How does Atlas handle Build.cs files for Unreal Engine dependencies?

Atlas uses bash to directly modify Build.cs files, adding or updating module dependencies as required by the upgrade, ensuring proper integration with Unreal Build Tool.

Can Atlas run Unreal Engine tests?

Yes, Atlas can run Unreal Automation Framework tests via bash commands, typically through UnrealEditor-Cmd, and iterate on fixes until all tests pass.

What if an Unreal Engine dependency upgrade has breaking changes?

Atlas uses webfetch to retrieve release notes, providing context for breaking changes. It then uses edit and lsp to fix affected C++ code, inspecting new signatures.

How does Atlas ensure code style in Unreal Engine projects?

After making changes, Atlas can apply the engine's .clang-format rules, ensuring the code adheres to Epic's style guide before presenting the final diff for approval.

Is it safe to let Atlas modify my Unreal Engine C++ code?

Yes, Atlas operates with permission-gated tool calls, drafts plans in a read-only agent, and presents a unified diff for every file edit for your explicit approval before writing any changes to your Unreal Engine project.

Does Atlas understand Unreal Engine specific macros like UCLASS?

Yes, Atlas builds its code index using AST declarations via tree-sitter, allowing it to understand UCLASS, UPROPERTY, and UFUNCTION macros and their impact on the Unreal Engine reflection system.

How does Atlas handle large compiler outputs from Unreal Engine?

Atlas captures the full output of bash commands, including large compiler logs. If the output exceeds terminal limits, it saves it to a file that you can read, ensuring no information is lost.

Upgrade a Dependency and Fix the Breakage in Unreal Engine with Atlas in 2026

In 2026, Atlas empowers Unreal Engine developers to efficiently upgrade dependencies and resolve resulting breakage by automating interactions with Unreal Build Tool (Build.cs), parsing real compiler output, and fixing C++ code with precision. It streamlines the entire migration workflow, from updating module rules to ensuring Unreal Automation Framework tests pass, all within your terminal.

Automating Unreal Engine Dependency Bumps with Atlas

Atlas streamlines the process of upgrading Unreal Engine dependencies in 2026 by directly interacting with Unreal Build Tool (Build.cs) via bash. It captures the full output of the upgrade command, which can sometimes exceed 1000 lines, saving it to a file for comprehensive review.

Atlas drives Unreal Build Tool through bash commands, allowing it to modify the Build.cs files that define your Unreal Engine project's module dependencies. For instance, when bumping a library like MyThirdPartyLibrary to a new major version, Atlas can update the PublicDependencyModuleNames.AddRange or PrivateDependencyModuleNames.AddRange sections within Source/MyModule/MyModule.Build.cs. It executes the upgrade command and captures the entire output, which can be extensive, sometimes containing hundreds of lines of diagnostic information. If this output exceeds the terminal's display limits, Atlas automatically saves it to a temporary file, which you can then read using the read tool, ensuring no critical information about the upgrade process is missed. This direct interaction with the native Unreal Engine build system ensures compatibility and accuracy.

Resolving Compile and Test Failures in Unreal Engine with Atlas

When upgrading a library in Unreal Engine, Atlas systematically resolves compile and test failures by parsing real compiler output and fixing code with its edit tool. This process involves iterating through 10s or even 100s of errors, ensuring each is addressed accurately.

After an Unreal Build Tool upgrade, compile errors are inevitable. Atlas uses bash to invoke the Unreal Engine compiler, typically through UnrealEditor-Cmd -run=Compile -project=MyProject.uproject, and meticulously reads the resulting error messages. For each reported error in your C++ source files, such as Source/MyModule/Private/MyActor.cpp, Atlas employs its edit tool to propose precise code modifications. When a breaking change alters a function signature, Atlas utilizes the lsp tool's goToDefinition operation to inspect the new API in the upgraded package, ensuring the fix matches the actual new signature. Once compile errors are resolved, Atlas then runs your Unreal Automation Framework tests via bash (e.g., UnrealEditor-Cmd -run=AutomationTool -project=MyProject.uproject -test=MyModuleTests). It continues this cycle of fixing and re-running tests until the entire codebase is clean and all 0 tests fail.

Integrating Release Notes for Accurate Unreal Engine Migrations

To ensure accurate fixes during a major Unreal Engine dependency upgrade, Atlas leverages its webfetch tool to retrieve the library's release notes. This provides critical context for breaking changes, often detailing 5-10 key API modifications that require specific adjustments in your C++ code.

Major version bumps in Unreal Engine dependencies frequently introduce breaking changes that require more than simple type adjustments. Atlas addresses this by using its webfetch tool to pull the official release notes or changelog for the upgraded library. This crucial step provides the agent with explicit details on API deprecations, signature changes, or new usage patterns, preventing guesswork. For example, if a UFUNCTION macro's signature has changed, the release notes will guide Atlas to the correct C++ syntax. By having the actual breaking changes in context, Atlas can generate fixes that are not only syntactically correct but also semantically aligned with the library's new design, ensuring a robust and future-proof migration for your Unreal Engine project.

Ensuring Safety and Approval for Unreal Engine Code Changes

Atlas prioritizes safety and developer control throughout the Unreal Engine dependency upgrade process, presenting a unified diff for every file edit before writing. This allows developers to review 100% of proposed changes, including those formatted by clang-format to match Epic's style guide.

Before any modification is written to your Unreal Engine project, Atlas operates under a strict approval workflow. It first drafts a plan in a read-only agent, outlining the steps it intends to take. Every tool call, including those to bash for Unreal Build Tool or edit for C++ files, is permission-gated, requiring your explicit allow, ask, or deny rule. Crucially, Atlas computes a unified diff for every proposed file edit, surfacing it for your approval. This means you see exactly what changes will be applied to files like Source/MyModule/Public/MyHeader.h or Source/MyModule/Private/MyClass.cpp. After all functional fixes are complete, Atlas can apply the engine's .clang-format rules to ensure the code matches the Epic style guide, and this formatting change is also presented as part of the diff. Atlas also snapshots file changes as git patches, allowing for easy rollback if needed, and can stage and create commits on your behalf, providing full transparency and control over the entire upgrade process.

Step by step

01Execute the dependency upgrade for your Unreal Engine project using bash to interact with Unreal Build Tool (Build.cs), capturing the full output for review.
02Fetch the library's release notes or changelog with the webfetch tool to understand breaking changes relevant to your Unreal Engine C++ codebase.
03Build your Unreal Engine project by running the compiler via bash (e.g., UnrealEditor-Cmd -run=Compile) to enumerate all compile-time breakage.
04Fix each identified C++ error using the edit tool, leveraging lsp's goToDefinition to inspect new signatures in the upgraded Unreal Engine package.
05Continuously re-run the build and Unreal Automation Framework tests with bash (e.g., UnrealEditor-Cmd -run=AutomationTool) until all compile errors are resolved and 0 tests fail.
06Review the entire unified diff of all proposed changes, including those applied by clang-format to match the Epic style guide, and approve them.
07Let Atlas stage and create a git commit on your behalf, finalizing the Unreal Engine dependency upgrade.

Frequently asked questions

How does Atlas handle Build.cs files for Unreal Engine dependencies?: Atlas uses bash to directly modify Build.cs files, adding or updating module dependencies as required by the upgrade, ensuring proper integration with Unreal Build Tool.
Can Atlas run Unreal Engine tests?: Yes, Atlas can run Unreal Automation Framework tests via bash commands, typically through UnrealEditor-Cmd, and iterate on fixes until all tests pass.
What if an Unreal Engine dependency upgrade has breaking changes?: Atlas uses webfetch to retrieve release notes, providing context for breaking changes. It then uses edit and lsp to fix affected C++ code, inspecting new signatures.
How does Atlas ensure code style in Unreal Engine projects?: After making changes, Atlas can apply the engine's .clang-format rules, ensuring the code adheres to Epic's style guide before presenting the final diff for approval.
Is it safe to let Atlas modify my Unreal Engine C++ code?: Yes, Atlas operates with permission-gated tool calls, drafts plans in a read-only agent, and presents a unified diff for every file edit for your explicit approval before writing any changes to your Unreal Engine project.
Does Atlas understand Unreal Engine specific macros like UCLASS?: Yes, Atlas builds its code index using AST declarations via tree-sitter, allowing it to understand UCLASS, UPROPERTY, and UFUNCTION macros and their impact on the Unreal Engine reflection system.
How does Atlas handle large compiler outputs from Unreal Engine?: Atlas captures the full output of bash commands, including large compiler logs. If the output exceeds terminal limits, it saves it to a file that you can read, ensuring no information is lost.

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