bug: failed to run container process received unexpected message: InitReady, expected: IntermediateReady(0)

[yyquiet]

Version Info

• boxlite: v0.8.2
• OS: Windows + WSL2

Describe the bug

When running consecutive or concurrent exec commands against the same sandbox, the operation fails with the error:
failed to run container process received unexpected message: InitReady, expected: IntermediateReady(0)

Details

• Concurrent test cases: error occurs probabilistically
• Rapid serial test cases: error occurs probabilistically when interval between exec calls is short
• Only occurs when targeting the same sandbox
• Same test cases pass without issues on macOS

Steps to Reproduce

1. Create a single sandbox
2. Run multiple boxlite exec commands concurrently on the same sandbox OR Run multiple boxlite exec commands in rapid sequence on the same sandbox
3. Error occurs immediately

Test cases

async def exec_task(task_id: int):
    result = await sandbox.exec("sh", "-c", f"echo 'Task {task_id}'")
    assert result.success
    assert f"Task {task_id}" in result.stdout
    return task_id

tasks = [exec_task(i) for i in range(10)]
results = await asyncio.gather(*tasks)

local_path = "/local/uploaded.txt"
remote_path = "/root/uploaded.txt"
await sandbox.exec("test", "-e", remote_path)
temp_remote = "/var/tmp/temp.txt"
await sandbox.exec("mkdir", "-p", "/var/tmp")
await sandbox.copy_in(local_path, temp_remote, overwrite=True)
await sandbox.exec("test", "-f", temp_remote)
remote_dir = os.path.dirname(remote_path)
if remote_dir:
    await sandbox.exec("mkdir", "-p", remote_dir)
result = await sandbox.exec("mv", temp_remote, remote_path)
if result.exit_code != 0:
    await sandbox.exec("rm", "-f", temp_remote)

Expected Behavior

exec commands should run successfully without errors in both concurrent and rapid serial scenarios.

Error Log

2026-04-08T07:12:32.434677Z ERROR libcontainer::container::builder_impl: failed to run container process received unexpected message: InitReady, expected: IntermediateReady(0)
2026-04-08T07:12:32.435128Z ERROR boxlite_guest::container::command: zygote build failed container_id=66996230db2d83b9819e8d76748eeb0e4c230e74788984998d16756126a6fea2 program=test args=["test", "-e", "/mnt/data/uploaded_to_volume.txt"] error=internal error: build failed: failed to create container: received unexpected message: InitReady, expected: IntermediateReady(0)