Why does my Custom Function HLSL include fail at compile?

Shader Graph requires the include path to be relative to Assets/ (e.g. Assets/Shaders/Helpers.hlsl). Relative paths or paths outside the project don't resolve. Move the .hlsl into Assets/ and use the full path.

What's the right include format?

In the Custom Function node Source field: Assets/Shaders/MyHelpers.hlsl. The file must end in .hlsl. Use forward slashes regardless of OS.

Should I copy or symlink to share between projects?

Copy or use a Package. Symlinks may not be picked up by all import paths reliably; Packages are the supported way to share HLSL code across projects.

Fix: Unity Shader Graph Custom Function Include Not Found

Quick answer: Custom Function Source field expects a path relative to Assets/, with .hlsl extension and forward slashes. Assets/Shaders/MyHelpers.hlsl works; relative or external paths don’t.

Custom Function fails to find the include. Editor preview works (file path is local), build breaks (path resolution differs).

The Symptom

Shader Graph compile error: “Could not open include file.” Editor sometimes works; builds reliably fail.

The Fix

Custom Function node:
  Type:    File (not String)
  Source:  Assets/Shaders/MyHelpers.hlsl
  Name:    MyFunction
  Inputs:  In Vector3
  Outputs: Out Vector3

Path starts at Assets/. Forward slashes. Save the .hlsl in Assets so the path resolves.

Inside the .hlsl:

// Assets/Shaders/MyHelpers.hlsl
void MyFunction_float(float3 In, out float3 Out)
{
    Out = normalize(In);
}

Function name plus _float suffix matches what Shader Graph generates as the call.

Sharing Across Projects

Wrap the .hlsl in a Package (custom or git-based). Reference via Packages/com.you.shaders/Helpers.hlsl. Versioned and shared.

Verifying

Build for the target. No include errors. Frame Debugger shows the function in the generated code.

“Path from Assets. .hlsl extension. Function name + suffix. Includes resolve.”

Related Issues

For Shader Graph stencil URP, see stencil URP. For Shader Graph keyword instancing, see keyword instancing.

Path right. Function suffixed. Compiles.