Claude Code 2.1.312 limits concurrent hooks, widens automatic model switches and adds an OIDC claim setting

Claude Code v2.1.312, released October 27, 2026, per its release notes:

• Hooks: prompt and agent hooks now run at most 24 at a time per session, sub-agents included, plus at most 12 that have waited longer than their event's timeout. A timeout under 1 second now counts as 1 second.
• Cloud providers: on Bedrock, Vertex, Foundry and Mantle, model names Claude Code doesn't recognize (custom deployment names, inference profile ARNs) now get the shorter system prompt, even when they front Sonnet or Haiku; set CLAUDE_CODE_SIMPLE_SYSTEM_PROMPT=0 to keep the full prompt.
• Model switches: automatic model switches after a flagged message now also cover unrecognized model names; set CLAUDE_CODE_DISABLE_REFUSAL_FALLBACK=1 to turn them off.
• Claude apps gateway: new oidc.user_id_claim identifies people by an id_token claim other than sub, such as Microsoft Entra ID's oid.
• Subagents: a subagent's autoCompactWindow now lowers the window set by CLAUDE_CODE_AUTO_COMPACT_WINDOW; it never raises it.
• Telemetry: Claude Code no longer sends the claude_code.safety_event OpenTelemetry event, and mcp_server.name now reports the real name of fixed-URL remote MCP servers declared by plugins from the official Anthropic marketplace instead of custom.
• Interface: in fullscreen, clicking the "to send now" hint under a queued message sends it right away. Usage limit messages call the 5-hour window the "5-hour limit" instead of the "session limit". The effort indicator says a mid-task change may wait for your next message.
• Writes and skills: Write now asks Claude to read a very large CLAUDE.md, rules file or @-included file in full, or edit it in place, instead of overwriting it after seeing only its start; per-directory and paths: skills are found again after a Bash cd deeper into a repository.
• Cloud sessions and Claude Tag: cloud routines get an effort level in the model picker and the setup script box gets a Bash editor; Claude Tag's Slack retry notice names the model in use or says rate limits were hit, and fixes cover replies in channels with network access set to None and files posted in the wrong thread.
• Code Review: it now reviews the pull request's current commit when GitHub delivers a push event late.

The release also fixes managed settings not being fetched after signing in from the VS Code extension, a command with an invalid name stopping all commands from loading, PDF reads failing during session clean-up, and several agent view and vim mode problems.