tech-log-backend/docs/superpowers/plans/2026-08-02-client-safe-error-boundary.md

Client-Safe Error Boundary Implementation Plan

Execution: Follow superpowers:test-driven-development; request an independent code review before advancing to the next P1 batch.

Goal: Ensure public HTTP error envelopes contain only allowlisted messages and bounded safe metadata, never raw exceptions or request values.

Architecture: The inbound web adapter maps operational codes to fixed public messages. The sample consumer owns a parallel domain-code mapping. Exception diagnostics stay behind the transport boundary.

Tech Stack: Java 21, Spring Boot 4.0.0, JUnit 6/JUnit Jupiter, AssertJ, MockMvc.

Constraints

• Preserve all completed P0 and verification-purity changes in the dirty worktree.
• Preserve every error code/status/category/retryable value.
• Preserve safe protocol details and required headers.
• Do not leak request DTOs or transport types into application/domain.
• Do not stage, commit, amend, or push.

Task 1: Operational Handler RED Contracts

Files:

• Modify: src/adapter/inbound/web/src/test/java/dev/caskeleton/adapter/inbound/web/error/GlobalExceptionHandlerTest.java

• Modify: src/adapter/inbound/web/src/test/java/dev/caskeleton/adapter/inbound/web/error/TransportErrorHandlingTest.java

• Create: src/adapter/inbound/web/src/test/java/dev/caskeleton/adapter/inbound/web/error/NoResourceFoundErrorHandlingTest.java

• Add secret-sentinel tests for mapping, illegal argument, adapter disabled, authentication, authorization, precondition, pagination, and cursor exceptions.

• Add validation tests proving rejected values, interpolated/default messages, and iterable keys/indices are absent while normalized fields plus allowlisted reason codes/fixed messages remain.

• Add transport tests proving raw request URLs and content-type values are not echoed.

• Add a real MVC resource-resolver test for a sentinel-bearing static-resource 404.

• Run the focused tests and record RED against the current raw-message implementation (30 tests, 9 expected failures).

Task 2: Operational Allowlist Implementation

Files:

• Modify: src/adapter/inbound/web/src/main/java/dev/caskeleton/adapter/inbound/web/error/ClientSafeErrorMessages.java

• Create: src/adapter/inbound/web/src/main/java/dev/caskeleton/adapter/inbound/web/error/ClientSafeValidationDetails.java

• Modify: src/adapter/inbound/web/src/main/java/dev/caskeleton/adapter/inbound/web/error/GlobalExceptionHandler.java

• Modify: src/adapter/inbound/web/README.md

• Add code-specific fixed operational messages with a safe category fallback.

• Replace every public ex.getMessage()/rejected-value/raw-URL path.

• Discard validation message/value data, normalize field paths, strip iterable keys/indices, and emit only allowlisted reason codes with fixed messages.

• Route both NoHandlerFoundException and NoResourceFoundException through the same safe 404 envelope.

• Retain safe field/reason/expected-type/supported-method/media-type details and Allow.

• Run the operational/transport tests and confirm GREEN.

Task 3: Sample Domain RED and Implementation

Files:

• Create: src/sample-portfolio/src/main/java/dev/caskeleton/sample/portfolio/adapter/inbound/web/error/PortfolioClientSafeErrorMessages.java

• Modify: src/sample-portfolio/src/main/java/dev/caskeleton/sample/portfolio/adapter/inbound/web/error/DomainExceptionHandler.java

• Modify: src/sample-portfolio/src/test/java/dev/caskeleton/sample/portfolio/adapter/inbound/web/error/DomainExceptionHandlerTest.java

• Add ID/title/reason sentinel tests and confirm RED (4 expected failures).

• Map every PortfolioErrorCode to fixed public text and use it from the advice.

• Confirm code/status/category remain unchanged and sentinels are absent.

Task 4: Focused and Architecture Verification

• Run ./gradlew :adapter:inbound:web:test --console=plain.
• Run ./gradlew :sample-portfolio:test --console=plain.
• Run focused Spotless/Checkstyle/SpotBugs tasks for both modules.
• Run ./gradlew verifyCleanArchitectureDependencies --console=plain.
• Run git diff --check and request an independent read-only review.
• Apply the independent review findings and receive a no-Critical/no-Important code re-review; align this design/plan with the final validation and resource-404 contract.