Claude Code port: skills this file names (for example how, why, unslop, arena, or a ... principle skill) are sibling skills in this plugin. They are user-invoked, so the Skill tool can't load them. To use one, read ${CLAUDE_SKILL_DIR}/../<name>/SKILL.md (principle skills: ${CLAUDE_SKILL_DIR}/../principle-<name>/SKILL.md) and follow it. Subagents use the Agent tool; valid model values are fable, opus, sonnet, haiku.
Separate Before Serializing Shared State
When concurrent actors might share mutable state, first ask whether they need the same mutable object. If not, eliminate the sharing. When sharing is real, enforce serialization structurally: lockfiles, sequential phases, exclusive ownership. Instructions and conventions are not concurrency control.
Why: Concurrent writes to shared state create race conditions that are intermittent, hard to reproduce, and expensive to debug.
Pattern:
- Identify shared mutable state (files both read and write, branches both push to, APIs both define and consume).
- Default: eliminate the shared write target. Ask: do these actors need one canonical object, or are they publishing independent facts? Give each actor its own owned file, key, branch, or state directory, and merge only at the read/reporting boundary. Two workers writing their own
lastX field into one state.json is still shared mutation. indexer-state.json + metrics-state.json is not.
- Only when one shared write target is a real invariant, serialize access structurally (lockfiles, sequential phases, single-writer actor, or atomic compare-and-swap). Treat "we need a lock" as a design smell to check, not as the default answer.
1---2name: principle-separate-before-serializing-shared-state3description: Apply when concurrent actors might write to the same file, branch, key, or state object. Eliminate the sharing first; serialize structurally only when one shared writer is a real invariant.4---56> **Claude Code port:** skills this file names (for example **how**, **why**, **unslop**, **arena**, or a **...** principle skill) are sibling skills in this plugin. They are user-invoked, so the Skill tool can't load them. To use one, read `${CLAUDE_SKILL_DIR}/../<name>/SKILL.md` (principle skills: `${CLAUDE_SKILL_DIR}/../principle-<name>/SKILL.md`) and follow it. Subagents use the Agent tool; valid `model` values are `fable`, `opus`, `sonnet`, `haiku`.78# Separate Before Serializing Shared State910When 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.1112**Why:** Concurrent writes to shared state create race conditions that are intermittent, hard to reproduce, and expensive to debug.1314**Pattern:**151. **Identify shared mutable state** (files both read and write, branches both push to, APIs both define and consume).162. **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.173. **Only when one shared write target is a real invariant, serialize access structurally** (lockfiles, sequential phases, single-writer actor, or atomic compare-and-swap). Treat "we need a lock" as a design smell to check, not as the default answer.
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