CLAUDE

Claude Sonnet 5.5 (claude-sonnet-5-5) is Anthropic's new mid-tier model: $2/$10 per million tokens, 70.6% on Terminal-Bench 4.0, 1M context, now GA in GitHub Copilot and on Vercel AI Gateway. The pricing math, the five breaking API changes, and where it fits next to Opus 5.5 and Sonnet 5.

TypeSafe's Jev dropped its waitlist on September 27. Every verified way to call it (API, Python SDK, llm CLI, Pydantic AI, Cloudflare, Vercel, OpenRouter), the Jev + Claude Opus 5.5 coding-agent pattern driving searches, and how the open alternatives Laya, Kev, and Ollaya compare.

Three frontier launches in 48 hours repriced the agentic workhorse tier: Grok 4.7 at $2/$6 (Sep 21), Claude Opus 5.5 at $4/$20 with $0.20 cache reads (Sep 22), and GPT-6 Sol at $2/$10 with Luna at $0.10/$0.50 (Sep 22). Same-day-verified rates, honest benchmark attribution, and a decision guide.

Claude Opus 5.5 (claude-opus-5-5) is Anthropic's new default Opus: $4/$20 per million tokens, $0.20 cache reads, 1M context, thinking always on with medium default effort. Runnable TypeScript and Python SDK examples, Claude Code setup, before/after prompts, and a decision guide vs Sonnet 5, Haiku 4.5, and Fable 5.1.

Anthropic retuned Claude Fable 5's biology classifiers on August 7, cutting biology-related fallbacks by about 85% while keeping dual-use domains like virology, toxicology, and molecular design routed to Opus 5. Here is what changed, what stays blocked, and what it means for Claude Code and API users.

Andrej Karpathy gave Opus 5 the first paragraph of the Lord of the Rings, a 1M-token budget (about $10), and asked for a three.js render. Two hours and 5,500 lines of code later, the model had procedurally built a 3D world - and exposed a real weakness in how agents verify their own work.

The cheap coding tier repriced again: GPT-6 Luna opened at $0.10/$0.50 and took the floor from DeepSeek, whose V4.1-Flash cut rates to $0.15/$0.60 off-peak. Gemini 3.5 Flash and Claude Haiku 4.5 hold the hosted middle. Prices verified September 26, 2026.

Claude Mythos Preview is the model that found thousands of zero-days, and you could not buy it. Here is what it is, who got access through Project Glasswing, what it actually found, and where the model line went after it retired.

A practical guide to routing between Claude Opus 5, Sonnet 5, Haiku 4.5, GPT-5.6 Sol/Terra/Luna, and Kimi K3 based on task complexity, cost budget, and latency requirements - with decision frameworks and code examples.

MCP gives an agent live access to tools and data. Agent Skills give it packaged procedure. They solve different halves of the same problem, and the MCP working group is now standardizing how skills ship over MCP. Here is the decision rule.

Running Opus 5 through SlopCodeBench's multi-checkpoint gauntlet reveals that frontier models still degrade codebases over time. 24% strict pass rate, 5x more functions than Opus 4.8, and 93% of code lines trigger slop detectors.

Anthropic's Claude Mythos Preview found novel attacks on the HAWK post-quantum signature scheme and reduced-round AES. The HN community debates the real significance, the $100K price tag, and what it means for prompt engineering.

Tom Lockwood investigated the Bun Rust rewrite six weeks after it merged to main - 2,475 open PRs, no release tag, and costs that may far exceed the claimed $165K. We break down the evidence, Jarred Sumner's response, and what the HN community thinks.

Anthropic released Opus 5 on July 24, 2026 - same price as Opus 4.8, within 0.5% of Fable 5 on CursorBench, and the new #1 on Artificial Analysis. We break down the benchmarks, HN reaction, and what it means for every developer choosing a daily-driver model.

Claude Opus 5 launched July 24, 2026 at $5/$25 per MTok - matching Opus 4.8 pricing while delivering near-Fable 5 intelligence. Full benchmark comparison across 7 evals, pricing breakdown, and decision guide.

Anthropic launched the Claude Cookbook - 80+ practical guides from their engineers covering tool use, agent patterns, evals, and production deployment. The HN discussion debates whether cookbook resources still matter when you can just ask the AI.

Claude Opus 5 ships today with Frontier-Bench SOTA, near-Fable-5 coding at half the price, and self-verification that catches its own bugs. Here is what changed, what to migrate, and when the price-performance curve makes Opus 5 the right default.

Terence Tao published a deep mathematical digestion of the Jacobian conjecture counterexample discovered by Claude Fable 5. Here is what happened, what HN is saying, and what it means for AI-assisted research.

A Hacker News discussion blows up over LLM vocabulary quirks, with developers sharing hooks, filters, and coping mechanisms for repetitive Claude-isms.

A companion guide to the Claude Fable 5 video: what the first general-use Mythos class model is, the walkthrough beats from the review, hands-on developer takeaways, and the pricing and context specs from primary sources.