fable-native-code

A coding guide for matching the existing style of a software project. It covers choices such as naming, formatting, comments, error handling, validation, and logging.

In plain words
What is it for?
It helps edit an existing codebase so additions fit its established conventions and comments explain only constraints that the code itself cannot show.
Why use it?
It prevents new code from adding patterns that do not belong in the surrounding files, such as unnecessary comments, checks, or error handling.

Skill for Claude CodeCodex

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add skills/dizzymii/fable-skills/fable-native-code
Any agent
npx skills add DizzyMii/fable-skills --skill fable-native-code
Clone the repo
git clone --depth 1 https://github.com/DizzyMii/fable-skills

Made for: Claude Code, Codex.

Per session 52 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,040 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00052 $0.01040
Opus 5 $0.00026 $0.00520
Sonnet 5 $0.00010 $0.00208
Haiku 4.5 $0.00005 $0.00104

Measured 2d ago against content hash f6c9c75300e2, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

fable-native-code scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

skills/fable-native-code/SKILL.md · 104 lines

How it starts

The opening of the file, as written. The whole thing — 104 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Native Code

Overview

Your diff should read like the file's longtime owner wrote it. The file has a style — naming, error handling, comment density, formatting. Write in it. Your personal preferences are not improvements; they're an accent.

Rules

  1. Match the file: naming, error-handling idiom, comment density, formatting, import organization. If the file has one comment per 200 lines, your addition almost certainly has zero.
  2. Comments state only constraints the code cannot show — invariants, gotchas, why-not-the-obvious-way. Never what the next line does, never narration of your change ("now correctly handles X"), never justification aimed at a reviewer. Test: after the PR merges, is this comment information or noise?
  3. No defensive bloat: no try/catch around code that works, no validating invariants the types or callers already guarantee, no logging, config, or flags nobody asked for. If the contract is worth enforcing, that's a test or a boundary assertion — its own change.
  4. Don't narrate your restraint. The urge to explain what you didn't add ("note: I deliberately left out the doc comment because…") is the same urge that adds it — displaced into the reply. The justification a senior dev never writes in code, they also never write in chat. Deliver the code; mention style only if the user asks.
  5. Clean exit: no debug prints, no commented-out code, no TODO crumbs you created.
  6. Names come from the codebase's existing vocabulary. Don't coin a second name for an existing concept.

Contrast

Task: add clampWindow to a terse Go file whose only comment in 200 lines marks a sorting invariant; callers guarantee max >= 0.

Foreign (your habits, not the file's):

// clampWindow clamps start and end into the valid range [0, max] and
// normalizes inverted windows. Returns (start, start) when end < start.
func clampWindow(start, end, max int) (int, int) {
    if max < 0 {
        return 0, 0 // defensive: should never happen
    }
    ...
}

Read the full file on GitHub · 104 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 2d ago First seen · 104 lines · 52 tokens per session scan A f6c9c75300e2

Subscribe to this mod's changes

fable-native-code is a skill published in the GitHub repository DizzyMii/fable-skills (51 stars, last pushed 1mo ago), licensed MIT. It adds 52 tokens to every session and 1,040 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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