Claude Code 2.1.154: Opus 4.8, Dynamic Workflows, Fast Mode Pricing

TL;DR

• Opus 4.8 now default with high-effort mode for complex tasks
• Dynamic workflows let Claude orchestrate tens to hundreds of agents automatically
• Fast mode on Opus 4.8 costs 2x standard rate for 2.5x speed
• Lean system prompt becomes default; multiple bug fixes and security improvements

New

• Opus 4.8 default — Claude Code now defaults to Opus 4.8 with `/effort xhigh` enabled for your hardest tasks
• Dynamic workflows — Ask Claude to create a workflow and it orchestrates work across tens to hundreds of agents in the background. Run `/workflows` to view your runs
• Fast mode pricing on Opus 4.8 — 2x the standard rate for 2.5x the speed, making it more accessible than before
• Lean system prompt default — Now the default for all models except Haiku, Sonnet, and Opus 4.7 and earlier
• Claude agents shell commands — Type `! <command>` to run shell commands as background sessions you can attach to and detach from
• Browser selection in Chrome — Pick which connected browser to use via `/chrome` → "Select browser…"
• Plugin control improvements — Plugins can declare `defaultEnabled: false` in `plugin.json`; enable with `/plugin`. Discover tab now pins plugins suggested for your directory
• MCP environment variables — Stdio MCP server subprocesses now receive `CLAUDE_CODE_SESSION_ID` and `CLAUDECODE=1`

Improved

• Multiple-choice prompts — Claude now reserves these for decisions it genuinely cannot make, instead of asking when it already has enough context
• /simplify command — Now runs cleanup-only review (reuse, simplification, efficiency, altitude) and applies fixes instead of full bug-hunting review
• /effort slider labels — Renamed from "Speed"/"Intelligence" to "Faster"/"Smarter" for clarity
• Agents view on Bedrock/Vertex — `←←` to open agents view now works on Bedrock, Vertex, Foundry, and with telemetry disabled
• Streaming tool execution — Now always enabled, including when telemetry is disabled or on Bedrock/Vertex/Foundry
• MCP server approval flow — `claude mcp list`/`get` now show unapproved `.mcp.json` servers as `⏸ Pending approval` instead of auto-approving
• Auto-mode safety classifier — Improved detection of data exfiltration, particularly bulk transfers of repository contents

Fixed

• Dangerous path blocking when `HOME` has a trailing slash
• `$TMPDIR` resolving to different directories in sandboxed vs unsandboxed Bash commands within the same session
• Unreadable highlighted-row text in `claude agents` when theme doesn't match terminal background
• Background-agent completion notifications triggering premature "out of context" behavior
• Background-session classifier losing user's goal when scheduled `/command` fires
• Pinned background sessions respawning every minute after Claude Code update, causing repeated notifications and process churn
• Background sessions stuck at "blocked", "running", or "working" not retiring after idle grace period
• Subagents in background sessions bypassing worktree-isolation guard and writing to shared checkout
• Orphaned `claude --bg-pty-host` processes spinning at 100% CPU after daemon exits on macOS
• Number key shortcuts not working for options below divider in option dialogs
• `worktree.baseRef: "head"` resolving to main checkout's HEAD instead of current worktree's HEAD when spawning subagents
• Stray leading space on wrapped lines when previous line ended exactly at terminal width
• Intermittent terminal rendering corruption in VS Code from thinking spinner colors
• Plan file names including `[Image #N]` / `[Pasted text #N]` placeholders when plan-mode prompt starts with pasted images or text
• Phantom expand/click affordance on colored tool output
• Single invalid `allowedMcpServers`/`deniedMcpServers` entry discarding all managed-settings policy
• API 400 errors on models that don't support effort parameter when `CLAUDE_CODE_ALWAYS_ENABLE_EFFORT` is set
• Windows update failures showing generic error instead of telling you to close other sessions
• Task panel showing stray unselectable "main" row when only workflow is running
• `/mcp tools list` and tool detail rendering with long or multi-line tool names
• `/model` picker not showing fast mode pricing on Default option for API users
• Auto mode incorrectly blocking actions with "could not evaluate this action" when safety classifier ran out of output tokens

Breaking Changes

• Deprecated environment variable — `CLAUDE_CODE_OPUS_4_6_FAST_MODE_OVERRIDE` will be removed on 06/01. Switch to Opus 4.8 or use `/model claude-opus-4-6` then `/fast on`
• /logout behavior change — Now signs you out instead of sending you to a background session

Update Claude Code via your IDE extension marketplace or run `npm install -g @anthropic-ai/claude-code` for CLI.

Source: Claude Code