diff --git a/pathwaysutils/experimental/shared_pathways_service/isc_pathways.py b/pathwaysutils/experimental/shared_pathways_service/isc_pathways.py
index 9af27e4..7c65132 100644
--- a/pathwaysutils/experimental/shared_pathways_service/isc_pathways.py
+++ b/pathwaysutils/experimental/shared_pathways_service/isc_pathways.py
@@ -48,21 +48,30 @@ class ProxyOptions:
     use_insecure_credentials: Whether to use insecure gRPC credentials for the
       proxy server.
     xla_flags: A list of XLA flags to pass to the proxy server.
+    sidecar_name: The name of the colocated Python sidecar to register with the
+      proxy. When set (e.g. to "external"), the proxy passes
+      ``--sidecar_name=<value>`` so that ``jax.experimental.colocated_python``
+      can reach the sidecar containers running on the worker pods.  Leave as
+      ``None`` when no sidecar is deployed.
   """
   use_insecure_credentials: bool = False
   xla_flags: list[str] = dataclasses.field(default_factory=list)
+  sidecar_name: str | None = None
 
   @classmethod
   def from_list(cls, options: Iterable[str] | None) -> "ProxyOptions":
     """Creates a ProxyOptions object from a list of 'key:value' strings."""
     use_insecure = False
     xla_flags = []
+    sidecar_name = None
     for option in options or []:
       if ":" in option:
         key, value = option.split(":", 1)
         key_strip = key.strip().lower()
         if key_strip == "use_insecure_credentials":
           use_insecure = value.strip().lower() == "true"
+        elif key.strip().lower() == "sidecar_name":
+          sidecar_name = value.strip()
         elif key_strip == "xla_flags":
           val_strip = value.strip()
           if (
@@ -78,7 +87,10 @@ def from_list(cls, options: Iterable[str] | None) -> "ProxyOptions":
     if xla_flags:
       validators.validate_xla_flags(xla_flags)
 
-    return cls(use_insecure_credentials=use_insecure, xla_flags=xla_flags)
+    return cls(
+        use_insecure_credentials=use_insecure, xla_flags=xla_flags,
+        sidecar_name=sidecar_name,
+    )
 
 
 def _deploy_pathways_proxy_server(
@@ -134,6 +146,12 @@ def _deploy_pathways_proxy_server(
     )
     proxy_args_str = "\n" + proxy_args_str
 
+  sidecar_args_str = ""
+  if proxy_options.sidecar_name:
+    sidecar_args_str = (
+        f"- --sidecar_name={proxy_options.sidecar_name}"
+    )
+
   template = string.Template(yaml_template)
   substituted_yaml = template.substitute(
       PROXY_JOB_NAME=proxy_job_name,
@@ -145,6 +163,7 @@ def _deploy_pathways_proxy_server(
       PROXY_SERVER_IMAGE=proxy_server_image,
       PROXY_ENV=proxy_env_str,
       PROXY_ARGS=proxy_args_str,
+      SIDECAR_ARGS=sidecar_args_str,
   )
 
   _logger.info("Deploying Pathways proxy: %s", proxy_job_name)
diff --git a/pathwaysutils/experimental/shared_pathways_service/yamls/pw-proxy.yaml b/pathwaysutils/experimental/shared_pathways_service/yamls/pw-proxy.yaml
index e0ee244..6a55e8c 100644
--- a/pathwaysutils/experimental/shared_pathways_service/yamls/pw-proxy.yaml
+++ b/pathwaysutils/experimental/shared_pathways_service/yamls/pw-proxy.yaml
@@ -21,6 +21,7 @@ spec:
         - --resource_manager_address=${PATHWAYS_HEAD_HOSTNAME}:${PATHWAYS_HEAD_PORT}
         - --gcs_scratch_location=${GCS_SCRATCH_LOCATION}
         - --virtual_slices=${EXPECTED_INSTANCES}${PROXY_ARGS}
+        ${SIDECAR_ARGS}
         env:
 ${PROXY_ENV}
         ports: