fix(llm): surface code, type, and nested fields on provider stream errors (#28757)

packages/llm/src/protocols/anthropic-messages.ts

@@ -206,7 +206,13 @@ const AnthropicEvent = Schema.Struct({
   content_block: Schema.optional(AnthropicStreamBlock),
   delta: Schema.optional(AnthropicStreamDelta),
   usage: Schema.optional(AnthropicUsage),
-  error: Schema.optional(Schema.Struct({ type: Schema.String, message: Schema.String })),
+  // `type` and `message` are both required per Anthropic's spec, but
+  // OpenAI-compatible proxies and gateway translations occasionally drop one
+  // or the other; mark them optional so a partial payload still parses and
+  // the parser can fall back to whichever field is populated.
+  error: Schema.optional(
+    Schema.Struct({ type: Schema.optional(Schema.String), message: Schema.optional(Schema.String) }),
+  ),
 })
 type AnthropicEvent = Schema.Schema.Type<typeof AnthropicEvent>
 
@@ -701,9 +707,18 @@ const onMessageDelta = (state: ParserState, event: AnthropicEvent): StepResult =
   return [{ ...state, lifecycle, usage }, events]
 }
 
+// Prefix `error.type` so overloads, rate limits, and quota errors are visible
+// even when the provider message is generic or empty.
+const providerErrorMessage = (event: AnthropicEvent): string => {
+  const type = event.error?.type
+  const message = event.error?.message
+  if (type && message) return `${type}: ${message}`
+  return message || type || "Anthropic Messages stream error"
+}
+
 const onError = (state: ParserState, event: AnthropicEvent): StepResult => [
   state,
-  [LLMEvent.providerError({ message: event.error?.message ?? "Anthropic Messages stream error" })],
+  [LLMEvent.providerError({ message: providerErrorMessage(event) })],
 ]
 
 const step = (state: ParserState, event: AnthropicEvent) => {

packages/llm/src/protocols/openai-responses.ts

@@ -178,6 +178,17 @@ const OpenAIResponsesStreamItem = Schema.Struct({
 })
 type OpenAIResponsesStreamItem = Schema.Schema.Type<typeof OpenAIResponsesStreamItem>
 
+// OpenAI Responses surfaces provider failures in two related shapes. The
+// streaming `error` event carries the details at the top level
+// (`{ type: "error", code, message, param, sequence_number }`), while
+// `response.failed` carries them under `response.error`. We capture both so
+// the parser can surface a useful provider-error message in either path.
+const OpenAIResponsesErrorPayload = Schema.Struct({
+  code: optionalNull(Schema.String),
+  message: optionalNull(Schema.String),
+  param: optionalNull(Schema.String),
+})
+
 const OpenAIResponsesEvent = Schema.Struct({
   type: Schema.String,
   delta: Schema.optional(Schema.String),
@@ -190,12 +201,14 @@ const OpenAIResponsesEvent = Schema.Struct({
         service_tier: optionalNull(Schema.String),
         incomplete_details: optionalNull(Schema.Struct({ reason: Schema.String })),
         usage: optionalNull(OpenAIResponsesUsage),
+        error: optionalNull(OpenAIResponsesErrorPayload),
       }),
       [Schema.Record(Schema.String, Schema.Unknown)],
     ),
   ),
   code: Schema.optional(Schema.String),
   message: Schema.optional(Schema.String),
+  param: Schema.optional(Schema.String),
 })
 type OpenAIResponsesEvent = Schema.Schema.Type<typeof OpenAIResponsesEvent>
 
@@ -633,14 +646,27 @@ const onResponseFinish = (state: ParserState, event: OpenAIResponsesEvent): Step
   return [{ ...state, lifecycle }, events]
 }
 
+// Build a single human-readable message from whatever the provider supplied.
+// When both code and message are present, prefix the code so consumers see
+// the failure mode (e.g. `rate_limit_exceeded: Slow down`) instead of just
+// the bare message — production rate limits and context-length failures used
+// to be indistinguishable from generic stream drops.
+const providerErrorMessage = (event: OpenAIResponsesEvent, fallback: string): string => {
+  const nested = event.response?.error ?? undefined
+  const message = event.message || nested?.message || undefined
+  const code = event.code || nested?.code || undefined
+  if (message && code) return `${code}: ${message}`
+  return message || code || fallback
+}
+
 const onResponseFailed = (state: ParserState, event: OpenAIResponsesEvent): StepResult => [
   state,
-  [LLMEvent.providerError({ message: event.message ?? event.code ?? "OpenAI Responses response failed" })],
+  [LLMEvent.providerError({ message: providerErrorMessage(event, "OpenAI Responses response failed") })],
 ]
 
 const onError = (state: ParserState, event: OpenAIResponsesEvent): StepResult => [
   state,
-  [LLMEvent.providerError({ message: event.message ?? event.code ?? "OpenAI Responses stream error" })],
+  [LLMEvent.providerError({ message: providerErrorMessage(event, "OpenAI Responses stream error") })],
 ]
 
 const step = (state: ParserState, event: OpenAIResponsesEvent) => {

packages/llm/test/provider/anthropic-messages.test.ts

@@ -337,7 +337,29 @@ describe("Anthropic Messages route", () => {
         ),
       )
 
-      expect(response.events).toEqual([{ type: "provider-error", message: "Overloaded" }])
+      // Prefix the error type so consumers can distinguish overloads, rate
+      // limits, and quota errors without parsing the message string.
+      expect(response.events).toEqual([{ type: "provider-error", message: "overloaded_error: Overloaded" }])
+    }),
+  )
+
+  it.effect("falls back to error type when no message is present", () =>
+    Effect.gen(function* () {
+      const response = yield* LLMClient.generate(request).pipe(
+        Effect.provide(fixedResponse(sseEvents({ type: "error", error: { type: "overloaded_error", message: "" } }))),
+      )
+
+      expect(response.events).toEqual([{ type: "provider-error", message: "overloaded_error" }])
+    }),
+  )
+
+  it.effect("falls back to a stable default when error payload is absent", () =>
+    Effect.gen(function* () {
+      const response = yield* LLMClient.generate(request).pipe(
+        Effect.provide(fixedResponse(sseEvents({ type: "error" }))),
+      )
+
+      expect(response.events).toEqual([{ type: "provider-error", message: "Anthropic Messages stream error" }])
     }),
   )
 

packages/llm/test/provider/openai-responses.test.ts

@@ -877,7 +877,11 @@ describe("OpenAI Responses route", () => {
         Effect.provide(fixedResponse(sseEvents({ type: "error", code: "rate_limit_exceeded", message: "Slow down" }))),
       )
 
-      expect(response.events).toEqual([{ type: "provider-error", message: "Slow down" }])
+      // Prefix the code so consumers see the failure mode, not just the
+      // sometimes-generic provider message. The bare message alone meant
+      // production errors like rate limits were indistinguishable from
+      // unrelated stream failures.
+      expect(response.events).toEqual([{ type: "provider-error", message: "rate_limit_exceeded: Slow down" }])
     }),
   )
 
@@ -891,6 +895,103 @@ describe("OpenAI Responses route", () => {
     }),
   )
 
+  it.effect("falls back to error code when message is empty", () =>
+    Effect.gen(function* () {
+      const response = yield* LLMClient.generate(request).pipe(
+        Effect.provide(fixedResponse(sseEvents({ type: "error", code: "internal_error", message: "" }))),
+      )
+
+      expect(response.events).toEqual([{ type: "provider-error", message: "internal_error" }])
+    }),
+  )
+
+  // Regression: `response.failed` carries the failure details under
+  // `response.error`, not at the top level. The previous handler only
+  // checked top-level `message`/`code` and so always emitted the bare
+  // "OpenAI Responses response failed" string, hiding the real cause.
+  it.effect("surfaces response.failed details from response.error", () =>
+    Effect.gen(function* () {
+      const response = yield* LLMClient.generate(request).pipe(
+        Effect.provide(
+          fixedResponse(
+            sseEvents({
+              type: "response.failed",
+              response: {
+                id: "resp_failed_1",
+                error: { code: "server_error", message: "Upstream model unavailable" },
+              },
+            }),
+          ),
+        ),
+      )
+
+      expect(response.events).toEqual([
+        { type: "provider-error", message: "server_error: Upstream model unavailable" },
+      ])
+    }),
+  )
+
+  it.effect("surfaces response.failed code when no nested message is present", () =>
+    Effect.gen(function* () {
+      const response = yield* LLMClient.generate(request).pipe(
+        Effect.provide(
+          fixedResponse(
+            sseEvents({
+              type: "response.failed",
+              response: { id: "resp_failed_2", error: { code: "invalid_prompt" } },
+            }),
+          ),
+        ),
+      )
+
+      expect(response.events).toEqual([{ type: "provider-error", message: "invalid_prompt" }])
+    }),
+  )
+
+  it.effect("surfaces error event details even when they arrive nested under response.error", () =>
+    Effect.gen(function* () {
+      // Some OpenAI-compatible proxies and older SDK versions wrap the
+      // top-level error fields into a nested `response.error` payload
+      // when they bubble up an HTTP error as an SSE `error` event. Honour
+      // both shapes so the user still sees the underlying cause instead
+      // of the catch-all string.
+      const response = yield* LLMClient.generate(request).pipe(
+        Effect.provide(
+          fixedResponse(
+            sseEvents({
+              type: "error",
+              response: { error: { code: "context_length_exceeded", message: "prompt too long" } },
+            }),
+          ),
+        ),
+      )
+
+      expect(response.events).toEqual([
+        { type: "provider-error", message: "context_length_exceeded: prompt too long" },
+      ])
+    }),
+  )
+
+  it.effect("falls back to a stable default when both error and response are absent", () =>
+    Effect.gen(function* () {
+      const response = yield* LLMClient.generate(request).pipe(
+        Effect.provide(fixedResponse(sseEvents({ type: "error" }))),
+      )
+
+      expect(response.events).toEqual([{ type: "provider-error", message: "OpenAI Responses stream error" }])
+    }),
+  )
+
+  it.effect("falls back to a stable default when response.failed has no error payload", () =>
+    Effect.gen(function* () {
+      const response = yield* LLMClient.generate(request).pipe(
+        Effect.provide(fixedResponse(sseEvents({ type: "response.failed", response: { id: "resp_failed_3" } }))),
+      )
+
+      expect(response.events).toEqual([{ type: "provider-error", message: "OpenAI Responses response failed" }])
+    }),
+  )
+
   it.effect("fails HTTP provider errors before stream parsing", () =>
     Effect.gen(function* () {
       const error = yield* LLMClient.generate(request).pipe(