diff --git a/schema/app-block.manifest.schema.json b/schema/app-block.manifest.schema.json
index 4c3d7071..ff11cd26 100644
--- a/schema/app-block.manifest.schema.json
+++ b/schema/app-block.manifest.schema.json
@@ -480,9 +480,21 @@
                     "type": "string",
                     "pattern": "^(/[A-Za-z_][A-Za-z0-9_]{0,63}){1,4}$"
                   }
+                },
+                "schema": {
+                  "description": "Optional. A JSON Schema SUBSET that every document's `data` in this collection must match. The server checks it on every create and update and refuses a document that does not match with 400 `schema_violation`, whose message names the first failing JSON pointer into `data` (for example \"/title\"); counters and marks are not checked. Without a schema, documents are not checked. Supported keywords only: type (object, array, string, number, integer, boolean, null, or an array of them), properties, required, additionalProperties (true, false or a schema), items (one schema for every element), enum, const, minLength, maxLength, pattern, minimum, maximum, minItems, maxItems and description; any other keyword is refused at submit with a message naming it. Keywords that do not apply to a value's type are ignored; string lengths count code points; `pattern` is a JavaScript regular expression (the \"u\" flag), unanchored, of at most 256 characters, and a schema with a `pattern` must also declare a `maxLength` of at most 1000; a pattern that can backtrack catastrophically (analysed with the \"u\" flag, as the store runs it) is refused at submit. At most 16 patterns per schema and 32 across all of the manifest's collection schemas together, schemas nested at most 16 deep, and at most 16384 bytes of JSON. Not allowed on a `write` \"none\" collection. Changing a schema does not re-check documents already stored; they are checked when next written.",
+                  "$ref": "#/$defs/storageCollectionSchema"
                 }
               },
               "allOf": [
+                {
+                  "$comment": "No document body is ever written in a write:\"none\" collection, so a schema there would check nothing.",
+                  "if": {
+                    "required": ["write"],
+                    "properties": { "write": { "const": "none" } }
+                  },
+                  "then": { "properties": { "schema": false } }
+                },
                 {
                   "$comment": "A shared collection must state its write policy; a private one carries none of the shared-only fields.",
                   "if": {
@@ -560,6 +572,50 @@
       }
     }
   },
+  "$defs": {
+    "storageCollectionSchema": {
+      "type": "object",
+      "description": "One schema of the storage collection-schema subset (see `storage.collections.<name>.schema`). Depth, size, pattern-count and min-greater-than-max limits, and whether a pattern compiles, are checked by the server, not by this schema.",
+      "additionalProperties": false,
+      "properties": {
+        "type": {
+          "anyOf": [
+            { "$ref": "#/$defs/storageCollectionSchemaType" },
+            {
+              "type": "array",
+              "minItems": 1,
+              "uniqueItems": true,
+              "items": { "$ref": "#/$defs/storageCollectionSchemaType" }
+            }
+          ]
+        },
+        "properties": {
+          "type": "object",
+          "additionalProperties": { "$ref": "#/$defs/storageCollectionSchema" }
+        },
+        "required": { "type": "array", "uniqueItems": true, "items": { "type": "string" } },
+        "additionalProperties": {
+          "anyOf": [{ "type": "boolean" }, { "$ref": "#/$defs/storageCollectionSchema" }]
+        },
+        "items": { "$ref": "#/$defs/storageCollectionSchema" },
+        "enum": { "type": "array", "minItems": 1 },
+        "const": {},
+        "minLength": { "type": "integer", "minimum": 0 },
+        "maxLength": { "type": "integer", "minimum": 0 },
+        "pattern": { "type": "string", "maxLength": 256 },
+        "minimum": { "type": "number" },
+        "maximum": { "type": "number" },
+        "minItems": { "type": "integer", "minimum": 0 },
+        "maxItems": { "type": "integer", "minimum": 0 },
+        "description": { "type": "string" }
+      },
+      "if": { "required": ["pattern"] },
+      "then": { "required": ["maxLength"], "properties": { "maxLength": { "maximum": 1000 } } }
+    },
+    "storageCollectionSchemaType": {
+      "enum": ["object", "array", "string", "number", "integer", "boolean", "null"]
+    }
+  },
   "allOf": [
     {
       "$comment": "outputDir is required whenever buildCommand is set. NOTE: the server-owned iframe.src and trustTier fields are rejected by the platform validator (and the CLI in Go) with clearer error messages than JSON Schema's `not`; they are declared in `properties` above only so the schema documents them.",