Framework Update | Agno 3.0.6

TL;DR Agno 3.0.6 highlights: (1) `MCPConfig(stateless=True)` serves `/mcp` without session tracking so any replica can answer any request, removing the need for session affinity in multi-instance deployments (at the cost of server-initiated notifications and SSE resumability); (2) `MCPTools(protocol_mode="auto")` negotiates the newest MCP protocol era both sides support, including the sessionless capability from the 2026-07-28 spec, while the default `"legacy"` mode keeps today's behavior unchanged; (3) adds an AgentOS MCP Server Card (`GET /mcp/server-card`), `.zip`/`.eml` file uploads, `AuthorizationConfig.excluded_route_paths`, and fixes for Anthropic thinking-block replay, Gemini image MIME types, and more. No breaking changes in this release.

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Table of Contents

Version Info
Why This Release Matters
Key Changes
Breaking Changes
Migration Guide
How It Compares to Other Frameworks
Today's Takeaway
References

Series: AI Framework Changelog (15 / 15)

Framework Update | Mastra @mastra/core@1.64.0

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Version Info

Item	Value
Framework	Agno
Version	v3.0.6
Previous	v3.0.5
Release Date	2026-09-04
Release Notes	GitHub Release
GitHub	agno-agi/agno
Stars	42.0k

Why This Release Matters

The previous entry (3.0.5) fixed Knowledge ingestion's data-integrity contract. 3.0.6 goes back to fix the deployment model of MCP serving itself. Until now, MCP servers — including Agno's own AgentOS MCP endpoint — defaulted to session-based: once a client connects, its session state is pinned to a specific process, so scaling to multiple replicas meant either routing every request from the same client to the same machine via session affinity, or building your own session-sharing layer. 3.0.6 adds MCPConfig(stateless=True), which serves /mcp without tracking session state at all — any replica can answer any request. That means horizontally scaling an MCP server can finally look like any stateless HTTP API behind a load balancer, with no sticky routing required. The same release also teaches MCPTools to negotiate the MCP protocol version (protocol_mode="auto"), following the sessionless negotiation capability added in this year's 2026-07-28 spec, connecting the client-side and server-side statelessness together.

Key Changes

Stateless MCP serving: MCPConfig(stateless=True) serves /mcp without session tracking, so any replica can answer any request and multi-instance deployments no longer need session affinity → the cost is losing server-initiated notifications and SSE resumability, so it's off by default — deployments that need horizontal scaling can weigh the tradeoff and opt in
MCPTools(protocol_mode=...) protocol negotiation: defaults to "legacy", preserving today's session-based behavior unchanged; "auto" negotiates the newest protocol era both sides support (sessionless capability comes from the MCP 2026-07-28 spec) → existing servers are unaffected and still accept the legacy handshake; MCP clients are now built internally on fastmcp.Client
AgentOS MCP Server Card: a new GET /mcp/server-card endpoint lists the currently served tools and carries a configurable name, version, and instructions → lets a client self-discover what an AgentOS instance offers
.zip/.eml file uploads: AgentOS now supports uploading and unpacking these archive formats
AuthorizationConfig.excluded_route_paths: marks specific custom routes as public without disabling auth globally
Bedrock custom async client: models and embedders can now be passed a caller-supplied async client
Several stability fixes: Anthropic now replays prior assistant turns verbatim so thinking blocks stop getting rejected; Gemini resolves the actual image MIME type instead of hard-coding image/jpeg; RecursiveChunking no longer emits duplicate trailing chunks; AG-UI now sends wire fields instead of the whole RunContext to remote entities and exposes streamed run errors

Breaking Changes

No breaking changes in this release. Both stateless=True and protocol_mode="auto" are opt-in — the defaults preserve today's session-based behavior.

Upgrade directly, no code changes required.

Migration Guide

pip install --upgrade agno==3.0.6

To let AgentOS's MCP endpoint support multi-replica deployment, enable stateless serving:

from agno.os.mcp import MCPConfig

mcp_config = MCPConfig(stateless=True)
# /mcp can now sit behind a plain load balancer, no session affinity needed
# Tradeoff: no server-initiated notifications or SSE resumability

To let the MCP client auto-negotiate the newest protocol version:

from agno.tools.mcp import MCPTools

mcp_tools = MCPTools(
    url="https://example.com/mcp",
    protocol_mode="auto",  # defaults to "legacy"
)

How It Compares to Other Frameworks

The MCP spec only formalized sessionless negotiation earlier this year (2026-07-28), and Agno 3.0.6 implements it on both the client and server side almost immediately — consistent with Agno treating "absorb the newest MCP ecosystem capabilities fast" as a core selling point, in line with its #1 Agentic Index ranking and multi-model-flexibility positioning. By comparison, LangGraph and CrewAI don't yet support MCP protocol version negotiation at this level of granularity, giving Agno a temporary lead on the path to MCP-native production deployment.

Today's Takeaway

I used to assume MCP servers inherently needed session affinity to scale horizontally. Seeing Agno add stateless=True at the protocol level made it clear that session-based design was just an early implementation default, not a hard constraint of the protocol — as long as you're willing to give up features like server-initiated notifications that need a long-lived connection state, an MCP server can scale just as easily as a plain stateless REST API. Evaluating an Agent framework's MCP support should look beyond how many tools it wires up, to whether it has designed multi-replica deployment into the protocol layer itself.