Describe the bug

add_comment_to_pending_review is silently failed when line, side or startLine, startSide are referencing a line/block of code that is not part of the PR changes

Affected version

GitHub MCP Server
Version: v0.18.0
Commit: f9343e62fd825d77ff741c7909016c461402783b
Build Date: 2025-10-10T08:49:22Z

Steps to reproduce the behavior

1. Create a pending PR review using Github MCP pull_request_review_write tool and then use add_comment_to_pending_review tool to add a new comment to this pending PR with argument line and side refers to an unchanged line of code (not part of the PR changes)

gh - Add review comment to the requester's latest pending pull request review (MCP)(owner: "xxx", repo: "utx", pullNumber: 13992, path:
                                                                                     "projects/utx/src/path/to/file.ts", line: 47, side: "RIGHT", subjectType: "LINE",
                                                                                     body: "**Issue 1: Code Duplication in Document Type Lookup (Performance Improvement)**\n\nWhile ....")

2. The output show as success but the comment is not submitted (no indication of any error)

  ⎿  pull request review comment successfully added to pending review

3. Expected vs Actual behavior

Expected
The add_comment_to_pending_review tool should return an error with message to suggest to change the subjectType from "LINE" to "FILE" in-order for the comment to be submitted with a line + side referencing an unchanged line of code. The actual line of code can be included in the comment message.

Actual behavior
The MCP tool is returning a success message which is an incorrectly status of the operation (silently failed).

Logs

As show in code block above. These are logs from Claude Code when using Github MCP to create pending PR review and add comments