diff --git a/cmd_gen/main.go b/cmd_gen/main.go
index 3e82e21..9c768af 100644
--- a/cmd_gen/main.go
+++ b/cmd_gen/main.go
@@ -200,7 +200,7 @@ function run-dir() {
   status=0
   $cmd "${options[@]}" "${script_options[@]}" "$@" &> ${prefix}pass || status=1
   if [[ $status -eq "0" ]]; then
-    python "${output_file}" &> ${prefix}pass || status=1
+    python "${output_file}" &>> ${prefix}pass || status=1
   fi
   if [[ $status -eq "1" ]]; then
     mv ${prefix}pass ${prefix}fail
@@ -236,9 +236,9 @@ function run-dir() {
   $cmd "${options[@]}" "${script_options[@]}" "$@" &> ${prefix}pass || status=1
   cd "$outdir"
   if [[ $status -eq "0" ]]; then
-    go mod init &> ${prefix}pass || status=1
-    go mod tidy &> ${prefix}pass || status=1
-    go build &> ${prefix}pass || status=1
+    go mod init &>> ${prefix}pass || status=1
+    go mod tidy &>> ${prefix}pass || status=1
+    go build &>> ${prefix}pass || status=1
   fi
   if [[ $status -eq "1" ]]; then
     mv ${prefix}pass ${prefix}fail
diff --git a/cmd_gen/main_test.go b/cmd_gen/main_test.go
index 83b9f34..1bac902 100644
--- a/cmd_gen/main_test.go
+++ b/cmd_gen/main_test.go
@@ -166,7 +166,7 @@ function run-dir() {
   status=0
   $cmd "${options[@]}" "${script_options[@]}" "$@" &> ${prefix}pass || status=1
   if [[ $status -eq "0" ]]; then
-    python "${output_file}" &> ${prefix}pass || status=1
+    python "${output_file}" &>> ${prefix}pass || status=1
   fi
   if [[ $status -eq "1" ]]; then
     mv ${prefix}pass ${prefix}fail
@@ -206,9 +206,9 @@ function run-dir() {
   $cmd "${options[@]}" "${script_options[@]}" "$@" &> ${prefix}pass || status=1
   cd "$outdir"
   if [[ $status -eq "0" ]]; then
-    go mod init &> ${prefix}pass || status=1
-    go mod tidy &> ${prefix}pass || status=1
-    go build &> ${prefix}pass || status=1
+    go mod init &>> ${prefix}pass || status=1
+    go mod tidy &>> ${prefix}pass || status=1
+    go build &>> ${prefix}pass || status=1
   fi
   if [[ $status -eq "1" ]]; then
     mv ${prefix}pass ${prefix}fail
diff --git a/post_results/main.go b/post_results/main.go
index fbabae8..3d40d45 100644
--- a/post_results/main.go
+++ b/post_results/main.go
@@ -99,6 +99,10 @@ func init() {
 	flag.StringVar(&version, "version", "", "(optional) specific version of the validator tool.")
 }
 
+func blockQuote(s string) string {
+	return "```\n" + s + "\n```"
+}
+
 // sprintLineHTML prints a single list item to be put under a top-level summary item.
 func sprintLineHTML(format string, a ...interface{}) string {
 	return fmt.Sprintf("  <li>"+format+"</li>\n", a...)
@@ -440,11 +444,12 @@ func parseModelResultsHTML(validatorId, validatorResultDir string, condensed boo
 			}
 
 			if !condensed || !modelPass {
-				// Display bash command that produced the validator result.
+				// Display bash command that produced the validator result if it exists.
 				var bashCommandSummary string
 				if bashCommand != "" && bashCommandModelDirName == modelDirName && bashCommandModelName == modelName {
 					bashCommandSummary = fmt.Sprintf("%s&nbsp; %s\n<pre>%s</pre>\n", commonci.Emoji("cmd"), "bash command", bashCommand)
 				}
+				// Also display the error string.
 				modelHTML.WriteString(sprintSummaryHTML(status, modelName, bashCommandSummary+outString))
 			}
 		}
@@ -496,7 +501,7 @@ func getResult(validatorId, resultsDir string, condensed bool) (string, bool, ve
 		}
 		// For per-model validators, an execution failure suggests a CI infra failure.
 		if validator.IsPerModel {
-			outString = "Validator script failed -- infra bug?\n" + outString
+			outString = fmt.Sprintf("Validator script failed -- infra bug?\n%s", blockQuote(outString))
 		}
 		pass = false
 	case validator.IsPerModel && validatorId == "misc-checks":
diff --git a/post_results/main_test.go b/post_results/main_test.go
index 55bfb0e..7f7514d 100644
--- a/post_results/main_test.go
+++ b/post_results/main_test.go
@@ -317,7 +317,9 @@ Passed.
 		inValidatorId:        "oc-pyang",
 		wantPass:             false,
 		wantOut: `Validator script failed -- infra bug?
-Test failed with no stderr output.`,
+` + "```" + `
+Test failed with no stderr output.
+` + "```",
 		wantCondensedOutSame: true,
 	}, {
 		name:                 "basic non-pyang pass",
@@ -510,7 +512,7 @@ Failed.
 		inValidatorResultDir: "testdata/oc-pyang-script-fail",
 		inValidatorId:        "oc-pyang",
 		wantPass:             false,
-		wantOut:              "Validator script failed -- infra bug?\nI failed\n",
+		wantOut:              "Validator script failed -- infra bug?\n```\nI failed\n\n```",
 		wantCondensedOutSame: true,
 	}, {
 		name:                 "openconfig-version, revision version, and .spec.yml checks all pass",