Verification of spawn_stream_json_reader

Function Signatures

Primary public function (src/emitter.rs:98-100)

pub fn spawn_stream_json_reader(transcript_path: PathBuf, start_offset: u64) -> StreamJsonHandle

Testable variant with writer injection (src/emitter.rs:103-116)

pub fn spawn_stream_json_reader_to(
    transcript_path: PathBuf,
    start_offset: u64,
    writer: Box<dyn Write + Send + 'static>,
) -> StreamJsonHandle

Both return a StreamJsonHandle containing:

drain_tx: mpsc::SyncSender<()> - channel to signal "drain then exit"
join_handle: thread::JoinHandle<()> - thread handle for joining/waiting

Retry Logic Verification (src/emitter.rs:127-149)

Confirmed: 50ms retries up to 5 seconds are correctly implemented.

The retry logic in stream_json_reader_loop works as follows:

5-second deadline: let deadline = std::time::Instant::now() + Duration::from_secs(5);
Retry loop with 50ms sleep: thread::sleep(Duration::from_millis(50));
On File::open failure:
- First checks for drain signal via drain_rx.try_recv() → exit if received
- Then checks if 5-second deadline expired → exit if timed out
- Otherwise sleeps 50ms and retries
On success: break f exits the retry loop with the opened File

The logic correctly handles:

File appearing mid-retry (opens and continues)
Drain signal during retry (exits immediately)
Timeout after 5 seconds (exits, file never appeared)

mpsc Channel Drain Verification (src/emitter.rs:157-194)

Confirmed: The function correctly drains to the mpsc channel.

The channel usage:

Creation: mpsc::sync_channel(1) - bounded sync channel with capacity 1
Normal mode: Continuously reads lines and writes to writer
Drain signal: Sending () via drain_tx sets draining = true, causing the loop to finish the current line then exit
Immediate exit: Dropping StreamJsonHandle without sending causes Disconnected error → immediate return

Summary

All acceptance criteria verified:

✅ Function signature documented (takes PathBuf transcript path and u64 start_offset, returns StreamJsonHandle)
✅ 50ms/5s retry logic confirmed in reader loop
✅ mpsc channel drain logic confirmed correct
✅ No code changes required

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