diff --git a/.github/workflows/regression-report.yml b/.github/workflows/regression-report.yml
index 7b69e2680c6..0abafc74642 100644
--- a/.github/workflows/regression-report.yml
+++ b/.github/workflows/regression-report.yml
@@ -148,8 +148,9 @@ jobs:
             const MAX_REPORT = 60000;
             let report = fs.readFileSync(path, 'utf8');
             if (report.length > MAX_REPORT) {
-              const [head, ...blocks] = report.split('<details>\n');
-              let kept = head;
+              // The first <details> block is the table, which is always kept.
+              const [head, table, ...blocks] = report.split('<details>\n');
+              let kept = head + '<details>\n' + table;
               let shown = 0;
               for (const block of blocks) {
                 if (kept.length + block.length > MAX_REPORT) break;
diff --git a/acceptance/regression_test.go b/acceptance/regression_test.go
index c37ad214c4e..bcae5a96a84 100644
--- a/acceptance/regression_test.go
+++ b/acceptance/regression_test.go
@@ -226,8 +226,10 @@ func renderRegressionReport(selected string, columns []regrColumn) string {
 	var b strings.Builder
 	b.WriteString("## Regression test report\n\n")
 	fmt.Fprintf(&b, "%s\n\n", selected)
-	fmt.Fprintf(&b, "%d tests: %s\n\n", len(tests), formatCounts(countByCategory(tests, branch, refs)))
 
+	// The table has a row per test variant, often hundreds, so it is collapsed. The workflow
+	// that posts the report always keeps this first <details> block when it trims the comment.
+	fmt.Fprintf(&b, "<details>\n<summary>%d tests: %s</summary>\n\n", len(tests), formatCounts(countByCategory(tests, branch, refs)))
 	b.WriteString("| test | " + strings.Join(columnTitles(columns), " | ") + " |\n")
 	b.WriteString("|---|" + strings.Repeat("---|", len(columns)) + "\n")
 	for _, test := range tests {
@@ -237,7 +239,7 @@ func renderRegressionReport(selected string, columns []regrColumn) string {
 		}
 		fmt.Fprintf(&b, "| %s | %s |\n", test, strings.Join(marks, " | "))
 	}
-	b.WriteString("\n")
+	b.WriteString("\n</details>\n\n")
 
 	for _, test := range tests {
 		renderDetails(&b, test, columns)
diff --git a/acceptance/regression_unit_test.go b/acceptance/regression_unit_test.go
index 8a5900ce10c..4583e04d2b2 100644
--- a/acceptance/regression_unit_test.go
+++ b/acceptance/regression_unit_test.go
@@ -62,8 +62,9 @@ func TestRenderRegressionReport(t *testing.T) {
 	}}
 
 	report := renderRegressionReport("Selected 2", []regrColumn{branch, main})
-	assert.Contains(t, report, "| test | branch | main (abc) |")
+	assert.Contains(t, report, "<details>\n<summary>2 tests: regression=1 unreleased=0 coverage=0 failing=1</summary>\n\n| test | branch | main (abc) |")
 	assert.Contains(t, report, "| TestAccept/bundle/a | ❌ | ❌ |")
+	assert.Contains(t, report, "| TestAccept/bundle/inv/DMS=true/INPUT_CONFIG=x.yml.tmpl | ✅ | ➖ |\n\n</details>\n")
 	assert.Contains(t, report, "**main (abc):**\n````\nmain failure\n````")
 	assert.Contains(t, report, "failing=1")
 }