Shell resource runner

This installed helper applies OS resource limits, then replaces itself with the selected executable. It is normally invoked by the shell runtime, not by an LLM. Build it with dune build bin/ochat_shell_resource_runner.exe or install Ochat so ochat-shell-resource-runner is discoverable. OCHAT_SHELL_RESOURCE_RUNNER can select an explicit helper path; protect that executable as part of host trust.

Interface

ochat-shell-resource-runner [--cpu SECONDS] [--memory BYTES]
  [--file-size BYTES] [--open-files COUNT] -- /absolute/executable [ARG ...]

These are integer OS limit values, not ChatMD strings such as 2GiB. The shell compiler/runtime lowers declared values into this interface. The helper does not search PATH for the final executable, parse shell syntax, or create filesystem/ network confinement. Wall/idle timeouts and output bounds are runtime controls, not additional helper flags.

Limits use the platform’s available rlimit facilities. Memory support depends on availability of the virtual-memory resource. An unavailable resource, malformed argument, failed limit application, or exec failure terminates rather than pretending the limit was enforced. Successful exec inherits the target’s exit behavior. Required confinement still needs the selected Seatbelt/bubblewrap or approved external backend; the helper alone is not a sandbox.

See shell limits/backends and host setup.