feat: let AI chat read lesson video transcripts on demand

Add get_lesson_transcript (teacher) and read_lesson_transcript (student)
tools that fetch a lesson's uploaded-video transcript from media_transcript
by the video assetIds. The agents call them only when a question is about
the video's spoken content, so text-only chats keep a cacheable prefix.

packages/ai-assistant/src/prompt/student.ts

@@ -181,6 +181,7 @@ You have read-only, course-scoped tools:
 
 - \`list_course_outline\` — see all sections, lessons, and exercises in this course.
 - \`read_lesson\` — fetch the body of a specific lesson by ID.
+- \`read_lesson_transcript\` — fetch the transcript of a lesson's uploaded video. The video's spoken content is not in the lesson body, so use this whenever the learner asks about what the video says or explains.
 - \`read_exercise\` — fetch an exercise prompt (no answer keys).
 - \`search_course\` — keyword search across this course\u2019s lessons and exercise prompts.
 

packages/ai-assistant/src/prompt/teacher.ts

@@ -37,7 +37,7 @@ export function buildTeacherSystemPrompt(context: AgentContext, options?: BuildT
 
 ## Your Capabilities
 
-You have access to specific tools listed below. Use them to read course content, create sections and lessons, update existing course-outline section metadata via update_section, update existing lesson metadata via update_lesson, write lesson content, create exercises with questions, create exercise question blocks via create_exercise_section, edit exercise-level metadata (title, description, linked lesson, course section placement, order, due date, lock state, allow-multiple-attempts) via update_exercise, edit each existing in-exercise question block heading and intro via update_exercise_section (ids from get_exercise_details sections array — not course section ids), add or update questions inside an existing exercise (use add_questions with exerciseSectionId from that sections array when the exercise groups questions into blocks), update course landing-page copy/settings, check go-live readiness, and publish the course when it is ready. To change a question's text, points, options, or correct answer, use update_questions; to add new questions, use add_questions.
+You have access to specific tools listed below. Use them to read course content, read a lesson's uploaded video transcript via get_lesson_transcript (the video's spoken content is not in the lesson body — use this whenever a question is about what the video says or explains), create sections and lessons, update existing course-outline section metadata via update_section, update existing lesson metadata via update_lesson, write lesson content, create exercises with questions, create exercise question blocks via create_exercise_section, edit exercise-level metadata (title, description, linked lesson, course section placement, order, due date, lock state, allow-multiple-attempts) via update_exercise, edit each existing in-exercise question block heading and intro via update_exercise_section (ids from get_exercise_details sections array — not course section ids), add or update questions inside an existing exercise (use add_questions with exerciseSectionId from that sections array when the exercise groups questions into blocks), update course landing-page copy/settings, check go-live readiness, and publish the course when it is ready. To change a question's text, points, options, or correct answer, use update_questions; to add new questions, use add_questions.
 
 ## Question Types
 

packages/core/src/services/agent/agent-tool-schemas.ts

@@ -14,6 +14,7 @@ import { ZCourseLandingPageUpdate, ZCourseLandingPageMetadataUpdate } from '@cio
 
 export const emptyParam = z.object({});
 export const lessonReadParam = z.object({ lessonId: z.string(), locale: z.string().default('en') });
+export const lessonTranscriptParam = z.object({ lessonId: z.string() });
 export const exerciseReadParam = z.object({ exerciseId: z.string() });
 export const createSectionParam = z.object({ title: z.string().min(1), order: z.number().int().min(0) });
 export const updateSectionParam = z

packages/core/src/services/agent/chat-tools.ts

@@ -27,6 +27,7 @@ import {
 } from '../exercise/exercise';
 import { reorderCourseContent } from '../course/content';
 import { normalizeAgentLessonContent } from './lesson-content';
+import { getLessonVideoTranscript } from './lesson-transcript';
 import { buildUpdatedQuestions } from './question-update';
 import { updateCourseLandingPageService } from '../course/landing-page';
 import { getCourseGoLiveReadiness, publishCourseWhenReady } from '../course/go-live-readiness';
@@ -50,6 +51,7 @@ import {
   fetchDocumentationUrlParam,
   goLiveParam,
   lessonReadParam,
+  lessonTranscriptParam,
   reorderContentParam,
   updateContentParam,
   updateCourseLandingPageParam,
@@ -487,6 +489,19 @@ export function buildAgentTools(
       }
     }),
 
+    get_lesson_transcript: tool({
+      description:
+        "Get the transcript of a lesson's uploaded video(s). The spoken content of a video is NOT part of the lesson's HTML content, so call this whenever a question is about what the video says, explains, or demonstrates. Only uploaded videos are transcribed — embedded links (YouTube, etc.) return no transcript.",
+      inputSchema: lessonTranscriptParam,
+      execute: async (args) => {
+        return executeAgentTool('get_lesson_transcript', { orgId, userId, courseId, args }, async () => {
+          await verifyLessonBelongsToCourse(args.lessonId, courseId);
+
+          return getLessonVideoTranscript(args.lessonId, orgId);
+        });
+      }
+    }),
+
     get_exercise_details: tool({
       description:
         'Get an exercise with sections, questions, and answer options from this course. Each sections entry has an id — use it with update_exercise_section to change that question block title or description.',

packages/core/src/services/agent/lesson-transcript.ts

@@ -0,0 +1,65 @@
+import { listMediaTranscriptsByAssetIds } from '@cio/db/queries/media-transcript';
+import { getLesson } from '../lesson/lesson';
+
+export interface LessonVideoTranscriptResult {
+  lessonId: string;
+  title: string;
+  hasTranscript: boolean;
+  transcript: string | null;
+  message?: string;
+}
+
+/**
+ * Assembles the transcript text for a lesson's uploaded video(s).
+ *
+ * Lesson `videos[]` carry an `assetId` for uploaded videos; the transcription
+ * pipeline stores Whisper output in `media_transcript` keyed by that assetId.
+ * YouTube/embedded links have no assetId and are never transcribed.
+ */
+export async function getLessonVideoTranscript(lessonId: string, orgId: string): Promise<LessonVideoTranscriptResult> {
+  const lesson = await getLesson(lessonId);
+  const lessonWithVideos = lesson as {
+    id: string;
+    title: string;
+    videos?: Array<{ assetId?: string }> | null;
+  };
+
+  const assetIds = (lessonWithVideos.videos ?? [])
+    .map((video) => video.assetId)
+    .filter((assetId): assetId is string => typeof assetId === 'string' && assetId.length > 0);
+
+  if (assetIds.length === 0) {
+    return {
+      lessonId: lesson.id,
+      title: lesson.title,
+      hasTranscript: false,
+      transcript: null,
+      message:
+        'This lesson has no uploaded video with a transcript. Only uploaded videos are transcribed — embedded links (YouTube, Google Drive, etc.) are not.'
+    };
+  }
+
+  const transcripts = await listMediaTranscriptsByAssetIds(assetIds, orgId);
+  const transcript = transcripts
+    .map((row) => row.text?.trim())
+    .filter((text): text is string => Boolean(text))
+    .join('\n\n');
+
+  if (!transcript) {
+    return {
+      lessonId: lesson.id,
+      title: lesson.title,
+      hasTranscript: false,
+      transcript: null,
+      message:
+        'This lesson has an uploaded video, but no transcript is available yet — transcription may still be processing.'
+    };
+  }
+
+  return {
+    lessonId: lesson.id,
+    title: lesson.title,
+    hasTranscript: true,
+    transcript
+  };
+}