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Greptile Summary

This PR introduces resolveOpenRouterCompatAlias, a helper that intercepts the two provider-less OpenRouter shorthands (openrouter:auto and openrouter:free) before the legacy Anthropic fallback fires. The openrouter:auto branch is straightforward and correct; the openrouter:free branch scans cfg.agents.defaults.models for the first openrouter/...:free entry, which is the right approach for ordered, user-controlled model preference.

Key observations:

• openrouter:auto → normalizeModelRef(\"openrouter\", \"auto\", …) → { provider: \"openrouter\", model: \"openrouter/auto\" }. Matches expected behavior and the new test.
• openrouter:free scanning uses Object.keys insertion order, which is deterministic in modern V8/Node but worth noting as the selection criterion.
• Missing zero-match warning for openrouter:free: when no free model is configured, resolveOpenRouterCompatAlias returns null and the caller falls through to the Anthropic path, producing { provider: \"anthropic\", model: \"openrouter:free\" } — an invalid ref — with a misleading warning. A targeted log message should be added for this case.
• No test covers the openrouter:free zero-match scenario.

Confidence Score: 4/5

Safe to merge for the happy paths, but the unguarded zero-match fallback for openrouter:free can produce a silently invalid Anthropic model ref that will fail at runtime.

Both new happy-path cases are correct and tested. The P1 finding is that openrouter:free with no configured free models falls through to the Anthropic fallback, returning an invalid model ref and a misleading warning. This is a present defect on the new feature path that should be fixed before merge.

src/agents/model-selection.ts — the zero-match return path at the end of resolveOpenRouterCompatAlias for the openrouter:free branch.

This is a comment left during a code review.
Path: src/agents/model-selection.ts
Line: 361-365

Comment:
**Silent invalid fallback when no free models are configured**

When `openrouter:free` is the primary model but no `openrouter/...:free` entries exist in `cfg.agents.defaults.models`, this function returns `null`. Execution then falls through to the legacy Anthropic path, which logs a misleading warning and returns `{ provider: "anthropic", model: "openrouter:free" }`. That model ref is invalid and will fail at the API level.

Since this function now owns the `openrouter:free` case, it should emit a targeted warning rather than silently delegating to the wrong code path. For example:

```ts
  // exhausted all configured models — warn explicitly before returning null
  getLog().warn(
    `"openrouter:free" was specified but no free OpenRouter models are configured under agents.defaults.models. ` +
      `Add at least one "openrouter/<vendor>/<model>:free" entry to your config.`,
  );
  return null;
```

Without this guard the caller still produces a bad `{ provider: "anthropic", model: "openrouter:free" }` ref, and the user sees "please use 'anthropic/openrouter:free' in your config" instead of a useful diagnostic.

How can I resolve this? If you propose a fix, please make it concise.

_{Reviews (1): Last reviewed commit: "fix: handle openrouter compatibility ali..." | Re-trigger Greptile}