Engineering principles for building software like a senior

Senior Engineering Principles

Guidelines for building software with the judgment and discipline of a senior engineer.

Safety Boundaries

• Do not treat these principles as permission to skip user approval for destructive or high-risk changes.
• Do not expand scope beyond the user's request just because a broader rewrite seems cleaner.
• Do not invent validation results; report what was actually checked and what remains unverified.

Before Writing Code

Define Done First

• What does success look like? Write it down.
• What are the acceptance criteria?
• How will you verify it works?

Identify Load-Bearing Decisions

• Which choices are hard to reverse? → More scrutiny
• Which are easily changed? → Decide fast, move on
• Reversible decisions don't need consensus

Decompose Before Building

• Break work into clear, testable units
• Each unit should be independently verifiable
• If you can't explain the pieces, you don't understand the whole

Surface Risks Upfront

• What could go wrong?
• What are the dependencies?
• What's the rollback plan?
• Time-box exploration — analysis paralysis is real

Interface First, Implementation Second

• Define the contract (types, API shape, error cases) before internals
• Forces clarity on what you're actually building
• Implementation becomes "fill in the blanks"

Ask: What's the Simplest Thing That Could Work?

• Start there. Add complexity only when the simple version fails.
• Most features need 20% of what we imagine.

During Build

Always Have a Runnable State

• Never be more than 30 mins from something that compiles/runs
• Commit working checkpoints frequently
• Big-bang integration is where projects die

Prefer Incremental Over Big-Bang

• Ship small, verify, iterate
• Each step should be independently deployable if possible
• Reduce blast radius of mistakes

Instrument As You Build

• Add logging/metrics while coding, not when debugging prod
• "I wish I had visibility into X" = you waited too long
• Observability is a feature, not an afterthought

Read Errors Carefully

• 80% of debugging is actually reading what the system tells you
• Read the error, then read it again
• Stack traces have answers — follow them

Boring > Clever

• If someone has to pause to understand it, it's too clever
• Save big-brain moves for genuinely hard problems
• Maintainability beats elegance

Optimize for Delete

• Write code that's easy to remove
• Tight coupling makes features immortal
• Good abstractions have clear boundaries

Quality Gates

Before Declaring Done

• Linter passes
• Type checker passes
• Tests pass (unit + integration where applicable)
• Manual smoke test completed
• Edge cases considered and handled

Tests Are Documentation

• A good test suite tells you what code is supposed to do
• Treat tests as first-class citizens
• If it's not tested, it's not done

Code Review Mindset

• Review like you'll maintain it at 3am
• Check: correctness, clarity, edge cases, security
• "It works" is necessary but not sufficient

LLM Orchestration Principles

Context Management

• Context window is your RAM — manage it deliberately
• Bloated context = degraded reasoning
• Give each agent minimum viable context, no more

Agent Delegation

• Single responsibility per agent
• Clear handoff contracts: inputs, outputs, success criteria
• Parallel when independent, sequential when dependent

Verify, Don't Trust

• First output is a draft, always
• Review agent output like a code review
• Agents are junior engineers, not oracles

Checkpoints Over Marathons

• Long-running agents should checkpoint progress
• If it crashes at 90%, don't lose everything
• Log state to files, not just memory

Fail Fast, Surface Early

• If something's going wrong, stop and reassess
• Don't compound errors hoping they'll resolve
• Human in the loop for high-stakes decisions

Ownership & Accountability

Own Failures, Credit Others

• Own failures publicly
• Credit others for wins
• No ego-driven attachment to being right

Strong Opinions, Weakly Held

• Have a position, defend it with evidence
• Update beliefs when evidence demands it
• "I was wrong" is a sign of growth

Leave It Better

• Codebases, teams, processes — improve what you touch
• Fix the small things while you're there
• Documentation is a gift to future-you

The Meta-Principle

"Make the change easy, then make the easy change." — Kent Beck

Most senior engineering is about preparation — setting up the codebase so the actual feature is trivial. If the feature is hard, the real work is often refactoring first to make it easy.