Glossary
This glossary defines terms as Aether uses them. It is intentionally more precise than their generic software meanings.
Runtime and identity
Actor
A state owner that receives typed mail serially through a mailbox. An actor may be native or hosted in wasm.
Mailbox
The addressable inbox of one actor instance. A mailbox name identifies the recipient; it is not a message kind.
Mailbox lineage
The hierarchical name of an actor within one engine, including component and inline-child/instance placement. The same lineage may exist in another engine.
Kind
A canonical message contract: stable name/id plus a schema and encoding.
Schema
The portable structural description used to encode/decode values at boundaries, including MCP JSON adaptation.
Canonical id
The deterministic typed id derived from the contract's canonical name/shape as specified by the data layer. Tagged rendering is diagnostic; the integer is the wire identity.
One addressed kind payload plus source/correlation/lineage metadata.
Chain root
The mail id whose causal descendants form one settlement tree.
Settlement
The state in which all tracked descendants and explicit holds for a chain root have completed. It is stronger than “the first handler returned.”
Hold
An explicit promise that asynchronous work still belongs to a settlement chain and will later resolve or release it.
Detached mail
Mail started as a new causal root rather than a descendant of the current handler. Long-lived stream chunks use short detached chains.
Registry
Engine-local mappings for mailboxes, kinds, handlers, and related runtime metadata. Do not confuse it with the hub's artifact stores.
Hosted and native code
Guest
Code hosted by the substrate, normally a wasm component.
Component
A deployable wasm module exporting one or more actor identities. The module is stored/selected as an artifact; loading creates actor instances.
Export
One actor identity declared by a multi-actor wasm module. Export order carries no meaning; a load or boot entry that names none must resolve to the module's sole selectable export, or is refused, naming every export.
Default actor
The module's sole selectable (non-boot) export — the one a load or boot entry that names no export resolves to. A module exporting several has no such actor: the load is refused, naming every export.
Trampoline
The native host actor a guest runs in, born under the guest's own published
name, with the diagnostics label aether.component.trampoline; it routes mail
into the loaded instance and carries state across a republish.
Inline actor / cluster
Actors co-located in one wasm instance and composed below a component root. They still have distinct mailbox lineage.
Capability
A native actor that owns host policy or resources—filesystem, render, HTTP, audio, lifecycle, and so on—behind typed mail.
Marker layer
Lightweight identity/kind types that guest code can use without linking a native runtime implementation.
Runtime layer
Native state, adapters, handlers, and heavyweight dependencies enabled by a runtime feature and installed by a chassis.
Transform
A linked, discoverable, bounded value-to-value native operation. It is not a stateful actor or arbitrary host call.
Processes and operation
Substrate
The native runtime mechanism: registry, scheduler, mail, actor hosts, settlement, and chassis integration.
Engine
One running substrate instance with its own engine id, registry, scheduler, capabilities, and components.
Chassis
A process composition that selects drivers, capability runtimes, and frame-loop behavior. Desktop, headless, hub, and substrate harness are distinct checked-in chassis profiles.
Hub
The control-plane chassis that stores binary/component artifacts, supervises a fleet of child engines, and routes engine RPC.
Engine proxy
The hub-side actor/state representing one connected child engine and its heartbeat/routing relationship.
MCP coordinator
aether-mcp: the agent-facing service that converts tool JSON to engine
RPC/mail and projects replies/evidence.
Tunnel
The stable MCP-facing endpoint in front of volatile coordinator/hub processes. Starting it cannot retroactively add tools to an already-open client session.
Binary selector
A name/version/hash or attribute query resolved against the hub's chassis binary store. It is not a host executable path.
Component selector
A hash, stored name, or module/export selection resolved against the hub's wasm store. Upload precedes selection for new bytes.
Boot manifest
Staged component/config instructions consumed while a substrate starts.
Package depot
The shippable directory cargo xtask package emits: one chassis binary, the
workspace licenses, a persisted pack/manifest, and content-addressed objects
under pack/objects/: the component and config objects boot loads, and the
named objects the manifest lists under the paths a running engine reads them
at. Its chassis boots by resolving the manifest against those objects, so it
does not require the development hub.
Asset bundle
A component that carries payload bytes in a wasm custom section, transforms them
into an engine resident, usually in wire, and afterwards holds only
the handle (ADR-0163 §4). test.asset_resident, in aether-test-fixtures-bundle, is the reference actor. Distinct
from the package depot above, which is a shipping layout rather than an actor.
Frames, rendering, and I/O
Frame lifecycle
The ordered lifecycle stages that advance input/tick, render, present, and shutdown work for one engine frame.
Capture
A bounded readback of the render target, optionally with pre/after mail applied at defined points around it.
Namespace root
One configured filesystem root (save, assets, config) exposed through a
logical capability path rather than raw guest host access.
Stream id
An explicit id naming one long-lived HTTP/websocket data phase across many short mail chains. It is not the engine id or a mailbox id.
Credit
A bounded allowance for producer chunks. Exceeding credit is a protocol error; not granting more applies backpressure.
Workflow and maturity
The four scoped-issue terms below — managed Plan, approval record, landable
draft, and surface overflow — belong to the checked-in
scope / approve / implement / land skills. Those skills are still in the
tree and still define these artifacts when a session uses them; they are not the
repository's default path today, which is an ordinary focused pull request
landed on green CI.
ADR
An Architecture Decision Record under docs/adr/. Accepted governs intended
design; Proposed does not; Superseded remains history.
Realization
How much of a decision or proposal current code implements. Realization and ADR status are independent facts.
Managed Plan
The scope-owned issue-body sections that define the problem, design, implementation steps, dependencies, declared surface, and exact size/model routing lines. Their canonical digest is the approval identity.
Approval record
A trusted hidden issue-body record binding one managed-Plan digest and route to an exact base commit and resolved approval policy. Labels and visible comments are not substitutes.
Landable draft
A draft pull request whose approval ancestry holds, priced surface overflow is settled, required current-head checks pass, and native change requests and review threads are clear. No review record is part of it. It still needs explicit landing authorization.
Surface overflow
The changed paths outside the approved declared surface, each priced auto, judge, or human at landing against the rules frozen when work started.
Worktree owner
The task/agent that created or was explicitly handed a worktree. Existence or set difference does not prove cleanup authority.