Bedrock AgentCore Memory: list_events returns blob as string instead of document (JSON) when saved via create_event

[kun432]

Describe the bug

When I save a JSON object in payload[0].blob with create_event(), list_events(..., includePayloads=True) returns that blob as a string (e.g., "{content=hi, role=user}").

Docs say blob is a document (JSON value) in request and response:

https://boto3.amazonaws.com/v1/documentation/api/latest/reference/services/bedrock-agentcore/client/create_event.html
https://boto3.amazonaws.com/v1/documentation/api/latest/reference/services/bedrock-agentcore/client/list_events.html

Notes: I know Amazon Bedrock AgentCore is in preview release.

Regression Issue

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

Expected Behavior

Return a document (JSON value) for blob (object -> dict, array -> list, number -> number, etc.).

Current Behavior

Always return string, not a JSON document. Especially for dict, returns some like Java-style {k=v, ...} strings.

Reproduction Steps

import boto3
from datetime import datetime, timezone

REGION = "us-east-1"
MEMORY_ID = "<PUT-YOUR-MEMORY-ID>"  # created beforehand

client = boto3.client("bedrock-agentcore", region_name=REGION)

# Save a JSON object into blob (document)
client.create_event(
    memoryId=MEMORY_ID,
    actorId="user_123",
    sessionId="session_123",
    eventTimestamp=datetime.now(timezone.utc),
    payload=[{"blob": {"role": "user", "content": "hi"}}],
)

# Read it back
out = client.list_events(
    memoryId=MEMORY_ID,
    actorId="user_123",
    sessionId="session_123",
    includePayloads=True,
    maxResults=1,
)
blob = out["events"][0]["payload"][0]["blob"]
print(type(blob), blob)

output:

<class 'str'> {content=hi, role=user}

Possible Solution

current workaround:

serialize as JSON strings before create and de-serialize after retrieve, by myself.

import json

client.create_event(
    memoryId=MEMORY_ID,
    actorId="user_123",
    sessionId="session_123",
    eventTimestamp=datetime.now(timezone.utc),
    payload=[{"blob": json.dumps({"role": "user", "content": "hi"})}],  # serialize
)

out = client.list_events(
    memoryId=MEMORY_ID,
    actorId="user_123",
    sessionId="session_123",
    includePayloads=True,
    maxResults=1,
)
blob = json.loads(out["events"][0]["payload"][0]["blob"])  # de-serialize
print(type(blob), blob)

output:

<class 'dict'> {'role': 'user', 'content': 'hi'}

Additional Information/Context

AWS-CLI(aws-cli/2.29.1 Python/3.13.7 Darwin/23.6.0 source/arm64) seems the same behavior, so this comes from upstream API behavior?

REGION="us-east-1"
MEMORY_ID=$(
  aws bedrock-agentcore-control create-memory \
    --region $REGION \
    --name blob_cli_test \
    --event-expiry-duration 30 \
    --query 'memory.id' --output text
)

aws bedrock-agentcore create-event \
  --region $REGION \
  --memory-id "$MEMORY_ID" \
  --actor-id "user_123" \
  --session-id "session_123" \
  --event-timestamp "$(date -u +%Y-%m-%dT%H:%M:%SZ)" \
  --payload '[{"blob":{"role":"user","content":"hello"}}]'

aws bedrock-agentcore list-events \
  --region $REGION \
  --memory-id "$MEMORY_ID" \
  --actor-id "user_123" \
  --session-id "session_123" \
  --include-payloads \
  --max-results 1 \
  --output json \
| jq '.events[0].payload[0].blob | (type), .'

"string"
"{content=hello, role=user}"

SDK version used

1.40.25

Environment details (OS name and version, etc.)

ubuntu: 24.04, Python: 3.12.11

[adev-code]

Hi @kun432, thanks for reaching out. I have repro'd the issue and and response is coming from the Bedrock itself. It gives:
"payload":[{"blob":"{content=hi, role=user}"}].
I have reached out to the Service Team in regards and it does not conform their documentation. An update will be given once the team has updates.

Internal Ref: P303288467