---
title: Renaming various execution things
document: P4154R0
date: 2026-03-27
audience: LWG
reply-to:
  - "Tim Song <t.canens.cpp@gmail.com>"
  - "Ruslan Arutyunyan <ruslan.arutyunyan@intel.com>"
  - "Arthur O’Dwyer <arthur.j.odwyer@gmail.com>"
paper-type: proposal
---

# Introduction

This paper provides replacement wording for the following papers:

- [P3940R0]: Rename concept tags for C++26: `sender_t` to `sender_tag`
- [P4031R1]: Rename `system_context_replaceability` namespace

This resolves the following national body comment on the C++26 CD:

- [US 205-320](https://github.com/cplusplus/nbballot/issues/895)

and partially addresses the following national body comment on the C++26 CD:

- [RO 4-395](https://github.com/cplusplus/nbballot/issues/970)

Because there are multiple papers in flight targeting 33 [[exec]](https://eel.is/c++draft/exec), LWG requested replacement wording for renames to minimize merge conflicts.

# Wording

Instructions to the editor:

After applying *all other papers* moved during the Croydon meeting, please make the following replacements in 33 [[exec]](https://eel.is/c++draft/exec):

- Replace each instance of `sender_t` with `sender_tag`.
- Replace each instance of `scheduler_t` with `scheduler_tag`.
- Replace each instance of `operation_state_t` with `operation_state_tag`.
- Replace each instance of `system_context_replaceability` with `parallel_scheduler_replacement`.
- Replace each instance of `sysctxrepl` in a stable name with `parschedrepl`.
- Replace each instance of `receiver_t` **outside** [exec.continues.on]<sup>1</sup> with `receiver_tag`.
- In [exec.continues.on], replace `using receiver_concept = receiver_t;` with `using receiver_concept = receiver_tag;`.

# References

[N5032] Thomas Köppe. 2025-12-15. Working Draft, Standard for Programming Language C++.

[P3826R5] Eric Niebler. 2026. Fix Sender Algorithm Customization.

[P3940R0] Arthur O’Dwyer, Yi’an Ye. 2025-12-10. Rename concept tags for C++26: sender_t to sender_tag.

[P4031R1] Ruslan Arutyunyan. 2026. Rename `system_context_replaceability` namespace.

---

1. In particular, this cross-reference is after [P3826R5] has been applied (in the current working draft [N5032], the relevant wording is located in 33.9.12.7 [[exec.schedule.from]](https://eel.is/c++draft/exec.schedule.from)).↩︎