diff --git a/schema/content-manifest.schema.json b/schema/content-manifest.schema.json
index bbddda5..60f813c 100644
--- a/schema/content-manifest.schema.json
+++ b/schema/content-manifest.schema.json
@@ -380,5 +380,5 @@
   ],
   "title": "ContentManifest",
   "type": "object",
-  "x-schema-version": "1.11"
+  "x-schema-version": "1.13"
 }
diff --git a/schema/engine-version.txt b/schema/engine-version.txt
index 5a03fb7..ca222b7 100644
--- a/schema/engine-version.txt
+++ b/schema/engine-version.txt
@@ -1 +1 @@
-0.20.0
+0.23.0
diff --git a/schema/lesson.schema.json b/schema/lesson.schema.json
index c97637b..861b102 100644
--- a/schema/lesson.schema.json
+++ b/schema/lesson.schema.json
@@ -266,6 +266,19 @@
           "default": null,
           "description": "Optional placeholder text shown inside the input (``type`` mode) before the user starts typing.",
           "title": "Placeholder"
+        },
+        "stable_id": {
+          "anyOf": [
+            {
+              "$ref": "#/$defs/SlugId"
+            },
+            {
+              "type": "null"
+            }
+          ],
+          "default": null,
+          "title": "Stable Id",
+          "description": "engine#91 - schema 1.12 (additive). Element-level counterpart to the exercise/card stable_id (engine#90): identifies THIS blank for progress/SRS joins below the exercise level, so an answer-text correction (moving `accept[0]`) does not orphan its learner row. Once published it NEVER changes. Shares the SAME per-set stable_id namespace as card/exercise ids (checked the same way: collectStableIds set-wide, the schema's E-STABLE-ID-DUP rule per-document). Opaque mint-once value, NOT derived from content. Optional: content without it validates unchanged. Uses the strict $defs/SlugId shape (hyphens only) - unlike the card/exercise field, this is a brand-new field with no legacy underscore-bearing ids to grandfather."
         }
       },
       "required": [
@@ -396,6 +409,20 @@
           "description": "Optional inline worked examples shown BEFORE the answer controls, to help the learner understand the task (schema v1.5, additive). Each is plain text or a syntax-highlighted code snippet (see ``InlineExample.language``). Author responsibility not to spoil the answer. Independent of the per-type fields; absent on exercises that need no example.",
           "title": "Examples"
         },
+        "explanation": {
+          "anyOf": [
+            {
+              "maxLength": 2000,
+              "type": "string"
+            },
+            {
+              "type": "null"
+            }
+          ],
+          "default": null,
+          "description": "Optional Markdown explanation of WHY the answer/grammar is what it is (e.g. word order, a grammatical case), shown AFTER the learner answers - regardless of correct or incorrect - unlike ``hint`` (on demand, before/during answering) and ``examples`` (worked examples shown before answering, must not spoil it). 2000 chars, twice ``hint``'s 1000: Markdown structure (a short list, bold terms) eats characters faster than a single-line nudge, and a real \"why\" often runs longer than a hint. Not restricted to any exercise type. Additive; schema_version 1.13.",
+          "title": "Explanation"
+        },
         "ext_payload": {
           "additionalProperties": true,
           "description": "Opaque per-exercise payload for an ``ext:`` extension type. The core engine does not interpret it; the registered extension validator does. Absent on core exercises.",
@@ -899,6 +926,19 @@
           "title": "Correct",
           "type": "boolean"
         },
+        "stable_id": {
+          "anyOf": [
+            {
+              "$ref": "#/$defs/SlugId"
+            },
+            {
+              "type": "null"
+            }
+          ],
+          "default": null,
+          "title": "Stable Id",
+          "description": "engine#91 - schema 1.12 (additive). Element-level counterpart to the exercise/card stable_id (engine#90): identifies THIS option for progress/SRS joins below the exercise level. Once published it NEVER changes. Shares the SAME per-set stable_id namespace as card/exercise ids (checked the same way: collectStableIds set-wide, the schema's E-STABLE-ID-DUP rule per-document). Opaque mint-once value, NOT derived from content. Optional: content without it validates unchanged. Uses the strict $defs/SlugId shape (hyphens only) - unlike the card/exercise field, this is a brand-new field with no legacy underscore-bearing ids to grandfather."
+        },
         "text": {
           "description": "The option text shown to the learner. Unique within the exercise - the text IS the option, so a duplicate would be ambiguous.",
           "maxLength": 500,
@@ -930,6 +970,19 @@
           "minLength": 1,
           "title": "Right",
           "type": "string"
+        },
+        "stable_id": {
+          "anyOf": [
+            {
+              "$ref": "#/$defs/SlugId"
+            },
+            {
+              "type": "null"
+            }
+          ],
+          "default": null,
+          "title": "Stable Id",
+          "description": "engine#91 - schema 1.12 (additive). Element-level counterpart to the exercise/card stable_id (engine#90): identifies THIS pair for progress/SRS joins below the exercise level, so an answer-text correction (moving `left`/`right`) does not orphan its learner row. Once published it NEVER changes. Shares the SAME per-set stable_id namespace as card/exercise ids (checked the same way: collectStableIds set-wide, the schema's E-STABLE-ID-DUP rule per-document). Opaque mint-once value, NOT derived from content. Optional: content without it validates unchanged. Uses the strict $defs/SlugId shape (hyphens only) - unlike the card/exercise field, this is a brand-new field with no legacy underscore-bearing ids to grandfather."
         }
       },
       "required": [
@@ -1205,5 +1258,5 @@
   ],
   "title": "Lesson",
   "type": "object",
-  "x-schema-version": "1.11"
+  "x-schema-version": "1.13"
 }
diff --git a/schema/quality-rules.json b/schema/quality-rules.json
index 849974f..bb6f88f 100644
--- a/schema/quality-rules.json
+++ b/schema/quality-rules.json
@@ -1,5 +1,5 @@
 {
-  "$schema-version": "1.11",
+  "$schema-version": "1.13",
   "_comment": "GENERATED from scripts/generate_lesson_schema.py (EXP-039). Do not edit. Shared quality minimums for the content quality gate (app + content repo).",
   "rules": {
     "minExerciseTypes": 2,
diff --git a/scripts/validate_with_engine.mjs b/scripts/validate_with_engine.mjs
index 5e86953..156b6a5 100644
--- a/scripts/validate_with_engine.mjs
+++ b/scripts/validate_with_engine.mjs
@@ -47,6 +47,11 @@ const ADOPTED_EXTENSIONS = [
   "ext:al-error-correction",
   "ext:al-reading-comprehension",
   "ext:al-graded-quiz",
+  "ext:al-dictation",
+  "ext:al-image-description",
+  "ext:al-speak-and-record",
+  "ext:al-audio-choice",
+  "ext:al-audio-tiles",
 ].map((type) => ({ type, major: 1, validate: () => [] }));
 
 const withExtensions = { extensions: ADOPTED_EXTENSIONS };