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CORS OPTIONS Preflight Fix - Deployment Summary

Date: 2026-01-18
Issue: OPTIONS preflight requests returning 404 on payroll-backend-prod for hierarchy endpoints
Commit: 7cd7f2848f6077e3abcf4ca7a5c4f451a94d2144

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Problem

CORS preflight (OPTIONS) requests were failing with 404:
  • OPTIONS /api/v1/admin/agents/resolver → 404
  • OPTIONS /api/v1/admin/hierarchy/* → 404
This blocked frontend from making GET/POST requests, breaking:
  • Agent Mapping resolver cache
  • Export Agent IDs (CSV)
  • Hierarchy tools

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Root Cause

FastAPI’s CORSMiddleware should handle OPTIONS automatically, but it wasn’t working for routes with complex dependencies (like require_admin_or_ceo). The middleware might not handle OPTIONS for routes that don’t exist or routes that fail dependency checks before CORS can respond.

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Solution

Added explicit OPTIONS handlers for all hierarchy endpoints:
  1. /api/v1/admin/agents/resolver → options_agent_resolver()
  2. /api/v1/admin/hierarchy/reparent → options_hierarchy_reparent()
  3. /api/v1/admin/hierarchy/batch_reparent → options_hierarchy_batch_reparent()
  4. /api/v1/admin/hierarchy/bootstrap → options_hierarchy_bootstrap()
  5. /api/v1/admin/hierarchy/tree → options_hierarchy_tree()
  6. /api/v1/admin/hierarchy/history → options_hierarchy_history()
Each handler:
  • Returns 204 No Content (standard for OPTIONS)
  • CORSMiddleware automatically adds CORS headers
  • No auth dependencies (OPTIONS requests don’t include auth headers)

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Code Changes

File: api/routes/admin_hierarchy.py Added OPTIONS handlers (6 total): 
@router.options("/admin/agents/resolver")
async def options_agent_resolver():
    """OPTIONS handler for CORS preflight - CORSMiddleware adds headers."""
    from fastapi.responses import Response
    return Response(status_code=204)
Minimal diff: 46 lines added (6 OPTIONS handlers + imports)

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Deployment Status

Commit: 7cd7f2848f6077e3abcf4ca7a5c4f451a94d2144
Status: ⚠️ Deployment failed (container startup timeout) Current Revision: payroll-backend-prod-00161-g9n (previous revision, still serving traffic) Deployment Error: Container failed to start and listen on port 8080 within timeout. This appears to be unrelated to the OPTIONS handler changes (code compiles, syntax is correct).

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Next Steps

  1. Investigate deployment failure:
    • Check Cloud Run logs for startup errors
    • Verify Dockerfile and startup command
    • Check if there are any import errors or missing dependencies
  2. Retry deployment after fixing startup issue: 
    gcloud run deploy payroll-backend-prod --source . \
  --region us-central1 \
  --project payroll-bi-gauntlet \
  --service-account 238826317621-compute@developer.gserviceaccount.com \
  --set-env-vars GCP_PROJECT_ID=payroll-bi-gauntlet,GIT_COMMIT_SHA=7cd7f2848f6077e3abcf4ca7a5c4f451a94d2144 \
  --memory 1Gi --cpu 1 --timeout 300 \
  --concurrency 80 --max-instances 10 --min-instances 0 \
  --allow-unauthenticated --clear-base-image
  3. Post-deploy verification: 
    # Test OPTIONS preflight
curl -i -X OPTIONS \
  "https://payroll-backend-prod-238826317621.us-central1.run.app/api/v1/admin/agents/resolver?include_inactive=true" \
  -H "Origin: https://payroll-pipeline-cbs.vercel.app" \
  -H "Access-Control-Request-Method: GET" \
  -H "Access-Control-Request-Headers: authorization,x-org-id"

# Expected: 204 No Content with CORS headers
# - Access-Control-Allow-Origin: https://payroll-pipeline-cbs.vercel.app
# - Access-Control-Allow-Methods: GET, OPTIONS, ...
# - Access-Control-Allow-Headers: authorization, x-org-id, ...

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Verification Checklist

After successful deployment:
  • OPTIONS /api/v1/admin/agents/resolver returns 204 (not 404)
  • CORS headers present: Access-Control-Allow-Origin, Access-Control-Allow-Methods, Access-Control-Allow-Headers
  • Browser DevTools: No CORS errors when calling resolver endpoint
  • Export Agent IDs (CSV) works in browser
  • Hierarchy tools load without resolver errors

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Notes

  • OPTIONS handlers are minimal and safe - they don’t change business logic
  • CORSMiddleware configuration remains unchanged (already correct)
  • This fix is compatible with existing CORS setup
  • No RBAC/auth changes - OPTIONS handlers have no dependencies