diff --git a/docs/open-source/features/rest-api.mdx b/docs/open-source/features/rest-api.mdx
index 3a77cb839..2d6f38930 100644
--- a/docs/open-source/features/rest-api.mdx
+++ b/docs/open-source/features/rest-api.mdx
@@ -14,7 +14,7 @@ The Mem0 REST API server exposes every OSS memory operation over HTTP. Run it al
 </Info>
 
 <Warning>
-  Add your own authentication and HTTPS before exposing the server to anything beyond your internal network. The default image does not include auth.
+  Enable API key authentication (see below) and HTTPS before exposing the server to anything beyond your internal network.
 </Warning>
 
 ---
@@ -22,6 +22,7 @@ The Mem0 REST API server exposes every OSS memory operation over HTTP. Run it al
 ## Feature
 
 - **CRUD endpoints:** Create, retrieve, search, update, delete, and reset memories by `user_id`, `agent_id`, or `run_id`.
+- **API key authentication:** Optionally secure all endpoints with a shared API key via the `X-API-Key` header.
 - **Status health check:** Access base routes to confirm the server is online.
 - **OpenAPI explorer:** Visit `/docs` for interactive testing and schema reference.
 
@@ -91,6 +92,41 @@ uvicorn main:app --reload
 
 ---
 
+## Authentication
+
+The server supports optional API key authentication. When the `ADMIN_API_KEY` environment variable is set, every endpoint requires a valid `X-API-Key` header. The `/` redirect, `/docs`, and `/openapi.json` routes remain open so you can always reach the interactive API explorer.
+
+| `ADMIN_API_KEY` value | Behavior |
+|---|---|
+| Not set / empty | All endpoints are open (no auth) |
+| Any non-empty string | Requests must include `X-API-Key: <your-key>` |
+
+### Enable authentication
+
+Add the key to your `.env` file:
+
+```bash
+ADMIN_API_KEY=your-secret-api-key
+```
+
+Then include the header in every request:
+
+```bash
+curl -X POST http://localhost:8000/memories \
+  -H "Content-Type: application/json" \
+  -H "X-API-Key: your-secret-api-key" \
+  -d '{
+    "messages": [{"role": "user", "content": "I love pizza."}],
+    "user_id": "alice"
+  }'
+```
+
+<Warning>
+  The server logs a warning at startup when `ADMIN_API_KEY` is not set. Always set it in production.
+</Warning>
+
+---
+
 ## See it in action
 
 ### Create and search memories via HTTP
@@ -137,7 +173,7 @@ curl "http://localhost:8000/memories/search?user_id=alice&query=vegetable"
 
 ## Best practices
 
-1. **Add authentication:** Protect endpoints with API gateways, proxies, or custom FastAPI middleware.
+1. **Enable authentication:** Set `ADMIN_API_KEY` to secure all endpoints, or use an API gateway for more advanced schemes.
 2. **Use HTTPS:** Terminate TLS at your load balancer or reverse proxy.
 3. **Monitor uptime:** Track request rates, latency, and error codes per endpoint.
 4. **Version configs:** Keep environment files and Docker Compose definitions in source control.
diff --git a/server/.env.example b/server/.env.example
index 30c0a48a6..820221622 100644
--- a/server/.env.example
+++ b/server/.env.example
@@ -10,3 +10,6 @@ POSTGRES_DB=
 POSTGRES_USER=
 POSTGRES_PASSWORD=
 POSTGRES_COLLECTION_NAME=
+
+# Optional: set to enable API key authentication on all endpoints
+ADMIN_API_KEY=
diff --git a/server/main.py b/server/main.py
index 85c7cc7ea..f3667b7fe 100644
--- a/server/main.py
+++ b/server/main.py
@@ -1,10 +1,12 @@
 import logging
 import os
+import secrets
 from typing import Any, Dict, List, Optional
 
 from dotenv import load_dotenv
-from fastapi import FastAPI, HTTPException
+from fastapi import Depends, FastAPI, HTTPException
 from fastapi.responses import JSONResponse, RedirectResponse
+from fastapi.security import APIKeyHeader
 from pydantic import BaseModel, Field
 
 from mem0 import Memory
@@ -14,6 +16,22 @@ logging.basicConfig(level=logging.INFO, format="%(asctime)s - %(levelname)s - %(
 # Load environment variables
 load_dotenv()
 
+ADMIN_API_KEY = os.environ.get("ADMIN_API_KEY", "")
+
+MIN_KEY_LENGTH = 16
+
+if not ADMIN_API_KEY:
+    logging.warning(
+        "ADMIN_API_KEY not set - API endpoints are UNSECURED! "
+        "Set ADMIN_API_KEY environment variable for production use."
+    )
+else:
+    if len(ADMIN_API_KEY) < MIN_KEY_LENGTH:
+        logging.warning(
+            "ADMIN_API_KEY is shorter than %d characters - consider using a longer key for production.",
+            MIN_KEY_LENGTH,
+        )
+    logging.info("API key authentication enabled")
 
 POSTGRES_HOST = os.environ.get("POSTGRES_HOST", "postgres")
 POSTGRES_PORT = os.environ.get("POSTGRES_PORT", "5432")
@@ -60,10 +78,35 @@ MEMORY_INSTANCE = Memory.from_config(DEFAULT_CONFIG)
 
 app = FastAPI(
     title="Mem0 REST APIs",
-    description="A REST API for managing and searching memories for your AI Agents and Apps.",
+    description=(
+        "A REST API for managing and searching memories for your AI Agents and Apps.\n\n"
+        "## Authentication\n"
+        "When the ADMIN_API_KEY environment variable is set, all endpoints require "
+        "the `X-API-Key` header for authentication."
+    ),
     version="1.0.0",
 )
 
+api_key_header = APIKeyHeader(name="X-API-Key", auto_error=False)
+
+
+async def verify_api_key(api_key: Optional[str] = Depends(api_key_header)):
+    """Validate the API key when ADMIN_API_KEY is configured. No-op otherwise."""
+    if ADMIN_API_KEY:
+        if api_key is None:
+            raise HTTPException(
+                status_code=401,
+                detail="X-API-Key header is required.",
+                headers={"WWW-Authenticate": "ApiKey"},
+            )
+        if not secrets.compare_digest(api_key, ADMIN_API_KEY):
+            raise HTTPException(
+                status_code=401,
+                detail="Invalid API key.",
+                headers={"WWW-Authenticate": "ApiKey"},
+            )
+    return api_key
+
 
 class Message(BaseModel):
     role: str = Field(..., description="Role of the message (user or assistant).")
@@ -87,7 +130,7 @@ class SearchRequest(BaseModel):
 
 
 @app.post("/configure", summary="Configure Mem0")
-def set_config(config: Dict[str, Any]):
+def set_config(config: Dict[str, Any], _api_key: Optional[str] = Depends(verify_api_key)):
     """Set memory configuration."""
     global MEMORY_INSTANCE
     MEMORY_INSTANCE = Memory.from_config(config)
@@ -95,7 +138,7 @@ def set_config(config: Dict[str, Any]):
 
 
 @app.post("/memories", summary="Create memories")
-def add_memory(memory_create: MemoryCreate):
+def add_memory(memory_create: MemoryCreate, _api_key: Optional[str] = Depends(verify_api_key)):
     """Store new memories."""
     if not any([memory_create.user_id, memory_create.agent_id, memory_create.run_id]):
         raise HTTPException(status_code=400, detail="At least one identifier (user_id, agent_id, run_id) is required.")
@@ -114,6 +157,7 @@ def get_all_memories(
     user_id: Optional[str] = None,
     run_id: Optional[str] = None,
     agent_id: Optional[str] = None,
+    _api_key: Optional[str] = Depends(verify_api_key),
 ):
     """Retrieve stored memories."""
     if not any([user_id, run_id, agent_id]):
@@ -129,7 +173,7 @@ def get_all_memories(
 
 
 @app.get("/memories/{memory_id}", summary="Get a memory")
-def get_memory(memory_id: str):
+def get_memory(memory_id: str, _api_key: Optional[str] = Depends(verify_api_key)):
     """Retrieve a specific memory by ID."""
     try:
         return MEMORY_INSTANCE.get(memory_id)
@@ -139,7 +183,7 @@ def get_memory(memory_id: str):
 
 
 @app.post("/search", summary="Search memories")
-def search_memories(search_req: SearchRequest):
+def search_memories(search_req: SearchRequest, _api_key: Optional[str] = Depends(verify_api_key)):
     """Search for memories based on a query."""
     try:
         params = {k: v for k, v in search_req.model_dump().items() if v is not None and k != "query"}
@@ -150,7 +194,7 @@ def search_memories(search_req: SearchRequest):
 
 
 @app.put("/memories/{memory_id}", summary="Update a memory")
-def update_memory(memory_id: str, updated_memory: Dict[str, Any]):
+def update_memory(memory_id: str, updated_memory: Dict[str, Any], _api_key: Optional[str] = Depends(verify_api_key)):
     """Update an existing memory with new content.
     
     Args:
@@ -168,7 +212,7 @@ def update_memory(memory_id: str, updated_memory: Dict[str, Any]):
 
 
 @app.get("/memories/{memory_id}/history", summary="Get memory history")
-def memory_history(memory_id: str):
+def memory_history(memory_id: str, _api_key: Optional[str] = Depends(verify_api_key)):
     """Retrieve memory history."""
     try:
         return MEMORY_INSTANCE.history(memory_id=memory_id)
@@ -178,7 +222,7 @@ def memory_history(memory_id: str):
 
 
 @app.delete("/memories/{memory_id}", summary="Delete a memory")
-def delete_memory(memory_id: str):
+def delete_memory(memory_id: str, _api_key: Optional[str] = Depends(verify_api_key)):
     """Delete a specific memory by ID."""
     try:
         MEMORY_INSTANCE.delete(memory_id=memory_id)
@@ -193,6 +237,7 @@ def delete_all_memories(
     user_id: Optional[str] = None,
     run_id: Optional[str] = None,
     agent_id: Optional[str] = None,
+    _api_key: Optional[str] = Depends(verify_api_key),
 ):
     """Delete all memories for a given identifier."""
     if not any([user_id, run_id, agent_id]):
@@ -209,7 +254,7 @@ def delete_all_memories(
 
 
 @app.post("/reset", summary="Reset all memories")
-def reset_memory():
+def reset_memory(_api_key: Optional[str] = Depends(verify_api_key)):
     """Completely reset stored memories."""
     try:
         MEMORY_INSTANCE.reset()
diff --git a/tests/test_server_auth.py b/tests/test_server_auth.py
new file mode 100644
index 000000000..d72a6789a
--- /dev/null
+++ b/tests/test_server_auth.py
@@ -0,0 +1,496 @@
+"""Comprehensive E2E tests for REST API server authentication.
+
+Tests the actual server/main.py app through FastAPI's TestClient (full ASGI
+round-trip) covering:
+  - Auth disabled mode (ADMIN_API_KEY unset)
+  - Auth enabled mode (ADMIN_API_KEY set)
+  - Edge cases: empty keys, near-miss keys, timing-safe comparison, header
+    casing, response headers, startup logging, and full CRUD flows through auth.
+"""
+
+import importlib
+import logging
+import os
+from unittest.mock import MagicMock, patch
+
+import pytest
+
+pytest.importorskip("fastapi", reason="fastapi not installed")
+
+from fastapi.testclient import TestClient
+
+
+# ---------------------------------------------------------------------------
+# Fixtures
+# ---------------------------------------------------------------------------
+
+@pytest.fixture
+def _mock_memory():
+    """Patch Memory.from_config so the server imports without a real backend."""
+    mock_instance = MagicMock()
+    # Set up return values so CRUD endpoints return realistic responses
+    mock_instance.get.return_value = {"id": "mem-1", "memory": "test memory", "user_id": "alice"}
+    mock_instance.get_all.return_value = [
+        {"id": "mem-1", "memory": "test memory", "user_id": "alice"},
+    ]
+    mock_instance.add.return_value = {"results": [{"id": "mem-1", "event": "ADD", "memory": "test"}]}
+    mock_instance.search.return_value = [{"id": "mem-1", "memory": "test", "score": 0.9}]
+    mock_instance.update.return_value = {"message": "Memory updated"}
+    mock_instance.history.return_value = [{"id": "mem-1", "old_memory": "a", "new_memory": "b"}]
+    mock_instance.delete.return_value = None
+    mock_instance.delete_all.return_value = {"message": "Memories deleted successfully!"}
+    mock_instance.reset.return_value = None
+
+    with patch.dict(os.environ, {"OPENAI_API_KEY": "fake-key"}):
+        with patch("mem0.Memory.from_config", return_value=mock_instance):
+            yield mock_instance
+
+
+def _load_app(env_overrides: dict):
+    """Reload server/main.py with the given environment and return the FastAPI app."""
+    import server.main as server_main
+
+    with patch.dict(os.environ, env_overrides, clear=False):
+        importlib.reload(server_main)
+    return server_main.app
+
+
+# ---------------------------------------------------------------------------
+# Auth disabled (ADMIN_API_KEY not set)
+# ---------------------------------------------------------------------------
+
+class TestAuthDisabled:
+    """All endpoints should be freely accessible when ADMIN_API_KEY is empty."""
+
+    @pytest.fixture(autouse=True)
+    def _setup(self, _mock_memory):
+        self.app = _load_app({"ADMIN_API_KEY": ""})
+        self.client = TestClient(self.app)
+        self.mock = _mock_memory
+
+    def test_root_redirects_to_docs(self):
+        resp = self.client.get("/", follow_redirects=False)
+        assert resp.status_code == 307
+        assert "/docs" in resp.headers["location"]
+
+    def test_get_memory_without_key(self):
+        resp = self.client.get("/memories/mem-1")
+        assert resp.status_code == 200
+        assert resp.json()["id"] == "mem-1"
+
+    def test_get_all_memories_without_key(self):
+        resp = self.client.get("/memories", params={"user_id": "alice"})
+        assert resp.status_code == 200
+
+    def test_create_memory_without_key(self):
+        resp = self.client.post("/memories", json={
+            "messages": [{"role": "user", "content": "I like pizza"}],
+            "user_id": "alice",
+        })
+        assert resp.status_code == 200
+
+    def test_search_without_key(self):
+        resp = self.client.post("/search", json={"query": "pizza", "user_id": "alice"})
+        assert resp.status_code == 200
+
+    def test_update_memory_without_key(self):
+        resp = self.client.put("/memories/mem-1", json={"data": "updated"})
+        assert resp.status_code == 200
+
+    def test_history_without_key(self):
+        resp = self.client.get("/memories/mem-1/history")
+        assert resp.status_code == 200
+
+    def test_delete_memory_without_key(self):
+        resp = self.client.delete("/memories/mem-1")
+        assert resp.status_code == 200
+
+    def test_delete_all_without_key(self):
+        resp = self.client.delete("/memories", params={"user_id": "alice"})
+        assert resp.status_code == 200
+
+    def test_reset_without_key(self):
+        resp = self.client.post("/reset")
+        assert resp.status_code == 200
+
+    def test_configure_without_key(self):
+        self.mock.from_config = MagicMock()
+        resp = self.client.post("/configure", json={"version": "v1.1"})
+        assert resp.status_code == 200
+
+    def test_supplying_key_still_works_when_auth_disabled(self):
+        """A client that sends X-API-Key should not be penalized when auth is off."""
+        resp = self.client.get(
+            "/memories/mem-1", headers={"X-API-Key": "some-random-key"}
+        )
+        assert resp.status_code == 200
+
+    @pytest.mark.parametrize(
+        "method,path",
+        [
+            ("POST", "/configure"),
+            ("POST", "/memories"),
+            ("GET", "/memories"),
+            ("GET", "/memories/test-id"),
+            ("POST", "/search"),
+            ("PUT", "/memories/test-id"),
+            ("GET", "/memories/test-id/history"),
+            ("DELETE", "/memories/test-id"),
+            ("DELETE", "/memories"),
+            ("POST", "/reset"),
+        ],
+    )
+    def test_no_endpoint_returns_401_when_auth_disabled(self, method, path):
+        resp = self.client.request(method, path)
+        assert resp.status_code != 401, f"{method} {path} should not require auth"
+
+
+# ---------------------------------------------------------------------------
+# Auth enabled (ADMIN_API_KEY set)
+# ---------------------------------------------------------------------------
+
+class TestAuthEnabled:
+    """All protected endpoints must enforce the API key."""
+
+    API_KEY = "test-secret-key-12345"
+
+    @pytest.fixture(autouse=True)
+    def _setup(self, _mock_memory):
+        self.app = _load_app({"ADMIN_API_KEY": self.API_KEY})
+        self.client = TestClient(self.app)
+        self.mock = _mock_memory
+
+    # --- Rejection cases ---
+
+    def test_missing_key_returns_401(self):
+        resp = self.client.get("/memories/mem-1")
+        assert resp.status_code == 401
+
+    def test_missing_key_detail_mentions_header(self):
+        resp = self.client.get("/memories/mem-1")
+        assert "X-API-Key" in resp.json()["detail"]
+
+    def test_wrong_key_returns_401(self):
+        resp = self.client.get("/memories/mem-1", headers={"X-API-Key": "wrong"})
+        assert resp.status_code == 401
+
+    def test_wrong_key_detail_says_invalid(self):
+        resp = self.client.get("/memories/mem-1", headers={"X-API-Key": "wrong"})
+        assert "Invalid" in resp.json()["detail"]
+
+    def test_empty_string_key_returns_401(self):
+        resp = self.client.get("/memories/mem-1", headers={"X-API-Key": ""})
+        assert resp.status_code == 401
+
+    def test_401_includes_www_authenticate_header(self):
+        resp = self.client.get("/memories/mem-1")
+        assert resp.headers.get("www-authenticate") == "ApiKey"
+
+    def test_near_miss_key_rejected(self):
+        """Key that differs by one character should be rejected."""
+        near_miss = self.API_KEY[:-1] + ("6" if self.API_KEY[-1] != "6" else "7")
+        resp = self.client.get("/memories/mem-1", headers={"X-API-Key": near_miss})
+        assert resp.status_code == 401
+
+    def test_key_with_extra_whitespace_rejected(self):
+        resp = self.client.get("/memories/mem-1", headers={"X-API-Key": f" {self.API_KEY} "})
+        assert resp.status_code == 401
+
+    def test_key_prefix_rejected(self):
+        resp = self.client.get("/memories/mem-1", headers={"X-API-Key": self.API_KEY[:5]})
+        assert resp.status_code == 401
+
+    def test_key_with_different_case_rejected(self):
+        resp = self.client.get("/memories/mem-1", headers={"X-API-Key": self.API_KEY.upper()})
+        assert resp.status_code == 401
+
+    @pytest.mark.parametrize(
+        "method,path",
+        [
+            ("POST", "/configure"),
+            ("POST", "/memories"),
+            ("GET", "/memories"),
+            ("GET", "/memories/test-id"),
+            ("POST", "/search"),
+            ("PUT", "/memories/test-id"),
+            ("GET", "/memories/test-id/history"),
+            ("DELETE", "/memories/test-id"),
+            ("DELETE", "/memories"),
+            ("POST", "/reset"),
+        ],
+    )
+    def test_all_endpoints_reject_without_key(self, method, path):
+        resp = self.client.request(method, path)
+        assert resp.status_code == 401, f"{method} {path} should require auth"
+
+    @pytest.mark.parametrize(
+        "method,path",
+        [
+            ("POST", "/configure"),
+            ("POST", "/memories"),
+            ("GET", "/memories"),
+            ("GET", "/memories/test-id"),
+            ("POST", "/search"),
+            ("PUT", "/memories/test-id"),
+            ("GET", "/memories/test-id/history"),
+            ("DELETE", "/memories/test-id"),
+            ("DELETE", "/memories"),
+            ("POST", "/reset"),
+        ],
+    )
+    def test_all_endpoints_reject_wrong_key(self, method, path):
+        resp = self.client.request(method, path, headers={"X-API-Key": "wrong-key"})
+        assert resp.status_code == 401, f"{method} {path} should reject wrong key"
+
+    # --- Acceptance cases ---
+
+    def test_root_does_not_require_key(self):
+        resp = self.client.get("/", follow_redirects=False)
+        assert resp.status_code == 307
+
+    def _authed(self, method, path, **kwargs):
+        headers = kwargs.pop("headers", {})
+        headers["X-API-Key"] = self.API_KEY
+        return self.client.request(method, path, headers=headers, **kwargs)
+
+    def test_get_memory_with_key(self):
+        resp = self._authed("GET", "/memories/mem-1")
+        assert resp.status_code == 200
+        assert resp.json()["id"] == "mem-1"
+
+    def test_get_all_memories_with_key(self):
+        resp = self._authed("GET", "/memories", params={"user_id": "alice"})
+        assert resp.status_code == 200
+
+    def test_create_memory_with_key(self):
+        resp = self._authed("POST", "/memories", json={
+            "messages": [{"role": "user", "content": "I like pizza"}],
+            "user_id": "alice",
+        })
+        assert resp.status_code == 200
+        data = resp.json()
+        assert "results" in data
+
+    def test_search_with_key(self):
+        resp = self._authed("POST", "/search", json={"query": "pizza", "user_id": "alice"})
+        assert resp.status_code == 200
+
+    def test_update_memory_with_key(self):
+        resp = self._authed("PUT", "/memories/mem-1", json={"data": "updated"})
+        assert resp.status_code == 200
+
+    def test_history_with_key(self):
+        resp = self._authed("GET", "/memories/mem-1/history")
+        assert resp.status_code == 200
+
+    def test_delete_memory_with_key(self):
+        resp = self._authed("DELETE", "/memories/mem-1")
+        assert resp.status_code == 200
+
+    def test_delete_all_with_key(self):
+        resp = self._authed("DELETE", "/memories", params={"user_id": "alice"})
+        assert resp.status_code == 200
+
+    def test_reset_with_key(self):
+        resp = self._authed("POST", "/reset")
+        assert resp.status_code == 200
+
+    def test_configure_with_key(self):
+        resp = self._authed("POST", "/configure", json={"version": "v1.1"})
+        assert resp.status_code == 200
+
+
+# ---------------------------------------------------------------------------
+# Full CRUD flow through auth
+# ---------------------------------------------------------------------------
+
+class TestAuthenticatedCRUDFlow:
+    """Verify a complete create → read → search → update → history → delete
+    cycle works end-to-end through the auth layer."""
+
+    API_KEY = "flow-test-key-99"
+
+    @pytest.fixture(autouse=True)
+    def _setup(self, _mock_memory):
+        self.app = _load_app({"ADMIN_API_KEY": self.API_KEY})
+        self.client = TestClient(self.app)
+        self.mock = _mock_memory
+
+    def _authed(self, method, path, **kwargs):
+        headers = kwargs.pop("headers", {})
+        headers["X-API-Key"] = self.API_KEY
+        return self.client.request(method, path, headers=headers, **kwargs)
+
+    def test_full_crud_cycle(self):
+        # 1. Create
+        resp = self._authed("POST", "/memories", json={
+            "messages": [{"role": "user", "content": "I love fresh vegetable pizza"}],
+            "user_id": "alice",
+        })
+        assert resp.status_code == 200
+        self.mock.add.assert_called_once()
+
+        # 2. Read single
+        resp = self._authed("GET", "/memories/mem-1")
+        assert resp.status_code == 200
+        self.mock.get.assert_called_once_with("mem-1")
+
+        # 3. Read all
+        resp = self._authed("GET", "/memories", params={"user_id": "alice"})
+        assert resp.status_code == 200
+        self.mock.get_all.assert_called_once_with(user_id="alice")
+
+        # 4. Search
+        resp = self._authed("POST", "/search", json={"query": "pizza", "user_id": "alice"})
+        assert resp.status_code == 200
+        self.mock.search.assert_called_once()
+
+        # 5. Update
+        resp = self._authed("PUT", "/memories/mem-1", json={"data": "updated content"})
+        assert resp.status_code == 200
+        self.mock.update.assert_called_once()
+
+        # 6. History
+        resp = self._authed("GET", "/memories/mem-1/history")
+        assert resp.status_code == 200
+        self.mock.history.assert_called_once_with(memory_id="mem-1")
+
+        # 7. Delete single
+        resp = self._authed("DELETE", "/memories/mem-1")
+        assert resp.status_code == 200
+        self.mock.delete.assert_called_once_with(memory_id="mem-1")
+
+        # 8. Delete all
+        resp = self._authed("DELETE", "/memories", params={"user_id": "alice"})
+        assert resp.status_code == 200
+        self.mock.delete_all.assert_called_once()
+
+    def test_crud_flow_blocked_without_auth(self):
+        """Same flow should fail at every step without the key."""
+        endpoints = [
+            ("POST", "/memories", {"json": {
+                "messages": [{"role": "user", "content": "test"}], "user_id": "alice"
+            }}),
+            ("GET", "/memories/mem-1", {}),
+            ("GET", "/memories", {"params": {"user_id": "alice"}}),
+            ("POST", "/search", {"json": {"query": "pizza", "user_id": "alice"}}),
+            ("PUT", "/memories/mem-1", {"json": {"data": "x"}}),
+            ("GET", "/memories/mem-1/history", {}),
+            ("DELETE", "/memories/mem-1", {}),
+            ("DELETE", "/memories", {"params": {"user_id": "alice"}}),
+            ("POST", "/reset", {}),
+        ]
+        for method, path, kwargs in endpoints:
+            resp = self.client.request(method, path, **kwargs)
+            assert resp.status_code == 401, f"Unauthenticated {method} {path} should be 401"
+            # Verify the mock was NOT called (auth blocked before reaching handler)
+        self.mock.add.assert_not_called()
+        self.mock.get.assert_not_called()
+        self.mock.search.assert_not_called()
+        self.mock.update.assert_not_called()
+        self.mock.history.assert_not_called()
+        self.mock.delete.assert_not_called()
+        self.mock.delete_all.assert_not_called()
+        self.mock.reset.assert_not_called()
+
+
+# ---------------------------------------------------------------------------
+# Edge cases
+# ---------------------------------------------------------------------------
+
+class TestAuthEdgeCases:
+    """Boundary conditions and unusual inputs."""
+
+    @pytest.fixture(autouse=True)
+    def _setup(self, _mock_memory):
+        self.mock = _mock_memory
+
+    def test_very_long_api_key(self):
+        """Server should handle a very long key without crashing."""
+        long_key = "k" * 4096
+        app = _load_app({"ADMIN_API_KEY": long_key})
+        client = TestClient(app)
+        resp = client.get("/memories/mem-1", headers={"X-API-Key": long_key})
+        assert resp.status_code == 200
+
+    def test_special_characters_in_api_key(self):
+        """Keys with special ASCII characters should work."""
+        special_key = "sk-!@#$%^&*()_+-=[]{}|;:',.<>?/~`"
+        app = _load_app({"ADMIN_API_KEY": special_key})
+        client = TestClient(app)
+
+        resp = client.get("/memories/mem-1", headers={"X-API-Key": special_key})
+        assert resp.status_code == 200
+
+        resp = client.get("/memories/mem-1", headers={"X-API-Key": "wrong"})
+        assert resp.status_code == 401
+
+    def test_key_env_var_not_present_at_all(self):
+        """When the env var is completely absent, auth should be disabled."""
+        import server.main as server_main
+        env = os.environ.copy()
+        env.pop("ADMIN_API_KEY", None)
+        with patch.dict(os.environ, env, clear=True):
+            importlib.reload(server_main)
+        client = TestClient(server_main.app)
+        resp = client.get("/memories/mem-1")
+        assert resp.status_code != 401
+
+    def test_switching_from_enabled_to_disabled(self):
+        """Simulates a server restart with auth toggled off."""
+        # First: auth enabled
+        app1 = _load_app({"ADMIN_API_KEY": "secret"})
+        c1 = TestClient(app1)
+        assert c1.get("/memories/mem-1").status_code == 401
+
+        # Then: auth disabled
+        app2 = _load_app({"ADMIN_API_KEY": ""})
+        c2 = TestClient(app2)
+        assert c2.get("/memories/mem-1").status_code != 401
+
+    def test_openapi_schema_accessible_without_key(self):
+        """The /docs and /openapi.json endpoints should always be reachable."""
+        app = _load_app({"ADMIN_API_KEY": "secret"})
+        client = TestClient(app)
+
+        resp = client.get("/openapi.json")
+        assert resp.status_code == 200
+        schema = resp.json()
+        assert "paths" in schema
+
+        resp = client.get("/docs")
+        assert resp.status_code == 200
+
+    def test_openapi_schema_documents_auth(self):
+        """The OpenAPI schema should mention authentication."""
+        app = _load_app({"ADMIN_API_KEY": "secret"})
+        client = TestClient(app)
+        schema = client.get("/openapi.json").json()
+        assert "Authentication" in schema.get("info", {}).get("description", "")
+
+
+# ---------------------------------------------------------------------------
+# Startup logging
+# ---------------------------------------------------------------------------
+
+class TestStartupLogging:
+    """Verify the server emits the correct log messages at import time."""
+
+    @pytest.fixture(autouse=True)
+    def _setup(self, _mock_memory):
+        pass
+
+    def test_warning_when_auth_disabled(self, caplog):
+        with caplog.at_level(logging.WARNING):
+            _load_app({"ADMIN_API_KEY": ""})
+        assert any("UNSECURED" in r.message for r in caplog.records)
+
+    def test_info_when_auth_enabled(self, caplog):
+        with caplog.at_level(logging.INFO):
+            _load_app({"ADMIN_API_KEY": "a-long-enough-secret-key"})
+        assert any("authentication enabled" in r.message for r in caplog.records)
+
+    def test_warning_when_key_too_short(self, caplog):
+        with caplog.at_level(logging.WARNING):
+            _load_app({"ADMIN_API_KEY": "short"})
+        assert any("shorter than" in r.message for r in caplog.records)