Chunks were contiguous (start = prev end) with a naïve offset-concat stitch — no
overlap. That cut sentences at boundaries, denied the diarizer context at edges, and
let one voice split across chunks (the MH/Unknown_0 problem). Now each ~150s body is
sliced with a 15s margin on both sides ([bodyStart-15, bodyEnd+15]); the stitcher
keeps a segment only in the chunk that owns its MIDPOINT (body region) and drops it
from the neighbour's margin — so boundary-spanning speech is seen whole by the
backend and kept exactly once.
- SessionPackager.PlannedChunk gains bodyStart/bodyEnd; planChunks adds overlapSeconds.
- TranscriptAssembler.ChunkResult carries body bounds (defaults keep-all → no-overlap
behaviour preserved for existing callers); assemble dedups by midpoint-in-body.
- TranscriptPipeline passes body bounds through.
Complements (doesn't replace) the fragment-smoothing + reconciliation safety nets;
this is the upstream fix. ~+20% backend audio per interior chunk. 63/63 XCTest
(new: overlap window layout + boundary-segment dedup).
Grant Gilliam
ab910cf742