diff --git a/src/assets/__tests__/__snapshots__/assets.snapshot.test.ts.snap b/src/assets/__tests__/__snapshots__/assets.snapshot.test.ts.snap
index a5ba8136..617aec2b 100644
--- a/src/assets/__tests__/__snapshots__/assets.snapshot.test.ts.snap
+++ b/src/assets/__tests__/__snapshots__/assets.snapshot.test.ts.snap
@@ -44,8 +44,12 @@ function toEnvironment(target: AwsDeploymentTarget): Environment {
   };
 }
 
+function sanitize(name: string): string {
+  return name.replace(/_/g, '-');
+}
+
 function toStackName(projectName: string, targetName: string): string {
-  return \`AgentCore-\${projectName}-\${targetName}\`;
+  return \`AgentCore-\${sanitize(projectName)}-\${sanitize(targetName)}\`;
 }
 
 async function main() {
diff --git a/src/assets/cdk/bin/cdk.ts b/src/assets/cdk/bin/cdk.ts
index 92caa1f1..da7f9de3 100644
--- a/src/assets/cdk/bin/cdk.ts
+++ b/src/assets/cdk/bin/cdk.ts
@@ -11,8 +11,12 @@ function toEnvironment(target: AwsDeploymentTarget): Environment {
   };
 }
 
+function sanitize(name: string): string {
+  return name.replace(/_/g, '-');
+}
+
 function toStackName(projectName: string, targetName: string): string {
-  return `AgentCore-${projectName}-${targetName}`;
+  return `AgentCore-${sanitize(projectName)}-${sanitize(targetName)}`;
 }
 
 async function main() {
diff --git a/src/schema/schemas/__tests__/aws-targets.test.ts b/src/schema/schemas/__tests__/aws-targets.test.ts
index ed5160f5..3fc9cbfe 100644
--- a/src/schema/schemas/__tests__/aws-targets.test.ts
+++ b/src/schema/schemas/__tests__/aws-targets.test.ts
@@ -73,7 +73,10 @@ describe('DeploymentTargetNameSchema', () => {
     expect(DeploymentTargetNameSchema.safeParse('default').success).toBe(true);
     expect(DeploymentTargetNameSchema.safeParse('prod').success).toBe(true);
     expect(DeploymentTargetNameSchema.safeParse('dev-us-east').success).toBe(true);
-    expect(DeploymentTargetNameSchema.safeParse('staging_env').success).toBe(true);
+  });
+
+  it('rejects name with underscores', () => {
+    expect(DeploymentTargetNameSchema.safeParse('staging_env').success).toBe(false);
   });
 
   it('rejects name starting with digit', () => {
diff --git a/src/schema/schemas/aws-targets.ts b/src/schema/schemas/aws-targets.ts
index bfe303be..8b2c91b8 100644
--- a/src/schema/schemas/aws-targets.ts
+++ b/src/schema/schemas/aws-targets.ts
@@ -27,8 +27,8 @@ export const DeploymentTargetNameSchema = z
   .min(1)
   .max(64)
   .regex(
-    /^[a-zA-Z][a-zA-Z0-9_-]*$/,
-    'Name must start with a letter and contain only alphanumeric characters, hyphens, and underscores'
+    /^[a-zA-Z][a-zA-Z0-9-]*$/,
+    'Name must start with a letter and contain only alphanumeric characters and hyphens'
   )
   .describe('Unique identifier for the deployment target');