Surfaced during session-5 manual validation (probe #3, the bet-#1
shape from the framing pass): editing at a diagnostic boundary
left stale color fragments visible against now-different text. The
session-4 PR documented this as a "one-frame stale" artifact, but
in practice the LSP re-analysis window stretches the wrong-color
period to 100ms–5s — human-perceptible and confusing.
Mechanism: CrdtOp updates `current_text` but `current_spans` /
`current_decorations` still index into pre-edit byte positions.
`reshape()` paints them at those stale positions against the new
text, producing colored fragments over wrong characters until the
producer ships an updated frame. Between CrdtOp arrival and
clangd's next publishDiagnostics (LSP debounce + re-analysis), no
Decorations frame ships at all (the producer's
`changed_intervals(prev, curr)` sees identical sets because clangd
hasn't republished yet).
Fix: drop both vectors in the CrdtOp arm before `set_text`. Tree-
sitter re-emits StyleSpans within ~one frame; LSP decorations
re-emit when clangd republishes. Cost = a brief uncolored window
per edit. Gain = no wrong-position color persists.
Manual revalidation (post-rebase on #44 + #45 + #46):
edit-at-boundary in the TUI now drops the old diagnostic color
cleanly. New diagnostic colors paint once clangd republishes.
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
Levi Neuwirth
abd6f46eee