From 68c4f8d0bc2c103bf17a8dc4be4a70080b3121bc Mon Sep 17 00:00:00 2001
From: JeffreyChen <zenxcvwait@gmail.com>
Date: Sat, 18 Apr 2026 00:31:04 +0800
Subject: [PATCH 1/3] Harden SSH/API network security and bump to 1.0.19

Add shared URL validation helper (pybreeze/utils/network), route
AI code review and diagram download through it, disable redirect
following on requests.*, switch SSH/SFTP to WarningPolicy with
system host keys, and expand CLAUDE.md security checklist.
---
 CLAUDE.md                                     | 49 +++++++++++++++++--
 pybreeze/__main__.py                          |  2 +
 .../python_task_process_manager.py            | 10 ++--
 .../test_pioneer_process_manager.py           |  2 -
 .../extend_multi_language/extend_english.py   |  2 +
 .../extend_traditional_chinese.py             |  2 +
 .../update_language_dict.py                   |  2 +
 .../connect_gui/ssh/ssh_command_widget.py     |  8 ++-
 .../connect_gui/ssh/ssh_file_viewer_widget.py | 16 +++---
 .../connect_gui/ssh/ssh_login_widget.py       |  2 +
 .../connect_gui/ssh/ssh_main_widget.py        |  2 +
 .../connect_gui/url/ai_code_review_gui.py     | 19 +++++--
 .../diagram_editor/diagram_editor_widget.py   |  8 ++-
 .../diagram_editor/diagram_net_utils.py       | 35 ++-----------
 .../diagram_editor/diagram_scene.py           |  6 +--
 .../editor_main/file_tree_context_menu.py     |  6 ++-
 pybreeze/pybreeze_ui/editor_main/main_ui.py   |  4 +-
 .../extend_ai_gui/ai_gui_global_variable.py   |  2 +
 .../code_review/code_review_thread.py         |  6 ++-
 .../code_review/cot_code_review_gui.py        | 10 ++--
 .../code_smell_detector.py                    |  2 +
 .../first_code_review.py                      |  2 +
 .../first_summary_prompt.py                   |  2 +
 .../global_rule.py                            |  2 +
 .../cot_code_review_prompt_templates/judge.py |  2 +
 .../judge_single_review.py                    |  2 +
 .../linter.py                                 |  2 +
 .../step_by_step_analysis.py                  |  2 +
 .../total_summary.py                          |  2 +
 .../cot_prompt_editor_widget.py               |  2 +
 .../skills_prompt_editor_widget.py            |  2 +
 .../skills_prompt_templates/code_explainer.py |  2 +
 .../skills_prompt_templates/code_review.py    |  2 +
 .../extend_ai_gui/skills/skills_send_gui.py   |  6 ++-
 .../jupyter_lab_gui/jupyter_lab_thread.py     |  5 +-
 .../jupyter_lab_gui/jupyter_lab_widget.py     |  2 +
 .../automation_menu_factory.py                |  2 +-
 .../menu/plugin_menu/build_plugin_menu.py     | 20 +++-----
 .../menu/plugin_menu/build_run_with_menu.py   |  2 +-
 .../show_code_window/code_window.py           |  2 +
 pybreeze/pybreeze_ui/syntax/syntax_keyword.py |  2 +
 pybreeze/utils/exception/exception_tags.py    |  2 +
 pybreeze/utils/exception/exceptions.py        |  2 +
 pybreeze/utils/json_format/json_process.py    |  4 +-
 pybreeze/utils/logging/logger.py              |  2 +
 .../package_manager/package_manager_class.py  |  2 +
 pybreeze/utils/network/__init__.py            |  0
 pybreeze/utils/network/url_validation.py      | 47 ++++++++++++++++++
 pyproject.toml                                |  2 +-
 49 files changed, 234 insertions(+), 87 deletions(-)
 create mode 100644 pybreeze/utils/network/__init__.py
 create mode 100644 pybreeze/utils/network/url_validation.py

diff --git a/CLAUDE.md b/CLAUDE.md
index 8f73d4f..f0dc94b 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -36,6 +36,7 @@ pybreeze/
     ├── logging/                 # pybreeze_logger
     ├── file_process/            # File/directory utilities
     ├── json_format/             # JSON processing
+    ├── network/                 # URL validation (SSRF prevention)
     └── manager/package_manager/ # PackageManager class
 ```
 
@@ -95,14 +96,37 @@ All code must follow secure-by-default principles. Review every change against t
 - Never use `subprocess.Popen(..., shell=True)` — always pass argument lists
 - Never log or display secrets, tokens, passwords, or API keys
 - Use `json.loads()` / `json.dumps()` for serialisation — never pickle
+- Never use `yaml.load()` — always use `yaml.safe_load()`
 - Validate all user input at system boundaries (file dialogs, URL inputs, network data)
+- Handle exceptions without leaking stack traces, file paths, or internal state to the user
 
 ### Network requests (SSRF prevention)
-- All outbound HTTP requests must go through `diagram_net_utils.safe_download_image()` or equivalent guards
-- Only `http://` and `https://` schemes are allowed — block `file://`, `ftp://`, `data:`, `gopher://`
-- Resolved IP addresses must be checked against private/loopback/link-local ranges (`ipaddress.is_private`, `is_loopback`, `is_link_local`, `is_reserved`)
-- Enforce download size limits (default: 20 MB) and connection timeouts (default: 15s)
-- Never pass user-supplied URLs directly to `urlopen()` without validation
+- **All** outbound HTTP requests to user-specified URLs must validate the target before connecting:
+  1. Only `http://` and `https://` schemes — block `file://`, `ftp://`, `data:`, `gopher://`
+  2. Resolve the hostname and check IPs against private/loopback/link-local/reserved ranges (`ipaddress.is_private`, `is_loopback`, `is_link_local`, `is_reserved`)
+  3. Enforce connection timeouts (default: 15 s for downloads, 30 s for API calls)
+  4. Enforce response size limits where applicable (default: 20 MB for binary downloads)
+- Reference implementation: `diagram_net_utils._validate_url()` and `safe_download_image()`
+- For API-style requests (`requests.get/post`): create or reuse a URL validation helper that performs scheme + IP checks, then call it before every `requests.*` call
+- Disable automatic redirect following (`allow_redirects=False`) or re-validate the redirect target to prevent redirect-based SSRF
+- Never pass user-supplied URLs directly to `urlopen()` or `requests.*` without validation
+
+### Network requests (TLS / SSH)
+- All HTTPS requests must use default TLS verification — never set `verify=False`
+- SSH connections: `paramiko.AutoAddPolicy()` accepts any host key and is vulnerable to MITM. Document it as a known limitation in the SSH GUI. Prefer `paramiko.RejectPolicy()` or `paramiko.WarningPolicy()` when non-interactive verification is possible; at minimum, warn the user on first connection to an unknown host
+
+### Subprocess execution
+- Always pass argument lists to `subprocess.Popen` / `subprocess.run` — never `shell=True`
+- Explicitly set `shell=False` for clarity in new code
+- Never interpolate user input into command strings — pass as separate list elements
+- Set `timeout` on all `subprocess.run()` calls to prevent hangs
+- The IDE intentionally runs user-authored scripts; this is trusted local execution, not arbitrary remote code. Subprocess hardening protects against accidental shell injection, not against malicious local files
+
+### JupyterLab integration
+- The embedded JupyterLab server binds to `localhost` only and is intended for local development
+- `--ServerApp.token=` and `--ServerApp.password=` are deliberately empty to enable seamless embedding — this is safe only because the server is localhost-only
+- Do not change `--ServerApp.ip` to `0.0.0.0` or any externally-reachable address
+- `--ServerApp.disable_check_xsrf=True` is required for the embedded QWebEngineView; do not expose the server externally with XSRF disabled
 
 ### File I/O
 - File read/write paths from user dialogs (`QFileDialog`) are trusted (user-initiated)
@@ -110,10 +134,25 @@ All code must follow secure-by-default principles. Review every change against t
   - Local paths: check `path.is_file()` and verify extension is in an allowlist
   - URLs: pass through the same SSRF validation as user-entered URLs
 - Never construct file paths by string concatenation with user input — use `pathlib.Path` with validation
+- When writing to data directories (`.pybreeze/`), create the directory with `os.makedirs(exist_ok=True)` and always use `encoding="utf-8"`
+- Never follow symlinks from untrusted sources — use `Path.resolve(strict=True)` and verify the resolved path is still within expected boundaries
 
 ### Qt / UI
 - `QGraphicsTextItem` with `TextEditorInteraction` must not be enabled by default — use double-click-to-edit pattern to prevent unintended text selection issues in themed environments
 - Plugin loading (`jeditor_plugins/`) uses auto-discovery — only load `.py` files, skip files starting with `_` or `.`
+- `QWebEngineView.setUrl()` must only load trusted URLs (localhost or user-confirmed external URLs) — never load untrusted HTML or URLs without user consent
+- Never call `QWebEngineView.setHtml()` with unsanitised content — this enables XSS within the embedded browser
+
+### Secrets and credentials
+- SSH passwords and private key passphrases are held in memory only during the session — never persist to disk or logs
+- Password fields must use `QLineEdit.EchoMode.Password`
+- API endpoint URLs may contain embedded tokens — treat URL strings with the same care as credentials (do not log full URLs)
+- Environment variables (`PYBREEZE_LOG_MAX_BYTES`, etc.) must never contain secrets; use dedicated secure stores for credentials
+
+### Dependency security
+- Pin dependencies to exact versions in `requirements.txt` / `dev_requirements.txt`
+- Do not add new dependencies without reviewing their security posture (maintained? known CVEs?)
+- Avoid transitive dependency bloat — prefer stdlib solutions when the alternative is a single-function dependency
 
 ## Commit & PR rules
 
diff --git a/pybreeze/__main__.py b/pybreeze/__main__.py
index a465590..408a814 100644
--- a/pybreeze/__main__.py
+++ b/pybreeze/__main__.py
@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 from pybreeze import start_editor
 
 start_editor()
diff --git a/pybreeze/extend/process_executor/python_task_process_manager.py b/pybreeze/extend/process_executor/python_task_process_manager.py
index 2e4e5f8..baddfc9 100644
--- a/pybreeze/extend/process_executor/python_task_process_manager.py
+++ b/pybreeze/extend/process_executor/python_task_process_manager.py
@@ -5,7 +5,7 @@
 import subprocess
 import sys
 import threading
-import typing
+from typing import Callable
 from pathlib import Path
 from queue import Queue
 from threading import Thread
@@ -42,8 +42,8 @@ class TaskProcessManager:
     def __init__(
             self,
             main_window: CodeWindow,
-            task_done_trigger_function: typing.Callable | None = None,
-            error_trigger_function: typing.Callable | None = None,
+            task_done_trigger_function: Callable | None = None,
+            error_trigger_function: Callable | None = None,
             program_buffer_size: int = 1024,
             program_encoding: str = "utf-8"
     ):
@@ -60,8 +60,8 @@ def __init__(
         self.run_error_queue: Queue = Queue()
         self.process: subprocess.Popen | None = None
 
-        self.task_done_trigger_function: typing.Callable = task_done_trigger_function
-        self.error_trigger_function: typing.Callable = error_trigger_function
+        self.task_done_trigger_function: Callable = task_done_trigger_function
+        self.error_trigger_function: Callable = error_trigger_function
         self.program_buffer_size = program_buffer_size
 
     def renew_path(self) -> None:
diff --git a/pybreeze/extend/process_executor/test_pioneer/test_pioneer_process_manager.py b/pybreeze/extend/process_executor/test_pioneer/test_pioneer_process_manager.py
index cbc5399..7684c6e 100644
--- a/pybreeze/extend/process_executor/test_pioneer/test_pioneer_process_manager.py
+++ b/pybreeze/extend/process_executor/test_pioneer/test_pioneer_process_manager.py
@@ -10,7 +10,6 @@
 
 from PySide6.QtCore import QTimer
 from PySide6.QtGui import QTextCharFormat
-from PySide6.QtWidgets import QWidget
 from je_editor.pyside_ui.main_ui.save_settings.user_color_setting_file import actually_color_dict
 from je_editor.utils.venv_check.check_venv import check_and_choose_venv
 
@@ -31,7 +30,6 @@ def __init__(
             encoding: str = "utf-8",
     ):
         self._main_window: PyBreezeMainWindow = main_window
-        self._widget: QWidget = main_window.tab_widget.currentWidget()
         # Code window init
         self._code_window = CodeWindow()
         self._main_window.current_run_code_window.append(self._code_window)
diff --git a/pybreeze/extend_multi_language/extend_english.py b/pybreeze/extend_multi_language/extend_english.py
index cc54210..1468953 100644
--- a/pybreeze/extend_multi_language/extend_english.py
+++ b/pybreeze/extend_multi_language/extend_english.py
@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 from je_editor import english_word_dict
 
 # PyBreeze-specific English translations
diff --git a/pybreeze/extend_multi_language/extend_traditional_chinese.py b/pybreeze/extend_multi_language/extend_traditional_chinese.py
index a88d7e4..78a35cd 100644
--- a/pybreeze/extend_multi_language/extend_traditional_chinese.py
+++ b/pybreeze/extend_multi_language/extend_traditional_chinese.py
@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 from je_editor import traditional_chinese_word_dict
 
 # PyBreeze-specific Traditional Chinese translations
diff --git a/pybreeze/extend_multi_language/update_language_dict.py b/pybreeze/extend_multi_language/update_language_dict.py
index a25c004..84d0fa2 100644
--- a/pybreeze/extend_multi_language/update_language_dict.py
+++ b/pybreeze/extend_multi_language/update_language_dict.py
@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 from pybreeze.extend_multi_language.extend_english import update_english_word_dict
 from pybreeze.extend_multi_language.extend_traditional_chinese import \
     update_traditional_chinese_word_dict
diff --git a/pybreeze/pybreeze_ui/connect_gui/ssh/ssh_command_widget.py b/pybreeze/pybreeze_ui/connect_gui/ssh/ssh_command_widget.py
index c6e041c..f74548d 100644
--- a/pybreeze/pybreeze_ui/connect_gui/ssh/ssh_command_widget.py
+++ b/pybreeze/pybreeze_ui/connect_gui/ssh/ssh_command_widget.py
@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 import os
 import re
 
@@ -137,7 +139,11 @@ def connect_ssh(self):
 
         try:
             self.ssh_client = paramiko.SSHClient()
-            self.ssh_client.set_missing_host_key_policy(paramiko.AutoAddPolicy())
+            self.ssh_client.load_system_host_keys()
+            self.ssh_client.set_missing_host_key_policy(paramiko.WarningPolicy())
+            pybreeze_logger.warning(
+                f"SSH connecting to {host}:{port} — host key will be accepted without verification"
+            )
 
             if use_key:
                 if not os.path.exists(key_path):
diff --git a/pybreeze/pybreeze_ui/connect_gui/ssh/ssh_file_viewer_widget.py b/pybreeze/pybreeze_ui/connect_gui/ssh/ssh_file_viewer_widget.py
index c79727b..e59417f 100644
--- a/pybreeze/pybreeze_ui/connect_gui/ssh/ssh_file_viewer_widget.py
+++ b/pybreeze/pybreeze_ui/connect_gui/ssh/ssh_file_viewer_widget.py
@@ -1,4 +1,7 @@
+from __future__ import annotations
+
 import os
+import stat
 from pathlib import Path
 
 import paramiko
@@ -10,6 +13,7 @@
 from je_editor import language_wrapper
 
 from pybreeze.pybreeze_ui.connect_gui.ssh.ssh_login_widget import LoginWidget
+from pybreeze.utils.logging.logger import pybreeze_logger
 
 
 class SFTPClientWrapper:
@@ -32,7 +36,11 @@ def connect(self, host: str, port: int, username: str, password: str,
         """
         self.close()
         self._ssh = paramiko.SSHClient()
-        self._ssh.set_missing_host_key_policy(paramiko.AutoAddPolicy())
+        self._ssh.load_system_host_keys()
+        self._ssh.set_missing_host_key_policy(paramiko.WarningPolicy())
+        pybreeze_logger.warning(
+            f"SFTP connecting to {host}:{port} — host key will be accepted without verification"
+        )
         if use_key and key_path:
             pkey = None
             for KeyType in (paramiko.RSAKey, paramiko.Ed25519Key, paramiko.ECDSAKey):
@@ -96,8 +104,6 @@ def is_dir(self, path: str) -> bool:
             ))
         try:
             st = self._sftp.stat(path)
-            # S_ISDIR check via stat.S_ISDIR
-            import stat
             return stat.S_ISDIR(st.st_mode)
         except OSError:
             return False
@@ -294,7 +300,6 @@ def populate_children(self, parent_item: QTreeWidgetItem):
         try:
             entries = self.client.list_dir(path)
             # Sort: dirs first, then files
-            import stat
             dirs = []
             files = []
             for e in entries:
@@ -307,10 +312,9 @@ def populate_children(self, parent_item: QTreeWidgetItem):
                 else:
                     files.append((name, e))
             for name, e in dirs + files:
-                import stat as _stat
                 full_path = os.path.join(path if path != "/" else "", name)
                 full_path = full_path if full_path.startswith("/") else f"/{full_path}"
-                typ = "dir" if _stat.S_ISDIR(e.st_mode) else "file"
+                typ = "dir" if stat.S_ISDIR(e.st_mode) else "file"
                 size = e.st_size if typ == "file" else 0
                 child = self.make_item(name, typ, size, full_path)
                 parent_item.addChild(child)
diff --git a/pybreeze/pybreeze_ui/connect_gui/ssh/ssh_login_widget.py b/pybreeze/pybreeze_ui/connect_gui/ssh/ssh_login_widget.py
index c1ca6a9..071238a 100644
--- a/pybreeze/pybreeze_ui/connect_gui/ssh/ssh_login_widget.py
+++ b/pybreeze/pybreeze_ui/connect_gui/ssh/ssh_login_widget.py
@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 from PySide6.QtWidgets import (
     QWidget, QHBoxLayout, QVBoxLayout, QLabel,
     QLineEdit, QSpinBox, QCheckBox, QPushButton
diff --git a/pybreeze/pybreeze_ui/connect_gui/ssh/ssh_main_widget.py b/pybreeze/pybreeze_ui/connect_gui/ssh/ssh_main_widget.py
index f7a2e13..f82f382 100644
--- a/pybreeze/pybreeze_ui/connect_gui/ssh/ssh_main_widget.py
+++ b/pybreeze/pybreeze_ui/connect_gui/ssh/ssh_main_widget.py
@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 import sys
 
 from PySide6.QtCore import Qt
diff --git a/pybreeze/pybreeze_ui/connect_gui/url/ai_code_review_gui.py b/pybreeze/pybreeze_ui/connect_gui/url/ai_code_review_gui.py
index 72152e4..6dc6f3a 100644
--- a/pybreeze/pybreeze_ui/connect_gui/url/ai_code_review_gui.py
+++ b/pybreeze/pybreeze_ui/connect_gui/url/ai_code_review_gui.py
@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 import sys
 import requests
 import os
@@ -7,6 +9,8 @@
 )
 from je_editor import language_wrapper
 
+from pybreeze.utils.network.url_validation import UnsafeURLError, validate_url
+
 
 class AICodeReviewClient(QWidget):
     def __init__(self):
@@ -115,6 +119,13 @@ def send_request(self):
                 self.word_dict.get("ai_code_review_gui_message_enter_valid_url"))
             return
 
+        try:
+            validate_url(url)
+        except UnsafeURLError as e:
+            self.response_panel.setPlainText(
+                f"{self.word_dict.get('ai_code_review_gui_message_error')}: {e}")
+            return
+
         # 檢查 URL 是否已紀錄
         if os.path.exists(self.url_file):
             with open(self.url_file, encoding="utf-8") as f:
@@ -133,13 +144,13 @@ def send_request(self):
 
         try:
             if method == "GET":
-                response = requests.get(url, timeout=30)
+                response = requests.get(url, timeout=30, allow_redirects=False)
             elif method == "POST":
-                response = requests.post(url, data={"code": code_content}, timeout=30)
+                response = requests.post(url, data={"code": code_content}, timeout=30, allow_redirects=False)
             elif method == "PUT":
-                response = requests.put(url, data={"code": code_content}, timeout=30)
+                response = requests.put(url, data={"code": code_content}, timeout=30, allow_redirects=False)
             elif method == "DELETE":
-                response = requests.delete(url, timeout=30)
+                response = requests.delete(url, timeout=30, allow_redirects=False)
             else:
                 self.response_panel.setPlainText(
                     self.word_dict.get("ai_code_review_gui_message_unsupported_http_method"))
diff --git a/pybreeze/pybreeze_ui/diagram_editor/diagram_editor_widget.py b/pybreeze/pybreeze_ui/diagram_editor/diagram_editor_widget.py
index f06e082..0ebba53 100644
--- a/pybreeze/pybreeze_ui/diagram_editor/diagram_editor_widget.py
+++ b/pybreeze/pybreeze_ui/diagram_editor/diagram_editor_widget.py
@@ -4,7 +4,7 @@
 from pathlib import Path
 
 from PySide6.QtCore import QMarginsF, QRectF, QSizeF, Qt
-from PySide6.QtGui import QImage, QKeySequence, QPainter, QShortcut
+from PySide6.QtGui import QImage, QKeySequence, QPainter, QPixmap, QShortcut
 from PySide6.QtSvg import QSvgGenerator
 from PySide6.QtWidgets import (
     QCheckBox,
@@ -12,6 +12,7 @@
     QFileDialog,
     QFrame,
     QHBoxLayout,
+    QInputDialog,
     QLabel,
     QMenu,
     QMessageBox,
@@ -25,6 +26,7 @@
 from je_editor import language_wrapper
 
 from pybreeze.pybreeze_ui.diagram_editor.diagram_mermaid_parser import parse_mermaid
+from pybreeze.pybreeze_ui.diagram_editor.diagram_net_utils import safe_download_image
 from pybreeze.pybreeze_ui.diagram_editor.diagram_property_panel import DiagramPropertyPanel
 from pybreeze.pybreeze_ui.diagram_editor.diagram_scene import DiagramScene, ToolMode
 from pybreeze.pybreeze_ui.diagram_editor.diagram_view import DiagramView
@@ -516,7 +518,6 @@ def _add_image_from_file(self) -> None:
         )
         if not path:
             return
-        from PySide6.QtGui import QPixmap
         pix = QPixmap(path)
         if pix.isNull():
             QMessageBox.warning(self, _lang("diagram_editor_error_title", "Error"),
@@ -525,7 +526,6 @@ def _add_image_from_file(self) -> None:
         self._scene.add_image(pix, path)
 
     def _add_image_from_url(self) -> None:
-        from PySide6.QtWidgets import QInputDialog
         url, ok = QInputDialog.getText(
             self,
             _lang("diagram_editor_dialog_image_url", "Image URL"),
@@ -535,9 +535,7 @@ def _add_image_from_url(self) -> None:
             return
         url = url.strip()
         try:
-            from pybreeze.pybreeze_ui.diagram_editor.diagram_net_utils import safe_download_image
             data = safe_download_image(url)
-            from PySide6.QtGui import QPixmap
             pix = QPixmap()
             pix.loadFromData(data)
             if pix.isNull():
diff --git a/pybreeze/pybreeze_ui/diagram_editor/diagram_net_utils.py b/pybreeze/pybreeze_ui/diagram_editor/diagram_net_utils.py
index 3671748..b378f08 100644
--- a/pybreeze/pybreeze_ui/diagram_editor/diagram_net_utils.py
+++ b/pybreeze/pybreeze_ui/diagram_editor/diagram_net_utils.py
@@ -8,14 +8,12 @@
 """
 from __future__ import annotations
 
-import ipaddress
-import socket
-from urllib.parse import urlparse
 from urllib.request import Request, urlopen
 
+from pybreeze.utils.network.url_validation import UnsafeURLError, validate_url
+
 MAX_DOWNLOAD_BYTES = 20 * 1024 * 1024  # 20 MB
 TIMEOUT_SECONDS = 15
-_ALLOWED_SCHEMES = {"http", "https"}
 
 
 class ImageDownloadError(Exception):
@@ -24,33 +22,10 @@ class ImageDownloadError(Exception):
 
 def _validate_url(url: str) -> str:
     """Validate URL scheme and resolve hostname to block private/loopback IPs."""
-    parsed = urlparse(url)
-
-    # Scheme check
-    if parsed.scheme.lower() not in _ALLOWED_SCHEMES:
-        raise ImageDownloadError(
-            f"Scheme '{parsed.scheme}' is not allowed. Use http or https."
-        )
-
-    # Hostname check
-    hostname = parsed.hostname
-    if not hostname:
-        raise ImageDownloadError("URL has no hostname.")
-
-    # Resolve and check for private/loopback IPs (SSRF prevention)
     try:
-        infos = socket.getaddrinfo(hostname, None, socket.AF_UNSPEC, socket.SOCK_STREAM)
-    except socket.gaierror as e:
-        raise ImageDownloadError(f"Cannot resolve hostname '{hostname}': {e}") from e
-
-    for family, _, _, _, sockaddr in infos:
-        ip = ipaddress.ip_address(sockaddr[0])
-        if ip.is_private or ip.is_loopback or ip.is_link_local or ip.is_reserved:
-            raise ImageDownloadError(
-                f"Access to private/internal address {ip} is blocked."
-            )
-
-    return url
+        return validate_url(url)
+    except UnsafeURLError as exc:
+        raise ImageDownloadError(str(exc)) from exc
 
 
 def safe_download_image(url: str) -> bytes:
diff --git a/pybreeze/pybreeze_ui/diagram_editor/diagram_scene.py b/pybreeze/pybreeze_ui/diagram_editor/diagram_scene.py
index 624c7c3..fa83c04 100644
--- a/pybreeze/pybreeze_ui/diagram_editor/diagram_scene.py
+++ b/pybreeze/pybreeze_ui/diagram_editor/diagram_scene.py
@@ -2,12 +2,15 @@
 
 from contextlib import contextmanager
 from enum import Enum, auto
+from pathlib import Path
 
 from PySide6.QtCore import QPointF, Qt, Signal
 from PySide6.QtGui import QColor, QPen, QPixmap, QUndoStack
 from PySide6.QtWidgets import QGraphicsLineItem, QGraphicsScene, QMenu
+from je_editor import language_wrapper
 
 from pybreeze.pybreeze_ui.diagram_editor.diagram_commands import DiagramSnapshotCommand
+from pybreeze.pybreeze_ui.diagram_editor.diagram_net_utils import safe_download_image
 from pybreeze.pybreeze_ui.diagram_editor.diagram_items import (
     ConnectionStyle,
     DiagramConnection,
@@ -247,7 +250,6 @@ def keyPressEvent(self, event) -> None:
         super().keyPressEvent(event)
 
     def contextMenuEvent(self, event) -> None:
-        from je_editor import language_wrapper
         menu = QMenu()
         item = self._node_at(event.scenePos())
         conn = self._connection_at(event.scenePos())
@@ -578,7 +580,6 @@ def _try_load_image_source(self, img: DiagramImage, source: str) -> None:
         Local paths are restricted to existing image files.
         URLs are validated and size-limited via ``safe_download_image``.
         """
-        from pathlib import Path
         path = Path(source)
         # Only load if the file actually exists and has an image extension
         _IMAGE_SUFFIXES = {".png", ".jpg", ".jpeg", ".bmp", ".gif", ".svg", ".webp", ".ico"}
@@ -589,7 +590,6 @@ def _try_load_image_source(self, img: DiagramImage, source: str) -> None:
                 return
         if source.startswith(("http://", "https://")):
             try:
-                from pybreeze.pybreeze_ui.diagram_editor.diagram_net_utils import safe_download_image
                 data = safe_download_image(source)
                 pix = QPixmap()
                 pix.loadFromData(data)
diff --git a/pybreeze/pybreeze_ui/editor_main/file_tree_context_menu.py b/pybreeze/pybreeze_ui/editor_main/file_tree_context_menu.py
index 692bc2d..b5ee9be 100644
--- a/pybreeze/pybreeze_ui/editor_main/file_tree_context_menu.py
+++ b/pybreeze/pybreeze_ui/editor_main/file_tree_context_menu.py
@@ -1,5 +1,9 @@
+from __future__ import annotations
+
 import os
 import shutil
+import subprocess
+import sys
 from pathlib import Path
 
 from PySide6.QtCore import Qt, QModelIndex
@@ -248,8 +252,6 @@ def _action_copy_path(tree_view: QTreeView, path: Path | None, relative: bool =
 def _action_reveal_in_explorer(path: Path | None) -> None:
     if path is None:
         return
-    import subprocess
-    import sys
     target = path if path.is_dir() else path.parent
     if sys.platform == "win32":
         os.startfile(str(target))
diff --git a/pybreeze/pybreeze_ui/editor_main/main_ui.py b/pybreeze/pybreeze_ui/editor_main/main_ui.py
index 86baee5..2655281 100644
--- a/pybreeze/pybreeze_ui/editor_main/main_ui.py
+++ b/pybreeze/pybreeze_ui/editor_main/main_ui.py
@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 import os
 import sys
 from os import environ
@@ -16,6 +18,7 @@
 from pybreeze.pybreeze_ui.menu.build_menubar import add_menu_to_menubar
 from pybreeze.pybreeze_ui.syntax.syntax_extend import \
     syntax_extend_package
+from pybreeze.utils.logging.logger import pybreeze_logger
 
 
 EDITOR_EXTEND_TAB: dict[str, type[QWidget]] = {
@@ -108,7 +111,6 @@ def start_editor(debug_mode: bool = False, theme: str = "dark_amber.xml", **kwar
     try:
         window.startup_setting()
     except Exception as error:
-        from pybreeze.utils.logging.logger import pybreeze_logger
         pybreeze_logger.error(f"Startup setting error: {error}")
     ret = new_ide.exec()
     os._exit(ret)
diff --git a/pybreeze/pybreeze_ui/extend_ai_gui/ai_gui_global_variable.py b/pybreeze/pybreeze_ui/extend_ai_gui/ai_gui_global_variable.py
index d91be02..b4984d3 100644
--- a/pybreeze/pybreeze_ui/extend_ai_gui/ai_gui_global_variable.py
+++ b/pybreeze/pybreeze_ui/extend_ai_gui/ai_gui_global_variable.py
@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 from pybreeze.pybreeze_ui.extend_ai_gui.prompt_edit_gui.cot_code_review_prompt_templates.code_smell_detector import \
     CODE_SMELL_DETECTOR_TEMPLATE
 from pybreeze.pybreeze_ui.extend_ai_gui.prompt_edit_gui.cot_code_review_prompt_templates.first_code_review import \
diff --git a/pybreeze/pybreeze_ui/extend_ai_gui/code_review/code_review_thread.py b/pybreeze/pybreeze_ui/extend_ai_gui/code_review/code_review_thread.py
index d935445..e553f53 100644
--- a/pybreeze/pybreeze_ui/extend_ai_gui/code_review/code_review_thread.py
+++ b/pybreeze/pybreeze_ui/extend_ai_gui/code_review/code_review_thread.py
@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 # Worker Thread 負責傳送資料
 import requests
 from PySide6.QtCore import QThread, Signal
@@ -6,6 +8,7 @@
 from pybreeze.pybreeze_ui.extend_ai_gui.ai_gui_global_variable import COT_TEMPLATE_RELATION
 from pybreeze.pybreeze_ui.extend_ai_gui.prompt_edit_gui.cot_code_review_prompt_templates.global_rule import \
     build_global_rule_template
+from pybreeze.utils.network.url_validation import validate_url
 
 
 class SenderThread(QThread):
@@ -18,6 +21,7 @@ def __init__(self, files: list, code: str, url: str):
         self.url = url
 
     def run(self):
+        validate_url(self.url)
         code = self.code
         first_code_review_result = None
         first_summary_result = None
@@ -61,7 +65,7 @@ def run(self):
 
             try:
                 # 傳送到指定 URL
-                resp = requests.post(self.url, json={"prompt": prompt}, timeout=60)
+                resp = requests.post(self.url, json={"prompt": prompt}, timeout=60, allow_redirects=False)
                 reply_text = resp.text
                 match file:
                     case "first_summary_prompt.md":
diff --git a/pybreeze/pybreeze_ui/extend_ai_gui/code_review/cot_code_review_gui.py b/pybreeze/pybreeze_ui/extend_ai_gui/code_review/cot_code_review_gui.py
index f1e6861..9857fde 100644
--- a/pybreeze/pybreeze_ui/extend_ai_gui/code_review/cot_code_review_gui.py
+++ b/pybreeze/pybreeze_ui/extend_ai_gui/code_review/cot_code_review_gui.py
@@ -1,4 +1,4 @@
-from urllib.parse import urlparse
+from __future__ import annotations
 
 from PySide6.QtWidgets import QWidget, QVBoxLayout, QHBoxLayout, QLabel, QLineEdit, QTextEdit, QComboBox, QPushButton, \
     QMessageBox
@@ -6,6 +6,7 @@
 
 from pybreeze.pybreeze_ui.extend_ai_gui.ai_gui_global_variable import COT_TEMPLATE_FILES
 from pybreeze.pybreeze_ui.extend_ai_gui.code_review.code_review_thread import SenderThread
+from pybreeze.utils.network.url_validation import UnsafeURLError, validate_url
 
 
 class CoTCodeReviewGUI(QWidget):
@@ -69,9 +70,10 @@ def start_sending(self):
         if not url:
             QMessageBox.warning(self, "Warning", language_wrapper.language_word_dict.get("cot_gui_error_no_url"))
             return
-        parsed = urlparse(url)
-        if not parsed.scheme or not parsed.netloc:
-            QMessageBox.warning(self, "Warning", language_wrapper.language_word_dict.get("cot_gui_error_no_url"))
+        try:
+            validate_url(url)
+        except UnsafeURLError as e:
+            QMessageBox.warning(self, "Warning", str(e))
             return
 
         # 啟動傳送 Thread
diff --git a/pybreeze/pybreeze_ui/extend_ai_gui/prompt_edit_gui/cot_code_review_prompt_templates/code_smell_detector.py b/pybreeze/pybreeze_ui/extend_ai_gui/prompt_edit_gui/cot_code_review_prompt_templates/code_smell_detector.py
index 41b6274..80ca31c 100644
--- a/pybreeze/pybreeze_ui/extend_ai_gui/prompt_edit_gui/cot_code_review_prompt_templates/code_smell_detector.py
+++ b/pybreeze/pybreeze_ui/extend_ai_gui/prompt_edit_gui/cot_code_review_prompt_templates/code_smell_detector.py
@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 CODE_SMELL_DETECTOR_TEMPLATE = """
 You are a senior software engineer specializing in code quality reviews.  
 Carefully analyze the following code and identify all possible **code smells**.  
diff --git a/pybreeze/pybreeze_ui/extend_ai_gui/prompt_edit_gui/cot_code_review_prompt_templates/first_code_review.py b/pybreeze/pybreeze_ui/extend_ai_gui/prompt_edit_gui/cot_code_review_prompt_templates/first_code_review.py
index d884a5b..845eae4 100644
--- a/pybreeze/pybreeze_ui/extend_ai_gui/prompt_edit_gui/cot_code_review_prompt_templates/first_code_review.py
+++ b/pybreeze/pybreeze_ui/extend_ai_gui/prompt_edit_gui/cot_code_review_prompt_templates/first_code_review.py
@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 FIRST_CODE_REVIEW_TEMPLATE = """
 # Code Review Template
 
diff --git a/pybreeze/pybreeze_ui/extend_ai_gui/prompt_edit_gui/cot_code_review_prompt_templates/first_summary_prompt.py b/pybreeze/pybreeze_ui/extend_ai_gui/prompt_edit_gui/cot_code_review_prompt_templates/first_summary_prompt.py
index 07d3e90..72abc8c 100644
--- a/pybreeze/pybreeze_ui/extend_ai_gui/prompt_edit_gui/cot_code_review_prompt_templates/first_summary_prompt.py
+++ b/pybreeze/pybreeze_ui/extend_ai_gui/prompt_edit_gui/cot_code_review_prompt_templates/first_summary_prompt.py
@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 FIRST_SUMMARY_TEMPLATE = """
 # PR Summary Template
 
diff --git a/pybreeze/pybreeze_ui/extend_ai_gui/prompt_edit_gui/cot_code_review_prompt_templates/global_rule.py b/pybreeze/pybreeze_ui/extend_ai_gui/prompt_edit_gui/cot_code_review_prompt_templates/global_rule.py
index ba0392a..9da0630 100644
--- a/pybreeze/pybreeze_ui/extend_ai_gui/prompt_edit_gui/cot_code_review_prompt_templates/global_rule.py
+++ b/pybreeze/pybreeze_ui/extend_ai_gui/prompt_edit_gui/cot_code_review_prompt_templates/global_rule.py
@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 GLOBAL_RULE_TEMPLATE = """
 Please conduct a code review according to the following global rules:
 
diff --git a/pybreeze/pybreeze_ui/extend_ai_gui/prompt_edit_gui/cot_code_review_prompt_templates/judge.py b/pybreeze/pybreeze_ui/extend_ai_gui/prompt_edit_gui/cot_code_review_prompt_templates/judge.py
index 51c8b18..69e2c0e 100644
--- a/pybreeze/pybreeze_ui/extend_ai_gui/prompt_edit_gui/cot_code_review_prompt_templates/judge.py
+++ b/pybreeze/pybreeze_ui/extend_ai_gui/prompt_edit_gui/cot_code_review_prompt_templates/judge.py
@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 JUDGE_TEMPLATE = """
 # Code Review Comment Evaluation Template (Enhanced)
 
diff --git a/pybreeze/pybreeze_ui/extend_ai_gui/prompt_edit_gui/cot_code_review_prompt_templates/judge_single_review.py b/pybreeze/pybreeze_ui/extend_ai_gui/prompt_edit_gui/cot_code_review_prompt_templates/judge_single_review.py
index 90a888a..b606fb7 100644
--- a/pybreeze/pybreeze_ui/extend_ai_gui/prompt_edit_gui/cot_code_review_prompt_templates/judge_single_review.py
+++ b/pybreeze/pybreeze_ui/extend_ai_gui/prompt_edit_gui/cot_code_review_prompt_templates/judge_single_review.py
@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 JUDGE_SINGLE_REVIEW_TEMPLATE = """
 # Code Review Comment Evaluation Template (Enhanced)
 
diff --git a/pybreeze/pybreeze_ui/extend_ai_gui/prompt_edit_gui/cot_code_review_prompt_templates/linter.py b/pybreeze/pybreeze_ui/extend_ai_gui/prompt_edit_gui/cot_code_review_prompt_templates/linter.py
index f02c698..51fab82 100644
--- a/pybreeze/pybreeze_ui/extend_ai_gui/prompt_edit_gui/cot_code_review_prompt_templates/linter.py
+++ b/pybreeze/pybreeze_ui/extend_ai_gui/prompt_edit_gui/cot_code_review_prompt_templates/linter.py
@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 LINTER_TEMPLATE = """
     You are a strict code linter. 
     Your task is to analyze the given source code and produce structured linter_messages. 
diff --git a/pybreeze/pybreeze_ui/extend_ai_gui/prompt_edit_gui/cot_code_review_prompt_templates/step_by_step_analysis.py b/pybreeze/pybreeze_ui/extend_ai_gui/prompt_edit_gui/cot_code_review_prompt_templates/step_by_step_analysis.py
index 51f18c5..1000f39 100644
--- a/pybreeze/pybreeze_ui/extend_ai_gui/prompt_edit_gui/cot_code_review_prompt_templates/step_by_step_analysis.py
+++ b/pybreeze/pybreeze_ui/extend_ai_gui/prompt_edit_gui/cot_code_review_prompt_templates/step_by_step_analysis.py
@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 STEP_BY_STEP_ANALYSIS_TEMPLATE = """
 You are a code quality reviewer. 
 Analyze the code smell, and linter message step by step.
diff --git a/pybreeze/pybreeze_ui/extend_ai_gui/prompt_edit_gui/cot_code_review_prompt_templates/total_summary.py b/pybreeze/pybreeze_ui/extend_ai_gui/prompt_edit_gui/cot_code_review_prompt_templates/total_summary.py
index 60be5ee..56c6591 100644
--- a/pybreeze/pybreeze_ui/extend_ai_gui/prompt_edit_gui/cot_code_review_prompt_templates/total_summary.py
+++ b/pybreeze/pybreeze_ui/extend_ai_gui/prompt_edit_gui/cot_code_review_prompt_templates/total_summary.py
@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 TOTAL_SUMMARY_TEMPLATE = """
 # PR Total Summary Instructions
 
diff --git a/pybreeze/pybreeze_ui/extend_ai_gui/prompt_edit_gui/cot_prompt_editor_widget.py b/pybreeze/pybreeze_ui/extend_ai_gui/prompt_edit_gui/cot_prompt_editor_widget.py
index 60b4d75..af3b832 100644
--- a/pybreeze/pybreeze_ui/extend_ai_gui/prompt_edit_gui/cot_prompt_editor_widget.py
+++ b/pybreeze/pybreeze_ui/extend_ai_gui/prompt_edit_gui/cot_prompt_editor_widget.py
@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 import os
 
 from PySide6.QtCore import QFileSystemWatcher
diff --git a/pybreeze/pybreeze_ui/extend_ai_gui/prompt_edit_gui/skills_prompt_editor_widget.py b/pybreeze/pybreeze_ui/extend_ai_gui/prompt_edit_gui/skills_prompt_editor_widget.py
index c124311..5d54914 100644
--- a/pybreeze/pybreeze_ui/extend_ai_gui/prompt_edit_gui/skills_prompt_editor_widget.py
+++ b/pybreeze/pybreeze_ui/extend_ai_gui/prompt_edit_gui/skills_prompt_editor_widget.py
@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 import os
 
 from PySide6.QtCore import QFileSystemWatcher
diff --git a/pybreeze/pybreeze_ui/extend_ai_gui/prompt_edit_gui/skills_prompt_templates/code_explainer.py b/pybreeze/pybreeze_ui/extend_ai_gui/prompt_edit_gui/skills_prompt_templates/code_explainer.py
index 33487fb..a4cb285 100644
--- a/pybreeze/pybreeze_ui/extend_ai_gui/prompt_edit_gui/skills_prompt_templates/code_explainer.py
+++ b/pybreeze/pybreeze_ui/extend_ai_gui/prompt_edit_gui/skills_prompt_templates/code_explainer.py
@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 CODE_EXPLAINER_TEMPLATE = """
 You are a senior software engineer and educator. Explain the following code clearly and in detail.
 
diff --git a/pybreeze/pybreeze_ui/extend_ai_gui/prompt_edit_gui/skills_prompt_templates/code_review.py b/pybreeze/pybreeze_ui/extend_ai_gui/prompt_edit_gui/skills_prompt_templates/code_review.py
index 889be30..43214cf 100644
--- a/pybreeze/pybreeze_ui/extend_ai_gui/prompt_edit_gui/skills_prompt_templates/code_review.py
+++ b/pybreeze/pybreeze_ui/extend_ai_gui/prompt_edit_gui/skills_prompt_templates/code_review.py
@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 CODE_REVIEW_SKILL_TEMPLATE = """
 You are an expert software reviewer. Your task is to analyze one or more code diffs from a Pull Request (PR).  
 The input may contain multiple `code_diff` sections placed in different positions.  
diff --git a/pybreeze/pybreeze_ui/extend_ai_gui/skills/skills_send_gui.py b/pybreeze/pybreeze_ui/extend_ai_gui/skills/skills_send_gui.py
index 2e6cc76..fd9c81f 100644
--- a/pybreeze/pybreeze_ui/extend_ai_gui/skills/skills_send_gui.py
+++ b/pybreeze/pybreeze_ui/extend_ai_gui/skills/skills_send_gui.py
@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 import requests
 from PySide6.QtWidgets import (
     QWidget, QVBoxLayout, QLineEdit,
@@ -7,6 +9,7 @@
 from je_editor import language_wrapper
 
 from pybreeze.pybreeze_ui.extend_ai_gui.ai_gui_global_variable import SKILLS_TEMPLATE_FILES
+from pybreeze.utils.network.url_validation import validate_url
 
 
 class RequestThread(QThread):
@@ -20,7 +23,8 @@ def __init__(self, api_url, code_text):
 
     def run(self):
         try:
-            response = requests.post(self.api_url, json={"code": self.code_text}, timeout=30)
+            validate_url(self.api_url)
+            response = requests.post(self.api_url, json={"code": self.code_text}, timeout=30, allow_redirects=False)
             if response.ok:
                 self.finished.emit(response.text)
             elif response.is_redirect:
diff --git a/pybreeze/pybreeze_ui/jupyter_lab_gui/jupyter_lab_thread.py b/pybreeze/pybreeze_ui/jupyter_lab_gui/jupyter_lab_thread.py
index 7b945b1..d1b319f 100644
--- a/pybreeze/pybreeze_ui/jupyter_lab_gui/jupyter_lab_thread.py
+++ b/pybreeze/pybreeze_ui/jupyter_lab_gui/jupyter_lab_thread.py
@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 import os
 import socket
 import subprocess
@@ -49,6 +51,7 @@ def is_jupyter_installed(python_exe: str) -> bool:
     result = subprocess.run(
         [python_exe, "-m", "pip", "show", "jupyterlab"],
         capture_output=True,
+        timeout=30,
     )
     return result.returncode == 0
 
@@ -77,7 +80,7 @@ def run(self):
                     "install",
                     "jupyterlab",
                     "-U"
-                ], capture_output=True, text=True)
+                ], capture_output=True, text=True, timeout=300)
 
                 if result.returncode != 0:
                     raise RuntimeError(result.stderr)
diff --git a/pybreeze/pybreeze_ui/jupyter_lab_gui/jupyter_lab_widget.py b/pybreeze/pybreeze_ui/jupyter_lab_gui/jupyter_lab_widget.py
index 0e668b0..540d9e1 100644
--- a/pybreeze/pybreeze_ui/jupyter_lab_gui/jupyter_lab_widget.py
+++ b/pybreeze/pybreeze_ui/jupyter_lab_gui/jupyter_lab_widget.py
@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 import sys
 
 from PySide6.QtCore import QUrl
diff --git a/pybreeze/pybreeze_ui/menu/automation_menu/automation_menu_factory.py b/pybreeze/pybreeze_ui/menu/automation_menu/automation_menu_factory.py
index b25f92c..b038abd 100644
--- a/pybreeze/pybreeze_ui/menu/automation_menu/automation_menu_factory.py
+++ b/pybreeze/pybreeze_ui/menu/automation_menu/automation_menu_factory.py
@@ -1,5 +1,6 @@
 from __future__ import annotations
 
+import importlib
 from typing import TYPE_CHECKING, Callable
 
 from PySide6.QtGui import QAction
@@ -102,7 +103,6 @@ def safe_create_project(import_name: str) -> Callable:
     """Create a safe project creation function that handles ImportError."""
     def _create():
         try:
-            import importlib
             package = importlib.import_module(import_name)
             if package is not None:
                 package.create_project_dir()
diff --git a/pybreeze/pybreeze_ui/menu/plugin_menu/build_plugin_menu.py b/pybreeze/pybreeze_ui/menu/plugin_menu/build_plugin_menu.py
index 83bd20a..b6b3e99 100644
--- a/pybreeze/pybreeze_ui/menu/plugin_menu/build_plugin_menu.py
+++ b/pybreeze/pybreeze_ui/menu/plugin_menu/build_plugin_menu.py
@@ -1,5 +1,6 @@
 from __future__ import annotations
 
+from pathlib import Path
 from typing import TYPE_CHECKING
 
 from PySide6.QtGui import QAction
@@ -7,6 +8,13 @@
 
 from je_editor import language_wrapper
 from je_editor.plugins import get_all_plugin_metadata
+from je_editor.pyside_ui.main_ui.editor.editor_widget import EditorWidget
+from je_editor.pyside_ui.main_ui.plugin_browser.plugin_browser_widget import PluginBrowserWidget
+from je_editor.pyside_ui.dialog.file_dialog.save_file_dialog import choose_file_get_save_file_path
+from je_editor.utils.file.save.save_file import write_file
+
+from pybreeze.extend.process_executor.file_runner_process import FileRunnerProcess
+from pybreeze.pybreeze_ui.show_code_window.code_window import CodeWindow
 
 if TYPE_CHECKING:
     from pybreeze.pybreeze_ui.editor_main.main_ui import PyBreezeMainWindow
@@ -117,8 +125,6 @@ def _open_plugin_browser(ui_we_want_to_set: PyBreezeMainWindow) -> None:
     開啟插件瀏覽器分頁。
     Open plugin browser tab.
     """
-    from je_editor.pyside_ui.main_ui.plugin_browser.plugin_browser_widget import PluginBrowserWidget
-
     tab_name = language_wrapper.language_word_dict.get("plugin_browser_tab_name", "Plugin Browser")
     ui_we_want_to_set.tab_widget.addTab(
         PluginBrowserWidget(),
@@ -151,15 +157,6 @@ def _make_run_callback(ui_we_want_to_set: PyBreezeMainWindow, run_config: dict,
     Uses PyBreeze's FileRunnerProcess and CodeWindow.
     """
     def callback():
-        from pathlib import Path
-        from PySide6.QtWidgets import QMessageBox
-
-        from je_editor.pyside_ui.main_ui.editor.editor_widget import EditorWidget
-        from je_editor.utils.file.save.save_file import write_file
-
-        from pybreeze.extend.process_executor.file_runner_process import FileRunnerProcess
-        from pybreeze.pybreeze_ui.show_code_window.code_window import CodeWindow
-
         widget = ui_we_want_to_set.tab_widget.currentWidget()
         if not isinstance(widget, EditorWidget):
             return
@@ -169,7 +166,6 @@ def callback():
             write_file(widget.current_file, widget.code_edit.toPlainText())
             file_path = widget.current_file
         else:
-            from je_editor.pyside_ui.dialog.file_dialog.save_file_dialog import choose_file_get_save_file_path
             if not choose_file_get_save_file_path(ui_we_want_to_set):
                 return
             file_path = widget.current_file
diff --git a/pybreeze/pybreeze_ui/menu/plugin_menu/build_run_with_menu.py b/pybreeze/pybreeze_ui/menu/plugin_menu/build_run_with_menu.py
index 13c28b9..8e98860 100644
--- a/pybreeze/pybreeze_ui/menu/plugin_menu/build_run_with_menu.py
+++ b/pybreeze/pybreeze_ui/menu/plugin_menu/build_run_with_menu.py
@@ -13,6 +13,7 @@
 
 from je_editor import language_wrapper
 from je_editor.plugins import get_all_plugin_run_configs
+from je_editor.pyside_ui.dialog.file_dialog.save_file_dialog import choose_file_get_save_file_path
 from je_editor.pyside_ui.main_ui.editor.editor_widget import EditorWidget
 from je_editor.utils.file.save.save_file import write_file
 
@@ -35,7 +36,6 @@ def _get_current_file(main_window: PyBreezeMainWindow) -> str | None:
         return widget.current_file
 
     # No file yet — ask user to save first
-    from je_editor.pyside_ui.dialog.file_dialog.save_file_dialog import choose_file_get_save_file_path
     if choose_file_get_save_file_path(main_window):
         return widget.current_file
     return None
diff --git a/pybreeze/pybreeze_ui/show_code_window/code_window.py b/pybreeze/pybreeze_ui/show_code_window/code_window.py
index 2831c90..439fca6 100644
--- a/pybreeze/pybreeze_ui/show_code_window/code_window.py
+++ b/pybreeze/pybreeze_ui/show_code_window/code_window.py
@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 from PySide6.QtGui import QGuiApplication
 from PySide6.QtWidgets import QWidget, QGridLayout, QTextEdit, QScrollArea
 
diff --git a/pybreeze/pybreeze_ui/syntax/syntax_keyword.py b/pybreeze/pybreeze_ui/syntax/syntax_keyword.py
index 60344f4..782b711 100644
--- a/pybreeze/pybreeze_ui/syntax/syntax_keyword.py
+++ b/pybreeze/pybreeze_ui/syntax/syntax_keyword.py
@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 api_testka_keys: list = [
     "AT_test_api_method", "AT_delegate_async_httpx", "AT_test_api_method_httpx",
     "AT_generate_html", "AT_generate_html_report", "AT_generate_json",
diff --git a/pybreeze/utils/exception/exception_tags.py b/pybreeze/utils/exception/exception_tags.py
index 463b902..7150c39 100644
--- a/pybreeze/utils/exception/exception_tags.py
+++ b/pybreeze/utils/exception/exception_tags.py
@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 # add command exception
 add_command_type_exception_tag: str = "command execute_return_value type must be a method or function"
 add_command_not_allow_package_exception_tag: str = "chosen command package is not allowed"
diff --git a/pybreeze/utils/exception/exceptions.py b/pybreeze/utils/exception/exceptions.py
index 4a3b023..72b88a1 100644
--- a/pybreeze/utils/exception/exceptions.py
+++ b/pybreeze/utils/exception/exceptions.py
@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 class ITEException(Exception):
     pass
 
diff --git a/pybreeze/utils/json_format/json_process.py b/pybreeze/utils/json_format/json_process.py
index d9bcc1e..3cd8351 100644
--- a/pybreeze/utils/json_format/json_process.py
+++ b/pybreeze/utils/json_format/json_process.py
@@ -1,4 +1,6 @@
-import json.decoder
+from __future__ import annotations
+
+import json
 from json import dumps
 from json import loads
 
diff --git a/pybreeze/utils/logging/logger.py b/pybreeze/utils/logging/logger.py
index 2dee1e8..15171aa 100644
--- a/pybreeze/utils/logging/logger.py
+++ b/pybreeze/utils/logging/logger.py
@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 import logging
 import os
 from logging.handlers import RotatingFileHandler
diff --git a/pybreeze/utils/manager/package_manager/package_manager_class.py b/pybreeze/utils/manager/package_manager/package_manager_class.py
index 61c31b6..19616fd 100644
--- a/pybreeze/utils/manager/package_manager/package_manager_class.py
+++ b/pybreeze/utils/manager/package_manager/package_manager_class.py
@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 import os
 
 
diff --git a/pybreeze/utils/network/__init__.py b/pybreeze/utils/network/__init__.py
new file mode 100644
index 0000000..e69de29
diff --git a/pybreeze/utils/network/url_validation.py b/pybreeze/utils/network/url_validation.py
new file mode 100644
index 0000000..1445785
--- /dev/null
+++ b/pybreeze/utils/network/url_validation.py
@@ -0,0 +1,47 @@
+from __future__ import annotations
+
+import ipaddress
+import socket
+from urllib.parse import urlparse
+
+_ALLOWED_SCHEMES = frozenset({"http", "https"})
+
+
+class UnsafeURLError(Exception):
+    """Raised when a URL fails security validation."""
+
+
+def validate_url(url: str) -> str:
+    """Validate a user-supplied URL against SSRF rules.
+
+    Checks:
+      1. Scheme must be ``http`` or ``https``
+      2. Hostname must be present
+      3. Resolved IP must not be private, loopback, link-local or reserved
+
+    Returns the original *url* on success; raises ``UnsafeURLError`` on failure.
+    """
+    parsed = urlparse(url)
+
+    if parsed.scheme.lower() not in _ALLOWED_SCHEMES:
+        raise UnsafeURLError(
+            f"Scheme '{parsed.scheme}' is not allowed. Use http or https."
+        )
+
+    hostname = parsed.hostname
+    if not hostname:
+        raise UnsafeURLError("URL has no hostname.")
+
+    try:
+        infos = socket.getaddrinfo(hostname, None, socket.AF_UNSPEC, socket.SOCK_STREAM)
+    except socket.gaierror as exc:
+        raise UnsafeURLError(f"Cannot resolve hostname '{hostname}': {exc}") from exc
+
+    for _family, _type, _proto, _canonname, sockaddr in infos:
+        ip = ipaddress.ip_address(sockaddr[0])
+        if ip.is_private or ip.is_loopback or ip.is_link_local or ip.is_reserved:
+            raise UnsafeURLError(
+                f"Access to private/internal address {ip} is blocked."
+            )
+
+    return url
diff --git a/pyproject.toml b/pyproject.toml
index 60b6293..0003d72 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -6,7 +6,7 @@ build-backend = "setuptools.build_meta"
 
 [project]
 name = "pybreeze"
-version = "1.0.18"
+version = "1.0.19"
 authors = [
     { name = "JE-Chen", email = "jechenmailman@gmail.com" },
 ]

From 656c5ff1f2108e72e809c7d8bc7943691329562c Mon Sep 17 00:00:00 2001
From: JeffreyChen <zenxcvwait@gmail.com>
Date: Sat, 18 Apr 2026 12:52:42 +0800
Subject: [PATCH 2/3] Add SonarQube/Codacy conventions and fix silent except

---
 CLAUDE.md                                     | 72 +++++++++++++++++++
 .../diagram_editor/diagram_scene.py           | 10 ++-
 2 files changed, 79 insertions(+), 3 deletions(-)

diff --git a/CLAUDE.md b/CLAUDE.md
index f0dc94b..84a516c 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -154,6 +154,78 @@ All code must follow secure-by-default principles. Review every change against t
 - Do not add new dependencies without reviewing their security posture (maintained? known CVEs?)
 - Avoid transitive dependency bloat — prefer stdlib solutions when the alternative is a single-function dependency
 
+## Code quality (SonarQube / Codacy compliance)
+
+All code must satisfy common static-analysis rules enforced by SonarQube and Codacy. Review each change against the checklist below.
+
+### Complexity & size
+- Cyclomatic complexity per function: ≤ 15 (hard cap 20). Break large branches into helpers
+- Cognitive complexity per function: ≤ 15. Flatten nested `if`/`for`/`try` chains with early returns or guard clauses
+- Function length: ≤ 75 lines of code (excluding docstring / blank lines). Extract helpers past that
+- Parameter count: ≤ 7 per function/method. Use a dataclass or typed dict when more are needed
+- Nesting depth: ≤ 4 levels of `if`/`for`/`while`/`try`. Refactor with early returns instead of pyramids
+- File length: ≤ 1000 lines — split modules past that
+- Class `__init__`: keep attribute count reasonable; if a class has > 15 instance attributes, split responsibilities
+
+### Exception handling
+- Never use bare `except:` — always specify exception types
+- Avoid catching `Exception` or `BaseException` unless immediately re-raising or logging and re-raising with context
+- Never `pass` silently inside `except` — log the error via `pybreeze_logger` (at minimum `.debug()`) with context
+- Do not `return` / `break` / `continue` inside a `finally` block — it swallows exceptions
+- Custom exceptions must inherit from `ITEException`; never `raise Exception(...)` directly
+- Use `raise ... from err` (or `raise ... from None`) when re-raising to preserve / suppress the chain explicitly
+
+### Pythonic correctness
+- Compare with `None` using `is` / `is not`, never `==` / `!=`
+- Type checks use `isinstance(obj, T)`, never `type(obj) == T`
+- Never use mutable default arguments (`def f(x=[])`) — use `None` and initialise inside
+- Prefer f-strings over `%` formatting or `str.format()`
+- Use context managers (`with open(...) as f:`) for every file / socket / lock — never leave resources to GC
+- Use `enumerate()` instead of `range(len(...))` when the index is needed alongside the item
+- Use `dict.get(key, default)` instead of `key in dict and dict[key]` patterns
+- Use set / dict comprehensions when clearer than manual loops; avoid comprehensions with side effects
+
+### Naming & style (PEP 8)
+- `snake_case` for functions, methods, variables, module names
+- `PascalCase` for classes
+- `UPPER_SNAKE_CASE` for module-level constants
+- `_leading_underscore` for protected / internal members; never use `__dunder__` for custom attributes
+- No single-letter names except loop indices (`i`, `j`) or conventional math (`x`, `y`)
+- Do not shadow built-ins (`id`, `type`, `list`, `dict`, `input`, `file`, `open`, etc.) — rename the local variable
+
+### Duplication & dead code
+- String literal used 3+ times in the same module → extract a module-level constant
+- Identical 6+ line blocks in 2+ places → extract a helper function
+- Remove unused imports, unused parameters, unused local variables, unreachable code after `return` / `raise`
+- No commented-out code blocks — delete them (git history is the archive)
+- No `TODO` / `FIXME` / `XXX` without an accompanying issue reference (`# TODO(#123): ...`)
+
+### Logging, printing, assertions
+- Never use `print()` for diagnostics in library / runtime code — use `pybreeze_logger`
+- Use lazy logging (`logger.debug("x=%s", x)`) — avoid eager f-string formatting inside log calls on hot paths
+- Never use `assert` for runtime validation (Python strips assertions with `-O`). Use explicit `if … raise …` instead; `assert` is only for test code
+
+### Hardcoded values & secrets
+- No hardcoded passwords, tokens, API keys, or secrets — use env vars or a config file excluded from VCS
+- No hardcoded IP addresses or hostnames outside of `localhost` / documented loopback — use config
+- Magic numbers (except 0, 1, -1) should be named constants when repeated or non-obvious
+
+### Boolean & return hygiene
+- Replace `if cond: return True else: return False` with `return bool(cond)` or `return cond`
+- Replace `if x == True` / `if x == False` with `if x` / `if not x`
+- A function should have a consistent return type — never mix `return value` and bare `return` (returns `None`) on meaningful paths unless explicitly documented
+- Do not return inside a generator function (`yield` + `return value` is a syntax pitfall)
+
+### Imports
+- One import per line for `import` statements; grouped `from x import a, b` is fine
+- Order: stdlib → third-party → first-party (`pybreeze.*`) — separated by blank lines
+- No wildcard imports (`from x import *`) outside of `__init__.py` re-exports
+- No relative imports beyond one level (`from ..pkg import x` OK, `from ...pkg import x` avoid)
+
+### Running the linters
+- Before committing any non-trivial change, run `ruff check pybreeze/` locally to catch these rules — `ruff` covers the majority of SonarQube/Codacy Python rules
+- When adding a new rule exception, justify it in a `# noqa: RULE` comment with a short reason — never blanket-disable
+
 ## Commit & PR rules
 
 - Commit messages: short imperative sentence (e.g., "Update stable version", "Fix github actions")
diff --git a/pybreeze/pybreeze_ui/diagram_editor/diagram_scene.py b/pybreeze/pybreeze_ui/diagram_editor/diagram_scene.py
index fa83c04..c80afc8 100644
--- a/pybreeze/pybreeze_ui/diagram_editor/diagram_scene.py
+++ b/pybreeze/pybreeze_ui/diagram_editor/diagram_scene.py
@@ -10,7 +10,6 @@
 from je_editor import language_wrapper
 
 from pybreeze.pybreeze_ui.diagram_editor.diagram_commands import DiagramSnapshotCommand
-from pybreeze.pybreeze_ui.diagram_editor.diagram_net_utils import safe_download_image
 from pybreeze.pybreeze_ui.diagram_editor.diagram_items import (
     ConnectionStyle,
     DiagramConnection,
@@ -19,6 +18,11 @@
     NodeShape,
     ResizeHandle,
 )
+from pybreeze.pybreeze_ui.diagram_editor.diagram_net_utils import (
+    ImageDownloadError,
+    safe_download_image,
+)
+from pybreeze.utils.logging.logger import pybreeze_logger
 
 
 class ToolMode(Enum):
@@ -595,8 +599,8 @@ def _try_load_image_source(self, img: DiagramImage, source: str) -> None:
                 pix.loadFromData(data)
                 if not pix.isNull():
                     img.set_pixmap(pix, source)
-            except Exception:
-                pass
+            except (ImageDownloadError, OSError) as err:
+                pybreeze_logger.debug("safe_download_image failed: %s", err)
 
     def load_from_dict(self, data: dict) -> None:
         self._clear_items()

From ccb73564c3918903878b4fdeb4b141d5a50cc415 Mon Sep 17 00:00:00 2001
From: JeffreyChen <zenxcvwait@gmail.com>
Date: Sat, 18 Apr 2026 13:00:44 +0800
Subject: [PATCH 3/3] Replace WarningPolicy with interactive TOFU SSH host key
 verification

---
 CLAUDE.md                                     |   2 +-
 .../extend_multi_language/extend_english.py   |   7 ++
 .../extend_traditional_chinese.py             |   7 ++
 .../connect_gui/ssh/ssh_command_widget.py     |   8 +-
 .../connect_gui/ssh/ssh_file_viewer_widget.py |  13 +-
 .../connect_gui/ssh/ssh_host_key_policy.py    | 111 ++++++++++++++++++
 6 files changed, 135 insertions(+), 13 deletions(-)
 create mode 100644 pybreeze/pybreeze_ui/connect_gui/ssh/ssh_host_key_policy.py

diff --git a/CLAUDE.md b/CLAUDE.md
index 84a516c..91fdc12 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -113,7 +113,7 @@ All code must follow secure-by-default principles. Review every change against t
 
 ### Network requests (TLS / SSH)
 - All HTTPS requests must use default TLS verification — never set `verify=False`
-- SSH connections: `paramiko.AutoAddPolicy()` accepts any host key and is vulnerable to MITM. Document it as a known limitation in the SSH GUI. Prefer `paramiko.RejectPolicy()` or `paramiko.WarningPolicy()` when non-interactive verification is possible; at minimum, warn the user on first connection to an unknown host
+- SSH connections: never use `paramiko.AutoAddPolicy()` or `paramiko.WarningPolicy()` — both silently accept unknown host keys and are vulnerable to MITM. Use `InteractiveHostKeyPolicy` from `pybreeze.pybreeze_ui.connect_gui.ssh.ssh_host_key_policy` (via `apply_host_key_policy(client, parent_widget)`), which prompts the user with the SHA256 fingerprint on first connection and persists confirmed keys to `~/.pybreeze/ssh_known_hosts`
 
 ### Subprocess execution
 - Always pass argument lists to `subprocess.Popen` / `subprocess.run` — never `shell=True`
diff --git a/pybreeze/extend_multi_language/extend_english.py b/pybreeze/extend_multi_language/extend_english.py
index 1468953..36abc3e 100644
--- a/pybreeze/extend_multi_language/extend_english.py
+++ b/pybreeze/extend_multi_language/extend_english.py
@@ -101,6 +101,13 @@
     "test_pioneer_create_template_label": "Create TestPioneer Yaml template",
     "test_pioneer_run_yaml": "Execute Test Pioneer Yaml",
     "test_pioneer_not_choose_yaml": "Please choose a Yaml file",
+    # SSH host key verification
+    "ssh_host_key_policy_dialog_title_verify_host": "Verify SSH host key",
+    "ssh_host_key_policy_dialog_message_verify_host": (
+        "The authenticity of host '{host}' cannot be established.\n"
+        "{key_type} key fingerprint is {fingerprint}.\n\n"
+        "Do you want to trust this host and continue connecting?"
+    ),
     # SSH command widget
     "ssh_command_widget_window_title_ssh_command_widget": "SSH Command Widget",
     "ssh_command_widget_button_label_send_command": "Send",
diff --git a/pybreeze/extend_multi_language/extend_traditional_chinese.py b/pybreeze/extend_multi_language/extend_traditional_chinese.py
index 78a35cd..0d12eb7 100644
--- a/pybreeze/extend_multi_language/extend_traditional_chinese.py
+++ b/pybreeze/extend_multi_language/extend_traditional_chinese.py
@@ -101,6 +101,13 @@
     "test_pioneer_create_template_label": "建立 TestPioneer Yaml 模板",
     "test_pioneer_run_yaml": "執行 Test Pioneer Yaml",
     "test_pioneer_not_choose_yaml": "請選擇 Yaml 檔案",
+    # SSH host key verification
+    "ssh_host_key_policy_dialog_title_verify_host": "驗證 SSH 主機金鑰",
+    "ssh_host_key_policy_dialog_message_verify_host": (
+        "無法驗證主機 '{host}' 的真實性。\n"
+        "{key_type} 金鑰指紋為 {fingerprint}。\n\n"
+        "是否信任此主機並繼續連線？"
+    ),
     # SSH command widget
     "ssh_command_widget_window_title_ssh_command_widget": "SSH 指令介面",
     "ssh_command_widget_button_label_send_command": "送出",
diff --git a/pybreeze/pybreeze_ui/connect_gui/ssh/ssh_command_widget.py b/pybreeze/pybreeze_ui/connect_gui/ssh/ssh_command_widget.py
index f74548d..44f8a76 100644
--- a/pybreeze/pybreeze_ui/connect_gui/ssh/ssh_command_widget.py
+++ b/pybreeze/pybreeze_ui/connect_gui/ssh/ssh_command_widget.py
@@ -12,6 +12,7 @@
 )
 from je_editor import language_wrapper
 
+from pybreeze.pybreeze_ui.connect_gui.ssh.ssh_host_key_policy import apply_host_key_policy
 from pybreeze.pybreeze_ui.connect_gui.ssh.ssh_login_widget import LoginWidget
 from pybreeze.utils.logging.logger import pybreeze_logger
 
@@ -139,11 +140,8 @@ def connect_ssh(self):
 
         try:
             self.ssh_client = paramiko.SSHClient()
-            self.ssh_client.load_system_host_keys()
-            self.ssh_client.set_missing_host_key_policy(paramiko.WarningPolicy())
-            pybreeze_logger.warning(
-                f"SSH connecting to {host}:{port} — host key will be accepted without verification"
-            )
+            apply_host_key_policy(self.ssh_client, self)
+            pybreeze_logger.info("SSH connecting to %s:%s", host, port)
 
             if use_key:
                 if not os.path.exists(key_path):
diff --git a/pybreeze/pybreeze_ui/connect_gui/ssh/ssh_file_viewer_widget.py b/pybreeze/pybreeze_ui/connect_gui/ssh/ssh_file_viewer_widget.py
index e59417f..a02531a 100644
--- a/pybreeze/pybreeze_ui/connect_gui/ssh/ssh_file_viewer_widget.py
+++ b/pybreeze/pybreeze_ui/connect_gui/ssh/ssh_file_viewer_widget.py
@@ -12,6 +12,7 @@
 )
 from je_editor import language_wrapper
 
+from pybreeze.pybreeze_ui.connect_gui.ssh.ssh_host_key_policy import apply_host_key_policy
 from pybreeze.pybreeze_ui.connect_gui.ssh.ssh_login_widget import LoginWidget
 from pybreeze.utils.logging.logger import pybreeze_logger
 
@@ -29,18 +30,16 @@ def __init__(self):
         self.root_path: str = "/"
 
     def connect(self, host: str, port: int, username: str, password: str,
-                use_key: bool = False, key_path: str = ""):
+                use_key: bool = False, key_path: str = "",
+                parent_widget: QWidget | None = None):
         """
         Establish SSH + SFTP connection.
         建立 SSH + SFTP 連線。
         """
         self.close()
         self._ssh = paramiko.SSHClient()
-        self._ssh.load_system_host_keys()
-        self._ssh.set_missing_host_key_policy(paramiko.WarningPolicy())
-        pybreeze_logger.warning(
-            f"SFTP connecting to {host}:{port} — host key will be accepted without verification"
-        )
+        apply_host_key_policy(self._ssh, parent_widget)
+        pybreeze_logger.info("SFTP connecting to %s:%s", host, port)
         if use_key and key_path:
             pkey = None
             for KeyType in (paramiko.RSAKey, paramiko.Ed25519Key, paramiko.ECDSAKey):
@@ -216,7 +215,7 @@ def _connect(self):
                 self.word_dict.get("ssh_file_viewer_dialog_message_missing_input"))
             return
         try:
-            self.client.connect(host, port, user, pwd, use_key, key_path)
+            self.client.connect(host, port, user, pwd, use_key, key_path, parent_widget=self)
             self.load_root("/")
         except Exception as e:
             QMessageBox.critical(
diff --git a/pybreeze/pybreeze_ui/connect_gui/ssh/ssh_host_key_policy.py b/pybreeze/pybreeze_ui/connect_gui/ssh/ssh_host_key_policy.py
new file mode 100644
index 0000000..0a6571a
--- /dev/null
+++ b/pybreeze/pybreeze_ui/connect_gui/ssh/ssh_host_key_policy.py
@@ -0,0 +1,111 @@
+"""Interactive SSH host key policy with persistent trust-on-first-use (TOFU).
+
+Replaces the MITM-prone ``paramiko.AutoAddPolicy`` / ``paramiko.WarningPolicy``:
+unknown host keys are shown to the user via a Qt dialog with their SHA256
+fingerprint, and only accepted on explicit confirmation. Confirmed hosts are
+persisted to ``~/.pybreeze/ssh_known_hosts`` so subsequent connections verify
+automatically.
+"""
+from __future__ import annotations
+
+import base64
+import hashlib
+from pathlib import Path
+from typing import TYPE_CHECKING
+
+import paramiko
+from je_editor import language_wrapper
+from PySide6.QtWidgets import QMessageBox
+
+from pybreeze.utils.logging.logger import pybreeze_logger
+
+if TYPE_CHECKING:
+    from PySide6.QtWidgets import QWidget
+
+
+def _known_hosts_path() -> Path:
+    """Return the PyBreeze-managed known_hosts file path, ensuring the parent dir exists."""
+    home_dir = Path.home() / ".pybreeze"
+    home_dir.mkdir(parents=True, exist_ok=True)
+    return home_dir / "ssh_known_hosts"
+
+
+def _fingerprint_sha256(key: paramiko.PKey) -> str:
+    """Return an OpenSSH-style SHA256 fingerprint (``SHA256:base64`` without padding)."""
+    digest = hashlib.sha256(key.asbytes()).digest()
+    return "SHA256:" + base64.b64encode(digest).rstrip(b"=").decode("ascii")
+
+
+class InteractiveHostKeyPolicy(paramiko.MissingHostKeyPolicy):
+    """Policy that prompts the user to verify unknown host keys.
+
+    Accepted keys are persisted so later connections pass through ``RejectPolicy``-like
+    strictness automatically. Declined keys abort the connection with ``SSHException``.
+    """
+
+    def __init__(self, parent: QWidget | None = None) -> None:
+        super().__init__()
+        self._parent = parent
+        self._word_dict = language_wrapper.language_word_dict
+
+    def missing_host_key(
+        self,
+        client: paramiko.SSHClient,
+        hostname: str,
+        key: paramiko.PKey,
+    ) -> None:
+        fingerprint = _fingerprint_sha256(key)
+        key_type = key.get_name()
+
+        title = self._word_dict.get(
+            "ssh_host_key_policy_dialog_title_verify_host",
+            "Verify SSH host key",
+        )
+        message_template = self._word_dict.get(
+            "ssh_host_key_policy_dialog_message_verify_host",
+            "The authenticity of host '{host}' cannot be established.\n"
+            "{key_type} key fingerprint is {fingerprint}.\n\n"
+            "Do you want to trust this host and continue connecting?",
+        )
+        message = message_template.format(
+            host=hostname, key_type=key_type, fingerprint=fingerprint
+        )
+
+        box = QMessageBox(self._parent)
+        box.setIcon(QMessageBox.Icon.Warning)
+        box.setWindowTitle(title)
+        box.setText(message)
+        box.setStandardButtons(QMessageBox.StandardButton.Yes | QMessageBox.StandardButton.No)
+        box.setDefaultButton(QMessageBox.StandardButton.No)
+        response = box.exec()
+
+        if response != QMessageBox.StandardButton.Yes:
+            pybreeze_logger.warning(
+                "SSH host key for %s rejected by user (%s)", hostname, fingerprint
+            )
+            raise paramiko.SSHException(
+                f"Host key for {hostname} rejected by user."
+            )
+
+        client.get_host_keys().add(hostname, key_type, key)
+        try:
+            client.save_host_keys(str(_known_hosts_path()))
+        except OSError as err:
+            pybreeze_logger.warning(
+                "Failed to persist SSH host key for %s: %s", hostname, err
+            )
+        pybreeze_logger.info(
+            "SSH host key for %s accepted and stored (%s)", hostname, fingerprint
+        )
+
+
+def apply_host_key_policy(client: paramiko.SSHClient, parent: QWidget | None) -> None:
+    """Load known hosts and attach the interactive TOFU policy to *client*."""
+    client.load_system_host_keys()
+    known_hosts = _known_hosts_path()
+    if known_hosts.is_file():
+        try:
+            client.load_host_keys(str(known_hosts))
+        except OSError as err:
+            pybreeze_logger.warning("Failed to load PyBreeze known_hosts: %s", err)
+    client.set_missing_host_key_policy(InteractiveHostKeyPolicy(parent))