A desktop pixel pet that quietly watches your macOS Trash and grows from what you throw away.

It starts as an egg floating on your desktop. Every time you delete a file, Mochi takes note — .py is a magma snack, .psd is solar food, node_modules is toxin. Over the next few weeks Mochi locks an element coat (from your dominant diet), hatches into one of five species (decided by the rhythm of how you delete), and starts speaking lines in a voice tuned to who you turned out to be.

Status: v0.2 — evolution + sprites + personality engine all live. The pet is a real pet now.

5 species × 5 colors × 4 stages = 100 unique sprites · 999 feed-reaction frames · 125 bubble pools.

lsof, Activity Monitor, Finder — none of them tell you anything interesting about your digital habits. Mochi is a tiny opinionated mirror: a soft-pixel reminder of what you just chose to throw away today, this week, this month. And it's a desktop pet. That's it.

This is the first thing to know. Mochi:

• Reads extension + size + timestamp only — never the file contents, never the filename, never a hash.
• Has no network code. No telemetry. No crash reporters. No analytics.
• Stores everything locally in ~/Library/Application Support/Mochi/ — state.json (the pet) plus an append-only meals.jsonl ({ts, ext, size, category, hour, weekday}).
• Source is short enough you can audit it in 30 minutes — start at TrashWatcher.swift.

Requires macOS 13+, Apple Silicon. No dependencies.

git clone https://github.com/jieyefriic/mochi.git
cd mochi
./build.sh
open ~/Applications/Mochi.app

build.sh runs swiftc, flattens ~2,200 sprite PNGs into Resources/, ad-hoc codesigns the bundle, and installs it to ~/Applications/Mochi.app.

You'll see a small egg in the bottom-right of your screen with a speech bubble saying hungry... tap me.

Tap it. A setup window walks you through the one thing that needs doing:

1. Open System Settings — deep-links straight to Privacy & Security → Full Disk Access.
2. Reveal Mochi.app in Finder — opens Finder with Mochi.app pre-selected, ready to drag into the access list.
3. Drop Mochi into the list and flip its switch.

The setup window auto-detects the moment access is granted and dismisses itself. Mochi starts eating.

Why Full Disk Access? ~/.Trash is gated behind the strictest TCC tier on modern macOS — there is no purpose-string-driven prompt for it. This is the only path. Mochi will never read anything outside ~/.Trash.

Every Mochi specimen is fully described by three orthogonal axes, each driven by a different pattern in your deletion behavior. See DESIGN.md for the source of truth.

Locked at S1 (10 GP) by your dominant diet across the first 10 meals.

Color is immutable after stage 1.

Locked at S3 hatching (110 GP) by a 5-D centroid in your meal-rhythm space:

v_freq       mean meals per active day
v_size       log-mean file size
v_variance   stddev of meals per hour-of-day  (bursty vs steady)
v_diversity  unique extensions seen
v_workhours  fraction of meals in 9-18

Species is immutable after S3.

Re-evaluated on a rolling 30-day window. Up to two active at a time.

Traits don't change visuals — they pick which voice Mochi speaks in. A Magma DRAKKIN · Nocturnal · Polyglot says different things from a Solar TIDLE · Hibernator.

+1 GP per meal · daily soft cap 30 · no decay

S0 Common Egg     0 GP        (default)
S1 Elemental Egg  10 GP       — color locks, first ceremony
S2 Cracking       100 GP      — visual transition
S3 Hatchling      110 GP      — species locks
S4 Juvenile       300 GP
S5 Adult          700 GP
S6 Ultimate       1500 GP     — terminal (Mochi never dies)

For a steady ~15 meal/day user: S1 day 1 · S3 ~day 8 · S6 ~5 months.

• Left-click the egg — opens onboarding if FDA isn't set up; otherwise pulls a contextual idle bubble.
• Drag anywhere on the egg — moves Mochi (position is remembered across launches; .canJoinAllSpaces so it follows you between desktops and into full-screen apps).
• Right-click — menu with Wake Up Mochi (Setup), Reset Position, Quit. Build with -D MOCHI_DEBUG_MENU to expose stage / color / species jumps + +50 GP for development.

A standalone HTML inspector lives at the repo root. Open it directly in any browser — no server needed:

open codex.html

Pick (stage · color · species) from the segmented controls and watch the idle and feed animations cycle inline. Useful for sprite QA and for showing the full 100-variant evolution tree without running the app.

~/.Trash  ──FSEvents──►  TrashWatcher  ──TrashMeal──►  PetState
                                                            │
                                                            ▼
                                  EvolutionEngine.processMeal()
                                  → +GP → maybe color lock / stage jump / species hatch
                                  → TraitEvaluator (rolling 30d) → active trait set
                                                            │
                                                            ▼
                                  BubbleEngine.pick(tag, color, species, stage)
                                                            │
                                                            ▼
                                          NSPanel + EggSprite (idle + feed-reaction overlay)

All 111 sprites + ~2,200 animation frames were generated with PixelLab.ai using the scripts under scripts/:

• match_objects_full.py — Recovers cloud object_ids by sha256 byte-matching local PNGs against every cloud preview. (Necessary because vary_object-derived color variants inherit the parent's prompt, so prompt-keyword classification mis-buckets them — byte-match is the only reliable way.)
• feed_batch.py — Sequential animator: fires animate-object per (species × color × stage), polls until done, downloads 9 frames using the URL template, retries on SSL/network/CUDA OOM. Sequential because PixelLab's per-account concurrency cap is very low (parallel fires get 429: maximum number of concurrent jobs).
• objects_map_full.json — Persistent object_id registry. Commit this so the IDs survive even if a future PixelLab UI cleanup wipes their tags.

• Floating transparent panel + drag + position persistence
• FSEvents Trash watcher (local + iCloud staging)
• Onboarding flow for Full Disk Access
• 100-variant species sprite tree (5 species × 5 colors × 4 stages) + idle anims
• Feed-reaction animation (one-shot overlay per meal)
• Local meal/restore JSONL log (extension + size + category, no filenames)
• Evolution state machine — color election + 5-D species centroid + GP ladder
• Trait evaluator — 6 traits + COMPANION 1y anniversary, 30d rolling window
• Bubble corpus — 125 pools across (color × species × stage) with per-tag voices
• Special events — .git warning, ≥100-item feast bonus
• S3 / S6 hatch ceremony — full-screen dim + reveal card
• 7-day cooldown on Reset Mochi
• Bubble localization (zh)
• AFK detection so Mochi doesn't talk to an empty desk
• External volume Trashes (/Volumes/*/.Trashes/$UID)
• Alpha-aware hit testing (transparent regions of the sprite click through)

Issues and PRs welcome. Things that are particularly useful right now: macOS 14/15 testing, additional bubble lines (especially zh), tuning the species centroids against real meal logs, and ideas for non-gimmicky special events.

MIT — see LICENSE.