diff --git a/src/server/desktop_serve.py b/src/server/desktop_serve.py
index e2525e17..8b32652f 100644
--- a/src/server/desktop_serve.py
+++ b/src/server/desktop_serve.py
@@ -151,10 +151,12 @@ async def config(request: Request) -> Response:
                                     status_code=400)
             # The renderer wraps the payload as {"config": {...}}
             # (saveClawCodexConfig); accept the bare object too.
-            incoming = body.get("config") if isinstance(body.get("config"), dict) else body
-            return JSONResponse(_save_config_merged(incoming))
+            return JSONResponse(_save_config_merged(unwrap_config_envelope(body)))
 
-        return JSONResponse(redact_secrets(load_config()))
+        # Strip a stale envelope on the way out too, so a config that already
+        # picked one up can't be round-tripped straight back by the renderer's
+        # whole-record autosave.
+        return JSONResponse(redact_secrets(strip_config_envelope(load_config())))
 
     def _int_param(request: Request, name: str, default: int) -> int:
         try:
@@ -510,6 +512,35 @@ async def not_found(request: Request) -> Response:
     return Starlette(routes=routes)
 
 
+# ``config`` is not a key in the config schema — the file holds
+# default_provider / providers / session / settings / env / projects / … at the
+# top level. So a ``config`` key can only be a transport envelope that got
+# stored by mistake, and treating it as data is what let one escape into
+# ~/.clawcodex/config.json: the renderer autosaves the WHOLE record it last
+# read, so a single mis-nested write is copied forward on every later save.
+# It then shadows real settings — a voice/STT block written into the envelope
+# is invisible to the backend, which reads the top level.
+
+
+def unwrap_config_envelope(body: dict[str, Any]) -> dict[str, Any]:
+    """``{"config": {...}}`` → the record. Idempotent, and unwraps repeats.
+
+    A double wrap is the shape that does the damage: unwrapping once leaves a
+    ``config`` key that then merges in as data.
+    """
+    record = body
+    while isinstance(record, dict) and isinstance(record.get("config"), dict):
+        record = record["config"]
+    return record if isinstance(record, dict) else {}
+
+
+def strip_config_envelope(record: dict[str, Any]) -> dict[str, Any]:
+    """Drop a stored envelope key. Returns the same object when there is none."""
+    if not isinstance(record, dict) or "config" not in record:
+        return record
+    return {k: v for k, v in record.items() if k != "config"}
+
+
 def _save_config_merged(incoming: dict[str, Any]) -> dict[str, Any]:
     """Deep-merge the (secret-redacted) incoming config over the stored global
     config and persist it.
@@ -525,8 +556,11 @@ def _save_config_merged(incoming: dict[str, Any]) -> dict[str, Any]:
     try:
         manager = _get_default_manager()
         current = manager.load_global()
-        merged = _deep_merge(current, incoming)
-        manager.save_global(merged)
+        merged = _deep_merge(current, strip_config_envelope(incoming))
+        # `_deep_merge` only ever adds, so an envelope already on disk would
+        # outlive every future save. Dropping it here repairs a config that
+        # picked one up, on the next write, without a migration step.
+        manager.save_global(strip_config_envelope(merged))
         manager.invalidate()
         return {"ok": True}
     except Exception as exc:  # noqa: BLE001
diff --git a/tests/server/test_desktop_config_envelope.py b/tests/server/test_desktop_config_envelope.py
new file mode 100644
index 00000000..aa505d17
--- /dev/null
+++ b/tests/server/test_desktop_config_envelope.py
@@ -0,0 +1,94 @@
+"""`PUT /api/config` must never store its own transport envelope.
+
+The renderer sends `{"config": {...}}` and autosaves the WHOLE record it last
+read, so one mis-nested write is copied forward on every later save. A stored
+`config` key then shadows real settings — a voice/STT block written inside it
+is invisible to the backend, which reads the top level — and `_deep_merge`
+only ever adds, so it survives every subsequent write.
+
+Seen in the wild: a config carrying a full stale snapshot under `config`,
+with the live `stt` block stranded inside it.
+"""
+
+from __future__ import annotations
+
+import json
+
+import pytest
+
+from src.server.desktop_serve import (
+    _save_config_merged,
+    strip_config_envelope,
+    unwrap_config_envelope,
+)
+
+
+def test_unwraps_the_renderers_envelope() -> None:
+    assert unwrap_config_envelope({"config": {"stt": {"enabled": True}}}) == {
+        "stt": {"enabled": True}
+    }
+
+
+def test_unwraps_a_double_envelope() -> None:
+    """The shape that caused the damage: unwrapping once leaves a `config`
+    key behind, which then merges in as data."""
+    assert unwrap_config_envelope({"config": {"config": {"stt": {"enabled": True}}}}) == {
+        "stt": {"enabled": True}
+    }
+
+
+def test_leaves_a_bare_record_alone() -> None:
+    record = {"providers": {"openai": {"base_url": "u"}}}
+
+    assert unwrap_config_envelope(record) == record
+
+
+def test_strip_is_a_no_op_without_an_envelope() -> None:
+    record = {"stt": {"enabled": True}}
+
+    assert strip_config_envelope(record) is record
+
+
+@pytest.fixture
+def config_file(tmp_path, monkeypatch):
+    path = tmp_path / "config.json"
+    monkeypatch.setattr("src.config.get_global_config_path", lambda: path)
+    import src.config as config_mod
+
+    config_mod._get_default_manager().invalidate()
+    monkeypatch.setattr(config_mod, "GLOBAL_CONFIG_FILE", path, raising=False)
+
+    return path
+
+
+def test_a_wrapped_save_lands_at_the_top_level(config_file) -> None:
+    config_file.write_text(json.dumps({"providers": {"openai": {"api_key": "secret"}}}))
+
+    result = _save_config_merged(
+        unwrap_config_envelope({"config": {"stt": {"enabled": True, "provider": "openai"}}})
+    )
+
+    assert result["ok"] is True
+    saved = json.loads(config_file.read_text())
+    assert saved["stt"] == {"enabled": True, "provider": "openai"}
+    assert "config" not in saved
+    # The redacted round-trip must not cost the user their credentials.
+    assert saved["providers"]["openai"]["api_key"] == "secret"
+
+
+def test_an_existing_envelope_is_repaired_on_the_next_save(config_file) -> None:
+    """No migration step: the next ordinary write cleans up a config that
+    already picked one up."""
+    config_file.write_text(
+        json.dumps({
+            "providers": {"openai": {"api_key": "secret"}},
+            "config": {"stt": {"enabled": True}, "logoColor": "ocean"},
+        })
+    )
+
+    _save_config_merged(unwrap_config_envelope({"config": {"logoColor": "sunset"}}))
+
+    saved = json.loads(config_file.read_text())
+    assert "config" not in saved
+    assert saved["logoColor"] == "sunset"
+    assert saved["providers"]["openai"]["api_key"] == "secret"