ClaudeClaude ProThe paid subscription for the Claude AI assistant from Anthropic. It unlocks connectors to outside tools.Open the glossary Code 2.1.316 was released on 31 October 2026 and deprecates fast mode for Opus 4.8. From 30 November 2026, a fast mode request on Opus 4.8 returns an error and does not fall back to Opus 4.8 at standard speed. Move your sessions, scripts, and scheduled jobs to Opus 5.5 before that date.
Fast mode is an APIAPIThe official door 2 systems use to exchange data, without anybody copying it by hand.Open the glossary configuration for Claude Opus that gives answers up to 2.5 times faster, at a higher price per token. The model stays the same, so the answer quality does not change, according to the Claude Code fast mode documentation.
Releases 2.1.310 to 2.1.316 came out between 23 and 31 October 2026. In addition to fast mode, 3 changes affect daily work:
- a new setting that refuses file writes outside the working directories;
- idle compaction now also runs in VS Code and in the Code tab of the Desktop app;
- a separate effort setting for subagents.
We tested the new write setting on 1 November 2026. The test results are in the third section of this article.
What changed in Claude Code 2.1.310 to 2.1.316?
Five releases in 9 days changed the model choice, the file write limits, and how Claude Code summarizes long conversations.
| Version | Release date | Main change | Effect for you |
|---|---|---|---|
| 2.1.310 | 23 Oct 2026 | The Monitor tool is available on Bedrock, Vertex, and Foundry. Compaction after a "Prompt is too long" error keeps less text. | Sessions on cloud providers can monitor long processes. |
| 2.1.311 | 26 Oct 2026 | The word ultrathink runs that turn at xhigh effort. Standard-context sessions no longer stop with "Usage credits required for 1M context". | Ultrathink turns cost more. Sessions above 200K tokens are compacted and then continue. |
| 2.1.312 | 27 Oct 2026 | Write refuses to overwrite a large CLAUDE.md that Claude read only in part. Prompt and agentAI agentAn AI program that performs work steps by itself, for example reading a message, drafting a reply, and recording the result.Open the glossary hooks are limited to 24 at a time per session. | Project rule files are safer from overwrites. |
| 2.1.314 | 30 Oct 2026 | The permissions.blockWritesOutsideWorkingDirectories setting. Idle compaction in VS Code and Desktop. The sandbox now applies to a worktree opened with claude -p --resume. | Stricter write limits. Long idle sessions are summarized automatically. |
| 2.1.316 | 31 Oct 2026 | Opus 4.8 fast mode is deprecated. New variables CLAUDE_CODE_SUBAGENT_EFFORT and CLAUDE_CODE_DISABLE_ULTRATHINK. --restricted sessions no longer upload files from outside the working directories. | Migration is necessary before 30 November 2026. |
Source: official Anthropic release notes on GitHub for v2.1.316, v2.1.314, v2.1.312, v2.1.311, and v2.1.310. Dates use the GitHub release time in UTC.
Opus 4.8 fast mode stops on 30 November: who is affected?
You are affected if a session, a script, or a scheduled job runs fast mode with the Opus 4.8 model.
The 2.1.316 release notes give 2 dates. Opus 4.8 fast mode is deprecated from 30 October 2026 and is removed on 30 November 2026. After that date, a fast mode request on Opus 4.8 returns an error, and Claude Code does not move it to standard Opus 4.8.
Since version 2.1.280, the /fast command selects Opus 5.5 by default. The highest risk is in configurations that lock Opus 4.8: the model setting, the --model flag, the ANTHROPIC_MODEL variable, or a model list in a gateway.
This pattern occurred before. Opus 4.7 fast mode was deprecated on 25 June 2026 and removed on 24 July 2026, according to the fast mode documentation. A move now also decreases the fast mode price per token.
| Model | Fast mode input | Fast mode output | Status on 1 Nov 2026 |
|---|---|---|---|
| Opus 5.5 | $8 | $40 | Available, /fast default |
| Opus 5 | $10 | $50 | Research preview |
| Opus 4.8 | $10 | $50 | Deprecated, removed 30 Nov 2026 |
Prices are in US dollars per 1 million tokens, from the fast mode documentation that we read on 1 November 2026. On Pro, Max, Ultra, Team, and Enterprise plans, fast mode uses usage credits, not the plan limits.
Steps to move to Opus 5.5
- Check the version with
claude --version. Update to 2.1.316 or later. - Find Opus 4.8 in settings and scripts:
grep -rnE "opus-4[.-]8" ~/.claude .claude scripts. - Change the model to Opus 5.5 with
/model, or write"model": "claude-opus-5-5"in settings. - Run 1 real task with
/faston. Compare the result and the cost with/usage. - For
claude -p --settings '{"fastMode": true}'jobs, change the--modelvalue to Opus 5.5. - For Team and Enterprise, make sure that
availableModelsallows Opus 5.5.
Admins who want to control cost can set "fastModePerSessionOptIn": true. With that setting, fast mode does not start automatically in new sessions.
The new write block: what does it stop, and what does it not stop?
The permissions.blockWritesOutsideWorkingDirectories setting makes the Write, Edit, and NotebookEdit tools refuse paths outside the working directories, in all permission modes.
This setting came in version 2.1.314. Put it in ~/.claude/settings.json for all projects, or in .claude/settings.json for 1 project:
{
"permissions": {
"blockWritesOutsideWorkingDirectories": true
}
}We tested this setting on 1 November 2026 with Claude Code 2.1.316 on Linux, the Haiku model, the claude -p command, and the bypassPermissions mode. Each test asked Claude to write 1 file in a folder next to the working directory.
| Test | Setting | Write method | Result |
|---|---|---|---|
| A | On | Write tool | Refused. The error names the setting and suggests /add-dir. |
| B | Off | Write tool | File written. |
| C | On | Bash: echo hello > into the next folder | File written. |
Conclusion: this setting closes the file tool path, but it does not close shell commands. To limit Bash, also turn on the Claude Code sandbox. We discussed the sandbox limits in our article Claude Code 2.1.309 closes sandbox gaps.
For daily use, the error message is clear. In test A, the agent stopped and reported the error, and it did not try another path. You then choose: add the folder with /add-dir, or keep the write refused.
Idle compaction in VS Code and Desktop: lower cost, but you can lose context
Idle compaction summarizes a long conversation that you left, so your next message sends a summary, not the full conversation.
This feature was already in the terminal. Version 2.1.314 adds it to the VS Code chat panel and to the Code tab of the Desktop app. According to the official settings reference, it runs when all of these conditions are true:
- the conversation context reaches 200,000 tokens, the default value;
- the conversation uses the 1-hour prompt cache;
- approximately 1 hour has passed since the last request;
- auto-compaction is on.
Users do not agree about this feature. Issue #66115 (7 June 2026, 24 reactions) asked for compaction during idle time to decrease cold cache cost. Issue #98747 (1 October 2026, 32 reactions, 25 comments) came from a user with approximately 20 parallel sessions. That user reported that the automatic summary removed working context that took hours to build.
Turn the feature off if your sessions hold context that is difficult to build again:
{
"idleCompaction": false
}You can also change the token threshold with the CLAUDE_CODE_IDLE_COMPACT_MIN_TOKENS variable. Values below 100,000 are raised to 100,000.
Subagent effort and ultrathink: better cost control
The CLAUDE_CODE_SUBAGENT_EFFORT variable sets the subagent effort when no other setting names one, so subagents no longer inherit the main session effort.
This variable helps when the main session runs at high effort, but subagents only search files or summarize logs. Example in settings:
{
"env": {
"CLAUDE_CODE_SUBAGENT_EFFORT": "medium"
}
}Since 2.1.311, the word ultrathink in the terminal runs that turn at xhigh effort on Opus 5.5, Sonnet 5.5, Haiku 5.5, and Fable 5.1 through the Anthropic API. If your team does not want that word to increase cost, turn it off with CLAUDE_CODE_DISABLE_ULTRATHINK from version 2.1.316.
Example scenario: an agency with 3 developers
This scenario is an illustration of the effect. It is not customer data.
An agency uses Claude Code to revise client landing pages. The project locks "model": "claude-opus-4-8" in .claude/settings.json, and developers turn on /fast during live revisions with the client. One night job uses claude -p with fast mode to summarize the daily changes.
Without migration, the live revisions and the night job fail with an error from 30 November. The fix has 4 steps:
- Change the model in the project settings to
claude-opus-5-5. - Test 1 landing pageLanding pageThe page an ad points to. It carries 1 offer and 1 action, with no menu pulling the visitor elsewhere.What is a landing page? revision with
/faston. - Add
blockWritesOutsideWorkingDirectoriesso that the agent does not write to other client folders. - Turn on the sandbox so that Bash commands are also limited.
Do you need to upgrade now?
Yes, upgrade to 2.1.316 now if you use fast mode, an automatic permission mode, or --restricted sessions.
| Your condition | Action | Deadline |
|---|---|---|
| Fast mode with Opus 4.8 | Move to Opus 5.5, then test again | Before 30 November 2026 |
Agent in bypassPermissions or auto mode | Turn on blockWritesOutsideWorkingDirectories and the sandbox | This week |
claude -p --resume in a worktree | Update to 2.1.314 or later so that the sandbox applies | This week |
| Long sessions in VS Code or Desktop | Decide if idleCompaction stays on or off | Before your next long session |
| Team or Enterprise admin | Check availableModels and fastModePerSessionOptIn | Before 30 November 2026 |
Do you need help to install agents with safe permission limits? See our AI Agent Ops installation service. To train your team to use coding agents safely, see our agentic AI training.
Conclusion: actions for this week
Find all configurations that use fast mode with Opus 4.8, then move them to Opus 5.5 before 30 November 2026.
Next, turn on blockWritesOutsideWorkingDirectories for agents that run without supervision. Use this setting together with the sandbox, because our test shows that Bash can still write. Last, decide if idle compaction is correct for your long sessions.
Questions and answers
Does Claude Code also remove Opus 4.8?
The 2.1.316 release notes only name fast mode on Opus 4.8. Opus 4.8 at standard speed is not in that removal schedule.
Does blockWritesOutsideWorkingDirectories stop Bash commands?
No. In our test on 1 November 2026, an echo command through Bash still wrote a file outside the working directory. Use the sandbox to limit Bash.
How do I turn off idle compaction?
Write "idleCompaction": false in ~/.claude/settings.json on the machine where the session runs. In the terminal, you can also change the Idle compaction row in /config.
Does fast mode use my Claude plan limits?
No. On Pro, Max, Ultra, Team, and Enterprise plans, fast mode uses usage credits, also when your plan limits are not used up.
Is fast mode available on Amazon Bedrock or Google Cloud?
No. According to the fast mode documentation, fast mode is only available through the Anthropic API and Claude plans, not on Amazon Bedrock, Google Cloud Agent Platform, or Microsoft Foundry.
