codebase-design

A code-architecture design guide focused on modules with small interfaces that hide substantial behavior. An interface is the information callers need to use a module; a seam is a boundary where behavior can change without changing those callers.

In plain words
What is it for?
Choosing module boundaries, designing stable interfaces, and deciding when adapters or shared seams are justified by multiple independent implementations.
Why use it?
It helps keep policy in one place, reduce what callers must understand, and avoid splitting code into small pieces that merely move complexity around.

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/moontzai/folderbridge-mcp/codebase-design
Any agent
npx skills add MoonTzai/folderbridge-mcp --skill codebase-design
Clone the repo
git clone --depth 1 https://github.com/MoonTzai/folderbridge-mcp

Made for: Claude Code, Codex.

Per session 15 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 232 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 $0.00015 $0.00232
Opus 5 $0.00008 $0.00116
Sonnet 5 $0.00003 $0.00046
Haiku 4.5 $0.00002 $0.00023

Measured yesterday against content hash 63e8f4066bc4, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

codebase-design 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 yesterday.

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.

skill_packs/matt-pocock-engineering/skills/codebase-design/SKILL.md · 15 lines

What it actually says

Codebase Design — FolderBridge Adaptation

Use this when the problem is where a module's interface or seam should live, not merely how a function should be written.

Think in these terms: module is anything with an interface plus implementation; interface is everything callers must know, including invariants and failure modes; depth is how much useful behavior the implementation hides relative to interface complexity; a seam is a place where behavior can change without callers changing; an adapter translates another interface into that seam; leverage is benefit per fact callers must learn; locality keeps related decisions together.

Prefer deep modules: small stable interfaces that own substantial policy. Use the deletion test: if deleting a proposed module merely scatters the same knowledge across callers, the module was providing leverage; if deletion barely changes what callers must know, it may be shallow ceremony.

Treat the interface as the durable test surface. One adapter can justify a hypothetical seam; two independent adapters are stronger evidence the seam is real.

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. yesterday First seen · 15 lines · 15 tokens per session scan A 63e8f4066bc4

Subscribe to this mod's changes

codebase-design is a skill published in the GitHub repository MoonTzai/folderbridge-mcp (0 stars, last pushed yesterday), licensed Apache-2.0. It adds 15 tokens to every session and 232 once invoked, about $0.0001 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 2026-08-31.

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