sunpeak
Open-source MCP testing & app framework for building ChatGPT Apps and Claude Connectors.
If you're building ChatGPT Apps or Claude Connectors in React, sunpeak is the only dedicated open-source framework that covers development, testing, and deployment with real host replication. Its inspector and Playwright testing, including live host sessions, save weeks of manual debugging and host switching. For simpler projects, a minimal MCP library might suffice, but sunpeak's testing suite justifies the learning curve.
Verified 1d ago · liveness 67/100 · cite: rightaichoice.com/tools/sunpeak
- Developers building ChatGPT Apps with React
- Developers building Claude Connectors with custom UI
- Teams needing to test MCP servers in CI/CD without accounts
- Prototyping interactive chat-based AI apps for multiple hosts
- Non-developers looking for a no-code chat builder
- Organizations that require a hosted platform with SLAs
- Teams using non-React frontend frameworks
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Skip sunpeak if you're not building interactive UIs for AI hosts, don't use React, or just need a minimal MCP server without testing or inspector features.
Live host tests require you to have a ChatGPT or Claude account (and possibly API access), so you'll incur costs if you run those tests frequently.
sunpeak is completely free and open-source (MIT), so it's a zero-cost option for developers and teams already using MCP. Compared to commercial testing platforms or hosted services that charge per seat or per test run, sunpeak's pricing is a major advantage—you only pay for your own infrastructure. This makes it particularly attractive for startups and indie developers.
In short
sunpeak — Open-source MCP testing & app framework for building ChatGPT Apps and Claude Connectors. Best for Developers building ChatGPT Apps with React, Developers building Claude Connectors with custom UI, Teams needing to test MCP servers in CI/CD without accounts. Free to use.
What's new in sunpeak
Checked 5 days agoAcross the latest 7 updates: 7 feature updates.
Live Testing for Claude Connectors and ChatGPT Apps: Test Against Real Hosts with Playwright
Guide to testing Claude Connectors and ChatGPT Apps in real host sessions with Playwright, covering failures only live tests catch and when local testing is sufficient.
Debugging Claude Connectors: Fix Common Errors in Development and Production
Debug connection, OAuth, tool selection, MCP protocol, tool result, and UI failures with a repeatable local-to-production workflow.
Claude Connector Authentication: How OAuth Works and When You Need It
Developer guide to authentication for Claude Connectors: OAuth, CIMD, DCR, Anthropic-held credentials, static headers, Enterprise Managed Auth, callback URLs, token refresh, local testing.
What Are Claude Connectors? Data Access, Auth, Custom Setup, and Troubleshooting
Explains MCP-backed Claude Connectors: web connectors, custom remote MCP, desktop extensions, auth, permissions, interactive UI, and testing in 2026.
The Fastest Way to Prototype ChatGPT & MCP Apps
Guest post from Fractal on prototyping ChatGPT and MCP Apps before full engineering; validate trigger and UI with users, then test with sunpeak as app grows.
Claude Connectors Tutorial: Build and Deploy a Connector to Claude
Build interactive Claude Connector from scratch: remote MCP architecture, tools/resources, local testing, real Claude session, and Connectors Directory submission prep.
Claude Inspector for MCP Apps: Test Claude Connectors Locally with sunpeak
Use sunpeak Inspector to test Claude Connectors and MCP Apps locally; covers what to verify in Claude runtime, automated tests, and live host checks.
What people actually say about sunpeak — is it worth it?
We ran a structured research pass across product reviews, community discussions, and post-purchase forum threads to surface the patterns vendors won't publish themselves. Below: the recurring strengths, the hidden costs people mention most, and the cohort that consistently regrets adopting this tool.
32 mentions across 3 sources (Hacker News, YouTube, GitHub) · researched Sep 1, 2026.
- +Convention-over-configuration auto-discovery cuts boilerplate significantly.
- +Local inspector replicates ChatGPT and Claude runtimes for testing.
- +Hot-reloading dev server speeds up iteration with HMR support.
- +Built-in Playwright E2E and visual regression testing saves setup time.
- +Multi-model evals compare model behavior for tool calls.
- −OAuth support is incomplete; no standard way to pass Authorization headers.
- −Lack of Grok emulator, despite demand for it.
- −URL-backed state in the inspector is missing, hurting usability.
- −Learning curve for MCP newcomers; docs assume some familiarity.
- −Small community; limited third-party help and resources.
- • Potential need for third-party Playwright setup and additional infrastructure if you scale testing
- • Time investment for learning MCP and React hooks
Viability Score
How well maintained and how widely used is sunpeak? Built from what the vendor actually publishes (docs, changelog, tutorials, integrations, pricing), whether the site is live, and how much real users discuss it. How we calculate this
Last calculated: September 2026
How we score →Key Features
- Auto-discovery of tools, resources, and simulations
- Local inspector replicating ChatGPT and Claude runtimes
- Hot-reloading MCP dev server with HMR for ChatGPT
- 20+ typed React hooks (useToolData, useAppState, useTheme, useDisplayMode)
- Pre-built MCP App UI components following host design guidelines
- Playwright E2E tests with iframe traversal fixtures
- Visual regression testing across hosts and themes
- Live host tests against real ChatGPT and Claude sessions
- Multi-model tool calling evals for response quality
- CLI for scaffolding, building, testing, shipping (npx sunpeak new, test, inspect)
- Simulation fixtures for testing without accounts or API credits
- Server-agnostic MCP server support (Python, Go, TypeScript, Rust, Java)
- CI/CD integration with no paid accounts or API credits (GitHub Actions)
- OAuth flows for Claude Connector authentication
- Docs available via MCP for coding agents
About sunpeak
sunpeak is an open-source (MIT), server-agnostic MCP testing framework and full-stack MCP App framework for developers building interactive UIs that run inside AI hosts like ChatGPT and Claude. It lets you create ChatGPT Apps and Claude Connectors from a single codebase, without needing paid host accounts or AI credits. The framework uses a convention-over-configuration project structure where tools, resources, and simulations are auto-discovered from the file system, so you can focus on building features instead of wiring up protocol details. Development centers on three core pieces: a hot-reloading dev server, a multi-host inspector, and a full testing suite. The inspector replicates ChatGPT and Claude runtimes locally, letting you toggle between hosts, themes, display modes, and device types before you ever deploy. The testing framework includes Playwright E2E tests, visual regression testing across hosts and themes, and live host tests that run against real ChatGPT and Claude sessions. There’s also multi-model evals to compare how different models handle your tool calls. For building, sunpeak ships 20+ typed React hooks (like useToolData and useAppState), pre-built UI components that follow host design guidelines, and a CLI for scaffolding, building, testing, and shipping. You write your app once, then deploy to ChatGPT, Claude, and any future MCP-compatible host. The framework is server-agnostic — it works with any MCP server in Python, Go, TypeScript, Rust, or Java — making it flexible for teams already running MCP infrastructure. Recent tutorials (July–August 2026) cover building and deploying Claude Connectors, local testing with the Inspector, and live testing against real hosts with Playwright, confirming active development and community support. OAuth flows for Claude Connector authentication are documented, and the docs are available via MCP for coding agents. Compared to rolling your own MCP server or using a minimal library, sunpeak provides a structured framework with built-in testing and inspector tools, saving significant development and debugging time.
Behind the Verdict
sunpeak stands out in the MCP ecosystem as a complete, opinionated framework rather than just a library. Its strongest asset is the Inspector, which replicates ChatGPT and Claude runtimes locally — this is a genuine time-saver because you can see exactly how your UI renders and behaves across hosts, themes, display modes, and device types without deploying or paying for accounts. The testing framework is unusually deep for an open-source tool: Playwright E2E tests with iframe traversal fixtures, visual regression testing, live host tests against real ChatGPT/Claude sessions, and multi-model evals. This means you can validate everything from UI rendering to tool-call quality in CI/CD, which is rare in the MCP space. For correctness, the framework uses convention-over-configuration: tools, resources, and simulations are auto-discovered from the file system, which reduces boilerplate and keeps projects organized. The 20+ typed React hooks and pre-built UI components that follow host design guidelines help ensure your apps look native in each host. The server-agnostic design means you can test any MCP server regardless of language — Python, Go, TypeScript, Rust, Java — making it a flexible addition to existing MCP infrastructure. However, there are clear trade-offs. sunpeak requires knowledge of React, Node.js, and the MCP protocol; it's not for non-developers or teams using non-React frontends. The framework is relatively new, so the community and third-party integrations are still maturing compared to more established tools. Also, while you can test with real ChatGPT and Claude sessions, those live tests require you to have accounts and possibly API keys — the core value is that you don't need them for local development or CI. Where sunpeak fits best: teams building production-grade ChatGPT Apps or Claude Connectors that need rigorous testing and multi-host support. It's less ideal for rapid prototypes or one-off MCP servers where a minimal library like FastMCP or MCP.js would be lighter. For those exploring the MCP ecosystem, sunpeak is a strong foundation, but be prepared to invest time in learning its conventions and testing patterns.
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Real-world workflow fit
Concrete scenarios for the personas sunpeak actually fits — and what changes day-one when you adopt it.
Scaffold a new project with npx sunpeak new, then add a resource and tool. Start the dev server with npx sunpeak dev to see live changes in the Inspector.
Outcome: You get instant visual feedback of your app in a simulated ChatGPT runtime, with hot reload and auto-discovered files, reducing iteration time.
Run npx sunpeak test init --server http://localhost:8000/mcp in your CI pipeline, then run Playwright tests and visual regression checks across hosts and themes.
Outcome: You gain confidence that your MCP server works correctly in both ChatGPT and Claude without needing paid accounts, catching regressions early.
Use the Inspector to test your connector locally, simulate OAuth flows with fixtures, and then run live tests against a real Claude session to verify authentication and tool calls.
Outcome: You ensure your connector works in production before submission, avoiding common OAuth and protocol pitfalls via the documented workflow.
Use Cases
- Build a customer support chat widget that works in both ChatGPT and Claude.
- Test an MCP server's response quality with automated multi-model evals.
- Prototype a data visualization tool that renders as an interactive resource inside Claude.
- Create a Claude Connector that accesses a live database and returns formatted results.
- Run Playwright tests against a simulated ChatGPT runtime to catch UI regressions before deployment.
- Develop and debug a Claude Connector locally with the Inspector before submission.
Limitations
- sunpeak is a framework for building and testing MCP Apps, which are interactive UIs embedded in agent conversations with hosts like ChatGPT and Claude.
- It requires knowledge of React, Node.js, and the MCP protocol.
- Testing is primarily via CLI tools like Playwright and live host tests, with the Inspector providing a graphical runtime for inspection.
- The framework is open-source and relatively new, so community and third-party integrations are still emerging compared to established frameworks.
as of 2026-09-01
Verification history
We have re-verified sunpeak 7 times since . Each pass re-reads the vendor's own pages and re-checks every listed field against that evidence; passes where nothing had changed are marked as such.
- — re-verified summary, description, our verdict, our analysis, pricing model, pricing tiers, features, integrations, who it suits, who should skip it
- — re-verified summary, description, our verdict, our analysis, pricing model, pricing tiers, features, integrations, who it suits, who should skip it
- — re-verified summary, description, our verdict, our analysis, pricing model, pricing tiers, features, integrations, who it suits, who should skip it
- — re-verified summary, description, our verdict, our analysis, pricing model, pricing tiers, features, integrations, who it suits, who should skip it
- — re-verified summary, description, our verdict, our analysis, pricing model, pricing tiers, features, integrations, who it suits, who should skip it
- — re-verified summary, description, our verdict, our analysis, pricing model, pricing tiers, features, integrations, who it suits, who should skip it
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Free to cite with attribution — this page re-verifies continuously.
Where the pricing makes sense
The company stage and team size where sunpeak's pricing actually pencils out — and where peers do it cheaper.
sunpeak is completely free and open-source (MIT), so it's a zero-cost option for developers and teams already using MCP. Compared to commercial testing platforms or hosted services that charge per seat or per test run, sunpeak's pricing is a major advantage—you only pay for your own infrastructure. This makes it particularly attractive for startups and indie developers.
Setup time & first value
How long it actually takes to get something useful out of sunpeak — broken out by persona, not the marketing-page minute.
For a new project, npx sunpeak new scaffolds everything and you can have a basic app running in under 10 minutes. Adding tests might take an hour to configure. If you have an existing MCP server, setting up sunpeak test init takes about 5 minutes to get Playwright and fixtures ready. The learning curve for the full suite (evals, live tests) is a few days for developers new to MCP.
Switching to or from sunpeak
How to bring data in from common predecessors and how to get it back out — written for the switcher, not the buyer.
- →From a minimal MCP library (e.g., FastMCP) to sunpeak: restructure your project into sunpeak's convention, add components via JSX, and use sunpeak test for automated testing.
- →From a custom MCP server: you can keep your existing server and use sunpeak test init to add testing and the inspector without rewriting your server logic.
- ↗To a minimal MCP library: if you no longer need the UI or testing, you can extract tool handlers and resource logic and integrate them into a lighter framework.
- ↗To a hosted MCP platform: you can retain your MCP server code and deploy it to a cloud provider; sunpeak's server-agnostic approach allows for easy migration.
Integrations
Resources & Guides
Tutorials & Learning
Official links
Tools that pair well with sunpeak
Common stack mates teams adopt alongside sunpeak, with the specific reason each pairing earns its keep.
Featured Head-to-Head Comparisons
Sunpeak vs Spider Cloud
Choose sunpeak if you need to build and test interactive MCP apps for ChatGPT/Claude with a full React framework and CI/CD testing. Pick Spider Cloud if your priority is scraping large-scale web data for RAG pipelines or AI agents at low cost per page. They solve different problems – one is a development framework, the other a data extraction API.
Sunpeak vs Voyage Ai
Choose Voyage AI if you need domain-specific, high-accuracy embeddings for enterprise RAG on finance/legal documents and are willing to pay for it. Choose sunpeak if you are a developer building interactive MCP-based apps (ChatGPT Apps, Claude Connectors) with React and want a free, open-source framework with hot-reload and built-in testing.
Sunpeak vs Temporal Ai
Choose Temporal AI if you need battle-tested durability and orchestration for complex, long-running AI workflows or microservices, and you're willing to adopt a workflow-as-code model. Choose sunpeak if you're focused exclusively on building and testing interactive MCP apps for ChatGPT and Claude with React, especially with little overhead and no-hosting needed.
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