ProofShot – Give AI coding agents eyes to verify the UI they build
FrameworkFreeI use AI agents to build UI features daily. The thing that kept annoying me: the agent writes code but never sees what it actually looks like in the browser. It can’t tell if the layout is broken or if the console is throwing errors.So I built a CLI that lets the agent open a browser, interact with
Capabilities8 decomposed
visual assertion generation for ai-built uis
Medium confidenceCaptures screenshots of rendered UI components and generates machine-readable assertions that verify visual correctness. Uses image analysis to extract layout, styling, and element positioning data, then synthesizes assertions that AI agents can evaluate against expected output. Enables agents to close the feedback loop by comparing rendered output against specifications without human intervention.
Bridges the gap between AI code generation and visual verification by using vision models to generate executable assertions from screenshots, enabling agents to self-validate UI output without hardcoded test suites. Most tools require pre-written assertions; ProofShot generates them from visual inspection.
Unlike Playwright/Cypress visual regression tools that require baseline images and manual threshold tuning, ProofShot uses LLM vision to generate semantic assertions that understand intent, making it more adaptable to intentional design changes while catching unintended visual regressions.
screenshot capture with agent context injection
Medium confidenceCaptures full-page or component-level screenshots from a running browser instance and embeds metadata about the current agent state, task context, and UI specifications. Integrates with headless browser APIs (Puppeteer/Playwright) to trigger captures at specific points in the agent's execution flow, passing along task descriptions and expected outcomes as context for downstream assertion generation.
Integrates screenshot capture directly into agent execution loops with context injection, allowing assertions to reference the task specification and agent intent rather than just pixel-level comparisons. Most screenshot tools are passive; ProofShot's capture is agent-aware and specification-aware.
Differs from generic screenshot libraries (Puppeteer's screenshot()) by automatically embedding task context and UI specifications into the capture metadata, enabling vision models to generate assertions that understand intent rather than just visual appearance.
multi-modal assertion validation with llm reasoning
Medium confidenceEvaluates generated assertions against actual UI output using LLM reasoning over both visual and textual data. Sends screenshots, generated assertions, and UI specifications to a vision-capable LLM, which reasons about whether the rendered UI satisfies the assertions and specifications. Returns structured validation results with confidence scores and explanations of any mismatches, enabling agents to understand why assertions failed.
Uses LLM reasoning over both visual and textual data to validate assertions semantically rather than just executing them programmatically. Understands intent and context, not just pixel values. Provides natural language explanations of failures, enabling agents to learn from mistakes.
Unlike traditional assertion frameworks (Jest, Playwright assertions) that execute deterministically but provide no semantic reasoning, ProofShot uses LLM reasoning to understand whether a UI satisfies intent, making it more flexible for design variations while providing explainable feedback.
agentic feedback loop integration for iterative ui refinement
Medium confidenceEmbeds visual verification into agent execution loops, enabling agents to capture screenshots, generate assertions, validate them, and automatically refine code based on validation feedback. Implements a feedback mechanism where assertion failures trigger code regeneration with updated context, creating a closed loop where agents self-correct UI code until assertions pass. Integrates with agent frameworks via hooks or middleware.
Closes the loop between code generation, visual verification, and code refinement within a single agent execution flow. Most tools are linear (generate → test → report); ProofShot enables agents to autonomously iterate until quality criteria are met, implementing a feedback mechanism that mirrors human debugging workflows.
Unlike CI/CD pipelines that fail fast and require human intervention, ProofShot enables agents to autonomously refine code based on visual feedback, reducing iteration time from hours (human review) to minutes (agentic loops).
specification-aware assertion generation with design token support
Medium confidenceGenerates assertions that reference design tokens, component specifications, and UI requirements rather than hardcoded pixel values. Parses design token files (JSON, CSS variables, or Figma tokens) and component specifications to generate assertions that validate semantic properties (e.g., 'button uses primary color token' vs 'button is #007BFF'). Enables assertions to remain valid across design system updates and theme changes.
Generates assertions that reference design tokens and semantic properties rather than pixel values, making assertions resilient to design system updates. Integrates with design token standards (Figma tokens, design-tokens format) to enable cross-tool compatibility.
Unlike pixel-based visual regression tools that break when design tokens change, ProofShot generates semantic assertions that validate against design system specifications, reducing false positives and making assertions maintainable across design iterations.
component-level visual regression detection
Medium confidenceCompares screenshots of individual UI components across versions to detect unintended visual changes. Isolates component rendering in a test environment, captures screenshots before and after code changes, and uses image analysis or LLM vision to identify differences. Generates reports highlighting which components changed and whether changes are intentional or regressions.
Integrates component-level visual regression detection into agent workflows, enabling agents to validate that code changes don't break existing components. Uses LLM vision to understand whether changes are intentional or regressions, reducing false positives from pixel-level diffs.
Unlike traditional visual regression tools (Percy, Chromatic) that require manual baseline management and threshold tuning, ProofShot uses LLM reasoning to understand intent, distinguishing intentional design changes from unintended regressions.
cross-browser visual consistency validation
Medium confidenceCaptures screenshots of UI components across multiple browser engines (Chromium, Firefox, WebKit) and validates visual consistency. Compares rendered output across browsers to detect browser-specific rendering issues, CSS compatibility problems, or layout shifts. Generates reports identifying which browsers have visual discrepancies and suggests fixes.
Automates cross-browser visual validation within agent workflows, enabling agents to detect browser compatibility issues during code generation rather than after deployment. Uses LLM vision to understand whether differences are intentional or bugs.
Unlike manual cross-browser testing or cloud-based services (BrowserStack, Sauce Labs) that require manual setup and review, ProofShot automates detection and provides LLM-powered reasoning about whether differences are acceptable.
accessibility-aware visual assertion generation
Medium confidenceGenerates assertions that validate accessibility properties visible in screenshots, including color contrast, text size, button size, focus indicators, and semantic HTML structure. Uses vision models to analyze screenshots for accessibility issues and generates assertions that enforce WCAG compliance. Integrates with accessibility testing libraries to validate assertions programmatically.
Generates accessibility assertions from visual inspection, enabling agents to validate WCAG compliance during code generation. Combines vision analysis with accessibility standards to create assertions that enforce inclusive design.
Unlike accessibility testing tools (axe-core, Lighthouse) that require full DOM access and can miss visual issues, ProofShot uses vision analysis to detect accessibility problems visible in screenshots, complementing programmatic testing.
Capabilities are decomposed by AI analysis. Each maps to specific user intents and improves with match feedback.
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Best For
- ✓AI agent developers building autonomous code generation systems
- ✓Teams using LLM-based UI builders that need automated quality gates
- ✓Developers implementing agentic loops where visual feedback is required
- ✓Agentic UI builders that need visual checkpoints during code generation
- ✓Teams debugging why AI-generated UIs don't match specifications
- ✓Systems that need audit trails of visual changes made by agents
- ✓AI agents that need to understand and reason about assertion failures
- ✓Teams building self-correcting UI generation loops
Known Limitations
- ⚠Assertion generation accuracy depends on image analysis model quality — may miss subtle styling differences or accessibility issues
- ⚠Requires rendered output (browser/headless environment) — cannot verify static code without execution
- ⚠No built-in support for responsive design testing across multiple viewport sizes
- ⚠Assertion generation is non-deterministic — same screenshot may produce slightly different assertions on repeated runs
- ⚠Requires headless browser environment — cannot capture native mobile or desktop app UIs
- ⚠Screenshot timing is critical; race conditions may capture incomplete renders or loading states
Requirements
Input / Output
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