Best of Theo - t3․gg — February 2026

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    Avatar of t3dotggTheo - t3․gg·17w

    OpenAI just dropped their Cursor killer

    OpenAI released Codeex, a new AI coding tool combining CLI, web app, and desktop application for managing AI agents across projects. Unlike traditional code editors, it provides a GUI for orchestrating multiple parallel coding tasks, with features like work trees, cloud environments, automations, and cross-project thread management. The tool shares history between CLI and app, supports multiple editors, and enables developers to manage several concurrent development tasks simultaneously. While work tree implementation has limitations and environment variable management needs improvement, the orchestration layer represents a shift from direct code editing to agent management workflows.

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    Avatar of t3dotggTheo - t3․gg·16w

    GLM-5 is unbelievable (Opus for 20% the cost??)

    GLM-5, a new open-weight AI model from Chinese lab Zhipu AI, delivers performance comparable to Claude Opus 4.5 and Codex 5.2 at roughly 20% of the cost. With 744 billion parameters (40B active via mixture-of-experts), it excels at long-running agentic tasks, successfully completing hour-long code migrations that previously required closed-weight models. The model achieves the lowest hallucination rate on benchmarks to date, costs $3 per million output tokens versus $15-18 for top closed models, and is MIT-licensed without usage restrictions. While lacking multimodal image support, it demonstrates strong capabilities in code refactoring, UI generation, and extended autonomous work sessions.

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    Avatar of t3dotggTheo - t3․gg·14w

    Delete your CLAUDE.md (and your AGENT.md too)

    A study found that CLAUDE.md and AGENT.md context files used with AI coding agents either marginally improve performance (+4%) when developer-written, or slightly hurt it (-3%) when LLM-generated, while increasing costs by over 20%. The core argument is that modern LLMs are already good at exploring codebases autonomously, so bloated context files distract rather than help. Best practice is to keep these files minimal—only documenting consistent failure patterns the agent exhibits—and to focus instead on improving codebase structure, tests, and tooling. The author also shares unconventional prompting tricks like intentionally misleading agents to steer behavior, and recommends deleting auto-generated init files entirely.

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    Video
    Avatar of t3dotggTheo - t3․gg·14w

    The Future of TypeScript

    TypeScript 6 is now in beta and serves as a bridge to TypeScript 7, which rewrites the compiler in Go for dramatically faster type checking (10x+ performance gains). TypeScript 6 focuses on cleaning up legacy baggage, aligning with the Go-based compiler, and improving defaults: strict mode is now on by default, module defaults to ESNext, ES5 target is deprecated, AMD/UMD/SystemJS module resolution is deprecated, and baseURL is replaced with better path handling. TypeScript 7 (the Go rewrite) is already available as a native preview with full LSP support including code completion, go-to-definition, and find-all-references. The TypeScript team's philosophy has shifted from adding features to improving error clarity, performance, and agent-friendliness. The Go choice over Rust is justified by shared-memory multi-threading support and garbage collection being irrelevant for compiler workloads.

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