diff --git a/actions/setup/js/add_comment.cjs b/actions/setup/js/add_comment.cjs
index 1ed4a3c1945..8611d6ea52f 100644
--- a/actions/setup/js/add_comment.cjs
+++ b/actions/setup/js/add_comment.cjs
@@ -38,6 +38,38 @@ async function minimizeComment(github, nodeId, reason = "outdated") {
   };
 }
 
+/**
+ * Check if a comment should be hidden by the hideOlderComments function
+ * @param {string} commentBody - The comment body text
+ * @param {string} workflowId - The workflow ID to match
+ * @returns {boolean} true if the comment should be hidden, false otherwise
+ */
+function shouldHideComment(commentBody, workflowId) {
+  if (!commentBody) {
+    return false;
+  }
+
+  // Comment must have the workflow-id marker
+  const hasWorkflowId = commentBody.includes(`<!-- gh-aw-workflow-id: ${workflowId} -->`);
+  if (!hasWorkflowId) {
+    return false;
+  }
+
+  // Exclude reaction comments (activation comments)
+  const isReactionComment = commentBody.includes(`<!-- gh-aw-comment-type: reaction -->`);
+  if (isReactionComment) {
+    return false;
+  }
+
+  // Exclude append-only comments (should persist across runs)
+  const isAppendOnlyComment = commentBody.includes(`<!-- gh-aw-comment-type: append-only -->`);
+  if (isAppendOnlyComment) {
+    return false;
+  }
+
+  return true;
+}
+
 /**
  * Find comments on an issue/PR with a specific tracker-id
  * @param {any} github - GitHub REST API instance
@@ -66,10 +98,8 @@ async function findCommentsWithTrackerId(github, owner, repo, issueNumber, workf
       break;
     }
 
-    // Filter comments that contain the workflow-id and are NOT reaction comments
-    const filteredComments = data
-      .filter(comment => comment.body?.includes(`<!-- gh-aw-workflow-id: ${workflowId} -->`) && !comment.body.includes(`<!-- gh-aw-comment-type: reaction -->`))
-      .map(({ id, node_id, body }) => ({ id, node_id, body }));
+    // Filter comments that should be hidden
+    const filteredComments = data.filter(comment => shouldHideComment(comment.body, workflowId)).map(({ id, node_id, body }) => ({ id, node_id, body }));
 
     comments.push(...filteredComments);
 
@@ -122,9 +152,7 @@ async function findDiscussionCommentsWithTrackerId(github, owner, repo, discussi
       break;
     }
 
-    const filteredComments = result.repository.discussion.comments.nodes
-      .filter(comment => comment.body?.includes(`<!-- gh-aw-workflow-id: ${workflowId} -->`) && !comment.body.includes(`<!-- gh-aw-comment-type: reaction -->`))
-      .map(({ id, body }) => ({ id, body }));
+    const filteredComments = result.repository.discussion.comments.nodes.filter(comment => shouldHideComment(comment.body, workflowId)).map(({ id, body }) => ({ id, body }));
 
     comments.push(...filteredComments);
 
@@ -414,6 +442,11 @@ async function main(config = {}) {
       processedBody += "\n\n" + trackerIDComment;
     }
 
+    // Add append-only marker if enabled to prevent hiding by future runs
+    if (appendOnlyComments) {
+      processedBody += "\n\n<!-- gh-aw-comment-type: append-only -->";
+    }
+
     const workflowName = process.env.GH_AW_WORKFLOW_NAME || "Workflow";
     const runId = context.runId;
     const runUrl = `https://github.com/${context.repo.owner}/${context.repo.repo}/actions/runs/${runId}`;
diff --git a/actions/setup/js/add_comment.test.cjs b/actions/setup/js/add_comment.test.cjs
index f5a9b7beb67..6a17d300d07 100644
--- a/actions/setup/js/add_comment.test.cjs
+++ b/actions/setup/js/add_comment.test.cjs
@@ -527,5 +527,114 @@ describe("add_comment", () => {
       // Clean up
       delete process.env.GITHUB_WORKFLOW;
     });
+
+    it("should include append-only marker in comment body when append-only-comments is enabled", async () => {
+      const addCommentScript = fs.readFileSync(path.join(__dirname, "add_comment.cjs"), "utf8");
+
+      // Set up environment variable for append-only-comments
+      process.env.GH_AW_SAFE_OUTPUT_MESSAGES = JSON.stringify({
+        appendOnlyComments: true,
+      });
+      process.env.GITHUB_WORKFLOW = "test-workflow";
+
+      let capturedComment = null;
+      mockGithub.rest.issues.createComment = async params => {
+        capturedComment = params;
+        return {
+          data: {
+            id: 12345,
+            html_url: `https://github.com/owner/repo/issues/${params.issue_number}#issuecomment-12345`,
+          },
+        };
+      };
+
+      const handler = await eval(`(async () => { ${addCommentScript}; return await main({}); })()`);
+
+      const message = {
+        type: "add_comment",
+        body: "Append-only comment",
+      };
+
+      const result = await handler(message, {});
+
+      expect(result.success).toBe(true);
+      expect(capturedComment).toBeTruthy();
+      expect(capturedComment.body).toContain("<!-- gh-aw-comment-type: append-only -->");
+
+      // Clean up
+      delete process.env.GH_AW_SAFE_OUTPUT_MESSAGES;
+      delete process.env.GITHUB_WORKFLOW;
+    });
+
+    it("should not hide append-only comments from previous runs", async () => {
+      const addCommentScript = fs.readFileSync(path.join(__dirname, "add_comment.cjs"), "utf8");
+
+      // Set up environment WITHOUT append-only-comments (new run)
+      delete process.env.GH_AW_SAFE_OUTPUT_MESSAGES;
+      process.env.GITHUB_WORKFLOW = "test-workflow";
+
+      let hideCommentsWasCalled = false;
+      let hiddenCommentIds = [];
+
+      // Simulate finding an old append-only comment and a regular comment
+      mockGithub.rest.issues.listComments = async () => {
+        return {
+          data: [
+            {
+              id: 888,
+              node_id: "IC_kwDOTest888",
+              body: "Old append-only comment <!-- gh-aw-workflow-id: test-workflow --><!-- gh-aw-comment-type: append-only -->",
+            },
+            {
+              id: 999,
+              node_id: "IC_kwDOTest999",
+              body: "Old regular comment <!-- gh-aw-workflow-id: test-workflow -->",
+            },
+          ],
+        };
+      };
+
+      mockGithub.graphql = async (query, variables) => {
+        if (query.includes("minimizeComment")) {
+          hideCommentsWasCalled = true;
+          hiddenCommentIds.push(variables.nodeId);
+        }
+        return {
+          minimizeComment: {
+            minimizedComment: {
+              isMinimized: true,
+            },
+          },
+        };
+      };
+
+      mockGithub.rest.issues.createComment = async params => {
+        return {
+          data: {
+            id: 12345,
+            html_url: `https://github.com/owner/repo/issues/${params.issue_number}#issuecomment-12345`,
+          },
+        };
+      };
+
+      // Execute with hide-older-comments enabled (but not append-only)
+      const handler = await eval(`(async () => { ${addCommentScript}; return await main({ hide_older_comments: true }); })()`);
+
+      const message = {
+        type: "add_comment",
+        body: "New comment",
+      };
+
+      const result = await handler(message, {});
+
+      expect(result.success).toBe(true);
+      expect(hideCommentsWasCalled).toBe(true);
+      // Should only hide the regular comment, not the append-only comment
+      expect(hiddenCommentIds).toEqual(["IC_kwDOTest999"]);
+      expect(hiddenCommentIds).not.toContain("IC_kwDOTest888");
+
+      // Clean up
+      delete process.env.GITHUB_WORKFLOW;
+    });
   });
 });