[Bug] google-genai plugin deletes "falsy" parameters (e.g. addWatermark: false)

[CatoPaus]

Bug Report: google-genai Plugin Deletes "Falsy" Parameter Values (False / 0)

Package: @genkit-ai/google-genai
Version: 1.27.0 (and earlier)
Source File: js/plugins/google-genai/src/vertexai/converters.ts
Compiled File: lib/vertexai/converters.js
Function: toImagenParameters

Issue Description

The toImagenParameters function in the google-genai plugin sanitizes the config object by deleting any keys with "falsy" values. This is incorrect behavior for boolean flags (where false is a meaningful value) and numeric parameters (where 0 might be valid).

Specifically for Imagen, the addWatermark parameter defaults to true on the Vertex AI API side. To disable it, the client must send addWatermark: false.
However, because false is falsy in JavaScript, the current plugin logic deletes this parameter entirely. The API then receives a request without addWatermark, triggering the default true, making it impossible to disable watermarks (and consequently making it impossible to use seed, which conflicts with watermarks).

Code location

File: src/vertexai/converters.ts (approx line 97)

function toImagenParameters(request: any) {
  const params = {
    sampleCount: request.candidates ?? 1,
    ...request?.config,
  };
  for (const k in params) {
    // BUG: This deletes false, 0, undefined, null, ""
    if (!params[k]) delete params[k];
  }
  return params;
}

Recommended Fix

Update the filter condition to only remove keys that are strictly undefined or null.

function toImagenParameters(request: any) {
  const params = {
    sampleCount: request.candidates ?? 1,
    ...request?.config,
  };
  for (const k in params) {
    // FIX: Only delete if undefined or null
    if (params[k] === undefined || params[k] === null) delete params[k];
  }
  return params;
}

Impact

• Watermarks: Users cannot disable watermarks (addWatermark: false is stripped).
• Deterministic Generation: Users cannot use seed because it requires watermarks to be disabled.
• Zero Values: Any future parameter expecting a 0 index or value will differ from intent.