diff --git a/src/node/services/taskService.sendTreeMessage.test.ts b/src/node/services/taskService.sendTreeMessage.test.ts
new file mode 100644
index 00000000000..1d23d59ac31
--- /dev/null
+++ b/src/node/services/taskService.sendTreeMessage.test.ts
@@ -0,0 +1,247 @@
+import { afterEach, beforeEach, describe, expect, mock, spyOn, test } from "bun:test";
+import * as path from "node:path";
+import { Err, Ok, type Result } from "@/common/types/result";
+import type { Config, Workspace } from "@/node/config";
+import { findWorkspaceEntry } from "@/node/services/taskUtils";
+import type { WorkspaceHost } from "@/node/services/taskWorkspaceSeam";
+import {
+  createTestConfig,
+  createWorkspaceServiceMocks,
+  projectWorkspace,
+  saveWorkspacesWithCheckouts as saveWorkspaces,
+  testTaskSettings,
+  workspaceTurnManagerInternals,
+} from "@/node/services/taskService.testHarness";
+import {
+  createTaskServiceHarness,
+  createTaskServiceTestRoot,
+  registerLiveWorkspaceTurnHandle,
+  removeTaskServiceTestRoot,
+} from "@/node/services/taskService.shared.testHarness";
+
+// Paths of TaskService.sendTreeMessage (the peer route) that no other test reached: the
+// re-checks under the target's admission lock, the retry fences of a message that waited for a
+// delegated turn, and the admission probe the host re-runs inside sendMessage.
+
+type SendArgs = Parameters<WorkspaceHost["sendMessage"]>;
+type SendResult = Awaited<ReturnType<TaskServiceInternals["sendTreeMessage"]>>;
+
+interface TaskServiceInternals {
+  sendTreeMessage(spec: unknown): Promise<Result<unknown, { code: string }>>;
+  flushParkedPeerSends(targetId: string): Promise<void>;
+  workspaceEventLocks: { withLock<T>(key: string, fn: () => Promise<T>): Promise<T> };
+  interruptedParentWorkspaceIds: Set<string>;
+  workspaceUserStopEpochs: Map<string, number>;
+  peerSendParking: { hasParked(targetId: string): boolean };
+  resolveParentAutoResumeOptions(...args: unknown[]): Promise<unknown>;
+  agentPeerMessageBroker: { recordPeerDelivery(...args: unknown[]): void };
+}
+
+describe("TaskService.sendTreeMessage uncovered paths", () => {
+  let rootDir: string;
+  beforeEach(async () => {
+    rootDir = await createTaskServiceTestRoot();
+  });
+  afterEach(async () => {
+    await removeTaskServiceTestRoot(rootDir);
+  });
+
+  // Two tag-linked root chats: alpha sends, beta receives.
+  async function setUp() {
+    const config = await createTestConfig(rootDir);
+    const projectPath = path.join(rootDir, "repo");
+    const tagged = { messagingTag: "research", messagingTagGeneration: "gen-1" };
+    await saveWorkspaces(
+      config,
+      projectPath,
+      [
+        projectWorkspace(projectPath, "alpha", "alpha", tagged),
+        projectWorkspace(projectPath, "beta", "beta", tagged),
+      ],
+      testTaskSettings()
+    );
+    // While set, the next send runs this instead of the default accept.
+    let intercept: ((args: SendArgs) => Promise<Result<void>>) | undefined;
+    const sendMessage = mock(async (...args: SendArgs): Promise<Result<void>> => {
+      const next = intercept;
+      intercept = undefined;
+      if (next != null) return next(args);
+      await args[3]?.onAccepted?.();
+      return Ok(undefined);
+    });
+    const { workspaceService } = createWorkspaceServiceMocks({ sendMessage });
+    const { taskService } = createTaskServiceHarness(config, { workspaceService });
+    // The first load of the saved test config schedules a background migration persist. Run it
+    // now and wait for it (a no-op edit queues behind it), so no config write outlives a test.
+    config.loadConfigOrDefault();
+    await config.editConfig((cfg) => cfg);
+    const internals = taskService as unknown as TaskServiceInternals;
+    const interceptNextSend = (fn: (args: SendArgs) => Promise<Result<void>>) => {
+      intercept = fn;
+    };
+    return { config, projectPath, taskService, internals, sendMessage, interceptNextSend };
+  }
+
+  type Setup = Awaited<ReturnType<typeof setUp>>;
+
+  async function editWorkspace(config: Config, id: string, updates: Partial<Workspace>) {
+    await config.editConfig((cfg) => {
+      const entry = findWorkspaceEntry(cfg, id);
+      if (entry == null) throw new Error(`Missing test workspace: ${id}`);
+      Object.assign(entry.workspace, updates);
+      return cfg;
+    });
+  }
+
+  // The host re-runs the admission probe inside sendMessage; `interfere` changes state first.
+  // A refused probe makes the host fail the send, so the result carries the probe's refusal.
+  async function sendWithProbeInterference(s: Setup, interfere: () => Promise<void> | void) {
+    s.interceptNextSend(async ([, , , internal]) => {
+      await interfere();
+      expect(internal?.admissionStale?.()).toBe(true);
+      return Err("admission refused");
+    });
+    const result = await s.taskService.sendAgentTreeMessage("alpha", "beta", "Status?");
+    expect(s.sendMessage).toHaveBeenCalledTimes(1);
+    return result;
+  }
+
+  // Park a message from alpha behind another workspace's delegated turn on beta, run
+  // `beforeRetry`, release the turn, and return the retry's result once the drain finished.
+  async function retryAfterDelegatedTurn(s: Setup, beforeRetry: () => Promise<void>) {
+    await registerLiveWorkspaceTurnHandle(s.taskService, "beta", "wst_owner", "owner");
+    // Spied before the park, so the flush the park schedules is awaited below too.
+    const flushes = spyOn(s.internals, "flushParkedPeerSends");
+    expect(await s.taskService.sendAgentTreeMessage("alpha", "beta", "first")).toMatchObject(
+      Ok({ delivery: "queued", awaitsDelegatedTurn: true })
+    );
+    expect(s.sendMessage).not.toHaveBeenCalled();
+    await beforeRetry();
+    // The drain calls sendTreeMessage on the instance; the wrapper is an object so the
+    // retry's promise is handed over without being awaited here.
+    const original = s.internals.sendTreeMessage.bind(s.taskService);
+    const retries = spyOn(s.internals, "sendTreeMessage");
+    const retryStarted = new Promise<{ result: Promise<SendResult> }>((resolve) => {
+      retries.mockImplementationOnce((spec) => {
+        const result = original(spec);
+        resolve({ result });
+        return result;
+      });
+    });
+    const registrations = workspaceTurnManagerInternals(
+      s.taskService
+    ).activeWorkspaceTurnHandleByWorkspaceId;
+    registrations.delete("beta");
+    s.taskService.onWorkspaceTurnRegistrationReleased("beta");
+    const retry = await (await retryStarted).result;
+    // Every drain this test started has finished before the result is checked.
+    await Promise.all(flushes.mock.results.map((result) => result.value as Promise<void>));
+    expect(retries).toHaveBeenCalledTimes(1);
+    flushes.mockRestore();
+    retries.mockRestore();
+    registrations.delete("beta");
+    return retry;
+  }
+
+  test("a relation change while the send waits for the target's lock refuses it as invalid_scope", async () => {
+    const s = await setUp();
+    let release!: () => void;
+    const held = new Promise<void>((resolve) => (release = resolve));
+    const holder = s.internals.workspaceEventLocks.withLock("beta", () => held);
+    // Routed as tag-linked roots, then beta becomes alpha's finished sub-agent before the lock
+    // is free. A later gate would refuse that target as not_active; the lock-time re-check
+    // refuses first, before any target state is read.
+    const pending = s.taskService.sendAgentTreeMessage("alpha", "beta", "Status?");
+    await editWorkspace(s.config, "beta", { parentWorkspaceId: "alpha", taskStatus: "reported" });
+    release();
+    await holder;
+    expect(await pending).toEqual(Err({ code: "invalid_scope" }));
+    expect(s.sendMessage).not.toHaveBeenCalled();
+  });
+
+  test("a retry after a delegated turn is refused as invalid_scope when a tag was re-issued", async () => {
+    const s = await setUp();
+    // Same tag string, new generation: a clear/re-tag cycle is a new link.
+    const retry = await retryAfterDelegatedTurn(s, () =>
+      editWorkspace(s.config, "beta", { messagingTagGeneration: "gen-2" })
+    );
+    expect(retry).toEqual(Err({ code: "invalid_scope" }));
+    expect(s.sendMessage).not.toHaveBeenCalled();
+  });
+
+  test("an interrupted target chain seen only by the host's admission probe refuses the send", async () => {
+    const s = await setUp();
+    // Every production interrupt also bumps the stop epoch, which the probe checks first, so
+    // only the suppression entry is set here to reach the level check behind it.
+    const result = await sendWithProbeInterference(s, () => {
+      s.internals.interruptedParentWorkspaceIds.add("beta");
+    });
+    expect(result).toMatchObject(Err({ code: "refused" }));
+    // The same refusal a send gets when the target is already interrupted at entry.
+    expect(await s.taskService.sendAgentTreeMessage("alpha", "beta", "again")).toEqual(result);
+  });
+
+  test("a target removed before the host's admission probe refuses the send as not_found", async () => {
+    const s = await setUp();
+    const result = await sendWithProbeInterference(s, () =>
+      s.config.editConfig((cfg) => {
+        const project = cfg.projects.get(s.projectPath);
+        if (project == null) throw new Error("Missing test project");
+        project.workspaces = project.workspaces.filter((workspace) => workspace.id !== "beta");
+        return cfg;
+      })
+    );
+    expect(result).toEqual(Err({ code: "not_found" }));
+  });
+
+  test("a retry whose send fails after a new delegated turn refuses with the wait, not send_failed", async () => {
+    const s = await setUp();
+    const retry = await retryAfterDelegatedTurn(s, () => {
+      // Another workspace's delegated turn starts while the retry is inside sendMessage. A retry
+      // never waits twice, so the probe refuses it and the host fails the send.
+      s.interceptNextSend(async ([, , , internal]) => {
+        await registerLiveWorkspaceTurnHandle(s.taskService, "beta", "wst_next", "owner-2");
+        expect(internal?.admissionStale?.()).toBe(true);
+        return Err("admission refused");
+      });
+      return Promise.resolve();
+    });
+    expect(s.sendMessage).toHaveBeenCalledTimes(1);
+    // The wait's refusal (code refused), not the generic transport failure (send_failed).
+    expect(retry).toMatchObject(Err({ code: "refused" }));
+  });
+
+  test("a send that would wait for a delegated turn is refused when the user stopped the target since admission", async () => {
+    const s = await setUp();
+    // Another workspace's delegated turn runs on beta, so the pre-dispatch probe tells alpha's
+    // message to wait for it.
+    await registerLiveWorkspaceTurnHandle(s.taskService, "beta", "wst_owner", "owner");
+    // A user Stop bumps this count together with the stop epoch, which the probe checks first,
+    // so only the count is bumped here. The bump lands during the send-options await, after the
+    // send captured its baseline and before the wait parks the message.
+    const original = s.internals.resolveParentAutoResumeOptions.bind(s.taskService);
+    const resumeOptions = spyOn(s.internals, "resolveParentAutoResumeOptions");
+    resumeOptions.mockImplementationOnce((...args: unknown[]) => {
+      s.internals.workspaceUserStopEpochs.set(
+        "beta",
+        (s.internals.workspaceUserStopEpochs.get("beta") ?? 0) + 1
+      );
+      return original(...args);
+    });
+    const deliveries = spyOn(s.internals.agentPeerMessageBroker, "recordPeerDelivery");
+
+    const result = await s.taskService.sendAgentTreeMessage("alpha", "beta", "Status?");
+
+    expect(resumeOptions).toHaveBeenCalledTimes(1);
+    expect(result).toMatchObject(Err({ code: "refused" }));
+    // Refused, not parked: nothing waits for the turn, nothing reached beta, no delivery counted.
+    expect(s.internals.peerSendParking.hasParked("beta")).toBe(false);
+    expect(s.sendMessage).not.toHaveBeenCalled();
+    expect(deliveries).not.toHaveBeenCalled();
+    resumeOptions.mockRestore();
+    deliveries.mockRestore();
+    workspaceTurnManagerInternals(s.taskService).activeWorkspaceTurnHandleByWorkspaceId.delete(
+      "beta"
+    );
+  });
+});