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fix: set viewport to 1024x768 to make cua models work on advanced stealth #1023

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fix: set viewport to 1024x768 to make cua models work on advanced stealth #1023

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38 changes: 35 additions & 3 deletions lib/handlers/agentHandler.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -119,6 +119,18 @@ export class StagehandAgentHandler {
// Update viewport and URL for any client type
this.updateClientViewport();
this.updateClientUrl();

// For CUA models, ensure the browser viewport is set to the expected size
if (this.isCUAModel(this.agentClient.modelName)) {
// Set browser viewport to match what CUA models expect
this.page.setViewportSize({ width: 1024, height: 768 }).catch((error) => {
this.logger({
category: "agent",
message: `Warning: Could not set viewport to 1024x768 for CUA model: ${error instanceof Error ? error.message : String(error)}`,
level: 1,
});
});
}
}

/**
Expand Down Expand Up @@ -387,12 +399,32 @@ export class StagehandAgentHandler {
}

private updateClientViewport(): void {
const viewportSize = this.page.viewportSize();
if (viewportSize) {
this.agentClient.setViewport(viewportSize.width, viewportSize.height);
const isCUAModel = this.isCUAModel(this.agentClient.modelName);

if (isCUAModel) {
// For CUA models, preserve the default viewport (1024x768) regardless of page viewport. CUA models are trained on this specific viewport size
this.agentClient.setViewport(1024, 768);
} else {
// For other models, use the actual page viewport
const viewportSize = this.page.viewportSize();
if (viewportSize) {
this.agentClient.setViewport(viewportSize.width, viewportSize.height);
}
}
}

private isCUAModel(modelName: string): boolean {
// List of CUA models that require fixed viewport
const cuaModels = [
"computer-use-preview",
"computer-use-preview-2025-03-11",
"claude-3-7-sonnet-latest",
"claude-sonnet-4-20250514",
];

return cuaModels.includes(modelName);
}

private updateClientUrl(): void {
const url = this.page.url();
this.agentClient.setCurrentUrl(url);
Expand Down