diff --git a/hub/src/agent/runner.ts b/hub/src/agent/runner.ts
index e59b91a..76f25f8 100644
--- a/hub/src/agent/runner.ts
+++ b/hub/src/agent/runner.ts
@@ -140,9 +140,8 @@ export async function runAgent(req: RunRequest): Promise<RunResult> {
   let cleanupSecurity = async (): Promise<void> => {};
   try {
     await persistAgentMessage(req, "user", req.prompt);
-    // Role tools JSON null means unrestricted (omit), not "deny all".
+    // Role tools JSON null means the default single-agent tool set, not "deny all".
     const roleToolIds = req.tools === null ? undefined : req.tools;
-    const unrestricted = roleToolIds === undefined;
     const toolConfig = claudeSdkToolConfigForRole(roleToolIds);
     const workspaceRoot = req.project.workspaceRoot?.trim();
     if (workspaceRoot === undefined || workspaceRoot === "") {
@@ -158,25 +157,41 @@ export async function runAgent(req: RunRequest): Promise<RunResult> {
     cleanupSecurity = security.cleanup;
     const hasSkills = security.skillIds.length > 0;
     type QueryOptions = NonNullable<Parameters<typeof query>[0]["options"]>;
-    // When unrestricted, pass the SDK default toolset (`--tools default`) instead of
-    // an explicit subset. Native claude uses that path to register bundled tools like
-    // TodoWrite; listing names alone can omit them from the model's function list.
-    // allowedTools still carries explicit MCP names + TodoWrite for permission.
+    // Always use an explicit tool list — never the claude_code preset.
+    // The preset registers Agent/SendMessage/Task multi-agent machinery.
+    // Concurrent background agents abort with reason "background", and the
+    // Claude Agent SDK maps that to toolDenialKind "cancelled" with:
+    //   "The user doesn't want to take this action right now..."
+    // which freezes Bash mid-run while Read/Glob continue to work.
+    // Hub "unrestricted" means the default single-agent built-ins + MCP, not
+    // the full interactive Claude product surface.
     const skillExtras = hasSkills ? (["Skill"] as const) : ([] as const);
-    const toolsOption: QueryOptions["tools"] = unrestricted
-      ? { type: "preset", preset: "claude_code" }
-      : uniqueTools([...toolConfig.tools, "TodoWrite", ...skillExtras]);
+    const toolsOption: QueryOptions["tools"] = uniqueTools([
+      ...toolConfig.tools,
+      "TodoWrite",
+      ...skillExtras,
+    ]);
     const allowedToolsOption = uniqueTools([
       ...toolConfig.allowedTools,
       "TodoWrite",
       "mcp__cph_hub__todo_write",
       ...skillExtras,
     ]);
+    // Hard deny multi-agent orchestration even if a future preset/skills path
+    // reintroduces them — bypassPermissions would otherwise auto-allow them.
+    const disallowedToolsOption = [
+      "Agent",
+      "SendMessage",
+      "TeamCreate",
+      "Task",
+      "ScheduleWakeup",
+    ] as const;
 
     const options: QueryOptions = {
       cwd: security.cwd,
       tools: toolsOption,
       allowedTools: allowedToolsOption,
+      disallowedTools: [...disallowedToolsOption],
       maxTurns: cap,
       includePartialMessages: true,
       // ADR-0018: bypass interactive prompts (headless server); the sandbox
diff --git a/hub/test/unit/runner.test.ts b/hub/test/unit/runner.test.ts
index c51762c..df324f6 100644
--- a/hub/test/unit/runner.test.ts
+++ b/hub/test/unit/runner.test.ts
@@ -114,10 +114,9 @@ describe("runAgent", () => {
         allowDangerouslySkipPermissions: true,
         settingSources: [],
         settings: { disableBundledSkills: true, todoFeatureEnabled: true },
-        skills: [],
-        tools: { type: "preset", preset: "claude_code" },
-        allowedTools: expect.arrayContaining(["TodoWrite"]),
-        strictMcpConfig: true,
+        tools: expect.arrayContaining(["Read", "Write", "Bash", "Glob", "Grep", "TodoWrite"]),
+        allowedTools: expect.arrayContaining(["TodoWrite", "mcp__cph_hub__todo_write"]),
+        disallowedTools: expect.arrayContaining(["Agent", "SendMessage", "Task", "TeamCreate", "ScheduleWakeup"]),
         sandbox: expect.objectContaining({
           enabled: true,
           failIfUnavailable: true,
@@ -132,6 +131,38 @@ describe("runAgent", () => {
     });
   });
 
+  it("never exposes multi-agent orchestration tools on unrestricted roles", async () => {
+    queryMock.mockReturnValue(messages(assistantMessage("ok"), resultMessage("sdk-session-1")));
+
+    await runAgent({
+      prompt: "继续",
+      model: undefined,
+      project: { projectId: "p", boundChatId: "c", workspaceRoot, workspaceDir: workspace },
+      systemPrompt: undefined,
+      tools: null,
+      runId: "run-1",
+      sessionId: "hub-session-1",
+      prisma: stubPrisma,
+    });
+
+    const call = queryMock.mock.calls[0]?.[0] as {
+      options?: { tools?: unknown; disallowedTools?: string[] };
+    } | undefined;
+    expect(call?.options?.tools).toEqual([
+      "Read",
+      "Write",
+      "Bash",
+      "Glob",
+      "Grep",
+      "WebFetch",
+      "WebSearch",
+      "TodoWrite",
+    ]);
+    for (const blocked of ["Agent", "SendMessage", "Task", "TeamCreate", "ScheduleWakeup"]) {
+      expect(call?.options?.disallowedTools).toContain(blocked);
+    }
+  });
+
   it("does not send resume for a fresh Hub session", async () => {
     queryMock.mockReturnValue(messages(assistantMessage("fresh"), resultMessage("sdk-session-1")));
 
@@ -194,6 +225,7 @@ describe("runAgent", () => {
           "mcp__cph_hub__todo_write",
         ],
         settings: expect.objectContaining({ todoFeatureEnabled: true }),
+        disallowedTools: expect.arrayContaining(["Agent", "SendMessage"]),
       },
     });
   });
@@ -217,6 +249,7 @@ describe("runAgent", () => {
         tools: ["TodoWrite"],
         allowedTools: ["TodoWrite", "mcp__cph_hub__todo_write"],
         settings: expect.objectContaining({ todoFeatureEnabled: true }),
+        disallowedTools: expect.arrayContaining(["Agent", "SendMessage"]),
       },
     });
   });