fix(core): preserve the first terminal failure (#37705)

packages/core/src/aisdk.ts

@@ -642,8 +642,6 @@ function streamPartEvents(
                   id: event.toolCallId,
                   name: event.toolName,
                   raw: event.input,
-                  message: error.reason.message,
-                  providerMetadata: providerMetadata(event.providerMetadata),
                 }),
               ]),
         ),

packages/core/src/session/runner/llm.ts

@@ -259,7 +259,7 @@ const layer = Layer.effect(
                 step: currentStep,
               })
             }
-            yield* serialized(publisher.failAssistant(error, true))
+            yield* serialized(publisher.failAssistant(error))
           }
           // Provider error events only arrive from the stream, so the flag is final here.
           const providerFailed = publisher.hasProviderError()
@@ -280,7 +280,7 @@ const layer = Layer.effect(
           if (settled._tag === "Failure") yield* FiberSet.clear(toolFibers)
           if (userDeclined || streamInterrupted || toolsInterrupted) {
             yield* serialized(publisher.failUnsettledTools({ type: "aborted", message: "Tool execution interrupted" }))
-            yield* serialized(publisher.failAssistant({ type: "aborted", message: "Step interrupted" }, true))
+            yield* serialized(publisher.failAssistant({ type: "aborted", message: "Step interrupted" }))
           }
           // A settled tool fiber failure is one of two things. A defect from a tool
           // implementation becomes a failed tool call the model can read, and the step still
@@ -293,7 +293,7 @@ const layer = Layer.effect(
             const failure = infraError ?? Cause.squash(settledFailure)
             const error = toSessionError(failure)
             yield* serialized(publisher.failUnsettledTools(error))
-            if (infraError !== undefined) yield* serialized(publisher.failAssistant(error, true))
+            if (infraError !== undefined) yield* serialized(publisher.failAssistant(error))
           }
 
           // Fail unresolved calls before the terminal step event. Local calls have joined, so
@@ -321,13 +321,10 @@ const layer = Layer.effect(
               : false
           if (hostedResultMissing && !publisher.stepSettlement())
             yield* serialized(
-              publisher.failAssistant(
-                {
-                  type: "tool.result-missing",
-                  message: "Provider did not return a tool result",
-                },
-                true,
-              ),
+              publisher.failAssistant({
+                type: "tool.result-missing",
+                message: "Provider did not return a tool result",
+              }),
             )
 
           const stepFailure = publisher.stepFailure()

packages/core/src/session/runner/publish-llm-event.ts

@@ -262,11 +262,11 @@ export const createLLMEventPublisher = (events: Pick<EventV2.Interface, "publish
     return failed
   })
 
-  const failAssistant = Effect.fnUntraced(function* (error: SessionError.Error, replace = false) {
+  const failAssistant = Effect.fnUntraced(function* (error: SessionError.Error) {
     yield* flush()
     yield* failTools(error, "uncalled")
     yield* startAssistant()
-    if (replace || stepFailure === undefined) stepFailure = error
+    if (stepFailure === undefined) stepFailure = error
   })
 
   const publishStepFailure = Effect.fnUntraced(function* (details?: {
@@ -458,7 +458,7 @@ export const createLLMEventPublisher = (events: Pick<EventV2.Interface, "publish
         stepSettlement = { finish: event.reason, tokens: SessionUsage.tokens(event.usage) }
         if (event.reason === "content-filter") {
           providerFailed = true
-          yield* failAssistant({ type: "provider.content-filter", message: "Provider blocked the response" }, true)
+          yield* failAssistant({ type: "provider.content-filter", message: "Provider blocked the response" })
           return
         }
         return
@@ -466,7 +466,7 @@ export const createLLMEventPublisher = (events: Pick<EventV2.Interface, "publish
         return
       case "provider-error":
         providerFailed = true
-        yield* failAssistant({ type: "provider.unknown", message: event.message }, true)
+        yield* failAssistant({ type: "provider.unknown", message: event.message })
         return
     }
   })

packages/core/src/session/runner/to-llm-message.ts

@@ -137,11 +137,10 @@ const assistant = (message: SessionMessage.Assistant, model: ModelV2.Ref, provid
           ? [{ type: "text", text: item.text }]
           : []
     const reuseToolProviderMetadata =
-      sameModel &&
-      (message.error === undefined ||
-        (item.executed === true &&
-          (item.state.status === "completed" ||
-            (item.state.status === "error" && item.state.result !== undefined))))
+      reuseProviderMetadata ||
+      (sameModel &&
+        item.executed === true &&
+        (item.state.status === "completed" || (item.state.status === "error" && item.state.result !== undefined)))
     const call = toolCall(
       item,
       reuseToolProviderMetadata ? providerMetadata(providerMetadataKey, item.providerState) : undefined,