diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 7f36192..22a92a2 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -18,7 +18,7 @@ jobs:
       - uses: actions/checkout@v7
       - uses: actions/setup-node@v7
         with:
-          node-version: 22
+          node-version: 26
           cache: npm
       - run: npm ci --ignore-scripts
       - run: npm run typecheck
diff --git a/.github/workflows/publish.yml b/.github/workflows/publish.yml
index 109d5ee..c50e2a5 100644
--- a/.github/workflows/publish.yml
+++ b/.github/workflows/publish.yml
@@ -82,7 +82,7 @@ jobs:
           fetch-depth: 0
       - uses: actions/setup-node@v7
         with:
-          node-version: 22
+          node-version: 26
       - id: v
         run: |
           V="$(node scripts/version.mjs)"
diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
index 4e8ad60..2b2e2bb 100644
--- a/.github/workflows/release.yml
+++ b/.github/workflows/release.yml
@@ -52,7 +52,7 @@ jobs:
           fetch-depth: 0
       - uses: actions/setup-node@v7
         with:
-          node-version: 22
+          node-version: 26
       - id: decide
         env:
           GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}
diff --git a/Dockerfile b/Dockerfile
index 323f41b..adb1777 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -1,5 +1,5 @@
 # ---- build stage ----
-FROM node:22-alpine AS build
+FROM node:26-alpine AS build
 # What this build calls itself: 2.16.<PR>, worked out by whoever runs the
 # build. It cannot be worked out in here -- .dockerignore keeps .git out of the
 # context on purpose, and git is not installed either. `node scripts/version.mjs`
@@ -25,7 +25,7 @@ COPY . .
 RUN npm run build
 
 # ---- runtime stage ----
-FROM node:22-alpine AS runtime
+FROM node:26-alpine AS runtime
 # Re-declared: an ARG does not cross stages.
 ARG IHASMAIL_VERSION=""
 ARG BASE_PATH=""
diff --git a/README.md b/README.md
index fec0356..628d079 100644
--- a/README.md
+++ b/README.md
@@ -347,7 +347,7 @@ missing.
 
 ## Development
 
-Requirements: Node ≥ 20.19 (22 recommended), npm ≥ 10.
+Requirements: Node ≥ 20.19 (26 recommended), npm ≥ 10.
 
 ```bash
 npm install
diff --git a/package-lock.json b/package-lock.json
index ccb6d74..483f2e5 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -968,13 +968,13 @@
       "license": "MIT"
     },
     "node_modules/@types/node": {
-      "version": "22.20.2",
-      "resolved": "https://registry.npmjs.org/@types/node/-/node-22.20.2.tgz",
-      "integrity": "sha512-xlvWf4Vs9n1PEVYwP1n4vvG07M6y8WgvJ2t0vbrWTmijsIHp1cS+uJ2kMIRdY3nHZK0nCYKrPeD171+SzF4/zw==",
+      "version": "26.5.1",
+      "resolved": "https://registry.npmjs.org/@types/node/-/node-26.5.1.tgz",
+      "integrity": "sha512-CzNm2FezW4VR/LjG6yUdiEgLE/rAQ9Slj5gCu/C2VrdcW7I0ahNZ8DRbHT7zOZ6r3ONgd/bsQIeSaoDGrd1C6g==",
       "dev": true,
       "license": "MIT",
       "dependencies": {
-        "undici-types": "~6.21.0"
+        "undici-types": "~8.9.0"
       }
     },
     "node_modules/@types/react": {
@@ -2778,9 +2778,9 @@
       }
     },
     "node_modules/undici-types": {
-      "version": "6.21.0",
-      "resolved": "https://registry.npmjs.org/undici-types/-/undici-types-6.21.0.tgz",
-      "integrity": "sha512-iwDZqg0QAGrg9Rav5H4n0M64c3mkR59cJ6wQp+7C4nI0gsmExaedaYLNO44eT4AtBBwjbTiGPMlt2Md0T9H9JQ==",
+      "version": "8.9.0",
+      "resolved": "https://registry.npmjs.org/undici-types/-/undici-types-8.9.0.tgz",
+      "integrity": "sha512-KTDyRTYX8sWmKXAikPHHSyc63CRPETMctyjKFupcC6OBLXT3xsN0e9aF7m+mIXutFWpUXuedtowG7iLOzp0kQg==",
       "dev": true,
       "license": "MIT"
     },
@@ -3186,7 +3186,7 @@
         "hono": "^4.13.7"
       },
       "devDependencies": {
-        "@types/node": "^22.13.10",
+        "@types/node": "^26.5.1",
         "tsx": "^4.23.13",
         "typescript": "^7.0.2"
       }
diff --git a/server/package.json b/server/package.json
index 3fc14b2..a103e63 100644
--- a/server/package.json
+++ b/server/package.json
@@ -20,7 +20,7 @@
     "hono": "^4.13.7"
   },
   "devDependencies": {
-    "@types/node": "^22.13.10",
+    "@types/node": "^26.5.1",
     "tsx": "^4.23.13",
     "typescript": "^7.0.2"
   }