diff --git a/app/modules/proxy/http_bridge_forwarding.py b/app/modules/proxy/http_bridge_forwarding.py
index db5b16aa5..d0d2174ea 100644
--- a/app/modules/proxy/http_bridge_forwarding.py
+++ b/app/modules/proxy/http_bridge_forwarding.py
@@ -11,7 +11,7 @@
 
 import aiohttp
 
-from app.core.clients.proxy import ProxyResponseError
+from app.core.clients.proxy import ProxyResponseError, filter_inbound_headers
 from app.core.config.settings import get_settings
 from app.core.crypto import get_or_create_key
 from app.core.errors import OpenAIErrorEnvelope, openai_error, response_failed_event
@@ -22,6 +22,26 @@
 from app.modules.api_keys.service import ApiKeyUsageReservationData
 from app.modules.proxy._service.http_bridge.helpers import _http_bridge_request_budget_seconds
 
+# HTTP-only and hop-by-hop headers that must not be forwarded through the
+# internal bridge. These headers are either illegal in WebSocket handshakes or
+# carry HTTP framing semantics that the aiohttp upstream session manages itself.
+# Applies on top of filter_inbound_headers (which already strips authorization,
+# host, content-length, and x-forwarded-* / cf-* headers).
+_BRIDGE_UNSAFE_HEADER_NAMES = frozenset(
+    {
+        "accept",
+        "accept-encoding",
+        "connection",
+        "content-type",
+        "cookie",
+        "keep-alive",
+        "te",
+        "trailer",
+        "transfer-encoding",
+        "upgrade",
+    }
+)
+
 HTTP_BRIDGE_INTERNAL_FORWARD_PATH = "/internal/bridge/responses"
 HTTP_BRIDGE_FORWARDED_HEADER = "x-codex-bridge-forwarded"
 HTTP_BRIDGE_ORIGIN_INSTANCE_HEADER = "x-codex-bridge-origin-instance"
@@ -136,9 +156,27 @@ def build_owner_forward_headers(
     payload: ResponsesRequest,
     context: HTTPBridgeForwardContext,
 ) -> dict[str, str]:
-    forwarded = dict(headers)
-    forwarded.pop("host", None)
-    forwarded.pop("content-length", None)
+    filtered = filter_inbound_headers(headers)
+    # Per the hop-by-hop contract, also drop any header named by the inbound
+    # Connection header in addition to the fixed unsafe set.
+    connection_value = next(
+        (value for key, value in headers.items() if key.lower() == "connection"),
+        "",
+    )
+    connection_named = {token.strip().lower() for token in connection_value.split(",") if token.strip()}
+    drop = _BRIDGE_UNSAFE_HEADER_NAMES | connection_named
+    forwarded = {key: value for key, value in filtered.items() if key.lower() not in drop}
+    # filter_inbound_headers strips Authorization, but the owner instance
+    # re-validates the client API key from this header (see
+    # _validate_internal_bridge_api_key) before swapping in its own upstream
+    # access token. Preserve it so api_key_auth_enabled deployments still
+    # authenticate forwarded bridge requests.
+    authorization = next(
+        (value for key, value in headers.items() if key.lower() == "authorization"),
+        None,
+    )
+    if authorization is not None:
+        forwarded["authorization"] = authorization
     forwarded[HTTP_BRIDGE_FORWARDED_HEADER] = "1"
     forwarded[HTTP_BRIDGE_ORIGIN_INSTANCE_HEADER] = context.origin_instance
     forwarded[HTTP_BRIDGE_TARGET_INSTANCE_HEADER] = context.target_instance
diff --git a/tests/unit/test_http_bridge_forwarding.py b/tests/unit/test_http_bridge_forwarding.py
index e5b247bd8..538da2f76 100644
--- a/tests/unit/test_http_bridge_forwarding.py
+++ b/tests/unit/test_http_bridge_forwarding.py
@@ -338,3 +338,87 @@ def post(self, url: str, **kwargs: object) -> FakeResponse:
     assert '"type":"response.failed"' in events[0]
     assert '"code":"stream_incomplete"' in events[0]
     assert captured["trust_env"] is False
+
+
+def test_build_owner_forward_headers_strips_hop_by_hop_headers() -> None:
+    payload = _payload()
+    context = HTTPBridgeForwardContext(
+        origin_instance="instance-a",
+        target_instance="instance-b",
+        codex_session_affinity=False,
+        downstream_turn_state=None,
+    )
+    inbound = {
+        "Accept": "application/json",
+        "Accept-Encoding": "gzip, deflate",
+        "Connection": "keep-alive",
+        "Content-Type": "application/json",
+        "Cookie": "session=abc",
+        "x-request-id": "req-123",
+    }
+
+    headers = build_owner_forward_headers(headers=inbound, payload=payload, context=context)
+
+    assert "Accept" not in headers
+    assert "accept" not in headers
+    assert "Accept-Encoding" not in headers
+    assert "accept-encoding" not in headers
+    assert "Connection" not in headers
+    assert "connection" not in headers
+    assert "Content-Type" not in headers
+    assert "content-type" not in headers
+    assert "Cookie" not in headers
+    assert "cookie" not in headers
+    assert headers.get("x-request-id") == "req-123"
+    assert HTTP_BRIDGE_FORWARDED_HEADER in headers
+    assert HTTP_BRIDGE_TARGET_INSTANCE_HEADER in headers
+
+
+def test_build_owner_forward_headers_preserves_authorization_strips_host() -> None:
+    payload = _payload()
+    context = HTTPBridgeForwardContext(
+        origin_instance="instance-a",
+        target_instance="instance-b",
+        codex_session_affinity=False,
+        downstream_turn_state=None,
+    )
+    inbound = {
+        "Authorization": "Bearer downstream-key",
+        "Host": "client.example.com",
+        "content-length": "42",
+        "x-openai-client-version": "1.2.3",
+    }
+
+    headers = build_owner_forward_headers(headers=inbound, payload=payload, context=context)
+
+    # The owner instance re-validates the client API key from Authorization
+    # (see _validate_internal_bridge_api_key) before swapping in its own
+    # upstream token, so the header must survive the forward.
+    assert headers.get("authorization") == "Bearer downstream-key"
+    assert "Host" not in headers
+    assert "host" not in headers
+    assert "content-length" not in headers
+    assert headers.get("x-openai-client-version") == "1.2.3"
+
+
+def test_build_owner_forward_headers_drops_connection_named_headers() -> None:
+    payload = _payload()
+    context = HTTPBridgeForwardContext(
+        origin_instance="instance-a",
+        target_instance="instance-b",
+        codex_session_affinity=False,
+        downstream_turn_state=None,
+    )
+    inbound = {
+        "Connection": "keep-alive, X-Custom-Hop",
+        "X-Custom-Hop": "drop-me",
+        "x-request-id": "req-123",
+    }
+
+    headers = build_owner_forward_headers(headers=inbound, payload=payload, context=context)
+
+    assert "X-Custom-Hop" not in headers
+    assert "x-custom-hop" not in headers
+    assert "Connection" not in headers
+    assert "connection" not in headers
+    assert headers.get("x-request-id") == "req-123"