Learn Claude — Part 7: Coding with Claude & Claude Code

Coding is Claude's most celebrated strength, and it comes in two distinct modes: chat-assisted coding (you drive, Claude advises) and agentic coding with Claude Code (Claude drives, you review). Professionals use both — and know when each applies.

Mode 1: Chat-assisted coding, done properly

The four core moves — generate, debug, explain, review — you likely know. What separates effective use is how:

Debugging: give the full picture. The highest-value debugging prompt contains three things: the complete error message (or a screenshot — vision works), the relevant code, and what you already tried. That last one prevents Claude from suggesting the fix you've already ruled out.

State your environment, always. "React 18 + TypeScript, no external libraries, must support older browsers" transforms answer quality. Put your permanent stack in Project instructions (Part 6) so you never repeat it.

Review with a rubric. "Review this" gets generic praise. "Review for: security issues, error handling gaps, and anything that will confuse the next developer — cite line numbers" gets a real review. Then run the reversal from Part 3: "now argue why your suggested refactor might be a mistake."

Learn, don't just paste. The prompt "add comments explaining the why of each block, and tell me one concept I should study" turns every answer into a lesson. Beginners: combined with Artifacts (Part 5), you can build and understand real projects from day one.

Verify by execution. Claude's code is good but not guaranteed. The loop is: run it → paste any error back → repeat. Fast, and honest.

Mode 2: Claude Code — the agentic shift

Chat coding has a ceiling: you are the hands, copying snippets file by file. Claude Code removes it. It's a tool from Anthropic that runs in your terminal (with desktop and mobile apps too, and IDE integrations) with direct access to your project. Given a task, it:

1. Explores your codebase — reads files, understands structure

2. Plans the change and shows you the plan

3. Executes — edits multiple files, runs commands and tests

4. Self-corrects — sees failing tests and fixes its own work

5. Reports — you review the diff, like a pull request from a colleague

The difference in kind: "add password-reset flow to this app" is one instruction, not forty copy-pastes.

Getting started: requires a paid Claude plan or API access. Install via npm (npm install -g @anthropic-ai/claude-code), run claude inside your repo. Current setup details: docs.claude.com/en/docs/claude-code.

Working professionally with Claude Code

Write a CLAUDE.md. A file in your repo root that Claude Code reads automatically — your Project instructions, but for code: build commands, conventions, architecture notes, "never touch X" warnings. Ten minutes writing it pays back on every session.

Plan before executing. For non-trivial tasks, ask for a plan first and approve it before edits begin. Steering a plan is cheap; unwinding a wrong implementation is not.

Scope tasks like tickets. "Fix the timezone bug in report generation" succeeds. "Make the app better" wanders. If you couldn't hand it to a junior dev as written, don't hand it to the agent.

Review diffs like a reviewer, not a spectator. You remain the engineer of record. Agentic speed plus rubber-stamp review is how subtle bugs ship. Tests, permissions on risky commands, and git are your safety rails — commit before big agent sessions.

Know the escalation ladder. Quick question → chat. Single-file snippet → chat + Artifact. Multi-file feature, refactor, test-suite work → Claude Code. Choosing the right rung is the skill.

A realistic session

you:    (in repo) claude
you:    Our /export endpoint times out on large datasets.
        Find the cause and propose a fix — plan first.
claude: [reads code] The endpoint loads all rows into memory...
        Plan: stream results, add pagination, update 2 tests. Proceed?
you:    Proceed.
claude: [edits 3 files, runs tests, one fails, fixes it]
        Done — diff ready for review.

That's the shape of modern development: you supply judgment and intent; the agent supplies throughput.

Exercise

Non-developers: in chat, build a small web page in an Artifact, then ask Claude to explain every block and quiz you on it. Developers: install Claude Code on a side project, write a minimal CLAUDE.md, and delegate one well-scoped ticket — plan-first. Review the diff critically. Form your own opinion of where the ceiling is.

Next up

Part 8, the finale: the API, automation, and the habits that make all of this durable — the full professional's toolkit.