fix(gateway): route Bedrock models without a global profile

[steebchen]

Problem

The AWS Bedrock dashboard shows claude-opus-4-1-20250805:global failing 100% of the time with:

400 Bad Request
{"message":"The provided model identifier is invalid."}

Root cause

Bedrock's regionConfig uses defaultRegion: "global" + pinDefaultRegion: true, so by default all Bedrock traffic is pinned to the global cross-region inference profile. Most Claude models on Bedrock expose a global CRIS profile — but a handful expose only a us profile and no global one:

• claude-opus-4-1-20250805
• llama-3.1-70b-instruct
• llama-4-scout-17b-instruct
• llama-4-maverick-17b-instruct

For those, on the default routing path (managed key, no :region suffix):

1. applyPinnedDefaultRegions dropped the us variant (us !== global), leaving only the region-less synthetic root.
2. getProviderEndpoint applied the default global. prefix → e.g. global.anthropic.claude-opus-4-1-20250805-v1:0.
3. Bedrock rejects that id with the reported 400.

Verification (direct Bedrock calls)

Model id	Result
us.anthropic.claude-opus-4-1-20250805-v1:0	HTTP 200 ✅
global.anthropic.claude-opus-4-1-20250805-v1:0	HTTP 400 — "The provided model identifier is invalid." ❌
us.meta.llama3-1-70b-instruct-v1:0	HTTP 200 ✅
global.meta.llama3-1-70b-instruct-v1:0	HTTP 400 ❌

Fix

applyPinnedDefaultRegions now detects when a model has regional variants but none matching the provider's default region. In that case the synthetic root cannot be used (it would resolve to the invalid global. prefix), so it pins to the model's concrete regional variants (us) instead. Models that do have a global variant, and Bedrock mappings with no regional variants at all, are unchanged.

The helper was extracted into apps/gateway/src/chat/tools/pin-default-regions.ts with unit tests covering: global-capable models, us-only models (Opus 4.1 + Llama), region-less mappings, explicit :region requests, and provider-key region locks.

This keeps Opus 4.1 (and the Llama models) working on Bedrock via their us profile instead of deactivating them.

Summary by CodeRabbit

• Bug Fixes

  • Improved regional model selection to avoid invalid or unintended provider-region mappings.
  • Preserved explicit region requests and provider locks during model selection.
  • Correctly prioritizes global profiles or concrete default regions when available.

• Tests

  • Added coverage for regional mappings, global profiles, explicit region requests, provider locks, and providers without regional variants.

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[coderabbitai]

Walkthrough

The change extracts default-region pinning into a reusable helper, adds concrete regional mapping preference in chat routing, and introduces Vitest coverage for Bedrock region-selection scenarios and pass-through conditions.

Changes

Regional provider selection

Layer / File(s)	Summary
Centralize default-region selection apps/gateway/src/chat/tools/pin-default-regions.ts, apps/gateway/src/chat/chat.ts	applyPinnedDefaultRegions handles requested regions, explicit locks, provider pinning, default regions, and concrete regional mappings; chat imports the helper and prefers explicit regional variants when available.
Validate Bedrock mapping outcomes apps/gateway/src/chat/tools/pin-default-regions.spec.ts	Tests cover global and concrete-region selection, synthetic-root preservation, and pass-through for requested regions and explicit locks.

Estimated code review effort: 3 (Moderate) | ~20 minutes

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title is concise and matches the main change: fixing Bedrock routing for models that lack a global profile.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch bedrock-opus-4-1-invalid-model

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[coderabbitai]

🧹 Nitpick comments (1)

apps/gateway/src/chat/tools/pin-default-regions.ts (1)

40-51: 📐 Maintainability & Code Quality | 🔵 Trivial | 💤 Low value

Optimize provider lookup and avoid duplicate find operations.

The providers.find lookup is performed twice for every mapping (once in the setup loop and once in the filter loop). While the arrays are likely small, you can improve performance and readability by looking up the provider definition once and caching it.

Additionally, if providers is correctly typed from @llmgateway/models, the explicit as ProviderDefinition | undefined type assertions might be unnecessary.

♻️ Proposed refactor

-		const def = providers.find((p) => p.id === m.providerId) as
-			| ProviderDefinition
-			| undefined;
-		if (m.region === def?.regionConfig?.defaultRegion) {
+		const def = providers.find((p) => p.id === m.providerId);
+		if (def && m.region === def.regionConfig?.defaultRegion) {
 			providerHasDefaultRegion.add(m.providerId);
 		}
 	}
 	return mappings.filter((m) => {
-		const def = providers.find((p) => p.id === m.providerId) as
-			| ProviderDefinition
-			| undefined;
+		const def = providers.find((p) => p.id === m.providerId);
 		if (!def?.regionConfig?.pinDefaultRegion) {

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@apps/gateway/src/chat/tools/pin-default-regions.ts` around lines 40 - 51,
Refactor the provider lookup in the setup and filtering logic of the
pin-default-regions flow to resolve each mapping’s provider definition once and
reuse the cached result, eliminating both repeated providers.find calls. If the
providers collection is already typed as ProviderDefinition, remove the
redundant ProviderDefinition | undefined assertions while preserving the
existing default-region and pinDefaultRegion behavior.

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Nitpick comments:
In `@apps/gateway/src/chat/tools/pin-default-regions.ts`:
- Around line 40-51: Refactor the provider lookup in the setup and filtering
logic of the pin-default-regions flow to resolve each mapping’s provider
definition once and reuse the cached result, eliminating both repeated
providers.find calls. If the providers collection is already typed as
ProviderDefinition, remove the redundant ProviderDefinition | undefined
assertions while preserving the existing default-region and pinDefaultRegion
behavior.

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: Repository UI

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Plan: Pro

Run ID: 18a31774-1cc9-4dd2-bde3-a6fb29e62f15

📥 Commits

Reviewing files that changed from the base of the PR and between 8d6a2dc and cc51181.

📒 Files selected for processing (3)

• apps/gateway/src/chat/chat.ts
• apps/gateway/src/chat/tools/pin-default-regions.spec.ts
• apps/gateway/src/chat/tools/pin-default-regions.ts