Addresses the deferred half of PR #767 review issue 2: instead of just
documenting the "0/N misreport" with a logger.warning, propagate the
caller's None for chunk_index through the dataclass, position markers,
and response builders so callers can distinguish "unknown position"
from "actually chunk 0".
Changes:
- ChunkContext.chunk_index: int → int | None
- _insert_position_markers: chunk_index parameter is int | None; when
None, renders "Chunk ?/N" instead of "Chunk 1 of N"
- get_chunk_with_context: drops the effective_chunk_index local entirely.
Passes chunk_index (may be None) directly into both ChunkContext and
_insert_position_markers, in both the Qdrant fast path and the
doc-text fallback.
- Fast path: when chunk_index is None and chunk_text was retrieved via
the offset lookup (notes/cards), skip the adjacent-chunk fetch.
Index arithmetic from a default 0 would query the chunks at positions
-1 and 1 even when the actual chunk is, say, 5/20 — silently producing
wrong "before"/"after" text. Mark both sides as truncated instead.
- Drop the now-redundant logger.warning in the doc-text fallback (the
response correctly communicates the unknown state via chunk_index=None).
Both existing response builders (`api/visualization.py:657` and
`auth/viz_routes.py:717`) already serialise `chunk_context.chunk_index`
unconditionally; `None` becomes JSON `null`. No route changes needed.
Adds 5 regression tests:
- ChunkContext.chunk_index propagates as None in fast path
- ChunkContext.chunk_index propagates as None in doc-text fallback
- Fast path with chunk_index renders "Chunk N of M" correctly
- _insert_position_markers renders "?/N" for None chunk_index
- _insert_position_markers renders explicit index when supplied
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
