fix(ai-gateway): gate fallback reasoning variants

[chrarnoldus]

Summary

• only infer OpenRouter fallback variants when reasoning is advertised in supported_parameters
• preserve variants derived from OpenRouter metadata
• apply the same fallback guard to direct-BYOK model conversion and models.dev synchronization

Verification

• pnpm --filter web test -- --runInBand src/lib/ai-gateway/providers/openrouter/index.test.ts src/lib/ai-gateway/providers/direct-byok/index.test.ts src/lib/ai-gateway/providers/direct-byok/sync-direct-byok.test.ts
• pnpm --filter web typecheck
• targeted oxlint, oxfmt --check, and git diff --check

[kilo-code-bot]

Code Review Summary

Status: No Issues Found | Recommendation: Merge

Executive Summary

Incremental review of the latest commit: making allowFallbackVariants a required parameter is compile-time safe — every caller (openrouter/index.ts, auto-model/resolution.ts, internal pass-through) now passes it explicitly, and the auto-model routing path deliberately preserves the previous fallback-allowed behavior with true; the earlier fallback-variant gating across OpenRouter enhancement, direct-BYOK conversion, and models.dev sync remains sound.

Files Reviewed (8 files)

• apps/web/src/lib/ai-gateway/auto-model/resolution.ts
• apps/web/src/lib/ai-gateway/providers/model-settings.ts
• apps/web/src/lib/ai-gateway/providers/openrouter/index.ts
• apps/web/src/lib/ai-gateway/providers/openrouter/index.test.ts
• apps/web/src/lib/ai-gateway/providers/direct-byok/index.ts
• apps/web/src/lib/ai-gateway/providers/direct-byok/index.test.ts
• apps/web/src/lib/ai-gateway/providers/direct-byok/sync-direct-byok.ts
• apps/web/src/lib/ai-gateway/providers/direct-byok/sync-direct-byok.test.ts

Previous Review Summary (commit fe99f5d)

Current summary above is authoritative. Previous snapshots are kept for context only.

Previous review (commit fe99f5d)

Status: No Issues Found | Recommendation: Merge

Executive Summary

The fallback-variant gating is applied consistently across OpenRouter model enhancement, direct-BYOK conversion, and models.dev sync; the new optional allowFallbackVariants parameter is backwards-compatible for existing callers, explicit/derived variants still take precedence, downstream consumers already handle undefined variants, and test updates (including a Claude-named non-reasoning model) correctly pin the new behavior.

Files Reviewed (7 files)

• apps/web/src/lib/ai-gateway/providers/model-settings.ts
• apps/web/src/lib/ai-gateway/providers/openrouter/index.ts
• apps/web/src/lib/ai-gateway/providers/openrouter/index.test.ts
• apps/web/src/lib/ai-gateway/providers/direct-byok/index.ts
• apps/web/src/lib/ai-gateway/providers/direct-byok/index.test.ts
• apps/web/src/lib/ai-gateway/providers/direct-byok/sync-direct-byok.ts
• apps/web/src/lib/ai-gateway/providers/direct-byok/sync-direct-byok.test.ts

---

_{Reviewed by kimi-k3 · Input: 39.4K · Output: 5.6K · Cached: 263.2K}

_{Review guidance: REVIEW.md from base branch main}