diff --git a/.github/workflows/easter-eggs.yml b/.github/workflows/easter-eggs.yml
new file mode 100644
index 0000000..30a207b
--- /dev/null
+++ b/.github/workflows/easter-eggs.yml
@@ -0,0 +1,26 @@
+name: easter-egg keywords
+
+# Fails if any keyword in docs/easter-eggs.md's canonical keyword block is
+# absent from every v1-modern/src/scripts/*.narrat file. Prevents the silent
+# drift described in issue #6.
+#
+# This workflow does not use any untrusted input (no github.event.* in run:
+# commands); it only runs a checked-in script.
+
+on:
+  pull_request:
+    paths:
+      - 'docs/easter-eggs.md'
+      - 'v1-modern/src/scripts/**.narrat'
+      - 'scripts/check-easter-eggs.sh'
+      - '.github/workflows/easter-eggs.yml'
+  push:
+    branches: [main]
+
+jobs:
+  check:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - name: Verify every canonical keyword appears in some narrat script
+        run: bash scripts/check-easter-eggs.sh
diff --git a/HANDOVER.md b/HANDOVER.md
index 79e09df..8c29fae 100644
--- a/HANDOVER.md
+++ b/HANDOVER.md
@@ -15,7 +15,7 @@ You are the lead coder continuing development of **PNK Forever**, an anniversary
   - **Volume 2 — Modern Edition**: `v1-modern/` — a Narrat v3 visual novel with real backgrounds, sprites, and 5 chapters. This is where active development happens.
 - **Main characters**: P. (Phoenix — a bird-cat), K. (Ehecatl — a peacock-tailed shiba dog).
 - **Tone**: warm, witty, intimate. Easter-egg keywords in ALL-CAPS feel like inside jokes.
-- **Sacred easter-egg keywords that must keep appearing**: MANGO, TEA, CHOCOLATE, KITE, LOVE, FLY, TIGER, SNAKE, ZODIAC, FUTURE, NECKLACE, BROMPTON, JAFFA, JAPAN, and the discount code `PNK-n3zk7MAMBG-GIFT`.
+- **Sacred easter-egg keywords that must keep appearing**: see the canonical list in [`docs/easter-eggs.md`](docs/easter-eggs.md#canonical-keyword-list). That file is the single source of truth — do not re-list keywords here or anywhere else (playtest and CI read from it at runtime; duplicating invites silent drift).
 
 ### 2. Repo layout
 
diff --git a/docs/easter-eggs.md b/docs/easter-eggs.md
index 57809bb..f1fe86f 100644
--- a/docs/easter-eggs.md
+++ b/docs/easter-eggs.md
@@ -12,6 +12,40 @@ This gamification of reality creates a unique experience where:
 
 ---
 
+## Canonical Keyword List
+
+This is the authoritative machine-readable keyword list. It is parsed at
+runtime by `scripts/handoff/playtest.sh` (presence check in rendered page
+content) and by `scripts/check-easter-eggs.sh` (CI check that every keyword
+appears in at least one `v1-modern/src/scripts/*.narrat` file).
+
+**Format:** one keyword per line inside the fenced block below. Do not
+reformat, add prose, or split the block — the parsers look for
+```` ```keywords ```` as the block fence.
+
+```keywords
+MANGO
+TEA
+CHOCOLATE
+KITE
+LOVE
+FLY
+TIGER
+SNAKE
+ZODIAC
+FUTURE
+NECKLACE
+BROMPTON
+JAFFA
+JAPAN
+PNK-n3zk7MAMBG-GIFT
+```
+
+When adding a new easter egg, append its keyword here *and* reference this
+list from any runtime or docs that would otherwise hard-code it.
+
+---
+
 ## IFTTT Integration System
 
 All Easter eggs use IFTTT (If This Then That) webhooks to trigger real-world actions.
diff --git a/scripts/check-easter-eggs.sh b/scripts/check-easter-eggs.sh
new file mode 100755
index 0000000..5555fe8
--- /dev/null
+++ b/scripts/check-easter-eggs.sh
@@ -0,0 +1,46 @@
+#!/usr/bin/env bash
+# check-easter-eggs.sh — fails if any keyword from docs/easter-eggs.md's
+# canonical list is absent from every v1-modern/src/scripts/*.narrat file.
+#
+# Used by the easter-eggs CI workflow and can be run locally as a pre-commit
+# check. Part of the single-source-of-truth contract established in issue #6.
+
+set -euo pipefail
+
+REPO_ROOT="$(cd "$(dirname "$0")/.." && pwd)"
+KEYWORDS_FILE="$REPO_ROOT/docs/easter-eggs.md"
+NARRAT_DIR="$REPO_ROOT/v1-modern/src/scripts"
+
+if [[ ! -f "$KEYWORDS_FILE" ]]; then
+  echo "ERROR: $KEYWORDS_FILE not found" >&2
+  exit 2
+fi
+
+# Parse keywords from the fenced ```keywords ... ``` block.
+keywords=$(awk '
+  /^```keywords$/ { inblock=1; next }
+  /^```$/ && inblock { exit }
+  inblock && NF > 0 { print }
+' "$KEYWORDS_FILE")
+
+if [[ -z "$keywords" ]]; then
+  echo "ERROR: no keywords parsed from $KEYWORDS_FILE (missing or malformed \`\`\`keywords block)" >&2
+  exit 2
+fi
+
+total=$(printf '%s\n' "$keywords" | grep -c .)
+missing=()
+while IFS= read -r kw; do
+  [[ -z "$kw" ]] && continue
+  if ! grep -l -- "$kw" "$NARRAT_DIR"/*.narrat >/dev/null 2>&1; then
+    missing+=("$kw")
+  fi
+done <<<"$keywords"
+
+if (( ${#missing[@]} > 0 )); then
+  echo "ERROR: these keywords from $KEYWORDS_FILE are absent from every $NARRAT_DIR/*.narrat:" >&2
+  printf '  - %s\n' "${missing[@]}" >&2
+  exit 1
+fi
+
+echo "OK: all $total easter-egg keywords present in at least one narrat script"
diff --git a/scripts/handoff/playtest.sh b/scripts/handoff/playtest.sh
index 97a9a71..8a0e5e1 100755
--- a/scripts/handoff/playtest.sh
+++ b/scripts/handoff/playtest.sh
@@ -368,14 +368,23 @@ async function runPlaytest() {
     }
 
     // === Phase 7: Easter egg keywords ===
+    // Keywords are injected via EASTER_EGG_KEYWORDS env var. The single
+    // source of truth is docs/easter-eggs.md (see the ```keywords``` fenced
+    // block). If the env var is unset the check is skipped with a warning.
     const pageContent = await page.content();
-    const eggs = ['mango', 'tea', 'chocolate', 'kite', 'love', 'fly'];
-    const foundEggs = eggs.filter(e => pageContent.toLowerCase().includes(e));
-    if (foundEggs.length >= 3) {
-      findings.ready_criteria.easter_eggs_present = true;
-      findings.positives.push(`Easter egg keywords present: ${foundEggs.join(', ')}`);
+    const rawKeywords = process.env.EASTER_EGG_KEYWORDS || '';
+    const eggs = rawKeywords.split(',').map(k => k.trim()).filter(Boolean);
+    if (eggs.length === 0) {
+      findings.warnings.push('EASTER_EGG_KEYWORDS env var empty — keyword presence check skipped');
     } else {
-      findings.improvements.push(`Only ${foundEggs.length}/6 easter egg keywords found - may need more scenes played`);
+      const foundEggs = eggs.filter(e => pageContent.toLowerCase().includes(e.toLowerCase()));
+      const threshold = Math.max(3, Math.floor(eggs.length / 3));
+      if (foundEggs.length >= threshold) {
+        findings.ready_criteria.easter_eggs_present = true;
+        findings.positives.push(`Easter egg keywords present: ${foundEggs.join(', ')}`);
+      } else {
+        findings.improvements.push(`Only ${foundEggs.length}/${eggs.length} easter egg keywords found (threshold ${threshold}) - may need more scenes played`);
+      }
     }
 
     // === Phase 8: Console errors ===
@@ -403,7 +412,20 @@ console.log(JSON.stringify(results, null, 2));
 EOTEST
 
 echo "Running automated playtest..."
-RESULTS=$(PREVIEW_URL="$URL" node test.mjs 2>/tmp/playtest-stderr.log)
+
+# Parse canonical easter-egg keywords from docs/easter-eggs.md — single
+# source of truth per issue #6. Passed as comma-separated env var to test.mjs.
+EASTER_EGG_KEYWORDS=$(awk '
+  /^```keywords$/ { inblock=1; next }
+  /^```$/ && inblock { exit }
+  inblock && NF > 0 { printf "%s%s", sep, $0; sep="," }
+' "$REPO_ROOT/docs/easter-eggs.md")
+
+if [[ -z "$EASTER_EGG_KEYWORDS" ]]; then
+  echo "WARN: no keywords parsed from docs/easter-eggs.md — easter-egg check will be skipped"
+fi
+
+RESULTS=$(PREVIEW_URL="$URL" EASTER_EGG_KEYWORDS="$EASTER_EGG_KEYWORDS" node test.mjs 2>/tmp/playtest-stderr.log)
 STDERR_OUTPUT=$(cat /tmp/playtest-stderr.log 2>/dev/null || echo "")
 
 if [[ -n "$STDERR_OUTPUT" ]]; then