diff --git a/Cargo.lock b/Cargo.lock
index 154c621..6d5125f 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -840,6 +840,7 @@ dependencies = [
  "tower_governor",
  "tracing",
  "tracing-subscriber",
+ "utoipa",
  "uuid",
  "zip",
 ]
diff --git a/services/cms-service/Cargo.toml b/services/cms-service/Cargo.toml
index 4021874..144575d 100644
--- a/services/cms-service/Cargo.toml
+++ b/services/cms-service/Cargo.toml
@@ -28,6 +28,7 @@ openidconnect.workspace = true
 anyhow.workspace = true
 thiserror.workspace = true
 http.workspace = true
+utoipa.workspace = true
 zip = "0.6"
 mime_guess = "2.0"
 base64 = "0.22.1"
diff --git a/services/cms-service/migrations/20231219000000_initial_schema.sql b/services/cms-service/migrations/20231219000000_initial_schema.sql
index 420f88c..e898029 100644
--- a/services/cms-service/migrations/20231219000000_initial_schema.sql
+++ b/services/cms-service/migrations/20231219000000_initial_schema.sql
@@ -47,4 +47,4 @@ BEGIN
 END;
 $$ language 'plpgsql';
 
-CREATE TRIGGER update_courses_updated_at BEFORE UPDATE ON courses FOR EACH ROW EXECUTE PROCEDURE update_updated_at_column();
+CREATE TRIGGER update_courses_updated_at BEFORE UPDATE ON courses FOR EACH ROW EXECUTE PROCEDURE update_updated_at_column();
\ No newline at end of file
diff --git a/services/cms-service/migrations/20260427000000_add_external_sam_id_to_courses.sql b/services/cms-service/migrations/20260427000000_add_external_sam_id_to_courses.sql
new file mode 100644
index 0000000..e7c32de
--- /dev/null
+++ b/services/cms-service/migrations/20260427000000_add_external_sam_id_to_courses.sql
@@ -0,0 +1,6 @@
+ALTER TABLE courses
+ADD COLUMN IF NOT EXISTS external_sam_id BIGINT;
+
+CREATE INDEX IF NOT EXISTS idx_courses_org_external_sam_id
+ON courses (organization_id, external_sam_id)
+WHERE external_sam_id IS NOT NULL;
diff --git a/services/cms-service/src/external_handlers.rs b/services/cms-service/src/external_handlers.rs
index f137865..6100f25 100644
--- a/services/cms-service/src/external_handlers.rs
+++ b/services/cms-service/src/external_handlers.rs
@@ -42,10 +42,11 @@ pub async fn create_course_external(
     let description = payload.description.as_deref();
     
     let course = sqlx::query_as::<_, Course>(
-        "INSERT INTO courses (organization_id, title, description, instructor_id, pacing_mode) 
-         VALUES ($1, $2, $3, '00000000-0000-0000-0000-000000000001', $4) RETURNING *"
+        "INSERT INTO courses (organization_id, external_sam_id, title, description, instructor_id, pacing_mode) 
+         VALUES ($1, $2, $3, $4, '00000000-0000-0000-0000-000000000001', $5) RETURNING *"
     )
     .bind(org_id)
+    .bind(payload.external_sam_id)
     .bind(title)
     .bind(description)
     .bind(payload.pacing_mode.as_deref().unwrap_or("self_paced"))
@@ -94,6 +95,8 @@ pub struct ExternalCreateCoursePayload {
     pub title: String,
     pub description: Option<String>,
     pub pacing_mode: Option<String>,
+    #[serde(alias = "idcursoabierto", alias = "id_curso_abierto")]
+    pub external_sam_id: Option<i64>,
     // Selección directa de plantilla opcional
     pub template_id: Option<Uuid>,
     // Selección de respaldo (fallback) opcional por nivel/tipo de curso/tipo de test
diff --git a/services/cms-service/src/handlers_sam.rs b/services/cms-service/src/handlers_sam.rs
index dad7544..196e7c2 100644
--- a/services/cms-service/src/handlers_sam.rs
+++ b/services/cms-service/src/handlers_sam.rs
@@ -232,10 +232,9 @@ pub async fn sync_sam_assignments(
         // Obtener el ID del curso de OpenCCB a partir del ID del curso SAM
         // Esto asume que tienes una tabla de mapeo o que el ID del curso SAM coincide con el external_id del curso en OpenCCB
         let course_result = sqlx::query_as::<_, (Uuid,)>(
-            "SELECT id FROM courses WHERE external_sam_id = $1 OR id = $2"
+            "SELECT id FROM courses WHERE external_sam_id = $1"
         )
         .bind(assignment.id_curso_abierto as i64)
-        .bind(assignment.id_curso_abierto)
         .fetch_optional(&pool)
         .await;
 
@@ -484,10 +483,9 @@ pub async fn sync_all_sam(
 
         for assignment in sam_assignments {
             let course_result = sqlx::query_as::<_, (Uuid,)>(
-                "SELECT id FROM courses WHERE external_sam_id = $1 OR id = $2"
+                "SELECT id FROM courses WHERE external_sam_id = $1"
             )
             .bind(assignment.id_curso_abierto as i64)
-            .bind(assignment.id_curso_abierto)
             .fetch_optional(&pool)
             .await;
 
diff --git a/services/cms-service/src/main.rs b/services/cms-service/src/main.rs
index c16a5ba..23d65bc 100644
--- a/services/cms-service/src/main.rs
+++ b/services/cms-service/src/main.rs
@@ -16,6 +16,7 @@ mod handlers_admin;
 mod handlers_embeddings;
 mod handlers_sam;
 mod handlers_plugins;
+mod openapi;
 mod webhooks;
 
 use axum::{
@@ -34,6 +35,7 @@ use std::time::Duration;
 use tower_http::cors::CorsLayer;
 use tower_http::set_header::SetResponseHeaderLayer;
 use tower_http::trace::TraceLayer;
+use utoipa::OpenApi;
 
 #[tokio::main]
 async fn main() {
@@ -594,7 +596,26 @@ async fn main() {
             get(handlers_branding::get_organization_branding),
         );
 
-    let public_routes = Router::new()
+        let public_routes = Router::new()
+                .route("/api-docs/openapi.json", get(|| async {
+                        axum::Json(openapi::ApiDoc::openapi())
+                }))
+                .route("/scalar", get(|| async {
+                        axum::response::Html(r#"
+<!doctype html>
+<html>
+    <head>
+        <title>OpenCCB CMS API</title>
+        <meta charset="utf-8" />
+        <meta name="viewport" content="width=device-width, initial-scale=1" />
+    </head>
+    <body>
+        <script id="api-reference" data-url="./api-docs/openapi.json"></script>
+        <script src="https://cdn.jsdelivr.net/npm/@scalar/api-reference"></script>
+    </body>
+</html>
+                        "#)
+                }))
         .nest("/api/external", api_routes)
         .route(
             "/api/assets/s3-proxy/{bucket}/{*key}",
diff --git a/services/cms-service/src/openapi.rs b/services/cms-service/src/openapi.rs
new file mode 100644
index 0000000..f801bf1
--- /dev/null
+++ b/services/cms-service/src/openapi.rs
@@ -0,0 +1,107 @@
+#![allow(dead_code)]
+
+use utoipa::OpenApi;
+
+#[derive(utoipa::ToSchema, serde::Serialize, serde::Deserialize)]
+pub struct ExternalCreateCoursePayloadSchema {
+    /// Obligatorio. No debe ser vacío.
+    pub title: String,
+    /// Opcional: puede omitirse o enviarse como `null`.
+    pub description: Option<String>,
+    /// Opcional: puede omitirse o enviarse como `null`.
+    pub pacing_mode: Option<String>,
+    /// Opcional: idCursoAbierto del sistema SAM.
+    /// También se acepta como `idcursoabierto` o `id_curso_abierto` en el payload real.
+    pub external_sam_id: Option<i64>,
+    /// Opcional: UUID de plantilla específica.
+    pub template_id: Option<String>,
+    /// Opcional: fallback de selección de plantilla por nivel.
+    pub template_level: Option<String>,
+    /// Opcional: fallback de selección de plantilla por tipo de curso.
+    pub template_course_type: Option<String>,
+    /// Opcional: fallback de selección de plantilla por tipo de test.
+    pub template_test_type: Option<String>,
+    /// Opcional: título del módulo creado al aplicar plantilla.
+    pub module_title: Option<String>,
+    /// Opcional: título de la lección creada al aplicar plantilla.
+    pub lesson_title: Option<String>,
+}
+
+#[derive(utoipa::ToSchema, serde::Serialize)]
+pub struct ExternalCourseEnvelopeSchema {
+    pub course: serde_json::Value,
+    pub template_applied: bool,
+    pub template_id: Option<String>,
+    pub lesson_id: Option<String>,
+}
+
+#[derive(OpenApi)]
+#[openapi(
+    info(
+        title = "OpenCCB CMS API",
+        version = "1.0.0",
+        description = "API del CMS para gestión interna y endpoints externos por API key.\n\nReglas de nulabilidad y arreglos (aplican a todos los endpoints de esta API):\n- Campos opcionales (Option): pueden omitirse o enviarse como null.\n- Campos de arreglo no opcionales (Vec): deben enviarse como arreglo; pueden ser [] pero no null.\n- Objetos requeridos del payload: no deben enviarse como null."
+    ),
+    paths(
+        create_course_external,
+        get_course_external,
+        trigger_transcription_external,
+    ),
+    components(
+        schemas(
+            ExternalCreateCoursePayloadSchema,
+            ExternalCourseEnvelopeSchema,
+        )
+    ),
+    tags(
+        (name = "External", description = "Integración externa del CMS")
+    )
+)]
+pub struct ApiDoc;
+
+#[utoipa::path(
+    post,
+    path = "/api/external/v1/courses",
+    tag = "External",
+    request_body = ExternalCreateCoursePayloadSchema,
+    responses(
+        (status = 200, description = "Curso creado exitosamente"),
+        (status = 400, description = "Payload inválido o plantilla no encontrada"),
+        (status = 401, description = "X-API-Key inválida o ausente"),
+        (status = 500, description = "Error interno del servidor")
+    ),
+    security(("ApiKey" = []))
+)]
+pub fn create_course_external() {}
+
+#[utoipa::path(
+    get,
+    path = "/api/external/v1/courses/{id}",
+    tag = "External",
+    params(
+        ("id" = String, Path, description = "UUID del curso")
+    ),
+    responses(
+        (status = 200, description = "Curso encontrado"),
+        (status = 401, description = "X-API-Key inválida o ausente"),
+        (status = 404, description = "Curso no encontrado")
+    ),
+    security(("ApiKey" = []))
+)]
+pub fn get_course_external() {}
+
+#[utoipa::path(
+    post,
+    path = "/api/external/v1/lessons/{id}/transcribe",
+    tag = "External",
+    params(
+        ("id" = String, Path, description = "UUID de la lección")
+    ),
+    responses(
+        (status = 202, description = "Transcripción encolada"),
+        (status = 401, description = "X-API-Key inválida o ausente"),
+        (status = 404, description = "Lección no encontrada")
+    ),
+    security(("ApiKey" = []))
+)]
+pub fn trigger_transcription_external() {}
diff --git a/services/lms-service/migrations/20260427000000_add_external_sam_id_to_courses.sql b/services/lms-service/migrations/20260427000000_add_external_sam_id_to_courses.sql
new file mode 100644
index 0000000..e7c32de
--- /dev/null
+++ b/services/lms-service/migrations/20260427000000_add_external_sam_id_to_courses.sql
@@ -0,0 +1,6 @@
+ALTER TABLE courses
+ADD COLUMN IF NOT EXISTS external_sam_id BIGINT;
+
+CREATE INDEX IF NOT EXISTS idx_courses_org_external_sam_id
+ON courses (organization_id, external_sam_id)
+WHERE external_sam_id IS NOT NULL;
diff --git a/services/lms-service/src/handlers.rs b/services/lms-service/src/handlers.rs
index 8078c53..093e017 100644
--- a/services/lms-service/src/handlers.rs
+++ b/services/lms-service/src/handlers.rs
@@ -1009,8 +1009,8 @@ pub async fn ingest_course(
 
     // 2. Insertar o actualizar (Upsert) Curso
     sqlx::query(
-        "INSERT INTO courses (id, title, description, instructor_id, start_date, end_date, passing_percentage, certificate_template, updated_at, organization_id, pacing_mode, price, currency)
-         VALUES ($1, $2, $3, $4, $5, $6, $7, $8, $9, $10, $11, $12, $13)
+        "INSERT INTO courses (id, title, description, instructor_id, start_date, end_date, passing_percentage, certificate_template, updated_at, organization_id, pacing_mode, price, currency, external_sam_id)
+         VALUES ($1, $2, $3, $4, $5, $6, $7, $8, $9, $10, $11, $12, $13, $14)
          ON CONFLICT (id) DO UPDATE SET
             title = EXCLUDED.title,
             description = EXCLUDED.description,
@@ -1023,7 +1023,8 @@ pub async fn ingest_course(
             organization_id = EXCLUDED.organization_id,
             pacing_mode = EXCLUDED.pacing_mode,
             price = EXCLUDED.price,
-            currency = EXCLUDED.currency"
+                currency = EXCLUDED.currency,
+                external_sam_id = EXCLUDED.external_sam_id"
     )
     .bind(payload.course.id)
     .bind(&payload.course.title)
@@ -1038,6 +1039,7 @@ pub async fn ingest_course(
     .bind(&payload.course.pacing_mode)
     .bind(payload.course.price)
     .bind(&payload.course.currency)
+    .bind(payload.course.external_sam_id)
     .execute(&mut *tx)
     .await
     .map_err(|e: sqlx::Error| {
diff --git a/services/lms-service/src/main.rs b/services/lms-service/src/main.rs
index b8e0a94..b393695 100644
--- a/services/lms-service/src/main.rs
+++ b/services/lms-service/src/main.rs
@@ -470,7 +470,7 @@ async fn main() {
     <meta name="viewport" content="width=device-width, initial-scale=1" />
   </head>
   <body>
-    <script id="api-reference" data-url="/api-docs/openapi.json"></script>
+    <script id="api-reference" data-url="./api-docs/openapi.json"></script>
     <script src="https://cdn.jsdelivr.net/npm/@scalar/api-reference"></script>
   </body>
 </html>
diff --git a/services/lms-service/src/openapi.rs b/services/lms-service/src/openapi.rs
index 545c22e..f5bb3f0 100644
--- a/services/lms-service/src/openapi.rs
+++ b/services/lms-service/src/openapi.rs
@@ -50,13 +50,26 @@ pub struct LessonSchema {
     pub created_at: String,
 }
 
-/// Módulo de curso
+/// Módulo de curso dentro de la ingesta.
+///
+/// `lessons` puede venir como `[]` (vacío), pero no debe venir `null`.
 #[derive(utoipa::ToSchema, serde::Serialize)]
-pub struct ModuleSchema {
+pub struct IngestModuleSchema {
     pub id: String,
     pub title: String,
     pub position: i32,
     pub created_at: String,
+    pub lessons: Vec<LessonSchema>,
+}
+
+/// Instructor asignado al curso.
+#[derive(utoipa::ToSchema, serde::Serialize)]
+pub struct CourseInstructorSchema {
+    pub id: String,
+    pub user_id: String,
+    /// Ej: "primary", "instructor", "assistant"
+    pub role: String,
+    pub created_at: String,
 }
 
 /// Organización
@@ -71,6 +84,7 @@ pub struct OrgSchema {
 #[derive(utoipa::ToSchema, serde::Serialize)]
 pub struct CourseSchema {
     pub id: String,
+    pub external_sam_id: Option<i64>,
     pub title: String,
     pub description: Option<String>,
     pub price: f64,
@@ -82,12 +96,17 @@ pub struct CourseSchema {
 /// Payload completo de ingesta de curso — usado por el sistema externo para crear/actualizar cursos
 #[derive(utoipa::ToSchema, serde::Serialize)]
 pub struct IngestCourseRequest {
+    /// Obligatorio. No debe ser `null`.
     pub organization: OrgSchema,
+    /// Obligatorio. No debe ser `null`.
     pub course: CourseSchema,
+    /// Puede venir como `[]` (vacío), pero no `null`.
     pub grading_categories: Vec<GradingCategorySchema>,
-    pub modules: Vec<ModuleSchema>,
-    pub lessons: Vec<LessonSchema>,
-    pub instructors: Vec<String>,
+    /// Puede venir como `[]` (vacío), pero no `null`.
+    /// Las lecciones se envían dentro de cada módulo en `modules[].lessons`.
+    pub modules: Vec<IngestModuleSchema>,
+    /// Opcional. Puede omitirse o venir como `null` o `[]`.
+    pub instructors: Option<Vec<CourseInstructorSchema>>,
 }
 
 /// Entrada del catálogo Tipo Nota
@@ -107,7 +126,7 @@ pub struct TipoNotaSchema {
     info(
         title = "OpenCCB LMS — API de Integración",
         version = "1.0.0",
-        description = "API para integrar plataformas externas: creación de cursos, inscripción de alumnos y sincronización de notas."
+        description = "API para integrar plataformas externas: creación de cursos, inscripción de alumnos y sincronización de notas.\n\nReglas de nulabilidad y arreglos (aplican a todos los endpoints de esta API):\n- Campos opcionales (Option): pueden omitirse o enviarse como null.\n- Campos de arreglo no opcionales (Vec): deben enviarse como arreglo; pueden ser [] pero no null.\n- Objetos requeridos del payload: no deben enviarse como null.\n- En /ingest, enviar modules: [] reemplaza la estructura del curso y elimina módulos/lecciones previos en LMS."
     ),
     paths(
         ingest_course,
@@ -121,8 +140,9 @@ pub struct TipoNotaSchema {
             IngestCourseRequest,
             OrgSchema,
             CourseSchema,
-            ModuleSchema,
+            IngestModuleSchema,
             LessonSchema,
+            CourseInstructorSchema,
             GradingCategorySchema,
             EnrollRequest,
             GradeSubmissionRequest,
diff --git a/shared/common/src/models.rs b/shared/common/src/models.rs
index 4aca313..94d2555 100644
--- a/shared/common/src/models.rs
+++ b/shared/common/src/models.rs
@@ -8,6 +8,8 @@ use uuid::Uuid;
 pub struct Course {
     pub id: Uuid,
     pub organization_id: Uuid,
+    #[serde(default, alias = "idcursoabierto", alias = "id_curso_abierto")]
+    pub external_sam_id: Option<i64>,
     pub title: String,
     pub description: Option<String>,
     pub instructor_id: Uuid,
@@ -31,6 +33,7 @@ impl Default for Course {
         Self {
             id: Uuid::new_v4(),
             organization_id: Uuid::new_v4(),
+            external_sam_id: None,
             title: String::new(),
             description: None,
             instructor_id: Uuid::new_v4(),