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Qwen3-Coder sets new agentic coding records with 480B params and 1M token context length 🚀

7/23/2025

Don’t animate height!

Jim Fisher identifies animating CSS height as a major performance culprit causing 60% CPU and 25% GPU usage on an M2 MacBook due to triggering layout recalculation, painting, and compositing. Using Chrome DevTools, he demonstrates how pure CSS animations on layout properties degrade performance. Cheaper animation properties like transform and opacity avoid these costly steps. A naive fix using transform: scaleY() reduces CPU but distorts visuals. Fisher’s refined approach uses two rectangles animated via transform to simulate height changes without layout thrashing, cutting CPU load by 4-5x while preserving appearance. The article underscores the importance of choosing animation properties based on browser rendering mechanics for optimal efficiency.

TODOs aren’t for doing

The article argues against rigidly tracking or automatically deleting all TODO comments as actionable items. Instead, TODOs often capture the author’s contextual knowledge, edge case awareness, or informal insights that do not necessarily warrant immediate fixes or formal issue tracking. Well-placed TODOs act as lightweight annotations—mental bookmarks that help future readers understand nuanced code realities and trade-offs. Enforcing cleanup policies risks losing valuable embedded context, suggesting a balanced, pragmatic approach to using TODOs as informal documentation rather than strict task lists.

Many Lung Cancers Are Now in Nonsmokers

Lung cancer diagnosis increasingly affects nonsmokers, prompting research into non-tobacco risk factors including genetics, radon exposure, indoor air pollution, occupational hazards, and secondhand smoke. Radon is highlighted as a significant but underappreciated cause, especially in tightly sealed modern homes that concentrate pollutants. The article discusses challenges in public risk perception, early detection, and policy responses, while community commentary raises points on relative vs absolute risk shifts as smoking declines, numerous unstudied indoor chemicals, and the cost-benefit of mitigation efforts. This evolving epidemiology invites nuanced discussion on environmental health and preventive strategies.

Gemini CLI deletes files after hallucinating state

A detailed post-mortem describes how Google’s Gemini CLI AI agent catastrophically deleted user files on Windows by hallucinating successful directory creation (mkdir) commands that actually failed. Gemini misinterpreted the absent directory as existing, then issued destructive move commands overwriting multiple files into a nonexistent location, causing irreversible data loss. The failure stemmed from missing error checking and command state verification. This incident highlights critical risks of granting AI agents autonomous write access on real file systems without safeguards such as sandboxes or backups. The article invites debate on AI reliability, trust, and the design of safe AI-driven developer tools.

Qwen3-Coder: 480B parameter agentic coding model with 256K token context

Qwen Team presents Qwen3-Coder, a 480B parameter Mixture-of-Experts model specialized for agentic coding and tool-assisted multi-turn tasks. It supports an unprecedented native 256K token context length (extendable to 1 million), enabling handling of large-scale codebases and complex developer flows. Trained on 7.5 trillion tokens with 70% code content using large-scale reinforcement learning focused on execution-driven problem solving, it achieves state-of-the-art open-source benchmarks rivaling proprietary models. The team also open-sourced a CLI interface tailored to Qwen3-Coder and offers API access via Alibaba Cloud. Plans include smaller, local-deployable variants and exploration of self-improving coding agents aimed at advancing autonomous software engineering.


Don't animate height

The article presents the central insight that animating the height property in CSS is exceptionally costly for browser performance, particularly on complex or frequently updated interfaces. The author documents how a seemingly minor CSS animation in a web app resulted in significant CPU and GPU usage—over 60% CPU and 25% GPU utilization on a modern M2 MacBook—due to repeated triggering of browser layout recalculation, painting, and compositing. This highlights the importance of understanding which CSS properties are expensive to animate and why.

Further technical analysis reveals that not all CSS properties are equal in terms of rendering cost: layout properties like height and width trigger complete browser reflows and repaints, making them the worst candidates for smooth, real-time animation. In contrast, composite properties such as transform and opacity are handled by the GPU and bypass much of the render tree, enabling efficient animation without taxing the main thread. The author demonstrates practical profiling with Chrome DevTools, leading to an optimized solution using two rectangles animated by transform: translateY(), preserving visual fidelity while reducing resource usage four- to fivefold.

Community responses on Hacker News largely validate these findings, with the consensus underscoring the known risk of animating layout properties. Commenters appreciate the step-by-step debugging approach and share their own experiences with similar pitfalls in web animation work. Discussion also touches on alternative approaches, trade-offs between visual polish and technical efficiency, and the broader implications for responsive UI development. The article is widely regarded as an instructive case study in modern frontend performance engineering.

TODOs aren't for doing

The key argument presented is that TODO comments in code are most valuable as informal markers of thought process and context, not merely as tasks that must be completed or strictly tracked. The article emphasizes that encoding every TODO into a bug tracker or rigidly requiring their eventual resolution can erode their practical benefit—namely, to unobtrusively communicate subtle knowledge, edge cases, and developer intent. In certain cases, a TODO may highlight a non-critical limitation or a tentative improvement idea that is best left as a reference for future readers rather than an obligation for immediate action.

Further, the author notes that TODOs often act as lightweight context beacons, allowing subsequent maintainers to understand why certain decisions were made or what peculiarities to watch for in the code. This function is distinct from a formal backlog item, as it helps prevent accidental regressions and can answer silent questions like “did the previous author know about this oddity?” without needing heavy workflow interruptions. Enforcing strict automation or cleaning up all TODOs runs the risk of erasing this informal but highly practical documentation layer embedded in the code.

The Hacker News discussion reflects broad agreement with this human-centered approach to TODO management, with commenters highlighting the value of TODOs as embedded developer intent and cautioning against process-heavy policing. There is debate about the best balance between project hygiene and practical maintainability, but many share anecdotes about TODOs saving future debugging effort or providing insight into tricky code areas. Some voices note that, while egregiously stale or irrelevant TODOs should eventually be pruned, the practice of treating all TODOs as actionable backlog items is seen as counterproductive in most real-world teams.

Many lung cancers are now in nonsmokers

A significant shift is underway in lung cancer epidemiology, with an increasing proportion of new cases occurring in people who have never smoked. Researchers are intensively examining factors beyond tobacco use, including genetic predispositions, radon exposure, ambient air pollution, occupational hazards, and effects of secondhand smoke. The article emphasizes both the need for heightened awareness among nonsmokers—who may underestimate their risk—and the importance of early detection, since diagnoses among this group often happen at more advanced, less treatable stages.

Growing scrutiny of environmental contributors is bringing particular attention to radon as the second leading cause of lung cancer in nonsmokers, as well as to overlooked indoor air quality issues worsened by tightly sealed modern buildings. Discussions highlighted the complicated nature of mitigating risks—such as variability in radon exposure by locale, the challenge of quantifying the health impact of numerous under-studied household chemicals, and the limitations of current public understanding and policy. These factors have prompted calls for more robust regulation, widespread radon testing, and increased education regarding indoor pollutants.

Hacker News commenters offer nuanced perspectives, with many urging caution about interpreting raw trends; several point out that even as the absolute number of lung cancer cases declines, nonsmokers now account for a larger fraction due to the success of anti-smoking campaigns. Others express skepticism on risk communication, debate the practicality versus cost of broad radon mitigation, and share personal experiences with home radon testing. There is notable consensus on the complexity of the problem and the value of shifting attention to other, often invisible, environmental hazards that could now be driving lung cancer risk.

I watched Gemini CLI hallucinate and delete my files

A firsthand account details a severe incident where Gemini CLI, Google's AI-powered command-line tool, hallucinated the state of a Windows file system and inadvertently deleted critical user files. The user attempted a routine directory rename and file move, but Gemini misinterpreted a failed mkdir (directory creation) as successful, proceeding to execute a sequence of destructive move commands. Due to the missing destination directory, Gemini repeatedly renamed files to a nonexistent target, resulting in overwrites and permanent data loss.

Technical analysis reveals the root causes: Gemini omitted essential error-handling and state-verification steps in its command execution process. Specifically, there was no check of exit codes from shell commands, nor did it verify the existence of directories or files before or after operations. This absence of defensive programming caused the AI to develop and act on an erroneous "mental model" of the file system’s state—persisting even after data vanished—exposing critical limitations in relying on AI agents for file operations without comprehensive safeguards like sandboxing and enforced verification loops.

The Hacker News community reacted with a mix of concern, technical scrutiny, and humor, highlighting widespread distrust for AI tools that operate on critical systems without appropriate checks. Commenters drilled into Windows command semantics, the dangers of overlooking verification after destructive operations, and the need for robust guardrails in AI-augmented development tools. Notable sentiments included disbelief at the AI's apologetic self-awareness, candid reminders to never test new CLI agents on production data, and a preference for tools that prioritize reliability over innovative automation.

Qwen3-Coder: Agentic coding in the world

Qwen3-Coder represents a significant leap in agentic coding AI, introducing a 480 billion parameter Mixture-of-Experts architecture with 35 billion active parameters and native support for 256K-token context length, extendable to 1 million tokens. Developed by the Qwen Team, it is designed specifically for multi-turn, tool-assisted coding tasks, rivaling proprietary models like Claude Sonnet 4 in open benchmarks. The model is engineered to handle large-scale code repositories and complex, multi-step developer workflows, marking a new tier in open-source code generation and agent automation.

The technical advancement lies in Qwen3-Coder’s training approach, relying on large-scale reinforcement learning—including 7.5 trillion training tokens, with 70% code data and highly scalable RL infrastructure capable of simulating 20,000 environments in parallel. The team emphasizes execution-driven, multi-turn RL, prioritizing tasks that are difficult to solve but easy to verify, ensuring the model improves at real-world problem-solving and tool integration. The open-sourced Qwen Code CLI and API compatibility with major platforms demonstrate clear pathways for adoption into development pipelines, while showcased use cases underscore versatility across domains like physics, game development, and web apps.

Hacker News commenters are particularly focused on the combination of massive parameter count and unprecedented context window, expressing excitement as well as skepticism about the scalability and hardware requirements for practical use. There is lively debate over whether expanding token context is the logical next step for coding LLMs or if more efficient architectures are needed. Many appreciate the open-sourcing of both the model and tools, while others highlight the novelty of extensive reinforcement learning for multi-turn code reasoning as a key differentiator from prior open-source efforts. The general sentiment is that Qwen3-Coder sets a new benchmark for agentic programming assistants and may accelerate broader innovation in self-improving coding agents.