fix(memory): prevent infinite loop in chunk_text when overlap rewinds start#3027
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fix(memory): prevent infinite loop in chunk_text when overlap rewinds start#3027
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When rfind("\n\n") found a match near the beginning of the sliding window,
`end` advanced by fewer bytes than CHUNK_OVERLAP_CHARS. The subsequent
`end.saturating_sub(CHUNK_OVERLAP_CHARS)` produced a value less than the
current `start`, and `ceil_char_boundary` returned a position behind it.
The old safeguard (`if start >= end`) did not fire because new_start <
start < end, so `start` regressed and the loop ran forever.
Fix: guarantee forward progress by taking `end` when `new_start <= start`.
This was the root cause of 100% CPU / GB RAM consumption at startup: the
embed backfill spawned background tasks for unembedded messages (including
an 85 KB tool_result), all of which entered the infinite loop simultaneously,
saturating all tokio worker threads and blocking log flushing.
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Summary
chunk_textinzeph-memoryhad an infinite loop triggered by messages whererfind("\n\n")found a match very early in the 1600-byte sliding windowendadvanced by fewer bytes thanCHUNK_OVERLAP_CHARS; the overlap subtraction produced anew_startbehind the currentstartif start >= end) did not fire becausenew_start < start < end, sostartregressed and the loop ran foreverstart = if new_start > start { new_start } else { end }— always guarantees forward progressRoot Cause Evidence
macOS
sampleprofiler on the live zeph process (CPU: 1126%, RAM: ~1 GB) showed all 12 tokio worker threads stuck in:SQLite confirmed 12 unembedded messages, including an 85 KB
tool_result(line-numbered Rust source). The embed backfill spawned background tasks for all of them at startup; all entered the infinite loop simultaneously, saturating the thread pool and blocking log flushing — explaining both the CPU/RAM spike and the frozen TUI status ("Connecting tools...").Test plan
cargo nextest run -p zeph-memory --lib— 1114 tests passcargo +nightly fmt --check— cleancargo clippy -p zeph-memory -- -D warnings— clean