---
model: openai/gpt-5.6-sol
service: opencode
session: ses_3e4c90d3eafeqHEtRYSIHgHhpA
timestamp: 2026-08-18T19:30:03Z
git_ref: bf06b4f8
scope: code
substantive: true
raw_file: 20260818T193003Z_bf06b4f8_prompt_io.raw.md
---

## Prompt

Cancel a remote task when its caller is cancelled after `Start`
publication but before startup acknowledgement. Keep cancellation
bounded, prevent its private `_cancel_task` RPC from recursively
cancelling itself and preserve public target kwargs unchanged.

## Response summary

Add private portal startup policy, use it for non-recursive context
cancellation and clean caller-side startup state under a shield.

## Files changed

- `tractor/runtime/_portal.py` - separate private startup policy.
- `tractor/_context.py` - disable recursion for cancellation RPCs.
- `tractor/runtime/_runtime.py` - clean cancelled task startup.
- `tests/test_context_stream_semantics.py` - control cancellation
  between `Start` publication and acknowledgement.

## Human edits

The human required this cancellation behavior to remain a distinct
commit from general startup failures and from the public `to_actor`
API. The human also requested that its runtime comment describe the
actual length-prefixed transport guarantee and concrete `_cancel_task`
operation rather than referring to an unnamed wrapper.