Codex Pet generator on RunComfy. Build a Codex-compatible Codex Pet spritesheet.webp + pet.json from a single reference image, drop it into `${CODEX_HOME:-$HOME/.codex}/pets/<name>/` and Codex picks it up as a custom Codex Pet next to the 8 built-ins. This skill produces the exact Codex Pet atlas Co

Codex Pet — Pro Pack on RunComfy [runcomfy.com](https://www.runcomfy.com/?utm source=skills.sh&utm medium=skill&utm campaign=codex pet) · [GPT Image 2 edit endpoint](https://www.runcomfy.com/models/openai/gpt image 2/edit?utm source=skills.sh&utm medium=skill&utm campaign=codex pet) · [docs](https://docs.runcomfy.com/cli/introduction?utm source=skills.sh&utm medium=skill&utm campaign=codex pet) Codex Pet generator on RunComfy. Turn one source image into a Codex compatible custom Codex Pet — pet.json + spritesheet.webp — drop it into ${CODEX HOME: $HOME/.codex}/pets/<name / , Codex picks it up next to the 8 built in Codex Pets. What a Codex Pet is OpenAI Codex Pets (released May 2026) are pixel art animated companions that float over your desktop while Codex codes — they react to mouse interaction and Codex status (scratching head when thinking, popping a speech bubble when a task completes). Codex ships with 8 built in Codex Pets and supports custom Codex Pets installed locally as a folder under ${CODEX HOME: $HOME/.codex}/pets/ . Each custom Codex Pet folder contains exactly two files: pet.json — manifest with id , displayName , description , spritesheetPath . spritesheet.webp — Codex Pet sprite atlas, 1536x1872 PNG or WebP, 8 columns x 9 rows of 192x208 cells, transparent background. The 9 rows correspond to 9 animation states Codex plays. Each row uses a fixed number of leading frames; trailing cells stay fully transparent. Why this Codex Pet skill (vs OpenAI's official hatch pet ) OpenAI ships an official [ hatch pet ](https://github.com/openai/skills/blob/main/skills/.curated/hatch pet/SKILL.md) skill that produces the same Codex Pet artifact via the Codex internal $imagegen system skill (requires Codex Pro + $imagegen configured). This Codex Pet skill is a drop in alternative that runs via the RunComfy CLI : a single RUNCOMFY TOKEN plus runcomfy and magick binaries — no Codex Pro, no $imagegen , no OPENAI API KEY. The output Codex Pet artifact is identical — same pet.json shape, same spritesheet.webp 1536x1872 atlas, same 9 animation rows — so Codex treats this Codex Pet exactly like one made by hatch pet . This skill follows the same pattern Codex's built in Codex Pets use: one canonical pose, replicated across cells with ImageMagick micro transforms for subtle animation (1 2 px shifts, blink frames, tilt frames). That matches what the official hatch pet output actually looks like cell by cell — the Codex Pet animation visible in the Codex desktop app is intentionally subtle. Pick this skill when: You want a custom Codex Pet but don't have Codex Pro / $imagegen . You want a custom Codex Pet built via the RunComfy Model API. You want batch Codex Pet generation from a folder of source images (one canonical call per pet). You're entering the OpenAI Codex Pet contest with a different model behind the visuals. You said "codex pet", "/hatch", "make me a codex pet", "spritesheet.webp", "desktop pet for codex" explicitly. Codex Pet animation rows Codex reads one fixed atlas: 8 columns, 9 rows, 192x208 cells. Each Codex Pet row corresponds to one animation state with a specific number of leading frames. Row State Used columns Frames Codex Pet behavior 0 idle 0 5 6 calm breathing/blinking; the reduced motion first frame for the Codex Pet 1 running right 0 7 8 Codex Pet locomotion to the right 2 running left 0 7 8 mirrored locomotion to the left 3 waving 0 3 4 greeting / attention gesture 4 jumping 0 4 5 anticipation, lift, peak, descent, settle 5 failed 0 7 8 error / sad / deflated reaction 6 waiting 0 5 6 patient idle variant 7 running 0 5 6 active working / in progress loop (NOT foot running) 8 review 0 5 6 focused / inspecting / thinking Trailing cells after each row's last used column must be fully transparent. Codex Pet style The Codex Pet visual house style: EXAGGERATED chibi proportions : head occupies ~60 percent of total figure height; body and legs are tiny stubby and short. The whole figure should fit a near square bounding box. pixel art adjacent low resolution mascot, chunky silhouette thick dark 1 2 px outlines, visible stepped pixel edges limited palette, flat cel shading, simple expressive face, tiny limbs transparent background Avoid: motion lines, drop shadows, glows, sparkles, floating effects, text labels, scenery, white/black backgrounds. Prerequisites 1. RunComfy CLI — npm i g @runcomfy/cli 2. RunComfy account — runcomfy login . CI alternative: RUNCOMFY TOKEN=<token . 3. ImageMagick — brew install imagemagick (macOS) or apt get install imagemagick (Linux). Provides the magick command for the deterministic atlas assembly. 4. A source image URL — publicly fetchable HTTPS, JPEG/PNG/WebP, the subject the Codex Pet will be modeled on. Codex Pet pipeline (1 GPT Image 2 call, ~2 min) 1. Canonical Codex Pet — single runcomfy run openai/gpt image 2/edit call producing one 1024x1024 chibi pose on a magenta chroma key background. 2. Cell normalization — chroma key magenta → alpha 0, trim, aspect fit into 192x208 with transparent padding. 3. 9 row strips, programmatic — for each of 9 animation states, build the row's 8 cells via ImageMagick micro transforms (translate / mask / mirror) of the canonical cell. Trailing cells filled with transparent 192x208. 4. Atlas — stack 9 row strips vertically into the 1536x1872 Codex Pet atlas. 5. WebP — convert atlas PNG to WebP. 6. Manifest + install — write pet.json , copy both files into ${CODEX HOME: $HOME/.codex}/pets/<pet name / . The micro transform approach matches what Codex's built in Codex Pets actually do — the Codex Pet animation is intentionally subtle, so 1 2 px shifts and blink masks per cell give the right visual feel without burning 72 GPT Image 2 calls. Step 1: Generate the canonical Codex Pet (1 call) Step 2: Normalize the canonical into a 192x208 Codex Pet cell Chroma key magenta to alpha, trim to the pet sprite bounding box, aspect fit into 192x208 with transparent padding. The 18% fuzz is tuned for GPT Image 2's anti aliased magenta edges. Adjust to 25% if the Codex Pet has wider magenta halos, or to 8 10% if the pet has near magenta highlights getting clipped. Step 3: Build the 9 Codex Pet row strips programmatically For each row, build 8 cells from the canonical via ImageMagick micro transforms, fill unused trailing cells with transparent, then concatenate into a 1536x208 row strip. The micro transform table is what gives the Codex Pet its readable but subtle motion in Codex. Tweak the numbers per row to taste; the deltas are intentionally small (1 2 px) so the Codex Pet feels alive without becoming distracting. Step 4: Compose the Codex Pet atlas Stack the 9 row strips vertically into the 1536x1872 Codex Pet atlas, then convert to WebP. Step 5: Write the Codex Pet manifest Step 6: Install the Codex Pet Restart Codex (or reload the pet list) and the custom Codex Pet appears next to the 8 built ins. Prompting the canonical Codex Pet — what works The single GPT Image 2 call decides everything. Get this prompt right and the rest is deterministic. Lead with the chibi proportion lock. "EXAGGERATED chibi proportions, head ~60 percent of figure height" is the difference between a thin tall character (which fits the 192x208 cell badly with pillarbox) and a head dominant chibi (which fills the cell naturally). The latter is what Codex's built in Codex Pets look like. Demand the magenta FF00FF chroma key explicitly in every Codex Pet base prompt. GPT Image 2 only outputs RGB (no alpha), so the only way to get a transparent Codex Pet is to chroma key a known background color out post process. Forbid the chroma key color in the pet itself. Add: "The pet itself must not use the chroma key color or any close to magenta highlights." Otherwise the chroma key step removes Codex Pet body parts that happen to be magenta ish. Pin the style. "pixel art adjacent, chunky silhouette, 1 2 px outline, limited palette, flat cel shading" — pin every term that makes the Codex Pet match the Codex house style. Forbid the wrong styles. "No polished illustration, no painterly render, no anime key art, no 3D render, no glossy app icon polish, no realistic detail." Without this, GPT Image 2 will gravitate toward over rendered anime art. Anti patterns : Generic "transparent background" — GPT Image 2 paints near white instead. Use chroma key. Letting the model freestyle proportions — it will draw a tall narrow chibi that doesn't fit 192x208. Mixing styles in one prompt — pin one style anchor and stick to it. Tuning the micro animation The default ImageMagick recipe in step 3 produces a Codex Pet animation similar to the built in Codex Pets — subtle bob, occasional blink, jumping arc, head tilt. To make the animation more or less perceptible, tweak the deltas: Bigger idle bob : change shift:0: 1 to shift:0: 2 in row 0. Faster running cycle : increase the horizontal shifts in row 1 (e.g. shift:3:0 instead of shift:2: 1 ). Higher jump : change row 4's peak from shift:0: 8 to shift:0: 12 . Stronger head tilt in review: change rotate: 2 / rotate:2 to rotate: 4 / rotate:4 . Keep deltas small (≤ 4 px or ≤ 4°) so the Codex Pet doesn't become distracting. FAQ — Codex Pet What is a Codex Pet? OpenAI Codex Pets are pixel art animated companions launched May 2026 that float over your desktop and react to Codex's coding status. Custom Codex Pets live as pet.json + spritesheet.webp files under ${CODEX HOME: $HOME/.codex}/pets/<name / . Why use this Codex Pet skill instead of hatch pet ? Official hatch pet requires the Codex internal $imagegen system skill (Codex Pro). This skill needs only RUNCOMFY TOKEN and runs the same animation row spec via the RunComfy CLI, with one GPT Image 2 call total. How long does a Codex Pet generation take? ~2 minutes — 1 GPT Image 2 edit call (~90s) plus a few seconds of ImageMagick atlas assembly. Why only one API call? The Codex Pet animation in the Codex desktop app is intentionally subtle (you can confirm by inspecting any built in Codex Pet's atlas — 72 cells of nearly identical poses with tiny variations). One canonical pose plus deterministic ImageMagick micro transforms produces the same animation feel without burning 72 separate generation calls. Can the Codex Pet skill take a non human subject? Yes — pets, mascots, objects, foods all work. The base prompt simplifies the source into the Codex Pet house style automatically. How do I install my Codex Pet? Copy pet.json and spritesheet.webp into ${CODEX HOME: $HOME/.codex}/pets/<pet name / and reload Codex. What if the canonical Codex Pet drifts off identity? Re run step 1 with a tighter identity preservation prompt (e.g. name specific features: hair color, glasses, accessory). Steps 2 6 are deterministic and don't need to change. What size is each Codex Pet frame? 192x208 px. Each row strip is 1536x208 (8 frames). Final Codex Pet atlas is 1536x1872 (9 stacked rows). Can I add custom poses or replace rows? Yes — modify the build row calls in step 3. The atlas slot count per row must match the Codex contract (idle=6, running right/left=8, waving=4, jumping=5, failed=8, waiting/running/review=6) for Codex to play them correctly. Limitations One canonical pose per Codex Pet — animation is via ImageMagick transforms, not multi frame model generation. This matches the built in Codex Pets' subtle animation but won't produce dramatic motion (e.g. distinct frame by frame running cycle). GPT Image 2 doesn't output alpha — the magenta chroma key + post process is a workaround. If the Codex Pet has near magenta colors (rare for chibi palettes), sw

codex-pet