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Sweep 28 Aug 2026 · 00:00Z Build v2.1.250 478 read Stable v2.1.236 Latest v2.1.250 Next v2.1.250 Feeds RSS JSON llms.txt

DisclaimerUnofficial, and not affiliated with Anthropic. Nearly all of this is read straight out of what ships: npm bundles, captured prompts, published docs. Anthropic's own notes go in verbatim, marked as theirs. The rest is my reading, and every entry carries the strings behind it. If one looks wrong, vote it down and say why.

Reference / Feature flags

tengu_mcp_protocol_negotiation_

A Claude Code feature flag, read out of the shipped bundle. No mined inventory carries it: everything below comes from what this site has written about it.

What it is

MCP servers using a newer protocol era no longer get custom notification handlers, and you see a warning.

Not Anthropic's. This is the line from the earliest changelog entry here that named it, v2.1.221.

Presence across releases

The miner has never read a build containing this name. It is here because a changelog entry of ours names it, which is evidence that it existed and not evidence of which releases carried it. The inventory starts at v2.1.138 and everything older than that was never mined.

Gate readings

No release here has a gate table behind it for this flag. Most published releases have none at all: the readings exist only for versions the pipeline captured flag state on.

Changelog entries naming it

  1. v2.1.221Custom MCP notification handlers skipped on modern-era connections

    MCP servers using a newer protocol era no longer get custom notification handlers, and you see a warning.

    gate cited by this entry

Documentation pages

None of Anthropic's documentation pages this site has a copy of carries this name.

Names beside it

Every feature flag in the inventory starting tengu_mcp_protocol_negotiation, up to twelve of them.

tengu_mcp_protocol_negotiation_ccrThe ccr-proxy MCP transport can negotiate protocol versions, but stays on legacy unless a flag is turned on. 2.1.236 tengu_mcp_protocol_negotiation_claudeaiA newer MCP protocol handshake exists per transport but every gate falls back to legacy here. 2.1.221 tengu_mcp_protocol_negotiation_httpA newer MCP protocol handshake exists per transport but every gate falls back to legacy here. 2.1.221 tengu_mcp_protocol_negotiation_stdioA newer MCP protocol handshake exists per transport but every gate falls back to legacy here. 2.1.221

Read out of the published npm bundle release by release, and out of Anthropic's own documentation as this site captured it. Nothing on this page is a description anybody here wrote about what the feature flag does. All feature flags.