fix(evals): resolve windows EINVAL quoting issue in spawnSync

[tearf001]

Description

This PR resolves an issue where running pnpm install (and consequently the prepare script) fails on Windows environments due to spawnSync errors within the @browserbasehq/stagehand-evals package.

The Problem

1. EINVAL on .cmd files: On Windows, Node.js refuses to execute .cmd scripts (like pnpm or npm) via spawnSync without the shell: true option, resulting in a silent EINVAL crash.
2. Space Quoting Corruption: When shell: true is added to fix the EINVAL crash, the Windows cmd.exe parser inadvertently breaks spaced arguments. Specifically, the --banner:js="#!/usr/bin/env node" argument passed to esbuild was being split, causing esbuild to fail with: [ERROR] Must use "outdir" when there are multiple input files.

The Solution

• Refactored build-cli.ts to use the native esbuild Node API: Instead of spawning a child pnpm exec esbuild process, the script now uses esbuild.buildSync(). This entirely bypasses the Windows shell quoting nightmare, is more robust, and is slightly faster.
• Restored shell: true dynamically for safe commands: For other .cmd files like tsc and npm link that don't pass complex spaced arguments, shell: process.platform === "win32" was safely added to spawnSync to prevent the EINVAL crashes.

These changes are constrained to Windows using process.platform === "win32", ensuring that macOS and Linux builds remain 100% unaffected.

Testing

• Verified pnpm run build succeeds on Windows natively.
• Verified pnpm run build succeeds on WSL / Linux.

---

Summary by cubic

Fixes Windows install/build failures in @browserbasehq/stagehand-evals caused by spawnSync EINVAL on .cmd and broken argument quoting. Switches the CLI build to the esbuild Node API and adds safe Windows-specific spawning.

• Bug Fixes
  • Use esbuild.buildSync() instead of pnpm exec esbuild, preserving the #!/usr/bin/env node banner and existing bundling config.
  • Add Windows-only spawning fixes: shell: true for safe commands (pnpm run build, npm link) and platform-aware pnpm resolution (pnpm.cmd on Windows).
  • Changes are Windows-scoped; macOS/Linux paths unchanged.

^{Written for commit afcd7b4. Summary will update on new commits. Review in cubic}

[changeset-bot]

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Latest commit: afcd7b4

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[github-actions]

This PR is from an external contributor and must be approved by a stagehand team member with write access before CI can run.
Approving the latest commit mirrors it into an internal PR owned by the approver.
If new commits are pushed later, the internal PR stays open but is marked stale until someone approves the latest external commit and refreshes it.

[cubic-dev-ai]

No issues found across 3 files

Confidence score: 5/5

• Automated review surfaced no issues in the provided summaries.
• No files require special attention.

Architecture diagram

sequenceDiagram
    participant User as Developer / CLI
    participant Runner as run.ts
    participant BuildScript as build-cli.ts
    participant ESBuild as esbuild (Node API)
    participant OS as OS Shell (CMD/sh)
    participant PkgMgr as pnpm / npm

    User->>Runner: Execute eval runner
    
    rect rgb(240, 240, 240)
    Note over Runner,PkgMgr: Phase 1: Parent Build Process
    alt Platform is Windows
        Runner->>OS: CHANGED: spawnSync("pnpm run build") with { shell: true }
    else Platform is Unix/macOS
        Runner->>OS: spawnSync("pnpm run build")
    end
    OS->>PkgMgr: Execute build scripts
    PkgMgr->>BuildScript: Invoke build-cli.ts
    end

    rect rgb(230, 245, 230)
    Note over BuildScript,ESBuild: Phase 2: CLI Bundling (The "Quoting Bug" Fix)
    BuildScript->>ESBuild: NEW: esbuild.buildSync({ banner: { js: "#!..." }, ... })
    Note right of ESBuild: Direct Node API call bypasses<br/>Windows shell argument splitting
    ESBuild-->>BuildScript: Compilation complete (dist/cli/cli.js)
    end

    rect rgb(240, 240, 240)
    Note over BuildScript,PkgMgr: Phase 3: Post-Build & Linking
    BuildScript->>BuildScript: fs.chmodSync(cli.js, 0o755)
    
    alt Platform is Windows
        BuildScript->>OS: CHANGED: spawnSync("npm link") with { shell: true }
        OS->>PkgMgr: Execute npm.cmd link
    else Platform is Unix/macOS
        BuildScript->>OS: spawnSync("npm link")
        OS->>PkgMgr: Execute npm link
    end
    
    PkgMgr-->>BuildScript: Global link created
    end

    BuildScript-->>Runner: Success
    Runner-->>User: Process Exit (0)

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