diff --git a/actions/setup/js/add_workflow_run_comment.cjs b/actions/setup/js/add_workflow_run_comment.cjs
index 7b766e3177..b199783565 100644
--- a/actions/setup/js/add_workflow_run_comment.cjs
+++ b/actions/setup/js/add_workflow_run_comment.cjs
@@ -84,44 +84,25 @@ async function main() {
 
   try {
     switch (eventName) {
-      case "issues": {
-        const number = context.payload?.issue?.number;
-        if (!number) {
-          core.setFailed(`${ERR_NOT_FOUND}: Issue number not found in event payload`);
-          return;
-        }
-        commentEndpoint = `/repos/${owner}/${repo}/issues/${number}/comments`;
-        break;
-      }
-
+      case "issues":
       case "issue_comment": {
         const number = context.payload?.issue?.number;
         if (!number) {
           core.setFailed(`${ERR_NOT_FOUND}: Issue number not found in event payload`);
           return;
         }
-        // Create new comment on the issue itself, not on the comment
-        commentEndpoint = `/repos/${owner}/${repo}/issues/${number}/comments`;
-        break;
-      }
-
-      case "pull_request": {
-        const number = context.payload?.pull_request?.number;
-        if (!number) {
-          core.setFailed(`${ERR_NOT_FOUND}: Pull request number not found in event payload`);
-          return;
-        }
         commentEndpoint = `/repos/${owner}/${repo}/issues/${number}/comments`;
         break;
       }
 
+      case "pull_request":
       case "pull_request_review_comment": {
         const number = context.payload?.pull_request?.number;
         if (!number) {
           core.setFailed(`${ERR_NOT_FOUND}: Pull request number not found in event payload`);
           return;
         }
-        // Create new comment on the PR itself (using issues endpoint since PRs are issues)
+        // PRs use the issues comment endpoint
         commentEndpoint = `/repos/${owner}/${repo}/issues/${number}/comments`;
         break;
       }
@@ -156,123 +137,118 @@ async function main() {
     await addCommentWithWorkflowLink(commentEndpoint, runUrl, eventName);
   } catch (error) {
     const errorMessage = getErrorMessage(error);
-    core.error(`Failed to create comment: ${errorMessage}`);
     // Don't fail the job - just warn since this is not critical
     core.warning(`Failed to create comment with workflow link: ${errorMessage}`);
   }
 }
 
 /**
- * Add a comment with a workflow run link
- * @param {string} endpoint - The GitHub API endpoint to create the comment (or special format for discussions)
+ * Build the comment body text for a workflow run link.
+ * Sanitizes the content and appends all required markers.
+ * @param {string} eventName - The event type
  * @param {string} runUrl - The URL of the workflow run
- * @param {string} eventName - The event type (to determine the comment text)
+ * @returns {string} The assembled comment body
  */
-async function addCommentWithWorkflowLink(endpoint, runUrl, eventName) {
-  // Get workflow name from environment variable
+function buildCommentBody(eventName, runUrl) {
   const workflowName = process.env.GH_AW_WORKFLOW_NAME || "Workflow";
-
-  // Determine the event type description using lookup object
   const eventTypeDescription = EVENT_TYPE_DESCRIPTIONS[eventName] ?? "event";
 
-  // Use getRunStartedMessage for the workflow link text (supports custom messages)
-  const workflowLinkText = getRunStartedMessage({
-    workflowName: workflowName,
-    runUrl: runUrl,
-    eventType: eventTypeDescription,
-  });
-
-  // Sanitize the workflow link text to prevent injection attacks (defense in depth for custom message templates)
-  // This must happen BEFORE adding workflow markers to preserve them
-  let commentBody = sanitizeContent(workflowLinkText);
+  // Sanitize before adding markers (defense in depth for custom message templates)
+  let body = sanitizeContent(getRunStartedMessage({ workflowName, runUrl, eventType: eventTypeDescription }));
 
   // Add lock notice if lock-for-agent is enabled for issues or issue_comment
-  const lockForAgent = process.env.GH_AW_LOCK_FOR_AGENT === "true";
-  if (lockForAgent && (eventName === "issues" || eventName === "issue_comment")) {
-    commentBody += "\n\n🔒 This issue has been locked while the workflow is running to prevent concurrent modifications.";
+  if (process.env.GH_AW_LOCK_FOR_AGENT === "true" && (eventName === "issues" || eventName === "issue_comment")) {
+    body += "\n\n🔒 This issue has been locked while the workflow is running to prevent concurrent modifications.";
   }
 
-  // Add workflow-id and tracker-id markers for hide-older-comments feature
+  // Add workflow-id marker for hide-older-comments feature
   const workflowId = process.env.GITHUB_WORKFLOW || "";
-  const trackerId = process.env.GH_AW_TRACKER_ID || "";
-
-  // Add workflow-id marker if available
   if (workflowId) {
-    commentBody += `\n\n${generateWorkflowIdMarker(workflowId)}`;
+    body += `\n\n${generateWorkflowIdMarker(workflowId)}`;
   }
 
-  // Add tracker-id marker if available (for backwards compatibility)
+  // Add tracker-id marker for backwards compatibility
+  const trackerId = process.env.GH_AW_TRACKER_ID || "";
   if (trackerId) {
-    commentBody += `\n\n<!-- gh-aw-tracker-id: ${trackerId} -->`;
+    body += `\n\n<!-- gh-aw-tracker-id: ${trackerId} -->`;
   }
 
-  // Add comment type marker to identify this as a reaction comment
-  // This prevents it from being hidden by hide-older-comments
-  commentBody += `\n\n<!-- gh-aw-comment-type: reaction -->`;
+  // Identify this as a reaction comment (prevents it from being hidden by hide-older-comments)
+  body += `\n\n<!-- gh-aw-comment-type: reaction -->`;
 
-  // Handle discussion events specially
-  if (eventName === "discussion") {
-    // Parse discussion number from special format: "discussion:NUMBER"
-    const discussionNumber = parseInt(endpoint.split(":")[1], 10);
+  return body;
+}
 
-    // Get discussion node ID using helper function
-    const discussionId = await getDiscussionNodeId(discussionNumber);
+/**
+ * Post a GraphQL comment to a discussion, optionally as a threaded reply.
+ * @param {number} discussionNumber - The discussion number
+ * @param {string} commentBody - The comment body
+ * @param {string|null} replyToNodeId - Parent comment node ID for threading (null for top-level)
+ */
+async function postDiscussionComment(discussionNumber, commentBody, replyToNodeId = null) {
+  const discussionId = await getDiscussionNodeId(discussionNumber);
 
-    const result = await github.graphql(
+  /** @type {any} */
+  let result;
+  if (replyToNodeId) {
+    result = await github.graphql(
+      `
+      mutation($dId: ID!, $body: String!, $replyToId: ID!) {
+        addDiscussionComment(input: { discussionId: $dId, body: $body, replyToId: $replyToId }) {
+          comment { id url }
+        }
+      }`,
+      { dId: discussionId, body: commentBody, replyToId: replyToNodeId }
+    );
+  } else {
+    result = await github.graphql(
       `
       mutation($dId: ID!, $body: String!) {
         addDiscussionComment(input: { discussionId: $dId, body: $body }) {
-          comment { 
-            id 
-            url
-          }
+          comment { id url }
         }
       }`,
       { dId: discussionId, body: commentBody }
     );
+  }
 
-    const comment = result.addDiscussionComment.comment;
-    setCommentOutputs(comment.id, comment.url);
+  const comment = result.addDiscussionComment.comment;
+  setCommentOutputs(comment.id, comment.url);
+}
+
+/**
+ * Add a comment with a workflow run link
+ * @param {string} endpoint - The GitHub API endpoint to create the comment (or special format for discussions)
+ * @param {string} runUrl - The URL of the workflow run
+ * @param {string} eventName - The event type (to determine the comment text)
+ */
+async function addCommentWithWorkflowLink(endpoint, runUrl, eventName) {
+  const commentBody = buildCommentBody(eventName, runUrl);
+
+  if (eventName === "discussion") {
+    // Parse discussion number from special format: "discussion:NUMBER"
+    const discussionNumber = parseInt(endpoint.split(":")[1], 10);
+    await postDiscussionComment(discussionNumber, commentBody);
     return;
-  } else if (eventName === "discussion_comment") {
+  }
+
+  if (eventName === "discussion_comment") {
     // Parse discussion number from special format: "discussion_comment:NUMBER:COMMENT_ID"
     const discussionNumber = parseInt(endpoint.split(":")[1], 10);
 
-    // Get discussion node ID using helper function
-    const discussionId = await getDiscussionNodeId(discussionNumber);
-
-    // Get the comment node ID to use as the parent for threading.
-    // GitHub Discussions only supports two nesting levels, so if the triggering comment is
-    // itself a reply, we resolve the top-level parent's node ID.
+    // GitHub Discussions only supports two nesting levels, so resolve the top-level parent's node ID
     const commentNodeId = await resolveTopLevelDiscussionCommentId(github, context.payload?.comment?.node_id);
-
-    const result = await github.graphql(
-      `
-      mutation($dId: ID!, $body: String!, $replyToId: ID!) {
-        addDiscussionComment(input: { discussionId: $dId, body: $body, replyToId: $replyToId }) {
-          comment { 
-            id 
-            url
-          }
-        }
-      }`,
-      { dId: discussionId, body: commentBody, replyToId: commentNodeId }
-    );
-
-    const comment = result.addDiscussionComment.comment;
-    setCommentOutputs(comment.id, comment.url);
+    await postDiscussionComment(discussionNumber, commentBody, commentNodeId);
     return;
   }
 
   // Create a new comment for non-discussion events
   const createResponse = await github.request("POST " + endpoint, {
     body: commentBody,
-    headers: {
-      Accept: "application/vnd.github+json",
-    },
+    headers: { Accept: "application/vnd.github+json" },
   });
 
   setCommentOutputs(createResponse.data.id, createResponse.data.html_url);
 }
 
-module.exports = { main, addCommentWithWorkflowLink };
+module.exports = { main, addCommentWithWorkflowLink, buildCommentBody, postDiscussionComment };
diff --git a/actions/setup/js/add_workflow_run_comment.test.cjs b/actions/setup/js/add_workflow_run_comment.test.cjs
index 398848a0c9..51cde9c5c4 100644
--- a/actions/setup/js/add_workflow_run_comment.test.cjs
+++ b/actions/setup/js/add_workflow_run_comment.test.cjs
@@ -230,6 +230,20 @@ describe("add_workflow_run_comment", () => {
       );
       expect(mockCore.setFailed).not.toHaveBeenCalled();
     });
+
+    it("should fail when PR number is missing in pull_request_review_comment event", async () => {
+      global.context = {
+        eventName: "pull_request_review_comment",
+        runId: 12345,
+        repo: { owner: "testowner", repo: "testrepo" },
+        payload: {},
+      };
+
+      await runScript();
+
+      expect(mockCore.setFailed).toHaveBeenCalledWith(`${ERR_NOT_FOUND}: Pull request number not found in event payload`);
+      expect(mockGithub.request).not.toHaveBeenCalled();
+    });
   });
 
   describe("main() - discussion event", () => {
@@ -341,9 +355,9 @@ describe("add_workflow_run_comment", () => {
 
       await runScript();
 
-      expect(mockCore.error).toHaveBeenCalledWith(expect.stringContaining("Failed to create comment"));
       expect(mockCore.warning).toHaveBeenCalledWith(expect.stringContaining("Failed to create comment with workflow link"));
-      // Should NOT call setFailed - errors should only warn
+      // Should NOT use core.error or core.setFailed for non-critical errors
+      expect(mockCore.error).not.toHaveBeenCalled();
       expect(mockCore.setFailed).not.toHaveBeenCalled();
     });
   });
@@ -475,4 +489,84 @@ describe("add_workflow_run_comment", () => {
       );
     });
   });
+
+  describe("buildCommentBody()", () => {
+    it("should include the run URL in the comment body", async () => {
+      const { buildCommentBody } = await import("./add_workflow_run_comment.cjs?" + Date.now());
+      const body = buildCommentBody("issues", "https://github.com/testowner/testrepo/actions/runs/99");
+      expect(body).toContain("https://github.com/testowner/testrepo/actions/runs/99");
+    });
+
+    it("should always include reaction comment type marker", async () => {
+      const { buildCommentBody } = await import("./add_workflow_run_comment.cjs?" + Date.now());
+      const body = buildCommentBody("issues", "https://example.com/run/1");
+      expect(body).toContain("<!-- gh-aw-comment-type: reaction -->");
+    });
+
+    it("should include workflow-id marker when GITHUB_WORKFLOW is set", async () => {
+      process.env.GITHUB_WORKFLOW = "my-workflow.yml";
+      const { buildCommentBody } = await import("./add_workflow_run_comment.cjs?" + Date.now());
+      const body = buildCommentBody("issues", "https://example.com/run/1");
+      expect(body).toContain("<!-- gh-aw-workflow-id: my-workflow.yml -->");
+    });
+
+    it("should include tracker-id marker when GH_AW_TRACKER_ID is set", async () => {
+      process.env.GH_AW_TRACKER_ID = "my-tracker";
+      const { buildCommentBody } = await import("./add_workflow_run_comment.cjs?" + Date.now());
+      const body = buildCommentBody("issues", "https://example.com/run/1");
+      expect(body).toContain("<!-- gh-aw-tracker-id: my-tracker -->");
+    });
+
+    it("should add lock notice for issues event when GH_AW_LOCK_FOR_AGENT=true", async () => {
+      process.env.GH_AW_LOCK_FOR_AGENT = "true";
+      const { buildCommentBody } = await import("./add_workflow_run_comment.cjs?" + Date.now());
+      const body = buildCommentBody("issues", "https://example.com/run/1");
+      expect(body).toContain("🔒 This issue has been locked");
+    });
+
+    it("should not add lock notice for pull_request events", async () => {
+      process.env.GH_AW_LOCK_FOR_AGENT = "true";
+      const { buildCommentBody } = await import("./add_workflow_run_comment.cjs?" + Date.now());
+      const body = buildCommentBody("pull_request", "https://example.com/run/1");
+      expect(body).not.toContain("🔒 This issue has been locked");
+    });
+
+    it("should use unknown event type description for unrecognized events", async () => {
+      const { buildCommentBody } = await import("./add_workflow_run_comment.cjs?" + Date.now());
+      // Should not throw for unknown event types
+      const body = buildCommentBody("some_unknown_event", "https://example.com/run/1");
+      expect(body).toBeTruthy();
+      expect(body).toContain("<!-- gh-aw-comment-type: reaction -->");
+    });
+  });
+
+  describe("postDiscussionComment()", () => {
+    it("should post a top-level discussion comment when no replyToNodeId", async () => {
+      const { postDiscussionComment } = await import("./add_workflow_run_comment.cjs?" + Date.now());
+      await postDiscussionComment(10, "Test body");
+
+      expect(mockGithub.graphql).toHaveBeenCalled();
+      const mutationCall = mockGithub.graphql.mock.calls.find(call => call[0].includes("addDiscussionComment"));
+      expect(mutationCall).toBeDefined();
+      expect(mutationCall[1]).toMatchObject({ body: "Test body" });
+      expect(mutationCall[1]).not.toHaveProperty("replyToId");
+    });
+
+    it("should post a threaded comment when replyToNodeId is provided", async () => {
+      const { postDiscussionComment } = await import("./add_workflow_run_comment.cjs?" + Date.now());
+      await postDiscussionComment(10, "Reply body", "DC_kwParent123");
+
+      const mutationCall = mockGithub.graphql.mock.calls.find(call => call[0].includes("replyToId"));
+      expect(mutationCall).toBeDefined();
+      expect(mutationCall[1]).toMatchObject({ body: "Reply body", replyToId: "DC_kwParent123" });
+    });
+
+    it("should set comment outputs after posting", async () => {
+      const { postDiscussionComment } = await import("./add_workflow_run_comment.cjs?" + Date.now());
+      await postDiscussionComment(10, "Test body");
+
+      expect(mockCore.setOutput).toHaveBeenCalledWith("comment-id", "DC_kwDOTest456");
+      expect(mockCore.setOutput).toHaveBeenCalledWith("comment-url", expect.stringContaining("discussioncomment-456"));
+    });
+  });
 });