hasCursorAgentReattachPayloadScreenSignal built a char-by-char copy of the
entire reattach payload so it could read the last header plus 5000 chars. On a
2MB daemon snapshot that cost 17.5ms of synchronous renderer main-thread work —
~75% of what xterm then spends parsing the same bytes — and the miss case paid
it in full for a result that is always false.
Two changes, both matching existing in-tree precedent: bound the scan to a
256KB tail (as the kitty tracker already bounds its own scan), and strip via
the shared precompiled CSI_SEQUENCE_PATTERN instead of a hand-rolled loop,
which is also faster in V8 because it copies spans rather than building a rope
per character.
2MB snapshot, header hit 17.5ms -> 0.80ms (22x)
2MB snapshot, miss 8.7ms -> 0.52ms (17x)
200KB snapshot, header hit 1.5ms -> 0.62ms (2.4x)
config/scripts/terminal-reattach-payload-scan-benchmark.mjs reproduces this and
asserts every candidate agrees with the baseline before timing it. It also
records a negative result: porting the daemon mouse mirror's includes()
pre-filter to the kitty tracker makes reattach slower, because snapshots always
contain the introducer.
Adds guards for the two behaviours a future shortcut would silently break: a
CSI-split header must still match, and a header behind the tail bound must not.
Also byte-pins POST_REPLAY_REATTACH_RESET_KEEP_MOUSE, which shipped unpinned.
Co-authored-by: Orca <help@stably.ai>
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