From 8f2ddcf489ec8af4350af3cd746bc6203bd1ad4a Mon Sep 17 00:00:00 2001
From: Daniel Norman <daniel@norman.life>
Date: Wed, 12 Aug 2026 11:16:21 +0200
Subject: [PATCH] Cache npm dependencies in Buildkite

- Add twemoji as npm dependency instead of build download
- Package build assets with a Vite plugin instead of scripts
- Keep the eslint and prettier caches in one directory
---
 .buildkite/README.md           | 57 -------------------------
 .buildkite/e2e.yml             | 17 ++++++++
 .buildkite/node-checks.yml     | 53 +++++++++++++++++++++--
 .buildkite/pipeline.yml        |  7 +++
 .buildkite/rust.yml            | 17 +++++++-
 .buildkite/visual.yml          | 24 ++++++++---
 .gitignore                     |  6 ++-
 Dockerfile.e2e                 |  4 +-
 eslint.config.js               |  1 +
 flake.nix                      | 12 +-----
 package-lock.json              |  8 +++-
 package.json                   |  4 +-
 public/twemoji/.gitkeep        |  0
 scripts/check                  |  9 +++-
 scripts/copy-katex-assets      |  7 ---
 scripts/install-twemoji-assets |  9 ----
 vite-plugin-assets.ts          | 78 ++++++++++++++++++++++++++++++++++
 vite.config.ts                 |  3 ++
 18 files changed, 213 insertions(+), 103 deletions(-)
 delete mode 100644 .buildkite/README.md
 delete mode 100644 public/twemoji/.gitkeep
 delete mode 100755 scripts/copy-katex-assets
 delete mode 100755 scripts/install-twemoji-assets
 create mode 100644 vite-plugin-assets.ts

diff --git a/.buildkite/README.md b/.buildkite/README.md
deleted file mode 100644
index a40569071..000000000
--- a/.buildkite/README.md
+++ /dev/null
@@ -1,57 +0,0 @@
-# Buildkite CI
-
-The Garden Buildkite integration stores a bare `buildkite-agent pipeline
-upload`, so the agent finds `pipeline.yml` by its default name. The integration
-makes one pipeline per repo, so all suites land in the same build.
-
-## Cache volumes and artifacts
-
-A **cache volume** carries state between builds. It is an input: content that a
-step needs, but that the repo does not contain. Volume names are scoped to the
-pipeline.
-
-An **artifact** is a file that one build produces. It is an output: evidence for
-a person to read in the Buildkite UI. The agent uploads artifacts whatever the
-exit code of the step, so a failed step still reports its results.
-
-The visual suite uses both. The volume `visual-snapshots` holds the baseline
-images, which are gitignored and exist nowhere else. `artifact_paths` uploads
-the actual, expected, and diff images that a failed comparison writes. The two
-cannot be swapped: a volume is not visible in the UI, and an artifact does not
-persist as an input to the next build.
-
-## One writer per volume
-
-A job does not read its volume in place. It gets a private copy at start. That
-copy becomes the version that the next job sees, but only when the job exits 0.
-Every successful job is therefore a writer, whether or not it changed a file.
-
-Two consequences follow.
-
-Keep the volume names distinct across the uploaded files. A step that commits a
-version discards what a concurrent step wrote to the same volume. This is why
-`rust.yml` gives test, doc, and lint a separate volume each.
-
-The visual suite keeps exactly one writer. `master` updates the baselines, and
-`concurrency: 1` serializes the group. Other branches always exit non-zero, so
-Buildkite discards their copy and no branch can republish a stale baseline set.
-The branch step then cannot use the exit code to report the test result, so two
-codes carry both: 100 means no differences, which `soft_fail` keeps green, and
-any other non-zero code fails the build. An annotation reports the outcome in
-both cases.
-
-## Docker images
-
-Two images cover all Node steps:
-
-- `node:24-bookworm` tracks the major version in `.nvmrc` and the `engines`
-  field in `package.json`.
-- `mcr.microsoft.com/playwright:v1.61.1-noble` ships the browsers at
-  `/ms-playwright`, so no step installs them. The tag must match
-  `@playwright/test` in `package.json`. Playwright refuses browsers built for
-  another version.
-
-Node steps use no cache volume. Cache paths are relative to the step working
-directory, and the agent home is not visible inside a container, so npm
-downloads its dependencies on every run. The Rust steps run on the agent
-instead, so their `~`-rooted paths work.
diff --git a/.buildkite/e2e.yml b/.buildkite/e2e.yml
index ff6bd4aa9..2564d23bc 100644
--- a/.buildkite/e2e.yml
+++ b/.buildkite/e2e.yml
@@ -1,14 +1,27 @@
 # No explicit build step: tests/support/globalSetup.ts runs `npm run build` in
 # parallel with fixture creation, and asserts the pinned rad and radicle-httpd
 # versions are on PATH.
+#
+# This step shares the `deps` volume with the steps in node-checks.yml. Keep the
+# cache paths the same as the ones there, and see that file for how the volume
+# works and why this step waits for check.
 
 env:
   CI: "true"
+  NPM_CONFIG_CACHE: ".npm-cache"
 
 steps:
   - label: "🎭 e2e"
     key: e2e
+    # The check step in node-checks.yml seeds the shared volume.
+    depends_on: check
     timeout_in_minutes: 30
+    cache:
+      name: deps
+      paths:
+        - ".npm-cache"
+        - "tests/tmp/bin"
+        - ".lintcache"
     artifact_paths:
       - "tests/artifacts/**/*"
     plugins:
@@ -19,8 +32,12 @@ steps:
           image: "mcr.microsoft.com/playwright:v1.61.1-noble"
           # Chromium exhausts Docker's default 64MB /dev/shm.
           ipc: host
+          # Without this the cache volume links point at nothing.
+          volumes:
+            - "/cache/bkcache:/cache/bkcache"
           environment:
             - CI
+            - NPM_CONFIG_CACHE
     commands:
       - npm ci
       # The image ships no decompressors: install-binaries unpacks .tar.xz
diff --git a/.buildkite/node-checks.yml b/.buildkite/node-checks.yml
index c0dbcff56..75a7296b0 100644
--- a/.buildkite/node-checks.yml
+++ b/.buildkite/node-checks.yml
@@ -1,17 +1,38 @@
-# No cache volume: cache paths are relative to the step working directory, and
-# the agent's home is not visible inside a container, so npm downloads its
-# dependencies on every run.
+# One `deps` cache volume serves every step here and the e2e step in e2e.yml.
+# The volume is mounted at /cache/bkcache on the agent, and the configured paths
+# become links into it. A container step must therefore mount that directory, or
+# every link dangles and the job persists nothing.
+#
+# A job does not write the volume in place. It gets a private copy at start, and
+# that copy becomes the version the next job sees if the job exits 0. Concurrent
+# jobs are never merged: the last one to exit 0 publishes its whole copy, and
+# whatever a job that finished earlier committed is gone.
+#
+# check therefore runs first, and is the only step that writes content no other
+# step produces: the lint caches, and the pinned binaries. The four steps that
+# follow all copy its version and add nothing unique to it — `npm ci` against the
+# same lockfile fetches the same tarballs, and install-binaries does nothing once
+# the pinned version is there. Whichever of them commits last keeps everything.
+#
+# Stale content is safe. The npm cache is content-addressed, and install-binaries
+# keys its download on the pinned version.
 
 env:
   CI: "true"
+  # Applies to every npm and npx call in the step, not just to `npm ci`.
+  NPM_CONFIG_CACHE: ".npm-cache"
 
 __defs:
   # Tracks the major version in .nvmrc and the engines field in package.json.
   node_image: &node_image
     docker#v5.14.0:
       image: "node:24-bookworm"
+      # Without this the cache volume links point at nothing.
+      volumes:
+        - "/cache/bkcache:/cache/bkcache"
       environment:
         - CI
+        - NPM_CONFIG_CACHE
 
   # Ships the browsers at /ms-playwright, which is why no step installs them.
   # The tag must match @playwright/test in package.json — Playwright refuses to
@@ -21,22 +42,44 @@ __defs:
       image: "mcr.microsoft.com/playwright:v1.61.1-noble"
       # Chromium exhausts Docker's default 64MB /dev/shm.
       ipc: host
+      volumes:
+        - "/cache/bkcache:/cache/bkcache"
       environment:
         - CI
+        - NPM_CONFIG_CACHE
+
+  # Keep this list the same in every step that attaches the volume, here and in
+  # e2e.yml.
+  deps_cache: &deps_cache
+    name: deps
+    paths:
+      - ".npm-cache"
+      - "tests/tmp/bin"
+      # The eslint and prettier caches, which scripts/check keeps here rather
+      # than under node_modules so that `npm ci` cannot delete them. A cache
+      # path is always a directory, so the two files share one.
+      - ".lintcache"
 
 steps:
   - label: "🔎 check"
     key: check
     timeout_in_minutes: 10
+    cache: *deps_cache
     plugins:
       - *node_image
     commands:
       - npm ci
+      # check does not use the binaries. It installs them while it is the only
+      # writer of the volume, so that no later step has to win a race to keep
+      # them. The node image ships curl and xz, so nothing is installed first.
+      - ./scripts/install-binaries
       - npm run check
 
   - label: "🧪 unit-tests"
     key: unit-tests
+    depends_on: check
     timeout_in_minutes: 10
+    cache: *deps_cache
     plugins:
       - *node_image
     commands:
@@ -47,7 +90,9 @@ steps:
   # binaries on PATH even though it runs under vitest rather than Playwright.
   - label: "🔌 http-client-tests"
     key: http-client-tests
+    depends_on: check
     timeout_in_minutes: 15
+    cache: *deps_cache
     artifact_paths:
       - "tests/artifacts/**/*"
     plugins:
@@ -62,7 +107,9 @@ steps:
   # needs a browser but no Radicle binaries or fixtures.
   - label: "🏗 build-smoke"
     key: build-smoke
+    depends_on: check
     timeout_in_minutes: 30
+    cache: *deps_cache
     artifact_paths:
       - "tests/artifacts/**/*"
     plugins:
diff --git a/.buildkite/pipeline.yml b/.buildkite/pipeline.yml
index 612b33253..55bd82258 100644
--- a/.buildkite/pipeline.yml
+++ b/.buildkite/pipeline.yml
@@ -6,6 +6,13 @@
 # suite lands in this single build. Keep cache volume names distinct across the
 # uploaded files: volumes are scoped to the pipeline, and a step that commits a
 # volume version discards what a concurrent step wrote to the same volume.
+#
+# Upload node-checks.yml before e2e.yml: the e2e step depends on the `check` key
+# defined there, and Buildkite rejects a step whose dependency is not yet part of
+# the build.
+#
+# Superseded builds are not cancelled. Buildkite has no YAML equivalent of the
+# GitHub Actions cancel-in-progress.
 
 steps:
   - label: ":pipeline: upload"
diff --git a/.buildkite/rust.yml b/.buildkite/rust.yml
index cd9c66043..56a830912 100644
--- a/.buildkite/rust.yml
+++ b/.buildkite/rust.yml
@@ -22,11 +22,21 @@ __defs:
     if ! command -v rustup >/dev/null 2>&1; then
       curl -fsSL https://sh.rustup.rs | sh -s -- -y --no-modify-path --profile minimal
     fi
-    rustup component add rustfmt clippy
     rustc --version
 
+  # Only the parts of ~/.cargo that are expensive to fetch again. registry/src
+  # and git/checkouts are left out on purpose: cargo re-creates both from the
+  # cache and the git db, so caching them would double the size of the volume
+  # for no gain.
+  #
+  # Nothing prunes the target directory, so it keeps the artifacts of every
+  # dependency version the branch has ever built. Deleting the volume is the
+  # only cleanup, and it costs one full rebuild.
   cargo_cache: &cargo_cache
-    - "~/.cargo"
+    - "~/.cargo/bin"
+    - "~/.cargo/registry/index"
+    - "~/.cargo/registry/cache"
+    - "~/.cargo/git/db"
     - "~/.rustup"
     - "~/.cache/cargo-target"
 
@@ -62,5 +72,8 @@ steps:
       paths: *cargo_cache
     commands:
       - *install_rust
+      # The minimal profile ships neither, and rust-toolchain names no
+      # components. Only this step needs them.
+      - rustup component add rustfmt clippy
       - RUSTFLAGS="-D warnings" cargo clippy --workspace --all-features --tests
       - cargo fmt --all -- --check
diff --git a/.buildkite/visual.yml b/.buildkite/visual.yml
index df34ccf12..ec978182c 100644
--- a/.buildkite/visual.yml
+++ b/.buildkite/visual.yml
@@ -4,6 +4,10 @@
 # volume. Master updates them with --update-snapshots; every other branch
 # compares against them.
 #
+# A step can attach only one volume, so these two steps cannot also read the
+# `deps` volume from node-checks.yml. This volume carries the npm cache and the
+# Radicle binaries as well as the baselines.
+#
 # A job does not read the volume in place: it gets a private copy at start, and
 # that copy becomes the version the next job sees if the job exits 0. So every
 # successful job is a writer, whether or not it changed a file. The two steps
@@ -16,9 +20,15 @@
 #     --update-snapshots the mode is `missing`, under which Playwright still
 #     writes a baseline that does not exist yet. A branch therefore needs no
 #     concurrency limit, and any number of branch builds can run at once.
+#
+# The cost of that trick is that a branch build never adds to this volume, and
+# so never warms the npm cache it shares with the baselines. A branch that
+# changes package-lock.json therefore downloads the full dependency set on every
+# build until it lands on master.
 
 env:
   CI: "true"
+  NPM_CONFIG_CACHE: ".npm-cache"
 
 steps:
   - label: "📸 visual update snapshots"
@@ -29,10 +39,12 @@ steps:
     # jobs were created, so the newest master build commits last.
     concurrency: 1
     concurrency_group: "radicle-explorer/visual-snapshots"
-    cache:
+    cache: &visual_cache
       name: visual-snapshots
       paths:
         - "tests/visual/snapshots"
+        - ".npm-cache"
+        - "tests/tmp/bin"
     artifact_paths:
       - "tests/artifacts/**/*.png"
     plugins:
@@ -47,8 +59,13 @@ steps:
           ipc: host
           # buildkite-agent annotate runs inside the container.
           mount-buildkite-agent: true
+          # Without this the cache volume links point at nothing, which is why
+          # the baselines never persisted before.
+          volumes:
+            - "/cache/bkcache:/cache/bkcache"
           environment:
             - CI
+            - NPM_CONFIG_CACHE
     commands:
       - npm ci
       # The image ships no decompressors: install-binaries unpacks .tar.xz
@@ -78,10 +95,7 @@ steps:
     # produces, so only the success path below is soft.
     soft_fail:
       - exit_status: 100
-    cache:
-      name: visual-snapshots
-      paths:
-        - "tests/visual/snapshots"
+    cache: *visual_cache
     artifact_paths:
       - "tests/artifacts/**/*.png"
     plugins:
diff --git a/.gitignore b/.gitignore
index 87319a439..26c37d2e2 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,5 +1,7 @@
 /build/
 node_modules/
+.npm-cache/
+.lintcache/
 NOTES
 config/local*
 crates/radicle-httpd/build/artifacts
@@ -12,8 +14,8 @@ KaTeX_**.ttf
 KaTeX_**.woff
 KaTeX_**.woff2
 
-# Twemoji Assets
-public/twemoji/*.svg
+# Twemoji Assets, copied in by vite-plugin-assets
+public/twemoji/
 
 # Integration Tests
 tests/tmp/**/*
diff --git a/Dockerfile.e2e b/Dockerfile.e2e
index 145361fb5..c2e5830be 100644
--- a/Dockerfile.e2e
+++ b/Dockerfile.e2e
@@ -27,8 +27,8 @@ WORKDIR /work
 # Playwright version in package-lock.json so the baked browser matches the
 # @playwright/test that npm ci installs into the volume at runtime. Copying
 # only the lockfiles keeps this layer cached across source changes.
-# --ignore-scripts: the repo's postinstall (copy-katex/twemoji assets) needs
-# scripts/ which isn't in this layer; those run at runtime instead.
+# --ignore-scripts: this layer only warms the browser cache, so dependency
+# install scripts are not necessary.
 COPY package.json package-lock.json ./
 RUN npm ci --ignore-scripts \
     && npx playwright install --with-deps chromium \
diff --git a/eslint.config.js b/eslint.config.js
index eba67dc3b..758e98d5c 100644
--- a/eslint.config.js
+++ b/eslint.config.js
@@ -161,6 +161,7 @@ export default [
   {
     ignores: [
       "node_modules/**/*",
+      ".npm-cache/**/*",
       "build/**/*",
       "public/**/*",
       "radicle-httpd/**/*",
diff --git a/flake.nix b/flake.nix
index 1f235b364..dcc31bca0 100644
--- a/flake.nix
+++ b/flake.nix
@@ -81,13 +81,6 @@
       packages = {
         default = self.packages.${system}.radicle-explorer;
 
-        twemoji-assets = pkgs.fetchFromGitHub {
-          owner = "twitter";
-          repo = "twemoji";
-          rev = "v14.0.2";
-          hash = "sha256-YoOnZ5uVukzi/6bLi22Y8U5TpplPzB7ji42l+/ys5xI=";
-        };
-
         radicle-explorer = pkgs.callPackage ({
           lib,
           buildNpmPackage,
@@ -97,12 +90,9 @@
             pname = "radicle-explorer";
             version = (builtins.fromJSON (builtins.readFile ./package.json)).version;
             src = ./.;
-            npmDepsHash = "sha256-RC+QQXtvXC48uM0oOAFA0ni5AU/l9m8k1LgrxykSu5M=";
+            npmDepsHash = "sha256-pUyB56EJjuMYU//oMaFNV27Fg+Ga5jD0HQOB/v+gHa8=";
             postPatch = ''
               patchShebangs --build ./scripts
-              mkdir -p "public/twemoji"
-              cp -t public/twemoji -r -- ${self.packages.${system}.twemoji-assets}/assets/svg/*
-              : >scripts/install-twemoji-assets
             '';
             dontConfigure = true;
 
diff --git a/package-lock.json b/package-lock.json
index bc2cff6a6..87eee495d 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -7,8 +7,8 @@
     "": {
       "name": "radicle-explorer",
       "version": "1.0.0",
-      "hasInstallScript": true,
       "dependencies": {
+        "@twemoji/svg": "^15.0.0",
         "@wooorm/starry-night": "^3.10.0",
         "async-mutex": "^0.5.0",
         "baconjs": "^3.0.23",
@@ -1183,6 +1183,12 @@
       "dev": true,
       "license": "MIT"
     },
+    "node_modules/@twemoji/svg": {
+      "version": "15.0.0",
+      "resolved": "https://registry.npmjs.org/@twemoji/svg/-/svg-15.0.0.tgz",
+      "integrity": "sha512-ZSPef2B6nBaYnfgdTbAy4jgW95o7pi2xPGwGCU+WMTxo7J6B1lMPTWwSq/wTuiMq+N0khQ90CcvYp1wFoQpo/w==",
+      "license": "MIT"
+    },
     "node_modules/@tybys/wasm-util": {
       "version": "0.10.3",
       "resolved": "https://registry.npmjs.org/@tybys/wasm-util/-/wasm-util-0.10.3.tgz",
diff --git a/package.json b/package.json
index d18e4c684..8e4895634 100644
--- a/package.json
+++ b/package.json
@@ -6,8 +6,7 @@
     "start": "vite",
     "start:httpd": "cargo run -p radicle-httpd --release -- --listen 127.0.0.1:8080",
     "serve": "vite preview",
-    "build": "vite build && scripts/copy-katex-assets && scripts/install-twemoji-assets",
-    "postinstall": "scripts/copy-katex-assets && scripts/install-twemoji-assets",
+    "build": "vite build",
     "check": "scripts/check",
     "check:radicle-httpd": "cargo clippy --all --tests && cargo fmt --all --check",
     "format": "npx prettier '**/*.@(ts|js|svelte|json|css|html|yml)' --write",
@@ -63,6 +62,7 @@
     "wait-on": "^9.0.10"
   },
   "dependencies": {
+    "@twemoji/svg": "^15.0.0",
     "@wooorm/starry-night": "^3.10.0",
     "async-mutex": "^0.5.0",
     "baconjs": "^3.0.23",
diff --git a/public/twemoji/.gitkeep b/public/twemoji/.gitkeep
deleted file mode 100644
index e69de29bb..000000000
diff --git a/scripts/check b/scripts/check
index 5673783d2..583a1ab9b 100755
--- a/scripts/check
+++ b/scripts/check
@@ -3,5 +3,10 @@ set -e
 
 npx tsc --noEmit
 npx svelte-check --tsconfig tsconfig.json --config ./vite.config.ts --fail-on-warnings --compiler-warnings options_missing_custom_element:ignore
-npx eslint --cache --cache-location node_modules/.cache/eslint --max-warnings 0 .
-npx prettier "**/*.@(ts|js|svelte|json|css|html|yml)" --ignore-path .gitignore --ignore-path .prettierignore --check --cache
+# Both caches sit outside node_modules, which `npm ci` deletes, and both are
+# keyed on file contents rather than mtimes, which a fresh checkout changes.
+# CI can then carry them between builds. They share one directory because a
+# Buildkite cache path is always a directory, never a file.
+mkdir -p .lintcache
+npx eslint --cache --cache-location .lintcache/eslint --cache-strategy content --max-warnings 0 .
+npx prettier "**/*.@(ts|js|svelte|json|css|html|yml)" --ignore-path .gitignore --ignore-path .prettierignore --check --cache --cache-location .lintcache/prettier
diff --git a/scripts/copy-katex-assets b/scripts/copy-katex-assets
deleted file mode 100755
index aa83b2535..000000000
--- a/scripts/copy-katex-assets
+++ /dev/null
@@ -1,7 +0,0 @@
-#!/usr/bin/env bash
-set -Eeuo pipefail
-
-echo "Copying katex assets into bundle directory"
-
-cp -r node_modules/katex/dist/katex.min.css public/katex.min.css
-cp -r node_modules/katex/dist/fonts/* public/fonts/
diff --git a/scripts/install-twemoji-assets b/scripts/install-twemoji-assets
deleted file mode 100755
index 96a48b219..000000000
--- a/scripts/install-twemoji-assets
+++ /dev/null
@@ -1,9 +0,0 @@
-#!/usr/bin/env bash
-set -Eeou pipefail
-
-version="$(node -e 'console.log(require("twemoji/package.json").version)')"
-
-echo "Installing Twemoji SVG assets v${version}"
-
-curl -sSL "https://github.com/twitter/twemoji/archive/refs/tags/v${version}.tar.gz" \
-  | tar -x -z -C public/twemoji/ --strip-components=3 "twemoji-${version}/assets/svg"
diff --git a/vite-plugin-assets.ts b/vite-plugin-assets.ts
new file mode 100644
index 000000000..184037689
--- /dev/null
+++ b/vite-plugin-assets.ts
@@ -0,0 +1,78 @@
+import type { Plugin } from "vite";
+
+import fs from "node:fs/promises";
+import path from "node:path";
+import { createRequire } from "node:module";
+
+const require = createRequire(import.meta.url);
+
+function packageDir(name: string): string {
+  return path.dirname(require.resolve(`${name}/package.json`));
+}
+
+function packageVersion(name: string): string {
+  const { version } = require(`${name}/package.json`) as { version: string };
+  return version;
+}
+
+// index.html loads /katex.min.css, so the stylesheet and the fonts it
+// references must be in the public directory.
+async function copyKatexAssets(publicDir: string) {
+  const dist = path.join(packageDir("katex"), "dist");
+
+  await fs.copyFile(
+    path.join(dist, "katex.min.css"),
+    path.join(publicDir, "katex.min.css"),
+  );
+  await fs.cp(path.join(dist, "fonts"), path.join(publicDir, "fonts"), {
+    recursive: true,
+  });
+}
+
+// Emoji URLs are built at runtime, so the SVGs cannot be bundled and must be
+// in the public directory. The version stamp skips the copy of ~3700 files
+// when the assets are already installed. It lives outside the public directory
+// because Vite copies that directory into the build as it is. node_modules is
+// the right place for it: an install is what changes the package, and it is
+// also what discards the stamp.
+//
+// The stamp is not enough on its own, because it and the assets sit in
+// different places and either one can go without the other. The Docker e2e
+// setup keeps node_modules in a volume that outlives the working tree, so a
+// `git clean` there removes the assets and leaves the stamp behind. Checking
+// the target as well stops a stamp that has outlived its assets from producing
+// a build with no emoji in it, which nothing else would report.
+async function copyTwemojiAssets(root: string, publicDir: string) {
+  const version = packageVersion("@twemoji/svg");
+  const target = path.join(publicDir, "twemoji");
+  const stamp = path.join(root, "node_modules", ".cache", "twemoji-version");
+
+  const installed = await fs.readFile(stamp, "utf8").catch(() => undefined);
+  const present = await fs.stat(target).catch(() => undefined);
+  if (installed === version && present) {
+    return;
+  }
+
+  const source = packageDir("@twemoji/svg");
+  await fs.cp(source, target, {
+    recursive: true,
+    // The package also holds a readme, a license and package.json.
+    filter: entry => entry === source || entry.endsWith(".svg"),
+  });
+  await fs.mkdir(path.dirname(stamp), { recursive: true });
+  await fs.writeFile(stamp, version);
+}
+
+export function assets(): Plugin {
+  return {
+    name: "assets",
+    // Vitest loads this config too, but does not need the assets.
+    apply: () => !process.env.VITEST,
+    // The dev server reads the public directory right after the config is
+    // resolved, so the assets have to be in place before that.
+    async configResolved(config) {
+      await copyKatexAssets(config.publicDir);
+      await copyTwemojiAssets(config.root, config.publicDir);
+    },
+  };
+}
diff --git a/vite.config.ts b/vite.config.ts
index 6effa64b1..a3a2c86a7 100644
--- a/vite.config.ts
+++ b/vite.config.ts
@@ -3,6 +3,8 @@ import path from "node:path";
 import { defineConfig } from "vitest/config";
 import { svelte } from "@sveltejs/vite-plugin-svelte";
 
+import { assets } from "./vite-plugin-assets";
+
 export default defineConfig({
   define: {
     buildTimeConfig: JSON.stringify(config.util.toObject()),
@@ -13,6 +15,7 @@ export default defineConfig({
     reporters: "verbose",
   },
   plugins: [
+    assets(),
     svelte({
       extensions: [".svelte", ".md"],
       // Reference: https://github.com/sveltejs/vite-plugin-svelte/issues/270#issuecomment-1033190138