE_JUDGE_MODEL="claude-opus-4-7"
./run.sh

The Elvis Executor+Judge finding

A cheap executor paired with a frontier judge outperforms a frontier executor with no judge on long loops. The judge catches the executor's premature-victory claims that a mono-model run rationalises away when it runs out of context. Cost stays low because the judge only sees the diff, not the working history.