diff --git a/lib/Controller/ServiceController.php b/lib/Controller/ServiceController.php
index c86e82e2..6477a087 100644
--- a/lib/Controller/ServiceController.php
+++ b/lib/Controller/ServiceController.php
@@ -25,7 +25,7 @@
  */
 class ServiceController extends Controller {
 	/** Properties that may only be changed with a confirmed password */
-	private const SENSITIVE_PROPERTIES = ['url', 'api_key', 'basic_user', 'basic_password'];
+	private const SENSITIVE_PROPERTIES = ['url', 'api_key', 'basic_user', 'basic_password', 'extra_headers'];
 
 	public function __construct(
 		string $appName,
@@ -59,7 +59,7 @@ public function create(): DataResponse {
 	/**
 	 * Update the given properties of a service
 	 *
-	 * The URL and the credentials can only be set through
+	 * The URL, the credentials and the extra headers can only be set through
 	 * {@see self::updateSensitive()}.
 	 *
 	 * @param string $id ID of the service
@@ -76,7 +76,7 @@ public function update(string $id, array $values): DataResponse {
 	}
 
 	/**
-	 * Update the URL and the credentials of a service
+	 * Update the URL, the credentials and the extra headers of a service
 	 *
 	 * Secrets that are sent back unchanged (as the placeholder the frontend
 	 * received) are kept.
diff --git a/lib/Service/OpenAiAPIService.php b/lib/Service/OpenAiAPIService.php
index 56d121b0..1319151c 100644
--- a/lib/Service/OpenAiAPIService.php
+++ b/lib/Service/OpenAiAPIService.php
@@ -451,6 +451,7 @@ public function createStreamedChatCompletion(
 		?string $toolMessage = null,
 		?array $tools = null,
 		?array $files = null,
+		?string $conversationId = null,
 	): \Generator {
 		if ($this->isQuotaExceeded($userId, Application::QUOTA_TYPE_TEXT, $service)) {
 			throw new Exception($this->l10n->t('Text generation quota exceeded'), Http::STATUS_TOO_MANY_REQUESTS);
@@ -482,6 +483,7 @@ public function createStreamedChatCompletion(
 			true,
 			0,
 			true,
+			$this->resolveConversationId($conversationId),
 		);
 
 		$streamResult = yield from $this->streamingService->parseStreamChatResponse($response);
@@ -511,11 +513,12 @@ public function createChatCompletion(
 		?string $toolMessage = null,
 		?array $tools = null,
 		?array $files = null,
+		?string $conversationId = null,
 	): array {
 		$response = $this->requestChatCompletion(
 			$userId, $service, $model, $userPrompt, $systemPrompt, $history,
 			$n, $maxTokens, $extraParams, $toolMessage, $tools, $files,
-			false,
+			false, $conversationId,
 		);
 
 		if (isset($response['usage'], $response['usage']['total_tokens'])) {
@@ -560,6 +563,7 @@ public function requestChatCompletion(
 		?array $tools = null,
 		?array $files = null,
 		bool $stream = false,
+		?string $conversationId = null,
 	): array {
 		if ($this->isQuotaExceeded($userId, Application::QUOTA_TYPE_TEXT, $service)) {
 			throw new Exception($this->l10n->t('Text generation quota exceeded'), Http::STATUS_TOO_MANY_REQUESTS);
@@ -581,7 +585,7 @@ public function requestChatCompletion(
 			$stream,
 		);
 
-		return $this->request($userId, $service, 'chat/completions', $params, 'POST');
+		return $this->request($userId, $service, 'chat/completions', $params, 'POST', conversationId: $this->resolveConversationId($conversationId));
 	}
 
 	/**
@@ -1214,6 +1218,44 @@ private function requestLocalAiImageEdit(
 		return $this->request($userId, $service, 'images/generations', $params, 'POST');
 	}
 
+	/**
+	 * The conversation ID a chat completion request is sent with.
+	 *
+	 * Chat completion requests always carry a conversation ID: tasks which do
+	 * not belong to a conversation get a throwaway random one, regenerated per
+	 * request so unrelated requests never share state on services which key
+	 * conversations on that ID.
+	 */
+	private function resolveConversationId(?string $conversationId): string {
+		return $conversationId !== null && $conversationId !== ''
+			? $conversationId
+			: bin2hex(random_bytes(16));
+	}
+
+	/**
+	 * Merge the extra headers configured on the service into the request
+	 * options. They are applied before the authentication and content-type
+	 * headers, so the service's own credentials always win over a configured
+	 * Authorization header.
+	 *
+	 * Headers using the {$conversation_id} variable are dropped when the
+	 * request has no conversation ID, see {@see ServiceConfig::expandHeaderValue()}.
+	 *
+	 * @param string|null $conversationId
+	 * @param array<mixed> $options
+	 * @return array<mixed>
+	 */
+	private function addExtraHeaders(ServiceConfig $service, array $options, ?string $conversationId = null): array {
+		foreach ($service->getExtraHeaders() as $header) {
+			$value = ServiceConfig::expandHeaderValue($header['value'], $conversationId);
+			if ($value === null) {
+				continue;
+			}
+			$options['headers'][$header['name']] = $value;
+		}
+		return $options;
+	}
+
 	/**
 	 * @param string|null $userId
 	 * @return array
@@ -1226,6 +1268,7 @@ public function getImageRequestOptions(?string $userId, ServiceConfig $service):
 				'User-Agent' => Application::USER_AGENT,
 			],
 		];
+		$requestOptions = $this->addExtraHeaders($service, $requestOptions);
 
 		if ($service->getImageRequestAuth()) {
 			if ($service->usesBasicAuth()) {
@@ -1360,6 +1403,7 @@ private function updateExpProcessingTime(ServiceConfig $service, string $key, in
 	 * @param string|null $contentType
 	 * @param bool $logErrors if set to false error logs will be suppressed
 	 * @param int $retryCount number of retries that have been attempted so far
+	 * @param string|null $conversationId the conversation ID of the request, used to expand the {$conversation_id} token of the extra headers
 	 * @return array decoded request result or error
 	 * @throws Exception|UserFacingProcessingException
 	 */
@@ -1368,6 +1412,7 @@ public function request(
 		?string $contentType = null, bool $logErrors = true,
 		int $retryCount = 0,
 		bool $stream = false,
+		?string $conversationId = null,
 	): array {
 		try {
 			// the user's own credentials take precedence over the admin ones
@@ -1385,6 +1430,7 @@ public function request(
 					'User-Agent' => Application::USER_AGENT,
 				],
 			];
+			$options = $this->addExtraHeaders($service, $options, $conversationId);
 
 			if ($serviceUrl === Application::OPENAI_API_BASE_URL && $apiKey === '') {
 				return ['error' => 'An API key is required for api.openai.com'];
@@ -1517,7 +1563,7 @@ public function request(
 					}
 					$this->logger->warning("Rate limit exceeded, retrying in $sleep seconds", ['retry_count' => $retryCount]);
 					sleep($sleep);
-					return $this->request($userId, $service, $endPoint, $params, $method, $contentType, $logErrors, $retryCount + 1, $stream);
+					return $this->request($userId, $service, $endPoint, $params, $method, $contentType, $logErrors, $retryCount + 1, $stream, $conversationId);
 				} else {
 					$this->logger->warning('Rate limit exceeded, maximum retries reached', ['retry_count' => $retryCount]);
 				}
@@ -1567,6 +1613,16 @@ public function request(
 				intval($e->getCode()),
 				userFacingMessage: $this->l10n->t('%s API error: AI backend is currently not reachable. Contact your system administrator.', [$service->getDisplayName()]),
 			);
+		} catch (\InvalidArgumentException $e) {
+			// the HTTP client validates the headers while building the request and
+			// its message quotes the rejected value, which may hold credentials,
+			// so it only goes to the log and not into the error
+			$this->logger->warning('API request rejected with invalid headers on service ' . $service->getId(), ['exception' => $e]);
+			throw new Exception(
+				$this->l10n->t('The request headers configured for this service are invalid'),
+				Http::STATUS_BAD_REQUEST,
+				$e,
+			);
 		}
 	}
 
diff --git a/lib/Service/ServiceConfig.php b/lib/Service/ServiceConfig.php
index a978be25..71c2329b 100644
--- a/lib/Service/ServiceConfig.php
+++ b/lib/Service/ServiceConfig.php
@@ -56,11 +56,24 @@ class ServiceConfig implements JsonSerializable {
 		'stt_models' => 'array',
 		'tts_models' => 'array',
 		'quotas' => 'array',
+		'extra_headers' => 'array',
 	];
 
 	/** Properties that are stored encrypted and never sent to the frontend */
 	public const SECRET_PROPERTIES = ['api_key', 'basic_password'];
 
+	/** Characters an HTTP header name is made of (the RFC 7230 token, as checked by Guzzle) */
+	public const HEADER_NAME_PATTERN = '/^[a-zA-Z0-9!#$%&\'*+.^_`|~-]+$/D';
+
+	/** Characters an HTTP header value may be made of: HTAB, printable and ISO-8859-1 bytes (the RFC 9110 field-value, as accepted by Guzzle) */
+	public const HEADER_VALUE_PATTERN = '/^[\x09\x20-\x7E\x80-\xFF]*$/D';
+
+	/** The extra header value variable holding the conversation ID of a chat completion request */
+	public const CONVERSATION_ID_VARIABLE = '{$conversation_id}';
+
+	/** The variables extra header values may use */
+	public const SUPPORTED_HEADER_VARIABLES = [self::CONVERSATION_ID_VARIABLE];
+
 	/**
 	 * @param array<int, int> $quotas
 	 * @param list<string> $ttsVoices
@@ -68,6 +81,7 @@ class ServiceConfig implements JsonSerializable {
 	 * @param list<string> $imageModels
 	 * @param list<string> $sttModels
 	 * @param list<string> $ttsModels
+	 * @param list<array{name: string, value: string}> $extraHeaders
 	 */
 	public function __construct(
 		private string $id,
@@ -104,6 +118,7 @@ public function __construct(
 		private array $sttModels = [],
 		private array $ttsModels = [],
 		private array $quotas = Application::DEFAULT_QUOTAS,
+		private array $extraHeaders = [],
 	) {
 	}
 
@@ -186,6 +201,8 @@ public function with(array $values): self {
 					break;
 				case 'quotas': $new->quotas = self::normalizeQuotas($value, $new->quotas);
 					break;
+				case 'extra_headers': $new->extraHeaders = self::normalizeHeaders($value);
+					break;
 			}
 		}
 		return $new;
@@ -226,6 +243,32 @@ private static function normalizeQuotas(mixed $quotas, array $base): array {
 		return $normalized;
 	}
 
+	/**
+	 * Keep the name/value pairs that have a name, trim the rest. A row
+	 * without a name is one the admin has not filled in yet, and sending it
+	 * along in requests would only be confusing.
+	 *
+	 * @param mixed $headers
+	 * @return list<array{name: string, value: string}>
+	 */
+	private static function normalizeHeaders(mixed $headers): array {
+		if (!is_array($headers)) {
+			return [];
+		}
+		$normalized = [];
+		foreach ($headers as $header) {
+			if (!is_array($header)) {
+				continue;
+			}
+			$name = trim((string)($header['name'] ?? ''));
+			if ($name === '') {
+				continue;
+			}
+			$normalized[] = ['name' => $name, 'value' => trim((string)($header['value'] ?? ''))];
+		}
+		return $normalized;
+	}
+
 	public function getId(): string {
 		return $this->id;
 	}
@@ -456,6 +499,39 @@ public function getQuota(int $quotaType): int {
 		return $this->quotas[$quotaType] ?? 0;
 	}
 
+	/**
+	 * The extra headers to send with every request to this service
+	 *
+	 * @return list<array{name: string, value: string}>
+	 */
+	public function getExtraHeaders(): array {
+		return $this->extraHeaders;
+	}
+
+	/**
+	 * Replace the {$conversation_id} variable of an extra header value with
+	 * the ID of the conversation of the request being sent.
+	 *
+	 * A value using the variable of a request that has no conversation is not
+	 * meant to be sent at all: chat completion requests always have a
+	 * conversation ID (the one of their task, or a generated one), so the
+	 * header is dropped for the other requests, which is signalled by
+	 * returning null. Anything else in the value, including text that merely
+	 * looks like a variable, travels literally.
+	 */
+	public static function expandHeaderValue(string $value, ?string $conversationId): ?string {
+		if (!str_contains($value, self::CONVERSATION_ID_VARIABLE)) {
+			return $value;
+		}
+		if ($conversationId === null || $conversationId === '') {
+			return null;
+		}
+		$expanded = str_replace(self::CONVERSATION_ID_VARIABLE, $conversationId, $value);
+		// the ID comes from the task input of another app, so what it expands to
+		// must stay within the characters an HTTP client is willing to send
+		return preg_match(self::HEADER_VALUE_PATTERN, $expanded) === 1 ? $expanded : null;
+	}
+
 	/**
 	 * Full representation, including secrets, as stored in app config
 	 *
@@ -494,6 +570,7 @@ public function jsonSerialize(): array {
 			'stt_models' => $this->sttModels,
 			'tts_models' => $this->ttsModels,
 			'quotas' => $this->quotas,
+			'extra_headers' => $this->extraHeaders,
 		];
 	}
 
diff --git a/lib/Service/ServicesService.php b/lib/Service/ServicesService.php
index 57959b82..7b9867fe 100644
--- a/lib/Service/ServicesService.php
+++ b/lib/Service/ServicesService.php
@@ -429,6 +429,31 @@ private function validate(array $values): void {
 			&& preg_match('/^\d+x\d+$/', (string)$values['default_image_size']) !== 1) {
 			throw new Exception('Invalid image size value. Expected the format <width>x<height>');
 		}
+		if (isset($values['extra_headers'])) {
+			foreach ($values['extra_headers'] as $header) {
+				if (!is_array($header) || !isset($header['name'], $header['value'])
+					|| !is_string($header['name']) || !is_string($header['value'])) {
+					throw new Exception('Invalid extra header. Expected a name and a value');
+				}
+				$name = trim($header['name']);
+				if ($name === '') {
+					throw new Exception('Invalid extra header name. It cannot be empty');
+				}
+				if (preg_match(ServiceConfig::HEADER_NAME_PATTERN, $name) !== 1) {
+					throw new Exception('Invalid extra header name. Only the characters allowed in an HTTP header name are accepted: ' . $name);
+				}
+				if (preg_match(ServiceConfig::HEADER_VALUE_PATTERN, $header['value']) !== 1) {
+					throw new Exception('Invalid extra header value. Only the characters allowed in an HTTP header value are accepted: ' . $name);
+				}
+				if (preg_match_all('/\{\$[^}]*\}/', $header['value'], $variables) > 0) {
+					foreach ($variables[0] as $variable) {
+						if (!in_array($variable, ServiceConfig::SUPPORTED_HEADER_VARIABLES, true)) {
+							throw new Exception('Unknown variable in an extra header value: ' . $variable . '. Supported variables: ' . implode(', ', ServiceConfig::SUPPORTED_HEADER_VARIABLES));
+						}
+					}
+				}
+			}
+		}
 	}
 
 	/**
diff --git a/lib/Service/TranslateService.php b/lib/Service/TranslateService.php
index c3190688..4a093ea2 100644
--- a/lib/Service/TranslateService.php
+++ b/lib/Service/TranslateService.php
@@ -67,6 +67,7 @@ public static function getCoreLanguagesByCode(): array {
 	public function translate(
 		ServiceConfig $service, string $inputText, string $sourceLanguageCode, string $targetLanguageCode, string $model, ?int $maxTokens,
 		?string $userId, ?callable $reportProgress = null, bool $preferStreaming = false, ?callable $reportOutput = null,
+		?string $conversationId = null,
 	): string {
 		$chunks = $this->chunkService->chunkSplitPrompt($service, $inputText, true, $maxTokens);
 		$translation = '';
@@ -105,7 +106,8 @@ public function translate(
 
 			if ($service->isUsingOpenAi() || $service->getChatEndpointEnabled()) {
 				$completionsObj = $this->openAiAPIService->createChatCompletion(
-					$userId, $service, $model, $prompt, TranslateService::SYSTEM_PROMPT, null, 1, $maxTokens, TranslateService::JSON_RESPONSE_FORMAT
+					$userId, $service, $model, $prompt, TranslateService::SYSTEM_PROMPT, null, 1, $maxTokens, TranslateService::JSON_RESPONSE_FORMAT,
+					conversationId: $conversationId,
 				);
 				$completions = $completionsObj['messages'];
 			} else {
diff --git a/lib/TaskProcessing/AnalyzeImagesProvider.php b/lib/TaskProcessing/AnalyzeImagesProvider.php
index 8af1653a..f35c325e 100644
--- a/lib/TaskProcessing/AnalyzeImagesProvider.php
+++ b/lib/TaskProcessing/AnalyzeImagesProvider.php
@@ -64,6 +64,11 @@ public function getOptionalInputShape(): array {
 				$this->l->t('The maximum number of words/tokens that can be generated in the output.'),
 				EShapeType::Number
 			),
+			'conversation_id' => new ShapeDescriptor(
+				$this->l->t('Conversation ID'),
+				$this->l->t('The ID of the conversation this request belongs to.'),
+				EShapeType::Text
+			),
 		];
 	}
 
@@ -126,6 +131,10 @@ public function process(
 		if (isset($input['max_tokens']) && is_int($input['max_tokens'])) {
 			$maxTokens = $input['max_tokens'];
 		}
+
+		$conversationId = isset($input['conversation_id']) && is_string($input['conversation_id'])
+			? $input['conversation_id']
+			: null;
 		$fileSizeTotal = array_reduce(
 			$images,
 			function ($carry, $file) {
@@ -145,7 +154,7 @@ function ($carry, $file) {
 		try {
 			$systemPrompt = 'Take the user\'s question and answer it based on the provided images. Ensure that the answer matches the language of the user\'s question.';
 			if ($preferStreaming) {
-				$chunks = $this->openAiAPIService->createStreamedChatCompletion($userId, $this->service, $model, $prompt, $systemPrompt, $history, 1, $maxTokens, null, null, null, $images);
+				$chunks = $this->openAiAPIService->createStreamedChatCompletion($userId, $this->service, $model, $prompt, $systemPrompt, $history, 1, $maxTokens, null, null, null, $images, conversationId: $conversationId);
 				$time = microtime(true);
 				$streamedOutput = '';
 				$streamedReasoning = '';
@@ -183,7 +192,7 @@ function ($carry, $file) {
 				$completion = $returnValue['messages'];
 				$reasoning = $returnValue['reasoning_messages'];
 			} else {
-				$returnValue = $this->openAiAPIService->createChatCompletion($userId, $this->service, $model, $prompt, $systemPrompt, $history, 1, $maxTokens, null, null, null, $images);
+				$returnValue = $this->openAiAPIService->createChatCompletion($userId, $this->service, $model, $prompt, $systemPrompt, $history, 1, $maxTokens, null, null, null, $images, conversationId: $conversationId);
 				$completion = $returnValue['messages'];
 				$reasoning = $returnValue['reasoning_messages'];
 			}
diff --git a/lib/TaskProcessing/AudioToAudioChatProvider.php b/lib/TaskProcessing/AudioToAudioChatProvider.php
index d051057c..8f35ba4b 100644
--- a/lib/TaskProcessing/AudioToAudioChatProvider.php
+++ b/lib/TaskProcessing/AudioToAudioChatProvider.php
@@ -89,6 +89,11 @@ public function getOptionalInputShape(): array {
 					: $this->l->t('Speech speed modifier'),
 				EShapeType::Number
 			),
+			'conversation_id' => new ShapeDescriptor(
+				$this->l->t('Conversation ID'),
+				$this->l->t('The ID of the conversation this request belongs to.'),
+				EShapeType::Text
+			),
 		];
 	}
 
@@ -175,9 +180,13 @@ public function process(?string $userId, array $input, callable $reportProgress)
 			'audio' => ['voice' => $outputVoice, 'format' => 'mp3'],
 		];
 		$systemPrompt .= ' Producing text responses will break the user interface. Important: You have multimodal voice capability, and you use voice exclusively to respond.';
+		$conversationId = isset($input['conversation_id']) && is_string($input['conversation_id'])
+			? $input['conversation_id']
+			: null;
 		$completion = $this->openAiAPIService->createChatCompletion(
 			$userId, $this->service, $this->model, null, $systemPrompt, $history, 1, 1000,
-			$extraParams, null, null, [$inputFile]
+			$extraParams, null, null, [$inputFile],
+			conversationId: $conversationId,
 		);
 		$message = array_pop($completion['audio_messages']);
 		// TODO find a way to force the model to answer with audio when there is only text in the history
diff --git a/lib/TaskProcessing/AudioToAudioTranslateProvider.php b/lib/TaskProcessing/AudioToAudioTranslateProvider.php
index c2724663..f306f87c 100644
--- a/lib/TaskProcessing/AudioToAudioTranslateProvider.php
+++ b/lib/TaskProcessing/AudioToAudioTranslateProvider.php
@@ -107,6 +107,11 @@ public function getOptionalInputShape(): array {
 					: $this->l->t('Speech speed modifier'),
 				EShapeType::Number
 			),
+			'conversation_id' => new ShapeDescriptor(
+				$this->l->t('Conversation ID'),
+				$this->l->t('The ID of the conversation this request belongs to.'),
+				EShapeType::Text
+			),
 		];
 	}
 
@@ -210,6 +215,10 @@ public function process(
 		// translate
 		$maxTokens = $this->service->getMaxTokens();
 
+		$conversationId = isset($input['conversation_id']) && is_string($input['conversation_id'])
+			? $input['conversation_id']
+			: null;
+
 		try {
 			$reportTranslationOutput = function (string $translationOutput) use ($reportOutput, $transcription, $watermarkSuffix) {
 				$running = $reportOutput([
@@ -224,7 +233,7 @@ public function process(
 				$this->service,
 				$transcription, $input['origin_language'], $input['target_language'],
 				$this->textModel, $maxTokens, $userId, null,
-				$preferStreaming, $reportTranslationOutput,
+				$preferStreaming, $reportTranslationOutput, $conversationId,
 			);
 
 			if ($preferStreaming) {
diff --git a/lib/TaskProcessing/AudioToTextEnhancedProvider.php b/lib/TaskProcessing/AudioToTextEnhancedProvider.php
index d5f31d93..d89e1bc1 100644
--- a/lib/TaskProcessing/AudioToTextEnhancedProvider.php
+++ b/lib/TaskProcessing/AudioToTextEnhancedProvider.php
@@ -12,7 +12,9 @@
 use OCA\OpenAi\Service\OpenAiAPIService;
 use OCA\OpenAi\Service\ServiceConfig;
 use OCP\IL10N;
+use OCP\TaskProcessing\EShapeType;
 use OCP\TaskProcessing\ISynchronousProvider;
+use OCP\TaskProcessing\ShapeDescriptor;
 use OCP\TaskProcessing\TaskTypes\AudioToText;
 use Psr\Log\LoggerInterface;
 use Throwable;
@@ -64,7 +66,13 @@ public function getInputShapeDefaults(): array {
 	}
 
 	public function getOptionalInputShape(): array {
-		return $this->audioToTextProvider->getOptionalInputShape();
+		return array_merge($this->audioToTextProvider->getOptionalInputShape(), [
+			'conversation_id' => new ShapeDescriptor(
+				$this->l->t('Conversation ID'),
+				$this->l->t('The ID of the conversation this request belongs to.'),
+				EShapeType::Text
+			),
+		]);
 	}
 
 	public function getOptionalInputShapeEnumValues(): array {
@@ -95,8 +103,13 @@ public function process(?string $userId, array $input, callable $reportProgress)
 			return ['output' => $transcription];
 		}
 
+		$reformatInput = ['input' => $transcription];
+		if (isset($input['conversation_id']) && is_string($input['conversation_id'])) {
+			$reformatInput['conversation_id'] = $input['conversation_id'];
+		}
+
 		try {
-			$output = $this->reformatParagraphsProvider->process($userId, ['input' => $transcription], $reportProgress);
+			$output = $this->reformatParagraphsProvider->process($userId, $reformatInput, $reportProgress);
 			if (isset($output['output']) && is_string($output['output']) && $output['output'] !== '') {
 				return ['output' => $output['output']];
 			}
diff --git a/lib/TaskProcessing/ChangeToneProvider.php b/lib/TaskProcessing/ChangeToneProvider.php
index d473fef0..a1730f58 100644
--- a/lib/TaskProcessing/ChangeToneProvider.php
+++ b/lib/TaskProcessing/ChangeToneProvider.php
@@ -82,6 +82,11 @@ public function getOptionalInputShape(): array {
 				$this->l->t('The maximum number of words/tokens that can be generated in the completion.'),
 				EShapeType::Number
 			),
+			'conversation_id' => new ShapeDescriptor(
+				$this->l->t('Conversation ID'),
+				$this->l->t('The ID of the conversation this request belongs to.'),
+				EShapeType::Text
+			),
 		];
 	}
 
@@ -131,6 +136,10 @@ public function process(
 			$maxTokens = $input['max_tokens'];
 		}
 
+		$conversationId = isset($input['conversation_id']) && is_string($input['conversation_id'])
+			? $input['conversation_id']
+			: null;
+
 		$model = $this->model;
 
 		$chunks = $this->chunkService->chunkSplitPrompt($this->service, $textInput, true, $maxTokens);
@@ -145,7 +154,7 @@ public function process(
 			try {
 				if ($this->service->isUsingOpenAi() || $this->service->getChatEndpointEnabled()) {
 					if ($preferStreaming) {
-						$chunks = $this->openAiAPIService->createStreamedChatCompletion($userId, $this->service, $model, $prompt, null, null, 1, $maxTokens);
+						$chunks = $this->openAiAPIService->createStreamedChatCompletion($userId, $this->service, $model, $prompt, null, null, 1, $maxTokens, conversationId: $conversationId);
 						$time = microtime(true);
 						foreach ($chunks as $chunk) {
 							if (!in_array($chunk['kind'] ?? null, ['content', 'reasoning_content'], true)) {
@@ -181,7 +190,7 @@ public function process(
 						$completion = $returnValue['messages'];
 						$reasoning = $returnValue['reasoning_messages'];
 					} else {
-						$returnValue = $this->openAiAPIService->createChatCompletion($userId, $this->service, $model, $prompt, null, null, 1, $maxTokens);
+						$returnValue = $this->openAiAPIService->createChatCompletion($userId, $this->service, $model, $prompt, null, null, 1, $maxTokens, conversationId: $conversationId);
 						$completion = $returnValue['messages'];
 						$reasoning = $returnValue['reasoning_messages'];
 					}
diff --git a/lib/TaskProcessing/ContextWriteProvider.php b/lib/TaskProcessing/ContextWriteProvider.php
index a0833628..8d8f5fae 100644
--- a/lib/TaskProcessing/ContextWriteProvider.php
+++ b/lib/TaskProcessing/ContextWriteProvider.php
@@ -65,6 +65,11 @@ public function getOptionalInputShape(): array {
 				$this->l->t('The maximum number of words/tokens that can be generated in the completion.'),
 				EShapeType::Number
 			),
+			'conversation_id' => new ShapeDescriptor(
+				$this->l->t('Conversation ID'),
+				$this->l->t('The ID of the conversation this request belongs to.'),
+				EShapeType::Text
+			),
 		];
 	}
 
@@ -118,6 +123,10 @@ public function process(
 			$maxTokens = $input['max_tokens'];
 		}
 
+		$conversationId = isset($input['conversation_id']) && is_string($input['conversation_id'])
+			? $input['conversation_id']
+			: null;
+
 		$model = $this->model;
 
 		$chunks = $this->chunkService->chunkSplitPrompt($this->service, $sourceMaterial, true, $maxTokens);
@@ -141,7 +150,7 @@ public function process(
 			try {
 				if ($this->service->isUsingOpenAi() || $this->service->getChatEndpointEnabled()) {
 					if ($preferStreaming) {
-						$chunks = $this->openAiAPIService->createStreamedChatCompletion($userId, $this->service, $model, $prompt, null, null, 1, $maxTokens);
+						$chunks = $this->openAiAPIService->createStreamedChatCompletion($userId, $this->service, $model, $prompt, null, null, 1, $maxTokens, conversationId: $conversationId);
 						$time = microtime(true);
 						foreach ($chunks as $chunk) {
 							if (!in_array($chunk['kind'] ?? null, ['content', 'reasoning_content'], true)) {
@@ -177,7 +186,7 @@ public function process(
 						$completion = $returnValue['messages'];
 						$reasoning = $returnValue['reasoning_messages'];
 					} else {
-						$returnValue = $this->openAiAPIService->createChatCompletion($userId, $this->service, $model, $prompt, null, null, 1, $maxTokens);
+						$returnValue = $this->openAiAPIService->createChatCompletion($userId, $this->service, $model, $prompt, null, null, 1, $maxTokens, conversationId: $conversationId);
 						$completion = $returnValue['messages'];
 						$reasoning = $returnValue['reasoning_messages'];
 					}
diff --git a/lib/TaskProcessing/EmojiProvider.php b/lib/TaskProcessing/EmojiProvider.php
index 8c777189..56bbdbd7 100644
--- a/lib/TaskProcessing/EmojiProvider.php
+++ b/lib/TaskProcessing/EmojiProvider.php
@@ -61,6 +61,11 @@ public function getOptionalInputShape(): array {
 				$this->l->t('The maximum number of words/tokens that can be generated in the completion.'),
 				EShapeType::Number
 			),
+			'conversation_id' => new ShapeDescriptor(
+				$this->l->t('Conversation ID'),
+				$this->l->t('The ID of the conversation this request belongs to.'),
+				EShapeType::Text
+			),
 		];
 	}
 
@@ -100,11 +105,15 @@ public function process(?string $userId, array $input, callable $reportProgress)
 			$maxTokens = $input['max_tokens'];
 		}
 
+		$conversationId = isset($input['conversation_id']) && is_string($input['conversation_id'])
+			? $input['conversation_id']
+			: null;
+
 		$model = $this->model;
 
 		try {
 			if ($this->service->isUsingOpenAi() || $this->service->getChatEndpointEnabled()) {
-				$completion = $this->openAiAPIService->createChatCompletion($userId, $this->service, $model, $prompt, null, null, 1, $maxTokens);
+				$completion = $this->openAiAPIService->createChatCompletion($userId, $this->service, $model, $prompt, null, null, 1, $maxTokens, conversationId: $conversationId);
 				$completion = $completion['messages'];
 			} else {
 				$completion = $this->openAiAPIService->createCompletion($userId, $this->service, $prompt, 1, $model, $maxTokens);
diff --git a/lib/TaskProcessing/HeadlineProvider.php b/lib/TaskProcessing/HeadlineProvider.php
index 47efbee6..f610b37b 100644
--- a/lib/TaskProcessing/HeadlineProvider.php
+++ b/lib/TaskProcessing/HeadlineProvider.php
@@ -61,6 +61,11 @@ public function getOptionalInputShape(): array {
 				$this->l->t('The maximum number of words/tokens that can be generated in the completion.'),
 				EShapeType::Number
 			),
+			'conversation_id' => new ShapeDescriptor(
+				$this->l->t('Conversation ID'),
+				$this->l->t('The ID of the conversation this request belongs to.'),
+				EShapeType::Text
+			),
 		];
 	}
 
@@ -100,11 +105,15 @@ public function process(?string $userId, array $input, callable $reportProgress)
 			$maxTokens = $input['max_tokens'];
 		}
 
+		$conversationId = isset($input['conversation_id']) && is_string($input['conversation_id'])
+			? $input['conversation_id']
+			: null;
+
 		$model = $this->model;
 
 		try {
 			if ($this->service->isUsingOpenAi() || $this->service->getChatEndpointEnabled()) {
-				$completion = $this->openAiAPIService->createChatCompletion($userId, $this->service, $model, $prompt, null, null, 1, $maxTokens);
+				$completion = $this->openAiAPIService->createChatCompletion($userId, $this->service, $model, $prompt, null, null, 1, $maxTokens, conversationId: $conversationId);
 				$completion = $completion['messages'];
 			} else {
 				$completion = $this->openAiAPIService->createCompletion($userId, $this->service, $prompt, 1, $model, $maxTokens);
diff --git a/lib/TaskProcessing/ImageToTextOcrProvider.php b/lib/TaskProcessing/ImageToTextOcrProvider.php
index 7d91ed8f..6dbc8863 100644
--- a/lib/TaskProcessing/ImageToTextOcrProvider.php
+++ b/lib/TaskProcessing/ImageToTextOcrProvider.php
@@ -65,6 +65,11 @@ public function getOptionalInputShape(): array {
 				$this->l->t('The maximum number of words/tokens that can be generated in the output.'),
 				EShapeType::Number
 			),
+			'conversation_id' => new ShapeDescriptor(
+				$this->l->t('Conversation ID'),
+				$this->l->t('The ID of the conversation this request belongs to.'),
+				EShapeType::Text
+			),
 		];
 	}
 
@@ -116,6 +121,10 @@ public function process(
 			$maxTokens = $input['max_tokens'];
 		}
 
+		$conversationId = isset($input['conversation_id']) && is_string($input['conversation_id'])
+			? $input['conversation_id']
+			: null;
+
 		$fileSizeTotal = array_reduce(
 			$files,
 			function ($carry, $file) {
@@ -145,6 +154,7 @@ function ($carry, $file) {
 				if ($preferStreaming) {
 					$chunks = $this->openAiAPIService->createStreamedChatCompletion(
 						$userId, $this->service, $this->model, $userPrompt, $systemPrompt, null, 1, $maxTokens, null, null, null, [$file],
+						conversationId: $conversationId,
 					);
 					$time = microtime(true);
 					foreach ($chunks as $chunk) {
@@ -176,6 +186,7 @@ function ($carry, $file) {
 				} else {
 					$completion = $this->openAiAPIService->createChatCompletion(
 						$userId, $this->service, $this->model, $userPrompt, $systemPrompt, null, 1, $maxTokens, null, null, null, [$file],
+						conversationId: $conversationId,
 					);
 					$messages = $completion['messages'];
 				}
diff --git a/lib/TaskProcessing/MultimodalChatWithToolsProvider.php b/lib/TaskProcessing/MultimodalChatWithToolsProvider.php
index f460bdd2..f98af6a0 100644
--- a/lib/TaskProcessing/MultimodalChatWithToolsProvider.php
+++ b/lib/TaskProcessing/MultimodalChatWithToolsProvider.php
@@ -69,6 +69,11 @@ public function getOptionalInputShape(): array {
 				$this->l->t('The maximum number of words/tokens that can be generated in the completion.'),
 				EShapeType::Number
 			),
+			'conversation_id' => new ShapeDescriptor(
+				$this->l->t('Conversation ID'),
+				$this->l->t('The ID of the conversation this request belongs to.'),
+				EShapeType::Text
+			),
 		];
 	}
 
@@ -156,10 +161,16 @@ public function process(
 		if (isset($input['max_tokens']) && is_int($input['max_tokens'])) {
 			$maxTokens = $input['max_tokens'];
 		}
+
+		$conversationId = isset($input['conversation_id']) && is_string($input['conversation_id'])
+			? $input['conversation_id']
+			: null;
+
 		try {
 			if ($preferStreaming) {
 				$chunks = $this->openAiAPIService->createStreamedChatCompletion(
-					$userId, $this->service, $this->model, $userPrompt, $systemPrompt, $history, 1, $maxTokens, null, $toolMessage, $tools, $inputAttachments
+					$userId, $this->service, $this->model, $userPrompt, $systemPrompt, $history, 1, $maxTokens, null, $toolMessage, $tools, $inputAttachments,
+					conversationId: $conversationId,
 				);
 				$time = microtime(true);
 				$streamedOutput = '';
@@ -197,7 +208,8 @@ public function process(
 				$returnValue = $chunks->getReturn();
 			} else {
 				$returnValue = $this->openAiAPIService->createChatCompletion(
-					$userId, $this->service, $this->model, $userPrompt, $systemPrompt, $history, 1, $maxTokens, null, $toolMessage, $tools, $inputAttachments
+					$userId, $this->service, $this->model, $userPrompt, $systemPrompt, $history, 1, $maxTokens, null, $toolMessage, $tools, $inputAttachments,
+					conversationId: $conversationId,
 				);
 			}
 		} catch (UserFacingProcessingException $e) {
diff --git a/lib/TaskProcessing/ProofreadProvider.php b/lib/TaskProcessing/ProofreadProvider.php
index 9040da2c..c67b36dc 100644
--- a/lib/TaskProcessing/ProofreadProvider.php
+++ b/lib/TaskProcessing/ProofreadProvider.php
@@ -69,6 +69,11 @@ public function getOptionalInputShape(): array {
 				$this->l->t('The maximum number of words/tokens that can be generated in the completion.'),
 				EShapeType::Number
 			),
+			'conversation_id' => new ShapeDescriptor(
+				$this->l->t('Conversation ID'),
+				$this->l->t('The ID of the conversation this request belongs to.'),
+				EShapeType::Text
+			),
 		];
 	}
 
@@ -119,6 +124,10 @@ public function process(?string $userId, array $input, callable $reportProgress)
 			$maxTokens = $input['max_tokens'];
 		}
 
+		$conversationId = isset($input['conversation_id']) && is_string($input['conversation_id'])
+			? $input['conversation_id']
+			: null;
+
 		$model = $this->model;
 
 		$chunks = $this->chunkService->chunkSplitPrompt($this->service, $textInput, true, $maxTokens);
@@ -129,7 +138,7 @@ public function process(?string $userId, array $input, callable $reportProgress)
 		foreach ($chunks as $textInput) {
 			try {
 				if ($this->service->isUsingOpenAi() || $this->service->getChatEndpointEnabled()) {
-					$completion = $this->openAiAPIService->createChatCompletion($userId, $this->service, $model, $textInput, $systemPrompt, null, 1, $maxTokens);
+					$completion = $this->openAiAPIService->createChatCompletion($userId, $this->service, $model, $textInput, $systemPrompt, null, 1, $maxTokens, conversationId: $conversationId);
 					$completion = $completion['messages'];
 				} else {
 					$prompt = $systemPrompt . ' Here is the text:' . "\n\n" . $textInput;
@@ -156,7 +165,7 @@ public function process(?string $userId, array $input, callable $reportProgress)
 			$systemPrompt = 'Repeat the proofread feedback list. Ensure that no information is lost, but also not duplicated. ';
 			try {
 				if ($this->service->isUsingOpenAi() || $this->service->getChatEndpointEnabled()) {
-					$completion = $this->openAiAPIService->createChatCompletion($userId, $this->service, $model, $result, $systemPrompt, null, 1, $maxTokens);
+					$completion = $this->openAiAPIService->createChatCompletion($userId, $this->service, $model, $result, $systemPrompt, null, 1, $maxTokens, conversationId: $conversationId);
 					$completion = $completion['messages'];
 				} else {
 					$prompt = $systemPrompt . ' Here is the text:' . "\n\n" . $result;
diff --git a/lib/TaskProcessing/ReformatParagraphsProvider.php b/lib/TaskProcessing/ReformatParagraphsProvider.php
index acdd2cb1..21554a49 100644
--- a/lib/TaskProcessing/ReformatParagraphsProvider.php
+++ b/lib/TaskProcessing/ReformatParagraphsProvider.php
@@ -110,6 +110,11 @@ public function getOptionalInputShape(): array {
 				$this->l->t('The maximum number of words/tokens that can be generated in the completion.'),
 				EShapeType::Number
 			),
+			'conversation_id' => new ShapeDescriptor(
+				$this->l->t('Conversation ID'),
+				$this->l->t('The ID of the conversation this request belongs to.'),
+				EShapeType::Text
+			),
 		];
 	}
 
@@ -148,6 +153,10 @@ public function process(?string $userId, array $input, callable $reportProgress)
 			$maxTokens = $input['max_tokens'];
 		}
 
+		$conversationId = isset($input['conversation_id']) && is_string($input['conversation_id'])
+			? $input['conversation_id']
+			: null;
+
 		$model = $this->model;
 		$chunks = $this->chunkService->chunkSplitPrompt($this->service, $prompt, false);
 		$result = '';
@@ -170,7 +179,7 @@ public function process(?string $userId, array $input, callable $reportProgress)
 TEXT;
 			try {
 				if ($this->service->isUsingOpenAi() || $this->service->getChatEndpointEnabled()) {
-					$completion = $this->openAiAPIService->createChatCompletion($userId, $this->service, $model, $chunk, $systemPrompt, null, 1, $maxTokens);
+					$completion = $this->openAiAPIService->createChatCompletion($userId, $this->service, $model, $chunk, $systemPrompt, null, 1, $maxTokens, conversationId: $conversationId);
 					$completion = $completion['messages'];
 				} else {
 					$instruction = $systemPrompt . ' Here is the text:' . "\n\n" . $chunk;
diff --git a/lib/TaskProcessing/ReformulateProvider.php b/lib/TaskProcessing/ReformulateProvider.php
index 3f486597..25b76ea1 100644
--- a/lib/TaskProcessing/ReformulateProvider.php
+++ b/lib/TaskProcessing/ReformulateProvider.php
@@ -65,6 +65,11 @@ public function getOptionalInputShape(): array {
 				$this->l->t('The maximum number of words/tokens that can be generated in the completion.'),
 				EShapeType::Number
 			),
+			'conversation_id' => new ShapeDescriptor(
+				$this->l->t('Conversation ID'),
+				$this->l->t('The ID of the conversation this request belongs to.'),
+				EShapeType::Text
+			),
 		];
 	}
 
@@ -113,6 +118,10 @@ public function process(
 			$maxTokens = $input['max_tokens'];
 		}
 
+		$conversationId = isset($input['conversation_id']) && is_string($input['conversation_id'])
+			? $input['conversation_id']
+			: null;
+
 		$model = $this->model;
 		$chunks = $this->chunkService->chunkSplitPrompt($this->service, $prompt, true, $maxTokens);
 		$fullOutput = '';
@@ -127,7 +136,7 @@ public function process(
 			try {
 				if ($this->service->isUsingOpenAi() || $this->service->getChatEndpointEnabled()) {
 					if ($preferStreaming) {
-						$chunks = $this->openAiAPIService->createStreamedChatCompletion($userId, $this->service, $model, $prompt, null, null, 1, $maxTokens);
+						$chunks = $this->openAiAPIService->createStreamedChatCompletion($userId, $this->service, $model, $prompt, null, null, 1, $maxTokens, conversationId: $conversationId);
 						$time = microtime(true);
 						foreach ($chunks as $chunk) {
 							if (!in_array($chunk['kind'] ?? null, ['content', 'reasoning_content'], true)) {
@@ -163,7 +172,7 @@ public function process(
 						$completion = $returnValue['messages'];
 						$reasoning = $returnValue['reasoning_messages'];
 					} else {
-						$returnValue = $this->openAiAPIService->createChatCompletion($userId, $this->service, $model, $prompt, null, null, 1, $maxTokens);
+						$returnValue = $this->openAiAPIService->createChatCompletion($userId, $this->service, $model, $prompt, null, null, 1, $maxTokens, conversationId: $conversationId);
 						$completion = $returnValue['messages'];
 						$reasoning = $returnValue['reasoning_messages'];
 					}
diff --git a/lib/TaskProcessing/SummaryProvider.php b/lib/TaskProcessing/SummaryProvider.php
index 63c1e140..1d402f48 100644
--- a/lib/TaskProcessing/SummaryProvider.php
+++ b/lib/TaskProcessing/SummaryProvider.php
@@ -76,6 +76,11 @@ public function getOptionalInputShape(): array {
 				$this->l->t('The maximum number of words/tokens that can be generated in the completion.'),
 				EShapeType::Number
 			),
+			'conversation_id' => new ShapeDescriptor(
+				$this->l->t('Conversation ID'),
+				$this->l->t('The ID of the conversation this request belongs to.'),
+				EShapeType::Text
+			),
 		];
 	}
 
@@ -128,6 +133,10 @@ public function process(?string $userId, array $input, callable $reportProgress)
 			$maxTokens = $input['max_tokens'];
 		}
 
+		$conversationId = isset($input['conversation_id']) && is_string($input['conversation_id'])
+			? $input['conversation_id']
+			: null;
+
 		$model = $this->model;
 
 		$prompts = $this->chunkService->chunkSplitPrompt($this->service, $prompt);
@@ -164,7 +173,7 @@ public function process(?string $userId, array $input, callable $reportProgress)
 				if ($this->service->isUsingOpenAi() || $this->service->getChatEndpointEnabled()) {
 
 					foreach ($prompts as $p) {
-						$completion = $this->openAiAPIService->createChatCompletion($userId, $this->service, $model, $p, $summarySystemPrompt, null, 1, $maxTokens);
+						$completion = $this->openAiAPIService->createChatCompletion($userId, $this->service, $model, $p, $summarySystemPrompt, null, 1, $maxTokens, conversationId: $conversationId);
 						$completions[] = $completion['messages'];
 						$progress += $increase;
 						$running = $reportProgress($progress);
diff --git a/lib/TaskProcessing/TextToImageImprovedPromptProvider.php b/lib/TaskProcessing/TextToImageImprovedPromptProvider.php
index 155e4faf..3f0f38ca 100644
--- a/lib/TaskProcessing/TextToImageImprovedPromptProvider.php
+++ b/lib/TaskProcessing/TextToImageImprovedPromptProvider.php
@@ -67,7 +67,13 @@ public function getInputShapeDefaults(): array {
 	}
 
 	public function getOptionalInputShape(): array {
-		return $this->textToImageProvider->getOptionalInputShape();
+		return array_merge($this->textToImageProvider->getOptionalInputShape(), [
+			'conversation_id' => new ShapeDescriptor(
+				$this->l10n->t('Conversation ID'),
+				$this->l10n->t('The ID of the conversation this request belongs to.'),
+				EShapeType::Text
+			),
+		]);
 	}
 
 	public function getOptionalInputShapeEnumValues(): array {
@@ -125,8 +131,13 @@ public function process(?string $userId, array $input, callable $reportProgress,
 			. 'no preface, no markdown, no quotes around the JSON, no explanations.' . "\n\n"
 			. 'Original prompt:' . "\n" . $originalPrompt;
 		$improvedPrompts = array_fill(0, $nbImages, $originalPrompt);
+		$improveInput = ['input' => $instruction];
+		if (isset($input['conversation_id']) && is_string($input['conversation_id'])) {
+			$improveInput['conversation_id'] = $input['conversation_id'];
+		}
+
 		try {
-			$output = $this->textToTextProvider->process($userId, ['input' => $instruction], $reportProgress);
+			$output = $this->textToTextProvider->process($userId, $improveInput, $reportProgress);
 			if (isset($output['output']) && is_string($output['output']) && trim($output['output']) !== '') {
 				$parsed = $this->parseImprovedPrompts(trim($output['output']), $nbImages, $originalPrompt);
 				if ($parsed !== null) {
diff --git a/lib/TaskProcessing/TextToTextChatProvider.php b/lib/TaskProcessing/TextToTextChatProvider.php
index ad64b833..7ad10a3e 100644
--- a/lib/TaskProcessing/TextToTextChatProvider.php
+++ b/lib/TaskProcessing/TextToTextChatProvider.php
@@ -68,6 +68,11 @@ public function getOptionalInputShape(): array {
 				$this->l->t('The memories to be injected into the chat session.'),
 				EShapeType::ListOfTexts
 			),
+			'conversation_id' => new ShapeDescriptor(
+				$this->l->t('Conversation ID'),
+				$this->l->t('The ID of the conversation this request belongs to.'),
+				EShapeType::Text
+			),
 		];
 	}
 
@@ -129,9 +134,13 @@ public function process(
 			$maxTokens = $input['max_tokens'];
 		}
 
+		$conversationId = isset($input['conversation_id']) && is_string($input['conversation_id'])
+			? $input['conversation_id']
+			: null;
+
 		try {
 			if ($preferStreaming) {
-				$chunks = $this->openAiAPIService->createStreamedChatCompletion($userId, $this->service, $this->model, $userPrompt, $systemPrompt, $history, 1, $maxTokens);
+				$chunks = $this->openAiAPIService->createStreamedChatCompletion($userId, $this->service, $this->model, $userPrompt, $systemPrompt, $history, 1, $maxTokens, conversationId: $conversationId);
 				$time = microtime(true);
 				$streamedOutput = '';
 				$streamedReasoning = '';
@@ -169,7 +178,7 @@ public function process(
 				$completion = $returnValue['messages'];
 				$reasoning = $returnValue['reasoning_messages'];
 			} else {
-				$returnValue = $this->openAiAPIService->createChatCompletion($userId, $this->service, $this->model, $userPrompt, $systemPrompt, $history, 1, $maxTokens);
+				$returnValue = $this->openAiAPIService->createChatCompletion($userId, $this->service, $this->model, $userPrompt, $systemPrompt, $history, 1, $maxTokens, conversationId: $conversationId);
 				$completion = $returnValue['messages'];
 				$reasoning = $returnValue['reasoning_messages'];
 			}
diff --git a/lib/TaskProcessing/TextToTextChatWithToolsProvider.php b/lib/TaskProcessing/TextToTextChatWithToolsProvider.php
index d90cd00a..3b1b6fe2 100644
--- a/lib/TaskProcessing/TextToTextChatWithToolsProvider.php
+++ b/lib/TaskProcessing/TextToTextChatWithToolsProvider.php
@@ -63,6 +63,11 @@ public function getOptionalInputShape(): array {
 				$this->l->t('The maximum number of words/tokens that can be generated in the completion.'),
 				EShapeType::Number
 			),
+			'conversation_id' => new ShapeDescriptor(
+				$this->l->t('Conversation ID'),
+				$this->l->t('The ID of the conversation this request belongs to.'),
+				EShapeType::Text
+			),
 		];
 	}
 
@@ -138,10 +143,15 @@ public function process(
 			$maxTokens = $input['max_tokens'];
 		}
 
+		$conversationId = isset($input['conversation_id']) && is_string($input['conversation_id'])
+			? $input['conversation_id']
+			: null;
+
 		try {
 			if ($preferStreaming) {
 				$chunks = $this->openAiAPIService->createStreamedChatCompletion(
-					$userId, $this->service, $this->model, $userPrompt, $systemPrompt, $history, 1, $maxTokens, null, $toolMessage, $tools
+					$userId, $this->service, $this->model, $userPrompt, $systemPrompt, $history, 1, $maxTokens, null, $toolMessage, $tools,
+					conversationId: $conversationId,
 				);
 				$time = microtime(true);
 				$streamedOutput = '';
@@ -179,7 +189,8 @@ public function process(
 				$returnValue = $chunks->getReturn();
 			} else {
 				$returnValue = $this->openAiAPIService->createChatCompletion(
-					$userId, $this->service, $this->model, $userPrompt, $systemPrompt, $history, 1, $maxTokens, null, $toolMessage, $tools
+					$userId, $this->service, $this->model, $userPrompt, $systemPrompt, $history, 1, $maxTokens, null, $toolMessage, $tools,
+					conversationId: $conversationId,
 				);
 			}
 		} catch (UserFacingProcessingException $e) {
diff --git a/lib/TaskProcessing/TextToTextImproveProvider.php b/lib/TaskProcessing/TextToTextImproveProvider.php
index e9313a0e..11b66dfd 100644
--- a/lib/TaskProcessing/TextToTextImproveProvider.php
+++ b/lib/TaskProcessing/TextToTextImproveProvider.php
@@ -65,6 +65,11 @@ public function getOptionalInputShape(): array {
 				$this->l->t('The maximum number of words/tokens that can be generated in the completion.'),
 				EShapeType::Number
 			),
+			'conversation_id' => new ShapeDescriptor(
+				$this->l->t('Conversation ID'),
+				$this->l->t('The ID of the conversation this request belongs to.'),
+				EShapeType::Text
+			),
 		];
 	}
 
@@ -121,6 +126,10 @@ public function process(
 			$maxTokens = $input['max_tokens'];
 		}
 
+		$conversationId = isset($input['conversation_id']) && is_string($input['conversation_id'])
+			? $input['conversation_id']
+			: null;
+
 		$model = $this->model;
 		$chunks = $this->chunkService->chunkSplitPrompt($this->service, $textInput, true, $maxTokens);
 		$fullOutput = '';
@@ -137,7 +146,7 @@ public function process(
 			try {
 				if ($this->service->isUsingOpenAi() || $this->service->getChatEndpointEnabled()) {
 					if ($preferStreaming) {
-						$chunks = $this->openAiAPIService->createStreamedChatCompletion($userId, $this->service, $model, $prompt, null, null, 1, $maxTokens);
+						$chunks = $this->openAiAPIService->createStreamedChatCompletion($userId, $this->service, $model, $prompt, null, null, 1, $maxTokens, conversationId: $conversationId);
 						$time = microtime(true);
 						foreach ($chunks as $chunk) {
 							if (!in_array($chunk['kind'] ?? null, ['content', 'reasoning_content'], true)) {
@@ -173,7 +182,7 @@ public function process(
 						$completion = $returnValue['messages'];
 						$reasoning = $returnValue['reasoning_messages'];
 					} else {
-						$returnValue = $this->openAiAPIService->createChatCompletion($userId, $this->service, $model, $prompt, null, null, 1, $maxTokens);
+						$returnValue = $this->openAiAPIService->createChatCompletion($userId, $this->service, $model, $prompt, null, null, 1, $maxTokens, conversationId: $conversationId);
 						$completion = $returnValue['messages'];
 						$reasoning = $returnValue['reasoning_messages'];
 					}
diff --git a/lib/TaskProcessing/TextToTextProvider.php b/lib/TaskProcessing/TextToTextProvider.php
index aa1b08d7..98a33d0a 100644
--- a/lib/TaskProcessing/TextToTextProvider.php
+++ b/lib/TaskProcessing/TextToTextProvider.php
@@ -63,6 +63,11 @@ public function getOptionalInputShape(): array {
 				$this->l->t('The maximum number of words/tokens that can be generated in the completion.'),
 				EShapeType::Number,
 			),
+			'conversation_id' => new ShapeDescriptor(
+				$this->l->t('Conversation ID'),
+				$this->l->t('The ID of the conversation this request belongs to.'),
+				EShapeType::Text
+			),
 		];
 	}
 
@@ -111,12 +116,16 @@ public function process(
 			$maxTokens = $input['max_tokens'];
 		}
 
+		$conversationId = isset($input['conversation_id']) && is_string($input['conversation_id'])
+			? $input['conversation_id']
+			: null;
+
 		$model = $this->model;
 
 		try {
 			if ($this->service->isUsingOpenAi() || $this->service->getChatEndpointEnabled()) {
 				if ($preferStreaming) {
-					$chunks = $this->openAiAPIService->createStreamedChatCompletion($userId, $this->service, $model, $prompt, null, null, 1, $maxTokens);
+					$chunks = $this->openAiAPIService->createStreamedChatCompletion($userId, $this->service, $model, $prompt, null, null, 1, $maxTokens, conversationId: $conversationId);
 					$time = microtime(true);
 					$streamedOutput = '';
 					$streamedReasoning = '';
@@ -154,7 +163,7 @@ public function process(
 					$completion = $returnValue['messages'];
 					$reasoning = $returnValue['reasoning_messages'];
 				} else {
-					$returnValue = $this->openAiAPIService->createChatCompletion($userId, $this->service, $model, $prompt, null, null, 1, $maxTokens);
+					$returnValue = $this->openAiAPIService->createChatCompletion($userId, $this->service, $model, $prompt, null, null, 1, $maxTokens, conversationId: $conversationId);
 					$completion = $returnValue['messages'];
 					$reasoning = $returnValue['reasoning_messages'];
 				}
diff --git a/lib/TaskProcessing/TopicsProvider.php b/lib/TaskProcessing/TopicsProvider.php
index 456ab150..77f717fa 100644
--- a/lib/TaskProcessing/TopicsProvider.php
+++ b/lib/TaskProcessing/TopicsProvider.php
@@ -65,6 +65,11 @@ public function getOptionalInputShape(): array {
 				$this->l->t('The maximum number of words/tokens that can be generated in the completion.'),
 				EShapeType::Number
 			),
+			'conversation_id' => new ShapeDescriptor(
+				$this->l->t('Conversation ID'),
+				$this->l->t('The ID of the conversation this request belongs to.'),
+				EShapeType::Text
+			),
 		];
 	}
 
@@ -103,6 +108,10 @@ public function process(?string $userId, array $input, callable $reportProgress)
 			$maxTokens = $input['max_tokens'];
 		}
 
+		$conversationId = isset($input['conversation_id']) && is_string($input['conversation_id'])
+			? $input['conversation_id']
+			: null;
+
 		$model = $this->model;
 		$prompts = $this->chunkService->chunkSplitPrompt($this->service, $prompt);
 		$newNumChunks = count($prompts);
@@ -127,7 +136,7 @@ public function process(?string $userId, array $input, callable $reportProgress)
 					$topicsSystemPrompt = 'Extract topics from the following text. Detect the language of the text. Use the same language as the text. Output only the topics, comma separated.';
 
 					foreach ($prompts as $p) {
-						$completion = $this->openAiAPIService->createChatCompletion($userId, $this->service, $model, $p, $topicsSystemPrompt, null, 1, $maxTokens);
+						$completion = $this->openAiAPIService->createChatCompletion($userId, $this->service, $model, $p, $topicsSystemPrompt, null, 1, $maxTokens, conversationId: $conversationId);
 						$completions[] = $completion['messages'];
 						$progress += $increase;
 						$running = $reportProgress($progress);
diff --git a/lib/TaskProcessing/TranslateProvider.php b/lib/TaskProcessing/TranslateProvider.php
index 12647396..8b2c6edf 100644
--- a/lib/TaskProcessing/TranslateProvider.php
+++ b/lib/TaskProcessing/TranslateProvider.php
@@ -76,6 +76,11 @@ public function getOptionalInputShape(): array {
 				$this->l->t('The maximum number of words/tokens that can be generated in the completion.'),
 				EShapeType::Number
 			),
+			'conversation_id' => new ShapeDescriptor(
+				$this->l->t('Conversation ID'),
+				$this->l->t('The ID of the conversation this request belongs to.'),
+				EShapeType::Text
+			),
 		];
 	}
 
@@ -123,6 +128,10 @@ public function process(
 			$maxTokens = $input['max_tokens'];
 		}
 
+		$conversationId = isset($input['conversation_id']) && is_string($input['conversation_id'])
+			? $input['conversation_id']
+			: null;
+
 		$coreLanguages = TranslateService::getCoreLanguagesByCode();
 		$fromLanguage = $input['origin_language'];
 		$toLanguage = $coreLanguages[$input['target_language']] ?? $input['target_language'];
@@ -140,7 +149,7 @@ public function process(
 				$this->service,
 				$inputText, $input['origin_language'] ?? '', $input['target_language'] ?? '',
 				$model, $maxTokens, $userId, $reportProgress,
-				$preferStreaming, $reportTranslationOutput,
+				$preferStreaming, $reportTranslationOutput, $conversationId,
 			);
 
 			$endTime = time();
diff --git a/src/components/AdminSettings.vue b/src/components/AdminSettings.vue
index 91f9c0b6..1bb2914a 100644
--- a/src/components/AdminSettings.vue
+++ b/src/components/AdminSettings.vue
@@ -362,7 +362,8 @@ export default {
 		},
 		/**
 		 * @param {string} serviceId ID of the service to save
-		 * @param {boolean} sensitive whether to send the URL and the credentials
+		 * @param {boolean} sensitive whether to send the URL, the credentials
+		 *   and the extra headers
 		 */
 		async putService(serviceId, sensitive) {
 			const service = this.services.find(s => s.id === serviceId)
@@ -375,6 +376,7 @@ export default {
 					basic_user: (service.basic_user ?? '').trim(),
 					api_key: (service.api_key ?? '').trim(),
 					basic_password: (service.basic_password ?? '').trim(),
+					extra_headers: (service.extra_headers ?? []).map(header => ({ ...header })),
 				}
 				: {
 					name: service.name,
diff --git a/src/components/ServiceForm.vue b/src/components/ServiceForm.vue
index 6ccd22b5..6aa18fe9 100644
--- a/src/components/ServiceForm.vue
+++ b/src/components/ServiceForm.vue
@@ -153,6 +153,46 @@
 				</div>
 			</div>
 
+			<!-- Extra request headers -->
+			<h4>{{ t('integration_openai', 'Extra request headers') }}</h4>
+			<NcNoteCard type="info">
+				{{ t('integration_openai', 'Headers sent with every request to this service. The service\'s own authentication always takes precedence over a configured Authorization header.') }}
+				<br>
+				{{ t('integration_openai', 'The only supported variable is {example}: it is replaced with the conversation ID of the request, randomly generated when the task is not part of a conversation. Such a header is only sent with the chat completion requests.', { example: '{$conversation_id}' }) }}
+			</NcNoteCard>
+			<div v-for="(header, index) in extraHeaders" :key="index" class="line align-bottom">
+				<NcTextField
+					:id="'openai-extra-header-name-' + service.id + '-' + index"
+					v-model="header.name"
+					class="input"
+					:label="t('integration_openai', 'Header name')"
+					:placeholder="'X-Api-Key'"
+					:error="headerNameInvalid(header.name)"
+					:helper-text="headerNameInvalid(header.name) ? t('integration_openai', 'Not a valid header name yet, so it is not saved') : ''"
+					@update:model-value="onExtraHeadersInput" />
+				<NcTextField
+					:id="'openai-extra-header-value-' + service.id + '-' + index"
+					v-model="header.value"
+					class="input"
+					:label="t('integration_openai', 'Header value')"
+					:error="headerValueInvalid(header.value)"
+					:helper-text="headerValueInvalid(header.value) ? t('integration_openai', 'Not a supported variable yet, so it is not saved') : ''"
+					@update:model-value="onExtraHeadersInput" />
+				<NcButton variant="tertiary" :aria-label="t('integration_openai', 'Remove this header')" @click="removeExtraHeader(index)">
+					<template #icon>
+						<DeleteOutlineIcon :size="20" />
+					</template>
+				</NcButton>
+			</div>
+			<div class="line">
+				<NcButton variant="tertiary" @click="addExtraHeader">
+					<template #icon>
+						<PlusIcon :size="20" />
+					</template>
+					{{ t('integration_openai', 'Add a header') }}
+				</NcButton>
+			</div>
+
 			<!-- Models per modality -->
 			<h4>{{ t('integration_openai', 'Exposed models') }}</h4>
 			<NcNoteCard type="info">
@@ -402,6 +442,7 @@ import DeleteOutlineIcon from 'vue-material-design-icons/DeleteOutline.vue'
 import EarthIcon from 'vue-material-design-icons/Earth.vue'
 import HelpCircleOutlineIcon from 'vue-material-design-icons/HelpCircleOutline.vue'
 import KeyOutlineIcon from 'vue-material-design-icons/KeyOutline.vue'
+import PlusIcon from 'vue-material-design-icons/Plus.vue'
 import RefreshIcon from 'vue-material-design-icons/Refresh.vue'
 import UnfoldLessHorizontalIcon from 'vue-material-design-icons/UnfoldLessHorizontal.vue'
 import UnfoldMoreHorizontalIcon from 'vue-material-design-icons/UnfoldMoreHorizontal.vue'
@@ -430,6 +471,7 @@ export default {
 		EarthIcon,
 		HelpCircleOutlineIcon,
 		KeyOutlineIcon,
+		PlusIcon,
 		RefreshIcon,
 		UnfoldLessHorizontalIcon,
 		UnfoldMoreHorizontalIcon,
@@ -470,6 +512,11 @@ export default {
 			// other property of the same request
 			llmExtraParams: this.service.llm_extra_params ?? '',
 			defaultImageSize: this.service.default_image_size ?? '',
+			// edited locally like the two above: rows that are still being
+			// typed, or whose name is not a valid header name yet, are not
+			// sent to the backend, which would reject them and with them the
+			// rest of the sensitive payload
+			extraHeaders: (this.service.extra_headers ?? []).map(header => ({ ...header })),
 			// to prevent some browsers from filling fields with remembered passwords
 			readonly: true,
 			models: null,
@@ -498,6 +545,12 @@ export default {
 			const size = this.defaultImageSize.trim()
 			return size === '' || /^\d+x\d+$/.test(size)
 		},
+		/** Whether any row is new, empty or not registerable yet, so the backend must not overwrite the list */
+		extraHeadersPending() {
+			return this.extraHeaders.some(
+				header => this.headerIncomplete(header) || this.headerDirty(header),
+			)
+		},
 		modalities() {
 			return [
 				{
@@ -586,6 +639,11 @@ export default {
 				this.defaultImageSize = value ?? ''
 			}
 		},
+		'service.extra_headers'(value) {
+			if (!this.extraHeadersPending) {
+				this.extraHeaders = (value ?? []).map(header => ({ ...header }))
+			}
+		},
 	},
 
 	mounted() {
@@ -619,6 +677,43 @@ export default {
 			quotas[index] = isNaN(parsed) || parsed < 0 ? 0 : parsed
 			this.onInput({ quotas })
 		},
+		headerNameInvalid(name) {
+			const trimmed = name.trim()
+			return trimmed !== '' && !/^[a-zA-Z0-9!#$%&'*+.^_`|~-]+$/.test(trimmed)
+		},
+		headerValueInvalid(value) {
+			for (const variable of value.matchAll(/\{\$[^}]*\}/g)) {
+				if (variable[0] !== '{$conversation_id}') {
+					return true
+				}
+			}
+			return false
+		},
+		headerIncomplete(header) {
+			return header.name.trim() === '' || header.value.trim() === ''
+		},
+		headerDirty(header) {
+			return this.headerNameInvalid(header.name) || this.headerValueInvalid(header.value)
+		},
+		addExtraHeader() {
+			this.extraHeaders.push({ name: '', value: '' })
+		},
+		removeExtraHeader(index) {
+			this.extraHeaders.splice(index, 1)
+			this.onExtraHeadersInput()
+		},
+		onExtraHeadersInput() {
+			// a half-typed or invalid row must not reject the rest of the
+			// sensitive payload it travels with, so hold it back until it can
+			// be registered, skipping the ones that are still empty
+			if (this.extraHeaders.some(header => this.headerDirty(header))) {
+				return
+			}
+			const headers = this.extraHeaders
+				.filter(header => !this.headerIncomplete(header))
+				.map(header => ({ name: header.name.trim(), value: header.value.trim() }))
+			this.onSensitiveInput({ extra_headers: headers })
+		},
 		async loadModels() {
 			this.loadingModels = true
 			try {
@@ -705,6 +800,10 @@ export default {
 		align-items: start;
 	}
 
+	&.align-bottom {
+		align-items: flex-end;
+	}
+
 	.input {
 		width: 300px;
 	}
diff --git a/tests/unit/Service/MultiServiceTest.php b/tests/unit/Service/MultiServiceTest.php
index 704a03e3..fa4699dc 100644
--- a/tests/unit/Service/MultiServiceTest.php
+++ b/tests/unit/Service/MultiServiceTest.php
@@ -14,6 +14,7 @@
 
 use OCA\OpenAi\AppInfo\Application;
 use OCA\OpenAi\Db\QuotaUsageMapper;
+use OCA\OpenAi\Service\ChunkService;
 use OCA\OpenAi\Service\OpenAiAPIService;
 use OCA\OpenAi\Service\OpenAiFileService;
 use OCA\OpenAi\Service\OpenAiSettingsService;
@@ -21,12 +22,16 @@
 use OCA\OpenAi\Service\ServiceConfig;
 use OCA\OpenAi\Service\ServicesService;
 use OCA\OpenAi\Service\StreamingService;
+use OCA\OpenAi\Service\TranslateService;
 use OCA\OpenAi\Service\WatermarkingService;
 use OCA\OpenAi\TaskProcessing\AudioToTextProvider;
 use OCA\OpenAi\TaskProcessing\ImageToImageProvider;
 use OCA\OpenAi\TaskProcessing\ProviderFactory;
 use OCA\OpenAi\TaskProcessing\TextToImageProvider;
 use OCA\OpenAi\TaskProcessing\TextToSpeechProvider;
+use OCA\OpenAi\TaskProcessing\TextToTextChatProvider;
+use OCA\OpenAi\TaskProcessing\TextToTextProvider;
+use OCA\OpenAi\TaskProcessing\TranslateProvider;
 use OCP\Http\Client\IClient;
 use OCP\Http\Client\IClientService;
 use OCP\IAppConfig;
@@ -53,6 +58,8 @@ class MultiServiceTest extends TestCase {
 	public const APIKEY_TRANSCRIPTION = 'This is a transcription PHPUnit test API key';
 	public const REQUEST_TIMEOUT_TRANSCRIPTION = 14;
 	public const TRANSCRIPTION_MODEL = 'my-whisper-model';
+	public const TEXT_BASE = 'https://text-generator.ai/v1';
+	public const APIKEY_TEXT = 'This is a text PHPUnit test API key';
 	public const TEXT_MODEL = 'my/text-model';
 
 	private OpenAiAPIService $openAiApiService;
@@ -456,6 +463,455 @@ public function testAudioToTextProvider(): void {
 		$audioToTextProvider->process(self::TEST_USER1, ['input' => $file], fn () => null);
 	}
 
+	public function testExtraHeadersAreStoredNormalized(): void {
+		$service = $this->addService([
+			'url' => self::SPEECH_BASE,
+			'extra_headers' => [
+				['name' => ' X-Tenant ', 'value' => ' acme '],
+			],
+		]);
+
+		$this->assertSame(
+			[['name' => 'X-Tenant', 'value' => 'acme']],
+			$service->getExtraHeaders(),
+		);
+	}
+
+	/**
+	 * @dataProvider invalidExtraHeadersProvider
+	 */
+	public function testInvalidExtraHeadersAreRejected(array $extraHeaders): void {
+		$this->expectException(\Exception::class);
+		$this->servicesService->addService([
+			'url' => self::SPEECH_BASE,
+			'extra_headers' => $extraHeaders,
+		]);
+	}
+
+	public function invalidExtraHeadersProvider(): array {
+		return [
+			'a name that is not an HTTP token' => [[['name' => 'X Api Key', 'value' => 'secret']]],
+			'an empty name' => [[['name' => '', 'value' => 'secret']]],
+			'a name that is only spaces' => [[['name' => ' ', 'value' => 'secret']]],
+			'a name with an injected line break' => [[['name' => "X-Tenant\r\nX-Evil", 'value' => 'a']]],
+			'a value with an injected line break' => [[['name' => 'X-Tenant', 'value' => "a\r\nb"]]],
+			'a value with a control character' => [[['name' => 'X-Tenant', 'value' => "a\x01b"]]],
+			'a value with the DEL character' => [[['name' => 'X-Tenant', 'value' => "a\x7fb"]]],
+			'a row without a value' => [[['name' => 'X-Tenant']]],
+			'a row that is not a pair' => [[['nope']]],
+			'a value with an unknown variable' => [[['name' => 'X-Session', 'value' => '{$conversationid}']]],
+			'a value with a mistyped variable' => [[['name' => 'X-Session', 'value' => '{$Conversation_ID}']]],
+			'a value with an empty variable' => [[['name' => 'X-Session', 'value' => '{$}']]],
+		];
+	}
+
+	public function testExtraHeadersAreSentAndCannotOverrideTheApiKey(): void {
+		$service = $this->addService([
+			'url' => self::SPEECH_BASE,
+			'api_key' => self::APIKEY_SPEECH,
+			'request_timeout' => self::REQUEST_TIMEOUT_SPEECH,
+			'tts_models' => [self::SPEECH_MODEL],
+			'extra_headers' => [
+				['name' => 'X-Tenant', 'value' => 'acme'],
+				['name' => 'Authorization', 'value' => 'Bearer injected'],
+			],
+		]);
+
+		$ttsProvider = new TextToSpeechProvider(
+			$this->openAiApiService,
+			$this->createMock(\OCP\IL10N::class),
+			$this->createMock(\Psr\Log\LoggerInterface::class),
+			\OCP\Server::get(WatermarkingService::class),
+			$service,
+			self::SPEECH_MODEL,
+		);
+
+		$inputText = 'This is a test prompt';
+
+		$response = file_get_contents(__DIR__ . '/../../res/speech.mp3');
+
+		if (!$response) {
+			throw new \RuntimeException('Could not read test resourcce `speech.mp3`');
+		}
+
+		$url = self::SPEECH_BASE . '/audio/speech';
+
+		$options = ['timeout' => self::REQUEST_TIMEOUT_SPEECH, 'headers' => ['User-Agent' => Application::USER_AGENT, 'X-Tenant' => 'acme', 'Authorization' => 'Bearer ' . self::APIKEY_SPEECH, 'Content-Type' => 'application/json'], 'nextcloud' => ['allow_local_address' => true]];
+		$options['body'] = json_encode([
+			'input' => $inputText,
+			'voice' => Application::DEFAULT_SPEECH_VOICE,
+			'model' => self::SPEECH_MODEL,
+			'response_format' => 'mp3',
+			'speed' => 1,
+		]);
+
+		$iResponse = $this->createMock(\OCP\Http\Client\IResponse::class);
+		$iResponse->method('getBody')->willReturn($response);
+		$iResponse->method('getStatusCode')->willReturn(200);
+
+		$this->iClient->expects($this->once())->method('post')->with($url, $options)->willReturn($iResponse);
+
+		$ttsProvider->process(self::TEST_USER1, ['input' => $inputText], fn () => null, includeWatermark: false);
+	}
+
+	public function testExtraHeadersInImageRequestOptions(): void {
+		$service = $this->addService([
+			'url' => self::IMAGE_BASE,
+			'api_key' => self::APIKEY_IMAGE,
+			'image_request_auth' => false,
+			'extra_headers' => [['name' => 'X-Tenant', 'value' => 'acme']],
+		]);
+
+		$options = $this->openAiApiService->getImageRequestOptions(self::TEST_USER1, $service);
+
+		$this->assertSame([
+			'timeout' => Application::OPENAI_DEFAULT_REQUEST_TIMEOUT,
+			'headers' => ['User-Agent' => Application::USER_AGENT, 'X-Tenant' => 'acme'],
+		], $options);
+	}
+
+	public function testConversationIdHeaderIsExpandedOnChatRequests(): void {
+		$service = $this->addService([
+			'url' => self::TEXT_BASE,
+			'api_key' => self::APIKEY_TEXT,
+			'text_models' => [self::TEXT_MODEL],
+			'extra_headers' => [
+				['name' => 'X-Tenant', 'value' => 'acme'],
+				['name' => 'X-Session', 'value' => '{$conversation_id}'],
+			],
+		]);
+
+		$chatProvider = new TextToTextChatProvider(
+			$this->openAiApiService,
+			$this->createMock(\OCP\IL10N::class),
+			$service,
+			self::TEXT_MODEL,
+		);
+
+		$systemPrompt = 'You are a helpful assistant';
+		$userPrompt = 'Hello';
+
+		$response = json_encode([
+			'choices' => [
+				['message' => ['role' => 'assistant', 'content' => 'Chat answer']],
+			],
+		]);
+
+		$url = self::TEXT_BASE . '/chat/completions';
+		$options = ['timeout' => Application::OPENAI_DEFAULT_REQUEST_TIMEOUT, 'headers' => ['User-Agent' => Application::USER_AGENT, 'X-Tenant' => 'acme', 'X-Session' => '4242', 'Authorization' => 'Bearer ' . self::APIKEY_TEXT, 'Content-Type' => 'application/json'], 'nextcloud' => ['allow_local_address' => true]];
+		$options['body'] = json_encode([
+			'model' => self::TEXT_MODEL,
+			'messages' => [
+				['role' => 'system', 'content' => $systemPrompt],
+				['role' => 'user', 'content' => $userPrompt],
+			],
+			'n' => 1,
+			'stream' => false,
+			'max_tokens' => Application::DEFAULT_MAX_NUM_OF_TOKENS,
+		]);
+
+		$iResponse = $this->createMock(\OCP\Http\Client\IResponse::class);
+		$iResponse->method('getHeader')->with('Content-Type')->willReturn('application/json');
+		$iResponse->method('getBody')->willReturn($response);
+		$iResponse->method('getStatusCode')->willReturn(200);
+
+		$this->iClient->expects($this->once())->method('post')->with($url, $options)->willReturn($iResponse);
+
+		$result = $chatProvider->process(self::TEST_USER1, [
+			'input' => $userPrompt,
+			'system_prompt' => $systemPrompt,
+			'history' => [],
+			'conversation_id' => '4242',
+		], fn () => null);
+
+		$this->assertSame('Chat answer', $result['output']);
+	}
+
+	public function testConversationIdHeaderIsGeneratedWhenTheConversationIsUnknown(): void {
+		$service = $this->addService([
+			'url' => self::TEXT_BASE,
+			'api_key' => self::APIKEY_TEXT,
+			'text_models' => [self::TEXT_MODEL],
+			'extra_headers' => [
+				['name' => 'X-Tenant', 'value' => 'acme'],
+				['name' => 'X-Session', 'value' => 'conv-{$conversation_id}'],
+			],
+		]);
+
+		$chatProvider = new TextToTextChatProvider(
+			$this->openAiApiService,
+			$this->createMock(\OCP\IL10N::class),
+			$service,
+			self::TEXT_MODEL,
+		);
+
+		$systemPrompt = 'You are a helpful assistant';
+		$userPrompt = 'Hello';
+
+		$response = json_encode([
+			'choices' => [
+				['message' => ['role' => 'assistant', 'content' => 'Chat answer']],
+			],
+		]);
+
+		// the same request without the conversation_id input: the header is
+		// still sent, with a throwaway ID generated for the request
+		$url = self::TEXT_BASE . '/chat/completions';
+		$options = ['timeout' => Application::OPENAI_DEFAULT_REQUEST_TIMEOUT, 'headers' => ['User-Agent' => Application::USER_AGENT, 'X-Tenant' => 'acme', 'Authorization' => 'Bearer ' . self::APIKEY_TEXT, 'Content-Type' => 'application/json'], 'nextcloud' => ['allow_local_address' => true]];
+		$options['body'] = json_encode([
+			'model' => self::TEXT_MODEL,
+			'messages' => [
+				['role' => 'system', 'content' => $systemPrompt],
+				['role' => 'user', 'content' => $userPrompt],
+			],
+			'n' => 1,
+			'stream' => false,
+			'max_tokens' => Application::DEFAULT_MAX_NUM_OF_TOKENS,
+		]);
+
+		$iResponse = $this->createMock(\OCP\Http\Client\IResponse::class);
+		$iResponse->method('getHeader')->with('Content-Type')->willReturn('application/json');
+		$iResponse->method('getBody')->willReturn($response);
+		$iResponse->method('getStatusCode')->willReturn(200);
+
+		$generatedIds = [];
+		$this->iClient->expects($this->exactly(2))->method('post')->with(
+			$url,
+			$this->callback(static function (array $actualOptions) use ($options, &$generatedIds): bool {
+				$generatedId = $actualOptions['headers']['X-Session'] ?? null;
+				if (!is_string($generatedId) || preg_match('/^conv-[0-9a-f]{32}$/', $generatedId) !== 1) {
+					return false;
+				}
+				$generatedIds[] = $generatedId;
+				unset($actualOptions['headers']['X-Session']);
+				return $actualOptions == $options;
+			}),
+		)->willReturn($iResponse);
+
+		$result = $chatProvider->process(self::TEST_USER1, [
+			'input' => $userPrompt,
+			'system_prompt' => $systemPrompt,
+			'history' => [],
+		], fn () => null);
+
+		$this->assertSame('Chat answer', $result['output']);
+
+		$result = $chatProvider->process(self::TEST_USER1, [
+			'input' => $userPrompt,
+			'system_prompt' => $systemPrompt,
+			'history' => [],
+		], fn () => null);
+
+		$this->assertSame('Chat answer', $result['output']);
+
+		// a different throwaway ID per request: unrelated tasks must not share
+		// a stateful conversation on the service
+		$this->assertCount(2, $generatedIds);
+		$this->assertNotSame($generatedIds[0], $generatedIds[1]);
+	}
+
+	public function testConversationIdHeaderIsDroppedOnNonChatRequests(): void {
+		$service = $this->addService([
+			'url' => self::SPEECH_BASE,
+			'api_key' => self::APIKEY_SPEECH,
+			'request_timeout' => self::REQUEST_TIMEOUT_SPEECH,
+			'tts_models' => [self::SPEECH_MODEL],
+			'extra_headers' => [
+				['name' => 'X-Tenant', 'value' => 'acme'],
+				['name' => 'X-Session', 'value' => '{$conversation_id}'],
+			],
+		]);
+
+		$ttsProvider = new TextToSpeechProvider(
+			$this->openAiApiService,
+			$this->createMock(\OCP\IL10N::class),
+			$this->createMock(\Psr\Log\LoggerInterface::class),
+			\OCP\Server::get(WatermarkingService::class),
+			$service,
+			self::SPEECH_MODEL,
+		);
+
+		$inputText = 'This is a test prompt';
+
+		$response = file_get_contents(__DIR__ . '/../../res/speech.mp3');
+
+		if (!$response) {
+			throw new \RuntimeException('Could not read test resourcce `speech.mp3`');
+		}
+
+		// speech is not a chat, so the header referencing the conversation is
+		// not sent, while the static one is
+		$url = self::SPEECH_BASE . '/audio/speech';
+		$options = ['timeout' => self::REQUEST_TIMEOUT_SPEECH, 'headers' => ['User-Agent' => Application::USER_AGENT, 'X-Tenant' => 'acme', 'Authorization' => 'Bearer ' . self::APIKEY_SPEECH, 'Content-Type' => 'application/json'], 'nextcloud' => ['allow_local_address' => true]];
+		$options['body'] = json_encode([
+			'input' => $inputText,
+			'voice' => Application::DEFAULT_SPEECH_VOICE,
+			'model' => self::SPEECH_MODEL,
+			'response_format' => 'mp3',
+			'speed' => 1,
+		]);
+
+		$iResponse = $this->createMock(\OCP\Http\Client\IResponse::class);
+		$iResponse->method('getBody')->willReturn($response);
+		$iResponse->method('getStatusCode')->willReturn(200);
+
+		$this->iClient->expects($this->once())->method('post')->with($url, $options)->willReturn($iResponse);
+
+		$ttsProvider->process(self::TEST_USER1, ['input' => $inputText], fn () => null, includeWatermark: false);
+	}
+
+	/**
+	 * Non-chat providers that go through the chat completion endpoint must
+	 * expand the conversation ID too, otherwise services requiring the header
+	 * reject the request.
+	 */
+	public function testConversationIdHeaderIsExpandedOnFreePromptRequests(): void {
+		$service = $this->addService([
+			'url' => self::TEXT_BASE,
+			'api_key' => self::APIKEY_TEXT,
+			'text_models' => [self::TEXT_MODEL],
+			'extra_headers' => [
+				['name' => 'X-Tenant', 'value' => 'acme'],
+				['name' => 'X-Session', 'value' => '{$conversation_id}'],
+			],
+		]);
+
+		$freePromptProvider = new TextToTextProvider(
+			$this->openAiApiService,
+			$this->createMock(\OCP\IL10N::class),
+			$service,
+			self::TEXT_MODEL,
+		);
+
+		$userPrompt = 'Hello';
+
+		$response = json_encode([
+			'choices' => [
+				['message' => ['role' => 'assistant', 'content' => 'Free prompt answer']],
+			],
+		]);
+
+		$url = self::TEXT_BASE . '/chat/completions';
+		$options = ['timeout' => Application::OPENAI_DEFAULT_REQUEST_TIMEOUT, 'headers' => ['User-Agent' => Application::USER_AGENT, 'X-Tenant' => 'acme', 'X-Session' => '4242', 'Authorization' => 'Bearer ' . self::APIKEY_TEXT, 'Content-Type' => 'application/json'], 'nextcloud' => ['allow_local_address' => true]];
+		$options['body'] = json_encode([
+			'model' => self::TEXT_MODEL,
+			'messages' => [
+				['role' => 'user', 'content' => $userPrompt],
+			],
+			'n' => 1,
+			'stream' => false,
+			'max_tokens' => Application::DEFAULT_MAX_NUM_OF_TOKENS,
+		]);
+
+		$iResponse = $this->createMock(\OCP\Http\Client\IResponse::class);
+		$iResponse->method('getHeader')->with('Content-Type')->willReturn('application/json');
+		$iResponse->method('getBody')->willReturn($response);
+		$iResponse->method('getStatusCode')->willReturn(200);
+
+		$this->iClient->expects($this->once())->method('post')->with($url, $options)->willReturn($iResponse);
+
+		$result = $freePromptProvider->process(self::TEST_USER1, [
+			'input' => $userPrompt,
+			'conversation_id' => '4242',
+		], fn () => null);
+
+		$this->assertSame('Free prompt answer', $result['output']);
+	}
+
+	public function testConversationIdHeaderIsExpandedOnTranslationRequests(): void {
+		$service = $this->addService([
+			'url' => self::TEXT_BASE,
+			'api_key' => self::APIKEY_TEXT,
+			'text_models' => [self::TEXT_MODEL],
+			'extra_headers' => [
+				['name' => 'X-Tenant', 'value' => 'acme'],
+				['name' => 'X-Session', 'value' => '{$conversation_id}'],
+			],
+		]);
+
+		$translateProvider = new TranslateProvider(
+			$this->openAiApiService,
+			$this->createMock(\OCP\IL10N::class),
+			new TranslateService(
+				\OCP\Server::get(\Psr\Log\LoggerInterface::class),
+				$this->openAiApiService,
+				new ChunkService(),
+				\OCP\Server::get(ICacheFactory::class),
+			),
+			$service,
+			self::TEXT_MODEL,
+		);
+
+		$inputText = 'Hello world';
+		$coreLanguages = TranslateService::getCoreLanguagesByCode();
+		$toLanguage = $coreLanguages['fr'] ?? 'fr';
+		$prompt = 'Translate the following text to ' . $toLanguage . ': ' . PHP_EOL . PHP_EOL . $inputText;
+
+		$response = json_encode([
+			'choices' => [
+				['message' => ['role' => 'assistant', 'content' => json_encode(['translation' => 'Bonjour le monde'])]],
+			],
+		]);
+
+		$url = self::TEXT_BASE . '/chat/completions';
+		$options = ['timeout' => Application::OPENAI_DEFAULT_REQUEST_TIMEOUT, 'headers' => ['User-Agent' => Application::USER_AGENT, 'X-Tenant' => 'acme', 'X-Session' => '4242', 'Authorization' => 'Bearer ' . self::APIKEY_TEXT, 'Content-Type' => 'application/json'], 'nextcloud' => ['allow_local_address' => true]];
+		$options['body'] = json_encode([
+			'response_format' => TranslateService::JSON_RESPONSE_FORMAT['response_format'],
+			'model' => self::TEXT_MODEL,
+			'messages' => [
+				['role' => 'system', 'content' => TranslateService::SYSTEM_PROMPT],
+				['role' => 'user', 'content' => $prompt],
+			],
+			'n' => 1,
+			'stream' => false,
+			'max_tokens' => Application::DEFAULT_MAX_NUM_OF_TOKENS,
+		]);
+
+		$iResponse = $this->createMock(\OCP\Http\Client\IResponse::class);
+		$iResponse->method('getHeader')->with('Content-Type')->willReturn('application/json');
+		$iResponse->method('getBody')->willReturn($response);
+		$iResponse->method('getStatusCode')->willReturn(200);
+
+		$this->iClient->expects($this->once())->method('post')->with($url, $options)->willReturn($iResponse);
+
+		$result = $translateProvider->process(self::TEST_USER1, [
+			'input' => $inputText,
+			'origin_language' => 'detect_language',
+			'target_language' => 'fr',
+			'conversation_id' => '4242',
+		], fn () => null);
+
+		$this->assertSame('Bonjour le monde', $result['output']);
+	}
+
+	public function testInvalidHeaderFromTheHttpClientBecomesAConfigError(): void {
+		$service = $this->addService([
+			'url' => self::TEXT_BASE,
+			'api_key' => self::APIKEY_TEXT,
+			'text_models' => [self::TEXT_MODEL],
+		]);
+
+		// the HTTP client validates the headers when building the request and
+		// throws a bare InvalidArgumentException quoting the rejected value: the
+		// error must be reported without leaking the credentials it mentions
+		$this->iClient->expects($this->once())->method('post')->willThrowException(
+			new \InvalidArgumentException('"Bearer ' . self::APIKEY_TEXT . '" is not valid header value.'),
+		);
+
+		$thrown = null;
+		try {
+			$this->openAiApiService->createChatCompletion(
+				self::TEST_USER1, $service, self::TEXT_MODEL, 'Hello', 'You are a helpful assistant',
+			);
+		} catch (\Exception $e) {
+			$thrown = $e;
+		}
+
+		$this->assertInstanceOf(\Exception::class, $thrown);
+		$this->assertSame(\OCP\AppFramework\Http::STATUS_BAD_REQUEST, $thrown->getCode());
+		$this->assertStringNotContainsString(self::APIKEY_TEXT, $thrown->getMessage());
+	}
+
 	public function testProvidersOfDifferentServicesHaveDifferentIds(): void {
 		$first = $this->addService(['url' => self::IMAGE_BASE, 'image_models' => [self::IMAGE_MODEL]]);
 		$second = $this->addService(['url' => self::SPEECH_BASE, 'image_models' => [self::IMAGE_MODEL]]);
diff --git a/tests/unit/Service/ServiceConfigTest.php b/tests/unit/Service/ServiceConfigTest.php
new file mode 100644
index 00000000..ac974c7d
--- /dev/null
+++ b/tests/unit/Service/ServiceConfigTest.php
@@ -0,0 +1,62 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * SPDX-FileCopyrightText: 2026 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+namespace OCA\OpenAi\Tests\Unit\Service;
+
+use OCA\OpenAi\Service\ServiceConfig;
+use Test\TestCase;
+
+class ServiceConfigTest extends TestCase {
+	public function expandHeaderValueProvider(): array {
+		return [
+			'a value without the variable' => ['acme', '42', 'acme'],
+			'the variable alone' => ['{$conversation_id}', '42', '42'],
+			'the variable in a sentence' => ['conv-{$conversation_id}-v2', '42', 'conv-42-v2'],
+			'the variable twice' => ['{$conversation_id}/{$conversation_id}', '42', '42/42'],
+			'a request without a conversation' => ['{$conversation_id}', null, null],
+			'an empty conversation ID' => ['{$conversation_id}', '', null],
+			'a mistyped variable travels literally' => ['{$Conversation_ID}', '42', '{$Conversation_ID}'],
+			'a conversation ID smuggling line breaks' => ['{$conversation_id}', "42\r\nX-Evil: yes", null],
+			'a conversation ID smuggling control characters' => ['{$conversation_id}', "42\x01", null],
+			'a conversation ID with a tab' => ['{$conversation_id}', "42\x09id", "42\x09id"],
+		];
+	}
+
+	/**
+	 * @dataProvider expandHeaderValueProvider
+	 */
+	public function testExpandHeaderValue(string $value, ?string $conversationId, ?string $expected): void {
+		$this->assertSame($expected, ServiceConfig::expandHeaderValue($value, $conversationId));
+	}
+
+	public function testStoredServiceWithoutExtraHeadersDefaultsToNone(): void {
+		// a service stored before extra headers existed
+		$service = ServiceConfig::fromArray('s1', ['url' => 'https://example.com/v1']);
+		$this->assertSame([], $service->getExtraHeaders());
+	}
+
+	public function testExtraHeadersAreNormalizedOnStorage(): void {
+		$service = ServiceConfig::fromArray('s1', [
+			'extra_headers' => [
+				['name' => '  X-Tenant  ', 'value' => ' acme '],
+				['name' => '', 'value' => 'dropped with its name'],
+				['name' => 'X-Empty-Value', 'value' => ''],
+			],
+		]);
+
+		$this->assertSame([
+			['name' => 'X-Tenant', 'value' => 'acme'],
+			['name' => 'X-Empty-Value', 'value' => ''],
+		], $service->getExtraHeaders());
+
+		// what is normalized is also what the next read from storage gets back
+		$reread = ServiceConfig::fromArray('s1', $service->jsonSerialize());
+		$this->assertSame($service->getExtraHeaders(), $reread->getExtraHeaders());
+	}
+}