awsRDSToken PostgreSQL auth fails at startup: unrecognized configuration parameter "default_query_exec_mode"

[chtakahashi]

Pre-requisites

• I have double-checked my configuration
• I have tested with the :latest image tag (i.e. quay.io/argoproj/workflow-controller:latest) and can confirm the issue still exists on :latest. If not, I have explained why, in detail, in my description below.
• I have searched existing issues and could not find a match for this bug
• I'd like to contribute the fix myself (see contributing guide)

What happened? What did you expect to happen?

With persistence.postgresql.awsRDSToken.enabled: true against RDS for PostgreSQL, the
workflow-controller gets into a crashloopbackoff because it can't create a database session.

level=ERROR msg="Failed to update config" error="failed to create initial database session: failed to create upper/db session: pq: unrecognized configuration parameter "default_query_exec_mode" (42704)"

switching the same deployment to passwordAuth works just fine.

Spelunking with Claude, it seems like it's a similar issue to #16707 - I've had it piece together a solution but wanted to post this here first! chtakahashi#1

Version(s)

v4.1.0

Paste a minimal workflow that reproduces the issue. We must be able to run the workflow; don't enter a workflow that uses private images.

The controller is in crashloopbackoff so it can't start anything

Logs from the workflow controller

time=2026-08-21T15:23:14.334Z level=INFO msg="index config" indexWorkflowSemaphoreKeys=true
time=2026-08-21T15:23:14.334Z level=INFO msg="cron config" cronSyncPeriod=10s
time=2026-08-21T15:23:14.334Z level=INFO msg="Memoization caches will be garbage-collected if they have not been hit after" gcAfterNotHitDuration=30s
{"time":"2026-08-21T15:23:14.334266108Z","level":"INFO","msg":"not enabling pprof debug endpoints"}
{"time":"2026-08-21T15:23:14.352511418Z","level":"INFO","msg":"Configuration updated"}
{"time":"2026-08-21T15:23:14.352540218Z","level":"INFO","msg":"Persistence configuration enabled"}
{"time":"2026-08-21T15:23:14.722125697Z","level":"ERROR","msg":"Failed to update config","error":"failed to create initial database session: failed to create upper/db session: pq: unrecognized configuration parameter \"default_query_exec_mode\" (42704)"}

Logs from in your workflow's wait container

N/A