Repos that need to pin the review engine (e.g. 'this project requires
claude-sonnet-5 for the budget line' or 'route everything through
gpt-5.6-luna for now') can declare a top-level 'model' string in
.pr-review.json. The parser validates the value against cost_model.PRICES
(lazy import — ollama path stays dep-free) and silently drops unknown
values with a stderr pointer to the valid key set so a typo in the
config file surfaces in the logs instead of silently falling back.
The orchestrator gains a small _resolve_display_model(base, config)
helper that implements a 3-way precedence:
1. OPENCODE_MODEL env (operator override, used verbatim)
2. config['model'] (per-repo override)
3. f'headroom/{base}' (default)
review_pr resolves once (lazy fallback before config is loaded) and
re-resolves after .pr-review.json is fetched, then threads the result
into the opencode subprocess, REVIEW_HEADER, and the cost-line
parenthetical. Same single value everywhere — no more mix of bare
OLLAMA_MODEL id in the header and a stale free-tier literal in the cost
line.
Tests cover parsing acceptance, parsing rejection (capsys stderr),
type validation, precedence in all 4 (env×config) combinations, and an
end-to-end sanity check that format_review_body shows the override and
not the base id.
Marcos
d0f99b9763