Claude Code 2.1.316 Retires Opus 4.8 Fast Mode: October 31 Roundup

The headline today is a deadline. Claude Code 2.1.316 deprecates fast mode on Opus 4.8, and fast mode requests on that model will start returning errors on November 30, 2026. The same release adds a subagent effort setting and pooled budgets for the Claude apps gateway. Codex 0.166.0 is still the newest stable Codex build, and the GitHub Copilot changelog has no new entries since October 28.

Fast mode on Opus 4.8 is going away

According to the Claude Code release notes, fast mode for Opus 4.8 is deprecated as of October 30, 2026 and will be removed on November 30, 2026. After removal, fast mode requests on Opus 4.8 return an error and do not fall back to standard Opus 4.8. The notes say to migrate to Opus 5.5 to keep the speedup.

If you have fast mode pinned in scripts, shared settings or CI jobs, you have a month to switch the model. Otherwise those calls will fail rather than slow down.

Other additions in 2.1.316

• CLAUDE_CODE_SUBAGENT_EFFORT sets the effort level subagents run at when nothing else names one, instead of inheriting the session's level.
• CLAUDE_CODE_DISABLE_ULTRATHINK turns the ultrathink keyword off. In VS Code, ultrathink now runs its turn at xhigh effort.
• Claude apps gateway: pooled group budgets (one monthly budget members share, set with pooled_budget on the spend limits admin API), a layered policy mode (managed.policy_mode: layered), and guardrail.input_tagging for Amazon Bedrock upstreams.
• Security-relevant fixes: --restricted sessions no longer upload files from outside the working directories when a Read allow rule covered them, and the gateway now checks every model a request names against availableModels, deniedModels and models, returning a 400 that names the blocking field.
• Reliability: shell commands are no longer left running on macOS and Linux when Claude Code exits by itself, hung network requests on truncated compressed responses are fixed, and the sonnet, opus and haiku aliases on Vertex AI and Bedrock switch to an older model instead of erroring when the newest is not available to your account or region.
• Cloud sessions: a form card now lets you fill in or decline a form an MCP server asks for, and Enterprise members can add and delete network secrets on their own cloud environments.
• Changed: server-managed settings for Team and Enterprise logins fetched from Anthropic's API now apply without an approval prompt, and a stored copy that does not verify is refused.

Codex and Copilot: no new releases today

The Codex releases page still shows 0.166.0 (October 29) as the latest stable build, covered in yesterday's roundup. The GitHub Copilot changelog has nothing dated after October 28, when GitHub published its Universe batch, including Copilot Fusion and the Copilot app releases.

What to do this week

• Search your settings, scripts and CI for Opus 4.8 fast mode and move them to Opus 5.5 before November 30.
• If you run subagents heavily, set CLAUDE_CODE_SUBAGENT_EFFORT so they do not inherit a high session effort and burn extra tokens.
• Gateway admins: review the new layered policy mode and pooled budgets before rolling them out to groups.

References

Claude Code releases · Claude Code CHANGELOG.md · Codex releases · GitHub Copilot changelog