Attachments copied into a local computer's workspace were read whole from
the artifact store first, so a 500 MiB video sat in memory before it was
written to disk. attach_file did the same in the other direction: a large
file on a local computer was read whole before it was stored.
SandboxProvider gains optional readFileStream/writeFileStream. The desktop
(host workspace) provider implements them with the same path confinement
as its byte methods, one chunk in memory at a time, and removes a file
whose write fails or is aborted, including one that replaced an earlier
copy. The host-aware wrapper routes them, and providers without them
(remote computers, still capped at 12 MiB) receive the collected bytes.
Current-turn staging and attach_file now go through these helpers, and
unread streams are cancelled so the stored file is released. Media job
inputs stop copying when the job is cancelled.
The stream helpers move from the local artifact store into a shared
module so both use one implementation.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01MRtGG9ARfqqhma3t85Ro2u
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