Session. One running sandbox: an image plus an optional harness in one microVM on one host. Sessions are created, become active, go idle, resume, and end. See What is engrams.
Task. One unit of agent work, started from a profile with a prompt. A task owns one or
more sessions and is what the dashboard, Slack, and engrams task show.
Profile. An admin-curated bundle of session settings: image, repositories, environment, egress policy, integration access, skills, and session apps.
Automation. A trigger, a tree of blocks, and typed inputs that start and drive sessions without a person typing a prompt. Runs are durable and recorded step by step. See Automations.
Model router. A service such as OpenRouter that supplies models to a harness in place of the provider’s own API, with a per-model policy for who may launch them. See Model routers.
Session app. An HTTP service inside a session, published at its own hostname behind the login wall. See Session apps.
Image. A plain OCI image, built with docker build and pushed to any registry, that a
session boots from. See Images and harnesses.
Image config. The runtime settings for an image that are not in the image: name, environment, working directory, resources, and the warm hook. Entered in the dashboard when the image is enabled. See Images and harnesses.
Enable. The step that turns a pushed image into something sessions can boot: engrams materializes the image into chunks, boots a capture VM on the fleet, runs the warm hook, and freezes a base snapshot.
Base snapshot. The frozen memory and disk of an enabled image after its warm hook ran. Every session of that image starts from it.
Harness. The agent runtime inside the VM, such as Claude Code or Codex. Staged by the host as a read-only bundle and mounted at boot, never baked into the image.
Host. A Linux machine with KVM that runs microVMs. Hosts dial the coordinator and need no inbound port.
Backend. The virtual machine technology a host uses: Firecracker in production, Apple Virtualization on a Mac, or plain subprocesses. See Sandbox backends.
Snapshot. A session’s memory and disk, written as chunks so the VM can be destroyed and restored later. Taken when a session goes idle.
Chunk. A fixed-size, immutable block of disk or memory, stored under the hash of its content. Chunks are what make snapshots cheap and deduplicated. See Storage and snapshots.
Manifest. A versioned list of the chunks that make up one disk or memory image. A session’s manifest points at the base image’s chunks plus the ones the session changed.
Warm hook. A command run once inside the capture VM before the base snapshot is frozen, so sessions start with caches filled and daemons running. See Authoring a warm hook.
Connection. A configured, credentialed instance of an integration, such as a Slack workspace or a Google Cloud service account, that profiles can grant to sessions.
Skill. A read-only bundle of tools mounted into the VM alongside the harness: shared browser, IDE, git credentials, and admin-uploaded packs.
API key. A credential for the API and CLI. Personal keys come from engrams auth login;
admin service keys are minted in Settings for scripts and CI.