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Build Log — January 22, 2026

Build Log — January 22, 2026

Context / Focus for Today

Major focus on Garmin sync performance optimization - achieving 10x faster imports through batched database operations and smart skip logic. Also added pricing/subscription UI, fixed OAuth issues, and improved workout card interactions.

Things I Got Done Today

Garmin Sync Performance (10x Faster)

Batch Activity Upserts

  • Rewrote activity import to use batched database operations:
    • Pre-fetch existing workouts and potential matches in 2 queries
    • Process all activities in memory before writing
    • Batch insert new workouts in single query
    • Parallelize updates for existing workouts
    • Previously: 3-4 DB queries per activity (90+ for 30 activities)
    • Now: ~4 queries total regardless of activity count

Smart Skip Logic

  • Skip already-synced activities in manual sync:
    • Activities from real-time webhooks already have completed_at set
    • Avoids redundant DB updates
  • Skip webhook extraction when activities already exist:
    • If activities exist in date range from webhooks, skip slow extraction
    • Makes re-syncing nearly instant

Webhook Filtering

  • Filter webhooks to only activities/activityDetails:
    • Skip dailies, epochs, sleeps, etc. that don't contain activity data
    • Reduced webhooks fetched from 660 to ~104 (84% reduction)

Debug & Monitoring

  • Added timing logs to sync-stream for diagnosing slow syncs
  • Added /api/debug/garmin/webhook-status endpoint for backfill status
  • Logs duration of: garmin user lookup, existing check, webhook extraction, batch upsert

Garmin OAuth Fixes

State Format & Cookie Mismatch

  • Use generateOAuthState() for consistent state format (userId.timestamp.nonce)
  • Fixed cookie name to match callback expectation (garmin_code_verifier_${state})

Activity Deduplication

  • Fixed "ON CONFLICT DO UPDATE cannot affect row a second time" error:
    • Activities from multiple webhook logs were causing duplicates
    • Added deduplication by external_id before database insert
    • Added replace parameter to Garmin sync for force re-import

Pricing & Subscription

New Pricing Modal

  • Added pricing modal with monthly/yearly plan selection:
    • Monthly: $10/mo
    • Yearly: $100/yr (highlights 2 months free / $8.33/mo)
    • Accessible from trial banner upgrade button

Stripe Error Handling

  • Show actual Stripe error message in checkout failures:
    • Previously showed generic "Failed to create checkout session"
    • Now displays real error for better debugging

UX Improvements

Workout Card Click Handling

  • Changed WorkoutCard from <button> to <div role="button">:
    • Fixes click handling conflicts with draggable elements
  • Smart modal routing:
    • Only open ActivityStatsModal when actual_metrics data exists
    • Otherwise open edit modal (fixes blank modal for imported workouts)

Infrastructure

ESLint Config

  • Fixed ESLint config for Next.js 16 compatibility

GitHub Actions

  • Updated badge URL for renamed repository

In Progress

  • Garmin sync performance monitoring (optimizations complete)
  • OAuth stability (fixes deployed, monitoring)
  • Subscription flow testing (pricing modal complete)

Targets for Tomorrow

  1. Monitor sync performance — verify 10x improvement in production
  2. Test subscription flow — ensure Stripe checkout works end-to-end
  3. Garmin OAuth monitoring — confirm state/cookie fixes resolve issues
  4. User feedback — gather feedback on new pricing modal UX

Notes / Observations

  • Batch upserts are dramatically faster - O(1) vs O(n) database queries
  • Webhook filtering alone cut 84% of unnecessary data fetching
  • Smart skip logic makes re-syncs nearly instant for existing data
  • Cookie name mismatch was subtle OAuth bug - state generation and callback must match exactly
  • Deduplication needed because webhook logs can contain same activity multiple times
  • WorkoutCard button vs div is important for drag-and-drop compatibility
  • Pricing modal yearly savings (2 months free) is compelling value proposition
  • Real Stripe errors help users troubleshoot payment issues

Momentum Score: 9 / 10

Exceptional day focused on Garmin sync performance. Achieved 10x speed improvement through batched database operations, smart skip logic, and webhook filtering. Fixed critical OAuth cookie mismatch and activity deduplication bugs. Added full pricing modal with monthly/yearly subscription options. Improved Stripe error handling and workout card interactions. Strong infrastructure work on ESLint and CI/CD. Performance and reliability significantly improved.