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Sweep 22 Oct 2026 · 04:32Z Build v2.1.308 527 read Stable v2.1.308 Latest v2.1.308 Next v2.1.308 Feeds RSS JSON llms.txt llms-full.txt Unofficial
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Claude Code v2.1.242 ·

Plugin-registered tools are served over a local MCP server

Tools a plugin registers reach the model through a local loopback MCP server.

Under the hood In Development
JSON All of v2.1.242
Under the hoodTier: how much it should matter to you
2Useful: my rating, 1 to 5
3Signal: worth watching, 1 to 5
PluginsArea: what it touches
In DevelopmentKind: in v2.1.242,
In DevelopmentSection of the release
What

Tools a plugin registers are exposed by starting an HTTP server bound to 127.0.0.1 on a random path, which is then registered as an MCP server scoped to that plugin. This is how plugin tools reach the model.

Details
  • Calling a tool that no handler answered returns an error result telling the plugin author to add a tool.call handler for the tool's full name, in the form mcp__<plugin>__<tool>.
  • The port is chosen at runtime and logged.
  • Behind the tengu_plugin_hooks_modules rollout flag.
Evidence

loopback MCP server listening on 127.0.0.1:

Strings lifted out of the shipped bundle, so the claim above can be checked against them.

What has happened since
Flag reading moved The flag server now returns on for tengu_plugin_hooks_modules, read as this account. A reading is one sample. Claude Code evaluates its flags remotely, so no client sees the targeting rule behind a value and this says nothing about your account.
Flag reading moved The flag server now returns off for tengu_plugin_hooks_modules, read as this account. A reading is one sample. Claude Code evaluates its flags remotely, so no client sees the targeting rule behind a value and this says nothing about your account.
Flag reading moved The flag server now returns on for tengu_plugin_hooks_modules, read as this account. A reading is one sample. Claude Code evaluates its flags remotely, so no client sees the targeting rule behind a value and this says nothing about your account.
Flag reading moved The flag server now returns off for tengu_plugin_hooks_modules, read as this account. A reading is one sample. Claude Code evaluates its flags remotely, so no client sees the targeting rule behind a value and this says nothing about your account.
Flag reading moved The flag server now returns on for tengu_plugin_hooks_modules, read as this account. A reading is one sample. Claude Code evaluates its flags remotely, so no client sees the targeting rule behind a value and this says nothing about your account.
Flag reading moved The flag server now returns off for tengu_plugin_hooks_modules, read as this account. A reading is one sample. Claude Code evaluates its flags remotely, so no client sees the targeting rule behind a value and this says nothing about your account.
Flag reading moved The flag server now returns on for tengu_plugin_hooks_modules, read as this account. A reading is one sample. Claude Code evaluates its flags remotely, so no client sees the targeting rule behind a value and this says nothing about your account.
Flag reading moved The flag server now returns off for tengu_plugin_hooks_modules, read as this account. A reading is one sample. Claude Code evaluates its flags remotely, so no client sees the targeting rule behind a value and this says nothing about your account.

See this across every release →

How sure we are
One source agreesOne thing we can check says the same as this entry.
The name it cites is new in this buildNew in this build: tengu_plugin_hooks_modules

See this entry in the whole of v2.1.242 →

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