hermes - 💡(How to fix) Fix [BUG] hindsight_retain fails with 'retain_async' unexpected keyword argument in v0.10.0 [1 comments, 2 participants]

Bug Description

In Hermes v0.10.0, calling hindsight_retain fails with:

Failed to store memory: Hindsight.aretain() got an unexpected keyword argument 'retain_async'

hindsight_reflect also fails with an empty error message (Failed to reflect:).

hindsight_recall works normally.

Root Cause Analysis

The Hindsight Python client (vectorize-io/hindsight) defines two different methods:

1. aretain() (single memory) — does NOT accept retain_async parameter
2. aretain_batch() (batch memories) — does accept retain_async parameter

Source: hindsight_client.py

It appears that Hermes v0.10.0 is incorrectly passing retain_async to aretain() instead of aretain_batch(), or the internal retain logic was changed to use a parameter that the single-memory API does not support.

Steps to Reproduce

1. Configure Hermes with external Hindsight (provider: hindsight, mode local_external)
2. Run any operation that triggers hindsight_retain
3. Observe the retain_async error

Expected Behavior

hindsight_retain should store memory without errors, as it did in previous versions.

Actual Behavior

• hindsight_retain → TypeError: Hindsight.aretain() got an unexpected keyword argument 'retain_async'
• hindsight_reflect → Failed to reflect: (likely related)
• hindsight_recall → Works fine (read-only, unaffected)

Environment

• Hermes Agent Version: v0.10.0 (2026.4.16)
• Python: 3.11.15
• Hindsight Mode: local_external
• Hindsight Server: external instance (tested with v0.5.3)

Additional Context

• The Hindsight server itself responds correctly (HTTP 200, <3ms latency), so this is not a connectivity or server-side issue.
• Upgrading the Hindsight server to the latest version (v0.5.3) does not resolve the error, confirming the bug is in the Hermes client code, not the server.

Possible Fix

Remove the retain_async parameter from the aretain() call path in Hermes, or route single-memory retain operations through the correct API method that does not require this parameter.