How to Group Code Changes by Importance in PR Review Workflows Using Cursor's Canvas Renderer

Cursor's PR Review Canvas skill renders pull request diffs as interactive Canvases that automatically stratify changes into core logic, wiring, and boilerplate tiers using JavaScript heuristics defined in the renderer layer.

Effective code review requires focusing on what matters most. The cursor/plugins repository implements an intelligent grouping code changes by importance in PR review workflows strategy through its PR Review Canvas skill, which transforms standard file-tree diffs into a hierarchical view that surfaces risky modifications while de-emphasizing mechanical noise.

The Three-Tier Importance Classification System

The renderer organizes every pull request into three distinct importance levels, ensuring reviewers encounter changes in order of semantic risk rather than alphabetical file order.

Core Logic Changes

Core logic modifications receive full visual prominence. This tier contains new behavior implementations, algorithmic updates, and API surface changes. In cursor-team-kit/skills/pr-review-canvas/renderer.js, these changes render with complete context diffs using the CSS classes diff-add, diff-del, and diff-ctx, providing maximum visibility into the "real" changes that impact system behavior.

Wiring and Integration

Wiring and integration changes occupy the middle tier. These include route registration, dependency injection updates, and configuration plumbing. While visually similar to core logic rows, these diffs are automatically condensed—the renderer filters out import statements and surrounding noise, showing only the structural connections without the clutter of mechanical dependencies.

Boilerplate and Mechanical Changes

Boilerplate and mechanical changes receive minimal visual weight. Import statements, symbol renames, generated code, and formatting updates appear as summarized lists without inline diff expansions. The isImport() function (lines 11-13 of renderer.js) specifically identifies and omits lines beginning with import, collapsing mechanical overhead into skimmable metadata.

How the Renderer Implements Importance Grouping

The grouping logic lives entirely within the JavaScript renderer, which parses diff strings and constructs an HTML table stratified by significance.

Filtering Boilerplate with isImport()

The renderer first sanitizes the diff to remove distracting noise. The isImport() heuristic detects import statements and prevents them from receiving visual row status, effectively shifting mechanical dependency updates into the boilerplate tier regardless of their position in the file.

Collapsing Whitespace-Only Changes

Consecutive deletion and addition lines that differ only in whitespace are merged into a single "no-op" line (wsOut). The loop beginning at line 100 in renderer.js executes this collapse, ensuring that formatting-only changes do not clutter the core logic view or trigger false positives in the review process.

Detecting Code Moves with detectMoves()

The detectMoves(dels, adds) function identifies blocks of code that have been relocated rather than modified. By detecting these moves, the renderer marks them with the CSS classes diff-moved-add and diff-moved-del, preventing the same logical change from appearing twice in the review and helping reviewers focus on what moved rather than where it moved.

Constructing the Visual Hierarchy

After processing, each parsed token—add, del, ctx, or hunk—becomes a table row with a role-specific CSS class. Core logic rows retain full context lines; wiring rows appear shortened due to import filtering; boilerplate rows render without the standard "+" or "-" markers. The final HTML table injects into any element carrying a data-diff attribute (lines 60-69), which the surrounding Canvas UI then organizes with tier-specific headings.

Setting Up the PR Review Canvas

To implement importance-based grouping in your own workflow, include the renderer script and provide a JSON diff payload with a target container:

<!-- Target element that receives the rendered diff -->
<div id="my-diff" data-diff="myPr"></div>

<!-- Diff payload structured as an array of diff lines -->
<script id="pr-diffs-json" type="application/json">
{
  "myPr": [
    "diff --git a/src/foo.ts b/src/foo.ts",
    "index 123..456 100644",
    "--- a/src/foo.ts",
    "+++ b/src/foo.ts",
    "@@ -1,5 +1,7 @@",
    "+export function newFeature() {",
    "+  // core logic",
    "+}",
    " import { oldHelper } from './helper';",
    "-const old = 1;",
    "+const updated = 2;"
  ]
}
</script>

<script src="renderer.js"></script>

Trigger rendering manually or allow automatic execution on DOMContentLoaded:

// Manual invocation (optional)
renderDiff('my-diff', document.getElementById('pr-diffs-json').textContent);

The renderDiff function (lines 78-84 of renderer.js) processes the input through the importance heuristics, filtering imports, collapsing whitespace-only modifications, and detecting moves before injecting the stratified table into the DOM.

File Architecture and Customization

The PR Review Canvas skill distributes functionality across several specialized files:

• cursor-team-kit/skills/pr-review-canvas/renderer.js – Core implementation containing isImport(), detectMoves(), and the row construction logic
• cursor-team-kit/skills/pr-review-canvas/template.html – HTML scaffold defining placeholders for the three importance sections
• cursor-team-kit/skills/pr-review-canvas/styles.css – Visual styling for core, wiring, and boilerplate tiers, plus moved-code indicators
• pr-review-canvas/README.md – High-level documentation explaining the grouping philosophy
• pr-review-canvas/skills/pr-review-canvas/SKILL.md – Skill definition consumed by the Cursor engine

The separation between the parsing logic (renderer.js) and presentation layer (template.html/styles.css) allows teams to customize visual weightings—such as adjusting what constitutes "core" versus "boilerplate"—without modifying the underlying diff parsing algorithms.

Summary

• Cursor's PR Review Canvas stratifies diffs into three tiers: core logic, wiring/integration, and boilerplate, enabling top-down review workflows.
• The isImport() function (lines 11-13) and whitespace collapse logic (line 100+) in renderer.js automatically filter noise from the visual presentation.
• detectMoves(dels, adds) identifies relocated code blocks to prevent duplicate review effort and marks them with diff-moved-add/diff-moved-del classes.
• The renderer injects stratified HTML tables into elements marked with data-diff attributes, with styling defined in styles.css controlling the visual hierarchy.

Frequently Asked Questions

How does the Cursor PR Review Canvas determine what constitutes "core logic" versus "boilerplate"?

The classification relies on syntactic heuristics rather than semantic analysis. Lines matching the isImport() pattern or containing only whitespace changes get relegated to boilerplate. Algorithmic changes and API modifications that survive these filters and appear in hunks with substantial context lines receive diff-add or diff-del classes that the CSS renders as core logic with full context visibility.

Can the importance grouping heuristics be customized for specific codebases?

Yes, though modifications require editing cursor-team-kit/skills/pr-review-canvas/renderer.js. You can adjust the isImport() regex to recognize additional mechanical patterns (such as generated protobuf code or specific framework annotations) or modify the whitespace collapse threshold in the line-100 loop to be more or less aggressive regarding formatting changes.

What happens when the same code block is both modified and moved in a single PR?

The detectMoves(dels, adds) function identifies blocks that appear as both deletions and additions with high similarity. When detected, the renderer marks these with diff-moved-add and diff-moved-del classes rather than treating them as independent additions and deletions. This prevents reviewers from analyzing the same logical code twice, though true modifications within moved blocks still render as standard add/del rows for careful examination.

Does the PR Review Canvas support monorepos with mixed programming languages?

The renderer operates on unified diff format rather than AST parsing, making it language-agnostic for the core grouping functionality. However, the isImport() heuristic specifically targets import statement patterns common in JavaScript/TypeScript. For polyglot monorepos, you would need to extend renderer.js to recognize language-specific boilerplate patterns—such as #include directives in C++ or using statements in C#—to maintain effective noise filtering across all file types.

{
  "mcpServers": {
    "instagit": {
      "command": "npx",
      "args": ["-y", "instagit@latest"]
    }
  }
}