diff --git a/README.md b/README.md
index b79b920..9c47b57 100644
--- a/README.md
+++ b/README.md
@@ -364,7 +364,7 @@ The output looks like:
 | `~/.codex/config.toml` | Codex |
 | `~/.claude/settings.json` | Claude Code |
 | `~/.gemini/.env` | Gemini CLI |
-| `~/.config/opencode/opencode.json` | OpenCode |
+| `~/.ucode/opencode-xdg/opencode/opencode.json` | OpenCode — a config layer above your own `~/.config/opencode/opencode.json`, which OpenCode still reads |
 | `~/.copilot/.env` | GitHub Copilot CLI |
 | `~/.pi/agent/models.json` | Pi |
 | `~/.cursor/mcp.json` | Cursor Agent (MCP servers only) |
diff --git a/src/ucode/agents/opencode.py b/src/ucode/agents/opencode.py
index 19adff7..c091068 100644
--- a/src/ucode/agents/opencode.py
+++ b/src/ucode/agents/opencode.py
@@ -25,8 +25,11 @@
 from ucode.state import mark_tool_managed, save_state
 from ucode.telemetry import agent_version, ucode_version
 
-OPENCODE_XDG_CONFIG_HOME = APP_DIR / "opencode-xdg"
-OPENCODE_CONFIG_DIR = OPENCODE_XDG_CONFIG_HOME / "opencode"
+# ucode keeps its config outside `~/.config/opencode` so it never writes to the
+# user's own config. The `opencode-xdg` directory name is historical: ucode used
+# to export it as XDG_CONFIG_HOME. The path stays as it is so MCP servers that
+# `ucode mcp add` already registered survive an upgrade.
+OPENCODE_CONFIG_DIR = APP_DIR / "opencode-xdg" / "opencode"
 OPENCODE_CONFIG_PATH = OPENCODE_CONFIG_DIR / "opencode.json"
 OPENCODE_BACKUP_PATH = APP_DIR / "opencode-config.backup.json"
 
@@ -260,7 +263,15 @@ def _refresh_forever(state: dict, stop_event: threading.Event) -> None:
 def build_runtime_env(token: str, state: dict | None = None) -> dict[str, str]:
     env = os.environ.copy()
     env["OAUTH_TOKEN"] = token
-    env["XDG_CONFIG_HOME"] = str(OPENCODE_XDG_CONFIG_HOME)
+    # Name the config file instead of a redirect of XDG_CONFIG_HOME. A redirect
+    # hides all of `~/.config/opencode`: permissions, the user's MCP servers,
+    # `disabled_providers`, global skills, agents, commands, plugins, tui.json
+    # and the global AGENTS.md. OPENCODE_CONFIG is a layer above the user's
+    # global config, and opencode merges the layers — it does not replace them.
+    # Objects merge one key at a time and the later scalar wins, so ucode keeps
+    # control of `model` and `provider`. Do not put a top-level array in this
+    # file: opencode replaces an array, it does not merge it.
+    env["OPENCODE_CONFIG"] = str(OPENCODE_CONFIG_PATH)
     return env
 
 
diff --git a/tests/test_agent_opencode.py b/tests/test_agent_opencode.py
index c83e845..786d5b1 100644
--- a/tests/test_agent_opencode.py
+++ b/tests/test_agent_opencode.py
@@ -3,6 +3,7 @@
 from __future__ import annotations
 
 import json
+from pathlib import Path
 from unittest.mock import patch
 
 from ucode.agents import opencode
@@ -28,10 +29,9 @@ def test_package(self):
     def test_display(self):
         assert opencode.SPEC["display"] == "OpenCode"
 
-    def test_config_path_is_under_ucode_xdg_home(self):
-        assert opencode.SPEC["config_path"] == (
-            opencode.OPENCODE_XDG_CONFIG_HOME / "opencode" / "opencode.json"
-        )
+    def test_config_path_is_outside_the_user_config_dir(self):
+        assert opencode.SPEC["config_path"] == opencode.OPENCODE_CONFIG_DIR / "opencode.json"
+        assert Path.home() / ".config" not in opencode.OPENCODE_CONFIG_PATH.parents
 
 
 class TestRenderOverlay:
@@ -307,10 +307,27 @@ def test_sets_oauth_token_for_mcp(self):
 
         assert env["OAUTH_TOKEN"] == "tok"
 
-    def test_sets_ucode_xdg_config_home(self):
+    def test_names_the_ucode_config_file(self):
+        env = opencode.build_runtime_env("tok")
+
+        assert env["OPENCODE_CONFIG"] == str(opencode.OPENCODE_CONFIG_PATH)
+
+    # A redirect of XDG_CONFIG_HOME hides the whole of ~/.config/opencode:
+    # permissions, the user's MCP servers, skills, agents and tui.json. So ucode
+    # must neither add the variable nor overwrite the value the user set.
+    def test_passes_the_users_xdg_config_home_through(self, monkeypatch):
+        monkeypatch.setenv("XDG_CONFIG_HOME", "/sentinel/xdg")
+
+        env = opencode.build_runtime_env("tok")
+
+        assert env["XDG_CONFIG_HOME"] == "/sentinel/xdg"
+
+    def test_adds_no_xdg_config_home(self, monkeypatch):
+        monkeypatch.delenv("XDG_CONFIG_HOME", raising=False)
+
         env = opencode.build_runtime_env("tok")
 
-        assert env["XDG_CONFIG_HOME"] == str(opencode.OPENCODE_XDG_CONFIG_HOME)
+        assert "XDG_CONFIG_HOME" not in env
 
 
 class TestOpencodeDefaultModel:
diff --git a/tests/test_e2e.py b/tests/test_e2e.py
index 01127a1..90711cc 100644
--- a/tests/test_e2e.py
+++ b/tests/test_e2e.py
@@ -784,12 +784,14 @@ def test_launch_opencode_per_model(
             pytest.skip("No OpenCode models available on this workspace")
 
         monkeypatch.setattr(config_io_mod, "APP_DIR", tmp_path)
-        xdg = tmp_path / "opencode-xdg"
-        config_path = xdg / "opencode" / "opencode.json"
+        config_path = tmp_path / "opencode-xdg" / "opencode" / "opencode.json"
         backup_path = tmp_path / "opencode-config.backup.json"
-        monkeypatch.setattr(opencode, "OPENCODE_XDG_CONFIG_HOME", xdg)
         monkeypatch.setattr(opencode, "OPENCODE_CONFIG_PATH", config_path)
         monkeypatch.setattr(opencode, "OPENCODE_BACKUP_PATH", backup_path)
+        # ucode no longer redirects XDG_CONFIG_HOME, so the spawned opencode
+        # would read the developer's own ~/.config/opencode. Send it to an empty
+        # directory to keep the test hermetic.
+        monkeypatch.setenv("XDG_CONFIG_HOME", str(tmp_path / "empty-xdg"))
 
         import sys
         import time
@@ -863,11 +865,11 @@ def test_launch_deepseek_v4_pro(
 
         monkeypatch.setattr(config_io_mod, "APP_DIR", tmp_path)
         xdg = tmp_path / "opencode-xdg"
-        monkeypatch.setattr(opencode, "OPENCODE_XDG_CONFIG_HOME", xdg)
         monkeypatch.setattr(opencode, "OPENCODE_CONFIG_PATH", xdg / "opencode" / "opencode.json")
         monkeypatch.setattr(
             opencode, "OPENCODE_BACKUP_PATH", tmp_path / "opencode-config.backup.json"
         )
+        monkeypatch.setenv("XDG_CONFIG_HOME", str(tmp_path / "empty-xdg"))
         monkeypatch.setattr("ucode.state.save_state", lambda state: None)
         monkeypatch.setattr(
             "ucode.agents.opencode.get_databricks_token",
diff --git a/tests/test_e2e_user_agent.py b/tests/test_e2e_user_agent.py
index e6cec21..51aed1f 100644
--- a/tests/test_e2e_user_agent.py
+++ b/tests/test_e2e_user_agent.py
@@ -242,8 +242,6 @@ def test_user_agent_arrives_at_gateway(self, tmp_path, monkeypatch, capture_serv
         from ucode.agents import opencode
 
         _require_binary("opencode")
-        # Redirect via XDG_CONFIG_HOME so the spawned opencode reads from
-        # tmp_path instead of the developer's real ~/.config/opencode.
         xdg = tmp_path / "xdg"
         opencode_dir = xdg / "opencode"
         opencode_dir.mkdir(parents=True)
@@ -272,7 +270,15 @@ def test_user_agent_arrives_at_gateway(self, tmp_path, monkeypatch, capture_serv
             )
             opencode.write_tool_config(state, "test-claude-model", token="test-token")
 
-        env = {**os.environ, "OAUTH_TOKEN": "test-token", "XDG_CONFIG_HOME": str(xdg)}
+        # OPENCODE_CONFIG names ucode's file. XDG_CONFIG_HOME goes to an empty
+        # directory so the spawned opencode does not read the developer's own
+        # ~/.config/opencode.
+        env = {
+            **os.environ,
+            "OAUTH_TOKEN": "test-token",
+            "OPENCODE_CONFIG": str(config_path),
+            "XDG_CONFIG_HOME": str(tmp_path / "empty-xdg"),
+        }
         result = _run_until_first_request(opencode.validate_cmd("opencode"), env)
 
         req = capture_server.first_request_with_path_prefix("/ai-gateway/anthropic")