a builder's codex
codex · operators · Simon Willison · ins_personal-pattern-hoarding

Hoard a personal repository of things that worked — coding agents will recombine them

By Simon Willison · Independent AI/engineering writer; co-creator of Django · 2026-04-02 · podcast · Simon Willison on agentic engineering and the November 2025 inflection — Lenny's Podcast

Tier A · TL;DR
Hoard a personal repository of things that worked — coding agents will recombine them

Claim

Maintain a public-or-private GitHub repo of every small thing you ship — tools, research scripts, one-off pages. When a new task comes in, point a coding agent at the repo and let it search, recombine, and adapt prior solutions instead of starting from scratch.

Mechanism

Coding agents are "phenomenally good at sticking to existing patterns." A local corpus of working code biases the agent toward your style, your conventions, and your past solutions. Search-over-corpus is now cheap; starting from a similar working artifact is faster and lower-defect than starting from a blank file. The corpus compounds: each new artifact joins the haystack and accelerates the next one.

Conditions

Holds when:

Fails when:

Evidence

"The code is cheap now."

Simon maintains two corpora: simonw/tools (193 small HTML/JS tools) and simonw/research (75 AI-driven research projects, each with a markdown report after running real code). Claude Code searches these to combine prior solutions for new problems.

— Simon Willison on Lenny's Podcast, 2026-04-02

Signals

Counter-evidence

A messy hoard is worse than no hoard — the agent picks up bad patterns. Karpathy's LLM-wiki pattern (An LLM should maintain a wiki, not re-derive knowledge per query) is the disciplined version: append-only raw, synthesized pages, explicit indexing. Without that discipline the corpus rots and recommends old approaches that the model has since obsoleted. The hoard must be re-pruned as model capability shifts.

Cross-references

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