diff --git a/src/plugin/config/updater.test.ts b/src/plugin/config/updater.test.ts
index f8ea48e..03a1205 100644
--- a/src/plugin/config/updater.test.ts
+++ b/src/plugin/config/updater.test.ts
@@ -8,14 +8,22 @@ import { OPENCODE_MODEL_DEFINITIONS } from "./models";
 describe("updateOpencodeConfig", () => {
   let tempDir: string;
   let configPath: string;
+  let originalXdgConfigHome: string | undefined;
 
   beforeEach(() => {
+    originalXdgConfigHome = process.env.XDG_CONFIG_HOME;
     // Create a temporary directory for each test
     tempDir = fs.mkdtempSync(path.join(os.tmpdir(), "opencode-test-"));
     configPath = path.join(tempDir, "opencode.json");
   });
 
   afterEach(() => {
+    if (originalXdgConfigHome === undefined) {
+      delete process.env.XDG_CONFIG_HOME;
+    } else {
+      process.env.XDG_CONFIG_HOME = originalXdgConfigHome;
+    }
+
     // Clean up temp directory
     if (fs.existsSync(tempDir)) {
       fs.rmSync(tempDir, { recursive: true, force: true });
@@ -203,6 +211,50 @@ describe("updateOpencodeConfig", () => {
     }
   });
 
+  test("parses existing jsonc config files with comments and trailing commas", async () => {
+    const jsoncPath = path.join(tempDir, "opencode.jsonc");
+    const existingJsoncConfig = `{
+  // Keep existing plugin
+  "plugin": [
+    "other-plugin",
+  ],
+  "provider": {
+    "google": {
+      "region": "us-central1",
+    },
+  },
+}`;
+    fs.writeFileSync(jsoncPath, existingJsoncConfig);
+
+    const result = await updateOpencodeConfig({ configPath: jsoncPath });
+
+    expect(result.success).toBe(true);
+    expect(result.configPath).toBe(jsoncPath);
+
+    const writtenConfig = JSON.parse(fs.readFileSync(jsoncPath, "utf-8"));
+    expect(writtenConfig.plugin).toContain("other-plugin");
+    expect(writtenConfig.plugin).toContain("opencode-antigravity-auth@latest");
+    expect(writtenConfig.provider.google.region).toBe("us-central1");
+    expect(writtenConfig.provider.google.models["antigravity-gemini-3-pro"]).toBeDefined();
+  });
+
+  test("prefers existing opencode.jsonc when using default config path", async () => {
+    const opencodeDir = path.join(tempDir, "opencode");
+    const jsonPath = path.join(opencodeDir, "opencode.json");
+    const jsoncPath = path.join(opencodeDir, "opencode.jsonc");
+
+    fs.mkdirSync(opencodeDir, { recursive: true });
+    fs.writeFileSync(jsoncPath, JSON.stringify({ plugin: ["other-plugin"], provider: {} }, null, 2));
+    process.env.XDG_CONFIG_HOME = tempDir;
+
+    const result = await updateOpencodeConfig();
+
+    expect(result.success).toBe(true);
+    expect(result.configPath).toBe(jsoncPath);
+    expect(fs.existsSync(jsonPath)).toBe(false);
+    expect(fs.existsSync(jsoncPath)).toBe(true);
+  });
+
   test("creates parent directory if it does not exist", async () => {
     const nestedPath = path.join(tempDir, "nested", "dir", "opencode.json");
 
diff --git a/src/plugin/config/updater.ts b/src/plugin/config/updater.ts
index 52f6309..b13ca4d 100644
--- a/src/plugin/config/updater.ts
+++ b/src/plugin/config/updater.ts
@@ -1,7 +1,7 @@
 /**
  * OpenCode configuration file updater.
  *
- * Updates ~/.config/opencode/opencode.json with plugin models.
+ * Updates ~/.config/opencode/opencode.json(c) with plugin models.
  */
 
 import { existsSync, readFileSync, writeFileSync, mkdirSync } from "node:fs";
@@ -43,6 +43,17 @@ export interface UpdateConfigOptions {
 
 const PLUGIN_NAME = "opencode-antigravity-auth@latest";
 const SCHEMA_URL = "https://opencode.ai/config.json";
+const OPENCODE_JSON_FILENAME = "opencode.json";
+const OPENCODE_JSONC_FILENAME = "opencode.jsonc";
+
+function stripJsonCommentsAndTrailingCommas(json: string): string {
+  return json
+    .replace(
+      /\\"|"(?:\\"|[^"])*"|(\/\/.*|\/\*[\s\S]*?\*\/)/g,
+      (match: string, group: string | undefined) => (group ? "" : match)
+    )
+    .replace(/,(\s*[}\]])/g, "$1");
+}
 
 /**
  * Get the opencode config directory path.
@@ -53,10 +64,24 @@ export function getOpencodeConfigDir(): string {
 }
 
 /**
- * Get the opencode.json config file path.
+ * Get the opencode config file path.
+ *
+ * Prefers opencode.jsonc when present so we update the active config file
+ * instead of creating a new opencode.json.
  */
 export function getOpencodeConfigPath(): string {
-  return join(getOpencodeConfigDir(), "opencode.json");
+  const configDir = getOpencodeConfigDir();
+  const jsoncPath = join(configDir, OPENCODE_JSONC_FILENAME);
+  const jsonPath = join(configDir, OPENCODE_JSON_FILENAME);
+
+  if (existsSync(jsoncPath)) {
+    return jsoncPath;
+  }
+  if (existsSync(jsonPath)) {
+    return jsonPath;
+  }
+
+  return jsonPath;
 }
 
 // =============================================================================
@@ -64,10 +89,10 @@ export function getOpencodeConfigPath(): string {
 // =============================================================================
 
 /**
- * Updates the opencode.json configuration file with plugin models.
+ * Updates the opencode configuration file with plugin models.
  *
  * This function:
- * 1. Reads existing opencode.json (or creates default structure)
+ * 1. Reads existing opencode.json/opencode.jsonc (or creates default structure)
  * 2. Replaces `provider.google.models` with plugin models
  * 3. Writes back to disk with proper formatting
  *
@@ -90,7 +115,7 @@ export async function updateOpencodeConfig(
     // Read existing config or create default
     if (existsSync(configPath)) {
       const content = readFileSync(configPath, "utf-8");
-      config = JSON.parse(content) as OpencodeConfig;
+      config = JSON.parse(stripJsonCommentsAndTrailingCommas(content)) as OpencodeConfig;
     } else {
       // Create default config structure
       config = {
diff --git a/src/plugin/ui/auth-menu.ts b/src/plugin/ui/auth-menu.ts
index 554ba93..5476983 100644
--- a/src/plugin/ui/auth-menu.ts
+++ b/src/plugin/ui/auth-menu.ts
@@ -54,7 +54,7 @@ export async function showAuthMenu(accounts: AccountInfo[]): Promise<AuthMenuAct
     { label: 'Add new account', value: { type: 'add' } },
     { label: 'Check quotas', value: { type: 'check' } },
     { label: 'Manage accounts (enable/disable)', value: { type: 'manage' } },
-    { label: 'Configure models in opencode.json', value: { type: 'configure-models' } },
+    { label: 'Configure models in opencode config', value: { type: 'configure-models' } },
 
     ...accounts.map(account => {
       const badge = getStatusBadge(account.status);