Unity Behavior

Behavior Skills

Unity Behavior (com.unity.behavior, validated against 1.0.16) graph asset discovery, agent wiring, and blackboard variable access.

The package is optional and is not a declared dependency of UnitySkills. Every skill in this module reaches it through reflection; when it is absent each skill returns the same structured PACKAGE_NOT_INSTALLED response pointing at package_install.

Operating Mode

• Query skills (behavior_status, behavior_graph_list, behavior_graph_info, behavior_agent_get, behavior_agent_list, behavior_blackboard_list) are SkillMode.SemiAuto — they run in all three modes without a grant.
• Mutators (behavior_graph_create, behavior_agent_add, behavior_agent_set_graph, behavior_blackboard_set) are SkillMode.FullAuto — under Approval they need a user grant; under Auto / Bypass they execute directly.
• No skill in this module carries SkillOperation.Delete, so none is auto-forbidden in Approval / Auto mode.

Prerequisites

Install the package first if behavior_status reports installed: false:

package_install  packageName="com.unity.behavior"

Installation triggers a Domain Reload; wait for it to finish, then call behavior_status again before using any other skill in this module.

The two asset types (read this before binding graphs)

A "Behavior Graph" .asset file contains two objects, and mixing them up is the most common failure:

| Object | Role | Where it lives |

|--------|------|----------------|

| BehaviorAuthoringGraph | Editing representation — nodes, blackboard, story. Main asset. | The .asset file itself |

| BehaviorGraph | Baked runtime graph. What BehaviorGraphAgent.Graph actually requires. | Sub-asset nested inside the same file |

Skills in this module always take the file path (graphAssetPath / assetPath) and resolve the correct object internally — you never address the sub-asset directly. behavior_agent_set_graph finds the nested BehaviorGraph for you and refuses the bind with RUNTIME_GRAPH_MISSING when the graph has never been compiled.

Guardrails

Routing:

• Behavior graphs / blackboards / BehaviorGraphAgent: this module
• Animator state machines: use animator_*
• Generic component attach on a GameObject: component_add works, but behavior_agent_add additionally binds the graph and validates it

Runtime-first rules:

• Always call behavior_blackboard_list before behavior_blackboard_set — the variable name is case-sensitive and the declared CLR type decides which value shapes are accepted.
• Never invent a graphAssetPath from memory; get it from behavior_graph_list.
• If a skill returns errorCode: "API_MISMATCH", the installed package version has a different member layout than this integration expects. Do not retry with different arguments — report the version mismatch and fall back to the Behavior editor window or direct .asset text editing.
• A graph created by behavior_graph_create is empty apart from the auto-inserted Start root. Adding actual behavior nodes requires the Behavior editor window (see Limitations).

Skills

behavior_status

Report package availability: installed, version, which core types resolved, project graph asset count, and scene agent count. Safe to call when the package is missing — this is the one skill that answers instead of erroring.

behavior_graph_list

List behavior graph assets with path, guid, nodeCount, variableCount, and hasRuntimeGraph. Optional filter (substring on path), folder, limit.

behavior_graph_info

Structure summary for one graph asset: node count with a per-type breakdown, individual nodes (id / type / position, capped by maxNodes), root count, the full blackboard variable list with types and default values, subgraph dependencies, and runtime graph state.

behavior_graph_create

Create an empty BehaviorAuthoringGraph at savePath and force a reimport so Unity bakes the blackboard, the runtime BehaviorGraph sub-asset, the debug info sub-asset, and the mandatory Start root. Returns hasRuntimeGraph; a warning is returned when baking did not happen and the graph must be opened once in the editor window.

behavior_agent_add

Add a BehaviorGraphAgent to a GameObject (name / instanceId / path), optionally binding graphAssetPath in the same call. The graph is resolved and validated before the component is added, so a bad path never leaves a half-configured agent. Idempotent — an existing agent is reused and reported via componentAdded: false.

behavior_agent_get

Read one agent: bound graph name and asset path, isInitialised / isStarted / isRunning, the graph's blackboard variables, and the agent-level overrides.

behavior_agent_set_graph

Bind graphAssetPath to an existing agent. Resolves the nested runtime graph and rejects uncompiled graphs.

behavior_agent_list

Every BehaviorGraphAgent in the loaded scenes with hierarchy path, bound graph, active/enabled flags, and run state. Optional graphFilter, includeInactive, limit.

behavior_blackboard_list

List blackboard variables. Pass graphAssetPath to read the asset's authoring defaults (source: "asset"), or a GameObject locator to read an agent's graph variables plus its overrides (source: "agent"). One of the two is required.

behavior_blackboard_set

Set one variable value.

| Parameter | Meaning |

|-----------|---------|

| variable | Variable name, case-sensitive. Required. |

| value | New value. Accepted shapes depend on the declared type (see below). |

| name / instanceId / path | GameObject locator — writes the agent-level override. |

| graphAssetPath | Writes the graph asset default and rebakes the runtime blackboard. |

Provide either the GameObject locator or graphAssetPath; the GameObject wins if both are given.

Returns: target ("agent" or "asset"), variable, type, the normalized value, and a note explaining where the write landed.

Supported value types and accepted input shapes:

| Declared type | Accepted value |

|---------------|------------------|

| int / float / double / bool / string | JSON scalar, or a parseable string |

| enum | Member name (case-insensitive) |

| Vector2 / Vector3 / Vector4 / Quaternion | [1,2,3], {"x":1,"y":2,"z":3}, or "1,2,3" |

| Color | {"r":1,"g":0,"b":0,"a":1}, [1,0,0,1], or "#FF0000" |

| Vector2Int / Vector3Int | Same as the float vectors, truncated |

| GameObject / Component | Assets/... prefab path, scene hierarchy path, or scene object name |

| Other UnityEngine.Object | Assets/... or Packages/... asset path |

Setting an unknown variable returns the available names in availableVariables.

Edit mode vs Play mode

BehaviorGraphAgent instantiates a private copy of its graph on Init(), which only happens in Play mode. This changes what reads and writes mean:

• Edit mode — behavior_blackboard_set with a GameObject writes an *agent-level override* (exactly what the Inspector shows). Reads of the graph variables return the shared asset defaults, not per-agent values; the per-agent values are in the overrides array.
• Play mode — writes go to the running graph instance, so they take effect immediately on that agent only.

This is why behavior_blackboard_list reports both variables and overrides for an agent.

Workflow

• behavior_status — confirm the package is installed.
• behavior_graph_list — locate the graph, or behavior_graph_create to make a new one.
• Author the node graph in the Behavior editor window (node editing is not scriptable — see Limitations).
• behavior_graph_info — confirm the node topology and read the blackboard contract.
• behavior_agent_add with graphAssetPath — attach and bind in one call.
• behavior_blackboard_list — read the exact variable names and declared types.
• behavior_blackboard_set — per-agent overrides, or graph-wide defaults via graphAssetPath.
• behavior_agent_list — verify the whole scene's agent wiring.

Limitations

Node-level graph editing is not supported. There is no skill to add, remove, connect, or reconfigure nodes inside a behavior graph. This is a deliberate exclusion, not an oversight:

• The authoring node graph is stored as a [SerializeReference] polymorphic List<NodeModel> with PortModel cross-references, an embedded SerializableCommandBuffer, and a version-stamped NodeModelInfo cache. Writing it correctly means reproducing the package's command/dispatcher pipeline, not just setting fields.
• Every edit must be followed by a consistent rebake of three sub-assets (runtime graph, runtime blackboard, debug info) plus VersionTimestamp synchronization, or the asset silently desyncs from its baked runtime graph.
• The serialization schema is explicitly versioned (kLatestSerializationVersion, currently 3) and has changed within the 1.0.x line. Reflection-driven topology writes would break on a patch release.

Alternatives when you need node-level changes:

• Preferred — author the graph in the Behavior editor window (Window > AI > Behavior, or double-click the asset), then use this module to inspect and wire it up.
• Duplicate a known-good graph with asset_duplicate and rebind it, instead of building topology from nothing.
• For mechanical, repetitive edits to an existing graph, edit the .asset YAML directly — load the yaml-editing advisory first for the managed-reference and fileID rules, and re-verify with behavior_graph_info afterwards.

Other limitations:

• behavior_graph_create produces an empty graph. Node authoring still requires the editor window.
• Blackboard variables cannot be created, renamed, retyped, or deleted — only existing variables can be assigned. Add variables in the Behavior editor's Blackboard panel.
• Event channels, subgraph dynamic linking, and runtime serialization (Serialize / Deserialize) are not exposed.
• behavior_blackboard_set against graphAssetPath changes the shared default for every agent that has no override for that variable.
• Agent lifecycle control (Init / Start / End / Restart) is not exposed; those are Play-mode runtime concerns better handled from game code.

Version Sensitivity

Type and member names were taken from com.unity.behavior 1.0.16 sources and cross-checked against the published Scripting API. Public surface (BehaviorGraphAgent, BehaviorGraph, BlackboardReference, Blackboard, BlackboardVariable, VariableModel) is documented and stable. Authoring surface (BehaviorAuthoringGraph, GraphAsset, BlackboardAsset, BehaviorBlackboardAuthoringAsset) is internal to the package and reached by name — a package upgrade can move it. Every such lookup is null-checked and reports API_MISMATCH rather than throwing; behavior_status shows exactly which types resolved.

Exact Signatures

Exact names, parameters, defaults, and returns are defined by GET /skills/schema or unity_skills.get_skill_schema(), not by this file.