fix: download sandbox logs in PrimeRuntime.run to avoid read-file 10MB limit

[mikasenghaas]

Summary

• PrimeRuntime.run polled get_background_job, which reads the job's stdout/stderr logs inline via the SDK's read_file → gateway /read-file endpoint. That endpoint caps reads at 10MB and returns HTTP 413 (File size (...) exceeds max read size (10485760 bytes). Use /download instead). Any command emitting >10MB of output (e.g. a verbose test runner) therefore killed the whole rollout with SandboxError: prime exec failed: Read file failed: HTTP 413 ....
• Fix: poll the tiny exit file directly with read_file, then fetch stdout/stderr via download_file (no size limit) once the job completes. This mirrors read(), which already downloads to dodge this exact limit. The download is factored into a shared _download_bytes helper that read() now reuses.

This is a latent bug for any env whose program emits >10MB on stdout/stderr; it surfaced first in scaleswe_v1 (its pytest -vv scorer produced ~28MB of stdout).

Verification

Before: a scaleswe-v1 rollout whose scorer emitted 28MB of stdout failed with

SandboxError: prime exec failed: Read file failed: HTTP 413 GET .../read-file?path=%2Ftmp%2Fjob_d370cedb.stdout.log: {"error":"File size (28135205 bytes) exceeds max read size (10485760 bytes). Use /download instead."}

After: stdout/stderr are downloaded rather than read inline, so the 10MB read-file cap no longer applies. (No behavior change for small output; the background-job wrapper always creates both log files via redirection, so the download cannot 404.)

🤖 Generated with Claude Code

Note

Download sandbox logs in PrimeRuntime.run to avoid the 10MB read-file limit

• Replaces the get_background_job polling approach in prime.py with direct polling of the job's exit file via client.read_file, parsing the exit code from its contents.
• After detecting job completion, stdout and stderr are fetched via a new _download_bytes helper that uses client.download_file to a temp location, bypassing the gateway's inline read-file size limit.
• Refactors PrimeRuntime.read to delegate to the same _download_bytes helper for consistency.
• Behavioral Change: run now returns stdout/stderr decoded from downloaded files rather than inline API responses; large log outputs that previously failed or were truncated will now be returned in full.

^{Macroscope summarized 8d5cc55.}