From a476e557c9cbdddb987c3bc2488c745945e2857f Mon Sep 17 00:00:00 2001
From: MoerAI <skyinbss@gmail.com>
Date: Fri, 27 Mar 2026 10:35:48 +0900
Subject: [PATCH 1/2] fix(delegate-task): reject when both category and
 subagent_type provided (fixes #2847)

---
 src/tools/delegate-task/tools.ts | 17 ++++++++++-------
 1 file changed, 10 insertions(+), 7 deletions(-)

diff --git a/src/tools/delegate-task/tools.ts b/src/tools/delegate-task/tools.ts
index c149f8025..a1d69d228 100644
--- a/src/tools/delegate-task/tools.ts
+++ b/src/tools/delegate-task/tools.ts
@@ -102,20 +102,23 @@ export function createDelegateTask(options: DelegateTaskToolOptions): ToolDefini
       prompt: tool.schema.string().describe("Full detailed prompt for the agent"),
       run_in_background: tool.schema.boolean().describe("REQUIRED. true=async (returns task_id), false=sync (waits). Use false for task delegation, true ONLY for parallel exploration."),
       category: tool.schema.string().optional().describe(`REQUIRED if subagent_type not provided. Do NOT provide both category and subagent_type.`),
-      subagent_type: tool.schema.string().optional().describe("REQUIRED if category not provided. Do NOT provide both category and subagent_type."),
+      subagent_type: tool.schema.string().optional().describe("REQUIRED if category not provided. Do NOT provide both category and subagent_type. Valid values: explore, librarian, oracle, metis, momus"),
       session_id: tool.schema.string().optional().describe("Existing Task session to continue"),
       command: tool.schema.string().optional().describe("The command that triggered this task"),
     },
     async execute(args: DelegateTaskArgs, toolContext) {
       const ctx = toolContext as ToolContextWithMetadata
 
+      if (args.category && args.subagent_type) {
+        throw new Error(
+          `Invalid arguments: 'category' and 'subagent_type' are mutually exclusive. Provide EXACTLY ONE.\n` +
+          `  - You provided: category="${args.category}", subagent_type="${args.subagent_type}"\n` +
+          `  - Use category for task delegation (e.g., category="${categoryExamples.split(", ")[0]}")\n` +
+          `  - Use subagent_type for direct agent invocation (e.g., subagent_type="explore")\n` +
+          `  - Valid subagent_type values: explore, librarian, oracle, metis, momus`
+        )
+      }
       if (args.category) {
-        if (args.subagent_type && args.subagent_type !== SISYPHUS_JUNIOR_AGENT) {
-          log("[task] category provided - overriding subagent_type to sisyphus-junior", {
-            category: args.category,
-            subagent_type: args.subagent_type,
-          })
-        }
         args.subagent_type = SISYPHUS_JUNIOR_AGENT
       }
       await ctx.metadata?.({

From 8136679b1cc10ea24d5a535594cda18a53044781 Mon Sep 17 00:00:00 2001
From: MoerAI <skyinbss@gmail.com>
Date: Fri, 27 Mar 2026 11:53:54 +0900
Subject: [PATCH 2/2] test: update test to expect mutual exclusion error for
 category+subagent_type

---
 src/tools/delegate-task/tools.test.ts | 19 ++++---------------
 1 file changed, 4 insertions(+), 15 deletions(-)

diff --git a/src/tools/delegate-task/tools.test.ts b/src/tools/delegate-task/tools.test.ts
index 550e87b78..b56096493 100644
--- a/src/tools/delegate-task/tools.test.ts
+++ b/src/tools/delegate-task/tools.test.ts
@@ -465,7 +465,7 @@ describe("sisyphus-task", () => {
        expect(args.subagent_type).toBe("Sisyphus-Junior")
     }, { timeout: 10000 })
 
-    test("category overrides subagent_type and still maps to sisyphus-junior", async () => {
+    test("rejects when both category and subagent_type are provided", async () => {
       //#given
       const { createDelegateTask } = require("./tools")
 
@@ -507,14 +507,7 @@ describe("sisyphus-task", () => {
         abort: new AbortController().signal,
       }
 
-      const args: {
-        description: string
-        prompt: string
-        category: string
-        subagent_type: string
-        run_in_background: boolean
-        load_skills: string[]
-      } = {
+      const args = {
         description: "Override test",
         prompt: "Do something",
         category: "quick",
@@ -523,12 +516,8 @@ describe("sisyphus-task", () => {
         load_skills: [],
       }
 
-      //#when
-      const result = await tool.execute(args, toolContext)
-
-      //#then
-      expect(args.subagent_type).toBe("Sisyphus-Junior")
-      expect(result).toContain("Background task launched")
+      //#when + #then
+      await expect(tool.execute(args, toolContext)).rejects.toThrow("mutually exclusive")
     }, { timeout: 10000 })
 
     test("proceeds without error when systemDefaultModel is undefined", async () => {