skill updates

skills/codebase-agent/SKILL.md

@@ -24,6 +24,42 @@ and leverage proven approaches.
 3. **Follow conventions**: Adhere to project conventions discovered in learnings
 4. **Note discoveries**: When you find something new (pattern, failure, edge case), mention it
 
+## Code Simplicity
+
+**Default to the simplest solution that works.** Resist the urge to over-engineer.
+
+### Write Less Code
+
+- Solve the actual problem, not hypothetical future problems
+- If a function is called once, consider inlining it
+- Three similar lines are better than a premature abstraction
+- Use standard library and built-ins before writing custom code
+- Delete code paths that can't happen
+
+### Keep It Flat
+
+- Use early returns and guard clauses to reduce nesting
+- Avoid callback pyramids - flatten with async/await or composition
+- One level of abstraction per function
+
+### Avoid Premature Abstraction
+
+- Don't add parameters "in case we need them later"
+- Don't create base classes until you have 2+ implementations
+- Don't add config for things that could be hardcoded
+- Don't create wrapper functions that just call another function
+
+### Trust Your Code
+
+- Don't defensively code against impossible internal states
+- Don't catch errors you can't meaningfully handle
+- Don't validate data that's already validated upstream
+- Validate at system boundaries (user input, external APIs), trust internal code
+
+### When in Doubt
+
+Ask: "What's the least code that makes this work?" Write that first. Add complexity only when reality demands it.
+
 ## Codebase Context
 
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