fix(ai): classify gateway account limits as quota and keep 4xx non-retryable

packages/ai/src/provider-error.ts

@@ -59,7 +59,15 @@ export const isContextOverflowFailure = (failure: unknown) =>
     : Schema.is(ProviderErrorEvent)(failure) && failure.classification === "context-overflow"
 
 const decodeJson = Schema.decodeUnknownOption(Schema.fromJsonString(Schema.Unknown))
-const QUOTA_CODES = new Set(["insufficient_quota", "usage_not_included", "billing_error"])
+// OpenCode Zen reports account caps as typed 429/402 errors that are not throttles.
+const QUOTA_CODES = new Set([
+  "insufficient_quota",
+  "usage_not_included",
+  "billing_error",
+  "gousagelimiterror",
+  "freeusagelimiterror",
+  "creditlimitexceeded",
+])
 const AUTH_CODES = new Set(["authentication_error", "permission_error"])
 const SERVER_CODES = new Set([
   "api_error",
@@ -87,7 +95,8 @@ const CONTENT_POLICY_CODES = new Set([
 // as a `[code]` label at the start of the rewritten message.
 const GATEWAY_CODE_LABEL = /^[^:\n]+: \[([A-Za-z0-9_.-]+)\]/
 const RATE_LIMIT_TEXT = /rate increased too quickly|rate[-_\s]?limit|too[_\s]?many[_\s]?requests/i
-const QUOTA_TEXT = /insufficient[-_\s]?quota|quota[-_\s]?exceeded/i
+// Only consulted on 429, where throttles and account caps share a status.
+const QUOTA_TEXT = /insufficient[-_\s]?quota|quota[-_\s]?exceeded|budget exceeded|usage limit/i
 // Policy rejections without a dedicated code, matched against the provider's own
 // explanation only. OpenAI reuses `invalid_prompt` for usage-policy rejections while
 // Bedrock Mantle reuses it for schema validation; Anthropic reports blocked output
@@ -143,7 +152,11 @@ export function classifyProviderFailure(input: ProviderFailure): AIError["reason
     return new InvalidRequestError({ ...details, classification: "payload-too-large" })
   if (codes.some((code) => CONTENT_POLICY_CODES.has(code)) || (clientScoped && CONTENT_POLICY_TEXT.test(input.message)))
     return new ContentPolicyError(details)
-  if (codes.some((code) => QUOTA_CODES.has(code)) || (input.status === 429 && QUOTA_TEXT.test(text)))
+  if (
+    input.status === 402 ||
+    codes.some((code) => QUOTA_CODES.has(code)) ||
+    (input.status === 429 && QUOTA_TEXT.test(text))
+  )
     return new QuotaExceededError(details)
   if (input.status === 401 || input.status === 403 || codes.some((code) => AUTH_CODES.has(code)))
     return new AuthenticationError(details)
@@ -163,10 +176,12 @@ export function classifyProviderFailure(input: ProviderFailure): AIError["reason
     input.status === 408 ||
     input.status === 409 ||
     (input.status !== undefined && input.status >= 500) ||
+    // Server codes and phrasing only decide when no HTTP status contradicts them:
+    // gateways such as OpenCode Zen substitute `server_error` for codes they do
+    // not forward, so a 4xx with a server code is still a rejected request.
     ((input.status === undefined || input.status < 400) &&
-      !codes.some((code) => INVALID_REQUEST_CODES.has(code)) &&
-      SERVER_ERROR_TEXT.test(text)) ||
-    codes.some((code) => SERVER_CODES.has(code) || code.includes("exhausted") || code.includes("unavailable"))
+      ((!codes.some((code) => INVALID_REQUEST_CODES.has(code)) && SERVER_ERROR_TEXT.test(text)) ||
+        codes.some((code) => SERVER_CODES.has(code) || code.includes("exhausted") || code.includes("unavailable"))))
   )
     return new ProviderInternalError({
       ...details,

packages/ai/test/executor.test.ts

@@ -309,7 +309,7 @@ describe("RequestExecutor", () => {
     }),
   )
 
-  it.effect("classifies provider overloads hidden behind HTTP 400", () =>
+  it.effect("does not let server codes override a 4xx rejection", () =>
     Effect.gen(function* () {
       const classify = (body: string) =>
         Effect.gen(function* () {
@@ -317,11 +317,11 @@ describe("RequestExecutor", () => {
           const error = yield* executor.execute(request).pipe(Effect.flip)
 
           expectAIError(error)
-          expect(error.reason).toMatchObject({ _tag: "ProviderInternal" })
+          expect(error.reason).toMatchObject({ _tag: "InvalidRequest" })
         }).pipe(Effect.provide(fixedResponse(body, { status: 400 })))
 
       yield* classify('{"code":"resource_exhausted"}')
-      yield* classify('{"code":"service_unavailable"}')
+      yield* classify('{"error":{"type":"server_error","message":"Upstream request failed: Model is unavailable."}}')
     }),
   )
 

packages/ai/test/provider-error.test.ts

@@ -249,10 +249,54 @@ describe("provider error classification", () => {
 
   test("classifies any remaining 4xx status as an invalid request", () => {
     expect(
-      [400, 402, 404, 418, 422, 451].map(
-        (status) => classifyProviderFailure({ message: `HTTP ${status}`, status })._tag,
+      [400, 404, 418, 422, 451].map((status) => classifyProviderFailure({ message: `HTTP ${status}`, status })._tag),
+    ).toEqual(Array(5).fill("InvalidRequest"))
+  })
+
+  test("classifies 402 as exhausted quota", () => {
+    expect(classifyProviderFailure({ message: "Payment Required", status: 402 })._tag).toBe("QuotaExceeded")
+  })
+
+  test("classifies OpenCode Zen account limits as quota rather than throttling", () => {
+    const typed = (type: string, message: string) => ({ type: "error", error: { type, message } })
+    const substituted = (message: string) => ({
+      error: { type: "server_error", message: `Upstream request failed: ${message}` },
+    })
+    const cases: ReadonlyArray<[number, { error: { message: string } }]> = [
+      [429, typed("GoUsageLimitError", "Go usage limit exceeded")],
+      [429, typed("FreeUsageLimitError", "Rate limit exceeded. Please try again later.")],
+      [402, typed("CreditLimitExceeded", "Credit limit exceeded.")],
+      [402, substituted("Insufficient account funds")],
+      [402, substituted("Account invoice is overdue")],
+      [429, substituted("Account budget exceeded")],
+    ]
+    expect(
+      cases.map(
+        ([status, body]) =>
+          classifyProviderFailure({ message: body.error.message, status, rawBody: JSON.stringify(body) })._tag,
       ),
-    ).toEqual(Array(6).fill("InvalidRequest"))
+    ).toEqual(Array(6).fill("QuotaExceeded"))
+  })
+
+  test("does not let substituted server codes make a 4xx retryable", () => {
+    const openai = { error: { type: "server_error", message: "Upstream request failed: Model is unavailable." } }
+    const anthropic = {
+      type: "error",
+      error: { type: "api_error", message: "Upstream request failed: Model is unavailable." },
+    }
+    expect(
+      [openai, anthropic].map(
+        (body) =>
+          classifyProviderFailure({ message: body.error.message, status: 400, rawBody: JSON.stringify(body) })._tag,
+      ),
+    ).toEqual(["InvalidRequest", "InvalidRequest"])
+    // Without a contradicting status the same codes still mark provider trouble.
+    expect(classifyProviderFailure({ message: openai.error.message, rawBody: JSON.stringify(openai) })._tag).toBe(
+      "ProviderInternal",
+    )
+    expect(
+      classifyProviderFailure({ message: openai.error.message, status: 200, rawBody: JSON.stringify(openai) })._tag,
+    ).toBe("ProviderInternal")
   })
 
   test("classifies nested provider codes when a top-level code is also present", () => {

packages/core/test/aisdk.test.ts

@@ -804,12 +804,12 @@ it.effect("classifies retryable AI SDK failures with retry-after details", () =>
 it.effect("classifies data-only AI SDK provider codes", () =>
   Effect.gen(function* () {
     const data = {
-      error: { code: "api_error", metadata: { requestId: "data-request", retryable: true } },
+      error: { code: "rate_limit_error", metadata: { requestId: "data-request", retryable: true } },
       trace: { region: "test-region" },
     }
     const cause = apiCallError({ statusCode: 400, data })
     const error = yield* streamFailure(cause)
-    expect(error.reason).toMatchObject({ _tag: "ProviderInternal" })
+    expect(error.reason).toMatchObject({ _tag: "RateLimit" })
     expect(error.reason.http?.status).toBe(400)
     expect(SessionRunnerRetry.isRetryable(error)).toBeTrue()
     expect(error.reason.body).toBe(JSON.stringify(data))