diff --git a/apps/settings/routes.py b/apps/settings/routes.py
index b1e9d8da6..6bcbfb4ce 100644
--- a/apps/settings/routes.py
+++ b/apps/settings/routes.py
@@ -229,6 +229,11 @@ def update_config() -> Any:
                 if old_value != new_value:
                     changed_fields[key] = {"old": old_value, "new": new_value}
                 config[section][key] = new_value
+                if section == "env":
+                    if new_value:
+                        os.environ[key] = new_value
+                    else:
+                        os.environ.pop(key, None)
 
         # Hash password before writing to disk
         if section == "convey" and "password" in data:
diff --git a/tests/test_validate_key.py b/tests/test_validate_key.py
index 9986292a9..19de7006e 100644
--- a/tests/test_validate_key.py
+++ b/tests/test_validate_key.py
@@ -4,6 +4,7 @@
 from __future__ import annotations
 
 import json
+import os
 from unittest.mock import Mock, patch
 
 import pytest
@@ -309,6 +310,34 @@ def test_update_config_clears_key_validation(settings_client):
     assert "google" not in saved["providers"]["key_validation"]
 
 
+def test_update_config_env_mirrors_os_environ(settings_client, monkeypatch):
+    """The HTTP env-section save path must mirror into os.environ in-process,
+    matching the CLI pattern (apps/settings/call.py keys_set/keys_clear).
+    Without this, /api/providers reports `configured: false` until restart."""
+    client, _ = settings_client
+    monkeypatch.delenv("GOOGLE_API_KEY", raising=False)
+
+    with patch(
+        "think.providers.validate_key",
+        return_value={"valid": True},
+    ):
+        response = client.put(
+            "/app/settings/api/config",
+            json={"section": "env", "data": {"GOOGLE_API_KEY": "live-key"}},
+        )
+
+    assert response.status_code == 200
+    assert os.environ.get("GOOGLE_API_KEY") == "live-key"
+
+    response = client.put(
+        "/app/settings/api/config",
+        json={"section": "env", "data": {"GOOGLE_API_KEY": ""}},
+    )
+
+    assert response.status_code == 200
+    assert "GOOGLE_API_KEY" not in os.environ
+
+
 def test_get_providers_includes_key_validation(settings_client):
     client, journal = settings_client
     config_path = journal / "config" / "journal.json"