Anthropic shipped Claude Code v2.1.284 on 2026-09-28 (@anthropic-ai/[email protected]): claude-sonnet-5-5 is now the default Sonnet on the Anthropic API—1M context, $2/$10 per MTok, $0.20/MTok cache reads. Adds “Yes, but ask again next time” for auto-mode reads, /mcp reconnect all, dollar spend limits in /usage and the status line (used_usd/limit_usd/period), and rebindable effort-slider keybindings. Stability fixes: damaged streams writing undefined, overloaded errors after thinking blocks, and double-compact when Prompt-too-long persists.

Key Takeaways

  • ✓v2.1.284 makes claude-sonnet-5-5 the default Sonnet (1M ctx, $2/$10, $0.20 cache reads)
  • ✓/usage + status line show dollar spend limits; /mcp reconnect all retries failed MCP servers
  • ✓Auto-mode: Yes-but-ask-again for out-of-cwd reads; effort slider keybindings rebindable
  • ✓Stability: damaged-stream/undefined fixes; retry after thinking-block overload; second compact on Prompt-too-long
🧭

Finished reading? Explore benchmark rankings & pricing

Real-world SWE-bench scores & $20/mo vs API cost break-even calculator

🏆 Leaderboard→💰 Compare Plans↗
🔗

Project Links & Resources

Direct Access
Direct access to official project resources and documentation
🐙
GitHub Release v2.1.284
github.com/anthropics/claude-code/releases/tag/v2.1.284
↗
📖
npm @anthropic-ai/claude-code
www.npmjs.com/package/@anthropic-ai/claude-code
↗
📖
Claude Code docs
code.claude.com/docs/en/overview
↗
🐙
claude-agent-sdk-python v0.2.161
github.com/anthropics/claude-agent-sdk-python/releases/tag/v0.2.161
↗
📖
PyPI claude-agent-sdk 0.2.161
pypi.org/project/claude-agent-sdk/0.2.161/
↗
🔬

In-Depth Technical Analysis

Core Background & Industry Pain Points After Sonnet 5.5 launched, CLI defaults lagging the model tier confuse users; MCP auth failures need per-server reconnects; gateway spend is hard to see inside the TUI. ### Architecture Highlights & Internals v2.1.284 defaults Sonnet to claude-sonnet-5-5 (1M ctx, $2/$10, $0.20 cache reads). Adds Yes-but-ask-again for out-of-cwd auto-mode reads; dollar spend in /usage/status line; effort-slider keybindings; /mcp reconnect all; Google OTLP auth and private_key_jwt for gateway IdP. Fixes damaged-stream undefined writes, post-thinking overload retries, and a second compact when Prompt-too-long persists. ### Authoritative Benchmarks & Measured Scores No new Terminal-Bench numbers in this CLI release—use the Sonnet 5.5 model launch figures. Pricing/context specs above are from the v2.1.284 notes. ### Developer Hands-on Guide npm i -g @anthropic-ai/[email protected]. Check /usage, use /mcp reconnect all on MCP failures. Python SDK: 0.2.161. Docs: overview.