Responsive screenshot preview crashes under Node 20

[webstudio-issue-reporter]

User story

An agent updating responsive navigation needs to capture tablet, mobile, and desktop screenshots after committing a visual change.

Summary

The Webstudio responsive screenshot workflow cannot start its generated preview under Node 20.

What the agent tried

1. Refreshed linked session.
2. Committed focused responsive navigation.
3. Verified bindings and static audit.
4. Called screenshot.responsive for three viewport widths.

Expected behavior

The generated preview should start and return screenshots for all requested viewports.

Actual result

The preview subprocess exits before readiness because encoding initialization calls a Set union API unavailable in the active Node 20 runtime. The operation returns MCP_TOOL_FAILED.

Recovery attempts

1. Retried through current CLI using documented shortcut.
2. Used targeted static validation as fallback.

User impact

The mutation can be verified structurally, but local responsive visual verification cannot run.

Technical context

Webstudio CLI 0.292.0; Node 20; screenshot.responsive; MCP_TOOL_FAILED.

Agent environment

• Client: Codex desktop
• Provider: unknown
• Model: GPT-5
• Reasoning effort: unknown
• Trigger: automatic-friction
• Category: hang-or-crash

Technical runtime

• CLI: 0.291.0
• Node.js: 18.20.8
• Operating system: darwin 25 (arm64)
• Execution mode: mcp
• API contract: public-api:iqd6ok

Acceptance criteria

1. Support the documented preview workflow under Node 20 or report a clear minimum Node version.
2. Return desktop, tablet, and mobile captures from one call.