Claude Code This Week: Seven Releases, v2.1.306 to v2.1.312

Summary

Claude Code, the coding tool built on Anthropic’s Super Intelligence (SI) models, published seven releases in seven days, from v2.1.306 on Oct 21, 2026 to v2.1.312 on Oct 27, 2026. Almost all of the changes are fixes. This article sorts them by theme so you can see which ones might affect you.

We have not run these versions. This summary comes from the release notes on GitHub, read on Oct 28, 2026. Where a note was long, we read the first part and left the rest.

Seven releases between Oct 21 and Oct 27, 2026. v2.1.312 is the newest in the notes we read. Chart by SI Build Lab · github.com/anthropics/claude-code/releases · read Oct 28, 2026

Key points

• Sandbox and permission fixes (v2.1.309). The release fixes several cases where a sandboxed command could do more than it should.
• MCP reliability (v2.1.306, v2.1.307, v2.1.311). MCP servers were the subject of many fixes: timeouts, sleep and wake, locked keychains and duplicate calls.
• New options. v2.1.307 adds /claude-api api-version, v2.1.311 adds two flags for self-hosted-runner, and v2.1.312 adds click to send.
• Large CLAUDE.md files. Three releases (v2.1.309, v2.1.311, v2.1.312) fix problems with very large CLAUDE.md files.
• Newest version. The newest version in the notes is v2.1.312.

What Anthropic says: versions and dates

The table below follows the release notes Anthropic publishes on GitHub. Dates are as shown on each GitHub release page. Depending on your timezone, a date may be off by one day.

Version	Date	Main change
v2.1.306	Oct 21	Fixes for claude -p in cloud sessions and for a wrong “prompt is too long” error
v2.1.307	Oct 21	New /claude-api api-version; MCP fixes; a telemetry safety event that v2.1.312 later stopped sending
v2.1.308	Oct 22	“Bug fixes and reliability improvements”
v2.1.309	Oct 22	Sandbox, permission-check and worktree-guard fixes; hook and large CLAUDE.md fixes
v2.1.310	Oct 23	Monitor tool on Bedrock, Vertex and Foundry; compaction and hook fixes
v2.1.311	Oct 26	Two self-hosted-runner flags; many fixes for freezes, hooks and subagents
v2.1.312	Oct 27	oidc.user_id_claim for the Claude apps gateway; click to send; more fixes

Which release notes touched which area. We sorted these ourselves. Chart by SI Build Lab · github.com/anthropics/claude-code/releases · read Oct 28, 2026

What changed, by theme

Sandbox and permissions. v2.1.309 is the security-flavored release. Its notes say it fixed sandboxed Bash commands on macOS and Linux running the shell’s startup files outside the sandbox before each command. They also list a fix so that sandboxed commands and auto-accepted edits can no longer modify the MCP config file passed with --mcp-config, and fixes to several Bash permission checks for compound commands. If you rely on the sandbox, read the full v2.1.309 notes.

MCP servers. v2.1.307 fixed MCP servers showing “needs authentication” in claude -p on macOS while the login keychain was locked, and servers being reported as timed out when a computer went to sleep during connection. It also fixed HTTP MCP tool calls being sent twice when a connection closed mid-call; now only read-only or idempotent tools are retried. v2.1.306 fixed an API error being replaced by “prompt is too long” in sessions with many MCP tools. v2.1.311 fixed subagents being unable to use MCP tools from servers that finish connecting after the subagent starts.

New options. Four additions are worth knowing:

• /claude-api api-version (v2.1.307) moves Claude API code to API version 2026-10-21.
• The Monitor tool and plugin monitors (v2.1.310) now work on Bedrock, Vertex and Foundry, and when telemetry or nonessential traffic is disabled.
• --hold-idle-file and --max-hold-min (v2.1.311) for self-hosted-runner keep an idle session open while your host reports processes it left running.
• Click to send (v2.1.312): in fullscreen, clicking the “to send now” hint under a queued message sends it right away.

One addition did not last. v2.1.307 added a claude_code.safety_event telemetry event, and six days later the v2.1.312 notes say Claude Code stopped sending it.

The options added this week, by version. Chart by SI Build Lab · github.com/anthropics/claude-code/releases · read Oct 28, 2026

Context and CLAUDE.md. v2.1.309 fixed sessions compacting again and again after reading files under a very large nested CLAUDE.md; a nested CLAUDE.md over the size limit now loads only its start. v2.1.311 fixed long freezes at startup when a CLAUDE.md holds a very long list item, and standard-context sessions stopping with “Usage credits required for 1M context”; Claude Code now compacts the conversation and continues. v2.1.312 fixed Claude overwriting a very large CLAUDE.md, rules file or included file after seeing only its start. Write now asks Claude to read it all or edit in place.

Hooks. v2.1.309 fixed hooks that run in PowerShell not blocking when the hook program exits with code 2, and Windows PreToolUse and PermissionRequest hooks with the PowerShell shell setting letting a call through when Git for Windows is not installed. v2.1.310 fixed a similar Windows case, where those hooks let a tool call through when Git Bash is missing and the hook’s command is only quoted strings. v2.1.311 fixed SubagentStop hooks running about twice a minute for each running subagent instead of once at the end. If you use hooks as a guard on Windows, these three fixes are the ones to have.

How to get it

Each release has its own notes page on the project’s GitHub releases; the links are in the Sources list. The release notes do not explain how to update or how to check which version you have. Follow Anthropic’s current install documentation for the steps that match how you installed it, then compare your version with v2.1.312.

Our observations

We did not run these versions, so we have no results of our own. From reading the notes: the cadence is fast, with seven releases in a week, and the notes are mostly bug fixes. That is normal for a tool in heavy use, but it also means that pinning a version in a team setup may be worth considering. We did not check Anthropic’s guidance on that.

Limits

1. Not tested. We read the notes but did not install or run v2.1.306 to v2.1.312.
2. Partial reading. Several release notes are long. We read the first part of each and did not summarize every item.
3. Selection. We picked the items that looked most relevant to developers. Your setup may care about others.
4. Moving target. A newer version may already be out by the time you read this.

What we read and what we skipped. Chart by SI Build Lab · github.com/anthropics/claude-code/releases · read Oct 28, 2026

Conclusion

This was a maintenance week, with extra attention on the sandbox and on MCP reliability. If you run Claude Code in automation or behind a sandbox, v2.1.309 and v2.1.307 are the two releases to read in full. Everyone else can update and move on.