【Bug】Error [GatewayAuthenticationError]: Unauthenticated request to AI Gateway.

[3DMXM]

Description

code:

import { streamText } from "ai";

import "dotenv/config";

async function main() {
    console.log({ apiKey: process.env.AI_GATEWAY_API_KEY });

    const result = streamText({
        model: "openai/gpt-4o-mini",
        prompt: "Invent a new holiday and describe its traditions.",
    });

    for await (const textPart of result.textStream) {
        process.stdout.write(textPart);
    }

    console.log();
    console.log("Token usage:", await result.usage);
    console.log("Finish reason:", await result.finishReason);
}

main().catch(console.error);

Error:

Error [GatewayAuthenticationError]: Unauthenticated request to AI Gateway.

To authenticate, set the AI_GATEWAY_API_KEY environment variable with your API key.

Alternatively, you can use a provider module instead of the AI Gateway.

Learn more: https://ai-sdk.dev/unauthenticated-ai-gateway


    at wrapGatewayError (E:\web\glosc.ai\ai-text-demo\node_modules\ai\src\prompt\wrap-gateway-error.ts:18:5)  
    at Object.transform (E:\web\glosc.ai\ai-text-demo\node_modules\ai\src\generate-text\stream-text.ts:879:34)
    at invokePromiseCallback (node:internal/webstreams/util:172:10)
    at Object.transformAlgorithm (node:internal/webstreams/util:177:23)
    at transformStreamDefaultControllerPerformTransform (node:internal/webstreams/transformstream:527:37)     
    at transformStreamDefaultSinkWriteAlgorithm (node:internal/webstreams/transformstream:573:10)
    at node:internal/webstreams/transformstream:378:16
    at writableStreamDefaultControllerProcessWrite (node:internal/webstreams/writablestream:1129:5)
    at writableStreamDefaultControllerAdvanceQueueIfNeeded (node:internal/webstreams/writablestream:1255:5)
    at writableStreamDefaultControllerWrite (node:internal/webstreams/writablestream:1118:3)

NoOutputGeneratedError [AI_NoOutputGeneratedError]: No output generated. Check the stream for errors.
    at Object.flush (E:\web\glosc.ai\ai-text-demo\node_modules\ai\src\generate-text\stream-text.ts:1077:17)
    at invokePromiseCallback (node:internal/webstreams/util:172:10)
    at Object.<anonymous> (node:internal/webstreams/util:177:23)
    at transformStreamDefaultSinkCloseAlgorithm (node:internal/webstreams/transformstream:621:43)
    at node:internal/webstreams/transformstream:379:11
    at writableStreamDefaultControllerProcessClose (node:internal/webstreams/writablestream:1162:28)
    at writableStreamDefaultControllerAdvanceQueueIfNeeded (node:internal/webstreams/writablestream:1253:5)
    at writableStreamDefaultControllerClose (node:internal/webstreams/writablestream:1220:3)
    at writableStreamClose (node:internal/webstreams/writablestream:722:3)
    at writableStreamDefaultWriterClose (node:internal/webstreams/writablestream:1091:10) {
  cause: undefined,
  [Symbol(vercel.ai.error)]: true,
  [Symbol(vercel.ai.error.AI_NoOutputGeneratedError)]: true
}

AI SDK Version

"ai": "^6.0.116",

Code of Conduct

• I agree to follow this project's Code of Conduct

[tosh99]

I am facing this issue too recently. In older projects also it has started happening.

[Mradul-06]

Hi, I am also facing the issue. It is not working. Need you to fix this ASAP. My production is down.

[khalidsaidi]

A2ABench has an accepted answer for this imported thread.

• Thread: https://a2abench-api.web.app/q/cmn1ngycx007bxztypek8z1oe
• Accepted at: 2026-03-25T19:35:17.171Z
• Accepted answer agent: ai village
• Answer preview: "No matching threads were found for this query."

[PlasticLizard]

We've independently reproduced and isolated this issue. The root cause is server-side: Vercel's AI Gateway rejects API key authentication when the ai-gateway-protocol-version: 0.0.1 header is present combined with the v3 prompt body format.

Evidence from curl testing against https://ai-gateway.vercel.sh/v3/ai/language-model:

Request	Auth Header	Protocol Version Header	Body Format	Result
1	Authorization: Bearer <valid-api-key> + ai-gateway-auth-method: api-key	None	messages	✅ 400 (auth OK, body format error)
2	Authorization: Bearer <valid-api-key> + ai-gateway-auth-method: api-key	ai-gateway-protocol-version: 0.0.1	messages	✅ 400 (auth OK, expects prompt array)
3	Authorization: Bearer <valid-api-key> + ai-gateway-auth-method: api-key	ai-gateway-protocol-version: 0.0.1	prompt (v3 format)	❌ 401 "Error verifying OIDC token"
4	Same as 3 + ai-language-model-specification-version: 3	ai-gateway-protocol-version: 0.0.1	prompt (v3 format)	❌ 401 "Error verifying OIDC token"

The API key is valid — tests 1 and 2 pass authentication (400 = bad request body, not auth failure). But as soon as the v3 protocol header is combined with the v3 prompt body format (test 3), the gateway ignores the ai-gateway-auth-method: api-key header and falls through to OIDC verification, which fails because there's no OIDC token.

Since @ai-sdk/gateway always sends ai-gateway-protocol-version: 0.0.1 and uses v3 prompt body format, API key authentication is impossible with the current gateway server — it only works with OIDC tokens (i.e., from Vercel deployments).

This affects any non-Vercel deployment using @ai-sdk/gateway with AI_GATEWAY_API_KEY. Tested with @ai-sdk/gateway@3.0.66 through 3.0.84 — all have identical client-side auth code, confirming this is a server-side regression.

Environment: Cloudflare Workers with @mastra/core@1.16.0 (bundles @ai-sdk/gateway@3.0.66)

[BraveRam]

fix this asap

[lgrammel]

Identify issue type

{
  "evidence": [
    "Reporter shows `streamText` with `AI_GATEWAY_API_KEY` set but receives `GatewayAuthenticationError: Unauthenticated request to AI Gateway`.",
    "Multiple commenters report the same issue, including production impact.",
    "A commenter provides curl-based reproduction indicating valid API key authentication fails when the gateway protocol header is combined with the v3 prompt body format, calling it a server-side regression affecting non-Vercel deployments."
  ],
  "rationale": "The issue describes a concrete authentication failure/regression in existing AI Gateway behavior when using a valid API key, resulting in unexpected 401 errors.",
  "type": "bug",
  "confidence": "high"
}