fix(ai-gateway): prefer Bedrock, Anthropic, then Vertex for Fable models

[chrarnoldus]

Summary

Fable models (anthropic/claude-fable-5) were excluded from the Claude preferred provider order, so OpenRouter and Vercel routed them without a preference. This removes the exclusion so Fable uses the same order as every other Claude model: Amazon Bedrock, then Anthropic, then Google Vertex.

The removed guard carried the comment "specifying this for fable breaks the opus fallback on vercel". Fable requests on OpenRouter and Vercel still get models: [fable, opus-4.8] from applyGatewayModelsFallback; with this change they also carry provider.order, which Vercel receives as providerOptions.gateway.order alongside models.

Verification

• jest src/lib/ai-gateway/providers: 32 suites, 507 tests pass. The Fable test in apply-provider-specific-logic.test.ts now expects the Claude order instead of no order.
• Model-list pricing: getPreferredProviderOrder(...).at(0) now selects the amazon-bedrock endpoint for Fable. OpenRouter lists Bedrock for anthropic/claude-fable-5 at $10/M input and $50/M output, the same as endpoints[0], so displayed pricing is unchanged.
• Not verified: an end-to-end Fable request on Vercel that fails over to Opus 4.8 while order is set. This needs a manual check after deploy, because the removed comment documents a previous regression here.

[kilo-code-bot]

Code Review Summary

Status: 1 Issue Found | Recommendation: Address before merge

Overview

Severity	Count
CRITICAL	0
WARNING	1
SUGGESTION	0

Issue Details (click to expand)

WARNING

File	Line	Issue
apps/web/src/lib/ai-gateway/providers/apply-provider-specific-logic.ts	140	Fable now receives the Claude provider order. The removed guard comment ("specifying this for fable breaks the opus fallback on vercel") documented a Vercel Opus-4.8 fallback regression; the author confirms the end-to-end fallback still needs a manual post-deploy check, so this risk remains open.

Files Reviewed (2 files)

• apps/web/src/lib/ai-gateway/providers/apply-provider-specific-logic.test.ts
• apps/web/src/lib/ai-gateway/providers/apply-provider-specific-logic.ts - 1 issue

Fix these issues in Kilo Cloud

Previous Review Summary (commit 23167bd)

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

Previous review (commit 23167bd)

Status: 2 Issues Found | Recommendation: Address before merge

Overview

Severity	Count
CRITICAL	1
WARNING	1
SUGGESTION	0

Issue Details (click to expand)

CRITICAL

File	Line	Issue
apps/web/src/lib/ai-gateway/providers/apply-provider-specific-logic.ts	139	Fable models now receive the Claude provider order, but the existing test does not set a provider order for Fable (apply-provider-specific-logic.test.ts:442) still asserts no order is set, so CI will fail.

WARNING

File	Line	Issue
apps/web/src/lib/ai-gateway/providers/apply-provider-specific-logic.ts	140	Removal of the documented workaround ("specifying this for fable breaks the opus fallback on vercel"); confirm the Vercel Opus-4.8 fallback still works. Also shifts Fable's model-list displayed pricing to the amazon-bedrock endpoint via openrouter/index.ts:148.

Files Reviewed (1 file)

• apps/web/src/lib/ai-gateway/providers/apply-provider-specific-logic.ts - 2 issues

Fix these issues in Kilo Cloud

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