Six per-match helpers in the scanner read the line around every match, so a line dense in matches costs the square of its length, independently of the generic-account check. (1) inAnySpan and atURLPathRoot scan the whole URL span list for every identity match, and atURLPathRoot searches each span from its start for the path root; (2) the footer SkipAt runs its line-prefix regex over the whole line before every footer match, and footerLinkTarget searches the rest of the line for the link; (3) isDottedNamespaceComponent walks and re-splits the whole dotted run for every login occurrence in it; (4) colonRunGroups walks and splits the whole hex/colon run for every address candidate in it. The cost meter's linearity guard (TestScanLineWorkIsLinear) measures 8-16x per quadrupling on each shape where linear work is 4x; wall-clock probes agree (a dotted run of a non-generic login, 8000 units: 35, 127, 479 ms). Pre-existing: none of these came in with the scanner cluster lane, and no guard reached them.

Six per-match helpers in the scanner read the line around every match, so a line dense in matches costs the square of its length, independently of the generic-account check. (1) inAnySpan and atURLPathRoot scan the whole URL span list for every identity match, and atURLPathRoot searches each span from its start for the path root; (2) the footer SkipAt runs its line-prefix regex over the whole line before every footer match, and footerLinkTarget searches the rest of the line for the link; (3) isDottedNamespaceComponent walks and re-splits the whole dotted run for every login occurrence in it; (4) colonRunGroups walks and splits the whole hex/colon run for every address candidate in it. The cost meter's linearity guard (TestScanLineWorkIsLinear) measures 8-16x per quadrupling on each shape where linear work is 4x; wall-clock probes agree (a dotted run of a non-generic login, 8000 units: 35, 127, 479 ms). Pre-existing: none of these came in with the scanner cluster lane, and no guard reached them.

Grounds

• pursued: the six helpers now do bounded or amortised work per match, so the scan is linear in line length; a TestScanLineWorkIsLinear shape growing past 6x per quadrupling would show it wrong.