The desktop payloads shipped the builder's full uv cache (2.0GB mac,
1.1GB win-x64, 800MB win-arm64) so a mutable-venv rebuild could run
offline. But the bundle contract never needed offline rebuilds — it
needs rebuilds that never invoke a compiler: packages with no
downloadable wheel (sdist-only or platform gaps) would otherwise
demand Xcode CLT/MSVC/Rust on the user's machine.
prune_uv_cache_to_built keeps only what the builder compiled itself,
detected from the cache's own records (sdists-v9 entries, cached
wheels not listed in uv.lock, archive-v0 buckets by dist-info) and
drops the ~245 packages whose wheels PyPI re-serves in seconds.
Validated live on a clean host per target:
- macos arm64 (iris, no uv): 2.0GB -> 3MB; sync online, 0 builds,
pilk/psutil/alibabacloud-tea installed from the slim
- win11 arm64 (promise, no uv/MSVC): 800MB -> 48MB; sync online,
0 dependency builds, all 12 CI-built packages (cryptography,
httptools, brotlicffi, dependency-injector, ruamel-yaml-clib,
obstore, davey, firecrawl-anydoc, pilk, psutil, alibabacloud set)
import clean. The kept set matched the CI build log's Built list
exactly (12/12, no false positives).
Index-dir detection is name-agnostic (pypi/ vs custom --index-url
hashed dir), proven by the rewritten bundle test: sdist-only survives
the slim, downloadable wheels are dropped, the build machine's cache
is untouched, and an online rebuild compiles nothing.
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