Module entry 

Log entry prefix identification and multi-line JSON accumulation.

Detects log entry boundaries using the [UnityCrossThreadLogger], [ConnectionManager], and Matchmaking: header patterns, then accumulates subsequent lines until the entry is structurally complete.

Header classification (Phase 1 of #153)

Each detected header is classified as either single-line or multi-line:

• Single-line: [UnityCrossThreadLogger] followed by anything other than a date digit (e.g., alpha labels like STATE CHANGED, Client.SceneChange, or ==> API request markers), [ConnectionManager]…, and Matchmaking:…. These entries are flushed in the same LineBuffer::push_line call that received them — no continuation accumulation.
• Multi-line: [UnityCrossThreadLogger]<digit> (date-prefixed API responses, match events). These entries accumulate continuation lines until the entry’s JSON body is structurally complete (brace-balance flush) or the next header arrives (fallback for non-JSON bodies).

Brace-balance flush (Phase 3 of #153 / #193)

Multi-line entries whose body contains a { are flushed the moment the brace depth returns to 0 — they no longer wait for the next header to arrive. A small state machine counts { and } while tracking string literals (") and backslash escapes (\\), so braces appearing inside JSON string values do not count. Corpus analysis (44 sessions, 47,412 multi-line entries) shows every entry that opens a { closes it within the entry boundary; bodies that never open a { (a few true-only REST responses and the EntryHeader::TruncationMarker entries whose follow-on :: ... Count = N lines carry no JSON braces) still flush on the next header via the original fallback path.

This behavior is enabled by default via the brace_depth_flush cargo feature. Disabling the feature reverts to the original “flush on next header” behavior for every multi-line entry — kept as a one-flip rollback in case a string-literal edge case surfaces in live Arena traffic.

Frame-counter prefix stripping (#240)

The newer MTGA Mac client (UTC_Log archive variant) prepends a monotonic Unity frame counter of the form [<digits>] to every line (e.g. [2841] [UnityCrossThreadLogger]…). LineBuffer::push_line strips this prefix before any byte-0-anchored detector runs, so the same log content parses identically whether or not it carries the prefix. Callers and tests need not pre-strip the counter.

Data flow

File Tailer ──(lines)──▸ LineBuffer ──(complete entries)──▸ Router

The LineBuffer receives individual lines from the file tailer, normalizes each line (strips the optional frame-counter prefix), then classifies and accumulates. When a new log entry header is detected, it flushes the previously accumulated lines as a complete LogEntry and either emits the new entry immediately (single-line class) or begins accumulating it (multi-line class).

Structs

LineBuffer

Accumulates raw lines and produces complete LogEntry values when an entry is structurally complete.

LogEntry

A complete log entry extracted from the line buffer.

Enums

EntryHeader

The known log entry header prefixes in MTG Arena’s Player.log.