[ai-gateway-provider] Dynamic Workers AI route fails through universal endpoint but succeeds through /compat

[Aqua-123]

Summary

A documented ai-gateway-provider dynamic route targeting Workers AI fails when it is sent through the AI Gateway universal endpoint. The same model, prompt, and OpenAI-compatible request succeeds when sent directly to the gateway's /compat/chat/completions endpoint.

This also reproduces with a raw universal-endpoint request, without ai-gateway-provider, so the failure appears to be in the universal endpoint's dynamic-route -> Workers AI translation rather than the AI SDK request serializer.

Environment

• ai-gateway-provider@3.2.0
• ai@6.0.174
• @ai-sdk/openai-compatible@2.0.45
• Node/Bun REST path using an authenticated AI Gateway
• Dynamic route target observed in response headers: @cf/moonshotai/kimi-k2.7-code

Reproduction with ai-gateway-provider

import { generateText } from "ai";
import { createAiGateway } from "ai-gateway-provider";
import { createUnified } from "ai-gateway-provider/providers/unified";

const gateway = createAiGateway({
  accountId: process.env.CLOUDFLARE_ACCOUNT_ID!,
  gateway: process.env.CLOUDFLARE_AI_GATEWAY_ID!,
  apiKey: process.env.CF_AIG_TOKEN!,
});
const unified = createUnified({ name: "cloudflare-ai-gateway" });

await generateText({
  model: gateway(unified("dynamic/cloudflare")),
  prompt: "Reply with exactly: OK",
  maxOutputTokens: 64,
});

Result: HTTP 400.

Adding parallel_tool_calls: false through OpenAI-compatible provider options does not change the result.

Minimal raw universal-endpoint reproduction

curl -X POST \
  "https://gateway.ai.cloudflare.com/v1/<ACCOUNT_ID>/<GATEWAY_ID>" \
  -H "cf-aig-authorization: Bearer <CF_AIG_TOKEN>" \
  -H "content-type: application/json" \
  --data '[{
    "provider": "compat",
    "endpoint": "chat/completions",
    "headers": {},
    "query": {
      "model": "dynamic/cloudflare",
      "messages": [{"role": "user", "content": "Reply exactly OK"}],
      "max_tokens": 64,
      "parallel_tool_calls": false
    }
  }]'

Response:

{
  "name": "AiError",
  "internalCode": 5006,
  "httpCode": 400,
  "description": "Error: anyOf at '/' not met: required properties at '/audio' are 'voice,format', Cannot read properties of undefined (reading 'parallel_tool_calls'), oneOf at '/' not met, 0 matches"
}

Cloudflare request ID: 3fb00f66-9124-4421-b607-79465a53cc6f

Control request that succeeds

Sending the same query object directly to the documented compat endpoint succeeds:

curl -X POST \
  "https://gateway.ai.cloudflare.com/v1/<ACCOUNT_ID>/<GATEWAY_ID>/compat/chat/completions" \
  -H "cf-aig-authorization: Bearer <CF_AIG_TOKEN>" \
  -H "content-type: application/json" \
  --data '{
    "model": "dynamic/cloudflare",
    "messages": [{"role": "user", "content": "Reply exactly OK"}],
    "max_tokens": 64,
    "parallel_tool_calls": false
  }'

Result: HTTP 200, model @cf/moonshotai/kimi-k2.7-code, response text OK.

Cloudflare request ID: 62b2a517-554c-431b-8dad-79f68729ffee

The direct compat path was also verified with AI SDK text generation, streaming, and forced tool calling.

Expected behavior

The documented pattern below should work for a dynamic route whose selected model is a Workers AI model:

gateway(unified("dynamic/<route-name>"))

The universal endpoint should either forward the OpenAI-compatible query to the selected Workers AI model or return the same successful result as /compat/chat/completions.

Actual behavior

The universal endpoint returns HTTP 400 during request-shape validation/translation before inference, while the direct compat endpoint succeeds with the same query.

Impact

Applications using ai-gateway-provider cannot use documented dynamic routes that resolve to this Workers AI model through the package's REST universal-endpoint transport. A working application-level workaround is to use @ai-sdk/openai-compatible directly against /compat, but that bypasses ai-gateway-provider's universal-endpoint fallback behavior.

Testing gap noticed

The package README documents aigateway(unified("dynamic/customer-support")), but the current live E2E suite appears to cover provider/BYOK routing rather than a dynamic route resolving to Workers AI. A dynamic-route E2E regression case may help prevent this path from going unverified.

[dhruvil-codes]

Thanks for the detailed reproduction. The raw universal-endpoint failure is particularly useful here since it appears to rule out the AI SDK serializer/provider layer.

I'm going to trace the ai-gateway-provider universal transport and the existing E2E coverage for dynamic routes resolving to Workers AI.

If the request shape is already being forwarded as documented and the failure is entirely in the gateway-side translation path, I'll report back with the exact boundary rather than trying to mask the backend failure in the provider. If there is a provider-side routing or serialization gap, I'll put together a focused fix and regression test.

[dhruvil-codes]

I added a targeted live E2E regression case for the unified dynamic-route path in #619.

The test exercises aigateway(unified(DYNAMIC_ROUTE)) through the universal-endpoint REST transport and is gated by CLOUDFLARE_AI_GATEWAY_DYNAMIC_ROUTE.

When configured with a Workers AI-backed dynamic route, it should reproduce the validation/translation failure described here rather than silently skipping it.