Bug: Cannot save edited prompt back to Prompt Hub after opening trace run in Playground

[denyskorolkov]

Bug Description

When opening a trace run in Playground and editing the system prompt, it's impossible to save the changes back to an existing prompt in the Prompt Hub.

Steps to Reproduce

1. Go to Tracing and open a trace run that produced undesired output
2. Click "Open in Playground" on that run — Playground loads with the exact inputs, messages, tools, and model config from the trace
3. Edit the system prompt to fix the issue
4. Click Save → the "Save prompt" dialog appears
5. Type the name of the existing prompt (e.g. agent_review)
6. Result: Error message appears — "A prompt with this name already exists" — and the Save button is disabled entirely

Expected Behavior

Typing an existing prompt name should save the changes as a new commit to that prompt (same behavior as client.push_prompt() in the SDK), not block the Save button.

Actual Behavior

The Save button is disabled with the error "A prompt with this name already exists". The only option is to use a different name, which creates a brand new prompt instead of updating the existing one.

Workaround Attempts

• Using "Load prompt" first resets all messages, tools, and model configuration — losing all the context loaded from the trace run, which defeats the entire purpose of the "Open in Playground from trace" workflow.

Impact

The core workflow of "Open trace in Playground → edit prompt → save back to Hub" is completely broken for existing prompts. This makes iterating on prompts from real trace runs very painful.

Environment

• LangSmith UI (web)
• Playground opened from a trace run (not from Prompts section)

[vivek12345]

Can I pick this?