usageTokensLogPattern top-level property
The pinned one-line shape (AC7): every field documented in gh-1241,
compact JSON, fixed key order. source is the segment's marker (I3).
Implementation
final RegExp usageTokensLogPattern = RegExp(
r'^fa-tokens: \{"sessionId":"[^"]*","segment":[0-9]+,'
r'"input":[0-9]+,"output":[0-9]+,"cacheRead":[0-9]+,'
r'"requests":[0-9]+,"source":"(reported|estimated|mixed)"\}$',
);