diff --git a/.claude/hooks/session-start.sh b/.claude/hooks/session-start.sh
new file mode 100755
index 0000000..b7c2a49
--- /dev/null
+++ b/.claude/hooks/session-start.sh
@@ -0,0 +1,36 @@
+#!/bin/bash
+# Canonical Tap House SessionStart hook for Claude Code on the web.
+#
+# Fresh web-session containers clone the repo bare: no submodules, no
+# pre-commit hook installed — so `git commit` runs unformatted and the
+# clang-format CI gate fails on code a local clone would have fixed at commit
+# time. This hook closes that gap at session start:
+#
+#   1. init submodules recursively (kernels, SDKs, vendored test harnesses)
+#   2. install pre-commit and register the repo's canonical hook
+#      (.pre-commit-config.yaml — the Tap-wide pinned clang-format)
+#   3. warm the pinned clang-format binary so the first commit doesn't
+#      pay the download (the container snapshot caches it)
+#
+# Canonical copy: taphouse (distributed by scripts/sync.sh alongside
+# .clang-format / .clang-tidy / .pre-commit-config.yaml; drift-guarded where
+# present). Web-only; local clones are untouched.
+set -euo pipefail
+
+if [ "${CLAUDE_CODE_REMOTE:-}" != "true" ]; then
+    exit 0
+fi
+
+cd "$CLAUDE_PROJECT_DIR"
+
+echo "session-start: initializing submodules ..."
+git submodule update --init --recursive
+
+echo "session-start: installing pre-commit ..."
+if ! python3 -m pre_commit --version >/dev/null 2>&1; then
+    python3 -m pip install --quiet pre-commit
+fi
+python3 -m pre_commit install
+python3 -m pre_commit install-hooks
+
+echo "session-start: done."
diff --git a/.claude/settings.json b/.claude/settings.json
new file mode 100644
index 0000000..e06b033
--- /dev/null
+++ b/.claude/settings.json
@@ -0,0 +1,14 @@
+{
+  "hooks": {
+    "SessionStart": [
+      {
+        "hooks": [
+          {
+            "type": "command",
+            "command": "$CLAUDE_PROJECT_DIR/.claude/hooks/session-start.sh"
+          }
+        ]
+      }
+    ]
+  }
+}
diff --git a/.github/workflows/style.yml b/.github/workflows/style.yml
index a18d4ef..9178d13 100644
--- a/.github/workflows/style.yml
+++ b/.github/workflows/style.yml
@@ -7,9 +7,9 @@ on: [push, pull_request]
 
 jobs:
   drift:
-    uses: tap/taphouse/.github/workflows/drift-check.yml@v4
+    uses: tap/taphouse/.github/workflows/drift-check.yml@v5
     with:
-      ref: v4
+      ref: v5
 
   clang-tidy:
     runs-on: ubuntu-latest
diff --git a/.gitignore b/.gitignore
index 9bcf3dd..0461d61 100644
--- a/.gitignore
+++ b/.gitignore
@@ -4,6 +4,8 @@ compile_commands.json
 CMakeUserPresets.json
 .vscode/
 .idea/
-.claude/
+.claude/*
+!.claude/settings.json
+!.claude/hooks/
 book/book/
 __pycache__/