Anthropic files S-1 for a proposed Nasdaq listing under the symbol ANT

A proposed public offering, with the terms still open

On October 26 Anthropic announced that it had filed a registration statement on Form S-1 with the U.S. Securities and Exchange Commission. The filing relates to a proposed initial public offering of its Class A common stock, which the company intends to list on the Nasdaq Global Select Market under the symbol “ANT”. The announcement says the number of shares and the price range have not yet been determined.

The announcement is limited to the mechanics. The offering will be made only by means of a prospectus, and the notice names Goldman Sachs & Co. LLC and Morgan Stanley & Co. LLC as sources from which copies of the preliminary prospectus may be obtained once available. It states that the registration statement has been filed but has not yet become effective, that the securities may not be sold nor offers to buy accepted before it does, and that the notice is neither an offer to sell nor a solicitation. The page footer describes Anthropic as a Public Benefit Corporation whose mission is to ensure the world safely makes the transition through transformative AI.

Sources: Anthropic files S-1 with the SEC for proposed initial public offering — Anthropic

Two service incidents, both now resolved

The status page lists two incidents of elevated errors, both now marked resolved. The first concerned requests to Claude Mythos 5.1, Claude Fable 5.1, Claude Opus 5.5, Claude Sonnet 5.5 and Claude Haiku 5.5. It was opened as an investigation, with no cause stated at that stage.

The second was specific to Claude Fable 5.1. Its update says the cause of the elevated errors had been identified and a fix was being worked on. The entries as published do not give the duration of either incident or the underlying cause. They also do not say whether the two were related, so this edition does not draw a link between them.

Sources: Elevated errors for Claude Sonnet 5.5 and other models — status.claude.com · Elevated errors for Claude Fable 5.1 — status.claude.com

Claude Code: tighter sandboxing and wider compatibility

Three consecutive Claude Code releases share a focus on containment and on non-default environments. Version 2.1.309 fixes three sandbox problems. Shell startup files were running outside the sandbox before each sandboxed Bash command on macOS and Linux. On macOS, denyWrite glob patterns did not apply at a path's real location when the pattern's folder was reached through a symlink. Sandboxed commands and auto-accepted edits could modify the MCP config file passed with --mcp-config.

Version 2.1.310 makes the Monitor tool and plugin monitors available on Bedrock, Vertex and Foundry, and when telemetry or nonessential traffic is disabled. Long foreground sleeps are now blocked there too. It also stops requests failing behind gateways and compatible servers that reject the effort-2025-11-24 beta value or mid-conversation system messages, because Claude Code now retries without them. A third fix stops background cleanup deleting recent files, such as pasted images, when cleanupPeriodDays is set very high.

Version 2.1.311 adds --hold-idle-file and --max-hold-min to self-hosted-runner, to keep an idle session while the host reports processes it left running. It also adds a tip for the Explanatory output style and fixes long freezes at startup, and after reading or editing files, when a CLAUDE.md file holds a very long list item. Separately, the API release notes describe a beta Claude Tag API for Claude Enterprise organizations, enabled with the experimental-claude-tag-2026-10-21 beta header. Its /v1/organizations/claude_tag/ endpoints read and change Claude Tag settings on Slack channels and Slack workspaces.

Sources: Claude Code 2.1.309 — Claude Code · Claude Code 2.1.310 — Claude Code · Claude Code 2.1.311 — Claude Code · Claude Tag API beta (API release notes) — Anthropic (release notes)

Research outreach and two assessments

On October 22 Anthropic opened a call for guest investigators in the life sciences. Principal investigators at academic institutions, nonprofits or government labs can propose projects in areas such as causal human biology, structural and computational molecular biology, medicinal chemistry, drug discovery and clinical science. Selected teams would work with Anthropic researchers for 8 to 12 weeks, with Anthropic running its models and harnesses at no cost to them. The company says it will work with them to publish outputs and open-source the accompanying data and code, and that investigators keep the rights to their data and to independent follow-on research. Applications stay open for approximately 14 days, and applicants are asked to include only publicly available information. Anthropic says it aims to notify selected participants about 14 days after applications close.

Two further Anthropic items appear in the day's feed with only their titles. One is “An alignment assessment of the UK AISI cybertesting incident”. The other is “LLMs are making formal software verification feasible at a much larger scale”. The material available for this edition contains no text beyond those titles, so it describes neither the incident nor the arguments and findings behind them. Readers should consult the publications themselves.

Sources: Open call for guest investigators in the life sciences — Anthropic · An alignment assessment of the UK AISI cybertesting incident — Anthropic · LLMs are making formal software verification feasible at a much larger scale — Anthropic