https://emsenn.net/tags/agentdesign/ Recent content in AgentDesign on emsenn.net Hugo en-us Mon, 30 Mar 2026 00:00:00 +0000 https://emsenn.net/library/domains/engineering/domains/tech/domains/computing/domains/artificial-intelligence/domains/software/domains/claude-code/texts/claude-code-extension-architecture/ Mon, 30 Mar 2026 00:00:00 +0000 https://emsenn.net/library/domains/engineering/domains/tech/domains/computing/domains/artificial-intelligence/domains/software/domains/claude-code/texts/claude-code-extension-architecture/ <h1 id="extension-architecture-in-claude-code">Extension Architecture in Claude Code</h1> <p><a href="../terms/claude-code.md" class="link-internal">Claude Code</a> is extensible through four mechanisms. They operate at different levels of the system and serve different purposes. Understanding which mechanism to use for a given customization is the central design decision when configuring Claude Code for a project.</p> <h2 id="the-four-mechanisms">The four mechanisms</h2> <table> <thead> <tr> <th>Mechanism</th> <th>What it is</th> <th>When it loads</th> <th>What it affects</th> <th>Deterministic?</th> </tr> </thead> <tbody> <tr> <td><a href="../terms/claude-md.md" class="link-internal">CLAUDE.md</a></td> <td>Markdown instruction file</td> <td>Every session (root) or lazily (subdirectory)</td> <td>Model reasoning and decisions</td> <td>No — advisory</td> </tr> <tr> <td><a href="../terms/slash-commands.md" class="link-internal">Skills</a></td> <td>SKILL.md files invoked with <code>/name</code></td> <td>On demand (user or model invocation)</td> <td>Model reasoning for a specific task</td> <td>No — advisory</td> </tr> <tr> <td><a href="../terms/hooks.md" class="link-internal">Hooks</a></td> <td>Shell commands in settings.json</td> <td>On tool-call lifecycle events</td> <td>Runtime behavior before/after tool execution</td> <td>Yes — mandatory</td> </tr> <tr> <td><a href="../../../../agents/domains/model-context-protocol/terms/model-context-protocol.md" class="link-internal">MCP servers</a></td> <td>External processes exposing tools/resources</td> <td>At session start (configured servers)</td> <td>Available tool set and data sources</td> <td>Yes — tool availability is deterministic; tool invocation is model-decided</td> </tr> </tbody> </table> <h2 id="the-distinction-that-matters">The distinction that matters</h2> <p>The four mechanisms split along two axes:</p>