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fix(a2a): drop unparseable A2A metadata instead of aborting conversion #1401

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Merged
copybara-service merged 1 commit into from
Aug 6, 2026
+147 −34
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fix(a2a): drop unparseable A2A metadata instead of aborting conversion #1401

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82 changes: 56 additions & 26 deletions a2a/src/main/java/com/google/adk/a2a/converters/ResponseConverter.java
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Original file line number Diff line number Diff line change
Expand Up @@ -20,7 +20,7 @@
import static com.google.common.collect.Streams.zip;

import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.core.type.TypeReference;
import com.fasterxml.jackson.databind.JavaType;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.google.adk.agents.InvocationContext;
import com.google.adk.events.Event;
Expand Down Expand Up @@ -59,6 +59,8 @@
public final class ResponseConverter {
private static final ObjectMapper objectMapper = new ObjectMapper();
private static final Logger logger = LoggerFactory.getLogger(ResponseConverter.class);
private static final JavaType CUSTOM_METADATA_LIST_TYPE =
objectMapper.getTypeFactory().constructCollectionType(List.class, CustomMetadata.class);
private static final ImmutableSet<TaskState> PENDING_STATES =
ImmutableSet.of(TaskState.WORKING, TaskState.SUBMITTED);

Expand All @@ -69,6 +71,8 @@ private ResponseConverter() {}
* empty optional if the event should be ignored (e.g. if the event is not a final update for
* TaskArtifactUpdateEvent or if the message is empty for TaskStatusUpdateEvent).
*
* <p>Unparseable ADK metadata is logged and dropped; the rest of the event is still converted.
*
* @throws IllegalArgumentException if the event type is not supported.
*/
public static Optional<Event> clientEventToEvent(
Expand Down Expand Up @@ -187,7 +191,11 @@ public static Event messageToFailedEvent(Message message, InvocationContext invo
return builder.build();
}

/** Converts an A2A message back to ADK events. */
/**
* Converts an A2A message back to ADK events.
*
* <p>Unparseable ADK metadata is logged and dropped; the rest of the event is still converted.
*/
public static Event messageToEvent(Message message, InvocationContext invocationContext) {
return updateEventMetadata(
remoteAgentEventBuilder(invocationContext)
Expand Down Expand Up @@ -217,6 +225,8 @@ public static Event messageToEvent(
* Converts an A2A {@link Task} to an ADK {@link Event}. If the artifacts are present, the last
* artifact is used. If not, the status message is used. If not, the last history message is used.
* If none of these are present, an empty event is returned.
*
* <p>Unparseable ADK metadata is logged and dropped; the rest of the event is still converted.
*/
public static Event taskToEvent(Task task, InvocationContext invocationContext) {
ImmutableList.Builder<Part> genaiParts = ImmutableList.builder();
Expand Down Expand Up @@ -298,13 +308,13 @@ private static Event updateEventMetadata(
clientMetadata = ImmutableMap.of();
}
Event.Builder eventBuilder = event.toBuilder();
Object groundingMetadata = clientMetadata.get(A2AMetadataKey.GROUNDING_METADATA.getType());
// if groundingMetadata is null, parseMetadata will return null as well.
eventBuilder.groundingMetadata(parseMetadata(groundingMetadata, GroundingMetadata.class));
Object usageMetadata = clientMetadata.get(A2AMetadataKey.USAGE_METADATA.getType());
// if usageMetadata is null, parseMetadata will return null as well.
eventBuilder.groundingMetadata(
parseMetadata(clientMetadata, A2AMetadataKey.GROUNDING_METADATA, GroundingMetadata.class));
eventBuilder.usageMetadata(
parseMetadata(usageMetadata, GenerateContentResponseUsageMetadata.class));
parseMetadata(
clientMetadata,
A2AMetadataKey.USAGE_METADATA,
GenerateContentResponseUsageMetadata.class));

ImmutableList.Builder<CustomMetadata> customMetadataList = ImmutableList.builder();
customMetadataList
Expand All @@ -318,43 +328,63 @@ private static Event updateEventMetadata(
.key(AdkMetadataKey.CONTEXT_ID.getType())
.stringValue(contextId)
.build());
Object customMetadata = clientMetadata.get(A2AMetadataKey.CUSTOM_METADATA.getType());
if (customMetadata != null) {
customMetadataList.addAll(
parseMetadata(customMetadata, new TypeReference<List<CustomMetadata>>() {}));
List<CustomMetadata> parsedCustomMetadata =
parseMetadata(clientMetadata, A2AMetadataKey.CUSTOM_METADATA, CUSTOM_METADATA_LIST_TYPE);
if (parsedCustomMetadata != null) {
customMetadataList.addAll(parsedCustomMetadata);
}
eventBuilder.customMetadata(customMetadataList.build());

Object errorCode = clientMetadata.get(A2AMetadataKey.ERROR_CODE.getType());
eventBuilder.errorCode(parseMetadata(errorCode, FinishReason.class));
eventBuilder.errorCode(
parseMetadata(clientMetadata, A2AMetadataKey.ERROR_CODE, FinishReason.class));

return eventBuilder.build();
}

private static <T> @Nullable T parseMetadata(@Nullable Object metadata, Class<T> type) {
try {
if (metadata instanceof String jsonString) {
return objectMapper.readValue(jsonString, type);
} else {
return objectMapper.convertValue(metadata, type);
}
} catch (IllegalArgumentException | JsonProcessingException e) {
throw new IllegalArgumentException("Failed to parse metadata of type " + type, e);
}
/**
* Reads {@code key} out of the peer-supplied {@code clientMetadata} and deserializes it.
*
* <p>Returns null when the key is absent, and also when its value cannot be parsed: metadata is
* peer-controlled, so a malformed value is logged and dropped rather than failing the whole
* conversion.
*/
private static <T> @Nullable T parseMetadata(
Map<String, Object> clientMetadata, A2AMetadataKey key, Class<T> type) {
return parseMetadata(clientMetadata, key, objectMapper.getTypeFactory().constructType(type));
}

private static <T> @Nullable T parseMetadata(@Nullable Object metadata, TypeReference<T> type) {
/** Overload of {@link #parseMetadata(Map, A2AMetadataKey, Class)} for generic target types. */
private static <T> @Nullable T parseMetadata(
Map<String, Object> clientMetadata, A2AMetadataKey key, JavaType type) {
Object metadata = clientMetadata.get(key.getType());
try {
if (metadata instanceof String jsonString) {
return objectMapper.readValue(jsonString, type);
} else {
return objectMapper.convertValue(metadata, type);
}
} catch (IllegalArgumentException | JsonProcessingException e) {
throw new IllegalArgumentException("Failed to parse metadata of type " + type.getType(), e);
logDroppedMetadata(key, e);
return null;
}
}

/**
* Reports a dropped metadata value.
*
* <p>The parser's message quotes the peer's bytes, so the warning carries only the key and the
* exception type. A peer that streams malformed metadata would otherwise be able to write
* arbitrary content and a stack trace into the log on every event. The full exception is
* available at debug level.
*/
private static void logDroppedMetadata(A2AMetadataKey key, Exception e) {
logger.warn(
"Dropping unparseable A2A metadata for key {} ({})",
key.getType(),
e.getClass().getSimpleName());
logger.debug("Unparseable A2A metadata for key {}", key.getType(), e);
}

private static Event emptyEvent(InvocationContext invocationContext) {
Event.Builder builder =
Event.builder()
Expand Down
99 changes: 91 additions & 8 deletions a2a/src/test/java/com/google/adk/a2a/converters/ResponseConverterTest.java
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Original file line number Diff line number Diff line change
Expand Up @@ -19,7 +19,6 @@
import static com.google.common.truth.Truth.assertThat;
import static java.nio.charset.StandardCharsets.UTF_8;
import static java.util.stream.Collectors.joining;
import static org.junit.Assert.assertThrows;

import com.google.adk.agents.BaseAgent;
import com.google.adk.agents.InvocationContext;
Expand Down Expand Up @@ -214,6 +213,92 @@ public void taskToEvent_withCustomMetadata_returnsEvent() {
.inOrder();
}

@Test
public void taskToEvent_withMalformedMetadata_dropsFieldsAndConverts() {
Message statusMessage =
new Message.Builder()
.role(Message.Role.AGENT)
.parts(ImmutableList.of(new TextPart("Status message")))
.build();
TaskStatus status = new TaskStatus(TaskState.WORKING, statusMessage, null);
Task task =
testTask()
.status(status)
.artifacts(null)
.metadata(
ImmutableMap.of(
A2AMetadataKey.GROUNDING_METADATA.getType(), "not-valid-json",
A2AMetadataKey.USAGE_METADATA.getType(), "not-valid-json",
A2AMetadataKey.CUSTOM_METADATA.getType(), "not-valid-json",
A2AMetadataKey.ERROR_CODE.getType(), "not-valid-json"))
.build();

Event event = ResponseConverter.taskToEvent(task, invocationContext);

assertThat(event.content().get().parts().get().get(0).text()).hasValue("Status message");
assertThat(event.groundingMetadata()).isEmpty();
assertThat(event.usageMetadata()).isEmpty();
assertThat(event.errorCode()).isEmpty();
assertThat(event.customMetadata().get())
.containsExactly(
CustomMetadata.builder().key("a2a:task_id").stringValue("task-1").build(),
CustomMetadata.builder().key("a2a:context_id").stringValue("context-1").build());
}

@Test
public void taskToEvent_withUnrecognizedMetadataField_dropsField() {
Message statusMessage =
new Message.Builder()
.role(Message.Role.AGENT)
.parts(ImmutableList.of(new TextPart("Status message")))
.build();
TaskStatus status = new TaskStatus(TaskState.WORKING, statusMessage, null);
Task task =
testTask()
.status(status)
.artifacts(null)
.metadata(
ImmutableMap.of(
// A nested object takes the convertValue branch rather than readValue. The
// genai builders reject unknown fields, so snake_case fails to convert.
A2AMetadataKey.GROUNDING_METADATA.getType(),
ImmutableMap.of("web_search_queries", ImmutableList.of("test-query"))))
.build();

Event event = ResponseConverter.taskToEvent(task, invocationContext);

assertThat(event.groundingMetadata()).isEmpty();
assertThat(event.content().get().parts().get().get(0).text()).hasValue("Status message");
}

@Test
public void taskToEvent_withOneMalformedMetadataField_keepsTheValidFields() {
GroundingMetadata groundingMetadata =
GroundingMetadata.builder().webSearchQueries("test-query").build();
Message statusMessage =
new Message.Builder()
.role(Message.Role.AGENT)
.parts(ImmutableList.of(new TextPart("Status message")))
.build();
TaskStatus status = new TaskStatus(TaskState.WORKING, statusMessage, null);
Task task =
testTask()
.status(status)
.artifacts(null)
.metadata(
ImmutableMap.of(
A2AMetadataKey.GROUNDING_METADATA.getType(),
groundingMetadata.toJson(),
A2AMetadataKey.USAGE_METADATA.getType(),
"not-valid-json"))
.build();

Event event = ResponseConverter.taskToEvent(task, invocationContext);

assertThat(event.groundingMetadata()).hasValue(groundingMetadata);
assertThat(event.usageMetadata()).isEmpty();
}

@Test
public void messageToEvent_withMissingTaskId_returnsEvent() {
Message a2aMessage =
Expand Down Expand Up @@ -543,7 +628,7 @@ public void clientEventToEvent_withFailedTaskStatusUpdateEvent_returnsErrorEvent
}

@Test
public void taskToEvent_withInvalidMetadata_throwsException() {
public void taskToEvent_withInvalidMetadata_dropsFieldInsteadOfThrowing() {
Message statusMessage =
new Message.Builder()
.role(Message.Role.AGENT)
Expand All @@ -558,12 +643,10 @@ public void taskToEvent_withInvalidMetadata_throwsException() {
ImmutableMap.of(A2AMetadataKey.GROUNDING_METADATA.getType(), "{ invalid json ]"))
.build();

IllegalArgumentException exception =
assertThrows(
IllegalArgumentException.class,
() -> ResponseConverter.taskToEvent(task, invocationContext));
assertThat(exception).hasMessageThat().contains("Failed to parse metadata");
assertThat(exception).hasMessageThat().contains("GroundingMetadata");
Event event = ResponseConverter.taskToEvent(task, invocationContext);

assertThat(event.groundingMetadata()).isEmpty();
assertThat(event.content().get().parts().get().get(0).text()).hasValue("Status message");
}

@Test
Expand Down
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