principle-encode-lessons-in-structure

A design principle for turning repeated instructions or recurring corrections into rules enforced by code, metadata, checks, or automation. It prefers mechanisms that prevent an error rather than more text telling people to avoid it.

In plain words
What is it for?
Use it when the same bug, correction, or instruction appears repeatedly, to decide whether it should become a type constraint, lint rule, runtime check, helper, or script.
Why use it?
Rules in prose can be missed, while structural checks can catch the same mistake consistently and closer to its source.

Skill for Claude CodeCodex

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.

agentmods
npx agentmods add skills/backnotprop/pstack/principle-encode-lessons-in-structure
Any agent
npx skills add backnotprop/pstack --skill principle-encode-lessons-in-structure
Clone the repo
git clone --depth 1 https://github.com/backnotprop/pstack

Made for: Claude Code, Codex.

Per session 49 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 475 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found 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 $0.00049 $0.00475
Opus 5 $0.00024 $0.00237
Sonnet 5 $0.00010 $0.00095
Haiku 4.5 $0.00005 $0.00047

Measured 2d ago against content hash 4acdb3f466ef, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

principle-encode-lessons-in-structure 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 2d 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

Copies of this mod

4 near-identical copies found in the catalogue:

skills/principle-encode-lessons-in-structure/SKILL.md · 32 lines

What it actually says

Encode Lessons in Structure

Encode recurring fixes in mechanisms (tools, code, metadata, automation) instead of textual instructions. Every error, human correction, and unexpected outcome is a learning signal. Capture it, route it, and close the loop.

Why: Textual instructions are easy to miss. They require the reader to notice, remember, and comply. Structural mechanisms (lint rules, metadata flags, runtime checks, automation scripts) enforce the rule without cooperation.

Pattern: When you catch yourself writing the same instruction a second time:

  1. Ask: can this be a lint rule, a metadata flag, a runtime check, or a script?
  2. If yes, encode it. Delete the instruction
  3. If no (genuinely requires judgment), make the instruction more prominent and add an example of the failure mode

Pick the strongest rung. When more than one mechanism would work, choose the strongest the situation allows (an unrepresentable state that cannot compile, then a lint or banned API that fails CI, then a canonical helper, then a runtime check), because agents copy whatever the surrounding code already does and a weaker guard becomes the next template.

Corollary: Don't paper over symptoms. If the fix is structural, ONLY use the structural fix. The instruction IS the symptom.

Feedback loop:

  • Capture every correction. When the human intervenes or tests fail, decide if it's a one-off or a pattern.
  • Route to the right layer. One-off -> brain note. Recurring fix -> skill or lint rule. Systemic issue -> principle.
  • Close the loop. Don't just record. Apply now or create a concrete todo.

Anti-patterns:

  • Acknowledging without recording ("I'll keep that in mind" does not persist)
  • Recording without routing (a brain note about a lint rule that should exist is wasted unless the lint rule gets implemented)
  • Fixing without generalizing (fixing one instance while leaving the recurring pattern intact)
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. 2d ago First seen · 32 lines · 49 tokens per session scan A 4acdb3f466ef

Subscribe to this mod's changes

principle-encode-lessons-in-structure is a skill published in the GitHub repository backnotprop/pstack (181 stars, last pushed 13d ago), licensed MIT. It adds 49 tokens to every session and 475 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.