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).
The backend shipped dual-channel mode; wire the client to it. We already capture
mic (you) and system (others) separately, so send them as two files instead of the
mono mix — fixing the misattribution at the source.
- SparkControlClient: labelMergeDual(mic_file, system_file, self_name, self_vad);
multipart generalized to N files; shared POST/retry/decode extracted.
- SessionPackager.rebasedSelfVadData: chunk-local [{start,end}] for self_vad;
sliceAudio reused for both tracks.
- TranscriptPipeline.process: dual-channel chunking (slice mic+system, rebase
timeline + self_vad per chunk) when system audio is healthy; mono mixed-file
fallback (self folded into the timeline) otherwise.
- VisualCapture.finish: write the full visual_timeline.json (remote + self merged)
but return REMOTE (vision) segments only — self travels via the mic channel.
- TranscriptAssembler: rank mic_channel highest (the user's own track wins).
- VoiceprintStore: store the clean mic_channel self voiceprint.
- SessionController: pass mic/system URLs + remote timeline + channel self-spans +
self_name + systemHealthy; self_vad.json now reflects the channel-verified spans.
Validated END-TO-END against the live backend on the real misattributing session:
'Go Bitcoin' (remote) is now attributed to Unknown_0, NOT the user; the user's own
lines come back source=mic_channel; per-channel ASR recovered fuller remote text.
36/36 XCTest (4 new: self_vad rebase, mic_channel ranking + voiceprint storage).
Grant Gilliam