diff --git a/.github/ISSUE_TEMPLATE/bug_report.yml b/.github/ISSUE_TEMPLATE/bug_report.yml
index f66ab6f..d385cb0 100644
--- a/.github/ISSUE_TEMPLATE/bug_report.yml
+++ b/.github/ISSUE_TEMPLATE/bug_report.yml
@@ -21,6 +21,31 @@ body:
         - Other
     validations:
       required: true
+  - type: dropdown
+    id: browser
+    attributes:
+      label: Browser (for cookie extraction)
+      options:
+        - Arc
+        - Chrome
+        - Edge
+        - Firefox
+        - Brave
+        - Other / N/A (using env vars)
+    validations:
+      required: true
+  - type: dropdown
+    id: access_method
+    attributes:
+      label: Access Method
+      description: How are you accessing the machine where twitter-cli runs?
+      options:
+        - Local terminal
+        - SSH
+        - Docker / container
+        - Other
+    validations:
+      required: true
   - type: textarea
     id: description
     attributes:
@@ -41,6 +66,12 @@ body:
       label: Steps to reproduce
       description: "Commands or steps to reproduce the issue. Use `twitter -v <command>` for debug output."
       render: bash
+  - type: textarea
+    id: diagnostics
+    attributes:
+      label: Diagnostics
+      description: "Paste the output of `twitter doctor` here. This helps us diagnose cookie and auth issues quickly."
+      render: text
   - type: textarea
     id: logs
     attributes:
diff --git a/README.md b/README.md
index b395674..0d29a84 100644
--- a/README.md
+++ b/README.md
@@ -241,6 +241,14 @@ Mode behavior:
 - `Cookie expired or invalid (HTTP 401/403)`
   - Re-login to `x.com` and retry.
 
+- `Unable to get key for cookie decryption` (macOS Keychain)
+  - **SSH sessions**: Keychain is locked by default over SSH. Run:
+    ```bash
+    security unlock-keychain ~/Library/Keychains/login.keychain-db
+    ```
+  - **Local terminal**: Open **Keychain Access** → search for **"\<Browser\> Safe Storage"** → **Access Control** → add your Terminal app → **Save Changes**.
+  - Or click **"Always Allow"** when the Keychain authorization popup appears.
+
 - `Twitter API error 404`
   - This can happen when upstream GraphQL query IDs rotate.
   - Retry the command; the client attempts a live queryId fallback.
@@ -248,6 +256,8 @@ Mode behavior:
 - `Invalid tweet JSON file`
   - Regenerate input using `twitter feed --json > tweets.json`.
 
+**Diagnostics command**: Run `twitter doctor` to output a full diagnostic report (version, OS, browser detection, Keychain status, cookie extraction results). Paste this output into bug reports.
+
 Structured error codes commonly include `not_authenticated`, `not_found`, `invalid_input`, `rate_limited`, and `api_error`.
 
 ### Development
@@ -458,7 +468,17 @@ score = likes_w * likes
 - 报错 `No Twitter cookies found`：请先登录 `x.com`，并确认浏览器为 Arc/Chrome/Edge/Firefox/Brave 之一，或手动设置环境变量。
 - 如需查看浏览器提取细节，可加 `-v` 打开诊断日志。
 - 报错 `Cookie expired or invalid`：Cookie 过期，重新登录后重试。
+- 报错 `Unable to get key for cookie decryption`（macOS Keychain 问题）：
+  - **SSH 远程登录**：Keychain 默认锁定，需手动解锁：
+    ```bash
+    security unlock-keychain ~/Library/Keychains/login.keychain-db
+    ```
+  - **本地终端**：打开 **钥匙串访问** → 搜索 **"\<浏览器\> Safe Storage"** → **访问控制** → 添加你的终端 app → **保存更改**。
+  - 或在弹出 Keychain 授权时点击 **"始终允许"**。
 - 报错 `Twitter API error 404`：通常是 queryId 轮换，重试即可。
+
+**诊断命令**：运行 `twitter doctor` 可输出完整诊断报告（版本、OS、浏览器检测、Keychain 状态、cookie 提取结果），方便提交 bug report。
+
 - 结构化错误码通常会区分 `not_authenticated`、`not_found`、`invalid_input`、`rate_limited`、`api_error`。
 
 ### 使用建议（防封号）
diff --git a/tests/test_auth.py b/tests/test_auth.py
index f2b84bd..3e7e9bc 100644
--- a/tests/test_auth.py
+++ b/tests/test_auth.py
@@ -30,8 +30,8 @@ def test_get_cookies_reextracts_after_verify_failure(monkeypatch) -> None:
     monkeypatch.setattr(auth, "load_from_env", lambda: None)
     extracted = iter(
         [
-            {"auth_token": "stale-token", "ct0": "stale-csrf", "cookie_string": "stale=1"},
-            {"auth_token": "fresh-token", "ct0": "fresh-csrf", "cookie_string": "fresh=1"},
+            ({"auth_token": "stale-token", "ct0": "stale-csrf", "cookie_string": "stale=1"}, []),
+            ({"auth_token": "fresh-token", "ct0": "fresh-csrf", "cookie_string": "fresh=1"}, []),
         ]
     )
     monkeypatch.setattr(auth, "extract_from_browser", lambda: next(extracted))
@@ -84,11 +84,11 @@ def test_extract_cookies_from_jar_logs_missing_required_cookies(caplog) -> None:
 
 
 def test_extract_from_browser_logs_warning_when_all_methods_fail(monkeypatch, caplog) -> None:
-    monkeypatch.setattr(auth, "_extract_in_process", lambda: None)
-    monkeypatch.setattr(auth, "_extract_via_subprocess", lambda: None)
+    monkeypatch.setattr(auth, "_extract_in_process", lambda: (None, []))
+    monkeypatch.setattr(auth, "_extract_via_subprocess", lambda: (None, []))
 
     with caplog.at_level("WARNING"):
-        cookies = auth.extract_from_browser()
+        cookies, diagnostics = auth.extract_from_browser()
 
     assert cookies is None
     assert "Twitter cookie extraction failed in both in-process and subprocess modes" in caplog.text
@@ -110,7 +110,7 @@ def test_extract_in_process_supports_arc(monkeypatch) -> None:
     )
     monkeypatch.setitem(sys.modules, "browser_cookie3", fake_module)
 
-    cookies = auth._extract_in_process()
+    cookies, diagnostics = auth._extract_in_process()
 
     assert cookies is not None
     assert cookies["auth_token"] == "token"
@@ -132,7 +132,7 @@ def test_extract_via_subprocess_script_includes_arc(monkeypatch) -> None:
 
     monkeypatch.setattr(auth.subprocess, "run", _run)
 
-    cookies = auth._extract_via_subprocess()
+    cookies, diagnostics = auth._extract_via_subprocess()
 
     assert cookies is None
     assert '("arc", browser_cookie3.arc)' in seen["script"]
@@ -154,7 +154,7 @@ def test_extract_via_subprocess_retries_uv_when_current_env_has_no_output(monkey
 
     monkeypatch.setattr(auth.subprocess, "run", _run)
 
-    cookies = auth._extract_via_subprocess()
+    cookies, diagnostics = auth._extract_via_subprocess()
 
     assert cookies == {"auth_token": "token", "ct0": "csrf"}
     assert len(calls) == 2
@@ -285,8 +285,85 @@ def test_extract_in_process_tries_multiple_profiles(monkeypatch, tmp_path) -> No
     )
     monkeypatch.setitem(sys.modules, "browser_cookie3", fake_module)
 
-    cookies = auth._extract_in_process()
+    cookies, diagnostics = auth._extract_in_process()
 
     assert cookies is not None
     assert cookies["auth_token"] == "tok123"
     assert cookies["ct0"] == "csrf456"
+
+
+def test_diagnose_keychain_issues_detects_decryption_error(monkeypatch) -> None:
+    """_diagnose_keychain_issues should detect Keychain-related error strings."""
+    monkeypatch.setattr("sys.platform", "darwin")
+    monkeypatch.delenv("SSH_CLIENT", raising=False)
+    monkeypatch.delenv("SSH_TTY", raising=False)
+    monkeypatch.delenv("SSH_CONNECTION", raising=False)
+
+    diagnostics = ["arc[Default]: Unable to get key for cookie decryption"]
+    hint = auth._diagnose_keychain_issues(diagnostics)
+
+    assert hint is not None
+    assert "Keychain" in hint
+
+
+def test_diagnose_keychain_issues_ssh_hint(monkeypatch) -> None:
+    """When SSH env vars are set, hint should suggest unlock-keychain."""
+    monkeypatch.setattr("sys.platform", "darwin")
+    monkeypatch.setenv("SSH_CLIENT", "1.2.3.4 54321 22")
+
+    diagnostics = ["arc: Unable to get key for cookie decryption"]
+    hint = auth._diagnose_keychain_issues(diagnostics)
+
+    assert hint is not None
+    assert "SSH session detected" in hint
+    assert "security unlock-keychain" in hint
+
+
+def test_diagnose_keychain_issues_returns_none_for_unrelated_errors() -> None:
+    """Should return None when diagnostics don't mention Keychain."""
+    diagnostics = ["chrome[Default]=no-cookies", "firefox: profile not found"]
+    hint = auth._diagnose_keychain_issues(diagnostics)
+
+    assert hint is None
+
+
+def test_get_cookies_includes_keychain_hint_in_error(monkeypatch) -> None:
+    """When extraction fails with Keychain errors, error msg should contain the hint."""
+    monkeypatch.setattr("sys.platform", "darwin")
+    monkeypatch.setenv("SSH_CLIENT", "1.2.3.4 54321 22")
+    monkeypatch.setattr(auth, "load_from_env", lambda: None)
+    monkeypatch.setattr(
+        auth,
+        "extract_from_browser",
+        lambda: (None, ["arc: Unable to get key for cookie decryption"]),
+    )
+
+    with pytest.raises(RuntimeError) as exc_info:
+        auth.get_cookies()
+
+    msg = str(exc_info.value)
+    assert "security unlock-keychain" in msg
+    assert "twitter doctor" in msg
+
+
+def test_extract_in_process_returns_diagnostics_on_failure(monkeypatch) -> None:
+    """_extract_in_process should return diagnostics containing error strings."""
+    from types import SimpleNamespace
+
+    class BrowserError(Exception):
+        pass
+
+    fake_module = SimpleNamespace(
+        arc=lambda: (_ for _ in ()).throw(BrowserError("Unable to get key for cookie decryption")),
+        chrome=lambda: [],
+        edge=lambda: (_ for _ in ()).throw(BrowserError("Edge not found")),
+        firefox=lambda: (_ for _ in ()).throw(BrowserError("Firefox not found")),
+        brave=lambda: (_ for _ in ()).throw(BrowserError("Brave not found")),
+    )
+    monkeypatch.setitem(sys.modules, "browser_cookie3", fake_module)
+
+    cookies, diagnostics = auth._extract_in_process()
+
+    assert cookies is None
+    assert any("cookie decryption" in d for d in diagnostics)
+
diff --git a/twitter_cli/auth.py b/twitter_cli/auth.py
index 5a198d4..a5bf28c 100644
--- a/twitter_cli/auth.py
+++ b/twitter_cli/auth.py
@@ -30,6 +30,48 @@ def _is_twitter_domain(domain: str) -> bool:
     return domain in _TWITTER_DOMAINS or domain.endswith(".x.com") or domain.endswith(".twitter.com")
 
 
+# ---------------------------------------------------------------------------
+# Keychain / environment diagnostics
+# ---------------------------------------------------------------------------
+
+_KEYCHAIN_ERROR_KEYWORDS = (
+    "key for cookie decryption",
+    "safe storage",
+    "keychain",
+    "secretstorage",
+)
+
+
+def _diagnose_keychain_issues(diagnostics: List[str]) -> Optional[str]:
+    """Analyse extraction diagnostics for Keychain permission issues.
+
+    Returns a user-friendly hint string, or None.
+    """
+    lowered = " ".join(diagnostics).lower()
+    if not any(kw in lowered for kw in _KEYCHAIN_ERROR_KEYWORDS):
+        return None
+
+    is_ssh = bool(os.environ.get("SSH_CLIENT") or os.environ.get("SSH_TTY") or os.environ.get("SSH_CONNECTION"))
+
+    if sys.platform == "darwin":
+        if is_ssh:
+            return (
+                "macOS Keychain is locked (SSH session detected).\n"
+                "  Fix: security unlock-keychain ~/Library/Keychains/login.keychain-db\n"
+                "  Then retry the command."
+            )
+        return (
+            "macOS Keychain permission denied — your terminal is not authorized to read browser cookie encryption keys.\n"
+            "  Fix: Open Keychain Access → search for \"<Browser> Safe Storage\" → Access Control → add your Terminal app.\n"
+            "  Or click \"Always Allow\" when the Keychain authorization popup appears."
+        )
+    # Linux: gnome-keyring / SecretStorage issues
+    return (
+        "System keyring access failed — the cookie encryption key could not be retrieved.\n"
+        "  If running headless or via SSH, ensure your keyring daemon is unlocked."
+    )
+
+
 def load_from_env() -> Optional[Dict[str, str]]:
     """Load cookies from environment variables."""
     auth_token = os.environ.get("TWITTER_AUTH_TOKEN", "")
@@ -197,7 +239,7 @@ def _iter_chrome_cookie_files(browser_name: str) -> List[str]:
     return paths
 
 
-def _extract_in_process() -> Optional[Dict[str, str]]:
+def _extract_in_process() -> Tuple[Optional[Dict[str, str]], List[str]]:
     """Extract cookies in the main process (required on macOS for Keychain access).
 
     On macOS, Chrome encrypts cookies using a key stored in the system Keychain.
@@ -205,12 +247,14 @@ def _extract_in_process() -> Optional[Dict[str, str]]:
     browser_cookie3 must run in the main process to decrypt cookies.
 
     For Chromium-based browsers, iterates all profiles to find Twitter cookies.
+
+    Returns (cookies_dict | None, diagnostics_list).
     """
     try:
         import browser_cookie3
     except ImportError:
         logger.debug("browser_cookie3 not installed, skipping in-process extraction")
-        return None
+        return None, ["browser-cookie3 not installed"]
 
     browsers = [
         ("arc", browser_cookie3.arc),
@@ -219,7 +263,8 @@ def _extract_in_process() -> Optional[Dict[str, str]]:
         ("firefox", browser_cookie3.firefox),
         ("brave", browser_cookie3.brave),
     ]
-    attempts = []
+    attempts: List[str] = []
+    diagnostics: List[str] = []
 
     for name, fn in browsers:
         if name in _CHROMIUM_BASE_DIRS:
@@ -232,11 +277,12 @@ def _extract_in_process() -> Optional[Dict[str, str]]:
                 except Exception as e:
                     logger.debug("%s in-process extraction failed: %s", name, e)
                     attempts.append("%s=%s" % (name, type(e).__name__))
+                    diagnostics.append("%s: %s" % (name, e))
                     continue
                 cookies = _extract_cookies_from_jar(jar, source="%s(in-process)" % name)
                 if cookies:
                     logger.info("Found cookies in %s (in-process, default)", name)
-                    return cookies
+                    return cookies, diagnostics
                 attempts.append("%s=no-cookies" % name)
                 continue
 
@@ -247,11 +293,12 @@ def _extract_in_process() -> Optional[Dict[str, str]]:
                 except Exception as e:
                     logger.debug("%s[%s] in-process extraction failed: %s", name, profile_name, e)
                     attempts.append("%s[%s]=%s" % (name, profile_name, type(e).__name__))
+                    diagnostics.append("%s[%s]: %s" % (name, profile_name, e))
                     continue
                 cookies = _extract_cookies_from_jar(jar, source="%s[%s](in-process)" % (name, profile_name))
                 if cookies:
                     logger.info("Found cookies in %s profile '%s' (in-process)", name, profile_name)
-                    return cookies
+                    return cookies, diagnostics
                 attempts.append("%s[%s]=no-cookies" % (name, profile_name))
         else:
             # Non-Chromium (Firefox): use default behavior
@@ -260,20 +307,24 @@ def _extract_in_process() -> Optional[Dict[str, str]]:
             except Exception as e:
                 logger.debug("%s in-process extraction failed: %s", name, e)
                 attempts.append("%s=%s" % (name, type(e).__name__))
+                diagnostics.append("%s: %s" % (name, e))
                 continue
             cookies = _extract_cookies_from_jar(jar, source="%s(in-process)" % name)
             if cookies:
                 logger.info("Found cookies in %s (in-process)", name)
-                return cookies
+                return cookies, diagnostics
             attempts.append("%s=no-cookies" % name)
 
     if attempts:
         logger.debug("In-process extraction attempts: %s", ", ".join(attempts))
-    return None
+    return None, diagnostics
 
 
-def _extract_via_subprocess() -> Optional[Dict[str, str]]:
-    """Extract cookies via subprocess (fallback if in-process fails, e.g. SQLite lock)."""
+def _extract_via_subprocess() -> Tuple[Optional[Dict[str, str]], List[str]]:
+    """Extract cookies via subprocess (fallback if in-process fails, e.g. SQLite lock).
+
+    Returns (cookies_dict | None, diagnostics_list).
+    """
     extract_script = '''
 import glob, json, os, sys
 try:
@@ -351,7 +402,7 @@ for name, fn in browsers:
             try:
                 jar = fn()
             except Exception as exc:
-                attempts.append(f"{name}={type(exc).__name__}")
+                attempts.append(f"{name}={type(exc).__name__}: {exc}")
                 continue
             r = extract_from_jar(jar, name)
             if r:
@@ -364,7 +415,7 @@ for name, fn in browsers:
             try:
                 jar = fn(cookie_file=cf)
             except Exception as exc:
-                attempts.append(f"{name}[{pname}]={type(exc).__name__}")
+                attempts.append(f"{name}[{pname}]={type(exc).__name__}: {exc}")
                 continue
             r = extract_from_jar(jar, name, pname)
             if r:
@@ -375,7 +426,7 @@ for name, fn in browsers:
         try:
             jar = fn()
         except Exception as exc:
-            attempts.append(f"{name}={type(exc).__name__}")
+            attempts.append(f"{name}={type(exc).__name__}: {exc}")
             continue
         r = extract_from_jar(jar, name)
         if r:
@@ -390,6 +441,8 @@ print(json.dumps({
 sys.exit(1)
 '''
 
+    diagnostics: List[str] = []
+
     def _run_extract_command(
         cmd: list[str],
         timeout: int,
@@ -427,6 +480,7 @@ sys.exit(1)
             attempts = data.get("attempts") or []
             if attempts:
                 logger.debug("Subprocess extraction attempts (%s): %s", label, ", ".join(str(item) for item in attempts))
+                diagnostics.extend(str(item) for item in attempts)
             retryable = data.get("error") == "browser-cookie3 not installed"
             return None, retryable
 
@@ -446,7 +500,7 @@ sys.exit(1)
             )
 
         if data is None:
-            return None
+            return None, diagnostics
         logger.info("Found cookies in %s (subprocess)", data.get("browser", "unknown"))
 
         # Build full cookie string from all extracted cookies
@@ -456,30 +510,36 @@ sys.exit(1)
             cookie_str = "; ".join("%s=%s" % (k, v) for k, v in all_cookies.items())
             cookies["cookie_string"] = cookie_str
             logger.info("Extracted %d total cookies for full browser fingerprint", len(all_cookies))
-        return cookies
+        return cookies, diagnostics
     except KeyError as exc:
         logger.debug("Cookie extraction subprocess returned incomplete payload: %s", exc)
-        return None
+        return None, diagnostics
 
 
-def extract_from_browser() -> Optional[Dict[str, str]]:
+def extract_from_browser() -> Tuple[Optional[Dict[str, str]], List[str]]:
     """Auto-extract ALL Twitter cookies from local browser using browser-cookie3.
 
     Strategy:
     1. Try in-process first (required on macOS for Keychain access)
     2. Fall back to subprocess (handles SQLite lock when browser is running)
+
+    Returns (cookies_dict | None, diagnostics_list).
     """
+    all_diagnostics: List[str] = []
+
     # 1. In-process (works on macOS, may fail with SQLite lock)
-    cookies = _extract_in_process()
+    cookies, diag = _extract_in_process()
+    all_diagnostics.extend(diag)
     if cookies:
-        return cookies
+        return cookies, all_diagnostics
 
     # 2. Subprocess fallback (handles SQLite lock, but fails on macOS Keychain)
     logger.debug("In-process extraction failed, trying subprocess fallback")
-    cookies = _extract_via_subprocess()
+    cookies, diag = _extract_via_subprocess()
+    all_diagnostics.extend(diag)
     if not cookies:
         logger.warning("Twitter cookie extraction failed in both in-process and subprocess modes")
-    return cookies
+    return cookies, all_diagnostics
 
 
 def get_cookies() -> Dict[str, str]:
@@ -488,6 +548,7 @@ def get_cookies() -> Dict[str, str]:
     Raises RuntimeError if no cookies found.
     """
     cookies: Optional[Dict[str, str]] = None
+    diagnostics: List[str] = []
 
     # 1. Try environment variables
     cookies = load_from_env()
@@ -497,14 +558,22 @@ def get_cookies() -> Dict[str, str]:
     # 2. Try browser extraction (auto-detect)
     if not cookies:
         logger.debug("Attempting browser cookie extraction")
-        cookies = extract_from_browser()
+        cookies, diagnostics = extract_from_browser()
 
     if not cookies:
-        raise RuntimeError(
-            "No Twitter cookies found.\n"
-            "Option 1: Set TWITTER_AUTH_TOKEN and TWITTER_CT0 environment variables\n"
-            "Option 2: Make sure you are logged into x.com in your browser (Arc/Chrome/Edge/Firefox/Brave)"
-        )
+        lines = ["No Twitter cookies found."]
+        # Add actionable Keychain hint when relevant
+        hint = _diagnose_keychain_issues(diagnostics)
+        if hint:
+            lines.append("")
+            lines.append("Likely cause:")
+            lines.extend("  " + l for l in hint.splitlines())
+            lines.append("")
+        lines.append("Option 1: Set TWITTER_AUTH_TOKEN and TWITTER_CT0 environment variables")
+        lines.append("Option 2: Make sure you are logged into x.com in your browser (Arc/Chrome/Edge/Firefox/Brave)")
+        lines.append("")
+        lines.append("Run 'twitter doctor' for full diagnostics.")
+        raise RuntimeError("\n".join(lines))
 
     # Verify only for explicit auth failures; transient endpoint issues are tolerated.
     try:
@@ -512,7 +581,7 @@ def get_cookies() -> Dict[str, str]:
     except RuntimeError:
         # Auth failure — re-extract from browser and retry verification
         logger.info("Cookie verification failed, re-extracting from browser")
-        fresh_cookies = extract_from_browser()
+        fresh_cookies, _ = extract_from_browser()
         if fresh_cookies:
             # Verify fresh cookies — if this also fails, let it raise
             verify_cookies(fresh_cookies["auth_token"], fresh_cookies["ct0"], fresh_cookies.get("cookie_string"))
diff --git a/twitter_cli/cli.py b/twitter_cli/cli.py
index 25acfc7..ed10c75 100644
--- a/twitter_cli/cli.py
+++ b/twitter_cli/cli.py
@@ -28,6 +28,7 @@ Write commands:
 from __future__ import annotations
 
 import logging
+import os
 import re
 import sys
 import time
@@ -992,5 +993,137 @@ def unbookmark(tweet_id, as_json, as_yaml):
     _write_action("🔖", "Removing bookmark", "unbookmark_tweet", tweet_id, as_json=as_json, as_yaml=as_yaml)
 
 
+@cli.command(name="doctor")
+@structured_output_options
+def doctor(as_json, as_yaml):
+    # type: (bool, bool) -> None
+    """Run diagnostics for cookie extraction and authentication.
+
+    Useful for troubleshooting auth issues and for pasting into bug reports.
+    """
+    import platform
+
+    from .auth import (
+        _diagnose_keychain_issues,
+        _extract_in_process,
+        _extract_via_subprocess,
+        extract_from_browser,
+        load_from_env,
+        verify_cookies,
+    )
+
+    info: Dict[str, Any] = {}
+    mode = _structured_mode(as_json=as_json, as_yaml=as_yaml)
+
+    # -- System info --
+    info["version"] = __version__
+    info["python"] = sys.version.split()[0]
+    info["platform"] = platform.platform()
+    info["os"] = sys.platform
+
+    # -- Environment --
+    is_ssh = bool(
+        os.environ.get("SSH_CLIENT")
+        or os.environ.get("SSH_TTY")
+        or os.environ.get("SSH_CONNECTION")
+    )
+    info["ssh_session"] = is_ssh
+    info["env_auth_token_set"] = bool(os.environ.get("TWITTER_AUTH_TOKEN"))
+    info["env_ct0_set"] = bool(os.environ.get("TWITTER_CT0"))
+    info["chrome_profile_override"] = os.environ.get("TWITTER_CHROME_PROFILE", "")
+
+    # -- Cookie extraction --
+    env_cookies = load_from_env()
+    info["env_cookies"] = "found" if env_cookies else "not set"
+
+    # In-process extraction
+    in_proc_cookies, in_proc_diag = _extract_in_process()
+    info["in_process"] = {
+        "status": "ok" if in_proc_cookies else "failed",
+        "diagnostics": in_proc_diag,
+    }
+
+    # Subprocess extraction
+    sub_cookies, sub_diag = _extract_via_subprocess()
+    info["subprocess"] = {
+        "status": "ok" if sub_cookies else "failed",
+        "diagnostics": sub_diag,
+    }
+
+    # Combined diagnostics
+    all_diag = in_proc_diag + sub_diag
+    cookies = in_proc_cookies or sub_cookies or env_cookies
+
+    # Keychain hint
+    hint = _diagnose_keychain_issues(all_diag)
+    if hint:
+        info["keychain_hint"] = hint
+
+    # Verification
+    if cookies:
+        try:
+            result = verify_cookies(
+                cookies["auth_token"],
+                cookies["ct0"],
+                cookies.get("cookie_string"),
+            )
+            info["verification"] = "ok"
+            info["screen_name"] = result.get("screen_name", "")
+        except RuntimeError as exc:
+            info["verification"] = "failed: %s" % exc
+    else:
+        info["verification"] = "skipped (no cookies)"
+
+    # -- Output --
+    if _emit_mode_payload(info, mode):
+        return
+
+    console.print("\n🩺 [bold]twitter-cli doctor[/bold]\n")
+    console.print("  Version:      %s" % info["version"])
+    console.print("  Python:       %s" % info["python"])
+    console.print("  Platform:     %s" % info["platform"])
+    console.print("  SSH session:  %s" % ("yes ⚠️" if is_ssh else "no"))
+    console.print()
+
+    console.print("[bold]Environment:[/bold]")
+    console.print("  TWITTER_AUTH_TOKEN: %s" % ("set ✅" if info["env_auth_token_set"] else "not set"))
+    console.print("  TWITTER_CT0:        %s" % ("set ✅" if info["env_ct0_set"] else "not set"))
+    if info["chrome_profile_override"]:
+        console.print("  TWITTER_CHROME_PROFILE: %s" % info["chrome_profile_override"])
+    console.print()
+
+    console.print("[bold]Cookie Extraction:[/bold]")
+    in_status = info["in_process"]["status"]
+    console.print(
+        "  In-process:   %s" % ("[green]ok ✅[/green]" if in_status == "ok" else "[red]failed ❌[/red]")
+    )
+    for d in info["in_process"]["diagnostics"]:
+        console.print("    [dim]• %s[/dim]" % d)
+
+    sub_status = info["subprocess"]["status"]
+    console.print(
+        "  Subprocess:   %s" % ("[green]ok ✅[/green]" if sub_status == "ok" else "[red]failed ❌[/red]")
+    )
+    for d in info["subprocess"]["diagnostics"]:
+        console.print("    [dim]• %s[/dim]" % d)
+    console.print()
+
+    if hint:
+        console.print("[yellow]💡 Hint:[/yellow]")
+        for line in hint.splitlines():
+            console.print("  [yellow]%s[/yellow]" % line)
+        console.print()
+
+    v = info["verification"]
+    if v == "ok":
+        screen = info.get("screen_name", "")
+        console.print("[green]✅ Authentication: OK[/green]%s" % (" (@%s)" % screen if screen else ""))
+    elif v.startswith("failed"):
+        console.print("[red]❌ Authentication: %s[/red]" % v)
+    else:
+        console.print("[yellow]⚠️  Authentication: %s[/yellow]" % v)
+    console.print()
+
+
 if __name__ == "__main__":
     cli()