This file is byte-identical to the first copy the registry indexed, one of 6 indexed copies. Same content hash, so the same checks give both the same grade.
principle-separate-before-serializing-shared-state from backnotprop/pstack is an agent skill: a SKILL.md folder an AI agent loads when a task calls for it.
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.
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
# Separate Before Serializing Shared State
When concurrent actors might share mutable state, first ask whether they need the same mutable object. If not, eliminate the sharing. When sharing is real, enforce serialization structurally: lockfiles, sequential phases, exclusive ownership. Instructions and conventions are not concurrency control.
**Why:** Concurrent writes to shared state create race conditions that are intermittent, hard to reproduce, and expensive to debug.
**Pattern:**
1. **Identify shared mutable state** (files both read and write, branches both push to, APIs both define and consume).
2. **Default: eliminate the shared write target.** Ask: do these actors need one canonical object, or are they publishing independent facts? Give each actor its own owned file, key, branch, or state directory, and merge only at the read/reporting boundary. Two workers writing their own `lastX` field into one `state.json` is still shared mutation. `indexer-state.json` + `metrics-state.json` is not.
…
The line at the top of this page pins the label git:20260914.55bfdc2, 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.
A 17 of 17 checks passed. Fixed automatic checks with no AI involved, so the same checks give the same answer every run.
pass: Frontmatter block present
pass: Frontmatter declares a name
pass: Frontmatter declares a description
pass: Size between 200 bytes and 200 KB (1565 bytes)
pass: No zero-width or bidi control characters
pass: No instruction hidden inside an HTML comment
pass: No link to an exfiltration or paste host
pass: No credential-shaped string
pass: No instruction to send local credentials anywhere
pass: No text hidden with inline styles
pass: No prompt-injection phrasing
pass: No curl or wget piped into a shell
pass: No recursive delete of root, home or parent
pass: No instruction to read or print local credentials
pass: No base64 blob over 200 characters
pass: No link to a raw IP address
pass: No script tag
Source
GitHub
backnotprop/pstack · 3,337 stars · license MIT · pushed 2026-10-28 · branch main
API
GET https://markdownregistry.com/api/v1/artifacts/art_rtgclznlm3kz2zjw
GET https://markdownregistry.com/api/v1/resolve?ref=backnotprop/pstack/principle-separate-before-serializing-shared-state
GET https://markdownregistry.com/api/v1/blob/05294b40448e927c5da1c7b6f5c6b9fed3744637e3833d2d948b9154a9dd00bb
Your AI assistant does the legwork. You hear about the deals worth your word. Hand yours the standing instructions at modelranch.com and it joins the network that reads files like this one.
backnotprop/pstack · automations/benny/skills/reproduce-and-fix-issues/SKILL.md · Reproduce triaged Slack bugs through a configured app-control adapter, verify existing fixes, and open a bounded draft…
backnotprop/pstack · automations/benny/skills/setup-benny/SKILL.md · Configure Benny and prepare its triage and repro automations. Use when installing Benny or changing its Slack, tracker…
backnotprop/pstack · skills/architect/SKILL.md · Sketch types, signatures, and module structure before code, then stay in the loop while implementation fills in. Use…
backnotprop/pstack · skills/arena/SKILL.md · Spawn N parallel candidates at the same task, pick a base, graft the strongest parts of the losers into it. Use for…
backnotprop/pstack · skills/automate-me/SKILL.md · Use for "automate me", "create/update/refresh my -mode skill", "turn/capture my preferences or working style into a…
backnotprop/pstack · skills/benchmark-checklist/SKILL.md · Vet a perf measurement (limiter, tuning, limits, errors, repeatability, relevance, and whether the work happened)…
backnotprop/pstack · skills/blast-radius/SKILL.md · Find what a change could break somewhere else before it ships, beyond the diff, and prove the one fact it's safe…
backnotprop/pstack · skills/correct/SKILL.md · Find the mistakes agents keep repeating in this repo and make each one impossible. Try architecture first, then types…
backnotprop/pstack · skills/create-formal-verification-skill/SKILL.md · Generate a project-local skill that formally verifies the code where a bug costs the most and tests reach the least, in…
backnotprop/pstack · skills/create-verification-skill/SKILL.md · Generate a project-local verification skill that drives your app the way a user does — any language, framework, or…
cursor/plugins · harness/pstack/claude-code/skills/principle-separate-before-serializing-shared-state/SKILL.md · Apply when concurrent actors might write to the same file, branch, key, or state object. Eliminate the sharing first…
cursor/plugins · pstack/skills/principle-separate-before-serializing-shared-state/SKILL.md · Apply when concurrent actors might write to the same file, branch, key, or state object. Eliminate the sharing first…
nightly-labs/openbot · marketplace/production-catalog/bundles/pstack/skills/principle-separate-before-serializing-shared-state/SKILL.md · Apply when concurrent actors might write to the same file, branch, key, or state object. Eliminate the sharing first…
michael-denyer/pstack-claude · plugins/pstack/skills/principle-separate-before-serializing-shared-state/SKILL.md · Apply when concurrent actors might write to the same file, branch, key, or state object. Eliminate the sharing first…
iap/pstack-hermes · skills/principle-separate-before-serializing-shared-state/SKILL.md · Apply when concurrent actors might write to the same file, branch, key, or state object. Eliminate the sharing first…
j-star-films-studios/vibecode-protocol-suite · assets/.agent/skills/engineering-principles/separate-before-serializing-shared-state/SKILL.md · Apply when concurrent actors might write to the same file, branch, key, or state object. Eliminate the sharing first…
barbieri/local-openfinance · .agents/skills/principle-separate-before-serializing-shared-state/SKILL.md · Apply when concurrent actors might write to the same file, branch, key, or state object. Eliminate the sharing first…
theonlyfusioncube/potetos-for-everyone · skills/principle-separate-before-serializing-shared-state/SKILL.md · Eliminate unnecessary sharing or partition ownership before adding locks, queues, or coordination. Use when…
