diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 8f81e57..b9c7168 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -38,6 +38,7 @@ jobs:
               - 'tests/integration/test_sharded_archive_atomicity.py'
               - 'tests/compat/**'
               - 'compatibility/**'
+              - 'tests/i3/test_scalar_http_*.py'
               - 'pyproject.toml'
             api:
               - 'openblade/api/**'
@@ -127,6 +128,8 @@ jobs:
       - run: pytest tests/compat -q --tb=short
       # Whole safety suite (was only test_safety_regression.py) so the SAFETY_003
       # import guard is enforced and cannot silently rot again.
+      # scalar_http real-i3 client contract tests (in-process via TestClient, no server).
+      - run: pytest tests/i3/test_scalar_http_session.py tests/i3/test_scalar_http_library_backend.py tests/i3/test_scalar_http_move_medium.py tests/i3/test_scalar_http_wiring.py -q --tb=short
       - run: pytest tests/safety -q --tb=short
 
   api-aml-integration:
diff --git a/openblade/hardware/scalar_http/session.py b/openblade/hardware/scalar_http/session.py
index e126ddf..25c1c87 100644
--- a/openblade/hardware/scalar_http/session.py
+++ b/openblade/hardware/scalar_http/session.py
@@ -50,8 +50,9 @@ def login(self) -> None:
         """Establish a session. Raises ``ScalarHttpError`` on failure.
 
         The AML login accepts a JSON body and aliases ``username`` to ``name``; the
-        session cookie lands in the client cookie jar. The bearer token in the body
-        is captured as a fallback for clients whose jar is not shared across calls.
+        session cookie lands in the client cookie jar and authenticates every
+        subsequent request. The emulator also returns a token in the body — retained
+        for diagnostics only, NOT sent as a Bearer header (see ``_headers``).
         """
         response = self._client.post(
             self._login_path,
@@ -65,10 +66,12 @@ def login(self) -> None:
         self._logged_in = True
 
     def _headers(self) -> dict[str, str]:
-        headers = dict(_JSON_HEADERS)
-        if self._token:
-            headers["Authorization"] = f"Bearer {self._token}"
-        return headers
+        # Cookie-session only, to match the real i3: authentication rides on the
+        # ``sessionID`` cookie persisted in the client's cookie jar from login. We do
+        # NOT send an ``Authorization: Bearer`` header — that is an emulator-only
+        # artifact the appliance does not accept, and relying on it would let the
+        # client "work" against the emulator while diverging from the real contract.
+        return dict(_JSON_HEADERS)
 
     def request(
         self,
diff --git a/tests/i3/test_scalar_http_session.py b/tests/i3/test_scalar_http_session.py
index 83835d8..0b491b1 100644
--- a/tests/i3/test_scalar_http_session.py
+++ b/tests/i3/test_scalar_http_session.py
@@ -63,3 +63,16 @@ def test_scalar_http_session_bad_credentials_raise(emulator_client: TestClient)
         session.login()
 
     assert exc_info.value.status_code == 401
+
+
+def test_scalar_http_session_authenticates_via_cookie_not_bearer(
+    emulator_client: TestClient,
+) -> None:
+    # Real i3 fidelity: auth rides on the sessionID cookie, never an Authorization
+    # header. Guards against regressing to the emulator-only Bearer artifact.
+    session = _session(emulator_client)
+    session.login()
+
+    assert "Authorization" not in session._headers()
+    assert "sessionID" in emulator_client.cookies  # cookie jar carries the session
+    assert session.get_json("/aml/system/status")  # cookie-authenticated read works