feat: make Rivet endpoint optional for self-hosted runtime

RIVET_ENDPOINT and RIVET_PUBLIC_ENDPOINT are now optional in the agent
env schema; empty strings are coerced to undefined. The agent runtime
only passes an endpoint override to the Rivet client when one is set,
so the client falls back to its default (suitable for self-hosted
Rivet where no explicit endpoint is required).

packages/agents/src/runtime/agent-os.ts

@@ -80,9 +80,10 @@ export const executeAgentOsAttempt = async (
       decodeWorkAttemptExecutionInput(rawInput)
     );
     const env = parseAgentEnv(process.env);
+    const endpoint = env.RIVET_PUBLIC_ENDPOINT ?? env.RIVET_ENDPOINT;
     const client = createClient<typeof runtimeRegistry>({
       disableMetadataLookup: true,
-      endpoint: env.RIVET_PUBLIC_ENDPOINT ?? env.RIVET_ENDPOINT,
+      ...(endpoint ? { endpoint } : {}),
     });
     const vm = client.workspace.getOrCreate([input.workspaceKey], {
       params: { token: env.RIVET_WORKSPACE_TOKEN },
@@ -243,9 +244,10 @@ export const cancelAgentOsAttempt = async (
   attemptId: string
 ) => {
   const env = parseAgentEnv(process.env);
+  const endpoint = env.RIVET_PUBLIC_ENDPOINT ?? env.RIVET_ENDPOINT;
   const client = createClient<typeof runtimeRegistry>({
     disableMetadataLookup: true,
-    endpoint: env.RIVET_PUBLIC_ENDPOINT ?? env.RIVET_ENDPOINT,
+    ...(endpoint ? { endpoint } : {}),
   });
   await client.workspace
     .getOrCreate([workspaceKey], {

packages/env/src/agent.ts

@@ -14,8 +14,14 @@ const agentEnvSchema = z.object({
   GITEA_TOKEN: z.string().min(1).optional(),
   GITEA_URL: z.url().default("https://git.openputer.com"),
   OPENROUTER_API_KEY: z.string().min(1).optional(),
-  RIVET_ENDPOINT: z.url(),
-  RIVET_PUBLIC_ENDPOINT: z.url().optional(),
+  RIVET_ENDPOINT: z.preprocess(
+    (value) => (value === "" ? undefined : value),
+    z.url().optional()
+  ),
+  RIVET_PUBLIC_ENDPOINT: z.preprocess(
+    (value) => (value === "" ? undefined : value),
+    z.url().optional()
+  ),
   RIVET_WORKSPACE_TOKEN: z.string().min(32),
   ZOPU_SOURCE_REPOSITORY: z.string().min(1).default("/opt/zopu-source"),
 });