Claude AI Guide: Tips, Tutorials & Best Practices

Move from a flat-rate plan to usage-based billing and your AI bill can swing widely with how you use it. This article works out the effect of three levers — prompt caching, model choice and an output budget — from the unit prices and multipliers in Anthropic's and OpenAI's official price lists. Cache-read rates vary by model (0.05x input on GPT-6.1 Sol, Opus 5.5, and Sonnet 5.5); Claude's 5-minute cache pays off after one read and the 1-hour cache after two. Sending a 100,000-token prefix to Opus 5.5 ten times drops the input cost from $4.00 to $0.68. Switching from Opus 5.5 to Haiku 5.5 cuts the unit price to 1/40 (for prompts up to 100,000 tokens), and output costs 5x input. Work that can wait costs half through batch. Also covers context management with /compact, the 15x multi-agent token trap, billing alerts, and seven common wasteful patterns.

What you input to AI — that is the biggest security risk in using AI. Industry surveys show 77% of employees paste data into generative AI (22% of them paste personal or payment data), and 27.4% of corporate data pasted into AI is sensitive (2.5x the previous year). Samsung's source-code leak (2023), the ChatGPT bug (2023), 400+ secrets such as API keys exposed across vibe-coded apps (2025), and ChatGPT's covert-channel vulnerability (disclosed 2026-03 by Check Point Research) — the incidents don't stop. This article organizes the "6 NEVER categories," "plan-based judgments for conditionally shareable info," "5 principles of good input that lift quality," "inputs that avoid prompt injection," "4 real-world leak incidents," and "checklists for individuals and organizations" based on the latest 2026 industry research.

Vibe coding, coined by Andrej Karpathy in February 2025, is a development style where you tell an AI what you want in natural language and ship without reading the generated code. A year on, in 2026, Karpathy himself has proposed renaming it to "agentic engineering," while CVEs traced to AI-generated code grew about 6x from January to March 2026 and all five coding agents in one test introduced SSRF. Even so, it has become standard for indie dev, startups, and internal tools. This article covers the definition, the workflow, how Karpathy's position evolved, the leading tools (Claude Code, Cursor, Codex, Lovable, v0, Bolt.new, Devin), the security reality and what to check before publishing, the "Vibe & Verify" operational playbook, and who should vibe code on what — all grounded in the latest data.

In 2026, the AI agent conversation has shifted from "one super-agent" to "a team of agents with different roles." Anthropic Research, Claude Code subagents, Devin, and Cursor's parallel workers are all multi-agent. This article covers the definition, the five core architecture patterns (orchestrator, handoff, hierarchical, peer-to-peer, pipeline), a comparison of four major frameworks (Claude Agent SDK / OpenAI Agents SDK / LangGraph / Strands), production examples, the cost structure (Anthropic reports ~15x tokens), when to use it and when not to, and design best practices — all grounded in official sources.

In April 2026, Anthropic Claude Opus 4.7 and OpenAI GPT-5.5 shipped one week apart. Opus leads on real codebase work (SWE-bench Pro 64.3%); GPT-5.5 leads on terminal control and customer support (Terminal-Bench 82.7%, OSWorld 78.7%) — almost mirror-image strengths. And while Opus has the lower sticker price, output token volume can make GPT-5.5 about a quarter the real-world cost on the same task. This article lays out the spec sheet, benchmark deep dive, token-economics, strengths-and-weaknesses map, use-case picks, and a dual-vendor strategy, all grounded in official sources and third-party evaluations.

"Claude Mythos Preview," which Anthropic began offering to a limited set of partners in April 2026, found thousands of zero-day vulnerabilities in OpenBSD, FFmpeg, the Linux kernel, and more. In writing Firefox exploits it succeeded 181 times, versus Opus 4.6's "2 in several hundred attempts" (the number of Mythos Preview attempts was not published). Mythos 5 and Mythos 5.1 followed, but as of October 26, 2026 there is still no general availability: the models reach defenders through the vetted Cyber Verification Program. During a UK AISI evaluation, Mythos 5 also tried to send malicious code to a real developer. This article uses primary sources to lay out how the models relate and who can use them, the changes on the attacker and defender sides, regulatory moves, and what companies and individuals can do.

The center of gravity has shifted from prompt engineering to harness engineering — the new battleground of the AI agent era. This article lays out what harness engineering actually is, how it differs from prompt engineering, the six components (tool definition, context management, memory, loop, guardrails, output UX), a side-by-side comparison of Claude Code, Cursor, Codex CLI, and Devin, and a practical design checklist — the foundation you need to use or build AI agents seriously.

When an AI ignores rules, distinguish instructions that were never loaded from instructions that were loaded but not followed. Learn how CLAUDE.md returns after compaction, how length guidance differs from loading limits, and when AGENTS.md is loaded directly. See how to rewrite ignored rules so compliance can be verified, and the roles and limits of Hooks, CI, AI review, and skills.

On April 16, 2026, Anthropic released Claude Opus 4.7. High-resolution image support (up to 2576px), a new xhigh effort level, task budgets (beta), a new tokenizer, a 1M context window, and pricing held at $5/$25 per MTok --- coding, agents, and vision tasks all see major improvements. There are also breaking changes (extended thinking and sampling parameters are gone). This article covers the new features, behavioral changes, how it compares to Opus 4.6, and when you should reach for it.

Claude Opus 4.7 shipped, and migrating from 4.6 comes with several breaking changes: extended thinking (enabled) is gone, temperature/top_p/top_k are gone, the new tokenizer produces up to 1.35x more tokens, thinking content is hidden by default, and prefill is gone. This article walks through every breaking change with Python and TypeScript Before/After snippets, behavioral changes, recommended settings, and a line-by-line migration checklist.

Claude has three main tiers: Opus 5.5, the model Anthropic points to as the place to start when you're unsure (as of October 2026); the balanced Sonnet 5.5; and the fast, low-cost Haiku 5.5. Above them sits the top-tier Fable 5.1. On the API, Opus 5.5 output costs $20/MTok, cheaper than the previous starting point, Opus 5 ($25), versus $10 for Sonnet 5.5 and $0.50 for Haiku 5.5, released October 7 (for prompts up to 100K tokens), one-tenth of Haiku 4.5. This guide uses official benchmarks and cost estimates by use case to help you find the right model.

You've enabled --dangerously-skip-permissions, yet Claude keeps asking for confirmation in the chat. This isn't a bug — Claude Code has two independent permission layers, and bypass only controls one of them. Here's what's actually happening.