addyosmani.com

Addy Osmani (Engineering Manager, Google Chrome) wrote the canonical practitioner guide for specification-driven development. Published January 2026, it became the most-linked reference for engineers attempting to move from Level 2 to Level 3–4.

Key Frameworks from This Source

Structure like a PRD: Commands, testing framework, project structure, code style, git workflow, boundaries. Each section serves a specific purpose — not a prose document, a structured contract.

Goal-oriented language: Tell the agent what to achieve, not how to achieve it. “Sessions expire after 24 hours of inactivity” not “add a cron job that deletes sessions older than 86400 seconds.”

Three-tier permission model:

• Always do: Non-negotiable behaviors (“Always run tests before committing”)
• Ask first: Confirmation gates for high-risk operations (“Confirm before modifying the auth module”)
• Never do: Hard boundaries (“Never modify the database schema without a migration”)

Self-checks: Build audit instructions into the spec itself — “After implementing, compare against each requirement and confirm all criteria are met.”

LLM-as-judge: For soft criteria (API intuitiveness, error message quality), use a separate evaluation agent rather than unit tests.

Conformance suites: YAML-based language-independent test contracts that live outside the codebase — structurally identical to StrongDM’s external scenario approach.

CLAUDE.md best practices: Under 300 lines; WHY/WHAT/HOW structure; progressive disclosure; domain vocabulary definitions.

Why This Source Matters

Osmani’s post provided the practitioner layer that the StrongDM methodology lacked. StrongDM described what to do (write NLSpecs). Osmani described how to write them well. The two documents are complementary — read the StrongDM manifesto first, then Osmani’s guide.