# Calarin plan ready for review — 2026-04-12

## Executive summary
Calarin is now at a clean and honest review point.

What is done:
- live schematic verified from the Mini project
- KiCad project wrapper fixed (`calarin.kicad_pro`)
- ERC rerun successfully on the live synced project
- final ERC result: `0 messages / 0 errors / 0 warnings`
- review artifacts are durable on the Mini, not trapped in `/tmp`

What changed at the product level:
- old battery reasoning was partially based on misreading LiPo size codes
- we are no longer optimizing around a fake `3 mm battery box`
- product is now framed correctly as a MagSafe-backed recorder on the back of an iPhone
- the right trade is: spend footprint before spending thickness

## Recommended v1 product direction
### Shape
- flat vertical MagSafe slab
- more wallet-like than puck-like
- centered on the MagSafe zone on the back of the phone

### Battery direction
- primary target: `302540`
- stretch target: `302560`
- bring-up fallback: `402030`

### Geometry target for review
- outer envelope: about `56 x 86 x 9.5–10 mm`
- acceptable philosophy: slightly larger flat slab > smaller chunky block

## Why this is the right answer
- aligns with Nate’s clarified product intent
- keeps v1 workable without pretending it is final industrial design
- protects the phone-back product concept from being hijacked by a thick battery shortcut
- still leaves a clean fallback if sourcing slows down electronics work

## Buy recommendation
If buying only one battery class now:
- buy `302540`

If buying with schedule protection:
- buy `302540` for the real product direction
- buy `402030` as bring-up insurance

## Files prepared for review
In `/Users/nb/calarin-hardware/review-2026-04-12/` on the Mini:
- `FINAL-STATUS-2026-04-12.md`
- `REVIEW-NOTES.txt`
- `BATTERY-NOTES.txt`
- `BATTERY-DECISION-REFRAME-2026-04-12.md`
- `BATTERY-SHORTLIST-2026-04-12.md`
- `MAGSAFE-GEOMETRY-PLAN-2026-04-12.md`
- `erc-live-kicadpro.rpt`
- fresh SVG renders

## What I updated locally
- `/Users/nb/calarin-spec.md`
  - removed stale “ready to build” framing
  - replaced stale battery assumptions
  - reframed geometry around MagSafe-backed thin slab direction

## Review questions
1. Do we lock `302540` as the default v1 battery target?
2. Do we also buy `402030` as a pure bring-up hedge?
3. Does the `56 x 86 x 9.5–10 mm` envelope feel directionally right for v1?
4. Do we want to preserve a square puck branch at all, or kill it now?

## My recommendation
Lock all of this for v1 review:
- shape: MagSafe vertical slab
- battery: `302540`
- fallback: `402030`
- envelope: `56 x 86 x ~10 mm`

That is the current best balance of product truth, speed, and buildability.