Feat: Decouple Model Definitions using Host config Hook

packages/opencode/src/plugin.ts

@@ -1464,7 +1464,7 @@ export const createAntigravityPlugin = (providerId: string) => async (
 
   return {
     config: async (opencodeConfig: Record<string, unknown>) => {
-      applyAntigravityProviderCatalog(opencodeConfig, providerId);
+      applyAntigravityProviderCatalog(opencodeConfig, providerId, config);
       const mutableConfig = opencodeConfig as Record<string, unknown> & {
         command?: Record<string, unknown>;
       };
@@ -3851,16 +3851,29 @@ type OpencodeMutableConfig = Record<string, unknown> & {
   }>;
 };
 
-function applyAntigravityProviderCatalog(config: Record<string, unknown>, providerId: string): void {
-  const mutableConfig = config as OpencodeMutableConfig;
+function applyAntigravityProviderCatalog(
+  opencodeConfig: Record<string, unknown>,
+  providerId: string,
+  pluginConfig: AntigravityConfig
+): void {
+  const mutableConfig = opencodeConfig as OpencodeMutableConfig;
   mutableConfig.provider ??= {};
 
   const providerConfig = mutableConfig.provider[providerId] ?? {};
+
+  // Merge order (lowest to highest priority):
+  // 1. Built-in defaults: OPENCODE_MODEL_DEFINITIONS
+  // 2. Decoupled models (from antigravity.json / antigravity-models.json): pluginConfig.models
+  // 3. User's main opencode.json models (preserves backwards compatibility / custom overrides)
   providerConfig.models = {
-    ...(providerConfig.models ?? {}),
     ...OPENCODE_MODEL_DEFINITIONS,
+    ...(pluginConfig.models ?? {}),
+    ...(providerConfig.models ?? {}),
   };
-  providerConfig.whitelist = getAntigravityOpencodeModelIds();
+
+  // Whitelist should be the union of all registered models so they aren't pruned by OpenCode
+  providerConfig.whitelist = Object.keys(providerConfig.models);
+
   mutableConfig.provider[providerId] = providerConfig;
 }
 

packages/opencode/src/plugin/config/loader.ts

@@ -112,12 +112,56 @@ function mergeConfigs(
 // Main Loader
 // =============================================================================
 
-/**
- * Load the complete configuration.
- * 
- * @param directory - The project directory (for project-level config)
- * @returns Fully resolved configuration
- */
+function stripJsonCommentsAndTrailingCommas(json: string): string {
+  return json
+    .replace(
+      /\\"|"(?:\\"|[^"])*"|(\/\/.*|\/\*[\s\S]*?\*\/)/g,
+      (match: string, group: string | undefined) => (group ? "" : match)
+    )
+    .replace(/,(\s*[}\]])/g, "$1");
+}
+
+function loadModelsFile(path: string): Record<string, any> | null {
+  try {
+    if (!existsSync(path)) {
+      return null;
+    }
+    const content = readFileSync(path, "utf-8");
+    const parsed = JSON.parse(stripJsonCommentsAndTrailingCommas(content));
+    if (parsed && typeof parsed === "object" && !Array.isArray(parsed)) {
+      return parsed;
+    }
+    return null;
+  } catch (error) {
+    log.warn("Failed to load decoupled models file", { path, error: String(error) });
+    return null;
+  }
+}
+
+export function loadDecoupledModels(directory: string): Record<string, any> {
+  let mergedModels: Record<string, any> = {};
+
+  const configDir = getConfigDir();
+  const userJsonPath = join(configDir, "antigravity-models.json");
+  const userJsoncPath = join(configDir, "antigravity-models.jsonc");
+  const projectJsonPath = join(directory, ".opencode", "antigravity-models.json");
+  const projectJsoncPath = join(directory, ".opencode", "antigravity-models.jsonc");
+
+  // User level (prefer jsonc if both exist)
+  const userModels = loadModelsFile(existsSync(userJsoncPath) ? userJsoncPath : userJsonPath);
+  if (userModels) {
+    mergedModels = { ...mergedModels, ...userModels };
+  }
+
+  // Project level (prefer jsonc if both exist) - overrides user level
+  const projectModels = loadModelsFile(existsSync(projectJsoncPath) ? projectJsoncPath : projectJsonPath);
+  if (projectModels) {
+    mergedModels = { ...mergedModels, ...projectModels };
+  }
+
+  return mergedModels;
+}
+
 export function loadConfig(directory: string): AntigravityConfig {
   // Start with defaults
   let config: AntigravityConfig = { ...DEFAULT_CONFIG };
@@ -136,6 +180,15 @@ export function loadConfig(directory: string): AntigravityConfig {
     config = mergeConfigs(config, projectConfig);
   }
 
+  // Load decoupled models from antigravity-models.json(c) and merge into config.models
+  const decoupledModels = loadDecoupledModels(directory);
+  if (Object.keys(decoupledModels).length > 0) {
+    config.models = {
+      ...(config.models ?? {}),
+      ...decoupledModels,
+    };
+  }
+
   return config;
 }
 

packages/opencode/src/plugin/config/schema.ts

@@ -503,6 +503,11 @@ export const AntigravityConfigSchema = z.object({
    */
   auto_update: z.boolean().default(true),
 
+  /**
+   * Decoupled model definitions to inject.
+   */
+  models: z.record(z.string(), z.any()).optional(),
+
 });
 
 export type AntigravityConfig = z.infer<typeof AntigravityConfigSchema>;