diff --git a/scripts/dev-api.js b/scripts/dev-api.js
index 4020083..47be666 100644
--- a/scripts/dev-api.js
+++ b/scripts/dev-api.js
@@ -6851,11 +6851,15 @@ function secretAwareAccountDisplayValue(value) {
   return formatSecretRefPlaceholder(value)
 }
 
-function resolvePlatformConfigEntry(channelRoot, platform, accountId) {
+export function resolvePlatformConfigEntry(channelRoot, platform, accountId) {
   if (!channelRoot || typeof channelRoot !== 'object') return null
   const accountKey = typeof accountId === 'string' ? accountId.trim() : ''
   if (platformStorageKey(platform) === 'tlon' && accountKey === QQBOT_DEFAULT_ACCOUNT_ID) return channelRoot
-  if (accountKey) return channelRoot.accounts?.[accountKey] || channelRoot
+  if (accountKey) {
+    const entry = channelRoot.accounts?.[accountKey]
+    if (entry && typeof entry === 'object') return entry
+    return null
+  }
   if (platformStorageKey(platform) === 'qqbot' && !channelHasQqbotCredentials(channelRoot)) {
     return channelRoot.accounts?.[QQBOT_DEFAULT_ACCOUNT_ID] || channelRoot
   }
diff --git a/src-tauri/src/commands/messaging.rs b/src-tauri/src/commands/messaging.rs
index beefccc..6fffa1d 100644
--- a/src-tauri/src/commands/messaging.rs
+++ b/src-tauri/src/commands/messaging.rs
@@ -1426,10 +1426,9 @@ fn resolve_platform_config_entry(
         if let Some(value) = root.get("accounts").and_then(|a| a.get(acct)) {
             return Some(value.clone());
         }
-        if platform_storage_key(platform) == "qqbot" && !qqbot_channel_has_credentials(root) {
-            return None;
-        }
-        return Some(root.clone());
+        // Missing account must not fall back to root: preserve_messaging_credential_refs
+        // would copy the default account's SecretRefs into a new accounts.<id> entry.
+        None
     }
 
     if platform_storage_key(platform) == "qqbot" && !qqbot_channel_has_credentials(root) {
@@ -7593,6 +7592,27 @@ mod tests {
         );
     }
 
+    #[test]
+    fn resolve_platform_config_entry_missing_account_does_not_fallback_to_root() {
+        let root = json!({
+            "enabled": true,
+            "botToken": {
+                "source": "env",
+                "provider": "default",
+                "id": "TELEGRAM_BOT_TOKEN"
+            },
+            "accounts": {
+                "default": { "botToken": "default-token" }
+            }
+        });
+        let resolved =
+            resolve_platform_config_entry(Some(&root), "telegram", Some("work"));
+        assert!(
+            resolved.is_none(),
+            "unknown account id must not resolve to root credentials"
+        );
+    }
+
     #[test]
     fn channel_save_preserves_unchanged_secret_ref_placeholder() {
         let current = json!({
diff --git a/src/locales/modules/channels.js b/src/locales/modules/channels.js
index 3f3c4b5..77d45bc 100644
--- a/src/locales/modules/channels.js
+++ b/src/locales/modules/channels.js
@@ -544,6 +544,7 @@ export default {
   accountIdentifier: _('账号标识', 'Account Identifier', '账號標識'),
   accountIdPlaceholder: _('留空为默认账号；修改会创建新账号', 'Leave empty for default account; changing creates a new account', '留空為預設账號；修改會建立新账號'),
   accountIdHint: _('每个账号对应一个独立机器人。不同账号可绑定不同 Agent。', 'Each account corresponds to an independent bot. Different accounts can bind to different Agents.', '每個账號对應一個獨立機器人。不同账號可綁定不同 Agent。'),
+  accountIdLockedHint: _('编辑已有账号时不可修改标识，避免误写入根配置。', 'Account identifier cannot be changed when editing an existing account; this prevents writing to the root config by mistake.', '編輯已有账號時不可修改標識，避免誤寫入根設定。'),
   bindAgent: _('绑定 Agent', 'Bind Agent', '綁定 Agent', 'Agent をバインド', 'Agent 바인딩', 'Liên kết Agent', 'Vincular Agent', 'Vincular Agent', 'Привязать агента', 'Lier un Agent', 'Agent verknüpfen'),
   bindAgentHint: _('该账号收到的消息路由到哪个 Agent（可在「Agent 对接」页添加更多绑定）。', 'Which Agent receives messages for this account (add more bindings in "Agent Binding" tab).', '該账號收到的訊息路由到哪個 Agent（可在「Agent 对接」頁新增更多綁定）。'),
   show: _('显示', 'Show', '顯示'),
diff --git a/src/pages/channels.js b/src/pages/channels.js
index d41292b..0976f00 100644
--- a/src/pages/channels.js
+++ b/src/pages/channels.js
@@ -2524,17 +2524,22 @@ async function openConfigDialog(pid, page, state, accountId) {
   }
 
   // 尝试加载已有配置（accountId 用于多账号读取）
+  // 「添加账号」传入 ''，且 readPlatformConfig 会把 '' 当成 null；此处直接跳过读取，避免预填默认账号凭证。
+  const dialogAccountId = accountId != null ? String(accountId).trim() : ''
+  const isNewAccountDialog = supportsMessagingMultiAccount(pid) && accountId === ''
   let existing = {}
   let isEdit = false
-  try {
-    const res = await api.readPlatformConfig(pid, accountId)
-    if (res?.values) {
-      existing = res.values
-    }
-    if (res?.exists) {
-      isEdit = true
-    }
-  } catch {}
+  if (!isNewAccountDialog) {
+    try {
+      const res = await api.readPlatformConfig(pid, accountId)
+      if (res?.values) {
+        existing = res.values
+      }
+      if (res?.exists) {
+        isEdit = true
+      }
+    } catch {}
+  }
 
   // 加载 Agent 列表（不预选，因为一个 channel+accountId 可以被多个 agent 绑定）
   let agents = []
@@ -2547,11 +2552,12 @@ async function openConfigDialog(pid, page, state, accountId) {
   const supportsMultiAccount = supportsMessagingMultiAccount(pid)
 
   // 账号标识（多账号）；编辑时 accountId 非空会在 input value 中显示
+  const accountIdReadonly = isEdit && dialogAccountId
   const accountIdHtml = supportsMultiAccount ? `
     <div class="form-group">
       <label class="form-label">${t('channels.accountIdentifier')}</label>
-      <input class="form-input" name="__accountId" placeholder="${t('channels.accountIdPlaceholder')}" value="${escapeAttr(accountId != null ? accountId : '')}">
-      <div class="form-hint">${t('channels.accountIdHint')}</div>
+      <input class="form-input" name="__accountId" placeholder="${t('channels.accountIdPlaceholder')}" value="${escapeAttr(accountId != null ? accountId : '')}" ${accountIdReadonly ? 'readonly' : ''}>
+      <div class="form-hint">${accountIdReadonly ? t('channels.accountIdLockedHint') : t('channels.accountIdHint')}</div>
     </div>
   ` : ''
 
diff --git a/tests/channel-config-normalization.test.js b/tests/channel-config-normalization.test.js
index 8e4dea0..8e13c9b 100644
--- a/tests/channel-config-normalization.test.js
+++ b/tests/channel-config-normalization.test.js
@@ -7,6 +7,7 @@ import {
   listPlatformAccounts,
   mergeOpenClawMessagingPlatformConfig,
   resolveMessagingCredentialValueForSave,
+  resolvePlatformConfigEntry,
   normalizeMessagingPlatformForm,
 } from '../scripts/dev-api.js'
 
@@ -1028,6 +1029,15 @@ test('渠道读取会把 SecretRef 密钥显示为安全占位并携带原始对
   assert.deepEqual(values.__secretRefs, { botToken: secretRef })
 })
 
+test('未知账号标识不会回落到渠道根配置', () => {
+  const root = {
+    enabled: true,
+    botToken: { source: 'env', provider: 'default', id: 'TELEGRAM_BOT_TOKEN' },
+    accounts: { default: { botToken: 'default-token' } },
+  }
+  assert.equal(resolvePlatformConfigEntry(root, 'telegram', 'work'), null)
+})
+
 test('渠道保存时用户未改动 SecretRef 占位会保留原始密钥引用', () => {
   const secretRef = { source: 'env', provider: 'default', id: 'SLACK_BOT_TOKEN' }
   const value = resolveMessagingCredentialValueForSave({