API / SDK
Developer guides for the Claude API and SDKs — auth, streaming, tool use, cost control, and agent building, with working code and production-ready patterns.
I Ran 1,000 App Store Reviews Through Claude API — Here's What My Data Was Hiding
Lessons from 10+ years of indie app development and 50M+ downloads: how to use Claude API to batch-analyze App Store reviews, auto-generate improvement priorities, and fix the blind spots human reading creates.
Combining Haiku 4.5, Streaming, and Prompt Caching to Cut Costs in a Personal App — An Implementation Record
A hands-on record of combining Claude Haiku 4.5, streaming, and prompt caching to improve both cost and response speed in a personal iOS/Android app — including the mistakes made along the way.
What metadata.user_id in the Claude API Is Actually For — Designing the Abuse-Detection vs. Privacy Trade-off
The metadata.user_id field in the Messages API exists to sharpen abuse detection, but sending raw email addresses creates a privacy problem. Here is the HMAC-based stable pseudo-ID pattern I use, plus a clear set of rules for when to send it and when not to.
Bulletproof JSON Output with Claude API Prefill: A Four-Layer Defense Pattern from Indie SaaS
How I went from late-night JSON parse failures to a 99.98% parse success rate across thousands of monthly Claude API requests, and what a 1,081-sample truncation benchmark revealed about the repair code I had originally published here.
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.
Type-Safe Claude API Tool Calling with Zod: Patterns for TypeScript Developers
How to implement Claude API tool calling with TypeScript and Zod for full type safety. Covers schema-to-API conversion, runtime validation, and three common pitfalls with practical code examples.
Implementing the Saga Pattern in Claude Agent SDK — Compensating Transactions and Idempotency
A practical guide to building safe multi-step Claude Agent SDK workflows. We cover compensating transactions, idempotency keys, and partial-failure state recovery, all from patterns that have run in production.
Implementing the Transactional Outbox Pattern with Claude Agent SDK — Eliminating Lost Side Effects in Production
Stop the 'the row was inserted but the email never went out' class of bugs in Claude Agent SDK apps. A production-grade walkthrough of the Transactional Outbox pattern using Postgres and Cloudflare Queues.
Maximizing Profit Margins with Claude Haiku / Sonnet / Opus Model Switching
A complete implementation guide for dynamically routing Claude API requests to the right model based on task complexity. Includes cost calculation formulas, routing engine code, quality fallback logic, and real-world margin impact data.
The AI Sales Automation Your Team Actually Wants — Building a Multi-Agent Sales System with Claude Agent SDK
A complete guide to building a production-grade multi-agent sales automation system using Claude Agent SDK — covering lead scoring, proposal drafting, human review gates, CRM integration, and cost optimization with real code examples.
Building an Autonomous Research Agent with Claude API: Web Search, Summarization, and Knowledge Management
A complete guide to designing and implementing an autonomous research agent using Claude API and web search tools. Covers budget control, quality assurance, and knowledge base storage for production use.
Claude API × Python in Practice: Building an AI Assistant with Tool Calling and Streaming
A practical guide to combining Claude API's Tool Use and Streaming in Python. Build a working AI assistant with real tool execution, complete source code included, plus a breakdown of the tricky parts that trip up most developers.
Let Claude Diagnose Its Own Tool Errors — Building a Self-Correction Loop with the Anthropic API
Learn how to handle Tool Use failures gracefully by feeding error details back to Claude using the is_error flag, enabling self-diagnosis and automatic retry. Includes working Python code and production antipatterns to avoid.
Building an Internal Document Search Agent with Claude API — Hybrid RAG, Role-Based Access Control, and Audit Logging in Production
Build a production-grade internal document search agent using Claude API and Python. Covers hybrid RAG (pgvector + BM25), department-level RBAC via PostgreSQL RLS, and compliance-ready audit logging — with working code for each component.
Stop Writing Weekly Reports Manually — Automate Them with Claude API, GitHub, Linear, and Slack
Automate your team's weekly Slack progress reports using Claude API. This guide walks through a Node.js system that pulls GitHub and Linear data, formats it with Claude API, and posts it to Slack automatically.
The Real Cost of Claude API Extended Thinking in Production — ROI Data by Task Type
Three months of measured cost, quality, and speed data for Extended Thinking across five task categories. Learn exactly when extended thinking is worth it—and when it's not.
Building a 'Think-and-Search' AI Agent — Claude API Extended Thinking × Tool Use
A deep dive into combining Claude API Extended Thinking and Tool Use. Covers frequent errors, a complete research agent implementation in Python, plus cost estimation, timeout design, and error recovery for production use.
Claude API stop_sequences Not Working — 5 Things to Check Before You Give Up
Diagnose why your Claude API stop_sequences parameter isn't halting generation as expected. Practical breakdown of token boundaries, whitespace mismatches, Tool Use interactions, and streaming pitfalls — with copy-paste code examples.
Claude API on Bun in Production: Migration Decisions and Implementation Patterns That Actually Survive Real Traffic
A practical guide to running Claude API services on Bun in production. Covers migration triggers from Node.js, built-in SQLite/WebSocket usage, streaming optimization, and the pitfalls that only surface after deployment — with working code and measured numbers.
Implementing Usage-Based Billing with Claude API + Stripe: A Minimal Setup for Indie Developers
Learn how to measure Claude API token consumption and implement usage-based billing with Stripe Meter Events. A minimal Node.js setup that indie developers can ship in a weekend, with real gotchas from production.
7 Common Errors When Getting Started with Claude API in Python (With Fixes)
A practical troubleshooting guide covering the 7 most common errors Python developers hit when starting with the Claude API SDK — from AuthenticationError and RateLimitError to response parsing mistakes and streaming pitfalls.
Auto-Classify and Draft Gmail Replies with Claude API and Google Apps Script
A hands-on guide to building a Gmail automation system using Claude API and Google Apps Script. Automatically classify incoming emails and generate reply drafts — with copy-paste code.
Building Stateful AI Agents with Cloudflare Durable Objects and Claude API — Session Management, Context Persistence, and Scale-Out Design
A complete production guide for building stateful AI agents using Cloudflare Durable Objects and Claude API. Covers session management, context persistence, compaction strategies, and scale-out design with fully working code examples.
Building a Production-Grade Contract Review System with the Claude API — Risk Detection, Version Diffing, and Remediation Suggestions
A complete production guide for automating contract review with the Claude API: PDF parsing, risk clause detection, structured JSON output, version diffing, and remediation suggestions.
Building an Offline-Capable AI Notes App with Claude API and Local-First Sync — A Production Design with Replicache and IndexedDB
A production design guide for combining Claude API with a local-first sync engine. Walks through Replicache, IndexedDB, mutation queues, and idempotency keys with full TypeScript code.
Building a Subscription SaaS with Claude API and Stripe — A Complete 2026 Implementation Guide
An end-to-end implementation guide for shipping a subscription SaaS built on Claude API, Stripe, and Cloudflare Workers — covering checkout, webhooks, KV-backed access control, usage limits, and the production edge cases that always bite.
Claude API temperature and top_p Explained — Optimal Settings by Task with Real-World Testing
A practical guide to Claude API's temperature and top_p parameters: how they work, why temperature=0 isn't fully deterministic, and optimal settings for code generation, creative writing, RAG, and more.
Building a Cost-Optimized Multi-Provider AI Gateway with Claude API and LiteLLM — Fallback Design, A/B Testing, and Provider Migration Strategy
Learn how to build a production-grade multi-provider AI gateway centered on Claude API using LiteLLM. Covers fallback chain design, A/B testing, cost-based routing, and provider migration strategy with complete code examples.
Designing a Claude API Monthly Budget That Doesn't Blow Up — Cost Management for Solo Developers
When you embed Claude API into a side-project app, the first thing you hit is the end-of-month invoice. Here are the budgeting math, logging, caps, and retry rules I use to keep costs predictable, including the places where I tripped.
Cancelling Claude API Streams the Right Way: AbortController, Token Billing, and Connection Hygiene
I measured 100 cancelled Claude API streams to find out what actually gets billed. The drift numbers, the $18.70/month a missing close handler costs you, the proxy buffering trap, and a ledger that never loses a usage event — Node.js and Python.
Building a Budget Circuit Breaker for Claude API in Production — Auto-Halt When Daily Token Spend Exceeds Your Cap
A practical guide to enforcing daily and monthly Claude API budget caps in production. Includes copy-paste Cloudflare Workers + KV / Durable Objects code, three response strategies (halt, degrade, alert), and the operational habits that keep the breaker honest.
Calling Claude API from iOS Shortcuts: A Personal Setup for Reshaping Selected Text on the Fly
A personal setup guide for invoking the Claude API directly from iOS Shortcuts. Reshape selected text in seconds with a Cloudflare Workers proxy that keeps your API key off the device.
Stop Claude API Prompt Regressions with Golden-Dataset Testing
A complete production guide to catching the silent quality drift that hits Claude API prompts when models or prompts change — using golden datasets and LLM-as-a-Judge wired into CI.
When Your Claude API Retry Logic Made Rate Limits Worse — The Retry-After Header You Forgot to Read
If 429 errors went up after you added retry logic to your Claude API client, the cause is almost always the same: ignoring the Retry-After header and using exponential backoff without jitter. Here is how to diagnose and fix it.
Claude API Telemetry on ClickHouse: A Production Guide to Cost, Latency, and Error Analytics
Stream per-request Claude API telemetry into ClickHouse, build sub-second dashboards with materialized views, and detect cost spikes, retry loops, and silent failures with practical SQL recipes.
Fix Claude API's 'messages.X.role must alternate' in One Minute — Common 400 invalid_request_error Patterns
A pattern-by-pattern guide to fixing the 'messages.X.role must alternate' error in Claude's Messages API — covering user/assistant alternation, tool_use and tool_result pairing, and history-trimming pitfalls with working code.
Building a Production Multilingual Translation SaaS with Claude API — Glossaries, Style, and Domain Adaptation in Practice
A practical, code-first design guide for running a translation SaaS on Claude API: glossaries, style guides, domain adaptation, quality gates, and cost controls that survive real production traffic.
Building a Production Claude API Pipeline on Cloudflare Queues: Fault Tolerance, Backpressure, and Cost Control
A practical, code-first walkthrough for routing Claude API calls through Cloudflare Queues — covering producer/consumer code, retry-vs-DLQ branching, priority lanes, and token budgeting for production workloads.
Infrastructure Requirements for Claude API Deployment: Sizing, SLA, and Compliance Decisions Before Production
Your prototype works. But what does 'production-ready' actually mean? This guide walks through how to derive infrastructure requirements from traffic, SLA, and data-residency decisions — with concrete numbers and a sizing formula.
Production Semantic Cache for Claude API — Similarity Thresholds, Pollution Defense, and What to Track
A production playbook for adding a semantic cache in front of Claude API — threshold tuning, multi-tenant isolation, pollution prevention, fallbacks, how it stacks with Anthropic's prompt caching, and the metrics that actually prove it works.