From the Inside Claude Code: The Claude Code Ecosystem architecture map
Plugins are fully independent and deploy on their own
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No first-party plugin imports another; every import resolves within a plugin's own directory. Each plugin ships as its own marketplace entry, so any plugin can change, version and release without coordinating with the others.
The marketplace entry is the only shared contract. Keeping cross-plugin reuse out (or in an explicitly versioned package) preserves this.
The trail
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- Session Store is a single point of failure for 7 modules, from the clients to the package exports
- Optional SessionStore methods raise instead of being absent, so a change in Types reaches 13 modules
- Every defence against hidden instructions rests on one small sanitizer
- Interrupt and other control calls stall when nobody is reading messages
- Day 1: start with marketplace.json, the contract everything else serves
- Day 2: follow the install path from Claude Code into one plugin
- Session Store is shared by three groups of code, so a change to it reaches all of them
- Every SDK module imports its exceptions from one file, _errors.py
- can_use_tool is a ready gate seam with subagent provenance
- PR-controlled agent config is restored from the base branch before Claude starts
- Start with the gate order in the Run Orchestrator
- Then follow untrusted text from GitHub into the prompt
- The action and the base action share an untyped prompt-file contract
- The transport is the only translator from options to Claude Code CLI flags
- Both public entry points share one control-protocol engine
- Learn issue automation as one loop from GitHub event back to GitHub
- The gh.sh wrapper is the safety contract both Claude jobs rest on
- The triage and dedupe agents are boxed in identity, tools and network
- Claude jobs reach GitHub only through a read-only wrapper and event-bound writes
- Day 3: the chat-channel flow shows the only long-running code
- Day 4: CI keeps the catalogue honest and current
- Public API code reaches straight into Session Store instead of going through a session entry point
- A failed SessionStore append is retried, then dropped; mirror_error is the only signal
- Channel messages carry sender identity, giving the session provenance
- CI already gates external plugins with an agent and reverts on failure
- Sessions copies the CLI's folder-naming hash, and 6 modules depend on that copy
- Spend and run length are bounded at the transport
- Tag mode gives Claude a narrow, workspace-bound tool list
- Skip post-run reporting and branch plumbing at first
- Command-line construction is hardened against argument injection
- Tool permission requests fail closed
- Skip the engine, mods and examples when the goal is issue automation
- Lifecycle timeouts are restated outside their single source of truth
- The duplicate comment script is pinned to the upstream repository
- Every agent-driven closure has a human override before it happens
- Skip for now: config-only integrations, CI plumbing and single-file plugins
- Key vocabulary: marketplace entry, plugin, channel, pairing, permission relay, SHA bump
- External-PR workflows never execute contributor code
- Channel servers keep bot tokens owner-only and refuse injected pairing requests