Hera Agent Unity

hera-agent-unity

Give your AI coding agent hands, eyes, and a checklist inside Unity.

Codex, Claude, Cursor, Copilot, AntiGravity, and other shell-capable agents can inspect your live Unity Editor, change it, run it, test it, see the result, and keep fixing until the evidence says it is done.

Start in 3 steps · What can it do? · Why Hera? · How good is it? · Examples · Commands

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Hera in one minute

An AI can write Unity C# without Hera, but it cannot reliably know what your live Editor looks like after the code is written.

Normally the loop looks like this:

You ask the AI

↓ AI writes code ↓ You open Unity and wait for compile ↓ You copy the error back to the AI ↓ AI fixes it ↓ You press Play and explain what happened ↓ repeat...

Hera closes that loop:

You ask the AI

↓ AI uses Hera ↓ Unity compiles, runs, tests, clicks UI, captures the result ↓ Hera gives the real result back to the AI ↓ AI fixes what failed and checks again ↓ verified result

A simple way to think about it:

The AI is the brain. Hera gives that brain hands to operate Unity, eyes to inspect the result, and a checklist so it does not stop while the project is still broken.

Hera does not replace Unity and it does not replace the coding agent. It connects the two so the agent can work with facts from your actual project instead of guessing from source code alone.

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What problem does it solve?

Unity development has a feedback loop that lives outside the source files.

A change can look correct in code and still fail because:

• Unity did not compile it;
• the wrong Scene is open;
• a GameObject or Component is missing;
• the Inspector has a different serialized value;
• a Unity API changed in your Editor version;
• the Console contains an exception;
• Play Mode behaves differently from Edit Mode;
• a button is visually present but cannot receive input;
• a UI layout is technically valid but looks wrong;
• the AI says "done" before it has actually checked any of those things.

Hera lets the agent ask the real Editor instead.

hera-agent-unity status

hera-agent-unity console --type error hera-agent-unity scene info hera-agent-unity editor play --wait hera-agent-unity test --mode PlayMode

If the selected Editor is not running, Hera can bootstrap the exact project before Connector discovery:

hera-agent-unity --project C:/Projects/Game editor launch

hera-agent-unity --project C:/Projects/Game editor restart

The project version comes from ProjectSettings/ProjectVersion.txt; the matching Unity Hub install comes from UNITY_HUB_EDITOR or the platform default (%ProgramFiles%\Unity\Hub\Editor on Windows). Pass --hub-root for a custom Hub location. Startup uses normal Package Manager behavior, not -noUpm, and returns when the new process publishes that exact project's heartbeat. On Windows, Hera also restores the standard common-profile environment for the Unity child when an agent shell omitted it, so UPM path resolution still starts with the same baseline as a normal desktop launch.

The important part is not the command names. The important part is that the agent can observe → change → run → verify → repair without making you act as the courier between the AI and Unity.

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What can it actually do?

You can use Hera for tiny one-line checks or for a full AI-assisted Unity workflow.

In short, Hera is not just a "press Play" remote. It is a bridge for the whole edit-and-check loop around a running Unity project.

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Why use Hera?

1. The AI can check its own work

Without Editor access, the agent often ends with:

"This should work."

With Hera, it can finish with evidence such as:

compile: passed

console errors: 0 EditMode tests: 18/18 PlayMode tests: 6/6 button click: verified through EventSystem final Game View: captured

That difference is the main reason Hera exists.

2. You stop being the copy-and-paste bridge

You no longer need to repeatedly:

1. copy code from the AI;
2. switch to Unity;
3. wait for compile;
4. copy errors back;
5. explain the Scene hierarchy;
6. press Play;
7. describe what happened.

The AI can perform most of that loop itself.

3. It works with the tools you already use

The normal production path is a CLI. Any agent that can run shell commands can use it.

• Codex
• Claude Code
• Cursor
• GitHub Copilot
• AntiGravity
• scripts and CI jobs
• your own automation

No Python server is required, and no host protocol has to be configured.

4. It is designed for AI context, not just humans

A giant tool response becomes more input for the model to read. Hera therefore gives common commands compact views such as IDs-only GameObject searches and on-demand tool schemas.

The goal is simple: send the agent the smallest amount of Unity state that is enough to make the next decision.

5. It knows that "request sent" is not the same as "work finished"

Unity recompiles scripts, reloads domains, changes ports, enters Play Mode, runs tests, and sometimes drops a connection while doing it.

Hera tracks these workflows instead of treating a successful HTTP send as proof that Unity is finished.

6. It can grow with your project

Start with the built-in commands. Later you can add a [HeraTool] for the workflow your own project repeats every day: build a dungeon room, validate a quest graph, bake a table, spawn a test battle, or check your studio-specific asset rules.

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How good is it?

Hera avoids vague "AI magic" claims. The repository keeps concrete measurements and compatibility evidence instead.

Small responses for common agent reads

Measured low-token baselines for list --compact are about 93 estimated tokens across the tested Unity versions. find_gameobjects --ids measured 49 to 55 estimated tokens in the retained cross-version fixtures.

| Unity Editor | list --compact | find_gameobjects --ids |

T is a simple ceil(UTF-8 bytes / 4) estimate for Hera's CLI payload only. It is not provider billing telemetry. Full methodology: token-reduction benchmark.

Developer Mode on Unity 2022.3

Connector 0.3.0 compiles on Unity 2022.3, but dispatched requests are refused by default with DEVELOPER_MODE_REQUIRED. Enable Developer Mode (Unity 2022.3) in Hera Settings or run hera-agent-unity asset-config developer-mode on; use off to disable it. asset-config developer-mode shows the value and asset-config --json includes developer_mode (read-only).

The setting applies to every Unity 2022.3 project on this machine. Unity 6.6+ ignores it. A missing file/key defaults to off; malformed or locked configuration reads keep the last good value until a successful refresh. Changes need no domain reload. Status and ping still work while locked; cached local-only catalog queries and validation can also succeed, but dispatched requests are refused.

This is an unsupported opt-in line. On 2022.3.62f2, scoped paths for TMP 3.0.7, Timeline 1.7.7, Input System 1.14.0 and AI Navigation 1.1.6 passed independent verification; the package-present Hera suite passed 51/51. Keyboard and mouse delivery matched the same probe on 6000.6.6f1 with Input System 1.20.0. See versions, paths and evidence. unity_docs uses the 6000.6 corpus: both its unity_version and docs_version describe documentation, so compare them with the Editor version in status. With test-framework older than 1.4.0, cancel cannot stop a run whose callback is active in this domain; it preserves its pending record until completion. Stale records without an active callback can still be released.

All other Editor lines (including 2023.x and 6000.0–6000.5) hit an explicit #error. This stops normal project compilation, and other compiler errors may appear alongside it. Remove the package or use one of the two allowed lines.

Compatibility is checked across Unity generations

Supported Unity versions are Unity 6.6+ (6000.6 minimum). The release compile gate installs the Connector's exact source as a normal UPM dependency in a disposable blank project of the representative Editor and requires a clean compile, a green release-gate suite, and zero console errors: