ChatGPT-Discord-Bot/docs/DISCORD_MESSAGE_LENGTH_FIX.md

Discord Message Length Fix

Problem

Discord has a 2000 character limit for messages. The bot was displaying code execution results without properly checking the total message length, causing this error:

400 Bad Request (error code: 50035): Invalid Form Body
In content: Must be 2000 or fewer in length.

Root Cause

The code was truncating individual parts (code, output, errors) but not checking the combined total length before sending. Even with truncated parts, the message could exceed 2000 characters when combined.

Example of the Issue:

# Each part was truncated individually:
execution_display += packages  # 100 chars
execution_display += input_data[:500]  # 500 chars
execution_display += code  # 800 chars
execution_display += output[:1000]  # 1000 chars
# Total: 2400 chars → EXCEEDS LIMIT! ❌

Solution

Implemented dynamic length calculation that:

1. Calculates remaining space before adding output/errors
2. Adjusts content length based on what's already in the message
3. Final safety check ensures total message < 2000 chars

Changes Made

File: src/module/message_handler.py

Before:

# Fixed truncation without considering total length
execution_display += output[:1000]  # ❌ Doesn't consider existing content

After:

# Dynamic truncation based on remaining space
remaining = 1900 - len(execution_display)  # ✅ Calculate available space
if remaining > 100:
    execution_display += output[:remaining]
    if len(output) > remaining:
        execution_display += "\n... (output truncated)"
else:
    execution_display += "(output too long)"

# Final safety check
if len(execution_display) > 1990:
    execution_display = execution_display[:1980] + "\n...(truncated)"

Implementation Details

Two Display Scenarios:

1. Normal Display (code < 3000 chars)

execution_display = "🐍 Python Code Execution\n\n"
+ packages (if any)
+ input_data (max 500 chars)
+ code (full, up to 3000 chars)
+ output (remaining space, min 100 chars)
+ final_check (ensure < 2000 total)

2. File Attachment Display (code >= 3000 chars)

execution_display = "🐍 Python Code Execution\n\n"
+ packages (if any)
+ input_data (max 500 chars)
+ "Code: *Attached as file*"
+ output (remaining space, min 100 chars)
+ final_check (ensure < 2000 total)
# Code sent as separate .py file attachment

Smart Truncation Strategy:

1. Priority Order (most to least important):

   • Header & metadata (packages, input info)
   • Code (inline or file attachment)
   • Output/Errors (dynamically sized)

2. Space Allocation:

   • Reserve 1900 chars (100 char buffer)
   • Calculate: remaining = 1900 - len(current_content)
   • Only add output/errors if remaining > 100

3. Safety Net:

   • Final check: if len(message) > 1990
   • Hard truncate at 1980 with "...(truncated)"

Benefits

✅ No More Discord Errors: Messages never exceed 2000 char limit ✅ Smart Truncation: Prioritizes most important information ✅ Better UX: Users see as much as possible within limits ✅ Graceful Degradation: Long content becomes file attachments ✅ Clear Indicators: Shows when content is truncated

Testing

To test the fix:

1. Short code + long output: Should display inline with truncated output
2. Long code + short output: Code as file, output inline
3. Long code + long output: Code as file, output truncated
4. Very long error messages: Should truncate gracefully

Example test case:

# Generate long output
for i in range(1000):
    print(f"Line {i}: " + "x" * 100)

Before: ❌ Discord 400 error After: ✅ Displays with "(output truncated)" indicator

Related Files

• src/module/message_handler.py (Lines 400-480)
  • Fixed both normal display and file attachment display
  • Added dynamic length calculation
  • Added final safety check

Prevention

To prevent similar issues in the future:

1. Always calculate remaining space before adding variable-length content
2. Use final safety check before sending to Discord
3. Test with extreme cases (very long code, output, errors)
4. Consider file attachments for content that might exceed limits

Discord Limits Reference

• Message content: 2000 characters max
• Embed description: 4096 characters max
• Embed field value: 1024 characters max
• Code blocks: Count toward message limit

Note: We use 1990 as safe limit (10 char buffer) to account for markdown formatting and edge cases.