# LEARNINGS.md - Mistakes & Lessons

**Purpose:** Append-only log of mistakes, bugs, and lessons learned. Review monthly.

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## 2026-02-22: Memory Optimization Implementation

### Lesson: BOOT.md vs BOOTSTRAP.md
**Mistake:** Initially confused about boot file naming.
**Reality:** BOOTSTRAP.md is correct (one-time setup), BOOT.md is unrecognized.
**Fix:** Verified only BOOTSTRAP.md exists, left it alone per AGENTS.md instructions.

### Lesson: Skills Audit Required
**Mistake:** 58 skills loaded but many unused (iOS-specific skills when mainly doing web).
**Reality:** Each unused skill burns tokens in system prompt.
**Fix:** Documented active skills, archived unused ones to knowledge base.

---

## 2026-02-20: Mission Control Database Design

### Lesson: Table Prefixes Critical
**Mistake:** Initially considered tables without project prefixes.
**Reality:** All Vercel apps share one Supabase - collisions possible.
**Fix:** Enforced `<project>_<table>` naming convention with underscores.

---

## 2026-02-22: Next.js Environment Variables on Vercel

### Lesson: Read Env Vars Inside Request Handlers
**Mistake:** Used module-level non-null assertions (`process.env.VAR!`) for Supabase config in API routes.
**Reality:** Environment variables may not be available at module load time in Vercel serverless functions. The non-null assertion hid the real issue.
**Fix:** Move `process.env.*` reads inside the request handler function. Add explicit validation with clear error messages for missing variables.
**Impact:** "Invalid API key" error was actually missing env var, not bad Supabase credentials.

## Format Template

```markdown
## YYYY-MM-DD: [Brief Title]

### Lesson: [What was learned]
**Mistake:** [What went wrong]
**Reality:** [What actually happened]
**Fix:** [How it was resolved]
```