diff --git a/test/_api_v3_test_helpers.py b/test/_api_v3_test_helpers.py
new file mode 100644
index 00000000..9bcb7984
--- /dev/null
+++ b/test/_api_v3_test_helpers.py
@@ -0,0 +1,75 @@
+"""
+Shared scaffolding for api_v3 blueprint tests.
+
+Not a test module (the leading underscore keeps pytest from collecting
+it). It is the pytest-fixture equivalent of ``_make_client()`` in
+test_uninstall_and_reconcile_endpoint.py, which is unittest-style and
+requires ``self.addCleanup``.
+
+The api_v3 blueprint keeps its managers as attributes on a module-level
+singleton, not in Flask app state, so replacing them with mocks leaks
+into every later test that imports api_v3 unless the originals are put
+back. ``api_v3_client`` snapshots and restores them around each test.
+"""
+
+from unittest.mock import MagicMock
+
+import pytest
+from flask import Flask
+
+
+# Every manager attribute the blueprint reads. Anything missing here keeps
+# whatever a previously-run test left on the singleton.
+API_V3_MANAGER_ATTRS = (
+    'config_manager', 'plugin_manager', 'plugin_store_manager',
+    'plugin_state_manager', 'saved_repositories_manager', 'schema_manager',
+    'operation_queue', 'operation_history', 'cache_manager',
+)
+
+_SENTINEL = object()
+
+
+def build_app(blueprint):
+    app = Flask(__name__)
+    app.config['TESTING'] = True
+    app.config['SECRET_KEY'] = 'test'
+    app.register_blueprint(blueprint, url_prefix='/api/v3')
+    return app
+
+
+@pytest.fixture
+def api_v3_module():
+    """The api_v3 module with every manager replaced by a MagicMock.
+
+    Restores the original attributes afterwards. Tests point individual
+    managers at real objects (a ConfigManager over tmp_path, say) or set
+    them to None to exercise the not-initialized branches.
+    """
+    from web_interface.blueprints import api_v3 as module
+
+    originals = {
+        name: getattr(module.api_v3, name, _SENTINEL)
+        for name in API_V3_MANAGER_ATTRS
+    }
+    for name in API_V3_MANAGER_ATTRS:
+        setattr(module.api_v3, name, MagicMock())
+    # Default to the direct path; queue tests opt in explicitly.
+    module.api_v3.operation_queue = None
+
+    yield module
+
+    for name, original in originals.items():
+        if original is _SENTINEL:
+            if hasattr(module.api_v3, name):
+                try:
+                    delattr(module.api_v3, name)
+                except AttributeError:
+                    pass
+        else:
+            setattr(module.api_v3, name, original)
+
+
+@pytest.fixture
+def api_v3_client(api_v3_module):
+    """Flask test client wired to the mocked blueprint."""
+    return build_app(api_v3_module.api_v3).test_client()
diff --git a/test/test_api_v3_optional_body.py b/test/test_api_v3_optional_body.py
new file mode 100644
index 00000000..c03db5a8
--- /dev/null
+++ b/test/test_api_v3_optional_body.py
@@ -0,0 +1,90 @@
+"""
+Regression tests: POST endpoints whose body is optional must accept a
+request that has no body at all.
+
+Six handlers in api_v3 read their body as ``request.get_json() or {}``.
+The ``or {}`` states the intent plainly — every field is optional, so a
+bodyless POST should fall back to defaults. But ``get_json()`` without
+``silent=True`` raises ``UnsupportedMediaType`` when the request carries
+no JSON Content-Type, and it raises *before* ``or {}`` is evaluated. Each
+handler's catch-all then turned that into a 500.
+
+So the natural way to call these endpoints — a POST with no body, which
+is what curl, a fetch() without options, and most HTTP clients send by
+default — failed on every one of them. The shipped UI always sends a JSON
+object, which is why this went unnoticed.
+
+This file covers the endpoints whose bodyless behaviour is not already
+tested in their own suite.
+"""
+
+import sys
+from pathlib import Path
+from unittest.mock import MagicMock
+
+import pytest
+
+sys.path.insert(0, str(Path(__file__).parent.parent))
+
+from test._api_v3_test_helpers import api_v3_client, api_v3_module  # noqa: F401,E402
+
+
+class TestOnDemandStart:
+    URL = "/api/v3/display/on-demand/start"
+
+    def test_bodyless_post_is_not_a_server_error(self, api_v3_client, api_v3_module):
+        response = api_v3_client.post(self.URL)
+        # The endpoint may still reject the request on its own terms (no
+        # plugin_id, nothing to display); what it must not do is fail with
+        # a 500 raised out of body parsing.
+        assert response.status_code != 500
+
+    def test_json_body_still_works(self, api_v3_client, api_v3_module):
+        assert api_v3_client.post(self.URL, json={}).status_code != 500
+
+
+class TestResetPluginConfig:
+    URL = "/api/v3/plugins/config/reset"
+
+    def test_bodyless_post_is_not_a_server_error(self, api_v3_client, api_v3_module):
+        assert api_v3_client.post(self.URL).status_code != 500
+
+    def test_json_body_still_works(self, api_v3_client, api_v3_module):
+        assert api_v3_client.post(self.URL, json={}).status_code != 500
+
+
+class TestDeleteOfTheDayJson:
+    URL = "/api/v3/plugins/of-the-day/json/delete"
+
+    def test_bodyless_post_is_not_a_server_error(self, api_v3_client, api_v3_module):
+        assert api_v3_client.post(self.URL).status_code != 500
+
+    def test_json_body_still_works(self, api_v3_client, api_v3_module):
+        assert api_v3_client.post(self.URL, json={}).status_code != 500
+
+
+class TestPluginLimits:
+    URL = "/api/v3/plugins/clock/limits"
+
+    def test_bodyless_post_is_not_a_server_error(self, api_v3_client, api_v3_module):
+        assert api_v3_client.post(self.URL).status_code != 500
+
+
+class TestNoToleratedBodyReadIsUnguarded:
+    def test_every_or_default_body_read_uses_silent(self):
+        """`get_json() or <default>` is a contradiction without silent=True.
+
+        Writing `or {}` declares the body optional; omitting silent=True
+        means the call raises before the default can apply. Catch the
+        combination here rather than waiting for each endpoint to be
+        exercised by hand.
+        """
+        source = Path(__file__).parent.parent.joinpath(
+            "web_interface/blueprints/api_v3.py").read_text()
+        offenders = [
+            line.strip() for line in source.splitlines()
+            if "request.get_json()" in line and " or " in line
+        ]
+        assert offenders == [], (
+            "these reads declare a default but raise before reaching it; "
+            f"use get_json(silent=True): {offenders}")
diff --git a/test/test_api_v3_registry_endpoints.py b/test/test_api_v3_registry_endpoints.py
new file mode 100644
index 00000000..e1968c39
--- /dev/null
+++ b/test/test_api_v3_registry_endpoints.py
@@ -0,0 +1,174 @@
+"""
+Endpoint tests for the plugin-registry routes in api_v3:
+POST /plugins/store/refresh and POST /plugins/registry-from-url.
+
+Both reach out to the network through PluginStoreManager (mocked here) and
+had no endpoint-level coverage; registry-from-url in particular takes a
+user-supplied URL and hands it straight to the manager.
+"""
+
+import sys
+from pathlib import Path
+
+import pytest
+
+sys.path.insert(0, str(Path(__file__).parent.parent))
+
+from test._api_v3_test_helpers import api_v3_client, api_v3_module  # noqa: F401,E402
+
+
+class TestRefreshPluginStore:
+    URL = "/api/v3/plugins/store/refresh"
+
+    def test_uninitialized_manager_is_a_500(self, api_v3_client, api_v3_module):
+        api_v3_module.api_v3.plugin_store_manager = None
+        response = api_v3_client.post(self.URL, json={})
+        assert response.status_code == 500
+        assert "not initialized" in response.get_json()["message"]
+
+    def test_success_reports_plugin_count(self, api_v3_client, api_v3_module):
+        api_v3_module.api_v3.plugin_store_manager.fetch_registry.return_value = {
+            "plugins": [{"id": "a"}, {"id": "b"}, {"id": "c"}]}
+        response = api_v3_client.post(self.URL, json={})
+        assert response.status_code == 200
+        assert response.get_json()["plugin_count"] == 3
+
+    def test_forces_a_refresh_rather_than_using_cache(self, api_v3_client, api_v3_module):
+        manager = api_v3_module.api_v3.plugin_store_manager
+        manager.fetch_registry.return_value = {"plugins": []}
+        api_v3_client.post(self.URL, json={})
+        manager.fetch_registry.assert_called_once_with(force_refresh=True)
+
+    def test_empty_registry_reports_zero(self, api_v3_client, api_v3_module):
+        api_v3_module.api_v3.plugin_store_manager.fetch_registry.return_value = {}
+        response = api_v3_client.post(self.URL, json={})
+        assert response.get_json()["plugin_count"] == 0
+
+    def test_no_body_is_accepted(self, api_v3_client, api_v3_module):
+        # Regression: `request.get_json() or {}` says a missing body is
+        # fine, but get_json() raises UnsupportedMediaType before `or {}`
+        # is reached, so a bodyless POST — the natural way to call a
+        # refresh endpoint — came back 500.
+        api_v3_module.api_v3.plugin_store_manager.fetch_registry.return_value = {"plugins": []}
+        assert api_v3_client.post(self.URL).status_code == 200
+
+    def test_body_without_json_content_type_is_accepted(
+            self, api_v3_client, api_v3_module):
+        api_v3_module.api_v3.plugin_store_manager.fetch_registry.return_value = {"plugins": []}
+        response = api_v3_client.post(self.URL, data="", content_type="text/plain")
+        assert response.status_code == 200
+
+    def test_malformed_json_body_falls_back_to_defaults(
+            self, api_v3_client, api_v3_module):
+        api_v3_module.api_v3.plugin_store_manager.fetch_registry.return_value = {"plugins": []}
+        response = api_v3_client.post(
+            self.URL, data="{not json", content_type="application/json")
+        assert response.status_code == 200
+
+    @pytest.mark.parametrize("key", ["fetch_commit_info", "fetch_latest_versions"])
+    def test_either_commit_info_key_extends_the_message(
+            self, api_v3_client, api_v3_module, key):
+        # fetch_latest_versions is the older spelling; both must work.
+        api_v3_module.api_v3.plugin_store_manager.fetch_registry.return_value = {"plugins": []}
+        response = api_v3_client.post(self.URL, json={key: True})
+        assert "commit metadata" in response.get_json()["message"]
+
+    def test_message_stays_plain_without_the_flag(self, api_v3_client, api_v3_module):
+        api_v3_module.api_v3.plugin_store_manager.fetch_registry.return_value = {"plugins": []}
+        response = api_v3_client.post(self.URL, json={})
+        assert response.get_json()["message"] == "Plugin store refreshed"
+
+    def test_network_failure_is_a_500(self, api_v3_client, api_v3_module):
+        api_v3_module.api_v3.plugin_store_manager.fetch_registry.side_effect = (
+            ConnectionError("github unreachable"))
+        response = api_v3_client.post(self.URL, json={})
+        assert response.status_code == 500
+        assert response.get_json()["message"] == "An error occurred; see logs for details"
+
+    def test_failure_body_carries_no_traceback_or_paths(
+            self, api_v3_client, api_v3_module):
+        api_v3_module.api_v3.plugin_store_manager.fetch_registry.side_effect = (
+            RuntimeError("failed at /home/user/LEDMatrix/src/secret.py line 42"))
+        body = api_v3_client.post(self.URL, json={}).get_json()
+        assert "Traceback" not in str(body)
+        # `details` is describe_exception output: one line, type-named,
+        # credential-redacted. It may quote the message, but never a stack.
+        assert body["details"].startswith("RuntimeError:")
+        assert "\n" not in body["details"]
+
+
+class TestRegistryFromUrl:
+    URL = "/api/v3/plugins/registry-from-url"
+
+    def test_uninitialized_manager_is_a_500(self, api_v3_client, api_v3_module):
+        api_v3_module.api_v3.plugin_store_manager = None
+        response = api_v3_client.post(self.URL, json={"repo_url": "http://x"})
+        assert response.status_code == 500
+
+    def test_missing_repo_url_is_a_400(self, api_v3_client, api_v3_module):
+        response = api_v3_client.post(self.URL, json={})
+        assert response.status_code == 400
+        assert "repo_url required" in response.get_json()["message"]
+        api_v3_module.api_v3.plugin_store_manager.fetch_registry_from_url.assert_not_called()
+
+    def test_success_returns_the_plugin_list(self, api_v3_client, api_v3_module):
+        api_v3_module.api_v3.plugin_store_manager.fetch_registry_from_url.return_value = {
+            "plugins": [{"id": "clock"}]}
+        response = api_v3_client.post(
+            self.URL, json={"repo_url": "https://github.com/o/r"})
+        assert response.status_code == 200
+        body = response.get_json()
+        assert body["plugins"] == [{"id": "clock"}]
+        assert body["registry_url"] == "https://github.com/o/r"
+
+    def test_url_is_trimmed_before_use(self, api_v3_client, api_v3_module):
+        manager = api_v3_module.api_v3.plugin_store_manager
+        manager.fetch_registry_from_url.return_value = {"plugins": []}
+        api_v3_client.post(self.URL, json={"repo_url": "  https://github.com/o/r  "})
+        manager.fetch_registry_from_url.assert_called_once_with("https://github.com/o/r")
+
+    def test_registry_without_plugins_key_returns_empty_list(
+            self, api_v3_client, api_v3_module):
+        api_v3_module.api_v3.plugin_store_manager.fetch_registry_from_url.return_value = {
+            "other": 1}
+        response = api_v3_client.post(self.URL, json={"repo_url": "http://x"})
+        assert response.get_json()["plugins"] == []
+
+    def test_no_registry_found_is_a_400(self, api_v3_client, api_v3_module):
+        api_v3_module.api_v3.plugin_store_manager.fetch_registry_from_url.return_value = None
+        response = api_v3_client.post(self.URL, json={"repo_url": "http://x/not-a-registry"})
+        assert response.status_code == 400
+        assert "Failed to fetch registry" in response.get_json()["message"]
+
+    @pytest.mark.parametrize("url", [
+        "not a url",
+        "javascript:alert(1)",
+        "file:///etc/passwd",
+        "http://localhost:8080/admin",
+    ])
+    def test_unusable_urls_fail_cleanly(self, api_v3_client, api_v3_module, url):
+        # Characterization: the handler performs no URL validation of its
+        # own — whatever the manager makes of the URL decides the outcome.
+        # What is pinned here is that a rejected URL produces a clean 400
+        # rather than a traceback or a 500.
+        api_v3_module.api_v3.plugin_store_manager.fetch_registry_from_url.return_value = None
+        response = api_v3_client.post(self.URL, json={"repo_url": url})
+        assert response.status_code == 400
+        assert "Traceback" not in str(response.get_json())
+
+    def test_fetch_exception_is_a_500_without_internals(
+            self, api_v3_client, api_v3_module):
+        api_v3_module.api_v3.plugin_store_manager.fetch_registry_from_url.side_effect = (
+            ValueError("parse failed in /srv/app/internal.py"))
+        response = api_v3_client.post(self.URL, json={"repo_url": "http://x"})
+        assert response.status_code == 500
+        body = response.get_json()
+        assert body["message"] == "An error occurred; see logs for details"
+        assert "Traceback" not in str(body)
+
+    def test_non_string_repo_url_is_a_500_not_a_crash(
+            self, api_v3_client, api_v3_module):
+        # .strip() on a non-string raises; the handler's catch-all turns
+        # that into a 500 rather than propagating.
+        response = api_v3_client.post(self.URL, json={"repo_url": 12345})
+        assert response.status_code == 500
diff --git a/test/test_api_v3_wifi_endpoints.py b/test/test_api_v3_wifi_endpoints.py
new file mode 100644
index 00000000..0c713ae2
--- /dev/null
+++ b/test/test_api_v3_wifi_endpoints.py
@@ -0,0 +1,240 @@
+"""
+Endpoint tests for the /wifi/* routes in api_v3.
+
+These routes drive the host's actual networking — connecting, dropping a
+connection, switching the radio off — and had no endpoint-level tests at
+all. WiFiManager is mocked throughout; nothing here may touch real
+networking.
+
+Each handler does `from src.wifi_manager import WiFiManager` inside the
+function body, so the patch target is the class at its definition site.
+"""
+
+import sys
+from pathlib import Path
+from unittest.mock import MagicMock, patch
+
+import pytest
+
+sys.path.insert(0, str(Path(__file__).parent.parent))
+
+from test._api_v3_test_helpers import api_v3_client, api_v3_module  # noqa: F401,E402
+
+
+@pytest.fixture
+def wifi_manager():
+    """Patch WiFiManager where it is defined; yield the instance mock."""
+    with patch("src.wifi_manager.WiFiManager") as cls:
+        instance = MagicMock()
+        cls.return_value = instance
+        yield instance
+
+
+class TestConnect:
+    URL = "/api/v3/wifi/connect"
+
+    def test_success(self, api_v3_client, wifi_manager):
+        wifi_manager.connect_to_network.return_value = (True, "Connected to HomeNet")
+        response = api_v3_client.post(self.URL, json={"ssid": "HomeNet", "password": "pw"})
+        assert response.status_code == 200
+        assert response.get_json()["message"] == "Connected to HomeNet"
+        wifi_manager.connect_to_network.assert_called_once_with("HomeNet", "pw")
+
+    def test_missing_body_rejected(self, api_v3_client, wifi_manager):
+        response = api_v3_client.post(self.URL, json={})
+        assert response.status_code == 400
+        wifi_manager.connect_to_network.assert_not_called()
+
+    def test_missing_ssid_rejected(self, api_v3_client, wifi_manager):
+        response = api_v3_client.post(self.URL, json={"password": "pw"})
+        assert response.status_code == 400
+        assert "SSID is required" in response.get_json()["message"]
+        wifi_manager.connect_to_network.assert_not_called()
+
+    @pytest.mark.parametrize("ssid", ["", "   ", "\t"])
+    def test_blank_ssid_rejected(self, api_v3_client, wifi_manager, ssid):
+        response = api_v3_client.post(self.URL, json={"ssid": ssid})
+        assert response.status_code == 400
+        wifi_manager.connect_to_network.assert_not_called()
+
+    def test_ssid_is_trimmed(self, api_v3_client, wifi_manager):
+        wifi_manager.connect_to_network.return_value = (True, "ok")
+        api_v3_client.post(self.URL, json={"ssid": "  HomeNet  "})
+        wifi_manager.connect_to_network.assert_called_once_with("HomeNet", "")
+
+    def test_missing_password_becomes_empty_string(self, api_v3_client, wifi_manager):
+        wifi_manager.connect_to_network.return_value = (True, "ok")
+        api_v3_client.post(self.URL, json={"ssid": "OpenNet"})
+        wifi_manager.connect_to_network.assert_called_once_with("OpenNet", "")
+
+    def test_null_password_becomes_empty_string(self, api_v3_client, wifi_manager):
+        wifi_manager.connect_to_network.return_value = (True, "ok")
+        api_v3_client.post(self.URL, json={"ssid": "OpenNet", "password": None})
+        wifi_manager.connect_to_network.assert_called_once_with("OpenNet", "")
+
+    def test_failure_reports_the_managers_reason(self, api_v3_client, wifi_manager):
+        wifi_manager.connect_to_network.return_value = (False, "Bad password")
+        response = api_v3_client.post(self.URL, json={"ssid": "HomeNet"})
+        assert response.status_code == 400
+        assert response.get_json()["message"] == "Bad password"
+
+    def test_failure_without_reason_uses_fallback_text(self, api_v3_client, wifi_manager):
+        wifi_manager.connect_to_network.return_value = (False, None)
+        response = api_v3_client.post(self.URL, json={"ssid": "HomeNet"})
+        assert response.status_code == 400
+        assert response.get_json()["message"] == "Failed to connect to network"
+
+    def test_manager_exception_is_a_500_without_leaking_internals(
+            self, api_v3_client, wifi_manager):
+        wifi_manager.connect_to_network.side_effect = RuntimeError(
+            "/usr/lib/secret/path blew up")
+        response = api_v3_client.post(self.URL, json={"ssid": "HomeNet"})
+        assert response.status_code == 500
+        body = response.get_json()
+        assert body["message"] == "An error occurred; see logs for details"
+        # `details` comes from describe_exception, which is deliberately
+        # safe to return (redacted, capped) — it names the type.
+        assert "RuntimeError" in body["details"]
+
+
+class TestDisconnect:
+    URL = "/api/v3/wifi/disconnect"
+
+    def test_success(self, api_v3_client, wifi_manager):
+        wifi_manager.disconnect_from_network.return_value = (True, "Disconnected")
+        response = api_v3_client.post(self.URL)
+        assert response.status_code == 200
+        assert response.get_json()["message"] == "Disconnected"
+
+    def test_failure(self, api_v3_client, wifi_manager):
+        wifi_manager.disconnect_from_network.return_value = (False, "Not connected")
+        response = api_v3_client.post(self.URL)
+        assert response.status_code == 400
+        assert response.get_json()["message"] == "Not connected"
+
+    def test_failure_without_reason_uses_fallback(self, api_v3_client, wifi_manager):
+        wifi_manager.disconnect_from_network.return_value = (False, "")
+        response = api_v3_client.post(self.URL)
+        assert response.get_json()["message"] == "Failed to disconnect from network"
+
+    def test_exception_is_a_500(self, api_v3_client, wifi_manager):
+        wifi_manager.disconnect_from_network.side_effect = OSError("nmcli missing")
+        assert api_v3_client.post(self.URL).status_code == 500
+
+
+class TestApMode:
+    ENABLE = "/api/v3/wifi/ap/enable"
+    DISABLE = "/api/v3/wifi/ap/disable"
+
+    def test_enable_success(self, api_v3_client, wifi_manager):
+        wifi_manager.enable_ap_mode.return_value = (True, "AP enabled")
+        response = api_v3_client.post(self.ENABLE, json={})
+        assert response.status_code == 200
+        wifi_manager.enable_ap_mode.assert_called_once_with(force=False)
+
+    @pytest.mark.parametrize("raw,expected", [
+        (True, True), (False, False),
+        ("true", True), ("TRUE", True), ("1", True),
+        ("false", False), ("no", False), ("yes", False),
+        (1, False),  # only real True or the listed strings count
+    ])
+    def test_force_coercion(self, api_v3_client, wifi_manager, raw, expected):
+        wifi_manager.enable_ap_mode.return_value = (True, "ok")
+        api_v3_client.post(self.ENABLE, json={"force": raw})
+        wifi_manager.enable_ap_mode.assert_called_once_with(force=expected)
+
+    def test_enable_without_body(self, api_v3_client, wifi_manager):
+        wifi_manager.enable_ap_mode.return_value = (True, "ok")
+        assert api_v3_client.post(self.ENABLE).status_code == 200
+
+    def test_enable_failure(self, api_v3_client, wifi_manager):
+        wifi_manager.enable_ap_mode.return_value = (False, "hostapd missing")
+        response = api_v3_client.post(self.ENABLE, json={})
+        assert response.status_code == 400
+        assert response.get_json()["message"] == "hostapd missing"
+
+    def test_disable_success(self, api_v3_client, wifi_manager):
+        wifi_manager.disable_ap_mode.return_value = (True, "AP disabled")
+        assert api_v3_client.post(self.DISABLE).status_code == 200
+
+    def test_disable_failure(self, api_v3_client, wifi_manager):
+        wifi_manager.disable_ap_mode.return_value = (False, "not running")
+        assert api_v3_client.post(self.DISABLE).status_code == 400
+
+    def test_enable_exception_is_a_500(self, api_v3_client, wifi_manager):
+        wifi_manager.enable_ap_mode.side_effect = RuntimeError("boom")
+        assert api_v3_client.post(self.ENABLE, json={}).status_code == 500
+
+
+class TestRadio:
+    URL = "/api/v3/wifi/radio"
+
+    def test_get_state(self, api_v3_client, wifi_manager):
+        wifi_manager.get_wifi_radio_state.return_value = {
+            "enabled": True, "ethernet_connected": False}
+        response = api_v3_client.get(self.URL)
+        assert response.status_code == 200
+        assert response.get_json()["data"]["enabled"] is True
+
+    def test_get_state_exception_is_a_500(self, api_v3_client, wifi_manager):
+        wifi_manager.get_wifi_radio_state.side_effect = OSError("rfkill missing")
+        assert api_v3_client.get(self.URL).status_code == 500
+
+    def test_enabled_is_required(self, api_v3_client, wifi_manager):
+        response = api_v3_client.post(self.URL, json={})
+        assert response.status_code == 400
+        assert "enabled is required" in response.get_json()["message"]
+        wifi_manager.set_wifi_radio.assert_not_called()
+
+    def test_enable_success(self, api_v3_client, wifi_manager):
+        wifi_manager.set_wifi_radio.return_value = (True, "Radio on", None)
+        wifi_manager.get_wifi_radio_state.return_value = {"enabled": True}
+        response = api_v3_client.post(self.URL, json={"enabled": True})
+        assert response.status_code == 200
+        wifi_manager.set_wifi_radio.assert_called_once_with(True, force=False)
+
+    @pytest.mark.parametrize("raw,expected", [
+        (True, True), ("true", True), ("1", True), ("yes", True),
+        (False, False), ("false", False), ("off", False), (0, False),
+    ])
+    def test_enabled_coercion_is_string_aware(
+            self, api_v3_client, wifi_manager, raw, expected):
+        # bool("false") is True, so the endpoint parses strings explicitly
+        # rather than trusting truthiness — it is a public contract, not
+        # only the shipped UI which always sends real JSON booleans.
+        wifi_manager.set_wifi_radio.return_value = (True, "ok", None)
+        wifi_manager.get_wifi_radio_state.return_value = {}
+        api_v3_client.post(self.URL, json={"enabled": raw})
+        wifi_manager.set_wifi_radio.assert_called_once_with(expected, force=False)
+
+    def test_force_passed_through(self, api_v3_client, wifi_manager):
+        wifi_manager.set_wifi_radio.return_value = (True, "ok", None)
+        wifi_manager.get_wifi_radio_state.return_value = {}
+        api_v3_client.post(self.URL, json={"enabled": False, "force": "true"})
+        wifi_manager.set_wifi_radio.assert_called_once_with(False, force=True)
+
+    def test_refusal_reports_reason(self, api_v3_client, wifi_manager):
+        # Disabling the radio without Ethernet would lock the user out of
+        # this very interface, so the manager can refuse with a reason.
+        wifi_manager.set_wifi_radio.return_value = (
+            False, "Refusing: no wired fallback", "no_ethernet")
+        response = api_v3_client.post(self.URL, json={"enabled": False})
+        assert response.status_code == 400
+        body = response.get_json()
+        assert body["reason"] == "no_ethernet"
+        assert "Refusing" in body["message"]
+
+    def test_exception_is_a_500(self, api_v3_client, wifi_manager):
+        wifi_manager.set_wifi_radio.side_effect = RuntimeError("boom")
+        assert api_v3_client.post(self.URL, json={"enabled": True}).status_code == 500
+
+
+class TestNoRealNetworking:
+    def test_wifi_manager_is_never_constructed_for_real(self, api_v3_client):
+        # Guard against a future refactor moving the import to module level,
+        # where the fixture's patch of the definition site would stop
+        # applying and the tests would start driving real networking.
+        with patch("src.wifi_manager.WiFiManager") as cls:
+            cls.return_value.disconnect_from_network.return_value = (True, "ok")
+            api_v3_client.post("/api/v3/wifi/disconnect")
+            assert cls.called
diff --git a/web_interface/blueprints/api_v3.py b/web_interface/blueprints/api_v3.py
index 06fef117..7f6e108c 100644
--- a/web_interface/blueprints/api_v3.py
+++ b/web_interface/blueprints/api_v3.py
@@ -2411,7 +2411,7 @@ def get_on_demand_status():
 def start_on_demand_display():
     """Request the display controller to run a specific plugin on-demand."""
     try:
-        data = request.get_json() or {}
+        data = request.get_json(silent=True) or {}
         plugin_id = data.get('plugin_id')
         mode = data.get('mode')
         duration = data.get('duration')
@@ -2935,7 +2935,7 @@ def manage_plugin_limits(plugin_id):
                 })
         else:
             # POST - Set limits
-            data = request.get_json() or {}
+            data = request.get_json(silent=True) or {}
             from src.plugin_system.resource_monitor import ResourceLimits
 
             limits = ResourceLimits(
@@ -4236,7 +4236,7 @@ def refresh_plugin_store():
         if not api_v3.plugin_store_manager:
             return jsonify({'status': 'error', 'message': 'Plugin store manager not initialized'}), 500
 
-        data = request.get_json() or {}
+        data = request.get_json(silent=True) or {}
         fetch_commit_info = data.get('fetch_commit_info', data.get('fetch_latest_versions', False))
 
         # Force refresh the registry
@@ -5822,7 +5822,7 @@ def reset_plugin_config():
         if not api_v3.config_manager:
             return jsonify({'status': 'error', 'message': 'Config manager not initialized'}), 500
 
-        data = request.get_json() or {}
+        data = request.get_json(silent=True) or {}
         plugin_id = data.get('plugin_id')
         preserve_secrets = data.get('preserve_secrets', True)
 
@@ -6209,7 +6209,7 @@ sys.exit(proc.returncode)
 def authenticate_spotify():
     """Run Spotify authentication script"""
     try:
-        data = request.get_json() or {}
+        data = request.get_json(silent=True) or {}
         redirect_url = data.get('redirect_url', '').strip()
 
         # Get plugin directory
@@ -7146,7 +7146,7 @@ def upload_of_the_day_json():
 def delete_of_the_day_json():
     """Delete a JSON file from of-the-day plugin"""
     try:
-        data = request.get_json() or {}
+        data = request.get_json(silent=True) or {}
         file_id = data.get('file_id')  # This is the category_name
 
         if not file_id: