fix(opencode): surface content-filter finish reason as visible error (#31745)

Co-authored-by: Aiden Cline <aidenpcline@gmail.com>

packages/opencode/test/session/prompt.test.ts

@@ -506,6 +506,52 @@ it.instance("loop calls LLM and returns assistant message", () =>
   }),
 )
 
+it.instance("loop surfaces content-filter finishes as session errors", () =>
+  Effect.gen(function* () {
+    const { llm } = yield* useServerConfig(providerCfg)
+    const events = yield* EventV2Bridge.Service
+    const prompt = yield* SessionPrompt.Service
+    const sessions = yield* Session.Service
+    const chat = yield* sessions.create({ title: "Pinned" })
+    const errors: NonNullable<SessionV1.Assistant["error"]>[] = []
+    const expected = {
+      name: "ContentFilterError",
+      data: { message: "The response was blocked by the provider's content filter" },
+    } satisfies NonNullable<SessionV1.Assistant["error"]>
+    const off = yield* events.listen((event) => {
+      if (event.type !== Session.Event.Error.type) return Effect.void
+      const data = event.data as typeof Session.Event.Error.data.Type
+      if (data.sessionID === chat.id && data.error) errors.push(data.error)
+      return Effect.void
+    })
+
+    yield* prompt.prompt({
+      sessionID: chat.id,
+      agent: "build",
+      noReply: true,
+      parts: [{ type: "text", text: "hello" }],
+    })
+    yield* llm.push(reply().text("partial response").contentFilter())
+
+    const result = yield* prompt.loop({ sessionID: chat.id })
+    const stored = yield* MessageV2.get({ sessionID: chat.id, messageID: result.info.id })
+    yield* off
+
+    expect(yield* llm.hits).toHaveLength(1)
+    expect(result.info.role).toBe("assistant")
+    expect(stored.info.role).toBe("assistant")
+    if (result.info.role === "assistant" && stored.info.role === "assistant") {
+      expect(result.info.finish).toBe("content-filter")
+      expect(result.info.error).toEqual(expected)
+      expect(stored.info.error).toEqual(result.info.error)
+      expect(errors).toContainEqual(expected)
+    }
+    expect(result.parts).toEqual(
+      expect.arrayContaining([expect.objectContaining({ type: "text", text: "partial response" })]),
+    )
+  }),
+)
+
 it.instance("loop stops provider overflow instead of auto-compacting when disabled", () =>
   Effect.gen(function* () {
     const { llm } = yield* useServerConfig((url) => ({