fix(ai-gateway): rewrite JSON Schema oneOf as anyOf when routed to friendli

[chrarnoldus]

Summary

• Friendli does not support the JSON Schema oneOf keyword. When a chat completions request is routed through Friendli (provider.order contains friendli), the upstream provider rejects schemas that use oneOf.
• Adds apps/web/src/lib/ai-gateway/schema-rewrite.ts:
  • isFriendliChatCompletionsRequest — a type guard that narrows a GatewayRequest to a chat completions request whose provider.order includes friendli.
  • rewriteChatCompletionsOneOfAsAnyOf — recursively rewrites every oneOf keyword as anyOf across both tool function parameters and response_format.json_schema.schema, mutating the schemas in place. Cycle-safe via a visited set; merges into any pre-existing anyOf instead of overwriting it. Logs once per request, but only when at least one oneOf was actually rewritten.
• Wires it into applyProviderSpecificLogic via isFriendliChatCompletionsRequest, placed after applyPreferredProvider so the effective provider.order is observed (GLM traffic that prefers Friendli is covered), scoped to chat_completions requests only.

Verification

• Sent a chat completions request containing a tool with a oneOf parameters schema while provider.order included friendli, and confirmed the outgoing schema used anyOf with no oneOf.
• Confirmed a comparable request without friendli in provider.order leaves oneOf schemas untouched.

Visual Changes

N/A

Reviewer Notes

• The rewrite runs after applyPreferredProvider, so it sees the effective provider.order regardless of whether Friendli was caller-supplied or preferred by the gateway (e.g. GLM models). It is gated to chat_completions; /responses and /messages are unaffected.
• When a schema already declares both anyOf and oneOf, the oneOf entries are appended to anyOf rather than overwriting it, to avoid silently dropping schemas.
• oneOf (XOR) → anyOf (OR) is a deliberate, lossy semantic downgrade: Friendli rejects oneOf, so the most compatible fallback is to accept any of the sub-schemas.
• The rewrite emits a single log (ai_gateway_chat_completions_one_of_rewritten, with model + count) per request, only when something actually changed.

[kilo-code-bot]

Code Review Summary

Status: No Issues Found | Recommendation: Merge

Executive Summary

Incremental diff (one commit since last review) removes an unnecessary try/catch wrapper around the log(...) call in rewriteChatCompletionsOneOfAsAnyOf. The default logger (warnExceptInTest → console.warn) cannot throw, so the guard was dead code; the refactor is correct and the clean-up is appropriate.

Files Reviewed (1 file, incremental)

• apps/web/src/lib/ai-gateway/schema-rewrite.ts — removed try/catch around diagnostic log() call; no logic change, no risk

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Previous review findings (unchanged files, carried forward):

• apps/web/src/lib/ai-gateway/schema-rewrite.ts — isFriendliChatCompletionsRequest type guard; BFS oneOf→anyOf rewrite with visited-set cycle guard; correct
• apps/web/src/lib/ai-gateway/schema-rewrite.test.ts — test coverage for logging behaviour and type guard
• apps/web/src/lib/ai-gateway/providers/apply-provider-specific-logic.ts — uses isFriendliChatCompletionsRequest; organizationId param removed
• apps/web/src/app/api/openrouter/[...path]/route.ts — organizationId arg removed to match updated signature
• apps/web/src/lib/ai-gateway/schema-logging.ts — deleted (reverted)

Notable non-blocking observations (unchanged):

• isRecord returns true for arrays, so array values are pushed onto the traversal stack and iterated via numeric Object.entries keys. Harmless but does slightly more work than necessary.
• oneOf (XOR) → anyOf (OR) is a deliberate, lossy semantic downgrade acknowledged in the PR description.

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_{Reviewed by claude-sonnet-4.6 · 399,263 tokens}

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