Add validation to prevent inputs on trigger-based workflows during serialization

[devin-ai-integration]

Summary

Adds SDK-side validation during serialization to prevent workflows with non-manual triggers (IntegrationTrigger, ScheduleTrigger) from having workflow inputs defined. This complements the copilot-side change in vellum-ai/vellum-copilot#1556 which prevents the agent builder from generating inputs.py for trigger workflows.

The validation now catches:

• Pure trigger workflows (only IntegrationTrigger or ScheduleTrigger) with inputs
• Mixed-trigger workflows (ManualTrigger + non-manual trigger) with inputs

Mixed-trigger workflows are flagged because when executed via the non-manual trigger, inputs won't be populated and can fail at runtime.

---

Review & Testing Checklist for Human

• Confirm this doesn't break any existing valid workflows in production that may have mixed triggers with inputs
• Test end-to-end with agent builder to verify the validation error surfaces correctly when attempting to serialize a trigger workflow with inputs
• Verify ManualTrigger-only workflows with inputs still serialize without errors

Notes

• Requested by: @NgoHarrison
• Session: https://app.devin.ai/sessions/0fdba2b9c284412884568bf201784655

[devin-ai-integration]

🤖 Devin AI Engineer

I'll be helping with this pull request! Here's what you should know:

✅ I will automatically:

• Address comments on this PR that start with 'DevinAI' or '@devin'.
• Look at CI failures and help fix them

Note: I can only respond to comments from users who have write access to this repository.

⚙️ Control Options:

• Disable automatic comment and CI monitoring

[NgoHarrison]

@codex review

[chatgpt-codex-connector]

💡 Codex Review

Here are some automated review suggestions for this pull request.

Reviewed commit: 70582907ab

ℹ️ About Codex in GitHub

Codex has been enabled to automatically review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review".

If Codex has suggestions, it will comment; otherwise it will react with 👍.

When you sign up for Codex through ChatGPT, Codex can also answer questions or update the PR, like "@codex address that feedback".

[chatgpt-codex-connector]

Catch mixed manual + trigger workflows with inputs

This validation only fires when no ManualTrigger is present, so a workflow that includes both a ManualTrigger and a non‑manual trigger (e.g., IntegrationTrigger) with workflow inputs will pass serialization. For non‑manual trigger executions, StateMeta skips default input population when trigger_attributes is set, so required workflow inputs will be None and any input references can fail at runtime. Because has_manual_trigger short‑circuits the check, the new validation misses this invalid configuration. Consider checking for any non‑manual trigger when inputs exist (e.g., has_non_manual_trigger) to avoid mixed‑trigger workflows silently breaking trigger executions.

Useful? React with 👍 / 👎.

[dvargas92495]

[nit] would say without any Manual Triggers instead of with non-manual triggers. For instance, a workflow with a Schedule and Manual trigger has non-manual triggers but can have Workflow Inputs.

As well as capitalize Workflow wherever possible