diff --git a/Classes/Backend/FormDataProvider/DecryptApiKey.php b/Classes/Backend/FormDataProvider/DecryptApiKey.php
new file mode 100644
index 0000000..b7229fd
--- /dev/null
+++ b/Classes/Backend/FormDataProvider/DecryptApiKey.php
@@ -0,0 +1,45 @@
+<?php
+
+declare(strict_types=1);
+
+/*
+ * This file is part of TYPO3 CMS-based extension "aim" by b13.
+ *
+ * It is free software; you can redistribute it and/or modify it under
+ * the terms of the GNU General Public License, either version 2
+ * of the License, or any later version.
+ */
+
+namespace B13\Aim\Backend\FormDataProvider;
+
+use B13\Aim\Crypto\ApiKeyEncryption;
+use TYPO3\CMS\Backend\Form\FormDataProviderInterface;
+
+/**
+ * Decrypts the api_key value before it is rendered in the backend form.
+ *
+ * Admins editing a tx_aim_configuration record see the plaintext key and
+ * can verify or replace it. On submit, the DataHandler hook encrypts the
+ * value again. If the admin re-saves the record without touching api_key,
+ * the form re-sends plaintext, which the hook re-encrypts — the value on
+ * disk stays encrypted throughout.
+ */
+final class DecryptApiKey implements FormDataProviderInterface
+{
+    public function __construct(private readonly ApiKeyEncryption $encryption) {}
+
+    public function addData(array $result): array
+    {
+        if (($result['tableName'] ?? '') !== 'tx_aim_configuration') {
+            return $result;
+        }
+
+        $value = (string)($result['databaseRow']['api_key'] ?? '');
+        if ($value === '' || !$this->encryption->isEncrypted($value)) {
+            return $result;
+        }
+
+        $result['databaseRow']['api_key'] = $this->encryption->decrypt($value);
+        return $result;
+    }
+}
diff --git a/Classes/Command/RotateApiKeys.php b/Classes/Command/RotateApiKeys.php
new file mode 100644
index 0000000..9c00f65
--- /dev/null
+++ b/Classes/Command/RotateApiKeys.php
@@ -0,0 +1,194 @@
+<?php
+
+declare(strict_types=1);
+
+/*
+ * This file is part of TYPO3 CMS-based extension "aim" by b13.
+ *
+ * It is free software; you can redistribute it and/or modify it under
+ * the terms of the GNU General Public License, either version 2
+ * of the License, or any later version.
+ */
+
+namespace B13\Aim\Command;
+
+use B13\Aim\Crypto\ApiKeyEncryption;
+use B13\Aim\Exception\ApiKeyEncryptionException;
+use Symfony\Component\Console\Attribute\AsCommand;
+use Symfony\Component\Console\Command\Command;
+use Symfony\Component\Console\Input\InputInterface;
+use Symfony\Component\Console\Input\InputOption;
+use Symfony\Component\Console\Output\OutputInterface;
+use TYPO3\CMS\Core\Database\Connection;
+use TYPO3\CMS\Core\Database\ConnectionPool;
+
+/**
+ * Re-encrypts stored AiM provider API keys after $TYPO3_CONF_VARS[SYS][encryptionKey]
+ * has been rotated.
+ *
+ * Workflow per row:
+ *   1. Skip plaintext / endpoint URL / unencrypted value
+ *   2. Decrypts with the current system key, skip already migrated
+ *   3. Decrypts with the supplied --old-key, re-encrypt with the current system key
+ *   4. Decrypts with neither is reported as unrecoverable, abort without writes
+ *
+ * Idempotent: a second run with the same --old-key is a no-op.
+ */
+#[AsCommand(
+    name: 'aim:rotateApiKeys',
+    description: 'Re-encrypt stored AiM API keys after a SYS/encryptionKey rotation.',
+)]
+final class RotateApiKeys extends Command
+{
+    private const TABLE = 'tx_aim_configuration';
+
+    public function __construct(
+        private readonly ApiKeyEncryption $encryption,
+        private readonly ConnectionPool $connectionPool,
+    ) {
+        parent::__construct();
+    }
+
+    protected function configure(): void
+    {
+        $this
+            ->setHelp(
+                'When $TYPO3_CONF_VARS[SYS][encryptionKey] has been rotated, existing encrypted '
+                . 'API keys can no longer be read. This command takes the previous value of the '
+                . 'system key, decrypts each stored API key with it, and re-encrypts using the '
+                . 'current system key.'
+            )
+            ->addOption(
+                'old-key',
+                null,
+                InputOption::VALUE_REQUIRED,
+                'The previous value of $TYPO3_CONF_VARS[SYS][encryptionKey].',
+            )
+            ->addOption(
+                'dry-run',
+                null,
+                InputOption::VALUE_NONE,
+                'Report what would change without writing.',
+            );
+    }
+
+    protected function execute(InputInterface $input, OutputInterface $output): int
+    {
+        $oldKey = (string)$input->getOption('old-key');
+        if ($oldKey === '') {
+            $output->writeln('<error>--old-key is required.</error>');
+            return Command::FAILURE;
+        }
+        $dryRun = (bool)$input->getOption('dry-run');
+
+        [$toRotate, $unrecoverable, $alreadyCurrent, $unencrypted] = $this->classifyRows($oldKey);
+
+        if ($unrecoverable !== []) {
+            $output->writeln('<error>The following rows cannot be decrypted with the supplied old key:</error>');
+            foreach ($unrecoverable as $uid => $message) {
+                $output->writeln(sprintf('  - uid=%d: %s', $uid, $message));
+            }
+            $output->writeln('<error>Aborting without writes. Verify the --old-key value.</error>');
+            return Command::FAILURE;
+        }
+
+        if ($toRotate === []) {
+            $output->writeln('Nothing to rotate.');
+            $this->writeSkipBreakdown($output, $alreadyCurrent, $unencrypted);
+            return Command::SUCCESS;
+        }
+
+        if ($dryRun) {
+            $output->writeln(sprintf(
+                '<info>[dry-run] Would re-encrypt %d row(s).</info>',
+                count($toRotate),
+            ));
+            $this->writeSkipBreakdown($output, $alreadyCurrent, $unencrypted);
+            return Command::SUCCESS;
+        }
+
+        $connection = $this->connectionPool->getConnectionForTable(self::TABLE);
+        foreach ($toRotate as $uid => $plaintext) {
+            $connection->update(
+                self::TABLE,
+                ['api_key' => $this->encryption->encrypt($plaintext)],
+                ['uid' => $uid],
+                ['api_key' => Connection::PARAM_STR],
+            );
+        }
+
+        $output->writeln(sprintf(
+            '<info>Re-encrypted %d API key(s).</info>',
+            count($toRotate),
+        ));
+        $this->writeSkipBreakdown($output, $alreadyCurrent, $unencrypted);
+        return Command::SUCCESS;
+    }
+
+    private function writeSkipBreakdown(OutputInterface $output, int $alreadyCurrent, int $unencrypted): void
+    {
+        if ($alreadyCurrent > 0) {
+            $output->writeln(sprintf(
+                '  - %d row(s) already use the current system key',
+                $alreadyCurrent,
+            ));
+        }
+        if ($unencrypted > 0) {
+            $output->writeln(sprintf(
+                '  - %d row(s) are not encrypted (endpoint URLs or empty values)',
+                $unencrypted,
+            ));
+        }
+    }
+
+    /**
+     * @return array{0: array<int, string>, 1: array<int, string>, 2: int, 3: int}
+     *         [uid => plaintext to re-encrypt], [uid => failure message], already-current count, unencrypted count
+     */
+    private function classifyRows(string $oldKey): array
+    {
+        $toRotate = [];
+        $unrecoverable = [];
+        $alreadyCurrent = 0;
+        $unencrypted = 0;
+
+        foreach ($this->fetchAllRows() as $row) {
+            $uid = (int)$row['uid'];
+            $value = (string)$row['api_key'];
+
+            if ($value === '' || $this->encryption->isEndpointUrl($value) || !$this->encryption->isEncrypted($value)) {
+                $unencrypted++;
+                continue;
+            }
+
+            try {
+                $this->encryption->decrypt($value);
+                $alreadyCurrent++;
+                continue;
+            } catch (ApiKeyEncryptionException) {
+                // Fall through to old-key attempt
+            }
+
+            try {
+                $toRotate[$uid] = $this->encryption->decryptWithSystemKey($value, $oldKey);
+            } catch (ApiKeyEncryptionException $e) {
+                $unrecoverable[$uid] = $e->getMessage();
+            }
+        }
+
+        return [$toRotate, $unrecoverable, $alreadyCurrent, $unencrypted];
+    }
+
+    /**
+     * @return list<array{uid: int|string, api_key: string|null}>
+     */
+    private function fetchAllRows(): array
+    {
+        $qb = $this->connectionPool->getQueryBuilderForTable(self::TABLE);
+        $qb->getRestrictions()->removeAll();
+        return $qb->select('uid', 'api_key')
+            ->from(self::TABLE)
+            ->executeQuery()
+            ->fetchAllAssociative();
+    }
+}
diff --git a/Classes/Crypto/ApiKeyEncryption.php b/Classes/Crypto/ApiKeyEncryption.php
new file mode 100644
index 0000000..b64fe66
--- /dev/null
+++ b/Classes/Crypto/ApiKeyEncryption.php
@@ -0,0 +1,191 @@
+<?php
+
+declare(strict_types=1);
+
+/*
+ * This file is part of TYPO3 CMS-based extension "aim" by b13.
+ *
+ * It is free software; you can redistribute it and/or modify it under
+ * the terms of the GNU General Public License, either version 2
+ * of the License, or any later version.
+ */
+
+namespace B13\Aim\Crypto;
+
+use B13\Aim\Exception\ApiKeyEncryptionException;
+use TYPO3\CMS\Core\Crypto\Cipher\CipherDecryptionFailedException;
+use TYPO3\CMS\Core\Crypto\Cipher\CipherException;
+use TYPO3\CMS\Core\Crypto\Cipher\CipherService;
+use TYPO3\CMS\Core\Crypto\Cipher\CipherValue;
+use TYPO3\CMS\Core\Crypto\Cipher\KeyFactory;
+use TYPO3\CMS\Core\Utility\GeneralUtility;
+
+/**
+ * Encrypts and decrypts AiM provider API keys stored in the database.
+ *
+ * On TYPO3 v14+ this delegates to the core CipherService (XChaCha20-Poly1305
+ * AEAD, key derived via sodium_crypto_kdf_derive_from_key from SYS/encryptionKey).
+ * On v12/v13 — where CipherService does not exist yet — we use a libsodium
+ * secretbox implementation (XSalsa20-Poly1305) with the same SYS/encryptionKey
+ * as input, derived through sodium_crypto_generichash.
+ *
+ * Wire format selects the path on decrypt:
+ *   aim:enc:v1: ... — local secretbox payload (used on v12/v13)
+ *   aim:enc:v2: ... — TYPO3 CipherService payload (used on v14+)
+ *
+ * Values without either prefix are treated as legacy plaintext and returned
+ * unchanged, so the upgrade wizard can migrate them in-place.
+ */
+final class ApiKeyEncryption
+{
+    public const PREFIX_V1 = 'aim:enc:v1:';
+    public const PREFIX_V2 = 'aim:enc:v2:';
+    public const PREFIX_ANY = 'aim:enc:';
+
+    private const KEY_DOMAIN = 'aim:apikey:v1';
+
+    public function encrypt(string $plaintext): string
+    {
+        if ($plaintext === '' || $this->isEncrypted($plaintext) || $this->isEndpointUrl($plaintext)) {
+            return $plaintext;
+        }
+
+        if ($this->coreCipherAvailable()) {
+            return self::PREFIX_V2 . $this->encryptViaCore($plaintext);
+        }
+        return self::PREFIX_V1 . $this->encryptViaSecretbox($plaintext);
+    }
+
+    /**
+     * The api_key column doubles as an endpoint URL for providers that
+     * expose a local HTTP service (Ollama, LM Studio, OpenAI-compatible
+     * proxies). Those values aren't secrets and shouldn't be encrypted.
+     */
+    public function isEndpointUrl(string $value): bool
+    {
+        return str_starts_with($value, 'http://') || str_starts_with($value, 'https://');
+    }
+
+    public function decrypt(string $value): string
+    {
+        if ($value === '') {
+            return $value;
+        }
+        if (str_starts_with($value, self::PREFIX_V2)) {
+            return $this->decryptViaCore(substr($value, strlen(self::PREFIX_V2)));
+        }
+        if (str_starts_with($value, self::PREFIX_V1)) {
+            return $this->decryptViaSecretbox(substr($value, strlen(self::PREFIX_V1)));
+        }
+        return $value;
+    }
+
+    /**
+     * Decrypts a value using a system encryption key other than the one
+     * currently in $TYPO3_CONF_VARS — needed by the rotation command after
+     * SYS/encryptionKey has changed but stored ciphertexts still use the old
+     * derivation.
+     *
+     * Both decryption paths (v1 secretbox and v2 CipherService) read the
+     * system key from globals, so we swap it temporarily and restore it via
+     * try/finally. The swap is local to this call.
+     */
+    public function decryptWithSystemKey(string $value, string $systemKey): string
+    {
+        if ($value === '' || !$this->isEncrypted($value)) {
+            return $value;
+        }
+
+        $previous = $GLOBALS['TYPO3_CONF_VARS']['SYS']['encryptionKey'] ?? null;
+        $GLOBALS['TYPO3_CONF_VARS']['SYS']['encryptionKey'] = $systemKey;
+        try {
+            return $this->decrypt($value);
+        } finally {
+            $GLOBALS['TYPO3_CONF_VARS']['SYS']['encryptionKey'] = $previous;
+        }
+    }
+
+    public function isEncrypted(string $value): bool
+    {
+        return str_starts_with($value, self::PREFIX_ANY);
+    }
+
+    private function coreCipherAvailable(): bool
+    {
+        return class_exists(CipherService::class) && class_exists(KeyFactory::class);
+    }
+
+    private function encryptViaCore(string $plaintext): string
+    {
+        $keyFactory = GeneralUtility::makeInstance(KeyFactory::class);
+        $cipher = GeneralUtility::makeInstance(CipherService::class);
+        $sharedKey = $keyFactory->deriveSharedKeyFromEncryptionKey(self::class);
+        return $cipher->encrypt($plaintext, $sharedKey)->encode();
+    }
+
+    private function decryptViaCore(string $payload): string
+    {
+        try {
+            $keyFactory = GeneralUtility::makeInstance(KeyFactory::class);
+            $cipher = GeneralUtility::makeInstance(CipherService::class);
+            $sharedKey = $keyFactory->deriveSharedKeyFromEncryptionKey(self::class);
+            return $cipher->decrypt(CipherValue::fromSerialized($payload), $sharedKey);
+        } catch (CipherDecryptionFailedException | CipherException $e) {
+            throw new ApiKeyEncryptionException(
+                'AiM API key could not be decrypted via core CipherService: ' . $e->getMessage(),
+                1773874410,
+                $e,
+            );
+        }
+    }
+
+    private function encryptViaSecretbox(string $plaintext): string
+    {
+        $key = $this->deriveSecretboxKey();
+        $nonce = random_bytes(SODIUM_CRYPTO_SECRETBOX_NONCEBYTES);
+        $ciphertext = sodium_crypto_secretbox($plaintext, $nonce, $key);
+        sodium_memzero($key);
+
+        return base64_encode($nonce . $ciphertext);
+    }
+
+    private function decryptViaSecretbox(string $payload): string
+    {
+        $bytes = base64_decode($payload, true);
+        if ($bytes === false || strlen($bytes) <= SODIUM_CRYPTO_SECRETBOX_NONCEBYTES) {
+            throw new ApiKeyEncryptionException('AiM API key ciphertext is malformed.', 1773874400);
+        }
+
+        $nonce = substr($bytes, 0, SODIUM_CRYPTO_SECRETBOX_NONCEBYTES);
+        $ciphertext = substr($bytes, SODIUM_CRYPTO_SECRETBOX_NONCEBYTES);
+        $key = $this->deriveSecretboxKey();
+        $plaintext = sodium_crypto_secretbox_open($ciphertext, $nonce, $key);
+        sodium_memzero($key);
+
+        if ($plaintext === false) {
+            throw new ApiKeyEncryptionException(
+                'AiM API key could not be decrypted. The system encryption key may have changed.',
+                1773874401,
+            );
+        }
+
+        return $plaintext;
+    }
+
+    private function deriveSecretboxKey(): string
+    {
+        $systemKey = (string)($GLOBALS['TYPO3_CONF_VARS']['SYS']['encryptionKey'] ?? '');
+        if ($systemKey === '') {
+            throw new ApiKeyEncryptionException(
+                'AiM API key encryption requires $GLOBALS[\'TYPO3_CONF_VARS\'][\'SYS\'][\'encryptionKey\'] to be set.',
+                1773874402,
+            );
+        }
+
+        return sodium_crypto_generichash(
+            self::KEY_DOMAIN . "\0" . $systemKey,
+            '',
+            SODIUM_CRYPTO_SECRETBOX_KEYBYTES,
+        );
+    }
+}
diff --git a/Classes/Domain/Repository/ProviderConfigurationRepository.php b/Classes/Domain/Repository/ProviderConfigurationRepository.php
index b0b554b..d0f8982 100644
--- a/Classes/Domain/Repository/ProviderConfigurationRepository.php
+++ b/Classes/Domain/Repository/ProviderConfigurationRepository.php
@@ -12,6 +12,7 @@
 
 namespace B13\Aim\Domain\Repository;
 
+use B13\Aim\Crypto\ApiKeyEncryption;
 use B13\Aim\Domain\Model\ProviderConfiguration;
 use B13\Aim\Domain\Model\ProviderConfigurationFactory;
 use TYPO3\CMS\Core\Database\Connection;
@@ -26,6 +27,7 @@ class ProviderConfigurationRepository
 
     public function __construct(
         private readonly ConnectionPool $connectionPool,
+        private readonly ApiKeyEncryption $encryption,
     ) {}
 
     public function findByUid(int $uid): ?ProviderConfiguration
@@ -188,6 +190,9 @@ protected function map(array $rows): array
 
     protected function mapSingleRow(array $row): ProviderConfiguration
     {
+        if (isset($row['api_key']) && $row['api_key'] !== '') {
+            $row['api_key'] = $this->encryption->decrypt((string)$row['api_key']);
+        }
         return ProviderConfigurationFactory::fromRow($row);
     }
 
diff --git a/Classes/Exception/ApiKeyEncryptionException.php b/Classes/Exception/ApiKeyEncryptionException.php
new file mode 100644
index 0000000..ee99154
--- /dev/null
+++ b/Classes/Exception/ApiKeyEncryptionException.php
@@ -0,0 +1,18 @@
+<?php
+
+declare(strict_types=1);
+
+/*
+ * This file is part of TYPO3 CMS-based extension "aim" by b13.
+ *
+ * It is free software; you can redistribute it and/or modify it under
+ * the terms of the GNU General Public License, either version 2
+ * of the License, or any later version.
+ */
+
+namespace B13\Aim\Exception;
+
+/**
+ * Thrown when an AiM API key cannot be encrypted or decrypted.
+ */
+final class ApiKeyEncryptionException extends \RuntimeException {}
diff --git a/Classes/Hooks/EncryptApiKey.php b/Classes/Hooks/EncryptApiKey.php
new file mode 100644
index 0000000..d75a60b
--- /dev/null
+++ b/Classes/Hooks/EncryptApiKey.php
@@ -0,0 +1,50 @@
+<?php
+
+declare(strict_types=1);
+
+/*
+ * This file is part of TYPO3 CMS-based extension "aim" by b13.
+ *
+ * It is free software; you can redistribute it and/or modify it under
+ * the terms of the GNU General Public License, either version 2
+ * of the License, or any later version.
+ */
+
+namespace B13\Aim\Hooks;
+
+use B13\Aim\Crypto\ApiKeyEncryption;
+use TYPO3\CMS\Core\DataHandling\DataHandler;
+
+/**
+ * Encrypts AiM provider API keys before they are written to the database.
+ *
+ * Runs in processDatamap_postProcessFieldArray so the encrypted value is
+ * what DataHandler persists. Idempotent: already-encrypted values pass
+ * through unchanged, which means re-saving an unchanged row does not
+ * double-encrypt the value.
+ */
+final class EncryptApiKey
+{
+    private const TABLE = 'tx_aim_configuration';
+
+    public function __construct(private readonly ApiKeyEncryption $encryption) {}
+
+    public function processDatamap_postProcessFieldArray(
+        string $status,
+        string $table,
+        $id,
+        array &$fieldArray,
+        DataHandler $dataHandler,
+    ): void {
+        if ($table !== self::TABLE || !array_key_exists('api_key', $fieldArray)) {
+            return;
+        }
+
+        $value = (string)$fieldArray['api_key'];
+        if ($value === '') {
+            return;
+        }
+
+        $fieldArray['api_key'] = $this->encryption->encrypt($value);
+    }
+}
diff --git a/Classes/Updates/EncryptApiKeysUpgrade.php b/Classes/Updates/EncryptApiKeysUpgrade.php
new file mode 100644
index 0000000..390a0f8
--- /dev/null
+++ b/Classes/Updates/EncryptApiKeysUpgrade.php
@@ -0,0 +1,108 @@
+<?php
+
+declare(strict_types=1);
+
+/*
+ * This file is part of TYPO3 CMS-based extension "aim" by b13.
+ *
+ * It is free software; you can redistribute it and/or modify it under
+ * the terms of the GNU General Public License, either version 2
+ * of the License, or any later version.
+ */
+
+namespace B13\Aim\Updates;
+
+use B13\Aim\Crypto\ApiKeyEncryption;
+use TYPO3\CMS\Core\Database\Connection;
+use TYPO3\CMS\Core\Database\ConnectionPool;
+use TYPO3\CMS\Install\Attribute\UpgradeWizard;
+use TYPO3\CMS\Install\Updates\DatabaseUpdatedPrerequisite;
+use TYPO3\CMS\Install\Updates\UpgradeWizardInterface;
+
+/**
+ * Encrypts plaintext api_key values
+ *
+ * Idempotent: rows whose api_key already carries the encryption prefix
+ * are skipped, and endpoint URLs (Ollama, LM Studio, …) are left as
+ * plaintext, so it is safe to re-run.
+ */
+#[UpgradeWizard('aimEncryptApiKeys')]
+final class EncryptApiKeysUpgrade implements UpgradeWizardInterface
+{
+    private const TABLE = 'tx_aim_configuration';
+
+    public function __construct(
+        private readonly ApiKeyEncryption $encryption,
+        private readonly ConnectionPool $connectionPool,
+    ) {}
+
+    public function getTitle(): string
+    {
+        return '[AiM] Encrypt stored provider API keys';
+    }
+
+    public function getDescription(): string
+    {
+        return 'Encrypts existing plaintext API keys in tx_aim_configuration using libsodium '
+            . '(XSalsa20-Poly1305) with a key derived from $TYPO3_CONF_VARS[SYS][encryptionKey]. '
+            . 'Already-encrypted rows are skipped.';
+    }
+
+    public function getPrerequisites(): array
+    {
+        return [
+            DatabaseUpdatedPrerequisite::class,
+        ];
+    }
+
+    public function updateNecessary(): bool
+    {
+        return $this->findRowsToEncrypt() !== [];
+    }
+
+    public function executeUpdate(): bool
+    {
+        $connection = $this->connectionPool->getConnectionForTable(self::TABLE);
+
+        foreach ($this->findRowsToEncrypt() as $row) {
+            $connection->update(
+                self::TABLE,
+                ['api_key' => $this->encryption->encrypt((string)$row['api_key'])],
+                ['uid' => (int)$row['uid']],
+                ['api_key' => Connection::PARAM_STR],
+            );
+        }
+
+        return true;
+    }
+
+    /**
+     * Returns plaintext rows that hold a real API key (not an endpoint URL).
+     *
+     * @return list<array{uid: int, api_key: string}>
+     */
+    private function findRowsToEncrypt(): array
+    {
+        $qb = $this->connectionPool->getQueryBuilderForTable(self::TABLE);
+        $qb->getRestrictions()->removeAll();
+
+        $rows = $qb->select('uid', 'api_key')
+            ->from(self::TABLE)
+            ->where(
+                $qb->expr()->neq('api_key', $qb->createNamedParameter('')),
+                $qb->expr()->notLike(
+                    'api_key',
+                    $qb->createNamedParameter(ApiKeyEncryption::PREFIX_ANY . '%'),
+                ),
+                $qb->expr()->notLike('api_key', $qb->createNamedParameter('http://%')),
+                $qb->expr()->notLike('api_key', $qb->createNamedParameter('https://%')),
+            )
+            ->executeQuery()
+            ->fetchAllAssociative();
+
+        return array_map(
+            static fn(array $row): array => ['uid' => (int)$row['uid'], 'api_key' => (string)$row['api_key']],
+            $rows,
+        );
+    }
+}
diff --git a/Configuration/Services.yaml b/Configuration/Services.yaml
index bf02247..e313a70 100644
--- a/Configuration/Services.yaml
+++ b/Configuration/Services.yaml
@@ -12,3 +12,12 @@ services:
 
   B13\Aim\Domain\Repository\ProviderConfigurationRepository:
     public: true
+
+  B13\Aim\Crypto\ApiKeyEncryption:
+    public: true
+
+  B13\Aim\Hooks\EncryptApiKey:
+    public: true
+
+  B13\Aim\Backend\FormDataProvider\DecryptApiKey:
+    public: true
diff --git a/README.md b/README.md
index 52d2a2e..a14f9d5 100644
--- a/README.md
+++ b/README.md
@@ -342,6 +342,29 @@ Install a bridge, flush caches. The provider appears automatically in the backen
 
 AiM provides a complete governance system for AI usage, built on native TYPO3 mechanisms.
 
+### API key encryption
+
+Provider API keys stored in `tx_aim_configuration.api_key` are encrypted using a key derived from `$GLOBALS['TYPO3_CONF_VARS']['SYS']['encryptionKey']`.
+
+| TYPO3 version | Cipher | Implementation |
+|---|---|---|
+| v14+ | XChaCha20-Poly1305 AEAD | Core `\TYPO3\CMS\Core\Crypto\Cipher\CipherService` |
+| v12 / v13 | XSalsa20-Poly1305 secretbox | Local libsodium implementation (CipherService not yet available) |
+
+Stored values carry a version prefix (`aim:enc:v1:` for the v12/v13 path, `aim:enc:v2:` for the v14 path) so decryption auto-selects the right routine even after an upgrade. Encryption is transparent: a DataHandler hook encrypts on save, a FormDataProvider decrypts for the backend edit form, and the repository decrypts on read. Legacy plaintext rows from earlier AiM versions are migrated via the **"[AiM] Encrypt stored provider API keys"** upgrade wizard in the Install Tool.
+
+For providers that put an **endpoint URL** in the `api_key` field instead of a real secret (Ollama, LM Studio, self-hosted OpenAI-compatible proxies), AiM detects the `http://` / `https://` prefix and skips encryption — the URL stays plaintext both in the column and in DB exports.
+
+If `SYS/encryptionKey` is rotated, existing API keys can no longer be decrypted with the new key. Run the rotation command *before* the rotation takes effect, or right after with the old value still in hand:
+
+```bash
+vendor/bin/typo3 aim:rotateApiKeys --old-key='<previous SYS/encryptionKey value>'
+```
+
+The command decrypts each stored key with the supplied old value, re-encrypts with the current one, and reports the result. It is idempotent (re-running with the same old key is a no-op) and aborts without writes if any row cannot be decrypted with the supplied value. Add `--dry-run` to preview.
+
+Without the previous key value, encrypted API keys cannot be recovered. This is by design. Save the old `SYS/encryptionKey` somewhere safe before rotating.
+
 ### Provider restrictions
 
 Restrict provider configurations to specific backend user groups via the `be_groups` field on each configuration record. Only members of the listed groups (or admins) can use that configuration.
diff --git a/Tests/Functional/Command/RotateApiKeysTest.php b/Tests/Functional/Command/RotateApiKeysTest.php
new file mode 100644
index 0000000..a5f51d3
--- /dev/null
+++ b/Tests/Functional/Command/RotateApiKeysTest.php
@@ -0,0 +1,197 @@
+<?php
+
+declare(strict_types=1);
+
+/*
+ * This file is part of TYPO3 CMS-based extension "aim" by b13.
+ *
+ * It is free software; you can redistribute it and/or modify it under
+ * the terms of the GNU General Public License, either version 2
+ * of the License, or any later version.
+ */
+
+namespace B13\Aim\Tests\Functional\Command;
+
+use B13\Aim\Command\RotateApiKeys;
+use B13\Aim\Crypto\ApiKeyEncryption;
+use PHPUnit\Framework\Attributes\Test;
+use Symfony\Component\Console\Tester\CommandTester;
+use TYPO3\CMS\Core\Console\CommandRegistry;
+use TYPO3\CMS\Core\Database\Connection;
+use TYPO3\CMS\Core\Database\ConnectionPool;
+use TYPO3\CMS\Core\Utility\GeneralUtility;
+use TYPO3\TestingFramework\Core\Functional\FunctionalTestCase;
+
+final class RotateApiKeysTest extends FunctionalTestCase
+{
+    private const TABLE = 'tx_aim_configuration';
+    private const OLD_KEY = 'old-system-key-aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa';
+    private const NEW_KEY = 'new-system-key-bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb';
+
+    protected array $testExtensionsToLoad = [
+        'b13/aim',
+    ];
+
+    #[Test]
+    public function commandIsRegisteredInTheConsoleRegistry(): void
+    {
+        $registry = $this->get(CommandRegistry::class);
+        self::assertTrue($registry->has('aim:rotateApiKeys'));
+        self::assertInstanceOf(RotateApiKeys::class, $registry->get('aim:rotateApiKeys'));
+    }
+
+    #[Test]
+    public function rotatesEncryptedRowsFromOldKeyToCurrent(): void
+    {
+        $encryption = $this->get(ApiKeyEncryption::class);
+
+        $GLOBALS['TYPO3_CONF_VARS']['SYS']['encryptionKey'] = self::OLD_KEY;
+        $uid = $this->insertRow($encryption->encrypt('sk-real-secret'));
+
+        $GLOBALS['TYPO3_CONF_VARS']['SYS']['encryptionKey'] = self::NEW_KEY;
+        // The old ciphertext must NOT decrypt with the new key
+        $this->assertThrows(fn() => $encryption->decrypt($this->fetchRawApiKey($uid)));
+
+        $exit = $this->runCommand(['--old-key' => self::OLD_KEY]);
+        self::assertSame(0, $exit);
+
+        // After rotation, the value decrypts with the current key
+        self::assertSame('sk-real-secret', $encryption->decrypt($this->fetchRawApiKey($uid)));
+    }
+
+    #[Test]
+    public function isIdempotentOnSecondRun(): void
+    {
+        $encryption = $this->get(ApiKeyEncryption::class);
+
+        $GLOBALS['TYPO3_CONF_VARS']['SYS']['encryptionKey'] = self::OLD_KEY;
+        $uid = $this->insertRow($encryption->encrypt('sk-real-secret'));
+
+        $GLOBALS['TYPO3_CONF_VARS']['SYS']['encryptionKey'] = self::NEW_KEY;
+
+        self::assertSame(0, $this->runCommand(['--old-key' => self::OLD_KEY]));
+        $afterFirst = $this->fetchRawApiKey($uid);
+
+        $tester = $this->runCommandAndReturnTester(['--old-key' => self::OLD_KEY]);
+        self::assertSame(0, $tester->getStatusCode());
+        $display = $tester->getDisplay();
+        self::assertStringContainsString('Nothing to rotate', $display);
+        self::assertStringContainsString('1 row(s) already use the current system key', $display);
+
+        // Same ciphertext (no double re-encryption)
+        self::assertSame($afterFirst, $this->fetchRawApiKey($uid));
+        self::assertSame('sk-real-secret', $encryption->decrypt($afterFirst));
+    }
+
+    #[Test]
+    public function endpointUrlsAreSkippedAndReportedDistinctly(): void
+    {
+        $GLOBALS['TYPO3_CONF_VARS']['SYS']['encryptionKey'] = self::NEW_KEY;
+        $uid = $this->insertRow('http://host.docker.internal:11434');
+
+        $tester = $this->runCommandAndReturnTester(['--old-key' => self::OLD_KEY]);
+        self::assertSame(0, $tester->getStatusCode());
+
+        $display = $tester->getDisplay();
+        self::assertStringContainsString('Nothing to rotate', $display);
+        self::assertStringContainsString('1 row(s) are not encrypted', $display);
+        self::assertStringNotContainsString('already use the current system key', $display);
+        self::assertSame('http://host.docker.internal:11434', $this->fetchRawApiKey($uid));
+    }
+
+    #[Test]
+    public function abortsAndReportsWhenOldKeyIsWrong(): void
+    {
+        $encryption = $this->get(ApiKeyEncryption::class);
+
+        $GLOBALS['TYPO3_CONF_VARS']['SYS']['encryptionKey'] = self::OLD_KEY;
+        $uid = $this->insertRow($encryption->encrypt('sk-real-secret'));
+        $beforeRotation = $this->fetchRawApiKey($uid);
+
+        $GLOBALS['TYPO3_CONF_VARS']['SYS']['encryptionKey'] = self::NEW_KEY;
+
+        $tester = $this->runCommandAndReturnTester(['--old-key' => 'definitely-not-the-old-key']);
+        self::assertSame(1, $tester->getStatusCode());
+        self::assertStringContainsString('cannot be decrypted', $tester->getDisplay());
+        self::assertStringContainsString('Aborting without writes', $tester->getDisplay());
+
+        // Row was not touched
+        self::assertSame($beforeRotation, $this->fetchRawApiKey($uid));
+    }
+
+    #[Test]
+    public function failsWithoutOldKey(): void
+    {
+        $tester = $this->runCommandAndReturnTester([]);
+        self::assertSame(1, $tester->getStatusCode());
+        self::assertStringContainsString('--old-key is required', $tester->getDisplay());
+    }
+
+    #[Test]
+    public function dryRunDoesNotWrite(): void
+    {
+        $encryption = $this->get(ApiKeyEncryption::class);
+
+        $GLOBALS['TYPO3_CONF_VARS']['SYS']['encryptionKey'] = self::OLD_KEY;
+        $uid = $this->insertRow($encryption->encrypt('sk-real-secret'));
+        $beforeRotation = $this->fetchRawApiKey($uid);
+
+        $GLOBALS['TYPO3_CONF_VARS']['SYS']['encryptionKey'] = self::NEW_KEY;
+
+        $tester = $this->runCommandAndReturnTester([
+            '--old-key' => self::OLD_KEY,
+            '--dry-run' => true,
+        ]);
+        self::assertSame(0, $tester->getStatusCode());
+        self::assertStringContainsString('[dry-run]', $tester->getDisplay());
+        self::assertSame($beforeRotation, $this->fetchRawApiKey($uid));
+    }
+
+    private function runCommand(array $options): int
+    {
+        return $this->runCommandAndReturnTester($options)->getStatusCode();
+    }
+
+    private function runCommandAndReturnTester(array $options): CommandTester
+    {
+        $tester = new CommandTester($this->get(RotateApiKeys::class));
+        $tester->execute($options);
+        return $tester;
+    }
+
+    private function insertRow(string $apiKey): int
+    {
+        $connection = GeneralUtility::makeInstance(ConnectionPool::class)
+            ->getConnectionForTable(self::TABLE);
+        $connection->insert(self::TABLE, [
+            'pid' => 0,
+            'ai_provider' => 'test',
+            'title' => 'Test',
+            'api_key' => $apiKey,
+            'model' => 'test-model',
+        ]);
+        return (int)$connection->lastInsertId();
+    }
+
+    private function fetchRawApiKey(int $uid): string
+    {
+        $qb = GeneralUtility::makeInstance(ConnectionPool::class)
+            ->getQueryBuilderForTable(self::TABLE);
+        $qb->getRestrictions()->removeAll();
+        return (string)$qb->select('api_key')
+            ->from(self::TABLE)
+            ->where($qb->expr()->eq('uid', $qb->createNamedParameter($uid, Connection::PARAM_INT)))
+            ->executeQuery()
+            ->fetchOne();
+    }
+
+    private function assertThrows(callable $callable): void
+    {
+        try {
+            $callable();
+        } catch (\Throwable) {
+            return;
+        }
+        self::fail('Expected an exception but none was thrown.');
+    }
+}
diff --git a/Tests/Functional/Crypto/ApiKeyEncryptionPersistenceTest.php b/Tests/Functional/Crypto/ApiKeyEncryptionPersistenceTest.php
new file mode 100644
index 0000000..6c23ac7
--- /dev/null
+++ b/Tests/Functional/Crypto/ApiKeyEncryptionPersistenceTest.php
@@ -0,0 +1,146 @@
+<?php
+
+declare(strict_types=1);
+
+/*
+ * This file is part of TYPO3 CMS-based extension "aim" by b13.
+ *
+ * It is free software; you can redistribute it and/or modify it under
+ * the terms of the GNU General Public License, either version 2
+ * of the License, or any later version.
+ */
+
+namespace B13\Aim\Tests\Functional\Crypto;
+
+use B13\Aim\Crypto\ApiKeyEncryption;
+use B13\Aim\Domain\Repository\ProviderConfigurationRepository;
+use B13\Aim\Updates\EncryptApiKeysUpgrade;
+use PHPUnit\Framework\Attributes\Test;
+use TYPO3\CMS\Core\Database\Connection;
+use TYPO3\CMS\Core\Database\ConnectionPool;
+use TYPO3\CMS\Core\Upgrades\UpgradeWizardRegistry;
+use TYPO3\CMS\Core\Utility\GeneralUtility;
+use TYPO3\TestingFramework\Core\Functional\FunctionalTestCase;
+
+/**
+ * Verifies the round-trip between an encrypted column and a decrypted
+ * ProviderConfiguration value object, plus the legacy-plaintext upgrade.
+ */
+final class ApiKeyEncryptionPersistenceTest extends FunctionalTestCase
+{
+    private const TABLE = 'tx_aim_configuration';
+
+    protected array $testExtensionsToLoad = [
+        'b13/aim',
+    ];
+
+    protected function setUp(): void
+    {
+        parent::setUp();
+        $GLOBALS['TYPO3_CONF_VARS']['SYS']['encryptionKey'] = str_repeat('a', 96);
+    }
+
+    #[Test]
+    public function repositoryDecryptsApiKeyOnRead(): void
+    {
+        $encryption = $this->get(ApiKeyEncryption::class);
+        $uid = $this->insertRow($encryption->encrypt('sk-plaintext-secret'));
+
+        $config = $this->get(ProviderConfigurationRepository::class)->findByUid($uid);
+
+        self::assertNotNull($config);
+        self::assertSame('sk-plaintext-secret', $config->apiKey);
+    }
+
+    #[Test]
+    public function repositoryReturnsLegacyPlaintextUnchanged(): void
+    {
+        $uid = $this->insertRow('sk-legacy-plaintext');
+
+        $config = $this->get(ProviderConfigurationRepository::class)->findByUid($uid);
+
+        self::assertNotNull($config);
+        self::assertSame('sk-legacy-plaintext', $config->apiKey);
+    }
+
+    #[Test]
+    public function upgradeWizardIsRegisteredInTheInstallToolRegistry(): void
+    {
+        $registry = $this->get(UpgradeWizardRegistry::class);
+        self::assertTrue($registry->hasUpgradeWizard('aimEncryptApiKeys'));
+        self::assertInstanceOf(EncryptApiKeysUpgrade::class, $registry->getUpgradeWizard('aimEncryptApiKeys'));
+    }
+
+    #[Test]
+    public function upgradeWizardEncryptsLegacyPlaintextRows(): void
+    {
+        $uid = $this->insertRow('sk-legacy-from-old-version');
+
+        $wizard = $this->get(UpgradeWizardRegistry::class)->getUpgradeWizard('aimEncryptApiKeys');
+        self::assertTrue($wizard->updateNecessary());
+        self::assertTrue($wizard->executeUpdate());
+        self::assertFalse($wizard->updateNecessary());
+
+        self::assertStringStartsWith(ApiKeyEncryption::PREFIX_ANY, $this->fetchRawApiKey($uid));
+
+        $config = $this->get(ProviderConfigurationRepository::class)->findByUid($uid);
+        self::assertNotNull($config);
+        self::assertSame('sk-legacy-from-old-version', $config->apiKey);
+    }
+
+    #[Test]
+    public function upgradeWizardLeavesEndpointUrlsAsPlaintext(): void
+    {
+        $uid = $this->insertRow('http://host.docker.internal:11434');
+
+        $wizard = $this->get(UpgradeWizardRegistry::class)->getUpgradeWizard('aimEncryptApiKeys');
+        self::assertFalse($wizard->updateNecessary());
+        self::assertTrue($wizard->executeUpdate());
+
+        self::assertSame('http://host.docker.internal:11434', $this->fetchRawApiKey($uid));
+
+        $config = $this->get(ProviderConfigurationRepository::class)->findByUid($uid);
+        self::assertNotNull($config);
+        self::assertSame('http://host.docker.internal:11434', $config->apiKey);
+    }
+
+    #[Test]
+    public function upgradeWizardLeavesAlreadyEncryptedRowsAlone(): void
+    {
+        $encryption = $this->get(ApiKeyEncryption::class);
+        $uid = $this->insertRow($encryption->encrypt('sk-already-encrypted'));
+        $before = $this->fetchRawApiKey($uid);
+
+        $wizard = $this->get(UpgradeWizardRegistry::class)->getUpgradeWizard('aimEncryptApiKeys');
+        self::assertFalse($wizard->updateNecessary());
+        self::assertTrue($wizard->executeUpdate());
+
+        self::assertSame($before, $this->fetchRawApiKey($uid));
+    }
+
+    private function insertRow(string $apiKey): int
+    {
+        $connection = GeneralUtility::makeInstance(ConnectionPool::class)
+            ->getConnectionForTable(self::TABLE);
+        $connection->insert(self::TABLE, [
+            'pid' => 0,
+            'ai_provider' => 'test',
+            'title' => 'Test',
+            'api_key' => $apiKey,
+            'model' => 'test-model',
+        ]);
+        return (int)$connection->lastInsertId();
+    }
+
+    private function fetchRawApiKey(int $uid): string
+    {
+        $qb = GeneralUtility::makeInstance(ConnectionPool::class)
+            ->getQueryBuilderForTable(self::TABLE);
+        $qb->getRestrictions()->removeAll();
+        return (string)$qb->select('api_key')
+            ->from(self::TABLE)
+            ->where($qb->expr()->eq('uid', $qb->createNamedParameter($uid, Connection::PARAM_INT)))
+            ->executeQuery()
+            ->fetchOne();
+    }
+}
diff --git a/Tests/Unit/Crypto/ApiKeyEncryptionTest.php b/Tests/Unit/Crypto/ApiKeyEncryptionTest.php
new file mode 100644
index 0000000..2d7f454
--- /dev/null
+++ b/Tests/Unit/Crypto/ApiKeyEncryptionTest.php
@@ -0,0 +1,177 @@
+<?php
+
+declare(strict_types=1);
+
+/*
+ * This file is part of TYPO3 CMS-based extension "aim" by b13.
+ *
+ * It is free software; you can redistribute it and/or modify it under
+ * the terms of the GNU General Public License, either version 2
+ * of the License, or any later version.
+ */
+
+namespace B13\Aim\Tests\Unit\Crypto;
+
+use B13\Aim\Crypto\ApiKeyEncryption;
+use B13\Aim\Exception\ApiKeyEncryptionException;
+use PHPUnit\Framework\Attributes\Test;
+use PHPUnit\Framework\TestCase;
+use TYPO3\CMS\Core\Crypto\Cipher\CipherService;
+
+final class ApiKeyEncryptionTest extends TestCase
+{
+    private string $originalKey;
+
+    protected function setUp(): void
+    {
+        parent::setUp();
+        $this->originalKey = (string)($GLOBALS['TYPO3_CONF_VARS']['SYS']['encryptionKey'] ?? '');
+        $GLOBALS['TYPO3_CONF_VARS']['SYS']['encryptionKey'] = str_repeat('a', 96);
+    }
+
+    protected function tearDown(): void
+    {
+        $GLOBALS['TYPO3_CONF_VARS']['SYS']['encryptionKey'] = $this->originalKey;
+        parent::tearDown();
+    }
+
+    #[Test]
+    public function encryptDecryptRoundTrip(): void
+    {
+        $service = new ApiKeyEncryption();
+        $plaintext = 'sk-proj-abc123-very-secret';
+
+        $encrypted = $service->encrypt($plaintext);
+
+        self::assertNotSame($plaintext, $encrypted);
+        self::assertTrue($service->isEncrypted($encrypted));
+        self::assertSame($plaintext, $service->decrypt($encrypted));
+    }
+
+    #[Test]
+    public function encryptPicksV2OnTypo3V14(): void
+    {
+        if (!class_exists(CipherService::class)) {
+            self::markTestSkipped('TYPO3 CipherService not available — only present on v14+.');
+        }
+        $encrypted = (new ApiKeyEncryption())->encrypt('sk-test');
+        self::assertStringStartsWith(ApiKeyEncryption::PREFIX_V2, $encrypted);
+    }
+
+    #[Test]
+    public function decryptOfV1PayloadStillWorksOnV14(): void
+    {
+        // A value persisted by v12/v13 must remain readable after upgrade.
+        // We build a v1 payload directly so the test is independent of which
+        // path encrypt() currently picks.
+        $v1 = $this->makeV1Payload('sk-from-old-typo3');
+        self::assertSame('sk-from-old-typo3', (new ApiKeyEncryption())->decrypt($v1));
+    }
+
+    #[Test]
+    public function encryptLeavesEndpointUrlsUntouched(): void
+    {
+        $service = new ApiKeyEncryption();
+        $endpoint = 'http://host.docker.internal:11434';
+
+        $result = $service->encrypt($endpoint);
+
+        self::assertSame($endpoint, $result);
+        self::assertFalse($service->isEncrypted($result));
+    }
+
+    #[Test]
+    public function encryptLeavesHttpsEndpointUrlsUntouched(): void
+    {
+        $service = new ApiKeyEncryption();
+        $endpoint = 'https://my-self-hosted-llm.example.com:8443';
+
+        self::assertSame($endpoint, $service->encrypt($endpoint));
+    }
+
+    #[Test]
+    public function encryptIsIdempotent(): void
+    {
+        $service = new ApiKeyEncryption();
+        $encrypted = $service->encrypt('sk-test');
+
+        self::assertSame($encrypted, $service->encrypt($encrypted));
+    }
+
+    #[Test]
+    public function encryptOfEmptyStringStaysEmpty(): void
+    {
+        $service = new ApiKeyEncryption();
+        self::assertSame('', $service->encrypt(''));
+    }
+
+    #[Test]
+    public function decryptOfLegacyPlaintextReturnsInputUnchanged(): void
+    {
+        $service = new ApiKeyEncryption();
+        self::assertSame('sk-legacy-plaintext', $service->decrypt('sk-legacy-plaintext'));
+    }
+
+    #[Test]
+    public function encryptUsesFreshNonceEachTime(): void
+    {
+        $service = new ApiKeyEncryption();
+        $first = $service->encrypt('sk-same-input');
+        $second = $service->encrypt('sk-same-input');
+
+        self::assertNotSame($first, $second);
+        self::assertSame('sk-same-input', $service->decrypt($first));
+        self::assertSame('sk-same-input', $service->decrypt($second));
+    }
+
+    #[Test]
+    public function decryptFailsWhenSystemKeyChanged(): void
+    {
+        $service = new ApiKeyEncryption();
+        $encrypted = $service->encrypt('sk-test');
+
+        $GLOBALS['TYPO3_CONF_VARS']['SYS']['encryptionKey'] = str_repeat('b', 96);
+
+        $this->expectException(ApiKeyEncryptionException::class);
+        $service->decrypt($encrypted);
+    }
+
+    #[Test]
+    public function isEncryptedDetectsBothPrefixes(): void
+    {
+        $service = new ApiKeyEncryption();
+        self::assertFalse($service->isEncrypted('sk-plaintext'));
+        self::assertTrue($service->isEncrypted(ApiKeyEncryption::PREFIX_V1 . 'whatever'));
+        self::assertTrue($service->isEncrypted(ApiKeyEncryption::PREFIX_V2 . 'whatever'));
+    }
+
+    #[Test]
+    public function encryptFailsWithoutSystemEncryptionKeyOnV1Path(): void
+    {
+        if (class_exists(CipherService::class)) {
+            self::markTestSkipped('On v14 the missing-key error is raised by core, not by us.');
+        }
+        $GLOBALS['TYPO3_CONF_VARS']['SYS']['encryptionKey'] = '';
+
+        $this->expectException(ApiKeyEncryptionException::class);
+        $this->expectExceptionCode(1773874402);
+        (new ApiKeyEncryption())->encrypt('sk-test');
+    }
+
+    /**
+     * Builds a v1 payload by replicating the libsodium secretbox path,
+     * so the test does not depend on which encryption path the service
+     * picks at runtime.
+     */
+    private function makeV1Payload(string $plaintext): string
+    {
+        $key = sodium_crypto_generichash(
+            "aim:apikey:v1\0" . $GLOBALS['TYPO3_CONF_VARS']['SYS']['encryptionKey'],
+            '',
+            SODIUM_CRYPTO_SECRETBOX_KEYBYTES,
+        );
+        $nonce = random_bytes(SODIUM_CRYPTO_SECRETBOX_NONCEBYTES);
+        $ciphertext = sodium_crypto_secretbox($plaintext, $nonce, $key);
+        return ApiKeyEncryption::PREFIX_V1 . base64_encode($nonce . $ciphertext);
+    }
+}
diff --git a/Tests/Unit/Hooks/EncryptApiKeyTest.php b/Tests/Unit/Hooks/EncryptApiKeyTest.php
new file mode 100644
index 0000000..be7fdf1
--- /dev/null
+++ b/Tests/Unit/Hooks/EncryptApiKeyTest.php
@@ -0,0 +1,100 @@
+<?php
+
+declare(strict_types=1);
+
+/*
+ * This file is part of TYPO3 CMS-based extension "aim" by b13.
+ *
+ * It is free software; you can redistribute it and/or modify it under
+ * the terms of the GNU General Public License, either version 2
+ * of the License, or any later version.
+ */
+
+namespace B13\Aim\Tests\Unit\Hooks;
+
+use B13\Aim\Crypto\ApiKeyEncryption;
+use B13\Aim\Hooks\EncryptApiKey;
+use PHPUnit\Framework\Attributes\Test;
+use PHPUnit\Framework\TestCase;
+use TYPO3\CMS\Core\DataHandling\DataHandler;
+
+final class EncryptApiKeyTest extends TestCase
+{
+    private string $originalKey;
+
+    protected function setUp(): void
+    {
+        parent::setUp();
+        $this->originalKey = (string)($GLOBALS['TYPO3_CONF_VARS']['SYS']['encryptionKey'] ?? '');
+        $GLOBALS['TYPO3_CONF_VARS']['SYS']['encryptionKey'] = str_repeat('a', 96);
+    }
+
+    protected function tearDown(): void
+    {
+        $GLOBALS['TYPO3_CONF_VARS']['SYS']['encryptionKey'] = $this->originalKey;
+        parent::tearDown();
+    }
+
+    #[Test]
+    public function encryptsPlaintextApiKeyOnSave(): void
+    {
+        $hook = new EncryptApiKey(new ApiKeyEncryption());
+        $fieldArray = ['api_key' => 'sk-secret', 'title' => 'My Provider'];
+
+        $hook->processDatamap_postProcessFieldArray('new', 'tx_aim_configuration', 'NEW1', $fieldArray, $this->createDataHandlerMock());
+
+        self::assertTrue((new ApiKeyEncryption())->isEncrypted($fieldArray['api_key']));
+        self::assertSame('My Provider', $fieldArray['title']);
+    }
+
+    #[Test]
+    public function leavesAlreadyEncryptedValueUntouched(): void
+    {
+        $encryption = new ApiKeyEncryption();
+        $hook = new EncryptApiKey($encryption);
+        $alreadyEncrypted = $encryption->encrypt('sk-secret');
+        $fieldArray = ['api_key' => $alreadyEncrypted];
+
+        $hook->processDatamap_postProcessFieldArray('update', 'tx_aim_configuration', 1, $fieldArray, $this->createDataHandlerMock());
+
+        self::assertSame($alreadyEncrypted, $fieldArray['api_key']);
+    }
+
+    #[Test]
+    public function ignoresOtherTables(): void
+    {
+        $hook = new EncryptApiKey(new ApiKeyEncryption());
+        $fieldArray = ['api_key' => 'sk-secret'];
+
+        $hook->processDatamap_postProcessFieldArray('new', 'tt_content', 'NEW1', $fieldArray, $this->createDataHandlerMock());
+
+        self::assertSame('sk-secret', $fieldArray['api_key']);
+    }
+
+    #[Test]
+    public function ignoresUpdatesThatDoNotTouchApiKey(): void
+    {
+        $hook = new EncryptApiKey(new ApiKeyEncryption());
+        $fieldArray = ['title' => 'Renamed'];
+
+        $hook->processDatamap_postProcessFieldArray('update', 'tx_aim_configuration', 1, $fieldArray, $this->createDataHandlerMock());
+
+        self::assertSame(['title' => 'Renamed'], $fieldArray);
+    }
+
+    #[Test]
+    public function ignoresEmptyApiKey(): void
+    {
+        $hook = new EncryptApiKey(new ApiKeyEncryption());
+        $fieldArray = ['api_key' => ''];
+
+        $hook->processDatamap_postProcessFieldArray('update', 'tx_aim_configuration', 1, $fieldArray, $this->createDataHandlerMock());
+
+        self::assertSame('', $fieldArray['api_key']);
+    }
+
+    private function createDataHandlerMock(): DataHandler
+    {
+        return $this->createMock(DataHandler::class);
+    }
+}
diff --git a/composer.json b/composer.json
index a48ff5b..04e60f1 100644
--- a/composer.json
+++ b/composer.json
@@ -5,6 +5,7 @@
 	"license": "GPL-2.0-or-later",
 	"require": {
 		"php": "^8.1",
+		"ext-sodium": "*",
 		"typo3/cms-core": "^12.4 || ^13.4 || ^14.0",
 		"typo3/cms-backend": "^12.4 || ^13.4 || ^14.0"
 	},
diff --git a/ext_localconf.php b/ext_localconf.php
index b83b7ca..9f0037d 100644
--- a/ext_localconf.php
+++ b/ext_localconf.php
@@ -2,9 +2,16 @@
 
 declare(strict_types=1);
 
+use B13\Aim\Backend\FormDataProvider\DecryptApiKey;
 use B13\Aim\Hooks\DefaultProviderHook;
+use B13\Aim\Hooks\EncryptApiKey;
 
 $GLOBALS['TYPO3_CONF_VARS']['SC_OPTIONS']['t3lib/class.t3lib_tcemain.php']['processDatamapClass'][DefaultProviderHook::class] = DefaultProviderHook::class;
+$GLOBALS['TYPO3_CONF_VARS']['SC_OPTIONS']['t3lib/class.t3lib_tcemain.php']['processDatamapClass'][EncryptApiKey::class] = EncryptApiKey::class;
+
+$GLOBALS['TYPO3_CONF_VARS']['SYS']['formEngine']['formDataGroup']['tcaDatabaseRecord'][DecryptApiKey::class] = [
+    'depends' => [\TYPO3\CMS\Backend\Form\FormDataProvider\DatabaseEditRow::class],
+];
 
 // Register AI capability permissions for backend user groups
 $GLOBALS['TYPO3_CONF_VARS']['BE']['customPermOptions']['aim'] = [
diff --git a/ext_tables.sql b/ext_tables.sql
index 027d60b..7167b24 100644
--- a/ext_tables.sql
+++ b/ext_tables.sql
@@ -3,7 +3,7 @@ CREATE TABLE tx_aim_configuration (
     title varchar(255) DEFAULT '' NOT NULL,
     description text,
     `default` tinyint(4) unsigned DEFAULT '0' NOT NULL,
-    api_key varchar(255) DEFAULT '' NOT NULL,
+    api_key text,
     model varchar(255) DEFAULT '' NOT NULL,
     total_cost double(10,6) DEFAULT '0.000000' NOT NULL,
     cost_currency varchar(10) DEFAULT 'USD' NOT NULL,