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Runtime Model

The runtime model covers build artifacts, execution, process image, control endpoint behavior, hot reload, and web/runtime-cloud surfaces.

Term Meaning
program.stbc Compiled bytecode artifact loaded by trust-runtime.
Control endpoint Local or configured API used for status, reload, and runtime control.
Hot reload Guarded bytecode replacement after diagnostics/build checks.
HMI Runtime-hosted browser operator surface.

Build Artifact

The executable runtime bundle centers on program.stbc, which is produced by:

trust-runtime build --project ./my-plc --sources src

Runtime Inputs

The runtime combines:

  • bytecode from program.stbc
  • runtime config from runtime.toml
  • I/O config from io.toml
  • optional simulation config from simulation.toml
  • optional HMI descriptors from hmi/

Control Options

The same underlying runtime can be driven through:

  • trust-runtime ctl
  • the runtime UI / web UI
  • the VS Code Runtime Panel
  • trust-dev agent serve

Reload Path

Hot reload works by rebuilding bytecode and sending bytecode.reload to the control endpoint. The agent method runtime.compile_reload wraps:

  1. diagnostics
  2. build
  3. bytecode read
  4. runtime reload

into one machine-readable response.

Fault / Retain / Watchdog

These behaviors are configured in runtime.toml and shape how the runtime reacts to deadline overruns, runtime faults, warm/cold restart, and safe-state output handling.

One Runtime, Multiple Operating Modes

The runtime can be used in several different ways without changing the project model:

  • local CLI-driven development
  • editor-driven compile/reload loops
  • agent-driven diagnostics, build, and reload
  • browser-hosted runtime/UI workflows
  • simulation-backed commissioning
  • runtime-cloud-connected deployment

The docs are organized so those are operating modes of one runtime, not different products.

What The Runtime Owns

The runtime owns:

  • loading and executing bytecode
  • maintaining process image and task scheduling
  • applying runtime and I/O configuration
  • exposing control/status endpoints
  • coordinating safe reload and lifecycle transitions

It does not replace the language server or the harness; those are adjacent tools built on the same project semantics.