diff --git a/.github/workflows/checks.yml b/.github/workflows/checks.yml
index 909638e..82e929f 100644
--- a/.github/workflows/checks.yml
+++ b/.github/workflows/checks.yml
@@ -84,3 +84,24 @@ jobs:
           distribution: goreleaser
           version: "~> v2"
           args: release --snapshot --clean --skip=sign,sbom
+      - name: shellcheck install.sh
+        run: shellcheck --shell=sh install.sh
+      - name: install.sh installs the snapshot
+        run: |
+          version=$(jq -r .version dist/metadata.json)
+          DEVLYFT_DOWNLOAD_BASE="file://$PWD/dist" DEVLYFT_VERSION="$version" \
+            DEVLYFT_INSTALL_DIR="$RUNNER_TEMP/bin" sh install.sh
+          "$RUNNER_TEMP/bin/devlyft" version | grep -F "devlyft $version"
+      - name: install.sh rejects a tampered archive
+        run: |
+          version=$(jq -r .version dist/metadata.json)
+          bad="$RUNNER_TEMP/tampered"
+          mkdir -p "$bad"
+          cp dist/devlyft_"$version"_* "$bad"/
+          cp "dist/devlyft_${version}_linux_arm64.tar.gz" "$bad/devlyft_${version}_linux_amd64.tar.gz"
+          if DEVLYFT_DOWNLOAD_BASE="file://$bad" DEVLYFT_VERSION="$version" \
+            DEVLYFT_INSTALL_DIR="$RUNNER_TEMP/bad-bin" sh install.sh; then
+            echo "install.sh accepted a tampered archive" >&2
+            exit 1
+          fi
+          test ! -e "$RUNNER_TEMP/bad-bin/devlyft"
diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
index dbe6f11..0b29db4 100644
--- a/.github/workflows/release.yml
+++ b/.github/workflows/release.yml
@@ -39,6 +39,9 @@ jobs:
           args: release --clean
         env:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+          # Write access to devlyft/homebrew-tap only. When unset, the cask
+          # is built but not pushed.
+          HOMEBREW_TAP_GITHUB_TOKEN: ${{ secrets.HOMEBREW_TAP_GITHUB_TOKEN }}
       - uses: actions/attest-build-provenance@4d101475d8b20a2381f78447822ac1eab6504dd8 # v4.2.2
         with:
           subject-path: |
diff --git a/.goreleaser.yaml b/.goreleaser.yaml
index f000978..a5b7bce 100644
--- a/.goreleaser.yaml
+++ b/.goreleaser.yaml
@@ -62,6 +62,41 @@ signs:
       - "--yes"
     output: true
 
+# Homebrew: `brew install devlyft/tap/devlyft`. Casks replace the deprecated
+# `brews` formulae. The cask is pushed to devlyft/homebrew-tap with a token
+# scoped to that repository only; without the token (for example before the
+# tap exists) the upload is skipped instead of failing the release.
+homebrew_casks:
+  - name: devlyft
+    ids: [devlyft]
+    binaries: [devlyft]
+    description: Deploy and operate apps on DevLyft
+    homepage: https://github.com/devlyft/cli
+    license: Apache-2.0
+    repository:
+      owner: devlyft
+      name: homebrew-tap
+      token: '{{ envOrDefault "HOMEBREW_TAP_GITHUB_TOKEN" "" }}'
+    directory: Casks
+    commit_author:
+      name: devlyft-release-bot
+      email: noreply@devlyft.io
+    commit_msg_template: "Brew cask update for {{ .ProjectName }} version {{ .Tag }}"
+    skip_upload: '{{ if not (envOrDefault "HOMEBREW_TAP_GITHUB_TOKEN" "") }}true{{ end }}'
+    # Runs `devlyft completion <shell>` at install time.
+    generate_completions_from_executable:
+      executable: devlyft
+      args: [completion]
+      shells: [bash, zsh, fish]
+    hooks:
+      post:
+        # The binaries are not notarized (see docs/releasing.md); without
+        # this, Gatekeeper refuses to run a cask-installed binary.
+        install_steps: |
+          on_macos do
+            run "/usr/bin/xattr", args: ["-dr", "com.apple.quarantine", "{{ .StagedPath }}/devlyft"]
+          end
+
 # release-please writes the changelog and the release notes.
 changelog:
   disable: true
diff --git a/README.md b/README.md
index 6b45aa7..4effec3 100644
--- a/README.md
+++ b/README.md
@@ -1,6 +1,30 @@
 # cli
 The official command-line interface for DevLyft
 
+## Install
+
+**Homebrew** (macOS and Linux):
+
+```sh
+brew install devlyft/tap/devlyft
+```
+
+**Install script** (macOS and Linux). It verifies the download's checksum and, if [cosign](https://docs.sigstore.dev/cosign/system_config/installation/) is installed, the release signature:
+
+```sh
+curl -fsSL https://raw.githubusercontent.com/devlyft/cli/main/install.sh | sh
+```
+
+Set `DEVLYFT_VERSION` to pin a version, `DEVLYFT_INSTALL_DIR` to choose where the binary goes (default `/usr/local/bin` if writable, otherwise `~/.local/bin`), and `DEVLYFT_REQUIRE_SIGNATURE=1` to refuse to install without a verified signature.
+
+**Go**:
+
+```sh
+go install github.com/devlyft/cli/cmd/devlyft@latest
+```
+
+Or download an archive from [Releases](https://github.com/devlyft/cli/releases); see [docs/releasing.md](docs/releasing.md#verifying-a-download) to verify it.
+
 ## Development
 
 Requires Go 1.26 or later.
diff --git a/docs/releasing.md b/docs/releasing.md
index eb0283a..6ba048a 100644
--- a/docs/releasing.md
+++ b/docs/releasing.md
@@ -13,9 +13,30 @@ Releases are automated. Nobody tags by hand.
    - write `devlyft_<version>_checksums.txt` covering every archive and SBOM;
    - sign the checksum file with [cosign](https://docs.sigstore.dev/) keyless signing, using the workflow's GitHub OIDC identity (no stored keys), producing `.sig`, `.pem` and `.sigstore.json`;
    - attach everything to the release.
-5. The workflow then records a GitHub build-provenance attestation for the archives and the checksum file.
+5. goreleaser also generates a Homebrew cask and pushes it to [devlyft/homebrew-tap](https://github.com/devlyft/homebrew-tap) (`Casks/devlyft.rb`), so `brew install devlyft/tap/devlyft` picks up the release. The push uses the `HOMEBREW_TAP_GITHUB_TOKEN` secret; when that secret is not set, the cask is built but not pushed and the release still succeeds. The cask installs bash, zsh and fish completions by running `devlyft completion <shell>`, and on macOS clears the quarantine attribute because the binary is not notarized.
+6. The workflow then records a GitHub build-provenance attestation for the archives and the checksum file.
 
-Every pull request also runs `checks / release-snapshot`, which builds all targets with the same config but skips signing, SBOMs and publishing. Run the same thing locally with `make snapshot`; the output lands in `dist/`.
+Every pull request also runs `checks / release-snapshot`, which builds all targets with the same config but skips signing, SBOMs and publishing, then runs `install.sh` against the snapshot (and checks it rejects a tampered archive). Run the same thing locally with `make snapshot`; the output lands in `dist/`.
+
+### Setting up the Homebrew tap
+
+One-off, before the first release that should reach Homebrew:
+
+1. Create the public repository `devlyft/homebrew-tap` with a README and a `Casks/` directory. Homebrew maps `devlyft/tap` to `github.com/devlyft/homebrew-tap`.
+2. Create a credential that can write only to that repository: a fine-grained personal access token owned by a bot account (or a GitHub App installation token) with **Contents: read and write** on `devlyft/homebrew-tap` and nothing else.
+3. Store it as the `HOMEBREW_TAP_GITHUB_TOKEN` secret in `devlyft/cli`, ideally in a protected environment used only by the release workflow.
+
+## The install script
+
+`install.sh` (served from `main` via raw.githubusercontent.com) installs on Linux and macOS:
+
+1. Works out the OS and architecture, and the version: `DEVLYFT_VERSION`, or the latest release.
+2. Downloads the archive and `devlyft_<version>_checksums.txt`.
+3. If cosign is installed, downloads `devlyft_<version>_checksums.txt.sigstore.json` and verifies it with the same identity and issuer as below; any failure, including a missing bundle, aborts. Without cosign it warns and continues, unless `DEVLYFT_REQUIRE_SIGNATURE=1`, in which case it aborts.
+4. Checks the archive's sha256 against the checksum file and aborts on a mismatch.
+5. Installs `devlyft` into `DEVLYFT_INSTALL_DIR`, `/usr/local/bin` if writable, or `~/.local/bin`. It never calls sudo.
+
+`DEVLYFT_DOWNLOAD_BASE` points it at another directory of release assets (a mirror, or `file://$PWD/dist` for testing) and requires `DEVLYFT_VERSION`.
 
 ## Verifying a download
 
@@ -54,4 +75,5 @@ To cut 1.0, merge a commit containing `Release-As: 1.0.0` in its body; release-p
 ## Known gaps
 
 - macOS binaries are not notarized and Windows binaries are not code-signed, so browser downloads trigger Gatekeeper and SmartScreen warnings. Installing through Homebrew or the install script avoids this.
-- Homebrew, Scoop, deb and rpm channels are tracked separately (devlyft/devlyft#258, devlyft/devlyft#260).
+- Scoop, deb and rpm channels are tracked separately (devlyft/devlyft#260).
+- The install script supports Linux and macOS only; Windows users install with Scoop or the zip archive.
diff --git a/install.sh b/install.sh
new file mode 100755
index 0000000..a067626
--- /dev/null
+++ b/install.sh
@@ -0,0 +1,165 @@
+#!/bin/sh
+# Install the DevLyft CLI on Linux or macOS.
+#
+#   curl -fsSL https://raw.githubusercontent.com/devlyft/cli/main/install.sh | sh
+#
+# The script downloads a release archive, checks it against the release's
+# sha256 checksum file and, when cosign is installed, verifies the keyless
+# signature on that checksum file before installing anything. It never uses
+# sudo.
+#
+# Environment variables:
+#   DEVLYFT_VERSION            version to install, e.g. 0.3.1 or v0.3.1
+#                              (default: the latest release)
+#   DEVLYFT_INSTALL_DIR        where to put the binary (default: /usr/local/bin
+#                              if writable, otherwise ~/.local/bin)
+#   DEVLYFT_REQUIRE_SIGNATURE  set to 1 to fail when the signature cannot be
+#                              verified (for example cosign is missing)
+#   DEVLYFT_DOWNLOAD_BASE      URL of the directory holding the release assets,
+#                              for mirrors and testing (requires DEVLYFT_VERSION)
+
+set -eu
+
+REPO="devlyft/cli"
+CERT_IDENTITY_REGEXP='^https://github\.com/devlyft/cli/\.github/workflows/release\.yml@refs/tags/v'
+OIDC_ISSUER="https://token.actions.githubusercontent.com"
+
+say() { printf '%s\n' "$*" >&2; }
+warn() { printf 'warning: %s\n' "$*" >&2; }
+fail() {
+	printf 'error: %s\n' "$*" >&2
+	exit 1
+}
+
+has() { command -v "$1" >/dev/null 2>&1; }
+
+download() {
+	# download URL DEST
+	if has curl; then
+		curl -fsSL --proto '=https,file' --tlsv1.2 -o "$2" "$1"
+	elif has wget; then
+		wget -q --https-only -O "$2" "$1"
+	else
+		fail "curl or wget is required"
+	fi
+}
+
+latest_version() {
+	has curl || fail "set DEVLYFT_VERSION, or install curl to find the latest release"
+	url=$(curl -fsSLI --proto '=https' --tlsv1.2 -o /dev/null -w '%{url_effective}' "https://github.com/$REPO/releases/latest") ||
+		fail "could not look up the latest release"
+	tag=${url##*/}
+	case $tag in
+	v[0-9]*) printf '%s\n' "${tag#v}" ;;
+	*) fail "could not find the latest release (got $url)" ;;
+	esac
+}
+
+detect_os() {
+	case $(uname -s) in
+	Linux) echo linux ;;
+	Darwin) echo darwin ;;
+	MINGW* | MSYS* | CYGWIN*) fail "on Windows, install with Scoop or download the zip from https://github.com/$REPO/releases" ;;
+	*) fail "unsupported operating system: $(uname -s)" ;;
+	esac
+}
+
+detect_arch() {
+	case $(uname -m) in
+	x86_64 | amd64) echo amd64 ;;
+	aarch64 | arm64) echo arm64 ;;
+	*) fail "unsupported architecture: $(uname -m)" ;;
+	esac
+}
+
+sha256() {
+	if has sha256sum; then
+		sha256sum "$1" | cut -d ' ' -f 1
+	elif has shasum; then
+		shasum -a 256 "$1" | cut -d ' ' -f 1
+	else
+		fail "sha256sum or shasum is required to verify the download"
+	fi
+}
+
+verify_signature() {
+	# verify_signature DIR CHECKSUMS BASE
+	if ! has cosign; then
+		if [ "${DEVLYFT_REQUIRE_SIGNATURE:-}" = 1 ]; then
+			fail "cosign is not installed and DEVLYFT_REQUIRE_SIGNATURE=1; install cosign (https://docs.sigstore.dev/cosign/system_config/installation/)"
+		fi
+		warn "cosign is not installed: checked the sha256 checksum but not the release signature"
+		return 0
+	fi
+	if ! download "$3/$2.sigstore.json" "$1/$2.sigstore.json"; then
+		fail "could not download the signature bundle $2.sigstore.json"
+	fi
+	cosign verify-blob \
+		--bundle "$1/$2.sigstore.json" \
+		--certificate-identity-regexp "$CERT_IDENTITY_REGEXP" \
+		--certificate-oidc-issuer "$OIDC_ISSUER" \
+		"$1/$2" >/dev/null 2>&1 ||
+		fail "signature verification failed for $2: do not use this download"
+	say "Verified the release signature."
+}
+
+choose_install_dir() {
+	if [ -n "${DEVLYFT_INSTALL_DIR:-}" ]; then
+		echo "$DEVLYFT_INSTALL_DIR"
+	elif [ -d /usr/local/bin ] && [ -w /usr/local/bin ]; then
+		echo /usr/local/bin
+	else
+		echo "$HOME/.local/bin"
+	fi
+}
+
+main() {
+	os=$(detect_os)
+	arch=$(detect_arch)
+
+	version=${DEVLYFT_VERSION:-}
+	if [ -n "${DEVLYFT_DOWNLOAD_BASE:-}" ] && [ -z "$version" ]; then
+		fail "DEVLYFT_DOWNLOAD_BASE requires DEVLYFT_VERSION"
+	fi
+	if [ -z "$version" ]; then
+		version=$(latest_version)
+	fi
+	version=${version#v}
+
+	base=${DEVLYFT_DOWNLOAD_BASE:-"https://github.com/$REPO/releases/download/v$version"}
+	archive="devlyft_${version}_${os}_${arch}.tar.gz"
+	checksums="devlyft_${version}_checksums.txt"
+
+	tmp=$(mktemp -d 2>/dev/null || mktemp -d -t devlyft)
+	trap 'rm -rf "$tmp"' EXIT INT TERM
+
+	say "Downloading devlyft $version for $os/$arch..."
+	download "$base/$archive" "$tmp/$archive" || fail "could not download $base/$archive"
+	download "$base/$checksums" "$tmp/$checksums" || fail "could not download $base/$checksums"
+
+	verify_signature "$tmp" "$checksums" "$base"
+
+	want=$(awk -v f="$archive" '$2 == f || $2 == "*" f { print $1 }' "$tmp/$checksums")
+	[ -n "$want" ] || fail "$archive is not listed in $checksums"
+	got=$(sha256 "$tmp/$archive")
+	[ "$got" = "$want" ] || fail "checksum mismatch for $archive: expected $want, got $got"
+
+	tar -xzf "$tmp/$archive" -C "$tmp" devlyft || fail "could not extract $archive"
+
+	dir=$(choose_install_dir)
+	mkdir -p "$dir" || fail "could not create $dir; set DEVLYFT_INSTALL_DIR to a writable directory"
+	[ -w "$dir" ] || fail "$dir is not writable; set DEVLYFT_INSTALL_DIR, or rerun with the permissions to write there"
+	# Install via a temporary name and rename, so a running devlyft is never
+	# left half-written.
+	cp "$tmp/devlyft" "$dir/.devlyft.tmp.$$"
+	chmod 0755 "$dir/.devlyft.tmp.$$"
+	mv -f "$dir/.devlyft.tmp.$$" "$dir/devlyft"
+
+	say "Installed $("$dir/devlyft" version) to $dir/devlyft"
+	case ":$PATH:" in
+	*":$dir:"*) ;;
+	*) warn "$dir is not on your PATH; add it, for example: export PATH=\"$dir:\$PATH\"" ;;
+	esac
+}
+
+main "$@"