Sources

Claude Code uses Bun written in Rust now simonwillison.net

In Rewriting Bun in Rust Jarred Sumner made the following claim: Claude Code v2.1.181 (released June 17th) and later use the Rust port of Bun. Startup got 10% faster on Linux but otherwise, barely anyone noticed. Boring is good. I decided to have a poke at my own Claude Code installation to see if I could find evidence that it was using Bun written in Rust. I found these two commands convincing: strings ~/.local/bin/claude | grep -m1 ‘Bun v1’ For me this outputs Bun v1.4.0 (macOS arm64) . The m…

Fine-tune video and image models at scale with NVIDIA NeMo Automodel and 🤗 Diffusers huggingface.co

SQLite Query Explainer simonwillison.net

Tool: SQLite Query Explainer Julia Evan’s, in Learning a few things about running SQLite : Maybe one day I’ll learn to read a query plan. Big same… which inspired me to have Fable build this interactive explain tool, which runs SQLite in Python in Pyodide in Web Assembly in the browser and adds a layer of explanation to the results of both EXPLAIN and EXPLAIN QUERY PLAN. Approach with caution, since I don’t know enough about SQLite query plans to verify the results myself, but it seems cromu…

References

Andrew Kelley, ‘My thoughts on the Bun Rust rewrite’ (via r/Zig) reddit.com

Kelley characterized the original Bun source code as ‘horrifying’ and filled with ‘beginner energy,’ claiming that the Zig core team had long viewed the project as a ‘net liability’ to the Zig Software Foundation

grigio.org — ‘Bun 1.4: the controversial AI-driven rewrite’ grigio.org

In benchmarks executing 2,000 parallel builds, memory consumption plummeted from 6.7 GB in the Zig-based v1.3.14 to just 609 MB in v1.4.0

Weekly Rust Substack — ‘The Great Zig to Rust Experiment’ weeklyrust.substack.com

A pre-release technical audit of the resulting Rust port identified 13,365 unsafe blocks, representing an unsafe density nearly double that of the Deno runtime… at least five unsound functions were initially discovered where UB was reachable from safe code

Medium (neonmaxima) — Claude Code source leak writeup medium.com

Version 2.1.88 was published with cli.js.map files that accidentally embedded… the original, unobfuscated TypeScript source, totaling over 512,000 lines… traced to… a known bug in Bun’s bundler, which reportedly ignored production: true flags

Anthropic — ‘Anthropic acquires Bun’ announcement anthropic.com

Claude Code is distributed as a single-file, 51MB binary that utilizes Bun’s ability to compile JavaScript into self-contained executables… Bun’s runtime reportedly begins execution in roughly three milliseconds

r/ClaudeCode — ‘Anthropic quietly killed third-party CLI tooling’ reddit.com

the move from a readable cli.js bundle to a compiled binary prevents community patching and custom hook injection, effectively ‘locking down’ the CLI

NVIDIA-NeMo/Automodel GitHub issue #2952 github.com

Checkpoint saving times with FSDP2 can be significantly longer than anticipated for models exceeding 40 billion parameters; Context Parallelism combined with sequence packing is currently broken, and precision anomalies have been reported during the FSDP2 reverse process.

Wccftech — MLPerf Training v5.1 coverage wccftech.com

NVIDIA’s submission trained the new FLUX.1 text-to-image benchmark in 12.5 minutes on 1,152 Blackwell GPUs using NVFP4 precision — and was the only vendor to submit a FLUX.1 result this round.

hyper.ai — NeMo 2.0 / Automodel adoption review hyper.ai

Full fine-tuning of FLUX.1-dev at 512px reaches ~35.5 images/s on 8×H100 and LoRA exceeds 53 images/s, but a ‘usability wall’ persists for non-enterprise users who still find NeMo buggy compared with ComfyUI when sharding VRAM on heterogeneous hardware.

YouTube comparison — ai-toolkit vs SimpleTuner vs diffusion-pipe youtube.com

ai-toolkit remains the standard for 24GB consumer cards, while diffusion-pipe is reportedly slower than competitors for FLUX LoRA on an RTX 4060 Ti — leaving NeMo squarely aimed at multi-node H100 clusters rather than prosumer setups.

Developers Digest recap of Julia Evans post developersdigest.tech

running the ANALYZE command resulted in a 100x performance boost for specific queries, dropping execution time from 5 seconds to 0.05 seconds

sqlite-users mailing list (narkive archive) sqlite-users.sqlite.narkive.com

EXPLAIN QUERY PLAN is not formally documented and is intended only for interactive debugging, meaning tools that parse its output may break frequently

r/sqlite thread on Tabularis ‘Visual EXPLAIN’ reddit.com

Tabularis parses the id and parent columns to reconstruct and render an interactive tree graph using ReactFlow… complex joins and subqueries are nearly impossible to track mentally in the standard list format

r/ClaudeAI discussion of Mythos/Fable tier reddit.com

up to three times slower than predecessors… often spends excessive time ‘mapping’ environments, leading to timeouts on tasks that simpler models finish quickly

Hacker News thread (via query 5 synthesis) news.ycombinator.com

576,000 lines of code successfully compiled and passed basic tests but executed 20,171 times slower than the original… correctly implemented the opcode syntax but failed to include critical performance checks, such as index flags

llm-works.ai coverage of Willison’s tool news.llm-works.ai

It distinguishes between ‘SCAN’ (full table scans) and ‘SEARCH’ (index-based lookups), highlighting potential performance pitfalls like missing indexes or the use of temporary B-trees for sorting

Sources

References

Jack Sun, writing.