feat(core): introduce `@boundary` control flow and programmatic error handling by JeanMeche · Pull Request #70463 · angular/angular

JeanMeche · 2026-08-29T00:22:19Z

Introduces a declarative way to catch rendering errors in templates using the new @boundary block, preventing local failures from crashing the entire application hierarchy.

@boundary {
  <complex-chart [data]="data" />
} @error (let err = $error; let r = $retry) {
  <p>Failed to load chart: {{err.message}}</p>
  <button (click)="r()">Retry</button>
}

Additionally, this adds programmatic error handling for dynamically created views by introducing an onError option to ViewContainerRef.createComponent,createEmbeddedView and the standalone alone createComponent function:

viewContainerRef.createComponent(DynamicComponent, {
  onError: (err: Error, details: ErrorDetails) => {
    console.error('Component rendering failed:', err);
    // Render an alternative UI or log metrics
  }
});

Additional changes:

ErrorHandler can now implement onViewError(err, details) to receive rich metadata about caught boundary errors.

Note: most of design & implementation was done by @alxhub.
Note2: Docs on the feature will be addressed in a follow-up PR.

splincode · 2026-08-30T17:08:49Z

Was @try {} / @catch {} considered? Why was @boundary {} / @error {} preferred?

JeanMeche · 2026-08-30T17:12:50Z

Error Boundaries are a common concept in frontend frameworks and try/catch felt more "imperative" to us.

leonsenft · 2026-09-03T00:06:30Z

+import * as t from './r3_ast';
+
+/** Pattern used to identify a boundary `let` parameter. */
+const LET_PATTERN = /^(let\s+)(.*)/;


It looks like this wasn't resolved?

JeanMeche · 2026-09-03T12:00:04Z

+export interface ErrorDetails {
+    readonly boundary?: {
+        readonly type: Type<any>;
+        readonly reset: () => void;


Note for: we need to settle on either retry or reset for consistency

Is the a precedent anywhere for this? @atscott Didn't you use something similar for reseting/retrying route resources, or was that reloading?

I think maybe you're referring to reload, potentially? There was something in there to trigger reloads on resources in an error state.

Ah okay. Maybe reset is most appropriate then? reload and retry to me imply some kind of network request operation, whereas reset more accurately reflects the fact that we're simply resetting some internal framework state?

atscott

AGENT: Thank you for working on this! I've reviewed the PR and left inline suggestions focusing on template variable scoping, binder visitor order, TCB resolution, and compiler reification cleanup.

leonsenft

reviewed-for: fw-compiler, fw-general

atscott

AGENT: Follow-up review focusing on compiler AST visiting, template pipeline dead code, and public API declarations.

Implement error interception during refreshView and provide onError callback options in ViewContainerRef for programmatic rendering and encapsulation of boundary errors.

Add the runtime primitives `ɵɵboundaryCreate` and `ɵɵboundaryUpdate` to the core instructions, which handle synchronous view destruction and provide the `ON_ERROR` interceptor hooks. Also include the initial compiler AST representations for the new syntax including the Lexer tokenization and HTML Parser integration. This lays the foundational structure for `@boundary` prior to code generation. Co-authored-by: Matthieu Riegler <kyro38@gmail.com>

Add support for `@boundary` blocks in the template type-checking pipeline.

Add support for the new `@boundary` and `@error` control flow blocks in the Angular Language Service. This includes: - Updating outlining spans to handle boundary blocks correctly. - Adding classification visitor methods for semantic tokens. - Adding template target visitor methods for navigation and hover support. - Updating the TextMate grammar to recognize `@boundary` and the `when` clause.

…ation Added some tests to ensure error boundaries work with SSR and hydration.

…ST nodes

crisbeto · 2026-09-09T13:56:09Z

This PR was merged into the repository. The changes were merged into the following branches:

main: d470afa

angular#70463) Add the runtime primitives `ɵɵboundaryCreate` and `ɵɵboundaryUpdate` to the core instructions, which handle synchronous view destruction and provide the `ON_ERROR` interceptor hooks. Also include the initial compiler AST representations for the new syntax including the Lexer tokenization and HTML Parser integration. This lays the foundational structure for `@boundary` prior to code generation. Co-authored-by: Matthieu Riegler <kyro38@gmail.com> PR Close angular#70463

…ngular#70463) Add support for `@boundary` blocks in the template type-checking pipeline. PR Close angular#70463

Add support for the new `@boundary` and `@error` control flow blocks in the Angular Language Service. This includes: - Updating outlining spans to handle boundary blocks correctly. - Adding classification visitor methods for semantic tokens. - Adding template target visitor methods for navigation and hover support. - Updating the TextMate grammar to recognize `@boundary` and the `when` clause. PR Close angular#70463

…ation (angular#70463) Added some tests to ensure error boundaries work with SSR and hydration. PR Close angular#70463

ngbot Bot added this to the Backlog milestone Aug 29, 2026

JeanMeche force-pushed the error-boundary branch 3 times, most recently from 2a70304 to c388ce6 Compare August 29, 2026 00:57

JeanMeche marked this pull request as ready for review August 31, 2026 16:59

JeanMeche requested a review from crisbeto August 31, 2026 16:59

pullapprove Bot requested review from atscott and kirjs August 31, 2026 16:59

JeanMeche requested review from leonsenft and removed request for kirjs August 31, 2026 17:00

JeanMeche force-pushed the error-boundary branch 3 times, most recently from cb16745 to dc7ed41 Compare August 31, 2026 17:26

atscott requested changes Sep 1, 2026

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Comment thread packages/core/src/render3/instructions/change_detection.ts Outdated

Comment thread packages/core/src/error_handler.ts

Comment thread packages/language-service/src/outlining_spans.ts

atscott reviewed Sep 1, 2026

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Comment thread goldens/public-api/core/index.api.md Outdated

atscott reviewed Sep 2, 2026

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leonsenft requested changes Sep 2, 2026

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JeanMeche force-pushed the error-boundary branch 3 times, most recently from 48c436e to c742892 Compare September 2, 2026 23:22

leonsenft requested changes Sep 3, 2026

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JeanMeche commented Sep 3, 2026

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JeanMeche mentioned this pull request Sep 3, 2026

docs: Add error boundaries entries #70560

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atscott reviewed Sep 3, 2026

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JeanMeche requested a review from atscott September 5, 2026 00:46

leonsenft approved these changes Sep 8, 2026

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atscott reviewed Sep 8, 2026

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alxhub and others added 7 commits September 8, 2026 21:40

feat(core): add ErrorBoundary programmatic APIs

bd88815

Implement error interception during refreshView and provide onError callback options in ViewContainerRef for programmatic rendering and encapsulation of boundary errors.

refactor(compiler): template type-checking support for @boundary

57668e4

Add support for `@boundary` blocks in the template type-checking pipeline.

refactor(platform-server): ensure error boundaries work with ssr/hydr…

2785704

…ation Added some tests to ensure error boundaries work with SSR and hydration.

fixup! refactor(core): implement @boundary runtime primitives and A…

ef53124

…ST nodes

fixup! feat(core): add ErrorBoundary programmatic APIs

9d39794

JeanMeche force-pushed the error-boundary branch from 593dce3 to 9d39794 Compare September 8, 2026 20:31

JeanMeche requested a review from atscott September 8, 2026 20:31

JeanMeche added 2 commits September 8, 2026 22:45

fixup! feat(core): add ErrorBoundary programmatic APIs

23d54b5

fixup! refactor(core): implement @boundary runtime primitives and A…

4a49dad

…ST nodes

atscott approved these changes Sep 9, 2026

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JeanMeche added action: merge The PR is ready for merge by the caretaker target: minor This PR is targeted for the next minor release labels Sep 9, 2026

crisbeto approved these changes Sep 9, 2026

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crisbeto closed this in f6afb80 Sep 9, 2026

JeanMeche mentioned this pull request Sep 9, 2026

Add support for Angular error boundaries in upcoming 22.2 prettier/prettier#20014

Closed

Yahiro025 mentioned this pull request Sep 10, 2026

Angular: Support @boundary / @error error boundaries Yahiro025/prettier#1

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6 tasks

fisker mentioned this pull request Sep 12, 2026

Angular: Support @boundary / @error error boundaries prettier/prettier#20015

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medbenmakhlouf mentioned this pull request Sep 13, 2026

feat(keys-manager): support @boundary/@error error-boundary block jsverse/transloco#1016

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JeanMeche commented Aug 29, 2026 •

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