GPU attach-path robustness batch from the repo audit. All three live in
pmacs-gpu; no protocol or daemon change.
F-003 — a daemon built without `--features crdt` advertises
`crdt_replica`/`semantic_render` as false in its `Hello`; negotiation then
"succeeds" but no BufferSnapshot ever arrives and the window hangs on
`(connecting...)`. The daemon already tells us its capabilities in Hello,
so check them client-side right after the handshake and fail with an
actionable in-window line ("daemon lacks CRDT support — restart it built
with --features crdt") instead of hanging. New CapabilityMismatch error +
missing_capabilities() + window_status(). No AttachResponse/daemon change.
F-008 — the outbound FrontendEvent queue was an unbounded mpsc, so a
stalled daemon grew memory without bound and replayed stale
viewport/pointer traffic on recovery. Replace it with a bounded,
coalescing Outbox (Mutex + Condvar): a Viewport or Pointer{Drag} whose
kind matches the queue tail replaces it (collapsing scroll/drag floods to
O(1) without reordering across a click or key), everything else is
appended lossless, and a lossless append past OUTBOX_MAX fails fast
(closes the outbox → clean disconnect/resync) rather than silently drop a
CrdtOp and desync the optimistic replica.
F-007 — the completion dropdown grew upward by n*row_height with no clamp,
so a short window rendered rows above y=0 with the selection off-screen.
Add mb_dropdown_window(n, selected, band_top) → (first, count): clamp the
count to rows that fit (hide when not even one fits, so top_y is never
negative) and scroll to keep the selection visible. glyphon's existing
TextBounds clip the scrolled-out rows; the buffer is still shaped once, so
no per-resize re-shape. The whole-fits path is (0, n) — byte-identical to
before.
Framing/as-built: docs/gpu-attach-robustness-framing.md.
Validated: fmt clean; clippy -p pmacs-gpu --all-targets clean; 51
pmacs-gpu unit tests pass (9 new across the three findings), incl. the two
headless render tests on the local Vulkan adapter. Still needs a human
eyeball (non-CRDT banner; tiny-window dropdown; normal attach renders).
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_014TXbAwk27agwhrNNrhLi2U
Levi Neuwirth
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