ly-wang19 435edbd8c6
fix(artifacts): offload blocking filesystem IO in artifact serving (#3551)
get_artifact ran its filesystem work directly on the event loop: virtual-path
resolution (os.path.abspath via .resolve()), exists/is_file probes, MIME sniffing
(mimetypes lazily stats the system MIME DB on first use), full-file
read_text/read_bytes, is_text_file_by_content (open+read), and .skill ZIP
open+extract. So serving any artifact blocked the loop for the whole read;
`make detect-blocking-io` flagged it. Same class as #3457 / #3529.

Offload each branch's IO via asyncio.to_thread: one sync helper per branch
(_load_skill_archive_member, _read_artifact_payload) folds stat + MIME + read /
extract into a single worker hop and returns a small (kind, mime, payload) plan
the handler turns into the response on the loop. FileResponse (download / active
content) keeps streaming the file itself. Behavior, branching, error codes, and
security boundaries are unchanged.

Add tests/blocking_io/test_artifacts_router.py anchor (text / binary / .skill
member), verified red->green under the strict Blockbuster gate. The gate also
caught a blocking call the static scan missed: resolve_thread_virtual_path's
.resolve() (os.path.abspath), now offloaded too.

Co-authored-by: ly-wang19 <ly-wang19@users.noreply.github.com>
Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
2026-06-24 10:44:46 +08:00
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