# seeded-determinism-and-golden-vectors

> Claude/Codex skill by [@zakariaf](https://omgskills.com/library/zakariaf/index.md) · 61 stars · Updated 2026-09-23

Enforces reproducible derived content — output every device must compute identically from a key, with no server. The key is injected, never read from a clock; a calendar-day key is a civil date, not an instant, and one day definition serves every comparison; the seed is a specified hash plus a mix step feeding a PRNG you own, never \`dart:math\`'s \`Random\`; entropy has exactly one source, so no \`DateTime.now()\`, no ambient \`Random()\`, no ordering by \`identityHashCode\`; content is regenerated from (key, generatorVersion) rather than stored; a shipped generator is frozen and an improvement is a versioned cutover, never an in-place edit that rewrites history; and it is pinned by a committed golden-vector table of fingerprints from an independent oracle, regenerated only by a reviewed command CI verifies but never blesses. Use when generating content from a seed or date, writing or regenerating golden vectors, versioning a generator, or debugging output that differs between devices or runs.

Tags: agent-skills, ai-agents, best-practices, claude-code, codex, coding-agent, cursor, dart, dartlang, developer-tools, drift, flutter, flutter-architecture, github-copilot, go-router, llm, material-design, mvvm, riverpod, skills

## Install

```sh
git clone https://github.com/zakariaf/Flutter-Skills /tmp/Flutter-Skills && ln -s /tmp/Flutter-Skills/skills/seeded-determinism-and-golden-vectors ~/.claude/skills/seeded-determinism-and-golden-vectors
```

## From README

Seeded determinism and golden vectors Some output must be a pure function of a key: the daily pick every user compares with their friends, a procedurally generated layout, a shareable result someone else can verify. It has to come out identical on every device, in every timezone, on the platform build you ship next year — with no server to arbitrate. That is a stronger property than "the tests pass", and it needs its own discipline plus a frozen oracle to keep it. testing-strategy owns how you test pure logic (seeded fuzz against an independent oracle, injected Clock). This skill owns what makes the output reproducible in the first place, and the committed vector table that pins it. A golden vector is not a golden image. Vectors are data fingerprints for a pure generator, asserted by dart test with no widget binding; reference PNGs of rendered UI belong to widget-golden-and-a11y-testing, and re-blessing them is the separate ritual in run-goldens-rebaseline.

## Links

- HTML page: https://omgskills.com/library/zakariaf/flutter-skills/skills/seeded-determinism-and-golden-vectors/
- GitHub: https://github.com/zakariaf/Flutter-Skills
- Author: [@zakariaf](https://omgskills.com/library/zakariaf/index.md)

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