fix: route Forgejo review comment updates to issue comment API

On Forgejo, the tracking comment for pull_request_review_comment events
is always created as a regular issue comment (because Forgejo's webhook
payload lacks the top-level comment object). The MCP server was
incorrectly setting isPullRequestReviewComment=true based on the event
name, causing every update to try pulls.updateReviewComment first —
which 404'd and silently swallowed Claude's responses.

Three fixes:
- MCP server: detect Forgejo and always use issue comment path
- update-comment-link: skip pulls.getReviewComment on Forgejo (saves
  one wasted 404 API call)
- update-claude-comment: expand fallback to also catch 422 (defense
  in depth for Forgejo edge cases)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/entrypoints/update-comment-link.ts

@@ -65,11 +65,13 @@ export async function updateCommentLink(
   try {
     // GitHub has separate ID namespaces for review comments and issue comments
     // We need to use the correct API based on the event type
-    if (isPullRequestReviewCommentEvent(context)) {
-      // For PR review comments, try the pulls API first.
-      // On Forgejo, the initial comment may have been created as a regular
-      // issue comment (because the payload lacks comment.id), so the pulls
-      // endpoint may 404. Fall through to issue comment fetch in that case.
+    //
+    // On Forgejo, the tracking comment is always an issue comment because
+    // Forgejo's pull_request_review_comment payload lacks the top-level
+    // `comment` object (so createInitialComment falls back to
+    // issues.createComment). Skip the pulls API attempt on Forgejo to avoid
+    // a wasted 404 round-trip.
+    if (isPullRequestReviewCommentEvent(context) && platform !== "forgejo") {
       try {
         console.log(`Fetching PR review comment ${commentId}`);
         const { data: prComment } = await octokit.rest.pulls.getReviewComment({

src/github/operations/comments/update-claude-comment.ts

@@ -49,8 +49,14 @@ export async function updateClaudeComment(
       });
     }
   } catch (error: any) {
-    // If PR review comment update fails with 404, fall back to issue comment API
-    if (isPullRequestReviewComment && error.status === 404) {
+    // If PR review comment update fails, fall back to issue comment API.
+    // 404 = comment ID not in PR review namespace (expected on Forgejo where
+    // tracking comments are always issue comments).
+    // 422 = some Forgejo versions return Unprocessable Entity instead of 404.
+    if (
+      isPullRequestReviewComment &&
+      (error.status === 404 || error.status === 422)
+    ) {
       response = await octokit.rest.issues.updateComment({
         owner,
         repo,

src/mcp/github-comment-server.ts

@@ -52,8 +52,18 @@ server.tool(
         baseUrl: GITHUB_API_URL,
       });
 
+      // The tracking comment is always created as a regular issue comment on
+      // Forgejo because Forgejo's pull_request_review_comment payload lacks the
+      // top-level `comment` object (so createInitialComment falls back to
+      // issues.createComment). On GitHub, the tracking comment IS a review
+      // comment reply (created via pulls.createReplyForReviewComment).
+      //
+      // Setting this wrong causes every MCP update to first try
+      // pulls.updateReviewComment (404), and if the fallback doesn't trigger,
+      // Claude's responses never reach the comment.
+      const isForgejo = (process.env.GITHUB_API_URL || "").includes("/api/v1");
       const isPullRequestReviewComment =
-        eventName === "pull_request_review_comment";
+        eventName === "pull_request_review_comment" && !isForgejo;
 
       const sanitizedBody = sanitizeContent(body);