Make --typecheck a true compile-only mode in launcher

[Copilot]

--typecheck previously continued into runtime execution after successful typecheck, which caused misleading ECONNREFUSED failures in CI environments without a Copilot server. The launcher now treats typecheck as a compile-only path and exits before runtime/session setup in both program-file and inline-stdin modes.

• Launcher control-flow fix

  • Return immediately after successful typecheck in:
    • program-file stdin mode (runRootAgentFromStdin)
    • inline program stdin mode (runProgramCodeFromStdin)
  • Prevents Copilot runtime initialization and root-agent execution in --typecheck mode.

• Typecheck diagnostics clarity

  • typecheckProgram now supports a display path so inline stdin errors are reported as Typecheck failed for <stdin> in the primary error message (instead of temp file path in the header).

• Inline import injection hardening

  • withInjectedRigImport now injects only referenced symbols (agent, p, s) rather than always injecting all three.
  • Avoids noUnusedLocals/TS6133 failures introduced by synthetic unused imports during inline typecheck.

• Docs alignment

  • Updated launcher docs in README.md and skills/rig/SKILL.md to state that --typecheck typechecks and exits without execution.

if (options.typecheck) {
  await typecheckProgram(resolvedPath, cwd);
  return; // no runtime/session setup, no agent execution
}

• Fixes [rig-tasks] Daily rig evaluation — 2026-07-23 — 4/5 passed #46

[github-actions]

🧠 Matt Pocock Skills Reviewer has completed the skills-based review. ✅

[github-actions]

Skills-Based Review 🧠

Applied /diagnosing-bugs and /tdd — approving. The fix is correct, well-scoped, and the test suite now properly asserts the compile-only contract.

📋 Key Themes & Highlights

Positive Highlights

• ✅ Root cause addressed at both call sites (runRootAgentFromStdin and runProgramCodeFromStdin) — no partial fixes
• ✅ Tests upgraded from 'does not reject' to asserting createSession is not called — a proper regression spec
• ✅ New inline-stdin test closes the coverage gap for that mode
• ✅ withInjectedRigImport hardening is a neat fix: only injecting referenced symbols avoids synthetic TS6133 failures cleanly
• ✅ displayPath parameter keeps error messages user-friendly without leaking temp paths

Minor Observation

The agent detection regex (/agent\s*\(/u) will also match a user-defined local function named agent, injecting an import that shadows it. This is a pre-existing edge case (previously the import was always injected), so it is out of scope here — worth noting for a future hardening pass.

🧠 Reviewed using Matt Pocock's skills by Matt Pocock Skills Reviewer · sonnet46 32.8 AIC · ⌖ 5.81 AIC · ⊞ 6.3K
_{Comment /matt to run again}