diff --git a/.github/scripts/install-php86-windows.sh b/.github/scripts/install-php86-windows.sh
new file mode 100644
index 00000000000..f7eebca091e
--- /dev/null
+++ b/.github/scripts/install-php86-windows.sh
@@ -0,0 +1,24 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+# setup-php supplies Composer, php.ini and CA certificates, but its 8.6
+# nightly has no matching development pack. Replace the runtime and bundled
+# extensions with the official prerelease, preserving that configuration.
+PHP_DIR="$(cygpath -u "$(php -r 'echo dirname(PHP_BINARY);')")"
+case "$MATRIX_TS" in
+  zts) INFIX="" ;;
+  nts) INFIX="-nts" ;;
+  *) echo "Unknown thread-safety mode: $MATRIX_TS" >&2; exit 1 ;;
+esac
+PACK="php-$PHP86_WINDOWS_VERSION$INFIX-Win32-vs18-x64.zip"
+ARCHIVE="$RUNNER_TEMP/$PACK"
+curl -fsSLo "$ARCHIVE" "https://downloads.php.net/~windows/qa/$PACK" \
+  || curl -fsSLo "$ARCHIVE" "https://downloads.php.net/~windows/qa/archives/$PACK"
+unzip -qo "$ARCHIVE" -d "$PHP_DIR"
+php -r '
+  if (PHP_VERSION !== getenv("PHP86_WINDOWS_VERSION") || (bool) PHP_ZTS !== (getenv("MATRIX_TS") === "zts")) {
+    fwrite(STDERR, "PHP prerelease version or thread-safety mismatch\n");
+    exit(1);
+  }
+  echo "Using PHP ", PHP_VERSION, PHP_ZTS ? " ZTS\n" : " NTS\n";
+'
diff --git a/.github/workflows/phar.yml b/.github/workflows/phar.yml
index 56396ef6804..e63efe2846d 100644
--- a/.github/workflows/phar.yml
+++ b/.github/workflows/phar.yml
@@ -29,6 +29,8 @@ env:
   # distro-default PHP.
   COMPOSER_VERSION: "2.9.2"
   COMPOSER_PHAR_SHA256: "471f2d857abf0ec18af7b055e61472214d91adb24f9bdbbb864c1c64faad7dd6"
+  # setup-php installs an 8.6 nightly, which has no matching Windows devel pack.
+  PHP86_WINDOWS_VERSION: "8.6.0beta3"
 
 jobs:
   compiler-tests:
@@ -319,9 +321,9 @@ jobs:
 
   turbo-compile:
     name: "Compile Turbo Extension"
-    runs-on: ${{ matrix.target.runs-on }}
+    runs-on: ${{ matrix.php-version == '8.6' && matrix.target.family == 'gnu' && (matrix.target.name == 'linux-gnu-arm64' && 'ubuntu-22.04-arm' || 'ubuntu-22.04') || matrix.target.runs-on }}
     # Container legs pin the built binaries' userland floor independently of
-    # the runner image. The gnu legs run in a prebuilt ubuntu:22.04-based
+    # the runner image. The 8.3–8.5 gnu legs run in a prebuilt ubuntu:22.04-based
     # image (.github/turbo-build/Dockerfile, published to GHCR by
     # turbo-build-image.yml) with the PHP toolchain baked in: the glibc
     # symbol floor stays at 2.34 (RHEL 9, Ubuntu 22.04+, Debian 12+) and the
@@ -339,7 +341,10 @@ jobs:
     # packages ZTS PHP (neither ppa:ondrej/php nor Alpine); setup-php
     # provides thread-safe builds. No musl ZTS for the same packaging
     # reason.
-    container: ${{ matrix.target.family == 'gnu' && format('ghcr.io/phpstan/turbo-build:gnu-php{0}', matrix.php-version) || matrix.target.container }}
+    # PHP 8.6 has no ondrej/php packages or prebuilt GNU image yet. Use
+    # setup-php on Jammy runners, preserving the shipped binary's glibc floor.
+    # Alpine's php86 packages are currently only in edge/testing.
+    container: ${{ matrix.target.family == 'gnu' && matrix.php-version != '8.6' && format('ghcr.io/phpstan/turbo-build:gnu-php{0}', matrix.php-version) || matrix.target.family == 'musl' && matrix.php-version == '8.6' && 'alpine:edge' || matrix.target.container }}
     timeout-minutes: 30
 
     env:
@@ -348,7 +353,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        php-version: ["8.3", "8.4", "8.5"]
+        php-version: ["8.3", "8.4", "8.5", "8.6"]
         target:
           - name: "linux-gnu-x86_64"
             runs-on: "ubuntu-latest"
@@ -391,13 +396,15 @@ jobs:
 
       # The Alpine leg installs PHP and tooling before checkout:
       # actions/checkout needs git inside the container, and the build needs
-      # php/php-config symlinks pointing at the matrix PHP version. The gnu
-      # legs need no install step — their prebuilt turbo-build image bakes
-      # all of this in.
+      # php/php-config symlinks pointing at the matrix PHP version. The GNU
+      # container legs have the toolchain baked in; 8.6 uses setup-php below.
       - name: "Install PHP and build tools (Alpine container)"
         if: matrix.target.family == 'musl'
         run: |
           V="$(echo "$PHP_MINOR" | tr -d .)"
+          if [ "$PHP_MINOR" = "8.6" ]; then
+            echo 'https://dl-cdn.alpinelinux.org/alpine/edge/testing' >> /etc/apk/repositories
+          fi
           apk add --no-cache bash curl git make g++ musl-dev linux-headers patch tar zstd \
             "php$V" "php$V-dev" "php$V-ctype" "php$V-curl" "php$V-mbstring" \
             "php$V-tokenizer" "php$V-iconv" "php$V-openssl" "php$V-phar" \
@@ -429,11 +436,11 @@ jobs:
           coverage: "none"
           php-version: "${{ matrix.php-version }}"
 
-      - name: "Install PHP (ZTS runner)"
-        if: matrix.target.family == 'zts'
+      - name: "Install PHP (GNU runners)"
+        if: matrix.target.family == 'zts' || (matrix.target.family == 'gnu' && matrix.php-version == '8.6')
         uses: "shivammathur/setup-php@f3e473d116dcccaddc5834248c87452386958240" # v2.37.2
         env:
-          phpts: "ts"
+          phpts: "${{ matrix.target.family == 'zts' && 'ts' || 'nts' }}"
         with:
           coverage: "none"
           php-version: "${{ matrix.php-version }}"
@@ -545,7 +552,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        php-version: ["8.3", "8.4", "8.5"]
+        php-version: ["8.3", "8.4", "8.5", "8.6"]
 
     steps:
       - name: Harden the runner (Audit all outbound calls)
@@ -564,16 +571,21 @@ jobs:
           fetch-depth: 0
 
       - name: "Start the Alpine build container"
+        env:
+          ALPINE_IMAGE: ${{ matrix.php-version == '8.6' && 'alpine:edge' || 'alpine:3.24' }}
         run: |
           docker run -d --name alpine-build \
             -v "$PWD:/work" -w /work \
             -e PHP_MINOR -e COMPOSER_VERSION -e COMPOSER_PHAR_SHA256 \
-            alpine:3.24 sleep 7200
+            "$ALPINE_IMAGE" sleep 7200
 
       - name: "Install PHP and build tools"
         run: |
           docker exec -i alpine-build sh -e <<'EOF'
           V="$(echo "$PHP_MINOR" | tr -d .)"
+          if [ "$PHP_MINOR" = "8.6" ]; then
+            echo 'https://dl-cdn.alpinelinux.org/alpine/edge/testing' >> /etc/apk/repositories
+          fi
           apk add --no-cache bash curl git make g++ musl-dev linux-headers patch tar zstd \
             "php$V" "php$V-dev" "php$V-ctype" "php$V-curl" "php$V-mbstring" \
             "php$V-tokenizer" "php$V-iconv" "php$V-openssl" "php$V-phar" \
@@ -666,7 +678,7 @@ jobs:
     # token-numbering bug: 2462 of 21065 tests fail and self-analysis
     # crashes on the Bison 3.0.4 image, both green on the matched one).
     # The 8.3 images are pinned to one release of each known numbering;
-    # 8.4/8.5 float on the minor tag on purpose so that a future patch
+    # 8.4/8.5 float on the minor tag and 8.6 on the prerelease tag so a future
     # release with a surprising build is picked up on the next run without
     # a workflow change. Legs run on linux-gnu-x86_64 only: the token
     # numbering comes from the bison that generated the tarball's parser,
@@ -677,6 +689,9 @@ jobs:
     runs-on: "ubuntu-latest"
     timeout-minutes: 60
 
+    env:
+      IMAGE: ${{ matrix.php-version == '8.6' && 'phpstan-turbo-test:8.6' || matrix.image }}
+
     permissions:
       contents: read
 
@@ -688,6 +703,7 @@ jobs:
           - "php:8.3.22-cli-bookworm"
           - "php:8.4-cli-bookworm"
           - "php:8.5-cli-bookworm"
+          - "php:8.6-rc-cli-bookworm"
         check: ["tests", "phpstan"]
         include:
           - image: "php:8.3.21-cli-bookworm"
@@ -698,6 +714,8 @@ jobs:
             php-version: "8.4"
           - image: "php:8.5-cli-bookworm"
             php-version: "8.5"
+          - image: "php:8.6-rc-cli-bookworm"
+            php-version: "8.6"
           # The tests legs invoke paratest directly instead of a literal
           # `make tests`: its install-paratest step needs a composer, which
           # the images do not carry — tests/vendor is installed on the
@@ -741,12 +759,25 @@ jobs:
           name: "phpstan_turbo-linux-gnu-x86_64-php${{ matrix.php-version }}"
           path: "turbo-ext"
 
+      - name: "Add mbstring to the PHP 8.6 prerelease image"
+        if: matrix.php-version == '8.6'
+        env:
+          PHP_IMAGE: ${{ matrix.image }}
+        # Unlike the stable images, the 8.6 prerelease omits mbstring,
+        # which PHPUnit and PHPStan's test fixtures require.
+        run: |
+          docker build --build-arg "PHP_IMAGE=$PHP_IMAGE" -t "$IMAGE" - <<'DOCKERFILE'
+          ARG PHP_IMAGE
+          FROM ${PHP_IMAGE}
+          RUN apt-get update && apt-get install -y --no-install-recommends libonig-dev \
+            && docker-php-ext-install mbstring \
+            && rm -rf /var/lib/apt/lists/*
+          DOCKERFILE
+
       # Fast fail with a one-line diagnosis: a token-numbering mismatch
       # would otherwise surface as thousands of unrelated-looking failures
       # in the suite run below.
       - name: "Token-id probe in ${{ matrix.image }}"
-        env:
-          IMAGE: ${{ matrix.image }}
         run: docker run --rm -v "$PWD:/work" -w /work "$IMAGE" php -d extension=/work/turbo-ext/phpstan_turbo.so turbo-ext/tests/token-id-probe.php
 
       # Bind-mounted into conf.d of every docker run below. The images
@@ -756,8 +787,6 @@ jobs:
         run: printf 'extension=/work/turbo-ext/phpstan_turbo.so\nmemory_limit=-1\n' > "$RUNNER_TEMP/turbo-docker.ini"
 
       - name: "Verify the extension is active in ${{ matrix.image }}"
-        env:
-          IMAGE: ${{ matrix.image }}
         run: |
           docker run --rm -v "$PWD:/work" -v "$RUNNER_TEMP/turbo-docker.ini:/usr/local/etc/php/conf.d/zz-turbo.ini" -w /work "$IMAGE" php -r '
             require "src/Turbo/TurboExtensionEnabler.php";
@@ -773,7 +802,6 @@ jobs:
         # --shm-size: the arena allocates cross-worker shared memory, and
         # docker's default 64M /dev/shm makes parallel analysis SIGBUS.
         env:
-          IMAGE: ${{ matrix.image }}
           SCRIPT: ${{ matrix.script }}
         run: docker run --rm --shm-size=1g -v "$PWD:/work" -v "$RUNNER_TEMP/turbo-docker.ini:/usr/local/etc/php/conf.d/zz-turbo.ini" -w /work "$IMAGE" bash -c "$SCRIPT"
 
@@ -784,7 +812,8 @@ jobs:
     # toolset 14.4x) refuse to load — PHP's loader rejects modules linked
     # with a newer toolset generation than the core. The windows-2022 image
     # is the one that ships VS2022.
-    runs-on: "windows-2022"
+    # PHP 8.6's vs18 development packs need the VS2026 toolchain.
+    runs-on: ${{ matrix.php-version == '8.6' && 'windows-2025-vs2026' || 'windows-2022' }}
     timeout-minutes: 40
 
     env:
@@ -795,7 +824,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        php-version: ["8.3", "8.4", "8.5"]
+        php-version: ["8.3", "8.4", "8.5", "8.6"]
         ts: ["nts", "zts"]
         # The official 8.3 Windows binaries are built with VS16 (linker
         # 14.2x) and PHP's module loader is one-directional (module toolset
@@ -810,6 +839,8 @@ jobs:
             vs: "vs17"
           - php-version: "8.5"
             vs: "vs17"
+          - php-version: "8.6"
+            vs: "vs18"
 
     steps:
       - name: "Checkout"
@@ -828,6 +859,13 @@ jobs:
           coverage: "none"
           php-version: "${{ matrix.php-version }}"
 
+      - name: "Install the matching PHP 8.6 prerelease runtime"
+        if: matrix.php-version == '8.6'
+        shell: bash
+        env:
+          MATRIX_TS: ${{ matrix.ts }}
+        run: bash .github/scripts/install-php86-windows.sh
+
       - name: "Compute the extension version and download the build tools"
         shell: bash
         env:
@@ -844,7 +882,9 @@ jobs:
           PACK="php-devel-pack-$FULL$INFIX-Win32-$MATRIX_VS-x64.zip"
           echo "devel pack: $PACK"
           curl -fsSLo devel-pack.zip "https://windows.php.net/downloads/releases/$PACK" \
-            || curl -fsSLo devel-pack.zip "https://windows.php.net/downloads/releases/archives/$PACK"
+            || curl -fsSLo devel-pack.zip "https://windows.php.net/downloads/releases/archives/$PACK" \
+            || curl -fsSLo devel-pack.zip "https://downloads.php.net/~windows/qa/$PACK" \
+            || curl -fsSLo devel-pack.zip "https://downloads.php.net/~windows/qa/archives/$PACK"
           unzip -q devel-pack.zip -d /c/php-devel
 
           git clone -q https://github.com/php/php-sdk-binary-tools.git /c/php-sdk
@@ -854,7 +894,7 @@ jobs:
         uses: ilammy/msvc-dev-cmd@0b201ec74fa43914dc39ae48a89fd1d8cb592756 # v1.13.0
         with:
           arch: x64
-          # empty on the vs17 legs = the image's default (latest) toolset
+          # empty on the vs17/vs18 legs = the image's default toolset
           toolset: ${{ matrix.toolset }}
 
       - name: "Build the extension"
@@ -989,7 +1029,7 @@ jobs:
       # vs17-built official PHP loads it fine.
       matrix:
         operating-system: ["ubuntu-latest", "windows-latest"]
-        php-version: ["8.3", "8.4", "8.5"]
+        php-version: ["8.3", "8.4", "8.5", "8.6"]
         ts: ["nts", "zts"]
         script: ["make tests", "make phpstan"]
         # macOS runs the shipped ad-hoc-signed arm64 binary; there is no
@@ -1003,6 +1043,14 @@ jobs:
             php-version: "8.5"
             ts: "nts"
             script: "make phpstan"
+          - operating-system: "macos-latest"
+            php-version: "8.6"
+            ts: "nts"
+            script: "make tests"
+          - operating-system: "macos-latest"
+            php-version: "8.6"
+            ts: "nts"
+            script: "make phpstan"
 
     steps:
       - name: Harden the runner (Audit all outbound calls)
@@ -1023,6 +1071,12 @@ jobs:
           coverage: "none"
           php-version: "${{ matrix.php-version }}"
 
+      - name: "Install the matching PHP 8.6 prerelease runtime"
+        if: matrix.operating-system == 'windows-latest' && matrix.php-version == '8.6'
+        env:
+          MATRIX_TS: ${{ matrix.ts }}
+        run: bash .github/scripts/install-php86-windows.sh
+
       - name: "Download extension artifact"
         uses: actions/download-artifact@3e5f45b2cfb9172054b4087a40e8e0b5a5461e7c # v8.0.1
         with: