diff --git a/e2e/changepw-form.playwright.ts b/e2e/changepw-form.playwright.ts
new file mode 100644
index 0000000..1a62de6
--- /dev/null
+++ b/e2e/changepw-form.playwright.ts
@@ -0,0 +1,56 @@
+// 增量 3 验收（2026-10-12 诊断报告）：改密弹窗表单语义——<form onSubmit> 承载提交
+//（Enter 可提交）、autocomplete 三段标注（username/current-password/new-password）、
+// 只读用户名关联、错误文案复用 humanChangePasswordError（401 不再一刀切）。
+// 驱动：scripts/e2e.sh 第 4 阶段（E2E_PLAIN_BASE=1）——表单语义与命令面无关，
+// 任意 auth-on 服务可验，普通基座段顺路覆盖；RDM 组合主跑（第 3 阶段）本文件自跳过。
+import { test, expect, type Page } from '@playwright/test'
+
+const OWNER = process.env.E2E_OWNER || 'e2e-auditor'
+const PASSWORD = process.env.E2E_PASSWORD || 'E2eAudit#2026'
+const PASSWORD2 = process.env.E2E_PASSWORD2 || 'E2eAudit#2026b'
+
+test.skip(!(process.env.PLAYWRIGHT_BASE_URL && process.env.E2E_PLAIN_BASE),
+  'set PLAYWRIGHT_BASE_URL + E2E_PLAIN_BASE (scripts/e2e.sh phase 4 drives this suite)')
+
+async function login(page: Page) {
+  await page.goto('/')
+  await page.getByPlaceholder('由管理员分配').fill(OWNER)
+  await page.getByPlaceholder('初始密码或常用密码').fill(PASSWORD)
+  await page.getByRole('button', { name: '登录', exact: true }).click()
+  const gate = page.getByText('修改密码')
+  const gated = await gate.waitFor({ state: 'visible', timeout: 5_000 }).then(() => true).catch(() => false)
+  if (gated) {
+    const pwInputs = page.locator('.lg-card input[type="password"]')
+    await pwInputs.nth(0).fill(PASSWORD)
+    await pwInputs.nth(1).fill(PASSWORD2)
+    await pwInputs.nth(2).fill(PASSWORD2)
+    await page.getByRole('button', { name: '设置新密码并进入' }).click()
+  } else {
+    await page.getByPlaceholder('初始密码或常用密码').fill(PASSWORD2)
+    await page.getByRole('button', { name: '登录', exact: true }).click()
+  }
+  await expect(page.locator('.tsb-tool', { hasText: '代理' })).toBeVisible({ timeout: 15_000 })
+}
+
+test('改密弹窗：form 提交、autocomplete/用户名关联、错误分类文案', async ({ page }) => {
+  await login(page)
+  await page.locator('.tsb-user').click()
+  await page.getByRole('button', { name: '修改密码…' }).click()
+  const dlg = page.getByRole('dialog', { name: '修改密码' })
+  await expect(dlg).toBeVisible()
+
+  // 用户名只读关联 + 三段 autocomplete。
+  const username = dlg.locator('input[autocomplete="username"]')
+  await expect(username).toHaveValue(OWNER)
+  await expect(username).toBeReadOnly()
+  await expect(dlg.locator('input[autocomplete="current-password"]')).toHaveCount(1)
+  await expect(dlg.locator('input[autocomplete="new-password"]')).toHaveCount(2)
+
+  // 表单语义：填错当前密码后按 Enter（不点按钮）提交——证明提交走 <form onSubmit>。
+  await dlg.locator('input[autocomplete="current-password"]').fill('definitely-wrong-pass')
+  await dlg.locator('input[autocomplete="new-password"]').first().fill('ANewPass#2026x')
+  await dlg.locator('input[autocomplete="new-password"]').nth(1).fill('ANewPass#2026x')
+  await dlg.locator('input[autocomplete="current-password"]').press('Enter')
+  // 后端 401 "current password incorrect" → humanChangePasswordError 的分类文案。
+  await expect(dlg.getByText('当前密码不正确')).toBeVisible({ timeout: 10_000 })
+})
diff --git a/src/components/AdminUsersModal.tsx b/src/components/AdminUsersModal.tsx
index a195626..511ec55 100644
--- a/src/components/AdminUsersModal.tsx
+++ b/src/components/AdminUsersModal.tsx
@@ -4,6 +4,7 @@ import { useState } from 'react'
 import { api } from '../api'
 import { store, useStore } from '../store'
 import { Icon } from '@ui'
+import { humanChangePasswordError } from './LoginPage'
 
 function Shell({ title, onClose, children }: { title: string; onClose: () => void; children: React.ReactNode }) {
   return (
@@ -20,7 +21,10 @@ function Shell({ title, onClose, children }: { title: string; onClose: () => voi
   )
 }
 
-/** 主动改密（账户菜单入口）：当前密码 + 新密码 + 确认。 */
+/** 主动改密（账户菜单入口）：用户名（只读关联）+ 当前密码 + 新密码 + 确认。
+ *  表单语义（2026-10-12 增量 3）：<form onSubmit> 承载提交（Enter 可用）、autocomplete
+ *  三段标注（username/current-password/new-password）、label 与 input 关联；
+ *  错误文案复用 humanChangePasswordError——401 不再一刀切成「当前密码不正确」。 */
 export function ChangePasswordModal({ onClose }: { onClose: () => void }) {
   const me = useStore(s => s.me)
   const [current, setCurrent] = useState('')
@@ -41,23 +45,28 @@ export function ChangePasswordModal({ onClose }: { onClose: () => void }) {
       store.toast('密码已更新')
       setTimeout(onClose, 900)
     } catch (e) {
-      setErr(String(e).includes('401') ? '当前密码不正确' : String(e))
+      setErr(humanChangePasswordError(String(e)))
     } finally { setBusy(false) }
   }
 
   return (
     <Shell title="修改密码" onClose={onClose}>
       {ok ? <div className="ad-notice">密码已更新，其他设备的会话已注销。</div> : (
-        <div className="ad-changepw">
-          <label className="lg-label">当前密码（{me?.owner ?? ''}）</label>
-          <input className="lg-input" type="password" value={current} onChange={e => setCurrent(e.target.value)} autoFocus />
-          <label className="lg-label">新密码（≥8 位）</label>
-          <input className="lg-input" type="password" value={next} onChange={e => setNext(e.target.value)} />
-          <label className="lg-label">确认新密码</label>
-          <input className="lg-input" type="password" value={confirm} onChange={e => setConfirm(e.target.value)} />
+        <form className="ad-changepw" onSubmit={e => { e.preventDefault(); submit() }}>
+          <label className="lg-label" htmlFor="changepw-username">用户名</label>
+          <input id="changepw-username" className="lg-input" value={me?.owner ?? ''} readOnly autoComplete="username" />
+          <label className="lg-label" htmlFor="changepw-current">当前密码</label>
+          <input id="changepw-current" className="lg-input" type="password" autoComplete="current-password"
+            value={current} onChange={e => setCurrent(e.target.value)} autoFocus />
+          <label className="lg-label" htmlFor="changepw-next">新密码（≥8 位）</label>
+          <input id="changepw-next" className="lg-input" type="password" autoComplete="new-password"
+            value={next} onChange={e => setNext(e.target.value)} />
+          <label className="lg-label" htmlFor="changepw-confirm">确认新密码</label>
+          <input id="changepw-confirm" className="lg-input" type="password" autoComplete="new-password"
+            value={confirm} onChange={e => setConfirm(e.target.value)} />
           {err && <div className="lg-err"><Icon name="alert" size={14} />{err}</div>}
-          <button className="lg-submit" disabled={busy || !current || !next || !confirm} onClick={submit}>{busy ? '提交中…' : '更新密码'}</button>
-        </div>
+          <button className="lg-submit" type="submit" disabled={busy || !current || !next || !confirm}>{busy ? '提交中…' : '更新密码'}</button>
+        </form>
       )}
     </Shell>
   )
diff --git a/src/components/SettingsModal.tsx b/src/components/SettingsModal.tsx
index cd426fb..51ca5d1 100644
--- a/src/components/SettingsModal.tsx
+++ b/src/components/SettingsModal.tsx
@@ -112,6 +112,16 @@ export function SettingsModal() {
   )
 }
 
+// 输入框语义（2026-10-12 增量 3）：仅秘密字段用密码框；普通文本用 text——
+// 无条件 type="password" 会把整排设置项当凭据表单（浏览器「password 不在 form 中/
+// 缺少 username」警告来源之一），也把普通文本无谓遮蔽。
+export function settingInputAttrs(desc: SettingDesc): { type: 'text' | 'password'; autoComplete: string } {
+  const isSecret = desc.secret || desc.type === 'secret'
+  return isSecret
+    ? { type: 'password', autoComplete: 'new-password' }
+    : { type: 'text', autoComplete: 'off' }
+}
+
 export function SettingInput({ desc, value, onChange }: { desc: SettingDesc; value: any; onChange: (v: any) => void }) {
   if (desc.type === 'boolean') {
     return <input type="checkbox" checked={value === true || value === 'true'} onChange={e => onChange(e.target.checked)} />
@@ -122,7 +132,8 @@ export function SettingInput({ desc, value, onChange }: { desc: SettingDesc; val
     </select>
   }
   const isSecret = desc.secret || desc.type === 'secret'
-  return <input type="password" autoComplete="new-password" style={{ width: '100%' }} value={typeof value === 'string' && value === '••••••' ? '' : (value ?? '')}
+  const attrs = settingInputAttrs(desc)
+  return <input type={attrs.type} autoComplete={attrs.autoComplete} style={{ width: '100%' }} value={typeof value === 'string' && value === '••••••' ? '' : (value ?? '')}
     placeholder={isSecret ? '（已配置，输入以覆盖）' : String(desc.default ?? '')}
     onChange={e => onChange(e.target.value)} />
 }
diff --git a/test/settings-input.test.ts b/test/settings-input.test.ts
new file mode 100644
index 0000000..6298107
--- /dev/null
+++ b/test/settings-input.test.ts
@@ -0,0 +1,25 @@
+import { describe, expect, it } from 'vitest'
+import { settingInputAttrs } from '../src/components/SettingsModal'
+
+// 2026-10-12 增量 3：配置输入按字段类型渲染——此前 SettingInput 默认分支无条件
+// type="password"，浏览器把整排设置项当凭据表单（「password 不在 form 中/缺少
+// username」警告的来源之一），且普通文本被无谓遮蔽。新契约：仅秘密字段用密码框。
+describe('settingInputAttrs', () => {
+  it('secret=true → 密码框 + new-password', () => {
+    expect(settingInputAttrs({ key: 'llm.apiKey', label: '密钥', type: 'string', secret: true } as any))
+      .toEqual({ type: 'password', autoComplete: 'new-password' })
+  })
+
+  it('type=secret → 密码框', () => {
+    expect(settingInputAttrs({ key: 'x', label: 'X', type: 'secret' } as any).type).toBe('password')
+  })
+
+  it('普通文本 → text + off（不遮蔽、不当凭据）', () => {
+    const a = settingInputAttrs({ key: 'llm.baseUrl', label: '地址', type: 'string' } as any)
+    expect(a).toEqual({ type: 'text', autoComplete: 'off' })
+  })
+
+  it('无类型标注的默认项 → text', () => {
+    expect(settingInputAttrs({ key: 'ui.language', label: '语言' } as any).type).toBe('text')
+  })
+})