---
model: openai/gpt-5.6-sol
service: opencode
session: pr490-landing-review
timestamp: 2026-08-28T01:42:47Z
git_ref: wkt/fix_broadcast_lag_count
scope: code
substantive: true
raw_file: 20260828T014247Z_d06ee34b_prompt_io.raw.md
---

## Prompt

Prime PR #490 for landing, review its concurrent broadcast changes,
fix valid findings, and keep the landing pass focused.

## Response summary

Rejected an invalid mutable-default finding under `msgspec.Struct`
semantics. Found and fixed a close-time race where concurrent receives
on one `BroadcastReceiver` could overwrite its sole cancellation scope
and strand an earlier waiter. The receiver now rejects overlapping
calls with `trio.BusyResourceError`. Public docs now define each
receiver as one logical subscription cursor and require one receiver
per concurrent lossless consumer. Busy errors identify the active Trio
task which owns the receiver.

## Files changed

- `tractor/trionics/_broadcast.py` - reject concurrent receives on one
  receiver handle.
- `tests/test_task_broadcasting.py` - prove the second call fails while
  the original receive remains usable.
- `docs/guide/streaming.rst` - document per-task receiver ownership and
  explicit lag behavior.

## Human edits

The human selected PR #490 as the next landing target, rebased it onto
current `main`, directed the agent to continue the landing pass, and
required a faster, tightly scoped execution after the review expanded.
The human then confirmed the per-receiver guard and required the public
method, type, and surrounding guide to emphasize lossless per-consumer
semantics. The human also required the regression's checkpoint loop to
explain its synchronization and the busy error to report the active
consumer task. The agent applied the source, test, and documentation
changes; no direct manual edits to these files were identified.
