diff --git a/examples/deployments/basic-ollama/config.yaml b/examples/deployments/basic-ollama/config.yaml
index e7dfaa691..1c83b9653 100644
--- a/examples/deployments/basic-ollama/config.yaml
+++ b/examples/deployments/basic-ollama/config.yaml
@@ -31,7 +31,7 @@ services:
     port: 7889
     external_port: 7889
     auth:
-      enabled: false # set to true and provide DM_API_TOKEN in .env for production
+      enabled: false # set to true for protected direct access; DM_API_TOKEN optionally overrides the default internal service token
 
 data_manager:
   sources:
diff --git a/examples/deployments/basic-openai/config.yaml b/examples/deployments/basic-openai/config.yaml
index 8ab55024a..c76542d39 100644
--- a/examples/deployments/basic-openai/config.yaml
+++ b/examples/deployments/basic-openai/config.yaml
@@ -35,7 +35,7 @@ services:
     port: 7889
     external_port: 7889
     auth:
-      enabled: false # set to true and provide DM_API_TOKEN in .env for production
+      enabled: false # set to true for protected direct access; DM_API_TOKEN optionally overrides the default internal service token
 
 data_manager:
   sources:
diff --git a/src/interfaces/chat_app/app.py b/src/interfaces/chat_app/app.py
index 6c3e877dc..8de0efd2e 100644
--- a/src/interfaces/chat_app/app.py
+++ b/src/interfaces/chat_app/app.py
@@ -48,6 +48,7 @@
 from src.utils.logging import get_logger
 from src.utils.config_access import get_full_config, get_services_config, get_global_config, get_dynamic_config
 from src.utils.config_service import ConfigService
+from src.utils.internal_auth import build_data_manager_auth_headers, resolve_data_manager_service_token
 from src.utils.sql import (
     SQL_INSERT_CONVO, SQL_INSERT_FEEDBACK, SQL_INSERT_TIMING, SQL_QUERY_CONVO,
     SQL_CREATE_CONVERSATION, SQL_UPDATE_CONVERSATION_TIMESTAMP,
@@ -2153,9 +2154,13 @@ def __init__(self, app, **configs):
         dm_host = dm_config.get("hostname") or dm_config.get("host", "localhost")
         dm_port = dm_config.get("port", 5001)
         self.data_manager_url = f"http://{dm_host}:{dm_port}"
-        # API token for service-to-service auth with data-manager
-        dm_token = read_secret("DM_API_TOKEN") or None
-        self._dm_headers = {"Authorization": f"Bearer {dm_token}"} if dm_token else {}
+        # Internal auth for service-to-service calls into data-manager
+        self._dm_headers = build_data_manager_auth_headers()
+        _, dm_auth_source = resolve_data_manager_service_token()
+        if self._dm_headers:
+            logger.info("Data manager proxy auth initialized via %s", dm_auth_source)
+        else:
+            logger.warning("Data manager proxy auth unavailable; uploads may fail if data-manager auth is enabled")
         logger.info(f"Data manager service URL: {self.data_manager_url}")
 
         # Initialize authentication methods
diff --git a/src/interfaces/uploader_app/app.py b/src/interfaces/uploader_app/app.py
index f7fd20cc8..3a85465f0 100644
--- a/src/interfaces/uploader_app/app.py
+++ b/src/interfaces/uploader_app/app.py
@@ -20,6 +20,7 @@
 from src.data_manager.vectorstore.loader_utils import load_text_from_path
 from src.interfaces.chat_app.document_utils import check_credentials
 from src.utils.env import read_secret
+from src.utils.internal_auth import resolve_data_manager_service_token
 from src.utils.logging import get_logger
 from src.data_manager.collectors.utils.catalog_postgres import _METADATA_COLUMN_MAP
 from src.utils.config_access import get_full_config
@@ -58,7 +59,8 @@ def __init__(
 
         self.auth_config = (self.services_config or {}).get("data_manager", {}).get("auth", {}) or {}
         self.auth_enabled = bool(self.auth_config.get("enabled", False))
-        self.api_token = read_secret("DM_API_TOKEN") or None
+        self.api_token, self.api_token_source = resolve_data_manager_service_token()
+        self.api_token = self.api_token or None
         self.admin_users = {
             user.strip().lower()
             for user in (self.auth_config.get("admins") or [])
@@ -69,6 +71,10 @@ def __init__(
         self.salt = read_secret("UPLOADER_SALT")
         self.accounts_path = self.global_config.get("ACCOUNTS_PATH")
         if self.auth_enabled:
+            if self.api_token:
+                logger.info("Data-manager API auth initialized via %s", self.api_token_source)
+            else:
+                logger.warning("Data-manager auth is enabled but no internal API token could be resolved")
             if not self.accounts_path:
                 logger.warning("ACCOUNTS_PATH not configured; only default auth account avilable. Set is as DM_ADMIN_PASSWD in your secrets file.")
                 self.auth_enabled = True
diff --git a/src/utils/internal_auth.py b/src/utils/internal_auth.py
new file mode 100644
index 000000000..a0cb2ec7c
--- /dev/null
+++ b/src/utils/internal_auth.py
@@ -0,0 +1,33 @@
+from __future__ import annotations
+
+import hashlib
+from typing import Dict, Tuple
+
+from src.utils.env import read_secret
+
+
+def resolve_data_manager_service_token() -> Tuple[str, str]:
+    """Return the internal token used by chat-app -> data-manager requests.
+
+    Prefer an explicit DM_API_TOKEN when provided. If it is absent, derive a
+    deterministic internal-only token from PG_PASSWORD so paired services can
+    still authenticate without extra configuration.
+    """
+    explicit_token = read_secret("DM_API_TOKEN")
+    if explicit_token:
+        return explicit_token, "DM_API_TOKEN"
+
+    pg_password = read_secret("PG_PASSWORD")
+    if not pg_password:
+        return "", "missing"
+
+    digest = hashlib.sha256()
+    digest.update(b"archi:data-manager:")
+    digest.update(pg_password.encode("utf-8"))
+    return digest.hexdigest(), "derived-from-PG_PASSWORD"
+
+
+def build_data_manager_auth_headers() -> Dict[str, str]:
+    """Build auth headers for requests to the data-manager service."""
+    token, _ = resolve_data_manager_service_token()
+    return {"Authorization": f"Bearer {token}"} if token else {}
diff --git a/tests/unit/test_internal_auth.py b/tests/unit/test_internal_auth.py
new file mode 100644
index 000000000..e86c925bf
--- /dev/null
+++ b/tests/unit/test_internal_auth.py
@@ -0,0 +1,61 @@
+import sys
+from unittest.mock import MagicMock, patch
+
+from flask import Flask
+
+
+def _secret_reader(values):
+    def _read_secret(name, default=""):
+        return values.get(name, default)
+
+    return _read_secret
+
+
+def test_resolve_data_manager_service_token_prefers_explicit_token():
+    from src.utils.internal_auth import resolve_data_manager_service_token
+
+    with patch("src.utils.internal_auth.read_secret", side_effect=_secret_reader({
+        "DM_API_TOKEN": "dm-explicit-token",
+        "PG_PASSWORD": "postgres-password",
+    })):
+        token, source = resolve_data_manager_service_token()
+
+    assert token == "dm-explicit-token"
+    assert source == "DM_API_TOKEN"
+
+
+def test_resolve_data_manager_service_token_falls_back_to_pg_password():
+    from src.utils.internal_auth import resolve_data_manager_service_token
+
+    with patch("src.utils.internal_auth.read_secret", side_effect=_secret_reader({
+        "PG_PASSWORD": "postgres-password",
+    })):
+        token, source = resolve_data_manager_service_token()
+
+    assert token == "33d35de0f59af35976eb8d71af05e4da047068346ee196f078f0e7113ecd2328"
+    assert source == "derived-from-PG_PASSWORD"
+
+
+def test_require_admin_accepts_internal_bearer_token():
+    from src.utils.internal_auth import resolve_data_manager_service_token
+
+    app = Flask(__name__)
+    app.secret_key = "test-secret"
+
+    with patch.dict(sys.modules, {"spacy": MagicMock()}):
+        from src.interfaces.uploader_app.app import FlaskAppWrapper
+
+    dummy_wrapper = type("DummyWrapper", (), {})()
+    dummy_wrapper.auth_enabled = True
+    with patch("src.utils.internal_auth.read_secret", side_effect=_secret_reader({
+        "PG_PASSWORD": "postgres-password",
+    })):
+        dummy_wrapper.api_token, dummy_wrapper.api_token_source = resolve_data_manager_service_token()
+
+    def handler():
+        return "ok"
+
+    protected = FlaskAppWrapper.require_admin(dummy_wrapper, handler)
+
+    with app.test_request_context("/", headers={"Authorization": f"Bearer {dummy_wrapper.api_token}"}):
+        assert protected() == "ok"