dify - 💡(How to fix) Fix [Feature Request] Dynamic model provider API key selection per workflow run / per client

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1. Is this request related to a challenge you're experiencing? Tell me about your story.

Summary

Currently, the model provider API key (e.g. OpenAI) is configured at the workspace level and cannot be overridden at runtime. As a service provider managing multiple clients — each with their own OpenAI API key — it's impossible to route LLM calls through the correct key within a single shared workflow.

Use Case

I manage multiple clients. Each client has their own OpenAI API key (for billing isolation, quota management, or contractual reasons). I want a single Dify workflow that dynamically uses the appropriate API key depending on which client is calling it.

Expected Behavior

One or more of the following approaches should be supported:

1. Input variable for API key — allow passing a model_api_key as a workflow input variable, which overrides the workspace-level key for that specific run.
2. Per-run credential override — support a credential_id or api_key parameter directly in the workflow trigger API call (e.g. in inputs or as a top-level field).
3. Named credential profiles — allow storing multiple named credentials per provider (e.g. client_a_openai, client_b_openai) and selecting one via a workflow variable or condition node.

2. Additional context or comments

No response

3. Can you help us with this feature?

• I am interested in contributing to this feature.