# How pxpipe sizes rendered images

Image geometry is selected by the exact model id. `/v1/responses` is only a
wire protocol: Claude, GPT, and Grok on that path do not share a renderer.

## Current behavior

A page is profile-width and variable-height. It is never padded to a square.

```text
cellWidth  = atlasWidth  + cellWBonus
cellHeight = atlasHeight + cellHBonus
width      = 2 * PAD_X + columns * cellWidth
height     = 2 * PAD_Y + usedRows * cellHeight
```

Width may shrink to the widest rendered line, capped by the profile. Height
grows with content until the profile cap, then overflow becomes another page.

| model rule | atlas / effective cell | columns | full width | max height |
|---|---|---:|---:|---:|
| Claude / Anthropic | Spleen + Unifont, 5×8 | 312 | 1568 px | 728 px |
| opt-in `gpt-5.6-sol` | Spleen + Unifont, 5×8 | 152 | 768 px | 1932 px |
| opt-in Grok 4.5 | Spleen + Unifont, 5×8 white AA + IDS + factsheet (no grid) | 152 | 768 px | 512 px |
| other OpenAI fallback | Spleen + Unifont, 5×8 | 152 | 768 px | 1932 px |

Complete profile values and evidence are in
[`MODEL_RENDER_PROFILES.md`](MODEL_RENDER_PROFILES.md).

The Sol row is the **currently configured** geometry, not a successful recall
claim. Paid raw-image calls tested both the earlier 6×11/126-column geometry and
this 5×8/152-column profile: each returned 0/4 exact identifiers with four
confabulations; 5×8 also missed gist. Sol is consequently opt-in. The effective 9×12/84-column Sol
candidate is local-only pending a model call. See
[`eval/sol-profile/RESULTS.md`](../eval/sol-profile/RESULTS.md).

## Provider boundaries

Anthropic resizes images to fit both a 1568px long edge and roughly 1.15MP.
The 1568×728 Claude page stays inside both bounds, so rasterized glyphs reach
the vision encoder without the old 0.555× resample.

OpenAI-shaped profiles use portrait strips at or below the 768px short-side
floor. GPT 5.6 Sol and Grok both use 152×5+8, a 768px strip (1932 px and 512 px
tall respectively).

## Font and Unicode

Atlases are generated at build time; runtime never loads font files. The compact
JetBrains atlas contains common code/Latin/symbol ranges. Missing codepoints
fall back to the full Spleen/Unifont atlas, preserving multilingual rendering.

Spacing, anti-aliasing, grid, color cycle, and newline-marker style are all part
of the model profile. The same style object is used for static slabs and history.

## Gate parity

The profitability gate resolves the same profile as the renderer and derives:

- cell width and height
- content-width shrink
- rows per page
- page count
- per-image token cost

Changing cell spacing or font therefore cannot leave cost prediction on a
hardcoded 5×8 canvas. Claude uses the Anthropic 28-px patch formula (with a
conservative margin at the gate), GPT uses model-specific tile/patch pricing, and
Grok uses the measured tokens-per-megapixel rate.

## Why not square pages

Billing follows pixel area or patches/tiles, not visual symmetry. Padding a
portrait or short final page to a square adds cost without adding information.
The target is readable characters per billed pixel under each provider's resize
contract, not a preferred aspect ratio.

## Measurement history

| date | change | finding |
|---|---|---|
| 2026-05-21 | R3 reflow | recovered line-end dead space by marking hard newlines with `↵` |
| 2026-05-22 | grayscale atlas + L1/L2 harness | measured style and instruction-band effects |
| 2026-06-09 | Fable-only 5×8 scope | Fable read dense cells better than Opus |
| 2026-06-17 | ~1932px experiment | fewer pages, later shown to be server-resampled on Anthropic |
| 2026-07-01 | Claude 1568×728 clamp | made billed pixels survive Anthropic preprocessing |
| 2026-07-09 | exact-model profiles | separated Claude, GPT 5.6 Sol, and Grok geometry/style |
| 2026-07-11 | Grok profile | Shared 5×8 + IDS + factsheet production stack; Grok opt-in only |
| 2026-07-11 | default scope | Fable only; Sol and Grok remain opt-in after broader quality tests |

Older benchmark receipts retain their historical geometry; do not rewrite those
numbers as if they were generated by the current profile.

## Changing a profile

1. Add or re-run a reader-specific recall/style harness.
2. Measure the provider's real image-token accounting.
3. Keep the strip inside its no-resize boundary.
4. Test slab, history, gate, and cache determinism together.
5. Do not generalize one variant's result to sibling model ids.