diff --git a/apps/penpal/justfile b/apps/penpal/justfile
index 58a14dec..4435388c 100644
--- a/apps/penpal/justfile
+++ b/apps/penpal/justfile
@@ -3,6 +3,15 @@ default: dev
 
 export PATH := env_var_or_default("CARGO_HOME", env_var("HOME") + "/.cargo") + "/bin:" + env_var("PATH")
 
+# Check that Block's internal network is reachable (requires Warp to be connected)
+_check-warp:
+    #!/usr/bin/env bash
+    if ! curl -sf --max-time 5 --head https://global.block-artifacts.com -o /dev/null 2>/dev/null; then
+        echo "Error: Block's internal network is unreachable." >&2
+        echo "Turn on Warp before running this command." >&2
+        exit 1
+    fi
+
 # Ensure required tools are installed
 ensure-deps:
     #!/usr/bin/env bash
@@ -40,7 +49,7 @@ build-go: ensure-deps
     ./scripts/build-go.sh
 
 # Install Penpal: build dev-branded desktop app and copy to /Applications
-install: ensure-deps build-go
+install: _check-warp ensure-deps build-go
     #!/usr/bin/env bash
     set -euo pipefail