diff --git a/.claude/hooks/session-start.sh b/.claude/hooks/session-start.sh
new file mode 100755
index 0000000..e095ebb
--- /dev/null
+++ b/.claude/hooks/session-start.sh
@@ -0,0 +1,22 @@
+#!/bin/bash
+# Install deps + wire prek git hooks so cloud commits run the same checks as local.
+# Scoped to remote (web/cloud) sessions; remove the guard to run locally too.
+set -euo pipefail
+[ "${CLAUDE_CODE_REMOTE:-}" != "true" ] && exit 0
+cd "${CLAUDE_PROJECT_DIR:-.}"
+
+export PATH="$HOME/.local/bin:$PATH"
+line='export PATH="$HOME/.local/bin:$PATH"'
+if [ -n "${CLAUDE_ENV_FILE:-}" ] && ! grep -qF "$line" "$CLAUDE_ENV_FILE" 2>/dev/null; then
+  echo "$line" >> "$CLAUDE_ENV_FILE"
+fi
+
+# --- Install deps for the TypeScript stack ---
+command -v bun >/dev/null || curl -fsSL https://bun.sh/install | bash
+export PATH="$HOME/.bun/bin:$PATH"
+bun install
+
+# Install prek (Rust binary, language-agnostic), then wire the git hooks.
+command -v prek >/dev/null 2>&1 || curl -LsSf https://prek.j178.dev/install.sh | sh
+prek install
+exit 0
diff --git a/.claude/settings.json b/.claude/settings.json
new file mode 100644
index 0000000..ea39e04
--- /dev/null
+++ b/.claude/settings.json
@@ -0,0 +1,15 @@
+{
+  "hooks": {
+    "SessionStart": [
+      {
+        "matcher": "startup|resume",
+        "hooks": [
+          {
+            "type": "command",
+            "command": "$CLAUDE_PROJECT_DIR/.claude/hooks/session-start.sh"
+          }
+        ]
+      }
+    ]
+  }
+}
diff --git a/.github/workflows/ci.yaml b/.github/workflows/ci.yaml
index 6418b62..52f3dda 100644
--- a/.github/workflows/ci.yaml
+++ b/.github/workflows/ci.yaml
@@ -15,6 +15,15 @@ permissions:
   id-token: write
 
 jobs:
+  ai-writing:
+    name: AI Writing Check
+    runs-on: ubuntu-latest
+    timeout-minutes: 5
+    steps:
+      - uses: actions/checkout@v7
+      - uses: oven-sh/setup-bun@v2
+      - run: bun scripts/check-ai-writing.ts
+
   quality:
     runs-on: ubuntu-latest
     timeout-minutes: 10
diff --git a/.github/workflows/folder-size.yaml b/.github/workflows/folder-size.yaml
new file mode 100644
index 0000000..be1ca13
--- /dev/null
+++ b/.github/workflows/folder-size.yaml
@@ -0,0 +1,27 @@
+name: Folder Size Check
+on:
+  workflow_dispatch:
+  pull_request:
+    paths:
+      - '**.ts'
+      - '**.tsx'
+      - '**.js'
+      - '**.jsx'
+      - '**.mjs'
+      - '**.cjs'
+jobs:
+  check-folder-sizes:
+    name: Folder File Count Limit
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v7
+        with: { fetch-depth: 0 }
+      - name: Check for oversized folders
+        run: |
+          if [ -n "${{ github.event.pull_request.base.sha }}" ]; then
+            mapfile -t files < <(git diff --name-only --diff-filter=d "${{ github.event.pull_request.base.sha }}...HEAD")
+            [ "${#files[@]}" -eq 0 ] && { echo "No files changed."; exit 0; }
+            scripts/check_folder_sizes.sh "${files[@]}"   # self-filters non-source via SOURCE_EXTS
+          else
+            scripts/check_folder_sizes.sh --all
+          fi
diff --git a/.github/workflows/large-files.yaml b/.github/workflows/large-files.yaml
new file mode 100644
index 0000000..f6237bf
--- /dev/null
+++ b/.github/workflows/large-files.yaml
@@ -0,0 +1,27 @@
+name: Large File Check
+on:
+  workflow_dispatch:
+  pull_request:
+    paths:
+      - '**.ts'
+      - '**.tsx'
+      - '**.js'
+      - '**.jsx'
+      - '**.mjs'
+      - '**.cjs'
+jobs:
+  check-file-sizes:
+    name: Source File Line Limit
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v7
+        with: { fetch-depth: 0 }
+      - name: Check for large source files
+        run: |
+          if [ -n "${{ github.event.pull_request.base.sha }}" ]; then
+            mapfile -t files < <(git diff --name-only --diff-filter=d "${{ github.event.pull_request.base.sha }}...HEAD")
+            [ "${#files[@]}" -eq 0 ] && { echo "No files changed."; exit 0; }
+            scripts/check_large_files.sh "${files[@]}"   # self-filters non-source via SOURCE_EXTS
+          else
+            scripts/check_large_files.sh --all
+          fi
diff --git a/.gitignore b/.gitignore
index 7bc3978..c31dd12 100644
--- a/.gitignore
+++ b/.gitignore
@@ -6,3 +6,6 @@ test-results/
 playwright-report/
 *.tsbuildinfo
 
+# bun is only a runtime for scripts/check-ai-writing.ts; npm manages deps
+bun.lock
+
diff --git a/prek.toml b/prek.toml
new file mode 100644
index 0000000..091fb33
--- /dev/null
+++ b/prek.toml
@@ -0,0 +1,30 @@
+[[repos]]
+repo = "https://github.com/pre-commit/pre-commit-hooks"
+rev = "v4.6.0"
+hooks = [
+    { id = "check-added-large-files" },
+]
+
+[[repos]]
+repo = "local"
+hooks = [
+    { id = "ai-writing-check", name = "AI writing check", entry = "bun scripts/check-ai-writing.ts", language = "system", pass_filenames = false, always_run = true },
+]
+
+# ── Source-size guardrails (mirror GitHub Actions) ────────────────
+[[repos]]
+repo = "local"
+
+[[repos.hooks]]
+id = "check-large-files"
+name = "fail if any source file exceeds the line-count error threshold"
+language = "system"
+entry = "scripts/check_large_files.sh"
+files = "\\.(ts|tsx|js|jsx|mjs|cjs)$"
+
+[[repos.hooks]]
+id = "check-folder-sizes"
+name = "fail if any source folder exceeds the file-count error threshold"
+language = "system"
+entry = "scripts/check_folder_sizes.sh"
+files = "\\.(ts|tsx|js|jsx|mjs|cjs)$"
diff --git a/scripts/check-ai-writing.ts b/scripts/check-ai-writing.ts
new file mode 100644
index 0000000..c5f7d0d
--- /dev/null
+++ b/scripts/check-ai-writing.ts
@@ -0,0 +1,95 @@
+#!/usr/bin/env bun
+import { readdirSync, statSync, readFileSync } from 'node:fs'
+import { join, relative, extname, resolve } from 'node:path'
+import { fileURLToPath } from 'node:url'
+
+const REPO_ROOT = resolve(fileURLToPath(import.meta.url), '../..')
+const SELF = resolve(fileURLToPath(import.meta.url))
+const EM_DASH = '\u2014'
+const ROOT_SKIP = new Set([
+  '.git',
+  '.venv',
+  'node_modules',
+  'dist',
+  'build',
+  'target',
+  '.next',
+  'coverage',
+  '.cache'
+])
+const REC_SKIP = new Set(['__pycache__', 'node_modules', 'dist', 'target', '.next'])
+const SKIP_EXT = new Set([
+  '.png',
+  '.jpg',
+  '.jpeg',
+  '.gif',
+  '.webp',
+  '.ico',
+  '.svg',
+  '.mp4',
+  '.mov',
+  '.mp3',
+  '.woff',
+  '.woff2',
+  '.ttf',
+  '.otf',
+  '.pdf',
+  '.zip',
+  '.gz',
+  '.bin',
+  '.lock'
+])
+const CONTRASTIVE: RegExp[] = [
+  /\bnot (?:just|only|merely|simply)\b[^.?!\n]{0,60}?\bbut\b/i,
+  /\b(?:it'?s|that'?s|this is)\s+not\b[^.?!\n]{0,60}?,?\s*(?:it'?s|that'?s|they'?re)\b/i,
+  /\b(?:isn'?t|aren'?t|wasn'?t|weren'?t)\s+(?:just|only|merely|simply)\b/i,
+  /\b(?:isn'?t|aren'?t)\s+(?:just\s+)?about\b[^.?!\n]{0,60}?\bit'?s about\b/i,
+  /\bmore than just\b/i,
+  /\bless about\b[^.?!\n]{0,60}?\bmore about\b/i,
+  /\bnot\b[^.?!\n]{0,40}?\bso much as\b/i,
+  /\bgoes? beyond\b/i // noisiest; drop if it over-flags
+]
+
+function* walk(dir: string): Generator<string> {
+  for (const name of readdirSync(dir)) {
+    const full = join(dir, name)
+    const top = relative(REPO_ROOT, full).split('/')[0]
+    if (ROOT_SKIP.has(top)) continue
+    if (statSync(full).isDirectory()) {
+      if (REC_SKIP.has(name)) continue
+      yield* walk(full)
+    } else {
+      if (resolve(full) === SELF || SKIP_EXT.has(extname(full).toLowerCase())) continue
+      yield full
+    }
+  }
+}
+
+const em: string[] = [],
+  contra: string[] = []
+for (const file of walk(REPO_ROOT)) {
+  let text: string
+  try {
+    text = readFileSync(file, 'utf8')
+  } catch {
+    continue
+  }
+  const rel = relative(REPO_ROOT, file)
+  text.split('\n').forEach((line, i) => {
+    if (line.includes(EM_DASH)) em.push(`${rel}:${i + 1}: ${line.trim()}`)
+    if (CONTRASTIVE.some((re) => re.test(line))) contra.push(`${rel}:${i + 1}: ${line.trim()}`)
+  })
+}
+if (em.length || contra.length) {
+  if (em.length) {
+    console.log('AI writing check failed: em dash (U+2014) detected')
+    console.log(em.join('\n'))
+  }
+  if (contra.length) {
+    console.log("AI writing check failed: contrastive parallelism ('not just X, but Y') detected")
+    console.log(contra.join('\n'))
+  }
+  console.log('Remove the flagged construction or explain why it is acceptable.')
+  process.exit(1)
+}
+console.log('AI writing check passed.')
diff --git a/scripts/check_folder_sizes.sh b/scripts/check_folder_sizes.sh
new file mode 100755
index 0000000..62a063c
--- /dev/null
+++ b/scripts/check_folder_sizes.sh
@@ -0,0 +1,82 @@
+#!/usr/bin/env bash
+#
+# Enforce a file-count limit on source folders (non-recursive). Shared by
+# .github/workflows/folder-size.yaml and prek.toml.
+#   check_folder_sizes.sh [file ...]   # check folders containing the given files
+#   check_folder_sizes.sh --all        # scan every folder
+# Thresholds via FOLDER_WARN_THRESHOLD / FOLDER_ERROR_THRESHOLD.
+set -euo pipefail
+
+WARN_THRESHOLD="${FOLDER_WARN_THRESHOLD:-20}"
+ERROR_THRESHOLD="${FOLDER_ERROR_THRESHOLD:-35}"
+
+# --- Set to YOUR stack (pick one): TS=(ts tsx js jsx mjs cjs)  Py=(py)  Rust=(rs) ---
+SOURCE_EXTS=(ts tsx js jsx mjs cjs)
+
+GRANDFATHERED=()   # folders allowed to exceed (warn instead of error)
+
+EXCLUDE_PATH_RE='(^|/)(node_modules|vendor|dist|build|\.next|coverage|storybook-static|visual-tests|e2e|tests|test|__tests__|\.git)(/|$)'
+GENERATED_RE='(^|/)(alembic[^/]*/versions|migrations)(/|$)'
+
+is_grandfathered() { local t="$1"; for g in "${GRANDFATHERED[@]}"; do [ "$t" = "$g" ] && return 0; done; return 1; }
+should_skip() {
+  local f="$1"; [ -z "$f" ] && return 0; [ "$f" = "." ] && return 0
+  echo "$f" | grep -qE "$EXCLUDE_PATH_RE" && return 0
+  echo "$f" | grep -qE "$GENERATED_RE" && return 0
+  return 1
+}
+
+count_folder() {
+  local fa=() first=1
+  for e in "${SOURCE_EXTS[@]}"; do
+    if [ "$first" = 1 ]; then fa+=( -name "*.$e" ); first=0; else fa+=( -o -name "*.$e" ); fi
+  done
+  find "$1" -mindepth 1 -maxdepth 1 -type f \( "${fa[@]}" \) \
+    -not -name 'test_*' -not -name '*_test.*' -not -name '*.test.*' \
+    -not -name '*.spec.*' -not -name '*.d.ts' -not -name 'conftest.py' | wc -l
+}
+
+collect_all_folders() {
+  find . -type d -not -path './.git/*' -not -path '*/node_modules/*' \
+    -not -path '*/dist/*' -not -path '*/build/*' | sed 's|^\./||'
+}
+
+folder_list=$(mktemp); trap 'rm -f "$folder_list"' EXIT
+if [ "${1:-}" = "--all" ]; then collect_all_folders > "$folder_list"
+else for f in "$@"; do [ -z "$f" ] && continue; dirname "$f"; done | sort -u > "$folder_list"; fi
+
+warnings=0; errors=0; warn_list=""; error_list=""
+while IFS= read -r folder; do
+  folder="${folder#./}"
+  should_skip "$folder" && continue
+  [ ! -d "$folder" ] && continue
+  count=$(count_folder "$folder")
+  if [ "$count" -gt "$ERROR_THRESHOLD" ]; then
+    if is_grandfathered "$folder"; then
+      warnings=$((warnings + 1)); warn_list="${warn_list}| \`${folder}/\` | ${count} | :warning: exceeds ${ERROR_THRESHOLD} (grandfathered) |\n"
+    else
+      errors=$((errors + 1)); error_list="${error_list}| \`${folder}/\` | ${count} | :x: exceeds ${ERROR_THRESHOLD} |\n"
+    fi
+  elif [ "$count" -gt "$WARN_THRESHOLD" ]; then
+    warnings=$((warnings + 1)); warn_list="${warn_list}| \`${folder}/\` | ${count} | :warning: exceeds ${WARN_THRESHOLD} |\n"
+  fi
+done < "$folder_list"
+
+if [ -n "${GITHUB_STEP_SUMMARY:-}" ] && { [ "$errors" -gt 0 ] || [ "$warnings" -gt 0 ]; }; then
+  {
+    echo "## Folder Size Report"; echo ""
+    echo "| Folder | Files | Status |"; echo "|--------|-------|--------|"
+    [ "$errors" -gt 0 ] && printf '%b' "$error_list"
+    [ "$warnings" -gt 0 ] && printf '%b' "$warn_list"
+    echo ""; echo "**Thresholds:** warn at ${WARN_THRESHOLD} files, error at ${ERROR_THRESHOLD} files. Immediate source children only - subfolders are the fix."
+  } >> "$GITHUB_STEP_SUMMARY"
+fi
+
+format_list() { if command -v column >/dev/null 2>&1; then printf '%b' "$1" | column -t -s '|'; else printf '%b' "$1"; fi; }
+
+if [ "$errors" -gt 0 ]; then echo "::error::${errors} folder(s) exceed the ${ERROR_THRESHOLD}-file error threshold" >&2; format_list "$error_list" >&2; fi
+if [ "$warnings" -gt 0 ]; then echo "::warning::${warnings} folder(s) exceed the ${WARN_THRESHOLD}-file warning threshold" >&2; format_list "$warn_list" >&2; fi
+if [ "$errors" -eq 0 ] && [ "$warnings" -eq 0 ]; then echo "All folders are within the ${WARN_THRESHOLD}-file limit."; fi
+
+[ "$errors" -gt 0 ] && exit 1
+exit 0
diff --git a/scripts/check_large_files.sh b/scripts/check_large_files.sh
new file mode 100755
index 0000000..b52dcad
--- /dev/null
+++ b/scripts/check_large_files.sh
@@ -0,0 +1,83 @@
+#!/usr/bin/env bash
+#
+# Enforce a line-count limit on source files. Shared by
+# .github/workflows/large-files.yaml and prek.toml.
+#   check_large_files.sh [file ...]   # check the given files
+#   check_large_files.sh --all        # scan the whole tree
+# Thresholds via LARGE_FILE_WARN_THRESHOLD / LARGE_FILE_ERROR_THRESHOLD.
+# Exit 1 on errors, 0 on warnings-only or clean.
+set -euo pipefail
+
+WARN_THRESHOLD="${LARGE_FILE_WARN_THRESHOLD:-500}"
+ERROR_THRESHOLD="${LARGE_FILE_ERROR_THRESHOLD:-800}"
+
+# --- Set to YOUR stack (pick one): TS=(ts tsx js jsx mjs cjs)  Py=(py)  Rust=(rs) ---
+SOURCE_EXTS=(ts tsx js jsx mjs cjs)
+
+declare -A _EXT_SET=()
+for e in "${SOURCE_EXTS[@]}"; do _EXT_SET[".$e"]=1; done
+
+# Trim to your stack: node_modules|dist|.next (TS), __pycache__|.venv (Py), target (Rust)
+EXCLUDE_PATH_RE='(^|/)(node_modules|vendor|dist|build|\.next|coverage|storybook-static|visual-tests|e2e|tests|test|__tests__|\.git)(/|$)'
+GENERATED_RE='(^|/)(alembic[^/]*/versions|migrations)(/|$)'
+EXCLUDE_NAME_RE='(.+\.test\..+|.+\.spec\..+|.+\.d\.ts)$'
+
+is_source_file() { local ext=".${1##*.}"; [ -n "${_EXT_SET[$ext]:-}" ]; }
+
+is_excluded() {
+  local f="$1" base
+  echo "$f" | grep -qE "$EXCLUDE_PATH_RE" && return 0
+  echo "$f" | grep -qE "$GENERATED_RE" && return 0
+  base=$(basename "$f")
+  echo "$base" | grep -qE "$EXCLUDE_NAME_RE" && return 0
+  return 1
+}
+
+collect_all() {
+  local fa=() first=1
+  for e in "${SOURCE_EXTS[@]}"; do
+    if [ "$first" = 1 ]; then fa+=( -name "*.$e" ); first=0; else fa+=( -o -name "*.$e" ); fi
+  done
+  find . -type f \( "${fa[@]}" \) \
+    -not -path './.git/*' -not -path '*/node_modules/*' \
+    -not -path '*/dist/*' -not -path '*/build/*' \
+    | sed 's|^\./||'
+}
+
+files=()
+if [ "${1:-}" = "--all" ]; then mapfile -t files < <(collect_all); else files=("$@"); fi
+
+warnings=0; errors=0; warn_list=""; error_list=""
+for file in "${files[@]}"; do
+  [ -z "$file" ] && continue
+  [ ! -f "$file" ] && continue
+  is_source_file "$file" || continue
+  is_excluded "$file" && continue
+  lines=$(wc -l < "$file")
+  if [ "$lines" -gt "$ERROR_THRESHOLD" ]; then
+    errors=$((errors + 1))
+    error_list="${error_list}| \`${file}\` | ${lines} | :x: exceeds ${ERROR_THRESHOLD} |\n"
+  elif [ "$lines" -gt "$WARN_THRESHOLD" ]; then
+    warnings=$((warnings + 1))
+    warn_list="${warn_list}| \`${file}\` | ${lines} | :warning: exceeds ${WARN_THRESHOLD} |\n"
+  fi
+done
+
+if [ -n "${GITHUB_STEP_SUMMARY:-}" ] && { [ "$errors" -gt 0 ] || [ "$warnings" -gt 0 ]; }; then
+  {
+    echo "## Large File Report"; echo ""
+    echo "| File | Lines | Status |"; echo "|------|-------|--------|"
+    [ "$errors" -gt 0 ] && printf '%b' "$error_list"
+    [ "$warnings" -gt 0 ] && printf '%b' "$warn_list"
+    echo ""; echo "**Thresholds:** warn at ${WARN_THRESHOLD} lines, error at ${ERROR_THRESHOLD} lines"
+  } >> "$GITHUB_STEP_SUMMARY"
+fi
+
+format_list() { if command -v column >/dev/null 2>&1; then printf '%b' "$1" | column -t -s '|'; else printf '%b' "$1"; fi; }
+
+if [ "$errors" -gt 0 ]; then echo "::error::${errors} file(s) exceed the ${ERROR_THRESHOLD}-line error threshold" >&2; format_list "$error_list" >&2; fi
+if [ "$warnings" -gt 0 ]; then echo "::warning::${warnings} file(s) exceed the ${WARN_THRESHOLD}-line warning threshold" >&2; format_list "$warn_list" >&2; fi
+if [ "$errors" -eq 0 ] && [ "$warnings" -eq 0 ]; then echo "All source files are within the ${WARN_THRESHOLD}-line limit."; fi
+
+[ "$errors" -gt 0 ] && exit 1
+exit 0