Level up at work

You use Claude Code every day. This page is the part fluent users tend to skip, plus what shipped this summer.

You already commit from Claude Code, build prototypes in it, run several sessions in parallel, and have opinions about which model to run. So nothing here explains what a skill or plan mode is. It covers four things you are probably not doing yet and a list of what landed in the last few months.

Delegation, the part after the pitch

You know the idea. A subagent is a separate Claude with its own context window and its own tool list, and it reports back a summary so your main session never fills with the 40 files it read. What you have not done is the mechanics, and they are small.

A subagent is one markdown file in .claude/agents/. The frontmatter is the whole configuration. model: haiku is the line that turns a 33-cent errand into a 2-cent one. tools: Read, Grep, Glob is the line that makes it physically unable to edit. Since June subagents run in the background by default, so you keep typing while they work, and they can now keep their own memory across sessions with a memory: field.

Two uses that pay off immediately. A read-only scout that finds where things live before you touch them, which is the try-now below. And a reviewer that sees only the diff and your plan, not the reasoning that produced the change, so the agent doing the work is not the one grading it.

The long version is on Delegation.

Verification as a gate, not a habit

You verify by hand every session, which is why you keep having to type “tell me how to verify it in the browser.” The structural forms are the ones you are likely not using. A Stop hook that runs your check and refuses to let the turn end until it passes. A /goal that a separate evaluator re-checks after every turn. /verify against the running app. A screenshot compared against the design through Chrome. The rule underneath all of them is that Claude shows the evidence, the test output or the screenshot, rather than asserting success.

Details on Verification.

The 33 cents

That context switch was expensive because it threw away the prompt cache. Claude Code caches the long unchanging prefix of a session, and anything that changes the prefix, a model switch included, forces a full uncached turn. The same applies to editing CLAUDE.md mid-session, which is also why those edits do not take effect until the next session. Once you know that, most of the cost advice is obvious. Switch models between tasks, not inside them. Use /btw for a side question so it never enters the history. Use /compact with instructions rather than letting auto-compact pick.

The mechanism and the numbers are on Context economics.

CLAUDE.md, trimmed

You have one. Run /doctor and it proposes cuts for anything Claude could derive from the codebase. Under 200 lines or Claude starts ignoring parts of it. Anything that only matters for some files goes in .claude/rules/ with a paths: frontmatter so it loads only when Claude touches those files. That is the whole update.

What shipped this summer

The list of things you may have missed, one line each, with the full set on What is new.

Try this now

Fifteen minutes. A read-only scout on Haiku, used for something you would otherwise do in your main session.

Create a subagent file at .claude/agents/scout.md with this frontmatter:
  name: scout
  description: Read-only investigator. Finds where things live in this codebase and reports file paths with the relevant line numbers. Never edits anything.
  tools: Read, Grep, Glob
  model: haiku
Body: "You find things and report locations. You do not fix, refactor, or suggest changes."

Then use it: "Use the scout subagent to find every place this codebase reads the feature flag FLAG_NAME and report file paths and line numbers." Show me its report.

Replace FLAG_NAME with a real flag from your repo.

How you know it worked. /agents lists scout. The report arrives in your main session as a few lines, not as 40 file reads. /context shows the files the scout opened are not in your context. /usage shows what the errand cost.

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