diff --git a/options/locale/locale_en-US.json b/options/locale/locale_en-US.json
index 2b2979380d..0f80f01695 100644
--- a/options/locale/locale_en-US.json
+++ b/options/locale/locale_en-US.json
@@ -4762,6 +4762,13 @@
   "vault.config_error_title": "Vault Not Configured",
   "vault.config_error_message": "The vault encryption key has not been configured. Secrets cannot be encrypted or decrypted.",
   "vault.config_error_fix": "Add MASTER_KEY to the [vault] section in app.ini or set the GITCADDY_VAULT_KEY environment variable.",
+  "vault.fallback_key_warning_title": "Vault Using Fallback Encryption Key",
+  "vault.fallback_key_warning_message": "The vault is currently using Gitea's SECRET_KEY for encryption because no dedicated vault key has been configured. If the SECRET_KEY is ever changed or lost, all vault secrets will become permanently unreadable.",
+  "vault.fallback_key_warning_fix": "To fix this, copy the current SECRET_KEY value and set it as MASTER_KEY in the [vault] section of app.ini, or set the GITCADDY_VAULT_KEY environment variable. This ensures vault encryption remains stable even if the SECRET_KEY changes.",
+  "vault.decryption_error_title": "Vault Decryption Failed",
+  "vault.decryption_error_message": "Unable to decrypt vault secrets. The encryption key may have been changed or is incorrect.",
+  "vault.decryption_error_fix": "Verify that the MASTER_KEY in the [vault] section of app.ini (or the GITCADDY_VAULT_KEY environment variable) matches the key that was used when the secrets were originally created.",
+  "vault.encryption_error_message": "Unable to encrypt the secret value. The vault encryption key may not be configured correctly.",
   "vault.type_file": "File",
   "vault.compare": "Compare",
   "vault.compare_version": "Compare this version",
diff --git a/routers/web/repo/vault/vault.go b/routers/web/repo/vault/vault.go
index d5a0207ce5..4d5ad73453 100644
--- a/routers/web/repo/vault/vault.go
+++ b/routers/web/repo/vault/vault.go
@@ -6,6 +6,7 @@ package vault
 import (
 	"net/http"
 	"strconv"
+	"strings"
 
 	unit "code.gitcaddy.com/server/v3/models/unit"
 	"code.gitcaddy.com/server/v3/modules/web"
@@ -73,6 +74,8 @@ func setVaultLicenseData(ctx *context.Context) {
 	// Configuration status (for admin warnings)
 	ctx.Data["VaultConfigured"] = vault_service.IsConfigured()
 	ctx.Data["VaultConfigError"] = vault_service.GetConfigurationError()
+	ctx.Data["VaultUsingFallbackKey"] = vault_service.IsUsingFallbackKey()
+	ctx.Data["VaultKeySource"] = vault_service.KeySource()
 }
 
 // List displays the vault secrets list
@@ -82,8 +85,18 @@ func List(ctx *context.Context) {
 		return
 	}
 
+	// Check configuration status upfront so the list page can show a warning
+	if !vault_service.IsConfigured() {
+		showConfigError(ctx)
+		return
+	}
+
 	secrets, err := vault_service.ListSecrets(ctx, ctx.Repo.Repository.ID, false)
 	if err != nil {
+		if isCryptoError(err) {
+			showConfigError(ctx)
+			return
+		}
 		ctx.ServerError("ListSecrets", err)
 		return
 	}
@@ -144,6 +157,10 @@ func View(ctx *context.Context) {
 	// Get decrypted value for display
 	value, err := vault_service.GetSecretValue(ctx, ctx.Repo.Repository.ID, name, 0) // 0 = current version
 	if err != nil {
+		if isCryptoError(err) {
+			showConfigError(ctx)
+			return
+		}
 		ctx.ServerError("GetSecretValue", err)
 		return
 	}
@@ -207,6 +224,10 @@ func CreateSecret(ctx *context.Context) {
 		CreatorID:   ctx.Doer.ID,
 	})
 	if err != nil {
+		if isCryptoError(err) {
+			showConfigError(ctx)
+			return
+		}
 		ctx.ServerError("CreateSecret", err)
 		return
 	}
@@ -236,6 +257,10 @@ func UpdateSecret(ctx *context.Context) {
 			ctx.NotFound(nil)
 			return
 		}
+		if isCryptoError(err) {
+			showConfigError(ctx)
+			return
+		}
 		ctx.ServerError("UpdateSecret", err)
 		return
 	}
@@ -485,3 +510,17 @@ func showPluginNotAvailable(ctx *context.Context) {
 	ctx.Data["VaultPluginNotInstalled"] = true
 	ctx.HTML(http.StatusOK, "repo/vault/not_installed")
 }
+
+// isCryptoError returns true if the error is a vault encryption or decryption failure
+func isCryptoError(err error) bool {
+	msg := err.Error()
+	return strings.Contains(msg, "decryption failed") || strings.Contains(msg, "encryption failed")
+}
+
+// showConfigError shows a user-friendly error page for vault configuration/crypto issues
+func showConfigError(ctx *context.Context) {
+	ctx.Data["PageIsVault"] = true
+	ctx.Data["VaultConfigured"] = vault_service.IsConfigured()
+	ctx.Data["IsRepoAdmin"] = ctx.Repo.IsAdmin()
+	ctx.HTML(http.StatusOK, "repo/vault/config_error")
+}
diff --git a/services/vault/vault.go b/services/vault/vault.go
index 5fe80a9181..f8cb6a5332 100644
--- a/services/vault/vault.go
+++ b/services/vault/vault.go
@@ -62,6 +62,11 @@ type ConfigurablePlugin interface {
 	IsConfigured() bool
 	// ConfigurationError returns the configuration error message, if any
 	ConfigurationError() string
+	// IsUsingFallbackKey returns true if the vault is using Gitea's SECRET_KEY as
+	// the encryption key instead of an explicit vault-specific key.
+	IsUsingFallbackKey() bool
+	// KeySource returns a human-readable description of where the master key was loaded from.
+	KeySource() string
 }
 
 // Secret represents a vault secret
@@ -199,6 +204,33 @@ func GetConfigurationError() string {
 	return ""
 }
 
+// IsUsingFallbackKey returns true if the vault is using Gitea's SECRET_KEY
+// as the encryption key instead of an explicit vault-specific key.
+// Returns false if the plugin doesn't implement the ConfigurablePlugin interface.
+func IsUsingFallbackKey() bool {
+	vp := GetPlugin()
+	if vp == nil {
+		return false
+	}
+	if cp, ok := vp.(ConfigurablePlugin); ok {
+		return cp.IsUsingFallbackKey()
+	}
+	return false
+}
+
+// KeySource returns a human-readable description of where the master key was loaded from.
+// Returns empty string if the plugin doesn't implement the ConfigurablePlugin interface.
+func KeySource() string {
+	vp := GetPlugin()
+	if vp == nil {
+		return ""
+	}
+	if cp, ok := vp.(ConfigurablePlugin); ok {
+		return cp.KeySource()
+	}
+	return ""
+}
+
 // GetLicenseInfo returns the license info for the vault plugin
 // Returns default Solo license if no license file is present
 func GetLicenseInfo() *plugins.LicenseInfo {
diff --git a/templates/repo/vault/config_error.tmpl b/templates/repo/vault/config_error.tmpl
new file mode 100644
index 0000000000..168b10a9d4
--- /dev/null
+++ b/templates/repo/vault/config_error.tmpl
@@ -0,0 +1,42 @@
+{{template "base/head" .}}
+<div role="main" aria-label="{{.Title}}" class="page-content repository vault">
+	{{template "repo/header" .}}
+	<div class="ui container">
+		<div class="ui center aligned segment">
+			<div class="ui icon header">
+				{{svg "octicon-alert" 64}}
+				<div class="content">
+					{{if .VaultConfigured}}
+						{{ctx.Locale.Tr "vault.decryption_error_title"}}
+					{{else}}
+						{{ctx.Locale.Tr "vault.config_error_title"}}
+					{{end}}
+					<div class="sub header">GitCaddy Vault</div>
+				</div>
+			</div>
+
+			<div class="ui warning message" style="text-align: left;">
+				<div class="header">
+					{{if .VaultConfigured}}
+						{{ctx.Locale.Tr "vault.decryption_error_message"}}
+					{{else}}
+						{{ctx.Locale.Tr "vault.config_error_message"}}
+					{{end}}
+				</div>
+				<p style="margin-top: 0.5em;">
+					{{if .VaultConfigured}}
+						{{ctx.Locale.Tr "vault.decryption_error_fix"}}
+					{{else}}
+						{{ctx.Locale.Tr "vault.config_error_fix"}}
+					{{end}}
+				</p>
+			</div>
+
+			{{if and .IsRepoAdmin (not .VaultConfigured)}}
+			<div class="ui divider"></div>
+			<p class="ui small text grey">{{ctx.Locale.Tr "vault.config_error_fix"}}</p>
+			{{end}}
+		</div>
+	</div>
+</div>
+{{template "base/footer" .}}
diff --git a/templates/repo/vault/list.tmpl b/templates/repo/vault/list.tmpl
index 8e82221ff4..39a39dd337 100644
--- a/templates/repo/vault/list.tmpl
+++ b/templates/repo/vault/list.tmpl
@@ -12,6 +12,13 @@
 			</div>
 	</div>
 	{{else}}
+	{{if .VaultUsingFallbackKey}}
+	<div class="ui warning message">
+		<div class="header">{{svg "octicon-alert" 16}} {{ctx.Locale.Tr "vault.fallback_key_warning_title"}}</div>
+		<p>{{ctx.Locale.Tr "vault.fallback_key_warning_message"}}</p>
+		{{if .IsRepoAdmin}}<p class="tw-text-sm">{{ctx.Locale.Tr "vault.fallback_key_warning_fix"}}</p>{{end}}
+	</div>
+	{{end}}
 	<div class="ui segment">
 			<div class="tw-flex tw-items-center tw-justify-between tw-w-full">
 					<h4 class="ui header tw-mb-0">