Running plugins out of process (plugins.isolation)
By default third-party Python plugins are imported into the Hermes process, as they always have been. Setting plugins.isolation: host moves them into a plugin host : one separate Python process per profile, started on demand, that imports the profile's user-installed plugins and talks to Hermes over a private pipe. Plugins do not change. They receive the same ctx and register tools, hooks, slash commands, skills and provider objects (image/video generation, web search, browser, TTS/STT, memory, context engines, model-provider profiles) exactly as before; Hermes registers matching entries on its side that call into the host. Dashboard plugin APIs are served by the host too. Bundled plugins keep running in-process. What changes in host mode: No shared interpreter. A plugin's module never enters the Hermes process, so it cannot read another profile's data from memory or patch Hermes internals. Under the multiplex gateway every profile gets its own host, started with only that profile's environment and secrets. Crashes stay contained. A plugin that crashes or exits kills its host, not Hermes; the call in flight returns a tool error and Hermes restarts the host and reloads its plugins (…
From the official Hermes Agent documentation.
plugins:
isolation: host # default: in_process
host:
launcher: [] # optional argv prefix for the host, e.g. a sandbox runner