diff --git a/modules/programs/opencode.nix b/modules/programs/opencode.nix
index 62a728653..92a28fd7e 100644
--- a/modules/programs/opencode.nix
+++ b/modules/programs/opencode.nix
@@ -39,6 +39,7 @@ in
       description = ''
         Configuration written to {file}`$XDG_CONFIG_HOME/opencode/config.json`.
         See <https://opencode.ai/docs/config/> for the documentation.
+        '"$schema": "https://opencode.ai/config.json"' is automatically added to the config.
       '';
     };
     rules = lib.mkOption {
@@ -79,7 +80,12 @@ in
 
     xdg.configFile = {
       "opencode/config.json" = mkIf (cfg.settings != { }) {
-        source = jsonFormat.generate "config.json" cfg.settings;
+        source = jsonFormat.generate "config.json" (
+          {
+            "$schema" = "https://opencode.ai/config.json";
+          }
+          // cfg.settings
+        );
       };
       "opencode/AGENTS.md" = mkIf (cfg.rules != "") {
         text = cfg.rules;
diff --git a/tests/modules/programs/opencode/config.json b/tests/modules/programs/opencode/config.json
index 5e8f692ca..2ff8e5e1e 100644
--- a/tests/modules/programs/opencode/config.json
+++ b/tests/modules/programs/opencode/config.json
@@ -1,4 +1,5 @@
 {
+  "$schema": "https://opencode.ai/config.json",
   "autoshare": false,
   "autoupdate": true,
   "model": "anthropic/claude-sonnet-4-20250514",