Before You Switch Models, Replay Your Own Call Shapes Against the Candidate for a Few Tokens
Change a model ID and the first production request is where a 400 shows up. Here is a small replay script that checks your own call shapes against a candidate model with max_tokens 16 before you switch.
The Skill Call That Returned Nothing — Pinning Down Name Resolution Before an Unattended Run
A skill whose name collides with a built-in terminal command may never resolve in a non-interactive session. Here is a preflight that builds the effective-name table before launch, plus the measured run where the checker itself silently skipped two entries.
A Five-Layer Preflight Design for Claude API — How I Cut Hundreds of 400/422/529 Errors to Zero
A production-tested five-layer preflight design that catches Claude API failures before the network call — schema, token budget, model capability, content policy, and spend cap — with full TypeScript implementation and one month of operational numbers.
The MCP Server I Declared Vanished from the List — Designing Config for a Namespace You Share with the Vendor
When a vendor reserves an MCP server name, your .mcp.json declaration goes quiet instead of failing. Here is the preflight check and prefix convention I use to turn that silent gap into a loud stop before an unattended run.
claude-opus-4-7 Fast Mode Retires on 7/24 — Guard It at the Capability-Pair Level
Opus 4.7 fast mode is being retired on 2026-07-24. The model ID stays valid while only the speed parameter starts failing, so model-ID audits miss it. Here's a capability-pair preflight with automatic migration.
When the Model Survives but One Parameter Expires: A Dated Deprecation Calendar for Claude API Requests
Your model ID can stay valid while a parameter you pinned quietly reaches its sunset date and takes the batch down with it. Here is a design that breaks a request into parts, gives each part its own expiry date, and catches the problem before the call goes out — with working TypeScript and real operational numbers.