Claude Code v2.1.159 to v2.1.160 Major Updates
I will explain the main improvements, including security enhancements, background agent stabilization, and the trigger keyword change for Dynamic Workflows (`workflow` → `ultracode`).
2026.06.02
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This is Ishikawa from the Cloud Business Division. Here is a summary of the Claude Code updates for v2.1.159 ~ v2.1.160 (May 31 ~ June 1, 2026).
Update Summary
This covers 2 versions (v2.1.159 ~ v2.1.160, May 31 ~ June 1, 2026). v2.1.159 includes only internal infrastructure improvements, with user-facing changes concentrated in v2.1.160. The main highlights this time are security enhancements such as confirmation prompts before writing to shell startup files, stability improvements around background agents (claude agents), and a breaking change that renames the Dynamic Workflows trigger keyword from workflow to ultracode.
Notable Updates
- Improvement: When Claude views a single file using
grep/egrep/fgrep, it no longer needs to call the Read tool separately before editing (relaxed read-before-edit check. v2.1.160). - Bug Fix: Fixed an issue where chat history was lost and the first prompt was re-executed (potentially causing side-effectful operations to run twice) when restoring completed sessions in
claude agentsor re-attaching background sessions after overnight retirement (v2.1.160). - Security: A confirmation prompt is now displayed before writing to shell startup files,
~/.config/git/, and build tool configuration files (v2.1.160).
Target Versions and Period
| Version | Release Date | Notes |
|---|---|---|
| v2.1.159 | 2026-05-31 | Internal infrastructure improvements only (no user-facing changes) |
| v2.1.160 | 2026-06-01 | Main body of user-facing changes |
Security
Confirmation prompts have been added for writes that could lead to unintended command execution.
- Confirmation before writing to shell startup files and Git configuration (v2.1.160): A confirmation prompt is now displayed before writing to shell startup files such as
.zshenv,.zlogin,.bash_login, or files under~/.config/git/. These files had the potential to lead to unintended command execution if overwritten. - Confirmation before writing to build tool configuration even in
acceptEditsmode (v2.1.160): Even inacceptEditsmode, which automatically approves edits, a confirmation prompt is now displayed before writing to build tool configuration files that could permit code execution (such as.npmrc,.yarnrc*,bunfig.toml,.bazelrc,.pre-commit-config.yaml,.devcontainer/, etc.).
Improvements
- Files viewed with
grepno longer require an additional Read before Edit (v2.1.160): Claude Code has a safety mechanism (read-before-edit check) that requires a file to be read before it can be edited. This is a constraint placed on the agent's tool operations, not something the user manually executes withRead. Previously, even if the contents were confirmed withgrep, a separate Read tool call was required before editing. In v2.1.160, viewing a single file withgrep/egrep/fgrepis now treated as satisfying this check, allowing the agent to proceed directly to editing immediately after confirming the relevant section withgrep. As a result, the agent's redundant read steps are reduced and responses proceed more efficiently. - Background agent behavior improvements (v2.1.160): Performance has been improved when opening recently inactive sessions in
claude agents. The latency of the auto mode classifier has also improved, reducing how often routine operations are blocked with "could not evaluate this action." Furthermore, during termination (claude rm/stop, idle collection), SIGTERM is now sent to running shell subprocesses before SIGKILL, ensuring cleanup processes are reliably executed. - Removed JetBrains plugin installation suggestion at startup (v2.1.160): The JetBrains plugin installation suggestion that appeared at startup has been removed.
Fixes (Major)
A selection of fixes related to stability and usability.
- Fixed history loss when restoring completed sessions in
claude agents(v2.1.160): Restoring a completed session caused chat history to be lost and the first prompt to be re-executed. This risked redoing already completed work and double-executing side-effectful operations. - Fixed conversation loss when re-attaching background sessions (v2.1.160): Fixed an issue where background sessions re-attached after overnight retirement lost their conversation content and re-executed the first prompt.
- Fixed Japanese IME composition display position (v2.1.160): Fixed an issue in the
claude agentsview where CJK IME composition text such as Japanese was displayed at the bottom-left of the screen instead of at the input position. - Fixed voice mode connection failure with non-ASCII paths (v2.1.160): Voice mode was failing to connect when the project directory name or branch name contained non-ASCII or special characters.
- Fixed several-second freeze when returning to
claude agentslist (v2.1.160): Fixed an issue where the auto-updater re-checked every time the session list was returned to, causing a several-second freeze. - Fixed key input unresponsiveness under high CPU load on Windows (v2.1.160): Fixed an issue on Windows where Esc, arrow keys, and input became unresponsive under high CPU load while attached to a background session or viewing the agent display.
- Fixed history disappearance when resuming a session in brief mode (v2.1.160): Fixed an issue where turning off brief mode and resuming a brief mode session caused past replies to disappear from the scroll-back buffer.
- Fixed clipboard copy failure in WSL (v2.1.160): Fixed an issue where copy-on-select was not being written to the Windows clipboard in WSL. It now uses PowerShell integration instead of OSC 52, and works with terminals that do not support OSC 52, such as MobaXterm.
- In addition, numerous minor bugs have been fixed, including startup failures in
claude --bgdue to "socket missing," deletion of session start directories on Windows, incorrect "Completed" display in the agent list, display corruption in some terminals (Apple Terminal, tmux), brokenfile:///C:/...links, paste position in vim mode, and error messages with third-party providers.
Breaking Changes and Deprecations
- Dynamic Workflows trigger keyword changed from
workflowtoultracode(v2.1.160): The keyword for launching Dynamic Workflows has been changed fromworkflowtoultracode. As a result, the word "workflow" will no longer trigger the workflow (you can still use it by making a request in your own words). The trigger keyword is highlighted in violet in the prompt input field. As a related fix,/effort ultracodewill no longer be displayed for models that cannot run xhigh, and the incorrect display blaming Dynamic Workflows settings for why a feature is unavailable has also been resolved. - Removed environment variable
CLAUDE_CODE_OPUS_4_6_FAST_MODE_OVERRIDE(v2.1.160): The environment variable has been removed and setting it will have no effect (no-op).
Closing
This update consisted of v2.1.159 with only internal improvements and v2.1.160 as the main body of user-facing changes. The focus is on security enhancements such as confirmation prompts before writing to shell startup files and build tool configuration files, and stabilization of background agents. In particular, the change of the Dynamic Workflows trigger keyword from workflow to ultracode will affect those who have been launching it with "workflow." If any of the changes catch your attention, please update and check them out.
Recent Updates
References