Backplane Agent Runtime

A standalone embedded OTP execution package. Hosts own sessions, repositories, configuration, history, UI and public protocols. Optional tools and their backends start only when selected by the host. No Phoenix, database, Sigma or Backplane server application is required.

Trusted host backends can return ToolEffects.reject(operation, error) for a proved rejection before dispatch, preserving provider continuation without weakening uncertain-effect handling. Existing adapters returning plain errors must adopt this explicit contract; see EMBEDDING.md.

The package uses jsonschex 0.10.0 as its production JSON Schema Draft 2020-12 engine; it is intentionally not dependency-free.

Embeddings can set provider_output_limit: :infinity for unlimited generated provider content, or select a finite non-negative byte budget per response. Repeated stream snapshots count each logical content block once. The finite output_limit tool-result bound remains independent; see EMBEDDING.md for defaults, content representation and structured limit errors.

Backplane.AgentRuntime.Conversation drives prompt → lazy provider stream → authorized tools → provider continuation → settlement. It is an alternative owner to the existing explicit-command ExecutionController, not another controller to run beside it. See EMBEDDING.md for contracts and an example, SCHEMAS.md for the Draft 2020-12 tool-schema boundary, and PERSISTENCE.md for host storage and recovery requirements.

examples/embedded.exs is a deterministic complete provider/tool turn. Run it from a consumer with mix run examples/embedded.exs after installing this package (or run the file from the extracted artifact). It makes no network requests.

This is not a completed Sigma migration. Codex profiles are explicit, opt-in host integrations; selecting no profile starts no command worker, extension runtime, collaboration tree, network client, or provider-hosted capability.

The local, interaction/context, collaboration V1/V2, stateful extension, dynamic MCP/plugin, Code Mode, service-backed, and composed Codex profiles are documented in CODEX.md. Model-callable tools use the strict catalog and Conversation -> Execution path. Provider-hosted tools are negotiated and projected separately and never become local registry entries. The implementation is assessed compatibility, not unqualified Codex parity; platform, durable backend, provider-wire, and live-service limits are recorded in the coverage ledger under docs/agent-runtime/codex-tools/.