fix(webapp): normalize empty RUNTIME_API_ORIGIN to undefined so '??' fallback works

The docker-compose passthrough `RUNTIME_API_ORIGIN: ${RUNTIME_API_ORIGIN:-}`
resolves to an empty string when the user hasn't set it, which the nullish
coalescing chain (`env.RUNTIME_API_ORIGIN ?? env.API_ORIGIN ?? env.APP_ORIGIN`)
doesn't fall through (`??` only treats null/undefined as missing). Result was
`TRIGGER_API_URL=""` and `TRIGGER_STREAM_URL=""` reaching runner pods,
breaking their webapp connection.

Apply the normalization at the schema level via `.transform(v => v || undefined)`
so any caller (current docker-compose, future templates) is protected without
having to remember to special-case empty strings at each use site.

Also clarify in `.env.example` that this var intentionally feeds both
TRIGGER_API_URL and TRIGGER_STREAM_URL (keep all runner traffic on the same
bypass hop), and tells operators who need a dedicated stream endpoint to use
STREAM_ORIGIN instead.

Author: ThullyoCunha

apps/webapp/app/env.server.ts

@@ -127,14 +127,18 @@ const EnvironmentSchema = z
     LOGIN_RATE_LIMITS_ENABLED: BoolEnv.default(true),
     APP_ORIGIN: z.string().default("http://localhost:3030"),
     API_ORIGIN: z.string().optional(),
-    // Origin that the webapp publishes to runner pods as `TRIGGER_API_URL`.
-    // When self-hosting behind a tracing-enabled gateway (Envoy/Istio/etc.)
-    // that rewrites the W3C `traceparent` on egress, point this at an
-    // in-cluster service URL so runner-to-webapp traffic stays inside the
-    // cluster and the parent->child run link in the trace tree is preserved.
-    // Falls back to API_ORIGIN/APP_ORIGIN, so the existing behavior is
-    // unchanged when this is unset.
-    RUNTIME_API_ORIGIN: z.string().optional(),
+    // Origin that the webapp publishes to runner pods as both `TRIGGER_API_URL`
+    // and (as the first fallback) `TRIGGER_STREAM_URL`. When self-hosting
+    // behind a tracing-enabled gateway (Envoy/Istio/etc.) that rewrites the
+    // W3C `traceparent` on egress, point this at an in-cluster service URL so
+    // runner-to-webapp traffic stays inside the cluster and the parent->child
+    // run link in the trace tree is preserved. Empty string is normalized to
+    // unset so blank `${RUNTIME_API_ORIGIN:-}` passthroughs in
+    // `docker-compose.yml` don't short-circuit the `??` fallback chain.
+    RUNTIME_API_ORIGIN: z
+      .string()
+      .optional()
+      .transform((v) => v || undefined),
     STREAM_ORIGIN: z.string().optional(),
     ELECTRIC_ORIGIN: z.string().default("http://localhost:3060"),
     // A comma separated list of electric origins to shard into different electric instances by environmentId

hosting/docker/.env.example

@@ -46,10 +46,14 @@ API_ORIGIN=http://localhost:8030
 DEV_OTEL_EXPORTER_OTLP_ENDPOINT=http://localhost:8030/otel
 # You may need to set this when testing locally or when using the combined setup
 # API_ORIGIN=http://webapp:3000
-# Optional: origin advertised to runner pods as TRIGGER_API_URL. When unset,
-# runners fall back to API_ORIGIN/APP_ORIGIN. Set this to an in-cluster
-# service URL when running behind a tracing-enabled gateway that rewrites
-# the W3C `traceparent` header on egress (e.g. Envoy/Istio with tracing on).
+# Optional: origin advertised to runner pods as both TRIGGER_API_URL and
+# TRIGGER_STREAM_URL (intentional: keeps all runner traffic on the same
+# bypass hop). When unset, runners fall back to STREAM_ORIGIN/API_ORIGIN/
+# APP_ORIGIN as before. Set this to an in-cluster service URL when running
+# behind a tracing-enabled gateway that rewrites the W3C `traceparent`
+# header on egress (e.g. Envoy/Istio with tracing on). If you need streams
+# on a dedicated endpoint (CDN, etc.), keep RUNTIME_API_ORIGIN unset and
+# use STREAM_ORIGIN instead.
 # RUNTIME_API_ORIGIN=http://webapp:3000
 
 # Webapp - memory management