The ternary rule treats every ? as the start of a conditional expression and waits for a : to close it. Nullish coalescing therefore opens a meta.ternary-if.js scope that never closes, corrupting highlighting for the rest of the file — including past </script> when the grammar is embedded in HTML:

const x = a ?? b
// everything after this line is mis-highlighted

Before (gtm scope output — note the two unclosed scopes swallowing the next line):

a <meta.ternary-if.js><keyword.operator.ternary.js>?</keyword.operator.ternary.js><meta.ternary-if.js><keyword.operator.ternary.js>?</keyword.operator.ternary.js> b
const leak = "a string parsed inside meta.ternary-if.js…"

After:

a <keyword.operator.logical.js>??</keyword.operator.logical.js> b
<storage.modifier.js>const</storage.modifier.js> leak <keyword.operator.assignment.js>=</keyword.operator.assignment.js> <string.quoted.double.js>…</string.quoted.double.js>

Changes:

• Guard the ternary begin pattern: (?<!\?)\?(?!\?|\.(?![0-9])) — it no longer matches ?? or optional chaining ?., but still matches a ?.5 : b, where the . belongs to the number (matching the spec's tokenizer lookahead for ?.).
• Scope the modern operators: ?? and ?. (ES2020), ??=/&&=/||= as keyword.operator.assignment.compound.logical.js (ES2021), ** and **= (ES2016).
• Numeric separators (1_000_000, ES2021) and BigInt literals (123n, 0xFF_EEn, ES2020) in all four number rules.
• Regular expression flags s (ES2018), d (ES2021), v (ES2024).

Verified by running TextMate's gtm parser over a test file covering each construct plus regressions (plain and nested ternaries, signed numbers, .5 literals).