diff --git a/auth/auth.go b/auth/auth.go
index 85fd915..6a6faa8 100644
--- a/auth/auth.go
+++ b/auth/auth.go
@@ -30,7 +30,6 @@ import (
 	"crypto/rand"
 	"encoding/hex"
 	"encoding/json"
-	"errors"
 	"fmt"
 	"strings"
 	"sync"
@@ -642,16 +641,18 @@ func (a *Authenticator) ReadResponseFile(userID, path string) (*Session, error)
 // Tries Argon2id (.hash) first, then falls back to legacy LTHN (.lthn).
 // Returns nil on success, or an error describing the failure.
 func (a *Authenticator) verifyPassword(userID, password string) error {
+	const op = "auth.verifyPassword"
+
 	// Try Argon2id hash first (.hash file)
 	if a.medium.IsFile(userPath(userID, ".hash")) {
 		storedHash, err := a.medium.Read(userPath(userID, ".hash"))
 		if err == nil && strings.HasPrefix(storedHash, "$argon2id$") {
 			valid, verr := crypt.VerifyPassword(password, storedHash)
 			if verr != nil {
-				return errors.New("failed to verify password")
+				return coreerr.E(op, "failed to verify password", nil)
 			}
 			if !valid {
-				return errors.New("invalid password")
+				return coreerr.E(op, "invalid password", nil)
 			}
 			return nil
 		}
@@ -660,10 +661,10 @@ func (a *Authenticator) verifyPassword(userID, password string) error {
 	// Fall back to legacy LTHN hash (.lthn file)
 	storedHash, err := a.medium.Read(userPath(userID, ".lthn"))
 	if err != nil {
-		return errors.New("user not found")
+		return coreerr.E(op, "user not found", nil)
 	}
 	if !lthn.Verify(password, storedHash) {
-		return errors.New("invalid password")
+		return coreerr.E(op, "invalid password", nil)
 	}
 	return nil
 }
@@ -671,9 +672,11 @@ func (a *Authenticator) verifyPassword(userID, password string) error {
 // createSession generates a cryptographically random session token and
 // stores the session via the SessionStore.
 func (a *Authenticator) createSession(userID string) (*Session, error) {
+	const op = "auth.createSession"
+
 	tokenBytes := make([]byte, 32)
 	if _, err := rand.Read(tokenBytes); err != nil {
-		return nil, fmt.Errorf("auth: failed to generate session token: %w", err)
+		return nil, coreerr.E(op, "failed to generate session token", err)
 	}
 
 	session := &Session{
@@ -683,7 +686,7 @@ func (a *Authenticator) createSession(userID string) (*Session, error) {
 	}
 
 	if err := a.store.Set(session); err != nil {
-		return nil, fmt.Errorf("auth: failed to persist session: %w", err)
+		return nil, coreerr.E(op, "failed to persist session", err)
 	}
 
 	return session, nil
diff --git a/crypt/chachapoly/chachapoly.go b/crypt/chachapoly/chachapoly.go
index 2520c67..7a1f326 100644
--- a/crypt/chachapoly/chachapoly.go
+++ b/crypt/chachapoly/chachapoly.go
@@ -5,6 +5,8 @@ import (
 	"fmt"
 	"io"
 
+	coreerr "forge.lthn.ai/core/go-log"
+
 	"golang.org/x/crypto/chacha20poly1305"
 )
 
@@ -32,7 +34,7 @@ func Decrypt(ciphertext []byte, key []byte) ([]byte, error) {
 
 	minLen := aead.NonceSize() + aead.Overhead()
 	if len(ciphertext) < minLen {
-		return nil, fmt.Errorf("ciphertext too short: got %d bytes, need at least %d bytes", len(ciphertext), minLen)
+		return nil, coreerr.E("chachapoly.Decrypt", fmt.Sprintf("ciphertext too short: got %d bytes, need at least %d bytes", len(ciphertext), minLen), nil)
 	}
 
 	nonce, ciphertext := ciphertext[:aead.NonceSize()], ciphertext[aead.NonceSize():]
diff --git a/crypt/pgp/pgp.go b/crypt/pgp/pgp.go
index 67170d5..627c43b 100644
--- a/crypt/pgp/pgp.go
+++ b/crypt/pgp/pgp.go
@@ -6,10 +6,10 @@ package pgp
 
 import (
 	"bytes"
-	"errors"
-	"fmt"
 	"io"
 
+	coreerr "forge.lthn.ai/core/go-log"
+
 	"github.com/ProtonMail/go-crypto/openpgp"
 	"github.com/ProtonMail/go-crypto/openpgp/armor"
 	"github.com/ProtonMail/go-crypto/openpgp/packet"
@@ -25,9 +25,11 @@ type KeyPair struct {
 // If password is non-empty, the private key is encrypted with it.
 // Returns a KeyPair with armored public and private keys.
 func CreateKeyPair(name, email, password string) (*KeyPair, error) {
+	const op = "pgp.CreateKeyPair"
+
 	entity, err := openpgp.NewEntity(name, "", email, nil)
 	if err != nil {
-		return nil, fmt.Errorf("pgp: failed to create entity: %w", err)
+		return nil, coreerr.E(op, "failed to create entity", err)
 	}
 
 	// Sign all the identities
@@ -39,12 +41,12 @@ func CreateKeyPair(name, email, password string) (*KeyPair, error) {
 	if password != "" {
 		err = entity.PrivateKey.Encrypt([]byte(password))
 		if err != nil {
-			return nil, fmt.Errorf("pgp: failed to encrypt private key: %w", err)
+			return nil, coreerr.E(op, "failed to encrypt private key", err)
 		}
 		for _, subkey := range entity.Subkeys {
 			err = subkey.PrivateKey.Encrypt([]byte(password))
 			if err != nil {
-				return nil, fmt.Errorf("pgp: failed to encrypt subkey: %w", err)
+				return nil, coreerr.E(op, "failed to encrypt subkey", err)
 			}
 		}
 	}
@@ -53,11 +55,11 @@ func CreateKeyPair(name, email, password string) (*KeyPair, error) {
 	pubKeyBuf := new(bytes.Buffer)
 	pubKeyWriter, err := armor.Encode(pubKeyBuf, openpgp.PublicKeyType, nil)
 	if err != nil {
-		return nil, fmt.Errorf("pgp: failed to create armored public key writer: %w", err)
+		return nil, coreerr.E(op, "failed to create armored public key writer", err)
 	}
 	if err := entity.Serialize(pubKeyWriter); err != nil {
 		pubKeyWriter.Close()
-		return nil, fmt.Errorf("pgp: failed to serialize public key: %w", err)
+		return nil, coreerr.E(op, "failed to serialize public key", err)
 	}
 	pubKeyWriter.Close()
 
@@ -65,18 +67,18 @@ func CreateKeyPair(name, email, password string) (*KeyPair, error) {
 	privKeyBuf := new(bytes.Buffer)
 	privKeyWriter, err := armor.Encode(privKeyBuf, openpgp.PrivateKeyType, nil)
 	if err != nil {
-		return nil, fmt.Errorf("pgp: failed to create armored private key writer: %w", err)
+		return nil, coreerr.E(op, "failed to create armored private key writer", err)
 	}
 	if password != "" {
 		// Manual serialization to avoid re-signing encrypted keys
 		if err := serializeEncryptedEntity(privKeyWriter, entity); err != nil {
 			privKeyWriter.Close()
-			return nil, fmt.Errorf("pgp: failed to serialize private key: %w", err)
+			return nil, coreerr.E(op, "failed to serialize private key", err)
 		}
 	} else {
 		if err := entity.SerializePrivate(privKeyWriter, nil); err != nil {
 			privKeyWriter.Close()
-			return nil, fmt.Errorf("pgp: failed to serialize private key: %w", err)
+			return nil, coreerr.E(op, "failed to serialize private key", err)
 		}
 	}
 	privKeyWriter.Close()
@@ -115,27 +117,29 @@ func serializeEncryptedEntity(w io.Writer, e *openpgp.Entity) error {
 // Encrypt encrypts data for the recipient identified by their armored public key.
 // Returns the encrypted data as armored PGP output.
 func Encrypt(data []byte, publicKeyArmor string) ([]byte, error) {
+	const op = "pgp.Encrypt"
+
 	keyring, err := openpgp.ReadArmoredKeyRing(bytes.NewReader([]byte(publicKeyArmor)))
 	if err != nil {
-		return nil, fmt.Errorf("pgp: failed to read public key ring: %w", err)
+		return nil, coreerr.E(op, "failed to read public key ring", err)
 	}
 
 	buf := new(bytes.Buffer)
 	armoredWriter, err := armor.Encode(buf, "PGP MESSAGE", nil)
 	if err != nil {
-		return nil, fmt.Errorf("pgp: failed to create armor encoder: %w", err)
+		return nil, coreerr.E(op, "failed to create armor encoder", err)
 	}
 
 	w, err := openpgp.Encrypt(armoredWriter, keyring, nil, nil, nil)
 	if err != nil {
 		armoredWriter.Close()
-		return nil, fmt.Errorf("pgp: failed to create encryption writer: %w", err)
+		return nil, coreerr.E(op, "failed to create encryption writer", err)
 	}
 
 	if _, err := w.Write(data); err != nil {
 		w.Close()
 		armoredWriter.Close()
-		return nil, fmt.Errorf("pgp: failed to write data: %w", err)
+		return nil, coreerr.E(op, "failed to write data", err)
 	}
 	w.Close()
 	armoredWriter.Close()
@@ -146,16 +150,18 @@ func Encrypt(data []byte, publicKeyArmor string) ([]byte, error) {
 // Decrypt decrypts armored PGP data using the given armored private key.
 // If the private key is encrypted, the password is used to decrypt it first.
 func Decrypt(data []byte, privateKeyArmor, password string) ([]byte, error) {
+	const op = "pgp.Decrypt"
+
 	keyring, err := openpgp.ReadArmoredKeyRing(bytes.NewReader([]byte(privateKeyArmor)))
 	if err != nil {
-		return nil, fmt.Errorf("pgp: failed to read private key ring: %w", err)
+		return nil, coreerr.E(op, "failed to read private key ring", err)
 	}
 
 	// Decrypt the private key if it is encrypted
 	for _, entity := range keyring {
 		if entity.PrivateKey != nil && entity.PrivateKey.Encrypted {
 			if err := entity.PrivateKey.Decrypt([]byte(password)); err != nil {
-				return nil, fmt.Errorf("pgp: failed to decrypt private key: %w", err)
+				return nil, coreerr.E(op, "failed to decrypt private key", err)
 			}
 		}
 		for _, subkey := range entity.Subkeys {
@@ -168,17 +174,17 @@ func Decrypt(data []byte, privateKeyArmor, password string) ([]byte, error) {
 	// Decode armored message
 	block, err := armor.Decode(bytes.NewReader(data))
 	if err != nil {
-		return nil, fmt.Errorf("pgp: failed to decode armored message: %w", err)
+		return nil, coreerr.E(op, "failed to decode armored message", err)
 	}
 
 	md, err := openpgp.ReadMessage(block.Body, keyring, nil, nil)
 	if err != nil {
-		return nil, fmt.Errorf("pgp: failed to read message: %w", err)
+		return nil, coreerr.E(op, "failed to read message", err)
 	}
 
 	plaintext, err := io.ReadAll(md.UnverifiedBody)
 	if err != nil {
-		return nil, fmt.Errorf("pgp: failed to read plaintext: %w", err)
+		return nil, coreerr.E(op, "failed to read plaintext", err)
 	}
 
 	return plaintext, nil
@@ -188,19 +194,21 @@ func Decrypt(data []byte, privateKeyArmor, password string) ([]byte, error) {
 // the armored private key. If the key is encrypted, the password is used
 // to decrypt it first.
 func Sign(data []byte, privateKeyArmor, password string) ([]byte, error) {
+	const op = "pgp.Sign"
+
 	keyring, err := openpgp.ReadArmoredKeyRing(bytes.NewReader([]byte(privateKeyArmor)))
 	if err != nil {
-		return nil, fmt.Errorf("pgp: failed to read private key ring: %w", err)
+		return nil, coreerr.E(op, "failed to read private key ring", err)
 	}
 
 	signer := keyring[0]
 	if signer.PrivateKey == nil {
-		return nil, errors.New("pgp: private key not found in keyring")
+		return nil, coreerr.E(op, "private key not found in keyring", nil)
 	}
 
 	if signer.PrivateKey.Encrypted {
 		if err := signer.PrivateKey.Decrypt([]byte(password)); err != nil {
-			return nil, fmt.Errorf("pgp: failed to decrypt private key: %w", err)
+			return nil, coreerr.E(op, "failed to decrypt private key", err)
 		}
 	}
 
@@ -208,7 +216,7 @@ func Sign(data []byte, privateKeyArmor, password string) ([]byte, error) {
 	config := &packet.Config{}
 	err = openpgp.ArmoredDetachSign(buf, signer, bytes.NewReader(data), config)
 	if err != nil {
-		return nil, fmt.Errorf("pgp: failed to sign message: %w", err)
+		return nil, coreerr.E(op, "failed to sign message", err)
 	}
 
 	return buf.Bytes(), nil
@@ -217,14 +225,16 @@ func Sign(data []byte, privateKeyArmor, password string) ([]byte, error) {
 // Verify verifies an armored detached signature against the given data
 // and armored public key. Returns nil if the signature is valid.
 func Verify(data, signature []byte, publicKeyArmor string) error {
+	const op = "pgp.Verify"
+
 	keyring, err := openpgp.ReadArmoredKeyRing(bytes.NewReader([]byte(publicKeyArmor)))
 	if err != nil {
-		return fmt.Errorf("pgp: failed to read public key ring: %w", err)
+		return coreerr.E(op, "failed to read public key ring", err)
 	}
 
 	_, err = openpgp.CheckArmoredDetachedSignature(keyring, bytes.NewReader(data), bytes.NewReader(signature), nil)
 	if err != nil {
-		return fmt.Errorf("pgp: signature verification failed: %w", err)
+		return coreerr.E(op, "signature verification failed", err)
 	}
 
 	return nil
diff --git a/crypt/rsa/rsa.go b/crypt/rsa/rsa.go
index 9f1cd0c..a20ea0d 100644
--- a/crypt/rsa/rsa.go
+++ b/crypt/rsa/rsa.go
@@ -6,8 +6,9 @@ import (
 	"crypto/sha256"
 	"crypto/x509"
 	"encoding/pem"
-	"errors"
 	"fmt"
+
+	coreerr "forge.lthn.ai/core/go-log"
 )
 
 // Service provides RSA functionality.
@@ -20,12 +21,14 @@ func NewService() *Service {
 
 // GenerateKeyPair creates a new RSA key pair.
 func (s *Service) GenerateKeyPair(bits int) (publicKey, privateKey []byte, err error) {
+	const op = "rsa.GenerateKeyPair"
+
 	if bits < 2048 {
-		return nil, nil, fmt.Errorf("rsa: key size too small: %d (minimum 2048)", bits)
+		return nil, nil, coreerr.E(op, fmt.Sprintf("key size too small: %d (minimum 2048)", bits), nil)
 	}
 	privKey, err := rsa.GenerateKey(rand.Reader, bits)
 	if err != nil {
-		return nil, nil, fmt.Errorf("failed to generate private key: %w", err)
+		return nil, nil, coreerr.E(op, "failed to generate private key", err)
 	}
 
 	privKeyBytes := x509.MarshalPKCS1PrivateKey(privKey)
@@ -36,7 +39,7 @@ func (s *Service) GenerateKeyPair(bits int) (publicKey, privateKey []byte, err e
 
 	pubKeyBytes, err := x509.MarshalPKIXPublicKey(&privKey.PublicKey)
 	if err != nil {
-		return nil, nil, fmt.Errorf("failed to marshal public key: %w", err)
+		return nil, nil, coreerr.E(op, "failed to marshal public key", err)
 	}
 	pubKeyPEM := pem.EncodeToMemory(&pem.Block{
 		Type:  "PUBLIC KEY",
@@ -48,24 +51,26 @@ func (s *Service) GenerateKeyPair(bits int) (publicKey, privateKey []byte, err e
 
 // Encrypt encrypts data with a public key.
 func (s *Service) Encrypt(publicKey, data, label []byte) ([]byte, error) {
+	const op = "rsa.Encrypt"
+
 	block, _ := pem.Decode(publicKey)
 	if block == nil {
-		return nil, errors.New("failed to decode public key")
+		return nil, coreerr.E(op, "failed to decode public key", nil)
 	}
 
 	pub, err := x509.ParsePKIXPublicKey(block.Bytes)
 	if err != nil {
-		return nil, fmt.Errorf("failed to parse public key: %w", err)
+		return nil, coreerr.E(op, "failed to parse public key", err)
 	}
 
 	rsaPub, ok := pub.(*rsa.PublicKey)
 	if !ok {
-		return nil, errors.New("not an RSA public key")
+		return nil, coreerr.E(op, "not an RSA public key", nil)
 	}
 
 	ciphertext, err := rsa.EncryptOAEP(sha256.New(), rand.Reader, rsaPub, data, label)
 	if err != nil {
-		return nil, fmt.Errorf("failed to encrypt data: %w", err)
+		return nil, coreerr.E(op, "failed to encrypt data", err)
 	}
 
 	return ciphertext, nil
@@ -73,19 +78,21 @@ func (s *Service) Encrypt(publicKey, data, label []byte) ([]byte, error) {
 
 // Decrypt decrypts data with a private key.
 func (s *Service) Decrypt(privateKey, ciphertext, label []byte) ([]byte, error) {
+	const op = "rsa.Decrypt"
+
 	block, _ := pem.Decode(privateKey)
 	if block == nil {
-		return nil, errors.New("failed to decode private key")
+		return nil, coreerr.E(op, "failed to decode private key", nil)
 	}
 
 	priv, err := x509.ParsePKCS1PrivateKey(block.Bytes)
 	if err != nil {
-		return nil, fmt.Errorf("failed to parse private key: %w", err)
+		return nil, coreerr.E(op, "failed to parse private key", err)
 	}
 
 	plaintext, err := rsa.DecryptOAEP(sha256.New(), rand.Reader, priv, ciphertext, label)
 	if err != nil {
-		return nil, fmt.Errorf("failed to decrypt data: %w", err)
+		return nil, coreerr.E(op, "failed to decrypt data", err)
 	}
 
 	return plaintext, nil
diff --git a/trust/trust.go b/trust/trust.go
index 69e4a24..9794a6e 100644
--- a/trust/trust.go
+++ b/trust/trust.go
@@ -11,11 +11,12 @@
 package trust
 
 import (
-	"errors"
 	"fmt"
 	"iter"
 	"sync"
 	"time"
+
+	coreerr "forge.lthn.ai/core/go-log"
 )
 
 // Tier represents an agent's trust level in the system.
@@ -98,10 +99,10 @@ func NewRegistry() *Registry {
 // Returns an error if the agent name is empty or the tier is invalid.
 func (r *Registry) Register(agent Agent) error {
 	if agent.Name == "" {
-		return errors.New("trust.Register: agent name is required")
+		return coreerr.E("trust.Register", "agent name is required", nil)
 	}
 	if !agent.Tier.Valid() {
-		return fmt.Errorf("trust.Register: invalid tier %d for agent %q", agent.Tier, agent.Name)
+		return coreerr.E("trust.Register", fmt.Sprintf("invalid tier %d for agent %q", agent.Tier, agent.Name), nil)
 	}
 	if agent.CreatedAt.IsZero() {
 		agent.CreatedAt = time.Now()