Anthropic Breaking News | Claude Code 2.1.143 and Python SDK Breaking Changes

[1] Claude Code v2.1.143 — Enforced Plugin Dependencies and New worktree.bgIsolation: "none"

Claude Code v2.1.143 has been released (primary source: https://github.com/anthropics/claude-code/releases, 2026-05-15 22:28 UTC).

Impact for engineer readers: ★★★

The biggest change is enforced plugin dependency management. claude plugin disable will now be rejected if another enabled plugin depends on the target plugin, and a hint for the disable chain will be displayed. On the claude plugin enable side, transitive dependencies are automatically enabled. This is a spec change that directly reduces operational overhead for teams running multiple plugins in combination.

Additionally, the /plugin marketplace reference pane now displays projected costs (token estimates) per turn and per invocation, giving you more information to aid in selection. The new worktree.bgIsolation: "none" setting is a long-awaited option for background sessions that edit the working copy directly without going through EnterWorktree. It allows CI and auto-fix background agents to avoid the overhead of worktree switching.

Other changes include: PowerShell tools now default to -ExecutionPolicy Bypass (opt-out env var: CLAUDE_CODE_POWERSHELL_RESPECT_EXECUTION_POLICY=1); PowerShell tools on Windows are now enabled by default for Bedrock / Vertex / Foundry users; and claude agents has been extended to accept --add-dir / --settings / --mcp-config / --plugin-dir / --permission-mode / --model / --effort / --dangerously-skip-permissions flags.

Bug fixes include: preserving model/effort level on background session idle resume; fixing a CLI hang when the scopes value in .credentials.json is not an array; right-click paste in claude agents for Windows Terminal / WSL; and Stop hook infinite loop suppression (exits after 8 consecutive blocks).

[2] Claude Agent SDK Python v0.2.82 — Breaking Changes: MCP Background Connections and Task-Based Tool Switch

Claude Agent SDK Python v0.2.82 has been released (primary source: https://github.com/anthropics/claude-agent-sdk-python/releases, 2026-05-15 03:47 UTC). This release contains 2 breaking changes.

Impact for engineer readers: ★★★

The first breaking change is that MCP servers now connect in the background by default. Sessions start immediately, and slow servers are reported with status: "pending" until they are ready. While this allows sessions to start immediately without being held up by MCP server startup latency, note that you may need to implement status: "pending" handling in some cases.

The second breaking change is that headless sessions / SDK sessions now use Task-based tools instead of TodoWrite. Specifically, they switch to four tools: TaskCreate / TaskUpdate / TaskGet / TaskList. Code that relied on TodoWrite's return values or side effects will require migration.

As a new feature, the public type EffortLevel has been added to represent effort string levels ("low" / "medium" / "high" / "max" / "xhigh"), enabling type-safe effort specification. Bug fixes include a stderr callback isolation issue, CancelledError in eager-flush completion callbacks, and improved accuracy of permission_suggestions types. The mcp dependency has been bumped to >=1.23.0, announced as a security fix. The bundled Claude CLI has been updated to v2.1.142.

Install with pip install claude-agent-sdk==0.2.82. Teams operating Python-based automation infrastructure are recommended to validate early.

[3] Claude Agent SDK TypeScript v0.3.143 — peerDependencies Change and yarn classic Considerations

Claude Agent SDK TypeScript v0.3.143 has been released (primary source: https://github.com/anthropics/claude-agent-sdk-typescript/releases, 2026-05-15 22:28 UTC).

Impact for engineer readers: ★★

The main change is moving @anthropic-ai/sdk and @modelcontextprotocol/sdk from dependencies to peerDependencies. There is no change in runtime behavior, and both SDKs are still bundled. npm / bun / pnpm will install them automatically, but yarn classic users need to add them explicitly for full TypeScript type resolution. To avoid type resolution failures, explicitly add @anthropic-ai/sdk and @modelcontextprotocol/sdk to your package.json.

Installation commands: npm install @anthropic-ai/claude-agent-sdk@0.3.143 / yarn add @anthropic-ai/claude-agent-sdk@0.3.143 / pnpm add @anthropic-ai/claude-agent-sdk@0.3.143 / bun add @anthropic-ai/claude-agent-sdk@0.3.143. This is a synchronized release with Claude Code v2.1.143, and the discontinuous version number (v0.2.141 → v0.3.143) appears to be a jump due to version synchronization with the Python version (v0.2.82).

[What to Watch Next] Python SDK Task-Based Tool Migration and Plugin Dependency Design Review

From the editorial team's perspective, the migration from TodoWrite to Task-based tools in the Python SDK is the most pressing action item in the near term. Before deploying to production, verify the behavior of the Task-based tools (TaskCreate / TaskUpdate / TaskGet / TaskList) in local/staging environments and implement status: "pending" handling for MCP servers. On the Claude Code side, plugin dependencies are now enforced, so developers combining multiple plugins should audit their dependency graph once, and align their design with the disable chain hints for safety. For TypeScript, yarn classic users only need to update package.json and they are done.

[Sources] Primary Source Links Referenced in This Article

• Claude Code release list: https://github.com/anthropics/claude-code/releases
• Claude Agent SDK Python release list: https://github.com/anthropics/claude-agent-sdk-python/releases
• Claude Agent SDK TypeScript release list: https://github.com/anthropics/claude-agent-sdk-typescript/releases