When the Same Model Has a Different Name Everywhere — Designing a Cross-Provider Model Identity Resolver for Claude
Now that Fable 5 is available on the API, Bedrock, and Vertex at once, the same model carries a different identifier on each. Here is how to untangle hardcoded model strings with a small resolver that maps logical names to physical IDs, carries capability flags, and verifies identifiers at startup.
When Claude API Prompt Caching Quietly Stops Hitting in Production — Field Notes on TTL and Measured Savings
Prompt caching works beautifully the day you ship it, then quietly stops hitting in production. The five things that break the prefix, how to choose between 5-minute and 1-hour TTL, and how to measure real savings from usage instead of guessing.
Claude API Streaming Breaks the "Everything Arrives" Assumption — Field Notes on Recovering from Partial Failure
Once concurrency climbs, Claude API streams disconnect mid-response, replay events, and emit half-finished tool arguments. Treating partial failure as the norm rather than an anomaly, here is how I rebuilt the implementation and monitoring to recover quietly.
Putting a Ceiling on the pause_turn Loop: Running Long Server Tools Safely Unattended
A production design for continuing pause_turn safely in unattended runs, where long server tools like web_search and code execution are involved. Covers branching all four stop_reason values in one loop, capping continuations and wall-clock time, and accumulating usage across paused segments.
When Claude Code Still Writes Stale Code With Context7 Installed — Verifying the Injection Actually Worked
You installed Context7 MCP, yet Claude returns code against a deprecated API. Most of the time the documentation injection silently no-ops. Here are field notes on a hook that detects misses, pinning doc versions, and a harness that checks generated code every time.
Reserving Priority Capacity for User Traffic with service_tier
If you pay for Priority Tier but your user-facing responses still slow down at peak, the culprit is often your own background jobs eating the priority pool. Here is how to read service_tier, prove the contention, and isolate background work.
Putting Cloudflare AI Gateway in Front of Claude Made the Numbers I Needed Disappear — Field Notes on Instrumentation
After putting Cloudflare AI Gateway in front of Claude API, here is where I actually got stung — cost attribution, semantic-cache false hits, fallback quietly lowering quality, and budgets that don't really stop anything — with the code I used to fix each.
When Your Claude × Playwright Browser Agent Fails While Reporting Success — Verifying Actions and Catching UI Drift
A vision-driven Claude + Playwright browser agent fails quietly: it reports success while nothing actually changed. Here is how to stop trusting self-reports, verify each action against the goal, and detect UI drift before it breaks you.
When Your Claude API Response Cache Returns Stale Answers and Near-Miss Wrong Ones — Field Notes on Freshness and False-Hit Suppression
A Claude API response cache improves latency and cost immediately, but the problems that hurt in production are not average hit rate — they are stale hits and semantic false hits. Here is the key design, freshness management, false-hit suppression, and observability that keep a cache honest.
When Claude API Extracts the Wrong Value With Full Confidence — Designing the Verification Layer
When you extract invoices or contracts with Claude API, the scariest failure isn't an exception — it's plausible-but-wrong JSON. Here is how I build a verification layer that catches silent extraction errors with schema checks, arithmetic reconciliation, and dual-extraction agreement, in TypeScript.
Making the Numbers Add Up in a Multi-Tenant Claude API SaaS — Field Notes on Isolation and Cost Attribution
The first thing that breaks when you make a Claude API SaaS multi-tenant is the month-end reconciliation. Here are field notes on a single metering chokepoint, atomic counters, reconciling against Anthropic's bill, and proving tenant isolation with adversarial tests — with production TypeScript.
Keep a Decision Rationale Ledger for Autonomous Agents — So You Can Explain 'Why' Later
When an autonomous agent takes hard-to-reverse actions like a production deploy or a bulk delete, capture the chosen option, rejected alternatives, and assumptions in a structured ledger. Includes structured output, an append-only log, and tiering by impact.