Add a SessionStart hook for Claude Code cloud sessions

.claude/hooks/install-dotnet.sh

@@ -0,0 +1,107 @@
+#!/bin/bash
+# Installs the .NET SDK into ~/.dotnet for Claude Code cloud sessions.
+#
+# The SDK is unpacked from the layers of the official
+# mcr.microsoft.com/dotnet/sdk container image, each checked against the
+# sha256 digest its manifest names. dotnet-install.sh is not used: it comes from
+# builds.dotnet.microsoft.com, which the default cloud network policy does not
+# allow, and it is a script fetched and run with nothing to check it against.
+# Ubuntu's own dotnet-sdk-10.0 package is the 1xx feature band, whose compiler
+# is too old for ktsu.Sdk.Analyzers (CS9057).
+#
+# Usage: install-dotnet.sh <channel> <minimum sdk version> [runtime channel...]
+#   e.g. install-dotnet.sh 10.0 10.0.400 8.0 9.0
+# The extra runtime channels are for test projects that multi-target older
+# frameworks: building them needs only the SDK, running them needs the runtime.
+set -euo pipefail
+
+channel="${1:-10.0}"
+minimum="${2:-${channel}.100}"
+shift 2 || shift $#
+runtimes=("$@")
+root="${DOTNET_INSTALL_DIR:-$HOME/.dotnet}"
+
+version_at_least() {
+	[ "$(printf '%s\n%s\n' "$2" "$1" | sort -V | head -n1)" = "$2" ]
+}
+
+has_runtime() {
+	[ -x "$root/dotnet" ] && "$root/dotnet" --list-runtimes 2>/dev/null | grep -q "^Microsoft.NETCore.App $1\."
+}
+
+has_sdk() {
+	[ -x "$root/dotnet" ] || return 1
+	local sdk
+	for sdk in $("$root/dotnet" --list-sdks 2>/dev/null | awk '{print $1}'); do
+		case "$sdk" in
+			"$channel".*) version_at_least "$sdk" "$minimum" && return 0 ;;
+		esac
+	done
+	return 1
+}
+
+# install_from_container_image <image> <tag>, e.g. sdk 10.0 or runtime 8.0
+install_from_container_image() {
+	local registry="https://mcr.microsoft.com/v2/dotnet/$1"
+	local arch
+	case "$(uname -m)" in
+		x86_64) arch=amd64 ;;
+		aarch64 | arm64) arch=arm64 ;;
+		*) echo "install-dotnet: unsupported architecture $(uname -m)" >&2; return 1 ;;
+	esac
+
+	local index manifest digest layer work
+	index="$(curl -fsSL -H 'Accept: application/vnd.oci.image.index.v1+json,application/vnd.docker.distribution.manifest.list.v2+json' \
+		"$registry/manifests/$2-noble")"
+	digest="$(jq -r --arg arch "$arch" \
+		'.manifests[] | select(.platform.os == "linux" and .platform.architecture == $arch and (.platform.variant // "") == "") | .digest' \
+		<<<"$index" | head -n1)"
+	manifest="$(curl -fsSL -H 'Accept: application/vnd.oci.image.manifest.v1+json,application/vnd.docker.distribution.manifest.v2+json' \
+		"$registry/manifests/$digest")"
+
+	# A runtime image contributes its shared framework and nothing else, so its
+	# older dotnet host never replaces the one the SDK brought.
+	local wanted='usr/share/dotnet/*'
+	[ "$1" = sdk ] || wanted='usr/share/dotnet/shared/*'
+
+	work="$(mktemp -d)"
+	mkdir -p "$root"
+	# Only the files under usr/share/dotnet are taken: the runtime, ASP.NET Core
+	# and SDK layers. The rest of the image is its operating system. Layers are
+	# extracted over what is there, so an SDK and older runtimes share one root.
+	# Each layer is checked against the sha256 digest its manifest names before
+	# anything in it is unpacked, since what it contains is run as dotnet.
+	while IFS= read -r layer; do
+		case "$layer" in
+			sha256:*) ;;
+			*) echo "install-dotnet: unsupported layer digest $layer" >&2; rm -rf "$work"; return 1 ;;
+		esac
+		curl -fsSL -o "$work/layer.tgz" "$registry/blobs/$layer"
+		if [ "sha256:$(sha256sum "$work/layer.tgz" | awk '{print $1}')" != "$layer" ]; then
+			echo "install-dotnet: layer $layer does not match its digest" >&2
+			rm -rf "$work"
+			return 1
+		fi
+		tar -xzf "$work/layer.tgz" -C "$root" --strip-components=3 --wildcards "$wanted" 2>/dev/null || true
+	done < <(jq -r '.layers[].digest' <<<"$manifest")
+	rm -rf "$work"
+}
+
+if ! has_sdk; then
+	echo "install-dotnet: installing the .NET $channel SDK (at least $minimum) into $root" >&2
+	install_from_container_image sdk "$channel"
+	if ! has_sdk; then
+		echo "install-dotnet: no .NET $channel SDK at or above $minimum after installing" >&2
+		exit 1
+	fi
+fi
+
+for runtime in "${runtimes[@]}"; do
+	has_runtime "$runtime" && continue
+	echo "install-dotnet: installing the .NET $runtime runtime into $root" >&2
+	install_from_container_image runtime "$runtime"
+	if ! has_runtime "$runtime"; then
+		echo "install-dotnet: no .NET $runtime runtime after installing" >&2
+		exit 1
+	fi
+done

.claude/hooks/session-start.sh

@@ -0,0 +1,36 @@
+#!/bin/bash
+# SessionStart hook for Claude Code cloud sessions: installs the .NET SDK this
+# repository's global.json asks for and restores its packages, so a session
+# can build and test straight away.
+set -euo pipefail
+
+if [ "${CLAUDE_CODE_REMOTE:-}" != "true" ]; then
+	exit 0
+fi
+
+cd "$CLAUDE_PROJECT_DIR"
+
+minimum=10.0.100
+if [ -f global.json ]; then
+	minimum="$(jq -r '.sdk.version // "10.0.100"' global.json)"
+fi
+# The test projects multi-target, so the older runtimes are needed to run them.
+bash .claude/hooks/install-dotnet.sh "${minimum%.*}" "$minimum" 8.0 9.0
+
+export DOTNET_ROOT="$HOME/.dotnet"
+export PATH="$DOTNET_ROOT:$DOTNET_ROOT/tools:$PATH"
+export DOTNET_CLI_TELEMETRY_OPTOUT=1
+export DOTNET_NOLOGO=1
+if [ -n "${CLAUDE_ENV_FILE:-}" ]; then
+	{
+		echo "export DOTNET_ROOT=\"$DOTNET_ROOT\""
+		echo "export PATH=\"$DOTNET_ROOT:$DOTNET_ROOT/tools:\$PATH\""
+		echo 'export DOTNET_CLI_TELEMETRY_OPTOUT=1'
+		echo 'export DOTNET_NOLOGO=1'
+	} >>"$CLAUDE_ENV_FILE"
+fi
+
+if [ -f .config/dotnet-tools.json ]; then
+	dotnet tool restore
+fi
+dotnet restore

.claude/settings.json

@@ -0,0 +1,14 @@
+{
+  "hooks": {
+    "SessionStart": [
+      {
+        "hooks": [
+          {
+            "type": "command",
+            "command": "$CLAUDE_PROJECT_DIR/.claude/hooks/session-start.sh"
+          }
+        ]
+      }
+    ]
+  }
+}