Research post by Anthropic's **Frontier Red Team** (authors: **Andrew Fasano**, **Marius Fleischer**, Cole McFaul, Robert Xiao, Tripp Gallagher), published on **September 29, 2026**; approximately **2,300 words**, six figures. It analyzes **GLM-5.3** from **Zhipu AI (Z.ai)**, an open-weight model, five months after the announcement of Claude Mythos Preview. **(A)** Capability: on ExploitBench (41 Chrome V8 bugs), GLM-5.3 builds a complete exploit in **50 out of 410 trials**, versus **56 out of 410** for Mythos Preview; on the internal memory-corruption benchmark, control-flow hijacking in **4%** of trials versus **6%**; Claude Opus 4.6 and GLM-5.2: 0. **(B)** Trials with human experts: a browser 0-day vulnerability chain culminating in reading the visitor's files; with **GLM-5.3-Flash**, an N-day exploit chain (CVE-2026-11645) bypassing PAC on ARM64, **20 minutes** of human attention, eight hours of compute, **$20.40** at API prices. **(C)** Safeguards: bypassed in **64%** of cases via a false red-team context, **92%** via reasoning prefill, **100%** via *abliteration* (about 2,200 GPU-hours, $4,400); the Claude models tested remain at 0%. **(D)** Recommendations: broaden defenders' access to frontier models, independent government testing. Cites NIST's **CAISI** evaluation (September 17): "the most capable open-weight model in cyber released to date," roughly four months behind the US frontier. Extends the corpus's notes on Mythos and Glasswing.
#GLM-5.3#Zhipu AI#Z.ai
Andrew Fasano · Marius Fleischer · Cole McFaul · Robert Xiao · Tripp Gallagher ; Frontier Red Team · Anthropic (billet de recherche du site anthropic.com).
Manifesto-style article by **Thariq Shihipar** (Engineer & serial entrepreneur, Claude Code team at Anthropic) announcing a **change in the default output format for agents**: replacing **Markdown with HTML**. Thesis: Markdown has been the dominant format between humans and agents (simple, portable, editable, readable) but has become **a bottleneck** as agents produce longer and richer artifacts (specs, plans, reports, code review). Beyond ~100 lines, no one reads a Markdown file anymore. HTML solves six limitations simultaneously: **information density** (tables, CSS, SVG, scripts, canvas, images), **visual clarity** (navigable, mobile-responsive layout), **ease of sharing** (an S3 link directly openable in a browser), **two-way interactivity** (sliders, knobs, "copy as JSON/prompt" buttons to loop back into Claude Code), **native contextual ingestion** (Claude Code reads the codebase + MCP Slack/Linear + git history + Chrome) and **enjoyment** (the author explicitly claims *"it's joyful"*). Five canonical uses detailed: (1) **specs/plans/exploration** in a comparative grid, (2) **PR review** with inline annotated diff, (3) **design & prototypes** with animation sliders, (4) **reports/research/learning** (the author had a prompt-caching explainer generated from git history), (5) **custom throwaway editors** (drag-and-drop of Linear tickets, feature-flag editors, side-by-side prompt-tuner) that produce a re-injectable "copy as markdown/diff/JSON" export. Explicit anti-pattern: *"I'm a little bit afraid that people will read this article and turn it into a /html skill"* — the author **rejects premature skill-ification**, recommending prompting from scratch ("make a HTML file"). Pragmatic FAQ: token cost absorbed by **Opus 4.7**'s 1MM context, 2-4× longer generation, noisy HTML diffs (a real downside), style kept in check via a reference HTML design system.
#HTML#Markdown#output format
Thariq Shihipar (Engineer & serial entrepreneur, équipe Claude Code chez Anthropic — site : thariqs.github.io/html-effectiveness ; X : @trq212)