Python's experimental JIT is on its way out

Plus Cloudflare's 1 MB speed store, a Next.js patch date, and Anthropic's monorepo move off Git

The main thing

If you were waiting for CPython to make your hot loops fast for free, keep the Cython file open. The experimental JIT looks finished.

According to LWN, the JIT maintainers have withdrawn PEP 836 ("JIT Go Brrr: The Path to a Supported JIT Compiler for CPython"). In June the steering council paused JIT work in CPython's main branch. It gave the team six months to get a standards-track PEP accepted, and said the JIT code would have to leave main if that did not happen.

Some history explains the friction. Brandt Bucher merged the JIT in early 2024 for Python 3.13 without a standards-track PEP. The work ran on PEP 744, an informational PEP, which never meant formal consensus to go ahead.

The council's September 21 statement said PEP 836 did answer its questions, "although perhaps some less convincingly than others." Its real concern was running the experiment in main at all, because changing behaviour and API surfaces leave core developers, package maintainers and users guessing. It sent a ten-point list of concerns that ran from memory impact to security to platform parity.

• Added: CPython 3.13, in 2024, marked experimental
• The plan: PEP 836, by Bucher, Savannah Ostrowski and Ken Jin, posted July 3, now withdrawn
• Python 3.15: the council said it was OK with the status quo for 3.15
• Removal release: not given in the report
• Separate projects: external JITs such as CinderX, and JIT-adjacent tools such as Numba and PyTorch's compile

What to do today: nothing in production. If a roadmap counts on CPython's JIT for a speedup, take that line out.

Quick bits

Workers KV Instant opens Cloudflare's internal Quicksilver store as a private beta, with 1.62 ms p99 reads against 287 ms for classic KV. The limits are tight: 10,000 keys, 1 MB per namespace and one write per namespace per second. Use it for feature flags, not sessions.

Next.js security release on November 3 will fix seven medium vulnerabilities. Affected versions and upgrade steps come out with the patches, so there is nothing to install yet. Keep time free on Tuesday to upgrade.

Anthropic moved its monorepo from Git to Scion, a source control system that does commits, history and blame on the server, for about 25 million CI checkouts a day. Scion is built for Anthropic's internal systems. Anthropic recommends bringing selected ideas into existing Git platforms.

Four undici advisories affect Node's HTTP client. One, affecting versions from 4.0.0, silently drops a checkServerIdentity callback passed through Agent's tls option, which can bypass a certificate pinning check supplied through that option. Upgrade to undici@8.12.2, undici@7.30.1 or undici@6.29.1.

Ghostty 1.4 completes Kitty graphics support, including animation, and compresses idle scrollback to use 70% to 90% less memory. It also fixes ten security advisories, including malicious output that could crash it or touch files outside its temp directories. Upgrade.

Copilot server-to-server auth is in public preview. Give a GitHub App the read-only Copilot Requests permission and pass an installation token to the Copilot SDK. Usage is billed to the organization, not to whoever is signed in.

ElevenLabs on Vercel AI Gateway adds 14 models (speech-to-text, streaming speech, realtime voice agents, music, sound effects and dialogue) behind one gateway key. They are 50% off through November 9.

Aurora Serverless now goes to 384 ACUs, about 768 GiB of memory, for Aurora PostgreSQL only. You need Platform Version 4 and engine 18.4, 17.10, 16.14, 15.18 or 14.23.

Also happening

• LiteLLM proxy admin escalation (CVE-2026-114612): an internal_user can become proxy_admin and run commands. Affected release lines start at 1.91.0 by default; versions 1.87.0 through 1.90.x are also affected when EXPERIMENTAL_UI_LOGIN=true. Upgrade to litellm==1.100.4, litellm==1.101.3, litellm==1.102.2, litellm==1.103.1 or litellm==1.104.0rc2, whichever matches your line.
• Atlantis shell injection (CVE-2026-116676): a PR eligible for atlantis plan can run commands if Atlantis reads its atlantis.yaml from the PR branch; fork PRs also require --allow-fork-prs. Versions 0.4.0 through 0.47.0 are affected; upgrade to github.com/runatlantis/atlantis@0.47.1.
• vLLM multimodal RCE (CVE-2026-114053): affects only --trust-remote-code servers whose model processor loads dynamic auto_map code, from 0.7.3 up to, not including, 0.31.0. Upgrade to vllm==0.31.0.
• pnpm 12.16.1: fixes cold-store install hangs in workspaces that install Cargo crates.
• Kubernetes 1.37.2, 1.36.6, 1.35.10 and 1.34.13: patch releases on four branches; the CHANGELOG has the details.
• React Router 8.5.1 and 7.18.5: maintenance releases; read the changelog before you bump.
• Codex 0.165.0: adds a built-in Vertex AI provider (model_provider = "gcp") and GPT-6.1 Terra.
• tar-codec from Astral: uv's new sdist parser, about twice as fast and with fewer parser differentials.
• JetBrains terminal now runs on libghostty: from 2026.3, Shift+Enter finally works in Claude Code and Neovim.
• Amazon ECS GPU sharing with NVIDIA MPS: run several tasks on one GPU.
• Dockerfiles on Vercel: Guillermo Rauch says a root Dockerfile now deploys.
• Serving LLMs at scale: the KV cache advantage: prefill, decode and GPU utilization, explained by a distributed-systems engineer.
• Anthropic files its S-1: planned Nasdaq listing as "ANT"; share count and price not yet set.
• Is my data used for model training?: commercial Claude data isn't used for training by default, but thumbs-up/down feedback can be.
• Here be monsters: what you still need to know when agents code; the discussion argues about breadth.
• AI promised less work. I've never worked more: a VP of Technology's GitHub graph is back at full-time-coder levels.

Patch roundup

• Authlib: Authlib==1.9.1
• Better Auth: the fix is better-auth@1.7.7, but the advisory says "That package is not available yet"; until it ships, apply one of the advisory's workarounds
• MLflow: mlflow==3.17.0
• Adobe Commerce and Magento: CISA lists this as exploited; check Adobe for the security update, since the source gives no fixed version
• Grafana: 13.3.0 fixes the listed security issues; older maintained branches have separate backports, so check which advisories apply

Somewhere, a Cython file you wrote in 2019 just felt very seen.

← All issues