Locus Unity Bridge

Locus Unity Bridge

Use the bundled PowerShell client to inspect or control a real Unity Editor. Do not rewrite its named-pipe client. Always pass the exact Unity root to -ProjectPath; it identifies the bridge connection.

Safety

execute can run arbitrary C# in Unity, and the property-tree write messages (property_tree_write, property_tree_apply) mutate the user's project. Use any of them only for the project and task the user authorized, and prefer the read path when the task is inspection. A connected bridge requires Locus to already be installed and enabled in the target project. Do not install or repair Locus, create its marker, launch or close Unity, or modify a project merely to connect the bridge.

Command map

The client has six top-level commands. send is a transport command: its -MessageType selects a curated Locus protocol message. Do not treat a message type as a value for -Command.

All commands except recompile use -TimeoutSeconds (default 10, range 1–600) for their final pipe response. Increase it only for an operation that is expected to take longer. recompile instead uses its dedicated timeout options below.

Resolve the client once:

$locusBridge = Join-Path $env:USERPROFILE '.agents\skills\locus-unity-bridge\scripts\locus-unity.ps1'

1. Probe first

& pwsh.exe -NoLogo -NoProfile -NonInteractive -File $locusBridge `
    -Command probe -ProjectPath 'E:\Source\SomeUnityProject'

The probe recognizes canonical and legacy package layouts. It uses a bridge marker when present, otherwise it computes the project-specific pipe name.

2. Inspect with send

Use this shape for all entries in the table. Successful responses are JSON; parse a nested JSON payload from the envelope's message field when noted.

& pwsh.exe -NoLogo -NoProfile -NonInteractive -File $locusBridge `
    -Command send -ProjectPath 'E:\Source\SomeUnityProject' `
    -MessageType <message-type> -Message '<json-or-empty-string>'

get_console_text is a large compatibility snapshot, not a default query.

For capture_viewport, set target to game, scene, or editor_window. maxLongEdge defaults to 1280, accepts 0 for source size, and is capped at 8192; editor_window optionally accepts windowTitle. The response returns a PNG path under Library/Locus/Screenshots/; report it and do not delete it.

{"target":"game","maxLongEdge":1280}

Writing properties (mutating — confirm authorization first)

Everything above is read-only. Unity's property write path is a separate, explicitly authorized step:

A write reuses the read targets (selection, asset, scriptableobject, material, gameobject, component) plus the target.propertyPath reported by a preceding read or discover. valueJson is the JSON-encoded value. mode: "preview" applies a transient drag preview instead of committing; omit mode for a real commit. bindingId is only echoed back and may be omitted.

property_tree_write records Undo, marks the object and scene dirty, and returns a fresh read plus a beforeSnapshot. It does not save the asset — live writes keep Property Tree commit semantics, so the asset can still be waiting for Unity to save it. Never report a write as persisted without a separate save step, and say so when the file is still dirty.

Writes that must be persisted, revision-checked, or correct against Prefab inheritance use a different surface: asset_api (transaction id, expected_revision, dependencies, persist: "disk", array operations, batches up to 256 files / 10,000 operations). That is the transactional YAML backend, not a raw file writer; treat it as its own task and confirm scope with the user before using it.

Do not hand-edit .unity/.prefab YAML as a substitute for either path: exact fileIDs/GUIDs, Prefab variant override/revert topology, import ordering, and stale-revision rejection are precisely what the transactional layer exists to handle.

3. Use a top-level operation

Asset images

Do not send asset_thumbnail or asset_preview_render directly: their PNG responses contain Base64. These commands decode it locally and return only a path plus image metadata. Use -OutputDirectory to choose a local destination; otherwise the client uses its local temporary folder.

# Any asset under Assets/ or Packages/; -MaxSize is 64-512 (default 192).
& pwsh.exe -NoLogo -NoProfile -NonInteractive -File $locusBridge `
    -Command thumbnail -ProjectPath 'E:\Source\SomeUnityProject' `
    -AssetPath 'Assets\Art\Icon.png' -MaxSize 192

# Prefab or model only; width/height are 96-640.
& pwsh.exe -NoLogo -NoProfile -NonInteractive -File $locusBridge `
    -Command render-preview -ProjectPath 'E:\Source\SomeUnityProject' `
    -AssetPath 'Assets\Props\Chair.prefab' `
    -PreviewWidth 320 -PreviewHeight 220 -Yaw 25 -Pitch -12 -Distance 1.15

Use -PanX, -PanY, and -PanZ only when reframing the model preview is necessary. Rendering does not modify the source asset.

Execute authorized C# or recompile

Use execute only when the curated operations do not answer the task. Use -Code for a short snippet or -CodeFile for multi-line/reusable code; provide exactly one. Prefer print(...) or printJson(...) for returned data.

Snippet contract

• The supplied code is the body of a Locus-generated entry method, not an independent C# file. Write direct statements and local functions; do not declare Main, class, struct, or namespace.
• print, printJson, clear, ctx, and ct are injected. A non-null return value is printed as text.
• For structured output, use printJson(new { key = value, items = values }). It serializes anonymous objects, dictionaries, and ordinary property-bearing values to JSON; do not declare a DTO class solely to return data.

Execute safety

• Every loop in an execute snippet needs an explicit completion condition and an iteration or time bound. Do not use unbounded while, for, or polling loops.
• Long-running loops must call ct.ThrowIfCancellationRequested() regularly; use await ctx... for waits that continue with Unity API access.
• -TimeoutSeconds only stops this client from waiting; it does not stop Unity code already running. Treat it as a wait limit, not a recovery mechanism.
• The client can cancel a running snippet only when -AcceptCancel is set and its stdin stays writable. It then sends cancel_execute_code carrying the execution id injected into the snippet (//__LOCUS_EXECUTION_ID__:<id>, the same id execute_code_progress uses). Without -AcceptCancel there is no cancel path, so a timed-out snippet simply keeps running.
• Locus also has a 30-second inactivity watchdog. It requests cancellation and returns a timeout, but cannot preempt code already blocking Unity's main thread. Do not treat that watchdog as a hard stop.
• The watchdog only fires on silence, so a snippet that keeps emitting print or ctx.Progress(...) can run indefinitely.
• Never re-send an execute merely because it timed out: the snippet may still be running and would then execute a second time. Use -AcceptCancel when you may need to stop it, keep snippets bounded and repeat-safe, and tell the user when a snippet might still be live instead of retrying silently.