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Merged
Issacboy123 merged 2 commits into from
Aug 29, 2026
Merged

fix(coding-agent): bind spawn provenance to the selected branch #145

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5e1d737
fix(coding-agent): bind spawn origin to selected branch
Issacboy123 Aug 27, 2026
215e46d
docs(coding-agent): remove changelog update
Pepps233 Aug 29, 2026
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30 changes: 17 additions & 13 deletions packages/coding-agent/src/core/subagents/controller.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -136,23 +136,27 @@ function captureSpawnOrigin(parent: AgentSession, toolCallId: string): SubagentS
});
}

const matchingEntries = parent.sessionManager
.getEntries()
.filter(
(entry) =>
entry.type === "message" &&
entry.message.role === "assistant" &&
entry.message.content.some(
(content) => content.type === "toolCall" && content.id === toolCallId && content.name === "spawn_agent",
),
);
if (matchingEntries.length !== 1) {
const branch = parent.sessionManager.getBranch();
let assistantEntry: (typeof branch)[number] | undefined;
for (let index = branch.length - 1; index >= 0; index -= 1) {
const entry = branch[index];
if (
entry.type === "message" &&
entry.message.role === "assistant" &&
entry.message.content.some(
(content) => content.type === "toolCall" && content.id === toolCallId && content.name === "spawn_agent",
)
) {
assistantEntry = entry;
break;
}
}
if (!assistantEntry) {
throw new Error(
`Invariant violation: active spawn_agent call ${toolCallId} matched ${matchingEntries.length} persisted assistant entries`,
`Invariant violation: active spawn_agent call ${toolCallId} matched 0 persisted assistant entries`,
);
}

const assistantEntry = matchingEntries[0];
return Object.freeze({
type: "agent_tool_call",
toolCallId,
Expand Down
107 changes: 93 additions & 14 deletions packages/coding-agent/test/suite/subagent-registration.test.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -134,6 +134,35 @@ function getActiveTool(session: AgentSession, name: string): AgentTool {
return tool;
}

function appendAssistantToolCall(sessionManager: SessionManager, toolName: string, toolCallId: string): string {
return sessionManager.appendMessage(
fauxAssistantMessage(fauxToolCall(toolName, {}, { id: toolCallId }), { stopReason: "toolUse" }),
);
}

async function executeActiveSpawn(session: AgentSession, toolCallId: string, name: string): Promise<void> {
const internalState = session as unknown as { _isAgentRunActive: boolean };
internalState._isAgentRunActive = true;
try {
await getActiveTool(session, "spawn_agent").execute(toolCallId, { name, task: `${name} task` });
} finally {
internalState._isAgentRunActive = false;
}
}

function captureSubagentSessionManagerRequests(): SubagentSessionManagerRequest[] {
const requests: SubagentSessionManagerRequest[] = [];
const originalCreate = RootLocalEphemeralSubagentSessionManagerFactory.prototype.create;
vi.spyOn(RootLocalEphemeralSubagentSessionManagerFactory.prototype, "create").mockImplementation(function (
this: RootLocalEphemeralSubagentSessionManagerFactory,
request,
) {
requests.push(request);
return originalCreate.call(this, request);
});
return requests;
}

describe("root subagent tool registration", () => {
const harnesses: Harness[] = [];
const sessions: AgentSession[] = [];
Expand Down Expand Up @@ -576,23 +605,73 @@ describe("root subagent tool registration", () => {
}
});

it("binds reused tool-call identifiers to the newest selected-branch spawn", async () => {
const harness = await setupHarness();
harness.setResponses([fauxAssistantMessage("child complete")]);
const requests = captureSubagentSessionManagerRequests();
const { session } = await createRoot(harness);
appendAssistantToolCall(session.sessionManager, "spawn_agent", "reused-call");
const newestEntryId = appendAssistantToolCall(session.sessionManager, "spawn_agent", "reused-call");

await executeActiveSpawn(session, "reused-call", "worker");

expect(requests).toHaveLength(1);
expect(requests[0]?.origin).toMatchObject({
type: "agent_tool_call",
toolCallId: "reused-call",
assistantEntryId: newestEntryId,
});
});

it("ignores newer calls to other tools that reuse the spawn identifier", async () => {
const harness = await setupHarness();
harness.setResponses([fauxAssistantMessage("child complete")]);
const requests = captureSubagentSessionManagerRequests();
const { session } = await createRoot(harness);
const spawnEntryId = appendAssistantToolCall(session.sessionManager, "spawn_agent", "shared-call");
appendAssistantToolCall(session.sessionManager, "agents", "shared-call");

await executeActiveSpawn(session, "shared-call", "worker");

expect(requests).toHaveLength(1);
expect(requests[0]?.origin).toMatchObject({
type: "agent_tool_call",
toolCallId: "shared-call",
assistantEntryId: spawnEntryId,
});
});

it("ignores matching spawn calls on abandoned branches", async () => {
const harness = await setupHarness();
harness.setResponses([fauxAssistantMessage("child complete")]);
const requests = captureSubagentSessionManagerRequests();
const { session } = await createRoot(harness);
const branchPointId = session.sessionManager.appendCustomEntry("branch-point");
appendAssistantToolCall(session.sessionManager, "spawn_agent", "branched-call");
session.sessionManager.branch(branchPointId);
const selectedEntryId = appendAssistantToolCall(session.sessionManager, "spawn_agent", "branched-call");

await executeActiveSpawn(session, "branched-call", "worker");

expect(requests).toHaveLength(1);
expect(requests[0]?.origin).toMatchObject({
type: "agent_tool_call",
toolCallId: "branched-call",
assistantEntryId: selectedEntryId,
});
});

it("rejects unmatched spawn calls during an active agent run", async () => {
const harness = await setupHarness();
const { session } = await createRoot(harness);
const internalState = session as unknown as { _isAgentRunActive: boolean };
internalState._isAgentRunActive = true;
try {
await expect(
getActiveTool(session, "spawn_agent").execute("missing-call", {
name: "worker",
task: "task",
}),
).rejects.toThrow(
"Invariant violation: active spawn_agent call missing-call matched 0 persisted assistant entries",
);
} finally {
internalState._isAgentRunActive = false;
}
const branchPointId = session.sessionManager.appendCustomEntry("branch-point");
appendAssistantToolCall(session.sessionManager, "spawn_agent", "missing-call");
session.sessionManager.branch(branchPointId);
appendAssistantToolCall(session.sessionManager, "agents", "missing-call");

await expect(executeActiveSpawn(session, "missing-call", "worker")).rejects.toThrow(
"Invariant violation: active spawn_agent call missing-call matched 0 persisted assistant entries",
);
});

it("applies configured concurrency and captures parent state when spawning", async () => {
Expand Down
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