[sfroment]

Summary

-        binary_data = b"Binary data: \x00\x01\x02\x03\xff\xfe\xfd"
-        fs.write_file("/tmp/binary.bin", binary_data, encoding="base64")
-        file_info = fs.read_file("/tmp/binary.bin", encoding="base64")
+        binary_data = b"Binary data: \x00\x01\x02\x03\xff\xfe\xfd"
+        fs.write_file("/tmp/binary.bin", binary_data)
+        file_info = fs.read_file("/tmp/binary.bin", encoding=None)
         assert binary_data == file_info.content

encoding="base64" means two different things across executor generations: the legacy JSON routes take raw bytes and encode them; the streamed /files routes (executor v0.0.24+) decode content that is base64 text. The example passed raw bytes, so against the streamed routes it hit base64.b64decode(raw) → Incorrect padding.

The example pins koyeb/sandbox:slim, which sandbox-container CI rebuilds from main on every merge — so it always runs the streamed routes (that's exactly what turned the reconciler sandbox-suite red on merge). So drop the base64 dance and showcase the binary-safe routes directly: raw bytes in, raw bytes out with encoding=None. Executor v0.0.24+ required, same as stat() and streamed writes.

Evidence

• Before: reconciler e2e, staging pods ...-fra-ccqck/sbq67/zrnnt, Oct 28:

  File ".../koyeb/sandbox/filesystem.py", line 130, in _put_body
    return base64.b64decode(content)
binascii.Error: Incorrect padding
SandboxFilesystemError: Failed to write file: Incorrect padding

• After: the example modules driven end-to-end through the real SandboxFilesystem/AsyncSandboxFilesystem against stateful fakes:

[streamed(v0.0.24+) sync] PASS   disk=b'Binary data: \x00\x01\x02\x03\xff\xfe\xfd'  (real bytes on disk)
[streamed(v0.0.24+) async] PASS   disk=b'Binary data: \x00\x01\x02\x03\xff\xfe\xfd'
[legacy(JSON)         sync] expected-raise  UnicodeDecodeError  ← v0.0.24+ by design
[legacy(JSON)         async] expected-raise  UnicodeDecodeError

• pytest koyeb/sandbox → 372 passed

Merge Danger

Door: two-way

Blast Radius: examples only — no library code touched; revert is trivial. The reconciler sandbox-suite flow goes green on the next run after this lands. On pre-v0.0.24 executors the example now raises instead of round-tripping — unreachable in practice since the pinned :slim tag tracks main, but note the write failure there surfaces as a raw UnicodeDecodeError rather than the SDK's "requires v0.0.24+" error; a cleaner legacy guard for bytes writes might be worth a follow-up in the SDK itself.