Pre-Execution Checklist

Before writing the first line of feature code, confirm all of these. Do not trade resolution for speed.

Environment health gate — run the project's health check script; do not proceed if it exits non-zero
Clean baseline — run lint and build; if either fails, fix it first. Never build on a broken base
Known-good state — confirm the working tree is clean or WIP is intentional
Relevant spec exists — read the spec for the thing being implemented; if none exists for a task over ~1 hour, write one first
Scope defined — list which files are in scope before touching anything
Done criteria agreed — negotiate a Sprint Contract: which specific files change, which commands prove it works, which user-visible behaviour confirms completion

Session Lifecycle

Three phases. Do not skip or collapse them.