Csharp on Tokenise

Pin legacy behaviour before an agent refactors it, then grade the tests with mutation testing

Fri, 09 Oct 2026 11:06:00 +0000

You’re about to refactor a shipping calculator that nobody on the team wrote and nobody wants to touch. You ask an agent for tests first, it hands back four neat ones, they pass, and you start the refactor with a green light that means almost nothing. Four tests can’t pin forty decisions.

Moving to Sonnet 5.5? Four requests that now return a 400

Mon, 05 Oct 2026 23:18:00 +0000

Claude Sonnet 5.5 shipped on 28 September at the same price as Sonnet 5: $2 per million input tokens and $10 per million output. Anthropic says it runs 30% or more faster. If you call the API directly, though, changing claude-sonnet-5 to claude-sonnet-5-5 isn’t the whole migration. Several requests that worked yesterday now fail.

Stop telling your AI agent to 'fix the bug'. Make it reproduce it first

Wed, 30 Sep 2026 12:00:00 +0000

“Fix the login bug” is a terrible prompt for a coding agent, and a frustrating one to debug when it goes wrong. The agent will read some code, find something plausible, change it, and tell you it’s fixed. Sometimes it is. Sometimes it has patched a bug you didn’t have.