Hosts and sessions

Ownership

TUI / custom client / stdio gateway
                │
        Unix socket or HTTP
                │
      protocol dispatcher + authorization
                │
        session actor (one writer)
            ┌───┴──────────────┐
      runtime/workers     durable store
     tools and ChatML    journals/snapshots/artifacts

Embedded hosts connect directly to the same core instead of opening a daemon listener. The TUI renders a client projection; it does not own the daemon’s turn loop. Workers execute outside the serialized actor and return results to it. Subscribers have bounded queues: a slow reader is disconnected rather than blocking every other reader or the agent.

Three independent lifetimes

• Connection: one transport/logical client channel. It can have multiple session attachments. HTTP uses a connection ID across requests.
• Liveness: detached agents outlive clients; owner-bound agents use renewable ownership and disconnect grace; process-bound agents live inside their host.
• Persistence: durable state can be loaded after restart; transient state is disposable. Neither persists an executing process or OCaml continuation.

Host	Workspace	State and lifetime	Entry point
Native local TUI	Launch cwd	Transient, process-bound	chat-tui --local -file FILE
Local stdio	Cwd or --workspace	Process-bound; durable with --data-root, otherwise transient	ochat-agent-stdio --local --prompt FILE
Daemon-connected TUI	Configured catalog workspace	Durable; detached by default on creation, optional owner-bound	chat-tui --connect URI ...
Daemon stdio gateway	Selected through protocol	Daemon session lifetime; gateway EOF only drops its connection	ochat-agent-stdio --connect URI
HTTP/Unix client	Selected through protocol	Daemon session lifetime	Initialize, create/attach
OCaml embedding	Host-supplied	Host-selected supported options	Agent_server.Embedded.start / Daemon.start
Legacy local TUI	Launch cwd	Older file-backed session options	Implicit local mode with compatibility flags

Native local TUI is also the default without mode-selecting compatibility flags. For standalone local stdio, the current binary needs the documented private-data-root workaround for transient-root RNG startup. --session, --new-session, --export-file, --no-persist, --auto-persist, parallel-tool flags and --authorize-shell-manifest select the older implicit local path. They cannot be combined with explicit --local. Daemon --session instead selects a daemon session. See the TUI CLI.

Prompts, workspaces, and authority

A prompt catalog entry names a ChatMD source and an allowed set of workspace entries. A session pins a prompt revision and resolved workspace. Workspace selection sets ${workspace}; it does not grant filesystem or network access. Tools, shell manifests, permission profiles, and host policy determine authority. The operator must avoid unintended conflicts between allowed prompt/workspace pairs.

ChatMD is the authoring/interchange format. Daemon journals, snapshots, prompt artifacts, blobs, security state and indexes are the authoritative persisted state. Exporting ChatMD is not backing up that state. Recovery classifies uncertain in-flight effects; it does not promise exactly-once execution of external tools.

Protocol versus MCP

Ochat’s agent protocol is not MCP. A generic MCP client cannot connect to an Ochat stdio gateway just because both use JSON. MCP tools in ChatMD are maintained outbound integrations. The old MCP server that publishes ChatMD prompts is a separate deprecated compatibility host.