generating-custom-lightning-type

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name: generating-custom-lightning-type description: "Use this skill when users need to create Custom Lightning Types (CLTs) for Einstein Agent actions or structured input/output schemas. Trigger when users mention CLT, Custom Lightning Types, Custom Lightning Types (CLTs) with widget/mosaic/fragment rendition/renderer, JSON schemas for agents, type definitions, lightning__objectType, or editor/renderer configurations. When widget renditions are requested, you MUST first read the widget-rendition.md reference file in this skill's references/ directory and follow its complete workflow. This is complex - always use this skill for CLT work." metadata: version: "1.0"

When to Use This Skill

Use this skill when you need to:

• Create Custom Lightning Types (CLTs) for structured inputs/outputs
• Generate JSON Schema-based type definitions for Lightning Platform
• Configure CLTs for Einstein Agent actions
• Set up editor and renderer configurations for custom UI
• Create CLTs with widget/mosaic/fragment rendition
• Troubleshoot deployment errors related to Custom Lightning Types

Specification

CustomLightningType Metadata Specification

Overview & Purpose

Custom Lightning Types (CLTs) are JSON Schema-based type definitions used by the Lightning Platform (including Einstein Agent actions) to describe structured inputs/outputs and drive editor/renderer experiences.

Configuration

• Choose referenced CLT pattern for nested objects - When you need a reusable or separately deployed nested type, create a CLT for that shape and reference it with "lightning:type": "c__<CLTName>". That string is the referenced type’s lightning:type value / FQN / registered identifier — not the JSON Schema title.
• Choose standard Lightning types when the structure is simple and can be expressed with properties and supported primitive lightning:type identifiers.
• Choose Apex class types (@apexClassType/...) when the structure already exists server-side and you want the Apex class to define the shape.
• Include editor/renderer config only when you need custom UI behavior (custom LWC input/output components). Otherwise, omit.

Critical Rules (Read First)

• CRITICAL: NEVER include the "$schema" field in schema.json
  • Salesforce CLT validator WILL REJECT schemas with this field, even if it's a valid JSON Schema $schema declaration.
• Root object schemas MUST include:
  • "type": "object"
  • "title"
  • "lightning:type": "lightning__objectType"
  • "unevaluatedProperties": false
• "unevaluatedProperties" is enforced as false by the CLT metaschema. Do not set it to true.
• Root object schemas MUST NOT include "examples" when "unevaluatedProperties": false is set.
• Nested objects (inside properties) MUST NOT set "lightning:type": "lightning__objectType".
  • Nested objects can be: references to other CLTs using c__<CLTName> syntax.
• List/array properties are highly restricted by the CLT metaschema:
  • CRITICAL LIMITATION: the CLT metaschema may reject the items keyword entirely. Treat items as disallowed by default.
  • Root-level arrays (direct children of the root properties):
    • MUST include "lightning:type": "lightning__listType"
    • MUST NOT include "items"
    • OPTIONAL "type": "array"
  • Nested arrays (arrays inside nested objects) are the most common failure:
    • MUST include "type": "array"
    • MUST NOT include "lightning:type": "lightning__listType"
    • MUST NOT include "items"
• When "unevaluatedProperties": false is set, any unknown keyword will fail validation. Prefer removing keywords over relaxing strictness.
• Apex class CLTs are minimal:
  • Include only title, description (optional), and lightning:type set to @apexClassType/....
  • Do not add type, properties, required, or unevaluatedProperties.

Additional CLT Metaschema Validations

• Org namespace validation: titles/descriptions and other string fields may be validated to ensure you are not using an org namespace in places that are disallowed.
• Lightning type validation: CLTs are validated to prevent referencing internal namespaces (for example, disallowing types from internal namespaces like sfdc_cms where not permitted).
• Object type validation: the CLT root is validated to ensure lightning:type is exactly lightning__objectType.

Primitive Types & Constraints

When you need the full list of supported primitive lightning:type identifiers, their constraints, and the allowed property-level keywords, read assets/primitive-types-and-constraints.md in this skill's directory.

Generation Workflow

1. Confirm the CLT approach
   • If referencing Apex: capture the exact class reference (@apexClassType/namespace__ClassName$InnerClass).
   • If using standard primitives: list the fields, their Lightning primitive types, and which fields are required.
2. Draft schema.json
   • DO NOT include "$schema" at the top
   • Start with the root object structure (required root fields).
   • Add properties using valid primitive lightning:type identifiers.
   • For nested-object properties, use CLT Reference pattern:
     • "lightning:type": "c__<CLTName>" to reference another CLT
     • The referenced CLT must be deployed to the org before the parent CLT.
   • For Apex-based nested objects: Use @apexClassType/... when structure exists server-side.
   • If the prompt explicitly requires true nested object output, prefer an Apex-based CLT (@apexClassType/...) for deploy-safe nested structures.
   • For arrays: follow the strict list rules (avoid items; avoid lightning:type on nested arrays).
   • Before deployment, verify exact lightning:type spellings (for example, use lightning__richTextType, not misspelled variants).
3. (Optional) Draft editor.json (only if custom UI is required)
   • Supported shape: Top-level editor object with editor.componentOverrides and editor.layout.
     • Top-level editor object.
     • Use editor.componentOverrides for component overrides.
     • Use editor.layout for layout.
     • DEPRECATED: Do NOT use propertyRenderers or view — these are legacy keys. Always use componentOverrides and layout instead.
   • Root override pattern (most common for fully custom editing UI):
     • editor.componentOverrides["$"] = { "definition": "c/<yourEditorComponent>", "attributes": { ... } }
     • When passing schema data into a custom LWC, use attribute mapping with the {!$attrs.<name>} syntax: e.g. "attributes": { "myField": "{!$attrs.value}" } so the runtime binds schema values to your component's attributes.
     • CRITICAL: The <name> in {!$attrs.<name>} must be a property defined in your type schema. For example, if your schema has a property called temperature, use {!$attrs.temperature}, not {!$attrs.value} unless value is an actual property.
   • Property-level override pattern (for individual fields):
     • editor.componentOverrides["<propertyName>"] = { "definition": "es_property_editors/<...>" }
     • Valid editor components (examples): es_property_editors/inputText, es_property_editors/inputNumber, es_property_editors/inputRichText, es_property_editors/inputImage, es_property_editors/inputTextarea. Do not use es_property_editors/inputList.
   • Collection editor (for root-level lightning__listType properties): Use a collection-level override so the list is edited by a custom component: collection.editor.componentOverrides["$"] = { "definition": "c/<yourCollectionEditorComponent>" }. Alternatively, use editor.layout with lightning/propertyLayout and attributes.property = "<listPropertyName>" for default list editing.
   • Layout pattern:
     • editor.layout.definition = "lightning/verticalLayout"
     • editor.layout.children[*].definition = "lightning/propertyLayout" with attributes.property = "<propertyName>"
     • CRITICAL: lightning/propertyLayout only accepts the property attribute. Do NOT add label, title, or any other attributes — these will fail validation with additionalProperties: false errors.
   • Avoid known-invalid patterns:
     • Do not use es_property_editors/inputList.
     • Do not use itemSchema attributes.
4. (Optional) Draft renderer.json (only if custom UI or mosaic rendition is required)
   • Supported shape: Top-level renderer object with renderer.componentOverrides and renderer.layout.
     • Top-level renderer object.
     • Use renderer.componentOverrides for component overrides.
     • Use renderer.layout for layout.
     • DEPRECATED: Do NOT use propertyRenderers or view — these are legacy keys. Always use componentOverrides and layout instead.
   • Root override pattern (most common for fully custom rendering UI):
     • renderer.componentOverrides["$"] = { "definition": "c/<yourRendererComponent>", "attributes": { ... } }
     • Use {!$attrs.<name>} in attribute mappings when binding schema data to custom renderer component attributes.
     • CRITICAL: Attribute mappings like {!$attrs.propertyName} must reference properties that actually exist in your type schema. Referencing non-existent properties will fail validation.
     • Type matching: Attribute values must match the expected type for the component. For example, if a component expects a string attribute, passing an integer will fail validation.
   • Widget renderer pattern (for widget rendition):
     • When to use: Use this when users request "mosaic", "widget", "fragment", or "cross-platform rendering" for their CLT.
     • Structure: renderer.componentOverrides["$"] = { "type": "mosaic", "definition": "tile/mosaic", "children": [ /* UEM tree of blocks and regions */ ] }
     • REQUIRED workflow:
       • STOP: Do NOT attempt to create the widget renderer yourself.
       • MANDATORY FIRST STEP: You MUST fetch the reference file references/widget-rendition.md located in this skill's directory before proceeding.
       • Follow the complete workflow documented in widget-rendition.md using the generated CLT schema as the grounding schema.
       • The widget-rendition.md reference contains the full widget generation workflow: discovering UEM blocks via discoverUiComponents, calling getUiComponentSchemas, building the UEM tree, and writing renderer.json.
       • Do not attempt to generate widget rendition without first fetching the widget-rendition.md reference file.
   • Property-level override pattern:
     • renderer.componentOverrides["<propertyName>"] = { "definition": "es_property_editors/outputText" | "es_property_editors/outputNumber" | "es_property_editors/outputImage" | ... }. Valid renderer components (examples): es_property_editors/outputText, es_property_editors/outputNumber, es_property_editors/outputImage. Avoid input-style components in the renderer.
   • Layout pattern for renderer:
     • renderer.layout.definition = "lightning/verticalLayout"
     • renderer.layout.children[*].definition = "lightning/propertyLayout" with attributes.property = "<propertyName>"
     • CRITICAL: Same as editor layouts, lightning/propertyLayout only accepts the property attribute. Do NOT add label, title, or any other attributes.
   • Collection renderer (for root-level lightning__listType properties): Use collection.renderer.componentOverrides["$"] = { "definition": "c/<yourListRendererComponent>" } or es_property_editors/genericListTypeRenderer to render the list.
5. Place files in the correct bundle structure
   • lightningTypes/<TypeName>/schema.json
   • (Optional) lightningTypes/<TypeName>/lightningDesktopGenAi/editor.json
   • (Optional) lightningTypes/<TypeName>/lightningDesktopGenAi/renderer.json
   • For Gen AI / Copilot the standard path is lightningDesktopGenAi/. Other targets (e.g. Experience Builder, Mobile Copilot, Enhanced Web Chat) use different subfolders when supported: experienceBuilder/, lightningMobileGenAi/, enhancedWebChat/.
6. Configure custom LWC components (if using custom components)
   • CRITICAL: Custom LWC components referenced in editor/renderer configs MUST have the correct target configuration in their -meta.xml files:
     • For editor components (c/<componentName> used in editor.json): The LWC's -meta.xml file must include <target>lightning__AgentforceInput</target>
     • For renderer components (c/<componentName> used in renderer.json): The LWC's -meta.xml file must include <target>lightning__AgentforceOutput</target>
   • Without the correct target, deployment will fail with: Invalid target configuration. To use 'c/componentName' as a renderer/editor, your js-meta.xml file must include valid target 'lightning__AgentforceOutput/Input'.
   • Example -meta.xml for a renderer component:

     <?xml version="1.0" encoding="UTF-8"?>
     <LightningComponentBundle xmlns="http://soap.sforce.com/2006/04/metadata">
         <apiVersion>60.0</apiVersion>
         <isExposed>true</isExposed>
         <targets>
             <target>lightning__AgentforceOutput</target>
         </targets>
     </LightningComponentBundle>
     

Common Deployment Errors

Error / Symptom	Likely Cause	Fix
Schema validation fails due to unknown keyword	unevaluatedProperties: false + disallowed keyword (commonly examples, items)	Remove the offending keyword; keep schema minimal
Nested object validation failure	Org/channel validation rejects nested object typing in LightningTypeBundle	Use CLT reference (c__<CLTName>) or Apex class types
Invalid CLT reference	Referenced CLT doesn't exist in org or incorrect syntax	Deploy the referenced CLT first; c__<CLTName> must match the referenced type’s lightning:type value / FQN / registered identifier, not title
Invalid or misspelled lightning:type (for example, lightning__richtextType instead of lightning__richTextType)	Incorrect generated type name	Cross-check all lightning:type values against supported type names and correct them before deployment
Array property rejected	Use of items (or lightning:type in nested arrays) rejected by validator	For nested arrays: keep only type: "array". For root arrays: use minimal structure; remove items if rejected
Apex-based CLT rejected	Extra fields added (e.g., type, properties)	Use only title, optional description, and lightning:type
Editor config rejected	Use of invalid patterns (es_property_editors/inputList, itemSchema) or unrecognized top-level keys	Use editor.componentOverrides and editor.layout; keep config minimal
additionalProperties error on layout attributes	Adding label or other attributes to lightning/propertyLayout	Only use property attribute in lightning/propertyLayout. Remove label, title, or any other attributes
Invalid target configuration for custom LWC	Custom LWC component's -meta.xml missing required target (lightning__AgentforceInput or lightning__AgentforceOutput)	Add correct target to LWC's -meta.xml: use lightning__AgentforceInput for editors, lightning__AgentforceOutput for renderers
Attribute mapping doesn't exist in type schema	Using {!$attrs.propertyName} where propertyName is not defined in schema	Ensure all attribute mappings reference actual properties in your type schema's properties section
additionalProperties error with deprecated keys	Using propertyRenderers or view in editor/renderer config	Replace deprecated propertyRenderers with componentOverrides and view with layout
Type mismatch in component attributes	Passing wrong type for component attribute (e.g., integer instead of string)	Ensure attribute values match the expected type defined by the component

Verification Checklist

• Root schema has type: "object", title, lightning:type: "lightning__objectType", and unevaluatedProperties: false
• Root schema does not include examples when strict validation is enabled
• No nested object includes lightning:type: "lightning__objectType"
• Arrays are defined minimally (especially nested arrays)
• Only supported primitive lightning:type identifiers are used for leaf properties
• Apex class CLTs contain only title/description and lightning:type: "@apexClassType/..."
• Bundle structure and filenames match Lightning Types requirements
• Editor config uses only allowed patterns (no es_property_editors/inputList, no itemSchema); use valid components (e.g. es_property_editors/inputText, es_property_editors/inputNumber) or custom c/ components
• Renderer config uses output-style components (e.g. es_property_editors/outputText, es_property_editors/outputNumber) where applicable, not input editors
• Layout configurations use lightning/propertyLayout with ONLY the property attribute (no label, title, or other attributes)
• All attribute mappings ({!$attrs.propertyName}) reference properties that exist in the type schema
• Custom LWC components have correct targets in -meta.xml: lightning__AgentforceInput for editors, lightning__AgentforceOutput for renderers
• Root schema does NOT include "$schema" field