diff --git a/backend/apps/agents/agents.py b/backend/apps/agents/agents.py
index abe8c6fe..87fcc367 100644
--- a/backend/apps/agents/agents.py
+++ b/backend/apps/agents/agents.py
@@ -29,6 +29,8 @@ from backend.apps.agents.agent_utils.create_sdk_hooks import create_sdk_hooks
 from backend.apps.agents.agent_utils.build_search_text import build_search_text
 from backend.apps.agents.COMMS_MANAGER.COMMS_MANAGER import COMMS_MANAGER
 from backend.apps.settings.settings import load_settings
+from backend.apps.modes.modes import get_mode_by_id
+from backend.apps.modes.Mode import Mode
 from backend.core.llm.resolve_sdk_env import resolve_sdk_env
 from backend.ports import NINE_ROUTER_PORT
 from claude_agent_sdk import ClaudeAgentOptions
@@ -102,7 +104,12 @@ class LaunchBody(BaseModel):
 
 @agents.router.post("/launch")
 async def launch(body: LaunchBody) -> dict:
+    settings = load_settings()
+    mode_def: Optional[Mode] = await get_mode_by_id(body.mode)
+
     system_prompt = compose_system_prompt(
+        global_default=settings.default_system_prompt,
+        mode_prompt=mode_def.system_prompt if mode_def else None,
         session_prompt=body.system_prompt or None,
     )
     agent: Agent = Agent(
@@ -119,9 +126,13 @@ async def launch(body: LaunchBody) -> dict:
     mcp_servers: Dict[str, McpServerConfig] = toolkit.collect_mcp_servers()
     allowed_tools, disallowed_tools = toolkit.collect_tool_permissions()
 
+    if mode_def and mode_def.tools is not None:
+        mode_tool_set: set[str] = set[str](mode_def.tools)
+        disallowed_tools += [t for t in allowed_tools if t not in mode_tool_set]
+        allowed_tools = [t for t in allowed_tools if t in mode_tool_set]
+
     can_use_tool, pre_tool_hook, post_tool_hook = create_sdk_hooks(agent)
 
-    settings = load_settings()
     env = resolve_sdk_env(
         api_key=settings.anthropic_api_key,
         nine_router_port=NINE_ROUTER_PORT if not settings.anthropic_api_key else None,
@@ -132,6 +143,7 @@ async def launch(body: LaunchBody) -> dict:
         model=body.model,
         system_prompt=system_prompt,
         max_turns=body.max_turns,
+        cwd=mode_def.default_folder if mode_def and mode_def.default_folder else None,
         mcp_servers=mcp_servers if mcp_servers else None,
         allowed_tools=allowed_tools,
         disallowed_tools=disallowed_tools,
@@ -192,10 +204,36 @@ class MessageBody(BaseModel):
 @agents.router.post("/SESSIONS/{session_id}/message")
 async def send_message(session_id: str, body: MessageBody) -> dict:
     agent: Agent = get_agent(session_id)
-    if body.mode and body.mode != agent.mode:
-        agent.mode = body.mode
-    if body.model and body.model != agent.model:
-        agent.model = body.model
+    mode_changed: bool = bool(body.mode and body.mode != agent.mode)
+    model_changed: bool = bool(body.model and body.model != agent.model)
+
+    if mode_changed:
+        agent.mode = body.mode  # type: ignore[assignment]
+    if model_changed:
+        agent.model = body.model  # type: ignore[assignment]
+
+    if mode_changed or model_changed:
+        settings = load_settings()
+        mode_def: Optional[Mode] = await get_mode_by_id(agent.mode)
+
+        system_prompt = compose_system_prompt(
+            global_default=settings.default_system_prompt,
+            mode_prompt=mode_def.system_prompt if mode_def else None,
+            session_prompt=agent.config.system_prompt,
+        )
+
+        allowed_tools, disallowed_tools = agent.toolkit.collect_tool_permissions()
+        if mode_def and mode_def.tools is not None:
+            mode_tool_set = set(mode_def.tools)
+            disallowed_tools += [t for t in allowed_tools if t not in mode_tool_set]
+            allowed_tools = [t for t in allowed_tools if t in mode_tool_set]
+
+        agent.config.system_prompt = system_prompt
+        agent.config.model = agent.model
+        agent.config.allowed_tools = allowed_tools
+        agent.config.disallowed_tools = disallowed_tools
+        if mode_def and mode_def.default_folder:
+            agent.config.cwd = mode_def.default_folder
 
     msg: UserMessage = UserMessage(
         content=body.prompt,
diff --git a/backend/apps/modes/modes.py b/backend/apps/modes/modes.py
index 11058d06..099e21b4 100644
--- a/backend/apps/modes/modes.py
+++ b/backend/apps/modes/modes.py
@@ -102,3 +102,8 @@ async def delete_mode(mode_id: str):
         raise HTTPException(status_code=403, detail="Cannot delete built-in modes")
     MODE_STORE.delete(mode_id)
     return {"ok": True}
+
+
+@modes.router.post("/get_mode_by_id")
+async def get_mode_by_id(mode_id: str) -> Optional[Mode]:
+    return MODE_STORE.load_or_none(item_id=mode_id)
\ No newline at end of file
diff --git a/backend/main.py b/backend/main.py
index 81725e7e..823be5e8 100644
--- a/backend/main.py
+++ b/backend/main.py
@@ -7,14 +7,15 @@ import uvicorn
 from typeguard import typechecked
 from backend.ports import get_backend_port
 from backend.config.Apps import MainApp
-from backend.apps.health.health import health
 from backend.apps.agents.agents import agents
-from backend.apps.settings.settings import settings
 from backend.apps.dashboards.dashboards import dashboards
+from backend.apps.health.health import health
+from backend.apps.settings.settings import settings
+from backend.apps.modes.modes import modes
 from fastapi.middleware.cors import CORSMiddleware
 
 main_app = MainApp([
-    health, agents, settings, dashboards
+    health, agents, settings, dashboards, modes
 ])
 app = main_app.app