diff --git a/__tests__/installer-targets.test.ts b/__tests__/installer-targets.test.ts
index 27fcbd6e..39b60000 100644
--- a/__tests__/installer-targets.test.ts
+++ b/__tests__/installer-targets.test.ts
@@ -339,6 +339,42 @@ describe('Installer targets — partial-state idempotency', () => {
     expect(fs.existsSync(path.join(process.cwd(), 'AGENTS.md'))).toBe(false);
   });
 
+  it.runIf(process.platform === 'win32')('opencode: prefers ~/.config/opencode/ over %APPDATA% when it exists (#535)', () => {
+    const opencode = getTarget('opencode')!;
+    // Simulate Windows layout where APPDATA and ~/.config are different
+    // directories. On Windows, globalConfigDir() should prefer
+    // ~/.config/opencode/ (XDG-style) when it exists, matching
+    // opencode's own behavior (issue #535).
+    const tmpRoaming = fs.mkdtempSync(path.join(os.tmpdir(), 'appdata-'));
+    process.env.APPDATA = tmpRoaming;
+    const configDir = path.join(tmpHome, '.config', 'opencode');
+    fs.mkdirSync(configDir, { recursive: true });
+    const result = opencode.install('global', { autoAllow: true });
+    expect(result.files[0].action).toBe('created');
+    // Must land under ~/.config/opencode, not %APPDATA%/opencode.
+    const normalised = result.files[0].path.replace(/\\/g, '/');
+    expect(normalised).toContain('.config/opencode');
+    expect(normalised).not.toMatch(/appdata-[^/]*\/opencode\/opencode\.jsonc$/);
+    fs.rmSync(tmpRoaming, { recursive: true, force: true });
+  });
+
+  it.runIf(process.platform === 'win32')('opencode: falls back to %APPDATA% when ~/.config/opencode/ does not exist (#535)', () => {
+    const opencode = getTarget('opencode')!;
+    // When ~/.config/opencode/ is absent on Windows, globalConfigDir()
+    // must fall back to %APPDATA%/opencode/ (legacy layout).
+    const tmpRoaming = fs.mkdtempSync(path.join(os.tmpdir(), 'appdata-'));
+    process.env.APPDATA = tmpRoaming;
+    // Explicitly do NOT create ~/.config/opencode — simulates a user
+    // who has never used the XDG-style path.
+    const result = opencode.install('global', { autoAllow: true });
+    expect(result.files[0].action).toBe('created');
+    const normalised = result.files[0].path.replace(/\\/g, '/');
+    const normalisedRoaming = tmpRoaming.replace(/\\/g, '/');
+    expect(normalised).toContain(normalisedRoaming);
+    expect(normalised).not.toContain('.config');
+    fs.rmSync(tmpRoaming, { recursive: true, force: true });
+  });
+
   it('gemini: install writes settings.json (mcpServers.codegraph) and no GEMINI.md (#529)', () => {
     const gemini = getTarget('gemini')!;
     const result = gemini.install('global', { autoAllow: true });
diff --git a/src/installer/targets/opencode.ts b/src/installer/targets/opencode.ts
index 5ec97436..3d228bd2 100644
--- a/src/installer/targets/opencode.ts
+++ b/src/installer/targets/opencode.ts
@@ -2,7 +2,8 @@
  * opencode target.
  *
  *   - MCP server entry to `~/.config/opencode/opencode.jsonc` (global,
- *     XDG-style; `%APPDATA%/opencode/opencode.jsonc` on Windows) or
+ *     XDG-style; on Windows, `%APPDATA%/opencode/opencode.jsonc` when
+ *     `~/.config/opencode/` doesn't exist) or
  *     `./opencode.jsonc` (local). Falls back to `opencode.json` when a
  *     `.json` file already exists; defaults new installs to `.jsonc`
  *     because that's what opencode itself creates on first run.
@@ -49,6 +50,10 @@ import {
 
 function globalConfigDir(): string {
   if (process.platform === 'win32') {
+    // opencode itself prefers ~/.config/opencode/ when it exists on
+    // Windows, matching its POSIX behaviour (issue #535).
+    const xdgCandidate = path.join(os.homedir(), '.config', 'opencode');
+    if (fs.existsSync(xdgCandidate)) return xdgCandidate;
     const appData = process.env.APPDATA ?? path.join(os.homedir(), 'AppData', 'Roaming');
     return path.join(appData, 'opencode');
   }