---
model: openai/gpt-5.6-sol
service: opencode
session: 7b9c97c4-fff7-4ac4-97fb-35720453308e
timestamp: 2026-08-20T15:02:50Z
git_ref: pformat_caller_frame_render_guard
scope: code
substantive: true
raw_file: 20260820T150250Z_9afda1c6_prompt_io.raw.md
---

## Prompt

Fix both newly exposed send-side `MsgTypeError` formatting failures
and pin them with an end-to-end regression in PR #503.

## Response summary

Corrected codec-spec formatting and default error-message assembly so
`_mk_send_mte()` returns a printable error instead of raising another
formatter exception.

## Files changed

- `tractor/msg/_codec.py` - pass the codec to its supported formatter.
- `tractor/_exceptions.py` - assemble the default message as `str`.
- `tests/devx/test_pformat.py` - render the complete default error.

## Human edits

The human selected both one-line fixes and the single end-to-end test
as coherent additions to PR #503, while leaving broader formatter
cleanup out of scope.