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record_projection_snapshot in leeguooooo/claude-code-usage-bar

The author described this change as “fix(predict): 旧高频快照一次性重抽稀——不然 300KB 文件要拖 8 小时才瘦身”. It counts as a record because the check below fails on the code as it stood at 06a604980 and passes on a704f1d28, with nothing else changed between the two runs.

Projectleeguooooo/claude-code-usage-bar
Fix saved2026-07-10
Sharing licenceMIT · LICENSE
Change size+20 −0

What the code was meant to do, written into the code itself as a docstring

Append a (used, projected) snapshot for offline backtesting. Throttled to one per window per SNAPSHOT_MIN_GAP_S: unthrottled, every compute appended one (observed live: 0.4s average gap), so the 1000-entry cap covered 8.5 MINUTES of history — useless for backtesting — while the ~150KB of snapshots were re-parsed and re-written by the daemon every second, its single largest CPU line.

The change

2828 break
2929 snaps.append(snap)
3030 del snaps[:-MAX_PROJECTION_SNAPSHOTS]
31+ # One-shot migration for stores written before throttling existed: a
32+ # legacy list holds ~1000 entries at 0.4s spacing, and at one append per
33+ # minute they'd take ~8 hours to age out — keeping the file fat the whole
34+ # time. Re-decimate in place whenever the grid is violated.
35+ last_by_window: Dict[str, float] = {}
36+ kept = []
37+ for entry in snaps:
38+ if not isinstance(entry, dict):
39+ continue
40+ w = str(entry.get("window") or "")
41+ at = _coerce(entry.get("observed_at"))
42+ if at is None:
43+ continue
44+ prev_at = last_by_window.get(w)
45+ if prev_at is not None and at - prev_at < SNAPSHOT_MIN_GAP_S:
46+ continue
47+ last_by_window[w] = at
48+ kept.append(entry)
49+ if len(kept) != len(snaps):
50+ snaps[:] = kept
3151 return store

The check that tells the two apart

fail→pass·tests/test_projection.py::test_legacy_dense_snapshots_are_redecimated_on_append

Check file tests/test_projection.py, taken without changes from the fix and copied onto the older code, so the exact same check runs against both versions.

Origin and history

The fixa704f1d289af18ab2107fb2ba92e0e9745b80f5a
The code before it06a604980fab78a26e599b8564d8bf2c2887578d
Broken version dated2026-07-10
Moduleclaude_statusbar.predict
Units changedrecord_projection_snapshot
Fingerprinta884558cd831290b
Checked2026-08-18 by goldset/0.1

Every field above is generated by our program. None of it is written by hand.

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