Summer Engine vs Ziva vs Flockbay: which Godot AI tool to pick in 2026

On 6 June 2026, Summer Engine published its comparison with Ziva. Its sharpest line is about the running game. Ziva, it says, "cannot play the game and it cannot read what the running game printed, because it does not run the game." The verdict follows from that line: "Choose Summer Engine if you want the AI to run the game and debug it, not just edit it."

Read Ziva's own pages on 13 October and they say the opposite. Its playtesting docs say Ziva "opens it in the Game tab, can send input, captures the final screen, and reads runtime errors." Its listing on the official Godot Asset Store says it can "launch a scene in the Game tab, send keyboard and mouse input, and take screenshots to check its own work." On its Pro and Ultra plans, a Full Game Playtest Agent plays the whole game, turn by turn.

Ziva's comparison, dated 22 May, is just as wary of Summer. It calls Summer "a separate AI-native editor that opens .godot projects" and says "The engine claims compatibility with existing Godot 4 projects." Its verdict leaves the choice to you: "The right answer for your project is the editor you're faster in by day four."

Each of those pages was written by one of the two products, and neither mentions a third. This page reads both sites on the same day, quotes each in its own words, and puts Flockbay in the table as the third option. Where a product's pages contradict each other, it says what each one says.

Ziva describes itself as "an AI coding agent that works inside the Godot editor." It installs as an add-on in your project, for Godot 4.2 and later, and its store listing names Windows (x64 and arm64), macOS (Universal) and Linux (x64 and arm64). It writes and refactors GDScript and C#, builds and edits scenes, nodes, signals and resources, reads editor errors, generates sprites and textures, adds 3D models to a scene, and has TileMapLayer tools from Godot 4.3.

It runs on Claude, GPT or Gemini through its hosted models, on your own Claude Code or ChatGPT Codex subscription on every plan, or on a local model through Ollama or LM Studio. It also serves its tools to other agents. As a local MCP server, it lets Claude Code, Codex, Cursor, Windsurf, Zed and others inspect the scene tree, create or update nodes, scenes, scripts and resources, read Godot errors, and run and stop the game, as long as the project is open in Godot.

Leaving is cheap. In Ziva's words, "If you uninstall the plugin tomorrow, your project is still a normal Godot project." The cost sits elsewhere: Claude Sonnet and Opus, Ziva Genius and the full playtester are on Pro at $50 a month, and its installation docs say an internet connection is "Required for AI features".

Verdict: Ziva is the pick if you want an AI agent inside the Godot editor you already use, running on your own Claude Code or Codex subscription or on its hosted models.

Summer Engine calls itself "The AI game engine for people and agents", and its docs draw the line against plugins: Summer is "a full game engine, not an AI addon." Its migration docs give Godot Engine 4.7.2 as its "current upstream technical base", its homepage counts "more than a million lines of custom code" on top, and its MCP page calls the engine "compatible with Godot 4". You open an existing Godot project with File, then Open Project, and it indexes the files for its AI.

The AI lives in Summer's own editor. It runs the game and reads the output, and it generates 3D models, images, audio and video on credits. Its MCP server is free and MIT-licensed, offers "105 tools to build, run and test real games in the engine", and installs for Claude Code, Codex, Cursor and many other agents with one npx command. The engine exports to "Windows, Mac, iOS, Android and the web, all from Summer", with desktop builds you can ship on Steam or itch.io.

Where it breaks: it is not the Godot you download from godotengine.org. Its docs say a project can go back to official Godot, but "Summer-only AI and platform surfaces will not be present." It does not take your own API key for hosted generation; your own model works through MCP instead. The desktop app is "free proprietary software", and its installation docs list Windows 10 or later and macOS 10.14 or later, with no Linux build stated.

Verdict: Summer Engine is the pick if you want hosted AI, generated art and sound, and mobile export in one engine, and you are happy to work in its editor.

Flockbay builds and play-tests a whole Godot game for free: free AI every day or your own Claude or ChatGPT, on the official Godot engine. The engine is the official Godot 4.7.2 release, bundled with the app, not a fork. The app hosts the full Godot editor, with its Scene dock, Inspector, FileSystem, Script editor, Output and Debugger. A Simple view is the default and Full is one switch away, and existing Godot projects open in it.

The AI is also called Flockbay. Before it builds, it works out a brief with you, and it builds nothing until you approve it. Then it writes GDScript and scenes, builds the world with world tools for terrain, water, sky, weather, the player controller and props, and plays the game to check its work: it runs the game, sends input events, takes viewport captures and reads the errors from the running game.

The AI costs nothing. The hosted model, Demo, is free every day. Your own Claude plan (Pro or Max) or ChatGPT account, on any plan including Free, runs inside the app. Your own agent connects over one MCP server, registered as flockbay-stage. Or you add an OpenAI or Anthropic API key. Pictures and sound come with the free AI, and a 3D model runs on your own Tripo key. No sign-in stands in front of the first build: the app makes a guest account when it first opens.

Where it breaks: it runs on Windows and on Linux, as an x86_64 AppImage that an Intel or AMD Chromebook runs once Linux is turned on. The Mac build is an earlier release, without Claude in the app or the full editor. The app is closed source, and building needs an internet connection, though the game runs locally.

Verdict: Flockbay is the pick if you want the whole game built and play-tested on stock Godot without paying for AI.

Ziva's prices depend on which of its pages you read. Its site says "Hobby is free with your own Claude Code/Codex provider or local models" and "Basic includes Ziva-hosted models", at $20 a month after a seven-day trial for eligible accounts. Its Godot Asset Store listing, updated 9 October, gives Hobby more: "50 Ziva Baby messages a day, 10 Ziva Smart messages, and $3/month of included AI usage." The same listing prices Basic at $20 a month with $60 of AI usage, Pro at $50 with $150 and Ultra at $200 with $600.

Summer's pricing page lists a free app, Pro at $20 a month, Pro+ at $60 and Ultra at $200, and its docs say yearly billing saves 20% on all three. The free app reads "Try hosted Summer AI when you create an account", which its docs describe as "Limited hosted agent use + limited AI asset creations". A $5 Basic plan exists too, and the docs say it "is not shown on the public pricing page". Pro+ adds "MCP skills and hooks" and "3x limits on all AI usage".

Flockbay has no paid plans, tiers or top-ups. All three are free if you bring a model you already pay for: Ziva on every plan, Summer over MCP, Flockbay in the app or over MCP. The difference shows when you bring nothing. Ziva's site starts its hosted models at Basic, Summer's free tier has limited hosted use, and Flockbay's Demo is free every day.

Summer runs the game inside its own engine. Its comparison describes the loop as pressing play, watching the game run and reading the real runtime error and console output, and its MCP tools cover play, stop, screenshots, the debugger's errors and game input.

Ziva runs it from the editor. Its quick check opens the game in the Game tab, sends input, captures the final screen and reads runtime errors. On Pro and Ultra, its Full Game Playtest Agent launches the game in a sandbox and pauses it, "giving time for the LLM to think", then plays it turn by turn with keyboard, mouse and gesture input. It returns pass, fail or blocked with reproduction steps, does not edit your project, and in Ziva's words "can run dozens of instances in parallel".

Flockbay's AI plays the game to check its own work, on the free AI. It runs the game, sends input events with timing, takes viewport captures and reads errors with file, line and call stack. An outside agent over MCP gets the same tools, plus the live scene tree, and every change it makes in the editor is one Ctrl+Z.

The difference that matters for a bug hunt is who pays for the check. Summer's checks run on its hosted AI or on your agent. Ziva names no plan for its quick check, and its full playtester costs $50 a month. Flockbay's costs nothing.

Ziva takes your subscription into its own chat. You connect Claude Code or ChatGPT Codex in its settings, on any plan, and requests come out of that subscription's allowance rather than Ziva's. It also works the other way round, as an MCP server your agent calls.

Summer takes your model only the second way. Its docs say "Summer does not accept your own provider API keys for hosted generation" and point you to its MCP server, where Claude Code, Codex or Cursor drives the editor on the model you already pay for. Local MCP is free on every plan.

Flockbay takes both. Your Claude plan (Pro or Max) runs Claude Code inside the app, and a ChatGPT account on any plan, Free included, runs through the bundled Codex engine. An agent outside the app connects over the flockbay-stage MCP server, and the app writes its setup line with your machine's paths filled in. The Godot MCP guide has that line for every agent.

Ziva leaves a normal Godot project, because it never was anything else. Flockbay leaves one too: a real Godot 4 project in a folder on your own computer, which stock Godot 4.7.2 opens, and nothing is uploaded unless you invite a team member. Summer keeps its source formats "upstream-compatible", but a project that goes back to official Godot loses the Summer-only surfaces.

The catch is the engine version. Ziva supports Godot 4.2 and later, so a project pinned to an older 4.x stays where it is. Flockbay works on the Godot 4.7.2 it ships, and Summer on its own engine with a 4.7.2 base, so a project from an older 4.x opens in a newer engine there. Commit before you open it, as you would before any Godot upgrade.

Pick Ziva if you want an AI agent inside your own Godot editor, on Windows, macOS or Linux, and you already pay for Claude or ChatGPT or are happy to pay for its hosted models.

Pick Summer Engine if you want hosted AI, generated art and sound, and mobile and web export in one engine, on Windows or a Mac.

Pick Flockbay if you want the whole game built and play-tested on the official Godot engine, with AI that costs nothing, on Windows or Linux.

If you are still unsure, give each one the same small task, such as a door that opens when three switches are pressed, and play the results yourself. Flockbay vs Summer Engine and Flockbay vs Ziva go deeper on each pairing, and the Ziva alternatives add the free MCP servers.