Drop #21: Claude Opus 5 Becomes the Default, and MCP Goes Stateless
Two upgrades landed back to back this month: a stronger default model, and a simpler foundation for the protocol connecting Claude to your tools. Anthropic shipped Claude Opus 5 on July 24, and the MCP 2026-07-28 spec on July 28.
Claude Opus 5 Is Now the Default on Max
On July 24, Anthropic released Claude Opus 5, succeeding Opus 4.8 as the Opus-tier model. It's now the default model on Claude Max and the strongest model available on Claude Pro, priced the same as its predecessor at $5 per million input tokens and $25 per million output tokens.
For Cowork, Opus 5 brings gains in agentic coding, computer use, and long-horizon knowledge work - the multi-step, unattended tasks Cowork is built to chain together - along with improvements to mathematical reasoning.
MCP Moves to a Stateless Core
On July 28, the Model Context Protocol shipped its fifth spec release, MCP 2026-07-28. The core change: MCP moves from a stateful, bidirectional protocol to a stateless request/response model, so MCP servers can run on serverless and edge infrastructure instead of holding open connections.
The spec also graduates MCP Apps and Tasks into a versioned extensions framework and hardens authorization to match production OAuth 2.0 and OIDC deployments, so MCP servers can connect to enterprise identity systems like Entra or Okta without workarounds. Support is rolling out across Claude products, including Cowork's connector directory of more than 950 MCP servers.
Tip of the Week: Recheck Recurring Tasks After a Default Model Change
When the model powering Cowork changes, tasks you've been running on autopilot can quietly behave differently. A default-model swap like Opus 5 replacing Opus 4.8 on Max is a good moment to double check anything that needs to stay consistent.
❌ Weak
Assume a scheduled Cowork task will keep producing the same kind of output forever, without ever checking which model version is actually running it.✅ Strong
After a default-model change, spot-check a couple of your recurring Cowork tasks against the new model before trusting the output unchanged.The rule of thumb: Cowork's default model isn't fixed - if a task's output needs to stay predictable, it's worth knowing, and occasionally re-verifying, which model version produced it.
Worth Reading This Week
- → Bringing MCP 2026-07-28 to Claude - Claude by Anthropic - Anthropic's overview of the new stateless MCP spec, its extensions framework, and hardened auth.
- → Introducing Claude Opus 5 - Anthropic - Anthropic's announcement of the new default Opus-tier model and its performance gains.
- → MCP 2026-07-28 Specification - Model Context Protocol - The full spec text for MCP's stateless core and its new extensions framework.
A stronger default model and a simpler protocol underneath it point the same direction: more of Cowork's work happens without you having to think about the plumbing. Worth keeping an eye on both as they finish rolling out.
Until next time.
— The ClaudeCowork.com team