diff --git a/AGENTS.md b/AGENTS.md
index 209f4d4..5812d18 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -35,6 +35,7 @@ Instructions for AI agents working in this repository.
 - Listeners auto-discovered from `src/Listeners/`, translations from `lang/`.
 - Encryption: `Crypt::encryptString` with `enc:v1:` marker prefix. No double encryption.
 - Handle decrypt failures gracefully — log warning, return raw ciphertext.
+- `DecryptingSubmissionRepository` and `DecryptingSubmissionQueryBuilder` mirror identical `decryptSubmission()` / `isAuthorizedForForm()` logic. Any change to either file **must** be applied to the other.
 - Field config toggle scoped to `Text` and `Textarea` fieldtypes only (not global `Fieldtype::`).
 - Permission: `view decrypted sensitive fields`. Super admins always authorized.
 - Compatible with both Stache (flat-file) and Eloquent Driver.
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 9f6321c..03de790 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -8,6 +8,7 @@ This changelog is used as the base for GitHub Release notes.
 
 - [new] PRO: `sensitive-fields:rekey` — re-encrypts sensitive field values from an old `APP_KEY` to the current one (supports `--old-key`, `--form`, `--dry-run`)
 - [new] PRO: per-form permission granularity — `view decrypted {form-handle} sensitive fields` grants access to a single form; the global `view decrypted sensitive fields` acts as a wildcard (backward-compatible)
+- [new] CP error toast on decrypt failure — shown once per form per hour when a sensitive field cannot be decrypted (e.g. after an APP_KEY rotation); suppressed in CLI context
 
 ## 1.0.0 (2026-02-17)
 
diff --git a/README.md b/README.md
index 30f1fe3..5cee628 100644
--- a/README.md
+++ b/README.md
@@ -112,7 +112,7 @@ Go to **CP → Tools → Addons → Sensitive Form Fields → Settings**:
    - **Pro, authorized** — decrypts and returns plain text
    - **Pro, unauthorized** — returns the configured mask string
 3. Values already prefixed with `enc:v1:` are never double-encrypted.
-4. If decryption fails (e.g. after `APP_KEY` rotation), the raw ciphertext is returned and a warning is logged.
+4. If decryption fails (e.g. after `APP_KEY` rotation), the raw ciphertext is returned, a warning is logged, and an error toast is shown in the CP (once per form per hour to avoid notification spam).
 
 ---
 
diff --git a/docs/OVERVIEW.md b/docs/OVERVIEW.md
index c999fa0..fe94b30 100644
--- a/docs/OVERVIEW.md
+++ b/docs/OVERVIEW.md
@@ -60,7 +60,7 @@ tests/
    - Checks the current user's permission (`view decrypted sensitive fields`).
    - **Authorized**: strips `enc:v1:` prefix and decrypts the value.
    - **Unauthorized**: replaces the value with the mask string (default `••••••`).
-4. If decryption fails (e.g. key rotation), returns raw ciphertext and logs a warning.
+4. If decryption fails (e.g. key rotation), returns raw ciphertext, logs a warning, and dispatches a CP error toast to the current user (HTTP context only; deduplicated to once per form per hour via `Cache::add`).
 
 ### Addon Settings
 
@@ -98,8 +98,9 @@ vendor/bin/phpunit
 
 ### Test Coverage
 
-- **Unit tests** (`FieldEncryptorTest`, 7 tests): marker detection, encrypt/decrypt round-trip, double-encryption prevention, non-string skipping, decrypt failure handling, mask value.
+- **Unit tests** (`FieldEncryptorTest`, 9 tests): marker detection, encrypt/decrypt round-trip, double-encryption prevention, non-string skipping, decrypt failure handling, mask value, CP toast console guard.
 - **Feature tests** (`SensitiveFieldsTest`, 12 tests): full write/read flow, free/pro mode, permission-based masking, query-builder decryption, per-form permission scoping.
+- **Unit tests** (`FieldEncryptorTest`, 9 tests): marker detection, encrypt/decrypt round-trip, double-encryption prevention, non-string skipping, decrypt failure handling, mask value, CP toast console guard.
 - **PRO command tests** (`ProCommandsTest`, 6 tests): bulk encrypt/decrypt, dry-run, skip-already-encrypted.
 
 ### PRO Commands
diff --git a/docs/PLAN.md b/docs/PLAN.md
index a0849a6..0692e3a 100644
--- a/docs/PLAN.md
+++ b/docs/PLAN.md
@@ -172,7 +172,7 @@ Edition is detected via the **Statamic Editions API**: `Addon::edition()` reads
 
 ## Tests
 
-### Unit (FieldEncryptorTest, 7 tests)
+### Unit (FieldEncryptorTest, 9 tests)
 1. Encrypts value with marker prefix
 2. Decrypts back to plaintext
 3. No double encryption
@@ -180,6 +180,8 @@ Edition is detected via the **Statamic Editions API**: `Addon::edition()` reads
 5. isEncrypted detects prefix
 6. mask returns configured value
 7. decrypt returns non-encrypted as-is
+8. Failed decrypt does not dispatch toast in console context
+9. Failed decrypt without context does not dispatch toast in console context
 
 ### Feature (SensitiveFieldsTest, 12 tests)
 1. Sensitive field stored encrypted
@@ -243,11 +245,11 @@ Larger teams need per-form control (e.g. HR form vs. contact form handled by dif
 
 ---
 
-### [FREE/PRO] CP notification on decrypt failure — Planned
+### [FREE/PRO] CP notification on decrypt failure — Implemented
 
-Currently, decryption failures (e.g. after an unrecovered APP_KEY rotation) are only logged via `Log::warning`. A Statamic CP notification dispatched to super admins would make data corruption visible without requiring log monitoring.
+Decryption failures are now surfaced in the CP as an error toast in addition to the existing `Log::warning`.
 
-Implementation sketch:
-- Hook into the existing `catch (\Throwable)` path in `FieldEncryptor::decrypt()`.
-- Dispatch a Statamic `Notification` to super admins (or use a Statamic flash/CP alert).
-- Add a rate-limit or deduplication guard to avoid notification spam.
+- `FieldEncryptor::decrypt()` accepts an optional `string $context` parameter (form handle) for deduplication.
+- In HTTP context, `Cache::add('sffields.decrypt_failure_notified.{context}', true, 3600)` is used as an atomic set-if-not-exists guard — at most one toast per form per hour.
+- `Toast::error()` is skipped entirely when `app()->runningInConsole()` is true (commands, queue workers).
+- `DecryptingSubmissionRepository` passes the form handle as `$context` when calling `decrypt()`.
diff --git a/lang/en/messages.php b/lang/en/messages.php
index 873e101..b7e9f60 100644
--- a/lang/en/messages.php
+++ b/lang/en/messages.php
@@ -12,6 +12,8 @@
     'permission_form_label' => 'View Decrypted Sensitive Fields',
     'permission_form_description' => 'Allow viewing decrypted values of sensitive fields in this form only',
 
+    'decrypt_failure_toast' => 'One or more sensitive field values could not be decrypted. Your APP_KEY may have changed. Use sensitive-fields:rekey (Pro) to recover.',
+
     'settings_enabled_display' => 'Enabled',
     'settings_enabled_instructions' => 'Enable or disable field encryption.',
     'settings_mask_display' => 'Mask String',
diff --git a/src/Encryption/FieldEncryptor.php b/src/Encryption/FieldEncryptor.php
index c9cddfa..26c9b42 100644
--- a/src/Encryption/FieldEncryptor.php
+++ b/src/Encryption/FieldEncryptor.php
@@ -4,9 +4,12 @@
 
 namespace Isapp\SensitiveFormFields\Encryption;
 
+use Illuminate\Support\Facades\Cache;
 use Illuminate\Support\Facades\Crypt;
 use Illuminate\Support\Facades\Log;
 use Statamic\Addons\Addon;
+use Statamic\Facades\CP\Toast;
+use Statamic\Statamic;
 
 class FieldEncryptor
 {
@@ -14,6 +17,9 @@ class FieldEncryptor
     // Allows detecting already-encrypted values and future format migrations.
     protected const PREFIX = 'enc:v1:';
 
+    // Suppress repeated CP toasts for the same form within this window (seconds).
+    protected const NOTIFY_TTL = 3600;
+
     public function __construct(
         protected Addon $addon,
     ) {}
@@ -31,7 +37,12 @@ public function encrypt(string $value): string
     // Returns the value unchanged (with a log warning) on decryption failure,
     // e.g. after an APP_KEY rotation. Callers should treat the raw ciphertext
     // as an opaque fallback rather than a fatal error.
-    public function decrypt(string $value): string
+    //
+    // $context is an optional form handle used to deduplicate CP toasts so that
+    // bulk failures (e.g. many submissions after an APP_KEY rotation) produce at
+    // most one toast per form per hour. Pass the form handle from repository callers;
+    // omit from CLI callers (toast is suppressed in console context anyway).
+    public function decrypt(string $value, string $context = ''): string
     {
         if (! $this->isEncrypted($value)) {
             return $value;
@@ -42,6 +53,29 @@ public function decrypt(string $value): string
         } catch (\Throwable $e) {
             Log::warning('Failed to decrypt sensitive field value: ' . $e->getMessage());
 
+            // Only dispatch CP toasts on actual CP requests — not API or frontend
+            // requests, which could consume the dedup window before a CP user visits.
+            // Cache::add() is atomic set-if-not-exists; the key is rolled back via
+            // Cache::forget() when toast delivery fails so the dedup window is not
+            // consumed without a toast being shown. Wrapped in try/catch so that
+            // cache or session failures never break the graceful fallback.
+            try {
+                if (Statamic::isCpRoute()) {
+                    $cacheKey = 'sffields.decrypt_failure_notified.' . ($context ?: 'unknown');
+                    if (Cache::add($cacheKey, true, self::NOTIFY_TTL)) {
+                        try {
+                            Toast::error(__('statamic-sensitive-form-fields::messages.decrypt_failure_toast'));
+                        } catch (\Throwable) {
+                            // Roll back the dedup key so a future request with an active
+                            // CP session can still deliver the toast.
+                            Cache::forget($cacheKey);
+                        }
+                    }
+                }
+            } catch (\Throwable) {
+                // Cache failure must never convert a recoverable decrypt error into a fatal one.
+            }
+
             return $value;
         }
     }
diff --git a/src/Repositories/DecryptingSubmissionQueryBuilder.php b/src/Repositories/DecryptingSubmissionQueryBuilder.php
index c2d4788..0dc9e50 100644
--- a/src/Repositories/DecryptingSubmissionQueryBuilder.php
+++ b/src/Repositories/DecryptingSubmissionQueryBuilder.php
@@ -81,7 +81,7 @@ protected function decryptSubmission(Submission $submission): void
             }
 
             if ($canDecrypt) {
-                $submission->set($handle, $this->encryptor->decrypt($value));
+                $submission->set($handle, $this->encryptor->decrypt($value, $submission->form()->handle()));
             } else {
                 $submission->set($handle, $this->encryptor->mask());
             }
diff --git a/src/Repositories/DecryptingSubmissionRepository.php b/src/Repositories/DecryptingSubmissionRepository.php
index 28eadd7..48d2fa1 100644
--- a/src/Repositories/DecryptingSubmissionRepository.php
+++ b/src/Repositories/DecryptingSubmissionRepository.php
@@ -104,7 +104,7 @@ protected function decryptSubmission(Submission $submission): void
             }
 
             if ($canDecrypt) {
-                $submission->set($handle, $this->encryptor->decrypt($value));
+                $submission->set($handle, $this->encryptor->decrypt($value, $submission->form()->handle()));
             } else {
                 $submission->set($handle, $this->encryptor->mask());
             }
diff --git a/tests/Unit/FieldEncryptorTest.php b/tests/Unit/FieldEncryptorTest.php
index 217fdb7..a3c63a4 100644
--- a/tests/Unit/FieldEncryptorTest.php
+++ b/tests/Unit/FieldEncryptorTest.php
@@ -66,4 +66,25 @@ public function test_decrypt_returns_non_encrypted_value_as_is()
     {
         $this->assertSame('plaintext', $this->encryptor->decrypt('plaintext'));
     }
+
+    public function test_failed_decrypt_does_not_dispatch_toast_in_console_context()
+    {
+        // The test suite runs in console context (app()->runningInConsole() === true),
+        // so the Toast must never be called — verified by spying on the facade.
+        \Statamic\Facades\CP\Toast::spy();
+
+        $this->encryptor->decrypt('enc:v1:corrupted-ciphertext', 'contact');
+
+        \Statamic\Facades\CP\Toast::shouldNotHaveReceived('error');
+    }
+
+    public function test_failed_decrypt_without_context_does_not_dispatch_toast_in_console_context()
+    {
+        \Statamic\Facades\CP\Toast::spy();
+
+        // Backward-compatible: context parameter is optional.
+        $this->encryptor->decrypt('enc:v1:corrupted-ciphertext');
+
+        \Statamic\Facades\CP\Toast::shouldNotHaveReceived('error');
+    }
 }