Dev Final Pass

Run a systematic quality review on any lesson (GPU, math, engine, UI, physics, audio, or asset pipeline) before creating a PR with /dev-create-pr. This skill encodes recurring themes from PR review feedback across the project's history.

The user provides:

• Lesson number or name (e.g. 17 or normal-maps)

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

How to run this skill

Work through each section below in order. For each check, read the relevant files and verify compliance. Report a summary at the end with pass/fail per section and specific issues found.

Be literal and exhaustive. This is C — no RAII, no garbage collector. Every resource you acquire must be released on every exit path, every struct field must be documented, every error must be handled. Do not rationalize away findings with "it's probably fine" or "the section comment covers it." If the check says every field, check every field. If it says every error path, trace every error path.

Use a Task agent (model: haiku) for builds, shader compilation, linting, and other command execution — never run those directly from the main agent.

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0. Required files

Verify the lesson has all required pieces.

What to check:

• [ ] lessons//NN-name/README.md exists
• [ ] lessons//NN-name/main.c exists (GPU, physics, audio, engine

lessons) — asset lessons may use Python entry points instead

• [ ] lessons//NN-name/CMakeLists.txt exists (C lessons only — asset

lessons that are pure Python do not need one)

• [ ] lessons//NN-name/assets/screenshot.png exists (GPU, physics,

audio lessons) — not just a placeholder

• [ ] .claude/skills//SKILL.md exists (the matching skill)
• [ ] Root CMakeLists.txt includes add_subdirectory(lessons//NN-name)

(C lessons only)

• [ ] Root PLAN.md has the lesson checked off or added

Shader directory: Only required if the lesson has its own shaders beyond what forge_scene.h provides. GPU lessons using forge_scene.h for the rendering baseline do not need a shaders/ directory unless they add lesson-specific shaders.

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1. SDL GPU bool return checks (40+ PR comments historically)

This is the single most common PR finding. Every SDL function that returns bool must be checked. Search all .c and .h files in the lesson directory (not just main.c) for every SDL call and verify each one that returns bool has error handling.

Functions that return bool (non-exhaustive):

• SDL_Init
• SDL_ClaimWindowForGPUDevice
• SDL_SetGPUSwapchainParameters
• SDL_SubmitGPUCommandBuffer
• SDL_CancelGPUCommandBuffer
• SDL_UploadToGPUBuffer (via command buffer submit)
• SDL_WindowSupportsGPUSwapchainComposition
• SDL_SetGPUBufferName / SDL_SetGPUTextureName

Required pattern:

if (!SDL_SomeFunction(args)) {
    SDL_Log("SDL_SomeFunction failed: %s", SDL_GetError());
    /* clean up any resources allocated so far */
    return false; /* or SDL_APP_FAILURE */
}

What to check:

• [ ] Every SDL_SubmitGPUCommandBuffer call checks the return value
• [ ] Every SDL_SetGPUSwapchainParameters call checks the return value
• [ ] SDL_Init return is checked in SDL_AppInit
• [ ] SDL_ClaimWindowForGPUDevice return is checked
• [ ] Helper functions that call SDL submit propagate failure (return NULL or false)
• [ ] Failure paths log the function name and SDL_GetError()
• [ ] Failure paths clean up resources allocated before the failure point

How to search: Use Grep for patterns like SDL_Submit, SDL_SetGPUSwapchain, SDL_Init(, SDL_Claim across all .c and .h files in the lesson directory and verify each has an if (!...) wrapper.

Skip for: math lessons, engine lessons, UI lessons, asset lessons (no SDL GPU calls).

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2. Command buffer lifecycle (acquired from Lesson 24 review)

Every acquired command buffer must be either submitted or canceled. There is no automatic cleanup — an abandoned command buffer is a resource leak. This is C: if you acquire it, you release it, on every path.

Key SDL3 constraint: SDL_CancelGPUCommandBuffer is not allowed after a swapchain texture has been acquired on that command buffer. After swapchain acquisition, you must submit (even on error).

What to check:

• [ ] Every SDL_AcquireGPUCommandBuffer has a matching submit or cancel on

every code path that follows — including early returns from failed BeginRenderPass, failed ensure_* helpers, etc.

• [ ] Error paths before swapchain acquisition use

SDL_CancelGPUCommandBuffer(cmd)

• [ ] Error paths after swapchain acquisition use

SDL_SubmitGPUCommandBuffer(cmd) (submit the partial/empty command buffer)

• [ ] The !swapchain_tex (minimized window) path submits the empty

command buffer and returns SDL_APP_CONTINUE

Skip for: math, engine, UI, asset lessons.

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3. Magic numbers (20+ PR comments)

Every numeric literal that represents a tuning parameter, spec-defined default, buffer size, or domain constant must be a #define or enum at the top of the file (or in a shared header if reused).

What to check:

• [ ] No bare float literals used as thresholds, cutoffs, or defaults (e.g. 0.5f

alpha cutoff, 0.3f rotation speed, 50.0f light distance)

• [ ] No bare integer literals for array sizes, cascade counts, sample counts
• [ ] Spec-defined values cite the spec (e.g. /* glTF 2.0 sec 3.9.4 */)
• [ ] Sentinel values like 1e30f or FLT_MAX are named

(#define AABB_SENTINEL 1e30f)

• [ ] Mathematical constants like 2.0f in formulas are acceptable only when

they are inherent to the math (e.g. 2.0 * dot(N, I) in reflection) — but domain-specific multipliers should be named

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4. Resource leaks on error paths (15+ PR comments)

When initialization fails partway through, all resources allocated before the failure point must be released. This is C — no destructors, no RAII, no GC. If you allocate it, you must free it on every exit path.

What to check:

• [ ] Every early-return in init/load functions releases GPU buffers, textures,

and samplers allocated earlier in the same function

• [ ] gpu_primitive_count (or equivalent) is updated incrementally so cleanup

can release partial uploads

• [ ] Transfer buffer failures don't leak the destination GPU buffer
• [ ] Sampler creation failures don't leak previously created samplers
• [ ] Helper functions (e.g. upload_gpu_buffer, create_white_texture) return

NULL on failure and don't leak internal resources

• [ ] init_fail cleanup matches SDL_AppQuit cleanup — every resource freed

in SDL_AppQuit must also be freed in init_fail (including conditional resources like #ifdef FORGE_CAPTURE)

• [ ] ensure_* functions that destroy-then-recreate handle partial failure

(some resources recreated, some not) without leaking

Skip for: math, engine, UI, asset lessons (no GPU resources).

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5. Naming conventions (15+ PR comments)

Public API (in common/ headers): Prefix_PascalCase for types (e.g. ForgeGltfScene), prefix_snake_case for functions (e.g. forge_gltf_load).

Internal typedefs (in lesson main.c): PascalCase for struct typedefs (e.g. SceneVertex, VertUniforms, GpuPrimitive). This is the project convention, confirmed in .coderabbit.yaml and consistent across all lessons.

Local variables and app_state: lowercase_snake_case.

What to check:

• [ ] Public types in common/ use Forge prefix (e.g. ForgeGltfScene)
• [ ] Internal typedefs in main.c use PascalCase consistently

(e.g. VertUniforms, not vertUniforms or vert_uniforms)

• [ ] The app_state struct uses lowercasesnakecase (exception: it holds

all per-session state and is always lowercase by convention)

• [ ] Local helper functions use snake_case (not camelCase)
• [ ] #define constants use UPPER_SNAKE_CASE

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6. Per-field intent comments (15+ PR comments)

Every struct field needs an inline comment — no exceptions, no "the section header covers it." Section headers group related fields; inline comments explain each individual field's purpose, units, format, or valid range.

What to check:

• [ ] Uniform struct fields have inline comments (units, range, purpose)
• [ ] Vertex layout fields document their semantic meaning
• [ ] app_state fields each have an inline comment — not just section

headers. Every pipeline, texture, sampler, buffer, setting, and state variable gets its own comment explaining what it is, its format/units where applicable, and how it's used

• [ ] Push constant structs explain each member
• [ ] GPU type struct fields (e.g. GpuPrimitive, GpuMaterial, ModelData)

document each field

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7. Spec and documentation accuracy (5+ PR comments)

When referencing specifications (glTF 2.0, Vulkan, etc.) or external standards, the wording must match the spec's normative language.

What to check:

• [ ] "MUST" vs "SHOULD" vs "MAY" matches the source spec exactly
• [ ] Section numbers or clause references are correct
• [ ] Algorithm descriptions match the reference (not a paraphrase that changes

the meaning)

• [ ] External links are valid and point to the right section

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8. Skill documentation completeness (5+ PR comments)

The matching skill in .claude/skills//SKILL.md must have all required sections.

What to check:

• [ ] YAML frontmatter with name and description
• [ ] Overview paragraph explaining when to use the skill
• [ ] "Key API calls" section listing the SDL/math functions introduced
• [ ] "Correct order" or workflow section showing the sequence of operations
• [ ] "Common mistakes" section documenting gotchas
• [ ] "Ready-to-use template" or code skeleton

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9. README structure and content

What to check:

• [ ] Starts with # Lesson NN — Title
• [ ] Has "What you'll learn" section near the top
• [ ] GPU/physics/audio lessons: Has screenshot in a "Result" section near

the top (not a placeholder)

• [ ] Math lessons: "Result" section comes after "Building" (not near

the top) — math results are text output that would be intimidating before the lesson content

• [ ] GPU lessons only: If the lesson has shader files, has a "Shaders"

section immediately before "Building" that lists each shader file with a brief description of what it does

• [ ] Has "Building" section with build commands
• [ ] Has "AI skill" section linking to the skill
• [ ] Ends with "Exercises" section (3-4 exercises)
• [ ] "What's next" comes before "Exercises" (not after)
• [ ] No use of banned words: "trick", "hack", "magic", "clever", "neat"

(per CLAUDE.md tone principles)

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10. Concept introduction for new readers

Lessons are written for readers who know nothing unless a previous lesson taught it. Every concept, API, tool, or term that appears for the first time must be briefly defined in the README — or the README must link to the specific earlier lesson or engine/math lesson that introduced it.

What to check:

• [ ] Every SDL API function used for the first time in the lesson series is

briefly explained (what it does, why it is needed) — not just named

• [ ] Every graphics or GPU concept introduced for the first time (e.g.

swapchain, render pass, command buffer, pipeline, vertex buffer, shader, depth buffer) has a plain-language definition before or alongside its first use

• [ ] Domain-specific terms (e.g. "sRGB", "linear color space", "NDC",

"back-face culling") are defined when first used, or explicitly deferred with a note pointing to the future lesson that will cover them

• [ ] Links to engine lessons are provided where they offer deeper

background on foundational topics

• [ ] Links to math lessons are provided when the lesson uses math

concepts (vectors, matrices, coordinate spaces) for the first time

• [ ] No concept is used in the README or code comments with the implicit

assumption that "everyone knows what this is"

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11. main.c structure (from publish-lesson validation)

What to check:

• [ ] Uses #define SDL_MAIN_USE_CALLBACKS 1
• [ ] Implements all 4 callbacks: SDL_AppInit, SDL_AppEvent,

SDL_AppIterate, SDL_AppQuit

• [ ] Uses SDL_calloc for app_state allocation
• [ ] Includes error handling with SDL_Log on all GPU calls
• [ ] Window size is 1280x720 (16:9) — standard for consistent screenshots
• [ ] Has comprehensive comments explaining why and purpose, not just

what

• [ ] No bare C stdlib calls — use SDL-prefixed APIs where available

(SDL_fabsf, SDL_sinf, SDL_memset, etc.), and approved project wrappers for C99 functions SDL lacks (forge_isfinite, forge_fmaxf, forge_fminf)

Skip SDL_MAIN_USE_CALLBACKS check for: math, engine lessons that use main() directly.

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12. forge_scene.h usage (GPU, physics, audio lessons)

All GPU lessons, all physics lessons, and all audio lessons must use forge_scene.h for the rendering baseline (shadow map, Blinn-Phong, grid, sky, camera, UI). This eliminates hundreds of lines of boilerplate and ensures a consistent rendering foundation.

What to check:

• [ ] main.c includes #define FORGE_SCENE_IMPLEMENTATION followed by

#include "scene/forge_scene.h"

• [ ] app_state contains a ForgeScene scene field instead of individual

pipelines, textures, and samplers for the baseline rendering

• [ ] Rendering uses forge_scene_begin_frame / forge_scene_begin_shadow_pass

/ forge_scene_begin_main_pass / forge_scene_end_frame pattern

• [ ] No duplicate baseline shaders in the lesson's shaders/ directory

(scene, grid, shadow, sky, UI shaders are provided by forge_scene.h)

• [ ] Lesson-specific shaders (if any) serve a purpose beyond the baseline

Skip this check for: math, engine, UI, asset lessons.

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13. Markdown linting

Run the linter and resolve all issues.

npx markdownlint-cli2 "lessons//NN-name/**/*.md" ".claude/skills//SKILL.md"

Common issues from PR feedback:

• [ ] All code blocks have language tags (c, bash, text, hlsl)
• [ ] Display math uses 3-line format ($$\n...\n$$), not inline $$...$$
• [ ] Tables have consistent column counts
• [ ] No trailing whitespace or missing blank lines around headings

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14. Python linting (if scripts were modified)

If any Python scripts in scripts/ were added or modified:

uv run ruff check scripts/
uv run ruff format --check scripts/

• [ ] No lint errors from ruff check
• [ ] No format issues from ruff format --check
• [ ] Auto-fix with uv run ruff check --fix scripts/ && uv run ruff format scripts/ if needed

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15. Pyright type checking (if Python files were modified)

If any Python files in scripts/ or pipeline/ were added or modified:

uv run pyright

• [ ] No errors from pyright
• [ ] No private import usage (reportPrivateImportUsage)
• [ ] No unresolved imports (reportMissingImports)

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16. SDL stdinc compliance

Never use bare C stdlib calls when an SDL_ equivalent exists. This is a cross-platform portability requirement.

What to check:

• [ ] No bare C stdlib calls (fabsf, sinf, memset, strcmp, malloc,

etc.) when an SDL equivalent exists. Grep for bare names in .c and .h files and verify all matches use the SDL_ prefix.

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17. Build and shader compilation

Verify the lesson compiles and shaders are up to date.

For GPU, physics, and audio lessons (C with shaders):

python scripts/compile_shaders.py NN -v
cmake --build build --target NN-name

• [ ] Shaders compile to both SPIRV and DXIL without warnings
• [ ] Lesson builds with no errors or warnings
• [ ] Generated shader headers are up to date (not stale from a previous edit)

For math/engine lessons (C without shaders):

cmake --build build --target NN-name

• [ ] Lesson

…

Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: Nebulavenus
• Source: Nebulavenus/forge-gpu
• License: Zlib

Install and usage instructions live in the source repository linked above.