Make docker_server nginx max payload size configurable

truss/base/truss_config.py

@@ -1193,6 +1193,17 @@ class DockerServer(custom_types.ConfigModel):
         default=None,
         description="Skip the build step and deploy the base image as-is. Baseten copies the image to its container registry without running docker build or modifying the image in any way.",
     )
+    max_payload_size: Optional[str] = pydantic.Field(
+        default=None,
+        description="The maximum inbound request body size for the container's reverse proxy. Accepts nginx size syntax, such as 64M, 128M, or 1G. Defaults to 64M.",
+    )
+
+    @pydantic.field_validator("max_payload_size")
+    @classmethod
+    def _validate_max_payload_size(cls, v: Optional[str]) -> Optional[str]:
+        if v is not None and not re.fullmatch(r"[0-9]+[kKmMgG]?", v):
+            raise ValueError(f"Invalid max_payload_size {v!r}.")
+        return v
 
     @pydantic.field_validator("run_as_user_id")
     @classmethod

truss/config.schema.json

@@ -415,6 +415,19 @@
           "default": null,
           "description": "Skip the build step and deploy the base image as-is. Baseten copies the image to its container registry without running docker build or modifying the image in any way.",
           "title": "No Build"
+        },
+        "max_payload_size": {
+          "anyOf": [
+            {
+              "type": "string"
+            },
+            {
+              "type": "null"
+            }
+          ],
+          "default": null,
+          "description": "The maximum inbound request body size for the container's reverse proxy. Accepts nginx size syntax, such as 64M, 128M, or 1G. Defaults to 64M.",
+          "title": "Max Payload Size"
         }
       },
       "required": [

truss/contexts/image_builder/serving_image_builder.py

@@ -458,7 +458,9 @@ def generate_docker_server_nginx_config(build_dir, config):
         readiness_endpoint=config.docker_server.readiness_endpoint,
         liveness_endpoint=config.docker_server.liveness_endpoint,
         server_port=config.docker_server.server_port,
-        client_max_body_size=TRUSSLESS_MAX_PAYLOAD_SIZE,
+        client_max_body_size=config.docker_server.max_payload_size
+        if config.docker_server.max_payload_size is not None
+        else TRUSSLESS_MAX_PAYLOAD_SIZE,
         transport_kind=config.runtime.transport.kind,
     )
     nginx_filepath = build_dir / "proxy.conf"

truss/tests/contexts/image_builder/test_serving_image_builder.py

@@ -1033,14 +1033,22 @@ class MockConfig:
         assert cfg.has_section("eventlistener:quit_on_failure")
 
 
-def test_nginx_config_disables_disk_writes(tmp_path):
+@pytest.mark.parametrize(
+    "max_payload_size,expected_max_payload_size", [(None, "64M"), ("128M", "128M")]
+)
+def test_nginx_config_disables_disk_writes(
+    tmp_path, max_payload_size, expected_max_payload_size
+):
     """Test that nginx configuration disables all disk writes."""
 
     class MockDockerServer:
         predict_endpoint = "/predict"
         readiness_endpoint = "/readiness"
         liveness_endpoint = "/health"
         server_port = 8090
+        max_payload_size = None
+
+    MockDockerServer.max_payload_size = max_payload_size
 
     class MockTransport:
         kind = "http"
@@ -1060,6 +1068,7 @@ class MockConfig:
     # Verify logging is disabled
     assert "access_log off;" in nginx_config
     assert "error_log /dev/null;" in nginx_config
+    assert f"client_max_body_size {expected_max_payload_size};" in nginx_config
 
     # Verify temp paths use /dev/shm (in-memory filesystem)
     assert "client_body_temp_path /dev/shm/nginx_client_temp;" in nginx_config

truss/tests/test_config.py

@@ -1421,6 +1421,20 @@ def test_docker_server_run_as_user_id(run_as_user_id, expected, raises):
         assert docker_server.run_as_user_id == expected
 
 
+def test_docker_server_invalid_max_payload_size():
+    with pytest.raises(
+        pydantic.ValidationError, match="Invalid max_payload_size '64MB'"
+    ):
+        DockerServer(
+            start_command="python main.py",
+            server_port=8000,
+            predict_endpoint="/predict",
+            readiness_endpoint="/health",
+            liveness_endpoint="/health",
+            max_payload_size="64MB",
+        )
+
+
 # =============================================================================
 # Weights Configuration Tests
 # =============================================================================