October 29 agent guide: Cursor marketplace incident and Mistral Large 4

October 29, 2026 split into two jobs that should not be mixed. Cursor disclosed a marketplace incident in which tampered Claude Code extension packages ran on Windows and macOS. Mistral published open weights for Large 4, completing the October 6 public preview. One is an incident response. The other is a license-and-bench decision.

What shipped on October 29

Cursor marketplace incident: tampered Claude Code packages

On October 29 Cursor published a security notice for malicious marketplace copies of Anthropic.claude-code versions 2.1.312 and 2.1.313. The window Cursor names is about 2:27am to 1:35pm Pacific Time. Affected platforms are Windows and macOS. Cursor states that the packages were not developed by Anthropic and that official Claude Code was not affected. The version numbers match a real Anthropic release line. The artifacts in the Cursor marketplace did not.

Cursor describes a payload that performs host reconnaissance, installs an SSH key under a svc-telemetry identity, opens a reverse tunnel, and sets persistence through LaunchAgent on macOS or SysMon-style paths on Windows. Uninstalling the extension is not enough. Cursor updated indicators of compromise on October 30 at 11:30am PT. Use that update, not a screenshot of the first post.

This is an agent supply-chain event. Coding agents load extensions, MCP servers, and marketplace packages with the same privileges as the developer. Pin publisher identity, restrict auto-update on agent hosts, and record which extension versions ran during the incident window. Pair the notice with the existing supply-chain playbook: /blog/agentic-ai-supply-chain-security.

Mistral Large 4 weights close the October 6 preview

On October 29 Mistral released open weights for Mistral Large 4, also called Le Chonk. Hugging Face publishes mistralai/Mistral-Large-4-1T-A52B as a natively multimodal mixture-of-experts model with about 1 trillion total parameters and about 49 billion active parameters per token (52 billion including embeddings and output layers). Context is listed at 1 million tokens. Input is text and image. Output is text.

The Hugging Face card describes 128 routed experts with 4 active per token plus 1 shared expert, a Pixtral-style vision encoder, and an embedded DSpark speculative-decoding draft head. Checkpoints include FP8 and NVFP4. vLLM published day-0 support the same day. API pricing on Mistral’s post is $0.70 input, $0.07 cached input, and $2.10 output per million tokens.

The license is the operational detail. Mistral uses the Mistral Ecosystem Open-Weight License, a modified MIT license. The company says the model may be used, modified, fine-tuned, and commercialized, with one condition: businesses that operate a Model-as-a-Service offering must obtain a separate commercial license. Legal effect is described as starting October 29. Preview context: /blog/mistral-large-4-le-chonk-agent-routing-2026.

Pilot steps

1. 01
   Hunt Cursor marketplace versions 2.1.312 and 2.1.313

   Inventory Windows and macOS hosts that had Anthropic.claude-code installed on October 29. Follow Cursor’s notice and the October 30 IOC update. Uninstall is not containment. Official Claude Code upgrades are a separate task.
2. 02
   License-check Large 4 before serving it

   Download mistralai/Mistral-Large-4-1T-A52B only after legal reads the Ecosystem Open-Weight License. Bench the vLLM image on a fixed coding and tool-call set. Do not advertise an API wrapper until the MaaS clause is cleared.

Common mistakes

• Treating Cursor’s Anthropic.claude-code 2.1.312 and 2.1.313 as official Anthropic builds.
• Uninstalling the Cursor extension and closing the incident.
• Calling Mistral Large 4 Apache 2.0. The card names the Mistral Ecosystem Open-Weight License and a MaaS restriction.
• Skipping the October 30 Claude Code write-block release because the version numbers look similar. That changelog is a different artifact.

Conclusion

October 29 is incident first, then a licensed self-host bench. Do not wait on Large 4 weights to finish the marketplace hunt. Official Claude Code policy changes continue on October 30.

Related reading

• October 28: Copilot MCP connectors and Gemini 4 Carbon: /blog/october-28-copilot-mcp-gemini-carbon-2026
• October 30: Claude Code write blocks and gateway groups: /blog/october-30-claude-code-write-blocks-2026
• Agentic AI supply-chain security: /blog/agentic-ai-supply-chain-security
• Mistral Large 4 preview routing notes: /blog/mistral-large-4-le-chonk-agent-routing-2026
• Agentic AI topic map: /topics/agentic-ai

Need this incident and license review on a production stack?

Bacancy Technology reviews agent supply-chain controls and open-weight licenses against the systems a team already runs. Speak with the consulting team or use the contact form. Consulting: /consulting/ . Contact: /contact/ .

Sources: Cursor, October 29, 2026, Cursor changelog . Mistral, October 29, 2026, mistral.ai — mistral large 4 oss . Hugging Face, mistralai/Mistral-Large-4-1T-A52B, Hugging Face . vLLM, October 29, 2026, vllm-project.github.io — mistral large 4.html .