How to Attach Line-Specific Review Comments to Pull Requests

This guide explains how to add line-specific review comments to pull requests using the GitHub CLI (gh ) API or mcp__github_inline_comment__create_inline_comment if it not available, similar to how the GitHub UI allows commenting on specific lines of code.

Preferred Approach: Using MCP GitHub Tools

If available, use the mcp__github_inline_comment__create_inline_comment MCP tool for posting line-specific inline comments on pull requests. This approach provides better integration with GitHub's UI and is the recommended method.

Fallback: If the MCP tool is not available, use the GitHub CLI (gh ) API methods described below:

For single comments: Use the /comments endpoint (see Adding a Single Line-Specific Comment)
For multiple comments: Use the /reviews endpoint (see Adding Multiple Line-Specific Comments Together)

Overview

While gh pr review provides basic review functionality (approve, request changes, general comments), it does not support line-specific comments directly. To add comments on specific lines of code, you must use the lower-level gh api command to call GitHub's REST API directly.

Prerequisites

GitHub CLI installed and authenticated:

gh auth status

Access to the repository and pull request you want to review

Understanding GitHub's Review Comment System

GitHub has two types of PR comments:

Issue Comments - General comments on the PR conversation
Review Comments - Line-specific comments on code changes

Review comments can be added in two ways:

Single comment - Using the /pulls/{pr}/comments endpoint
Review with multiple comments - Using the /pulls/{pr}/reviews endpoint

Adding a Single Line-Specific Comment

Basic Syntax

gh api repos/{owner}/{repo}/pulls/{pr_number}/comments
-f body='Your comment text here'
-f commit_id='<commit-sha>'
-f path='path/to/file.js'
-F line=42
-f side='RIGHT'

Parameters Explained

Parameter Type Required Description

body

string Yes The text of the review comment (supports Markdown)

commit_id

string Yes The SHA of the commit to comment on

path

string Yes Relative path to the file being commented on

line

integer Yes The line number in the diff (use -F for integers)

side

string Yes RIGHT for new/modified lines, LEFT for deleted lines

start_line

integer No For multi-line comments, the starting line

start_side

string No For multi-line comments, the starting side

Parameter Flags

-f (--field) - For string values
-F (--field) - For integer values (note the capital F)

Complete Example

First, get the latest commit SHA for the PR

gh api repos/NeoLabHQ/learning-platform-app/pulls/4 --jq '.head.sha'

Then add your comment

gh api repos/NeoLabHQ/learning-platform-app/pulls/4/comments
-f body='Consider adding error handling here. Should we confirm the lesson was successfully marked as completed before navigating away?'
-f commit_id='e152d0dd6cf498467eadbeb638bf05abe11c64d4'
-f path='src/components/LessonNavigationButtons.tsx'
-F line=26
-f side='RIGHT'

Understanding Line Numbers

The line parameter refers to the position in the diff, not the absolute line number in the file:

For new files: Line numbers match the file's line numbers
For modified files: Use the line number as it appears in the "Files changed" tab
For multi-line comments: Use start_line and line to specify the range

Response

On success, returns a JSON object with comment details:

{ "id": 2532291222, "pull_request_review_id": 3470545909, "path": "src/components/LessonNavigationButtons.tsx", "line": 26, "body": "Consider adding error handling here...", "html_url": "https://github.com/NeoLabHQ/learning-platform-app/pull/4#discussion_r2532291222", "created_at": "2025-11-16T22:40:46Z" }

Adding Multiple Line-Specific Comments Together

To add multiple comments across different files in a single review, use the /reviews endpoint with JSON input.

Why Use Reviews for Multiple Comments?

Atomic operation - All comments are added together
Single notification - Doesn't spam with multiple notifications
Better UX - Appears as one cohesive review
Same mechanism as GitHub UI - "Start a review" → "Finish review"

Basic Syntax

cat <<'EOF' | gh api repos/{owner}/{repo}/pulls/{pr_number}/reviews --input - { "event": "COMMENT", "body": "Overall review summary (optional)", "comments": [ { "path": "file1.tsx", "body": "Comment on file 1", "side": "RIGHT", "line": 15 }, { "path": "file2.tsx", "body": "Comment on file 2", "side": "RIGHT", "line": 30 } ] } EOF

Review Event Types

Event Description When to Use

COMMENT

General review comment Just leaving feedback without approval

APPROVE

Approve the PR Changes look good, ready to merge

REQUEST_CHANGES

Request changes Issues that must be fixed before merge

Complete Example

cat <<'EOF' | gh api repos/NeoLabHQ/learning-platform-app/pulls/4/reviews --input - { "event": "COMMENT", "body": "Testing multiple line-specific comments via gh api", "comments": [ { "path": "src/components/CourseCard.tsx", "body": "Test comment generated by Claude", "side": "RIGHT", "line": 15 }, { "path": "src/components/CourseProgressWidget.tsx", "body": "Test comment generated by Claude", "side": "RIGHT", "line": 30 }, { "path": "src/components/LessonProgressTracker.tsx", "body": "Test comment generated by Claude", "side": "RIGHT", "line": 20 } ] } EOF

Response

{ "id": 3470546747, "state": "COMMENTED", "html_url": "https://github.com/NeoLabHQ/learning-platform-app/pull/4#pullrequestreview-3470546747", "submitted_at": "2025-11-16T22:42:43Z", "commit_id": "e152d0dd6cf498467eadbeb638bf05abe11c64d4" }

Common Issues and Solutions

Issue 1: "user_id can only have one pending review per pull request"

Error Message:

gh: Validation Failed (HTTP 422) {"message":"Validation Failed","errors":[{"resource":"PullRequestReview","code":"custom","field":"user_id","message":"user_id can only have one pending review per pull request"}]}

Cause: GitHub only allows one pending (unsubmitted) review per user per PR. If you previously started a review through the UI or API and didn't submit it, it blocks new review creation.

Solution 1: Submit the pending review

Check for pending reviews

gh api repos/{owner}/{repo}/pulls/{pr_number}/reviews | jq '.[] | select(.state=="PENDING")'

Submit it through the UI or ask the user to submit it

Solution 2: Use the single comment endpoint instead

Add individual comments without creating a review

gh api repos/{owner}/{repo}/pulls/{pr_number}/comments
-f body='Comment text'
-f commit_id='<sha>'
-f path='file.tsx'
-F line=26
-f side='RIGHT'

Issue 2: Array syntax not working with --raw-field

Failed Attempt:

This does NOT work - GitHub API receives an object, not an array

gh api repos/{owner}/{repo}/pulls/{pr}/reviews
--raw-field 'comments[0][path]=file1.tsx'
--raw-field 'comments[0][line]=15'
--raw-field 'comments[1][path]=file2.tsx'
--raw-field 'comments[1][line]=30'

Error:

Invalid request. For 'properties/comments', {"0" => {...}, "1" => {...}} is not an array.

Solution: Use JSON input via heredoc:

cat <<'EOF' | gh api repos/{owner}/{repo}/pulls/{pr}/reviews --input - { "comments": [...] } EOF

Issue 3: Invalid line number

Error Message:

Pull request review thread line must be part of the diff

Cause: The line number doesn't exist in the diff for this file.

Solutions:

Verify the file was actually changed in this PR
Check the "Files changed" tab to see actual line numbers in the diff
Ensure you're using the correct commit_id (the latest commit in the PR)

Issue 4: Wrong commit_id

Error Message:

commit_sha is not part of the pull request

Solution: Get the latest commit SHA:

gh api repos/{owner}/{repo}/pulls/{pr_number} --jq '.head.sha'

Best Practices

Get PR Information First

Before adding comments, gather necessary information:

Get PR details

gh pr view {pr_number} --json headRefOid,files

Or use the API

gh api repos/{owner}/{repo}/pulls/{pr_number} --jq '{commit: .head.sha, files: [.changed_files]}'

List files changed

gh api repos/{owner}/{repo}/pulls/{pr_number}/files --jq '.[] | {filename: .filename, additions: .additions, deletions: .deletions}'

Check for Pending Reviews

Check if you have a pending review

gh api repos/{owner}/{repo}/pulls/{pr_number}/reviews
--jq '.[] | select(.state=="PENDING" and .user.login=="YOUR_USERNAME")'

Use Meaningful Comment Text

Be specific and constructive
Reference documentation or best practices
Suggest alternatives when requesting changes
Use code blocks for code suggestions:

Consider using async/await:

```typescript async function getData() { const result = await fetch(url); return result.json(); } ```

Batch Related Comments

Use the review endpoint to group related comments:

All comments for a single file/area
All comments for a specific concern (security, performance, etc.)
Complete review session

Choose the Right Event Type

For feedback during development

"event": "COMMENT"

When approving

"event": "APPROVE"

When blocking merge

"event": "REQUEST_CHANGES"

Workflow Examples

Example 1: Quick Single Comment

#!/bin/bash OWNER="NeoLabHQ" REPO="learning-platform-app" PR=4

Get latest commit

COMMIT=$(gh api repos/$OWNER/$REPO/pulls/$PR --jq '.head.sha')

Add comment

gh api repos/$OWNER/$REPO/pulls/$PR/comments
-f body='Consider extracting this into a separate function for better testability'
-f commit_id="$COMMIT"
-f path='src/utils/validation.ts'
-F line=45
-f side='RIGHT'

Example 2: Comprehensive Review

#!/bin/bash OWNER="NeoLabHQ" REPO="learning-platform-app" PR=4

Create review with multiple comments

cat <<EOF | gh api repos/$OWNER/$REPO/pulls/$PR/reviews --input - { "event": "COMMENT", "body": "Thanks for the PR! I've reviewed the changes and have a few suggestions.", "comments": [ { "path": "src/components/CourseCard.tsx", "body": "Consider memoizing this component to prevent unnecessary re-renders", "side": "RIGHT", "line": 25 }, { "path": "src/utils/courseProgress.ts", "body": "This function could benefit from error handling for invalid course IDs", "side": "RIGHT", "line": 12 }, { "path": "src/state/CourseProgressState.ts", "body": "Consider adding JSDoc comments to document the expected behavior", "side": "RIGHT", "line": 8 } ] } EOF

Example 3: Multi-line Comment

Comment on a range of lines (e.g., lines 10-15)

gh api repos/$OWNER/$REPO/pulls/$PR/comments
-f body='This entire block could be simplified using array destructuring'
-f commit_id="$COMMIT"
-f path='src/utils/parser.ts'
-F start_line=10
-f start_side='RIGHT'
-F line=15
-f side='RIGHT'

Helpful Helper Scripts

Get PR Files and Lines

#!/bin/bash

pr-files.sh - List all files changed in a PR with line counts

OWNER="$1" REPO="$2" PR="$3"

gh api repos/$OWNER/$REPO/pulls/$PR/files --jq '.[] | "(.filename): +(.additions)/-(.deletions)"'

Check Review Status

#!/bin/bash

check-reviews.sh - Check review status for a PR

OWNER="$1" REPO="$2" PR="$3"

echo "=== Reviews ===" gh api repos/$OWNER/$REPO/pulls/$PR/reviews --jq '.[] | "(.user.login): (.state) at (.submitted_at)"'

echo -e "\n=== Pending Reviews ===" gh api repos/$OWNER/$REPO/pulls/$PR/reviews --jq '.[] | select(.state=="PENDING") | "(.user.login): (.state)"'

git:attach-review-to-pr

Safety Notice

Copy this and send it to your AI assistant to learn

First, get the latest commit SHA for the PR

Then add your comment

Check for pending reviews

Submit it through the UI or ask the user to submit it

Add individual comments without creating a review

This does NOT work - GitHub API receives an object, not an array

Get PR details

Or use the API

List files changed

Check if you have a pending review

For feedback during development

When approving

When blocking merge

Get latest commit

Add comment

Create review with multiple comments

Comment on a range of lines (e.g., lines 10-15)

pr-files.sh - List all files changed in a PR with line counts

check-reviews.sh - Check review status for a PR

Source Transparency

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