Runtime model
Caltra separates durable agent state from the workers that perform model and tool steps. This keeps a process restart from becoming a lost conversation.
An agent is the durable principal: it owns instructions, permissions, memory, and continuity. A runtime is the executor available to a workspace. Agents select one authorized default runtime, and principal bindings determine which agent or user identity that executor may use.
Hosted and external runtimes
A Caltra-hosted runtime belongs to one immutable agent or tenant-user principal and owns its default platform model, reasoning level, and capabilities. New sessions snapshot the selected runtime, model, and reasoning level so later default changes do not rewrite history.
External MCP runtimes keep model selection outside Caltra and may be granted to multiple principals. Connecting one creates a credential for the organization’s stable MCP endpoint and displays the client secret once; hosted runtimes stay inside Caltra’s trust boundary and therefore do not create external connection credentials.
Durable sessions
PostgreSQL is authoritative for sessions, turns, queued input, transcripts, model context, and execution checkpoints. Workers claim work with leases and persist progress between steps.
Messages sent while a turn is running are accepted durably and become eligible at the next model-step boundary. Caltra does not interrupt an in-flight provider request or tool execution to inject steering.
Worker wake-ups
The runtime uses a shared queue to wake workers when sessions may have work. Queue entries are signals, not the source of truth: durable database state determines what can execute and lets reconciliation recover missed wake-ups.
Tenant boundaries
Runtime access is evaluated against organization, workspace, principal, and resource grants. Interactive administrator requests and non-interactive system work use different database roles so background processing does not impersonate a platform administrator.
Early-access availability
Workspace administrators can create and configure hosted runtimes, connect external MCP runtimes, select an agent’s default runtime, and create origin-bound SDK authorizations. Tool configuration and broader interactive MCP authorization remain incremental early-access capabilities.