j-star-films-studios Engineering Principles Suite
A catalogue of 21 foundational principles for software architecture, code quality, state management, and agentic workflows.
Principles Catalog
Read the specific principle file via view_file on demand when applying its rule:
| Principle | When to Apply | File Path |
|---|---|---|
boundary-discipline |
Apply when wiring validation, error handling, or framework adapters. Concentrate guards at system boundaries (CLI, config, network, external APIs); trust internal types and keep business logic in pure functions. | boundary-discipline/SKILL.md |
build-the-lever |
Apply to any non-trivial work, not just bulk work: edits, migrations, analyses, checks. Build the tool that does it or proves it (codemod, script, generator, or a skill your subagents follow) instead of working by hand. The tool is the artifact a reviewer can rerun. | build-the-lever/SKILL.md |
encode-lessons-in-structure |
Apply when you catch yourself writing the same instruction a second time, or notice a recurring correction. Encode the rule as a lint, metadata flag, runtime check, or script instead of more text. | encode-lessons-in-structure/SKILL.md |
exhaust-the-design-space |
Apply when facing a novel UI interaction or architectural decision with no precedent in the codebase. Build 2-3 competing prototypes and compare side by side before committing. | exhaust-the-design-space/SKILL.md |
experience-first |
Apply when product, UX, or feature-scope tradeoffs come up. Choose user delight over implementation convenience; ship fewer polished features over more rough ones. | experience-first/SKILL.md |
fix-root-causes |
Apply when debugging. Trace each symptom to its root cause and fix it there; reproduce first, ask why until you reach it, resist nil-check guards that silence crashes. | fix-root-causes/SKILL.md |
foundational-thinking |
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. | foundational-thinking/SKILL.md |
guard-the-context-window |
Apply when context is filling up: large outputs, long files, repeated reads, fan-out planning. Route bulk to subagents; keep summaries in the main thread, not raw payloads. | guard-the-context-window/SKILL.md |
laziness-protocol |
Apply when refactoring, evaluating diff size, or tempted to add abstractions, layers, or signal threading. Bias toward deletion and the smallest change that solves the problem. | laziness-protocol/SKILL.md |
make-operations-idempotent |
Apply when designing commands, lifecycle steps, or processing loops that run amid crashes, restarts, and retries. Converge to the same end state regardless of partial prior runs. | make-operations-idempotent/SKILL.md |
migrate-callers-then-delete-legacy-apis |
Apply when introducing a new internal API while old callers still exist. Migrate callers and delete the old API in the same wave instead of preserving compatibility layers. | migrate-callers-then-delete-legacy-apis/SKILL.md |
minimize-reader-load |
Apply when reviewing or shaping code that's hard to trace. Count layers between question and answer, and hidden state in the reader's head; collapse one-caller wrappers and shrink mutable scope. | minimize-reader-load/SKILL.md |
model-the-domain |
Apply when writing stateful logic, or when code branches a lot or repeats a shape assumption across files. Encode the domain in a structure instead of scattered conditionals. | model-the-domain/SKILL.md |
never-block-on-the-human |
Apply when tempted to ask 'should I do X?' on reversible work. Proceed, present the result, let the human course-correct after the fact; reserve confirmation for irreversible actions. | never-block-on-the-human/SKILL.md |
outcome-oriented-execution |
Apply during planned rewrites and migrations with explicit phase boundaries. Converge on the target architecture; don't preserve smooth intermediate states with throwaway compatibility code. | outcome-oriented-execution/SKILL.md |
prove-it-works |
Apply after completing a task, before declaring done. Verify against the real artifact (run the feature, read the actual value, inspect the diff), not a proxy, self-report, or 'it compiles.' | prove-it-works/SKILL.md |
redesign-from-first-principles |
Apply when integrating a new requirement into an existing design. Redesign as if the requirement had been a foundational assumption from day one, instead of bolting it on. | redesign-from-first-principles/SKILL.md |
separate-before-serializing-shared-state |
Apply when concurrent actors might write to the same file, branch, key, or state object. Eliminate the sharing first; serialize structurally only when one shared writer is a real invariant. | separate-before-serializing-shared-state/SKILL.md |
sequence-verifiable-units |
Apply to multi-step work (sweeps, migrations, runs of similar edits) and to how you stack commits and PRs. Break work into small units that each end in a verifiable state, check each before the next, and order delivery so the sequence proves itself to a reviewer. | sequence-verifiable-units/SKILL.md |
subtract-before-you-add |
Apply when sequencing an addition, refactor, or rewrite. Remove dead weight, redundant validators, and stub references first, then build on the simpler base. | subtract-before-you-add/SKILL.md |
type-system-discipline |
Apply when designing types, reviewing a function signature, or writing code in any statically-typed language. Make illegal states unrepresentable, brand semantic primitives, parse external data at boundaries, refuse to lie to the compiler, exhaust variants, derive from authoritative schemas. | type-system-discipline/SKILL.md |