diff --git a/Development.md b/Development.md
index ec2a847..b9bdadf 100644
--- a/Development.md
+++ b/Development.md
@@ -12,13 +12,14 @@ npm run check        # typecheck + lint + format:check + tests, the gate CI runs
                      #   code is lost (tail's is reported), so a red run reads as green
 npm run build        # writes dist/ and regenerates index.html
 ./build.sh           # the same under `set -o pipefail`, for callers that pipe the output
-node tools/seed-e2e.mjs && node tools/e2e.mjs                 # 727 editor checks, screenshots in /tmp/gm-e2e-*.png
+node tools/seed-e2e.mjs && node tools/e2e.mjs                 # 728 editor checks, screenshots in /tmp/gm-e2e-*.png
 GM_STEPS=20 node tools/e2e.mjs                                # or 1-12, or 6,20 — a subset while working on one step
 ./e2e.sh start [GM_STEPS]                                     # the same run detached, see below
 ./e2e.sh status                                               # live progress, or the last run's result
 node tools/seed-jumprun.mjs && node tools/smoke-jumprun.mjs   # 24 checks: the example game, played end to end
 node tools/seed-tetris.mjs && node tools/smoke-tetris.mjs     # 19 checks: the Tetris example, played end to end
 node tools/seed-actor.mjs && node tools/smoke-actor.mjs       # 21 checks: the walk demo (the seed uploads its own sheet)
+node tools/seed-e2e.mjs && node tools/perf-shaders.mjs        # what a shader costs per sprite; a measuring tool, not a check
 ```
 
 **A run needs a working GPU.** An idle editor page keeps rendering a picture that never changes, and
@@ -62,7 +63,7 @@ to touch it.
 The e2e run is a list of steps in `tools/e2e/` (hierarchy, inspector, play, assets, drawing,
 graph, parenting, colliders, containers, text/enabled, menus, textures, frames, overflow, aspect,
 container tab, run-in-editor, pause, nested behaviors, key repeat, list tab, struct variable,
-variable nodes, property nodes, animations, state machines, console) that build on each other's
+variable nodes, property nodes, animations, state machines, console, shaders) that build on each other's
 scene state and share the CDP driver in `tools/lib/harness.mjs` — `press`, `undo`, `play`,
 `object(id)`, `world()`, `mutate(js)` and friends, so a check reads like the interaction it
 exercises.
@@ -150,4 +151,4 @@ widths to find click points. The **render device is not in this repo** — `/dev
 and a 1 GB `/dev/shm` come from `container.options` in the runner's own `config.yaml`, which
 applies to every job on that runner. Without them chromium falls back to llvmpipe, which gets
 WebGL 1.0 only. Measured in the job container: `ANGLE (Intel, Vulkan 1.3.230, HD Graphics 630)`,
-WebGL 2.0, and the same 727 checks as here.
+WebGL 2.0, and the same 728 checks as here.
diff --git a/Shaders.md b/Shaders.md
index 4631da9..8b2ede3 100644
--- a/Shaders.md
+++ b/Shaders.md
@@ -83,7 +83,19 @@ deviations while their shader is not worn.
 ## What it costs, and where it stops
 
 A shader is a Pixi filter: the sprite is rendered into an intermediate texture and drawn back with
-the fragment, one pass per sprite wearing one. Fine for dozens, not for thousands. The pass runs at
+the fragment, one pass per sprite wearing one. Measured with `tools/perf-shaders.mjs` on an Intel
+HD 630 (the GPU CI uses as well), sprites of 48x48 inside a 640x360 camera, neutral values, three
+runs agreeing to within 1 fps:
+
+| shaded sprites | 25 | 50 | 100 | 200 | 400 | 800 |
+| --- | --- | --- | --- | --- | --- | --- |
+| frames per second | 58 | 56 | 54 | 48 | 34 | 20 |
+
+The very same scene without shaders holds 60 fps at every one of those counts, 800 included, so the
+whole drop is the passes: about 20 microseconds each up to 200 sprites, 40 at 800. Sprite size
+hardly matters — four times the area (96x96) measures the same, so what costs is the pass, not the
+pixels in it. A few dozen shaded sprites are free in practice; a few hundred cost half the frame
+rate. The pass runs at
 screen resolution, so pixel art stays sharp: measured in play at a fractional camera scale (1.43
 screen pixels per world unit), a *Nearest* texture keeps its hard border pixel for pixel with a
 neutral shader on, and brightness 0.5 darkens every one of those pixels — the pass runs there, and