Sandbox validation

--sandbox is the fourth and most rigorous stage of the Axint pipeline. It takes the generated Swift, drops it into a deterministic Swift Package Manager project in a temp directory, and runs swift build.

If the build succeeds, you know the generated Swift is actually valid — not just plausible-looking. If it fails, you get the real Swift compiler output as a diagnostic, pointing at the generated line.

How it works

           ┌─────────────────────────┐
IR ──────► │ generator.ts            │
           └──────────┬──────────────┘
                      │ Swift source
                      ▼
           ┌─────────────────────────┐
           │ sandbox/                │   ← created in $TMPDIR
           │  ├── Package.swift      │     on first run, reused after
           │  ├── Sources/           │
           │  │   └── Intent.swift   │
           │  └── .build/            │     warm cache ≈ 1.2s
           └──────────┬──────────────┘
                      │ swift build
                      ▼
                  pass / fail

The sandbox lives at $TMPDIR/axint-sandbox/ by default. The .build/ cache survives across runs, which is why the first run takes ~4 seconds (cold) and every subsequent run takes ~1.2 seconds (warm).

When to use it

• Locally — when you want direct confirmation that the intent compiles before opening Xcode.
• CI — on a macOS runner, the sandbox gives you end-to-end validation for every PR.
• From MCP — set sandbox: true in axint_compile and the MCP server will include the Swift build output in its response. This is how Claude Code and Cursor know whether an intent is actually valid.

Requirements

• macOS
• Xcode 16 or later, or xcode-select --install for the command-line tools only

On Linux or Windows, the sandbox stage is skipped with a friendly warning unless you pass --strict-sandbox, which will exit non-zero.

Programmatic use

You can also use the sandbox from your own code via the reusable sandboxCompile() API exported from @axint/compiler:

import { sandboxCompile } from "@axint/compiler";

const result = await sandboxCompile(swiftCode);
if (!result.success) {
  console.error(result.stderr);
  process.exit(1);
}