UI allows message submission before LLM providers are loaded, causing failures

[tomkis]

Pre-requisities

• I am using the newest version of the platform (agentstack version shows that CLI and platform are the same version, and there is no newer version available)

Describe the bug
When the agent run page takes longer to load, specifically when fetching the list of LLM providers takes time, users can still submit messages before the LLM providers are fully loaded. This results in a failure because the fulfillments are incomplete (missing LLM provider selections).

To Reproduce
Steps to reproduce the behavior:

1. Navigate to an agent run page
2. If the LLM provider list is still loading (slow network or slow API response)
3. Submit a message before the LLM list finishes loading
4. The message submission fails due to incomplete fulfillments

Expected behavior
The UI should prevent message submission until all required fulfillments (including LLM provider selections) are ready. The submit button should remain disabled until the LLM provider list has finished loading.

Additional context
The issue occurs in the agent run page UI where the isReady status doesn't account for the async LLM provider fetching. The form submission is enabled based on isReady which only checks for contextId and agentClient existence, but doesn't wait for matchedLLMProviders to be available.

[dosubot]

The submit button is currently enabled based on an isReady status that only checks for contextId, agentClient, and whether a request is pending. It does not wait for LLM providers (matchedLLMProviders) to finish loading, which is why users can submit messages prematurely and encounter failures due to incomplete fulfillments. The logic for loading and selecting LLM providers is handled asynchronously in the AgentDemandsProvider, but there’s no gating in the UI to prevent submission until these providers are ready (AgentRunProvider.tsx, AgentDemandsProvider.tsx).

To fix this, update the readiness logic to include a check for LLM provider loading—specifically, ensure that matchedLLMProviders are loaded and selectedLLMProviders are set before enabling the submit button. You could also show a loading indicator or disable the input field until all required providers are ready. There are proposals to improve this UX by replacing the input field with a loading element until the agent and its providers are fully loaded (issue #750). No existing PRs or issues directly address this readiness gating for LLM providers, so this would be a new improvement.

To reply, just mention @dosu.

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