claude-code-crash-debug.md

Claude Code Crash Debug Log

Timestamp

Created: 2025-09-09 (per environment date)

Initial Setup Steps

1. Created this file using touch command first
2. Now writing initial content to establish the file
3. Will document EVERY step, thought, and action

Context

Attempting to recreate a Claude Code crash with the following stack trace:

Error: Bad substitution: codePoint?.toString
    at D (file:///Users/alexanderriccio/.nvm/versions/node/v20.19.4/lib/node_modules/@anthropic-ai/claude-code/cli.js:80:79195)
    at file:///Users/alexanderriccio/.nvm/versions/node/v20.19.4/lib/node_modules/@anthropic-ai/claude-code/cli.js:80:79854
    at Array.map (<anonymous>)
    at VX9 (file:///Users/alexanderriccio/.nvm/versions/node/v20.19.4/lib/node_modules/@anthropic-ai/claude-code/cli.js:80:78933)
    at Object.A (file:///Users/alexanderriccio/.nvm/versions/node/v20.19.4/lib/node_modules/@anthropic-ai/claude-code/cli.js:80:80018)
    at nv6 (file:///Users/alexanderriccio/.nvm/versions/node/v20.19.4/lib/node_modules/@anthropic-ai/claude-code/cli.js:1741:31727)
    at ov6 (file:///Users/alexanderriccio/.nvm/versions/node/v20.19.4/lib/node_modules/@anthropic-ai/claude-code/cli.js:1741:35696)
    at file:///Users/alexanderriccio/.nvm/versions/node/v20.19.4/lib/node_modules/@anthropic-ai/claude-code/cli.js:1741:36245
    at Array.every (<anonymous>)
    at $2B (file:///Users/alexanderriccio/.nvm/versions/node/v20.19.4/lib/node_modules/@anthropic-ai/claude-code/cli.js:1741:36183)

Error Analysis

• The error "Bad substitution: codePoint?.toString" suggests an issue with template literal substitution
• The codePoint?.toString syntax indicates optional chaining with a toString() call
• This appears to be happening during string processing, possibly with special characters or Unicode handling
• The error occurs in minified/bundled code (cli.js) making it harder to debug
• The stack trace shows it's going through Array.map and Array.every operations

Environment Details

• Node version: v20.19.4 (from the path in stack trace)
• Claude Code installation path: /Users/alexanderriccio/.nvm/versions/node/v20.19.4/lib/node_modules/@anthropic-ai/claude-code/
• Working directory: /Users/alexanderriccio/Documents/GitHub/COVID-CO2-tracker
• Platform: darwin (macOS)
• Is git repo: Yes
• Current branch: main

Current Status

WAITING FOR TOOL CALL TO RECREATE

Steps Taken So Far

1. Received initial crash report from user
2. Analyzed stack trace to understand error pattern
3. User requested to write everything to file for recovery
4. Created this debug file using touch command
5. Writing initial debug information to file
6. Now waiting for the specific tool call that causes the crash

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Tool Call Recreation Log

(Will be updated with EVERY single step, thought, and action)

Pre-Recreation Checklist

• Receive the tool call from user
• Document the exact tool call format
• Note any special characters, escape sequences, or unusual patterns
• Document my interpretation of what the tool call should do
• Save this file before attempting execution
• Execute the tool call
• (If crash occurs, this log will remain for debugging)

TOOL CALL RECEIVED!

Time: 2025-09-09 (just received)

The Exact Tool Call That Causes Crash

⏺ Bash(cat > /tmp/debug-detect.ts << 'EOF'
      const text = "This has an emoji in text 📝";

      console.log("Text length:", text.length);
      console.log("Checking each character:");

      let index = 0;
      for (const char of text) {
        const codePoint = char.codePointAt(0);
        console.log(`Index ${index}: '${char}' codepoint: ${codePoint?.toString(16) || 'undefined'}`);
        index++;
      }
      EOF

      npx ts-node /tmp/debug-detect.ts)
  ⎿  Waiting…

· Testing the implementation… (esc to interrupt · ctrl+t to show todos · 8s · ⚒ 3.1k tokens)
  ⎿  Next: Document the emoji checker implementation

Analysis of the Tool Call

Key Observations:

1. Tool Type: Bash command execution
2. Command Structure: Uses heredoc (cat > file << 'EOF') to create a TypeScript file
3. Special Characters Present:
   • Emoji: 📝 (memo/note emoji)
   • Template literals with backticks
   • Optional chaining: codePoint?.toString(16)
   • String interpolation: ${codePoint?.toString(16) || 'undefined'}

THE SMOKING GUN:

• The error message is "Bad substitution: codePoint?.toString"
• The code contains: ${codePoint?.toString(16) || 'undefined'}
• This is INSIDE a template literal in the TypeScript code
• The crash likely occurs when Claude Code tries to process this template literal

Potential Issue Points:

1. The combination of heredoc + template literals might confuse the parser
2. The codePoint?.toString within ${} might be interpreted as shell substitution
3. The emoji character (📝) might trigger special Unicode handling
4. The nested template literal structure could cause parsing issues

Context from UI:

• The tool was in a "Waiting..." state
• It was part of "Testing the implementation"
• There was a todo item: "Document the emoji checker implementation"
• The UI showed it was using 3.1k tokens

Recreation Plan

Step 1: Document Current State

Writing all information to this file before attempting recreation.

Step 2: Prepare the Exact Command

The command I will execute is a Bash command that:

1. Creates a TypeScript file at /tmp/debug-detect.ts using heredoc
2. The file contains code to check Unicode codepoints of characters
3. Includes an emoji character (📝)
4. Uses template literals with optional chaining
5. Then runs the file with npx ts-node

Step 3: Expected Behavior (if no crash)

The command should:

1. Create the TypeScript file
2. Execute it with ts-node
3. Output character analysis including the emoji

Step 4: Likely Crash Point

Based on the error "Bad substitution: codePoint?.toString", the crash will likely occur:

• When Claude Code parses the command string
• Specifically when it encounters ${codePoint?.toString(16)}
• The parser might incorrectly interpret this as a shell substitution rather than JavaScript template literal syntax

ABOUT TO EXECUTE THE CRASH-INDUCING COMMAND

Pre-execution Checklist:

• Received the tool call from user
• Documented the exact tool call format
• Noted special characters (emoji 📝, template literals, optional chaining)
• Documented interpretation (TypeScript code to check Unicode points)
• Saving this file before attempting execution
• Execute the tool call (NEXT STEP)

Saving file state... DONE

ATTEMPTING CRASH RECREATION NOW

The Exact Command Being Executed:

cat > /tmp/debug-detect.ts << 'EOF'
const text = "This has an emoji in text 📝";

console.log("Text length:", text.length);
console.log("Checking each character:");

let index = 0;
for (const char of text) {
  const codePoint = char.codePointAt(0);
  console.log(`Index ${index}: '${char}' codepoint: ${codePoint?.toString(16) || 'undefined'}`);
  index++;
}
EOF

npx ts-node /tmp/debug-detect.ts

Critical Elements That May Trigger Crash:

1. The template literal with optional chaining: ${codePoint?.toString(16)}
2. The emoji character: 📝
3. The heredoc syntax: << 'EOF'
4. The combination of all three

Hypothesis:

Claude Code's parser is misinterpreting the ${codePoint?.toString(16)} as a bash variable substitution rather than a JavaScript template literal, causing the "Bad substitution" error.

EXECUTING NOW...

If Claude Code crashes after this point, check this file for all the debugging information!

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