diff --git a/hive-c0re/src/main.rs b/hive-c0re/src/main.rs
index 4c506284..81c1bdf9 100644
--- a/hive-c0re/src/main.rs
+++ b/hive-c0re/src/main.rs
@@ -88,11 +88,11 @@ enum Cmd {
         /// Keys are matched case-insensitively as a substring of the
         /// model id; models not covered fall back to the built-in
         /// estimate. Set via the `services.hyperhive.modelPrices` NixOS
-        /// option.
-        #[arg(
-            long,
-            default_value = r#"{"opus":{"input":15.0,"output":75.0,"cache_read":1.5,"cache_write":18.75},"sonnet":{"input":3.0,"output":15.0,"cache_read":0.3,"cache_write":3.75},"haiku":{"input":0.8,"output":4.0,"cache_read":0.08,"cache_write":1.0}}"#
-        )]
+        /// option (whose default carries the full opus/sonnet/haiku
+        /// table). Defaults to `{}` here so a bare `hive-c0re serve`
+        /// leans entirely on the in-code `builtin_prices` fallback —
+        /// keeping a single source of truth for the numbers.
+        #[arg(long, default_value = "{}")]
         model_prices: String,
     },
     /// Spawn a new agent container directly (`hive-agent-<name>`). Bypasses
diff --git a/nix/modules/hive-c0re.nix b/nix/modules/hive-c0re.nix
index 4ef9e2dd..9b0d7b1f 100644
--- a/nix/modules/hive-c0re.nix
+++ b/nix/modules/hive-c0re.nix
@@ -428,19 +428,19 @@ in
         lib.types.submodule {
           options = {
             input = lib.mkOption {
-              type = lib.types.float;
+              type = lib.types.numbers.nonnegative;
               description = "USD per million input tokens.";
             };
             output = lib.mkOption {
-              type = lib.types.float;
+              type = lib.types.numbers.nonnegative;
               description = "USD per million output tokens.";
             };
             cache_read = lib.mkOption {
-              type = lib.types.float;
+              type = lib.types.numbers.nonnegative;
               description = "USD per million cache-read tokens.";
             };
             cache_write = lib.mkOption {
-              type = lib.types.float;
+              type = lib.types.numbers.nonnegative;
               description = "USD per million cache-creation (write) tokens.";
             };
           };