Mid-Session Save 150 Protocol

Core Principle: Don't wait for session end to save. Checkpoint early, checkpoint often.

What This Skill Does

This skill provides quick checkpoints during active work:

• Capture current progress without full handoff
• Track what worked and what didn't (raw material for lessons)
• Persist lessons learned so far
• Update session state for continuity
• Can be invoked multiple times per development cycle

Key Insight: Progress Log as Lesson Source

The session progress log captures:

• ✅ What worked (successful approaches)
• ❌ What didn't work (failed attempts, dead ends)
• 🔄 What was tried (experiments, approaches tested)

This raw data becomes the source for extracting lessons later. Don't just save "what's done" — save the journey including failures.

When to Use This Skill

Triggers:

• Context window running low (but not ending session)
• Significant progress made (feature partially done)
• Important lesson learned (don't risk losing it)
• Before complex/risky operation
• User says "save progress", "checkpoint", "зберегти"
• Every 30-45 min of active work (recommended cadence)

NOT for:

• Full session end → use 72-close-session-150
• Just recording a single lesson → use 73-close-lessons-learn-150

The 150% Checkpoint Rule

• 100% Core: What changed + current state
• 50% Enhancement: Key learnings + immediate next step

Quick Checkpoint Protocol

Step 1: IDENTIFY CHANGES

What happened since last checkpoint:

• Files touched
• Decisions made
• Problems solved

Step 2: LOG SESSION PROGRESS (Critical!)

Track the journey, not just the destination:

• ✅ What worked — successful approaches, solutions that fixed issues
• ❌ What didn't work — failed attempts, dead ends, wrong assumptions
• 🔄 What was tried — experiments, approaches tested, hypotheses
• 💡 Why it worked/failed — root cause understanding (if known)

Write to: .sessions/SESSION_[date]-[name].md in ## Progress Log section Purpose: Raw material for extracting lessons later

Step 3: CAPTURE LESSONS (if ready)

If a clear lesson emerged:

• Add to MEMORY.md Lessons (Inbox)
• Don't skip this — context loss = lesson loss
• If lesson not yet clear, progress log will preserve the data

Step 4: UPDATE SESSION LOG STATE

Current state in the session log:

• Update the ## Current State block (or add it if missing)
• Keep it brief and current

Step 5: QUICK CONTEXT SAVE

Final state in .sessions/SESSION_[date]-[name].md:

• Current focus + next action
• Ready for immediate continuation

Output Format: Mid-Session Checkpoint

⏱️ **MID-SESSION CHECKPOINT**

**Checkpoint:** #N | [HH:MM]
**Task:** [Current task name]

## Since Last Checkpoint
- [Change 1]
- [Change 2]

## Progress Log (What Worked / What Didn't)
✅ Worked:
- [Successful approach 1]
- [Solution that fixed issue]

❌ Didn't Work:
- [Failed attempt 1] — reason: [why it failed]
- [Dead end 2] — reason: [wrong assumption]

🔄 Tried:
- [Experiment/hypothesis tested]

## Current State
- Working on: [Current focus]
- Status: [Progress indicator]

## Lessons Captured
- [Lesson added to MEMORY.md, or "Pending — data in progress log"]

## Next Action
→ [Immediate next step]

---
✅ Checkpoint saved | Ready to continue

Ultra-Quick Format

When time is very short (< 1 min):

⏱️ CHECKPOINT #N

Done: [What completed]
Worked: [What succeeded]
Failed: [What didn't work + why]
Now: [Current state]  
Next: [Immediate action]

What Gets Updated

Progress Log → Lessons Pipeline

Checkpoint #1: Log what worked/failed (raw data)
       ↓
Checkpoint #2: More data accumulated
       ↓
Checkpoint #3: Pattern emerges → Extract lesson → MEMORY.md Lessons (Inbox)
       ↓
Session End: Review all progress logs → Extract remaining lessons

Key principle: Not every checkpoint produces a lesson. The progress log is the raw material — lessons are extracted when patterns become clear.

Checkpoint Cadence Recommendations

Comparison with Related Skills

Operational Rules

1. CHECKPOINT OFTEN: Better too many than too few
2. LOG FAILURES TOO: What didn't work is as valuable as what did
3. LESSONS FIRST: Don't lose learnings
4. BE BRIEF: Quick saves, not essays
5. STAY CURRENT: Update, don't accumulate
6. IMMEDIATE NEXT: Always know what's next
7. PROGRESS = RAW DATA: Not every checkpoint needs a lesson — collect data first

Example: Development Cycle with Checkpoints

Start Session
    ↓
Load context (session-start-memory)
    ↓
Work on Feature Part 1
    ↓
⏱️ CHECKPOINT #1 (45 min in)
   └─ Progress: ✅ API route works | ❌ Hook failed (stale closure)
    ↓
Work on Feature Part 2
    ↓
⏱️ CHECKPOINT #2 (problem solved)
   └─ Progress: ✅ useCallback fixed closure | Pattern emerges → LESSON CAPTURED
    ↓
Work on Feature Part 3
    ↓
⏱️ CHECKPOINT #3 (context getting low)
   └─ Progress: 🔄 Trying SSR approach | ❌ hydration mismatch
    ↓
Continue or End Session
    ↓
Close session (close-session-150)
   └─ Review all progress logs → Extract lessons from ❌ patterns

Example Progress Log Entry

## Progress Log

### Checkpoint #1 — 14:30
✅ Worked:
- API route returns correct data
- Zod schema validates input

❌ Didn't Work:
- Direct state update in useEffect — caused infinite loop
- Reason: dependency array included computed object

🔄 Tried:
- useMemo for computed dependency — testing now

### Checkpoint #2 — 15:15
✅ Worked:
- useMemo solved the loop — stable reference now
- Component renders correctly

❌ Didn't Work:
- (none this round)

💡 Lesson extracted: "Never use computed objects in useEffect deps — use useMemo or extract IDs"

Failure Modes & Recovery

Remember: Checkpoints are cheap. Lost context is expensive. When in doubt, checkpoint.