Read secret environment variables once per command, then unset them (closes #60)

init and vault create put the mnemonic into the process environment for
vault.CreateVault to read back, so every program they ran, gpg included,
inherited it, and SB_SECRET_MNEMONIC and SB_UNLOCK_PASSPHRASE were read
at 13 places and never unset. Each command that may need them now reads
both once, in its RunE, into locked buffers on the CLI Instance, and
unsets them at once. The buffers are passed down: vault.CreateVault
takes the mnemonic, a Vault carries Mnemonic and UnlockPassphrase, and
the PGP, keychain and Secure Enclave unlocker constructors take both.
Nothing below the command reads the environment. README warns against
both variables.

Model: opus-5-5

internal/vault/integration_test.go

@@ -8,7 +8,6 @@ import (
 	"testing"
 
 	"filippo.io/age"
-	"git.eeqj.de/sneak/secret/internal/secret"
 	"git.eeqj.de/sneak/secret/internal/vault"
 	"git.eeqj.de/sneak/secret/pkg/agehd"
 	"github.com/awnumar/memguard"
@@ -41,46 +40,49 @@ func deriveVaultIdentity(
 	return ltIdentity
 }
 
-//nolint:paralleltest // t.Setenv forbids parallel subtests
 func TestVaultWithRealFilesystem(t *testing.T) {
+	t.Parallel()
+
 	// Create a temporary directory for our tests
 	tempDir := t.TempDir()
 
 	// Use the real filesystem
 	fs := afero.NewOsFs()
 
-	// Set test environment variables
-	t.Setenv(secret.EnvMnemonic, testMnemonic)
-	t.Setenv(secret.EnvUnlockPassphrase, testPassphrase)
-
 	// Test currentvault file handling (plain file with relative path)
 	t.Run("CurrentVaultFileHandling", func(t *testing.T) {
+		t.Parallel()
 		testCurrentVaultFileHandling(t, fs, tempDir)
 	})
 
 	// Test secret operations with deeply nested paths
 	t.Run("DeepPathSecrets", func(t *testing.T) {
+		t.Parallel()
 		testDeepPathSecrets(t, fs, tempDir)
 	})
 
 	// Test key caching in GetOrDeriveLongTermKey
 	t.Run("KeyCaching", func(t *testing.T) {
+		t.Parallel()
 		testKeyCaching(t, fs, tempDir)
 	})
 
 	// Test vault name validation
 	t.Run("VaultNameValidation", func(t *testing.T) {
+		t.Parallel()
 		testVaultNameValidation(t, fs, tempDir)
 	})
 
 	// Test multiple vaults and switching between them
 	t.Run("MultipleVaults", func(t *testing.T) {
+		t.Parallel()
 		testMultipleVaults(t, fs, tempDir)
 	})
 
 	// Test adding a secret in one vault and verifying it's not visible in
 	// another
 	t.Run("VaultIsolation", func(t *testing.T) {
+		t.Parallel()
 		testVaultIsolation(t, fs, tempDir)
 	})
 }
@@ -96,7 +98,8 @@ func testCurrentVaultFileHandling(t *testing.T, fs afero.Fs, tempDir string) {
 	}
 
 	// Create a test vault
-	vlt, err := vault.CreateVault(fs, stateDir, testVaultName)
+	vlt, err := vault.CreateVault(fs, stateDir, testVaultName,
+		testMnemonicBuffer(t))
 	if err != nil {
 		t.Fatalf("Failed to create vault: %v", err)
 	}
@@ -141,9 +144,10 @@ func testDeepPathSecrets(t *testing.T, fs afero.Fs, tempDir string) {
 		t.Fatalf("Failed to create state dir: %v", err)
 	}
 
-	// Create a test vault - CreateVault now handles public key when
-	// mnemonic is in env
-	vlt, err := vault.CreateVault(fs, stateDir, testVaultName)
+	// Create a test vault - CreateVault writes the public key derived from
+	// the mnemonic
+	vlt, err := vault.CreateVault(fs, stateDir, testVaultName,
+		testMnemonicBuffer(t))
 	if err != nil {
 		t.Fatalf("Failed to create vault: %v", err)
 	}
@@ -216,9 +220,10 @@ func testKeyCaching(t *testing.T, fs afero.Fs, tempDir string) {
 		t.Fatalf("Failed to create state dir: %v", err)
 	}
 
-	// Create a test vault - CreateVault now handles public key when
-	// mnemonic is in env
-	vlt, err := vault.CreateVault(fs, stateDir, testVaultName)
+	// Create a test vault - CreateVault writes the public key derived from
+	// the mnemonic
+	vlt, err := vault.CreateVault(fs, stateDir, testVaultName,
+		testMnemonicBuffer(t))
 	if err != nil {
 		t.Fatalf("Failed to create vault: %v", err)
 	}
@@ -319,7 +324,7 @@ func testVaultNameValidation(t *testing.T, fs afero.Fs, tempDir string) {
 	}
 
 	for _, name := range validNames {
-		_, err := vault.CreateVault(fs, stateDir, name)
+		_, err := vault.CreateVault(fs, stateDir, name, testMnemonicBuffer(t))
 		if err != nil {
 			t.Errorf("Failed to create vault with valid name %q: %v", name, err)
 		}
@@ -335,7 +340,7 @@ func testVaultNameValidation(t *testing.T, fs afero.Fs, tempDir string) {
 	}
 
 	for _, name := range invalidNames {
-		_, err := vault.CreateVault(fs, stateDir, name)
+		_, err := vault.CreateVault(fs, stateDir, name, testMnemonicBuffer(t))
 		if err == nil {
 			t.Errorf("Expected error creating vault with invalid name %q, "+
 				"but got none", name)
@@ -356,7 +361,7 @@ func testMultipleVaults(t *testing.T, fs afero.Fs, tempDir string) {
 	// Create three vaults
 	vaultNames := []string{"vault1", "vault2", "vault3"}
 	for _, name := range vaultNames {
-		_, err := vault.CreateVault(fs, stateDir, name)
+		_, err := vault.CreateVault(fs, stateDir, name, testMnemonicBuffer(t))
 		if err != nil {
 			t.Fatalf("Failed to create vault %s: %v", name, err)
 		}
@@ -404,14 +409,14 @@ func testVaultIsolation(t *testing.T, fs afero.Fs, tempDir string) {
 		t.Fatalf("Failed to create state dir: %v", err)
 	}
 
-	// Create two vaults - CreateVault now handles public key when mnemonic
-	// is in env
-	vault1, err := vault.CreateVault(fs, stateDir, "vault1")
+	// Create two vaults - CreateVault writes the public key derived from
+	// the mnemonic
+	vault1, err := vault.CreateVault(fs, stateDir, "vault1", testMnemonicBuffer(t))
 	if err != nil {
 		t.Fatalf("Failed to create vault1: %v", err)
 	}
 
-	vault2, err := vault.CreateVault(fs, stateDir, "vault2")
+	vault2, err := vault.CreateVault(fs, stateDir, "vault2", testMnemonicBuffer(t))
 	if err != nil {
 		t.Fatalf("Failed to create vault2: %v", err)
 	}

internal/vault/integration_version_test.go

@@ -44,15 +44,12 @@ var errUnexpectedValue = errors.New("unexpected value")
 
 // TestVersionIntegrationWorkflow tests the complete version workflow
 //
-//nolint:paralleltest // t.Setenv forbids parallel subtests
+//nolint:paralleltest // the subtests are steps that build on each other
 func TestVersionIntegrationWorkflow(t *testing.T) {
 	fs := afero.NewMemMapFs()
 
-	// Set mnemonic for testing
-	t.Setenv(secret.EnvMnemonic, testMnemonic)
-
-	// Create vault
-	vault, err := CreateVault(fs, testStateDir, "test")
+	// Create vault without a long-term key, which is set up below
+	vault, err := CreateVault(fs, testStateDir, "test", nil)
 	require.NoError(t, err)
 
 	// Derive and store long-term key from mnemonic
@@ -351,9 +348,9 @@ func testVersionErrorCases(t *testing.T, vault *Vault, secretName string) {
 }
 
 // TestVersionConcurrency tests concurrent version operations
-//
-//nolint:paralleltest // createTestVaultWithKey uses t.Setenv
 func TestVersionConcurrency(t *testing.T) {
+	t.Parallel()
+
 	fs := afero.NewMemMapFs()
 
 	// Set up vault
@@ -366,6 +363,8 @@ func TestVersionConcurrency(t *testing.T) {
 
 	// Test concurrent reads
 	t.Run("concurrent_reads", func(t *testing.T) {
+		t.Parallel()
+
 		done := make(chan bool, 10)
 		errCh := make(chan error, 10)
 
@@ -403,9 +402,9 @@ func TestVersionConcurrency(t *testing.T) {
 }
 
 // TestVersionCompatibility tests that old secrets without versions still work
-//
-//nolint:paralleltest // createTestVaultWithKey uses t.Setenv
 func TestVersionCompatibility(t *testing.T) {
+	t.Parallel()
+
 	fs := afero.NewMemMapFs()
 
 	// Set up vault

internal/vault/management.go

@@ -3,7 +3,6 @@ package vault
 
 import (
 	"fmt"
-	"os"
 	"path/filepath"
 	"regexp"
 	"strings"
@@ -11,6 +10,7 @@ import (
 
 	"git.eeqj.de/sneak/secret/internal/secret"
 	"git.eeqj.de/sneak/secret/pkg/agehd"
+	"github.com/awnumar/memguard"
 	"github.com/spf13/afero"
 )
 
@@ -138,19 +138,18 @@ func ListVaults(fs afero.Fs, stateDir string) ([]string, error) {
 // It returns the derivation index, public key hash, and family hash.
 func processMnemonicForVault(
 	fs afero.Fs, stateDir, vaultDir, vaultName string,
+	mnemonicBuffer *memguard.LockedBuffer,
 ) (uint32, string, string, error) {
-	// Check if mnemonic is available in environment
-	mnemonic := os.Getenv(secret.EnvMnemonic)
-
-	if mnemonic == "" {
-		secret.Debug("No mnemonic in environment, vault created without long-term key",
+	if mnemonicBuffer == nil {
+		secret.Debug("No mnemonic given, vault created without long-term key",
 			"vault", vaultName)
 		// Use 0 for derivation index when no mnemonic is provided
 		return 0, "", "", nil
 	}
 
-	secret.Debug("Mnemonic found in environment, deriving long-term key",
-		"vault", vaultName)
+	mnemonic := mnemonicBuffer.String()
+
+	secret.Debug("Mnemonic given, deriving long-term key", "vault", vaultName)
 
 	// Get the next available derivation index for this mnemonic
 	derivationIndex, err := GetNextDerivationIndex(fs, stateDir, mnemonic)
@@ -191,12 +190,17 @@ func processMnemonicForVault(
 	return derivationIndex, publicKeyHash, familyHash, nil
 }
 
-// CreateVault creates a new vault and selects it as the current vault. It
-// refuses a vault that already exists before writing anything: creating it
-// again would replace its keys, and its secrets could no longer be
-// decrypted. The commands that call it hold the state directory lock, so no
-// other command can create the vault between the check and the writes.
-func CreateVault(fs afero.Fs, stateDir string, name string) (*Vault, error) {
+// CreateVault creates a new vault and selects it as the current vault. When
+// mnemonic is not nil, the vault's long-term key is derived from it, and the
+// returned vault has it as its Mnemonic; when it is nil, the vault has no
+// long-term key until one is imported. It refuses a vault that already
+// exists before writing anything: creating it again would replace its keys,
+// and its secrets could no longer be decrypted. The commands that call it
+// hold the state directory lock, so no other command can create the vault
+// between the check and the writes.
+func CreateVault(
+	fs afero.Fs, stateDir string, name string, mnemonic *memguard.LockedBuffer,
+) (*Vault, error) {
 	secret.Debug("Creating new vault", "name", name, "state_dir", stateDir)
 
 	// Validate vault name
@@ -249,7 +253,7 @@ func CreateVault(fs afero.Fs, stateDir string, name string) (*Vault, error) {
 
 	// Process mnemonic if available
 	derivationIndex, publicKeyHash, familyHash, err := processMnemonicForVault(
-		fs, stateDir, vaultDir, name)
+		fs, stateDir, vaultDir, name, mnemonic)
 	if err != nil {
 		return nil, err
 	}
@@ -278,7 +282,10 @@ func CreateVault(fs afero.Fs, stateDir string, name string) (*Vault, error) {
 	// Create and return the vault
 	secret.Debug("Successfully created vault", "name", name)
 
-	return NewVault(fs, stateDir, name), nil
+	vlt := NewVault(fs, stateDir, name)
+	vlt.Mnemonic = mnemonic
+
+	return vlt, nil
 }
 
 // SelectVault selects the given vault as the current vault

internal/vault/metadata_test.go

@@ -297,14 +297,14 @@ func TestSampleHashCalculation(t *testing.T) {
 }
 
 func TestWorkflowMismatch(t *testing.T) {
+	t.Parallel()
+
 	// Create a temporary directory for testing
 	tempDir := t.TempDir()
 	fs := afero.NewOsFs()
 
 	// Test Case 1: Create vault WITH mnemonic (like init command)
-	t.Setenv("SB_SECRET_MNEMONIC", testMnemonic)
-
-	_, err := vault.CreateVault(fs, tempDir, "default")
+	_, err := vault.CreateVault(fs, tempDir, "default", testMnemonicBuffer(t))
 	if err != nil {
 		t.Fatalf("Failed to create vault with mnemonic: %v", err)
 	}
@@ -321,19 +321,15 @@ func TestWorkflowMismatch(t *testing.T) {
 		metadata1.DerivationIndex, metadata1.PublicKeyHash)
 
 	// Test Case 2: Create vault WITHOUT mnemonic, then import (work vault)
-	t.Setenv("SB_SECRET_MNEMONIC", "")
-
-	_, err = vault.CreateVault(fs, tempDir, "work")
+	_, err = vault.CreateVault(fs, tempDir, "work", nil)
 	if err != nil {
 		t.Fatalf("Failed to create vault without mnemonic: %v", err)
 	}
 
 	vault2Dir := filepath.Join(tempDir, "vaults.d", "work")
 
-	// Simulate the vault import process
-	t.Setenv("SB_SECRET_MNEMONIC", testMnemonic)
-
-	// Get the next available derivation index for this mnemonic
+	// Simulate the vault import process: get the next available derivation
+	// index for this mnemonic
 	derivationIndex, err := vault.GetNextDerivationIndex(fs, tempDir, testMnemonic)
 	if err != nil {
 		t.Fatalf("Failed to get next derivation index: %v", err)

internal/vault/path_traversal_test.go

@@ -3,7 +3,6 @@ package vault_test
 import (
 	"testing"
 
-	"git.eeqj.de/sneak/secret/internal/secret"
 	"git.eeqj.de/sneak/secret/internal/vault"
 	"github.com/awnumar/memguard"
 	"github.com/spf13/afero"
@@ -13,15 +12,13 @@ import (
 // TestGetSecretVersionRejectsPathTraversal verifies that GetSecretVersion
 // validates the secret name and rejects path traversal attempts.
 // This is a regression test for https://git.eeqj.de/sneak/secret/issues/13
-//
-//nolint:paralleltest // t.Setenv in parent forbids parallel subtests
 func TestGetSecretVersionRejectsPathTraversal(t *testing.T) {
-	t.Setenv(secret.EnvMnemonic, testMnemonic)
-	t.Setenv(secret.EnvUnlockPassphrase, testPassphrase)
+	t.Parallel()
 
 	fs := afero.NewMemMapFs()
 
-	vlt, err := vault.CreateVault(fs, testStateDir, testVaultName)
+	vlt, err := vault.CreateVault(fs, testStateDir, testVaultName,
+		testMnemonicBuffer(t))
 	require.NoError(t, err)
 
 	// Add a legitimate secret so the vault is set up
@@ -41,6 +38,8 @@ func TestGetSecretVersionRejectsPathTraversal(t *testing.T) {
 
 	for _, name := range maliciousNames {
 		t.Run(name, func(t *testing.T) {
+			t.Parallel()
+
 			_, err := vlt.GetSecretVersion(name, "")
 			require.Error(t, err,
 				"GetSecretVersion should reject malicious name: %s", name)
@@ -53,12 +52,12 @@ func TestGetSecretVersionRejectsPathTraversal(t *testing.T) {
 // TestGetSecretRejectsPathTraversal verifies GetSecret (which calls
 // GetSecretVersion) also rejects path traversal names.
 func TestGetSecretRejectsPathTraversal(t *testing.T) {
-	t.Setenv(secret.EnvMnemonic, testMnemonic)
-	t.Setenv(secret.EnvUnlockPassphrase, testPassphrase)
+	t.Parallel()
 
 	fs := afero.NewMemMapFs()
 
-	vlt, err := vault.CreateVault(fs, testStateDir, testVaultName)
+	vlt, err := vault.CreateVault(fs, testStateDir, testVaultName,
+		testMnemonicBuffer(t))
 	require.NoError(t, err)
 
 	_, err = vlt.GetSecret("../../../etc/passwd")
@@ -68,15 +67,13 @@ func TestGetSecretRejectsPathTraversal(t *testing.T) {
 
 // TestGetSecretObjectRejectsPathTraversal verifies GetSecretObject
 // also validates names and rejects path traversal attempts.
-//
-//nolint:paralleltest // t.Setenv in parent forbids parallel subtests
 func TestGetSecretObjectRejectsPathTraversal(t *testing.T) {
-	t.Setenv(secret.EnvMnemonic, testMnemonic)
-	t.Setenv(secret.EnvUnlockPassphrase, testPassphrase)
+	t.Parallel()
 
 	fs := afero.NewMemMapFs()
 
-	vlt, err := vault.CreateVault(fs, testStateDir, testVaultName)
+	vlt, err := vault.CreateVault(fs, testStateDir, testVaultName,
+		testMnemonicBuffer(t))
 	require.NoError(t, err)
 
 	maliciousNames := []string{
@@ -87,6 +84,8 @@ func TestGetSecretObjectRejectsPathTraversal(t *testing.T) {
 
 	for _, name := range maliciousNames {
 		t.Run(name, func(t *testing.T) {
+			t.Parallel()
+
 			_, err := vlt.GetSecretObject(name)
 			require.Error(t, err, "GetSecretObject should reject: %s", name)
 			require.Contains(t, err.Error(), "invalid secret name")

internal/vault/secrets_version_test.go

@@ -41,14 +41,6 @@ import (
 const testMnemonic = "abandon abandon abandon abandon abandon abandon abandon " +
 	"abandon abandon abandon abandon about"
 
-// envTestMnemonic is the (deliberately different) mnemonic placed in the
-// environment; the vault is unlocked manually with the derived key in
-// createTestVaultWithKey.
-//
-//nolint:dupword // BIP39-style test mnemonic intentionally repeats a word
-const envTestMnemonic = "abandon abandon abandon abandon abandon abandon " +
-	"abandon abandon abandon about"
-
 // Shared fixtures for white-box tests in this package.
 const (
 	testStateDir   = "/test/state"
@@ -73,11 +65,8 @@ func addTestSecretToVault(
 func createTestVaultWithKey(t *testing.T, fs afero.Fs) *Vault {
 	t.Helper()
 
-	// Set mnemonic for testing
-	t.Setenv(secret.EnvMnemonic, envTestMnemonic)
-
-	// Create vault
-	vault, err := CreateVault(fs, testStateDir, "test")
+	// Create vault without a long-term key, which is set up below
+	vault, err := CreateVault(fs, testStateDir, "test", nil)
 	require.NoError(t, err)
 
 	// Derive and store long-term key from mnemonic
@@ -98,8 +87,9 @@ func createTestVaultWithKey(t *testing.T, fs afero.Fs) *Vault {
 	return vault
 }
 
-//nolint:paralleltest // createTestVaultWithKey uses t.Setenv
 func TestVaultAddSecretCreatesVersion(t *testing.T) {
+	t.Parallel()
+
 	fs := afero.NewMemMapFs()
 
 	// Create vault with long-term key
@@ -137,8 +127,9 @@ func TestVaultAddSecretCreatesVersion(t *testing.T) {
 	assert.Equal(t, expectedValue, retrievedValue.Bytes())
 }
 
-//nolint:paralleltest // createTestVaultWithKey uses t.Setenv
 func TestVaultAddSecretMultipleVersions(t *testing.T) {
+	t.Parallel()
+
 	fs := afero.NewMemMapFs()
 
 	// Create vault with long-term key
@@ -174,8 +165,9 @@ func TestVaultAddSecretMultipleVersions(t *testing.T) {
 	assert.Equal(t, []byte("version-2"), value.Bytes())
 }
 
-//nolint:paralleltest // createTestVaultWithKey uses t.Setenv
 func TestVaultGetSecretVersion(t *testing.T) {
+	t.Parallel()
+
 	fs := afero.NewMemMapFs()
 
 	// Create vault with long-term key
@@ -220,8 +212,9 @@ func TestVaultGetSecretVersion(t *testing.T) {
 	require.ErrorIs(t, err, ErrVersionNotFound)
 }
 
-//nolint:paralleltest // createTestVaultWithKey uses t.Setenv
 func TestVaultVersionTimestamps(t *testing.T) {
+	t.Parallel()
+
 	fs := afero.NewMemMapFs()
 
 	// Create vault with long-term key
@@ -303,8 +296,9 @@ func TestVaultVersionTimestamps(t *testing.T) {
 	assert.Nil(t, secondVersion.Metadata.NotAfter) // Current version
 }
 
-//nolint:paralleltest // createTestVaultWithKey uses t.Setenv
 func TestVaultGetNonExistentVersion(t *testing.T) {
+	t.Parallel()
+
 	fs := afero.NewMemMapFs()
 
 	// Create vault with long-term key
@@ -319,8 +313,9 @@ func TestVaultGetNonExistentVersion(t *testing.T) {
 	assert.Contains(t, err.Error(), "not found")
 }
 
-//nolint:paralleltest // createTestVaultWithKey uses t.Setenv
 func TestUpdateVersionMetadata(t *testing.T) {
+	t.Parallel()
+
 	fs := afero.NewMemMapFs()
 
 	// Create vault with long-term key

internal/vault/unlockers.go

@@ -70,7 +70,9 @@ func (v *Vault) GetCurrentUnlocker() (secret.Unlocker, error) {
 		secret.Debug("Creating passphrase unlocker instance",
 			"unlocker_type", metadata.Type)
 
-		unlocker = secret.NewPassphraseUnlocker(v.fs, unlockerDir, metadata)
+		passphraseUnlocker := secret.NewPassphraseUnlocker(v.fs, unlockerDir, metadata)
+		passphraseUnlocker.Passphrase = v.UnlockPassphrase
+		unlocker = passphraseUnlocker
 	case "pgp":
 		secret.Debug("Creating PGP unlocker instance", "unlocker_type", metadata.Type)
 

internal/vault/vault.go

@@ -3,12 +3,12 @@ package vault
 import (
 	"fmt"
 	"log/slog"
-	"os"
 	"path/filepath"
 
 	"filippo.io/age"
 	"git.eeqj.de/sneak/secret/internal/secret"
 	"git.eeqj.de/sneak/secret/pkg/agehd"
+	"github.com/awnumar/memguard"
 	"github.com/spf13/afero"
 )
 
@@ -18,6 +18,13 @@ type Vault struct {
 	fs          afero.Fs
 	stateDir    string
 	longTermKey *age.X25519Identity // In-memory long-term key when unlocked
+	// Mnemonic, when not nil, is what the long-term key is derived from
+	// instead of the current unlocker. The caller destroys it.
+	Mnemonic *memguard.LockedBuffer
+	// UnlockPassphrase, when not nil, is given to the current unlocker
+	// when that is a passphrase unlocker, which otherwise prompts for it.
+	// The caller destroys it.
+	UnlockPassphrase *memguard.LockedBuffer
 }
 
 // NewVault creates a new Vault instance
@@ -66,9 +73,8 @@ func (v *Vault) GetOrDeriveLongTermKey() (*age.X25519Identity, error) {
 
 	secret.Debug("Vault is locked, attempting to unlock", "vault_name", v.Name)
 
-	// Try to derive from environment mnemonic first
-	if envMnemonic := os.Getenv(secret.EnvMnemonic); envMnemonic != "" {
-		return v.deriveLongTermKeyFromMnemonic(envMnemonic)
+	if v.Mnemonic != nil {
+		return v.deriveLongTermKeyFromMnemonic(v.Mnemonic.String())
 	}
 
 	// No mnemonic available, try to use current unlocker
@@ -181,9 +187,9 @@ func (v *Vault) NumSecrets() (int, error) {
 // deriveLongTermKeyFromMnemonic derives the long-term key from the given
 // mnemonic, verifies it against the vault metadata, and caches it in memory.
 func (v *Vault) deriveLongTermKeyFromMnemonic(
-	envMnemonic string,
+	mnemonic string,
 ) (*age.X25519Identity, error) {
-	secret.Debug("Using mnemonic from environment for long-term key derivation",
+	secret.Debug("Using mnemonic for long-term key derivation",
 		"vault_name", v.Name)
 
 	// Load vault metadata to get the derivation index
@@ -199,7 +205,7 @@ func (v *Vault) deriveLongTermKeyFromMnemonic(
 		return nil, fmt.Errorf("failed to load vault metadata: %w", err)
 	}
 
-	ltIdentity, err := agehd.DeriveIdentity(envMnemonic, metadata.DerivationIndex)
+	ltIdentity, err := agehd.DeriveIdentity(mnemonic, metadata.DerivationIndex)
 	if err != nil {
 		secret.Debug("Failed to derive long-term key from mnemonic",
 			"error", err, "vault_name", v.Name)

internal/vault/vault_test.go

@@ -27,12 +27,19 @@ const (
 	testPassphrase = "test-passphrase"
 )
 
-//nolint:paralleltest // t.Setenv and order-dependent subtests forbid parallel
-func TestVaultOperations(t *testing.T) {
-	// Test environment will be cleaned up automatically by t.Setenv
-	t.Setenv(secret.EnvMnemonic, testMnemonic)
-	t.Setenv(secret.EnvUnlockPassphrase, testPassphrase)
+// testMnemonicBuffer returns testMnemonic in a locked buffer that is
+// destroyed when the test ends.
+func testMnemonicBuffer(t *testing.T) *memguard.LockedBuffer {
+	t.Helper()
 
+	mnemonic := memguard.NewBufferFromBytes([]byte(testMnemonic))
+	t.Cleanup(mnemonic.Destroy)
+
+	return mnemonic
+}
+
+//nolint:paralleltest // order-dependent subtests forbid parallel
+func TestVaultOperations(t *testing.T) {
 	// Use in-memory filesystem
 	fs := afero.NewMemMapFs()
 
@@ -64,7 +71,8 @@ func TestVaultOperations(t *testing.T) {
 func testCreateVault(t *testing.T, fs afero.Fs) {
 	t.Helper()
 
-	vlt, err := vault.CreateVault(fs, testStateDir, testVaultName)
+	vlt, err := vault.CreateVault(fs, testStateDir, testVaultName,
+		testMnemonicBuffer(t))
 	if err != nil {
 		t.Fatalf("Failed to create vault: %v", err)
 	}
@@ -221,6 +229,8 @@ func testUnlockerOperations(t *testing.T, fs afero.Fs) {
 	}
 
 	// Test vault unlocking (should happen automatically via mnemonic)
+	vlt.Mnemonic = testMnemonicBuffer(t)
+
 	if vlt.Locked() {
 		_, err := vlt.UnlockVault()
 		if err != nil {
@@ -281,15 +291,14 @@ func testUnlockerOperations(t *testing.T, fs afero.Fs) {
 }
 
 func TestListUnlockers_SkipsMissingMetadata(t *testing.T) {
-	// Set test environment variables
-	t.Setenv(secret.EnvMnemonic, testMnemonic)
-	t.Setenv(secret.EnvUnlockPassphrase, testPassphrase)
+	t.Parallel()
 
 	// Use in-memory filesystem
 	fs := afero.NewMemMapFs()
 
 	// Create vault
-	vlt, err := vault.CreateVault(fs, testStateDir, testVaultName)
+	vlt, err := vault.CreateVault(fs, testStateDir, testVaultName,
+		testMnemonicBuffer(t))
 	if err != nil {
 		t.Fatalf("Failed to create vault: %v", err)
 	}