diff --git a/.github/workflows/build-tarball.yml b/.github/workflows/build-tarball.yml
index 53e625ef889..feaac740d07 100644
--- a/.github/workflows/build-tarball.yml
+++ b/.github/workflows/build-tarball.yml
@@ -66,7 +66,7 @@ concurrency:
 env:
   PYTHON_VERSION: '3.14'
   FLAKY_TESTS: keep_retrying
-  CLANG_VERSION: '19'
+  CLANG_VERSION: '21'
   NODE_VERSION: lts/*
 
 permissions:
@@ -102,10 +102,10 @@ jobs:
           archive: false
   test-tarball-linux:
     needs: build-tarball
-    runs-on: ubuntu-24.04-arm
+    runs-on: ubuntu-26.04-arm
     env:
-      CC: ${{ (github.base_ref == 'main' || github.ref_name == 'main') && 'sccache' || '' }} clang-19
-      CXX: ${{ (github.base_ref == 'main' || github.ref_name == 'main') && 'sccache' || '' }} clang++-19
+      CC: ${{ (github.base_ref == 'main' || github.ref_name == 'main') && 'sccache' || '' }} clang-21
+      CXX: ${{ (github.base_ref == 'main' || github.ref_name == 'main') && 'sccache' || '' }} clang++-21
       SCCACHE_GHA_ENABLED: ${{ github.base_ref == 'main' || github.ref_name == 'main' }}
       SCCACHE_IDLE_TIMEOUT: '0'
     steps:
diff --git a/.github/workflows/coverage-linux-without-intl.yml b/.github/workflows/coverage-linux-without-intl.yml
index aa5ed3a3747..c37344cfd5c 100644
--- a/.github/workflows/coverage-linux-without-intl.yml
+++ b/.github/workflows/coverage-linux-without-intl.yml
@@ -36,9 +36,9 @@ concurrency:
 env:
   PYTHON_VERSION: '3.14'
   FLAKY_TESTS: keep_retrying
-  CLANG_VERSION: '19'
-  CC: ${{ (github.base_ref == 'main' || github.ref_name == 'main') && 'sccache' || '' }} clang-19
-  CXX: ${{ (github.base_ref == 'main' || github.ref_name == 'main') && 'sccache' || '' }} clang++-19
+  CLANG_VERSION: '21'
+  CC: ${{ (github.base_ref == 'main' || github.ref_name == 'main') && 'sccache' || '' }} clang-21
+  CXX: ${{ (github.base_ref == 'main' || github.ref_name == 'main') && 'sccache' || '' }} clang++-21
   SCCACHE_GHA_ENABLED: ${{ github.base_ref == 'main' || github.ref_name == 'main' }}
   SCCACHE_IDLE_TIMEOUT: '0'
 
@@ -48,7 +48,7 @@ permissions:
 jobs:
   coverage-linux-without-intl:
     if: github.event.pull_request.draft == false
-    runs-on: ubuntu-24.04
+    runs-on: ubuntu-26.04
     steps:
       - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1  # v7.0.1
         with:
@@ -80,7 +80,7 @@ jobs:
         env:
           NODE_OPTIONS: --max-old-space-size=8192
       - name: Report C++
-        run: gcovr --object-directory=out -v --filter src --xml -o ./coverage/coverage-cxx.xml --root=./ --gcov-executable="llvm-cov-18 gcov"
+        run: gcovr --object-directory=out -v --filter src --xml -o ./coverage/coverage-cxx.xml --root=./ --gcov-executable="llvm-cov-$CLANG_VERSION gcov"
       # Clean temporary output from gcov and c8, so that it's not uploaded:
       - name: Clean tmp
         run: rm -rf coverage/tmp && rm -rf out
diff --git a/.github/workflows/coverage-linux.yml b/.github/workflows/coverage-linux.yml
index 63ac4fa5f2e..b43ba3b2477 100644
--- a/.github/workflows/coverage-linux.yml
+++ b/.github/workflows/coverage-linux.yml
@@ -36,9 +36,9 @@ concurrency:
 env:
   PYTHON_VERSION: '3.14'
   FLAKY_TESTS: keep_retrying
-  CLANG_VERSION: '19'
-  CC: ${{ (github.base_ref == 'main' || github.ref_name == 'main') && 'sccache' || '' }} clang-19
-  CXX: ${{ (github.base_ref == 'main' || github.ref_name == 'main') && 'sccache' || '' }} clang++-19
+  CLANG_VERSION: '21'
+  CC: ${{ (github.base_ref == 'main' || github.ref_name == 'main') && 'sccache' || '' }} clang-21
+  CXX: ${{ (github.base_ref == 'main' || github.ref_name == 'main') && 'sccache' || '' }} clang++-21
   SCCACHE_GHA_ENABLED: ${{ github.base_ref == 'main' || github.ref_name == 'main' }}
   SCCACHE_IDLE_TIMEOUT: '0'
 
@@ -48,7 +48,7 @@ permissions:
 jobs:
   coverage-linux:
     if: github.event.pull_request.draft == false
-    runs-on: ubuntu-24.04-arm
+    runs-on: ubuntu-26.04-arm
     steps:
       - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1  # v7.0.1
         with:
@@ -80,7 +80,7 @@ jobs:
         env:
           NODE_OPTIONS: --max-old-space-size=8192
       - name: Report C++
-        run: gcovr --object-directory=out -v --filter src --xml -o ./coverage/coverage-cxx.xml --root=./ --gcov-executable="llvm-cov-18 gcov"
+        run: gcovr --object-directory=out -v --filter src --xml -o ./coverage/coverage-cxx.xml --root=./ --gcov-executable="llvm-cov-$CLANG_VERSION gcov"
       # Clean temporary output from gcov and c8, so that it's not uploaded:
       - name: Clean tmp
         run: rm -rf coverage/tmp && rm -rf out
diff --git a/.github/workflows/daily-wpt-fyi.yml b/.github/workflows/daily-wpt-fyi.yml
index d15f21010cd..bbab25d2f93 100644
--- a/.github/workflows/daily-wpt-fyi.yml
+++ b/.github/workflows/daily-wpt-fyi.yml
@@ -36,7 +36,7 @@ jobs:
       matrix:
         node-version: ${{ fromJSON(needs.collect-versions.outputs.matrix) }}
       fail-fast: false
-    runs-on: ubuntu-24.04-arm
+    runs-on: ubuntu-26.04-arm
     steps:
       - name: Set up Python ${{ env.PYTHON_VERSION }}
         uses: actions/setup-python@5fda3b95a4ea91299a34e894583c3862153e4b97  # v7.0.0
diff --git a/.github/workflows/daily.yml b/.github/workflows/daily.yml
index b7a616e2df5..ce38ab65244 100644
--- a/.github/workflows/daily.yml
+++ b/.github/workflows/daily.yml
@@ -14,7 +14,7 @@ permissions:
 jobs:
   build-lto:
     if: github.repository == 'nodejs/node' || github.event_name == 'workflow_dispatch'
-    runs-on: ubuntu-24.04-arm
+    runs-on: ubuntu-26.04-arm
     steps:
       - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1  # v7.0.1
         with:
diff --git a/.github/workflows/stress-test.yml b/.github/workflows/stress-test.yml
index 0f17615671c..ded509432b0 100644
--- a/.github/workflows/stress-test.yml
+++ b/.github/workflows/stress-test.yml
@@ -14,8 +14,8 @@ on:
         type: choice
         options:
           - macos-15
-          - ubuntu-24.04
-          - ubuntu-24.04-arm
+          - ubuntu-26.04
+          - ubuntu-26.04-arm
       repeat:
         description: Number of times to repeat each test (--repeat)
         required: true
@@ -35,7 +35,7 @@ on:
 env:
   PYTHON_VERSION: '3.14'
   XCODE_VERSION: '16.4'
-  CLANG_VERSION: '19'
+  CLANG_VERSION: '21'
   RUSTC_VERSION: '1.88'
 
 permissions:
@@ -46,8 +46,8 @@ jobs:
     runs-on: ${{ inputs.os }}
     env:
       # Linux builds with clang (matching test-linux.yml), macOS with gcc/g++.
-      CC: ${{ startsWith(inputs.os, 'ubuntu') && 'sccache clang-19' || 'sccache gcc' }}
-      CXX: ${{ startsWith(inputs.os, 'ubuntu') && 'sccache clang++-19' || 'sccache g++' }}
+      CC: ${{ startsWith(inputs.os, 'ubuntu') && 'sccache clang-21' || 'sccache gcc' }}
+      CXX: ${{ startsWith(inputs.os, 'ubuntu') && 'sccache clang++-21' || 'sccache g++' }}
       # Enable sccache - this is okay for a manually-dispatched workflow that is typically used to
       # test lib-only or test-only deflaking changes. This should be able to pick up cache from
       # test-linux.yml and test-macos.yml running on the main branch.
diff --git a/.github/workflows/test-internet.yml b/.github/workflows/test-internet.yml
index 672893a999a..5ea2f8878b1 100644
--- a/.github/workflows/test-internet.yml
+++ b/.github/workflows/test-internet.yml
@@ -41,9 +41,9 @@ concurrency:
 env:
   PYTHON_VERSION: '3.14'
   FLAKY_TESTS: keep_retrying
-  CLANG_VERSION: '19'
-  CC: ${{ (github.base_ref == 'main' || github.ref_name == 'main') && 'sccache' || '' }} clang-19
-  CXX: ${{ (github.base_ref == 'main' || github.ref_name == 'main') && 'sccache' || '' }} clang++-19
+  CLANG_VERSION: '21'
+  CC: ${{ (github.base_ref == 'main' || github.ref_name == 'main') && 'sccache' || '' }} clang-21
+  CXX: ${{ (github.base_ref == 'main' || github.ref_name == 'main') && 'sccache' || '' }} clang++-21
   SCCACHE_GHA_ENABLED: ${{ github.base_ref == 'main' || github.ref_name == 'main' }}
   SCCACHE_IDLE_TIMEOUT: '0'
 
@@ -53,7 +53,7 @@ permissions:
 jobs:
   test-internet:
     if: (github.event_name == 'schedule' && github.repository == 'nodejs/node') || (github.event.pull_request && github.event.pull_request.draft == false)
-    runs-on: ubuntu-24.04-arm
+    runs-on: ubuntu-26.04-arm
     steps:
       - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1  # v7.0.1
         with:
diff --git a/.github/workflows/test-linux-perfetto.yml b/.github/workflows/test-linux-perfetto.yml
index f11970e8f6f..d5f64f5026a 100644
--- a/.github/workflows/test-linux-perfetto.yml
+++ b/.github/workflows/test-linux-perfetto.yml
@@ -22,9 +22,9 @@ concurrency:
 env:
   PYTHON_VERSION: '3.14'
   FLAKY_TESTS: keep_retrying
-  CLANG_VERSION: '19'
-  CC: ${{ (github.base_ref == 'main' || github.ref_name == 'main') && 'sccache' || '' }} clang-19
-  CXX: ${{ (github.base_ref == 'main' || github.ref_name == 'main') && 'sccache' || '' }} clang++-19
+  CLANG_VERSION: '21'
+  CC: ${{ (github.base_ref == 'main' || github.ref_name == 'main') && 'sccache' || '' }} clang-21
+  CXX: ${{ (github.base_ref == 'main' || github.ref_name == 'main') && 'sccache' || '' }} clang++-21
   SCCACHE_GHA_ENABLED: ${{ github.base_ref == 'main' || github.ref_name == 'main' }}
   SCCACHE_IDLE_TIMEOUT: '0'
   RUSTC_VERSION: '1.88'
@@ -35,7 +35,7 @@ permissions:
 jobs:
   test-perfetto:
     if: github.event.pull_request.draft == false
-    runs-on: ubuntu-24.04-arm
+    runs-on: ubuntu-26.04-arm
     steps:
       - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1  # v7.0.1
         with:
diff --git a/.github/workflows/test-linux-quic.yml b/.github/workflows/test-linux-quic.yml
index eca8521a310..7d5470f4b14 100644
--- a/.github/workflows/test-linux-quic.yml
+++ b/.github/workflows/test-linux-quic.yml
@@ -32,9 +32,9 @@ concurrency:
 env:
   PYTHON_VERSION: '3.14'
   FLAKY_TESTS: keep_retrying
-  CLANG_VERSION: '19'
-  CC: ${{ (github.base_ref == 'main' || github.ref_name == 'main') && 'sccache' || '' }} clang-19
-  CXX: ${{ (github.base_ref == 'main' || github.ref_name == 'main') && 'sccache' || '' }} clang++-19
+  CLANG_VERSION: '21'
+  CC: ${{ (github.base_ref == 'main' || github.ref_name == 'main') && 'sccache' || '' }} clang-21
+  CXX: ${{ (github.base_ref == 'main' || github.ref_name == 'main') && 'sccache' || '' }} clang++-21
   SCCACHE_GHA_ENABLED: ${{ github.base_ref == 'main' || github.ref_name == 'main' }}
   SCCACHE_IDLE_TIMEOUT: '0'
   RUSTC_VERSION: '1.88'
@@ -45,7 +45,7 @@ permissions:
 jobs:
   test-quic:
     if: github.event.pull_request.draft == false
-    runs-on: ubuntu-24.04-arm
+    runs-on: ubuntu-26.04-arm
     steps:
       - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1  # v7.0.1
         with:
diff --git a/.github/workflows/test-linux.yml b/.github/workflows/test-linux.yml
index 65aead07b92..bbe3371365f 100644
--- a/.github/workflows/test-linux.yml
+++ b/.github/workflows/test-linux.yml
@@ -41,9 +41,9 @@ concurrency:
 env:
   PYTHON_VERSION: '3.14'
   FLAKY_TESTS: keep_retrying
-  CLANG_VERSION: '19'
-  CC: ${{ (github.base_ref == 'main' || github.ref_name == 'main') && 'sccache' || '' }} clang-19
-  CXX: ${{ (github.base_ref == 'main' || github.ref_name == 'main') && 'sccache' || '' }} clang++-19
+  CLANG_VERSION: '21'
+  CC: ${{ (github.base_ref == 'main' || github.ref_name == 'main') && 'sccache' || '' }} clang-21
+  CXX: ${{ (github.base_ref == 'main' || github.ref_name == 'main') && 'sccache' || '' }} clang++-21
   SCCACHE_GHA_ENABLED: ${{ github.base_ref == 'main' || github.ref_name == 'main' }}
   SCCACHE_IDLE_TIMEOUT: '0'
   RUSTC_VERSION: '1.88'
@@ -58,7 +58,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        os: [ubuntu-24.04, ubuntu-24.04-arm]
+        os: [ubuntu-26.04, ubuntu-26.04-arm]
     steps:
       - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1  # v7.0.1
         with:
diff --git a/.github/workflows/test-macos.yml b/.github/workflows/test-macos.yml
index c5638281e5a..fc153f648df 100644
--- a/.github/workflows/test-macos.yml
+++ b/.github/workflows/test-macos.yml
@@ -66,7 +66,7 @@ concurrency:
 
 env:
   PYTHON_VERSION: '3.14'
-  XCODE_VERSION: '16.4'
+  XCODE_VERSION: '26.4'
   FLAKY_TESTS: keep_retrying
   RUSTC_VERSION: '1.88'
 
@@ -78,7 +78,7 @@ jobs:
     if: github.event.pull_request.draft == false
     strategy:
       fail-fast: false
-    runs-on: macos-15
+    runs-on: macos-26
     env:
       CC: ${{ (github.base_ref == 'main' || github.ref_name == 'main') && 'sccache' || '' }} gcc
       CXX: ${{ (github.base_ref == 'main' || github.ref_name == 'main') && 'sccache' || '' }} g++
diff --git a/BUILDING.md b/BUILDING.md
index 6fc93ca2ad0..410482f5a8d 100644
--- a/BUILDING.md
+++ b/BUILDING.md
@@ -147,7 +147,7 @@ platforms. This is true regardless of entries in the table below.
 [^4]: Our macOS Binaries are compiled with 13.5 as a target. Xcode 16 is
     required to compile.
 
-[^5]: Native riscv64 builds need GCC >= 14 or Clang >= 19 because V8
+[^5]: Native riscv64 builds need GCC >= 14 or Clang >= 21 because V8
     includes `<riscv_vector.h>` and uses `target("arch=+v")` in
     `deps/v8/src/base/cpu.cc`. GCC 13's `riscv_vector.h` errors out without
     `-march=rv64gcv` and doesn't support the `target` attribute at all.
@@ -162,9 +162,9 @@ Depending on the host platform, the selection of toolchains may vary.
 
 | Operating System | Compiler Versions                                                   |
 | ---------------- | ------------------------------------------------------------------- |
-| Linux            | GCC >= 13.2 or Clang >= 19.1                                        |
+| Linux            | GCC >= 13.2 or Clang >= 21                                          |
 | Windows          | Visual Studio 2022 or 2026 with the Windows 11 SDK on a 64-bit host |
-| macOS            | Xcode >= 16.4 (Apple LLVM >= 19)                                    |
+| macOS            | Xcode >= 26.4 (Apple LLVM >= 21)                                    |
 
 ### Official binary platforms and toolchains
 
@@ -241,7 +241,7 @@ tarball and/or browse the git repository checked out at the relevant tag.
 
 #### Unix prerequisites
 
-* `gcc` and `g++` >= 13.2 or `clang` and `clang++` >= 19.1
+* `gcc` and `g++` >= 13.2 or `clang` and `clang++` >= 21
 * GNU Make 3.81 or newer
 * [A supported version of Python][Python versions]
   * For test coverage, your Python installation must include pip.
@@ -259,7 +259,7 @@ FreeBSD and OpenBSD users may also need to install `libexecinfo`.
 
 #### macOS prerequisites
 
-* Xcode Command Line Tools >= 16.4 for macOS
+* Xcode Command Line Tools >= 26.4 for macOS
 * [A supported version of Python][Python versions]
   * For test coverage, your Python installation must include pip.
 
@@ -1036,7 +1036,7 @@ Node.js supports the [Temporal](https://github.com/tc39/proposal-temporal) APIs,
 linking statically or dynamically with a version of [temporal\_rs](https://github.com/boa-dev/temporal).
 Building it requires a Rust toolchain:
 
-* rustc >= 1.88 (with LLVM >= 19)
+* rustc >= 1.88 (with LLVM >= 21)
 * cargo >= 1.86
 
 Refer to [Install Rust](https://rust-lang.org/tools/install/) for instructions.