diff --git a/src/modes/agent/index.ts b/src/modes/agent/index.ts
index b648716cf..20dfa6578 100644
--- a/src/modes/agent/index.ts
+++ b/src/modes/agent/index.ts
@@ -6,6 +6,8 @@ import {
   setupSshSigning,
 } from "../../github/operations/git-config";
 import { checkHumanActor } from "../../github/validation/actor";
+import { createInitialComment } from "../../github/operations/comments/create-initial";
+import { isEntityContext } from "../../github/context";
 import type { GitHubContext } from "../../github/context";
 import type { Octokits } from "../../github/api/client";
 
@@ -95,6 +97,15 @@ export async function prepareAgentMode({
     process.env.GITHUB_REF_NAME ||
     defaultBranch;
 
+  // Create a sticky comment when requested and we have an entity (PR or issue) to comment on.
+  // Without this, the MCP comment server starts without CLAUDE_COMMENT_ID and every
+  // update_claude_comment call fails with "CLAUDE_COMMENT_ID environment variable is required".
+  let commentId: number | undefined;
+  if (context.inputs.useStickyComment && isEntityContext(context)) {
+    const commentData = await createInitialComment(octokit.rest, context);
+    commentId = commentData.id;
+  }
+
   // Get our GitHub MCP servers config
   const ourMcpConfig = await prepareMcpConfig({
     githubToken,
@@ -102,7 +113,7 @@ export async function prepareAgentMode({
     repo: context.repository.repo,
     branch: currentBranch,
     baseBranch: baseBranch,
-    claudeCommentId: undefined, // No tracking comment in agent mode
+    claudeCommentId: commentId?.toString(),
     allowedTools,
     mode: "agent",
     context,
@@ -122,7 +133,7 @@ export async function prepareAgentMode({
   claudeArgs = `${claudeArgs} ${userClaudeArgs}`.trim();
 
   return {
-    commentId: undefined,
+    commentId,
     branchInfo: {
       baseBranch: baseBranch,
       currentBranch: baseBranch, // Use base branch as current when creating new branch
diff --git a/test/modes/agent.test.ts b/test/modes/agent.test.ts
index 1404b0d64..3e1cb2fcb 100644
--- a/test/modes/agent.test.ts
+++ b/test/modes/agent.test.ts
@@ -8,9 +8,13 @@ import {
   mock,
 } from "bun:test";
 import { prepareAgentMode } from "../../src/modes/agent";
-import { createMockAutomationContext } from "../mockContext";
+import {
+  createMockAutomationContext,
+  createMockContext,
+} from "../mockContext";
 import * as core from "@actions/core";
 import * as gitConfig from "../../src/github/operations/git-config";
+import * as createInitialModule from "../../src/github/operations/comments/create-initial";
 
 describe("Agent Mode", () => {
   let exportVariableSpy: any;
@@ -257,4 +261,125 @@ describe("Agent Mode", () => {
     // Should be empty or just whitespace when no MCP servers are included
     expect(result.claudeArgs).not.toContain("--mcp-config");
   });
+
+  test("prepare creates sticky comment when useStickyComment is true and context is entity", async () => {
+    // Use entity context (pull_request) so isEntityContext returns true
+    const entityContext = createMockContext({
+      eventName: "pull_request",
+      eventAction: "labeled",
+      isPR: true,
+      entityNumber: 42,
+      inputs: {
+        useStickyComment: true,
+        prompt: "Review this PR",
+      },
+    });
+
+    const createInitialCommentSpy = spyOn(
+      createInitialModule,
+      "createInitialComment",
+    ).mockResolvedValue({ id: 99999 } as any);
+
+    const mockOctokit = {
+      rest: {
+        users: {
+          getByUsername: mock(() =>
+            Promise.resolve({
+              data: { login: "test-user", id: 12345, type: "User" },
+            }),
+          ),
+        },
+      },
+    } as any;
+
+    const result = await prepareAgentMode({
+      context: entityContext,
+      octokit: mockOctokit,
+      githubToken: "test-token",
+    });
+
+    expect(createInitialCommentSpy).toHaveBeenCalledTimes(1);
+    expect(result.commentId).toBe(99999);
+
+    createInitialCommentSpy.mockRestore();
+  });
+
+  test("prepare skips sticky comment when useStickyComment is false", async () => {
+    const entityContext = createMockContext({
+      eventName: "pull_request",
+      eventAction: "labeled",
+      isPR: true,
+      entityNumber: 42,
+      inputs: {
+        useStickyComment: false,
+        prompt: "Review this PR",
+      },
+    });
+
+    const createInitialCommentSpy = spyOn(
+      createInitialModule,
+      "createInitialComment",
+    ).mockResolvedValue({ id: 99999 } as any);
+
+    const mockOctokit = {
+      rest: {
+        users: {
+          getByUsername: mock(() =>
+            Promise.resolve({
+              data: { login: "test-user", id: 12345, type: "User" },
+            }),
+          ),
+        },
+      },
+    } as any;
+
+    const result = await prepareAgentMode({
+      context: entityContext,
+      octokit: mockOctokit,
+      githubToken: "test-token",
+    });
+
+    expect(createInitialCommentSpy).not.toHaveBeenCalled();
+    expect(result.commentId).toBeUndefined();
+
+    createInitialCommentSpy.mockRestore();
+  });
+
+  test("prepare skips sticky comment for non-entity events even when useStickyComment is true", async () => {
+    const automationContext = createMockAutomationContext({
+      eventName: "workflow_dispatch",
+      inputs: {
+        useStickyComment: true,
+        prompt: "Run analysis",
+      },
+    });
+
+    const createInitialCommentSpy = spyOn(
+      createInitialModule,
+      "createInitialComment",
+    ).mockResolvedValue({ id: 99999 } as any);
+
+    const mockOctokit = {
+      rest: {
+        users: {
+          getByUsername: mock(() =>
+            Promise.resolve({
+              data: { login: "test-user", id: 12345, type: "User" },
+            }),
+          ),
+        },
+      },
+    } as any;
+
+    const result = await prepareAgentMode({
+      context: automationContext,
+      octokit: mockOctokit,
+      githubToken: "test-token",
+    });
+
+    expect(createInitialCommentSpy).not.toHaveBeenCalled();
+    expect(result.commentId).toBeUndefined();
+
+    createInitialCommentSpy.mockRestore();
+  });
 });