feat(core): finalize session event lifecycle (#35272)

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

@@ -619,6 +619,11 @@ const onOutputTextDelta = (state: ParserState, event: OpenAIResponsesEvent): Ste
   ]
 }
 
+const onOutputTextDone = (state: ParserState, event: OpenAIResponsesEvent): StepResult => {
+  const events: LLMEvent[] = []
+  return [{ ...state, lifecycle: Lifecycle.textEnd(state.lifecycle, events, event.item_id ?? "text-0") }, events]
+}
+
 const onReasoningDelta = (state: ParserState, event: OpenAIResponsesEvent): StepResult => {
   if (!event.delta) return [state, NO_EVENTS]
   const events: LLMEvent[] = []
@@ -810,6 +815,8 @@ const onOutputItemDone = Effect.fn("OpenAIResponses.onOutputItemDone")(function*
   const item = event.item
   if (!item) return [state, NO_EVENTS] satisfies StepResult
 
+  if (item.type === "message" && item.id) return onOutputTextDone(state, { ...event, item_id: item.id })
+
   if (item.type === "function_call") {
     if (!item.id || !item.call_id || !item.name) return [state, NO_EVENTS] satisfies StepResult
     const tools = state.tools[item.id]
@@ -920,6 +927,7 @@ const onError = (state: ParserState, event: OpenAIResponsesEvent): StepResult =>
 
 const step = (state: ParserState, event: OpenAIResponsesEvent) => {
   if (event.type === "response.output_text.delta") return Effect.succeed(onOutputTextDelta(state, event))
+  if (event.type === "response.output_text.done") return Effect.succeed(onOutputTextDone(state, event))
   if (
     event.type === "response.reasoning_text.delta" ||
     event.type === "response.reasoning_summary.delta" ||

packages/llm/src/schema/ids.ts

@@ -1,5 +1,5 @@
 import { Schema } from "effect"
-import { ProviderMetadata } from "@opencode-ai/schema/llm"
+import { LLM, ProviderMetadata } from "@opencode-ai/schema/llm"
 
 export { ProviderMetadata }
 
@@ -36,7 +36,7 @@ export type TextVerbosity = Schema.Schema.Type<typeof TextVerbosity>
 export const MessageRole = Schema.Literals(["system", "user", "assistant", "tool"])
 export type MessageRole = Schema.Schema.Type<typeof MessageRole>
 
-export const FinishReason = Schema.Literals(["stop", "length", "tool-calls", "content-filter", "error", "unknown"])
+export const FinishReason = LLM.FinishReason
 export type FinishReason = Schema.Schema.Type<typeof FinishReason>
 
 export const JsonSchema = Schema.Record(Schema.String, Schema.Unknown)

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

@@ -764,6 +764,35 @@ describe("OpenAI Responses route", () => {
     }),
   )
 
+  // OpenAI's documented stream orders output text within one message item; no
+  // provider-valid same-kind overlap is evidenced, so done boundaries close it.
+  it.effect("closes sequential output messages before starting the next", () =>
+    Effect.gen(function* () {
+      const response = yield* LLMClient.generate(request).pipe(
+        Effect.provide(
+          fixedResponse(
+            sseEvents(
+              { type: "response.output_text.delta", item_id: "msg_1", delta: "First" },
+              { type: "response.output_text.done", item_id: "msg_1" },
+              { type: "response.output_text.delta", item_id: "msg_2", delta: "Second" },
+              { type: "response.output_item.done", item: { type: "message", id: "msg_2" } },
+              { type: "response.completed", response: { id: "resp_1" } },
+            ),
+          ),
+        ),
+      )
+
+      expect(response.events.filter((event) => event.type.startsWith("text-"))).toEqual([
+        { type: "text-start", id: "msg_1" },
+        { type: "text-delta", id: "msg_1", text: "First" },
+        { type: "text-end", id: "msg_1" },
+        { type: "text-start", id: "msg_2" },
+        { type: "text-delta", id: "msg_2", text: "Second" },
+        { type: "text-end", id: "msg_2" },
+      ])
+    }),
+  )
+
   it.effect("parses reasoning summary stream fixtures", () =>
     Effect.gen(function* () {
       const body = sseEvents(