Apply before writing logic: choosing core types and data structures, sequencing scaffold-vs-feature work, asking what concurrent actors share. Get the data structures right so downstream code becomes obvious.
Collected from public GitHub. Every version is saved exactly as it was and never changes. Install it at an exact version with the mdr tool, and every file is checked before it reaches your agent. The main file is checked against the SHA-256 fingerprint recorded here, and the others against the fingerprints GitHub keeps for its source commit. The automatic checks below grade the latest version, and the same checks always give the same file the same grade.
What the file 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.
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The line at the top of this page pins the label git:20260825.847374d, which is what most people want. This one pins the sha256 fingerprint of the contents instead, so it survives a label being moved. Either way the exact version is written to mdr.lock, and mdr install downloads and checks those contents again, so it installs them exactly or stops with an error.
GET https://markdownregistry.com/api/v1/artifacts/art_3x4zdhxlfixfox27
GET https://markdownregistry.com/api/v1/resolve?ref=edbertchan/catstack/principle-foundational-thinking
GET https://markdownregistry.com/api/v1/blob/eecfdb1b627ab3dc51e3b03f57d573646fe72bf1909727f7be16439236f3443b
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edbertchan/catstack · corpus/skills/cat-mode/SKILL.md · Edbert's personal working conventions, mined from real session history across his projects. Use when Edbert asks to…
edbertchan/catstack · corpus/skills/principle-assert-invariants-not-last-bug/SKILL.md · Apply after a bug ships past review or a passing grade/check: assert the general class of failure instead of patching…
edbertchan/catstack · corpus/skills/principle-bind-to-named-inventory/SKILL.md · Apply after an audit, scoring review, or a request for a "real classifier" / "less arbitrary weights" when existing…
edbertchan/catstack · corpus/skills/principle-build-the-lever/SKILL.md · Apply to any non-trivial work, not just bulk work: edits, migrations, analyses, checks. Build the tool that does it or…
edbertchan/catstack · corpus/skills/principle-encode-lessons-in-structure/SKILL.md · Apply when you catch yourself writing the same instruction a second time, or notice a recurring correction. Encode the…
edbertchan/catstack · corpus/skills/principle-experience-first/SKILL.md · Apply when product, UX, or feature-scope tradeoffs come up. Choose user delight over implementation convenience; ship…
edbertchan/catstack · corpus/skills/principle-fix-root-causes/SKILL.md · Apply when debugging. Trace each symptom to its root cause and fix it there; reproduce first, ask why until you reach…
edbertchan/catstack · corpus/skills/principle-flag-your-own-corrections/SKILL.md · Apply whenever you are about to admit fault in any wording — a fact, number, claim, or check you already stated turns…
edbertchan/catstack · corpus/skills/principle-generalize-from-rejection/SKILL.md · Apply when a mechanical gate — a lint, validator, blocked-command guard, or CI check — rejects your output for the same…
edbertchan/catstack · corpus/skills/principle-guard-the-context-window/SKILL.md · Apply when context is filling up: large outputs, long files, repeated reads, fan-out planning. Route bulk to subagents…
