★ THE AGENT STACK · ROLLING STONE · #150

Anthropic acquires Stainless to bolster API infrastructure

Anthropic has acquired Stainless, a company specializing in API development tools and infrastructure. The move strengthens Anthropic's ability to manage and scale its API services for Claude integrations. This acquisition signals investment in developer tooling and platform reliability as Claude adoption grows.

Thursday · May 21 · 2026
anthropic.com
⚡ release

2.Claude Code adds cross-session feedback and reliability fixes

The latest Claude Code update enables the `/feedback` command to reference sessions from the previous 24 hours, improving debugging for intermittent issues. Additional stability improvements address hook management, background session handling, and platform-specific behavior across Windows and macOS, enhancing overall reliability.

github.com
⚡ release

3.Microsoft launches Agent Framework, shifting agentic AI investment away from AutoGen

Microsoft unveiled Microsoft Agent Framework as its new open-source foundation for building agentic AI applications, with integration planned across Microsoft 365 Agents SDK, Azure AI Foundry, and VS Code AI Toolkit. While AutoGen and Semantic Kernel remain supported, the company is concentrating most new development on the unified Agent Framework, which consolidates orchestration concepts like GroupChat and GraphFlow into a new Workflow abstraction.

devblogs.microsoft.com
⚡ release

4.Claude Code expands output limits and improves context handling

Claude Code now supports expanded output limits and refined context memory management, allowing for longer, more complex code generation sessions. Improvements to async control, hooks, and workflows give developers finer-grained control over extended coding tasks and multi-step operations.

builder.io
⚡ release

5.Sonnet 4.6 enters beta with 1M token context window

Anthropic expanded Sonnet's capabilities by introducing a 1M token context window option in beta testing. This represents a significant jump in context handling for the mid-tier model, enabling processing of much longer documents and codebases without truncation, which should benefit users working with large-scale projects.

support.claude.com
⚡ opinion

6.Code engineering fixes quality regressions in recent updates

Anthropic published a postmortem addressing quality issues in Claude Code and related products, acknowledging that recent default reasoning effort changes and session-idle thinking bugs had degraded performance. The team reverted problematic updates and fixed underlying issues, signaling a course correction after community complaints on Hacker News.

anthropic.com
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