Last Week In Claude Code #5 — Cross-Session Message, MCP Stateless, DeepSeek V4 & More
Agents That Talk to Each Other, MCP's Biggest Update, and Free Model Testing
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This is Issue #5 of the Last Week In Claude Code series.
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The last week had a lot going on:
Agents can now message each other across machines
MCP shipped its biggest update since launch
Claude Code can now run on your own servers
I tested DeepSeek V4-Flash against Fable 5 with some surprising results
We are also adding a new section starting this week: External Models Testing & Tools, where I share what I am testing outside of Anthropic models and what is worth your time.
What Happened Last Week In Claude Code?
#1) Cross-Session SendMessage — Agents Can Now Talk to Each Other
Version: 2.1.224
Claude Code sessions can now send messages to each other across tabs, machines, and projects
What It Does
Before this, agents were isolated. You could run parallel sessions, but no way for sessions to coordinate without your input
Now one session can message another directly using SendMessage and use ListAgents to discover all available sessions across your machines.
# List all available sessions (including other machines)
ListAgents
# Sessions appear as:
# name [ref] — local or remote
SendMessage can also start a new conversation with a Remote Control session on another machine by name.
Auto mode now evaluates messages sent between agents via SendMessage before dispatch, so one compromised agent cannot instruct another to bypass permissions.
Multi-agent workflows just got coordination. A parent agent can now delegate to a specialist agent, check its progress, and act on the result.
I shared the complete test results in my Medium tutorial; learn more here
#2) Auto Mode — Now the Default for Everyone
Version: 2.1.207+
Auto mode is now the default permission mode across all Claude Code sessions.
What Changed
Previously, you had to opt in or configure auto mode manually using the shift+tab.
Now, it is on by default for all users.
Auto mode classifies every tool call before it runs, deciding automatically whether it is safe to allow or needs your approval. The goal is fewer interruptions on routine work.
What You Can Still Control
Auto mode does not mean Claude does everything without asking. It means the classifier makes the call instead of defaulting to a prompt.
You can still:
# Switch to manual at any time
/config → Permission mode → Manual
# Or via settings
{ "defaultMode": "manual" }
# Disable auto mode entirely
{ "disableAutoMode": true }
Recent improvements to auto mode worth knowing:
Parallel tool call checks are now cache-efficient; faster decisions when multiple tools run at once
Safety filter refusals no longer count toward the consecutive-block limit; Claude moves on instead of retrying
SendMessage between agents now goes through the classifier before delivery
I shared a quick tutorial on Medium to help you learn how Auto mode works.
#3) Anthropic MCP Stateless — The Biggest MCP Update Since Launch
Spec: MCP 2026-07-28
The Model Context Protocol just shipped its most significant update since it launched.
MCP is now stateless.
What Changed?
The old MCP used a bidirectional stateful protocol; every connection needed a persistent session, a handshake, and a session ID. Servers had to maintain state between calls.
MCP is now a request/response model like HTTP:
MCP servers can now run on serverless and edge infrastructure (Cloudflare Workers, AWS Lambda)
No more session management to work around
Easier to scale, easier to deploy, easier to build
MCP recently surpassed 400 million monthly SDK downloads. There are now over 950 MCP servers in the Claude connector directory.
What is Deprecated?
The old spec is not going away immediately, but they gave a 12-month deprecation window, so you should start planning:
Roots,Sampling,Logging, andSSEare deprecatedThe
initialize/initializedhandshake is removedThe
Mcp-Session-Idheader is removed
I created a complete Stateless MCP demo that you can follow to see how to carry out the updates or build your new MCP using the stateless protocol
For Claude Code Users
If you use MCP servers in your workflows, check whether your servers have been updated to the new spec.
Many MCP servers will need a refactor; check out my full walkthrough on Medium: Anthropic Just Overhauled MCP (I Built My First Stateless MCP Server)
#4) Self-Hosted Runner — Run Claude Code on Your Own Machines
Version: 2.1.224
You can now turn your own machines or containers into a place where Claude Code sessions run.
Available on Team and Enterprise plans.
What It Does
claude self-hosted-runnerThis registers your machine as a runner. Claude Code web, mobile, and desktop sessions can then execute on it instead of Anthropic’s cloud infrastructure.
For teams with compliance requirements, air-gapped environments, or sensitive codebases, running Claude Code on your own infrastructure changes what is possible.
What to Know
Available on Team and Enterprise plans only
If the
--base-dircannot be created or written, it exits at startup with a clear error instead of registering and failing every sessionArchive plugin installs (zip over HTTPS) are also supported in this version; useful for air-gapped setups
# Register your machine as a runner
claude self-hosted-runner
# With a custom base directory
claude self-hosted-runner --base-dir /path/to/dirI have not yet tested the self-hosted runner since I don’t have a team or max plan; in the future, I will demonstrate how this works.
#5) Quick Wins — Subagent Cap Removed & Plugins Activate Immediately
Two smaller changes that improve Claude Code daily workflows.
Subagent Cap Removed
The 200-subagent-per-session spawn limit is gone. Long-running sessions no longer refuse to spawn new agents after hitting the cap.
Plugins Activate Immediately
Installing a plugin no longer requires /reload-plugins to take effect.
# Before: install, then reload
/plugin install my-plugin
/reload-plugins
# Now: install and it is live
/plugin install my-pluginExternal Models Testing & Tools
A new section where I share what I am testing outside of Anthropic models and what is worth your time.
DeepSeek V4-Flash on Claude Code — 71x Cheaper Than Fable 5
DeepSeek just released the V4-Flash API into public beta, and I ran it on Claude Code.
The benchmark: Terminal-Bench 2.1, the evaluation for agentic coding — DeepSeek V4-Flash scores 82.7. That beats Fable 5 on this benchmark.
71x cheaper on input. 178x cheaper on output.
My real session cost: Built a full Windows screen time monitor app; background tracker, dashboard with three tabs, alerts, SQLite storage. Total cost: $0.13.
Two ways to run it:
Via Ollama:
ollama launch claude --model deepseek-v4-flash
Via Direct API:
export ANTHROPIC_BASE_URL="https://api.deepseek.com/v1"
export ANTHROPIC_API_KEY="your-deepseek-api-key"
export ANTHROPIC_DEFAULT_SONNET_MODEL="deepseek-v4-flash"
claudeThe direct API gives you lower latency and the full 1M context window.
You can see my full test of DeepSeek v4 Flash on Claude Code here — I Tried DeepSeek V4-Flash on Claude Code (It Beats Fable 5 at 71x Lower Cost)
Finally, I built and open-sourced a framework for structured AI coding that works across Claude Code, Codex, Cursor, and OpenCode. We will feature it in next week's issue.
You are now up to date with the latest major Claude Code updates.
I appreciate your support, and feel free to reach out. You can access the premium tutorials, newsletters, and course updates or modules as they are released in our membership area. You can also get in touch with me anytime in our private community, via email, or direct message here on Substack. Claude Code Masterclass Pro is live; join us today and let’s keep this going.
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Claude Code Masterclass
Let’s Build It Together
— Joe Njenga
Thanks for all the information. You yourself are a machine man, great job.