Comments im ganzen Projekt

backend/agent/coding_agent.py

@@ -279,9 +279,12 @@ def trim_messages(messages: list) -> list:
     tail = messages[2:]
     original_task = messages[1]["content"] if len(messages) > 1 else ""
 
+    # Drop the oldest messages first (index 2 onwards) until we are under the limit.
+    # The system prompt (0) and original task (1) are never dropped.
     while tail and sum(len(m["content"]) for m in head + tail) > MAX_HISTORY_CHARS:
         tail.pop(0)
 
+    # Inject a reminder so the agent doesn't lose track of its goal after trimming.
     reminder = {
         "role": "user",
         "content": (
@@ -344,7 +347,7 @@ class CodingAgent:
         payload = {
             "model": self.model,
             "messages": messages,
-            "temperature": 0.2,
+            "temperature": 0.2,   # low temperature → deterministic, more reliable tool calls
             "max_tokens": 4096,
             "stream": False,
         }
@@ -445,7 +448,9 @@ class CodingAgent:
         result = dispatch_tool(tool_name, arguments)
         result = truncate_result(result)
 
-        # Build feedback – nudge agent to replan on errors
+        # Wrap the tool output in an XML tag so the LLM can easily find it.
+        # Append a <replan> tag on errors to force the agent to reconsider
+        # its plan rather than blindly retrying the same failing action.
         feedback = f'<tool_result tool="{tool_name}">\n{result}\n</tool_result>'
         if result.startswith("ERROR") or result.startswith("SYNTAX ERROR"):
             feedback += (

backend/managers/chat_manager.py

@@ -1,4 +1,4 @@
-"""Chat Manager - Handles chat history and AI communication"""
+"""Manages the chat history and communication with the AI model API."""
 
 import os
 from dotenv import load_dotenv
@@ -9,6 +9,13 @@ load_dotenv()
 
 
 class ChatManager:
+    """Handles sending messages and maintaining conversation history.
+
+    Connects to an OpenAI-compatible REST endpoint configured via environment
+    variables. All messages (user, assistant, system) are kept in memory so
+    the full conversation is sent with every request.
+    """
+
     def __init__(self):
         self.api_host = os.getenv("HOST")
         self.api_port = os.getenv("PORT")
@@ -22,15 +29,23 @@ class ChatManager:
         self.chat_history = []
 
     def add_message(self, role: str, content: str) -> None:
+        """Append a single message to the conversation history."""
         self.chat_history.append({"role": role, "content": content})
 
     def get_history(self) -> list:
+        """Return the full conversation history."""
         return self.chat_history
 
     def clear_history(self) -> None:
+        """Wipe the conversation history (starts a fresh chat)."""
         self.chat_history = []
 
     def send_message(self, user_message: str) -> str:
+        """Send a user message to the AI and return its reply.
+
+        Adds the user message to history, calls the API with the full history
+        as context, and appends the AI reply to history before returning it.
+        """
         # Add user message to history
         self.add_message("user", user_message)
 
@@ -44,6 +59,7 @@ class ChatManager:
             if self.api_key and self.api_key != "EMPTY":
                 headers["Authorization"] = f"Bearer {self.api_key}"
 
+            # Full history is sent so the model has multi-turn conversation context
             payload = {
                 "model": self.model,
                 "messages": self.chat_history,
@@ -91,6 +107,7 @@ class ChatManager:
             raise Exception(error_msg)
 
     def get_chat_display(self) -> list:
+        """Return a copy of the history suitable for display in the UI."""
         return [
             {"role": msg["role"], "content": msg["content"]}
             for msg in self.chat_history

backend/managers/debug_logger.py

@@ -1,9 +1,14 @@
+# Simple in-memory logger used during code execution.
+# Messages are collected in a list and can be retrieved for display or debugging.
+
 class DebugLogger:
     def __init__(self):
         self.logs = []
 
     def log(self, message):
+        """Append a log message to the in-memory list."""
         self.logs.append(message)
 
     def get_logs(self):
+        """Return all collected log messages."""
         return self.logs

backend/managers/execution_engine.py

@@ -1,19 +1,38 @@
 import subprocess
 from pathlib import Path
 
-RUN_TIMEOUT = 30  # seconds
+# Maximum time (seconds) a subprocess is allowed to run before being killed.
+RUN_TIMEOUT = 30
+
 
 class ExecutionEngine:
+    """Runs files from the editor in a subprocess and returns the output.
+
+    Currently supports Python (.py) and LaTeX (.tex) files.
+    Returns a dict with keys: stdout, stderr, rc (return code).
+    """
+
     def __init__(self):
         pass
 
     def run_code(self, active_file: Path) -> dict:
+        """Execute the given file and return its output.
+
+        Args:
+            active_file: Absolute path to the file that should be run.
+
+        Returns:
+            {"stdout": str, "stderr": str, "rc": int}
+            rc == 0 means success, anything else is an error.
+        """
         suffix = active_file.suffix
         current_dir = active_file.parent.resolve()
 
+        # Build the shell command depending on file type
         if suffix == ".py":
             cmd = ["py", active_file.name]
         elif suffix == ".tex":
+            # pdflatex in non-interactive mode so it never waits for input
             cmd = [
                 "pdflatex",
                 "-interaction=nonstopmode",
@@ -26,7 +45,7 @@ class ExecutionEngine:
         try:
             proc = subprocess.run(
                 cmd,
-                cwd=current_dir,
+                cwd=current_dir,        # run inside the file's own directory
                 capture_output=True,
                 text=True,
                 timeout=RUN_TIMEOUT,
@@ -36,6 +55,7 @@ class ExecutionEngine:
         except subprocess.TimeoutExpired:
             return {"stdout": "", "stderr": f"Timed out after {RUN_TIMEOUT}s", "rc": -1}
         except FileNotFoundError as e:
+            # Raised when the interpreter/compiler binary is not found on PATH
             return {"stdout": "", "stderr": str(e), "rc": -1}
         except Exception as e:
             return {"stdout": "", "stderr": str(e), "rc": -1}

backend/managers/file_manager.py

@@ -1,6 +1,13 @@
+"""Manages all file and folder operations inside the workspace directory.
+
+Every method validates that the target path stays inside the workspace before
+touching the filesystem, preventing path-traversal attacks.
+"""
+
 import streamlit as st
 from pathlib import Path
 
+# The workspace folder is created at module load so it always exists.
 WORKSPACE = Path("workspace")
 WORKSPACE.mkdir(exist_ok=True)
 
@@ -10,10 +17,14 @@ class FileManager:
         self.base_path.mkdir(exist_ok=True)
 
     def create_folder(self, relative_path: str, name: str) -> bool:
+        """Create a new sub-folder at relative_path/name inside the workspace.
+        Returns True on success, False on any error.
+        """
         if not name:
             st.error(f"Invalid folder name: {name}")
             return False
 
+        # Slashes in the name would silently create nested paths — reject them.
         if "/" in name or "\\" in name:
             st.error(f"Invalid folder name (no slashes allowed): {name}")
             return False
@@ -26,6 +37,7 @@ class FileManager:
 
         folder_path = (self.base_path / relative_path / name).resolve()
 
+        # Ensure the resolved path is still inside the workspace (prevents path traversal).
         if not str(folder_path).startswith(str(self.base_path.resolve())):
             st.error(f"Access denied: {relative_path}")
             return False
@@ -41,6 +53,10 @@ class FileManager:
             return False
 
     def create_file(self, relative_path: str, name: str) -> bool:
+        """Create a new empty file at relative_path/name inside the workspace.
+        If name has no extension, .txt is used as the default.
+        Returns True on success, False on any error.
+        """
         if not name or name.strip() == ""  :
             st.error(f"Invalid file name: {name}")
             return False
@@ -56,6 +72,7 @@ class FileManager:
 
         file_path = (self.base_path / relative_path / name).resolve()
 
+        # Ensure the resolved path is still inside the workspace (prevents path traversal).
         if not str(file_path).startswith(str(self.base_path.resolve())):
             st.error(f"Access denied: {relative_path}")
             return False
@@ -71,6 +88,9 @@ class FileManager:
             return False
 
     def read_file(self, relative_path: Path) -> str:
+        """Read and return the text content of a file.
+        Returns an empty string and shows a Streamlit error on failure.
+        """
         file_path = (relative_path).resolve()
 
         if not file_path.exists():
@@ -79,6 +99,7 @@ class FileManager:
         if not file_path.is_file():
             st.error(f"Path is not a file: {relative_path}")
             return ""
+        # Ensure the resolved path is still inside the workspace (prevents path traversal).
         if not str(file_path).startswith(str(self.base_path.resolve())):
             st.error(f"Access denied: {relative_path}")
             return ""
@@ -94,8 +115,12 @@ class FileManager:
             return ""
 
     def save_file(self, relative_path: str, content: str):
+        """Overwrite a file with new content.
+        Returns True on success, False on any error.
+        """
         file_path = (Path(relative_path)).resolve()
 
+        # Ensure the resolved path is still inside the workspace (prevents path traversal).
         if not str(file_path).startswith(str(self.base_path.resolve())):
             st.error(f"Access denied: {relative_path}")
             return False
@@ -109,6 +134,10 @@ class FileManager:
             return False
 
     def rename_file(self, old_relative_path: str, new_name: str) -> bool:
+        """Rename a file while preserving its original extension.
+        If new_name carries a different extension it is ignored; the original
+        suffix is always kept. Returns True on success, False on any error.
+        """
         if not new_name or new_name.strip() == "":
             st.error(f"Invalid file name: {new_name}")
             return False
@@ -116,12 +145,14 @@ class FileManager:
         file_type = Path(old_relative_path).suffix
         new_name = Path(new_name)
 
+        # Force the original extension so the file type cannot be changed by renaming.
         if not Path(new_name).suffix == file_type:
             new_name = Path(new_name).with_suffix(file_type)  # Ensure the file extension remains the same
 
         old_file_path = (Path(old_relative_path)).resolve()
         new_file_path = old_file_path.parent / new_name
 
+        # Both old and new paths must stay inside the workspace.
         if not str(old_file_path).startswith(str(self.base_path.resolve())) or not str(new_file_path).startswith(str(self.base_path.resolve())):
             st.error(f"Access denied: {old_relative_path}")
             return False
@@ -134,8 +165,12 @@ class FileManager:
             return False
 
     def delete_folder(self, relative_path) -> bool:
+        """Delete a folder and all its contents recursively.
+        Returns True on success, False on any error.
+        """
         folder_path = (self.base_path / relative_path).resolve()
 
+        # Ensure the resolved path is still inside the workspace (prevents path traversal).
         if not str(folder_path).startswith(str(self.base_path.resolve())):
             st.error(f"Access denied: {relative_path}")
             return False
@@ -153,8 +188,12 @@ class FileManager:
             return False
 
     def delete_file(self, relative_path):
+        """Delete a single file from the workspace.
+        Returns True on success, False on any error.
+        """
         file_path = Path(relative_path).resolve()
 
+        # Ensure the resolved path is still inside the workspace (prevents path traversal).
         if not str(file_path).startswith(str(self.base_path.resolve())):
             st.error(f"Access denied: {relative_path}")
             return False
@@ -170,15 +209,19 @@ class FileManager:
             return False
 
     def get_file_tree(self):
+        """Return a nested dict representing the workspace directory tree.
+        Folders are dicts; files are None values.
+        Example: {"src": {"main.py": None}, "README.txt": None}
+        """
         def build_tree(path: Path):
 
             tree = {}
 
             for item in sorted(path.iterdir()):
                 if item.is_dir():
-                    tree[item.name] = build_tree(item)
+                    tree[item.name] = build_tree(item)  # recurse into sub-folders
                 else:
-                    tree[item.name] = None
+                    tree[item.name] = None              # leaf node for files
             return tree
         return build_tree(self.base_path)
 

backend/managers/system_prompter.py

@@ -1,18 +1,26 @@
-"""System Prompter - Builds system prompts with optional file context"""
+"""Builds the system prompt that is sent to the AI at the start of each chat session."""
 
-MAX_FILE_CHARS = 4000  # Limit file context to avoid token overflow
+# Prevents very large files from flooding the context window with tokens.
+MAX_FILE_CHARS = 4000
 
 
 class SystemPrompter:
+    """Generates system prompts for the chat assistant.
+
+    When a file is open in the editor it can be embedded in the prompt so the
+    AI has direct context of the code the user is currently working on.
+    """
+
     @staticmethod
     def generate_prompt(file_context: dict | None = None) -> str:
         """Build a system prompt, optionally embedding a file's content.
 
         Args:
-            file_context: dict with keys 'name' and 'content', or None.
+            file_context: dict with keys 'name' (filename) and 'content' (raw text),
+                          or None if no file should be included.
 
         Returns:
-            A system prompt string.
+            A ready-to-use system prompt string.
         """
         base = (
             "You are an expert code assistant integrated into a lightweight code editor. "
@@ -23,9 +31,11 @@ class SystemPrompter:
         if file_context:
             name = file_context.get("name", "unknown")
             content = file_context.get("content", "")
-            # Truncate large files to avoid exceeding token limits
+
+            # Truncate large files to avoid exceeding the model's token limit
             if len(content) > MAX_FILE_CHARS:
                 content = content[:MAX_FILE_CHARS] + "\n... [truncated]"
+
             file_section = (
                 f"\n\nThe user currently has the following file open in the editor:\n"
                 f"<file name=\"{name}\">\n"

frontend/app.py

@@ -1,8 +1,20 @@
+"""Entry point for the Streamlit app.
+
+Runs with: streamlit run frontend/app.py
+
+Responsibilities:
+- Configure the page layout
+- Inject global CSS tweaks
+- Render the sidebar (navigation + file explorer)
+- Delegate to the correct view (Chat or Code Editor) based on the radio selection
+"""
+
 import streamlit as st
 import sys
 from pathlib import Path
 
-# Add project root to Python path for imports
+# Add the project root to sys.path so backend imports work regardless of
+# where streamlit is launched from.
 sys.path.insert(0, str(Path(__file__).parent.parent))
 
 from frontend.sidebar import render_sidebar
@@ -10,12 +22,16 @@ from frontend.editor import render_editor
 from frontend.chat import render_chat
 from frontend.state import init_state
 
+# Initialise all session-state keys before any widget is rendered
 init_state()
 
 
 def main():
     st.set_page_config(page_title="Lightweight code editor", layout="wide")
 
+    # Small spacing corrections applied globally:
+    # - Reduce the default top padding of the main content area
+    # - Pull the sidebar content up so the logo sits at the very top
     st.markdown(
         """
         <style>
@@ -28,14 +44,17 @@ def main():
 
     st.title("Lightweight code editor")
 
+    # Re-run init_state to cover any keys that might have been missed on cold start
     init_state()
 
     render_sidebar()
 
+    # Switch between the two main views based on the sidebar radio button
     if st.session_state.get("radio_interface_options") == "Code Editor":
         render_editor()
     elif st.session_state.get("radio_interface_options") == "Chat with AI Assistant":
         render_chat()
 
+
 if __name__ == "__main__":
     main()

frontend/chat.py

@@ -1,3 +1,5 @@
+"""Chat view — renders both the normal chat interface and the Coding Agent mode."""
+
 import streamlit as st
 from backend.managers.chat_manager import ChatManager
 from backend.managers.system_prompter import SystemPrompter
@@ -6,12 +8,14 @@ from backend.managers.system_prompter import SystemPrompter
 # ── Agent Mode helpers ────────────────────────────────────────────────────────
 
 def _start_agent(task: str):
-    """Initialise a fresh CodingAgent, start the task, 
-    and propose the first action."""
+    """Create a new CodingAgent, feed it the task, and propose the first action.
+    Stores the agent and its state in session_state so Streamlit can reference
+    them across reruns without losing progress.
+    """
     from backend.agent.coding_agent import CodingAgent
     agent = CodingAgent()
     agent.start_task(task)
-    action = agent.propose_next_action()
+    action = agent.propose_next_action()  # ask LLM: what is the first step?
     st.session_state.coding_agent = agent
     st.session_state.agent_pending_action = action
     st.session_state.agent_status = "waiting_approval"
@@ -19,13 +23,13 @@ def _start_agent(task: str):
 
 
 def _approve_action():
-    """Execute the pending action, 
-    append it to the log, then propose the next step."""
+    """Execute the pending action, log it, then immediately propose the next step."""
     agent = st.session_state.coding_agent
     pending = st.session_state.agent_pending_action
 
-    result = agent.approve()
+    result = agent.approve()  # actually runs the tool
 
+    # Append a record to the log so the user can review every completed step.
     st.session_state.agent_log.append({
         "thought":   pending.get("thought", ""),
         "tool":      result["tool"],
@@ -34,16 +38,21 @@ def _approve_action():
     })
 
     if result["is_done"]:
+        # Agent called the "done" tool — task is fully complete.
         st.session_state.agent_status = "done"
         st.session_state.agent_pending_action = None
     else:
+        # More steps needed — get the next proposed action.
         next_action = agent.propose_next_action()
         st.session_state.agent_pending_action = next_action
         st.session_state.agent_status = "waiting_approval"
 
 
 def _reject_action(feedback: str):
-    """Reject the pending action with optional feedback, then replan."""
+    """Reject the pending action with feedback so the agent replans.
+    The pending action is discarded; the agent receives the user's feedback and
+    proposes a different approach on the next call to propose_next_action().
+    """
     agent = st.session_state.coding_agent
     agent.reject(feedback or "Please try a different approach.")
     next_action = agent.propose_next_action()
@@ -52,7 +61,7 @@ def _reject_action(feedback: str):
 
 
 def _followup_agent(question: str):
-    """Inject a follow-up question into the finished agent and resume the loop."""
+    """Continue a finished task by injecting a follow-up question and resuming the loop."""
     agent = st.session_state.coding_agent
     agent.follow_up(question)
     action = agent.propose_next_action()
@@ -61,7 +70,7 @@ def _followup_agent(question: str):
 
 
 def _reset_agent():
-    """Reset all agent state back to idle."""
+    """Clear all agent state and return to the idle (task input) screen."""
     st.session_state.coding_agent = None
     st.session_state.agent_status = "idle"
     st.session_state.agent_log = []
@@ -71,13 +80,21 @@ def _reset_agent():
 # ── Agent Mode UI ─────────────────────────────────────────────────────────────
 
 def render_agent_mode():
-    # Toggle must always be rendered so Streamlit keeps agent_mode=True in session_state
+    """Render the step-by-step agent UI.
+
+    Three distinct screens based on agent_status:
+      - "idle"             → task description input + Start button
+      - "waiting_approval" → show proposed action, Approve / Reject / Abort
+      - "done"             → success message, follow-up input, New Task button
+    """
+    # The toggle must always render so Streamlit keeps agent_mode=True in session_state.
     st.toggle("Agent Mode", key="agent_mode")
 
     agent_status = st.session_state.get("agent_status", "idle")
     agent_log    = st.session_state.get("agent_log", [])
 
     # ── Agent Log ────────────────────────────────────────────────────────────
+    # Collapsed by default so it doesn't clutter the UI during active tasks.
     if agent_log:
         with st.expander(f"Agent Log — {len(agent_log)} step(s) completed", expanded=False):
             for i, step in enumerate(agent_log):
@@ -87,6 +104,7 @@ def render_agent_mode():
                     if step.get("arguments"):
                         st.json(step["arguments"])
                     result_text = step.get("result", "")
+                    # Colour the result based on whether the tool succeeded or failed.
                     if result_text.startswith("ERROR") or result_text.startswith("SYNTAX ERROR"):
                         st.error(result_text)
                     elif result_text.startswith("OK") or result_text.startswith("DONE"):
@@ -120,6 +138,8 @@ def render_agent_mode():
 
             args = pending.get("arguments", {})
             if args:
+                # Show file content separately as a code block for readability;
+                # other arguments are displayed as JSON.
                 if "content" in args:
                     display_args = {k: v for k, v in args.items() if k != "content"}
                     if display_args:
@@ -182,7 +202,13 @@ def render_agent_mode():
 # ── Normal Chat ───────────────────────────────────────────────────────────────
 
 def render_normal_chat():
-    # Chat history as bubbles
+    """Render the standard multi-turn chat interface.
+
+    On the first message the system prompt is injected into the history.
+    Each subsequent message appends to the same conversation so the AI retains
+    full context throughout the session.
+    """
+    # Replay the conversation history as chat bubbles (skip system messages).
     for message in st.session_state.chat_history:
         role = message["role"]
         if role == "system":
@@ -195,16 +221,17 @@ def render_normal_chat():
     if user_input:
         chat_manager = st.session_state.chat_manager
 
-        # Inject system prompt on the first message
+        # On the very first user message, prepend the system prompt so the AI
+        # knows it is a code assistant embedded in an editor.
         if not chat_manager.get_history():
             system_prompt = SystemPrompter.generate_prompt()
             chat_manager.add_message("system", system_prompt)
 
-        # Show user message immediately without waiting for response
+        # Show user message immediately without waiting for response.
         with st.chat_message("user"):
             st.markdown(user_input)
 
-        # Show response with spinner while API is called
+        # Call the AI and show its response with a spinner while waiting.
         with st.chat_message("assistant"):
             with st.spinner("Thinking..."):
                 try:
@@ -227,6 +254,7 @@ def render_normal_chat():
 # ── Entry point ───────────────────────────────────────────────────────────────
 
 def render_chat():
+    """Top-level chat view — switches between Agent Mode and normal chat."""
     if st.session_state.get("agent_mode", False):
         st.subheader("Coding Agent")
         render_agent_mode()

frontend/editor.py

@@ -1,3 +1,5 @@
+"""Code Editor view — renders the Ace editor, file tabs, and execution output."""
+
 import streamlit as st
 import streamlit_ace as st_ace
 from pathlib import Path
@@ -6,6 +8,7 @@ from backend.managers.file_manager import FileManager
 from backend.managers.execution_engine import ExecutionEngine
 from backend.managers.debug_logger import DebugLogger
 
+# Maps file extensions to Ace editor language modes for syntax highlighting.
 LANG_MAP = {
     ".py": "python", ".tex": "latex", ".js": "javascript",
     ".html": "html", ".css": "css", ".sh": "bash",
@@ -17,6 +20,10 @@ LANG_MAP = {
 
 @st.dialog("Rename File")
 def _rename_dialog(file_path: str):
+    """Dialog for renaming the given file.
+    Updates open_files, files_content and active_file in session_state so
+    all tabs and the editor reference the new path immediately.
+    """
     fm = FileManager()
     st.write(f"Current name: **{Path(file_path).name}**")
     new_name = st.text_input("New name:", value=Path(file_path).stem)
@@ -32,10 +39,13 @@ def _rename_dialog(file_path: str):
                 if fm.rename_file(file_path, new_name.strip()):
                     ext = Path(file_path).suffix
                     new_file_path = str(Path(file_path).parent / (Path(new_name.strip()).stem + ext))
+                    # Update the open-files list in place so the tab order is preserved.
                     i = st.session_state.open_files.index(file_path)
                     st.session_state.open_files[i] = new_file_path
+                    # Transfer cached editor content to the new path key.
                     st.session_state.files_content[new_file_path] = \
                         st.session_state.files_content.pop(file_path)
+                    # Update active_file if the renamed file was the active one.
                     if st.session_state.active_file == file_path:
                         st.session_state.active_file = new_file_path
                     st.rerun()
@@ -48,6 +58,10 @@ def _rename_dialog(file_path: str):
 
 @st.dialog("Delete File")
 def _delete_dialog(file_path: str):
+    """Confirmation dialog before permanently deleting a file.
+    Removes the file from the filesystem and cleans up all session-state
+    references (open_files, files_content, active_file).
+    """
     fm = FileManager()
     st.warning(f"Delete **{Path(file_path).name}**? This cannot be undone.")
 
@@ -57,6 +71,7 @@ def _delete_dialog(file_path: str):
             if fm.delete_file(file_path):
                 st.session_state.open_files.remove(file_path)
                 st.session_state.files_content.pop(file_path, None)
+                # Fall back to the first remaining open file, or None if none are left.
                 if st.session_state.active_file == file_path:
                     st.session_state.active_file = (
                         st.session_state.open_files[0]
@@ -71,6 +86,10 @@ def _delete_dialog(file_path: str):
 
 
 def run_active_file():
+    """Execute the currently active file and store the result in session_state.
+    Returns the execution result dict {stdout, stderr, return_code}, or None
+    if no active file is set.
+    """
     active_file = st.session_state.active_file
 
     if not active_file:
@@ -96,6 +115,7 @@ def run_active_file():
     return result
 
 def render_editor():
+    """Render the full Code Editor view with tabs, Ace editor, and run output."""
     st.subheader("Code Editor")
 
     if not st.session_state.open_files:
@@ -105,16 +125,19 @@ def render_editor():
     fm = FileManager()
 
     # ── Tab bar via st.tabs() ─────────────────────────────────────────────────
+    # Build one tab per open file, named by the file's basename.
     tab_names = [Path(f).name for f in st.session_state.open_files]
     tabs = st.tabs(tab_names)
 
     for idx, file_path in enumerate(st.session_state.open_files):
         with tabs[idx]:
+            # Load file content from disk on first open; afterwards use the cached version.
             if file_path not in st.session_state.files_content:
                 st.session_state.files_content[file_path] = fm.read_file(Path(file_path))
 
             file_language = LANG_MAP.get(Path(file_path).suffix, "text")
 
+            # Ace editor widget — auto_update sends content to Python on each keystroke.
             code = st_ace.st_ace(
                 value=st.session_state.files_content[file_path],
                 language=file_language,
@@ -124,6 +147,7 @@ def render_editor():
                 height=400,
             )
 
+            # Keep the in-memory cache in sync with what the editor currently shows.
             if code != st.session_state.files_content[file_path]:
                 st.session_state.files_content[file_path] = code
 
@@ -137,6 +161,7 @@ def render_editor():
                 if st.button("Close File", key=f"close_{file_path}"):
                     st.session_state.open_files.remove(file_path)
                     st.session_state.files_content.pop(file_path, None)
+                    # Switch active_file to the next available tab.
                     st.session_state.active_file = (
                         st.session_state.open_files[0]
                         if st.session_state.open_files else None
@@ -158,6 +183,7 @@ def render_editor():
 
             st.subheader("Execution Output")
 
+            # Green on exit code 0 (success), red on anything else (error/crash).
             if result["return_code"] == 0:
                 st.success(f"Exit code: {result['return_code']}")
             else:

frontend/sidebar.py

@@ -1,10 +1,15 @@
+"""Sidebar — navigation radio, logo, and the workspace file explorer."""
+
 import streamlit as st
 from streamlit_arborist import tree_view
 from pathlib import Path
 from backend.managers.file_manager import FileManager
 
+# Shared FileManager instance for all sidebar operations.
 fm = FileManager()
 
+# Maps file extensions (and special keys "folder"/"default") to display emojis
+# shown next to each entry in the file tree.
 SUFFIX_MAP = {
     ".py": "🐍",     # Python
     ".js": "🟨",     # JavaScript (Gelbes Quadrat/Logo)
@@ -29,11 +34,13 @@ SUFFIX_MAP = {
 
 @st.dialog("Delete Folder")
 def _delete_folder_dialog(folder_rel: str, folder_name: str):
+    """Confirmation dialog before permanently deleting a folder and its contents."""
     st.warning(f"Delete **{folder_name}** and all its contents? This cannot be undone.")
     col1, col2 = st.columns(2)
     with col1:
         if st.button("Delete", type="primary", use_container_width=True):
             if fm.delete_folder(folder_rel):
+                # Clear the selected-folder state so the action bar disappears.
                 st.session_state.selected_folder = None
                 st.session_state.selected_folder_rel = None
                 st.rerun()
@@ -46,6 +53,7 @@ def _delete_folder_dialog(folder_rel: str, folder_name: str):
 
 @st.dialog("Add File")
 def _add_file_dialog(parent_path: str = ""):
+    """Dialog for creating a new file inside parent_path (or workspace root if empty)."""
     name = st.text_input("File name:", placeholder="e.g. script.py")
     col1, col2 = st.columns(2)
     with col1:
@@ -64,6 +72,7 @@ def _add_file_dialog(parent_path: str = ""):
 
 @st.dialog("Add Folder")
 def _add_folder_dialog(parent_path: str = ""):
+    """Dialog for creating a new sub-folder inside parent_path (or workspace root if empty)."""
     name = st.text_input("Folder name:", placeholder="e.g. utils")
     col1, col2 = st.columns(2)
     with col1:
@@ -83,19 +92,33 @@ def _add_folder_dialog(parent_path: str = ""):
 # ── File tree ─────────────────────────────────────────────────────────────────
 
 def build_arborist_tree(tree, parent_path=Path()):
+    """Convert the FileManager dict tree into the node format expected by streamlit-arborist.
+
+    Folders become nodes with a "children" list; files become leaf nodes
+    with an emoji prefix derived from their extension.
+
+    Args:
+        tree: Nested dict from FileManager.get_file_tree()
+        parent_path: Accumulates the relative path while recursing.
+
+    Returns:
+        List of node dicts accepted by tree_view().
+    """
     nodes = []
 
     for name, content in sorted(tree.items()):
         full_path = parent_path / name
-        node_id = str(full_path.as_posix())
+        node_id = str(full_path.as_posix())  # forward-slash IDs work cross-platform
 
         if isinstance(content, dict):
+            # Directory — recurse to build child nodes.
             nodes.append({
                 "id": node_id,
                 "name": f"{name}",
                 "children": build_arborist_tree(content, full_path)
             })
         else:
+            # File — pick an emoji based on extension, fall back to default.
             suffix = Path(name).suffix
             icon = SUFFIX_MAP.get(suffix, SUFFIX_MAP["default"])
 
@@ -109,6 +132,7 @@ def build_arborist_tree(tree, parent_path=Path()):
 
 
 def render_filetree_arborist(tree):
+    """Render the interactive file tree and return the currently selected node dict."""
     data = build_arborist_tree(tree)
 
     selected = tree_view(
@@ -116,7 +140,7 @@ def render_filetree_arborist(tree):
         icons={"open": "📂", "closed": "📁"},
         height=200,
         selection=None,
-        select_internal_nodes=True,
+        select_internal_nodes=True,  # allow clicking folder names, not just files
         open_by_default=False
     )
 
@@ -126,6 +150,12 @@ def render_filetree_arborist(tree):
 # ── Sidebar ───────────────────────────────────────────────────────────────────
 
 def render_sidebar():
+    """Render the full sidebar: navigation radio and workspace file explorer.
+
+    Tree click handling:
+    - Clicking a file   → appended to open_files, set as active_file
+    - Clicking a folder → stored in selected_folder so the action bar appears
+    """
     st.sidebar.title("Navigation")
 
     navigation_section = st.sidebar.container()
@@ -155,11 +185,14 @@ def render_sidebar():
                     if selected:
                         selected_path = selected.get("id")
 
+                        # Only react when the user clicks a *different* node to
+                        # avoid re-running on every Streamlit rerender.
                         if st.session_state.last_selected != selected_path:
                             st.session_state.last_selected = selected_path
                             abs_path = fm.base_path / selected_path
 
                             if abs_path.is_file():
+                                # Open the file in the editor.
                                 st.session_state.selected_folder = None
                                 st.session_state.selected_folder_rel = None
                                 file_str = str(abs_path)
@@ -169,11 +202,13 @@ def render_sidebar():
                                 st.rerun()
 
                             elif abs_path.is_dir():
+                                # Select the folder so its action bar appears below.
                                 st.session_state.selected_folder = str(abs_path)
                                 st.session_state.selected_folder_rel = selected_path
                                 st.rerun()
 
-            # Folder actions — rendered outside the selection block so they persist across reruns
+            # Folder action bar — rendered unconditionally outside the selection
+            # block so it persists across reruns even when no new click happens.
             if st.session_state.get("selected_folder"):
                 folder_name = Path(st.session_state.selected_folder).name
                 folder_rel  = st.session_state.selected_folder_rel
@@ -188,6 +223,7 @@ def render_sidebar():
                         _delete_folder_dialog(folder_rel, folder_name)
 
         with add_more:
+            # Popover for workspace-root actions (not tied to any selected folder).
             with st.popover("⚙️ Explorer Options", key="popover_options", use_container_width=True):
                 if st.button("Add File", key="btn_add_file", use_container_width=True):
                     _add_file_dialog("")

frontend/state.py

@@ -1,12 +1,21 @@
+"""Centralised session-state initialisation for the Streamlit app.
+
+All keys used throughout the app are declared here with their default values.
+Calling init_state() at the top of app.py ensures every key exists before any
+page tries to read it, preventing KeyError on the first load.
+"""
+
 import streamlit as st
 from backend.managers.chat_manager import ChatManager
 
 
 def init_state():
     # Sidebar state initialization
+    # last_selected tracks the previously clicked tree node to detect new clicks
     if "last_selected" not in st.session_state:
         st.session_state.last_selected = None
 
+    # Absolute path and workspace-relative path of the currently highlighted folder
     if "selected_folder" not in st.session_state:
         st.session_state.selected_folder = None
 
@@ -14,19 +23,24 @@ def init_state():
         st.session_state.selected_folder_rel = None
 
     # Chat manager (persists across reruns)
+    # ChatManager keeps the full conversation history in memory across reruns
     if "chat_manager" not in st.session_state:
         st.session_state.chat_manager = ChatManager()
 
     # Editor state initialization
+    # List of absolute file paths that are currently open as tabs
     if "open_files" not in st.session_state:
         st.session_state.open_files = []
 
+    # Dict mapping file path → current editor content (may be unsaved)
     if "files_content" not in st.session_state:
         st.session_state.files_content = {}
 
+    # Absolute path of the file whose tab is currently active
     if "active_file" not in st.session_state:
         st.session_state.active_file = None
 
+    # Index of the active tab (used by st.tabs)
     if "active_tab" not in st.session_state:
         st.session_state.active_tab = 0
 
@@ -36,26 +50,33 @@ def init_state():
     if "code_suggestions" not in st.session_state:
         st.session_state.code_suggestions = []
 
+    # Output dict from the last code run: {stdout, stderr, return_code}
     if "code_execution_output" not in st.session_state:
         st.session_state.code_execution_output = ""
 
     # Chat state initialization
+    # Flat list of {"role": ..., "content": ...} dicts shown as chat bubbles
     if "chat_history" not in st.session_state:
         st.session_state.chat_history = []
 
     # Agent Mode state
+    # Whether the UI is currently in Agent Mode (vs normal chat)
     if "agent_mode" not in st.session_state:
         st.session_state.agent_mode = False
 
+    # The live CodingAgent instance while a task is running
     if "coding_agent" not in st.session_state:
         st.session_state.coding_agent = None
 
+    # Current status of the agent: "idle" | "waiting_approval" | "done"
     if "agent_status" not in st.session_state:
         st.session_state.agent_status = "idle"
 
+    # List of completed steps shown in the collapsible Agent Log
     if "agent_log" not in st.session_state:
         st.session_state.agent_log = []
 
+    # The action the agent proposed but has not yet been approved or rejected
     if "agent_pending_action" not in st.session_state:
         st.session_state.agent_pending_action = None