I completed the next step, Full application/problem+json error model, and updated the plan in docs/video-clipping-service-implementation-plan.md:701.

The main change is in src/main/java/org/example/videoclips/api/ApiExceptionHandler.java:1. It now consistently returns problem details for:

  - validation errors
  - malformed JSON
  - unsupported request content type
  - method not allowed
  - quota/conflict/not-found/media-type domain exceptions
  - unexpected internal errors

  I also extended src/test/java/org/example/videoclips/api/VideoAssetControllerTest.java:1 to assert application/problem+json and cover malformed JSON, unsupported request content type, and method-not-allowed responses.

docs/video-clipping-service-implementation-plan.md

@@ -704,7 +704,7 @@ Keep the domain independent from Spring framework details. Adapters implement st
 2. [x] Idempotency keys.
 3. [x] Retry and DLQ handling.
 4. [x] Tenant quotas.
-5. [~] Full `application/problem+json` error model.
+5. [x] Full `application/problem+json` error model.
 6. [x] Cleanup lifecycle jobs.
 7. [~] Security review.
 

src/main/java/org/example/videoclips/api/ApiExceptionHandler.java

@@ -12,11 +12,14 @@ import org.springframework.http.HttpStatusCode;
 import org.springframework.http.ProblemDetail;
 import org.springframework.http.ResponseEntity;
 import org.springframework.validation.FieldError;
+import org.springframework.web.HttpMediaTypeNotSupportedException;
+import org.springframework.web.HttpRequestMethodNotSupportedException;
 import org.springframework.web.bind.MethodArgumentNotValidException;
 import org.springframework.web.bind.annotation.ExceptionHandler;
 import org.springframework.web.bind.annotation.RestControllerAdvice;
 import org.springframework.web.context.request.ServletWebRequest;
 import org.springframework.web.context.request.WebRequest;
+import org.springframework.http.converter.HttpMessageNotReadableException;
 import org.springframework.web.servlet.mvc.method.annotation.ResponseEntityExceptionHandler;
 
 import java.net.URI;
@@ -75,6 +78,63 @@ public class ApiExceptionHandler extends ResponseEntityExceptionHandler {
         return problem(HttpStatus.BAD_REQUEST, "validation-error", ex.getMessage(), request.getRequestURI(), null);
     }
 
+    @ExceptionHandler(Exception.class)
+    ProblemDetail handleUnexpected(Exception ex, HttpServletRequest request) {
+        return problem(HttpStatus.INTERNAL_SERVER_ERROR, "internal-error", "An unexpected error occurred", request.getRequestURI(), null);
+    }
+
+    @Override
+    protected ResponseEntity<Object> handleHttpMessageNotReadable(
+            HttpMessageNotReadableException ex,
+            org.springframework.http.HttpHeaders headers,
+            HttpStatusCode status,
+            WebRequest request
+    ) {
+        return ResponseEntity.badRequest()
+                .body(problem(HttpStatus.BAD_REQUEST, "malformed-json", "Malformed JSON request", requestPath(request), null));
+    }
+
+    @Override
+    protected ResponseEntity<Object> handleHttpMediaTypeNotSupported(
+            HttpMediaTypeNotSupportedException ex,
+            org.springframework.http.HttpHeaders headers,
+            HttpStatusCode status,
+            WebRequest request
+    ) {
+        return ResponseEntity.status(HttpStatus.UNSUPPORTED_MEDIA_TYPE)
+                .body(problem(HttpStatus.UNSUPPORTED_MEDIA_TYPE, "unsupported-media-type", "Content type is not supported", requestPath(request), null));
+    }
+
+    @Override
+    protected ResponseEntity<Object> handleHttpRequestMethodNotSupported(
+            HttpRequestMethodNotSupportedException ex,
+            org.springframework.http.HttpHeaders headers,
+            HttpStatusCode status,
+            WebRequest request
+    ) {
+        return ResponseEntity.status(HttpStatus.METHOD_NOT_ALLOWED)
+                .body(problem(HttpStatus.METHOD_NOT_ALLOWED, "method-not-allowed", "HTTP method is not supported for this endpoint", requestPath(request), null));
+    }
+
+    @Override
+    protected ResponseEntity<Object> handleExceptionInternal(
+            Exception ex,
+            Object body,
+            org.springframework.http.HttpHeaders headers,
+            HttpStatusCode statusCode,
+            WebRequest request
+    ) {
+        if (body instanceof ProblemDetail) {
+            return super.handleExceptionInternal(ex, body, headers, statusCode, request);
+        }
+        HttpStatus status = HttpStatus.resolve(statusCode.value());
+        HttpStatus resolvedStatus = status == null ? HttpStatus.INTERNAL_SERVER_ERROR : status;
+        return ResponseEntity.status(resolvedStatus)
+                .body(problem(resolvedStatus, "internal-error", resolvedStatus == HttpStatus.INTERNAL_SERVER_ERROR
+                        ? "An unexpected error occurred"
+                        : resolvedStatus.getReasonPhrase(), requestPath(request), null));
+    }
+
     private Map<String, String> fieldError(FieldError error) {
         return Map.of(
                 "field", error.getField(),
@@ -82,6 +142,12 @@ public class ApiExceptionHandler extends ResponseEntityExceptionHandler {
         );
     }
 
+    private String requestPath(WebRequest request) {
+        return request instanceof ServletWebRequest servletWebRequest
+                ? servletWebRequest.getRequest().getRequestURI()
+                : "";
+    }
+
     private ProblemDetail problem(
             HttpStatus status,
             String type,

src/test/java/org/example/videoclips/api/VideoAssetControllerTest.java

@@ -147,11 +147,41 @@ class VideoAssetControllerTest {
                                 }
                                 """))
                 .andExpect(status().isBadRequest())
+                .andExpect(org.springframework.test.web.servlet.result.MockMvcResultMatchers.content().contentTypeCompatibleWith("application/problem+json"))
                 .andExpect(jsonPath("$.type").value("https://api.example.com/problems/validation-error"))
                 .andExpect(jsonPath("$.title").value("Bad Request"))
                 .andExpect(jsonPath("$.errors").isArray());
     }
 
+    @Test
+    void returnsProblemDetailsForMalformedJson() throws Exception {
+        mockMvc.perform(post("/v1/video-assets")
+                        .contentType(MediaType.APPLICATION_JSON)
+                        .content("{"))
+                .andExpect(status().isBadRequest())
+                .andExpect(org.springframework.test.web.servlet.result.MockMvcResultMatchers.content().contentTypeCompatibleWith("application/problem+json"))
+                .andExpect(jsonPath("$.type").value("https://api.example.com/problems/malformed-json"))
+                .andExpect(jsonPath("$.title").value("Bad Request"));
+    }
+
+    @Test
+    void returnsProblemDetailsForUnsupportedRequestContentType() throws Exception {
+        mockMvc.perform(post("/v1/video-assets")
+                        .contentType(MediaType.TEXT_PLAIN)
+                        .content("plain-text"))
+                .andExpect(status().isUnsupportedMediaType())
+                .andExpect(org.springframework.test.web.servlet.result.MockMvcResultMatchers.content().contentTypeCompatibleWith("application/problem+json"))
+                .andExpect(jsonPath("$.type").value("https://api.example.com/problems/unsupported-media-type"));
+    }
+
+    @Test
+    void returnsProblemDetailsForMethodNotAllowed() throws Exception {
+        mockMvc.perform(org.springframework.test.web.servlet.request.MockMvcRequestBuilders.put("/v1/video-assets"))
+                .andExpect(status().isMethodNotAllowed())
+                .andExpect(org.springframework.test.web.servlet.result.MockMvcResultMatchers.content().contentTypeCompatibleWith("application/problem+json"))
+                .andExpect(jsonPath("$.type").value("https://api.example.com/problems/method-not-allowed"));
+    }
+
     @Test
     void returnsNotFoundProblemForMissingClip() throws Exception {
         mockMvc.perform(post("/v1/clips/{clipId}/download-url", "clip_missing")