diff --git a/libs/a2ui/schemas/README.md b/libs/a2ui/schemas/README.md
new file mode 100644
index 000000000..825182b76
--- /dev/null
+++ b/libs/a2ui/schemas/README.md
@@ -0,0 +1,17 @@
+# Vendored official A2UI v0.9 schemas
+
+These JSON schemas are vendored **verbatim** from the official A2UI
+specification and exist solely as fixtures for the drift tests in
+`src/lib/schema-conformance.spec.ts`. They are **not** part of the published
+npm package (the build copies from `src/` only).
+
+Sources:
+
+- `server_to_client.json` — https://a2ui.org/specification/v0_9/server_to_client.json
+- `common_types.json` — https://a2ui.org/specification/v0_9/common_types.json
+- `basic-catalog.json` — https://a2ui.org/specification/v0_9/catalogs/basic/catalog.json
+
+To refresh, re-download the files from the URLs above (keep the local
+filenames). If the conformance spec then fails, the upstream spec changed —
+update `src/lib/types.ts` / `src/lib/functions.ts` and the expectations in the
+spec accordingly.
diff --git a/libs/a2ui/schemas/basic-catalog.json b/libs/a2ui/schemas/basic-catalog.json
new file mode 100644
index 000000000..f8131a857
--- /dev/null
+++ b/libs/a2ui/schemas/basic-catalog.json
@@ -0,0 +1,1383 @@
+{
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "$id": "https://a2ui.org/specification/v0_9/catalogs/basic/catalog.json",
+  "title": "A2UI Basic Catalog",
+  "description": "Unified catalog of basic A2UI components and functions.",
+  "catalogId": "https://a2ui.org/specification/v0_9/catalogs/basic/catalog.json",
+  "components": {
+    "Text": {
+      "type": "object",
+      "allOf": [
+        {
+          "$ref": "https://a2ui.org/specification/v0_9/common_types.json#/$defs/ComponentCommon"
+        },
+        {
+          "$ref": "#/$defs/CatalogComponentCommon"
+        },
+        {
+          "type": "object",
+          "properties": {
+            "component": {
+              "const": "Text"
+            },
+            "text": {
+              "$ref": "https://a2ui.org/specification/v0_9/common_types.json#/$defs/DynamicString",
+              "description": "The text content to display. While simple Markdown formatting is supported (i.e. without HTML, images, or links), utilizing dedicated UI components is generally preferred for a richer and more structured presentation."
+            },
+            "variant": {
+              "type": "string",
+              "description": "A hint for the base text style.",
+              "enum": ["h1", "h2", "h3", "h4", "h5", "caption", "body"],
+              "default": "body"
+            }
+          },
+          "required": ["component", "text"]
+        }
+      ],
+      "unevaluatedProperties": false
+    },
+    "Image": {
+      "type": "object",
+      "allOf": [
+        {
+          "$ref": "https://a2ui.org/specification/v0_9/common_types.json#/$defs/ComponentCommon"
+        },
+        {
+          "$ref": "#/$defs/CatalogComponentCommon"
+        },
+        {
+          "type": "object",
+          "properties": {
+            "component": {
+              "const": "Image"
+            },
+            "url": {
+              "$ref": "https://a2ui.org/specification/v0_9/common_types.json#/$defs/DynamicString",
+              "description": "The URL of the image to display."
+            },
+            "description": {
+              "$ref": "https://a2ui.org/specification/v0_9/common_types.json#/$defs/DynamicString",
+              "description": "Accessibility text for the image."
+            },
+            "fit": {
+              "type": "string",
+              "description": "Specifies how the image should be resized to fit its container. This corresponds to the CSS 'object-fit' property.",
+              "enum": ["contain", "cover", "fill", "none", "scaleDown"],
+              "default": "fill"
+            },
+            "variant": {
+              "type": "string",
+              "description": "A hint for the image size and style.",
+              "enum": ["icon", "avatar", "smallFeature", "mediumFeature", "largeFeature", "header"],
+              "default": "mediumFeature"
+            }
+          },
+          "required": ["component", "url"]
+        }
+      ],
+      "unevaluatedProperties": false
+    },
+    "Icon": {
+      "type": "object",
+      "allOf": [
+        {
+          "$ref": "https://a2ui.org/specification/v0_9/common_types.json#/$defs/ComponentCommon"
+        },
+        {
+          "$ref": "#/$defs/CatalogComponentCommon"
+        },
+        {
+          "type": "object",
+          "properties": {
+            "component": {
+              "const": "Icon"
+            },
+            "name": {
+              "description": "The name of the icon to display.",
+              "oneOf": [
+                {
+                  "type": "string",
+                  "enum": [
+                    "accountCircle",
+                    "add",
+                    "arrowBack",
+                    "arrowForward",
+                    "attachFile",
+                    "calendarToday",
+                    "call",
+                    "camera",
+                    "check",
+                    "close",
+                    "delete",
+                    "download",
+                    "edit",
+                    "event",
+                    "error",
+                    "fastForward",
+                    "favorite",
+                    "favoriteOff",
+                    "folder",
+                    "help",
+                    "home",
+                    "info",
+                    "locationOn",
+                    "lock",
+                    "lockOpen",
+                    "mail",
+                    "menu",
+                    "moreVert",
+                    "moreHoriz",
+                    "notificationsOff",
+                    "notifications",
+                    "pause",
+                    "payment",
+                    "person",
+                    "phone",
+                    "photo",
+                    "play",
+                    "print",
+                    "refresh",
+                    "rewind",
+                    "search",
+                    "send",
+                    "settings",
+                    "share",
+                    "shoppingCart",
+                    "skipNext",
+                    "skipPrevious",
+                    "star",
+                    "starHalf",
+                    "starOff",
+                    "stop",
+                    "upload",
+                    "visibility",
+                    "visibilityOff",
+                    "volumeDown",
+                    "volumeMute",
+                    "volumeOff",
+                    "volumeUp",
+                    "warning"
+                  ]
+                },
+                {
+                  "type": "object",
+                  "properties": {
+                    "svgPath": {
+                      "type": "string"
+                    }
+                  },
+                  "required": ["svgPath"],
+                  "additionalProperties": false
+                },
+                {
+                  "$ref": "https://a2ui.org/specification/v0_9/common_types.json#/$defs/DataBinding"
+                }
+              ]
+            }
+          },
+          "required": ["component", "name"]
+        }
+      ],
+      "unevaluatedProperties": false
+    },
+    "Video": {
+      "type": "object",
+      "allOf": [
+        {
+          "$ref": "https://a2ui.org/specification/v0_9/common_types.json#/$defs/ComponentCommon"
+        },
+        {
+          "$ref": "#/$defs/CatalogComponentCommon"
+        },
+        {
+          "type": "object",
+          "properties": {
+            "component": {
+              "const": "Video"
+            },
+            "url": {
+              "$ref": "https://a2ui.org/specification/v0_9/common_types.json#/$defs/DynamicString",
+              "description": "The URL of the video to display."
+            }
+          },
+          "required": ["component", "url"]
+        }
+      ],
+      "unevaluatedProperties": false
+    },
+    "AudioPlayer": {
+      "type": "object",
+      "allOf": [
+        {
+          "$ref": "https://a2ui.org/specification/v0_9/common_types.json#/$defs/ComponentCommon"
+        },
+        {
+          "$ref": "#/$defs/CatalogComponentCommon"
+        },
+        {
+          "type": "object",
+          "properties": {
+            "component": {
+              "const": "AudioPlayer"
+            },
+            "url": {
+              "$ref": "https://a2ui.org/specification/v0_9/common_types.json#/$defs/DynamicString",
+              "description": "The URL of the audio to be played."
+            },
+            "description": {
+              "description": "A description of the audio, such as a title or summary.",
+              "$ref": "https://a2ui.org/specification/v0_9/common_types.json#/$defs/DynamicString"
+            }
+          },
+          "required": ["component", "url"]
+        }
+      ],
+      "unevaluatedProperties": false
+    },
+    "Row": {
+      "type": "object",
+      "allOf": [
+        {
+          "$ref": "https://a2ui.org/specification/v0_9/common_types.json#/$defs/ComponentCommon"
+        },
+        {
+          "$ref": "#/$defs/CatalogComponentCommon"
+        },
+        {
+          "type": "object",
+          "description": "A layout component that arranges its children horizontally. To create a grid layout, nest Columns within this Row.",
+          "properties": {
+            "component": {
+              "const": "Row"
+            },
+            "children": {
+              "description": "Defines the children. Use an array of strings for a fixed set of children, or a template object to generate children from a data list. Children cannot be defined inline, they must be referred to by ID.",
+              "$ref": "https://a2ui.org/specification/v0_9/common_types.json#/$defs/ChildList"
+            },
+            "justify": {
+              "type": "string",
+              "description": "Defines the arrangement of children along the main axis (horizontally). Use 'spaceBetween' to push items to the edges, or 'start'/'end'/'center' to pack them together.",
+              "enum": [
+                "center",
+                "end",
+                "spaceAround",
+                "spaceBetween",
+                "spaceEvenly",
+                "start",
+                "stretch"
+              ],
+              "default": "start"
+            },
+            "align": {
+              "type": "string",
+              "description": "Defines the alignment of children along the cross axis (vertically). This is similar to the CSS 'align-items' property, but uses camelCase values (e.g., 'start').",
+              "enum": ["start", "center", "end", "stretch"],
+              "default": "stretch"
+            }
+          },
+          "required": ["component", "children"]
+        }
+      ],
+      "unevaluatedProperties": false
+    },
+    "Column": {
+      "type": "object",
+      "allOf": [
+        {
+          "$ref": "https://a2ui.org/specification/v0_9/common_types.json#/$defs/ComponentCommon"
+        },
+        {
+          "$ref": "#/$defs/CatalogComponentCommon"
+        },
+        {
+          "type": "object",
+          "description": "A layout component that arranges its children vertically. To create a grid layout, nest Rows within this Column.",
+          "properties": {
+            "component": {
+              "const": "Column"
+            },
+            "children": {
+              "description": "Defines the children. Use an array of strings for a fixed set of children, or a template object to generate children from a data list. Children cannot be defined inline, they must be referred to by ID.",
+              "$ref": "https://a2ui.org/specification/v0_9/common_types.json#/$defs/ChildList"
+            },
+            "justify": {
+              "type": "string",
+              "description": "Defines the arrangement of children along the main axis (vertically). Use 'spaceBetween' to push items to the edges (e.g. header at top, footer at bottom), or 'start'/'end'/'center' to pack them together.",
+              "enum": [
+                "start",
+                "center",
+                "end",
+                "spaceBetween",
+                "spaceAround",
+                "spaceEvenly",
+                "stretch"
+              ],
+              "default": "start"
+            },
+            "align": {
+              "type": "string",
+              "description": "Defines the alignment of children along the cross axis (horizontally). This is similar to the CSS 'align-items' property.",
+              "enum": ["center", "end", "start", "stretch"],
+              "default": "stretch"
+            }
+          },
+          "required": ["component", "children"]
+        }
+      ],
+      "unevaluatedProperties": false
+    },
+    "List": {
+      "type": "object",
+      "allOf": [
+        {
+          "$ref": "https://a2ui.org/specification/v0_9/common_types.json#/$defs/ComponentCommon"
+        },
+        {
+          "$ref": "#/$defs/CatalogComponentCommon"
+        },
+        {
+          "type": "object",
+          "properties": {
+            "component": {
+              "const": "List"
+            },
+            "children": {
+              "description": "Defines the children. Use an array of strings for a fixed set of children, or a template object to generate children from a data list.",
+              "$ref": "https://a2ui.org/specification/v0_9/common_types.json#/$defs/ChildList"
+            },
+            "direction": {
+              "type": "string",
+              "description": "The direction in which the list items are laid out.",
+              "enum": ["vertical", "horizontal"],
+              "default": "vertical"
+            },
+            "align": {
+              "type": "string",
+              "description": "Defines the alignment of children along the cross axis.",
+              "enum": ["start", "center", "end", "stretch"],
+              "default": "stretch"
+            }
+          },
+          "required": ["component", "children"]
+        }
+      ],
+      "unevaluatedProperties": false
+    },
+    "Card": {
+      "type": "object",
+      "allOf": [
+        {
+          "$ref": "https://a2ui.org/specification/v0_9/common_types.json#/$defs/ComponentCommon"
+        },
+        {
+          "$ref": "#/$defs/CatalogComponentCommon"
+        },
+        {
+          "type": "object",
+          "properties": {
+            "component": {
+              "const": "Card"
+            },
+            "child": {
+              "$ref": "https://a2ui.org/specification/v0_9/common_types.json#/$defs/ComponentId",
+              "description": "The ID of the single child component to be rendered inside the card. To display multiple elements, you MUST wrap them in a layout component (like Column or Row) and pass that container's ID here. Do NOT pass multiple IDs or a non-existent ID."
+            }
+          },
+          "required": ["component", "child"]
+        }
+      ],
+      "unevaluatedProperties": false
+    },
+    "Tabs": {
+      "type": "object",
+      "allOf": [
+        {
+          "$ref": "https://a2ui.org/specification/v0_9/common_types.json#/$defs/ComponentCommon"
+        },
+        {
+          "$ref": "#/$defs/CatalogComponentCommon"
+        },
+        {
+          "type": "object",
+          "properties": {
+            "component": {
+              "const": "Tabs"
+            },
+            "tabs": {
+              "type": "array",
+              "description": "An array of objects, where each object defines a tab with a title and a child component.",
+              "minItems": 1,
+              "items": {
+                "type": "object",
+                "properties": {
+                  "title": {
+                    "description": "The tab title.",
+                    "$ref": "https://a2ui.org/specification/v0_9/common_types.json#/$defs/DynamicString"
+                  },
+                  "child": {
+                    "$ref": "https://a2ui.org/specification/v0_9/common_types.json#/$defs/ComponentId",
+                    "description": "The ID of the child component."
+                  }
+                },
+                "required": ["title", "child"],
+                "additionalProperties": false
+              }
+            }
+          },
+          "required": ["component", "tabs"]
+        }
+      ],
+      "unevaluatedProperties": false
+    },
+    "Modal": {
+      "type": "object",
+      "allOf": [
+        {
+          "$ref": "https://a2ui.org/specification/v0_9/common_types.json#/$defs/ComponentCommon"
+        },
+        {
+          "$ref": "#/$defs/CatalogComponentCommon"
+        },
+        {
+          "type": "object",
+          "properties": {
+            "component": {
+              "const": "Modal"
+            },
+            "trigger": {
+              "$ref": "https://a2ui.org/specification/v0_9/common_types.json#/$defs/ComponentId",
+              "description": "The ID of the component that opens the modal when interacted with (e.g., a button)."
+            },
+            "content": {
+              "$ref": "https://a2ui.org/specification/v0_9/common_types.json#/$defs/ComponentId",
+              "description": "The ID of the component to be displayed inside the modal."
+            }
+          },
+          "required": ["component", "trigger", "content"]
+        }
+      ],
+      "unevaluatedProperties": false
+    },
+    "Divider": {
+      "type": "object",
+      "allOf": [
+        {
+          "$ref": "https://a2ui.org/specification/v0_9/common_types.json#/$defs/ComponentCommon"
+        },
+        {
+          "$ref": "#/$defs/CatalogComponentCommon"
+        },
+        {
+          "type": "object",
+          "properties": {
+            "component": {
+              "const": "Divider"
+            },
+            "axis": {
+              "type": "string",
+              "description": "The orientation of the divider.",
+              "enum": ["horizontal", "vertical"],
+              "default": "horizontal"
+            }
+          },
+          "required": ["component"]
+        }
+      ],
+      "unevaluatedProperties": false
+    },
+    "Button": {
+      "type": "object",
+      "allOf": [
+        {
+          "$ref": "https://a2ui.org/specification/v0_9/common_types.json#/$defs/ComponentCommon"
+        },
+        {
+          "$ref": "#/$defs/CatalogComponentCommon"
+        },
+        {
+          "$ref": "https://a2ui.org/specification/v0_9/common_types.json#/$defs/Checkable"
+        },
+        {
+          "type": "object",
+          "properties": {
+            "component": {
+              "const": "Button"
+            },
+            "child": {
+              "$ref": "https://a2ui.org/specification/v0_9/common_types.json#/$defs/ComponentId",
+              "description": "The ID of the child component. Use a 'Text' component for a labeled button. Only use an 'Icon' if the requirements explicitly ask for an icon-only button."
+            },
+            "variant": {
+              "type": "string",
+              "description": "A hint for the button style. If omitted, a default button style is used. 'primary' indicates this is the main call-to-action button. 'borderless' means the button has no visual border or background, making its child content appear like a clickable link.",
+              "enum": ["default", "primary", "borderless"],
+              "default": "default"
+            },
+            "action": {
+              "$ref": "https://a2ui.org/specification/v0_9/common_types.json#/$defs/Action"
+            }
+          },
+          "required": ["component", "child", "action"]
+        }
+      ],
+      "unevaluatedProperties": false
+    },
+    "TextField": {
+      "type": "object",
+      "allOf": [
+        {
+          "$ref": "https://a2ui.org/specification/v0_9/common_types.json#/$defs/ComponentCommon"
+        },
+        {
+          "$ref": "#/$defs/CatalogComponentCommon"
+        },
+        {
+          "$ref": "https://a2ui.org/specification/v0_9/common_types.json#/$defs/Checkable"
+        },
+        {
+          "type": "object",
+          "properties": {
+            "component": {
+              "const": "TextField"
+            },
+            "label": {
+              "$ref": "https://a2ui.org/specification/v0_9/common_types.json#/$defs/DynamicString",
+              "description": "The text label for the input field."
+            },
+            "value": {
+              "$ref": "https://a2ui.org/specification/v0_9/common_types.json#/$defs/DynamicString",
+              "description": "The value of the text field."
+            },
+            "variant": {
+              "type": "string",
+              "description": "The type of input field to display.",
+              "enum": ["longText", "number", "shortText", "obscured"],
+              "default": "shortText"
+            },
+            "validationRegexp": {
+              "type": "string",
+              "description": "A regular expression used for client-side validation of the input."
+            }
+          },
+          "required": ["component", "label"]
+        }
+      ],
+      "unevaluatedProperties": false
+    },
+    "CheckBox": {
+      "type": "object",
+      "allOf": [
+        {
+          "$ref": "https://a2ui.org/specification/v0_9/common_types.json#/$defs/ComponentCommon"
+        },
+        {
+          "$ref": "#/$defs/CatalogComponentCommon"
+        },
+        {
+          "$ref": "https://a2ui.org/specification/v0_9/common_types.json#/$defs/Checkable"
+        },
+        {
+          "type": "object",
+          "properties": {
+            "component": {
+              "const": "CheckBox"
+            },
+            "label": {
+              "$ref": "https://a2ui.org/specification/v0_9/common_types.json#/$defs/DynamicString",
+              "description": "The text to display next to the checkbox."
+            },
+            "value": {
+              "$ref": "https://a2ui.org/specification/v0_9/common_types.json#/$defs/DynamicBoolean",
+              "description": "The current state of the checkbox (true for checked, false for unchecked)."
+            }
+          },
+          "required": ["component", "label", "value"]
+        }
+      ],
+      "unevaluatedProperties": false
+    },
+    "ChoicePicker": {
+      "type": "object",
+      "allOf": [
+        {
+          "$ref": "https://a2ui.org/specification/v0_9/common_types.json#/$defs/ComponentCommon"
+        },
+        {
+          "$ref": "#/$defs/CatalogComponentCommon"
+        },
+        {
+          "$ref": "https://a2ui.org/specification/v0_9/common_types.json#/$defs/Checkable"
+        },
+        {
+          "type": "object",
+          "description": "A component that allows selecting one or more options from a list.",
+          "properties": {
+            "component": {
+              "const": "ChoicePicker"
+            },
+            "label": {
+              "$ref": "https://a2ui.org/specification/v0_9/common_types.json#/$defs/DynamicString",
+              "description": "The label for the group of options."
+            },
+            "variant": {
+              "type": "string",
+              "description": "A hint for how the choice picker should be displayed and behave.",
+              "enum": ["multipleSelection", "mutuallyExclusive"],
+              "default": "mutuallyExclusive"
+            },
+            "options": {
+              "type": "array",
+              "description": "The list of available options to choose from.",
+              "items": {
+                "type": "object",
+                "properties": {
+                  "label": {
+                    "description": "The text to display for this option.",
+                    "$ref": "https://a2ui.org/specification/v0_9/common_types.json#/$defs/DynamicString"
+                  },
+                  "value": {
+                    "type": "string",
+                    "description": "The stable value associated with this option."
+                  }
+                },
+                "required": ["label", "value"],
+                "additionalProperties": false
+              }
+            },
+            "value": {
+              "$ref": "https://a2ui.org/specification/v0_9/common_types.json#/$defs/DynamicStringList",
+              "description": "The list of currently selected values. This should be bound to a string array in the data model."
+            },
+            "displayStyle": {
+              "type": "string",
+              "description": "The display style of the component.",
+              "enum": ["checkbox", "chips"],
+              "default": "checkbox"
+            },
+            "filterable": {
+              "type": "boolean",
+              "description": "If true, displays a search input to filter the options.",
+              "default": false
+            }
+          },
+          "required": ["component", "options", "value"]
+        }
+      ],
+      "unevaluatedProperties": false
+    },
+    "Slider": {
+      "type": "object",
+      "allOf": [
+        {
+          "$ref": "https://a2ui.org/specification/v0_9/common_types.json#/$defs/ComponentCommon"
+        },
+        {
+          "$ref": "#/$defs/CatalogComponentCommon"
+        },
+        {
+          "$ref": "https://a2ui.org/specification/v0_9/common_types.json#/$defs/Checkable"
+        },
+        {
+          "type": "object",
+          "properties": {
+            "component": {
+              "const": "Slider"
+            },
+            "label": {
+              "$ref": "https://a2ui.org/specification/v0_9/common_types.json#/$defs/DynamicString",
+              "description": "The label for the slider."
+            },
+            "min": {
+              "type": "number",
+              "description": "The minimum value of the slider.",
+              "default": 0
+            },
+            "max": {
+              "type": "number",
+              "description": "The maximum value of the slider."
+            },
+            "value": {
+              "$ref": "https://a2ui.org/specification/v0_9/common_types.json#/$defs/DynamicNumber",
+              "description": "The current value of the slider."
+            }
+          },
+          "required": ["component", "value", "max"]
+        }
+      ],
+      "unevaluatedProperties": false
+    },
+    "DateTimeInput": {
+      "type": "object",
+      "allOf": [
+        {
+          "$ref": "https://a2ui.org/specification/v0_9/common_types.json#/$defs/ComponentCommon"
+        },
+        {
+          "$ref": "#/$defs/CatalogComponentCommon"
+        },
+        {
+          "$ref": "https://a2ui.org/specification/v0_9/common_types.json#/$defs/Checkable"
+        },
+        {
+          "type": "object",
+          "properties": {
+            "component": {
+              "const": "DateTimeInput"
+            },
+            "value": {
+              "$ref": "https://a2ui.org/specification/v0_9/common_types.json#/$defs/DynamicString",
+              "description": "The selected date and/or time value in ISO 8601 format. If not yet set, initialize with an empty string."
+            },
+            "enableDate": {
+              "type": "boolean",
+              "description": "If true, allows the user to select a date.",
+              "default": false
+            },
+            "enableTime": {
+              "type": "boolean",
+              "description": "If true, allows the user to select a time.",
+              "default": false
+            },
+            "min": {
+              "allOf": [
+                {
+                  "$ref": "https://a2ui.org/specification/v0_9/common_types.json#/$defs/DynamicString"
+                },
+                {
+                  "if": {
+                    "type": "string"
+                  },
+                  "then": {
+                    "oneOf": [
+                      {
+                        "format": "date"
+                      },
+                      {
+                        "format": "time"
+                      },
+                      {
+                        "format": "date-time"
+                      }
+                    ]
+                  }
+                }
+              ],
+              "description": "The minimum allowed date/time in ISO 8601 format."
+            },
+            "max": {
+              "allOf": [
+                {
+                  "$ref": "https://a2ui.org/specification/v0_9/common_types.json#/$defs/DynamicString"
+                },
+                {
+                  "if": {
+                    "type": "string"
+                  },
+                  "then": {
+                    "oneOf": [
+                      {
+                        "format": "date"
+                      },
+                      {
+                        "format": "time"
+                      },
+                      {
+                        "format": "date-time"
+                      }
+                    ]
+                  }
+                }
+              ],
+              "description": "The maximum allowed date/time in ISO 8601 format."
+            },
+            "label": {
+              "$ref": "https://a2ui.org/specification/v0_9/common_types.json#/$defs/DynamicString",
+              "description": "The text label for the input field."
+            }
+          },
+          "required": ["component", "value"]
+        }
+      ],
+      "unevaluatedProperties": false
+    }
+  },
+  "functions": {
+    "required": {
+      "type": "object",
+      "description": "Checks that the value is not null, undefined, or empty.",
+      "properties": {
+        "call": {
+          "const": "required"
+        },
+        "args": {
+          "type": "object",
+          "properties": {
+            "value": {
+              "description": "The value to check."
+            }
+          },
+          "required": ["value"],
+          "additionalProperties": false
+        },
+        "returnType": {
+          "const": "boolean"
+        }
+      },
+      "required": ["call", "args"],
+      "unevaluatedProperties": false
+    },
+    "regex": {
+      "type": "object",
+      "description": "Checks that the value matches a regular expression string.",
+      "properties": {
+        "call": {
+          "const": "regex"
+        },
+        "args": {
+          "type": "object",
+          "properties": {
+            "value": {
+              "$ref": "https://a2ui.org/specification/v0_9/common_types.json#/$defs/DynamicString"
+            },
+            "pattern": {
+              "type": "string",
+              "description": "The regex pattern to match against."
+            }
+          },
+          "required": ["value", "pattern"],
+          "unevaluatedProperties": false
+        },
+        "returnType": {
+          "const": "boolean"
+        }
+      },
+      "required": ["call", "args"],
+      "unevaluatedProperties": false
+    },
+    "length": {
+      "type": "object",
+      "description": "Checks string length constraints.",
+      "properties": {
+        "call": {
+          "const": "length"
+        },
+        "args": {
+          "type": "object",
+          "properties": {
+            "value": {
+              "$ref": "https://a2ui.org/specification/v0_9/common_types.json#/$defs/DynamicString"
+            },
+            "min": {
+              "type": "integer",
+              "minimum": 0,
+              "description": "The minimum allowed length."
+            },
+            "max": {
+              "type": "integer",
+              "minimum": 0,
+              "description": "The maximum allowed length."
+            }
+          },
+          "required": ["value"],
+          "anyOf": [
+            {
+              "required": ["min"]
+            },
+            {
+              "required": ["max"]
+            }
+          ],
+          "unevaluatedProperties": false
+        },
+        "returnType": {
+          "const": "boolean"
+        }
+      },
+      "required": ["call", "args"],
+      "unevaluatedProperties": false
+    },
+    "numeric": {
+      "type": "object",
+      "description": "Checks numeric range constraints.",
+      "properties": {
+        "call": {
+          "const": "numeric"
+        },
+        "args": {
+          "type": "object",
+          "properties": {
+            "value": {
+              "$ref": "https://a2ui.org/specification/v0_9/common_types.json#/$defs/DynamicNumber"
+            },
+            "min": {
+              "type": "number",
+              "description": "The minimum allowed value."
+            },
+            "max": {
+              "type": "number",
+              "description": "The maximum allowed value."
+            }
+          },
+          "required": ["value"],
+          "anyOf": [
+            {
+              "required": ["min"]
+            },
+            {
+              "required": ["max"]
+            }
+          ],
+          "unevaluatedProperties": false
+        },
+        "returnType": {
+          "const": "boolean"
+        }
+      },
+      "required": ["call", "args"],
+      "unevaluatedProperties": false
+    },
+    "email": {
+      "type": "object",
+      "description": "Checks that the value is a valid email address.",
+      "properties": {
+        "call": {
+          "const": "email"
+        },
+        "args": {
+          "type": "object",
+          "properties": {
+            "value": {
+              "$ref": "https://a2ui.org/specification/v0_9/common_types.json#/$defs/DynamicString"
+            }
+          },
+          "required": ["value"],
+          "unevaluatedProperties": false
+        },
+        "returnType": {
+          "const": "boolean"
+        }
+      },
+      "required": ["call", "args"],
+      "unevaluatedProperties": false
+    },
+    "formatString": {
+      "type": "object",
+      "description": "Performs string interpolation of data model values and other functions in the catalog functions list and returns the resulting string. The value string can contain interpolated expressions in the `${expression}` format. Supported expression types include: JSON Pointer paths to the data model (e.g., `${/absolute/path}` or `${relative/path}`), and client-side function calls (e.g., `${now()}`). Function arguments must be named (e.g., `${formatDate(value:${/currentDate}, format:'MM-dd')}`). To include a literal `${` sequence, escape it as `\\${`.",
+      "properties": {
+        "call": {
+          "const": "formatString"
+        },
+        "args": {
+          "type": "object",
+          "properties": {
+            "value": {
+              "$ref": "https://a2ui.org/specification/v0_9/common_types.json#/$defs/DynamicString"
+            }
+          },
+          "required": ["value"],
+          "unevaluatedProperties": false
+        },
+        "returnType": {
+          "const": "string"
+        }
+      },
+      "required": ["call", "args"],
+      "unevaluatedProperties": false
+    },
+    "formatNumber": {
+      "type": "object",
+      "description": "Formats a number with the specified grouping and decimal precision.",
+      "properties": {
+        "call": {
+          "const": "formatNumber"
+        },
+        "args": {
+          "type": "object",
+          "properties": {
+            "value": {
+              "$ref": "https://a2ui.org/specification/v0_9/common_types.json#/$defs/DynamicNumber",
+              "description": "The number to format."
+            },
+            "decimals": {
+              "$ref": "https://a2ui.org/specification/v0_9/common_types.json#/$defs/DynamicNumber",
+              "description": "Optional. The number of decimal places to show. Defaults to 0 or 2 depending on locale."
+            },
+            "grouping": {
+              "$ref": "https://a2ui.org/specification/v0_9/common_types.json#/$defs/DynamicBoolean",
+              "description": "Optional. If true, uses locale-specific grouping separators (e.g. '1,000'). If false, returns raw digits (e.g. '1000'). Defaults to true."
+            }
+          },
+          "required": ["value"],
+          "unevaluatedProperties": false
+        },
+        "returnType": {
+          "const": "string"
+        }
+      },
+      "required": ["call", "args"],
+      "unevaluatedProperties": false
+    },
+    "formatCurrency": {
+      "type": "object",
+      "description": "Formats a number as a currency string.",
+      "properties": {
+        "call": {
+          "const": "formatCurrency"
+        },
+        "args": {
+          "type": "object",
+          "properties": {
+            "value": {
+              "$ref": "https://a2ui.org/specification/v0_9/common_types.json#/$defs/DynamicNumber",
+              "description": "The monetary amount."
+            },
+            "currency": {
+              "$ref": "https://a2ui.org/specification/v0_9/common_types.json#/$defs/DynamicString",
+              "description": "The ISO 4217 currency code (e.g., 'USD', 'EUR')."
+            },
+            "decimals": {
+              "$ref": "https://a2ui.org/specification/v0_9/common_types.json#/$defs/DynamicNumber",
+              "description": "Optional. The number of decimal places to show. Defaults to 0 or 2 depending on locale."
+            },
+            "grouping": {
+              "$ref": "https://a2ui.org/specification/v0_9/common_types.json#/$defs/DynamicBoolean",
+              "description": "Optional. If true, uses locale-specific grouping separators (e.g. '1,000'). If false, returns raw digits (e.g. '1000'). Defaults to true."
+            }
+          },
+          "required": ["currency", "value"],
+          "unevaluatedProperties": false
+        },
+        "returnType": {
+          "const": "string"
+        }
+      },
+      "required": ["call", "args"],
+      "unevaluatedProperties": false
+    },
+    "formatDate": {
+      "type": "object",
+      "description": "Formats a timestamp into a string using a pattern.",
+      "properties": {
+        "call": {
+          "const": "formatDate"
+        },
+        "args": {
+          "type": "object",
+          "properties": {
+            "value": {
+              "$ref": "https://a2ui.org/specification/v0_9/common_types.json#/$defs/DynamicValue",
+              "description": "The date to format."
+            },
+            "format": {
+              "$ref": "https://a2ui.org/specification/v0_9/common_types.json#/$defs/DynamicString",
+              "description": "A Unicode TR35 date pattern string.\n\nToken Reference:\n- Year: 'yy' (26), 'yyyy' (2026)\n- Month: 'M' (1), 'MM' (01), 'MMM' (Jan), 'MMMM' (January)\n- Day: 'd' (1), 'dd' (01), 'E' (Tue), 'EEEE' (Tuesday)\n- Hour (12h): 'h' (1-12), 'hh' (01-12) - requires 'a' for AM/PM\n- Hour (24h): 'H' (0-23), 'HH' (00-23) - Military Time\n- Minute: 'mm' (00-59)\n- Second: 'ss' (00-59)\n- Period: 'a' (AM/PM)\n\nExamples:\n- 'MMM dd, yyyy' -> 'Jan 16, 2026'\n- 'HH:mm' -> '14:30' (Military)\n- 'h:mm a' -> '2:30 PM'\n- 'EEEE, d MMMM' -> 'Friday, 16 January'"
+            }
+          },
+          "required": ["format", "value"],
+          "unevaluatedProperties": false
+        },
+        "returnType": {
+          "const": "string"
+        }
+      },
+      "required": ["call", "args"],
+      "unevaluatedProperties": false
+    },
+    "pluralize": {
+      "type": "object",
+      "description": "Returns a localized string based on the Common Locale Data Repository (CLDR) plural category of the count (zero, one, two, few, many, other). Requires an 'other' fallback. For English, just use 'one' and 'other'.",
+      "properties": {
+        "call": {
+          "const": "pluralize"
+        },
+        "args": {
+          "type": "object",
+          "properties": {
+            "value": {
+              "$ref": "https://a2ui.org/specification/v0_9/common_types.json#/$defs/DynamicNumber",
+              "description": "The numeric value used to determine the plural category."
+            },
+            "zero": {
+              "$ref": "https://a2ui.org/specification/v0_9/common_types.json#/$defs/DynamicString",
+              "description": "String for the 'zero' category (e.g., 0 items)."
+            },
+            "one": {
+              "$ref": "https://a2ui.org/specification/v0_9/common_types.json#/$defs/DynamicString",
+              "description": "String for the 'one' category (e.g., 1 item)."
+            },
+            "two": {
+              "$ref": "https://a2ui.org/specification/v0_9/common_types.json#/$defs/DynamicString",
+              "description": "String for the 'two' category (used in Arabic, Welsh, etc.)."
+            },
+            "few": {
+              "$ref": "https://a2ui.org/specification/v0_9/common_types.json#/$defs/DynamicString",
+              "description": "String for the 'few' category (e.g., small groups in Slavic languages)."
+            },
+            "many": {
+              "$ref": "https://a2ui.org/specification/v0_9/common_types.json#/$defs/DynamicString",
+              "description": "String for the 'many' category (e.g., large groups in various languages)."
+            },
+            "other": {
+              "$ref": "https://a2ui.org/specification/v0_9/common_types.json#/$defs/DynamicString",
+              "description": "The default/fallback string (used for general plural cases)."
+            }
+          },
+          "required": ["value", "other"],
+          "unevaluatedProperties": false
+        },
+        "returnType": {
+          "const": "string"
+        }
+      },
+      "required": ["call", "args"],
+      "unevaluatedProperties": false
+    },
+    "openUrl": {
+      "type": "object",
+      "description": "Opens the specified URL in a browser or handler. This function has no return value.",
+      "properties": {
+        "call": {
+          "const": "openUrl"
+        },
+        "args": {
+          "type": "object",
+          "properties": {
+            "url": {
+              "type": "string",
+              "format": "uri",
+              "description": "The URL to open."
+            }
+          },
+          "required": ["url"],
+          "additionalProperties": false
+        },
+        "returnType": {
+          "const": "void"
+        }
+      },
+      "required": ["call", "args"],
+      "unevaluatedProperties": false
+    },
+    "and": {
+      "type": "object",
+      "description": "Performs a logical AND operation on a list of boolean values.",
+      "properties": {
+        "call": {
+          "const": "and"
+        },
+        "args": {
+          "type": "object",
+          "properties": {
+            "values": {
+              "type": "array",
+              "description": "The list of boolean values to evaluate.",
+              "items": {
+                "$ref": "https://a2ui.org/specification/v0_9/common_types.json#/$defs/DynamicBoolean"
+              },
+              "minItems": 2
+            }
+          },
+          "required": ["values"],
+          "unevaluatedProperties": false
+        },
+        "returnType": {
+          "const": "boolean"
+        }
+      },
+      "required": ["call", "args"],
+      "unevaluatedProperties": false
+    },
+    "or": {
+      "type": "object",
+      "description": "Performs a logical OR operation on a list of boolean values.",
+      "properties": {
+        "call": {
+          "const": "or"
+        },
+        "args": {
+          "type": "object",
+          "properties": {
+            "values": {
+              "type": "array",
+              "description": "The list of boolean values to evaluate.",
+              "items": {
+                "$ref": "https://a2ui.org/specification/v0_9/common_types.json#/$defs/DynamicBoolean"
+              },
+              "minItems": 2
+            }
+          },
+          "required": ["values"],
+          "unevaluatedProperties": false
+        },
+        "returnType": {
+          "const": "boolean"
+        }
+      },
+      "required": ["call", "args"],
+      "unevaluatedProperties": false
+    },
+    "not": {
+      "type": "object",
+      "description": "Performs a logical NOT operation on a boolean value.",
+      "properties": {
+        "call": {
+          "const": "not"
+        },
+        "args": {
+          "type": "object",
+          "properties": {
+            "value": {
+              "$ref": "https://a2ui.org/specification/v0_9/common_types.json#/$defs/DynamicBoolean",
+              "description": "The boolean value to negate."
+            }
+          },
+          "required": ["value"],
+          "unevaluatedProperties": false
+        },
+        "returnType": {
+          "const": "boolean"
+        }
+      },
+      "required": ["call", "args"],
+      "unevaluatedProperties": false
+    }
+  },
+  "$defs": {
+    "CatalogComponentCommon": {
+      "type": "object",
+      "properties": {
+        "weight": {
+          "type": "number",
+          "description": "The relative weight of this component within a Row or Column. This is similar to the CSS 'flex-grow' property. Note: this may ONLY be set when the component is a direct descendant of a Row or Column."
+        }
+      }
+    },
+    "theme": {
+      "type": "object",
+      "properties": {
+        "primaryColor": {
+          "type": "string",
+          "description": "The primary brand color used for highlights (e.g., primary buttons, active borders). Renderers may generate variants of this color for different contexts. Format: Hexadecimal code (e.g., '#00BFFF').",
+          "pattern": "^#[0-9a-fA-F]{6}$"
+        },
+        "iconUrl": {
+          "type": "string",
+          "format": "uri",
+          "description": "A URL for an image that identifies the agent or tool associated with the surface."
+        },
+        "agentDisplayName": {
+          "type": "string",
+          "description": "Text to be displayed next to the surface to identify the agent or tool that created it."
+        }
+      },
+      "additionalProperties": true
+    },
+    "anyComponent": {
+      "oneOf": [
+        {
+          "$ref": "#/components/Text"
+        },
+        {
+          "$ref": "#/components/Image"
+        },
+        {
+          "$ref": "#/components/Icon"
+        },
+        {
+          "$ref": "#/components/Video"
+        },
+        {
+          "$ref": "#/components/AudioPlayer"
+        },
+        {
+          "$ref": "#/components/Row"
+        },
+        {
+          "$ref": "#/components/Column"
+        },
+        {
+          "$ref": "#/components/List"
+        },
+        {
+          "$ref": "#/components/Card"
+        },
+        {
+          "$ref": "#/components/Tabs"
+        },
+        {
+          "$ref": "#/components/Modal"
+        },
+        {
+          "$ref": "#/components/Divider"
+        },
+        {
+          "$ref": "#/components/Button"
+        },
+        {
+          "$ref": "#/components/TextField"
+        },
+        {
+          "$ref": "#/components/CheckBox"
+        },
+        {
+          "$ref": "#/components/ChoicePicker"
+        },
+        {
+          "$ref": "#/components/Slider"
+        },
+        {
+          "$ref": "#/components/DateTimeInput"
+        }
+      ],
+      "discriminator": {
+        "propertyName": "component"
+      }
+    },
+    "anyFunction": {
+      "oneOf": [
+        {
+          "$ref": "#/functions/required"
+        },
+        {
+          "$ref": "#/functions/regex"
+        },
+        {
+          "$ref": "#/functions/length"
+        },
+        {
+          "$ref": "#/functions/numeric"
+        },
+        {
+          "$ref": "#/functions/email"
+        },
+        {
+          "$ref": "#/functions/formatString"
+        },
+        {
+          "$ref": "#/functions/formatNumber"
+        },
+        {
+          "$ref": "#/functions/formatCurrency"
+        },
+        {
+          "$ref": "#/functions/formatDate"
+        },
+        {
+          "$ref": "#/functions/pluralize"
+        },
+        {
+          "$ref": "#/functions/openUrl"
+        },
+        {
+          "$ref": "#/functions/and"
+        },
+        {
+          "$ref": "#/functions/or"
+        },
+        {
+          "$ref": "#/functions/not"
+        }
+      ]
+    }
+  }
+}
diff --git a/libs/a2ui/schemas/common_types.json b/libs/a2ui/schemas/common_types.json
new file mode 100644
index 000000000..51c5b036b
--- /dev/null
+++ b/libs/a2ui/schemas/common_types.json
@@ -0,0 +1,305 @@
+{
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "$id": "https://a2ui.org/specification/v0_9/common_types.json",
+  "title": "A2UI Common Types",
+  "description": "Common type definitions used across A2UI schemas.",
+  "$defs": {
+    "ComponentId": {
+      "type": "string",
+      "description": "The unique identifier for a component, used for both definitions and references within the same surface."
+    },
+    "AccessibilityAttributes": {
+      "type": "object",
+      "description": "Attributes to enhance accessibility when using assistive technologies like screen readers.",
+      "properties": {
+        "label": {
+          "$ref": "#/$defs/DynamicString",
+          "description": "A short string, typically 1 to 3 words, used by assistive technologies to convey the purpose or intent of an element. For example, an input field might have an accessible label of 'User ID' or a button might be labeled 'Submit'."
+        },
+        "description": {
+          "$ref": "#/$defs/DynamicString",
+          "description": "Additional information provided by assistive technologies about an element such as instructions, format requirements, or result of an action. For example, a mute button might have a label of 'Mute' and a description of 'Silences notifications about this conversation'."
+        }
+      }
+    },
+    "ComponentCommon": {
+      "type": "object",
+      "properties": {
+        "id": {
+          "$ref": "#/$defs/ComponentId"
+        },
+        "accessibility": {
+          "$ref": "#/$defs/AccessibilityAttributes"
+        }
+      },
+      "required": ["id"]
+    },
+    "ChildList": {
+      "oneOf": [
+        {
+          "type": "array",
+          "items": {
+            "$ref": "#/$defs/ComponentId"
+          },
+          "description": "A static list of child component IDs."
+        },
+        {
+          "type": "object",
+          "description": "A template for generating a dynamic list of children from a data model list. The `componentId` is the component to use as a template.",
+          "properties": {
+            "componentId": {
+              "$ref": "#/$defs/ComponentId"
+            },
+            "path": {
+              "type": "string",
+              "description": "The path to the list of component property objects in the data model."
+            }
+          },
+          "required": ["componentId", "path"],
+          "additionalProperties": false
+        }
+      ]
+    },
+    "DataBinding": {
+      "type": "object",
+      "properties": {
+        "path": {
+          "type": "string",
+          "description": "A JSON Pointer path to a value in the data model."
+        }
+      },
+      "required": ["path"],
+      "additionalProperties": false
+    },
+    "DynamicValue": {
+      "description": "A value that can be a literal, a path, or a function call returning any type.",
+      "oneOf": [
+        {
+          "type": "string"
+        },
+        {
+          "type": "number"
+        },
+        {
+          "type": "boolean"
+        },
+        {
+          "type": "array"
+        },
+        {
+          "$ref": "#/$defs/DataBinding"
+        },
+        {
+          "$ref": "#/$defs/FunctionCall"
+        }
+      ]
+    },
+    "DynamicString": {
+      "description": "Represents a string",
+      "oneOf": [
+        {
+          "type": "string"
+        },
+        {
+          "$ref": "#/$defs/DataBinding"
+        },
+        {
+          "allOf": [
+            {
+              "$ref": "#/$defs/FunctionCall"
+            },
+            {
+              "properties": {
+                "returnType": {
+                  "const": "string"
+                }
+              }
+            }
+          ]
+        }
+      ]
+    },
+    "DynamicNumber": {
+      "description": "Represents a value that can be either a literal number, a path to a number in the data model, or a function call returning a number.",
+      "oneOf": [
+        {
+          "type": "number"
+        },
+        {
+          "$ref": "#/$defs/DataBinding"
+        },
+        {
+          "allOf": [
+            {
+              "$ref": "#/$defs/FunctionCall"
+            },
+            {
+              "properties": {
+                "returnType": {
+                  "const": "number"
+                }
+              }
+            }
+          ]
+        }
+      ]
+    },
+    "DynamicBoolean": {
+      "description": "A boolean value that can be a literal, a path, or a function call returning a boolean.",
+      "oneOf": [
+        {
+          "type": "boolean"
+        },
+        {
+          "$ref": "#/$defs/DataBinding"
+        },
+        {
+          "allOf": [
+            {
+              "$ref": "#/$defs/FunctionCall"
+            },
+            {
+              "properties": {
+                "returnType": {
+                  "const": "boolean"
+                }
+              }
+            }
+          ]
+        }
+      ]
+    },
+    "DynamicStringList": {
+      "description": "Represents a value that can be either a literal array of strings, a path to a string array in the data model, or a function call returning a string array.",
+      "oneOf": [
+        {
+          "type": "array",
+          "items": {
+            "type": "string"
+          }
+        },
+        {
+          "$ref": "#/$defs/DataBinding"
+        },
+        {
+          "allOf": [
+            {
+              "$ref": "#/$defs/FunctionCall"
+            },
+            {
+              "properties": {
+                "returnType": {
+                  "const": "array"
+                }
+              }
+            }
+          ]
+        }
+      ]
+    },
+    "FunctionCall": {
+      "type": "object",
+      "description": "Invokes a named function on the client.",
+      "properties": {
+        "call": {
+          "type": "string",
+          "description": "The name of the function to call."
+        },
+        "args": {
+          "type": "object",
+          "description": "Arguments passed to the function.",
+          "additionalProperties": {
+            "anyOf": [
+              {
+                "$ref": "#/$defs/DynamicValue"
+              },
+              {
+                "type": "object",
+                "description": "A literal object argument (e.g. configuration)."
+              }
+            ]
+          }
+        },
+        "returnType": {
+          "type": "string",
+          "description": "The expected return type of the function call.",
+          "enum": ["string", "number", "boolean", "array", "object", "any", "void"],
+          "default": "boolean"
+        }
+      },
+      "required": ["call"],
+      "oneOf": [{"$ref": "catalog.json#/$defs/anyFunction"}]
+    },
+    "CheckRule": {
+      "type": "object",
+      "description": "A single validation rule applied to an input component.",
+      "properties": {
+        "condition": {
+          "$ref": "#/$defs/DynamicBoolean"
+        },
+        "message": {
+          "type": "string",
+          "description": "The error message to display if the check fails."
+        }
+      },
+      "required": ["condition", "message"],
+      "additionalProperties": false
+    },
+    "Checkable": {
+      "description": "Properties for components that support client-side checks.",
+      "type": "object",
+      "properties": {
+        "checks": {
+          "type": "array",
+          "description": "A list of checks to perform. These are function calls that must return a boolean indicating validity.",
+          "items": {
+            "$ref": "#/$defs/CheckRule"
+          }
+        }
+      }
+    },
+    "Action": {
+      "description": "Defines an interaction handler that can either trigger a server-side event or execute a local client-side function.",
+      "oneOf": [
+        {
+          "type": "object",
+          "description": "Triggers a server-side event.",
+          "properties": {
+            "event": {
+              "type": "object",
+              "description": "The event to dispatch to the server.",
+              "properties": {
+                "name": {
+                  "type": "string",
+                  "description": "The name of the action to be dispatched to the server."
+                },
+                "context": {
+                  "type": "object",
+                  "description": "A JSON object containing the key-value pairs for the action context. Values can be literals or paths. Use literal values unless the value must be dynamically bound to the data model. Do NOT use paths for static IDs.",
+                  "additionalProperties": {
+                    "$ref": "#/$defs/DynamicValue"
+                  }
+                }
+              },
+              "required": ["name"],
+              "additionalProperties": false
+            }
+          },
+          "required": ["event"],
+          "additionalProperties": false
+        },
+        {
+          "type": "object",
+          "description": "Executes a local client-side function.",
+          "properties": {
+            "functionCall": {
+              "$ref": "#/$defs/FunctionCall"
+            }
+          },
+          "required": ["functionCall"],
+          "additionalProperties": false
+        }
+      ]
+    }
+  }
+}
diff --git a/libs/a2ui/schemas/server_to_client.json b/libs/a2ui/schemas/server_to_client.json
new file mode 100644
index 000000000..005980642
--- /dev/null
+++ b/libs/a2ui/schemas/server_to_client.json
@@ -0,0 +1,132 @@
+{
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "$id": "https://a2ui.org/specification/v0_9/server_to_client.json",
+  "title": "A2UI Message Schema",
+  "description": "Describes a JSON payload for an A2UI (Agent to UI) message, which is used to dynamically construct and update user interfaces.",
+  "type": "object",
+  "oneOf": [
+    {"$ref": "#/$defs/CreateSurfaceMessage"},
+    {"$ref": "#/$defs/UpdateComponentsMessage"},
+    {"$ref": "#/$defs/UpdateDataModelMessage"},
+    {"$ref": "#/$defs/DeleteSurfaceMessage"}
+  ],
+  "$defs": {
+    "CreateSurfaceMessage": {
+      "type": "object",
+      "properties": {
+        "version": {
+          "const": "v0.9"
+        },
+        "createSurface": {
+          "type": "object",
+          "description": "Signals the client to create a new surface and begin rendering it. It is an error to send 'createSurface' for a surfaceId that already exists without first deleting it. When this message is sent, the client will expect 'updateComponents' and/or 'updateDataModel' messages for the same surfaceId that define the component tree.",
+          "properties": {
+            "surfaceId": {
+              "type": "string",
+              "description": "The unique identifier for the UI surface to be rendered."
+            },
+            "catalogId": {
+              "description": "A string that uniquely identifies this catalog. It is recommended to prefix this with an internet domain that you own, to avoid conflicts e.g. mycompany.com:somecatalog'.",
+              "type": "string"
+            },
+            "theme": {
+              "$ref": "catalog.json#/$defs/theme",
+              "description": "Theme parameters for the surface (e.g., {'primaryColor': '#FF0000'}). These must validate against the 'theme' schema defined in the catalog."
+            },
+            "sendDataModel": {
+              "type": "boolean",
+              "description": "If true, the client will send the full data model of this surface in the metadata of every A2A message sent to the server that created the surface. Defaults to false."
+            }
+          },
+          "required": ["surfaceId", "catalogId"],
+          "additionalProperties": false
+        }
+      },
+      "required": ["createSurface", "version"],
+      "additionalProperties": false
+    },
+    "UpdateComponentsMessage": {
+      "type": "object",
+      "properties": {
+        "version": {
+          "const": "v0.9"
+        },
+        "updateComponents": {
+          "type": "object",
+          "description": "Updates a surface with a new set of components. This message can be sent multiple times to update the component tree of an existing surface. One of the components in one of the components lists MUST have an 'id' of 'root' to serve as the root of the component tree. The createSurface message MUST have been previously sent with the 'catalogId' that is in this message.",
+          "properties": {
+            "surfaceId": {
+              "type": "string",
+              "description": "The unique identifier for the UI surface to be updated."
+            },
+
+            "components": {
+              "type": "array",
+              "description": "A list containing all UI components for the surface.",
+              "minItems": 1,
+              "items": {
+                "$ref": "catalog.json#/$defs/anyComponent"
+              }
+            }
+          },
+          "required": ["surfaceId", "components"],
+          "additionalProperties": false
+        }
+      },
+      "required": ["updateComponents", "version"],
+      "additionalProperties": false
+    },
+    "UpdateDataModelMessage": {
+      "type": "object",
+      "properties": {
+        "version": {
+          "const": "v0.9"
+        },
+        "updateDataModel": {
+          "type": "object",
+          "description": "Updates the data model for an existing surface. This message can be sent multiple times to update the data model. The createSurface message MUST have been previously sent with the 'catalogId' that is in this message.",
+          "properties": {
+            "surfaceId": {
+              "type": "string",
+              "description": "The unique identifier for the UI surface this data model update applies to."
+            },
+            "path": {
+              "type": "string",
+              "description": "An optional path to a location within the data model (e.g., '/user/name'). If omitted, or set to '/', refers to the entire data model."
+            },
+            "value": {
+              "description": "The data to be updated in the data model. If present, the value at 'path' is replaced (or created). If omitted, the key at 'path' is removed.",
+              "additionalProperties": true
+            }
+          },
+          "required": ["surfaceId"],
+          "additionalProperties": false
+        }
+      },
+      "required": ["updateDataModel", "version"],
+      "additionalProperties": false
+    },
+    "DeleteSurfaceMessage": {
+      "type": "object",
+      "properties": {
+        "version": {
+          "const": "v0.9"
+        },
+        "deleteSurface": {
+          "type": "object",
+          "description": "Signals the client to delete the surface identified by 'surfaceId'. The createSurface message MUST have been previously sent with the 'catalogId' that is in this message.",
+          "properties": {
+            "surfaceId": {
+              "type": "string",
+              "description": "The unique identifier for the UI surface to be deleted."
+            }
+          },
+          "required": ["surfaceId"],
+          "additionalProperties": false
+        }
+      },
+      "required": ["deleteSurface", "version"],
+      "additionalProperties": false
+    }
+  }
+}
diff --git a/libs/a2ui/src/lib/schema-conformance.spec.ts b/libs/a2ui/src/lib/schema-conformance.spec.ts
new file mode 100644
index 000000000..62061468a
--- /dev/null
+++ b/libs/a2ui/src/lib/schema-conformance.spec.ts
@@ -0,0 +1,246 @@
+// SPDX-License-Identifier: MIT
+//
+// Drift tripwire against the OFFICIAL A2UI v0.9 JSON schemas vendored in
+// libs/a2ui/schemas/ (see the README there for source URLs + refresh steps).
+//
+// These are hand-rolled structural checks, not a JSON-schema validator: the
+// expectations below were derived by reading the vendored files once and
+// writing them out explicitly. When the vendored schemas are refreshed and
+// upstream changed (or a local prop typo sneaks in), these tests fail and
+// point at what to update.
+
+import { readFileSync } from 'node:fs';
+import { join } from 'node:path';
+import { describe, expect, it } from 'vitest';
+
+import { createA2uiFunctionRegistry } from './functions';
+import { A2UI_WIRE_VERSION } from './types';
+
+// eslint-disable-next-line @typescript-eslint/no-explicit-any
+type JsonSchema = Record<string, any>;
+
+function loadSchema(name: string): JsonSchema {
+  return JSON.parse(readFileSync(join(__dirname, '../../schemas', name), 'utf8'));
+}
+
+const catalog = loadSchema('basic-catalog.json');
+const envelope = loadSchema('server_to_client.json');
+
+// --- Structural extraction helpers ------------------------------------------
+// Merges allOf/oneOf/anyOf branches, resolves only local #/$defs refs, and
+// treats external refs (common_types.json etc.) as opaque.
+
+function resolveLocal(root: JsonSchema, node: unknown): JsonSchema | undefined {
+  if (node === null || typeof node !== 'object') return undefined;
+  const schema = node as JsonSchema;
+  const ref = schema['$ref'];
+  if (typeof ref === 'string') {
+    if (!ref.startsWith('#/$defs/')) return schema; // external ref: opaque
+    return resolveLocal(root, root['$defs']?.[ref.slice('#/$defs/'.length)]);
+  }
+  return schema;
+}
+
+interface ExtractedShape {
+  props: Set<string>;
+  enums: Record<string, string[]>;
+}
+
+function extractShape(
+  root: JsonSchema,
+  node: unknown,
+  out: ExtractedShape = { props: new Set(), enums: {} },
+): ExtractedShape {
+  const schema = resolveLocal(root, node);
+  if (!schema) return out;
+  for (const key of ['allOf', 'oneOf', 'anyOf'] as const) {
+    if (Array.isArray(schema[key])) {
+      for (const branch of schema[key]) extractShape(root, branch, out);
+    }
+  }
+  if (schema['properties'] && typeof schema['properties'] === 'object') {
+    for (const [name, propNode] of Object.entries(schema['properties'])) {
+      out.props.add(name);
+      const prop = resolveLocal(root, propNode);
+      if (!prop) continue;
+      if (Array.isArray(prop['enum'])) out.enums[name] = prop['enum'];
+      if (Array.isArray(prop['oneOf'])) {
+        for (const branch of prop['oneOf']) {
+          const resolved = resolveLocal(root, branch);
+          if (resolved && Array.isArray(resolved['enum'])) {
+            out.enums[name] = resolved['enum'];
+          }
+        }
+      }
+    }
+  }
+  return out;
+}
+
+// --- (a) Component set -------------------------------------------------------
+
+/**
+ * The 18 basic-catalog components our `A2uiCatalogComponent` union covers —
+ * see libs/a2ui/src/lib/types.ts. If this assertion fails after refreshing
+ * the vendored catalog, upstream added/removed/renamed a component: update
+ * the union in types.ts (and the renderer) plus this list.
+ */
+const OUR_COMPONENTS = [
+  'AudioPlayer',
+  'Button',
+  'Card',
+  'CheckBox',
+  'ChoicePicker',
+  'Column',
+  'DateTimeInput',
+  'Divider',
+  'Icon',
+  'Image',
+  'List',
+  'Modal',
+  'Row',
+  'Slider',
+  'Tabs',
+  'Text',
+  'TextField',
+  'Video',
+] as const;
+
+describe('vendored catalog component set', () => {
+  it('matches the components our A2uiCatalogComponent union covers', () => {
+    const catalogComponents = Object.keys(catalog['components']).sort();
+    expect(catalogComponents).toEqual([...OUR_COMPONENTS]);
+  });
+});
+
+// --- (b) Per-component properties + enums ------------------------------------
+
+const JUSTIFY = ['start', 'center', 'end', 'spaceAround', 'spaceBetween', 'spaceEvenly', 'stretch'];
+const ALIGN = ['start', 'center', 'end', 'stretch'];
+
+/**
+ * Expected structural shape of each catalog component schema, transcribed
+ * from the vendored basic-catalog.json (props are the schema's own property
+ * names after merging allOf branches; shared base props like `id`, `checks`
+ * and `accessibility` live behind external/common refs and are opaque here).
+ * A mismatch after a refresh means upstream changed a component contract —
+ * reconcile types.ts and the renderer, then update this map.
+ */
+const EXPECTED_SHAPES: Record<string, { props: string[]; enums?: Record<string, string[]> }> = {
+  Text: {
+    props: ['component', 'text', 'variant', 'weight'],
+    enums: { variant: ['h1', 'h2', 'h3', 'h4', 'h5', 'caption', 'body'] },
+  },
+  Image: {
+    props: ['component', 'description', 'fit', 'url', 'variant', 'weight'],
+    enums: {
+      fit: ['contain', 'cover', 'fill', 'none', 'scaleDown'],
+      variant: ['icon', 'avatar', 'smallFeature', 'mediumFeature', 'largeFeature', 'header'],
+    },
+  },
+  Icon: {
+    // `name` is a large enum of standard icon names (or an svgPath object);
+    // we intentionally pass names through without enumerating them.
+    props: ['component', 'name', 'weight'],
+  },
+  Video: { props: ['component', 'url', 'weight'] },
+  AudioPlayer: { props: ['component', 'description', 'url', 'weight'] },
+  Row: {
+    props: ['align', 'children', 'component', 'justify', 'weight'],
+    enums: { justify: JUSTIFY, align: ALIGN },
+  },
+  Column: {
+    props: ['align', 'children', 'component', 'justify', 'weight'],
+    enums: { justify: JUSTIFY, align: ALIGN },
+  },
+  List: {
+    props: ['align', 'children', 'component', 'direction', 'weight'],
+    enums: { direction: ['vertical', 'horizontal'], align: ALIGN },
+  },
+  Card: { props: ['child', 'component', 'weight'] },
+  Tabs: { props: ['component', 'tabs', 'weight'] },
+  Modal: { props: ['component', 'content', 'trigger', 'weight'] },
+  Divider: {
+    props: ['axis', 'component', 'weight'],
+    enums: { axis: ['horizontal', 'vertical'] },
+  },
+  Button: {
+    props: ['action', 'child', 'component', 'variant', 'weight'],
+    enums: { variant: ['default', 'primary', 'borderless'] },
+  },
+  TextField: {
+    props: ['component', 'label', 'validationRegexp', 'value', 'variant', 'weight'],
+    enums: { variant: ['shortText', 'longText', 'number', 'obscured'] },
+  },
+  CheckBox: { props: ['component', 'label', 'value', 'weight'] },
+  ChoicePicker: {
+    props: ['component', 'displayStyle', 'filterable', 'label', 'options', 'value', 'variant', 'weight'],
+    enums: {
+      variant: ['mutuallyExclusive', 'multipleSelection'],
+      displayStyle: ['checkbox', 'chips'],
+    },
+  },
+  Slider: { props: ['component', 'label', 'max', 'min', 'value', 'weight'] },
+  DateTimeInput: {
+    props: ['component', 'enableDate', 'enableTime', 'label', 'max', 'min', 'value', 'weight'],
+  },
+};
+
+describe('vendored catalog component shapes', () => {
+  for (const name of OUR_COMPONENTS) {
+    it(`${name} properties and enums match the implemented contract`, () => {
+      const expected = EXPECTED_SHAPES[name];
+      expect(expected, `missing EXPECTED_SHAPES entry for ${name}`).toBeDefined();
+      const shape = extractShape(catalog, catalog['components'][name]);
+      expect([...shape.props].sort()).toEqual([...expected.props].sort());
+      for (const [prop, values] of Object.entries(expected.enums ?? {})) {
+        expect(
+          [...(shape.enums[prop] ?? [])].sort(),
+          `${name}.${prop} enum drifted`,
+        ).toEqual([...values].sort());
+      }
+      // No unexpected enums appeared on props we treat as free-form
+      // (Icon.name's icon-name enum is deliberately exempt).
+      const knownEnums = new Set(Object.keys(expected.enums ?? {}));
+      if (name === 'Icon') knownEnums.add('name');
+      for (const prop of Object.keys(shape.enums)) {
+        expect(knownEnums.has(prop), `${name}.${prop} gained an enum upstream`).toBe(true);
+      }
+    });
+  }
+});
+
+// --- (c) Envelope messages ---------------------------------------------------
+
+describe('vendored server_to_client envelope', () => {
+  const MESSAGES = [
+    'CreateSurfaceMessage',
+    'UpdateComponentsMessage',
+    'UpdateDataModelMessage',
+    'DeleteSurfaceMessage',
+  ];
+
+  it('defines exactly the four messages we parse', () => {
+    const refs = (envelope['oneOf'] as JsonSchema[]).map((b) => b['$ref']);
+    expect(refs.sort()).toEqual(MESSAGES.map((m) => `#/$defs/${m}`).sort());
+    expect(Object.keys(envelope['$defs']).sort()).toEqual([...MESSAGES].sort());
+  });
+
+  for (const message of MESSAGES) {
+    it(`${message} requires version const A2UI_WIRE_VERSION`, () => {
+      const def = envelope['$defs'][message];
+      expect(def['required']).toContain('version');
+      expect(def['properties']['version']['const']).toBe(A2UI_WIRE_VERSION);
+    });
+  }
+});
+
+// --- (d) Client-side functions -----------------------------------------------
+
+describe('vendored catalog functions map', () => {
+  it('equals our registry keys plus openUrl (action-only, handled by the renderer)', () => {
+    const schemaFunctions = Object.keys(catalog['functions']).sort();
+    const ourFunctions = [...createA2uiFunctionRegistry().keys(), 'openUrl'].sort();
+    expect(schemaFunctions).toEqual(ourFunctions);
+  });
+});