Summary
With agent-device 0.20.6, an Android snapshot -i --json --force-full request can finish successfully in the daemon and the CLI can exit 0 while emitting zero bytes on stdout.
A caller that correctly treats --json stdout as the response then has no snapshot envelope to parse, even though agent-device recorded the request as successful.
Observed evidence
Command shape:
agent-device snapshot -i --json --force-full --platform android
In a session with the expected Android app foregrounded:
- the CLI process exited 0;
- captured stdout was an empty string;
- the session event log recorded one
snapshot request with status: ok and durationMs: 9646;
- no interaction command ran;
- an independent snapshot immediately afterward returned a complete JSON envelope for the unchanged screen:
success=true, 13 visible nodes, truncated=false, visibility.partial=false.
This was observed after upgrading both the client and daemon to 0.20.6. It is separate from Android helper content failures: the request was not reported as COMMAND_FAILED, and the outer caller received neither an error envelope nor a typed error.
Expected
When --json is requested, exit code 0 always emits one complete success JSON envelope on stdout. If a response cannot be serialized or flushed, the CLI should exit nonzero with a typed error.
Actual
The command can exit 0 with empty stdout even though the daemon records the request as successful.
Likely boundary
The generic success path writes JSON through process.stdout.write, while explicit failure/early-exit paths use the exitAfterFlush helper. The retained evidence cannot prove whether the response was dropped before the writer or during process shutdown, so this is a boundary hypothesis rather than a claimed root cause.
Suggested regression
Run the real CLI as a piped child process against a stub/local daemon success response and assert:
- exit code is 0;
- stdout is non-empty;
- stdout parses as JSON;
- the envelope has
success === true;
- the child does not resolve until the full payload has been read.
A companion negative should force stdout/serialization failure and assert a nonzero typed failure rather than exit 0 with an empty payload.
Summary
With agent-device 0.20.6, an Android
snapshot -i --json --force-fullrequest can finish successfully in the daemon and the CLI can exit 0 while emitting zero bytes on stdout.A caller that correctly treats
--jsonstdout as the response then has no snapshot envelope to parse, even though agent-device recorded the request as successful.Observed evidence
Command shape:
In a session with the expected Android app foregrounded:
snapshotrequest withstatus: okanddurationMs: 9646;success=true, 13 visible nodes,truncated=false,visibility.partial=false.This was observed after upgrading both the client and daemon to 0.20.6. It is separate from Android helper content failures: the request was not reported as
COMMAND_FAILED, and the outer caller received neither an error envelope nor a typed error.Expected
When
--jsonis requested, exit code 0 always emits one complete success JSON envelope on stdout. If a response cannot be serialized or flushed, the CLI should exit nonzero with a typed error.Actual
The command can exit 0 with empty stdout even though the daemon records the request as successful.
Likely boundary
The generic success path writes JSON through
process.stdout.write, while explicit failure/early-exit paths use theexitAfterFlushhelper. The retained evidence cannot prove whether the response was dropped before the writer or during process shutdown, so this is a boundary hypothesis rather than a claimed root cause.Suggested regression
Run the real CLI as a piped child process against a stub/local daemon success response and assert:
success === true;A companion negative should force stdout/serialization failure and assert a nonzero typed failure rather than exit 0 with an empty payload.