diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
index 456b816..be5c8a4 100644
--- a/.github/workflows/release.yml
+++ b/.github/workflows/release.yml
@@ -74,5 +74,5 @@ jobs:
           git config user.email "github-actions[bot]@users.noreply.github.com"
           git add Formula/td.rb
           git diff --cached --quiet && echo "No changes" && exit 0
-          git commit -m "td: bump to ${{ steps.version.outputs.version }}"
+          git commit -m "chore(homebrew): bump td to ${{ steps.version.outputs.version }}"
           git push
diff --git a/CLAUDE.md b/CLAUDE.md
index cd0ab66..a3b35dc 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -34,13 +34,12 @@ go test ./...              # Test all
 ```bash
 # Commit changes with proper message
 git add .
-git commit -m "feat: description of changes
+git commit -m "feat: describe changes (td-<id>)
 
 Details here
 
-🤖 Generated with Claude Code
-
-Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>"
+Nightshift-Task: <task-id>
+Nightshift-Ref: https://github.com/marcus/nightshift"
 
 # Create version tag (bump from current version, e.g., v0.2.0 → v0.3.0)
 git tag -a v0.3.0 -m "Release v0.3.0: description"
diff --git a/Makefile b/Makefile
index 18da511..c3c1d0e 100644
--- a/Makefile
+++ b/Makefile
@@ -1,4 +1,4 @@
-.PHONY: help fmt test install tag release check-clean check-version install-hooks
+.PHONY: help fmt test test-hooks install tag release check-clean check-version install-hooks
 
 SHELL := /bin/sh
 
@@ -13,8 +13,9 @@ help:
 	@printf "%s\n" \
 		"Targets:" \
 		"  make fmt                       # gofmt -w ." \
-		"  make install-hooks             # install git pre-commit hook" \
+		"  make install-hooks             # install git pre-commit and commit-msg hooks" \
 		"  make test                      # go test ./..." \
+		"  make test-hooks                # run hook regression tests" \
 		"  make install                   # build and install with version from git" \
 		"  make tag VERSION=vX.Y.Z        # create annotated git tag (requires clean tree)" \
 		"  make release VERSION=vX.Y.Z    # tag + push (triggers GoReleaser via GitHub Actions)"
@@ -25,6 +26,9 @@ fmt:
 test:
 	go test ./...
 
+test-hooks:
+	./scripts/test-commit-msg.sh
+
 install:
 	@V="$(GIT_DESCRIBE)"; V=$${V:-dev}; \
 	echo "Installing td $$V"; \
@@ -52,6 +56,18 @@ release: tag
 	git push origin "$(VERSION)"
 
 install-hooks:
-	@echo "Installing git pre-commit hook..."
-	@ln -sf ../../scripts/pre-commit.sh .git/hooks/pre-commit
-	@echo "Done. Hook installed at .git/hooks/pre-commit"
+	@hooks_dir=$$(git rev-parse --git-path hooks); \
+	echo "Installing git hooks in $$hooks_dir..."; \
+	mkdir -p "$$hooks_dir"; \
+	for hook in pre-commit commit-msg; do \
+		hook_path="$$hooks_dir/$$hook"; \
+		rm -f "$$hook_path"; \
+		printf '%s\n' \
+			'#!/bin/sh' \
+			'set -eu' \
+			'repo_root=$$(git rev-parse --show-toplevel)' \
+			"exec \"\$$repo_root/scripts/$$hook.sh\" \"\$$@\"" \
+			> "$$hook_path"; \
+		chmod +x "$$hook_path"; \
+	done; \
+	echo "Done. Hooks installed at $$hooks_dir/pre-commit and $$hooks_dir/commit-msg"
diff --git a/README.md b/README.md
index 684416a..83861a4 100644
--- a/README.md
+++ b/README.md
@@ -189,10 +189,16 @@ make install-dev
 # Format code
 make fmt
 
-# Install git pre-commit hook (gofmt, go vet, go build on staged files)
+# Install git hooks:
+#   pre-commit -> gofmt, go vet, go build
+#   commit-msg -> normalize commit subjects
 make install-hooks
 ```
 
+`make install-hooks` installs wrappers into the repo's resolved git hooks directory, so the same setup works from linked worktrees too.
+
+Commit subjects are normalized to `type: summary` or `type(scope): summary`, with an optional trailing ` (td-<id>)`. The `commit-msg` hook rewrites obvious cases like `Docs - Update changelog` to `docs: update changelog`, preserves commit bodies and trailers, leaves Git-generated merge/fixup/squash/revert subjects alone, and stops the commit with guidance when the subject cannot be safely interpreted.
+
 ## Tests & Quality Checks
 
 ```bash
diff --git a/docs/guides/releasing-new-version.md b/docs/guides/releasing-new-version.md
index ca98e52..e0f0c5b 100644
--- a/docs/guides/releasing-new-version.md
+++ b/docs/guides/releasing-new-version.md
@@ -53,9 +53,11 @@ Add entry at the top of `CHANGELOG.md`:
 Commit the changelog:
 ```bash
 git add CHANGELOG.md
-git commit -m "docs: Update changelog for vX.Y.Z"
+git commit -m "docs: update changelog for vX.Y.Z"
 ```
 
+If you have run `make install-hooks`, the local `commit-msg` hook will normalize obvious subject formatting issues, preserve the commit body and trailers, and reject subjects it cannot safely interpret. Use `type: summary` or `type(scope): summary`, plus an optional trailing ` (td-<id>)` when the release prep is tied to a task.
+
 ### 3. Verify Tests Pass
 
 ```bash
@@ -137,7 +139,7 @@ go test ./...
 # Update changelog
 # (Edit CHANGELOG.md, add entry at top)
 git add CHANGELOG.md
-git commit -m "docs: Update changelog for vX.Y.Z"
+git commit -m "docs: update changelog for vX.Y.Z"
 
 # Push commits, then tag (tag push triggers automated release)
 git push origin main
diff --git a/scripts/commit-msg.sh b/scripts/commit-msg.sh
new file mode 100755
index 0000000..29b885a
--- /dev/null
+++ b/scripts/commit-msg.sh
@@ -0,0 +1,233 @@
+#!/usr/bin/env bash
+# commit-msg hook for td
+# Install: make install-hooks  (recommended; resolves the active hooks path for linked worktrees too)
+set -euo pipefail
+
+message_file=${1:-}
+
+trim() {
+  local value=${1-}
+  value=${value#"${value%%[![:space:]]*}"}
+  value=${value%"${value##*[![:space:]]}"}
+  printf '%s' "$value"
+}
+
+normalize_type() {
+  local raw normalized
+
+  raw=$(trim "${1-}")
+  raw=$(printf '%s' "$raw" | tr '[:upper:]' '[:lower:]')
+  raw=${raw//_/-}
+
+  case "$raw" in
+    feat|feature|features)
+      normalized="feat"
+      ;;
+    fix|bug|bugfix|bug-fix|hotfix)
+      normalized="fix"
+      ;;
+    docs|doc|documentation)
+      normalized="docs"
+      ;;
+    chore|chores)
+      normalized="chore"
+      ;;
+    build|ci|perf|refactor|revert|style)
+      normalized="$raw"
+      ;;
+    test|tests|testing)
+      normalized="test"
+      ;;
+    *)
+      return 1
+      ;;
+  esac
+
+  printf '%s' "$normalized"
+}
+
+normalize_scope() {
+  local raw normalized
+
+  raw=$(trim "${1-}")
+  raw=${raw#[}
+  raw=${raw%]}
+  raw=$(printf '%s' "$raw" | tr '[:upper:]' '[:lower:]')
+  normalized=$(printf '%s' "$raw" | sed -E 's/[[:space:]_]+/-/g; s/^-+//; s/-+$//; s/-+/-/g')
+
+  if [[ -z "$normalized" || ! "$normalized" =~ ^[a-z0-9][a-z0-9._/-]*$ ]]; then
+    return 1
+  fi
+
+  printf '%s' "$normalized"
+}
+
+normalize_summary() {
+  local summary first_char
+
+  summary=$(trim "${1-}")
+  summary=$(printf '%s' "$summary" | sed -E 's/[[:space:]]+/ /g')
+
+  if [[ "$summary" == *"." && "$summary" != *"..." ]]; then
+    summary=${summary%.}
+  fi
+
+  if [[ "$summary" =~ ^([A-Z])([a-z].*)$ ]]; then
+    first_char=$(printf '%s' "${BASH_REMATCH[1]}" | tr '[:upper:]' '[:lower:]')
+    summary="${first_char}${BASH_REMATCH[2]}"
+  fi
+
+  printf '%s' "$summary"
+}
+
+print_error() {
+  local subject=${1-}
+
+  cat >&2 <<EOF
+commit-msg: could not safely normalize this subject:
+  $subject
+
+Use one of:
+  type: summary
+  type(scope): summary
+
+Optional suffix:
+  type: summary (td-1234)
+
+Examples:
+  feat: add commit message normalizer
+  fix(sync): preserve trailers (td-527bd4-0006)
+  chore(homebrew): bump td to v1.2.3
+EOF
+}
+
+is_valid_td_suffix() {
+  local value
+
+  value=$(trim "${1-}")
+  [[ "$value" =~ ^[Tt][Dd]-[A-Za-z0-9._-]+$ ]]
+}
+
+is_td_like_suffix() {
+  local value
+
+  value=$(trim "${1-}")
+  value=$(printf '%s' "$value" | tr '[:upper:]' '[:lower:]')
+
+  [[ "$value" =~ ^td($|[^[:alpha:]].*) ]]
+}
+
+normalize_subject() {
+  local subject trimmed base td_suffix type scope summary trailing_paren
+
+  subject=${1-}
+  trimmed=$(trim "$subject")
+
+  if [[ -z "$trimmed" ]]; then
+    print_error "$subject"
+    return 1
+  fi
+
+  case "$trimmed" in
+    Merge\ *|fixup!\ *|squash!\ *|Revert\ \"*\")
+      printf '%s' "$trimmed"
+      return 0
+      ;;
+  esac
+
+  td_suffix=""
+  base="$trimmed"
+  if [[ "$base" =~ ^(.+)[[:space:]]+\(([^()]*)\)[[:space:]]*$ ]]; then
+    trailing_paren=$(trim "${BASH_REMATCH[2]}")
+
+    if ! is_valid_td_suffix "$trailing_paren" && is_td_like_suffix "$trailing_paren"; then
+      print_error "$subject"
+      return 1
+    fi
+  fi
+
+  if [[ "$base" =~ ^(.+)[[:space:]]+\(([Tt][Dd]-[A-Za-z0-9._-]+)\)[[:space:]]*$ ]]; then
+    base=$(trim "${BASH_REMATCH[1]}")
+    td_suffix=" ($(printf '%s' "${BASH_REMATCH[2]}" | tr '[:upper:]' '[:lower:]'))"
+  fi
+
+  scope=""
+  summary=""
+
+  if [[ "$base" =~ ^([[:alpha:]][[:alnum:]_-]*)(\(([^()]*)\))?[[:space:]]*:[[:space:]]*(.+)$ ]]; then
+    type=${BASH_REMATCH[1]}
+    scope=${BASH_REMATCH[3]:-}
+    summary=${BASH_REMATCH[4]}
+  elif [[ "$base" =~ ^([[:alpha:]][[:alnum:]_-]*)(\(([^()]*)\))?[[:space:]]*-[[:space:]]*(.+)$ ]]; then
+    type=${BASH_REMATCH[1]}
+    scope=${BASH_REMATCH[3]:-}
+    summary=${BASH_REMATCH[4]}
+  elif [[ "$base" =~ ^([[:alpha:]][[:alnum:]_-]*)[[:space:]]+([[:alnum:]_./-]+)[[:space:]]*[:-][[:space:]]*(.+)$ ]]; then
+    type=${BASH_REMATCH[1]}
+    scope=${BASH_REMATCH[2]}
+    summary=${BASH_REMATCH[3]}
+  elif [[ "$base" =~ ^([[:alpha:]][[:alnum:]_-]*)[[:space:]]+(.+)$ ]]; then
+    type=${BASH_REMATCH[1]}
+    summary=${BASH_REMATCH[2]}
+  else
+    print_error "$subject"
+    return 1
+  fi
+
+  if ! type=$(normalize_type "$type"); then
+    print_error "$subject"
+    return 1
+  fi
+
+  if [[ -n "$scope" ]]; then
+    if ! scope=$(normalize_scope "$scope"); then
+      print_error "$subject"
+      return 1
+    fi
+  fi
+
+  summary=$(normalize_summary "$summary")
+  if [[ -z "$summary" ]]; then
+    print_error "$subject"
+    return 1
+  fi
+
+  if [[ -n "$scope" ]]; then
+    printf '%s(%s): %s%s' "$type" "$scope" "$summary" "$td_suffix"
+  else
+    printf '%s: %s%s' "$type" "$summary" "$td_suffix"
+  fi
+}
+
+if [[ -z "$message_file" || ! -f "$message_file" ]]; then
+  echo "commit-msg: expected path to the commit message file" >&2
+  exit 1
+fi
+
+lines=()
+while IFS= read -r line || [[ -n "$line" ]]; do
+  lines+=("$line")
+done < "$message_file"
+subject_index=-1
+
+for i in "${!lines[@]}"; do
+  line=${lines[$i]}
+  if [[ -z $(trim "$line") || "$line" =~ ^# ]]; then
+    continue
+  fi
+  subject_index=$i
+  break
+done
+
+if (( subject_index < 0 )); then
+  exit 0
+fi
+
+original_subject=${lines[$subject_index]}
+normalized_subject=$(normalize_subject "$original_subject")
+
+if [[ "$normalized_subject" != "$(trim "$original_subject")" ]]; then
+  lines[$subject_index]=$normalized_subject
+  printf '%s\n' "${lines[@]}" > "$message_file"
+  echo "commit-msg: normalized subject to '$normalized_subject'" >&2
+fi
diff --git a/scripts/loop-prompt.md b/scripts/loop-prompt.md
index 7f84db2..f9883b0 100644
--- a/scripts/loop-prompt.md
+++ b/scripts/loop-prompt.md
@@ -174,4 +174,4 @@ Use `td review`, not `td close` — self-closing is blocked.
 - **Don't break sync.** Deterministic IDs, proper event logging, no hard deletes.
 - **Session isolation is sacred.** Don't bypass review guards.
 - **If stuck, log and skip.** `td log <id> "Blocked: <reason>"` then `td block <id>`.
-- **Commit messages reference td.** Format: `feat|fix|chore: <summary> (td-<id>)`
+- **Commit messages follow the repo hook.** Format: `type: <summary>` or `type(scope): <summary>`, with optional ` (td-<id>)`.
diff --git a/scripts/pre-commit.sh b/scripts/pre-commit.sh
index 2b563f2..ddc8085 100755
--- a/scripts/pre-commit.sh
+++ b/scripts/pre-commit.sh
@@ -1,6 +1,6 @@
 #!/usr/bin/env bash
 # pre-commit hook for td
-# Install: make install-hooks  (or: ln -sf ../../scripts/pre-commit.sh .git/hooks/pre-commit)
+# Install: make install-hooks  (recommended; resolves the active hooks path for linked worktrees too)
 set -euo pipefail
 
 PASS=0
diff --git a/scripts/test-commit-msg.sh b/scripts/test-commit-msg.sh
new file mode 100755
index 0000000..ed44c80
--- /dev/null
+++ b/scripts/test-commit-msg.sh
@@ -0,0 +1,102 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+repo_root=$(git rev-parse --show-toplevel)
+hook_script="$repo_root/scripts/commit-msg.sh"
+tmp_dir=$(mktemp -d "${TMPDIR:-/tmp}/td-commit-msg-test.XXXXXX")
+
+cleanup() {
+  rm -rf "$tmp_dir"
+}
+
+fail() {
+  printf 'test-commit-msg: %s\n' "$1" >&2
+  exit 1
+}
+
+write_message() {
+  local path=$1
+  shift
+
+  printf '%s\n' "$@" > "$path"
+}
+
+assert_file_equals() {
+  local path=$1
+  local expected=$2
+  local actual
+
+  actual=$(cat "$path")
+  if [[ "$actual" != "$expected" ]]; then
+    printf 'Expected:\n%s\n\nActual:\n%s\n' "$expected" "$actual" >&2
+    fail "file contents did not match for $path"
+  fi
+}
+
+run_success_case() {
+  local name=$1
+  local expected=$2
+  shift 2
+
+  local message_file="$tmp_dir/$name.txt"
+  local stderr_file="$tmp_dir/$name.stderr"
+
+  write_message "$message_file" "$@"
+
+  if ! "$hook_script" "$message_file" > /dev/null 2> "$stderr_file"; then
+    cat "$stderr_file" >&2
+    fail "expected success for $name"
+  fi
+
+  assert_file_equals "$message_file" "$expected"
+}
+
+run_failure_case() {
+  local name=$1
+  local subject=$2
+  local message_file="$tmp_dir/$name.txt"
+  local stderr_file="$tmp_dir/$name.stderr"
+
+  write_message "$message_file" "$subject"
+
+  if "$hook_script" "$message_file" > /dev/null 2> "$stderr_file"; then
+    cat "$stderr_file" >&2
+    fail "expected failure for $name"
+  fi
+
+  grep -F "type: summary" "$stderr_file" > /dev/null || fail "expected guidance output for $name"
+  assert_file_equals "$message_file" "$subject"
+}
+
+trap cleanup EXIT
+
+run_success_case \
+  valid-subject \
+  "feat: add commit message normalizer (td-527bd4-0006)" \
+  "feat: add commit message normalizer (td-527bd4-0006)"
+
+run_success_case \
+  normalize-simple \
+  "docs: update changelog" \
+  "Docs - Update changelog"
+
+run_success_case \
+  preserve-body \
+  $'fix(sync): preserve trailers (td-527bd4-0006)\n\nBody line\n\nNightshift-Task: commit-normalize\nNightshift-Ref: https://github.com/marcus/nightshift' \
+  "Fix sync - Preserve trailers (td-527bd4-0006)" \
+  "" \
+  "Body line" \
+  "" \
+  "Nightshift-Task: commit-normalize" \
+  "Nightshift-Ref: https://github.com/marcus/nightshift"
+
+run_success_case \
+  normalize-release \
+  "chore(homebrew): bump td to v1.2.3" \
+  "Chore homebrew - Bump td to v1.2.3"
+
+run_failure_case "invalid-td-empty" "feat: add normalizer (td-)"
+run_failure_case "invalid-td-space" "feat: add normalizer (td 527bd4)"
+run_failure_case "invalid-td-symbols" "feat: add normalizer (Td-???)"
+
+printf 'commit-msg regression tests passed\n'