compute-stub

name	compute-stub
description	Diagnostic in-memory compute backend. Use ONLY when the user explicitly asks to verify that the compute pipeline (Registry → IPC → renderer) is wired correctly without invoking real shells or remote services. Off by default — register via ENABLE_COMPUTE_STUB=1.
category	Compute
tags	["compute","diagnostic","stub","qa"]
triggers	["diagnose compute","compute health check","verify pipeline","stub backend","test compute"]
license	MIT
metadata	{"skill-author":"Research Copilot"}

Stub Compute (diagnostic)

Stub backend (backend: 'stub', toolPrefix: 'stub') is an in-memory no-op that simulates plan/run/stop without invoking any real subprocess or remote API. Available only when the developer sets ENABLE_COMPUTE_STUB=1.

When to use

• The Compute tab seems broken — want to confirm whether the bug is in registry / IPC / renderer plumbing vs. a backend's internals.
• Validating that a new backend you're writing follows the same lifecycle the stub demonstrates.
• Smoke-testing event flow after refactors to lib/compute/.

Do NOT use for real work — there's no actual computation happening.

Behavior

The stub parses keywords from the command string:

Command contains	Behavior
(default)	Sleeps 100ms then completes with exit code 0
SLOW	Sleeps 5000ms (use to exercise stub_stop)
FAIL	Sleeps 100ms then exits with code 1 + sets failure.code = COMMAND_FAILED

Combine freely — e.g. SLOW job that may FAIL waits 5s then fails.

Tool flow

1. list_compute_backends() — confirm stub is registered.
2. compute_plan({ backend: 'stub', command: 'health check' }) — no approval gate.
3. stub_execute({ plan_id }) — kicks off the timer.
4. stub_wait({ run_id }) — blocks until terminal.
5. stub_stop({ run_id }) — cancels (useful for SLOW runs).

If the stub flow succeeds end-to-end but local_* / modal_* flows don't, the bug is backend-internal (sandbox provider, Modal CLI, etc.), not registry/IPC/renderer plumbing.

Reference for adding a new backend

lib/compute/backends/stub/stub-backend.ts is also the canonical reference implementation for RFC §19 (Adding a new compute backend). It demonstrates every ComputeBackend method against the simplest possible state (a Map + setTimeout), so you can read the whole file in under 5 minutes and see the contracts in action.