Extend Claude Code changedfeatures-overview
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3232Features range from always-on context that Claude sees every session, to on-demand capabilities you or Claude can invoke, to background automation that runs on specific events. The table below shows what's available and when each one makes sense.
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34| Feature | What it does | When to use it | Example |
35| -------------------------------------------------------------- | ---------------------------------------------------------------------------------- | -------------------------------------------------------------------------------------------------------------------- | ----------------------------------------------------------------------------------------------------------------- |
36| **CLAUDE.md** | Persistent context loaded every conversation | Project conventions, "always do X" rules | "Use pnpm, not npm. Run tests before committing." |
37| **[Output style](/docs/en/output-styles)** | Instructions that set Claude's role, tone, and response format for a whole session | A voice, length, or format you want in every response, or Claude working as something other than a software engineer | The built-in Concise style for shorter responses; a custom style that answers every question with a diagram first |
38| **Skill** | Instructions, knowledge, and workflows Claude can use | Reusable content, reference docs, repeatable tasks | `/deploy` runs your deployment checklist; API docs skill with endpoint patterns |
39| **Subagent** | Isolated execution context that returns summarized results | Context isolation, parallel tasks, specialized workers | Research task that reads many files but returns only key findings |
40| **[Dynamic workflow](/docs/en/workflows)** | Script Claude writes that runs many subagents in the background | Work that outgrows a handful of subagents, or findings you want cross-checked | Audit a whole codebase, with a second set of agents verifying each finding |
41| **[Cross-session messaging](/docs/en/cross-session-messaging)** | Claude delivers a message from one of your sessions to another | Sessions you run yourself that need each other's findings mid-task | One session warns another that a change it made breaks what the other is building on |
42| **[Code intelligence](/docs/en/tools-reference#lsp-tool-behavior)** | Language-server navigation and diagnostics | Typed languages, large codebases where grep is slow or imprecise | Jump to a symbol's definition instead of reading the whole file |
43| **MCP** | Connect to external services | External data or actions | Query your database, post to Slack, control a browser |
44| **Hook** | Script, HTTP request, MCP tool call, prompt, or subagent triggered by events | Automation that must run on every matching event | Run ESLint after every file edit |
45| **[Artifact](/docs/en/artifacts)** | Publish session output as a private, interactive web page | Output you want to see or share visually rather than as terminal text | An incident timeline that updates as Claude investigates |
34| Feature | What it does | When to use it | Example |
35| - | - | - | - |
36| **CLAUDE.md** | Persistent context loaded every conversation | Project conventions, "always do X" rules | "Use pnpm, not npm. Run tests before committing." |
37| **[Output style](/docs/en/output-styles)** | Instructions that set Claude's role, tone, and response format for a whole session | A voice, length, or format you want in every response, or Claude working as something other than a software engineer | The built-in Concise style for shorter responses; a custom style that answers every question with a diagram first |
38| **Skill** | Instructions, knowledge, and workflows Claude can use | Reusable content, reference docs, repeatable tasks | `/deploy` runs your deployment checklist; API docs skill with endpoint patterns |
39| **Subagent** | Isolated execution context that returns summarized results | Context isolation, parallel tasks, specialized workers | Research task that reads many files but returns only key findings |
40| **[Dynamic workflow](/docs/en/workflows)** | Script Claude writes that runs many subagents in the background | Work that outgrows a handful of subagents, or findings you want cross-checked | Audit a whole codebase, with a second set of agents verifying each finding |
41| **[Cross-session messaging](/docs/en/cross-session-messaging)** | Claude delivers a message from one of your sessions to another | Sessions you run yourself that need each other's findings mid-task | One session warns another that a change it made breaks what the other is building on |
42| **[Code intelligence](/docs/en/tools-reference#lsp-tool-behavior)** | Language-server navigation and diagnostics | Typed languages, large codebases where grep is slow or imprecise | Jump to a symbol's definition instead of reading the whole file |
43| **MCP** | Connect to external services | External data or actions | Query your database, post to Slack, control a browser |
44| **Hook** | Script, HTTP request, MCP tool call, prompt, or subagent triggered by events | Automation that must run on every matching event | Run ESLint after every file edit |
45| **[Artifact](/docs/en/artifacts)** | Publish session output as a private, interactive web page | Output you want to see or share visually rather than as terminal text | An incident timeline that updates as Claude investigates |
4646
4747**[Plugins](/docs/en/plugins/overview)** are the packaging layer. A plugin bundles skills, hooks, subagents, and MCP servers into a single installable unit. Plugin skills are namespaced (like `/my-plugin:review`) so multiple plugins can coexist. Use plugins when you want to reuse the same setup across multiple repositories or distribute to others via a **[marketplace](/docs/en/plugins/overview)**.
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5050
5151You don't need to configure everything up front. Each feature has a recognizable trigger, and most teams add them in roughly this order:
5252
53| Trigger | Add |
54| :------------------------------------------------------------------------------- | :------------------------------------------------------------------------------------ |
55| Claude gets a convention or command wrong twice | Add it to [CLAUDE.md](/docs/en/memory) |
56| You keep asking Claude to be shorter, explain more, or answer in the same format | Set an [output style](/docs/en/output-styles) |
57| You keep typing the same prompt to start a task | Save it as a user-invocable [skill](/docs/en/skills) |
58| You paste the same playbook or multi-step procedure into chat for the third time | Capture it as a [skill](/docs/en/skills) |
59| You keep copying data from a browser tab Claude can't see | Connect that system as an [MCP server](/docs/en/mcp) |
60| Claude reads many files to find where a symbol is defined or used | Install a [code intelligence plugin](/docs/en/plugins/code-intelligence) for your language |
61| A side task floods your conversation with output you won't reference again | Route it through a [subagent](/docs/en/sub-agents) |
62| You want something to happen every time without asking | Write a [hook](/docs/en/hooks-guide) |
63| A second repository needs the same setup | Package it as a [plugin](/docs/en/plugins/overview) |
53| Trigger | Add |
54| :- | :- |
55| Claude gets a convention or command wrong twice | Add it to [CLAUDE.md](/docs/en/memory) |
56| You keep asking Claude to be shorter, explain more, or answer in the same format | Set an [output style](/docs/en/output-styles) |
57| You keep typing the same prompt to start a task | Save it as a user-invocable [skill](/docs/en/skills) |
58| You paste the same playbook or multi-step procedure into chat for the third time | Capture it as a [skill](/docs/en/skills) |
59| You keep copying data from a browser tab Claude can't see | Connect that system as an [MCP server](/docs/en/mcp) |
60| Claude reads many files to find where a symbol is defined or used | Install a [code intelligence plugin](/docs/en/plugins/code-intelligence) for your language |
61| A side task floods your conversation with output you won't reference again | Route it through a [subagent](/docs/en/sub-agents) |
62| You want something to happen every time without asking | Write a [hook](/docs/en/hooks-guide) |
63| A second repository needs the same setup | Package it as a [plugin](/docs/en/plugins/overview) |
6464
6565The same triggers tell you when to update what you already have. A repeated mistake or a recurring review comment is a CLAUDE.md edit, not a one-off correction in chat. A workflow you keep tweaking by hand is a skill that needs another revision.
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7575 * **Skills** are reusable content you can load into any context
7676 * **Subagents** are isolated workers that run separately from your main conversation
7777
78 | Aspect | Skill | Subagent |
79 | ----------------------------------------------- | ---------------------------------------------- | ---------------------------------------------------------------- |
80 | **What it is** | Reusable instructions, knowledge, or workflows | Isolated worker with its own context |
81 | **Key benefit** | Share content across contexts | Context isolation. Work happens separately, only summary returns |
82 | **[Context window](/docs/en/context-window) impact** | Adds to your main window | Uses a separate window with its own input and output tokens |
83 | **Best for** | Reference material, invocable workflows | Tasks that read many files, parallel work, specialized workers |
78 | Aspect | Skill | Subagent |
79 | - | - | - |
80 | **What it is** | Reusable instructions, knowledge, or workflows | Isolated worker with its own context |
81 | **Key benefit** | Share content across contexts | Context isolation. Work happens separately, only summary returns |
82 | **[Context window](/docs/en/context-window) impact** | Adds to your main window | Uses a separate window with its own input and output tokens |
83 | **Best for** | Reference material, invocable workflows | Tasks that read many files, parallel work, specialized workers |
8484
8585 **Skills can be reference or action.** Reference skills provide knowledge Claude uses throughout your session (like your API style guide). Action skills tell Claude to do something specific (like `/deploy` that runs your deployment workflow).
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9292 <Tab title="CLAUDE.md vs Skill">
9393 Both store instructions, but they load differently and serve different purposes.
9494
95 | Aspect | CLAUDE.md | Skill |
96 | ------------------------- | ---------------------------- | --------------------------------------- |
97 | **Loads** | Every session, automatically | On demand |
98 | **Can include files** | Yes, with `@path` imports | Yes, with `@path` imports |
99 | **Can trigger workflows** | No | Yes, with `/<name>` |
100 | **Best for** | "Always do X" rules | Reference material, invocable workflows |
95 | Aspect | CLAUDE.md | Skill |
96 | - | - | - |
97 | **Loads** | Every session, automatically | On demand |
98 | **Can include files** | Yes, with `@path` imports | Yes, with `@path` imports |
99 | **Can trigger workflows** | No | Yes, with `/<name>` |
100 | **Best for** | "Always do X" rules | Reference material, invocable workflows |
101101
102102 **Put it in CLAUDE.md** if Claude should always know it: coding conventions, build commands, project structure, "never do X" rules.
103103
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109109 <Tab title="CLAUDE.md vs Output style">
110110 Both give Claude standing instructions. CLAUDE.md carries what Claude should know, and an output style sets how Claude responds.
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112 | Aspect | CLAUDE.md | Output style |
113 | ------------- | ----------------------------------------------- | --------------------------------------------------------------------------------------------------- |
114 | **Holds** | Facts and rules about your project | A role, tone, and response format |
115 | **Switching** | Always loaded | One active at a time; [switch styles](/docs/en/output-styles#change-your-output-style) whenever you want |
116 | **Best for** | Build commands, conventions, "never do X" rules | Shorter responses, explanations alongside code, a non-engineering role |
112 | Aspect | CLAUDE.md | Output style |
113 | - | - | - |
114 | **Holds** | Facts and rules about your project | A role, tone, and response format |
115 | **Switching** | Always loaded | One active at a time; [switch styles](/docs/en/output-styles#change-your-output-style) whenever you want |
116 | **Best for** | Build commands, conventions, "never do X" rules | Shorter responses, explanations alongside code, a non-engineering role |
117117
118118 **Put it in CLAUDE.md** if it's true of the project whatever style you're in: coding conventions, build commands, project structure.
119119
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125125 <Tab title="CLAUDE.md vs Rules vs Skills">
126126 All three store instructions, but they load differently:
127127
128 | Aspect | CLAUDE.md | `.claude/rules/` | Skill |
129 | ------------ | ----------------------------------- | -------------------------------------------------- | ---------------------------------------- |
130 | **Loads** | Every session | Every session, or when matching files are opened | On demand, when invoked or relevant |
131 | **Scope** | Whole project | Can be scoped to file paths | Task-specific |
128 | Aspect | CLAUDE.md | `.claude/rules/` | Skill |
129 | - | - | - | - |
130 | **Loads** | Every session | Every session, or when matching files are opened | On demand, when invoked or relevant |
131 | **Scope** | Whole project | Can be scoped to file paths | Task-specific |
132132 | **Best for** | Core conventions and build commands | Language-specific or directory-specific guidelines | Reference material, repeatable workflows |
133133
134134 **Use CLAUDE.md** for instructions every session needs: build commands, test conventions, project architecture.
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154154 <Tab title="MCP vs Skill">
155155 MCP connects Claude to external services. Skills extend what Claude knows, including how to use those services effectively.
156156
157 | Aspect | MCP | Skill |
158 | -------------- | ---------------------------------------------------- | ------------------------------------------------------- |
159 | **What it is** | Protocol for connecting to external services | Knowledge, workflows, and reference material |
160 | **Provides** | Tools and data access | Knowledge, workflows, reference material |
161 | **Examples** | Slack integration, database queries, browser control | Code review checklist, deploy workflow, API style guide |
157 | Aspect | MCP | Skill |
158 | - | - | - |
159 | **What it is** | Protocol for connecting to external services | Knowledge, workflows, and reference material |
160 | **Provides** | Tools and data access | Knowledge, workflows, reference material |
161 | **Examples** | Slack integration, database queries, browser control | Code review checklist, deploy workflow, API style guide |
162162
163163 These solve different problems and work well together:
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170170 <Tab title="Hook vs Skill">
171171 Claude Code runs a hook at a lifecycle event; it loads a skill into context for Claude to apply.
172172
173 | Aspect | Hook | Skill |
174 | ---------------- | --------------------------------------------------------------------------------- | --------------------------------------------------------------------- |
175 | **Runs** | A shell command, HTTP request, MCP tool call, LLM prompt, or subagent | Instructions Claude reads and follows |
173 | Aspect | Hook | Skill |
174 | - | - | - |
175 | **Runs** | A shell command, HTTP request, MCP tool call, LLM prompt, or subagent | Instructions Claude reads and follows |
176176 | **Triggered by** | [Lifecycle events](/docs/en/hooks#hook-events) such as `PostToolUse` or `SessionStart` | You typing `/<name>`, or Claude matching the description to your task |
177 | **Determinism** | Always fires on its event; the trigger is guaranteed | Claude interprets the instructions; outcome can vary |
178 | **Context cost** | Zero unless the hook returns output | Description loads each session; full content loads when used |
179 | **Best for** | Linting after edits, blocking unsafe commands, logging, notifications | Workflows that need reasoning, reference material, multi-step tasks |
177 | **Determinism** | Always fires on its event; the trigger is guaranteed | Claude interprets the instructions; outcome can vary |
178 | **Context cost** | Zero unless the hook returns output | Description loads each session; full content loads when used |
179 | **Best for** | Linting after edits, blocking unsafe commands, logging, notifications | Workflows that need reasoning, reference material, multi-step tasks |
180180
181181 **Use a hook** when the action must happen the same way every time and doesn't need Claude to think. For example: format on save, reject `rm -rf /`, post a Slack message when a session ends.
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203203
204204For example, you might use CLAUDE.md for project conventions, a skill for your deployment workflow, MCP to connect to your database, and a hook to run linting after every edit. Each feature handles what it's best at.
205205
206| Pattern | How it works | Example |
207| ---------------------- | -------------------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------- |
208| **Skill + MCP** | MCP provides the connection; a skill teaches Claude how to use it well | MCP connects to your database, a skill documents your schema and query patterns |
209| **Skill + Subagent** | A skill spawns subagents for parallel work | `/audit` skill kicks off security, performance, and style subagents that work in isolated context |
210| **CLAUDE.md + Skills** | CLAUDE.md holds always-on rules; skills hold reference material loaded on demand | CLAUDE.md says "follow our API conventions," a skill contains the full API style guide |
211| **Hook + MCP** | A hook triggers external actions through MCP | Post-edit hook sends a Slack notification when Claude modifies critical files |
206| Pattern | How it works | Example |
207| - | - | - |
208| **Skill + MCP** | MCP provides the connection; a skill teaches Claude how to use it well | MCP connects to your database, a skill documents your schema and query patterns |
209| **Skill + Subagent** | A skill spawns subagents for parallel work | `/audit` skill kicks off security, performance, and style subagents that work in isolated context |
210| **CLAUDE.md + Skills** | CLAUDE.md holds always-on rules; skills hold reference material loaded on demand | CLAUDE.md says "follow our API conventions," a skill contains the full API style guide |
211| **Hook + MCP** | A hook triggers external actions through MCP | Post-edit hook sends a Slack notification when Claude modifies critical files |
212212
213213## Understand context costs
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219219Each feature has a different loading strategy and context cost:
220220
221| Feature | When it loads | What loads | Context cost |
222| --------------------- | ----------------------------------------------- | -------------------------------------------------------------------------------------------------------------------------- | -------------------------------------------- |
223| **CLAUDE.md** | Session start | Full content | Every request |
224| **Output styles** | Session start, and again when you switch styles | The active style's full instructions; nothing for the Default style | Every request |
225| **Skills** | Session start + when used | Descriptions at start, full content when used | Low (descriptions every request)\* |
226| **MCP servers** | Session start | Tool names; full schemas on demand | Low until a tool is used |
227| **Code intelligence** | After file edits and on demand | Diagnostics after edits; symbol locations on lookup | Low; reduces file reads elsewhere |
228| **Subagents** | When spawned | Fresh context with specified skills, or the parent conversation for a [fork](/docs/en/sub-agents#fork-the-current-conversation) | Isolated from main session |
229| **Hooks** | On trigger | Nothing (runs externally) | Zero, unless hook returns additional context |
221| Feature | When it loads | What loads | Context cost |
222| - | - | - | - |
223| **CLAUDE.md** | Session start | Full content | Every request |
224| **Output styles** | Session start, and again when you switch styles | The active style's full instructions; nothing for the Default style | Every request |
225| **Skills** | Session start + when used | Descriptions at start, full content when used | Low (descriptions every request)\* |
226| **MCP servers** | Session start | Tool names; full schemas on demand | Low until a tool is used |
227| **Code intelligence** | After file edits and on demand | Diagnostics after edits; symbol locations on lookup | Low; reduces file reads elsewhere |
228| **Subagents** | When spawned | Fresh context with specified skills, or the parent conversation for a [fork](/docs/en/sub-agents#fork-the-current-conversation) | Isolated from main session |
229| **Hooks** | On trigger | Nothing (runs externally) | Zero, unless hook returns additional context |
230230
231231\*By default, skill descriptions load at session start so Claude can decide when to use them. Set `disable-model-invocation: true` in a skill's frontmatter to hide it from Claude entirely until you invoke it manually. For a skill you didn't write, set [`skillOverrides`](/docs/en/skills#override-skill-visibility-from-settings) in settings to do the same without editing its file.
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