fix(tui): surface sub-agent provider errors in parent task flow

packages/opencode/src/tool/task.ts

@@ -45,6 +45,14 @@ export const TaskTool = Tool.define("task", async (ctx) => {
     description,
     parameters,
     async execute(params: z.infer<typeof parameters>, ctx) {
+      function getSubagentFailureMessage(result: MessageV2.WithParts) {
+        const info = result.info
+        if (info.role !== "assistant" || !info.error) return
+        if (info.error.name === "MessageAbortedError") return
+        const detail = info.error.data.message?.trim()
+        return detail ? `Sub-agent failed: ${detail}` : "Sub-agent failed"
+      }
+
       const config = await Config.get()
 
       // Skip permission check when user explicitly invoked via @ or command subtask
@@ -144,6 +152,9 @@ export const TaskTool = Tool.define("task", async (ctx) => {
         parts: promptParts,
       })
 
+      const failure = getSubagentFailureMessage(result)
+      if (failure) throw new Error(failure)
+
       const text = result.parts.findLast((x) => x.type === "text")?.text ?? ""
 
       const output = [

packages/opencode/test/tool/task.test.ts

@@ -1,10 +1,18 @@
-import { describe, expect, test } from "bun:test"
+import { afterEach, describe, expect, mock, spyOn, test } from "bun:test"
 import { Agent } from "../../src/agent/agent"
 import { Instance } from "../../src/project/instance"
+import { Session } from "../../src/session"
+import { MessageV2 } from "../../src/session/message-v2"
+import { MessageID } from "../../src/session/schema"
+import { SessionPrompt } from "../../src/session/prompt"
 import { TaskTool } from "../../src/tool/task"
 import { tmpdir } from "../fixture/fixture"
 
 describe("tool.task", () => {
+  afterEach(() => {
+    mock.restore()
+  })
+
   test("description sorts subagents by name and is stable across calls", async () => {
     await using tmp = await tmpdir({
       config: {
@@ -42,4 +50,107 @@ describe("tool.task", () => {
       },
     })
   })
+
+  test("throws when subagent ends with provider error", async () => {
+    await using tmp = await tmpdir({
+      config: {
+        agent: {
+          scout: {
+            mode: "subagent",
+            description: "Scout agent",
+          },
+        },
+      },
+    })
+
+    await Instance.provide({
+      directory: tmp.path,
+      fn: async () => {
+        const parent = await Session.create({})
+        const parentMessageID = MessageID.ascending()
+
+        await Session.updateMessage({
+          id: parentMessageID,
+          sessionID: parent.id,
+          role: "assistant",
+          parentID: MessageID.ascending(),
+          mode: "build",
+          agent: "build",
+          path: { cwd: tmp.path, root: tmp.path },
+          cost: 0,
+          tokens: {
+            input: 0,
+            output: 0,
+            reasoning: 0,
+            cache: { read: 0, write: 0 },
+          },
+          modelID: "gpt-5.2",
+          providerID: "openai",
+          time: {
+            created: Date.now(),
+            completed: Date.now(),
+          },
+        } as unknown as MessageV2.Assistant)
+
+        const resolveSpy = spyOn(SessionPrompt, "resolvePromptParts").mockResolvedValue([
+          {
+            type: "text",
+            text: "subagent prompt",
+          },
+        ])
+
+        const promptSpy = spyOn(SessionPrompt, "prompt").mockResolvedValue({
+          info: {
+            id: MessageID.ascending(),
+            sessionID: parent.id,
+            role: "assistant",
+            parentID: MessageID.ascending(),
+            mode: "scout",
+            agent: "scout",
+            path: { cwd: tmp.path, root: tmp.path },
+            cost: 0,
+            tokens: {
+              input: 0,
+              output: 0,
+              reasoning: 0,
+              cache: { read: 0, write: 0 },
+            },
+            modelID: "gpt-5.2",
+            providerID: "openai",
+            time: { created: Date.now(), completed: Date.now() },
+            error: new MessageV2.APIError({
+              message: "You are rate-limited",
+              isRetryable: false,
+              statusCode: 429,
+            }).toObject(),
+          },
+          parts: [],
+        } as unknown as MessageV2.WithParts)
+
+        const tool = await TaskTool.init()
+        await expect(
+          tool.execute(
+            {
+              description: "Check provider state",
+              prompt: "Inspect provider state",
+              subagent_type: "scout",
+            },
+            {
+              sessionID: parent.id,
+              messageID: parentMessageID,
+              callID: "call-test",
+              agent: "build",
+              abort: AbortSignal.any([]),
+              messages: [],
+              metadata: () => {},
+              ask: async () => {},
+            },
+          ),
+        ).rejects.toThrow("Sub-agent failed: You are rate-limited")
+
+        expect(resolveSpy).toHaveBeenCalled()
+        expect(promptSpy).toHaveBeenCalled()
+      },
+    })
+  })
 })