diff --git a/packages/compiler-cli/src/ngtsc/typecheck/extended/api/BUILD.bazel b/packages/compiler-cli/src/ngtsc/typecheck/extended/api/BUILD.bazel
new file mode 100644
index 0000000000..a2174ecf81
--- /dev/null
+++ b/packages/compiler-cli/src/ngtsc/typecheck/extended/api/BUILD.bazel
@@ -0,0 +1,15 @@
+load("//tools:defaults.bzl", "ts_library")
+
+ts_library(
+    name = "api",
+    srcs = glob(
+        ["**/*.ts"],
+    ),
+    visibility = ["//packages/compiler-cli/src/ngtsc:__subpackages__"],
+    deps = [
+        "//packages/compiler",
+        "//packages/compiler-cli/src/ngtsc/diagnostics",
+        "//packages/compiler-cli/src/ngtsc/typecheck/api",
+        "@npm//typescript",
+    ],
+)
diff --git a/packages/compiler-cli/src/ngtsc/typecheck/extended/api/api.ts b/packages/compiler-cli/src/ngtsc/typecheck/extended/api/api.ts
new file mode 100644
index 0000000000..43ab0f1fec
--- /dev/null
+++ b/packages/compiler-cli/src/ngtsc/typecheck/extended/api/api.ts
@@ -0,0 +1,47 @@
+/**
+ * @license
+ * Copyright Google LLC All Rights Reserved.
+ *
+ * Use of this source code is governed by an MIT-style license that can be
+ * found in the LICENSE file at https://angular.io/license
+ */
+
+import {TmplAstNode} from '@angular/compiler';
+import * as ts from 'typescript';
+
+import {ErrorCode} from '../../../diagnostics';
+import {TemplateTypeChecker} from '../../api';
+
+/**
+ * A `ts.Diangostic` with a specific error code.
+ */
+export type TemplateDiagnostic<T extends ErrorCode> = ts.Diagnostic&{code: T};
+
+/**
+ * A Template Check receives information about the template it's checking and returns
+ * information about the diagnostics to be generated.
+ */
+export interface TemplateCheck<T extends ErrorCode> {
+  /** Unique template check code, used for configuration and searching the error. */
+  code: T;
+
+  /** Runs check and returns information about the diagnostics to be generated. */
+  run(ctx: TemplateContext, template: TmplAstNode[]): TemplateDiagnostic<T>[];
+}
+
+/**
+ * The TemplateContext provided to a Template Check to get diagnostic information.
+ */
+export interface TemplateContext {
+  /** Interface that provides information about template nodes. */
+  templateTypeChecker: TemplateTypeChecker;
+
+  /**
+   * TypeScript interface that provides type information about symbols that appear
+   * in the template (it is not to query types outside the Angular component).
+   */
+  typeChecker: ts.TypeChecker;
+
+  /** The `@Component()` class from which the template was obtained. */
+  component: ts.ClassDeclaration;
+}