fix(ai): preserve response message phases (#38777)

packages/ai/test/provider/openai-compatible-responses.test.ts

@@ -1,6 +1,6 @@
 import { describe, expect } from "bun:test"
 import { Effect } from "effect"
-import { LLM, LLMEvent } from "../../src"
+import { LLM, LLMEvent, Message } from "../../src"
 import { configure } from "../../src/providers/openai-compatible-responses"
 import { OpenAI } from "../../src/providers"
 import { OpenResponses } from "../../src/protocols/open-responses"
@@ -70,6 +70,31 @@ describe("Open Responses-compatible route", () => {
     }),
   )
 
+  it.effect("omits OpenAI-only nullable phases from the Open Responses baseline", () =>
+    Effect.gen(function* () {
+      const model = configure({
+        apiKey: "test-key",
+        baseURL: "https://responses.example.test/v1",
+      }).model("example-model")
+      const prepared = yield* LLMClient.prepare(
+        LLM.request({
+          model,
+          messages: [
+            Message.assistant({
+              type: "text",
+              text: "Unclassified.",
+              providerMetadata: { openresponses: { phase: null } },
+            }),
+          ],
+        }),
+      )
+
+      expect(prepared.body).toMatchObject({
+        input: [{ role: "assistant", content: [{ type: "output_text", text: "Unclassified." }] }],
+      })
+    }),
+  )
+
   it.effect("reads standard options from the Open Responses namespace", () =>
     Effect.gen(function* () {
       const model = configure({

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

@@ -882,6 +882,121 @@ describe("OpenAI Responses route", () => {
     }),
   )
 
+  it.effect("preserves and replays assistant message phases", () =>
+    Effect.gen(function* () {
+      const response = yield* LLMClient.generate(request).pipe(
+        Effect.provide(
+          fixedResponse(
+            sseEvents(
+              {
+                type: "response.output_item.added",
+                item: { type: "message", id: "msg_commentary" },
+              },
+              { type: "response.output_text.delta", item_id: "msg_commentary", delta: "Checking." },
+              { type: "response.output_text.done", item_id: "msg_commentary" },
+              {
+                type: "response.output_item.done",
+                item: { type: "message", id: "msg_commentary", phase: "commentary" },
+              },
+              {
+                type: "response.output_item.added",
+                item: { type: "message", id: "msg_final", phase: "final_answer" },
+              },
+              { type: "response.output_text.done", item_id: "msg_final", text: "Finished." },
+              {
+                type: "response.output_item.done",
+                item: { type: "message", id: "msg_final", phase: "final_answer" },
+              },
+              { type: "response.output_item.added", item: { type: "message", id: "msg_null", phase: null } },
+              { type: "response.output_text.delta", item_id: "msg_null", delta: "Unclassified." },
+              { type: "response.output_item.done", item: { type: "message", id: "msg_null", phase: null } },
+              { type: "response.completed", response: { id: "resp_1" } },
+            ),
+          ),
+        ),
+      )
+
+      expect(response.message.content).toEqual([
+        {
+          type: "text",
+          text: "Checking.",
+          providerMetadata: { openai: { phase: "commentary" } },
+        },
+        {
+          type: "text",
+          text: "Finished.",
+          providerMetadata: { openai: { phase: "final_answer" } },
+        },
+        {
+          type: "text",
+          text: "Unclassified.",
+          providerMetadata: { openai: { phase: null } },
+        },
+      ])
+
+      const prepared = yield* LLMClient.prepare<OpenAIResponses.OpenAIResponsesBody>(
+        LLM.request({ model, messages: [response.message] }),
+      )
+      expect(prepared.body.input).toEqual([
+        {
+          role: "assistant",
+          content: [{ type: "output_text", text: "Checking." }],
+          phase: "commentary",
+        },
+        {
+          role: "assistant",
+          content: [{ type: "output_text", text: "Finished." }],
+          phase: "final_answer",
+        },
+        {
+          role: "assistant",
+          content: [{ type: "output_text", text: "Unclassified." }],
+          phase: null,
+        },
+      ])
+    }),
+  )
+
+  it.effect("rejects output text events without the spec-required item id", () =>
+    Effect.gen(function* () {
+      const error = yield* LLMClient.generate(request).pipe(
+        Effect.provide(
+          fixedResponse(
+            sseEvents(
+              { type: "response.output_text.delta", delta: "orphaned" },
+              { type: "response.completed", response: { id: "resp_1" } },
+            ),
+          ),
+        ),
+        Effect.flip,
+      )
+
+      expect(error.reason._tag).toBe("InvalidProviderOutput")
+      expect(error.message).toContain("response.output_text.delta is missing item_id")
+    }),
+  )
+
+  it.effect("rejects reasoning events without the spec-required item id", () =>
+    Effect.gen(function* () {
+      const events = [
+        { type: "response.reasoning_summary_part.added", summary_index: 0 },
+        { type: "response.reasoning_summary_part.done", summary_index: 0 },
+        { type: "response.reasoning_text.done" },
+      ]
+
+      for (const event of events) {
+        const error = yield* LLMClient.generate(request).pipe(
+          Effect.provide(
+            fixedResponse(sseEvents(event, { type: "response.completed", response: { id: "resp_1" } })),
+          ),
+          Effect.flip,
+        )
+        expect(error.reason._tag).toBe("InvalidProviderOutput")
+        expect(error.message).toContain(`${event.type} is missing item_id`)
+      }
+    }),
+  )
+
   it.effect("maps incomplete response reasons", () =>
     Effect.gen(function* () {
       const generate = (incompleteDetails: object) =>