diff --git a/cmd/multi_service_csv_strict_test.go b/cmd/multi_service_csv_strict_test.go
index f629cac1c..ac0ed3fba 100644
--- a/cmd/multi_service_csv_strict_test.go
+++ b/cmd/multi_service_csv_strict_test.go
@@ -1,7 +1,7 @@
 package main
 
 import (
-	"os"
+	"context"
 	"path/filepath"
 	"testing"
 
@@ -11,9 +11,7 @@ import (
 
 func loadCSVContent(t *testing.T, content string) error {
 	t.Helper()
-	csvPath := filepath.Join(t.TempDir(), "recs.csv")
-	require.NoError(t, os.WriteFile(csvPath, []byte(content), 0o600))
-	_, err := loadRecommendationsFromCSV(csvPath)
+	_, err := loadRecommendationsFromCSV(writeTestRecommendationsCSV(t, content))
 	return err
 }
 
@@ -46,8 +44,7 @@ func TestLoadRecommendationsFromCSV_StrictCount(t *testing.T) {
 }
 
 func TestLoadRecommendationsFromCSV_CountTrimmed(t *testing.T) {
-	csvPath := filepath.Join(t.TempDir(), "recs.csv")
-	require.NoError(t, os.WriteFile(csvPath, []byte("Service,Region,ResourceType,Count\nrds,us-east-1,db.t3.micro,\" 3 \"\n"), 0o600))
+	csvPath := writeTestRecommendationsCSV(t, "Service,Region,ResourceType,Count\nrds,us-east-1,db.t3.micro,\" 3 \"\n")
 	recs, err := loadRecommendationsFromCSV(csvPath)
 	require.NoError(t, err)
 	require.Len(t, recs, 1)
@@ -86,10 +83,42 @@ func TestLoadRecommendationsFromCSV_StrictEstimatedSavings(t *testing.T) {
 // A blank EstimatedSavings cell stays absent-as-zero: requireRankingSignal
 // relies on it to refuse a binding --max-instances cap.
 func TestLoadRecommendationsFromCSV_BlankSavingsStillZero(t *testing.T) {
-	csvPath := filepath.Join(t.TempDir(), "recs.csv")
-	require.NoError(t, os.WriteFile(csvPath, []byte("Service,Region,ResourceType,Count,EstimatedSavings\nrds,us-east-1,db.t3.micro,2, \n"), 0o600))
+	csvPath := writeTestRecommendationsCSV(t, "Service,Region,ResourceType,Count,EstimatedSavings\nrds,us-east-1,db.t3.micro,2, \n")
 	recs, err := loadRecommendationsFromCSV(csvPath)
 	require.NoError(t, err)
 	require.Len(t, recs, 1)
 	assert.Zero(t, recs[0].EstimatedSavings)
 }
+
+func TestRunToolFromCSV_RejectsMalformedNumbers(t *testing.T) {
+	isolateAWSEnv(t)
+	tests := []struct {
+		name    string
+		count   string
+		savings string
+		column  string
+	}{
+		{"fractional count", "3.7", "100", `column 4 "Count"`},
+		{"count suffix", "12 units", "100", `column 4 "Count"`},
+		{"negative count", "-5", "100", `column 4 "Count"`},
+		{"count overflow", "99999999999999999999", "100", `column 4 "Count"`},
+		{"savings suffix", "2", "1000 USD", `column 5 "EstimatedSavings"`},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			cfg := Config{
+				CSVInput: writeTestRecommendationsCSV(t, "Service,Region,ResourceType,Count,EstimatedSavings\n"+
+					"rds,us-east-1,db.t3.micro,"+tt.count+","+tt.savings+"\n"),
+				CSVOutput:      filepath.Join(t.TempDir(), "report.csv"),
+				AuditLog:       filepath.Join(t.TempDir(), "audit.jsonl"),
+				ActualPurchase: false,
+				Coverage:       100,
+			}
+			err := runToolFromCSV(context.Background(), cfg)
+			require.Error(t, err)
+			assert.Contains(t, err.Error(), "failed to read CSV file: CSV line 2:")
+			assert.Contains(t, err.Error(), tt.column)
+			assert.NoFileExists(t, cfg.CSVOutput)
+		})
+	}
+}