Bug Description

I encountered two chat UI issues while using hermes-webui during an active model response stream.

1. Expanded Activity list collapses automatically when new activity arrives

When the assistant/model is streaming a response, I expand the collapsed Activity list to inspect the running activity. However, when the model produces a new activity/update, the Activity list closes/collapses by itself.

Expected behavior: once the user manually expands the Activity list, it should remain open while new activity items are appended or updated.

Actual behavior: the Activity list collapses automatically whenever new activity arrives, interrupting inspection of the live activity stream.

2. Latest user message disappears after clicking Stop/Cancel during streaming

During a conversation, while the model is still responding, I click the Stop/Cancel button to interrupt the generation. After stopping, the most recent user message I sent before the assistant response disappears from the chat.

Expected behavior: clicking Stop/Cancel should only stop the active assistant generation. The user message that triggered the generation should remain visible and persisted in the conversation.

Actual behavior: after clicking Stop/Cancel, the latest user message disappears from the chat.

Steps to Reproduce

Issue 1: Activity list auto-collapses

1. Open hermes-webui.
2. Start a chat request that produces visible activity/tool updates.
3. While the assistant is streaming, expand the collapsed Activity list.
4. Wait for the model/agent to produce a new activity update.
5. Observe that the Activity list collapses automatically.

Issue 2: Latest user message disappears after Stop/Cancel

1. Open hermes-webui.
2. Send a normal chat message.
3. While the assistant/model is streaming the response, click the Stop/Cancel button.
4. Observe the chat history after stopping.
5. The latest user message sent before the stopped response is no longer visible.

Expected Behavior

• The Activity list should preserve the user's manual expanded/collapsed state during streaming updates.
• New activity updates should not reset the Activity panel's UI state.
• Stop/Cancel should interrupt only the in-progress assistant response.
• The user message that initiated the request should remain visible and persisted after cancellation.

Actual Behavior

• The Activity list collapses automatically when new activity arrives during streaming.
• After clicking Stop/Cancel, the most recent user message disappears from the conversation.

Impact

These issues make it difficult to inspect live agent activity and can result in apparent loss of user input. The second issue is especially concerning because stopping generation should not remove or hide the user's own message.

Environment

• hermes-webui version: v0.50.240
• hermes-agent version: v0.11.0 (2026.4.23)
• Installation method: git clone
• Browser: chrome
• OS: macOS 15
• Whether the issue reproduces after page refresh: no