principle-foundational-thinking

principle-foundational-thinking is a skill for Claude Code from michael-denyer/pstack-claude. It costs 42 tokens per session (338 once invoked), scanned A, a copy of principle-foundational-thinking, MIT.

A set of design rules for writing code, especially for choosing data structures, ordering setup and feature work, and handling shared state between concurrent actors. It emphasizes making the data shape clear before adding behavior.

In plain words
What is it for?
Use it when starting a feature, choosing core types, designing concurrent code, or deciding what work should come first. It also guides testing behavior and edge cases without encouraging premature abstractions.
Why use it?
Early structural choices affect every later part of a program, while shared state can cause bugs when multiple actors change it at once. These rules help expose those decisions before they become expensive to change.

Skill for Claude Code

Written for Claude Code: user-invocable in frontmatter.

Part of the pstack plugin — 54 skills, 2 agents, 1 hook shipped together

Good fit Use it when starting a feature, choosing core types, designing concurrent code, or deciding what work should come first. It also guides testing behavior and edge cases without encouraging premature abstractions.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/michael-denyer/pstack-claude/principle-foundational-thinking
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.

Any agent
npx skills add michael-denyer/pstack-claude --skill principle-foundational-thinking
Clone the repo
git clone --depth 1 https://github.com/michael-denyer/pstack-claude

Made for: Claude Code.

Or install pstack, the plugin that ships this one along with the rest of its 54 skills, 2 agents, 1 hook.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for principle-foundational-thinking

README.md
[![agentmods](https://agentmods.dev/badge/skills/michael-denyer/pstack-claude/principle-foundational-thinking.svg)](https://agentmods.dev/skills/michael-denyer/pstack-claude/principle-foundational-thinking)
Your own site
<a href="https://agentmods.dev/skills/michael-denyer/pstack-claude/principle-foundational-thinking"><img src="https://agentmods.dev/badge/skills/michael-denyer/pstack-claude/principle-foundational-thinking.svg" alt="Measured on agentmods" height="20"></a>
Per session 42 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 338 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin 95% copy Near-identical to another mod 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 5.1 $0.00042 $0.00338
Opus 5 $0.00021 $0.00169
Sonnet 5 $0.00008 $0.00068
Haiku 4.5 $0.00004 $0.00034

Measured 8d ago against content hash afd90c29cd4e, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-07, from the pricing page.

Security

Grade A, and why

principle-foundational-thinking 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 8d 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.

Origin

This is a copy

95% identical to principle-foundational-thinking — 2 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.

plugins/pstack/skills/principle-foundational-thinking/SKILL.md · 22 lines

What it actually says

Foundational Thinking

Structural decisions protect option value. Code-level decisions protect simplicity. Over-engineering is often a premature decision that closes doors. The right foundational data structure keeps doors open.

Data structures first. Get the data shape right before writing logic. The right shape makes downstream code obvious. Define core types early, trace every access pattern, and choose structures that match the dominant paths. A data-structure change late is a rewrite. Early, it is often a one-line diff.

At code level, DRY the structure, not every line. Types and data models should converge. Three similar statements still beat a premature abstraction. Prefer explicit over clever. Test behavior and edge cases, not line counts.

Concurrency corollary. Before sharing state between actors, ask "what happens if another actor modifies this concurrently?" If not "nothing", isolate.

Scaffold first. If something helps every later phase, do it first. Ask "does every subsequent phase benefit from this existing?" CI, linting, test infrastructure, and shared types are scaffold. Sequence for option value: setup before features, tests before fixes. Keep commits small and single-purpose.

Each increment should land a coherent abstraction or deepen one that exists. Do not spread a new capability across callers as special-case coordination.

Subtraction comes before scaffolding: remove dead weight first, then lay foundations.

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. 8d ago First seen · 22 lines · 42 tokens per session scan A afd90c29cd4e

Subscribe to this mod's changes

principle-foundational-thinking is a skill published in the GitHub repository michael-denyer/pstack-claude (232 stars, last pushed yesterday), licensed MIT. It adds 42 tokens to every session and 338 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 0 findings. It is 95% identical to principle-foundational-thinking, differing in 2 lines, and is treated as a copy.

Related

Other skills, from other repositories

systematic-debugging

Use when encountering any bug, test failure, or unexpected behavior, before proposing fixes.

obra/superpowers · 21 tokens

local-ai-agents

Build local-first AI agents that run entirely on a developer workstation with Microsoft Foundry Local and Qwen function-calling models. Covers Small Language Models (SLMs), the OpenAI-compatible local endpoint, sandboxed local tools, local RAG with Chroma, local MCP servers, hybrid cloud/local routing, and the…

microsoft/ai-agents-for-beginners · 200 tokens

next-cache-components-adoption

Turn on Cache Components in a Next.js app and resolve the blocking routes it surfaces. Use when the user wants to enable, adopt, or migrate to Cache Components, flip the cacheComponents flag, work through a flood of blocking-prerender / instant validation errors, run the cache-components-instant-false codemod, or…

vercel/next.js · 95 tokens

next-partial-prefetching-adoption

Turn on Partial Prefetching in a Next.js app and work through the insights it surfaces. Use when the user wants to enable or adopt Partial Prefetching, flip the partialPrefetching flag, opt routes in with export const prefetch = 'partial', audit Link prefetch={true} behavior, preserve existing prefetched UI with…

vercel/next.js · 103 tokens

chronicle

Analyze Copilot session history for standup reports, usage tips, session search, and session reindexing. Use when the user asks for a standup, daily summary, usage tips, workflow recommendations, wants to search or find past sessions by keyword/file/PR, wants to reindex their session store, or asks about deleting…

microsoft/vscode · 72 tokens

babysit-pr

Babysit a GitHub pull request after creation by continuously polling review comments, CI checks/workflow runs, and mergeability state until the PR is merged/closed or user help is required. Diagnose failures, retry likely flaky failures up to 3 times, auto-fix/push branch-related issues when appropriate, and keep…

openai/codex · 114 tokens