can an AI coding agent write Unreal Engine C++?

Yes. Atlas reads your UCLASS, UPROPERTY, and UFUNCTION macros plus the dependencies declared in each Build.cs, and indexes code by AST declarations using tree-sitter, so the reflection markup is treated as part of the class rather than as decoration.

how do I set up Atlas on an Unreal Engine project?

Run atlas in a project with a .uproject and Source/ module folders. Atlas reads the reflection macros and the module rules in each Build.cs, which in Unreal Engine are the real API.

why does my AI agent keep breaking the Unreal build with includes?

Because it adds the include without the module rule. Atlas adds a module dependency in Build.cs before it adds the include, which is the step most C++ agents miss, and it treats both edits as one reviewed change.

can Atlas run Unreal automation tests?

Yes. Atlas can write Automation Spec tests and run them through UnrealEditor-Cmd behind a permission prompt. Every tool call is permission-gated against allow, ask, and deny rules, so a headless editor run never starts unannounced.

can an Unreal studio use Atlas without sending source code out?

Yes. Atlas can build its code index with local Ollama embeddings, keeping code off third-party servers, so the Source/ tree and any licensed engine modifications stay on hardware you control.

does Atlas understand UPROPERTY and garbage collection in Unreal?

Atlas reads UPROPERTY as part of the declaration it indexes, which is what lets it flag a member object declared without the macro, the classic Unreal bug where the garbage collector reclaims an object you still hold.

Atlas for Unreal Engine: Terminal-Native AI Coding for UCLASS and Build.cs in 2026

Atlas is a terminal-native AI coding agent paired with Unreal Engine C++ in 2026, where UCLASS macros, the reflection system, and Build.cs module rules are the real API. You run atlas in a project with a .uproject and Source/ module folders, and Atlas reads your UCLASS, UPROPERTY, and UFUNCTION macros plus the dependencies declared in each Build.cs before it proposes any edit.

Why Unreal Engine developers use Atlas

Unreal Engine developers use Atlas in 2026 because Unreal C++ is not standard C++. UCLASS macros, the reflection system, and Build.cs module rules are the real API, and Atlas indexes code by AST declarations using tree-sitter, not blind line windows, so a UCLASS and its UPROPERTY fields are indexed as declarations.

A general purpose coding agent writes Unreal C++ that looks correct and does not build. It declares a member without UPROPERTY, so the garbage collector reclaims the object out from under you. It writes a UFUNCTION without the specifiers that make it callable from Blueprint. It adds an include for a type in another module and never touches Build.cs. Every one of those is invisible to a text-level model and obvious once you index the macros as what they are. Atlas reads the reflection markup as part of the declaration, which is the only way to reason about an Unreal class at all.

Working across modules and Build.cs day to day

Day to day in 2026, Atlas reads the dependencies declared in each Build.cs alongside your Source/ module folders. Atlas searches code with hybrid semantic and keyword retrieval fused by reciprocal rank fusion, which is how a type in one module and the module rule that permits it surface together.

Unreal's module system is a real dependency graph, and the compiler enforces it. A class in your gameplay module cannot see a type from another module unless that module is listed in PublicDependencyModuleNames or PrivateDependencyModuleNames inside the Build.cs. Keyword retrieval pins the exact module names and the macros. Semantic retrieval finds the code that wants a capability without naming the module that provides it. Fusing them means Atlas can answer which module owns a type and whether your Build.cs already permits the dependency, before you spend a full rebuild finding out that it does not.

Adding the Build.cs dependency before the include

Ask Atlas to add a module dependency in Build.cs before it adds the include, the step most C++ agents still miss in Unreal Engine in 2026. Atlas drafts a plan in a read-only plan agent and asks before switching to a build agent, so the module rule and the include land as one reviewed change.

Ordering is the whole point. An agent that adds an include first produces a project that fails to compile with an error about an unresolved header, and the fix is not in the file it edited, it is in Build.cs. Atlas treats the dependency and the include as a single unit of work. The read-only plan agent enumerates them: which module owns the type, whether the dependency belongs in the public or private list, which Build.cs file to edit, and which header to include. You approve that plan, then Atlas makes both edits together.

Testing with Automation Spec and UnrealEditor-Cmd

Atlas writes Automation Spec tests and runs them through UnrealEditor-Cmd behind a permission prompt. Every Atlas tool call is permission-gated against allow, ask, and deny rules before it runs, so in 2026 a headless editor invocation never starts on your machine without an explicit allow.

Automation Specs are Unreal's BDD-style test format, declared with macros and discovered by the engine's automation system, which means running them means running the editor. UnrealEditor-Cmd does that headlessly. Gating matters more here than in most ecosystems because the command is expensive: a cold automation run can occupy a machine for a long time. Keeping it behind an ask rule means Atlas proposes the run and you decide when it happens. Because Atlas fans out work to subagents that can run in the foreground or in parallel background sessions, the run can proceed in the background while you keep working.

Review and the Epic style guide

In 2026, review in Unreal Engine is diff-first with Atlas. Atlas computes a unified diff for every file edit and surfaces it for approval before writing, and after you approve, Atlas applies the engine .clang-format so the code matches the Epic style guide as a separate, explicit step.

Formatting and semantics stay apart on purpose. Running .clang-format across a header full of UCLASS and UPROPERTY macros will reflow lines that had nothing to do with your change, and a reviewer cannot tell the difference in a combined diff. Atlas surfaces the semantic change first, you approve it, and then the engine's own .clang-format runs over the touched files. Atlas snapshots file changes as git patches so edits can be diffed and rolled back, which matters in a codebase where a bad edit to a Build.cs costs a full rebuild to discover.

Privacy and model choice for Unreal studios

Atlas can build its code index with local Ollama embeddings, keeping code off third-party servers, which in 2026 is a requirement for most Unreal Engine studios under an NDA. Atlas also lets you switch the active model and provider on the fly with favorites and recents.

Indexing an Unreal project encodes the Source/ tree, which is the studio's gameplay code and often its licensed engine modifications. Running the embedding step against a local Ollama model keeps that on hardware you control. Model choice follows the work: a fast model to add a UPROPERTY specifier or scaffold an Automation Spec, a stronger one to reason about why a UFUNCTION is not exposed to Blueprint or which module a type actually lives in. Atlas is extensible through plugins that contribute tools and hook into agent lifecycle events, so a studio's own build tooling can join the session.

Getting started

01Run atlas in a project with a .uproject and Source/ module folders
02Let Atlas read your UCLASS, UPROPERTY, and UFUNCTION macros plus the dependencies declared in each Build.cs
03Ask Atlas to add a module dependency in Build.cs before it adds the include, which is the step most C++ agents miss
04Let Atlas write Automation Spec tests and run them through UnrealEditor-Cmd behind a permission prompt
05Approve the diff, then let Atlas apply the engine .clang-format so the code matches the Epic style guide

Frequently asked questions

can an AI coding agent write Unreal Engine C++?: Yes. Atlas reads your UCLASS, UPROPERTY, and UFUNCTION macros plus the dependencies declared in each Build.cs, and indexes code by AST declarations using tree-sitter, so the reflection markup is treated as part of the class rather than as decoration.
how do I set up Atlas on an Unreal Engine project?: Run atlas in a project with a .uproject and Source/ module folders. Atlas reads the reflection macros and the module rules in each Build.cs, which in Unreal Engine are the real API.
why does my AI agent keep breaking the Unreal build with includes?: Because it adds the include without the module rule. Atlas adds a module dependency in Build.cs before it adds the include, which is the step most C++ agents miss, and it treats both edits as one reviewed change.
can Atlas run Unreal automation tests?: Yes. Atlas can write Automation Spec tests and run them through UnrealEditor-Cmd behind a permission prompt. Every tool call is permission-gated against allow, ask, and deny rules, so a headless editor run never starts unannounced.
does Atlas follow the Epic style guide?: Yes. After you approve the diff, Atlas applies the engine .clang-format so the code matches the Epic style guide, as a separate step from the change you actually reviewed.
can an Unreal studio use Atlas without sending source code out?: Yes. Atlas can build its code index with local Ollama embeddings, keeping code off third-party servers, so the Source/ tree and any licensed engine modifications stay on hardware you control.
does Atlas understand UPROPERTY and garbage collection in Unreal?: Atlas reads UPROPERTY as part of the declaration it indexes, which is what lets it flag a member object declared without the macro, the classic Unreal bug where the garbage collector reclaims an object you still hold.

Try Atlas in your terminal

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Install Atlas

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