diff --git a/src/create-prompt/index.ts b/src/create-prompt/index.ts
index 7b332f4..d498cf9 100644
--- a/src/create-prompt/index.ts
+++ b/src/create-prompt/index.ts
@@ -418,6 +418,7 @@ ${
 }
 <claude_comment_id>${context.claudeCommentId}</claude_comment_id>
 <trigger_username>${context.triggerUsername ?? "Unknown"}</trigger_username>
+<trigger_display_name>${githubData.triggerDisplayName ?? context.triggerUsername ?? "Unknown"}</trigger_display_name>
 <trigger_phrase>${context.triggerPhrase}</trigger_phrase>
 ${
   (eventData.eventName === "issue_comment" ||
@@ -503,12 +504,14 @@ ${context.directPrompt ? `   - DIRECT INSTRUCTION: A direct instruction was prov
           ? `
       - Push directly using mcp__github_file_ops__commit_files to the existing branch (works for both new and existing files).
       - Use mcp__github_file_ops__commit_files to commit files atomically in a single commit (supports single or multiple files).
-      - When pushing changes with this tool and TRIGGER_USERNAME is not "Unknown", include a "Co-authored-by: ${context.triggerUsername} <${context.triggerUsername}@users.noreply.github.com>" line in the commit message.`
+      - When pushing changes with this tool and the trigger user is not "Unknown", include a Co-authored-by trailer in the commit message.
+      - Use: "Co-authored-by: ${githubData.triggerDisplayName ?? context.triggerUsername} <${context.triggerUsername}@users.noreply.github.com>"`
           : `
       - You are already on the correct branch (${eventData.claudeBranch || "the PR branch"}). Do not create a new branch.
       - Push changes directly to the current branch using mcp__github_file_ops__commit_files (works for both new and existing files)
       - Use mcp__github_file_ops__commit_files to commit files atomically in a single commit (supports single or multiple files).
-      - When pushing changes and TRIGGER_USERNAME is not "Unknown", include a "Co-authored-by: ${context.triggerUsername} <${context.triggerUsername}@users.noreply.github.com>" line in the commit message.
+      - When pushing changes and the trigger user is not "Unknown", include a Co-authored-by trailer in the commit message.
+      - Use: "Co-authored-by: ${githubData.triggerDisplayName ?? context.triggerUsername} <${context.triggerUsername}@users.noreply.github.com>"
       ${
         eventData.claudeBranch
           ? `- Provide a URL to create a PR manually in this format:
diff --git a/src/entrypoints/prepare.ts b/src/entrypoints/prepare.ts
index 6b240d8..f8b5dc2 100644
--- a/src/entrypoints/prepare.ts
+++ b/src/entrypoints/prepare.ts
@@ -59,6 +59,7 @@ async function run() {
       repository: `${context.repository.owner}/${context.repository.repo}`,
       prNumber: context.entityNumber.toString(),
       isPR: context.isPR,
+      triggerUsername: context.actor,
     });
 
     // Step 8: Setup branch
diff --git a/src/github/api/queries/github.ts b/src/github/api/queries/github.ts
index 20b5db9..e0e4c25 100644
--- a/src/github/api/queries/github.ts
+++ b/src/github/api/queries/github.ts
@@ -104,3 +104,11 @@ export const ISSUE_QUERY = `
     }
   }
 `;
+
+export const USER_QUERY = `
+  query($login: String!) {
+    user(login: $login) {
+      name
+    }
+  }
+`;
diff --git a/src/github/data/fetcher.ts b/src/github/data/fetcher.ts
index a5b0b0a..b1dc26d 100644
--- a/src/github/data/fetcher.ts
+++ b/src/github/data/fetcher.ts
@@ -1,6 +1,6 @@
 import { execSync } from "child_process";
 import type { Octokits } from "../api/client";
-import { ISSUE_QUERY, PR_QUERY } from "../api/queries/github";
+import { ISSUE_QUERY, PR_QUERY, USER_QUERY } from "../api/queries/github";
 import type {
   GitHubComment,
   GitHubFile,
@@ -18,6 +18,7 @@ type FetchDataParams = {
   repository: string;
   prNumber: string;
   isPR: boolean;
+  triggerUsername?: string;
 };
 
 export type GitHubFileWithSHA = GitHubFile & {
@@ -31,6 +32,7 @@ export type FetchDataResult = {
   changedFilesWithSHA: GitHubFileWithSHA[];
   reviewData: { nodes: GitHubReview[] } | null;
   imageUrlMap: Map<string, string>;
+  triggerDisplayName?: string | null;
 };
 
 export async function fetchGitHubData({
@@ -38,6 +40,7 @@ export async function fetchGitHubData({
   repository,
   prNumber,
   isPR,
+  triggerUsername,
 }: FetchDataParams): Promise<FetchDataResult> {
   const [owner, repo] = repository.split("/");
   if (!owner || !repo) {
@@ -191,6 +194,12 @@ export async function fetchGitHubData({
     allComments,
   );
 
+  // Fetch trigger user display name if username is provided
+  let triggerDisplayName: string | null | undefined;
+  if (triggerUsername) {
+    triggerDisplayName = await fetchUserDisplayName(octokits, triggerUsername);
+  }
+
   return {
     contextData,
     comments,
@@ -198,5 +207,27 @@ export async function fetchGitHubData({
     changedFilesWithSHA,
     reviewData,
     imageUrlMap,
+    triggerDisplayName,
   };
 }
+
+export type UserQueryResponse = {
+  user: {
+    name: string | null;
+  };
+};
+
+export async function fetchUserDisplayName(
+  octokits: Octokits,
+  login: string,
+): Promise<string | null> {
+  try {
+    const result = await octokits.graphql<UserQueryResponse>(USER_QUERY, {
+      login,
+    });
+    return result.user.name;
+  } catch (error) {
+    console.warn(`Failed to fetch user display name for ${login}:`, error);
+    return null;
+  }
+}
diff --git a/src/github/types.ts b/src/github/types.ts
index 28c4aa1..c46c29f 100644
--- a/src/github/types.ts
+++ b/src/github/types.ts
@@ -1,6 +1,7 @@
 // Types for GitHub GraphQL query responses
 export type GitHubAuthor = {
   login: string;
+  name?: string;
 };
 
 export type GitHubComment = {
diff --git a/test/create-prompt.test.ts b/test/create-prompt.test.ts
index 65c5625..472ff65 100644
--- a/test/create-prompt.test.ts
+++ b/test/create-prompt.test.ts
@@ -316,7 +316,7 @@ describe("generatePrompt", () => {
 
     expect(prompt).toContain("<trigger_username>johndoe</trigger_username>");
     expect(prompt).toContain(
-      "Co-authored-by: johndoe <johndoe@users.noreply.github.com>",
+      'Use: "Co-authored-by: johndoe <johndoe@users.noreply.github.com>"',
     );
   });