AI tool comparison
CatDoes v4 vs Terrarium
Which one should you ship with? Here is the side-by-side panel verdict, pricing read, reviewer split, and community vote comparison.
Developer Tools
CatDoes v4
An AI agent with its own cloud computer builds your mobile apps
75%
Panel ship
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Community
Free
Entry
CatDoes v4 ships with Compose — an autonomous AI agent that runs on its own cloud computer to build mobile apps, websites, and internal tools from plain text descriptions. You describe what you want, Compose plans the work, writes code, runs tests, fixes its own errors, and deploys — even after you close the browser tab. Every project comes pre-wired with a full backend stack: database, authentication, storage, edge functions, and real-time events. The v4 release focuses on higher reliability and GitHub integration for developers who want to export and own their codebase. Free plans start at 25 credits; paid plans begin at $20/month with more projects and higher cloud limits. What distinguishes CatDoes from the crowded AI app builder space is the "own computer" framing. The agent doesn't just generate code for you to paste — it has an execution environment where it can actually run and debug the app, catching errors before you see them. Whether that closed-loop debugging holds up in practice for complex apps is the open question.
Developer Tools
Terrarium
Evals that actually simulate real deployment — stateful, multi-turn, alive
50%
Panel ship
—
Community
Paid
Entry
Terrarium is a multi-turn evaluation and optimization engine for LLM agents built by evolvent-ai. Unlike static benchmark suites that measure agents against fixed input-output pairs, Terrarium creates persistent, stateful "living environments" — simulated deployment contexts where agents operate over extended sessions, accumulate state, use tools, and interact with simulated external systems. You evaluate agents the way you'd test a car: by driving it, not by measuring its doors. The system supports configurable environment complexity, including simulated databases, APIs, file systems, and user personas. Agents are scored not just on final outputs but on trajectory quality — how efficiently they reached the answer, how often they hallucinated intermediate steps, and how well they recovered from dead ends. The engine also supports continuous optimization loops where poor-performing trajectories trigger automatic prompt refinement. With 17 stars and created April 14, Terrarium is extremely new. But it's addressing a genuine gap: the disconnect between how agents perform on static benchmarks versus how they behave in production. As enterprise AI deployments scale, the need for realistic pre-production evaluation is becoming critical.
Reviewer scorecard
“The closed-loop debugging is the real differentiator. Most AI code generators dump code on you and walk away — Compose actually runs the result and iterates. At $20/month with code export and GitHub sync, it's a serious prototyping accelerator even for experienced devs who just want to skip the boilerplate.”
“Static evals are lying to us constantly — agents that ace benchmarks fall apart in production because benchmarks don't have state, side effects, or accumulated context. Terrarium's living environments model is the right approach to catching real failure modes before deployment.”
“Every AI app builder claims autonomous error-fixing, and in practice they all hit the same wall: anything beyond CRUD starts failing in unpredictable ways. CatDoes is also a relatively unknown indie — if they fold or pivot, you're left with a codebase that was built in their proprietary stack. Export and own is a good safety valve, but validate it before depending on it.”
“Building a realistic simulation of your production environment is often harder than just running the agent in staging. The value proposition assumes your eval environment is meaningfully closer to production than your existing test suite — which is a big assumption for complex deployments.”
“This is the trajectory: agents that don't just write code but execute, test, and observe it running. When the agent can monitor its own output in production and self-correct, we've crossed into genuinely autonomous software development. CatDoes is an early bet on that future at an indie scale.”
“The eval-optimize loop is the missing piece in most AI agent development workflows. Tools that can automatically identify weak trajectories and suggest improvements will become as fundamental as unit tests. Terrarium is early, but the category is inevitable.”
“As a designer who occasionally needs a working prototype but doesn't want to learn Swift or React Native, this is a gift. Being able to describe an app in natural language and get something testable on a real device within an hour is exactly the kind of tool that removes the 'I need a developer' blocker from creative projects.”
“This is deeply technical infrastructure that won't affect my daily workflow. The people who need this know they need it — but for most creators building with AI tools, static evals are already more than they use.”
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