response.threadId with notifyCommitters is unreliable

[gvaughan-lbi]

Jenkins and plugins versions report

Environment

Jenkins: 2.346.1
OS: Linux - 4.14.256-197.484.amzn2.x86_64
---
ace-editor:1.1
ant:1.11
antisamy-markup-formatter:2.7
apache-httpcomponents-client-4-api:4.5.13-1.0
authentication-tokens:1.4
aws-credentials:191.vcb_f183ce58b_9
aws-java-sdk:1.11.995
aws-java-sdk-ec2:1.12.287-357.vf82d85a_6eefd
aws-java-sdk-minimal:1.12.287-357.vf82d85a_6eefd
blueocean:1.25.5
blueocean-autofavorite:1.2.5
blueocean-bitbucket-pipeline:1.25.5
blueocean-commons:1.25.5
blueocean-config:1.25.5
blueocean-core-js:1.25.5
blueocean-dashboard:1.25.5
blueocean-display-url:2.4.1
blueocean-events:1.25.5
blueocean-git-pipeline:1.25.5
blueocean-github-pipeline:1.25.5
blueocean-i18n:1.25.5
blueocean-jwt:1.25.5
blueocean-personalization:1.25.5
blueocean-pipeline-api-impl:1.25.5
blueocean-pipeline-editor:1.25.5
blueocean-pipeline-scm-api:1.25.5
blueocean-rest:1.25.5
blueocean-rest-impl:1.25.5
blueocean-web:1.25.5
bootstrap4-api:4.6.0-3
bootstrap5-api:5.1.3-7
bouncycastle-api:2.25
branch-api:2.1046.v0ca_37783ecc5
build-name-setter:2.2.0
build-timeout:1.20
caffeine-api:2.9.2-29.v717aac953ff3
checks-api:1.7.4
cloudbees-bitbucket-branch-source:773.v4b_9b_005b_562b_
cloudbees-disk-usage-simple:170.va_fd5b_4ee6858
cloudbees-folder:6.729.v2b_9d1a_74d673
code-coverage-api:3.0.4
command-launcher:90.v669d7ccb_7c31
copyartifact:1.46.1
credentials:1139.veb_9579fca_33b_
credentials-binding:523.vd859a_4b_122e6
dark-theme:245.vb_a_2b_b_010ea_96
dashboard-view:2.432.va_712ce35862d
data-tables-api:1.12.1-2
display-url-api:2.3.6
durable-task:496.va67c6f9eefa7
ec2:2.0.3
echarts-api:5.3.3-1
email-ext:2.83
favorite:2.4.1
font-awesome-api:6.1.1-1
forensics-api:1.15.1
git:4.11.5
git-client:3.11.1
git-server:1.10
github:1.34.5
github-api:1.123
github-branch-source:2.11.2
gradle:1.37.1
handlebars:3.0.8
handy-uri-templates-2-api:2.1.8-22.v77d5b_75e6953
htmlpublisher:1.30
http_request:1.16
ionicons-api:24.va_745a_b_a_97fc3
jackson2-api:2.13.3-285.vc03c0256d517
javadoc:226.v71211feb_e7e9
javax-activation-api:1.2.0-3
javax-mail-api:1.6.2-5
jaxb:2.3.6-1
jdk-tool:1.5
jenkins-design-language:1.25.5
jjwt-api:0.11.2-9.c8b45b8bb173
job-restrictions:0.8
jobConfigHistory:1176.v1b_4290db_41a_5
jquery3-api:3.6.0-4
jsch:0.1.55.2
junit:1119.1121.vc43d0fc45561
ldap:2.7
lockable-resources:2.11
mail-watcher-plugin:1.16
mailer:414.vcc4c33714601
material-theme:0.5.1-rc92.a_564b_ca_9f511
matrix-auth:3.1.3
matrix-combinations-parameter:1.3.1
matrix-project:772.v494f19991984
maven-plugin:3.19
metrics:4.1.6.2
momentjs:1.1.1
node-iterator-api:49.v58a_8b_35f8363
nodelabelparameter:1.11.0
okhttp-api:4.9.3-105.vb96869f8ac3a
p4:1.11.5
pam-auth:1.6
pipeline-build-step:2.18
pipeline-graph-analysis:1.11
pipeline-groovy-lib:593.va_a_fc25d520e9
pipeline-input-step:449.v77f0e8b_845c4
pipeline-milestone-step:101.vd572fef9d926
pipeline-model-api:2.2097.v33db_b_de764b_e
pipeline-model-definition:2.2097.v33db_b_de764b_e
pipeline-model-extensions:2.2097.v33db_b_de764b_e
pipeline-rest-api:2.24
pipeline-stage-step:293.v200037eefcd5
pipeline-stage-tags-metadata:2.2097.v33db_b_de764b_e
pipeline-stage-view:2.19
pipeline-utility-steps:2.13.0
plain-credentials:1.8
plugin-util-api:2.17.0
popper-api:1.16.1-2
popper2-api:2.11.5-2
powershell:1.7
prism-api:1.28.0-2
prometheus:2.0.11
pubsub-light:1.16
resource-disposer:0.16
s3:0.11.8
scm-api:608.vfa_f971c5a_a_e9
script-security:1175.v4b_d517d6db_f0
slack:2.48
snakeyaml-api:1.30.2-76.vc104f7ce9870
solarized-theme:0.1
sse-gateway:1.25
ssh-credentials:305.v8f4381501156
ssh-slaves:1.32.0
sshd:3.1.0
structs:318.va_f3ccb_729b_71
theme-manager:1.5
timestamper:1.13
token-macro:308.v4f2b_ed62b_b_16
trilead-api:1.67.vc3938a_35172f
uno-choice:2.6.3
variant:1.4
versioncolumn:2.2
workflow-aggregator:581.v0c46fa_697ffd
workflow-api:1164.v760c223ddb_32
workflow-basic-steps:948.v2c72a_091b_b_68
workflow-cps:2725.v7b_c717eb_12ce
workflow-durable-task-step:1139.v252a_e12e8463
workflow-job:1189.va_d37a_e9e4eda_
workflow-multibranch:716.vc692a_e52371b_
workflow-scm-step:400.v6b_89a_1317c9a_
workflow-step-api:625.vd896b_f445a_f8
workflow-support:820.vd1a_6cc65ef33
ws-cleanup:0.39

What Operating System are you using (both controller, and any agents involved in the problem)?

Controller
Operating System: Amazon Linux 2
CPE OS Name: cpe:2.3:o:amazon:amazon_linux:2
Kernel: Linux 4.14.256-197.484.amzn2.x86_64
Architecture: x86-64
Agents
Windows 10 Pro

Reproduction steps

def retVal = slackSend (
color: color,
channel: channel,
message: message,
notifyCommitters: true,
tokenCredentialId: creds,
botUser: true
);
def threadId = retVal.threadId

Expected Results

retVal.threadId is the value of the message posted to 'channel'

Actual Results

retVal.threadId is the value of a message sent to a random committer that was notified.

Anything else?

retVal.threadId in this case could be any of the committers' direct messages, and not necessarily the one that went to the channel. It would be great to get a map of each channel:threadId back, or at least know that the ID that's returned is for the primary message in the channel.