Claude Code Source Dissection

Setup

This skill requires the Claude Code source extracted from its sourcemap. To obtain it:

1. npm pack @anthropic-ai/claude-code → get the tarball
2. Extract cli.js.map from the tarball
3. Run the extraction script (see extract-sources.js in the repo) to restore source files

The extracted source tree should live somewhere in your project. The skill will auto-discover it by searching for restored-src/src/Tool.ts (a unique marker file).

How to use this skill

1. Locate the source root: search the project for restored-src/src/Tool.ts using Glob. The directory containing it (minus /Tool.ts) is SOURCE_ROOT. All file paths in the reference files are relative to this SOURCE_ROOT.
2. Identify the topic from the user's request
3. Read the matching reference file from references/ below
4. Read the actual source files listed in the reference — prepend SOURCE_ROOT/ to each path
5. Present your findings using the output format at the bottom

Routing Table

Topic	Reference File	Covers
Startup, init, bootstrap, state, session storage, git	references/bootstrap.md	Boot sequence, global state singleton, session JSONL, git worktree
Conversation loop, API call, streaming, retry, messages	references/engine.md	Query loop, streaming generator, retry strategies, message normalization
System prompt, CLAUDE.md, compaction, prompt cache, tokens	references/context.md	5-level prompt assembly, summarizer agent, cache strategy, token budget
Tool definition, execution, schema, deferral, Bash parser	references/tools.md	Tool interface, lazy schema, execution pipeline, ToolSearch, Bash AST
Permission, allow/deny, classifier, safety, rules	references/permissions.md	10-step pipeline, rule matching, YOLO classifier, filesystem guards
Hooks, PreToolUse, PostToolUse, lifecycle events	references/hooks.md	Hook definition, matching, execution, permission hooks
Agent, subagent, teammate, swarm, fork, multi-agent	references/agents.md	3 spawn modes, fork cache optimization, swarm backends, file mailbox
Memory, MEMORY.md, extraction, session memory	references/memory.md	3-layer memory, auto extraction, session summary, team sync
MCP, plugin, skill, marketplace, IDE bridge, UI, Ink	references/extensions.md	MCP client, plugin lifecycle, skill format, IDE bridge, Ink render engine

If the topic spans multiple areas, read the primary reference first, then follow its Neighbors section to related files.

If no topic matches, grep the source root for relevant keywords before giving up.

Output Format

Structure your response like this:

Pattern: one-line name Why it exists: 2-3 sentences on the problem it solves Data flow:

ASCII diagram showing runtime flow

Key code (from the source, simplified):

// The core abstraction, stripped to essentials

Files read: list with line numbers for critical sections How to adapt: what to keep, what to change for our project

Architecture Overview

For orientation, here's how the 9 subsystems connect:

User Input
    ↓
[bootstrap] → init, state singleton, session restore
    ↓
[engine] → query loop: message → API → stream → tool execution → continue/end
    ↓                                    ↓
[context] → prompt assembly        [tools] → validate → permission → hooks → call
    ↓           ↓                       ↓              ↓            ↓
[memory] ← compaction            [agents] ←──── [permissions] ← [hooks]
    ↑                               ↓
    └──── extraction ←────── [extensions] → MCP, plugins, skills, UI

Each reference file contains: architecture knowledge, key abstractions, reading order, file table with line counts, and neighbor cross-references.