diff --git a/.jules/sentinel.md b/.jules/sentinel.md
new file mode 100644
index 00000000..e69de29b
diff --git a/crates/gitlawb-attest/src/attestation.rs b/crates/gitlawb-attest/src/attestation.rs
index 5adc7411..a2eae0a4 100644
--- a/crates/gitlawb-attest/src/attestation.rs
+++ b/crates/gitlawb-attest/src/attestation.rs
@@ -16,7 +16,7 @@
 //! by exact match.
 
 use base64::{engine::general_purpose::URL_SAFE_NO_PAD as B64U, Engine};
-use ed25519_dalek::{Signature, Signer, SigningKey, Verifier, VerifyingKey};
+use ed25519_dalek::{Signature, Signer, SigningKey, VerifyingKey};
 use serde::{de::DeserializeOwned, Deserialize, Serialize};
 
 use crate::error::{Error, Result};
@@ -111,7 +111,8 @@ impl Attestation {
             .try_into()
             .map_err(|_| Error::Signature("signature must be 64 bytes".to_string()))?;
         let sig = Signature::from_bytes(&sig_bytes);
-        vk.verify(&bytes, &sig)
+        // Sentinel: Use verify_strict to prevent signature malleability (strict RFC 8032 compliance)
+        vk.verify_strict(&bytes, &sig)
             .map_err(|e| Error::Signature(format!("ed25519: {e}")))?;
 
         Ok(vk)
diff --git a/crates/gitlawb-core/src/identity.rs b/crates/gitlawb-core/src/identity.rs
index 511e1203..7f1defc0 100644
--- a/crates/gitlawb-core/src/identity.rs
+++ b/crates/gitlawb-core/src/identity.rs
@@ -78,10 +78,11 @@ impl Keypair {
 
 /// Verify an Ed25519 signature.
 pub fn verify(verifying_key: &VerifyingKey, msg: &[u8], sig_bytes: &[u8; 64]) -> Result<()> {
-    use ed25519_dalek::Verifier;
+
     let sig = Signature::from_bytes(sig_bytes);
+    // Sentinel: Use verify_strict to prevent signature malleability (strict RFC 8032 compliance)
     verifying_key
-        .verify(msg, &sig)
+        .verify_strict(msg, &sig)
         .map_err(|_| Error::SignatureInvalid)
 }