diff --git a/src/routes/auth.js b/src/routes/auth.js
index 88a5f19..ba50e24 100644
--- a/src/routes/auth.js
+++ b/src/routes/auth.js
@@ -10,6 +10,16 @@ const { verifyNip98Event } = require('../utils/nip98');
 const AUTH_WINDOW_MS = 60 * 1000;
 const AUTH_RATE_MAX_KEYS = 10000;
 
+// Shared with the real PostgreSQL lifecycle check so parameter inference is exercised
+// against the migrated schema, rather than accepted only by query mocks.
+const challengeInsertQuery = `
+  INSERT INTO smirk_challenges (challenge, socket_id, user_id)
+  SELECT $1::varchar(64), $2::varchar(255), id
+  FROM users
+  WHERE id = $3 AND socket_id = $2 AND anon_token = $4
+  RETURNING id
+`;
+
 /**
  * The host a NIP-98 auth event must be signed for.
  *
@@ -260,13 +270,7 @@ router.post('/api/auth/smirk/challenge', challengeRateLimit, asyncHandler(async
 
   // Store a stable user binding as well as the current socket. The user binding is what
   // prevents a public Tavern/Match socket id from being used to attach an attacker's key.
-  const inserted = await db.query(`
-    INSERT INTO smirk_challenges (challenge, socket_id, user_id)
-    SELECT $1, $2, id
-    FROM users
-    WHERE id = $3 AND socket_id = $2 AND anon_token = $4
-    RETURNING id
-  `, [challenge, socketId, session.userId, session.token]);
+  const inserted = await db.query(challengeInsertQuery, [challenge, socketId, session.userId, session.token]);
   if (inserted.rows.length !== 1) throw unauthorized();
 
   // Opportunistic cleanup of expired and long-used challenges.
@@ -470,3 +474,5 @@ router.get('/api/auth/smirk/status', asyncHandler(async (req, res) => {
 
   return router;
 };
+
+module.exports.challengeInsertQuery = challengeInsertQuery;
diff --git a/src/scripts/showcase-lifecycle-smoke.js b/src/scripts/showcase-lifecycle-smoke.js
index aacbde6..00bdf3e 100644
--- a/src/scripts/showcase-lifecycle-smoke.js
+++ b/src/scripts/showcase-lifecycle-smoke.js
@@ -12,6 +12,7 @@ const path = require('node:path');
 const { promisify } = require('node:util');
 const { Client } = require('pg');
 const { chromium } = require('playwright-core');
+const { challengeInsertQuery } = require('../routes/auth');
 
 const execFile = promisify(childProcess.execFile);
 const ROOT = path.resolve(__dirname, '../..');
@@ -143,6 +144,7 @@ function classifyStartupFailure(output) {
 
 function classifyHarnessFailure(error, phase) {
     const sqlStateCodes = {
+        '42P08': 'DATABASE_PARAMETER_TYPE_CONFLICT',
         '42P01': 'DATABASE_TABLE_UNDEFINED',
         '42703': 'DATABASE_COLUMN_UNDEFINED',
         '42883': 'DATABASE_FUNCTION_UNDEFINED',
@@ -370,6 +372,19 @@ async function main() {
             throw error;
         });
 
+        // PREPARE checks the route's actual parameter inference without generating a
+        // challenge, activating Smirk, or passing any authentication values to PostgreSQL.
+        phase = 'auth-query-compile';
+        const authDb = new Client({ host: socketDir, port: dbPort, database: dbName, user: dbUser,
+            connectionTimeoutMillis: 2000, statement_timeout: 5000, lock_timeout: 2000 });
+        try {
+            await authDb.connect();
+            await authDb.query(`PREPARE showcase_smirk_challenge AS ${challengeInsertQuery}`);
+            await authDb.query('DEALLOCATE showcase_smirk_challenge');
+        } finally {
+            await authDb.end();
+        }
+
         phase = 'browser-setup';
         browser = await chromium.launch({ headless: true });
         for (const role of ROLES) {