BUG #18938: Logical replication failure in 16.9: "invalid memory alloc request size 1372786672"

The following bug has been logged on the website:

Bug reference:      18938
Logged by:          John Hutchins
Email address:      john.hutchins@wicourts.gov
PostgreSQL version: 16.9
Operating system:   Ubuntu 24.04.2 LTS (GNU/Linux 6.8.0-60-generic x8
Description:

We encountered a critical logical replication failure after upgrading to
PostgreSQL 16.9 (Ubuntu package 16.9-0ubuntu0.24.04.1) that resolved upon
downgrading to 16.2.  I believe this is very similar to the bug reported in
this current thread:
https://www.postgresql.org/message-id/CAD21AoBCn7RR0EYbK%2B1n5UTksc3CVn5AKvxBRSr7zR2eWqTTOw%40mail.gmail.com
Environment:
OS: Ubuntu 24.04.2 LTS (Linux 6.8.0-60-generic)
Hardware: x86_64
Compiler: gcc 13.3.0
Upgraded production instance from 16.8 → 16.9
Subscribers began failing with error:
[2025-05-27 13:56:07.860 CDT] ERROR: invalid memory alloc request size
1372786672
Downgrade to 16.2 restored normal replication from point of failure.
Observations:
Currently affects 1/72 production instances using logical replication
Error occurs consistently across all subscribers to affected database,
regardless of publication (appears to be related to logical decoding)
No schema changes or unusual load during incident
Other 16.9 instances remain operational (for now)
Logged error:
[2025-05-27 13:56:07.860 CDT] 649724 <logicalrep@xxx.xxx.xx.xxx(42454)
publishingdb subscribername>
Versions:
-- 16.9 (failing):
PostgreSQL 16.9 (Ubuntu 16.9-0ubuntu0.24.04.1)
-- 16.2 (working):
PostgreSQL 16.2 (Ubuntu 16.2-1ubuntu4)
Suspected area:
Recent commits to logical decoding in 16.9 (specific changesets may be
relevant).
We urgently need assistance diagnosing this, as it blocks patch updates.
Full server logs and configuration details are available upon request.
Thank you for your time,
John Hutchins
Wisconsin Court System DBA