Cross Cutting Concerns

Concern	Rule
Cancellation	Every keystroke sends $/cancelRequest for the previous search. Daemon loops check ctx.Done(); the webview drops responses with an older seq
Offsets	Every Span, Range and Hit counts UTF-16 code units, like JavaScript and VS Code
Regexes	RE2 (Go regexp): linear time, no backreferences or lookaround
Limits	Queries up to 1,000 characters; count:all stops at 50,000 and reports truncated
Crashes	The host restarts the daemon after a pause that doubles from 200 ms to 30 s, at most 3 times a minute, then offers a Restart button. A daemon that stops answering while requests wait is killed and restarted the same way
Observability	SPELUNK_TRACE=<file> records the JSON-RPC transcript; the extension logs to the "Spelunk" output channel
Testing	Each contract has its own tests, so a change breaks the cheapest layer first. See Testing

Performance budgets (p95)

Path	Budget
Keystroke → chips and diagnostics	15 ms
Keystroke → first working-tree results	100 ms after the typing delay
Keystroke → first history results	250 ms after the typing delay
Select → preview	50 ms
File saved → findable	1 s
New commit → findable by author:	5 s

scripts/checkBudgets.mjs checks benchmark output against these on every release.