• Opus 4.8 ships as the default model with high effort baked in. /effort xhigh is the new top gear for your hardest tasks (more below).

• Dynamic workflows let you orchestrate tens to hundreds of agents from a single prompt. Run /workflows to view your active runs.

• /simplify is back, but it only runs cleanup (reuse, efficiency, altitude), not the full bug-hunting review. Use /code-review when you need correctness findings (more below).

• CLAUDE_CODE_OPUS_4_6_FAST_MODE_OVERRIDE is deprecated and removed June 1. Switch to /model claude-opus-4-6[1m] then /fast on instead.

• Lean system prompt is now the default for Opus 4.8 (and all models except Haiku, Sonnet, and 4.7 and earlier). If you see prompt-sensitive behavior changes, this is why.

New in 2.1.156, 2.1.154

2.1.156 (May 29, 2026)

• Fixed an issue when using Opus 4.8 where thinking blocks were modified, leading to API errors.

2.1.154 (May 29, 2026)

• Opus 4.8 is here! Now defaults to high effort; /effort xhigh for your hardest tasks
• Introducing dynamic workflows: ask Claude to create a workflow and it orchestrates work across tens to hundreds of agents in the background, so you can take on larger, more complex tasks. Run /workflows to view your runs
• Fast mode on Opus 4.8 is now available at a fraction of its previous cost: 2x the standard rate for 2.5x the speed
• The lean system prompt is now the default for all models except Haiku, Sonnet, and Opus 4.7 and earlier
• Claude now reserves the multiple-choice question prompt for decisions it genuinely cannot make itself, instead of asking when it already has enough context to proceed
• /simplify now runs a cleanup-only review (reuse, simplification, efficiency, altitude) and applies the fixes, instead of running the full /code-review --fix bug-hunting review
• Renamed the /effort slider labels from "Speed"/"Intelligence" to "Faster"/"Smarter" for clarity
• claude agents: type ! <command> to run a shell command as a background session you can attach to and detach from. Also available as claude --bg --exec '<command>'
• claude agents: /logout now signs you out instead of being sent to a background session
• ←← to open the agents view now works on Bedrock, Vertex, Foundry, and with telemetry disabled
• Claude in Chrome: pick which connected browser to use via /chrome, or in-chat when a browser action runs with multiple connected
• Plugins can now declare defaultEnabled: false in plugin.json or a marketplace entry; enable them with /plugin or claude plugin enable. Dependencies of enabled plugins are still enabled automatically
• The /plugin Discover tab now pins plugins whose relevance signals match the current directory with a "suggested for this directory" annotation
• Streaming tool execution is now always enabled, including when telemetry is disabled or on Bedrock/Vertex/Foundry (previously behind a feature flag)
• Stdio MCP server subprocesses now receive CLAUDE_CODE_SESSION_ID and CLAUDECODE=1 in their environment
• claude mcp list/get now show unapproved .mcp.json servers as "Pending approval" instead of auto-approving and connecting when output is piped
• /remote-control autocomplete now shows "Disconnect Remote Control" when Remote Control is already active
• Added Claude Opus 4.8 support and 4.7 to 4.8 migration guidance to the /claude-api skill
• Deprecated CLAUDE_CODE_OPUS_4_6_FAST_MODE_OVERRIDE (will be removed on 06/01). To use fast mode on Opus 4.6, switch with /model claude-opus-4-6[1m] and then /fast on
• Improved the auto-mode classifier's detection of data exfiltration, particularly bulk transfers of repository contents
• Fixed rm -rf $HOME not being blocked as a dangerous path when HOME has a trailing slash
• Fixed $TMPDIR resolving to different directories in sandboxed vs unsandboxed Bash commands within the same session
• Fixed unreadable highlighted-row text in claude agents when the Claude Code theme doesn't match the terminal background
• Fixed background-agent completion notifications triggering premature "out of context" behavior on some 1M-context models
• Fixed background-session classifier losing the user's goal when a scheduled /command fires
• Fixed pinned background sessions respawning every minute after a Claude Code update, causing repeated agent-start notifications and process churn at idle
• Fixed background sessions stuck at "blocked", "running", or "working" not retiring after the idle grace period
• Fixed subagents in background sessions bypassing the worktree-isolation guard and writing to the shared checkout
• Fixed orphaned claude --bg-pty-host processes spinning at 100% CPU after the daemon exits on macOS
• Fixed number key shortcuts not working for options shown below the divider in option dialogs
• Fixed worktree.baseRef: "head" resolving to the main checkout's HEAD instead of the current worktree's HEAD when spawning subagents or calling EnterWorktree from inside a linked worktree
• Fixed a stray leading space on wrapped lines when the previous line ended exactly at the terminal width
• Fixed intermittent terminal rendering corruption in VS Code by capping the number of distinct colors the thinking spinner produces
• Fixed plan file names including [Image #N] / [Pasted text #N] placeholders when a plan-mode prompt starts with pasted images or text
• Fixed a phantom expand/click affordance on colored tool output: short ANSI-colored lines that fit on screen no longer show a "ctrl+o to expand" hint
• Fixed a single invalid allowedMcpServers/deniedMcpServers entry in managed settings discarding all managed-settings policy; the bad entry is now dropped with a claude doctor warning
• Fixed API 400 errors on models that don't support the effort parameter when CLAUDE_CODE_ALWAYS_ENABLE_EFFORT is set
• Windows: Fixed update failures caused by claude.exe being in use showing a generic error instead of telling you to close other sessions and retry
• Removed the stale "& for background" hint from the shortcuts help panel
• [VSCode] Auto mode no longer requires the bypass-permissions setting to appear in the mode picker, and a dismissable notice on the new-session screen explains auto mode the first time it's active
• Fixed the task panel below the prompt showing a stray unselectable "main" row when only a workflow is running
• Fixed /mcp tools list and tool detail rendering when MCP servers have long or multi-line tool names or long descriptions
• Fixed the /model picker not showing fast mode pricing on the Default option for API (pay-as-you-go) users when fast mode is on
• Fixed auto mode incorrectly blocking actions with "could not evaluate this action" when the safety classifier ran out of output tokens while reasoning

Notes