list_objects_v2 with StartAfter returns wrong results when keys contain =

[tanelk]

When listing objects whose keys contain = and a StartAfter value is provided, LocalStack returns the wrong key set.

Minimal example

import boto3

s3 = boto3.client(
    "s3",
    endpoint_url="http://localhost:4566",
    aws_access_key_id="test",
    aws_secret_access_key="test",
    region_name="us-east-1"
)

s3.create_bucket(Bucket="test-bucket")

prefix = "data/NE=ABC/"
for i in range(100, 110):
    s3.put_object(Bucket="test-bucket", Key=f"{prefix}{i}.json", Body=b"x")

# StartAfter=prefix+"104" — expect keys 105..109 (5 keys)
start_after = f"{prefix}104"

# This is a workaround for localstack, that breaks real s3
# start_after = start_after.replace("=", "%3D")

res = s3.list_objects_v2(Bucket="test-bucket", Prefix=prefix, StartAfter=start_after)

for obj in res.get("Contents", []):
    print(obj)

On localstack 4.13.1 and boto3 1.43.89 this returns empty list.

[bentsku]

Hello @tanelk and thanks for your report! This issue has been fixed in LocalStack since February 2026, with LocalStack version 4.14 and above. We'd advise you to move to LocalStack 2026.08 to get most parity out of S3. Thanks!

I've validated that the sample now works, so I'll go ahead and close the issue. Please comment again if you still encounter the bug. Thanks again for the report!