diff --git a/src/skillspector/providers/_agent_cli.py b/src/skillspector/providers/_agent_cli.py
index a2f9e02b0..7d2a44319 100644
--- a/src/skillspector/providers/_agent_cli.py
+++ b/src/skillspector/providers/_agent_cli.py
@@ -503,7 +503,10 @@ def _prepare_opencode_env(
     independently as defense in depth.
 
     The real OpenCode authentication store remains available so this CLI
-    provider can use the user's existing login. All mutable config, cache,
+    provider can use the user's existing login. OpenCode's internal plugins stay
+    enabled for the same reason: they implement the OAuth logins (ChatGPT,
+    Copilot, GitLab, ...) and register no tools. External plugins remain off
+    through ``--pure`` / ``OPENCODE_PURE``. All mutable config, cache,
     state, database, and temporary paths are redirected below the invocation's
     already-isolated temporary root.
     """
@@ -536,7 +539,6 @@ def _prepare_opencode_env(
             "OPENCODE_DISABLE_AUTOCOMPACT": "1",
             "OPENCODE_DISABLE_AUTOUPDATE": "1",
             "OPENCODE_DISABLE_CLAUDE_CODE": "1",
-            "OPENCODE_DISABLE_DEFAULT_PLUGINS": "1",
             "OPENCODE_DISABLE_EXTERNAL_SKILLS": "1",
             "OPENCODE_DISABLE_LSP_DOWNLOAD": "1",
             "OPENCODE_DISABLE_MODELS_FETCH": "1",
@@ -674,7 +676,9 @@ def _build_opencode_argv(binary: str, model: str, max_output_tokens: int = 0) ->
         SKILLSPECTOR_MODEL is set).
 
     The shared runner also isolates every OpenCode config/state path, disables
-    ambient instructions, skills, plugins, auto-sharing, snapshots and updates,
+    ambient instructions, skills, external plugins (the internal OAuth/provider
+    plugins stay enabled, see ``_prepare_opencode_env``), auto-sharing,
+    snapshots and updates,
     scrubs secret-bearing environment variables, delivers untrusted content
     via stdin only, and never passes ``--auto``.
 
diff --git a/tests/provider/test_opencode_cli.py b/tests/provider/test_opencode_cli.py
index 1271f4b16..9028c4e8b 100644
--- a/tests/provider/test_opencode_cli.py
+++ b/tests/provider/test_opencode_cli.py
@@ -302,6 +302,8 @@ def test_policy_overrides_hostile_ambient_configuration(self, tmp_path: Path) ->
             "OPENCODE_CONFIG_CONTENT": '{"permission":"allow","share":"auto"}',
             "OPENCODE_PERMISSION": '{"*":"allow"}',
             "OPENCODE_EXPERIMENTAL": "1",
+            # An ambient value must not switch the OAuth login plugins back off (#809).
+            "OPENCODE_DISABLE_DEFAULT_PLUGINS": "1",
         }
 
         argv = _build_opencode_argv(OPENCODE_BINARY, "", 0)
@@ -317,7 +319,10 @@ def test_policy_overrides_hostile_ambient_configuration(self, tmp_path: Path) ->
         assert config["autoshare"] is False
         assert env["OPENCODE_AUTO_SHARE"] == "0"
         assert env["OPENCODE_DISABLE_PROJECT_CONFIG"] == "1"
-        assert env["OPENCODE_DISABLE_DEFAULT_PLUGINS"] == "1"
+        # Internal plugins carry the OAuth logins (ChatGPT, Copilot, ...) and
+        # register no tools; disabling them breaks the user's login (#809).
+        # External plugins stay off through OPENCODE_PURE below.
+        assert "OPENCODE_DISABLE_DEFAULT_PLUGINS" not in env
         assert env["OPENCODE_DISABLE_EXTERNAL_SKILLS"] == "1"
         assert env["OPENCODE_DISABLE_CLAUDE_CODE"] == "1"
         assert env["OPENCODE_PURE"] == "1"