Glossary

The words used across Harness, Switchboard and Cairn, in one place. Each entry is a sentence or two, names the product it belongs to, and links to the page that owns it. Every term has a stable anchor, such as glossary#endpoint, so other pages can link straight to it.

Entries marked coming are designed but not shipped yet. For how the three products fit together, read the stack.

Same word, different meaning

Some words mean different things in different products. When a page says one of these, it means the product's own sense:

Word	Switchboard	Cairn	Harness
channel	the MCP Channels extension that carries a doorbell into a live agent session. Never a chat channel.	not used	the same MCP extension: a [channel.*] trigger source
run	not used; a todo has attempts	a trace's resource name (run_create, /run/<id>)	one execution of a one-shot, with a run number and a log
trace	a routing rule's evaluation trace, in a dry run	a whole agent run, shared as an artifact	not used
lane	a queue name with a hyphen: lane-m	a tag with a colon: lane:m	not used
TTL	how long a lease or an endpoint lasts	how long an artifact lives	not used
webhook	an inbound ingest URL	outbound artifact.created events, and the HK Webhook share type (a request bin)	a [webhook.*] trigger source (coming)
persona	a least-privilege face of one agent, published as an A2A Agent Card	not used	a named agent role and its instructions (see persona)
operator	the human who runs an instance	the same	not used

A

Artifact

Cairn. One shared thing: a body with a share type (Markdown, code, an image, a file, a bundle, a trace and more), metadata, provenance, an access policy, a TTL and a stream of comments and reactions, addressed by a short URL. In the stack an artifact is evidence, linked from your tracker. Cairn: core concepts.

B

Bin

Cairn. The listing of artifacts, on the web and in the TUI. It is not a request bin; that is the HK Webhook share type. Cairn: introduction.

Bundle

Cairn. One artifact holding many files, browsed in a tabbed viewer and read file by file over MCP. Cairn: bundle.

C

Cairn

Product. Where agents put what they made: shareable artifacts (reports, diffs, logs, traces) with comments, reactions, expiry and a stable link. In the stack, Cairn is evidence. Cairn, the stack.

CGG

Tool named in guides. A call-graph generator: point it at a source tree and it maps which functions call which, across many languages. joestump/cgg.

Channel

Switchboard, Harness. The MCP Channels extension (notifications/claude/channel), defined by Claude Code Channels: an MCP server pushing a notification into a live agent session. Switchboard uses it to deliver a doorbell. A Harness [channel.*] source holds such a session itself and fires a triggered harness. It is never a chat channel. Push events, Switchboard: Claude Code.

Claude Code

Client. Anthropic's terminal coding agent (claude). Harness runs it as harness = "claude-code". It defines the Channels protocol Switchboard speaks. Claude Code, Push events: Claude Code.

Codex

Client. OpenAI's terminal coding agent (codex). Harness runs it as harness = "codex". openai/codex.

Crush

Client. Charm's terminal coding agent (crush). Harness runs it as harness = "crush". Waking on a doorbell needs a fork for now. charmbracelet/crush, Push events: Crush.

D

Dead letter

Switchboard. Where a todo ends up when its last attempt fails or its last lease runs out: it stays failed for good, until a human re-queues it. Switchboard: the lifecycle.

Doorbell

Switchboard. A one-line push into a live agent session, over a channel, saying a todo is waiting. It is only a hint: the queue is the record, and a doorbell nobody hears loses nothing. Switchboard re-rings an unclaimed todo after 5 minutes, 20 minutes, 1 hour and 6 hours. Switchboard: the queue is the record.

Drop-in

Harness. A .toml file holding more [harness.*] tables, in the directory that harness_d under [server] names (for example ~/.config/harness/harness.d). The daemon merges them into the main config. One file per agent keeps generated or per-machine agents apart. Drop-in harness files.

E

Endpoint

Switchboard. An agent's way into Switchboard: an MCP URL plus a bearer token (sbk_…), with a fixed scope of queues and tools, a lifetime, and instant revocation. You create one by vending it. Switchboard: the nouns.

H

Harness

Harness. Two meanings. The product: a daemon that supervises agent CLIs and other long-running processes, with a CLI and a TUI to attach to them. And a harness: one supervised process, declared as a [harness.NAME] table. Unless it is a one-shot, a harness is resident: the daemon keeps it running, restarts it by policy, and lets you attach. Your first supervised agent.

Heartbeat

Switchboard. A call a worker makes to extend its lease on a claimed todo, so a long job is not requeued under it. Switchboard: the lifecycle.

I

Ingest URL

Switchboard. The URL a sender posts webhooks to (https://<host>/webhooks/w/<token>), made with create_webhook. Its source type (github, gitea, cairn, generic and others) decides how each delivery is verified. Switchboard: first webhook.

Instance

Switchboard, Cairn. One deployment of the service, such as a self-hosted Switchboard. Its operator runs it. Switchboard ADR-0038.

L

Lane

Switchboard. A difficulty-lane queue on a worker pool: lane-s, lane-m, lane-l, lane-vision, plus triage and hold. A routing rule picks the lane from a handoff's tags, and the handoff arrives as a work order. Cairn spells the tag lane:m; Switchboard names the queue lane-m. Switchboard: handoff lanes.

Lease

Switchboard. What claiming a todo takes: 300 seconds by default, during which no other worker can claim it. A lease that runs out without a heartbeat puts the todo back on the queue. A Switchboard todo is a dispatch lease, not a second tracker. Switchboard: the lifecycle.

N

Notify hook

Switchboard, coming. An HTTPS URL an endpoint registers, which Switchboard signs and posts to when a todo becomes ready: a doorbell for a consumer that holds no live session. Designed in Switchboard's notify-hooks spec. Switchboard: notify hooks.

O

One-shot

Harness. A harness with a prompt or prompt_file instead of args, also called a prompt harness. Harness builds the agent's non-interactive command from the prompt, and each firing is one run that ends when the agent exits. It fires on a schedule, on triggers, or on harness trigger NAME, and never autostarts. Agent one-shot harnesses, Scheduled sweeps.

Operator

Switchboard, Cairn. The human who runs an instance. In today's Switchboard docs, "operator" also names the human-facing tools: the operator board (the web UI) and the operator CLI. Switchboard's tenancy design (coming) has the operator configure the instance but own nothing in it. Switchboard: operator CLI.

P

Persona

Harness. A named agent role (a coordinator, a reviewer, a drainer) and the instructions it runs with. Today a persona is a harness plus the instruction file in its workdir (CLAUDE.md for Claude Code, AGENTS.md for Crush). Generating personas from templates with harness init is coming (SPEC-0018). Switchboard uses the same word for an endpoint's A2A Agent Card.

Pi and OMP

Client. Pi is a minimal terminal coding agent; OMP (oh-my-pi) is a fork of it. Harness has no adapter for either yet: the command one-shot kind that will run them is coming (ADR-0023).

Profile

Harness. A named group of harnesses that switch together with harness use-profile NAME. Only one is active at a time, and with autostart = true its members start with the daemon. Profiles.

Q

QMD

Tool named in guides. A local search engine for Markdown: keyword, vector and reranked hybrid search over your notes, docs and specs. tobi/qmd.

Queue

Switchboard. A named list of todos, such as inbox or reviews, scoped to one endpoint: inbox on two endpoints is two queues. Switchboard: the nouns.

R

Receipt

Cairn. A Markdown artifact summing up a session's work, shared as a link. A structured receipt with its own schema is coming (Cairn ADR-0027).

Rule pack

Switchboard, coming. An installable, versioned preset of routing rules with parameters and fixtures that must pass on real deliveries before it is saved. Until it ships, a pack is a JSON file of rules you apply by hand. Switchboard ADR-0036.

S

SDD

Tool named in guides. Spec-driven development: a Claude Code plugin that keeps architecture decision records (ADRs) and specifications next to the code, and plans and reviews work against them. The ADRs and specs on this site are its output. joestump/claude-plugin-sdd.

Self-test

Harness, coming. The end-to-end check harness init and harness stack will finish with: a nonce goes in through a real webhook, and the check passes only when an agent has claimed and completed the todo it became (SPEC-0018).

Switchboard

Product. How work reaches agents: it verifies incoming webhooks, routes them into durable todos on queues, and rings a live session with a doorbell. In the stack, Switchboard is dispatch. Switchboard, the stack.

T

Team

Switchboard, coming. An owner that several users share, with member, admin and owner roles. Every resource belongs to exactly one user or team. Switchboard ADR-0038.

Todo

Switchboard. One unit of work, made from a verified webhook and carrying its payload. It moves from pending to claimed to done or failed. Claimed with claim_next, it is held under a lease. Switchboard: the lifecycle.

Trace

Cairn. A whole agent run, shared: a span waterfall plus an activity stream. It was called a trajectory, and the rename is in flight: the stored share type and some tool names still say trajectory or run. Harness still uses "trajectory" for an agent's own session transcript. Cairn: trace.

Triggered harness

Harness. A one-shot with triggers: each event on a bound source fires one run, and the event reaches the run as a private file named by HARNESS_EVENT_FILE. A [channel.*] source listens for Switchboard doorbells from behind NAT; a [webhook.*] source's HTTP listener is coming. A schedule can sit alongside triggers as a safety net. ADR-0021, events and schedules.

TTL

Cairn. How long an artifact lives: 7 days by default, 30 days at most. Switchboard uses TTL for a lease or an endpoint's lifetime. Cairn: expiry.

U

User

Switchboard, Cairn. Anyone who signs in to an instance. Every endpoint, webhook and artifact belongs to a user (or, coming to Switchboard, a team). Switchboard ADR-0038.

V

Vend

Switchboard. To create an endpoint, in the web wizard or with the operator CLI. The scope is fixed when you vend, and the token is shown once. Switchboard: first endpoint.

W

Work order

Switchboard. The work_order object a routing rule attaches to a lane todo: where the work came from, which rule admitted it, and whether the sender was verified. It picks the task and grants nothing; its contents are untrusted data. Switchboard: what a worker receives.