Unity C# Reference

Browse Unity Technologies' official UnityCsReference C# source as a read-only local cache. This skill is the sibling of unity-csharp-navigate (project sources) and unity-csharp-edit (writes). Hand off as soon as the request implies project-level reading or a write.

Use When

• The user asks about the exact signature, attributes, or behavior of a Unity API such as UnityEngine.Animator.Play or UnityEditor.AssetDatabase.Refresh.
• The user wants to read the internal implementation of a Unity type to predict performance characteristics or side effects.
• The user compares API differences between Unity versions (LTS vs Tech release branches).
• The user wants to validate an LLM-suggested Unity script against the canonical Unity source.

Do Not Use When

• The user wants to read project-local scripts; use unity-csharp-navigate.
• The user wants to write or refactor C# code; use unity-csharp-edit.
• The user wants Unity scene state, packages, or assets; use the matching scene, asset, or editor skill family.

Preferred Flow

1. Run the runtime checklist in runtime-checklist.md before the first fetch in a new environment.
2. Populate the cache for the project's Unity version with unity-cli reference fetch --accept-license (one-time per version).
3. Use unity-cli reference grep for line-level pattern lookups with optional context, or unity-cli reference search for filtered file hits.
4. Open the candidate file with unity-cli reference view --start-line N --max-lines M to read the relevant span.
5. Confirm the signature or behavior, then hand off to unity-csharp-navigate for project sources or unity-csharp-edit for writes.

unity-cli reference fetch --accept-license
unity-cli reference status --output json
unity-cli reference find-symbol --name Animator --kind class
unity-cli reference grep "class Animator " --context 3
unity-cli reference view Runtime/Export/Animation/Animator.bindings.cs --start-line 100 --max-lines 60
unity-cli reference diff --from 2022.3.10f1 --to 2023.2.20f1 --symbol UnityEngine.Animator
unity-cli reference resolve-symbol-at Assets/Scripts/Player.cs --line 42 --column 18
unity-cli reference embed-build --version 2023.2.20f1
unity-cli reference embed-search --query "animator state callback" --version 2023.2.20f1
unity-cli reference clean --keep 1 --dry-run

Use reference find-symbol first when you already know the type name (class / interface / struct / enum). It is backed by an on-disk index per Unity version (~/.unity/cache/UnityCsReference/<version>/.unity-cli-index/symbols.json) and is faster than grep for repeated lookups. Drop back to grep for free-text patterns or member-level matches.

Use reference diff to compare two cached Unity versions. The default symbol-only mode (--symbol <fqn>) returns a single before/after pair, and the opt-in path mode (--path <subpath> [--max-symbols N]) lists added / removed / changed type definitions in a directory.

Use reference resolve-symbol-at <project-rel-path> --line <n> --column <m> when the user is on a specific cursor position in a project file (Assets/... or Packages/...) and wants to see the canonical Unity reference for the type under the cursor. The tool is a thin wrapper: it reads the project file, extracts the identifier at the cursor, and feeds it through reference find-symbol + reference view for each cached version.

Use reference embed-build + reference embed-search --query "..." for semantic / natural-language lookup when the user has a concept ("animator state callback") instead of an exact symbol name. The first call downloads the BGE-Small-EN ONNX model (~130MB, cached under the platform-default fastembed cache) and writes a per-version .unity-cli-index/embeddings.bin. Subsequent embed-search calls only run a single query embedding and a linear cosine scan over that file, so they stay fast. The result is sorted by score (cosine similarity, higher is closer); find-symbol and grep remain the right tools when the exact symbol name is already known.

Examples

• "Show me how Unity implements Animator.Play so I can predict whether it allocates."
• "Compare UnityWebRequest.Get between Unity 2022.3 and Unity 6 staging."
• "Confirm the exact signature of EditorApplication.delayCall before I wire it into the build pipeline."

References

• runtime-checklist.md: runtime prerequisites and license acceptance before the first fetch.
• fetch-and-cache.md: reference fetch, status, and clean command details and branch mapping per Unity version.
• symbol-lookup-playbook.md: the canonical reference → navigate → edit workflow when validating LLM-suggested Unity code.