diff --git a/config/base-claude.settings.json b/config/base-claude.settings.json
index e9986c70..284681cc 100644
--- a/config/base-claude.settings.json
+++ b/config/base-claude.settings.json
@@ -1,10 +1,6 @@
 {
   "env": {
     "ANTHROPIC_BASE_URL": "http://127.0.0.1:8317/api/provider/claude",
-    "ANTHROPIC_AUTH_TOKEN": "ccs-internal-managed",
-    "ANTHROPIC_MODEL": "claude-sonnet-4-6",
-    "ANTHROPIC_DEFAULT_OPUS_MODEL": "claude-opus-4-7",
-    "ANTHROPIC_DEFAULT_SONNET_MODEL": "claude-sonnet-4-6",
-    "ANTHROPIC_DEFAULT_HAIKU_MODEL": "claude-haiku-4-5-20251001"
+    "ANTHROPIC_AUTH_TOKEN": "ccs-internal-managed"
   }
 }
diff --git a/src/api/services/cliproxy-profile-bridge.ts b/src/api/services/cliproxy-profile-bridge.ts
index 25ab7d21..6c8a5ca7 100644
--- a/src/api/services/cliproxy-profile-bridge.ts
+++ b/src/api/services/cliproxy-profile-bridge.ts
@@ -91,6 +91,12 @@ export function suggestCliproxyBridgeName(provider: CLIProxyProvider): string {
 }
 
 function resolveBridgeModelMapping(provider: CLIProxyProvider): ModelMapping {
+  // claude is model-neutral: model keys are absent from its base config so that
+  // Claude Code's own /model selection is respected end-to-end.  Return empty
+  // strings here; createSettingsFile skips writing empty model entries.
+  if (provider === 'claude') {
+    return { default: '', opus: '', sonnet: '', haiku: '' };
+  }
   const mapping = getModelMappingFromConfig(provider);
   return {
     default: mapping.defaultModel,
diff --git a/src/api/services/profile-writer.ts b/src/api/services/profile-writer.ts
index 2ef17caa..0c0df0e0 100644
--- a/src/api/services/profile-writer.ts
+++ b/src/api/services/profile-writer.ts
@@ -109,6 +109,15 @@ function createSettingsFile(
   });
 
   const isNative = isAnthropicDirect(baseUrl, apiKey);
+  // Model-neutral providers (e.g. claude built-in) pass empty strings to signal
+  // "omit this key".  Filter them out so the written settings file does not
+  // contain ANTHROPIC_MODEL:'' which could be treated as an unintended override.
+  const modelEnv = {
+    ...(models.default.trim() ? { ANTHROPIC_MODEL: models.default } : {}),
+    ...(models.opus.trim() ? { ANTHROPIC_DEFAULT_OPUS_MODEL: models.opus } : {}),
+    ...(models.sonnet.trim() ? { ANTHROPIC_DEFAULT_SONNET_MODEL: models.sonnet } : {}),
+    ...(models.haiku.trim() ? { ANTHROPIC_DEFAULT_HAIKU_MODEL: models.haiku } : {}),
+  };
   const settings = {
     env: {
       // Native mode: ANTHROPIC_API_KEY only, no BASE_URL/AUTH_TOKEN
@@ -120,10 +129,7 @@ function createSettingsFile(
             ANTHROPIC_AUTH_TOKEN: apiKey,
             ...(isOpenRouterUrl(baseUrl) && { ANTHROPIC_API_KEY: '' }),
           }),
-      ANTHROPIC_MODEL: models.default,
-      ANTHROPIC_DEFAULT_OPUS_MODEL: models.opus,
-      ANTHROPIC_DEFAULT_SONNET_MODEL: models.sonnet,
-      ANTHROPIC_DEFAULT_HAIKU_MODEL: models.haiku,
+      ...modelEnv,
       ...(extraModels && extraModels.length > 0
         ? { ANTHROPIC_EXTRA_MODELS: extraModels.join(',') }
         : {}),
@@ -202,6 +208,13 @@ function createApiProfileUnified(
   });
 
   const isNative = isAnthropicDirect(baseUrl, apiKey);
+  // Model-neutral providers pass empty strings; omit those keys.
+  const modelEnvUnified = {
+    ...(models.default.trim() ? { ANTHROPIC_MODEL: models.default } : {}),
+    ...(models.opus.trim() ? { ANTHROPIC_DEFAULT_OPUS_MODEL: models.opus } : {}),
+    ...(models.sonnet.trim() ? { ANTHROPIC_DEFAULT_SONNET_MODEL: models.sonnet } : {}),
+    ...(models.haiku.trim() ? { ANTHROPIC_DEFAULT_HAIKU_MODEL: models.haiku } : {}),
+  };
   const settings = {
     env: {
       ...(isNative
@@ -211,10 +224,7 @@ function createApiProfileUnified(
             ANTHROPIC_AUTH_TOKEN: apiKey,
             ...(isOpenRouterUrl(baseUrl) && { ANTHROPIC_API_KEY: '' }),
           }),
-      ANTHROPIC_MODEL: models.default,
-      ANTHROPIC_DEFAULT_OPUS_MODEL: models.opus,
-      ANTHROPIC_DEFAULT_SONNET_MODEL: models.sonnet,
-      ANTHROPIC_DEFAULT_HAIKU_MODEL: models.haiku,
+      ...modelEnvUnified,
       ...(extraModels && extraModels.length > 0
         ? { ANTHROPIC_EXTRA_MODELS: extraModels.join(',') }
         : {}),
diff --git a/src/cliproxy/__tests__/account-safety-ban-copy.test.ts b/src/cliproxy/__tests__/account-safety-ban-copy.test.ts
new file mode 100644
index 00000000..1814d413
--- /dev/null
+++ b/src/cliproxy/__tests__/account-safety-ban-copy.test.ts
@@ -0,0 +1,133 @@
+/**
+ * Tests for account-safety ban copy parameterization (Gap 3).
+ *
+ * Verifies that handleBanDetection uses provider-appropriate copy:
+ *   - "Anthropic" for the claude provider
+ *   - "Google"    for gemini / agy / codex
+ * and that isBanResponse matches both shared and Anthropic-specific patterns.
+ */
+
+import * as fs from 'fs';
+import * as os from 'os';
+import * as path from 'path';
+import { describe, expect, it, spyOn, afterEach, beforeEach } from 'bun:test';
+import { isBanResponse, handleBanDetection } from '../accounts/account-safety';
+
+// ── isBanResponse ─────────────────────────────────────────────────────────────
+
+describe('isBanResponse', () => {
+  it.each([
+    'disabled in this account',
+    'violation of terms of service',
+    'account has been disabled',
+    'account is disabled',
+    'account has been suspended',
+    'account has been banned',
+  ])('matches shared ban pattern for all providers: %s', (pattern) => {
+    expect(isBanResponse(pattern)).toBe(true);
+    expect(isBanResponse(pattern.toUpperCase())).toBe(true);
+    // Also matches when provider is specified
+    expect(isBanResponse(pattern, 'gemini')).toBe(true);
+    expect(isBanResponse(pattern, 'claude')).toBe(true);
+  });
+
+  it.each(['your account has been blocked', 'account is blocked'])(
+    'matches Anthropic-specific ban pattern for claude provider: %s',
+    (pattern) => {
+      expect(isBanResponse(pattern, 'claude')).toBe(true);
+    }
+  );
+
+  it.each(['your account has been blocked', 'account is blocked'])(
+    'does NOT match Anthropic-specific ban pattern for non-claude providers: %s',
+    (pattern) => {
+      expect(isBanResponse(pattern, 'gemini')).toBe(false);
+      expect(isBanResponse(pattern, 'agy')).toBe(false);
+      expect(isBanResponse(pattern, 'codex')).toBe(false);
+      // Without provider argument also should not match
+      expect(isBanResponse(pattern)).toBe(false);
+    }
+  );
+
+  it('does not match bare "usage policy" substring for any provider (avoids false positives)', () => {
+    // A rate-limit message mentioning "usage policy" should not trigger ban
+    const msg = 'Request exceeds usage policy limits for your plan';
+    expect(isBanResponse(msg)).toBe(false);
+    expect(isBanResponse(msg, 'gemini')).toBe(false);
+    expect(isBanResponse(msg, 'claude')).toBe(false);
+  });
+
+  it('returns false for a benign error message', () => {
+    expect(isBanResponse('rate limit exceeded')).toBe(false);
+    expect(isBanResponse('network timeout')).toBe(false);
+    expect(isBanResponse('')).toBe(false);
+  });
+});
+
+// ── handleBanDetection ban copy ────────────────────────────────────────────────
+
+describe('handleBanDetection ban copy', () => {
+  const stderrLines: string[] = [];
+  let writeSpy: ReturnType<typeof spyOn>;
+  let consoleSpy: ReturnType<typeof spyOn>;
+  let tempHome: string;
+  let originalCcsHome: string | undefined;
+
+  beforeEach(() => {
+    originalCcsHome = process.env.CCS_HOME;
+    tempHome = fs.mkdtempSync(path.join(os.tmpdir(), 'ccs-ban-copy-'));
+    process.env.CCS_HOME = tempHome;
+  });
+
+  const setup = () => {
+    stderrLines.length = 0;
+    writeSpy = spyOn(process.stderr, 'write').mockImplementation(
+      (chunk: string | Uint8Array): boolean => {
+        stderrLines.push(typeof chunk === 'string' ? chunk : '');
+        return true;
+      }
+    );
+    // Also capture console.error calls
+    consoleSpy = spyOn(console, 'error').mockImplementation((...args: unknown[]) => {
+      stderrLines.push(String(args[0] ?? ''));
+    });
+  };
+
+  afterEach(() => {
+    writeSpy?.mockRestore();
+    consoleSpy?.mockRestore();
+    process.env.CCS_HOME = originalCcsHome;
+    fs.rmSync(tempHome, { recursive: true, force: true });
+  });
+
+  it('uses "Anthropic" actor copy for the claude provider', () => {
+    setup();
+    handleBanDetection('claude', 'test@example.com', 'account has been disabled');
+    const output = stderrLines.join(' ');
+    expect(output).toContain('Anthropic');
+    expect(output).not.toContain('Google');
+  });
+
+  it('uses "Google" actor copy for the gemini provider', () => {
+    setup();
+    handleBanDetection('gemini', 'test@example.com', 'account has been disabled');
+    const output = stderrLines.join(' ');
+    expect(output).toContain('Google');
+    expect(output).not.toContain('Anthropic');
+  });
+
+  it('uses "Google" actor copy for the agy provider', () => {
+    setup();
+    handleBanDetection('agy', 'test@example.com', 'account has been banned');
+    const output = stderrLines.join(' ');
+    expect(output).toContain('Google');
+  });
+
+  it('returns false for a non-ban error (no actor copy emitted)', () => {
+    setup();
+    const result = handleBanDetection('claude', 'test@example.com', 'rate limit exceeded');
+    expect(result).toBe(false);
+    // No ban message written
+    expect(stderrLines.join(' ')).not.toContain('Anthropic');
+  });
+});
diff --git a/src/cliproxy/__tests__/claude-shadow-warning.test.ts b/src/cliproxy/__tests__/claude-shadow-warning.test.ts
new file mode 100644
index 00000000..c8087fa2
--- /dev/null
+++ b/src/cliproxy/__tests__/claude-shadow-warning.test.ts
@@ -0,0 +1,214 @@
+/**
+ * Tests for claude-shadow-warning.ts
+ *
+ * Gap 2: shadow warning — emitted once when a user profile named 'claude' or
+ *   'anthropic' is present; not repeated; not emitted without a collision.
+ * Gap 4: routing notice — emitted once on first claude provider launch.
+ *
+ * These tests use a temp CCS_HOME and a non-TTY stderr mock to confirm
+ * write behaviour without relying on an interactive terminal.
+ */
+
+import * as fs from 'fs';
+import * as os from 'os';
+import * as path from 'path';
+import { afterEach, beforeEach, describe, expect, it, spyOn } from 'bun:test';
+
+// Module under test — imported after CCS_HOME is set up in beforeEach via dynamic re-import.
+// Because Bun caches modules, we test the exported functions in isolation by
+// controlling the file-system state they depend on.
+import { maybeWarnClaudeShadow, maybeShowClaudeRoutingNotice } from '../claude-shadow-warning';
+
+// ── Helpers ───────────────────────────────────────────────────────────────────
+
+function writeLegacyConfig(ccsDir: string, profiles: Record<string, string>): void {
+  const configPath = path.join(ccsDir, 'config.json');
+  fs.mkdirSync(ccsDir, { recursive: true });
+  fs.writeFileSync(configPath, JSON.stringify({ profiles }), 'utf-8');
+}
+
+function markerDir(ccsDir: string): string {
+  return path.join(ccsDir, 'cliproxy');
+}
+
+function shadowMarker(ccsDir: string): string {
+  return path.join(markerDir(ccsDir), '.claude-shadow-warned');
+}
+
+function routingMarker(ccsDir: string): string {
+  return path.join(markerDir(ccsDir), '.claude-routing-noticed');
+}
+
+// ── Test setup ────────────────────────────────────────────────────────────────
+
+let tempHome: string;
+let originalCcsHome: string | undefined;
+let stderrLines: string[];
+let stderrSpy: ReturnType<typeof spyOn>;
+let originalIsTTYDescriptor: PropertyDescriptor | undefined;
+
+beforeEach(() => {
+  originalCcsHome = process.env.CCS_HOME;
+  tempHome = fs.mkdtempSync(path.join(os.tmpdir(), 'ccs-shadow-warn-'));
+  process.env.CCS_HOME = tempHome;
+
+  // Collect stderr writes without printing them
+  stderrLines = [];
+  stderrSpy = spyOn(process.stderr, 'write').mockImplementation(
+    (chunk: string | Uint8Array): boolean => {
+      stderrLines.push(typeof chunk === 'string' ? chunk : '');
+      return true;
+    }
+  );
+
+  // Save exact isTTY property descriptor so afterEach can restore it precisely
+  originalIsTTYDescriptor = Object.getOwnPropertyDescriptor(process.stderr, 'isTTY');
+
+  // Simulate a TTY so the TTY guard does not short-circuit
+  Object.defineProperty(process.stderr, 'isTTY', { value: true, configurable: true });
+});
+
+afterEach(() => {
+  process.env.CCS_HOME = originalCcsHome;
+  fs.rmSync(tempHome, { recursive: true, force: true });
+  stderrSpy.mockRestore();
+  // Restore isTTY to exactly what it was before the test
+  if (originalIsTTYDescriptor !== undefined) {
+    Object.defineProperty(process.stderr, 'isTTY', originalIsTTYDescriptor);
+  } else {
+    delete (process.stderr as { isTTY?: boolean }).isTTY;
+  }
+});
+
+// ── Shadow warning (Gap 2) ────────────────────────────────────────────────────
+
+describe('maybeWarnClaudeShadow', () => {
+  it('does not emit a warning when no shadowed profiles exist', () => {
+    const ccsDir = path.join(tempHome, '.ccs');
+    writeLegacyConfig(ccsDir, { myprofile: '/some/path' });
+
+    maybeWarnClaudeShadow();
+
+    expect(stderrLines.join('')).not.toContain('shadowed');
+    expect(stderrLines.join('')).not.toContain('claude');
+  });
+
+  it('emits a warning when a profile named "claude" exists', () => {
+    const ccsDir = path.join(tempHome, '.ccs');
+    writeLegacyConfig(ccsDir, { claude: '/path/to/claude.settings.json' });
+
+    maybeWarnClaudeShadow();
+
+    const output = stderrLines.join('');
+    expect(output).toContain('claude');
+    expect(output).toContain('shadowed');
+    // Ensure warn() prefix is not doubled ([!] [!] ...)
+    expect(output).not.toMatch(/\[!\]\s*\[!\]/);
+  });
+
+  it('emits a warning when a profile named "anthropic" exists', () => {
+    const ccsDir = path.join(tempHome, '.ccs');
+    writeLegacyConfig(ccsDir, { anthropic: '/path/to/anthropic.settings.json' });
+
+    maybeWarnClaudeShadow();
+
+    const output = stderrLines.join('');
+    expect(output).toContain('anthropic');
+    expect(output).toContain('shadowed');
+    // Ensure warn() prefix is not doubled
+    expect(output).not.toMatch(/\[!\]\s*\[!\]/);
+  });
+
+  it('creates the dismissal marker after warning', () => {
+    const ccsDir = path.join(tempHome, '.ccs');
+    writeLegacyConfig(ccsDir, { claude: '/path/to/settings.json' });
+
+    maybeWarnClaudeShadow();
+
+    expect(fs.existsSync(shadowMarker(ccsDir))).toBe(true);
+  });
+
+  it('does not repeat the warning when the marker already exists', () => {
+    const ccsDir = path.join(tempHome, '.ccs');
+    writeLegacyConfig(ccsDir, { claude: '/path/to/settings.json' });
+    // Pre-create marker
+    const mDir = markerDir(ccsDir);
+    fs.mkdirSync(mDir, { recursive: true });
+    fs.writeFileSync(shadowMarker(ccsDir), 'already-shown');
+
+    maybeWarnClaudeShadow();
+
+    const output = stderrLines.join('');
+    expect(output).not.toContain('shadowed');
+  });
+
+  it('does not warn when stderr is not a TTY', () => {
+    Object.defineProperty(process.stderr, 'isTTY', { value: false, configurable: true });
+    const ccsDir = path.join(tempHome, '.ccs');
+    writeLegacyConfig(ccsDir, { claude: '/path/to/settings.json' });
+
+    maybeWarnClaudeShadow();
+
+    expect(stderrLines.join('')).not.toContain('shadowed');
+  });
+
+  it('emits a warning when an account profile named "claude" exists in profiles.json (legacy mode)', () => {
+    const ccsDir = path.join(tempHome, '.ccs');
+    fs.mkdirSync(ccsDir, { recursive: true });
+    // Write an empty settings config (no settings profiles named claude)
+    writeLegacyConfig(ccsDir, { myprofile: '/some/path' });
+    // Write profiles.json with an account profile named 'claude'
+    const profilesData = {
+      version: '2.0.0',
+      profiles: { claude: { type: 'account', created: new Date().toISOString(), last_used: null } },
+      default: null,
+    };
+    fs.writeFileSync(path.join(ccsDir, 'profiles.json'), JSON.stringify(profilesData), 'utf-8');
+
+    maybeWarnClaudeShadow();
+
+    const output = stderrLines.join('');
+    expect(output).toContain('claude');
+    expect(output).toContain('shadowed');
+  });
+});
+
+// ── Routing notice (Gap 4) ────────────────────────────────────────────────────
+
+describe('maybeShowClaudeRoutingNotice', () => {
+  it('emits routing notice on first call', () => {
+    maybeShowClaudeRoutingNotice();
+
+    const output = stderrLines.join('');
+    expect(output).toContain('CLIProxy');
+    // Ensure info() prefix is not doubled ([i] [i] ...)
+    expect(output).not.toMatch(/\[i\]\s*\[i\]/);
+  });
+
+  it('creates the routing notice marker after first call', () => {
+    const ccsDir = path.join(tempHome, '.ccs');
+    maybeShowClaudeRoutingNotice();
+
+    expect(fs.existsSync(routingMarker(ccsDir))).toBe(true);
+  });
+
+  it('does not repeat the routing notice when the marker already exists', () => {
+    const ccsDir = path.join(tempHome, '.ccs');
+    const mDir = markerDir(ccsDir);
+    fs.mkdirSync(mDir, { recursive: true });
+    fs.writeFileSync(routingMarker(ccsDir), 'already-shown');
+
+    maybeShowClaudeRoutingNotice();
+
+    // No output at all
+    expect(stderrLines.join('')).not.toContain('CLIProxy');
+  });
+
+  it('does not emit when stderr is not a TTY', () => {
+    Object.defineProperty(process.stderr, 'isTTY', { value: false, configurable: true });
+
+    maybeShowClaudeRoutingNotice();
+
+    expect(stderrLines.join('')).not.toContain('CLIProxy');
+  });
+});
diff --git a/src/cliproxy/accounts/account-safety.ts b/src/cliproxy/accounts/account-safety.ts
index b3f48784..3cde38e8 100644
--- a/src/cliproxy/accounts/account-safety.ts
+++ b/src/cliproxy/accounts/account-safety.ts
@@ -568,8 +568,9 @@ export function restoreAutoPausedAccounts(provider: CLIProxyProvider): void {
   saveAutoPaused(data);
 }
 
-// Error patterns that indicate Google has disabled/banned an account
-const BAN_PATTERNS = [
+// Error patterns that indicate a provider has disabled/banned an account.
+// Shared patterns apply to all providers (Google and Anthropic OAuth flows).
+const SHARED_BAN_PATTERNS = [
   'disabled in this account',
   'violation of terms of service',
   'account has been disabled',
@@ -578,12 +579,28 @@ const BAN_PATTERNS = [
   'account has been banned',
 ];
 
+// Anthropic-specific disable patterns.  Only applied when provider === 'claude'
+// to avoid false-positive auto-pause on Google/Codex errors that may reference
+// "policy" in rate-limit or scope messages.
+const ANTHROPIC_BAN_PATTERNS = ['your account has been blocked', 'account is blocked'];
+
 /**
  * Check if an error message indicates an account ban/disable.
+ * Pass the provider so Anthropic-only patterns cannot trip Google providers.
  */
-export function isBanResponse(errorMessage: string): boolean {
+export function isBanResponse(errorMessage: string, provider?: CLIProxyProvider): boolean {
   const lower = errorMessage.toLowerCase();
-  return BAN_PATTERNS.some((pattern) => lower.includes(pattern));
+  if (SHARED_BAN_PATTERNS.some((pattern) => lower.includes(pattern))) return true;
+  if (provider === 'claude' && ANTHROPIC_BAN_PATTERNS.some((pattern) => lower.includes(pattern))) {
+    return true;
+  }
+  return false;
+}
+
+/** Return the actor name (Google, Anthropic, etc.) for ban copy. */
+function banActor(provider: CLIProxyProvider): string {
+  if (provider === 'claude') return 'Anthropic';
+  return 'Google';
 }
 
 /**
@@ -595,10 +612,11 @@ export function handleBanDetection(
   accountId: string,
   errorMessage: string
 ): boolean {
-  if (!isBanResponse(errorMessage)) return false;
+  if (!isBanResponse(errorMessage, provider)) return false;
 
+  const actor = banActor(provider);
   console.error('');
-  console.error(warn('Account safety: account appears disabled by Google'));
+  console.error(warn(`Account safety: account appears disabled by ${actor}`));
   console.error(`    Account "${maskEmail(accountId)}" (${provider}) returned:`);
   console.error(`    "${truncate(errorMessage, 120)}"`);
   console.error('');
diff --git a/src/cliproxy/claude-shadow-warning.ts b/src/cliproxy/claude-shadow-warning.ts
new file mode 100644
index 00000000..76496dd9
--- /dev/null
+++ b/src/cliproxy/claude-shadow-warning.ts
@@ -0,0 +1,179 @@
+/**
+ * Claude built-in provider — shadow warning and first-run routing notice
+ *
+ * Shadow warning
+ * --------------
+ * The claude and anthropic provider names are reserved built-ins (priority 0.5).
+ * A user who has a settings profile or account profile named 'claude' or 'anthropic'
+ * will silently get the built-in rather than their own profile.  This module emits
+ * a one-line, TTY-only, once-per-install warning with a rename hint in that case.
+ *
+ * First-run routing notice
+ * ------------------------
+ * On the very first launch of `ccs claude` a one-line notice is printed to stderr
+ * reminding the user that traffic routes through the local CLIProxy instance and
+ * that bare `ccs` still launches native Claude Code.
+ *
+ * Persistence: marker files inside ~/.ccs/cliproxy/ are used for both notices.
+ */
+
+import * as fs from 'fs';
+import * as path from 'path';
+import { warn, info } from '../utils/ui';
+import {
+  getCcsDir,
+  loadOrCreateUnifiedConfig,
+  isUnifiedMode,
+} from '../config/config-loader-facade';
+import { readConfig } from '../utils/config-manager';
+import { ProfileRegistry } from '../auth/profile-registry';
+
+/** Marker file name inside ~/.ccs/cliproxy/ */
+const SHADOW_WARNED_MARKER = '.claude-shadow-warned';
+
+/** Names that the claude built-in shadows */
+const SHADOWED_NAMES = new Set(['claude', 'anthropic']);
+
+/** Get path to the once-per-install dismissal marker. */
+function getShadowWarnedMarkerPath(): string {
+  return path.join(getCcsDir(), 'cliproxy', SHADOW_WARNED_MARKER);
+}
+
+/** Return true if this install has already shown the shadow warning. */
+function shadowWarnAlreadyShown(): boolean {
+  try {
+    return fs.existsSync(getShadowWarnedMarkerPath());
+  } catch {
+    return true; // If we can't read, skip warning.
+  }
+}
+
+/** Persist the warning dismissal. */
+function markShadowWarnShown(): void {
+  try {
+    const dir = path.join(getCcsDir(), 'cliproxy');
+    fs.mkdirSync(dir, { recursive: true });
+    fs.writeFileSync(getShadowWarnedMarkerPath(), new Date().toISOString(), {
+      encoding: 'utf8',
+      flag: 'w',
+    });
+  } catch {
+    // Best-effort — failure to persist is not fatal.
+  }
+}
+
+/**
+ * Check if the user has a settings or account profile named 'claude' or 'anthropic'
+ * that is being shadowed by the built-in provider.
+ */
+function detectShadowedProfile(): string | null {
+  try {
+    if (isUnifiedMode()) {
+      const unified = loadOrCreateUnifiedConfig();
+      const profileNames = Object.keys(unified.profiles || {});
+      const accountNames = Object.keys(unified.accounts || {});
+      const variantNames = Object.keys(unified.cliproxy?.variants || {});
+      for (const name of [...profileNames, ...accountNames, ...variantNames]) {
+        if (SHADOWED_NAMES.has(name.toLowerCase())) return name;
+      }
+    } else {
+      const config = readConfig();
+      const profileNames = Object.keys(config.profiles || {});
+      const cliproxyNames = Object.keys(config.cliproxy || {});
+      // Also check account-based profiles from profiles.json (mirror unified accounts check).
+      const registry = new ProfileRegistry();
+      const accountProfileNames = registry.listProfiles();
+      for (const name of [...profileNames, ...cliproxyNames, ...accountProfileNames]) {
+        if (SHADOWED_NAMES.has(name.toLowerCase())) return name;
+      }
+    }
+  } catch {
+    // If config is unreadable, skip the check silently.
+  }
+  return null;
+}
+
+/**
+ * Emit the shadow warning if conditions are met.
+ *
+ * Conditions:
+ * - Running in a TTY (no warning in pipes/CI)
+ * - Warning not already shown for this install
+ * - User has a profile named 'claude' or 'anthropic' that the built-in shadows
+ *
+ * Writes to stderr so it does not pollute stdout piped output.
+ */
+export function maybeWarnClaudeShadow(): void {
+  // TTY guard — no warning in non-interactive or CI environments
+  if (!process.stderr.isTTY) return;
+
+  if (shadowWarnAlreadyShown()) return;
+
+  const shadowedName = detectShadowedProfile();
+  if (!shadowedName) return;
+
+  markShadowWarnShown();
+
+  process.stderr.write('\n');
+  process.stderr.write(
+    warn(
+      `Profile '${shadowedName}' is shadowed by the built-in claude provider and cannot be reached via 'ccs ${shadowedName}'.`
+    ) + '\n'
+  );
+  process.stderr.write(
+    `    Rename it to continue using it: ccs config  (or edit ~/.ccs/config.yaml / config.json)\n`
+  );
+  process.stderr.write('\n');
+}
+
+// ── First-run routing notice ──────────────────────────────────────────────────
+
+/** Marker file for the once-per-install routing notice. */
+const ROUTING_NOTICE_MARKER = '.claude-routing-noticed';
+
+function getRoutingNoticeMarkerPath(): string {
+  return path.join(getCcsDir(), 'cliproxy', ROUTING_NOTICE_MARKER);
+}
+
+function routingNoticeAlreadyShown(): boolean {
+  try {
+    return fs.existsSync(getRoutingNoticeMarkerPath());
+  } catch {
+    return true;
+  }
+}
+
+function markRoutingNoticeShown(): void {
+  try {
+    const dir = path.join(getCcsDir(), 'cliproxy');
+    fs.mkdirSync(dir, { recursive: true });
+    fs.writeFileSync(getRoutingNoticeMarkerPath(), new Date().toISOString(), {
+      encoding: 'utf8',
+      flag: 'w',
+    });
+  } catch {
+    // Best-effort.
+  }
+}
+
+/**
+ * Print a one-time routing notice when the claude built-in provider first launches.
+ *
+ * Informs the user that traffic is routed through the local CLIProxy instance
+ * (not the Anthropic API directly) and that bare `ccs` still uses native Claude Code.
+ *
+ * TTY-only; written to stderr.
+ */
+export function maybeShowClaudeRoutingNotice(): void {
+  if (!process.stderr.isTTY) return;
+  if (routingNoticeAlreadyShown()) return;
+
+  markRoutingNoticeShown();
+
+  process.stderr.write(
+    info('ccs claude: traffic routes through the local CLIProxy instance.') + '\n'
+  );
+  process.stderr.write(
+    `    Native Claude Code (direct Anthropic API) is still available via bare \`ccs\`.\n`
+  );
+}
diff --git a/src/cliproxy/config/__tests__/claude-model-neutral.test.ts b/src/cliproxy/config/__tests__/claude-model-neutral.test.ts
new file mode 100644
index 00000000..989b642f
--- /dev/null
+++ b/src/cliproxy/config/__tests__/claude-model-neutral.test.ts
@@ -0,0 +1,383 @@
+/**
+ * Gap 1: claude provider is model-neutral (no ANTHROPIC_MODEL pins in env output).
+ * Snapshot test proving:
+ *   - getClaudeEnvVars('claude') emits no model env vars
+ *   - getClaudeEnvVars('gemini') still emits model env vars (no spillover)
+ *   - ensureProviderSettings does not write model pins for claude
+ */
+
+import * as fs from 'fs';
+import * as os from 'os';
+import * as path from 'path';
+import { afterEach, beforeEach, describe, expect, it } from 'bun:test';
+import { getClaudeEnvVars, ensureProviderSettings } from '../env-builder';
+import { clearConfigCache } from '../base-config-loader';
+
+const MODEL_KEYS = [
+  'ANTHROPIC_MODEL',
+  'ANTHROPIC_DEFAULT_OPUS_MODEL',
+  'ANTHROPIC_DEFAULT_SONNET_MODEL',
+  'ANTHROPIC_DEFAULT_HAIKU_MODEL',
+] as const;
+
+describe('claude provider model-neutral passthrough (Gap 1)', () => {
+  let tempHome: string;
+  let originalCcsHome: string | undefined;
+
+  beforeEach(() => {
+    originalCcsHome = process.env.CCS_HOME;
+    tempHome = fs.mkdtempSync(path.join(os.tmpdir(), 'ccs-claude-neutral-'));
+    process.env.CCS_HOME = tempHome;
+    clearConfigCache();
+  });
+
+  afterEach(() => {
+    process.env.CCS_HOME = originalCcsHome;
+    fs.rmSync(tempHome, { recursive: true, force: true });
+    clearConfigCache();
+  });
+
+  it('emits no model env vars for the claude provider', () => {
+    const env = getClaudeEnvVars('claude');
+
+    for (const key of MODEL_KEYS) {
+      expect(env[key]).toBeUndefined();
+    }
+  });
+
+  it('still sets ANTHROPIC_BASE_URL and ANTHROPIC_AUTH_TOKEN for claude', () => {
+    const env = getClaudeEnvVars('claude');
+
+    expect(env.ANTHROPIC_BASE_URL).toBe('http://127.0.0.1:8317/api/provider/claude');
+    expect(env.ANTHROPIC_AUTH_TOKEN).toBeDefined();
+  });
+
+  it('still emits model env vars for gemini provider (no spillover)', () => {
+    const env = getClaudeEnvVars('gemini');
+
+    for (const key of MODEL_KEYS) {
+      expect(typeof env[key]).toBe('string');
+      expect((env[key] as string).length).toBeGreaterThan(0);
+    }
+  });
+
+  it('ensureProviderSettings does not write model pins for claude', () => {
+    process.env.CCS_HOME = tempHome;
+    const ccsDir = path.join(tempHome, '.ccs');
+    fs.mkdirSync(ccsDir, { recursive: true });
+
+    ensureProviderSettings('claude');
+
+    // Non-cursor providers use the legacy top-level path: ~/.ccs/claude.settings.json
+    const settingsPath = path.join(ccsDir, 'claude.settings.json');
+    expect(fs.existsSync(settingsPath)).toBe(true);
+
+    const written = JSON.parse(fs.readFileSync(settingsPath, 'utf-8')) as {
+      env: Record<string, string | undefined>;
+    };
+
+    for (const key of MODEL_KEYS) {
+      // Model keys must not be present (or must be undefined/empty)
+      const value = written.env[key];
+      expect(!value || value.trim().length === 0).toBe(true);
+    }
+
+    // Transport keys must be present
+    expect(written.env.ANTHROPIC_BASE_URL).toBe('http://127.0.0.1:8317/api/provider/claude');
+    expect(written.env.ANTHROPIC_AUTH_TOKEN).toBeDefined();
+  });
+
+  // ── Upgrade-path: existing claude.settings.json with stale default model pins ──
+
+  it('strips stale default model pins from existing claude.settings.json on ensureProviderSettings', () => {
+    process.env.CCS_HOME = tempHome;
+    const ccsDir = path.join(tempHome, '.ccs');
+    fs.mkdirSync(ccsDir, { recursive: true });
+
+    // Simulate a user who ran `ccs claude` before the model-neutral change.
+    // These are the exact default values that were auto-written by older CCS.
+    const stalePins = {
+      ANTHROPIC_MODEL: 'claude-sonnet-4-6',
+      ANTHROPIC_DEFAULT_OPUS_MODEL: 'claude-opus-4-7',
+      ANTHROPIC_DEFAULT_SONNET_MODEL: 'claude-sonnet-4-6',
+      ANTHROPIC_DEFAULT_HAIKU_MODEL: 'claude-haiku-4-5-20251001',
+    };
+    const settingsPath = path.join(ccsDir, 'claude.settings.json');
+    fs.writeFileSync(
+      settingsPath,
+      JSON.stringify({
+        env: {
+          ANTHROPIC_BASE_URL: 'http://127.0.0.1:8317/api/provider/claude',
+          ANTHROPIC_AUTH_TOKEN: 'ccs-internal-managed',
+          ...stalePins,
+        },
+      }),
+      'utf-8'
+    );
+
+    ensureProviderSettings('claude');
+
+    const repaired = JSON.parse(fs.readFileSync(settingsPath, 'utf-8')) as {
+      env: Record<string, string | undefined>;
+    };
+
+    // All stale pins must be removed
+    for (const key of MODEL_KEYS) {
+      const value = repaired.env[key];
+      expect(!value || value.trim().length === 0).toBe(true);
+    }
+
+    // Transport keys must still be present
+    expect(repaired.env.ANTHROPIC_BASE_URL).toBe('http://127.0.0.1:8317/api/provider/claude');
+    expect(repaired.env.ANTHROPIC_AUTH_TOKEN).toBeDefined();
+  });
+
+  it('preserves user-customised model pin that differs from the stale default', () => {
+    process.env.CCS_HOME = tempHome;
+    const ccsDir = path.join(tempHome, '.ccs');
+    fs.mkdirSync(ccsDir, { recursive: true });
+
+    const settingsPath = path.join(ccsDir, 'claude.settings.json');
+    // User has customised ANTHROPIC_MODEL to a non-default value
+    fs.writeFileSync(
+      settingsPath,
+      JSON.stringify({
+        env: {
+          ANTHROPIC_BASE_URL: 'http://127.0.0.1:8317/api/provider/claude',
+          ANTHROPIC_AUTH_TOKEN: 'ccs-internal-managed',
+          ANTHROPIC_MODEL: 'claude-opus-4-7', // customised — not the stale sonnet default
+        },
+      }),
+      'utf-8'
+    );
+
+    ensureProviderSettings('claude');
+
+    const result = JSON.parse(fs.readFileSync(settingsPath, 'utf-8')) as {
+      env: Record<string, string | undefined>;
+    };
+
+    // Custom value must be preserved
+    expect(result.env.ANTHROPIC_MODEL).toBe('claude-opus-4-7');
+  });
+
+  // ── One-shot migration guard (launch N+1) ─────────────────────────────────────
+
+  it('stale-pin migration runs at most once (marker prevents re-strip on launch N+1)', () => {
+    process.env.CCS_HOME = tempHome;
+    const ccsDir = path.join(tempHome, '.ccs');
+    fs.mkdirSync(ccsDir, { recursive: true });
+
+    // Pre-place the migration marker so migration is considered done.
+    const markerDir = path.join(ccsDir, 'cliproxy');
+    fs.mkdirSync(markerDir, { recursive: true });
+    fs.writeFileSync(path.join(markerDir, '.claude-model-migrated'), new Date().toISOString());
+
+    // Write a settings file that contains stale default pins.
+    const stalePins = {
+      ANTHROPIC_MODEL: 'claude-sonnet-4-6',
+      ANTHROPIC_DEFAULT_OPUS_MODEL: 'claude-opus-4-7',
+    };
+    const settingsPath = path.join(ccsDir, 'claude.settings.json');
+    fs.writeFileSync(
+      settingsPath,
+      JSON.stringify({
+        env: {
+          ANTHROPIC_BASE_URL: 'http://127.0.0.1:8317/api/provider/claude',
+          ANTHROPIC_AUTH_TOKEN: 'ccs-internal-managed',
+          ...stalePins,
+        },
+      }),
+      'utf-8'
+    );
+
+    ensureProviderSettings('claude');
+
+    const result = JSON.parse(fs.readFileSync(settingsPath, 'utf-8')) as {
+      env: Record<string, string | undefined>;
+    };
+
+    // Migration already marked done — stale pins must NOT be stripped again.
+    // This proves a user re-pin that equals a stale default value survives on launch N+1.
+    expect(result.env.ANTHROPIC_MODEL).toBe('claude-sonnet-4-6');
+    expect(result.env.ANTHROPIC_DEFAULT_OPUS_MODEL).toBe('claude-opus-4-7');
+  });
+
+  it('settings file without ANTHROPIC_MODEL triggers no rewrite after migration marker set', () => {
+    process.env.CCS_HOME = tempHome;
+    const ccsDir = path.join(tempHome, '.ccs');
+    fs.mkdirSync(ccsDir, { recursive: true });
+
+    // Pre-place the migration marker.
+    const markerDir = path.join(ccsDir, 'cliproxy');
+    fs.mkdirSync(markerDir, { recursive: true });
+    fs.writeFileSync(path.join(markerDir, '.claude-model-migrated'), new Date().toISOString());
+
+    const settingsPath = path.join(ccsDir, 'claude.settings.json');
+    const originalContent = JSON.stringify(
+      {
+        env: {
+          ANTHROPIC_BASE_URL: 'http://127.0.0.1:8317/api/provider/claude',
+          ANTHROPIC_AUTH_TOKEN: 'ccs-internal-managed',
+        },
+      },
+      null,
+      2
+    );
+    fs.writeFileSync(settingsPath, originalContent + '\n', 'utf-8');
+    const statBefore = fs.statSync(settingsPath);
+
+    ensureProviderSettings('claude');
+
+    const statAfter = fs.statSync(settingsPath);
+    // mtime should not change — no rewrite triggered
+    expect(statAfter.mtimeMs).toBe(statBefore.mtimeMs);
+
+    const result = JSON.parse(fs.readFileSync(settingsPath, 'utf-8')) as {
+      env: Record<string, string | undefined>;
+    };
+    // ANTHROPIC_MODEL must still be absent
+    expect(result.env.ANTHROPIC_MODEL).toBeUndefined();
+  });
+
+  // ── Historical-default set coverage ──────────────────────────────────────────
+
+  it('strips gen-2 pins (sonnet-4-5-20250929 / opus-4-5-20251101) on migration', () => {
+    process.env.CCS_HOME = tempHome;
+    const ccsDir = path.join(tempHome, '.ccs');
+    fs.mkdirSync(ccsDir, { recursive: true });
+
+    const settingsPath = path.join(ccsDir, 'claude.settings.json');
+    fs.writeFileSync(
+      settingsPath,
+      JSON.stringify({
+        env: {
+          ANTHROPIC_BASE_URL: 'http://127.0.0.1:8317/api/provider/claude',
+          ANTHROPIC_AUTH_TOKEN: 'ccs-internal-managed',
+          ANTHROPIC_MODEL: 'claude-sonnet-4-5-20250929',
+          ANTHROPIC_DEFAULT_OPUS_MODEL: 'claude-opus-4-5-20251101',
+          ANTHROPIC_DEFAULT_SONNET_MODEL: 'claude-sonnet-4-5-20250929',
+          ANTHROPIC_DEFAULT_HAIKU_MODEL: 'claude-haiku-4-5-20251001',
+        },
+      }),
+      'utf-8'
+    );
+
+    ensureProviderSettings('claude');
+
+    const result = JSON.parse(fs.readFileSync(settingsPath, 'utf-8')) as {
+      env: Record<string, string | undefined>;
+    };
+
+    for (const key of MODEL_KEYS) {
+      const value = result.env[key];
+      expect(!value || value.trim().length === 0).toBe(true);
+    }
+  });
+
+  it('strips gen-3 mixed pin (opus-4-6) on migration', () => {
+    process.env.CCS_HOME = tempHome;
+    const ccsDir = path.join(tempHome, '.ccs');
+    fs.mkdirSync(ccsDir, { recursive: true });
+
+    const settingsPath = path.join(ccsDir, 'claude.settings.json');
+    fs.writeFileSync(
+      settingsPath,
+      JSON.stringify({
+        env: {
+          ANTHROPIC_BASE_URL: 'http://127.0.0.1:8317/api/provider/claude',
+          ANTHROPIC_AUTH_TOKEN: 'ccs-internal-managed',
+          ANTHROPIC_MODEL: 'claude-sonnet-4-6',
+          ANTHROPIC_DEFAULT_OPUS_MODEL: 'claude-opus-4-6',
+          ANTHROPIC_DEFAULT_SONNET_MODEL: 'claude-sonnet-4-6',
+          ANTHROPIC_DEFAULT_HAIKU_MODEL: 'claude-haiku-3-5-20241022',
+        },
+      }),
+      'utf-8'
+    );
+
+    ensureProviderSettings('claude');
+
+    const result = JSON.parse(fs.readFileSync(settingsPath, 'utf-8')) as {
+      env: Record<string, string | undefined>;
+    };
+
+    for (const key of MODEL_KEYS) {
+      const value = result.env[key];
+      expect(!value || value.trim().length === 0).toBe(true);
+    }
+  });
+
+  it('preserves an explicit user pin to a value not in any stale-defaults set (e.g. claude-opus-4-8)', () => {
+    process.env.CCS_HOME = tempHome;
+    const ccsDir = path.join(tempHome, '.ccs');
+    fs.mkdirSync(ccsDir, { recursive: true });
+
+    const settingsPath = path.join(ccsDir, 'claude.settings.json');
+    fs.writeFileSync(
+      settingsPath,
+      JSON.stringify({
+        env: {
+          ANTHROPIC_BASE_URL: 'http://127.0.0.1:8317/api/provider/claude',
+          ANTHROPIC_AUTH_TOKEN: 'ccs-internal-managed',
+          ANTHROPIC_MODEL: 'claude-opus-4-8',
+        },
+      }),
+      'utf-8'
+    );
+
+    ensureProviderSettings('claude');
+
+    const result = JSON.parse(fs.readFileSync(settingsPath, 'utf-8')) as {
+      env: Record<string, string | undefined>;
+    };
+
+    // claude-opus-4-8 is not in any stale-defaults set; must survive migration
+    expect(result.env.ANTHROPIC_MODEL).toBe('claude-opus-4-8');
+  });
+
+  // ── Fresh-file migration marker and tier-pin survival ─────────────────────────
+
+  it('marks migration done on fresh-file creation so tier pins written by ccs claude --config survive', () => {
+    process.env.CCS_HOME = tempHome;
+    const ccsDir = path.join(tempHome, '.ccs');
+    fs.mkdirSync(ccsDir, { recursive: true });
+
+    const settingsPath = path.join(ccsDir, 'claude.settings.json');
+    const markerPath = path.join(ccsDir, 'cliproxy', '.claude-model-migrated');
+
+    // Step 1: fresh ensureProviderSettings creates the file and the marker.
+    expect(fs.existsSync(settingsPath)).toBe(false);
+    ensureProviderSettings('claude');
+    expect(fs.existsSync(settingsPath)).toBe(true);
+    expect(fs.existsSync(markerPath)).toBe(true);
+
+    // Step 2: simulate 'ccs claude --config' pinning all four tier models.
+    const tierPins = {
+      ANTHROPIC_MODEL: 'claude-sonnet-4-6',
+      ANTHROPIC_DEFAULT_OPUS_MODEL: 'claude-sonnet-4-6',
+      ANTHROPIC_DEFAULT_SONNET_MODEL: 'claude-sonnet-4-6',
+      ANTHROPIC_DEFAULT_HAIKU_MODEL: 'claude-sonnet-4-6',
+    };
+    const existing = JSON.parse(fs.readFileSync(settingsPath, 'utf-8')) as {
+      env: Record<string, string>;
+    };
+    fs.writeFileSync(
+      settingsPath,
+      JSON.stringify({ ...existing, env: { ...existing.env, ...tierPins } }, null, 2) + '\n',
+      'utf-8'
+    );
+
+    // Step 3: second ensureProviderSettings must NOT strip the user-written pins
+    // because the migration marker already exists.
+    ensureProviderSettings('claude');
+
+    const result = JSON.parse(fs.readFileSync(settingsPath, 'utf-8')) as {
+      env: Record<string, string | undefined>;
+    };
+    expect(result.env.ANTHROPIC_MODEL).toBe('claude-sonnet-4-6');
+    expect(result.env.ANTHROPIC_DEFAULT_OPUS_MODEL).toBe('claude-sonnet-4-6');
+    expect(result.env.ANTHROPIC_DEFAULT_SONNET_MODEL).toBe('claude-sonnet-4-6');
+    expect(result.env.ANTHROPIC_DEFAULT_HAIKU_MODEL).toBe('claude-sonnet-4-6');
+  });
+});
diff --git a/src/cliproxy/config/base-config-loader.ts b/src/cliproxy/config/base-config-loader.ts
index 4f64121c..d4ea308f 100644
--- a/src/cliproxy/config/base-config-loader.ts
+++ b/src/cliproxy/config/base-config-loader.ts
@@ -16,10 +16,10 @@ interface BaseSettings {
   env: {
     ANTHROPIC_BASE_URL: string;
     ANTHROPIC_AUTH_TOKEN: string;
-    ANTHROPIC_MODEL: string;
-    ANTHROPIC_DEFAULT_OPUS_MODEL: string;
-    ANTHROPIC_DEFAULT_SONNET_MODEL: string;
-    ANTHROPIC_DEFAULT_HAIKU_MODEL: string;
+    ANTHROPIC_MODEL?: string;
+    ANTHROPIC_DEFAULT_OPUS_MODEL?: string;
+    ANTHROPIC_DEFAULT_SONNET_MODEL?: string;
+    ANTHROPIC_DEFAULT_HAIKU_MODEL?: string;
   };
 }
 
@@ -66,16 +66,20 @@ export function loadBaseConfig(provider: CLIProxyProvider): BaseSettings {
       throw new Error('Missing or invalid "env" object');
     }
 
-    const required = [
-      'ANTHROPIC_MODEL',
-      'ANTHROPIC_DEFAULT_OPUS_MODEL',
-      'ANTHROPIC_DEFAULT_SONNET_MODEL',
-      'ANTHROPIC_DEFAULT_HAIKU_MODEL',
-    ];
+    // claude provider is model-neutral: it does not pin model env vars so that
+    // the user's own Claude Code model selection is respected end-to-end.
+    if (provider !== 'claude') {
+      const required = [
+        'ANTHROPIC_MODEL',
+        'ANTHROPIC_DEFAULT_OPUS_MODEL',
+        'ANTHROPIC_DEFAULT_SONNET_MODEL',
+        'ANTHROPIC_DEFAULT_HAIKU_MODEL',
+      ];
 
-    for (const field of required) {
-      if (!settings.env[field as keyof BaseSettings['env']]) {
-        throw new Error(`Missing required field: env.${field}`);
+      for (const field of required) {
+        if (!settings.env[field as keyof BaseSettings['env']]) {
+          throw new Error(`Missing required field: env.${field}`);
+        }
       }
     }
 
@@ -90,14 +94,17 @@ export function loadBaseConfig(provider: CLIProxyProvider): BaseSettings {
 
 /**
  * Get model mapping from base config
- * Extracts model names from env vars
+ * Extracts model names from env vars.
+ * Returns undefined model fields for the claude provider (model-neutral passthrough).
  */
 export function getModelMappingFromConfig(provider: CLIProxyProvider): ProviderModelMapping {
   const config = loadBaseConfig(provider);
 
+  // claude is model-neutral: ANTHROPIC_MODEL is absent from its config; callers
+  // that need model IDs (e.g. getClaudeEnvVars) guard on provider !== 'claude'.
   return {
-    defaultModel: config.env.ANTHROPIC_MODEL,
-    claudeModel: config.env.ANTHROPIC_MODEL,
+    defaultModel: config.env.ANTHROPIC_MODEL ?? '',
+    claudeModel: config.env.ANTHROPIC_MODEL ?? '',
     opusModel: config.env.ANTHROPIC_DEFAULT_OPUS_MODEL,
     sonnetModel: config.env.ANTHROPIC_DEFAULT_SONNET_MODEL,
     haikuModel: config.env.ANTHROPIC_DEFAULT_HAIKU_MODEL,
diff --git a/src/cliproxy/config/env-builder.ts b/src/cliproxy/config/env-builder.ts
index 4b66f87f..0b9d08fb 100644
--- a/src/cliproxy/config/env-builder.ts
+++ b/src/cliproxy/config/env-builder.ts
@@ -31,7 +31,7 @@ import {
   normalizeIFlowLegacyModelAliases,
   normalizeModelIdForProvider,
 } from '../ai-providers/model-id-normalizer';
-import { getGlobalEnvConfig } from '../../config/config-loader-facade';
+import { getGlobalEnvConfig, getCcsDir } from '../../config/config-loader-facade';
 
 /** Settings file structure for user overrides */
 interface ProviderSettings {
@@ -52,6 +52,9 @@ const REQUIRED_PROVIDER_ENV_KEYS = [
   'ANTHROPIC_DEFAULT_SONNET_MODEL',
   'ANTHROPIC_DEFAULT_HAIKU_MODEL',
 ] as const;
+
+/** Minimum required env vars for the claude built-in provider (model-neutral). */
+const REQUIRED_CLAUDE_ENV_KEYS = ['ANTHROPIC_BASE_URL', 'ANTHROPIC_AUTH_TOKEN'] as const;
 const CURSOR_LEGACY_ENV_OVERRIDE_KEYS = new Set([
   'ANTHROPIC_BASE_URL',
   'ANTHROPIC_AUTH_TOKEN',
@@ -200,28 +203,18 @@ export function getModelMapping(provider: CLIProxyProvider): ProviderModelMappin
  * Get environment variables for Claude CLI (bundled defaults)
  * Uses provider-specific endpoint (e.g., /api/provider/gemini) for explicit routing.
  * This enables concurrent gemini/codex usage - each session routes to its provider via URL path.
+ *
+ * For the claude built-in provider the model env vars are intentionally omitted so that
+ * the user's own Claude Code /model selection is honored end-to-end (model-neutral passthrough).
  */
 export function getClaudeEnvVars(
   provider: CLIProxyProvider,
   port: number = CLIPROXY_DEFAULT_PORT
 ): NodeJS.ProcessEnv {
-  const models = getModelMapping(provider);
-
   // Base env vars from config file (includes ANTHROPIC_MAX_TOKENS, etc.)
   const baseEnvVars = getEnvVarsFromConfig(provider);
 
-  // Core env vars that we always set dynamically
-  const coreEnvVars = {
-    // Provider-specific endpoint - routes to correct provider via URL path
-    ANTHROPIC_BASE_URL: `http://127.0.0.1:${port}/api/provider/${provider}`,
-    ANTHROPIC_AUTH_TOKEN: getEffectiveApiKey(),
-    ANTHROPIC_MODEL: models.claudeModel,
-    ANTHROPIC_DEFAULT_OPUS_MODEL: models.opusModel || models.claudeModel,
-    ANTHROPIC_DEFAULT_SONNET_MODEL: models.sonnetModel || models.claudeModel,
-    ANTHROPIC_DEFAULT_HAIKU_MODEL: models.haikuModel || models.claudeModel,
-  };
-
-  // Filter out core env vars from base config to avoid conflicts
+  // Filter out model pins and URL/auth from base config (we set them dynamically)
   const {
     ANTHROPIC_BASE_URL: _baseUrl,
     ANTHROPIC_AUTH_TOKEN: _authToken,
@@ -232,6 +225,22 @@ export function getClaudeEnvVars(
     ...additionalEnvVars
   } = baseEnvVars;
 
+  // Core transport env vars set dynamically for all providers
+  const coreEnvVars: NodeJS.ProcessEnv = {
+    ANTHROPIC_BASE_URL: `http://127.0.0.1:${port}/api/provider/${provider}`,
+    ANTHROPIC_AUTH_TOKEN: getEffectiveApiKey(),
+  };
+
+  // Model pins: omitted for claude provider (model-neutral passthrough).
+  // For all other providers, set model vars from the base config model mapping.
+  if (provider !== 'claude') {
+    const models = getModelMapping(provider);
+    coreEnvVars.ANTHROPIC_MODEL = models.claudeModel;
+    coreEnvVars.ANTHROPIC_DEFAULT_OPUS_MODEL = models.opusModel || models.claudeModel;
+    coreEnvVars.ANTHROPIC_DEFAULT_SONNET_MODEL = models.sonnetModel || models.claudeModel;
+    coreEnvVars.ANTHROPIC_DEFAULT_HAIKU_MODEL = models.haikuModel || models.claudeModel;
+  }
+
   // Merge core env vars with additional env vars from base config
   const mergedEnv = {
     ...coreEnvVars,
@@ -509,6 +518,78 @@ export function getEffectiveEnvVars(
   return { ...globalEnv, ...getClaudeEnvVars(provider, port) };
 }
 
+/**
+ * All historically-shipped default model pins that CCS auto-wrote into
+ * claude.settings.json before the model-neutral passthrough change.
+ * A key is removed only when the stored value exactly matches one of the values
+ * in that key's set, so user-customised values are always preserved.
+ */
+const CLAUDE_STALE_MODEL_DEFAULTS: Record<string, Set<string>> = {
+  ANTHROPIC_MODEL: new Set([
+    'claude-sonnet-4-20250514',
+    'claude-sonnet-4-5-20250929',
+    'claude-sonnet-4-6',
+  ]),
+  ANTHROPIC_DEFAULT_OPUS_MODEL: new Set([
+    'claude-opus-4-20250514',
+    'claude-opus-4-5-20251101',
+    'claude-opus-4-6',
+    'claude-opus-4-7',
+  ]),
+  ANTHROPIC_DEFAULT_SONNET_MODEL: new Set([
+    'claude-sonnet-4-20250514',
+    'claude-sonnet-4-5-20250929',
+    'claude-sonnet-4-6',
+  ]),
+  ANTHROPIC_DEFAULT_HAIKU_MODEL: new Set([
+    'claude-haiku-3-5-20241022',
+    'claude-haiku-4-5-20251001',
+  ]),
+};
+
+/** Marker file that records when the one-time stale-pin migration has run. */
+const CLAUDE_MODEL_MIGRATED_MARKER = '.claude-model-migrated';
+
+/** Return true if the one-time stale-pin migration has already been applied. */
+function claudeModelMigrationDone(): boolean {
+  try {
+    return fs.existsSync(path.join(getCcsDir(), 'cliproxy', CLAUDE_MODEL_MIGRATED_MARKER));
+  } catch {
+    return true; // Cannot read — treat as done to avoid repeated rewrites.
+  }
+}
+
+/** Record that the one-time stale-pin migration has been applied. */
+function markClaudeModelMigrationDone(): void {
+  try {
+    const dir = path.join(getCcsDir(), 'cliproxy');
+    fs.mkdirSync(dir, { recursive: true });
+    fs.writeFileSync(path.join(dir, CLAUDE_MODEL_MIGRATED_MARKER), new Date().toISOString(), {
+      encoding: 'utf8',
+      flag: 'w',
+    });
+  } catch {
+    // Best-effort — failure to persist is not fatal.
+  }
+}
+
+/**
+ * Remove stale model pins from an existing claude.settings.json env block.
+ * Only removes keys whose values appear in the set of historically-shipped
+ * defaults for that key, preserving user-customised values.
+ * Returns true when at least one key was removed (signals file needs rewriting).
+ */
+function migrateClaudeStaleModelPins(env: Record<string, string>): boolean {
+  let mutated = false;
+  for (const [key, staleValues] of Object.entries(CLAUDE_STALE_MODEL_DEFAULTS)) {
+    if (staleValues.has(env[key])) {
+      delete env[key];
+      mutated = true;
+    }
+  }
+  return mutated;
+}
+
 /**
  * Copy bundled settings template to user directory if not exists
  * Called during installation/first run
@@ -525,8 +606,13 @@ export function ensureProviderSettings(provider: CLIProxyProvider): void {
   };
 
   // Create initial file when missing.
+  // A freshly created file has no stale pins by construction, so mark migration
+  // done immediately to prevent the one-time strip from running unnecessarily.
   if (!fs.existsSync(settingsPath)) {
     writeSettings({ env: defaultEnv });
+    if (provider === 'claude') {
+      markClaudeModelMigrationDone();
+    }
     return;
   }
 
@@ -564,11 +650,28 @@ export function ensureProviderSettings(provider: CLIProxyProvider): void {
       : {};
 
   let mutated = !(envCandidate && typeof envCandidate === 'object' && !Array.isArray(envCandidate));
-  for (const key of REQUIRED_PROVIDER_ENV_KEYS) {
+
+  // One-time migration: strip stale model pins written by older CCS versions into
+  // claude.settings.json.  Guarded by a marker file so a user-re-pin that happens
+  // to equal a stale default value is not silently stripped on every subsequent launch.
+  if (provider === 'claude' && !claudeModelMigrationDone()) {
+    if (migrateClaudeStaleModelPins(mergedEnv)) {
+      mutated = true;
+    }
+    markClaudeModelMigrationDone();
+  }
+
+  // claude is model-neutral: only transport keys (URL + auth) are required; model pins are omitted.
+  const requiredKeys =
+    provider === 'claude' ? REQUIRED_CLAUDE_ENV_KEYS : REQUIRED_PROVIDER_ENV_KEYS;
+  for (const key of requiredKeys) {
     const current = mergedEnv[key];
     if (typeof current !== 'string' || current.trim().length === 0) {
-      mergedEnv[key] = defaultEnv[key] || '';
-      mutated = true;
+      const fallback = defaultEnv[key];
+      if (fallback) {
+        mergedEnv[key] = fallback;
+        mutated = true;
+      }
     }
   }
 
@@ -689,7 +792,6 @@ export function getRemoteEnvVars(
 
   // Priority 3: Base config defaults
   if (Object.keys(userEnvVars).length === 0) {
-    const models = getModelMapping(provider);
     const baseEnvVars = getEnvVarsFromConfig(provider);
     // Filter out URL/auth from base config (we'll set those from remote config)
     const {
@@ -697,13 +799,25 @@ export function getRemoteEnvVars(
       ANTHROPIC_AUTH_TOKEN: _authToken,
       ...additionalEnvVars
     } = baseEnvVars;
-    userEnvVars = {
-      ...additionalEnvVars,
-      ANTHROPIC_MODEL: models.claudeModel,
-      ANTHROPIC_DEFAULT_OPUS_MODEL: models.opusModel || models.claudeModel,
-      ANTHROPIC_DEFAULT_SONNET_MODEL: models.sonnetModel || models.claudeModel,
-      ANTHROPIC_DEFAULT_HAIKU_MODEL: models.haikuModel || models.claudeModel,
-    };
+    // claude is model-neutral: omit model pins so Claude Code's own /model
+    // selection is respected on remote launches too.
+    if (provider === 'claude') {
+      // Filter out undefined values coming from NodeJS.ProcessEnv spread.
+      userEnvVars = Object.fromEntries(
+        Object.entries(additionalEnvVars).filter(
+          (entry): entry is [string, string] => typeof entry[1] === 'string'
+        )
+      );
+    } else {
+      const models = getModelMapping(provider);
+      userEnvVars = {
+        ...additionalEnvVars,
+        ANTHROPIC_MODEL: models.claudeModel,
+        ANTHROPIC_DEFAULT_OPUS_MODEL: models.opusModel || models.claudeModel,
+        ANTHROPIC_DEFAULT_SONNET_MODEL: models.sonnetModel || models.claudeModel,
+        ANTHROPIC_DEFAULT_HAIKU_MODEL: models.haikuModel || models.claudeModel,
+      };
+    }
   }
 
   // Build final env: global + user settings + remote URL/auth override
diff --git a/src/cliproxy/executor/__tests__/auth-coordinator.test.ts b/src/cliproxy/executor/__tests__/auth-coordinator.test.ts
index d7617fe6..bfe8ec14 100644
--- a/src/cliproxy/executor/__tests__/auth-coordinator.test.ts
+++ b/src/cliproxy/executor/__tests__/auth-coordinator.test.ts
@@ -484,4 +484,17 @@ describe('ensureModelConfiguration', () => {
     await ensureModelConfiguration('codex', cfg, false);
     expect(mockReconcileCodexModel).not.toHaveBeenCalled();
   });
+
+  // claude is model-neutral passthrough — must never auto-prompt at launch
+  it('claude non-composite → configureProviderModel NOT called (model-neutral)', async () => {
+    const cfg = { isComposite: false, customSettingsPath: undefined } as ExecutorConfig;
+    await ensureModelConfiguration('claude', cfg, false);
+    expect(mockConfigureProviderModel).not.toHaveBeenCalled();
+  });
+
+  it('claude composite → configureProviderModel NOT called', async () => {
+    const cfg = { isComposite: true } as ExecutorConfig;
+    await ensureModelConfiguration('claude', cfg, false);
+    expect(mockConfigureProviderModel).not.toHaveBeenCalled();
+  });
 });
diff --git a/src/cliproxy/executor/auth-coordinator.ts b/src/cliproxy/executor/auth-coordinator.ts
index 4e1f2f42..9a30b930 100644
--- a/src/cliproxy/executor/auth-coordinator.ts
+++ b/src/cliproxy/executor/auth-coordinator.ts
@@ -369,13 +369,17 @@ export function runAccountSafetyGuards(
  * Ensure provider model is configured on first run.
  * Skipped for composite variants and remote proxy mode.
  * Also reconciles Codex model for active plan.
+ *
+ * claude is model-neutral passthrough: the user's own /model selection inside
+ * Claude Code governs which model is used, so no auto-prompt at launch.
+ * Use `ccs claude --config` for an explicit pin opt-in.
  */
 export async function ensureModelConfiguration(
   provider: CLIProxyProvider,
   cfg: ExecutorConfig,
   verbose: boolean
 ): Promise<void> {
-  if (!cfg.isComposite && supportsModelConfig(provider)) {
+  if (!cfg.isComposite && provider !== 'claude' && supportsModelConfig(provider)) {
     await configureProviderModel(provider, false, cfg.customSettingsPath);
   }
 
diff --git a/src/cliproxy/executor/index.ts b/src/cliproxy/executor/index.ts
index 0a5ee7fa..9a4ee77a 100644
--- a/src/cliproxy/executor/index.ts
+++ b/src/cliproxy/executor/index.ts
@@ -67,6 +67,7 @@ import { resolveExecutorProxy, resolveExecutorProxyConfig } from './proxy-resolv
 import { buildProxyChain } from './proxy-chain-builder';
 import { warnBrokenModels } from './model-warnings';
 import { launchClaude } from './claude-launcher';
+import { maybeWarnClaudeShadow, maybeShowClaudeRoutingNotice } from '../claude-shadow-warning';
 
 /** Local alias so internal call sites need no change */
 const resolveRuntimeQuotaMonitorProviders = _resolveRuntimeQuotaMonitorProviders;
@@ -161,6 +162,11 @@ export async function execClaudeWithCLIProxy(
   const providerConfig = getProviderConfig(provider);
   log(`Provider: ${providerConfig.displayName}`);
 
+  // claude built-in: warn once if a user profile is being shadowed
+  if (provider === 'claude') {
+    maybeWarnClaudeShadow();
+  }
+
   // Variables for local proxy mode
   let sessionId: string | undefined;
 
@@ -279,6 +285,11 @@ export async function execClaudeWithCLIProxy(
   // 5. Check for broken models (multi-tier for composite)
   warnBrokenModels({ provider, cfg, compositeProviders, skipLocalAuth });
 
+  // 5a. claude built-in: one-time routing notice (first launch only)
+  if (provider === 'claude') {
+    maybeShowClaudeRoutingNotice();
+  }
+
   // 6. Ensure user settings file exists
   ensureProviderSettingsFile(provider);
 
diff --git a/src/commands/help-command.ts b/src/commands/help-command.ts
index c5fd340b..bc7e5c7f 100644
--- a/src/commands/help-command.ts
+++ b/src/commands/help-command.ts
@@ -122,12 +122,17 @@ export async function showProviderShortcutHelp(
   writeLine('');
   writeLine(`  ${providerEntry?.summary || 'CLIProxy OAuth provider shortcut'}.`);
   writeLine('');
+  const configSummary =
+    provider === 'claude'
+      ? 'Pin a model for this session (optional; use /model inside Claude Code instead)'
+      : 'Open the provider config flow';
+
   writeCommandTable(
     'Common Commands',
     [
       { name: `ccs ${provider} --auth`, summary: 'Authenticate the provider account via CLIProxy' },
       { name: `ccs ${provider} --accounts`, summary: 'List or manage stored CLIProxy accounts' },
-      { name: `ccs ${provider} --config`, summary: 'Open the provider config flow' },
+      { name: `ccs ${provider} --config`, summary: configSummary },
       { name: `ccs ${provider} "task"`, summary: 'Run Claude through this provider shortcut' },
     ],
     writeLine