fix(ai): align chat assistant content (#41210)

Co-authored-by: Aiden Cline <63023139+rekram1-node@users.noreply.github.com>

packages/ai/src/protocols/openai-chat.ts

@@ -371,12 +371,13 @@ const lowerAssistantMessage = Effect.fn("OpenAIChat.lowerAssistantMessage")(func
     return text
   })()
   const cached = message.content.findLast((part) => "cache" in part && part.cache !== undefined)
+  const cacheControl = options.cacheControl?.(cached && "cache" in cached ? cached.cache : undefined)
   const result = {
     role: "assistant" as const,
-    content: content.length === 0 ? null : ProviderShared.joinText(content),
-    tool_calls: toolCalls.length === 0 ? undefined : toolCalls,
-    reasoning_details: details,
-    cache_control: options.cacheControl?.(cached && "cache" in cached ? cached.cache : undefined),
+    content: content.length > 0 ? content.map((part) => part.text).join("") : toolCalls.length > 0 ? null : "",
+    ...(toolCalls.length > 0 ? { tool_calls: toolCalls } : {}),
+    ...(details !== undefined ? { reasoning_details: details } : {}),
+    ...(cacheControl !== undefined ? { cache_control: cacheControl } : {}),
   }
   if (field === undefined || reasoningText === undefined) return result
   return { ...result, [field]: reasoningText }
@@ -716,14 +717,13 @@ const step = (state: ParserState, event: OpenAIChatEvent) =>
       return [{ ...state, usage }, events] as const
     }
 
-    const reasoningField = state.reasoningField ?? (!state.lifecycle.text.has("text-0") ? reasoning?.field : undefined)
+    const reasoningField = state.reasoningField ?? reasoning?.field
     const detailDelta = Array.isArray(delta?.reasoning_details) ? delta.reasoning_details : undefined
     if (detailDelta !== undefined) appendReasoningDetails(state.reasoningDetails, detailDelta)
     const reasoningDetailsObserved = state.reasoningDetailsObserved || detailDelta !== undefined
     const deltaMetadata = reasoningMetadata(reasoningField)
     const text = detailDelta?.length ? (detailText(detailDelta) ?? reasoning?.text) : reasoning?.text
-    if (!state.lifecycle.text.has("text-0") && text !== undefined)
-      lifecycle = Lifecycle.reasoningDelta(lifecycle, events, "reasoning-0", text, deltaMetadata)
+    if (text !== undefined) lifecycle = Lifecycle.reasoningDelta(lifecycle, events, "reasoning-0", text, deltaMetadata)
     else if (
       reasoningDetailsObserved &&
       !lifecycle.reasoning.has("reasoning-0") &&
@@ -812,14 +812,18 @@ const step = (state: ParserState, event: OpenAIChatEvent) =>
 
 const finishEvents = (state: ParserState): ReadonlyArray<LLMEvent> => {
   const events: LLMEvent[] = []
-  const hasToolCalls = state.toolCallEvents.length > 0
+  const toolCallEvents =
+    state.finishReason === undefined && Object.keys(state.tools).length > 0
+      ? Effect.runSync(ToolStream.finishAll(ADAPTER, state.tools)).events
+      : state.toolCallEvents
+  const hasToolCalls = toolCallEvents.length > 0
   const reason = state.finishReason
     ? {
         ...state.finishReason,
         normalized:
           state.finishReason.normalized === "stop" && hasToolCalls ? "tool-calls" : state.finishReason.normalized,
       }
-    : undefined
+    : { normalized: hasToolCalls ? ("tool-calls" as const) : ("unknown" as const) }
   const metadata = reasoningMetadata(
     state.reasoningField,
     state.reasoningDetailsObserved ? state.reasoningDetails : undefined,
@@ -829,9 +833,9 @@ const finishEvents = (state: ParserState): ReadonlyArray<LLMEvent> => {
       ? Lifecycle.reasoningStart(state.lifecycle, events, "reasoning-0", reasoningMetadata(state.reasoningField))
       : state.lifecycle
   const ended = Lifecycle.reasoningEnd(started, events, "reasoning-0", metadata)
-  const lifecycle = state.toolCallEvents.length ? Lifecycle.stepStart(ended, events) : ended
-  events.push(...state.toolCallEvents)
-  if (reason) Lifecycle.finish(lifecycle, events, { reason, usage: state.usage })
+  const lifecycle = toolCallEvents.length ? Lifecycle.stepStart(ended, events) : ended
+  events.push(...toolCallEvents)
+  Lifecycle.finish(lifecycle, events, { reason, usage: state.usage })
   return events
 }
 

packages/ai/test/provider/openai-chat.test.ts

@@ -102,6 +102,24 @@ describe("OpenAI Chat route", () => {
     }),
   )
 
+  it.effect("concatenates assistant text parts without adding separators", () =>
+    Effect.gen(function* () {
+      const prepared = yield* compileRequest(
+        LLM.request({
+          model,
+          messages: [
+            Message.assistant([
+              { type: "text", text: "Hello" },
+              { type: "text", text: " world" },
+            ]),
+          ],
+        }),
+      )
+
+      expect(prepared.body.messages).toEqual([{ role: "assistant", content: "Hello world" }])
+    }),
+  )
+
   it.effect("writes reasoning to a configured custom field on every assistant message", () =>
     Effect.gen(function* () {
       const prepared = yield* compileRequest(
@@ -578,7 +596,7 @@ describe("OpenAI Chat route", () => {
         }),
       )
 
-      expect(prepared.body.messages).toEqual([{ role: "assistant", content: null, reasoning_content: "hidden" }])
+      expect(prepared.body.messages).toEqual([{ role: "assistant", content: "", reasoning_content: "hidden" }])
     }),
   )
 
@@ -827,7 +845,7 @@ describe("OpenAI Chat route", () => {
     }),
   )
 
-  it.effect("ignores scalar reasoning after content starts", () =>
+  it.effect("preserves scalar reasoning after content starts", () =>
     Effect.gen(function* () {
       const details = [{ type: "reasoning.text", text: "detail", format: "unknown", index: 0 }]
       const response = yield* LLMClient.generate(request).pipe(
@@ -843,11 +861,11 @@ describe("OpenAI Chat route", () => {
         ),
       )
 
-      expect(response.reasoning).toBe("detail")
-      expect(response.events.filter(LLMEvent.is.reasoningStart)).toHaveLength(1)
-      expect(response.events.filter(LLMEvent.is.reasoningEnd)).toHaveLength(1)
+      expect(response.reasoning).toBe("detailscalar")
+      expect(response.events.filter(LLMEvent.is.reasoningStart)).toHaveLength(2)
+      expect(response.events.filter(LLMEvent.is.reasoningEnd)).toHaveLength(2)
       expect(response.message.content.find((part) => part.type === "reasoning")?.providerMetadata).toEqual({
-        openai: { reasoningDetails: details },
+        openai: { reasoningField: "reasoning", reasoningDetails: details },
       })
     }),
   )
@@ -947,7 +965,7 @@ describe("OpenAI Chat route", () => {
       expect(response.events.filter(LLMEvent.is.reasoningEnd)).toHaveLength(1)
 
       const replay = yield* compileRequest(LLM.request({ model, messages: [response.message] }))
-      expect(replay.body.messages).toEqual([{ role: "assistant", content: null, reasoning_details: details }])
+      expect(replay.body.messages).toEqual([{ role: "assistant", content: "", reasoning_details: details }])
     }),
   )
 
@@ -997,7 +1015,7 @@ describe("OpenAI Chat route", () => {
       )
 
       expect(replay.body.messages).toEqual([
-        { role: "assistant", content: null, reasoning: "firstsecond", reasoning_details: [first, second] },
+        { role: "assistant", content: "", reasoning: "firstsecond", reasoning_details: [first, second] },
       ])
     }),
   )
@@ -1022,7 +1040,7 @@ describe("OpenAI Chat route", () => {
       )
 
       expect(replay.body.messages).toEqual([
-        { role: "assistant", content: null, reasoning_content: "AB", reasoning_details: [detail] },
+        { role: "assistant", content: "", reasoning_content: "AB", reasoning_details: [detail] },
       ])
     }),
   )
@@ -1044,7 +1062,7 @@ describe("OpenAI Chat route", () => {
       )
 
       expect(replay.body.messages).toEqual([
-        { role: "assistant", content: null, reasoning_content: "thinking", reasoning_details: details },
+        { role: "assistant", content: "", reasoning_content: "thinking", reasoning_details: details },
       ])
     }),
   )
@@ -1152,7 +1170,7 @@ describe("OpenAI Chat route", () => {
     }),
   )
 
-  it.effect("fails a streamed tool call when the provider ends without a finish reason", () =>
+  it.effect("finalizes a streamed tool call when the provider ends without a finish reason", () =>
     Effect.gen(function* () {
       const body = sseEvents(
         deltaChunk({
@@ -1164,27 +1182,31 @@ describe("OpenAI Chat route", () => {
       const input = LLMRequest.update(request, {
         tools: [ToolDefinition.make({ name: "lookup", description: "Lookup data", inputSchema: { type: "object" } })],
       })
-      const events: LLMEvent[] = []
-      const streamError = yield* LLMClient.stream(input).pipe(
-        Stream.runForEach((event) => Effect.sync(() => events.push(event))),
-        Effect.flip,
-        Effect.provide(fixedResponse(body)),
-      )
-      const error = yield* LLMClient.generate(input).pipe(Effect.provide(fixedResponse(body)), Effect.flip)
+      const response = yield* LLMClient.generate(input).pipe(Effect.provide(fixedResponse(body)))
 
-      expect(events).toEqual([
+      expect(response.events).toEqual([
         { type: "step-start", index: 0 },
         { type: "tool-input-start", id: "call_1", name: "lookup", providerMetadata: undefined },
         { type: "tool-input-delta", id: "call_1", name: "lookup", text: '{"query"' },
         { type: "tool-input-delta", id: "call_1", name: "lookup", text: ':"weather"}' },
+        { type: "tool-input-end", id: "call_1", name: "lookup", providerMetadata: undefined },
+        {
+          type: "tool-call",
+          id: "call_1",
+          name: "lookup",
+          input: { query: "weather" },
+          providerExecuted: undefined,
+          providerMetadata: undefined,
+        },
+        {
+          type: "step-finish",
+          index: 0,
+          reason: { normalized: "tool-calls" },
+          usage: undefined,
+          providerMetadata: undefined,
+        },
+        { type: "finish", reason: { normalized: "tool-calls" }, usage: undefined },
       ])
-      expect(events.filter(LLMEvent.is.toolCall)).toEqual([])
-      expect(streamError.reason).toMatchObject({
-        _tag: "InvalidProviderOutput",
-        classification: "incomplete-stream",
-      })
-      expect(streamError.message).toContain("The provider response ended unexpectedly.")
-      expect(error.message).toContain("The provider response ended unexpectedly.")
     }),
   )