thePunderWoman · Nov 11, 2026 · Jul 8, 2026
diff --git a/goldens/public-api/compiler-cli/compiler_options.api.md b/goldens/public-api/compiler-cli/compiler_options.api.md
@@ -77,6 +77,7 @@ export interface TypeCheckingOptions {
     strictInputAccessModifiers?: boolean;
     strictInputTypes?: boolean;
     strictLiteralTypes?: boolean;
+    strictNgTemplateTypes?: boolean;
     strictNullInputTypes?: boolean;
     strictOutputEventTypes?: boolean;
     strictSafeNavigationTypes?: boolean;

diff --git a/packages/compiler-cli/preprocessor/src/compiler_options.ts b/packages/compiler-cli/preprocessor/src/compiler_options.ts
@@ -103,6 +103,7 @@ export interface NgpCompilerOptions {
   strictLiteralTypes?: boolean;
   strictUnclaimedEventNames?: boolean;
   strictUnknownElements?: boolean;
+  strictNgTemplateTypes?: boolean;
   typeCheckHostBindings?: boolean;
 
   // Diagnostics (`DiagnosticOptions`).

diff --git a/packages/compiler-cli/preprocessor/src/tcb.ts b/packages/compiler-cli/preprocessor/src/tcb.ts
@@ -226,6 +226,7 @@ export function buildTypeCheckingConfig(
       allowDomEventAssertion: true,
       checkUnclaimedEventNames: false,
       checkUnknownElements: false,
+      checkTypeOfNgTemplateBindings: false,
     };
   } else {
     typeCheckingConfig = {
@@ -264,6 +265,7 @@ export function buildTypeCheckingConfig(
       allowDomEventAssertion: true,
       checkUnclaimedEventNames: false,
       checkUnknownElements: false,
+      checkTypeOfNgTemplateBindings: false,
     };
   }
 
@@ -305,6 +307,9 @@ export function buildTypeCheckingConfig(
   if (options.strictUnknownElements !== undefined) {
     typeCheckingConfig.checkUnknownElements = options.strictUnknownElements;
   }
+  if (options.strictNgTemplateTypes !== undefined) {
+    typeCheckingConfig.checkTypeOfNgTemplateBindings = options.strictNgTemplateTypes;
+  }
   typeCheckingConfig.typeCheckHostBindings = options.typeCheckHostBindings ?? true;
   typeCheckingConfig.usePoisonedData =
     usePoisonedData || Boolean(options._compilePoisonedComponents);

diff --git a/packages/compiler-cli/src/ngtsc/core/api/src/public_options.ts b/packages/compiler-cli/src/ngtsc/core/api/src/public_options.ts
@@ -235,6 +235,15 @@ export interface TypeCheckingOptions {
    * Defaults to `false`.
    */
   strictUnknownElements?: boolean;
+
+  /**
+   * Whether to check if unknown properties are bound to `<ng-template>`.
+   *
+   * If this is `true`, an error will be reported for unknown properties bound to an `<ng-template>`.
+   *
+   * Defaults to `false`.
+   */
+  strictNgTemplateTypes?: boolean;
 }
 
 /**

diff --git a/packages/compiler-cli/src/ngtsc/core/src/compiler.ts b/packages/compiler-cli/src/ngtsc/core/src/compiler.ts
@@ -1131,6 +1131,8 @@ export class NgCompiler {
           this.options.extendedDiagnostics?.defaultCategory || DiagnosticCategoryLabel.Warning,
         allowSignalsInTwoWayBindings,
         allowDomEventAssertion,
+        checkTypeOfNgTemplateBindings: false, // 3p-only
+        // g3-only checkTypeOfNgTemplateBindings: true,
       };
     } else {
       typeCheckingConfig = {
@@ -1164,6 +1166,8 @@ export class NgCompiler {
         allowSignalsInTwoWayBindings,
         allowDomEventAssertion,
         checkUnknownElements: false,
+        checkTypeOfNgTemplateBindings: false, // 3p-only
+        // g3-only checkTypeOfNgTemplateBindings: true,
       };
     }
 
@@ -1205,6 +1209,9 @@ export class NgCompiler {
     if (this.options.strictLiteralTypes !== undefined) {
       typeCheckingConfig.strictLiteralTypes = this.options.strictLiteralTypes;
     }
+    if (this.options.strictNgTemplateTypes !== undefined) {
+      typeCheckingConfig.checkTypeOfNgTemplateBindings = this.options.strictNgTemplateTypes;
+    }
     if (
       this.options.extendedDiagnostics?.checks?.controlFlowPreventingContentProjection !== undefined
     ) {

diff --git a/packages/compiler-cli/src/ngtsc/typecheck/src/dom.ts b/packages/compiler-cli/src/ngtsc/typecheck/src/dom.ts
@@ -115,21 +115,24 @@ export class RegistryDomSchemaChecker implements DomSchemaChecker<TemplateDiagno
 
       const decorator = hostIsStandalone ? '@Component' : '@NgModule';
       const schemas = `'${decorator}.schemas'`;
-      let errorMsg = `Can't bind to '${name}' since it isn't a known property of '${tagName}'.`;
-      if (tagName.startsWith('ng-')) {
+      const localTagName = tagName.startsWith(':')
+        ? tagName.slice(tagName.indexOf(':', 1) + 1)
+        : tagName;
+      let errorMsg = `Can't bind to '${name}' since it isn't a known property of '${localTagName}'.`;
+      if (localTagName.startsWith('ng-')) {
         errorMsg +=
           `\n1. If '${name}' is an Angular directive, then add 'CommonModule' to the '${decorator}.imports' of this component.` +
           `\n2. To allow any property add 'NO_ERRORS_SCHEMA' to the ${schemas} of this component.`;
-      } else if (tagName.indexOf('-') > -1) {
+      } else if (localTagName.indexOf('-') > -1) {
         errorMsg +=
           `\n1. If '${
-            tagName
+            localTagName
           }' is an Angular component and it has '${name}' input, then verify that it is ${
             hostIsStandalone
               ? "included in the '@Component.imports' of this component"
               : 'part of this module'
           }.` +
-          `\n2. If '${tagName}' is a Web Component then add 'CUSTOM_ELEMENTS_SCHEMA' to the ${schemas} of this component to suppress this message.` +
+          `\n2. If '${localTagName}' is a Web Component then add 'CUSTOM_ELEMENTS_SCHEMA' to the ${schemas} of this component to suppress this message.` +
           `\n3. To allow any property add 'NO_ERRORS_SCHEMA' to the ${schemas} of this component.`;
       }
 

diff --git a/packages/compiler-cli/src/ngtsc/typecheck/testing/index.ts b/packages/compiler-cli/src/ngtsc/typecheck/testing/index.ts
@@ -197,6 +197,7 @@ export function tcb(
     allowSignalsInTwoWayBindings: true,
     allowDomEventAssertion: true,
     checkUnknownElements: true,
+    checkTypeOfNgTemplateBindings: true,
     ...config,
   };
   options = options || {emitSpans: false};

diff --git a/packages/compiler-cli/src/ngtsc/typecheck/testing/src/test_support.ts b/packages/compiler-cli/src/ngtsc/typecheck/testing/src/test_support.ts
@@ -223,6 +223,7 @@ export const ALL_ENABLED_CONFIG: Readonly<TypeCheckingConfig> = {
   allowSignalsInTwoWayBindings: true,
   allowDomEventAssertion: true,
   checkUnknownElements: true,
+  checkTypeOfNgTemplateBindings: true,
 };
 
 // Remove 'ref' from TypeCheckableDirectiveMeta and add a 'selector' instead.

diff --git a/packages/compiler-cli/test/ngtsc/template_mapping_spec.ts b/packages/compiler-cli/test/ngtsc/template_mapping_spec.ts
@@ -800,13 +800,15 @@ runInEachFileSystem((os) => {
         import {Component, Directive, Input, Output, EventEmitter, Pipe, NgModule} from '@angular/core';
 
         @Directive({
-          selector: '[ngModel],[attr],[ngModelChange]',
+          selector: '[ngModel],[attr],[ngModelChange],[ngIf],[ngForOf]',
           standalone: false,
         })
         export class AllDirective {
           @Input() ngModel!: any;
           @Output() ngModelChange = new EventEmitter<any>();
           @Input() attr!: any;
+          @Input() ngIf!: any;
+          @Input() ngForOf!: any;
         }
 
         @Pipe({
@@ -826,6 +828,7 @@ runInEachFileSystem((os) => {
           name = '';
           isInitial = false;
           doSomething() {}
+          showMessage() { return true; }
           items: any[] = [];
           greeting = '';
         }