feat: Add slack-quote-formatter plugin for better quoted message display

Adds a new plugin that transforms plain Slack forwarded message blocks into
visually distinctive formatted boxes using Unicode box-drawing characters.

Before:
  [Forwarded Message]
  From: Felix Klock
  Message: Here is some text...

After:
  ╔════════════════════════════════════════════════════════════════════╗
  ║  FORWARDED MESSAGE                                                 ║
  ╠════════════════════════════════════════════════════════════════════╣
  ║  From: Felix Klock                                                 ║
  ╟────────────────────────────────────────────────────────────────────╢
  ║    Here is some text...                                            ║
  ╚════════════════════════════════════════════════════════════════════╝

The plugin uses a UserPromptSubmit hook to intercept prompts containing
[Forwarded Message] blocks and reformats them for better visual distinction.

https://claude.ai/code/session_01YNRC6p2gAMSQZPX2NGK5F1

plugins/README.md

@@ -25,6 +25,7 @@ Learn more in the [official plugins documentation](https://docs.claude.com/en/do
 | [pr-review-toolkit](./pr-review-toolkit/) | Comprehensive PR review agents specializing in comments, tests, error handling, type design, code quality, and code simplification | **Command:** `/pr-review-toolkit:review-pr` - Run with optional review aspects (comments, tests, errors, types, code, simplify, all)<br>**Agents:** `comment-analyzer`, `pr-test-analyzer`, `silent-failure-hunter`, `type-design-analyzer`, `code-reviewer`, `code-simplifier` |
 | [ralph-wiggum](./ralph-wiggum/) | Interactive self-referential AI loops for iterative development. Claude works on the same task repeatedly until completion | **Commands:** `/ralph-loop`, `/cancel-ralph` - Start/stop autonomous iteration loops<br>**Hook:** Stop - Intercepts exit attempts to continue iteration |
 | [security-guidance](./security-guidance/) | Security reminder hook that warns about potential security issues when editing files | **Hook:** PreToolUse - Monitors 9 security patterns including command injection, XSS, eval usage, dangerous HTML, pickle deserialization, and os.system calls |
+| [slack-quote-formatter](./slack-quote-formatter/) | Enhances visual display of Slack forwarded and quoted messages with distinctive Unicode box formatting | **Hook:** UserPromptSubmit - Transforms `[Forwarded Message]` blocks into visually distinctive formatted boxes with clear boundaries and indentation |
 
 ## Installation
 

plugins/slack-quote-formatter/.claude-plugin/plugin.json

@@ -0,0 +1,18 @@
+{
+  "name": "slack-quote-formatter",
+  "version": "1.0.0",
+  "description": "Enhances visual display of Slack forwarded and quoted messages with distinctive formatting",
+  "author": {
+    "name": "Anthropic",
+    "email": "support@anthropic.com"
+  },
+  "license": "MIT",
+  "keywords": [
+    "slack",
+    "formatting",
+    "quotes",
+    "messages",
+    "visual"
+  ],
+  "hooks": "./hooks/hooks.json"
+}

plugins/slack-quote-formatter/README.md

@@ -0,0 +1,87 @@
+# Slack Quote Formatter
+
+Enhances the visual display of Slack forwarded and quoted messages with distinctive Unicode box formatting.
+
+## Overview
+
+When Claude Code receives messages from Slack that include forwarded messages, they typically appear as plain text:
+
+```
+[Forwarded Message]
+From: Felix Klock
+Message: I assume it would be a matter of reviewing the entries...
+```
+
+This plugin transforms these plain blocks into visually distinctive formatted quotes:
+
+```
+╔════════════════════════════════════════════════════════════════════╗
+║  FORWARDED MESSAGE                                                 ║
+╠════════════════════════════════════════════════════════════════════╣
+║  From: Felix Klock                                                 ║
+╟────────────────────────────────────────────────────────────────────╢
+║    I assume it would be a matter of reviewing the entries...       ║
+╚════════════════════════════════════════════════════════════════════╝
+```
+
+## Features
+
+- Unicode box drawing characters for clear visual boundaries
+- Distinct header section highlighting "FORWARDED MESSAGE"
+- Sender information prominently displayed
+- Message content indented for quote-like appearance
+- Automatic text wrapping for long messages
+- Handles multiple forwarded messages in a single prompt
+
+## Installation
+
+This plugin is included in the Claude Code plugins repository. To enable it:
+
+1. Add the plugin to your project's `.claude/settings.json`:
+   ```json
+   {
+     "plugins": [
+       "path/to/plugins/slack-quote-formatter"
+     ]
+   }
+   ```
+
+2. Or install via the Claude Code plugin command:
+   ```
+   /plugin add slack-quote-formatter
+   ```
+
+## How It Works
+
+The plugin registers a `UserPromptSubmit` hook that:
+
+1. Intercepts incoming prompts
+2. Detects `[Forwarded Message]` blocks in the Slack context
+3. Transforms them into formatted boxes with visual distinction
+4. Passes the transformed prompt to Claude
+
+## Configuration
+
+No configuration required. The plugin automatically activates when Slack forwarded messages are detected.
+
+## Plugin Structure
+
+```
+slack-quote-formatter/
+├── .claude-plugin/
+│   └── plugin.json          # Plugin metadata
+├── hooks/
+│   ├── hooks.json           # Hook configuration
+│   └── format_slack_quotes.py  # Transformation logic
+└── README.md
+```
+
+## Why Visual Distinction Matters
+
+When working with Slack context in Claude Code, quoted messages can easily blend into the surrounding text, making it harder to:
+
+- Identify what content is quoted vs. original
+- Understand the source of different pieces of information
+- Parse complex threads with multiple forwarded messages
+
+This plugin makes quoted content immediately recognizable, improving readability and reducing confusion.

plugins/slack-quote-formatter/hooks/format_slack_quotes.py

@@ -0,0 +1,185 @@
+#!/usr/bin/env python3
+"""
+Slack Quote Formatter - UserPromptSubmit Hook
+
+Transforms plain Slack forwarded/quoted messages into visually distinctive
+formatted blocks with Unicode box characters and better layout.
+
+Before:
+    [Forwarded Message]
+    From: John Doe
+    Message: Here is some text...
+
+After:
+    ╔═══════════════════════════════════════════════════════════╗
+    ║  FORWARDED MESSAGE                                        ║
+    ╠═══════════════════════════════════════════════════════════╣
+    ║  From: John Doe                                           ║
+    ╟───────────────────────────────────────────────────────────╢
+    ║    Here is some text...                                   ║
+    ╚═══════════════════════════════════════════════════════════╝
+"""
+
+import json
+import re
+import sys
+
+
+def format_forwarded_message(from_line: str, message_content: str) -> str:
+    """Format a single forwarded message with visual box styling."""
+
+    # Box drawing characters
+    TOP_LEFT = "╔"
+    TOP_RIGHT = "╗"
+    BOTTOM_LEFT = "╚"
+    BOTTOM_RIGHT = "╝"
+    HORIZONTAL = "═"
+    VERTICAL = "║"
+    LEFT_T = "╠"
+    RIGHT_T = "╣"
+    LEFT_LIGHT = "╟"
+    RIGHT_LIGHT = "╢"
+    LIGHT_HORIZONTAL = "─"
+
+    # Configuration
+    BOX_WIDTH = 70
+    INNER_WIDTH = BOX_WIDTH - 4  # Account for "║  " and "  ║"
+
+    def pad_line(text: str, width: int = INNER_WIDTH) -> str:
+        """Pad a line to fill the box width."""
+        if len(text) > width:
+            return text[:width]
+        return text + " " * (width - len(text))
+
+    def wrap_text(text: str, width: int) -> list:
+        """Wrap text to fit within the specified width."""
+        words = text.split()
+        lines = []
+        current_line = []
+        current_length = 0
+
+        for word in words:
+            word_len = len(word)
+            if current_length + word_len + (1 if current_line else 0) <= width:
+                current_line.append(word)
+                current_length += word_len + (1 if len(current_line) > 1 else 0)
+            else:
+                if current_line:
+                    lines.append(" ".join(current_line))
+                current_line = [word]
+                current_length = word_len
+
+        if current_line:
+            lines.append(" ".join(current_line))
+
+        return lines if lines else [""]
+
+    lines = []
+
+    # Top border with header
+    lines.append(f"{TOP_LEFT}{HORIZONTAL * (BOX_WIDTH - 2)}{TOP_RIGHT}")
+
+    # Header line
+    header = "FORWARDED MESSAGE"
+    lines.append(f"{VERTICAL}  {pad_line(header)}{VERTICAL}")
+
+    # Separator after header
+    lines.append(f"{LEFT_T}{HORIZONTAL * (BOX_WIDTH - 2)}{RIGHT_T}")
+
+    # From line
+    from_display = from_line.strip()
+    lines.append(f"{VERTICAL}  {pad_line(from_display)}{VERTICAL}")
+
+    # Light separator before message
+    lines.append(f"{LEFT_LIGHT}{LIGHT_HORIZONTAL * (BOX_WIDTH - 2)}{RIGHT_LIGHT}")
+
+    # Message content (indented and wrapped)
+    message_lines = message_content.strip().split("\n")
+    for msg_line in message_lines:
+        # Handle each line, wrapping if necessary
+        wrapped = wrap_text(msg_line, INNER_WIDTH - 2)  # Extra indent
+        for wrapped_line in wrapped:
+            indented = "  " + wrapped_line  # Add indent for quote appearance
+            lines.append(f"{VERTICAL}  {pad_line(indented)}{VERTICAL}")
+
+    # Bottom border
+    lines.append(f"{BOTTOM_LEFT}{HORIZONTAL * (BOX_WIDTH - 2)}{BOTTOM_RIGHT}")
+
+    return "\n".join(lines)
+
+
+def transform_slack_context(text: str) -> str:
+    """
+    Find and transform [Forwarded Message] blocks in the text.
+
+    Matches patterns like:
+        [Forwarded Message]
+        From: Name Here
+        Message: Content here that may span
+        multiple lines until we hit the next section
+    """
+
+    # Pattern to match forwarded message blocks
+    # This handles the common format from Slack context
+    pattern = r'\[Forwarded Message\]\s*\n\s*From:\s*([^\n]+)\s*\nMessage:\s*(.+?)(?=\n\s*\[|\n\[pnkfelix\]|\n<|\Z)'
+
+    def replace_match(match):
+        from_name = match.group(1).strip()
+        message = match.group(2).strip()
+
+        formatted = format_forwarded_message(f"From: {from_name}", message)
+        return f"\n{formatted}\n"
+
+    # Apply transformation
+    result = re.sub(pattern, replace_match, text, flags=re.DOTALL)
+
+    return result
+
+
+def main():
+    """Main entry point for the UserPromptSubmit hook."""
+    try:
+        # Read input from stdin
+        input_data = json.load(sys.stdin)
+
+        # Get the user prompt if available
+        user_prompt = input_data.get("user_prompt", "")
+
+        if not user_prompt:
+            # No prompt to transform, just pass through
+            print(json.dumps({}))
+            sys.exit(0)
+
+        # Check if there are forwarded messages to format
+        if "[Forwarded Message]" not in user_prompt:
+            # Nothing to transform
+            print(json.dumps({}))
+            sys.exit(0)
+
+        # Transform the prompt
+        transformed_prompt = transform_slack_context(user_prompt)
+
+        # If we made changes, return the transformed prompt
+        if transformed_prompt != user_prompt:
+            result = {
+                "transformedPrompt": transformed_prompt
+            }
+            print(json.dumps(result))
+        else:
+            print(json.dumps({}))
+
+    except json.JSONDecodeError:
+        # No valid JSON input, pass through
+        print(json.dumps({}))
+    except Exception as e:
+        # Log error but don't block
+        error_output = {
+            "systemMessage": f"[slack-quote-formatter] Warning: {str(e)}"
+        }
+        print(json.dumps(error_output))
+
+    sys.exit(0)
+
+
+if __name__ == "__main__":
+    main()

plugins/slack-quote-formatter/hooks/hooks.json

@@ -0,0 +1,14 @@
+{
+  "UserPromptSubmit": [
+    {
+      "matcher": ".*",
+      "hooks": [
+        {
+          "type": "command",
+          "command": "python3 ${CLAUDE_PLUGIN_ROOT}/hooks/format_slack_quotes.py",
+          "timeout": 5000
+        }
+      ]
+    }
+  ]
+}