diff --git a/docker/devenv/defaults.env b/docker/devenv/defaults.env
index a41ae2c577..70368b3c64 100644
--- a/docker/devenv/defaults.env
+++ b/docker/devenv/defaults.env
@@ -48,6 +48,8 @@ PENPOT_PUBLIC_HTTP_PORT=3449
 PENPOT_MCP_SERVER_PORT=4401
 PENPOT_MCP_REPL_PORT=4403
 
+SHADOW_SERVER_URL=wss://localhost:3449
+
 # Serena (agentic devenv). These are the published host ports for ws0; ws1+
 # offset them by 10000*N. The container-internal ports (Serena MCP 14281,
 # dashboard 24282) are fixed by Serena and mapped to these in compose.
diff --git a/docker/devenv/docker-compose.main.yml b/docker/devenv/docker-compose.main.yml
index 1ea9858c66..fb8caf78c7 100644
--- a/docker/devenv/docker-compose.main.yml
+++ b/docker/devenv/docker-compose.main.yml
@@ -88,6 +88,7 @@ services:
       # Agentic devenv: set to a commit/tag to update Serena on startup,
       # leave empty to skip update and use the version baked into the image.
       - SERENA_UPDATE_VERSION=1.5.0
+      - SHADOW_SERVER_URL=${SHADOW_SERVER_URL}
 
     networks:
       - default
diff --git a/frontend/shadow-cljs.edn b/frontend/shadow-cljs.edn
index f596a34e19..15b4356387 100644
--- a/frontend/shadow-cljs.edn
+++ b/frontend/shadow-cljs.edn
@@ -11,7 +11,7 @@
    :asset-path "/js"
    :devtools {:watch-dir "resources/public"
               :reload-strategy :full
-              :server-url #shadow/env ["SHADOW_SERVER_URL" :default ""]}
+              :devtools-url #shadow/env ["SHADOW_SERVER_URL" :default ""]}
    :build-options {:manifest-name "manifest.json"}
    :modules
    {:shared
@@ -87,7 +87,7 @@
   {:target :browser
    :output-dir "resources/public/js/worker/"
    :asset-path "/js/worker"
-   :devtools {:server-url #shadow/env ["SHADOW_SERVER_URL" :default ""]
+   :devtools {:devtools-url #shadow/env ["SHADOW_SERVER_URL" :default ""]
               :browser-inject :main
               :watch-dir "resources/public"
               :reload-strategy :full}
diff --git a/manage.sh b/manage.sh
index 605cd5e0ef..89f8015c0e 100755
--- a/manage.sh
+++ b/manage.sh
@@ -322,7 +322,8 @@ function instance-env-overrides {
         "PENPOT_MCP_REPL_PORT=${mcp_repl}" \
         "SERENA_EXTERNAL_PORT=${serena}" \
         "SERENA_DASHBOARD_EXTERNAL_PORT=${serena_dash}" \
-        "PENPOT_BACKEND_WORKER=false"
+        "PENPOT_BACKEND_WORKER=false" \
+        "SHADOW_SERVER_URL=wss://localhost:${public}"
 }
 
 # Thin wrappers around .devenv/scripts/merge-mcp-config.py. The script does