diff --git a/.github/workflows/server-ci-report.yml b/.github/workflows/server-ci-report.yml
index 9f0335bc8fe..ca4dd45a65b 100644
--- a/.github/workflows/server-ci-report.yml
+++ b/.github/workflows/server-ci-report.yml
@@ -112,24 +112,58 @@ jobs:
           include_passed: true
           check_annotations: true
 
-      - name: Report retried tests (pull request)
-        uses: actions/github-script@ed597411d8f924073f98dfc5c65a23a2325f34cd # v8.0.0
-        if: ${{ steps.report.outputs.flaky_summary != '<table><tr><th>Test</th><th>Retries</th></tr></table>' && steps.report.outputs.failed == '0' && github.event.workflow_run.event == 'pull_request' }}
+      - name: Report retried tests to Mattermost channel (pull request)
+        if: >-
+          steps.report.outputs.flaky_summary != '<table><tr><th>Test</th><th>Retries</th></tr></table>'
+          && steps.report.outputs.failed == '0'
+          && github.event.workflow_run.event == 'pull_request'
+          && env.WEBHOOK_URL_FLAKY_TEST_MM != ''
+        continue-on-error: true
         env:
-          FLAKY_SUMMARY: "${{ steps.report.outputs.flaky_summary }}"
-          PR_NUMBER: "${{ steps.incoming-pr.outputs.NUMBER }}"
-          TEST_NAME: "${{ matrix.test.name }}"
+          WEBHOOK_URL_FLAKY_TEST_MM: ${{ secrets.WEBHOOK_URL_FLAKY_TEST_MM }}
+          FLAKY_SUMMARY: ${{ steps.report.outputs.flaky_summary }}
+          PR_NUMBER: ${{ steps.incoming-pr.outputs.NUMBER }}
+          TEST_NAME: ${{ matrix.test.name }}
+          REPO: ${{ github.repository }}
           WORKFLOW_RUN_HTML_URL: ${{ github.event.workflow_run.html_url }}
-        with:
-          script: |
-            const body = `#### ⚠️  One or more flaky tests detected ⚠️\n* Workflow run: [github.com/mattermost/mattermost:${process.env.TEST_NAME}](${process.env.WORKFLOW_RUN_HTML_URL})\n* Double check your code to ensure you have not introduced a flaky test.\n\n${process.env.FLAKY_SUMMARY}`
+          SERVER_URL: ${{ github.server_url }}
+        run: |
+          PR_URL="${SERVER_URL}/${REPO}/pull/${PR_NUMBER}"
 
-            await github.rest.issues.createComment({
-              issue_number: process.env.PR_NUMBER,
-              owner: context.repo.owner,
-              repo: context.repo.repo,
-              body: body
-            })
+          # Convert the HTML <table> flaky summary into a Mattermost markdown table.
+          # Escape content pipes FIRST (HTML tags contain no '|', so any '|' is cell
+          # text), then strip tags, decode entities, and build delimiters.
+          TABLE_MD=$(printf '%s' "$FLAKY_SUMMARY" \
+            | sed -E 's#\|#\\|#g' \
+            | sed -E 's#</tr>#\n#g; s#<tr>##g; s#</?t(head|body)>##g' \
+            | sed -E 's#</?table>##g' \
+            | sed -E 's#&lt;#<#g; s#&gt;#>#g; s#&amp;#\&#g; s#&quot;#"#g' \
+            | sed -E 's#<th>([^<]*)</th>#| \1 #g; s#<td>([^<]*)</td>#| \1 #g' \
+            | sed -E 's#[[:space:]]*$# |#' \
+            | sed '/^[[:space:]|]*$/d')
+          # Insert markdown header separator after the first (header) row
+          TABLE_MD=$(printf '%s' "$TABLE_MD" \
+            | awk 'NR==1{print; print "|---|---|"; next} {print}')
+
+          # Use real newlines; a literal "\n" renders verbatim in Mattermost.
+          NL=$'\n'
+          TEXT=":warning: **Flaky test(s) detected** in [${REPO}#${PR_NUMBER}](${PR_URL})"
+          TEXT="${TEXT}${NL}_Test job:_ [${TEST_NAME}](${WORKFLOW_RUN_HTML_URL})${NL}${NL}${TABLE_MD}"
+
+          PAYLOAD=$(jq -n \
+            --arg text "$TEXT" \
+            '{
+              username: "Flaky Test Report",
+              icon_url: "https://mattermost.com/wp-content/uploads/2022/02/icon_WS.png",
+              attachments: [{color: "#CCCC00", text: $text}]
+            }')
+
+          curl -X POST -fsSL \
+            --connect-timeout 5 \
+            --max-time 30 \
+            -H "Content-Type: application/json" \
+            -d "$PAYLOAD" \
+            "$WEBHOOK_URL_FLAKY_TEST_MM"
 
       - name: Report retried tests to flaky-test webhook (pull request)
         if: >-