Three places, because the finding has three audiences.
The display spec's §1 table said FR-DSP-3 was unmeasured and FR-DSP-5 untagged.
Both are now false, and §2's decision rule has fired. The body of §2 is left as
written with the verdict quoted above it: a plan overtaken by its own evidence
reads better in order than quietly edited into agreement with the outcome.
TD-4 is the stage that misses the budget. Clarity's kernel is a fraction of the
frame, so it reaches a 52-pixel radius at 4K and costs 34 ms — seven times the
entire fused chain, for one slider. It is debt rather than a bug because the
detail stage cannot yet write a target smaller than it reads, which
`local_contrast`'s own documentation has said since it was written. The entry
says plainly that tiles are the wrong tool for it, since that is exactly the
conclusion a reader arriving from ARCH §5.3 would otherwise draw.
TD-5 is the one nobody was looking for: composing the fused shader costs
2.8–5.2 ms of CPU per frame on a full chain, on the UI thread, which at
1920x1200 is more than the dispatch it precedes. The source depends only on the
graph's structure — what `structure_hash` already identifies and what does not
move during a drag — so the fix is the cache `AdjustPass` already keeps for
compiled pipelines, one level up.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Three compromises were taken deliberately over the last few days and none of
them was written anywhere a future reader would look. So `docs/technical-debt.md`,
and two corrections to the architecture document that the Android change made
untrue the moment it landed.
**TD-1, the Android readback.** §12/6.1 says GPU results never round-trip
through the CPU, and the develop view on Android now does exactly that. That
is worth recording as a breach with reasons rather than quietly leaving a
constraint the code no longer honours — the next person to read §6.1 and then
`DevelopSession::render` would otherwise conclude one of them is a mistake.
The entry carries the device measurements that forced it, why setting
`preTransform` is not a fix available to us, and the three separate things any
one of which would remove it.
**TD-2 and TD-3**, the serial thumbnail fetch and the unbounded drain, were
found while chasing the tearing and are still outstanding. Both have a known
shape for the fix; neither is a bug, and neither should be discovered again
from scratch.
The architecture document said the app renders "through wgpu to Vulkan on both
Linux and Android", which stopped being true at 6267802, and §12/6.1 claimed a
constraint with no exceptions. Both now say what the code does and point at
the debt entry for why.
The numbers are labelled with what they are. TD-1's readback cost has *not*
been measured on the device and says so, and TD-3's figures are from a debug
build and say so — a documented measurement that quietly turns out to be the
wrong build is worse than no measurement.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
dtourolleandClaude Opus 5