diff --git a/ui/web/src/pages/channels/channel-detail/channel-advanced-config.ts b/ui/web/src/pages/channels/channel-detail/channel-advanced-config.ts
new file mode 100644
index 00000000..f6a30691
--- /dev/null
+++ b/ui/web/src/pages/channels/channel-detail/channel-advanced-config.ts
@@ -0,0 +1,36 @@
+import { flattenConfig, unflattenConfig } from "@/lib/config-flatten";
+import { normalizeReasoningDeliveryConfig } from "../reasoning-delivery-config";
+
+export const ESSENTIAL_CONFIG_KEYS = new Set(["dm_policy", "group_policy", "require_mention", "mention_mode"]);
+
+function isAdvancedConfigKey(key: string): boolean {
+  return !ESSENTIAL_CONFIG_KEYS.has(key) && key !== "groups" && !key.startsWith("groups.");
+}
+
+export function deriveAdvancedInitialValues(config: Record<string, unknown> | null | undefined): Record<string, unknown> {
+  const normalized = normalizeReasoningDeliveryConfig({ ...((config ?? {}) as Record<string, unknown>) });
+  const flat = flattenConfig(normalized);
+  // Only keep advanced keys (exclude essential + group overrides).
+  return Object.fromEntries(
+    Object.entries(flat).filter(([k]) => isAdvancedConfigKey(k)),
+  );
+}
+
+export function buildAdvancedConfigUpdate(
+  existingConfig: Record<string, unknown> | null | undefined,
+  values: Record<string, unknown>,
+): Record<string, unknown> {
+  const normalized = normalizeReasoningDeliveryConfig({ ...((existingConfig ?? {}) as Record<string, unknown>) });
+  const flat = flattenConfig(normalized);
+
+  for (const [key, value] of Object.entries(values)) {
+    if (!isAdvancedConfigKey(key)) continue;
+    if (value === undefined || value === "" || value === null) {
+      delete flat[key];
+      continue;
+    }
+    flat[key] = value;
+  }
+
+  return normalizeReasoningDeliveryConfig(unflattenConfig(flat));
+}
diff --git a/ui/web/src/pages/channels/channel-detail/channel-advanced-dialog.test.ts b/ui/web/src/pages/channels/channel-detail/channel-advanced-dialog.test.ts
new file mode 100644
index 00000000..7b6068a5
--- /dev/null
+++ b/ui/web/src/pages/channels/channel-detail/channel-advanced-dialog.test.ts
@@ -0,0 +1,64 @@
+import { describe, expect, it } from "vitest";
+import { buildAdvancedConfigUpdate, deriveAdvancedInitialValues } from "./channel-advanced-config";
+
+describe("channel advanced config payload", () => {
+  it("removes a stale allow_from entry when the allowed users picker is cleared", () => {
+    const existing = {
+      dm_policy: "pairing",
+      group_policy: "open",
+      allow_from: ["195835936795841454"],
+      groups: {
+        "-100123": { allow_from: ["group-user"] },
+      },
+    };
+
+    const values = deriveAdvancedInitialValues(existing);
+    const next = buildAdvancedConfigUpdate(existing, { ...values, allow_from: undefined });
+
+    expect(next).not.toHaveProperty("allow_from");
+    expect(next.dm_policy).toBe("pairing");
+    expect(next.group_policy).toBe("open");
+    expect(next.groups).toEqual(existing.groups);
+  });
+
+  it("persists an explicit empty allow_from array when a tags field emits one", () => {
+    const existing = {
+      allow_from: ["195835936795841454"],
+      proxy: "http://localhost:8080",
+    };
+
+    const next = buildAdvancedConfigUpdate(existing, {
+      allow_from: [],
+      proxy: "",
+    });
+
+    expect(next.allow_from).toEqual([]);
+    expect(next).not.toHaveProperty("proxy");
+  });
+
+  it("flattens nested delivery config for editing and writes it back nested", () => {
+    const existing = {
+      chat_behavior: {
+        final_split: {
+          enabled: "inherit",
+        },
+      },
+    };
+
+    const values = deriveAdvancedInitialValues(existing);
+    expect(values["chat_behavior.final_split.enabled"]).toBe("inherit");
+
+    const next = buildAdvancedConfigUpdate(existing, {
+      ...values,
+      "chat_behavior.final_split.enabled": "off",
+    });
+
+    expect(next).toEqual({
+      chat_behavior: {
+        final_split: {
+          enabled: "off",
+        },
+      },
+    });
+  });
+});
diff --git a/ui/web/src/pages/channels/channel-detail/channel-advanced-dialog.tsx b/ui/web/src/pages/channels/channel-detail/channel-advanced-dialog.tsx
index 66f910d6..f0b44a4e 100644
--- a/ui/web/src/pages/channels/channel-detail/channel-advanced-dialog.tsx
+++ b/ui/web/src/pages/channels/channel-detail/channel-advanced-dialog.tsx
@@ -11,7 +11,11 @@ import {
 import { ConfigGroupHeader } from "@/components/shared/config-group-header";
 import { ChannelFields } from "../channel-fields";
 import { configSchema } from "../channel-schemas";
-import { normalizeReasoningDeliveryConfig } from "../reasoning-delivery-config";
+import {
+  buildAdvancedConfigUpdate,
+  deriveAdvancedInitialValues,
+  ESSENTIAL_CONFIG_KEYS,
+} from "./channel-advanced-config";
 import type { ChannelInstanceData } from "@/types/channel";
 
 interface ChannelAdvancedDialogProps {
@@ -21,8 +25,6 @@ interface ChannelAdvancedDialogProps {
   onUpdate: (updates: Record<string, unknown>) => Promise<void>;
 }
 
-const ESSENTIAL_CONFIG_KEYS = new Set(["dm_policy", "group_policy", "require_mention", "mention_mode"]);
-
 const NETWORK_KEYS = new Set(["api_server", "proxy", "domain", "connection_mode", "webhook_port", "webhook_path", "webhook_url"]);
 const LIMITS_KEYS = new Set(["history_limit", "media_max_mb", "text_chunk_limit"]);
 const STREAMING_KEYS = new Set(["dm_stream", "group_stream", "draft_transport", "reasoning_delivery", "native_stream", "debounce_delay", "thread_ttl"]);
@@ -41,14 +43,6 @@ function getAdvancedFields(channelType: string) {
   };
 }
 
-function deriveInitialValues(instance: ChannelInstanceData): Record<string, unknown> {
-  const config = normalizeReasoningDeliveryConfig((instance.config ?? {}) as Record<string, unknown>);
-  // Only keep advanced keys (exclude essential + groups)
-  return Object.fromEntries(
-    Object.entries(config).filter(([k]) => !ESSENTIAL_CONFIG_KEYS.has(k) && k !== "groups"),
-  );
-}
-
 export function ChannelAdvancedDialog({
   open,
   onOpenChange,
@@ -58,14 +52,13 @@ export function ChannelAdvancedDialog({
   const { t } = useTranslation("channels");
   const groups = getAdvancedFields(instance.channel_type);
 
-  const [values, setValues] = useState<Record<string, unknown>>(() => deriveInitialValues(instance));
+  const [values, setValues] = useState<Record<string, unknown>>(() => deriveAdvancedInitialValues(instance.config));
   const [saving, setSaving] = useState(false);
 
   // Re-sync local state when dialog opens
   useEffect(() => {
     if (!open) return;
-    setValues(deriveInitialValues(instance));
-     
+    setValues(deriveAdvancedInitialValues(instance.config));
   }, [open, instance]);
 
   const handleChange = useCallback((key: string, value: unknown) => {
@@ -75,13 +68,7 @@ export function ChannelAdvancedDialog({
   const handleSave = async () => {
     setSaving(true);
     try {
-      const existingConfig = (instance.config ?? {}) as Record<string, unknown>;
-      const cleanAdvanced = Object.fromEntries(
-        Object.entries(values).filter(([, v]) => v !== undefined && v !== "" && v !== null),
-      );
-      // Merge: preserve essential keys and groups from existing, overwrite advanced keys
-      const merged = normalizeReasoningDeliveryConfig({ ...existingConfig, ...cleanAdvanced });
-      await onUpdate({ config: merged });
+      await onUpdate({ config: buildAdvancedConfigUpdate(instance.config, values) });
       onOpenChange(false);
     } catch { // toast shown by hook
     } finally {