diff --git a/application/api/answer/services/stream_processor.py b/application/api/answer/services/stream_processor.py
index fe2d7d8c..79b6cc7b 100644
--- a/application/api/answer/services/stream_processor.py
+++ b/application/api/answer/services/stream_processor.py
@@ -112,6 +112,7 @@ class StreamProcessor:
         self._required_tool_actions: Optional[Dict[str, Set[Optional[str]]]] = None
         self.compressed_summary: Optional[str] = None
         self.compressed_summary_tokens: int = 0
+        self._agent_data: Optional[Dict[str, Any]] = None
 
     def initialize(self):
         """Initialize all required components for processing"""
@@ -359,22 +360,29 @@ class StreamProcessor:
         return data
 
     def _configure_source(self):
-        """Configure the source based on agent data"""
-        api_key = self.data.get("api_key") or self.agent_key
+        """Configure the source based on agent data.
 
-        if api_key:
-            agent_data = self._get_data_from_api_key(api_key)
+        The literal string ``"default"`` is a placeholder meaning "no
+        ingested source" and is normalized to an empty source so that no
+        retrieval is attempted.
+        """
+        if self._agent_data:
+            agent_data = self._agent_data
 
             if agent_data.get("sources") and len(agent_data["sources"]) > 0:
                 source_ids = [
-                    source["id"] for source in agent_data["sources"] if source.get("id")
+                    source["id"]
+                    for source in agent_data["sources"]
+                    if source.get("id") and source["id"] != "default"
                 ]
                 if source_ids:
                     self.source = {"active_docs": source_ids}
                 else:
                     self.source = {}
-                self.all_sources = agent_data["sources"]
-            elif agent_data.get("source"):
+                self.all_sources = [
+                    s for s in agent_data["sources"] if s.get("id") != "default"
+                ]
+            elif agent_data.get("source") and agent_data["source"] != "default":
                 self.source = {"active_docs": agent_data["source"]}
                 self.all_sources = [
                     {
@@ -387,11 +395,24 @@ class StreamProcessor:
                 self.all_sources = []
             return
         if "active_docs" in self.data:
-            self.source = {"active_docs": self.data["active_docs"]}
+            active_docs = self.data["active_docs"]
+            if active_docs and active_docs != "default":
+                self.source = {"active_docs": active_docs}
+            else:
+                self.source = {}
             return
         self.source = {}
         self.all_sources = []
 
+    def _has_active_docs(self) -> bool:
+        """Return True if a real document source is configured for retrieval."""
+        active_docs = self.source.get("active_docs") if self.source else None
+        if not active_docs:
+            return False
+        if active_docs == "default":
+            return False
+        return True
+
     def _resolve_agent_id(self) -> Optional[str]:
         """Resolve agent_id from request, then fall back to conversation context."""
         request_agent_id = self.data.get("agent_id")
@@ -433,48 +454,39 @@ class StreamProcessor:
         effective_key = self.data.get("api_key") or self.agent_key
 
         if effective_key:
-            data_key = self._get_data_from_api_key(effective_key)
-            if data_key.get("_id"):
-                self.agent_id = str(data_key.get("_id"))
+            self._agent_data = self._get_data_from_api_key(effective_key)
+            if self._agent_data.get("_id"):
+                self.agent_id = str(self._agent_data.get("_id"))
 
             self.agent_config.update(
                 {
-                    "prompt_id": data_key.get("prompt_id", "default"),
-                    "agent_type": data_key.get("agent_type", settings.AGENT_NAME),
+                    "prompt_id": self._agent_data.get("prompt_id", "default"),
+                    "agent_type": self._agent_data.get("agent_type", settings.AGENT_NAME),
                     "user_api_key": effective_key,
-                    "json_schema": data_key.get("json_schema"),
-                    "default_model_id": data_key.get("default_model_id", ""),
-                    "models": data_key.get("models", []),
+                    "json_schema": self._agent_data.get("json_schema"),
+                    "default_model_id": self._agent_data.get("default_model_id", ""),
+                    "models": self._agent_data.get("models", []),
+                    "allow_system_prompt_override": self._agent_data.get(
+                        "allow_system_prompt_override", False
+                    ),
                 }
             )
 
             # Set identity context
             if self.data.get("api_key"):
                 # External API key: use the key owner's identity
-                self.initial_user_id = data_key.get("user")
-                self.decoded_token = {"sub": data_key.get("user")}
+                self.initial_user_id = self._agent_data.get("user")
+                self.decoded_token = {"sub": self._agent_data.get("user")}
             elif self.is_shared_usage:
                 # Shared agent: keep the caller's identity
                 pass
             else:
                 # Owner using their own agent
-                self.decoded_token = {"sub": data_key.get("user")}
+                self.decoded_token = {"sub": self._agent_data.get("user")}
 
-            if data_key.get("source"):
-                self.source = {"active_docs": data_key["source"]}
-            if data_key.get("workflow"):
-                self.agent_config["workflow"] = data_key["workflow"]
-                self.agent_config["workflow_owner"] = data_key.get("user")
-            if data_key.get("retriever"):
-                self.retriever_config["retriever_name"] = data_key["retriever"]
-            if data_key.get("chunks") is not None:
-                try:
-                    self.retriever_config["chunks"] = int(data_key["chunks"])
-                except (ValueError, TypeError):
-                    logger.warning(
-                        f"Invalid chunks value: {data_key['chunks']}, using default value 2"
-                    )
-                    self.retriever_config["chunks"] = 2
+            if self._agent_data.get("workflow"):
+                self.agent_config["workflow"] = self._agent_data["workflow"]
+                self.agent_config["workflow_owner"] = self._agent_data.get("user")
         else:
             # No API key — default/workflow configuration
             agent_type = settings.AGENT_NAME
@@ -497,14 +509,45 @@ class StreamProcessor:
             )
 
     def _configure_retriever(self):
+        """Assemble retriever config with precedence: request > agent > default."""
         doc_token_limit = calculate_doc_token_budget(model_id=self.model_id)
 
+        # Start with defaults
+        retriever_name = "classic"
+        chunks = 2
+
+        # Layer agent-level config (if present)
+        if self._agent_data:
+            if self._agent_data.get("retriever"):
+                retriever_name = self._agent_data["retriever"]
+            if self._agent_data.get("chunks") is not None:
+                try:
+                    chunks = int(self._agent_data["chunks"])
+                except (ValueError, TypeError):
+                    logger.warning(
+                        f"Invalid agent chunks value: {self._agent_data['chunks']}, "
+                        "using default value 2"
+                    )
+
+        # Explicit request values win over agent config
+        if "retriever" in self.data:
+            retriever_name = self.data["retriever"]
+        if "chunks" in self.data:
+            try:
+                chunks = int(self.data["chunks"])
+            except (ValueError, TypeError):
+                logger.warning(
+                    f"Invalid request chunks value: {self.data['chunks']}, "
+                    "using default value 2"
+                )
+
         self.retriever_config = {
-            "retriever_name": self.data.get("retriever", "classic"),
-            "chunks": int(self.data.get("chunks", 2)),
+            "retriever_name": retriever_name,
+            "chunks": chunks,
             "doc_token_limit": doc_token_limit,
         }
 
+        # isNoneDoc without an API key forces no retrieval
         api_key = self.data.get("api_key") or self.agent_key
         if not api_key and "isNoneDoc" in self.data and self.data["isNoneDoc"]:
             self.retriever_config["chunks"] = 0
@@ -528,6 +571,9 @@ class StreamProcessor:
         if self.data.get("isNoneDoc", False) and not self.agent_id:
             logger.info("Pre-fetch skipped: isNoneDoc=True")
             return None, None
+        if not self._has_active_docs():
+            logger.info("Pre-fetch skipped: no active docs configured")
+            return None, None
         try:
             retriever = self.create_retriever()
             logger.info(
@@ -910,15 +956,23 @@ class StreamProcessor:
                 raw_prompt = get_prompt(prompt_id, self.prompts_collection)
             self._prompt_content = raw_prompt
 
-        rendered_prompt = self.prompt_renderer.render_prompt(
-            prompt_content=raw_prompt,
-            user_id=self.initial_user_id,
-            request_id=self.data.get("request_id"),
-            passthrough_data=self.data.get("passthrough"),
-            docs=docs,
-            docs_together=docs_together,
-            tools_data=tools_data,
-        )
+        # Allow API callers to override the system prompt when the agent
+        # has opted in via allow_system_prompt_override.
+        if (
+            self.agent_config.get("allow_system_prompt_override", False)
+            and self.data.get("system_prompt_override")
+        ):
+            rendered_prompt = self.data["system_prompt_override"]
+        else:
+            rendered_prompt = self.prompt_renderer.render_prompt(
+                prompt_content=raw_prompt,
+                user_id=self.initial_user_id,
+                request_id=self.data.get("request_id"),
+                passthrough_data=self.data.get("passthrough"),
+                docs=docs,
+                docs_together=docs_together,
+                tools_data=tools_data,
+            )
 
         provider = (
             get_provider_from_model_id(self.model_id)
diff --git a/application/api/user/agents/routes.py b/application/api/user/agents/routes.py
index 296b8ea0..7d3dc93a 100644
--- a/application/api/user/agents/routes.py
+++ b/application/api/user/agents/routes.py
@@ -73,6 +73,7 @@ AGENT_TYPE_SCHEMAS = {
             "token_limit",
             "limited_request_mode",
             "request_limit",
+            "allow_system_prompt_override",
             "createdAt",
             "updatedAt",
             "lastUsedAt",
@@ -96,6 +97,7 @@ AGENT_TYPE_SCHEMAS = {
             "token_limit",
             "limited_request_mode",
             "request_limit",
+            "allow_system_prompt_override",
             "createdAt",
             "updatedAt",
             "lastUsedAt",
@@ -220,6 +222,12 @@ def build_agent_document(
         base_doc["request_limit"] = int(
             data.get("request_limit", settings.DEFAULT_AGENT_LIMITS["request_limit"])
         )
+    if "allow_system_prompt_override" in allowed_fields:
+        base_doc["allow_system_prompt_override"] = (
+            data.get("allow_system_prompt_override") == "True"
+            if isinstance(data.get("allow_system_prompt_override"), str)
+            else bool(data.get("allow_system_prompt_override", False))
+        )
     return {k: v for k, v in base_doc.items() if k in allowed_fields}
 
 
@@ -292,6 +300,9 @@ class GetAgent(Resource):
                 "default_model_id": agent.get("default_model_id", ""),
                 "folder_id": agent.get("folder_id"),
                 "workflow": agent.get("workflow"),
+                "allow_system_prompt_override": agent.get(
+                    "allow_system_prompt_override", False
+                ),
             }
             return make_response(jsonify(data), 200)
         except Exception as e:
@@ -373,6 +384,9 @@ class GetAgents(Resource):
                     "default_model_id": agent.get("default_model_id", ""),
                     "folder_id": agent.get("folder_id"),
                     "workflow": agent.get("workflow"),
+                    "allow_system_prompt_override": agent.get(
+                        "allow_system_prompt_override", False
+                    ),
                 }
                 for agent in agents
                 if "source" in agent
@@ -450,6 +464,10 @@ class CreateAgent(Resource):
             "folder_id": fields.String(
                 required=False, description="Folder ID to organize the agent"
             ),
+            "allow_system_prompt_override": fields.Boolean(
+                required=False,
+                description="Allow API callers to override the system prompt via the v1 endpoint",
+            ),
         },
     )
 
@@ -674,6 +692,10 @@ class UpdateAgent(Resource):
             "folder_id": fields.String(
                 required=False, description="Folder ID to organize the agent"
             ),
+            "allow_system_prompt_override": fields.Boolean(
+                required=False,
+                description="Allow API callers to override the system prompt via the v1 endpoint",
+            ),
         },
     )
 
@@ -765,6 +787,7 @@ class UpdateAgent(Resource):
             "default_model_id",
             "folder_id",
             "workflow",
+            "allow_system_prompt_override",
         ]
 
         for field in allowed_fields:
@@ -983,6 +1006,13 @@ class UpdateAgent(Resource):
                 if workflow_error:
                     return workflow_error
                 update_fields[field] = workflow_id
+            elif field == "allow_system_prompt_override":
+                raw_value = data.get("allow_system_prompt_override", False)
+                update_fields[field] = (
+                    raw_value == "True"
+                    if isinstance(raw_value, str)
+                    else bool(raw_value)
+                )
             else:
                 value = data[field]
                 if field in ["name", "description", "prompt_id", "agent_type"]:
diff --git a/application/api/v1/routes.py b/application/api/v1/routes.py
index 4d5a513b..8b1be646 100644
--- a/application/api/v1/routes.py
+++ b/application/api/v1/routes.py
@@ -138,10 +138,18 @@ def chat_completions():
         if usage_error:
             return usage_error
 
+        should_save_conversation = bool(internal_data.get("save_conversation", False))
+
         if is_stream:
             return Response(
                 _stream_response(
-                    helper, question, agent, processor, model_name, continuation
+                    helper,
+                    question,
+                    agent,
+                    processor,
+                    model_name,
+                    continuation,
+                    should_save_conversation,
                 ),
                 mimetype="text/event-stream",
                 headers={
@@ -151,7 +159,13 @@ def chat_completions():
             )
         else:
             return _non_stream_response(
-                helper, question, agent, processor, model_name, continuation
+                helper,
+                question,
+                agent,
+                processor,
+                model_name,
+                continuation,
+                should_save_conversation,
             )
 
     except ValueError as e:
@@ -181,6 +195,7 @@ def _stream_response(
     processor: StreamProcessor,
     model_name: str,
     continuation: Optional[Dict],
+    should_save_conversation: bool,
 ) -> Generator[str, None, None]:
     """Generate translated SSE chunks for streaming response."""
     completion_id = f"chatcmpl-{int(time.time())}"
@@ -193,6 +208,7 @@ def _stream_response(
         decoded_token=processor.decoded_token,
         agent_id=processor.agent_id,
         model_id=processor.model_id,
+        should_save_conversation=should_save_conversation,
         _continuation=continuation,
     )
 
@@ -225,6 +241,7 @@ def _non_stream_response(
     processor: StreamProcessor,
     model_name: str,
     continuation: Optional[Dict],
+    should_save_conversation: bool,
 ) -> Response:
     """Collect full response and return as single JSON."""
     stream = helper.complete_stream(
@@ -235,6 +252,7 @@ def _non_stream_response(
         decoded_token=processor.decoded_token,
         agent_id=processor.agent_id,
         model_id=processor.model_id,
+        should_save_conversation=should_save_conversation,
         _continuation=continuation,
     )
 
diff --git a/application/api/v1/translator.py b/application/api/v1/translator.py
index 3d3c64fe..5330a029 100644
--- a/application/api/v1/translator.py
+++ b/application/api/v1/translator.py
@@ -80,6 +80,17 @@ def extract_conversation_id(messages: List[Dict]) -> Optional[str]:
     return None
 
 
+def extract_system_prompt(messages: List[Dict]) -> Optional[str]:
+    """Extract the first system message content from the messages array.
+
+    Returns None if no system message is present.
+    """
+    for msg in messages:
+        if msg.get("role") == "system":
+            return msg.get("content", "")
+    return None
+
+
 def convert_history(messages: List[Dict]) -> List[Dict]:
     """Convert chat completions messages array to DocsGPT history format.
 
@@ -148,20 +159,27 @@ def translate_request(
             break
 
     history = convert_history(messages)
+    system_prompt_override = extract_system_prompt(messages)
+
+    docsgpt = data.get("docsgpt", {})
 
     result = {
         "question": question,
         "api_key": api_key,
         "history": json.dumps(history),
-        "save_conversation": True,
+        # Conversations are NOT persisted by default on the v1 endpoint.
+        # Callers opt in via ``docsgpt.save_conversation: true``.
+        "save_conversation": bool(docsgpt.get("save_conversation", False)),
     }
 
+    if system_prompt_override is not None:
+        result["system_prompt_override"] = system_prompt_override
+
     # Client tools
     if data.get("tools"):
         result["client_tools"] = data["tools"]
 
     # DocsGPT extensions
-    docsgpt = data.get("docsgpt", {})
     if docsgpt.get("attachments"):
         result["attachments"] = docsgpt["attachments"]
 
diff --git a/docs/content/Agents/_meta.js b/docs/content/Agents/_meta.js
index c38c6e36..61900068 100644
--- a/docs/content/Agents/_meta.js
+++ b/docs/content/Agents/_meta.js
@@ -7,6 +7,10 @@ export default {
     "title": "🔌 Agent API",
     "href": "/Agents/api"
   },
+  "openai-compatible": {
+    "title": "🔄 OpenAI-Compatible API",
+    "href": "/Agents/openai-compatible"
+  },
   "webhooks": {
     "title": "🪝 Agent Webhooks",
     "href": "/Agents/webhooks"
diff --git a/docs/content/Agents/api.mdx b/docs/content/Agents/api.mdx
index 5b1313dd..ad77a69a 100644
--- a/docs/content/Agents/api.mdx
+++ b/docs/content/Agents/api.mdx
@@ -15,6 +15,10 @@ DocsGPT Agents can be accessed programmatically through API endpoints. This page
 
 When you use an agent `api_key`, DocsGPT loads that agent's configuration automatically (prompt, tools, sources, default model). You usually only need to send `question` and `api_key`.
 
+<Callout type="info">
+Looking to connect an existing OpenAI-compatible client (opencode, aider, the OpenAI SDKs, etc.) to a DocsGPT Agent? Use the [OpenAI-Compatible Chat Completions API](/Agents/openai-compatible) — it speaks the standard chat completions protocol so no adapter code is required.
+</Callout>
+
 ## Base URL
 
 <Callout type="info">
diff --git a/docs/content/Agents/basics.mdx b/docs/content/Agents/basics.mdx
index 3ad407df..741df77b 100644
--- a/docs/content/Agents/basics.mdx
+++ b/docs/content/Agents/basics.mdx
@@ -111,6 +111,7 @@ Once an agent is created, you can:
     * Modify any of its configuration settings (name, description, source, prompt, tools, type).
     * **Generate a Public Link:** From the edit screen, you can create a shareable public link that allows others to import and use your agent.
     * **Get a Webhook URL:** You can also obtain a Webhook URL for the agent. This allows external applications or services to trigger the agent and receive responses programmatically, enabling powerful integrations and automations.
+* **Use it via API:** Every agent exposes an API key that can be used with the native [Agent API](/Agents/api) or the [OpenAI-Compatible API](/Agents/openai-compatible) so you can drop DocsGPT Agents into any tool that already speaks the chat completions protocol.
 
 ## Seeding Premade Agents from YAML
 
diff --git a/docs/content/Agents/openai-compatible.mdx b/docs/content/Agents/openai-compatible.mdx
new file mode 100644
index 00000000..0994ec59
--- /dev/null
+++ b/docs/content/Agents/openai-compatible.mdx
@@ -0,0 +1,93 @@
+---
+title: OpenAI-Compatible API
+description: Connect any OpenAI-compatible client to DocsGPT Agents via /v1/chat/completions.
+---
+
+import { Callout, Tabs } from 'nextra/components';
+
+# OpenAI-Compatible API
+
+DocsGPT exposes `/v1/chat/completions` following the standard chat completions protocol. Point any compatible client — **opencode**, **Aider**, **LibreChat** or the OpenAI SDKs — at your DocsGPT Agent by changing only the base URL and API key.
+
+## Quick Start
+
+<Tabs items={['Python', 'cURL']}>
+  <Tabs.Tab>
+    ```python
+    from openai import OpenAI
+
+    client = OpenAI(
+        base_url="http://localhost:7091/v1",   # or https://gptcloud.arc53.com/v1
+        api_key="your_agent_api_key",
+    )
+
+    response = client.chat.completions.create(
+        model="docsgpt-agent",
+        messages=[{"role": "user", "content": "Summarize our refund policy"}],
+    )
+    print(response.choices[0].message.content)
+    ```
+  </Tabs.Tab>
+  <Tabs.Tab>
+    ```bash
+    curl -X POST http://localhost:7091/v1/chat/completions \
+      -H "Authorization: Bearer your_agent_api_key" \
+      -H "Content-Type: application/json" \
+      -d '{"model":"docsgpt-agent","messages":[{"role":"user","content":"Summarize our refund policy"}]}'
+    ```
+  </Tabs.Tab>
+</Tabs>
+
+The `model` field is accepted but ignored — the agent bound to your API key determines the model. The agent's prompt, sources, tools, and default model are loaded automatically.
+
+## Base URL & Auth
+
+| Environment | Base URL |
+| --- | --- |
+| Local | `http://localhost:7091/v1` |
+| Cloud | `https://gptcloud.arc53.com/v1` |
+
+Authenticate with `Authorization: Bearer <agent_api_key>`.
+
+## Endpoints
+
+| Method | Path | Description |
+| --- | --- | --- |
+| `POST` | `/v1/chat/completions` | Chat request (streaming or non-streaming) |
+| `GET` | `/v1/models` | List agents available to your key |
+
+## Streaming
+
+Set `"stream": true`. You'll receive SSE chunks with `choices[0].delta.content`. DocsGPT-specific events (sources, tool calls) arrive as extra frames with a `docsgpt` key — standard clients ignore them.
+
+```python
+stream = client.chat.completions.create(
+    model="docsgpt-agent",
+    stream=True,
+    messages=[{"role": "user", "content": "Explain vector search"}],
+)
+for chunk in stream:
+    print(chunk.choices[0].delta.content or "", end="", flush=True)
+```
+
+## System Prompt Override
+
+System messages are **dropped by default** — the agent's configured prompt is used. To allow callers to override it, enable **Allow prompt override** in the agent's Advanced settings.
+
+<Callout type="warning">
+When an override is active, the agent's prompt template is replaced wholesale — template variables like `{summaries}` are not substituted.
+</Callout>
+
+## Conversation Persistence
+
+Conversations are **not persisted by default** (stateless, like most OpenAI clients expect). Opt in per request:
+
+```json
+{ "docsgpt": { "save_conversation": true } }
+```
+
+The response will include `docsgpt.conversation_id`.
+
+## When to Use Native Endpoints Instead
+
+Use [`/api/answer` or `/stream`](/Agents/api) if you need server-side attachments, `passthrough` template variables, explicit `conversation_id` reuse, or persistence by default.
diff --git a/frontend/src/agents/NewAgent.tsx b/frontend/src/agents/NewAgent.tsx
index 133ffc7c..938b2e4f 100644
--- a/frontend/src/agents/NewAgent.tsx
+++ b/frontend/src/agents/NewAgent.tsx
@@ -73,6 +73,7 @@ export default function NewAgent({ mode }: { mode: 'new' | 'edit' | 'draft' }) {
     token_limit: undefined,
     limited_request_mode: false,
     request_limit: undefined,
+    allow_system_prompt_override: false,
     models: [],
     default_model_id: '',
   });
@@ -241,6 +242,11 @@ export default function NewAgent({ mode }: { mode: 'new' | 'edit' | 'draft' }) {
       formData.append('request_limit', '0');
     }
 
+    formData.append(
+      'allow_system_prompt_override',
+      agent.allow_system_prompt_override ? 'True' : 'False',
+    );
+
     if (imageFile) formData.append('image', imageFile);
 
     if (agent.tools && agent.tools.length > 0)
@@ -361,6 +367,11 @@ export default function NewAgent({ mode }: { mode: 'new' | 'edit' | 'draft' }) {
       formData.append('request_limit', '0');
     }
 
+    formData.append(
+      'allow_system_prompt_override',
+      agent.allow_system_prompt_override ? 'True' : 'False',
+    );
+
     if (agent.models && agent.models.length > 0) {
       formData.append('models', JSON.stringify(agent.models));
     }
@@ -1266,6 +1277,43 @@ export default function NewAgent({ mode }: { mode: 'new' | 'edit' | 'draft' }) {
                     }`}
                   />
                 </div>
+
+                <div className="mt-6">
+                  <div className="flex items-center justify-between gap-4">
+                    <div className="min-w-0 flex-1">
+                      <h2 className="text-sm font-medium">
+                        {t('agents.form.advanced.systemPromptOverride')}
+                      </h2>
+                      <p className="mt-1 text-xs text-gray-600 dark:text-gray-400">
+                        {t(
+                          'agents.form.advanced.systemPromptOverrideDescription',
+                        )}
+                      </p>
+                    </div>
+                    <button
+                      onClick={() =>
+                        setAgent({
+                          ...agent,
+                          allow_system_prompt_override:
+                            !agent.allow_system_prompt_override,
+                        })
+                      }
+                      className={`relative h-6 w-11 shrink-0 rounded-full transition-colors ${
+                        agent.allow_system_prompt_override
+                          ? 'bg-primary'
+                          : 'bg-gray-300 dark:bg-gray-600'
+                      }`}
+                    >
+                      <span
+                        className={`absolute top-0.5 h-5 w-5 transform rounded-full bg-white transition-transform ${
+                          agent.allow_system_prompt_override
+                            ? ''
+                            : '-translate-x-5'
+                        }`}
+                      />
+                    </button>
+                  </div>
+                </div>
               </div>
             )}
           </div>
diff --git a/frontend/src/agents/types/index.ts b/frontend/src/agents/types/index.ts
index 6e732401..12e27c8a 100644
--- a/frontend/src/agents/types/index.ts
+++ b/frontend/src/agents/types/index.ts
@@ -36,6 +36,7 @@ export type Agent = {
   default_model_id?: string;
   folder_id?: string;
   workflow?: string;
+  allow_system_prompt_override?: boolean;
 };
 
 export type AgentFolder = {
diff --git a/frontend/src/agents/workflow/WorkflowBuilder.tsx b/frontend/src/agents/workflow/WorkflowBuilder.tsx
index 2024ee7c..a817b048 100644
--- a/frontend/src/agents/workflow/WorkflowBuilder.tsx
+++ b/frontend/src/agents/workflow/WorkflowBuilder.tsx
@@ -18,6 +18,7 @@ import {
   X,
 } from 'lucide-react';
 import { useCallback, useEffect, useMemo, useRef, useState } from 'react';
+import { useTranslation } from 'react-i18next';
 import { useSelector } from 'react-redux';
 import { useNavigate, useParams, useSearchParams } from 'react-router-dom';
 import ReactFlow, {
@@ -301,6 +302,7 @@ function createWorkflowPayload(
 }
 
 function WorkflowBuilderInner() {
+  const { t } = useTranslation();
   const navigate = useNavigate();
   const token = useSelector(selectToken);
   const sourceDocs = useSelector(selectSourceDocs);
@@ -1142,6 +1144,10 @@ function WorkflowBuilderInner() {
               workflowDescription || `Workflow agent: ${workflowName}`,
             );
             agentFormData.append('status', 'published');
+            agentFormData.append(
+              'allow_system_prompt_override',
+              currentAgent.allow_system_prompt_override ? 'True' : 'False',
+            );
             if (imageFile) {
               agentFormData.append('image', imageFile);
             }
@@ -1203,6 +1209,10 @@ function WorkflowBuilderInner() {
         agentFormData.append('agent_type', 'workflow');
         agentFormData.append('status', 'published');
         agentFormData.append('workflow', savedWorkflowId || '');
+        agentFormData.append(
+          'allow_system_prompt_override',
+          currentAgent.allow_system_prompt_override ? 'True' : 'False',
+        );
         if (imageFile) {
           agentFormData.append('image', imageFile);
         }
@@ -1454,6 +1464,40 @@ function WorkflowBuilderInner() {
                       Image updates are included the next time you save.
                     </p>
                   </div>
+                  <div className="mb-3">
+                    <div className="flex items-center justify-between">
+                      <div>
+                        <label className="block text-sm font-medium text-gray-700 dark:text-gray-300">
+                          {t('agents.form.advanced.systemPromptOverride')}
+                        </label>
+                        <p className="mt-0.5 text-[11px] text-gray-500 dark:text-gray-400">
+                          {t('agents.form.advanced.systemPromptOverrideDescription')}
+                        </p>
+                      </div>
+                      <button
+                        onClick={() =>
+                          setCurrentAgent((prev) => ({
+                            ...prev,
+                            allow_system_prompt_override:
+                              !prev.allow_system_prompt_override,
+                          }))
+                        }
+                        className={`relative h-6 w-11 shrink-0 rounded-full transition-colors ${
+                          currentAgent.allow_system_prompt_override
+                            ? 'bg-primary'
+                            : 'bg-gray-300 dark:bg-gray-600'
+                        }`}
+                      >
+                        <span
+                          className={`absolute top-0.5 h-5 w-5 transform rounded-full bg-white transition-transform ${
+                            currentAgent.allow_system_prompt_override
+                              ? ''
+                              : '-translate-x-5'
+                          }`}
+                        />
+                      </button>
+                    </div>
+                  </div>
                   <button
                     onClick={handleWorkflowSettingsDone}
                     disabled={isPublishing}
diff --git a/frontend/src/locale/de.json b/frontend/src/locale/de.json
index eba0006b..97b098a4 100644
--- a/frontend/src/locale/de.json
+++ b/frontend/src/locale/de.json
@@ -619,7 +619,9 @@
         "tokenLimiting": "Token-Limitierung",
         "tokenLimitingDescription": "Begrenze die täglich von diesem Agenten verwendbaren Tokens",
         "requestLimiting": "Anfrage-Limitierung",
-        "requestLimitingDescription": "Begrenze die täglich an diesen Agenten gestellten Anfragen"
+        "requestLimitingDescription": "Begrenze die täglich an diesen Agenten gestellten Anfragen",
+        "systemPromptOverride": "Prompt-Überschreibung erlauben",
+        "systemPromptOverrideDescription": "Erlaubt v1-API-Aufrufern, den System-Prompt dieses Agenten zu ersetzen"
       },
       "preview": {
         "publishedPreview": "Veröffentlichte Agenten können hier in der Vorschau angezeigt werden"
diff --git a/frontend/src/locale/en.json b/frontend/src/locale/en.json
index 780eef13..1b7c347b 100644
--- a/frontend/src/locale/en.json
+++ b/frontend/src/locale/en.json
@@ -653,7 +653,9 @@
         "tokenLimiting": "Token limiting",
         "tokenLimitingDescription": "Limit daily total tokens that can be used by this agent",
         "requestLimiting": "Request limiting",
-        "requestLimitingDescription": "Limit daily total requests that can be made to this agent"
+        "requestLimitingDescription": "Limit daily total requests that can be made to this agent",
+        "systemPromptOverride": "Allow prompt override",
+        "systemPromptOverrideDescription": "Let v1 API callers replace this agent's system prompt"
       },
       "preview": {
         "publishedPreview": "Published agents can be previewed here"
diff --git a/frontend/src/locale/es.json b/frontend/src/locale/es.json
index adfb4cdf..5a0ed32c 100644
--- a/frontend/src/locale/es.json
+++ b/frontend/src/locale/es.json
@@ -641,7 +641,9 @@
         "tokenLimiting": "Límite de tokens",
         "tokenLimitingDescription": "Limita el total diario de tokens que puede usar este agente",
         "requestLimiting": "Límite de solicitudes",
-        "requestLimitingDescription": "Limita el total diario de solicitudes que se pueden hacer a este agente"
+        "requestLimitingDescription": "Limita el total diario de solicitudes que se pueden hacer a este agente",
+        "systemPromptOverride": "Permitir sobrescribir el prompt",
+        "systemPromptOverrideDescription": "Permitir que los llamadores de la API v1 reemplacen el prompt del sistema de este agente"
       },
       "preview": {
         "publishedPreview": "Los agentes publicados se pueden previsualizar aquí"
diff --git a/frontend/src/locale/jp.json b/frontend/src/locale/jp.json
index 88823ddd..c4fc8b53 100644
--- a/frontend/src/locale/jp.json
+++ b/frontend/src/locale/jp.json
@@ -641,7 +641,9 @@
         "tokenLimiting": "トークン制限",
         "tokenLimitingDescription": "このエージェントが使用できる1日の合計トークン数を制限します",
         "requestLimiting": "リクエスト制限",
-        "requestLimitingDescription": "このエージェントに対して行える1日の合計リクエスト数を制限します"
+        "requestLimitingDescription": "このエージェントに対して行える1日の合計リクエスト数を制限します",
+        "systemPromptOverride": "プロンプトの上書きを許可",
+        "systemPromptOverrideDescription": "v1 API呼び出し元がこのエージェントのシステムプロンプトを置き換えることを許可します"
       },
       "preview": {
         "publishedPreview": "公開されたエージェントはここでプレビューできます"
diff --git a/frontend/src/locale/ru.json b/frontend/src/locale/ru.json
index 367c1b9f..bec0a093 100644
--- a/frontend/src/locale/ru.json
+++ b/frontend/src/locale/ru.json
@@ -641,7 +641,9 @@
         "tokenLimiting": "Лимит токенов",
         "tokenLimitingDescription": "Ограничить ежедневное общее количество токенов, которые может использовать этот агент",
         "requestLimiting": "Лимит запросов",
-        "requestLimitingDescription": "Ограничить ежедневное общее количество запросов, которые можно сделать к этому агенту"
+        "requestLimitingDescription": "Ограничить ежедневное общее количество запросов, которые можно сделать к этому агенту",
+        "systemPromptOverride": "Разрешить замену промпта",
+        "systemPromptOverrideDescription": "Разрешить вызовам API v1 заменять системный промпт этого агента"
       },
       "preview": {
         "publishedPreview": "Опубликованные агенты можно просмотреть здесь"
diff --git a/frontend/src/locale/zh-TW.json b/frontend/src/locale/zh-TW.json
index 5eafcbaf..3f192a90 100644
--- a/frontend/src/locale/zh-TW.json
+++ b/frontend/src/locale/zh-TW.json
@@ -641,7 +641,9 @@
         "tokenLimiting": "權杖限制",
         "tokenLimitingDescription": "限制此代理每天可使用的總權杖數",
         "requestLimiting": "請求限制",
-        "requestLimitingDescription": "限制每天可向此代理發出的總請求數"
+        "requestLimitingDescription": "限制每天可向此代理發出的總請求數",
+        "systemPromptOverride": "允許覆蓋提示詞",
+        "systemPromptOverrideDescription": "允許 v1 API 呼叫者替換此代理的系統提示詞"
       },
       "preview": {
         "publishedPreview": "已發佈的代理可以在此處預覽"
diff --git a/frontend/src/locale/zh.json b/frontend/src/locale/zh.json
index b768fa99..77c4a874 100644
--- a/frontend/src/locale/zh.json
+++ b/frontend/src/locale/zh.json
@@ -641,7 +641,9 @@
         "tokenLimiting": "令牌限制",
         "tokenLimitingDescription": "限制此代理每天可使用的总令牌数",
         "requestLimiting": "请求限制",
-        "requestLimitingDescription": "限制每天可向此代理发出的总请求数"
+        "requestLimitingDescription": "限制每天可向此代理发出的总请求数",
+        "systemPromptOverride": "允许覆盖提示词",
+        "systemPromptOverrideDescription": "允许 v1 API 调用者替换此代理的系统提示词"
       },
       "preview": {
         "publishedPreview": "已发布的代理可以在此处预览"
diff --git a/tests/api/answer/services/test_stream_processor.py b/tests/api/answer/services/test_stream_processor.py
index 18f282b7..b0cc19ec 100644
--- a/tests/api/answer/services/test_stream_processor.py
+++ b/tests/api/answer/services/test_stream_processor.py
@@ -330,6 +330,170 @@ class TestStreamProcessorDocPrefetch:
         assert docs_together is not None
         assert "Agent doc content" in docs_together
 
+    def test_configure_source_treats_default_string_as_no_docs(self, mock_mongo_db):
+        from application.api.answer.services.stream_processor import StreamProcessor
+        from application.core.settings import settings
+
+        db = mock_mongo_db[settings.MONGO_DB_NAME]
+        agents_collection = db["agents"]
+
+        agent_id = ObjectId()
+        agents_collection.insert_one(
+            {
+                "_id": agent_id,
+                "key": "agent_default_source_key",
+                "user": "user_123",
+                "prompt_id": "default",
+                "agent_type": "classic",
+                "source": "default",
+            }
+        )
+
+        processor = StreamProcessor(
+            {"question": "Hi", "api_key": "agent_default_source_key"},
+            None,
+        )
+        processor._configure_agent()
+        processor._configure_source()
+
+        assert processor.source == {}
+        assert processor.all_sources == []
+
+    def test_prefetch_skipped_when_no_active_docs(self, mock_mongo_db):
+        from unittest.mock import MagicMock
+
+        from application.api.answer.services.stream_processor import StreamProcessor
+
+        processor = StreamProcessor(
+            {"question": "Hi there"},
+            {"sub": "user_123"},
+        )
+        processor.initialize()
+        processor.create_retriever = MagicMock()
+
+        docs_together, docs = processor.pre_fetch_docs("Hi there")
+
+        processor.create_retriever.assert_not_called()
+        assert docs_together is None
+        assert docs is None
+
+    def test_prefetch_skipped_when_active_docs_is_default(self, mock_mongo_db):
+        from unittest.mock import MagicMock
+
+        from application.api.answer.services.stream_processor import StreamProcessor
+
+        processor = StreamProcessor(
+            {"question": "Hi", "active_docs": "default"},
+            {"sub": "user_123"},
+        )
+        processor.initialize()
+        processor.create_retriever = MagicMock()
+
+        docs_together, docs = processor.pre_fetch_docs("Hi")
+
+        processor.create_retriever.assert_not_called()
+        assert docs_together is None
+        assert docs is None
+
+    def test_agent_retriever_and_chunks_propagate_to_retriever_config(self, mock_mongo_db):
+        from application.api.answer.services.stream_processor import StreamProcessor
+        from application.core.settings import settings
+
+        db = mock_mongo_db[settings.MONGO_DB_NAME]
+        agents_collection = db["agents"]
+        source_id = ObjectId()
+        db["sources"].insert_one(
+            {"_id": source_id, "name": "src", "retriever": "hybrid", "chunks": 5}
+        )
+
+        agent_id = ObjectId()
+        agents_collection.insert_one(
+            {
+                "_id": agent_id,
+                "key": "agent_ret_key",
+                "user": "user_123",
+                "prompt_id": "default",
+                "agent_type": "classic",
+                "retriever": "hybrid",
+                "chunks": 5,
+                "source": DBRef("sources", source_id),
+            }
+        )
+
+        processor = StreamProcessor(
+            {"question": "Test", "api_key": "agent_ret_key"},
+            None,
+        )
+        processor.initialize()
+
+        assert processor.retriever_config["retriever_name"] == "hybrid"
+        assert processor.retriever_config["chunks"] == 5
+
+    def test_request_retriever_and_chunks_override_agent_config(self, mock_mongo_db):
+        from application.api.answer.services.stream_processor import StreamProcessor
+        from application.core.settings import settings
+
+        db = mock_mongo_db[settings.MONGO_DB_NAME]
+        agents_collection = db["agents"]
+
+        agent_id = ObjectId()
+        agents_collection.insert_one(
+            {
+                "_id": agent_id,
+                "key": "agent_override_key",
+                "user": "user_123",
+                "prompt_id": "default",
+                "agent_type": "classic",
+                "retriever": "hybrid",
+                "chunks": 5,
+            }
+        )
+
+        processor = StreamProcessor(
+            {
+                "question": "Test",
+                "api_key": "agent_override_key",
+                "retriever": "classic",
+                "chunks": 7,
+            },
+            None,
+        )
+        processor.initialize()
+
+        assert processor.retriever_config["retriever_name"] == "classic"
+        assert processor.retriever_config["chunks"] == 7
+
+    def test_agent_data_fetched_once_per_request(self, mock_mongo_db):
+        from unittest.mock import patch
+
+        from application.api.answer.services.stream_processor import StreamProcessor
+        from application.core.settings import settings
+
+        db = mock_mongo_db[settings.MONGO_DB_NAME]
+        agents_collection = db["agents"]
+
+        agent_id = ObjectId()
+        agents_collection.insert_one(
+            {
+                "_id": agent_id,
+                "key": "agent_once_key",
+                "user": "user_123",
+                "prompt_id": "default",
+                "agent_type": "classic",
+            }
+        )
+
+        processor = StreamProcessor(
+            {"question": "Test", "api_key": "agent_once_key"},
+            None,
+        )
+
+        with patch.object(
+            processor, "_get_data_from_api_key", wraps=processor._get_data_from_api_key
+        ) as spy:
+            processor.initialize()
+            assert spy.call_count == 1
+
 
 @pytest.mark.unit
 class TestStreamProcessorAttachments:
diff --git a/tests/api/answer/test_stream_processor.py b/tests/api/answer/test_stream_processor.py
index d3f2d217..4435c78f 100644
--- a/tests/api/answer/test_stream_processor.py
+++ b/tests/api/answer/test_stream_processor.py
@@ -566,14 +566,13 @@ class TestConfigureSource:
                 decoded_token={"sub": "u"},
             )
         sp.agent_key = None
-        agent_data = {
+        sp._agent_data = {
             "sources": [
                 {"id": "src1", "retriever": "classic"},
                 {"id": "src2", "retriever": "hybrid"},
             ],
             "source": None,
         }
-        sp._get_data_from_api_key = MagicMock(return_value=agent_data)
         sp._configure_source()
         assert sp.source == {"active_docs": ["src1", "src2"]}
         assert len(sp.all_sources) == 2
@@ -593,12 +592,11 @@ class TestConfigureSource:
                 decoded_token={"sub": "u"},
             )
         sp.agent_key = None
-        agent_data = {
+        sp._agent_data = {
             "sources": [],
             "source": "single_src",
             "retriever": "classic",
         }
-        sp._get_data_from_api_key = MagicMock(return_value=agent_data)
         sp._configure_source()
         assert sp.source == {"active_docs": "single_src"}
         assert len(sp.all_sources) == 1
@@ -618,8 +616,7 @@ class TestConfigureSource:
                 decoded_token={"sub": "u"},
             )
         sp.agent_key = None
-        agent_data = {"sources": [], "source": None}
-        sp._get_data_from_api_key = MagicMock(return_value=agent_data)
+        sp._agent_data = {"sources": [], "source": None}
         sp._configure_source()
         assert sp.source == {}
         assert sp.all_sources == []
@@ -639,11 +636,10 @@ class TestConfigureSource:
                 decoded_token={"sub": "u"},
             )
         sp.agent_key = "agent_key_123"
-        agent_data = {
+        sp._agent_data = {
             "sources": [{"id": "s1", "retriever": "classic"}],
             "source": None,
         }
-        sp._get_data_from_api_key = MagicMock(return_value=agent_data)
         sp._configure_source()
         assert sp.source == {"active_docs": ["s1"]}
 
@@ -662,11 +658,10 @@ class TestConfigureSource:
                 decoded_token={"sub": "u"},
             )
         sp.agent_key = None
-        agent_data = {
+        sp._agent_data = {
             "sources": [{"id": None}, {"retriever": "classic"}],
             "source": None,
         }
-        sp._get_data_from_api_key = MagicMock(return_value=agent_data)
         sp._configure_source()
         assert sp.source == {}
 
@@ -1189,6 +1184,8 @@ class TestConfigureAgent:
             "chunks": "5",
         })
         sp._configure_agent()
+        sp.model_id = "test-model"
+        sp._configure_retriever()
         assert sp.agent_config["workflow"] == "wf_123"
         assert sp.agent_config["workflow_owner"] == "user1"
         assert sp.retriever_config["retriever_name"] == "hybrid"
@@ -1211,6 +1208,8 @@ class TestConfigureAgent:
             "chunks": "not_a_number",
         })
         sp._configure_agent()
+        sp.model_id = "test-model"
+        sp._configure_retriever()
         assert sp.retriever_config["chunks"] == 2
 
 
@@ -1763,8 +1762,8 @@ class TestConfigureAgentAdditionalPaths:
         assert sp.decoded_token == {"sub": "owner_user"}
 
     @pytest.mark.unit
-    def test_configure_agent_with_source_in_data_key(self):
-        """Cover line 463-464: data_key has 'source' set."""
+    def test_configure_source_picks_up_cached_agent_data(self):
+        """After _configure_agent caches _agent_data, _configure_source uses it."""
         sp = self._make_sp()
         sp._resolve_agent_id = MagicMock(return_value="agent_id_1")
         sp._get_agent_key = MagicMock(return_value=("agent_key", False, None))
@@ -1780,6 +1779,7 @@ class TestConfigureAgentAdditionalPaths:
             "source": "my_source",
         })
         sp._configure_agent()
+        sp._configure_source()
         assert sp.source == {"active_docs": "my_source"}
 
     @pytest.mark.unit
@@ -2067,7 +2067,7 @@ class TestPreFetchDocsFullPaths:
             "chunks": 2,
             "doc_token_limit": 50000,
         }
-        sp.source = {}
+        sp.source = {"active_docs": ["src1"]}
         sp.model_id = "test-model"
         sp.agent_id = None
         return sp
diff --git a/tests/test_v1_translator.py b/tests/test_v1_translator.py
index 92deb912..6974935c 100644
--- a/tests/test_v1_translator.py
+++ b/tests/test_v1_translator.py
@@ -11,6 +11,7 @@ import pytest
 from application.api.v1.translator import (
     _get_client_tool_name,
     convert_history,
+    extract_system_prompt,
     extract_tool_results,
     is_continuation,
     translate_request,
@@ -148,6 +149,48 @@ class TestConvertHistory:
         assert history == []
 
 
+# ---------------------------------------------------------------------------
+# extract_system_prompt
+# ---------------------------------------------------------------------------
+
+
+@pytest.mark.unit
+class TestExtractSystemPrompt:
+
+    def test_extracts_first_system_message(self):
+        messages = [
+            {"role": "system", "content": "You are a pirate"},
+            {"role": "user", "content": "Hello"},
+        ]
+        assert extract_system_prompt(messages) == "You are a pirate"
+
+    def test_returns_none_when_no_system_message(self):
+        messages = [{"role": "user", "content": "Hello"}]
+        assert extract_system_prompt(messages) is None
+
+    def test_returns_first_of_multiple_system_messages(self):
+        messages = [
+            {"role": "system", "content": "First"},
+            {"role": "system", "content": "Second"},
+            {"role": "user", "content": "Hello"},
+        ]
+        assert extract_system_prompt(messages) == "First"
+
+    def test_empty_content_returns_empty_string(self):
+        messages = [
+            {"role": "system", "content": ""},
+            {"role": "user", "content": "Hello"},
+        ]
+        assert extract_system_prompt(messages) == ""
+
+    def test_missing_content_returns_empty_string(self):
+        messages = [
+            {"role": "system"},
+            {"role": "user", "content": "Hello"},
+        ]
+        assert extract_system_prompt(messages) == ""
+
+
 # ---------------------------------------------------------------------------
 # translate_request
 # ---------------------------------------------------------------------------
@@ -167,11 +210,25 @@ class TestTranslateRequest:
         result = translate_request(data, "test-key")
         assert result["question"] == "What's 2+2?"
         assert result["api_key"] == "test-key"
-        assert result["save_conversation"] is True
+        # Conversations are not persisted by default on the v1 endpoint.
+        assert result["save_conversation"] is False
         history = json.loads(result["history"])
         assert len(history) == 1
         assert history[0]["prompt"] == "Hello"
 
+    def test_save_conversation_opt_in_via_docsgpt_extension(self):
+        data = {
+            "messages": [{"role": "user", "content": "Hi"}],
+            "docsgpt": {"save_conversation": True},
+        }
+        result = translate_request(data, "key")
+        assert result["save_conversation"] is True
+
+    def test_save_conversation_default_false(self):
+        data = {"messages": [{"role": "user", "content": "Hi"}]}
+        result = translate_request(data, "key")
+        assert result["save_conversation"] is False
+
     def test_continuation_request(self):
         data = {
             "messages": [
@@ -237,6 +294,23 @@ class TestTranslateRequest:
         result = translate_request(data, "key")
         assert result["attachments"] == ["att1", "att2"]
 
+    def test_system_prompt_override_included_when_present(self):
+        data = {
+            "messages": [
+                {"role": "system", "content": "Custom prompt"},
+                {"role": "user", "content": "Hello"},
+            ],
+        }
+        result = translate_request(data, "key")
+        assert result["system_prompt_override"] == "Custom prompt"
+
+    def test_system_prompt_override_absent_when_no_system_message(self):
+        data = {
+            "messages": [{"role": "user", "content": "Hello"}],
+        }
+        result = translate_request(data, "key")
+        assert "system_prompt_override" not in result
+
 
 # ---------------------------------------------------------------------------
 # translate_response