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+# Architecture: Custom Workouts & Flexible Sets
+
+**Project:** Gravl — PPL Workout Tracker
+**Researched:** 2026-02-15
+
+## Current State
+
+Fixed program structure:
+```
+Users → Programs (hardcoded id=1) → Program Days (6) → Program Exercises (fixed sets) → Workout Logs
+```
+
+## Proposed: Dual Data Paths
+
+Two parallel workout sources:
+1. **Program Workouts** (existing): Fixed PPL structure, unchanged
+2. **Custom Workouts** (new): User-built workouts with flexible sets
+
+### Schema Additions
+
+```sql
+-- User-created workout templates
+CREATE TABLE custom_workouts (
+  id SERIAL PRIMARY KEY,
+  user_id INTEGER REFERENCES users(id) ON DELETE CASCADE,
+  name VARCHAR(100) NOT NULL,
+  created_at TIMESTAMP DEFAULT NOW()
+);
+
+-- Exercises in custom workouts
+CREATE TABLE custom_workout_exercises (
+  id SERIAL PRIMARY KEY,
+  custom_workout_id INTEGER REFERENCES custom_workouts(id) ON DELETE CASCADE,
+  exercise_id INTEGER REFERENCES exercises(id),
+  sets INTEGER DEFAULT 3,
+  sort_order INTEGER DEFAULT 0
+);
+```
+
+Enhanced `workout_logs`:
+- Add `source_type` column ('program' | 'custom') — defaults to 'program' for backward compat
+- Add `custom_workout_exercise_id` column (nullable FK)
+
+### Frontend Components
+
+**New pages:**
+- `CustomWorkoutBuilder.jsx` — search exercises, build workout, save template
+- `ModifyWorkoutPage.jsx` — fork a program workout into custom
+
+**New components:**
+- `ExerciseSearchInput.jsx` — searchable exercise list
+- `SetCountEditor.jsx` — +/- controls for set count
+- `StepperInput.jsx` — number input with +/- buttons and unit label
+
+**Enhanced:**
+- `WorkoutSelectPage.jsx` — show both program and custom workouts
+- `WorkoutPage.jsx` — flexible set count, stepper inputs
+
+### Backend Endpoints
+
+New:
+- `POST /api/custom-workouts` — create custom workout
+- `GET /api/custom-workouts` — list user's custom workouts
+- `GET /api/custom-workouts/:id` — get custom workout with exercises
+- `PUT /api/custom-workouts/:id` — update custom workout
+- `DELETE /api/custom-workouts/:id` — delete custom workout
+- `GET /api/exercises` — list all exercises (for search/selection)
+
+Enhanced:
+- `POST /api/logs` — accept both program_exercise_id and custom_workout_exercise_id
+
+### Data Flow
+
+1. **Program Workout** (unchanged): Dashboard → WorkoutSelectPage → WorkoutPage → logs
+2. **Custom Workout Build**: Dashboard → CustomWorkoutBuilder → search exercises → save → POST /api/custom-workouts
+3. **Modify Program Workout**: WorkoutPage → "Modify" → fork to custom workout → edit exercises/sets
+4. **Flexible Sets**: User clicks "+Set" → local state adds entry → logs all sets on save
+
+## Build Order
+
+1. **Input UX fixes** — stepper inputs, validation, units (no backend changes)
+2. **Flexible sets** — local state for set count, backend accepts variable sets
+3. **Exercise list endpoint** — GET /api/exercises for search
+4. **Custom workout CRUD** — new tables + endpoints
+5. **Custom workout builder UI** — frontend page + components
+6. **Modify program workout** — fork program workout to custom
+
+Each phase builds on the previous. Phase 1 can ship independently.
diff --git a/.planning/research/FEATURES.md b/.planning/research/FEATURES.md
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+# Features: Workout Logging UX Improvements
+
+**Project:** Gravl — PPL Workout Tracker
+**Researched:** 2026-02-15
+
+## Table Stakes (Must-Have)
+
+| Feature | Complexity | Dependencies | Notes |
+|---------|-----------|--------------|-------|
+| Input validation (no negative reps, weight min 0) | Low | None | Currently broken — allows any value |
+| Weight unit display (kg suffix) | Low | None | Missing — only placeholder text |
+| Mobile input layout (44px min touch targets) | Low | None | Currently compressed inputs |
+| Add/remove sets per exercise | Medium | Backend log changes | Fixed set count is rigid |
+| Pre-fill last workout's weight/reps | Medium | Progression API | Users need reference for what to lift |
+| Exercise search/filter | Medium | Exercise list API | Needed for custom workout builder |
+
+## Differentiators (Competitive Advantage)
+
+| Feature | Complexity | Dependencies | Notes |
+|---------|-----------|--------------|-------|
+| Custom workout builder | High | New DB tables, new endpoints | Build workouts from exercise list |
+| Modify program workouts | Medium | Custom workout infra | Swap/add exercises mid-workout |
+| Rapid-fire set logging | Medium | Stepper inputs | Auto-advance, minimal taps per set |
+| Progressive overload visualization | Medium | History data | Show trend vs last workout clearly |
+| Rest timer with notifications | Low | Browser APIs | setInterval + Notification API |
+| Superset/circuit support | High | Schema changes | Group exercises for alternating sets |
+
+## Anti-Features (Deliberately Avoid)
+
+| Feature | Why to Avoid |
+|---------|-------------|
+| Social features | Users hate mandatory social in workout apps |
+| Complex periodization | Overcomplicates a personal PPL tracker |
+| Video exercise demos | Storage/bandwidth cost, not core value |
+| Gamification (badges, streaks) | Distracts from simple logging |
+| AI workout generation | Scope creep — user knows their program |
+
+## Priority for This Milestone
+
+1. **Input fixes** — validation, units, layout (table stakes, low effort)
+2. **Flexible sets** — add/remove sets (table stakes, medium effort)
+3. **Custom workouts** — build from scratch + modify program (differentiator, high effort)
diff --git a/.planning/research/PITFALLS.md b/.planning/research/PITFALLS.md
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+# Pitfalls: Workout App UX Improvements
+
+**Project:** Gravl — PPL Workout Tracker
+**Researched:** 2026-02-15
+
+## Critical Pitfalls (Address in This Milestone)
+
+### 1. Breaking Existing Logging Flow
+- **Risk:** Custom exercises don't integrate with `program_exercise_id` FK; progression and history break
+- **Warning signs:** Existing workout logs return empty after schema changes; progression graph gaps
+- **Prevention:** Add `source_type` column with default 'program'; never modify existing FK relationships; custom workouts use separate `custom_workout_exercise_id`
+- **Phase:** Database schema changes (early)
+
+### 2. Competing State on Shared Program
+- **Risk:** If users modify `program_exercises` directly, it affects ALL users sharing program_id=1
+- **Warning signs:** One user's set count change appears for another user
+- **Prevention:** Never modify program_exercises table for per-user changes. Custom modifications create a new custom_workout that forks from the program. Program data stays read-only
+- **Phase:** Custom workout architecture
+
+### 3. Backward Compatibility with Existing Logs
+- **Risk:** Existing logs assume fixed sets; schema changes break progression graphs and workout history
+- **Warning signs:** Historical workout data disappears or shows incorrectly
+- **Prevention:** `source_type` defaults to 'program'; all existing queries continue unchanged; new queries handle both source types
+- **Phase:** Database migration
+
+### 4. Input Validation Gaps
+- **Risk:** No validation on negative reps, extreme weights, or invalid set numbers
+- **Warning signs:** Corrupted data in database; nonsensical progression suggestions
+- **Prevention:** Frontend: `min=0` on inputs, stepper controls with bounds. Backend: validate before insert
+- **Phase:** Input UX fixes (Phase 1)
+
+### 5. Mobile Layout Breakage
+- **Risk:** Extra buttons (add set, remove set, modify workout) break 600px layout; unusable on small phones
+- **Warning signs:** Horizontal scroll appears; buttons overlap; touch targets too small
+- **Prevention:** Design all new controls within existing 600px constraint first; test on 320px width; maintain 44px minimum touch targets
+- **Phase:** All UI changes
+
+### 6. Scope Creep from "Add Set" to Full Program Builder
+- **Risk:** "Flexible sets" requirement grows into full periodization, program editor, template system
+- **Warning signs:** Conversations about "what if users want to plan a whole week" or "program templates"
+- **Prevention:** Strict scope: add/remove sets during a workout session. Custom workouts are simple exercise lists, not programs. No scheduling, no periodization
+- **Phase:** Scope discipline throughout
+
+### 7. Unclear Completion State
+- **Risk:** Flexible sets make "workout complete" ambiguous — did they skip a set or just not add one?
+- **Warning signs:** Users feel guilty about "incomplete" workouts; confusion about what counts as done
+- **Prevention:** No "complete workout" enforcement. Each logged set is saved independently. Summary shows what was actually done, not what was "expected"
+- **Phase:** Workout flow UI
+
+## Gravl-Specific Risks
+
+### Hardcoded program_id=1
+Dashboard directly fetches `programs/1`. Custom workouts that aren't program-linked will need their own navigation path in WorkoutSelectPage.
+
+### Upsert-Only Logging
+Current `/api/logs` only updates/inserts. If user removes a set, there's no delete mechanism. Need DELETE endpoint for individual log entries.
+
+### Component-Level State Loss
+Logs stored in React useState, not localStorage. If app closes mid-workout, all unlogged progress is lost. Consider auto-saving to localStorage as draft.
+
+### Single-File Backend
+Adding new endpoints to `backend/src/index.js` (already 425 lines) increases risk of accidentally breaking existing routes. Test existing endpoints after each backend change.
+
+## Pre-Shipping Checklist
+
+- [ ] Existing workout logging still works identically
+- [ ] Historical workout data displays correctly
+- [ ] Progression suggestions unchanged for program workouts
+- [ ] All inputs validate (no negative reps, no negative weight)
+- [ ] Layout works on 320px-600px width range
+- [ ] Custom workouts don't affect other users' program data
+- [ ] Set add/remove persists correctly in database
diff --git a/.planning/research/STACK.md b/.planning/research/STACK.md
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+# Technology Stack: Workout Logging UX Improvements
+
+**Project:** Gravl — PPL Workout Tracker (UX Milestone)
+**Researched:** 2026-02-15
+**Scope:** UX improvements to existing React 18 + Vite + Express + PostgreSQL app
+
+## What the Codebase Already Has
+
+| Layer | Technology | Version | Notes |
+|-------|------------|---------|-------|
+| Frontend framework | React | 18.2.0 | JSX, hooks-based |
+| Build tool | Vite | 5.0.8 | Already fast |
+| Routing | react-router-dom | 6.21.0 | Mostly unused — App.jsx uses manual `view` state |
+| Styling | Plain CSS + CSS custom properties | — | Dark fitness theme, `--accent`, `--bg-*` vars defined |
+| Backend | Express | — | REST API, `/api/*` endpoints |
+| Database | PostgreSQL | — | workout_logs, programs, exercises tables |
+| State | React useState | — | Local component state, no global store |
+| HTTP | Native fetch | — | Direct fetch() calls in App.jsx |
+
+## Recommended Stack Additions
+
+### Form Validation: React Hook Form + Zod
+
+| Technology | Version | Purpose | Why |
+|------------|---------|---------|-----|
+| react-hook-form | 7.x | Input registration, validation | Zero re-renders on keystroke. Integrates with native `<input>` without wrapping. |
+| zod | 3.x | Schema for weight/reps | `z.number().min(0).max(500)` reads as documentation. |
+| @hookform/resolvers | 3.x | Bridge RHF <-> Zod | Required; maintained by RHF team. |
+
+**Why not Formik:** Higher re-render cost. Context-based, creates overhead for per-set inline inputs.
+
+### Number Input Stepper: Custom Component (No Library)
+
+Build a custom `StepperInput` component with existing CSS variables. The requirement — +/- buttons flanking a number field with a unit label — is ~30 lines of React. Weight step: 2.5 kg. Reps step: 1.
+
+### Set Count Management: React State Only
+
+Add a `localSets` state initialized from `exercise.sets`. +/- controls add/remove entries. Copy last set's weight as default for added sets.
+
+### Custom Workout Creation: Existing Stack
+
+Use existing React + fetch + PostgreSQL. Add a `WorkoutBuilderPage.jsx`. No new global state needed initially.
+
+### Touch Target Sizing: CSS Only
+
+Critical rule: `font-size: 1rem` (minimum 16px) on all inputs prevents iOS Safari auto-zoom. Minimum 44px height on all interactive elements per iOS HIG.
+
+## What NOT to Add
+
+| Library | Why to Avoid |
+|---------|-------------|
+| Formik | Higher re-render cost; worse DX for inline per-row forms |
+| Material UI / Chakra UI | Conflicts with custom dark CSS; adds 200KB+ |
+| TanStack Query | Simple fetch pattern doesn't warrant it yet |
+| Framer Motion | Minimal animation intent; complex on budget phones |
+| Redux Toolkit | Overkill for 5-page single-user app |
+
+## Installation Summary
+
+```bash
+npm install react-hook-form zod @hookform/resolvers
+```
+
+**Bundle impact:** ~38KB gzipped total addition.
diff --git a/.planning/research/SUMMARY.md b/.planning/research/SUMMARY.md
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+# Research Summary: Workout UX Improvements
+
+**Project:** Gravl — PPL Workout Tracker
+**Synthesized:** 2026-02-15
+
+## Key Findings
+
+### Stack
+- Keep existing React 18 + Vite + Express + PostgreSQL stack
+- Add only: `react-hook-form` + `zod` + `@hookform/resolvers` (~38KB gzipped)
+- Build custom stepper input component (no library needed)
+- Do NOT add: UI frameworks, Redux, TanStack Query, Framer Motion
+- CSS-only fix for touch targets: min 44px height, 16px font-size prevents iOS zoom
+
+### Table Stakes (Must Ship)
+- Input validation: no negative reps/weights, proper number constraints
+- Weight unit display (kg suffix visible in input)
+- Mobile-optimized input layout (larger touch targets)
+- Add/remove sets per exercise
+- Pre-fill last workout's values for reference
+
+### Differentiators (Should Ship)
+- Custom workout builder (pick exercises, save as template)
+- Modify program workouts (fork to custom)
+- Stepper inputs for rapid logging (+/- buttons)
+
+### Watch Out For
+1. **Don't break existing flow** — program workout logging must stay identical
+2. **Don't modify shared program data** — fork to custom_workout for per-user changes
+3. **Don't let scope creep** — "add set" ≠ "full program builder"
+4. **Don't break mobile layout** — all new controls must fit 600px width
+5. **Backward compat** — existing workout_logs must keep working with new schema
+
+## Architecture Decision
+
+**Dual data path:**
+- Program workouts (existing, read-only) — unchanged
+- Custom workouts (new) — user-created, flexible sets, stored in new tables
+
+**New tables:** `custom_workouts`, `custom_workout_exercises`
+**Enhanced:** `workout_logs` gets `source_type` column (default 'program')
+
+## Suggested Build Order
+
+1. Input UX fixes (validation, units, stepper, layout) — no backend changes
+2. Flexible sets (local state + backend accepts variable set count)
+3. Exercise list endpoint (GET /api/exercises for search)
+4. Custom workout CRUD (new tables + endpoints)
+5. Custom workout builder UI (frontend page)
+6. Modify program workout (fork program → custom)
+
+Each phase is independently shippable. Phase 1 delivers immediate UX value with zero risk.
+
+## Research Files
+
+- `STACK.md` — Technology recommendations and what to avoid
+- `FEATURES.md` — Feature categorization (table stakes vs differentiators)
+- `ARCHITECTURE.md` — Schema design, component structure, data flow
+- `PITFALLS.md` — 7 critical pitfalls with prevention strategies