DynamoDB Enhanced - DurationAttributeConverter incorrectly converts negative durations with nanosecond offsets

[zachary-a-cook]

Describe the bug

When converting a negative Duration with a non-zero nanosecond offset, DynamoDB enhanced client's DurationAttributeConverter.transformFrom will return a value that does not match the input. Passing that returned value back into DurationAttributeConverter.transformTo will not return a Duration equal to the original value.

Regression Issue

• Select this option if this issue appears to be a regression.

Expected Behavior

I expect that I will receive an equivalent value after converting a negative Duration with a non-zero nanosecond offset to and from an AttributeValue with DurationAttributeConverter.

For example, if I create a DurationAttributeConverter named converter and call converter.transformFrom(Duration.ofMillis(-1)), I'd expect to receive AttributeValue.fromN("-0.001000000"). Subsequently calling converter.transformTo on that result should return Duration.ofMillis(-1).

Current Behavior

Rather than receiving an equivalent value, I received a different value Duration.parse("PT-1.999S") from the transformTo call and a value of AttributeValue.fromN("-1.999000000") from the transformFrom call.

Reproduction Steps

DurationAttributeConverter converter = DurationAttributeConverter.create();
Duration original = Duration.ofMillis(-1);
// This assertion will fail
assert original.equals(converter.transformTo(converter.transformFrom(original)));

Possible Solution

The most likely reason for this bug is the internal representation used by Java for negative durations. From the java.time.Duration.getSeconds Javadoc:

A negative duration is expressed by the negative sign of the seconds part. A duration of -1 nanosecond is stored as -1 seconds plus 999,999,999 nanoseconds.

Additional Information/Context

No response

AWS Java SDK version used

2.41.32

JDK version used

openjdk 25.0.3 2026-04-21 LTS OpenJDK Runtime Environment Corretto-25.0.3.9.1 (build 25.0.3+9-LTS) OpenJDK 64-Bit Server VM Corretto-25.0.3.9.1 (build 25.0.3+9-LTS, mixed mode, sharing)

Operating System and version

Rocky Linux release 8.10 (Green Obsidian), but will occur on any OS