diff --git a/Makefile b/Makefile
index 2c79ce7..66770c5 100644
--- a/Makefile
+++ b/Makefile
@@ -1,4 +1,4 @@
-.PHONY: preview dev build test typecheck lint
+.PHONY: preview dev build test typecheck lint check-install
 
 # Build the production bundle then serve it locally with vite preview.
 # Prints the URL (default http://localhost:4173/) once the server is ready.
@@ -21,3 +21,7 @@ typecheck:
 
 lint:
 	pnpm lint
+
+# Verify sibling citation-engine checkout, link dependency, and toolchain.
+check-install:
+	@bash scripts/check-install.sh
diff --git a/README.md b/README.md
index 5bc2eb9..44e6f11 100644
--- a/README.md
+++ b/README.md
@@ -55,6 +55,7 @@ Requirements: Node 20 LTS (see `.nvmrc`) and `pnpm` 9.
 
 ```bash
 # citation-engine must be checked out next to this repo (../citation-engine)
+make check-install   # diagnose layout problems before install
 pnpm install
 pnpm dev        # vite dev server (once src/app/ has a real entry)
 pnpm test       # vitest one-shot
diff --git a/scripts/check-install.sh b/scripts/check-install.sh
new file mode 100755
index 0000000..7ce22bb
--- /dev/null
+++ b/scripts/check-install.sh
@@ -0,0 +1,162 @@
+#!/usr/bin/env bash
+# Verify that citation-evidence is installed consistently with its ecosystem
+# layout. citation-evidence is the umbrella repo; @citation-evidence/engine
+# must resolve from a sibling citation-engine checkout (see CE-WP-0009).
+
+set -euo pipefail
+
+ROOT="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
+cd "$ROOT"
+
+ENGINE_SIBLING="$ROOT/../citation-engine"
+ENGINE_DEP="link:../citation-engine"
+ENGINE_PKG="@citation-evidence/engine"
+
+errors=0
+warnings=0
+
+ok()   { printf '  \033[32m✓\033[0m %s\n' "$1"; }
+fail() { printf '  \033[31m✗\033[0m %s\n' "$1"; errors=$((errors + 1)); }
+warn() { printf '  \033[33m!\033[0m %s\n' "$1"; warnings=$((warnings + 1)); }
+hint() { printf '    → %s\n' "$1"; }
+
+section() {
+  printf '\n%s\n' "$1"
+}
+
+fix_clone_engine() {
+  hint "Clone citation-engine as a sibling of this repo:"
+  hint "  cd $(dirname "$ROOT")"
+  hint "  git clone <citation-engine-remote-url> citation-engine"
+  hint "Expected layout:"
+  hint "  $(dirname "$ROOT")/citation-evidence/   (this repo)"
+  hint "  $(dirname "$ROOT")/citation-engine/    (required sibling)"
+}
+
+printf 'citation-evidence install consistency check\n'
+printf 'Umbrella root: %s\n' "$ROOT"
+
+section "Required sibling: citation-engine"
+if [[ -d "$ENGINE_SIBLING" ]]; then
+  ok "citation-engine directory exists at ../citation-engine"
+else
+  fail "citation-engine not found at ../citation-engine"
+  fix_clone_engine
+fi
+
+if [[ -f "$ENGINE_SIBLING/package.json" ]]; then
+  ok "citation-engine/package.json present"
+  engine_name="$(node -e "
+    const p = require('$ENGINE_SIBLING/package.json');
+    process.stdout.write(p.name ?? '');
+  " 2>/dev/null || true)"
+  if [[ "$engine_name" == "$ENGINE_PKG" ]]; then
+    ok "citation-engine package name is $ENGINE_PKG"
+  else
+    fail "citation-engine package name is '${engine_name:-<missing>}' (expected $ENGINE_PKG)"
+    hint "Check that ../citation-engine is the correct repository."
+  fi
+elif [[ -d "$ENGINE_SIBLING" ]]; then
+  fail "citation-engine/package.json missing"
+  hint "../citation-engine does not look like a valid checkout."
+fi
+
+for path in src/shared/index.ts src/engine/index.ts; do
+  if [[ -f "$ENGINE_SIBLING/$path" ]]; then
+    ok "citation-engine/$path present"
+  elif [[ -d "$ENGINE_SIBLING" ]]; then
+    fail "citation-engine/$path missing"
+    hint "Run 'git pull' in ../citation-engine or check out a complete tree."
+  fi
+done
+
+section "package.json link dependency"
+declared="$(node -e "
+  const p = require('$ROOT/package.json');
+  const v = p.dependencies?.['$ENGINE_PKG'];
+  process.stdout.write(v ?? '');
+" 2>/dev/null || true)"
+if [[ "$declared" == "$ENGINE_DEP" ]]; then
+  ok "package.json declares \"$ENGINE_PKG\": \"$ENGINE_DEP\""
+else
+  fail "package.json should declare \"$ENGINE_PKG\": \"$ENGINE_DEP\" (found: ${declared:-<missing>})"
+fi
+
+section "node_modules resolution"
+linked="$ROOT/node_modules/@citation-evidence/engine"
+if [[ -e "$linked" ]]; then
+  ok "node_modules/@citation-evidence/engine exists"
+  real="$(cd "$linked" && pwd -P 2>/dev/null || true)"
+  expected="$(cd "$ENGINE_SIBLING" 2>/dev/null && pwd -P || true)"
+  if [[ -n "$real" && -n "$expected" && "$real" == "$expected" ]]; then
+    ok "link resolves to ../citation-engine"
+  elif [[ -n "$real" && -n "$expected" ]]; then
+    fail "node_modules link points to $real (expected $expected)"
+    hint "Run 'pnpm install' from citation-evidence after fixing the sibling checkout."
+  fi
+else
+  fail "node_modules/@citation-evidence/engine not found"
+  hint "Run 'pnpm install' from the citation-evidence root."
+  if [[ ! -d "$ENGINE_SIBLING" ]]; then
+    fix_clone_engine
+  fi
+fi
+
+section "Toolchain"
+if command -v node >/dev/null 2>&1; then
+  node_ver="$(node -v | sed 's/^v//')"
+  ok "node $node_ver available"
+  if [[ -f "$ROOT/.nvmrc" ]]; then
+    want="$(tr -d '[:space:]' < "$ROOT/.nvmrc")"
+    node_major_minor="$(printf '%s' "$node_ver" | cut -d. -f1-2)"
+    want_major_minor="$(printf '%s' "$want" | cut -d. -f1-2)"
+    if [[ "$node_major_minor" == "$want_major_minor" ]]; then
+      ok "node version matches .nvmrc ($want)"
+    else
+      warn "node $node_ver does not match .nvmrc ($want) — use nvm/fnm to switch"
+      hint "  nvm use   # or: fnm use"
+    fi
+  fi
+else
+  fail "node not found on PATH"
+  hint "Install Node 20 LTS (see .nvmrc)."
+fi
+
+if command -v pnpm >/dev/null 2>&1; then
+  ok "pnpm $(pnpm -v) available"
+else
+  fail "pnpm not found on PATH"
+  hint "Enable corepack: corepack enable && corepack prepare pnpm@9.15.0 --activate"
+fi
+
+section "Optional sister repos (INTENT-only during MVP)"
+parent="$(dirname "$ROOT")"
+for repo in evidence-anchor evidence-source evidence-binder citation-work; do
+  if [[ -f "$parent/$repo/INTENT.md" ]]; then
+    ok "$repo checked out (optional)"
+  else
+    warn "$repo not present at ../$repo (optional — not required to run the umbrella)"
+  fi
+done
+
+section "Stale in-repo engine copies"
+if [[ -d "$ROOT/src/shared" || -d "$ROOT/src/engine" ]]; then
+  fail "src/shared/ or src/engine/ still present in citation-evidence (removed in CE-WP-0009)"
+  hint "Delete local copies; engine code must come from ../citation-engine only."
+else
+  ok "no duplicate src/shared or src/engine in umbrella"
+fi
+
+printf '\n'
+if [[ "$errors" -gt 0 ]]; then
+  printf '\033[31mInstall check failed (%d error(s), %d warning(s)).\033[0m\n' "$errors" "$warnings"
+  printf 'Fix the items above, then run: pnpm install && make check-install\n'
+  exit 1
+fi
+
+if [[ "$warnings" -gt 0 ]]; then
+  printf '\033[33mInstall check passed with %d warning(s).\033[0m\n' "$warnings"
+else
+  printf '\033[32mInstall check passed.\033[0m\n'
+fi
+exit 0
\ No newline at end of file