Project.generate() fails on second+ screens: projection assumes first-screen shape

[threepixel-dev]

Summary

Project.generate() works for the first screen in a project and then consistently throws StitchError: Incomplete API response from generate_screen_from_text: expected object at projection path on every subsequent screen in the same project. The underlying generate_screen_from_text MCP call succeeds and returns a complete screen; the SDK's hardcoded projection just lands in the wrong place.

Reproduce

SDK version: @google/stitch-sdk@0.1.0 (Node 22, Linux x64).

import { stitch } from "@google/stitch-sdk";

const project = await stitch.createProject("multi-screen-repro");
await project.generate("Home page");          // ✅ OK
await project.generate("Treatments page");    // ❌ throws StitchError

Root cause

packages/sdk/generated/src/project.ts hardcodes:

const _projected = raw?.outputComponents?.[1]?.design?.screens?.[0];

That index is correct for the first screen but not for subsequent screens in the same project. On call 1, Stitch returns a 6-component response that includes a designSystem prefix block at index 0, pushing the screen to index 1. On call 2+, the designSystem block is omitted (already established for the project), the response is one component shorter, and the screen sits at index 0.

Raw shape diff

Call 1 (fresh project, first screen) — 6 components:

outputComponents = [
  { designSystem: ... },      // index 0
  { design: { screens: [...] } },   // index 1 — SDK finds screen here
  { text: ... },
  { suggestion: ... },
  { suggestion: ... },
  { suggestion: ... }
]

Call 2 (same project, second screen) — 5 components:

outputComponents = [
  { design: { screens: [...] } },   // index 0 — SDK looks at index 1 and finds text instead
  { text: ... },
  { suggestion: ... },
  { suggestion: ... },
  { suggestion: ... }
]

Both responses contain a complete screen at <some index>.design.screens[0]; only the index varies.

Suggested fix

Scan outputComponents for the first entry whose .design.screens[0] is present, instead of hardcoding index 1:

let _projected;
for (const component of raw?.outputComponents ?? []) {
  const screen0 = component?.design?.screens?.[0];
  if (screen0) { _projected = screen0; break; }
}

Backwards-compatible with both the 6-component first-screen shape and the 5-component subsequent shape. Also forward-defensive against future shape drift — any additional prefix blocks that might get added won't break the lookup.

Workaround for consumers

Call generate_screen_from_text via callTool() directly and apply the scanning projection yourself. We've shipped this workaround in production for now.

Environment

• @google/stitch-sdk 0.1.0
• Node.js 22
• Linux x64 (Railway worker runtime)

Happy to provide additional repro artefacts if useful — we have the full raw JSON for both call shapes saved.