AI tool comparison
Cua vs Pretty Fish
Which one should you ship with? Here is the side-by-side panel verdict, pricing read, reviewer split, and community vote comparison.
Developer Tools
Cua
Open-source infra for AI agents that actually control computers — Mac, Linux, Windows, Android
75%
Panel ship
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Community
Paid
Entry
Cua is an open-source platform for building, running, and benchmarking AI agents that autonomously control computer interfaces. It provides a unified sandbox API that lets agents capture screenshots, move the mouse, type, and interact with native applications across Linux containers, VMs, macOS, Windows, and Android — all through a single consistent interface regardless of platform. The toolkit ships five components: Cua Sandbox (cross-platform agent execution), Cua Driver (background macOS automation that doesn't steal focus), Lume (macOS/Linux VM management on Apple Silicon via Apple's Virtualization Framework), CuaBot (CLI for running Claude Code and OpenClaw agents inside isolated sandboxes with native window rendering), and Cua-Bench (evaluation suite covering OSWorld, ScreenSpot, and Windows Arena benchmarks with trajectory export for training datasets). With 14.2k GitHub stars and 465 releases, Cua has quietly become the default infrastructure layer for developers building serious computer-use agents. It's trending again in April 2026 as the launch of Cursor 3's background agents and OpenAI's operator-style tooling sends developers looking for local, controllable sandboxes that don't phone home.
Developer Tools
Pretty Fish
Free, beautiful Mermaid diagram editor that works offline
75%
Panel ship
—
Community
Free
Entry
Pretty Fish is a free, open-source Mermaid diagram editor with live preview, 5 built-in themes, multi-page workspaces, and one-click SVG/PNG export. It works offline as a Progressive Web App (PWA) and requires no account, no login, and no installation. It supports all 14+ Mermaid diagram types including flowcharts, sequence diagrams, Gantt charts, entity-relationship diagrams, and Git graphs. The editor includes syntax highlighting, auto-completion, instant error feedback, and a clean split-pane layout. The multi-page workspace lets you manage entire diagram projects in a single session. Export quality is excellent — SVG output is clean and scaling-ready for use in presentations, docs, or design systems. Pretty Fish hit Hacker News front page today with 128 points and has the makings of the go-to Mermaid editor for developers who generate diagrams from AI-assisted documentation workflows. With LLMs increasingly generating Mermaid syntax in their outputs, having a polished renderer and editor matters more than ever.
Reviewer scorecard
“Cua is the plumbing that makes computer-use agents actually work in production. The fact that Cua Driver handles background macOS automation without stealing focus is the detail that separates a demo from something you can ship. 465 releases means this is battle-tested infrastructure, not a weekend project.”
“The official Mermaid live editor is clunky and slow. Pretty Fish loads instantly, works offline, and the multi-page workspace means I can manage all my architecture diagrams in one place. Bookmarking this immediately as my default Mermaid editor.”
“Computer-use agents are still fragile — UI changes in target apps silently break automation in ways that are hard to detect. The benchmark suite evaluates on static tasks, not real-world drift. And running full VMs per agent session has serious cost implications at scale. The infra is solid; the fundamental computer-use problem isn't solved.”
“It's a genuinely nice editor but it's solving a niche problem — most devs who need Mermaid diagrams already use VS Code extensions or embed them in Notion. And with no backend, there's no collaboration or sharing story, which limits its use in team workflows.”
“Cross-platform sandboxed execution is the prerequisite for every autonomous agent use case that isn't purely API-based. Cua normalizes the surface that agents operate on — once that layer stabilizes, the agents themselves can improve rapidly without infrastructure churn. This is foundational scaffolding for the agent era.”
“As AI tools increasingly output Mermaid syntax to explain architectures and flows, the need for a great rendering environment grows. Pretty Fish positions itself at the intersection of AI-generated diagrams and human editing — that's a well-timed niche.”
“I used Cua to build an agent that fills in repetitive design tool tasks — font checks, asset exports, spacing audits. The background automation on macOS is surprisingly clean. It's opened up automation use cases I assumed required paid SaaS.”
“Five beautiful themes and clean SVG exports mean I can finally use Mermaid diagrams in client-facing presentations without them looking like developer scratch notes. This is the Mermaid editor I've always wanted and the zero-friction setup seals it.”
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