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name: claude-code-internals description: >- This skill should be used when the user asks to "explore claude code source", "find internal features", "investigate cli.js", "check beta headers", "discover hidden settings", or mentions "minified code analysis", "anthropic-beta headers", "context management internals". context: fork

Claude Code Internals Explorer

Procedures for analyzing Claude Code's standalone binary.

Quick Start

Note: All script paths are relative to this skill's directory (where SKILL.md resides).

Delegate all binary exploration to subagent:

CopyTask tool (subagent_type: Explore)
Prompt: "Run scripts/find_installation.sh to get binary path.
        Then search for [keyword] using: strings $BINARY | grep -E '[pattern]' | head -50
        Return: version, matching lines with context (-B2 -A2)."

The subagent handles token-heavy strings output; main context receives only summarized findings.

Zero-Context Mode (Recommended)

Problem: Subagent output is recorded in session logs. Binary analysis can cause session file bloat → SIGTRAP crashes.

Solution: Write prompt to temp file, then execute via Headless CLI wrapper. Script internals are not logged; only final stdout is recorded.

Workflow

1. Write prompt to temp file (supports multiline)
2. Execute scripts/analyze-binary.sh <prompt_file> [allowed_tools]

Script Interface

The script injects BINARY_PATH automatically.

Example

Copy# Use unique ID in filename for parallel independence
PROMPT_FILE="/tmp/internals_prompt_$$.txt"

# 1. Write prompt to temp file
cat > "$PROMPT_FILE" << 'EOF'
Search the binary for beta headers.

Instructions:
1. Use: strings "$BINARY_PATH" | grep -E "anthropic-beta|20[0-9]{2}-[0-9]{2}" | head -30
2. List all matching headers with their apparent status
3. Note any patterns suggesting feature flags
EOF

# 2. Execute with tool restriction
scripts/analyze-binary.sh "$PROMPT_FILE" "Bash,Read,Glob,Grep"

# 3. Cleanup (optional - /tmp clears on reboot)
rm -f "$PROMPT_FILE"

Dynamic Prompting

The agent constructs prompts dynamically based on investigation context.

File naming convention: /tmp/internals_prompt_<unique_id>.txt

• Use $$ (PID) or UUID for parallel execution independence
• Multiple concurrent investigations won't conflict

CopyPROMPT_FILE="/tmp/internals_prompt_$(date +%s%N).txt"

cat > "$PROMPT_FILE" << 'EOF'
Investigate context management settings.
1. Search for contextWindow, warningThreshold, errorThreshold
2. Find related numeric constants (5-6 digit numbers)
3. Return: setting name, value, surrounding context
EOF

scripts/analyze-binary.sh "$PROMPT_FILE"

Tool Inheritance

Agent's tool restrictions are passed to Headless CLI via --allowedTools:

Why this works: Bash subagent executes the script as an external process. Only the script's stdout appears in session logs, not the intermediate 350K+ lines from strings.

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⚠️ Warning (Legacy Mode): If using direct subagent delegation below, subagent output is recorded in session logs. Large outputs (>1MB) can cause session file bloat, leading to SIGTRAP crashes on new Claude sessions. Always use | head -N to limit results.

Workflow

1. Delegate Binary Exploration

Call Task tool with:

• subagent_type: Explore
• prompt: Specify search target and expected output format

Example delegations:

Copy# Feature investigation
Find Claude Code binary using scripts/find_installation.sh.
Search for "anthropic-beta" using: strings $BINARY | grep -E "anthropic-beta|20[0-9]{2}-[0-9]{2}" | head -30
Return: version, matching lines (max 30).

# Settings discovery
Run find_installation.sh, then search for setting patterns:
strings $BINARY | grep -E "autoCompact|permission|default.*:" | head -50
Return: setting names and apparent default values (max 50 lines).

The subagent executes commands and returns summarized findings.

2. Subagent Search Commands (Reference)

Note: These commands are for subagent execution, not main context.

Copy# Get binary path using find_installation.sh
source scripts/find_installation.sh
# Sets: BINARY_PATH variable

# Search with context (ALWAYS limit output!)
strings "$BINARY_PATH" | grep -B2 -A2 "pattern" | head -50

# Cache for multiple searches (within subagent session)
strings "$BINARY_PATH" > /tmp/claude-strings.txt
grep "pattern1" /tmp/claude-strings.txt | head -30
grep "pattern2" /tmp/claude-strings.txt | head -30
# Remember to cleanup: rm /tmp/claude-strings.txt

3. Investigation Types

4. Analyze & Document

1. Use grep -B2 -A2 for context
2. Compare with references/known-features.md
3. Update known-features.md with new discoveries

Common Investigations

Resources

• scripts/find_installation.sh: Locate Claude Code binary
• references/search-patterns.md: Comprehensive search patterns by category
• references/known-features.md: Baseline of known features for comparison

Resource Map

Tips

1. Cache strings: strings $BINARY_PATH > /tmp/claude-strings.txt once, grep multiple times
2. Start narrow: Specific terms before broad exploration
3. Chain searches: Find one string, search nearby for related code
4. Clean up: Remove /tmp/claude-strings.txt after investigation