Claude Code at the Senior Level: Patterns I Only Unlocked After Ten Months

Everyone can run Claude Code on day one. Not everyone uses it well on day three hundred. The patterns that compound are rarely the ones you learn first.

Pattern 1: Verification Contracts

Every task I hand to Claude Code ships with a verification contract: the exact command or test that proves the work is done. Not a description of done. An executable. The agent reads it before starting, runs it before ending, and shows the output. This single practice cut my rework rate in half.

Pattern 2: Narrow Scope, Wide Context

Load the whole repo as context. Scope the task to one file. Load the whole team CLAUDE.md. Scope the diff to one function. Wide context plus narrow scope produces code that fits the codebase. Narrow context plus wide scope produces the opposite.

Pattern 3: Pre-commit Hooks as Agent Discipline

My pre-commit hook runs a grep for forbidden patterns (console.log, TODO without a ticket, em dashes in prose, print statements). The agent learns the house rules faster than any prompt can teach.

.git/hooks/pre-commit
grep -rn 'TODO' src/ | grep -v 'TODO(' && exit 1
grep -rn 'console.log' src/ && exit 1

Pattern 4: Model Routing by Task, Not by Vibe

Haiku for file finding, reading, and small edits. Sonnet for implementation. Opus for architecture and security reviews. The routing is not vibes. It is a table pinned to the wall.

Pattern 5: Fresh Sessions for Fresh Problems

Long sessions accumulate context that bleeds into unrelated tasks. I now start a fresh session for every orthogonal problem. The cost is twenty seconds. The benefit is no hidden assumptions.

Pattern 6: The Undo Rehearsal

Before any multi-file change, I rehearse the undo. Usually a git tag. Sometimes a branch. Once a database snapshot. If the undo is not rehearsed, I do not run the change.

What I Would Tell April Me

Slow down. Write CLAUDE.md first. Tag before big runs. Verify with commands, not vibes. Start fresh often. Do not chase new features of the tool; master the ones that already work.

Senior-level Claude Code is ninety percent discipline and ten percent tooling. The Anthropic engineering blog keeps reinforcing this.