Repoint an Interaction at Another Mod

You ship a normal sword. You want its right-click to open Hexcode's spell casting instead of the vanilla guard, but only when Hexcode is installed, and you want everything else about the sword left alone.

Goal

• The sword stays a sword: same identity, same Parent, same Primary swing, same Ability1 signature.
• Right-click (Secondary) opens Hexcode's casting interaction instead of the guard.
• Only happens when Riprod:Hexcode is installed.
• One slot changes. Nothing else.

The Asset

Server/Item/Items/Weapon/Sword/Template_Weapon_Sword.json

{
  "TranslationProperties": {
    "Name": "server.items.Template_Weapon_Sword.name"
  },
  "DroppedItemAnimation": "Items/Animations/Dropped/Dropped_Diagonal_Left.blockyanim",
  "Model": "Items/Weapons/Sword/Iron.blockymodel",
  "Texture": "Items/Weapons/Sword/Iron_Texture.png",
  "Icon": "Icons/ItemsGenerated/Weapon_Sword_Iron.png",
  "PlayerAnimationsId": "Sword",
  "Reticle": "DefaultMelee",
  "Quality": "Template",
  "ItemLevel": 15,
  "Categories": [
    "Items.Weapons"
  ],
  "IconProperties": {
    "Scale": 0.35,
    "Translation": [
      -22,
      -22
    ],
    "Rotation": [
      45,
      90,
      0
    ]
  },
  "Utility": {
    "Compatible": true
  },
  "Interactions": {
    "Primary": "Root_Weapon_Sword_Primary",
    "Secondary": "Root_Weapon_Sword_Secondary_Guard", // you only want to repoint this ONE slot
    "Ability1": "Root_Weapon_Sword_Signature_Vortexstrike"
  },
  "Tags": {
    "Type": [
      "Weapon"
    ],
    "Family": [
      "Sword"
    ]
  },
  "Weapon": {
    "EntityStatsToClear": [
      "SignatureEnergy"
    ],
    "StatModifiers": {
      "SignatureEnergy": [
        {
          "Amount": 20,
          "CalculationType": "Additive"
        }
      ]
    }
  },
  "ItemAppearanceConditions": {
    "SignatureEnergy": [
      {
        "Condition": [
          100,
          100
        ],
        "ConditionValueType": "Percent",
        "Particles": [
          {
            "SystemId": "Sword_Signature_Ready",
            "TargetNodeName": "Handle",
            "PositionOffset": {
              "X": 0.8
            },
            "TargetEntityPart": "PrimaryItem"
          },
          {
            "SystemId": "Sword_Signature_Status_Spawn",
            "TargetNodeName": "Handle",
            "PositionOffset": {
              "X": 0.5
            },
            "TargetEntityPart": "PrimaryItem"
          },
          {
            "SystemId": "Sword_Signature_Status",
            "TargetNodeName": "Handle",
            "PositionOffset": {
              "X": 0.55
            },
            "TargetEntityPart": "PrimaryItem",
            "Scale": 1.3
          }
        ],
        "FirstPersonParticles": [
          {
            "SystemId": "Sword_Signature_Ready",
            "TargetNodeName": "Handle",
            "PositionOffset": {
              "X": 0.8
            },
            "TargetEntityPart": "PrimaryItem"
          },
          {
            "SystemId": "Sword_Signature_Status_Spawn",
            "TargetNodeName": "Handle",
            "TargetEntityPart": "PrimaryItem",
            "PositionOffset": {
              "Y": -100
            }
          },
          {
            "SystemId": "Sword_Signature_Status",
            "TargetNodeName": "Handle",
            "PositionOffset": {
              "X": 0.5
            },
            "TargetEntityPart": "PrimaryItem"
          }
        ],
        "ModelVFXId": "Sword_Signature_Status"
      }
    ]
  },
  "ItemSoundSetId": "ISS_Weapons_Blade_Large",
  "MaxDurability": 80,
  "DurabilityLossOnHit": 0.21
}

Interactions is an object keyed by slot. Each value is the id of a root interaction asset. Hexcode ships its own roots, including Hexstaff_Secondary, the right-click that opens hex casting. To change just that one slot the old way, you had to ship and keep every other field above in sync forever.

The patch

Put it next to the target, .json swapped for .patch:

Server/Item/Items/Weapon/Sword/Template_Weapon_Sword.patch

{
  "$Requires": "Riprod:Hexcode",
  "Interactions": {
    "Secondary": "Hexstaff_Secondary"
  }
}

After

Because Interactions is an object, the merge recurses into it and only the named key changes:

{
  "Interactions": {
    "Primary": "Root_Weapon_Sword_Primary",
    "Secondary": "Hexstaff_Secondary",
    "Ability1": "Root_Weapon_Sword_Signature_Vortexstrike"
  }
}

• Secondary now resolves to Hexcode's Hexstaff_Secondary. Right-click opens casting.
• Primary stays Root_Weapon_Sword_Primary. The swing is unchanged.
• Ability1 stays Root_Weapon_Sword_Signature_Vortexstrike. The signature is unchanged.

When Hexcode is absent, $Requires is not satisfied, Patchly skips the patch, and the sword keeps its guard.

Notes

• $Requires: "Riprod:Hexcode" is not optional here. If you point a slot at an id that no installed pack provides, that slot breaks. Gating on the pack that ships the id guarantees the target exists before you reference it.
• This is the surgical opposite of the whole-template reparent in Conditional-Override. There you swap Parent and null the local interactions so the new template owns the whole behavior set. Here you keep the item exactly as it is and retarget a single slot.
• Object keys merge; they do not replace. That is why naming only Secondary leaves Primary and Ability1 intact. See Removing-Values for how null would instead delete a slot.