diff --git a/apps/desktop/src/main/__tests__/assistant-stream.test.ts b/apps/desktop/src/main/__tests__/assistant-stream.test.ts
index e0db00c5d5..1a0dc994ef 100644
--- a/apps/desktop/src/main/__tests__/assistant-stream.test.ts
+++ b/apps/desktop/src/main/__tests__/assistant-stream.test.ts
@@ -22,9 +22,18 @@ import { describe, it } from 'node:test';
 import {
   ASSISTANT_MAX_DELTA_CHARS,
   ASSISTANT_MAX_TOTAL_CHARS,
-  applyAssistantComplete,
-  applyAssistantDelta,
+  applyAssistantComplete as applyAssistantCompleteWithLocale,
+  applyAssistantDelta as applyAssistantDeltaWithLocale,
 } from '@maka/ui/assistant-stream';
+// Tests exercise stream mechanics, not copy; pin zh so markers stay verbatim.
+const applyAssistantDelta = (prev: string, delta: string, options?: Partial<Parameters<typeof applyAssistantDeltaWithLocale>[2]>) =>
+  applyAssistantDeltaWithLocale(prev, delta, { locale: 'zh', ...options });
+const applyAssistantComplete = (text: string, options?: Partial<Parameters<typeof applyAssistantCompleteWithLocale>[1]>) =>
+  applyAssistantCompleteWithLocale(text, { locale: 'zh', ...options });
+
+
+
+
 
 function visibleDeltaResult(result: ReturnType<typeof applyAssistantDelta>) {
   return {
diff --git a/apps/desktop/src/main/__tests__/health-center-copy.test.ts b/apps/desktop/src/main/__tests__/health-center-copy.test.ts
index e8f7a6aa5f..af4d24bdd2 100644
--- a/apps/desktop/src/main/__tests__/health-center-copy.test.ts
+++ b/apps/desktop/src/main/__tests__/health-center-copy.test.ts
@@ -19,6 +19,7 @@
 
 import assert from 'node:assert/strict';
 import { test } from 'node:test';
+import { connectionLastTestMessageDisplay } from '../../renderer/features/connection-settings/index.js';
 import { getHealthCenterCopy } from '../../renderer/locales/settings-health-copy.js';
 
 test('labels blocker counts as global across filtered health views', () => {
@@ -31,3 +32,85 @@ test('labels blocker counts as global across filtered health views', () => {
     'Across all health signals, 1 of 6 blocks sending',
   );
 });
+
+const signal = (overrides: Partial<import('@maka/core/health').HealthSignal>): import('@maka/core/health').HealthSignal => ({
+  id: 'connection:demo',
+  label: 'Demo',
+  scope: 'llm_connection',
+  layer: 'configuration',
+  status: 'info',
+  source: 'settings',
+  checkedAt: 0,
+  message: 'not_default_source',
+  ...overrides,
+});
+
+test('renders configuration message codes distinctly in both locales', () => {
+  const zh = getHealthCenterCopy('zh');
+  const en = getHealthCenterCopy('en');
+  assert.equal(zh.signalMessage(signal({ message: 'not_default_source' })), '不是工作区的默认模型来源。');
+  assert.equal(en.signalMessage(signal({ message: 'not_default_source' })), 'Not the workspace default model source.');
+  assert.equal(zh.signalMessage(signal({ message: 'no_models_enabled' })), '没有启用任何模型。');
+  assert.equal(en.signalMessage(signal({ message: 'no_models_enabled' })), 'No models are enabled on this connection.');
+});
+
+test('renders runtime probe details from structured params, not string parsing', () => {
+  const detail = { kind: 'runtime_probe_result', modelId: 'claude-sonnet-5', latencyMs: 812, errorClass: 'timeout' } as const;
+  assert.equal(
+    getHealthCenterCopy('zh').signalDetail(signal({ detail })),
+    '模型=claude-sonnet-5 · 延迟=812ms · 错误类型=请求超时',
+  );
+  assert.equal(
+    getHealthCenterCopy('en').signalDetail(signal({ detail })),
+    'Model=claude-sonnet-5 · Latency=812ms · Error type=Request timed out',
+  );
+
+  const unknown = { ...detail, errorClass: 'future_runtime_error' };
+  assert.equal(
+    getHealthCenterCopy('zh').signalDetail(signal({ detail: unknown })),
+    '模型=claude-sonnet-5 · 延迟=812ms · 错误类型=未知错误',
+  );
+  assert.equal(
+    getHealthCenterCopy('en').signalDetail(signal({ detail: unknown })),
+    'Model=claude-sonnet-5 · Latency=812ms · Error type=Unknown error',
+  );
+});
+
+test('degrades capability reasons safely in both locales', () => {
+  const unknown = { kind: 'capability_reason' } as const;
+  assert.equal(
+    getHealthCenterCopy('zh').signalDetail(signal({ detail: unknown })),
+    '状态详情请见对应设置页。',
+  );
+  assert.equal(
+    getHealthCenterCopy('en').signalDetail(signal({ detail: unknown })),
+    'See the corresponding settings page for details.',
+  );
+});
+
+test('maps connection test error classes without exposing machine tokens', () => {
+  const auth = { kind: 'last_test_error_class', errorClass: 'auth' } as const;
+  assert.equal(getHealthCenterCopy('zh').signalDetail(signal({ detail: auth })), '鉴权失败');
+  assert.equal(getHealthCenterCopy('en').signalDetail(signal({ detail: auth })), 'Authentication failed');
+
+  const unknown = { kind: 'last_test_message' } as const;
+  assert.equal(
+    getHealthCenterCopy('zh').signalDetail(signal({ detail: unknown })),
+    '连接测试状态暂时无法显示，请重新测试。',
+  );
+  assert.equal(
+    getHealthCenterCopy('en').signalDetail(signal({ detail: unknown })),
+    'The connection test status is temporarily unavailable. Test again.',
+  );
+});
+
+test('maps connection test error classes in connection details', () => {
+  assert.equal(connectionLastTestMessageDisplay('auth', 'zh'), '鉴权失败');
+  assert.equal(connectionLastTestMessageDisplay('auth', 'en'), 'Authentication failed');
+});
+
+test('suffixes runtime signal labels per locale from the id, not the producer', () => {
+  const runtime = signal({ id: 'connection:demo:runtime', label: 'Demo' });
+  assert.equal(getHealthCenterCopy('zh').signalLabel(runtime), 'Demo 运行态');
+  assert.equal(getHealthCenterCopy('en').signalLabel(runtime), 'Demo runtime');
+});
diff --git a/apps/desktop/src/main/__tests__/thinking-stream.test.ts b/apps/desktop/src/main/__tests__/thinking-stream.test.ts
index 8d33f1df80..78635afa9a 100644
--- a/apps/desktop/src/main/__tests__/thinking-stream.test.ts
+++ b/apps/desktop/src/main/__tests__/thinking-stream.test.ts
@@ -21,7 +21,16 @@
 
 import { strict as assert } from 'node:assert';
 import { describe, it } from 'node:test';
-import { applyThinkingComplete, applyThinkingDelta } from '@maka/ui';
+import { applyThinkingComplete as applyThinkingCompleteWithLocale, applyThinkingDelta as applyThinkingDeltaWithLocale } from '@maka/ui';
+// Tests exercise stream mechanics, not copy; pin zh so markers stay verbatim.
+const applyThinkingDelta = (prev: string, delta: string, options?: Partial<Parameters<typeof applyThinkingDeltaWithLocale>[2]>) =>
+  applyThinkingDeltaWithLocale(prev, delta, { locale: 'zh', ...options });
+const applyThinkingComplete = (text: string, options?: Partial<Parameters<typeof applyThinkingCompleteWithLocale>[1]>) =>
+  applyThinkingCompleteWithLocale(text, { locale: 'zh', ...options });
+
+
+
+
 
 describe('applyThinkingDelta — secondary redaction', () => {
   it('masks raw `Authorization: Bearer ...` text before storing', () => {
diff --git a/apps/desktop/src/main/__tests__/tool-output-stream.test.ts b/apps/desktop/src/main/__tests__/tool-output-stream.test.ts
index ca66c39051..630a008e83 100644
--- a/apps/desktop/src/main/__tests__/tool-output-stream.test.ts
+++ b/apps/desktop/src/main/__tests__/tool-output-stream.test.ts
@@ -48,9 +48,15 @@ import {
   TOOL_STREAM_MAX_CHUNKS,
   TOOL_STREAM_MAX_CHUNK_CHARS,
   TOOL_STREAM_MAX_TOTAL_CHARS,
-  applyToolOutputChunk,
+  applyToolOutputChunk as applyToolOutputChunkWithLocale,
   type ToolOutputChunk,
 } from '@maka/ui';
+// Tests exercise stream mechanics, not copy; pin zh so markers stay verbatim.
+const applyToolOutputChunk = (prev: Parameters<typeof applyToolOutputChunkWithLocale>[0], chunk: Parameters<typeof applyToolOutputChunkWithLocale>[1], options?: Partial<Parameters<typeof applyToolOutputChunkWithLocale>[2]>) =>
+  applyToolOutputChunkWithLocale(prev, chunk, { locale: 'zh', ...options });
+
+
+
 
 function chunk(seq: number, text: string, stream: 'stdout' | 'stderr' = 'stdout', redacted = false): ToolOutputChunk {
   return { seq, text, stream, redacted, createdAt: 1_700_000_000_000 + seq };
diff --git a/apps/desktop/src/renderer/features/connection-settings/settings-provider-copy.ts b/apps/desktop/src/renderer/features/connection-settings/settings-provider-copy.ts
index 28cfe0f7a9..59c5109a62 100644
--- a/apps/desktop/src/renderer/features/connection-settings/settings-provider-copy.ts
+++ b/apps/desktop/src/renderer/features/connection-settings/settings-provider-copy.ts
@@ -167,6 +167,7 @@ const zhCopy = {
     filterMatches: (count: number) => (count === 0 ? '没有匹配的结果' : `${count} 个匹配结果`),
     connectionStatuses: { retired: '已停用 · 请删除', reauth: '需要重新登录', disabledFailed: '暂不可用 · 上次连接失败', disabled: '暂不可用', failed: '上次连接失败' },
     lastTest: {
+      auth: '鉴权失败', timeout: '请求超时', provider_unavailable: '模型服务返回错误', network: '网络错误', invalid_response: '模型服务返回错误', unknown: '连接测试失败',
       '连接已验证': '连接已验证', '鉴权失败': '鉴权失败', '请求超时': '请求超时', '网络错误': '网络错误', '模型服务返回错误': '模型服务返回错误', '连接测试失败': '连接测试失败',
       'connection verified': '连接已验证', 'authentication failed': '鉴权失败', 'request timed out': '请求超时', 'network error': '网络错误', 'provider returned an error': '模型服务返回错误', 'connection test failed': '连接测试失败',
       'claude oauth 未登录。': 'Claude OAuth 未登录。', 'claude oauth 本地凭据读取失败。': 'Claude OAuth 本地凭据读取失败。', 'claude oauth 需要重新登录。': 'Claude OAuth 需要重新登录。', 'claude oauth 已登录。': 'Claude OAuth 已登录。', 'claude oauth 已退出登录。': 'Claude OAuth 已退出登录。',
@@ -337,6 +338,7 @@ const enCopy: ProviderSettingsCopy = {
     filterMatches: (count: number) => (count === 0 ? 'No matches' : count === 1 ? '1 match' : `${count} matches`),
     connectionStatuses: { retired: 'Retired · delete it', reauth: 'Sign-in required', disabledFailed: 'Unavailable · last connection failed', disabled: 'Unavailable', failed: 'Last connection failed' },
     lastTest: {
+      auth: 'Authentication failed', timeout: 'Request timed out', provider_unavailable: 'Model service returned an error', network: 'Network error', invalid_response: 'Model service returned an error', unknown: 'Connection test failed',
       '连接已验证': 'Connection verified', '鉴权失败': 'Authentication failed', '请求超时': 'Request timed out', '网络错误': 'Network error', '模型服务返回错误': 'Model service returned an error', '连接测试失败': 'Connection test failed',
       'connection verified': 'Connection verified', 'authentication failed': 'Authentication failed', 'request timed out': 'Request timed out', 'network error': 'Network error', 'provider returned an error': 'Model service returned an error', 'connection test failed': 'Connection test failed',
       'claude oauth 未登录。': 'Claude OAuth is signed out.', 'claude oauth 本地凭据读取失败。': 'Could not read local Claude OAuth credentials.', 'claude oauth 需要重新登录。': 'Claude OAuth requires sign-in.', 'claude oauth 已登录。': 'Claude OAuth is signed in.', 'claude oauth 已退出登录。': 'Claude OAuth signed out.',
diff --git a/apps/desktop/src/renderer/locales/settings-health-copy.ts b/apps/desktop/src/renderer/locales/settings-health-copy.ts
index 6bb4aebbb9..685c929b73 100644
--- a/apps/desktop/src/renderer/locales/settings-health-copy.ts
+++ b/apps/desktop/src/renderer/locales/settings-health-copy.ts
@@ -18,7 +18,15 @@
  */
 
 import type { StatusSemantic } from '@maka/ui';
-import type { HealthSignal, HealthSignalLayer, HealthSignalSource, HealthSignalStatus } from '@maka/core/health';
+import type {
+  HealthConnectionTestErrorClass,
+  HealthSignal,
+  HealthSignalDetail,
+  HealthSignalLayer,
+  HealthSignalMessageCode,
+  HealthSignalSource,
+  HealthSignalStatus,
+} from '@maka/core/health';
 
 import type { UiCatalog, UiLocale } from '@maka/core/ui-locale';
 
@@ -102,9 +110,9 @@ const SETTINGS_HEALTH_COPY = {
     scopes: { app: '应用', llm_connection: 'LLM 连接', bot: '机器人', capability: '能力', storage: '存储' },
     sources: { connection_test: '连接测试', capability_snapshot: '能力快照', permission_snapshot: '权限快照', runtime_probe: '运行态探测', settings: '设置', storage: '本地存储' },
     source: '来源：', blocksSend: '阻塞发送', blocksCapability: '阻塞能力',
-    signalLabel: (signal) => signal.label,
-    signalMessage: (signal) => signal.message,
-    signalDetail: (signal) => signal.detail,
+    signalLabel: (signal) => (signal.id.endsWith(':runtime') ? `${signal.label} 运行态` : signal.label),
+    signalMessage: (signal) => signalMessagesZh[signal.message],
+    signalDetail: (signal) => signalDetailZh(signal.detail),
   },
   en: {
     loading: 'Loading health snapshot', readFailed: 'Could not read health snapshot', noData: 'The health service returned no data.', readAgain: 'Read again',
@@ -121,9 +129,9 @@ const SETTINGS_HEALTH_COPY = {
     scopes: { app: 'App', llm_connection: 'LLM connection', bot: 'Bot', capability: 'Capability', storage: 'Storage' },
     sources: { connection_test: 'Connection test', capability_snapshot: 'Capability snapshot', permission_snapshot: 'Permission snapshot', runtime_probe: 'Runtime probe', settings: 'Settings', storage: 'Local storage' },
     source: 'Source: ', blocksSend: 'Blocks sending', blocksCapability: 'Blocks capability',
-    signalLabel: englishSignalLabel,
-    signalMessage: englishSignalMessage,
-    signalDetail: englishSignalDetail,
+    signalLabel: (signal) => (signal.id.endsWith(':runtime') ? `${signal.label} runtime` : signal.label),
+    signalMessage: (signal) => signalMessagesEn[signal.message],
+    signalDetail: (signal) => signalDetailEn(signal.detail),
   },
 } satisfies UiCatalog<HealthCenterCopy>;
 
@@ -131,57 +139,120 @@ export function getHealthCenterCopy(locale: UiLocale): HealthCenterCopy {
   return SETTINGS_HEALTH_COPY[locale];
 }
 
-function englishSignalLabel(signal: HealthSignal): string {
-  if (signal.id.endsWith(':runtime')) return `${signal.label.replace(/\s*运行态$/, '')} runtime`;
-  return signal.label;
-}
+const signalMessagesZh: Record<HealthSignalMessageCode, string> = {
+  connection_disabled: '连接已关闭。',
+  awaiting_default_model: '等待选择默认模型。',
+  validation_passed: '凭据与端点验证已通过。',
+  needs_reauth: '连接需要重新修复认证。',
+  validation_failed: '上次连接验证失败。',
+  no_models_enabled: '没有启用任何模型。',
+  not_default_source: '不是工作区的默认模型来源。',
+  awaiting_validation: '等待验证连接。',
+  runtime_probe_pending: '等待完成发送运行态探测。',
+  send_completed: '最近一次发送已完成。',
+  send_aborted: '最近一次发送已由用户停止。',
+  send_failed: '最近一次发送失败。',
+  capability_ok: '能力门禁已满足。',
+  capability_paused: '能力已关闭或暂停。',
+  capability_not_configured: '等待补齐能力配置。',
+  capability_denied: '能力被必要系统权限阻塞。',
+  capability_degraded: '能力运行态探测处于降级状态。',
+};
 
-function englishSignalMessage(signal: HealthSignal): string {
-  if (signal.scope === 'llm_connection') {
-    if (signal.layer === 'configuration') {
-      // Three-way split matching the producer's configuration states
-      // (packages/core/src/health.ts) — the message string is the anchor,
-      // the same way the runtime_probe branch below parses the producer's
-      // detail. Falling back on status alone described an enabled
-      // non-default connection as disabled.
-      if (signal.message === '不是工作区的默认模型来源。') {
-        return 'Not the workspace default model source.';
-      }
-      if (signal.message === '没有启用任何模型。') {
-        return 'No models are enabled on this connection.';
-      }
-      return signal.status === 'info' ? 'Connection is disabled.' : 'Select a default model.';
-    }
-    if (signal.layer === 'runtime_probe') {
-      return { ok: 'The latest send completed.', info: 'The latest send was stopped by the user.', warning: 'The latest send failed.', error: 'The latest send failed.', unknown: 'Waiting for a send-path runtime probe.' }[signal.status];
-    }
-    return { ok: 'Credentials and endpoint validation passed.', info: 'Connection validation needs attention.', warning: 'The latest connection validation failed.', error: 'The connection needs authentication repair.', unknown: 'Waiting to validate the connection.' }[signal.status];
-  }
-  if (signal.scope === 'capability' || signal.scope === 'bot') {
-    return { ok: 'Capability requirements are satisfied.', info: 'The capability is disabled or paused.', warning: 'Capability configuration is incomplete.', error: 'The capability is blocked or degraded.', unknown: 'Capability state is unknown.' }[signal.status];
+const signalMessagesEn: Record<HealthSignalMessageCode, string> = {
+  connection_disabled: 'Connection is disabled.',
+  awaiting_default_model: 'Select a default model.',
+  validation_passed: 'Credentials and endpoint validation passed.',
+  needs_reauth: 'The connection needs authentication repair.',
+  validation_failed: 'The latest connection validation failed.',
+  no_models_enabled: 'No models are enabled on this connection.',
+  not_default_source: 'Not the workspace default model source.',
+  awaiting_validation: 'Waiting to validate the connection.',
+  runtime_probe_pending: 'Waiting for a send-path runtime probe.',
+  send_completed: 'The latest send completed.',
+  send_aborted: 'The latest send was stopped by the user.',
+  send_failed: 'The latest send failed.',
+  capability_ok: 'Capability requirements are satisfied.',
+  capability_paused: 'The capability is disabled or paused.',
+  capability_not_configured: 'Capability configuration is incomplete.',
+  capability_denied: 'The capability is blocked by a required system permission.',
+  capability_degraded: 'The capability runtime probe is degraded.',
+};
+
+const connectionTestErrorMessages = {
+  zh: {
+    auth: '鉴权失败',
+    timeout: '请求超时',
+    provider_unavailable: '模型服务返回错误',
+    network: '网络错误',
+    invalid_response: '模型服务返回错误',
+    unknown: '连接测试失败',
+  },
+  en: {
+    auth: 'Authentication failed',
+    timeout: 'Request timed out',
+    provider_unavailable: 'Model service returned an error',
+    network: 'Network error',
+    invalid_response: 'Model service returned an error',
+    unknown: 'Connection test failed',
+  },
+} satisfies UiCatalog<Record<HealthConnectionTestErrorClass, string>>;
+
+function signalDetailZh(detail: HealthSignalDetail | undefined): string | undefined {
+  if (!detail) return undefined;
+  switch (detail.kind) {
+    case 'validation_scope_note':
+      return '这是连接验证结果，不代表发送、流式输出或中断通路已经运行通过。';
+    case 'no_models_enabled_hint':
+      return '在 设置 · 模型 的连接详情里启用至少一个模型后才能使用该连接。';
+    case 'not_default_source_hint':
+      return '在任务中显式选择该连接的模型即可正常使用;新对话的默认模型在 设置 · 通用 配置。';
+    case 'runtime_probe_layers_note':
+      return '凭据验证与真实发送、流式输出、中断通路是两层健康信号。';
+    case 'runtime_probe_result':
+      return [
+        `模型=${detail.modelId}`,
+        `延迟=${detail.latencyMs}ms`,
+        ...(detail.errorClass ? [`错误类型=${localizedRuntimeErrorClass(detail.errorClass, 'zh')}`] : []),
+      ].join(' · ');
+    case 'capability_reason':
+      return '状态详情请见对应设置页。';
+    case 'last_test_error_class':
+      return connectionTestErrorMessages.zh[detail.errorClass];
+    case 'last_test_message':
+      return '连接测试状态暂时无法显示，请重新测试。';
   }
-  return { ok: 'The health check passed.', info: 'Review this health signal.', warning: 'This health signal needs attention.', error: 'This health signal reports an error.', unknown: 'Health state is unknown.' }[signal.status];
 }
 
-function englishSignalDetail(signal: HealthSignal): string | undefined {
-  if (!signal.detail) return undefined;
-  if (signal.scope === 'llm_connection' && signal.layer === 'validation' && signal.status === 'ok') {
-    return 'This validates the connection only; it does not prove send, streaming, or interruption paths have run successfully.';
-  }
-  if (signal.scope === 'llm_connection' && signal.layer === 'runtime_probe') {
-    const model = signal.detail.match(/模型=([^·]+)/)?.[1]?.trim();
-    const latency = signal.detail.match(/延迟=([^·]+)/)?.[1]?.trim();
-    const errorClass = signal.detail.match(/错误类型=([^·]+)/)?.[1]?.trim();
-    const parts = [model && `Model=${model}`, latency && `Latency=${latency}`, errorClass && `Error type=${errorClass}`].filter(Boolean);
-    return parts.length > 0 ? parts.join(' · ') : 'Runtime details are available in Usage settings.';
-  }
-  if (signal.scope === 'llm_connection' && signal.layer === 'configuration') {
-    if (signal.message === '不是工作区的默认模型来源。') {
-      return 'Models on this connection stay usable when selected explicitly in a task; the default model for new chats lives in Settings · General.';
-    }
-    if (signal.message === '没有启用任何模型。') {
+function signalDetailEn(detail: HealthSignalDetail | undefined): string | undefined {
+  if (!detail) return undefined;
+  switch (detail.kind) {
+    case 'validation_scope_note':
+      return 'This validates the connection only; it does not prove send, streaming, or interruption paths have run successfully.';
+    case 'no_models_enabled_hint':
       return "Enable at least one model in this connection's detail view under Settings · Models.";
-    }
+    case 'not_default_source_hint':
+      return 'Models on this connection stay usable when selected explicitly in a task; the default model for new chats lives in Settings · General.';
+    case 'runtime_probe_layers_note':
+      return 'Credential validation and real send, streaming, and interruption paths are two separate health layers.';
+    case 'runtime_probe_result':
+      return [
+        `Model=${detail.modelId}`,
+        `Latency=${detail.latencyMs}ms`,
+        ...(detail.errorClass ? [`Error type=${localizedRuntimeErrorClass(detail.errorClass, 'en')}`] : []),
+      ].join(' · ');
+    case 'capability_reason':
+      return 'See the corresponding settings page for details.';
+    case 'last_test_error_class':
+      return connectionTestErrorMessages.en[detail.errorClass];
+    case 'last_test_message':
+      return 'The connection test status is temporarily unavailable. Test again.';
   }
-  return 'See the corresponding settings page for details.';
+}
+
+function localizedRuntimeErrorClass(errorClass: string, locale: UiLocale): string {
+  const messages: Readonly<Record<string, string | undefined>> = connectionTestErrorMessages[locale];
+  const normalized = errorClass.toLowerCase();
+  if (normalized === 'unknown') return locale === 'zh' ? '未知错误' : 'Unknown error';
+  return messages[normalized] ?? (locale === 'zh' ? '未知错误' : 'Unknown error');
 }
diff --git a/apps/desktop/stories/settings/settings-pages.stories.tsx b/apps/desktop/stories/settings/settings-pages.stories.tsx
index e3be3bb49e..098cf07c63 100644
--- a/apps/desktop/stories/settings/settings-pages.stories.tsx
+++ b/apps/desktop/stories/settings/settings-pages.stories.tsx
@@ -589,16 +589,6 @@ const capabilitySnapshot: CapabilitySnapshotCollection = {
 };
 
 const healthSignals: HealthSignal[] = [
-  {
-    id: 'app:config',
-    label: '应用配置',
-    scope: 'app',
-    layer: 'configuration',
-    status: 'ok',
-    source: 'settings',
-    checkedAt: NOW - 60_000,
-    message: '配置文件可读写，schema 版本为最新。',
-  },
   {
     id: 'conn:zai-live',
     label: 'Z.AI Live',
@@ -607,8 +597,8 @@ const healthSignals: HealthSignal[] = [
     status: 'ok',
     source: 'connection_test',
     checkedAt: NOW - 12 * 60_000,
-    message: '连接测试通过，延迟 210ms。',
-    detail: '验证通过只代表凭据可用，实际可用性仍需运行态探测确认。',
+    message: 'validation_passed',
+    detail: { kind: 'validation_scope_note' },
   },
   {
     id: 'conn:openai-review',
@@ -618,8 +608,8 @@ const healthSignals: HealthSignal[] = [
     status: 'error',
     source: 'connection_test',
     checkedAt: NOW - 3 * 60_000,
-    message: '连接测试失败：HTTP 401 invalid_api_key。',
-    detail: '凭据已失效或被吊销，请在「模型」页重新填写 API Key 后再次测试。',
+    message: 'needs_reauth',
+    detail: { kind: 'last_test_message' },
     blocksSend: true,
   },
   {
@@ -630,7 +620,7 @@ const healthSignals: HealthSignal[] = [
     status: 'info',
     source: 'capability_snapshot',
     checkedAt: NOW - 60_000,
-    message: '功能已开启，但仍以逐次审批模式运行。',
+    message: 'capability_paused',
     relatedCapabilityId: 'computer_use',
   },
   {
@@ -641,21 +631,11 @@ const healthSignals: HealthSignal[] = [
     status: 'warning',
     source: 'runtime_probe',
     checkedAt: NOW - 5 * 60_000,
-    message: '探测超时，已回落到只读观察模式。',
-    detail: 'maka-cu 未在 3000ms 内完成握手；下一次探测会在功能被调用时自动触发。',
+    message: 'capability_degraded',
+    detail: { kind: 'capability_reason' },
     relatedCapabilityId: 'computer_use',
     blocksCapability: true,
   },
-  {
-    id: 'storage:sessions',
-    label: '会话存储',
-    scope: 'storage',
-    layer: 'storage',
-    status: 'ok',
-    source: 'storage',
-    checkedAt: NOW - 60_000,
-    message: 'SQLite 库可写，WAL 检查点正常。',
-  },
 ];
 
 const healthSnapshot: HealthSnapshot = buildHealthSnapshot(NOW - 45_000, healthSignals);
@@ -2623,8 +2603,8 @@ export const HealthCenter: Story = {
       expect(errorFilter).toHaveAttribute('aria-pressed', 'true');
       expect(canvas.getByText('OpenAI Review')).toBeInTheDocument();
       expect(canvas.queryByText('Z.AI Live')).not.toBeInTheDocument();
-      expect(canvas.getByText('全部健康信号中，1/6 条会阻塞发送')).toBeInTheDocument();
-      expect(canvas.getByText('全部健康信号中，1/6 条会阻塞能力')).toBeInTheDocument();
+      expect(canvas.getByText('全部健康信号中，1/4 条会阻塞发送')).toBeInTheDocument();
+      expect(canvas.getByText('全部健康信号中，1/4 条会阻塞能力')).toBeInTheDocument();
     });
     await userEvent.click(errorFilter);
     await waitFor(() => {
diff --git a/packages/core/src/__tests__/health.test.ts b/packages/core/src/__tests__/health.test.ts
index 0e751851a0..9bb9bf8a19 100644
--- a/packages/core/src/__tests__/health.test.ts
+++ b/packages/core/src/__tests__/health.test.ts
@@ -44,6 +44,20 @@ describe('HealthSignal contract', () => {
     assert.strictEqual(result.source, 'connection_test');
   });
 
+  test('separates connection test error classes from legacy diagnostics', () => {
+    const coded = healthSignalFromConnection(
+      connection({ lastTestStatus: 'needs_reauth', lastTestMessage: 'auth' }),
+      20,
+    );
+    assert.deepStrictEqual(coded.detail, { kind: 'last_test_error_class', errorClass: 'auth' });
+
+    const legacy = healthSignalFromConnection(
+      connection({ lastTestStatus: 'error', lastTestMessage: 'HTTP 502 upstream failure' }),
+      20,
+    );
+    assert.deepStrictEqual(legacy.detail, { kind: 'last_test_message' });
+  });
+
   test('a missing default model warns only when the workspace has no default target', () => {
     // The catalog projects `defaultModel` onto exactly one connection (the
     // default target). With a default configured elsewhere, an enabled
diff --git a/packages/core/src/health.ts b/packages/core/src/health.ts
index e88582cc56..d36e1d5ab5 100644
--- a/packages/core/src/health.ts
+++ b/packages/core/src/health.ts
@@ -46,6 +46,43 @@ export type HealthSignalSource =
   | 'settings'
   | 'storage';
 
+export type HealthSignalMessageCode =
+  | 'connection_disabled'
+  | 'awaiting_default_model'
+  | 'validation_passed'
+  | 'needs_reauth'
+  | 'validation_failed'
+  | 'no_models_enabled'
+  | 'not_default_source'
+  | 'awaiting_validation'
+  | 'runtime_probe_pending'
+  | 'send_completed'
+  | 'send_aborted'
+  | 'send_failed'
+  | 'capability_ok'
+  | 'capability_paused'
+  | 'capability_not_configured'
+  | 'capability_denied'
+  | 'capability_degraded';
+
+export type HealthConnectionTestErrorClass =
+  | 'auth'
+  | 'timeout'
+  | 'provider_unavailable'
+  | 'network'
+  | 'invalid_response'
+  | 'unknown';
+
+export type HealthSignalDetail =
+  | { kind: 'validation_scope_note' }
+  | { kind: 'no_models_enabled_hint' }
+  | { kind: 'not_default_source_hint' }
+  | { kind: 'runtime_probe_layers_note' }
+  | { kind: 'runtime_probe_result'; modelId: string; latencyMs: number; errorClass?: string }
+  | { kind: 'capability_reason' }
+  | { kind: 'last_test_error_class'; errorClass: HealthConnectionTestErrorClass }
+  | { kind: 'last_test_message' };
+
 export interface HealthSignal {
   id: string;
   label: string;
@@ -54,8 +91,8 @@ export interface HealthSignal {
   status: HealthSignalStatus;
   source: HealthSignalSource;
   checkedAt: number;
-  message: string;
-  detail?: string;
+  message: HealthSignalMessageCode;
+  detail?: HealthSignalDetail;
   relatedCapabilityId?: CapabilityId;
   blocksSend?: boolean;
   blocksCapability?: boolean;
@@ -151,7 +188,7 @@ export function healthSignalFromConnection(
       status: 'info',
       source: 'settings',
       checkedAt,
-      message: '连接已关闭。',
+      message: 'connection_disabled',
       blocksSend: false,
     };
   }
@@ -165,7 +202,7 @@ export function healthSignalFromConnection(
       status: 'warning',
       source: 'settings',
       checkedAt,
-      message: '等待选择默认模型。',
+      message: 'awaiting_default_model',
       blocksSend: true,
     };
   }
@@ -179,8 +216,8 @@ export function healthSignalFromConnection(
       status: 'ok',
       source: 'connection_test',
       checkedAt: timeFromIso(connection.lastTestAt) ?? checkedAt,
-      message: '凭据与端点验证已通过。',
-      detail: '这是连接验证结果，不代表发送、流式输出或中断通路已经运行通过。',
+      message: 'validation_passed',
+      detail: { kind: 'validation_scope_note' },
       blocksSend: false,
     };
   }
@@ -194,8 +231,10 @@ export function healthSignalFromConnection(
       status: 'error',
       source: 'connection_test',
       checkedAt: timeFromIso(connection.lastTestAt) ?? checkedAt,
-      message: '连接需要重新修复认证。',
-      detail: connection.lastTestMessage,
+      message: 'needs_reauth',
+      ...(connection.lastTestMessage
+        ? { detail: connectionLastTestDetail(connection.lastTestMessage) }
+        : {}),
       blocksSend: true,
     };
   }
@@ -209,8 +248,10 @@ export function healthSignalFromConnection(
       status: 'warning',
       source: 'connection_test',
       checkedAt: timeFromIso(connection.lastTestAt) ?? checkedAt,
-      message: '上次连接验证失败。',
-      detail: connection.lastTestMessage,
+      message: 'validation_failed',
+      ...(connection.lastTestMessage
+        ? { detail: connectionLastTestDetail(connection.lastTestMessage) }
+        : {}),
       blocksSend: true,
     };
   }
@@ -230,8 +271,8 @@ export function healthSignalFromConnection(
         status: 'warning',
         source: 'settings',
         checkedAt,
-        message: '没有启用任何模型。',
-        detail: '在 设置 · 模型 的连接详情里启用至少一个模型后才能使用该连接。',
+        message: 'no_models_enabled',
+        detail: { kind: 'no_models_enabled_hint' },
         blocksSend: false,
       };
     }
@@ -243,8 +284,8 @@ export function healthSignalFromConnection(
       status: 'info',
       source: 'settings',
       checkedAt,
-      message: '不是工作区的默认模型来源。',
-      detail: '在任务中显式选择该连接的模型即可正常使用;新对话的默认模型在 设置 · 通用 配置。',
+      message: 'not_default_source',
+      detail: { kind: 'not_default_source_hint' },
       blocksSend: false,
     };
   }
@@ -257,7 +298,7 @@ export function healthSignalFromConnection(
     status: 'unknown',
     source: 'connection_test',
     checkedAt,
-    message: '等待验证连接。',
+    message: 'awaiting_validation',
     blocksSend: false,
   };
 }
@@ -272,14 +313,14 @@ export function healthSignalFromConnectionRuntime(
   if (!latestRuntimeProbe) {
     return {
       id: `connection:${connection.slug}:runtime`,
-      label: `${connection.name} 运行态`,
+      label: connection.name,
       scope: 'llm_connection',
       layer: 'runtime_probe',
       status: 'unknown',
       source: 'runtime_probe',
       checkedAt,
-      message: '等待完成发送运行态探测。',
-      detail: '凭据验证与真实发送、流式输出、中断通路是两层健康信号。',
+      message: 'runtime_probe_pending',
+      detail: { kind: 'runtime_probe_layers_note' },
       blocksSend: false,
     };
   }
@@ -287,7 +328,7 @@ export function healthSignalFromConnectionRuntime(
   const status = runtimeStatusToHealth(latestRuntimeProbe.status);
   return {
     id: `connection:${connection.slug}:runtime`,
-    label: `${connection.name} 运行态`,
+    label: connection.name,
     scope: 'llm_connection',
     layer: 'runtime_probe',
     status,
@@ -342,41 +383,42 @@ function healthLayerFromCapability(capability: CapabilitySnapshot): HealthSignal
   return 'feature';
 }
 
-function capabilityMessage(readiness: CapabilityReadinessState): string {
+function capabilityMessage(readiness: CapabilityReadinessState): HealthSignalMessageCode {
   switch (readiness) {
     case 'enabled':
-      return '能力门禁已满足。';
+      return 'capability_ok';
     case 'paused':
-      return '能力已关闭或暂停。';
+      return 'capability_paused';
     case 'not_configured':
-      return '等待补齐能力配置。';
+      return 'capability_not_configured';
     case 'denied':
-      return '能力被必要系统权限阻塞。';
+      return 'capability_denied';
     case 'degraded':
-      return '能力运行态探测处于降级状态。';
+      return 'capability_degraded';
   }
 }
 
-function capabilityDetail(capability: CapabilitySnapshot): string | undefined {
-  return userVisibleCapabilityReason(
-    capability.runtimeProbe.reason ?? capability.feature.reason ?? capability.configuration.reason,
-  );
+function capabilityDetail(capability: CapabilitySnapshot): HealthSignalDetail | undefined {
+  const reason = (
+    capability.runtimeProbe.reason ??
+    capability.feature.reason ??
+    capability.configuration.reason
+  )?.trim();
+  return reason ? { kind: 'capability_reason' } : undefined;
 }
 
-function userVisibleCapabilityReason(reason: string | undefined): string | undefined {
-  const raw = reason?.trim();
-  if (!raw) return undefined;
-  switch (raw) {
-    case 'disabled':
-      return '该能力当前已关闭。';
-    case 'missing platform credentials':
-      return '等待填写平台凭据。';
-    case 'macOS TCC only':
-      return '仅 macOS 系统权限可探测。';
-    case 'no Electron API for per-target Apple Events TCC status':
-      return '系统未提供可直接读取的授权状态。';
+function connectionLastTestDetail(message: string): HealthSignalDetail {
+  const normalized = message.trim().toLowerCase();
+  switch (normalized) {
+    case 'auth':
+    case 'timeout':
+    case 'provider_unavailable':
+    case 'network':
+    case 'invalid_response':
+    case 'unknown':
+      return { kind: 'last_test_error_class', errorClass: normalized };
     default:
-      return /[\u3400-\u9fff]/.test(raw) ? raw : '状态详情请见对应设置页。';
+      return { kind: 'last_test_message' };
   }
 }
 
@@ -397,19 +439,22 @@ function runtimeStatusToHealth(status: UsageLogRow['status']): HealthSignalStatu
   }
 }
 
-function runtimeProbeMessage(status: UsageLogRow['status']): string {
+function runtimeProbeMessage(status: UsageLogRow['status']): HealthSignalMessageCode {
   switch (status) {
     case 'success':
-      return '最近一次发送已完成。';
+      return 'send_completed';
     case 'aborted':
-      return '最近一次发送已由用户停止。';
+      return 'send_aborted';
     case 'error':
-      return '最近一次发送失败。';
+      return 'send_failed';
   }
 }
 
-function runtimeProbeDetail(row: UsageLogRow): string {
-  const parts = [`模型=${row.modelId}`, `延迟=${row.latencyMs}ms`];
-  if (row.errorClass) parts.push(`错误类型=${row.errorClass}`);
-  return parts.join(' · ');
+function runtimeProbeDetail(row: UsageLogRow): HealthSignalDetail {
+  return {
+    kind: 'runtime_probe_result',
+    modelId: row.modelId,
+    latencyMs: row.latencyMs,
+    ...(row.errorClass ? { errorClass: row.errorClass } : {}),
+  };
 }
diff --git a/packages/ui/src/__tests__/live-turn-projection.test.ts b/packages/ui/src/__tests__/live-turn-projection.test.ts
index 63d788c85f..0fb91fa557 100644
--- a/packages/ui/src/__tests__/live-turn-projection.test.ts
+++ b/packages/ui/src/__tests__/live-turn-projection.test.ts
@@ -21,7 +21,7 @@ import { strict as assert } from 'node:assert';
 import { describe, it } from 'node:test';
 import { encodeToolStepProgress } from '@maka/core/events';
 import {
-  applyLiveTurnEvent,
+  applyLiveTurnEvent as applyLiveTurnEventWithLocale,
   armLiveTurn,
   confirmLiveTurn,
   reconcileTerminalLiveTurn,
@@ -32,6 +32,25 @@ import { materializeTurns, overlayLiveTurn, type ToolActivityItem } from '../mat
 import { redactSecrets } from '../redact.js';
 import { getConversationCopy } from '../conversation-copy.js';
 
+import type { SessionEvent } from '@maka/core/events';
+type LiveTurnContentEvent = Extract<SessionEvent, { type: 'thinking_delta' | 'thinking_complete' | 'text_delta' | 'text_complete' | 'tool_start' | 'tool_output_delta' | 'tool_progress' | 'tool_result_preview' | 'tool_result' }>;
+// Tests exercise projection logic, not copy; pin zh so markers stay verbatim.
+function applyLiveTurnEvent(
+  current: LiveTurnProjection | undefined,
+  event: LiveTurnContentEvent,
+): LiveTurnProjection;
+function applyLiveTurnEvent(
+  current: LiveTurnProjection | undefined,
+  event: SessionEvent,
+): LiveTurnProjection | undefined;
+function applyLiveTurnEvent(
+  current: LiveTurnProjection | undefined,
+  event: SessionEvent,
+): LiveTurnProjection | undefined {
+  return applyLiveTurnEventWithLocale(current, event, 'zh');
+}
+
+
 // A client that just sent cannot read "has my turn started" off session status:
 // it is the same before the turn starts and after it ends. The arm carries
 // `unconfirmed` until the authority says something about THAT turn, which is
diff --git a/packages/ui/src/__tests__/materialize.test.ts b/packages/ui/src/__tests__/materialize.test.ts
index 179be9ea18..f5118dc61d 100644
--- a/packages/ui/src/__tests__/materialize.test.ts
+++ b/packages/ui/src/__tests__/materialize.test.ts
@@ -28,10 +28,30 @@ import {
   type TurnTimelineItem,
 } from "../materialize.js";
 import {
-  applyLiveTurnEvent,
+  applyLiveTurnEvent as applyLiveTurnEventWithLocale,
   armLiveTurn,
 } from "../live-turn-projection.js";
 
+import type { LiveTurnProjection } from '../live-turn-projection.js';
+import type { SessionEvent } from '@maka/core/events';
+type LiveTurnContentEvent = Extract<SessionEvent, { type: 'thinking_delta' | 'thinking_complete' | 'text_delta' | 'text_complete' | 'tool_start' | 'tool_output_delta' | 'tool_progress' | 'tool_result_preview' | 'tool_result' }>;
+// Tests exercise projection logic, not copy; pin zh so markers stay verbatim.
+function applyLiveTurnEvent(
+  current: LiveTurnProjection | undefined,
+  event: LiveTurnContentEvent,
+): LiveTurnProjection;
+function applyLiveTurnEvent(
+  current: LiveTurnProjection | undefined,
+  event: SessionEvent,
+): LiveTurnProjection | undefined;
+function applyLiveTurnEvent(
+  current: LiveTurnProjection | undefined,
+  event: SessionEvent,
+): LiveTurnProjection | undefined {
+  return applyLiveTurnEventWithLocale(current, event, 'zh');
+}
+
+
 const originalUser = {
   type: "user" as const,
   id: "original",
diff --git a/packages/ui/src/__tests__/streaming-display-redaction.test.ts b/packages/ui/src/__tests__/streaming-display-redaction.test.ts
index 3f9ebc1ffd..6c4fcd7de9 100644
--- a/packages/ui/src/__tests__/streaming-display-redaction.test.ts
+++ b/packages/ui/src/__tests__/streaming-display-redaction.test.ts
@@ -22,12 +22,32 @@ import { describe, it } from 'node:test';
 import { redactSecrets } from '../redact.js';
 import { applyAssistantComplete, applyAssistantDelta } from '../assistant-stream.js';
 import { applyThinkingComplete, applyThinkingDelta } from '../thinking-stream.js';
-import { applyLiveTurnEvent } from '../live-turn-projection.js';
+import { applyLiveTurnEvent as applyLiveTurnEventWithLocale } from '../live-turn-projection.js';
 import {
   appendStreamingDisplayRedaction,
   createStreamingDisplayRedactionState,
 } from '../streaming-display-redaction.js';
 
+import type { LiveTurnProjection } from '../live-turn-projection.js';
+import type { SessionEvent } from '@maka/core/events';
+type LiveTurnContentEvent = Extract<SessionEvent, { type: 'thinking_delta' | 'thinking_complete' | 'text_delta' | 'text_complete' | 'tool_start' | 'tool_output_delta' | 'tool_progress' | 'tool_result_preview' | 'tool_result' }>;
+// Tests exercise projection logic, not copy; pin zh so markers stay verbatim.
+function applyLiveTurnEvent(
+  current: LiveTurnProjection | undefined,
+  event: LiveTurnContentEvent,
+): LiveTurnProjection;
+function applyLiveTurnEvent(
+  current: LiveTurnProjection | undefined,
+  event: SessionEvent,
+): LiveTurnProjection | undefined;
+function applyLiveTurnEvent(
+  current: LiveTurnProjection | undefined,
+  event: SessionEvent,
+): LiveTurnProjection | undefined {
+  return applyLiveTurnEventWithLocale(current, event, 'zh');
+}
+
+
 function streamBySizes(input: string, sizes: readonly number[]): void {
   let projection: ReturnType<typeof applyLiveTurnEvent> | undefined;
   let source = '';
@@ -164,12 +184,14 @@ describe('streaming display redaction', () => {
     for (const apply of [applyAssistantDelta, applyThinkingDelta]) {
       const initialState = createStreamingDisplayRedactionState();
       const opener = apply('', 'Authorization:', {
+        locale: 'zh' as const,
         maxDeltaChars: 128,
         maxTotalChars: 512,
         redactionState: initialState,
       });
       const secret = `Bearer ${'s'.repeat(5_000)}`;
       const truncated = apply(opener.text, secret, {
+        locale: 'zh' as const,
         maxDeltaChars: 128,
         maxTotalChars: 512,
         redactionState: opener.redactionState,
@@ -183,6 +205,7 @@ describe('streaming display redaction', () => {
       );
 
       const total = apply('', 'safe '.repeat(200), {
+        locale: 'zh' as const,
         maxDeltaChars: 2_000,
         maxTotalChars: 128,
         redactionState: createStreamingDisplayRedactionState(),
diff --git a/packages/ui/src/assistant-stream.ts b/packages/ui/src/assistant-stream.ts
index f2aaca01c0..2cb10ab8e9 100644
--- a/packages/ui/src/assistant-stream.ts
+++ b/packages/ui/src/assistant-stream.ts
@@ -56,7 +56,7 @@ export const ASSISTANT_MAX_TOTAL_CHARS = 256 * 1024;
 
 export interface ApplyAssistantOptions extends ApplyStreamOptions {
   /** Resolved UI locale for user-visible truncation markers. */
-  locale?: UiLocale;
+  locale: UiLocale;
 }
 
 export type ApplyAssistantResult = ApplyStreamResult;
@@ -65,9 +65,9 @@ export type ApplyAssistantResult = ApplyStreamResult;
 export function applyAssistantDelta(
   prev: string,
   rawDelta: string,
-  options: ApplyAssistantOptions = {},
+  options: ApplyAssistantOptions,
 ): ApplyAssistantResult {
-  const copy = getSharedUiCopy(options.locale ?? 'zh').stream;
+  const copy = getSharedUiCopy(options.locale).stream;
   return applyStreamDelta(prev, rawDelta, {
     maxDeltaChars: options.maxDeltaChars ?? ASSISTANT_MAX_DELTA_CHARS,
     maxTotalChars: options.maxTotalChars ?? ASSISTANT_MAX_TOTAL_CHARS,
@@ -83,11 +83,11 @@ export function applyAssistantDelta(
 /** Apply a `text_complete` final payload (replace, total cap only). */
 export function applyAssistantComplete(
   rawText: string,
-  options: Pick<ApplyAssistantOptions, 'maxTotalChars' | 'locale'> = {},
+  options: Pick<ApplyAssistantOptions, 'maxTotalChars' | 'locale'>,
 ): ApplyAssistantResult {
   return applyStreamComplete(rawText, {
     maxTotalChars: options.maxTotalChars ?? ASSISTANT_MAX_TOTAL_CHARS,
     recovery: 'head',
-    totalMarker: getSharedUiCopy(options.locale ?? 'zh').stream.assistantTailTruncated,
+    totalMarker: getSharedUiCopy(options.locale).stream.assistantTailTruncated,
   });
 }
diff --git a/packages/ui/src/chat-view.tsx b/packages/ui/src/chat-view.tsx
index a4eedf79d6..335f5d2ed4 100644
--- a/packages/ui/src/chat-view.tsx
+++ b/packages/ui/src/chat-view.tsx
@@ -925,11 +925,11 @@ export function ChatView(props: {
 export function DeepResearchProgressPanel({
   run,
   onContinue,
-  copy = getConversationCopy('zh').chat.deepResearchProgress,
+  copy,
 }: {
   run: DeepResearchClientProgress;
   onContinue?: (run: DeepResearchClientProgress) => void;
-  copy?: ReturnType<typeof getConversationCopy>['chat']['deepResearchProgress'];
+  copy: ReturnType<typeof getConversationCopy>['chat']['deepResearchProgress'];
 }) {
   const completedItems = run.checklist.filter(
     (item) => item.status === 'completed' || item.status === 'skipped',
diff --git a/packages/ui/src/live-turn-projection.ts b/packages/ui/src/live-turn-projection.ts
index fd5f74afb2..f926290b3e 100644
--- a/packages/ui/src/live-turn-projection.ts
+++ b/packages/ui/src/live-turn-projection.ts
@@ -192,17 +192,17 @@ export function confirmLiveTurn(
 export function applyLiveTurnEvent(
   current: LiveTurnProjection | undefined,
   event: LiveTurnContentEvent,
-  locale?: UiLocale,
+  locale: UiLocale,
 ): LiveTurnProjection;
 export function applyLiveTurnEvent(
   current: LiveTurnProjection | undefined,
   event: SessionEvent,
-  locale?: UiLocale,
+  locale: UiLocale,
 ): LiveTurnProjection | undefined;
 export function applyLiveTurnEvent(
   current: LiveTurnProjection | undefined,
   event: SessionEvent,
-  locale: UiLocale = 'zh',
+  locale: UiLocale,
 ): LiveTurnProjection | undefined {
   if (event.type === 'steering_message') {
     const prior = current?.turnId === event.turnId
diff --git a/packages/ui/src/thinking-stream.ts b/packages/ui/src/thinking-stream.ts
index 05cfcfbe78..9c29e8a47e 100644
--- a/packages/ui/src/thinking-stream.ts
+++ b/packages/ui/src/thinking-stream.ts
@@ -65,7 +65,7 @@ export const THINKING_MAX_TOTAL_CHARS = 32 * 1024;
 
 export interface ApplyThinkingOptions extends ApplyStreamOptions {
   /** Resolved UI locale for user-visible truncation markers. */
-  locale?: UiLocale;
+  locale: UiLocale;
 }
 
 export type ApplyThinkingResult = ApplyStreamResult;
@@ -74,9 +74,9 @@ export type ApplyThinkingResult = ApplyStreamResult;
 export function applyThinkingDelta(
   prev: string,
   rawDelta: string,
-  options: ApplyThinkingOptions = {},
+  options: ApplyThinkingOptions,
 ): ApplyThinkingResult {
-  const copy = getSharedUiCopy(options.locale ?? 'zh').stream;
+  const copy = getSharedUiCopy(options.locale).stream;
   return applyStreamDelta(prev, rawDelta, {
     maxDeltaChars: options.maxDeltaChars ?? THINKING_MAX_DELTA_CHARS,
     maxTotalChars: options.maxTotalChars ?? THINKING_MAX_TOTAL_CHARS,
@@ -96,11 +96,11 @@ export function applyThinkingDelta(
  */
 export function applyThinkingComplete(
   rawText: string,
-  options: ApplyThinkingOptions = {},
+  options: ApplyThinkingOptions,
 ): ApplyThinkingResult {
   return applyStreamComplete(rawText, {
     maxTotalChars: options.maxTotalChars ?? THINKING_MAX_TOTAL_CHARS,
     recovery: 'tail',
-    totalMarker: getSharedUiCopy(options.locale ?? 'zh').stream.thinkingHeadTruncated,
+    totalMarker: getSharedUiCopy(options.locale).stream.thinkingHeadTruncated,
   });
 }
diff --git a/packages/ui/src/tool-activity/copy.ts b/packages/ui/src/tool-activity/copy.ts
index bc1fb04be6..7dcbd7f893 100644
--- a/packages/ui/src/tool-activity/copy.ts
+++ b/packages/ui/src/tool-activity/copy.ts
@@ -110,6 +110,9 @@ export interface ToolActivityCopy {
     genericAction: string;
     genericTitle: string;
     genericDescription: string;
+    fallbackLabel: string;
+    namedAction: (label: string) => string;
+    namedTitle: (label: string) => string;
     count: (count: number) => string;
     technicalDetails: string;
     groupId: string;
@@ -255,6 +258,9 @@ const TOOL_ACTIVITY_COPY = {
       genericAction: '启用工具能力',
       genericTitle: '工具能力已启用',
       genericDescription: '现在可以使用这组工具。',
+      fallbackLabel: '工具',
+      namedAction: (label) => `启用 ${label}`,
+      namedTitle: (label) => `${label} 已启用`,
       count: (n) => `${n} 项能力可用`,
       technicalDetails: '技术详情',
       groupId: '工具组',
@@ -356,6 +362,9 @@ const TOOL_ACTIVITY_COPY = {
       genericAction: 'Enable tool capabilities',
       genericTitle: 'Tool capabilities enabled',
       genericDescription: 'This tool group is ready to use.',
+      fallbackLabel: 'Tools',
+      namedAction: (label) => `Enable ${label}`,
+      namedTitle: (label) => `${label} enabled`,
       count: (n) => `${n} ${n === 1 ? 'capability' : 'capabilities'} available`,
       technicalDetails: 'Technical details',
       groupId: 'Group',
diff --git a/packages/ui/src/tool-activity/preview-utils.ts b/packages/ui/src/tool-activity/preview-utils.ts
index ce43242173..61a1db266f 100644
--- a/packages/ui/src/tool-activity/preview-utils.ts
+++ b/packages/ui/src/tool-activity/preview-utils.ts
@@ -47,7 +47,7 @@ export function formatDuration(ms: number | undefined): string | null {
   return `${minutes}m ${seconds}s`;
 }
 
-export function formatUserVisibleToolText(text: string, locale: UiLocale = 'zh'): string {
+export function formatUserVisibleToolText(text: string, locale: UiLocale): string {
   return text.replace(/\bUser denied permission(?: request)?\b|用户已拒绝权限请求/g, getToolActivityCopy(locale).permissionDenied);
 }
 
diff --git a/packages/ui/src/tool-activity/result-projection.ts b/packages/ui/src/tool-activity/result-projection.ts
index 8f635efcf8..7c23c2feee 100644
--- a/packages/ui/src/tool-activity/result-projection.ts
+++ b/packages/ui/src/tool-activity/result-projection.ts
@@ -114,7 +114,7 @@ function resultHasCapturedStreams(result: ToolActivityItem['result']): boolean {
 export function withLiveStreamFallback(
   result: NonNullable<ToolActivityItem['result']>,
   chunks: ToolActivityItem['outputChunks'] | undefined,
-  options?: { truncated?: boolean; locale?: UiLocale },
+  options: { truncated?: boolean; locale: UiLocale },
 ): NonNullable<ToolActivityItem['result']> {
   if (result.kind !== 'terminal' && result.kind !== 'shell_run') return result;
   if (resultHasCapturedStreams(result)) return result;
@@ -134,7 +134,7 @@ export function withLiveStreamFallback(
     else stdout += chunk.text;
   }
   const truncated = existing?.mode === 'pipes' && existing.stdoutTruncated === true
-    || options?.truncated === true;
+    || options.truncated === true;
   // Empty redacted/truncated live buffer still carries diagnosis — do not
   // early-return and drop "已脱敏" / "输出已截断".
   if (!stdout && !stderr && !anyRedacted && !truncated) return result;
@@ -142,7 +142,7 @@ export function withLiveStreamFallback(
   // Match live stream's "[已脱敏]" marker when a chunk was redacted
   // (including empty bodies that only suppressed secrets).
   if (anyRedacted) {
-    const marker = getToolActivityCopy(options?.locale ?? 'zh').output.redacted;
+    const marker = getToolActivityCopy(options.locale).output.redacted;
     if (stdout.length > 0) stdout = `${stdout}${stdout.endsWith('\n') ? '' : '\n'}${marker}`;
     else if (stderr.length > 0) stderr = `${stderr}${stderr.endsWith('\n') ? '' : '\n'}${marker}`;
     else stdout = marker;
diff --git a/packages/ui/src/tool-format.ts b/packages/ui/src/tool-format.ts
index 30c8d44709..ed40dca398 100644
--- a/packages/ui/src/tool-format.ts
+++ b/packages/ui/src/tool-format.ts
@@ -88,15 +88,11 @@ export function describeLoadToolResult(
     };
   }
 
-  const label = suppliedLabel ?? (locale === 'en' ? 'Tools' : '工具');
+  const label = suppliedLabel ?? copy.fallbackLabel;
   return {
     kind,
-    actionLabel: suppliedLabel
-      ? locale === 'en' ? `Enable ${suppliedLabel}` : `启用 ${suppliedLabel}`
-      : copy.genericAction,
-    title: suppliedLabel
-      ? locale === 'en' ? `${suppliedLabel} enabled` : `${suppliedLabel} 已启用`
-      : copy.genericTitle,
+    actionLabel: suppliedLabel ? copy.namedAction(suppliedLabel) : copy.genericAction,
+    title: suppliedLabel ? copy.namedTitle(suppliedLabel) : copy.genericTitle,
     description: suppliedDescription ?? copy.genericDescription,
     label,
     countLabel: copy.count(n),
diff --git a/packages/ui/src/tool-output-stream.ts b/packages/ui/src/tool-output-stream.ts
index 062c52de3e..c5fb39d9ad 100644
--- a/packages/ui/src/tool-output-stream.ts
+++ b/packages/ui/src/tool-output-stream.ts
@@ -99,7 +99,7 @@ export interface ApplyToolOutputChunkOptions {
   maxChunks?: number;
   maxTotalChars?: number;
   maxChunkChars?: number;
-  locale?: UiLocale;
+  locale: UiLocale;
 }
 
 export interface ApplyToolOutputChunkResult {
@@ -142,12 +142,12 @@ export interface ApplyToolOutputChunkResult {
 export function applyToolOutputChunk(
   prevChunks: ToolOutputChunk[] | undefined,
   rawChunk: ToolOutputChunk,
-  options: ApplyToolOutputChunkOptions = {},
+  options: ApplyToolOutputChunkOptions,
 ): ApplyToolOutputChunkResult {
   const maxChunks = options.maxChunks ?? TOOL_STREAM_MAX_CHUNKS;
   const maxTotalChars = options.maxTotalChars ?? TOOL_STREAM_MAX_TOTAL_CHARS;
   const maxChunkChars = options.maxChunkChars ?? TOOL_STREAM_MAX_CHUNK_CHARS;
-  const truncatedChunkMarker = getSharedUiCopy(options.locale ?? 'zh').stream.toolChunkTruncated;
+  const truncatedChunkMarker = getSharedUiCopy(options.locale).stream.toolChunkTruncated;
 
   const list = prevChunks ?? [];