# Follow-up meeting on REP 0157: Monday, 16 November 2026

**URL:** <https://discourse.openrobotics.org/t/follow-up-meeting-on-rep-0157-monday-16-november-2026/59725>\
**Category:** Projects\
**Created:** [November 12, 2026, 7:30am UTC](https://discourse.openrobotics.org/t/follow-up-meeting-on-rep-0157-monday-16-november-2026/59725 "2026-11-12T07:30:53Z")\
**Posts on this page:** 1\
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**Author:** ![ahcorde](https://sea2.discourse-cdn.com/flex022/user_avatar/discourse.openrobotics.org/ahcorde/32/36216_2.png) [@ahcorde](https://discourse.openrobotics.org/u/ahcorde)\
**Post date:** [November 12, 2026, 7:30am UTC](https://discourse.openrobotics.org/t/follow-up-meeting-on-rep-0157-monday-16-november-2026/59725/1 "2026-11-12T07:30:53Z")

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# Follow-up meeting on REP 0157: Monday, 16 November 2026

Hi everyone,

We held a dedicated meeting on **REP 0157** on 4 November and kept the discussion going afterwards. There are still open topics, so we’re holding a **follow-up meeting** before Michel Hidalgo leaves. Anyone interested in REP 0157 is welcome to join.

## When

**Monday, 16 November 2026 at 9:30 AM PST** (17:30 UTC)

Your local time: 2026-11-16T17:30:00Z

[Add the event to your calendar](https://calendar.google.com/calendar/event?action=TEMPLATE&tmeid=NDIzbTFoZTM0cnYxaWlkZGx0YzdiNTdhcTcgYWdmM2thamlya2V0OGtoa3R1cG05Z283NDhAZw&tmsrc=agf3kajirket8khktupm9go748%40group.calendar.google.com)

## What is REP 0157?

REP 0157 redesigns the `rosidl` messaging system so that ROS 2 gets native, universal **zero-copy transport across process boundaries** with minimal overhead. It introduces language-agnostic memory layouts and strict message constraints, and uses XCDR as the in-memory representation. It is designed to be backward compatible and supports C, C++ and Python.

## Where we left off

At the 4 November meeting we:

- reviewed the design and its backward-compatibility story, where old and new messages coexist and interoperate;
- discussed member-based vs. method-based message access. The proposed path is to support both and eventually deprecate member-based access;
- discussed decoupling serialization from the middleware implementations, with a Zenoh prototype planned to check non-DDS middleware;
- saw benchmark results showing that zero-copy gains become negligible for small payloads.

After the meeting, Miguel Company proposed making **views** a first-class concept: method-based views in a `views` namespace that can be built over a message or over a binary blob. Michel suggested generalizing constraints into a type support context that is passed to the middleware.

## Proposed agenda

1. Views as a first-class concept
2. Message access API: path from member-based to method-based access
3. Type support / middleware interface: generic type support context and payload bounds
4. Open questions on `rosidl` buffer integration and loaned messages
5. Status of the action items from the last meeting (benchmarks, README, REP revision, Zenoh prototype)
6. Next steps

## Background material

- **REP 0157 draft:** [reps/\_posts/rep-0157:2026.md at main · openrobotics/reps · GitHub](https://github.com/openrobotics/reps/blob/main/_posts/rep-0157:2026.md)
- **ROSCon 2026 talk:** [Breaking through the zero-copy bottleneck with REP-0157](https://vimeo.com/1235676412)
- **Reference implementation benchmarks:** [zero\_copy\_rosidl/code/constrained\_pubsub\_benchmark at benchmarks · Ekumen-OS/zero\_copy\_rosidl · GitHub](https://github.com/Ekumen-OS/zero_copy_rosidl/tree/benchmarks/code/constrained_pubsub_benchmark)

## How to contribute

If you can’t attend, or you want to raise something ahead of time, please reply in this thread or comment on the draft on GitHub. We will take written feedback into account during the meeting.

Notes from the meeting will be posted in this thread afterwards.

See you there!