Dev Review Diagrams

Pre-push validation skill that cross-checks every diagram function against the lesson README to catch correctness issues before they reach CodeRabbit review.

When to use this skill:

• Before pushing a lesson that includes diagrams
• As part of /dev-final-pass (section 18)
• After modifying diagram functions or the README sections they illustrate
• When CodeRabbit flagged diagram correctness issues in a previous round

The user provides:

• Lesson key: e.g. gpu/34, math/05, engine/04

If missing, infer from the current branch name or most recent lesson directory.

Steps

1. Identify all diagrams for the lesson

Read scripts/forge_diagrams/__main__.py and find the lesson's entry in the DIAGRAMS dict. List every (filename, function) pair registered for the lesson key.

If the lesson has no registered diagrams, report "No diagrams registered for this lesson" and exit.

2. Read the lesson README

Read the full lessons/<category>/<NN-name>/README.md. For each diagram file referenced in the README (via ![...](assets/<name>.png)), note:

• The surrounding text — what does the README claim this diagram shows?
• Any equations, coordinate systems, or algorithm steps described nearby
• Variable names and terminology used in the explanation
• Whether the README describes 2D or 3D, which axes, which orientation

3. Cross-check each diagram function

For each diagram function, read its source code in the relevant per-lesson file under scripts/forge_diagrams/<track>/lesson_NN.py and verify:

Geometry and math accuracy

• Plotted geometry matches the documented equations (if the README says y = sin(x), the code must plot np.sin(x), not np.cos(x))
• Coordinate systems are consistent (if the README says Y-up, the diagram must not show Z-up)
• If the README describes an OBB, the diagram draws a rotated box — not an axis-aligned one
• If the README describes a 3D concept, all three axes are present and labeled correctly
• Arrow directions match the data flow or vector directions described in the README

Labels and annotations

• Axis labels match the README's variable names (if README says "view-space depth", the axis label must not say "world-space Z")
• Annotations use the same terminology as the README — no synonyms that could confuse readers (e.g. "fragment" vs "pixel" must match)
• Mathematical notation in labels matches the README's notation

Algorithm and pipeline correctness

• If the README describes N pipeline stages, the diagram shows all N
• Stencil/blend operations match the described algorithm (increment vs decrement, src-alpha vs one-minus-src-alpha)
• State transitions match the order described in the README

Docstring accuracy

• The function's docstring accurately describes what the function actually plots (not a copy-paste from a different diagram)
• The docstring does not claim the diagram shows something it does not

4. Run each diagram

Execute each diagram and verify it generates without errors:

python scripts/forge_diagrams --lesson <lesson-key>

If any diagram raises an exception, report the error with traceback.

5. Report results

Present a checklist per diagram:

Diagram Review — Lesson NN: Name
==================================

1. diagram_name.png (function: diagram_diagram_name)
   [PASS] Geometry matches README equations
   [PASS] Axis labels match README terminology
   [PASS] Docstring matches actual content
   [FAIL] README says "3 cascade levels" but diagram only shows 2
   [PASS] Generates without errors

2. another_diagram.png (function: diagram_another)
   [PASS] All checks passed

Overall: 1 issue found — fix before pushing

For each failure, include:

• The specific README text that the diagram contradicts
• The specific line(s) in the diagram function that need fixing
• A suggested correction

What this skill does NOT do

• Does not check visual style (colors, fonts, spacing) — the STYLE dict and /dev-create-diagram handle that
• Does not check Python code quality — Ruff handles that
• Does not modify any files — it only reports findings
• Does not check screenshots — only matplotlib-generated diagrams