#303: operator-uploaded fonts — storage, API, PDF embedding, backup

An operator holding a font licence could only use it by baking the file into a custom image, which tied every change to a rebuild and left the file out of the backup. ADR 0016 said there is no runtime font management. It also listed this exact case under "Alternatives considered" — *may become a Site-Admin- level feature later*. The amendment takes that option and answers the two objections it raised: licensing risk (Site Admins only, licence recorded with the family) and file-format attack surface (magic-byte check and a size cap, never a parse). - `CUSTOM_FONTS_DIR` (default `./data/fonts`) — a sibling of uploads and plugins, NOT inside the image-baked `FONTS_DIR`, where a deploy would overwrite it and no backup would ever see it. - One list of data directories (`apps/backup/src/data-dirs.ts`) now feeds both the nightly archive and the restore, so they cannot drift. #306 and #307 add one line each instead of a second mechanism. - Both Dockerfiles bake the path. The backup image sets its volume paths itself ("self-sufficient without compose env" — #71's lesson) and reads no *_DIR from compose; without the ENV entry the archive would have skipped the directory silently. - The PDF path already read WOFF2 from disk at request time, so it only had to pick the other base directory for a custom family. - `fontStack`/`fontEntry` take the instance's uploaded families as an argument — they are runtime data. The catalog is searched first, and a colliding family name is rejected at upload, so a custom font can never shadow a catalog one. - Deletion is never blocked by usage: an unknown family already falls back to the system stack, so affected ponds degrade instead of breaking. The count of affected ponds travels into the audit entry. - Audit catalogue v1.6 (`font.uploaded`, `font.deleted`). Verified: api full suite against a fresh database, 102 files / 571 tests. The upload suite writes into a real temp directory and reads the bytes back off disk, so the storage layer is exercised rather than mocked.
2026-08-01 14:49:13 +02:00 · 2026-08-01 14:49:13 +02:00 · b96997501a
commit b96997501a
parent 5164801676
23 changed files with 1132 additions and 89 deletions
--- a/apps/api/Dockerfile
+++ b/apps/api/Dockerfile
@ -29,7 +29,7 @@ ARG APP_VERSION=0.0.0-dev
 # Default the data dirs to the writable, node-owned locations created below, so
 # the image works out of the box even where compose does not set them; compose
 # still mounts named volumes here for persistence (UPLOADS_DIR/PLUGINS_DIR).
-ENV NODE_ENV=production APP_VERSION=${APP_VERSION} UPLOADS_DIR=/data/uploads PLUGINS_DIR=/data/plugins SECRETS_FILE=/data/secrets/secrets.env BACKUPS_DIR=/data/backups
+ENV NODE_ENV=production APP_VERSION=${APP_VERSION} UPLOADS_DIR=/data/uploads PLUGINS_DIR=/data/plugins CUSTOM_FONTS_DIR=/data/fonts SECRETS_FILE=/data/secrets/secrets.env BACKUPS_DIR=/data/backups
 WORKDIR /app
 COPY --from=build --chown=node:node /out /app
 # Generate the Prisma client for this image's platform.
--- a/apps/api/prisma/migrations/20260801120000_custom_fonts/migration.sql
+++ b/apps/api/prisma/migrations/20260801120000_custom_fonts/migration.sql
@ -0,0 +1,45 @@
+-- #303: operator-uploaded font families (ADR 0016 §#303).
+-- The bytes live on disk under CUSTOM_FONTS_DIR; these rows record only what
+-- the upload form stated, because the api never parses the font file.
+
+CREATE TABLE "custom_fonts" (
+    "id" TEXT NOT NULL,
+    "family" TEXT NOT NULL,
+    "slug" TEXT NOT NULL,
+    "category" TEXT NOT NULL,
+    "licence" TEXT NOT NULL,
+    "licence_url" TEXT,
+    "uploaded_by" TEXT NOT NULL,
+    "created_at" TIMESTAMP(3) NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    "updated_at" TIMESTAMP(3) NOT NULL,
+
+    CONSTRAINT "custom_fonts_pkey" PRIMARY KEY ("id")
+);
+
+-- Both unique: `family` keeps `fonts.<slot>.family` in pond settings
+-- unambiguous, `slug` owns a directory under CUSTOM_FONTS_DIR.
+CREATE UNIQUE INDEX "custom_fonts_family_key" ON "custom_fonts"("family");
+CREATE UNIQUE INDEX "custom_fonts_slug_key" ON "custom_fonts"("slug");
+
+ALTER TABLE "custom_fonts" ADD CONSTRAINT "custom_fonts_uploaded_by_fkey"
+    FOREIGN KEY ("uploaded_by") REFERENCES "users"("id")
+    ON DELETE RESTRICT ON UPDATE CASCADE;
+
+CREATE TABLE "custom_font_weights" (
+    "id" TEXT NOT NULL,
+    "font_id" TEXT NOT NULL,
+    "weight" INTEGER NOT NULL,
+    "has_woff" BOOLEAN NOT NULL DEFAULT false,
+    "byte_size" INTEGER NOT NULL,
+
+    CONSTRAINT "custom_font_weights_pkey" PRIMARY KEY ("id")
+);
+
+CREATE UNIQUE INDEX "custom_font_weights_font_id_weight_key"
+    ON "custom_font_weights"("font_id", "weight");
+
+-- Deleting a family takes its weights with it; the files on disk are removed
+-- by the service in the same operation.
+ALTER TABLE "custom_font_weights" ADD CONSTRAINT "custom_font_weights_font_id_fkey"
+    FOREIGN KEY ("font_id") REFERENCES "custom_fonts"("id")
+    ON DELETE CASCADE ON UPDATE CASCADE;
--- a/apps/api/prisma/schema.prisma
+++ b/apps/api/prisma/schema.prisma
@ -31,42 +31,43 @@ enum UserStatus {
 /// Account profile. Login methods live in UserIdentity (OIDC-ready,
 /// ADR 0007); Site Admin is a user flag, all other roles are grants.
 model User {
-  id              String     @id @default(uuid())
-  username        String     @unique
-  email           String     @unique
-  displayName     String     @map("display_name")
-  locale          String     @default("en")
-  isSiteAdmin     Boolean    @default(false) @map("is_site_admin")
+  id                 String     @id @default(uuid())
+  username           String     @unique
+  email              String     @unique
+  displayName        String     @map("display_name")
+  locale             String     @default("en")
+  isSiteAdmin        Boolean    @default(false) @map("is_site_admin")
  /// True when the flag was last SET by the IdP claim mapping (issue #217):
  /// only then may the mapping revoke it again on a later login. A manual
  /// admin toggle clears the marker, so hand-granted admins are never
  /// demoted by a missing claim.
-  isSiteAdminManaged Boolean @default(false) @map("is_site_admin_managed")
+  isSiteAdminManaged Boolean    @default(false) @map("is_site_admin_managed")
  /// Auto-watch preferences (issue #93): watch pages I create / comment on.
-  autoWatchOwnPages  Boolean @default(true) @map("auto_watch_own_pages")
-  autoWatchOnComment Boolean @default(true) @map("auto_watch_on_comment")
+  autoWatchOwnPages  Boolean    @default(true) @map("auto_watch_own_pages")
+  autoWatchOnComment Boolean    @default(true) @map("auto_watch_on_comment")
  /// E-mail digest cadence (issue #95): hourly | daily | off.
-  digestFrequency    String  @default("hourly") @map("digest_frequency")
-  status          UserStatus @default(PENDING_VERIFICATION)
-  emailVerifiedAt DateTime?  @map("email_verified_at")
-  createdAt       DateTime   @default(now()) @map("created_at")
-  lastLoginAt     DateTime?  @map("last_login_at")
+  digestFrequency    String     @default("hourly") @map("digest_frequency")
+  status             UserStatus @default(PENDING_VERIFICATION)
+  emailVerifiedAt    DateTime?  @map("email_verified_at")
+  createdAt          DateTime   @default(now()) @map("created_at")
+  lastLoginAt        DateTime?  @map("last_login_at")

-  identities      UserIdentity[]
-  sessions        Session[]
-  authTokens      AuthToken[]
-  apiTokens       ApiToken[]
-  feedTokens      FeedToken[]
-  mentionRows     PageMention[]
-  ponds           Pond[]
-  pages           Page[]
-  attachments     Attachment[]
-  conversionJobs  ConversionJob[]
-  auditEntries    AuditEntry[]
-  comments        Comment[]
-  watches         Watch[]
-  notifications   Notification[]
-  favorites       PageFavorite[]
+  identities     UserIdentity[]
+  sessions       Session[]
+  authTokens     AuthToken[]
+  apiTokens      ApiToken[]
+  feedTokens     FeedToken[]
+  mentionRows    PageMention[]
+  ponds          Pond[]
+  pages          Page[]
+  attachments    Attachment[]
+  conversionJobs ConversionJob[]
+  auditEntries   AuditEntry[]
+  comments       Comment[]
+  watches        Watch[]
+  notifications  Notification[]
+  favorites      PageFavorite[]
+  customFonts    CustomFont[]

  @@map("users")
 }
@ -107,32 +108,32 @@ model AuditEntry {
 /// lives per partition there (a partitioned parent cannot carry it without
 /// the partition key); `db push` test databases get it on the plain table.
 model ReadEvent {
-  id         String   @default(uuid())
-  occurredAt DateTime @default(now()) @map("occurred_at")
+  id             String   @default(uuid())
+  occurredAt     DateTime @default(now()) @map("occurred_at")
  /// Null = anonymous reader (public grant); `sessionKey` still names the
  /// browsing session, so the anonymous marker is explicit, not an accident.
-  actorId    String?  @map("actor_id")
+  actorId        String?  @map("actor_id")
  /// `session:<id>` for cookie sessions, `token:<id>` for PATs, `job:<id>`
  /// for background builds (account data export), `anon` for anonymous
  /// visitors — the dedup-window key basis (#223).
-  sessionKey String   @map("session_key")
-  pageId     String?  @map("page_id")
-  pondId     String   @map("pond_id")
+  sessionKey     String   @map("session_key")
+  pageId         String?  @map("page_id")
+  pondId         String   @map("pond_id")
  /// Which read surface fired: `page_view` | `no_js_shell` | `public_api` |
  /// `attachment` | `export` | `collab_join` (READ_CHANNELS union in code).
-  channel    String
+  channel        String
  /// Classification at read time — a later reclassification must not
  /// rewrite history (ADR 0023).
  classification String
-  details    Json?
+  details        Json?
  /// Dedup window (issue #223): `<sessionKey>:<pageId|->:<channel>` plus the
  /// aligned bucket `floor(epoch / windowSeconds)`. The unique pair makes
  /// concurrent duplicate reads collapse race-free (insert or P2002-skip).
-  dedupKey      String @map("dedup_key")
-  windowBucket  BigInt @map("window_bucket")
+  dedupKey       String   @map("dedup_key")
+  windowBucket   BigInt   @map("window_bucket")
  /// Window length the event was recorded under — the row itself states it
  /// represents up to this many seconds, so the evidence is not overread.
-  windowSeconds Int    @map("window_seconds")
+  windowSeconds  Int      @map("window_seconds")

  @@id([id, occurredAt])
  @@unique([dedupKey, windowBucket])
@ -237,14 +238,14 @@ model Pond {
  deletedAt   DateTime? @map("deleted_at")
  deletedBy   String?   @map("deleted_by")

-  owner       User         @relation(fields: [ownerId], references: [id])
-  usage       PondUsage?
-  pages       Page[]
-  attachments Attachment[]
-  labels      Label[]
-  grants      RoleGrant[]
+  owner          User            @relation(fields: [ownerId], references: [id])
+  usage          PondUsage?
+  pages          Page[]
+  attachments    Attachment[]
+  labels         Label[]
+  grants         RoleGrant[]
  conversionJobs ConversionJob[]
-  pondPlugins PondPlugin[]
+  pondPlugins    PondPlugin[]

  @@index([ownerId])
  @@map("ponds")
@ -460,12 +461,12 @@ model CollabOpenSession {
 /// built from the Yjs state via the shared editor schema. `outline` is the
 /// heading tree (`OutlineEntry[]` from @dorfteich/shared) as jsonb.
 model PageContentCache {
-  pageId    String   @id @map("page_id")
-  plainText String   @map("plain_text")
-  markdown  String
-  html      String
-  outline   Json
-  updatedAt DateTime @updatedAt @map("updated_at")
+  pageId       String                   @id @map("page_id")
+  plainText    String                   @map("plain_text")
+  markdown     String
+  html         String
+  outline      Json
+  updatedAt    DateTime                 @updatedAt @map("updated_at")
  /// Weighted full-text search vector (title A, labels B, body C; issue #49,
  /// ADR 0010). Maintained by the SearchProvider and the collab persistence
  /// hook (both write it with the same weighting). The GIN index is added in
@ -854,9 +855,9 @@ model ConversionJob {
  sourceName   String? @map("source_name")
  resultPageId String? @map("result_page_id")

-  owner  User  @relation(fields: [ownerId], references: [id], onDelete: Cascade)
-  pond   Pond? @relation(fields: [pondId], references: [id], onDelete: Cascade)
-  page   Page? @relation(fields: [resultPageId], references: [id], onDelete: SetNull)
+  owner User  @relation(fields: [ownerId], references: [id], onDelete: Cascade)
+  pond  Pond? @relation(fields: [pondId], references: [id], onDelete: Cascade)
+  page  Page? @relation(fields: [resultPageId], references: [id], onDelete: SetNull)

  @@index([status, createdAt])
  @@map("conversion_jobs")
@ -913,3 +914,48 @@ model PondPlugin {
  @@id([pondId, pluginId])
  @@map("pond_plugins")
 }
+
+/// An operator-uploaded font family (issue #303, ADR 0016 §#303). The bytes
+/// live on disk under CUSTOM_FONTS_DIR — this row only records what the
+/// upload form stated, because the api never parses the font file itself.
+/// Additive to the compile-time catalog: a family whose name or slug
+/// collides with a catalog entry is rejected, so `fonts.<slot>.family` in a
+/// pond's settings stays unambiguous.
+model CustomFont {
+  id         String   @id @default(uuid())
+  /// CSS `font-family` name, as typed by the uploader.
+  family     String   @unique
+  /// URL/file-safe form; names the directory under CUSTOM_FONTS_DIR.
+  slug       String   @unique
+  /// Drives the system fallback stack, like FontCatalogEntry.category.
+  category   String
+  /// Free-text licence label, e.g. "Commercial — Foundry XY". Required so
+  /// an attribution obligation can be met on the font catalogue page.
+  licence    String
+  licenceUrl String?  @map("licence_url")
+  uploadedBy String   @map("uploaded_by")
+  createdAt  DateTime @default(now()) @map("created_at")
+  updatedAt  DateTime @updatedAt @map("updated_at")
+
+  uploader User               @relation(fields: [uploadedBy], references: [id])
+  weights  CustomFontWeight[]
+
+  @@map("custom_fonts")
+}
+
+/// One weight of a custom family. Style is always `normal`: the PDF
+/// `@font-face` builder emits only that, and browsers synthesise oblique —
+/// italic uploads are a follow-up, not a silent half-feature.
+model CustomFontWeight {
+  id       String  @id @default(uuid())
+  fontId   String  @map("font_id")
+  weight   Int
+  /// Whether a legacy WOFF was supplied next to the required WOFF2.
+  hasWoff  Boolean @default(false) @map("has_woff")
+  byteSize Int     @map("byte_size")
+
+  font CustomFont @relation(fields: [fontId], references: [id], onDelete: Cascade)
+
+  @@unique([fontId, weight])
+  @@map("custom_font_weights")
+}
--- a/apps/api/src/app.module.ts
+++ b/apps/api/src/app.module.ts
@ -17,6 +17,7 @@ import { FilesModule } from './files/files.module';
 import { GrantsModule } from './grants/grants.module';
 import { HealthModule } from './health/health.module';
 import { HomeModule } from './home/home.module';
+import { FontsModule } from './fonts/fonts.module';
 import { ImportExportModule } from './import-export/import-export.module';
 import { LabelsModule } from './labels/labels.module';
 import { LegalModule } from './legal/legal.module';
@ -81,6 +82,7 @@ import { VersionsModule } from './versions/versions.module';
    PublicModule,
    PublicApiModule,
    McpModule,
+    FontsModule,
    ImportExportModule,
    PluginsModule,
    AuthModule,
--- a/apps/api/src/audit/audit-actions.ts
+++ b/apps/api/src/audit/audit-actions.ts
@ -45,6 +45,8 @@ export const AUDIT_EVENTS = {
  'quota.override_set': { severity: 'notice' },
  'read_trail.pruned': { severity: 'info' },
  'settings.changed': { severity: 'notice' },
+  'font.uploaded': { severity: 'notice' },
+  'font.deleted': { severity: 'notice' },
  'setup.admin_created': { severity: 'notice' },
  'setup.completed': { severity: 'info' },
  'setup.preseeded': { severity: 'info' },
--- a/apps/api/src/fonts/custom-font-storage.service.ts
+++ b/apps/api/src/fonts/custom-font-storage.service.ts
@ -0,0 +1,55 @@
+import { mkdir, readFile, rm, writeFile } from 'node:fs/promises';
+import { join } from 'node:path';
+
+import { Injectable } from '@nestjs/common';
+import type { FontUploadFormat } from '@dorfteich/shared';
+
+import { AppConfig } from '../config/app-config.service';
+
+/**
+ * Filesystem binding for operator-uploaded fonts (issue #303, ADR 0016 §#303).
+ *
+ * The layout mirrors the baked-in catalog — `<slug>/<slug>-<weight>.woff2` —
+ * so the PDF exporter's `@font-face` builder needs no special case beyond
+ * choosing the directory.
+ *
+ * That directory is `CUSTOM_FONTS_DIR`, NOT `FONTS_DIR`: the latter is baked
+ * into the image, so anything written there disappears on the next deploy and
+ * never reaches a backup. This one is a sibling of the uploads and plugins
+ * mounts and travels in the restore set (`apps/backup/src/data-dirs.ts`).
+ */
+@Injectable()
+export class CustomFontStorageService {
+  constructor(private readonly config: AppConfig) {}
+
+  private dirFor(slug: string): string {
+    return join(this.config.env.CUSTOM_FONTS_DIR, slug);
+  }
+
+  fileNameFor(slug: string, weight: number, format: FontUploadFormat): string {
+    return `${slug}-${weight}.${format}`;
+  }
+
+  pathFor(slug: string, weight: number, format: FontUploadFormat): string {
+    return join(this.dirFor(slug), this.fileNameFor(slug, weight, format));
+  }
+
+  async save(slug: string, weight: number, format: FontUploadFormat, bytes: Buffer): Promise<void> {
+    await mkdir(this.dirFor(slug), { recursive: true });
+    await writeFile(this.pathFor(slug, weight, format), bytes);
+  }
+
+  read(slug: string, weight: number, format: FontUploadFormat): Promise<Buffer> {
+    return readFile(this.pathFor(slug, weight, format));
+  }
+
+  /** Removes the family's whole directory. Missing is fine — deletion must
+   * stay idempotent so a half-failed upload can still be cleaned up. */
+  async deleteFamily(slug: string): Promise<void> {
+    await rm(this.dirFor(slug), { recursive: true, force: true });
+  }
+
+  async deleteWeight(slug: string, weight: number, format: FontUploadFormat): Promise<void> {
+    await rm(this.pathFor(slug, weight, format), { force: true });
+  }
+}
--- a/apps/api/src/fonts/custom-fonts.controller.ts
+++ b/apps/api/src/fonts/custom-fonts.controller.ts
@ -0,0 +1,146 @@
+import {
+  BadRequestException,
+  Controller,
+  Delete,
+  Get,
+  HttpCode,
+  Param,
+  Post,
+  Req,
+  Res,
+  UploadedFiles,
+  UseGuards,
+  UseInterceptors,
+} from '@nestjs/common';
+import { AnyFilesInterceptor } from '@nestjs/platform-express';
+import {
+  CustomFontView,
+  FONT_WEIGHTS,
+  MAX_FONT_FILE_BYTES,
+  createCustomFontInputSchema,
+} from '@dorfteich/shared';
+import type { Response } from 'express';
+
+import { SiteAdminGuard } from '../admin/site-admin.guard';
+import { AuthedRequest, Public } from '../auth/auth.guard';
+import { CustomFontStorageService } from './custom-font-storage.service';
+import { CustomFontsService, WeightUpload } from './custom-fonts.service';
+
+/** Multipart field names: `woff2-<weight>` and the optional `woff-<weight>`. */
+const FILE_FIELD = /^(woff2|woff)-(\d{3})$/;
+
+function parseUploads(files: Express.Multer.File[] | undefined): WeightUpload[] {
+  const byWeight = new Map<number, WeightUpload>();
+  for (const file of files ?? []) {
+    const match = FILE_FIELD.exec(file.fieldname);
+    if (!match) throw new BadRequestException({ code: 'font_unexpected_field' });
+    const weight = Number(match[2]);
+    if (!(FONT_WEIGHTS as readonly number[]).includes(weight)) {
+      throw new BadRequestException({ code: 'font_weight_invalid' });
+    }
+    const entry = byWeight.get(weight) ?? { weight, woff2: Buffer.alloc(0) };
+    if (match[1] === 'woff2') entry.woff2 = file.buffer;
+    else entry.woff = file.buffer;
+    byWeight.set(weight, entry);
+  }
+  // A WOFF without its WOFF2 would produce a weight the PDF path cannot
+  // embed — the exporter reads WOFF2 only.
+  for (const entry of byWeight.values()) {
+    if (entry.woff2.length === 0) throw new BadRequestException({ code: 'font_woff2_missing' });
+  }
+  return [...byWeight.values()].sort((a, b) => a.weight - b.weight);
+}
+
+/** Site-Admin management of operator-uploaded fonts (issue #303). */
+@Controller('admin/fonts')
+@UseGuards(SiteAdminGuard)
+export class CustomFontsAdminController {
+  constructor(private readonly fonts: CustomFontsService) {}
+
+  @Get()
+  list(): Promise<CustomFontView[]> {
+    return this.fonts.list();
+  }
+
+  @Post()
+  @UseInterceptors(AnyFilesInterceptor({ limits: { fileSize: MAX_FONT_FILE_BYTES } }))
+  async create(
+    @Req() request: AuthedRequest,
+    @UploadedFiles() files: Express.Multer.File[] | undefined,
+  ): Promise<CustomFontView> {
+    // The metadata rides as ordinary multipart fields next to the files.
+    const input = createCustomFontInputSchema.parse({
+      family: request.body?.family,
+      category: request.body?.category,
+      licence: request.body?.licence,
+      licenceUrl: request.body?.licenceUrl || null,
+    });
+    return this.fonts.create(request.user!, input, parseUploads(files));
+  }
+
+  @Post(':id/weights')
+  @UseInterceptors(AnyFilesInterceptor({ limits: { fileSize: MAX_FONT_FILE_BYTES } }))
+  async addWeight(
+    @Param('id') id: string,
+    @Req() request: AuthedRequest,
+    @UploadedFiles() files: Express.Multer.File[] | undefined,
+  ): Promise<CustomFontView> {
+    const uploads = parseUploads(files);
+    if (uploads.length !== 1) throw new BadRequestException({ code: 'font_one_weight_expected' });
+    return this.fonts.addWeight(request.user!, id, uploads[0]!);
+  }
+
+  /** How many live ponds still use the family — shown before deleting. */
+  @Get(':id/usage')
+  async usage(@Param('id') id: string): Promise<{ pondsAffected: number }> {
+    const font = (await this.fonts.list()).find((entry) => entry.id === id);
+    if (!font) throw new BadRequestException({ code: 'not_found' });
+    return { pondsAffected: await this.fonts.pondsUsing(font.family) };
+  }
+
+  @Delete(':id')
+  @HttpCode(204)
+  async remove(@Param('id') id: string, @Req() request: AuthedRequest): Promise<void> {
+    await this.fonts.remove(request.user!, id);
+  }
+}
+
+/**
+ * Serving route. Unauthenticated on purpose: a font is referenced from CSS,
+ * and the login screen carries the pond-independent chrome — an authenticated
+ * font URL would simply not load. The bytes are branding, not content.
+ */
+@Controller('fonts/custom')
+export class CustomFontsFileController {
+  constructor(
+    private readonly storage: CustomFontStorageService,
+    private readonly fonts: CustomFontsService,
+  ) {}
+
+  @Public()
+  @Get(':slug/:file')
+  async serve(
+    @Param('slug') slug: string,
+    @Param('file') file: string,
+    @Res() res: Response,
+  ): Promise<void> {
+    const match = /^([a-z0-9-]+)-(\d{3})\.(woff2|woff)$/.exec(file);
+    // The slug must match the file's own prefix, so the path cannot be used
+    // to reach a different family's directory.
+    if (!match || match[1] !== slug) throw new BadRequestException({ code: 'not_found' });
+
+    const known = (await this.fonts.list()).find((entry) => entry.slug === slug);
+    if (!known) throw new BadRequestException({ code: 'not_found' });
+
+    const format = match[3] as 'woff2' | 'woff';
+    const bytes = await this.storage
+      .read(slug, Number(match[2]), format)
+      .catch(() => Promise.reject(new BadRequestException({ code: 'not_found' })));
+
+    res.setHeader('Content-Type', format === 'woff2' ? 'font/woff2' : 'font/woff');
+    // Slug + weight + format identify the bytes; a changed family is a new
+    // upload under a new id, so a long lifetime is safe.
+    res.setHeader('Cache-Control', 'public, max-age=31536000, immutable');
+    res.send(bytes);
+  }
+}
--- a/apps/api/src/fonts/custom-fonts.e2e.db.test.ts
+++ b/apps/api/src/fonts/custom-fonts.e2e.db.test.ts
@ -0,0 +1,220 @@
+import { mkdtemp, readFile, rm } from 'node:fs/promises';
+import { tmpdir } from 'node:os';
+import { join } from 'node:path';
+
+import { INestApplication } from '@nestjs/common';
+import { PrismaClient } from '@prisma/client';
+import request from 'supertest';
+import { afterAll, beforeAll, describe, expect, it } from 'vitest';
+
+import { createTestApp, sessionCookieOf } from '../testing/test-app';
+import { createTestPrisma, deletePondsWhere, hasTestDb, uniqueSuffix } from '../testing/test-db';
+import { UsersService } from '../users/users.service';
+
+/** Smallest bytes that pass the magic check — the api never parses further. */
+const woff2 = (): Buffer => Buffer.concat([Buffer.from('wOF2'), Buffer.alloc(64)]);
+const woff = (): Buffer => Buffer.concat([Buffer.from('wOFF'), Buffer.alloc(64)]);
+
+describe.skipIf(!hasTestDb)('custom fonts (e2e, issue #303)', () => {
+  let app: INestApplication;
+  let prisma: PrismaClient;
+  let fontsDir: string;
+  const suffix = uniqueSuffix();
+  const password = 'schriftverwaltung mit stil 1';
+  const admin = { username: `fa-${suffix}`, displayName: `Font Admin ${suffix}` };
+  const plain = { username: `fp-${suffix}`, displayName: `Font Plain ${suffix}` };
+  let adminCookie: string;
+  let plainCookie: string;
+
+  const api = () => request(app.getHttpServer());
+
+  beforeAll(async () => {
+    prisma = createTestPrisma();
+    await prisma.rateLimit.deleteMany({});
+    // A real directory so the storage layer is exercised, not mocked — the
+    // point of this suite is that bytes actually land somewhere retrievable.
+    fontsDir = await mkdtemp(join(tmpdir(), 'dorfteich-fonts-'));
+    process.env.CUSTOM_FONTS_DIR = fontsDir;
+    app = await createTestApp();
+    const users = app.get(UsersService);
+
+    const adminUser = await users.createUser({
+      username: admin.username,
+      email: `${admin.username}@example.org`,
+      displayName: admin.displayName,
+      password,
+      locale: 'en',
+    });
+    await users.markEmailVerified(adminUser.id);
+    await prisma.user.update({ where: { id: adminUser.id }, data: { isSiteAdmin: true } });
+    // additional_ponds defaults to 0 (ADR 0011) and the instance default is
+    // never raised — the usage test needs a pond, so grant an override.
+    await prisma.quotaOverride.create({
+      data: {
+        subjectType: 'USER',
+        subjectId: adminUser.id,
+        quotaKey: 'additional_ponds',
+        value: 10,
+      },
+    });
+
+    const plainUser = await users.createUser({
+      username: plain.username,
+      email: `${plain.username}@example.org`,
+      displayName: plain.displayName,
+      password,
+      locale: 'en',
+    });
+    await users.markEmailVerified(plainUser.id);
+
+    const login = async (username: string): Promise<string> =>
+      sessionCookieOf(
+        await api()
+          .post('/api/v1/auth/login')
+          .send({ usernameOrEmail: username, password })
+          .expect(200),
+      );
+    adminCookie = await login(admin.username);
+    plainCookie = await login(plain.username);
+  });
+
+  afterAll(async () => {
+    await prisma.customFont.deleteMany({});
+    const ids = (
+      await prisma.user.findMany({
+        where: { username: { contains: suffix } },
+        select: { id: true },
+      })
+    ).map((row) => row.id);
+    await prisma.quotaOverride.deleteMany({ where: { subjectId: { in: ids } } });
+    await deletePondsWhere(prisma, { owner: { username: { contains: suffix } } });
+    await prisma.user.deleteMany({ where: { username: { contains: suffix } } });
+    await prisma.$disconnect();
+    await app.close();
+    await rm(fontsDir, { recursive: true, force: true });
+    delete process.env.CUSTOM_FONTS_DIR;
+  });
+
+  it('uploads a family, writes the bytes, and serves them back', async () => {
+    const created = await api()
+      .post('/api/v1/admin/fonts')
+      .set('Cookie', adminCookie)
+      .field('family', `Hausschrift ${suffix}`)
+      .field('category', 'serif')
+      .field('licence', 'Commercial — Foundry XY')
+      .attach('woff2-400', woff2(), 'x.woff2')
+      .attach('woff-400', woff(), 'x.woff')
+      .expect(201);
+
+    expect(created.body.weights).toEqual([400]);
+    expect(created.body.licence).toBe('Commercial — Foundry XY');
+
+    const slug = created.body.slug as string;
+    // The bytes are really on disk, in the catalog's layout.
+    const onDisk = await readFile(join(fontsDir, slug, `${slug}-400.woff2`));
+    expect(onDisk.subarray(0, 4).toString()).toBe('wOF2');
+
+    // …and reachable without a session: a font is fetched from CSS.
+    const served = await api().get(`/api/v1/fonts/custom/${slug}/${slug}-400.woff2`).expect(200);
+    expect(served.headers['content-type']).toContain('font/woff2');
+  });
+
+  it('rejects a file that is not a font, whatever it is called', async () => {
+    const res = await api()
+      .post('/api/v1/admin/fonts')
+      .set('Cookie', adminCookie)
+      .field('family', `Fake ${suffix}`)
+      .field('category', 'sans-serif')
+      .field('licence', 'X')
+      .attach('woff2-400', Buffer.from('\x89PNG\r\n\x1a\n and more'), 'evil.woff2')
+      .expect(400);
+    expect(res.body.code).toBe('font_file_not_a_font');
+  });
+
+  it('refuses a family name that a catalog font already owns', async () => {
+    const res = await api()
+      .post('/api/v1/admin/fonts')
+      .set('Cookie', adminCookie)
+      .field('family', 'Roboto')
+      .field('category', 'sans-serif')
+      .field('licence', 'X')
+      .attach('woff2-400', woff2(), 'x.woff2')
+      .expect(409);
+    expect(res.body.code).toBe('font_family_reserved');
+  });
+
+  it('refuses a weight whose WOFF2 is missing', async () => {
+    const res = await api()
+      .post('/api/v1/admin/fonts')
+      .set('Cookie', adminCookie)
+      .field('family', `NurWoff ${suffix}`)
+      .field('category', 'sans-serif')
+      .field('licence', 'X')
+      .attach('woff-400', woff(), 'x.woff')
+      .expect(400);
+    expect(res.body.code).toBe('font_woff2_missing');
+  });
+
+  it('keeps every management route away from a non-admin', async () => {
+    await api().get('/api/v1/admin/fonts').set('Cookie', plainCookie).expect(403);
+    await api()
+      .post('/api/v1/admin/fonts')
+      .set('Cookie', plainCookie)
+      .field('family', `Nope ${suffix}`)
+      .field('category', 'serif')
+      .field('licence', 'X')
+      .attach('woff2-400', woff2(), 'x.woff2')
+      .expect(403);
+  });
+
+  it('counts the ponds a family is used by, and deletion leaves them working', async () => {
+    const created = await api()
+      .post('/api/v1/admin/fonts')
+      .set('Cookie', adminCookie)
+      .field('family', `Zählschrift ${suffix}`)
+      .field('category', 'sans-serif')
+      .field('licence', 'X')
+      .attach('woff2-400', woff2(), 'x.woff2')
+      .expect(201);
+
+    const pond = await api()
+      .post('/api/v1/ponds')
+      .set('Cookie', adminCookie)
+      .send({ name: `Schriftteich ${suffix}` })
+      .expect(201);
+    await api()
+      .patch(`/api/v1/ponds/${pond.body.id}`)
+      .set('Cookie', adminCookie)
+      .send({ fonts: { body: { family: `Zählschrift ${suffix}`, weight: 400 } } })
+      .expect(200);
+
+    const usage = await api()
+      .get(`/api/v1/admin/fonts/${created.body.id}/usage`)
+      .set('Cookie', adminCookie)
+      .expect(200);
+    expect(usage.body.pondsAffected).toBe(1);
+
+    // Deletion is never blocked by usage.
+    await api()
+      .delete(`/api/v1/admin/fonts/${created.body.id}`)
+      .set('Cookie', adminCookie)
+      .expect(204);
+
+    // The pond still resolves — it keeps the stored family name and falls
+    // back to the system stack, rather than breaking.
+    const after = await api()
+      .get(`/api/v1/ponds/${pond.body.slug}`)
+      .set('Cookie', adminCookie)
+      .expect(200);
+    expect(after.body.settings.fonts.body.family).toBe(`Zählschrift ${suffix}`);
+    expect(
+      await api().get('/api/v1/admin/fonts').set('Cookie', adminCookie).expect(200),
+    ).toBeTruthy();
+
+    const audit = await prisma.auditEntry.findFirst({
+      where: { action: 'font.deleted', targetId: created.body.id },
+    });
+    expect(audit).not.toBeNull();
+    expect(audit!.details).toMatchObject({ pondsAffected: 1 });
+  });
+});
--- a/apps/api/src/fonts/custom-fonts.service.ts
+++ b/apps/api/src/fonts/custom-fonts.service.ts
@ -0,0 +1,249 @@
+import {
+  BadRequestException,
+  ConflictException,
+  Injectable,
+  NotFoundException,
+} from '@nestjs/common';
+import {
+  CreateCustomFontInput,
+  CustomFontView,
+  FONT_CATALOG,
+  FontCategory,
+  FontUploadFormat,
+  MAX_FONT_FILE_BYTES,
+  MAX_FONT_WEIGHTS,
+  fontSlug,
+  hasFontMagic,
+} from '@dorfteich/shared';
+import { User } from '@prisma/client';
+import { PinoLogger } from 'nestjs-pino';
+
+import { AuditService } from '../audit/audit.service';
+import { PrismaService } from '../prisma/prisma.service';
+import { CustomFontStorageService } from './custom-font-storage.service';
+
+/** One weight's bytes as they arrive from the controller. */
+export interface WeightUpload {
+  weight: number;
+  woff2: Buffer;
+  woff?: Buffer;
+}
+
+/**
+ * Operator-uploaded font families (issue #303, ADR 0016 §#303).
+ *
+ * Site-Admin-only, additive to the compile-time catalog, and deliberately
+ * incurious about the files: the api validates the magic number and the size
+ * and then stores the bytes. Family, category and licence come from the form.
+ */
+@Injectable()
+export class CustomFontsService {
+  constructor(
+    private readonly prisma: PrismaService,
+    private readonly storage: CustomFontStorageService,
+    private readonly audit: AuditService,
+    private readonly logger: PinoLogger,
+  ) {
+    this.logger.setContext(CustomFontsService.name);
+  }
+
+  /**
+   * Rejects bytes that are not what they claim to be, before anything is
+   * written. Deliberately the ONLY inspection: parsing the font would gain
+   * metadata the form already carries, at the price of a known
+   * memory-safety surface (ADR 0016 §#303).
+   */
+  private assertUsableFont(bytes: Buffer, format: FontUploadFormat): void {
+    if (bytes.length === 0) throw new BadRequestException({ code: 'font_file_empty' });
+    if (bytes.length > MAX_FONT_FILE_BYTES) {
+      throw new BadRequestException({ code: 'font_file_too_large' });
+    }
+    if (!hasFontMagic(bytes, format)) {
+      throw new BadRequestException({ code: 'font_file_not_a_font' });
+    }
+  }
+
+  /**
+   * A custom family must not collide with a catalog one, by name or by slug:
+   * a pond stores `fonts.<slot>.family` as a plain string, so two families
+   * answering to the same name would make the PDF path embed whichever file
+   * it happened to find.
+   */
+  private async assertNameIsFree(family: string, slug: string): Promise<void> {
+    const catalogHit = FONT_CATALOG.some(
+      (entry) => entry.family === family || fontSlug(entry.family) === slug,
+    );
+    if (catalogHit) throw new ConflictException({ code: 'font_family_reserved' });
+    const existing = await this.prisma.customFont.findFirst({
+      where: { OR: [{ family }, { slug }] },
+      select: { id: true },
+    });
+    if (existing) throw new ConflictException({ code: 'font_family_exists' });
+  }
+
+  private viewOf(font: {
+    id: string;
+    family: string;
+    slug: string;
+    category: string;
+    licence: string;
+    licenceUrl: string | null;
+    createdAt: Date;
+    weights: { weight: number }[];
+  }): CustomFontView {
+    return {
+      id: font.id,
+      family: font.family,
+      slug: font.slug,
+      category: font.category as FontCategory,
+      licence: font.licence,
+      licenceUrl: font.licenceUrl,
+      weights: font.weights.map((row) => row.weight).sort((a, b) => a - b),
+      createdAt: font.createdAt.toISOString(),
+    };
+  }
+
+  async list(): Promise<CustomFontView[]> {
+    const fonts = await this.prisma.customFont.findMany({
+      orderBy: { family: 'asc' },
+      include: { weights: { select: { weight: true } } },
+    });
+    return fonts.map((font) => this.viewOf(font));
+  }
+
+  async create(
+    admin: User,
+    input: CreateCustomFontInput,
+    uploads: WeightUpload[],
+  ): Promise<CustomFontView> {
+    if (uploads.length === 0) throw new BadRequestException({ code: 'font_no_weights' });
+    if (uploads.length > MAX_FONT_WEIGHTS) {
+      throw new BadRequestException({ code: 'font_too_many_weights' });
+    }
+    for (const upload of uploads) {
+      this.assertUsableFont(upload.woff2, 'woff2');
+      if (upload.woff) this.assertUsableFont(upload.woff, 'woff');
+    }
+
+    const slug = fontSlug(input.family);
+    if (!slug) throw new BadRequestException({ code: 'font_family_unusable' });
+    await this.assertNameIsFree(input.family, slug);
+
+    // Row first, then bytes: a row without files is repairable (re-upload the
+    // weight), while files without a row would be invisible litter.
+    const font = await this.prisma.customFont.create({
+      data: {
+        family: input.family,
+        slug,
+        category: input.category,
+        licence: input.licence,
+        licenceUrl: input.licenceUrl,
+        uploadedBy: admin.id,
+        weights: {
+          create: uploads.map((upload) => ({
+            weight: upload.weight,
+            hasWoff: Boolean(upload.woff),
+            byteSize: upload.woff2.length,
+          })),
+        },
+      },
+      include: { weights: { select: { weight: true } } },
+    });
+
+    for (const upload of uploads) {
+      await this.storage.save(slug, upload.weight, 'woff2', upload.woff2);
+      if (upload.woff) await this.storage.save(slug, upload.weight, 'woff', upload.woff);
+    }
+
+    await this.audit.record({
+      action: 'font.uploaded',
+      actorId: admin.id,
+      targetType: 'font',
+      targetId: font.id,
+      details: { family: font.family },
+    });
+    return this.viewOf(font);
+  }
+
+  async addWeight(admin: User, fontId: string, upload: WeightUpload): Promise<CustomFontView> {
+    this.assertUsableFont(upload.woff2, 'woff2');
+    if (upload.woff) this.assertUsableFont(upload.woff, 'woff');
+
+    const font = await this.prisma.customFont.findUnique({
+      where: { id: fontId },
+      include: { weights: { select: { weight: true } } },
+    });
+    if (!font) throw new NotFoundException();
+    if (font.weights.length >= MAX_FONT_WEIGHTS) {
+      throw new BadRequestException({ code: 'font_too_many_weights' });
+    }
+    if (font.weights.some((row) => row.weight === upload.weight)) {
+      throw new ConflictException({ code: 'font_weight_exists' });
+    }
+
+    await this.prisma.customFontWeight.create({
+      data: {
+        fontId,
+        weight: upload.weight,
+        hasWoff: Boolean(upload.woff),
+        byteSize: upload.woff2.length,
+      },
+    });
+    await this.storage.save(font.slug, upload.weight, 'woff2', upload.woff2);
+    if (upload.woff) await this.storage.save(font.slug, upload.weight, 'woff', upload.woff);
+
+    await this.audit.record({
+      action: 'font.uploaded',
+      actorId: admin.id,
+      targetType: 'font',
+      targetId: fontId,
+      details: { family: font.family, weight: upload.weight },
+    });
+    const updated = await this.prisma.customFont.findUniqueOrThrow({
+      where: { id: fontId },
+      include: { weights: { select: { weight: true } } },
+    });
+    return this.viewOf(updated);
+  }
+
+  /**
+   * How many live ponds still name this family in any of their three font
+   * slots. Shown before deletion — those ponds keep working (an unknown
+   * family falls back to the system stack) but they visibly change.
+   */
+  async pondsUsing(family: string): Promise<number> {
+    const rows = await this.prisma.$queryRaw<{ count: bigint }[]>`
+      SELECT count(*)::bigint AS count
+        FROM ponds
+       WHERE deleted_at IS NULL
+         AND (settings #>> '{fonts,heading,family}' = ${family}
+           OR settings #>> '{fonts,body,family}' = ${family}
+           OR settings #>> '{fonts,mono,family}' = ${family})
+    `;
+    return Number(rows[0]?.count ?? 0);
+  }
+
+  /**
+   * Deletion is never blocked by usage. `fontStack` already yields the system
+   * fallback for an unknown family, so affected ponds degrade rather than
+   * break, and re-uploading the family restores them — but the count travels
+   * into the audit entry so the change is not silent.
+   */
+  async remove(admin: User, fontId: string): Promise<void> {
+    const font = await this.prisma.customFont.findUnique({ where: { id: fontId } });
+    if (!font) throw new NotFoundException();
+    const pondsAffected = await this.pondsUsing(font.family);
+
+    await this.prisma.customFont.delete({ where: { id: fontId } });
+    await this.storage.deleteFamily(font.slug);
+
+    await this.audit.record({
+      action: 'font.deleted',
+      actorId: admin.id,
+      targetType: 'font',
+      targetId: fontId,
+      details: { family: font.family, pondsAffected },
+    });
+    this.logger.info({ fontId, family: font.family, pondsAffected }, 'custom font deleted');
+  }
+}
--- a/apps/api/src/fonts/fonts.module.ts
+++ b/apps/api/src/fonts/fonts.module.ts
@ -0,0 +1,14 @@
+import { Module } from '@nestjs/common';
+
+import { CustomFontStorageService } from './custom-font-storage.service';
+import { CustomFontsAdminController, CustomFontsFileController } from './custom-fonts.controller';
+import { CustomFontsService } from './custom-fonts.service';
+
+/** Operator-uploaded fonts (issue #303, ADR 0016 §#303). Exports the service
+ * so the PDF exporter can resolve a pond's font to a custom family. */
+@Module({
+  controllers: [CustomFontsAdminController, CustomFontsFileController],
+  providers: [CustomFontsService, CustomFontStorageService],
+  exports: [CustomFontsService, CustomFontStorageService],
+})
+export class FontsModule {}
--- a/apps/api/src/import-export/export.service.ts
+++ b/apps/api/src/import-export/export.service.ts
@ -20,6 +20,7 @@ import { PinoLogger } from 'nestjs-pino';

 import { AppConfig } from '../config/app-config.service';
 import { FileStorageService } from '../files/file-storage.service';
+import { CustomFontsService } from '../fonts/custom-fonts.service';
 import { PermissionService } from '../permissions/permission.service';
 import { PluginFallbackRenderer } from '../plugins/plugin-fallback-renderer';
 import { PluginsService } from '../plugins/plugins.service';
@ -53,6 +54,7 @@ export class ExportService {
    private readonly plugins: PluginsService,
    private readonly fallbacks: PluginFallbackRenderer,
    private readonly config: AppConfig,
+    private readonly customFonts: CustomFontsService,
    private readonly readTrail: ReadTrailService,
    private readonly logger: PinoLogger,
  ) {
@ -371,12 +373,18 @@ export class ExportService {
    });
  }

-  /** Base64 `@font-face` rules for the pond's three fonts, read from the
-   * catalog baked into the image (ADR 0016). A font file that is absent (a
-   * native dev run without `FONTS_DIR` populated) is skipped — the render falls
-   * back to the system stack rather than failing. */
+  /** Base64 `@font-face` rules for the pond's three fonts. Catalog families
+   * come from the directory baked into the image (ADR 0016); operator-uploaded
+   * ones from `CUSTOM_FONTS_DIR` (issue #303) — same on-disk layout, so only
+   * the base directory differs. A font file that is absent (a native dev run
+   * without `FONTS_DIR` populated, or a family deleted between the settings
+   * write and the export) is skipped: the render falls back to the system
+   * stack rather than failing. */
  private async fontFaceCss(fonts: PondFonts): Promise<string> {
    const slots = [fonts.heading, fonts.body, fonts.mono];
+    const customSlugs = new Map(
+      (await this.customFonts.list()).map((font) => [font.family, font.slug]),
+    );
    // Dedup identical family+weight so a doc that repeats a font embeds it once.
    const seen = new Set<string>();
    const faces: string[] = [];
@ -384,8 +392,10 @@ export class ExportService {
      const key = `${slot.family}:${slot.weight}`;
      if (seen.has(key)) continue;
      seen.add(key);
-      const slug = fontSlug(slot.family);
-      const file = join(this.config.env.FONTS_DIR, slug, `${slug}-${slot.weight}.woff2`);
+      const customSlug = customSlugs.get(slot.family);
+      const slug = customSlug ?? fontSlug(slot.family);
+      const baseDir = customSlug ? this.config.env.CUSTOM_FONTS_DIR : this.config.env.FONTS_DIR;
+      const file = join(baseDir, slug, `${slug}-${slot.weight}.woff2`);
      try {
        const bytes = await readFile(file);
        faces.push(
@ -393,7 +403,7 @@ export class ExportService {
            ` src: url('data:font/woff2;base64,${bytes.toString('base64')}') format('woff2'); }`,
        );
      } catch {
-        this.logger.warn({ font: key }, 'pdf export: catalog font file missing, using fallback');
+        this.logger.warn({ font: key }, 'pdf export: font file missing, using fallback');
      }
    }
    return faces.join('\n');
--- a/apps/api/src/import-export/import-export.module.ts
+++ b/apps/api/src/import-export/import-export.module.ts
@ -2,6 +2,7 @@ import { Module, OnModuleInit } from '@nestjs/common';

 import { CommonModule } from '../common/common.module';
 import { FilesModule } from '../files/files.module';
+import { FontsModule } from '../fonts/fonts.module';
 import { LabelsModule } from '../labels/labels.module';
 import { PagesModule } from '../pages/pages.module';
 import { PluginsModule } from '../plugins/plugins.module';
@ -40,6 +41,7 @@ const PAYLOAD_PRUNE_CADENCE_SECONDS = 24 * 60 * 60;
  imports: [
    CommonModule,
    FilesModule,
+    FontsModule,
    LabelsModule,
    PagesModule,
    PluginsModule,
--- a/apps/backup/Dockerfile
+++ b/apps/backup/Dockerfile
@ -20,6 +20,7 @@ ENV NODE_ENV=production APP_VERSION=${APP_VERSION} \
    # Baked-in volume paths (self-sufficient without compose env, like the
    # api image's PLUGINS_DIR — issue #71's lesson).
    BACKUPS_DIR=/backups UPLOADS_DIR=/data/uploads PLUGINS_DIR=/data/plugins \
+    CUSTOM_FONTS_DIR=/data/fonts \
    SECRETS_FILE=/data/secrets/secrets.env
 # pg_dump/pg_restore matching the stack's postgres:17 server, GNU tar for the
 # volume archives, tzdata so BACKUP_TIME honors a configured TZ, and
--- a/apps/backup/src/data-dirs.ts
+++ b/apps/backup/src/data-dirs.ts
@ -0,0 +1,18 @@
+import type { BackupEnv } from '@dorfteich/shared';
+
+/**
+ * The data directories that travel in a restore set's archive (ADR 0015).
+ *
+ * ONE list, used by the nightly archive AND by the restore — they must not
+ * drift, or a backup would carry something the restore never puts back.
+ * Adding a new persistent data directory is a one-line change here plus the
+ * env entry and the compose mount.
+ *
+ * All of them must share a parent directory: `archiveBase` derives the tar
+ * root from that and throws otherwise.
+ */
+export function dataDirs(
+  env: Pick<BackupEnv, 'UPLOADS_DIR' | 'PLUGINS_DIR' | 'CUSTOM_FONTS_DIR'>,
+): string[] {
+  return [env.UPLOADS_DIR, env.PLUGINS_DIR, env.CUSTOM_FONTS_DIR];
+}
--- a/apps/backup/src/index.ts
+++ b/apps/backup/src/index.ts
@ -6,6 +6,7 @@ import { pino } from 'pino';

 import { createArchive } from './archive.js';
 import { createCommandListener } from './commands.js';
+import { dataDirs } from './data-dirs.js';
 import { loadBackupEnv } from './config.js';
 import { sendFailureMail } from './mail.js';
 import { mirrorSets, resolveMirrorConfig } from './mirror.js';
@ -50,7 +51,7 @@ async function buildRunnerDeps(trigger: 'scheduled' | 'manual'): Promise<RunnerD
    retentionDays: settings.localRetentionDays ?? env.BACKUP_RETENTION_DAYS,
    now: () => new Date(),
    dump: (outFile) => pgDump(env.DATABASE_URL, outFile),
-    archive: (outFile) => createArchive(outFile, [env.UPLOADS_DIR, env.PLUGINS_DIR]),
+    archive: (outFile) => createArchive(outFile, dataDirs(env)),
    onFailure: async (run) => {
      const sent = await sendFailureMail(env, run);
      if (!sent)
--- a/apps/backup/src/perform-restore.ts
+++ b/apps/backup/src/perform-restore.ts
@ -5,18 +5,22 @@ import type { BackupEnv } from '@dorfteich/shared';

 import { extractArchive } from './archive.js';
 import { archiveFileName, dumpFileName } from './backup-set.js';
+import { dataDirs } from './data-dirs.js';
 import { pgRestore } from './pg.js';
 import type { RemoteLogger } from './remote.js';

 /**
 * Restores one local set into the live database and data volumes:
 * `pg_restore --clean --if-exists` of the dump, then the volume archive
- * back over the uploads/plugins mounts. Shared by the operator CLI
+ * back over the data mounts (see data-dirs.ts). Shared by the operator CLI
 * (restore.js via restore.sh) and the in-app restore orchestrator (#103) —
 * one restore path, exercised by drills and the app alike.
 */
 export async function performRestore(
-  env: Pick<BackupEnv, 'BACKUPS_DIR' | 'DATABASE_URL' | 'UPLOADS_DIR' | 'PLUGINS_DIR'>,
+  env: Pick<
+    BackupEnv,
+    'BACKUPS_DIR' | 'DATABASE_URL' | 'UPLOADS_DIR' | 'PLUGINS_DIR' | 'CUSTOM_FONTS_DIR'
+  >,
  backupId: string,
  log: RemoteLogger,
 ): Promise<void> {
@ -29,6 +33,6 @@ export async function performRestore(
  }
  log.info({ backupId }, 'restoring database dump');
  await pgRestore(env.DATABASE_URL, dumpFile);
-  log.info({ backupId }, 'restoring uploads/plugins archive');
-  await extractArchive(archiveFile, [env.UPLOADS_DIR, env.PLUGINS_DIR]);
+  log.info({ backupId }, 'restoring the data-directory archive');
+  await extractArchive(archiveFile, dataDirs(env));
 }
--- a/deploy/compose/docker-compose.yml
+++ b/deploy/compose/docker-compose.yml
@ -87,6 +87,10 @@ services:
      # Matches the `plugins` volume mount below (ADR 0008, issue #71). A Site
      # Admin drops ZIPs into its `_dropzone/` subfolder; the watcher installs them.
      PLUGINS_DIR: /data/plugins
+      # Operator-uploaded fonts (issue #303, ADR 0016 §#303). A sibling of
+      # uploads/plugins so all three travel in one restore set — NOT inside
+      # the image-baked font catalog, which a deploy would overwrite.
+      CUSTOM_FONTS_DIR: /data/fonts
      # Read-only view of the backup sidecar's volume — the api only consumes
      # its status.json (readyz freshness #85, admin backup card #86).
      BACKUPS_DIR: /data/backups
@ -100,6 +104,7 @@ services:
    volumes:
      - uploads:/data/uploads
      - plugins:/data/plugins
+      - customfonts:/data/fonts
      - secrets:/data/secrets
      - backups:/data/backups:ro
    depends_on:
@ -184,10 +189,11 @@ services:
      SMTP_FROM: ${SMTP_FROM:-}
    networks: [internal]
    volumes:
-      # Write access to uploads/plugins is for the restore path only; the
+      # Write access to the data mounts is for the restore path only; the
      # nightly run just reads them into the archive.
      - uploads:/data/uploads
      - plugins:/data/plugins
+      - customfonts:/data/fonts
      - secrets:/data/secrets:ro
      - backups:/backups
    depends_on:
@ -273,6 +279,7 @@ volumes:
  db-data:
  uploads:
  plugins:
+  customfonts:
  secrets:
  backups:
  # Only used by the optional `caddy` profile (certificates + state).
--- a/docs/architecture/adr/0016-self-hosted-fonts.md
+++ b/docs/architecture/adr/0016-self-hosted-fonts.md
@ -38,6 +38,43 @@ itself (never from Google's CDN) to avoid GDPR issues. Defaults: Roboto 400
 - Image size grows by a few MiB per family (WOFF2, subset to latin/latin-ext
  by default) — negligible.

+## Decisions taken in #303 (2026-08-01)
+
+This ADR's "Consequences" said adding a font is a catalog PR plus an image
+rebuild, with **no runtime font management surface**. That is amended here,
+for the case this ADR already anticipated under "Alternatives considered":
+_arbitrary font upload … may become a Site-Admin-level feature later_.
+
+An operator running a private instance holds a licence for a typeface and
+wants to use it on screen and in exported PDFs. Baking it into a custom
+image works but ties every font change to a rebuild, and the file then
+lives in the image rather than in the backup.
+
+- **Site Admins only.** Not Pond Admins — which is what closes the
+  licensing-risk objection above: the operator who holds the licence is
+  the only one who can upload, and the licence is recorded with the font.
+  Uploaded families are additive; they never replace or shadow a catalog
+  family, and a name collision with one is rejected.
+- **Uploads are data, not code.** The api stores the submitted bytes and
+  serves them back with a pinned content type. It validates the magic
+  number (`wOF2`/`wOFF`) and a size cap, and it does **not** parse the
+  font — family, category and licence come from the form. This is the
+  answer to the file-format attack-surface objection: font parsers are a
+  known memory-safety surface and we gain nothing from entering it.
+- **WOFF2 required, WOFF optional, OTF not accepted.** WOFF2 covers both
+  consumers we have — the browser and Gotenberg's Chromium — and is the
+  format the PDF path already inlines. Storing OTF would enlarge uploads
+  and backups for no runtime benefit.
+- **The bytes live under `./data/`, not in `FONTS_DIR`.** `FONTS_DIR` is
+  the catalog directory baked into the image: anything written there is
+  lost on the next deploy and is never backed up. Custom fonts go to
+  `CUSTOM_FONTS_DIR` (default `./data/fonts`), a sibling of the uploads
+  and plugins directories, and are registered with the backup so a
+  restore brings them back.
+- **The GDPR guarantee is untouched.** Custom fonts are served from the
+  instance itself like the catalog ones; `font-src 'self' data:` stays as
+  it is, and a visitor's browser still makes zero third-party requests.
+
 ## Alternatives considered

 - **Runtime font download by the server on admin selection**: flexible but
--- a/docs/architecture/audit-events.md
+++ b/docs/architecture/audit-events.md
@ -1,6 +1,7 @@
 # Audit event catalogue

-**Catalogue version 1.5 (2026-07-31; 1.5 adds `plugin.rejected`,
+**Catalogue version 1.6 (2026-08-01; 1.6 adds `font.uploaded` and
+`font.deleted`, issue #303; 1.5 added `plugin.rejected`,
 issue #232; 1.4 added `auth.proxy_rejected`, issue #215; 1.3 added `auth.identity_linked`, issue #214; 1.2 added
 `read_trail.pruned`, issue #224; 1.1 added `page.classification_*`,
 issue #205).**
@ -124,13 +125,15 @@ failure), `warning` = feeds detection (suspicious or destructive),

 ### Plugins (`plugin.*`)

-| Id                    | Trigger                                                      | Severity | Actor                                | Target   | Fields                                                                                                                          |
-| --------------------- | ------------------------------------------------------------ | -------- | ------------------------------------ | -------- | ------------------------------------------------------------------------------------------------------------------------------- |
-| `plugin.installed`    | Plugin package installed or updated                          | notice   | admin, `null` for dropzone drop      | `plugin` | `version`, `update` (bool)                                                                                                      |
-| `plugin.rejected`     | Install or load blocked by the hash-pinning allowlist (#232) | warning  | admin for installs, `null` for loads | `plugin` | `surface` (`install`/`load`), `reason` (`not_pinned`/`hash_mismatch`/`unpinned`/`mismatch`), `version`, `bundleHash` (installs) |
-| `plugin.mode_set`     | Instance mode changed (disabled/optional/required)           | notice   | the admin                            | `plugin` | `mode`                                                                                                                          |
-| `plugin.uninstalled`  | Plugin removed                                               | notice   | the admin                            | `plugin` | —                                                                                                                               |
-| `plugin.pond_toggled` | Optional plugin toggled for one pond                         | info     | the pond admin                       | `pond`   | `plugin`, `enabled`                                                                                                             |
+| Id                    | Trigger                                                           | Severity | Actor                                | Target   | Fields                                                                                                                          |
+| --------------------- | ----------------------------------------------------------------- | -------- | ------------------------------------ | -------- | ------------------------------------------------------------------------------------------------------------------------------- |
+| `plugin.installed`    | Plugin package installed or updated                               | notice   | admin, `null` for dropzone drop      | `plugin` | `version`, `update` (bool)                                                                                                      |
+| `font.uploaded`       | Site Admin uploaded a custom font family or added a weight (#303) | notice   | admin                                | `font`   | `family`, `weight` (when a single weight was added)                                                                             |
+| `font.deleted`        | Site Admin removed a custom font family (#303)                    | notice   | admin                                | `font`   | `family`, `pondsAffected` (count of ponds still referencing it)                                                                 |
+| `plugin.rejected`     | Install or load blocked by the hash-pinning allowlist (#232)      | warning  | admin for installs, `null` for loads | `plugin` | `surface` (`install`/`load`), `reason` (`not_pinned`/`hash_mismatch`/`unpinned`/`mismatch`), `version`, `bundleHash` (installs) |
+| `plugin.mode_set`     | Instance mode changed (disabled/optional/required)                | notice   | the admin                            | `plugin` | `mode`                                                                                                                          |
+| `plugin.uninstalled`  | Plugin removed                                                    | notice   | the admin                            | `plugin` | —                                                                                                                               |
+| `plugin.pond_toggled` | Optional plugin toggled for one pond                              | info     | the pond admin                       | `pond`   | `plugin`, `enabled`                                                                                                             |

 ### Backup & restore (`backup.*`)

--- a/docs/architecture/security.md
+++ b/docs/architecture/security.md
@ -128,9 +128,21 @@ or sloppy plugin authors, compromised dependencies.
  for non-image types, no user content served same-origin as executable
  (`X-Content-Type-Options: nosniff`; uploads path never serves
  `text/html`).
+- **Font upload (issue #303, ADR 0016 §#303)**: Site Admins — not Pond
+  Admins — may upload licensed font families. The api validates the magic
+  number (`wOF2`/`wOFF`) and a per-file size cap and then stores the bytes;
+  it deliberately does **not** parse the font. Family, category and licence
+  come from the form, so nothing is gained by entering a font parser's
+  memory-safety surface. OTF is not accepted (no consumer needs it). Files
+  are served from `/api/v1/fonts/custom/<slug>/<file>` with a pinned
+  `font/woff2`-or-`font/woff` content type and the instance-wide `nosniff`
+  header; the path is validated against the file's own slug prefix, so it
+  cannot reach another family's directory. Uploads and deletions are
+  audited (`font.uploaded`, `font.deleted`).
 - App CSP (strict): `default-src 'self'`; `font-src 'self'` (ADR 0016);
  no third-party origins at all — the GDPR posture is "zero external
-  requests".
+  requests". Operator-uploaded fonts are served from the instance itself
+  like the catalog ones, so this is unchanged by #303.
 - **Attachment integrity (issue #199)**: every upload stores the SHA-256
  of its bytes, computed from the in-memory buffer as it is written (never
  by re-reading disk). Every download re-hashes the stored object BEFORE
--- a/packages/shared/src/custom-fonts.test.ts
+++ b/packages/shared/src/custom-fonts.test.ts
@ -0,0 +1,50 @@
+import { describe, expect, it } from 'vitest';
+
+import {
+  FONT_CATALOG,
+  customFontEntries,
+  fontEntry,
+  fontStack,
+  hasFontMagic,
+  type CustomFontView,
+} from './fonts';
+
+const view = (family: string, category: CustomFontView['category']): CustomFontView => ({
+  id: 'id',
+  family,
+  slug: 'x',
+  category,
+  licence: 'Commercial',
+  licenceUrl: null,
+  weights: [400],
+  createdAt: '2026-08-01T00:00:00.000Z',
+});
+
+describe('custom fonts (issue #303)', () => {
+  it('accepts only real WOFF2/WOFF signatures', () => {
+    expect(hasFontMagic(Buffer.from('wOF2rest'), 'woff2')).toBe(true);
+    expect(hasFontMagic(Buffer.from('wOFFrest'), 'woff')).toBe(true);
+    // A renamed file is the case this actually guards against.
+    expect(hasFontMagic(Buffer.from('\x89PNG\r\n'), 'woff2')).toBe(false);
+    expect(hasFontMagic(Buffer.from('wOFF'), 'woff2')).toBe(false);
+    expect(hasFontMagic(Buffer.alloc(0), 'woff2')).toBe(false);
+    // Shorter than the signature must not read past the end.
+    expect(hasFontMagic(Buffer.from('wO'), 'woff2')).toBe(false);
+  });
+
+  it('never lets a custom family shadow a catalog one', () => {
+    const catalogFamily = FONT_CATALOG[0]!.family;
+    const impostor = customFontEntries([view(catalogFamily, 'monospace')]);
+    // The catalog wins even when a same-named custom entry is passed in.
+    expect(fontEntry(catalogFamily, impostor)?.category).toBe(FONT_CATALOG[0]!.category);
+  });
+
+  it('builds a stack for a custom family and falls back once it is gone', () => {
+    const extra = customFontEntries([view('Hausschrift', 'serif')]);
+    expect(fontStack('Hausschrift', extra)).toContain("'Hausschrift'");
+    expect(fontStack('Hausschrift', extra)).toContain('Georgia');
+    // Deleting the font removes it from `extra` — the pond must degrade to
+    // the system stack, not render an unresolvable family name.
+    expect(fontStack('Hausschrift')).not.toContain('Hausschrift');
+  });
+});
--- a/packages/shared/src/env.ts
+++ b/packages/shared/src/env.ts
@ -118,6 +118,15 @@ export const apiEnvSchema = z.object({
   * dev/test runs point this at the web app's built `public/fonts`.
   */
  FONTS_DIR: z.string().min(1).default('./fonts'),
+  /**
+   * Directory of operator-uploaded fonts (issue #303, ADR 0016 §#303).
+   * Deliberately NOT under {@link FONTS_DIR}: that one is baked into the
+   * image, so anything written there is lost on the next deploy and never
+   * reaches a backup. This is a sibling of the uploads and plugins
+   * directories so it travels in the same restore set (ADR 0015).
+   * Layout mirrors the catalog: `<dir>/<slug>/<slug>-<weight>.woff2`.
+   */
+  CUSTOM_FONTS_DIR: z.string().min(1).default('./data/fonts'),
  /**
   * Directory holding installed plugin packages (ADR 0008, issue #71). Layout
   * `<PLUGINS_DIR>/<id>/<version>/…` for unpacked bundles the sandbox iframe
@ -249,9 +258,11 @@ export const backupEnvSchema = z.object({
  DATABASE_URL: databaseUrl,
  /** Where restore sets and `status.json` are written (the `backups` volume). */
  BACKUPS_DIR: z.string().min(1).default('./data/backups'),
-  /** Same mounts as the api — archived together as one restore set. */
+  /** Same mounts as the api — archived together as one restore set.
+   *  The authoritative list lives in `apps/backup/src/data-dirs.ts`. */
  UPLOADS_DIR: z.string().min(1).default('./data/uploads'),
  PLUGINS_DIR: z.string().min(1).default('./data/plugins'),
+  CUSTOM_FONTS_DIR: z.string().min(1).default('./data/fonts'),
  /** Daily run time as HH:MM, interpreted in the container's TZ. */
  BACKUP_TIME: z
    .string()
--- a/packages/shared/src/fonts.ts
+++ b/packages/shared/src/fonts.ts
@ -2,14 +2,19 @@
 * The curated self-hosted font catalog (ADR 0016). One maintained list drives
 * everything: the build step downloads these families' WOFF2 subsets into the
 * web image, the pond-settings Appearance UI offers them, and the attribution
- * page lists their licenses. Adding a font is a change here + an image rebuild
- * — there is no runtime font management (deliberately small surface).
+ * page lists their licenses. Adding a family HERE is a change plus an image
+ * rebuild. Since issue #303 an operator can additionally upload their own
+ * licensed families at runtime (ADR 0016 §#303); those live in the database
+ * and under CUSTOM_FONTS_DIR, are additive, and never shadow a catalog
+ * family — see {@link fontEntry}'s `extra` parameter.
 *
 * Fonts are served only from the instance itself (`font-src 'self' data:` —
 * the `data:` part covers fonts embedded inline in saved plugin SVGs, e.g.
 * Excalidraw sketches); a visitor's browser makes zero third-party requests
 * (the GDPR guarantee, security.md).
 */
+import { z } from 'zod';
+
 export type FontCategory = 'sans-serif' | 'serif' | 'monospace';
 export type FontLicense = 'OFL-1.1' | 'Apache-2.0';

@ -173,17 +178,120 @@ export function fontSlug(family: string): string {
    .replace(/(^-|-$)/g, '');
 }

-export function fontEntry(family: string): FontCatalogEntry | undefined {
-  return FONT_CATALOG.find((entry) => entry.family === family);
+/**
+ * Look up a family. `extra` carries the instance's operator-uploaded fonts
+ * (issue #303) — they are runtime data, so this package cannot hold them
+ * statically; callers in web and api pass what the api reported. A custom
+ * family never shadows a catalog one: uploads with a colliding name are
+ * rejected at the api, and the catalog is searched first regardless.
+ */
+export function fontEntry(
+  family: string,
+  extra: readonly FontCatalogEntry[] = [],
+): FontCatalogEntry | undefined {
+  return (
+    FONT_CATALOG.find((entry) => entry.family === family) ??
+    extra.find((entry) => entry.family === family)
+  );
 }

 /**
- * The `font-family` stack for a chosen family: the family itself (when it is in
- * the catalog) ahead of the category's system fallback, so text stays readable
- * before the WOFF2 loads or if the catalog font is unknown.
+ * The `font-family` stack for a chosen family: the family itself (when it is
+ * known) ahead of the category's system fallback, so text stays readable
+ * before the WOFF2 loads or if the family is unknown.
+ *
+ * Falling back for an unknown family is what makes deleting a custom font
+ * safe: the ponds using it degrade to the system stack instead of breaking,
+ * and re-uploading restores them.
 */
-export function fontStack(family: string): string {
-  const entry = fontEntry(family);
+export function fontStack(family: string, extra: readonly FontCatalogEntry[] = []): string {
+  const entry = fontEntry(family, extra);
  const fallback = FONT_FALLBACKS[entry?.category ?? 'sans-serif'];
  return entry ? `'${family}', ${fallback}` : fallback;
 }
+
+/** What the api reports about one uploaded family (issue #303). */
+export interface CustomFontView {
+  id: string;
+  family: string;
+  slug: string;
+  category: FontCategory;
+  licence: string;
+  licenceUrl: string | null;
+  weights: number[];
+  createdAt: string;
+}
+
+/** Adapts uploaded fonts to the shape {@link fontStack} understands. */
+export function customFontEntries(fonts: readonly CustomFontView[]): FontCatalogEntry[] {
+  return fonts.map((font) => ({
+    id: font.slug,
+    family: font.family,
+    category: font.category,
+    weights: font.weights,
+    // Not a catalog licence id — the label is free text and lives on the
+    // view; these two only satisfy the catalog shape.
+    license: 'OFL-1.1',
+    licenseUrl: font.licenceUrl ?? '',
+  }));
+}
+
+/** Formats accepted on upload. OTF is deliberately absent (ADR 0016 §#303):
+ *  neither the browser nor Gotenberg's Chromium needs it. */
+export const FONT_UPLOAD_FORMATS = ['woff2', 'woff'] as const;
+export type FontUploadFormat = (typeof FONT_UPLOAD_FORMATS)[number];
+
+/** Magic numbers of the accepted formats — the ONLY inspection the api does
+ *  on the bytes. Parsing the font would buy metadata we take from the form
+ *  anyway, at the cost of entering a known memory-safety surface. */
+const FONT_MAGIC: Readonly<Record<FontUploadFormat, string>> = {
+  woff2: 'wOF2',
+  woff: 'wOFF',
+};
+
+/** True when `bytes` starts with the format's signature. */
+export function hasFontMagic(bytes: Uint8Array, format: FontUploadFormat): boolean {
+  const magic = FONT_MAGIC[format];
+  if (bytes.length < magic.length) return false;
+  for (let i = 0; i < magic.length; i += 1) {
+    if (bytes[i] !== magic.charCodeAt(i)) return false;
+  }
+  return true;
+}
+
+/** Per-file cap. A latin-subset WOFF2 is tens of KB; a full CJK face can
+ *  reach a few MB, so 8 MiB leaves headroom without inviting abuse. */
+export const MAX_FONT_FILE_BYTES = 8 * 1024 * 1024;
+
+/** Cap on weights per family — the catalog's widest family offers five. */
+export const MAX_FONT_WEIGHTS = 12;
+
+/** Weights a custom family may declare: the CSS 100…900 ladder. */
+export const FONT_WEIGHTS = [100, 200, 300, 400, 500, 600, 700, 800, 900] as const;
+
+export const FONT_CATEGORIES = ['sans-serif', 'serif', 'monospace'] as const;
+
+/**
+ * Metadata half of a font upload (issue #303). The bytes travel as multipart
+ * files next to it. Everything here is what the OPERATOR states — the api
+ * does not read it out of the font, on purpose (ADR 0016 §#303).
+ */
+export const createCustomFontInputSchema = z.object({
+  family: z.string().trim().min(1).max(80),
+  category: z.enum(FONT_CATEGORIES),
+  /** Free text so any licence can be named, commercial ones included. */
+  licence: z.string().trim().min(1).max(200),
+  licenceUrl: z.string().url().max(500).nullable().default(null),
+});
+export type CreateCustomFontInput = z.infer<typeof createCustomFontInputSchema>;
+
+/** One weight of an upload; the files themselves ride as multipart parts. */
+export const customFontWeightInputSchema = z.object({
+  weight: z.coerce
+    .number()
+    .int()
+    .refine((w) => (FONT_WEIGHTS as readonly number[]).includes(w), {
+      message: 'validation.invalid',
+    }),
+});
+export type CustomFontWeightInput = z.infer<typeof customFontWeightInputSchema>;