diff --git a/fasta2a/applications.py b/fasta2a/applications.py
index 89a3cda..b835869 100644
--- a/fasta2a/applications.py
+++ b/fasta2a/applications.py
@@ -1,5 +1,7 @@
 from __future__ import annotations as _annotations
 
+import html
+import json
 from collections.abc import AsyncIterator, Sequence
 from contextlib import asynccontextmanager
 from pathlib import Path
@@ -8,7 +10,7 @@
 from starlette.applications import Starlette
 from starlette.middleware import Middleware
 from starlette.requests import Request
-from starlette.responses import FileResponse, Response, StreamingResponse
+from starlette.responses import Response, StreamingResponse
 from starlette.routing import Route
 from starlette.types import ExceptionHandler, Lifespan, Receive, Scope, Send
 
@@ -112,7 +114,11 @@ async def _agent_card_endpoint(self, request: Request) -> Response:
     async def _docs_endpoint(self, request: Request) -> Response:
         """Serve the documentation interface."""
         docs_path = Path(__file__).parent / 'static' / 'docs.html'
-        return FileResponse(docs_path, media_type='text/html')
+        root_path = request.scope.get('root_path', '').rstrip('/')
+        content = docs_path.read_text()
+        content = content.replace('__FASTA2A_API_ROOT_JSON__', json.dumps(root_path))
+        content = content.replace('__FASTA2A_API_ROOT__', html.escape(root_path, quote=True))
+        return Response(content=content, media_type='text/html')
 
     async def _agent_run_endpoint(self, request: Request) -> Response:
         """This is the main endpoint for the A2A server.
diff --git a/fasta2a/static/docs.html b/fasta2a/static/docs.html
index a1862a2..5e320e2 100644
--- a/fasta2a/static/docs.html
+++ b/fasta2a/static/docs.html
@@ -489,7 +489,7 @@ <h2>📋 Agent Information</h2>
                     <div class="loading">Loading agent information...</div>
                 </div>
                 <div class="agent-card-link">
-                    <a href="/.well-known/agent-card.json" target="_blank" rel="noopener noreferrer">
+                    <a href="__FASTA2A_API_ROOT__/.well-known/agent-card.json" target="_blank" rel="noopener noreferrer">
                         /.well-known/agent-card.json
                     </a>
                 </div>
@@ -526,11 +526,16 @@ <h2>💬 Chat Interface</h2>
         let agentCard = null;
         let currentTaskId = null;
         let contextId = null;
+        const apiRoot = __FASTA2A_API_ROOT_JSON__;
+
+        function apiUrl(path) {
+            return `${apiRoot}${path}`;
+        }
 
         // Load agent card information
         async function loadAgentCard() {
             try {
-                const response = await fetch('/.well-known/agent-card.json');
+                const response = await fetch(apiUrl('/.well-known/agent-card.json'));
                 if (!response.ok) throw new Error('Failed to load agent card');
 
                 agentCard = await response.json();
@@ -596,7 +601,7 @@ <h4>Skills:</h4>
 
             try {
                 // Send message to A2A endpoint
-                const response = await fetch('/', {
+                const response = await fetch(apiUrl('/'), {
                     method: 'POST',
                     headers: {
                         'Content-Type': 'application/json',
@@ -660,7 +665,7 @@ <h4>Skills:</h4>
             if (!currentTaskId) return;
 
             try {
-                const response = await fetch('/', {
+                const response = await fetch(apiUrl('/'), {
                     method: 'POST',
                     headers: {
                         'Content-Type': 'application/json',
diff --git a/tests/test_applications.py b/tests/test_applications.py
index 2385138..18a0fc7 100644
--- a/tests/test_applications.py
+++ b/tests/test_applications.py
@@ -6,6 +6,7 @@
 import pytest
 from asgi_lifespan import LifespanManager
 from inline_snapshot import snapshot
+from starlette.applications import Starlette
 
 from fasta2a.applications import FastA2A
 from fasta2a.broker import InMemoryBroker
@@ -56,6 +57,8 @@ async def test_docs_endpoint_default(self):
         async with create_test_client(app) as client:
             response = await client.get('/docs')
             assert response.status_code == 200
+            assert '__FASTA2A_API_ROOT__' not in response.text
+            assert 'const apiRoot = "";' in response.text
 
     async def test_docs_endpoint_custom_url(self):
         app = FastA2A(storage=InMemoryStorage(), broker=InMemoryBroker(), docs_url='/custom-docs')
@@ -63,6 +66,29 @@ async def test_docs_endpoint_custom_url(self):
             response = await client.get('/custom-docs')
             assert response.status_code == 200
 
+    async def test_docs_endpoint_mounted_app_uses_root_path(self):
+        a2a_app = FastA2A(storage=InMemoryStorage(), broker=InMemoryBroker())
+
+        @asynccontextmanager
+        async def lifespan(_app: Starlette):
+            async with a2a_app.router.lifespan_context(a2a_app):
+                yield
+
+        app = Starlette(lifespan=lifespan)
+        app.mount('/agent', a2a_app)
+
+        async with LifespanManager(app=app) as manager:
+            transport = httpx.ASGITransport(app=manager.app)
+            async with httpx.AsyncClient(transport=transport, base_url='http://testclient') as client:
+                response = await client.get('/agent/docs')
+                assert response.status_code == 200
+                assert '__FASTA2A_API_ROOT__' not in response.text
+                assert 'const apiRoot = "/agent";' in response.text
+                assert 'href="/agent/.well-known/agent-card.json"' in response.text
+
+                response = await client.get('/agent/.well-known/agent-card.json')
+                assert response.status_code == 200
+
     async def test_docs_endpoint_disabled(self):
         app = FastA2A(storage=InMemoryStorage(), broker=InMemoryBroker(), docs_url=None)
         async with create_test_client(app) as client: