diff --git a/routes/admin.cts b/routes/admin.cts
index fbd379c..12e394b 100644
--- a/routes/admin.cts
+++ b/routes/admin.cts
@@ -510,9 +510,12 @@ router.put('/bank-sync-config', (req: Req, res: Res) => {
     if (typeof debug_logging === 'boolean') config = setDebugLogging(debug_logging);
     res.json(config);
   } catch (err) {
-    res
-      .status(err.status || 500)
-      .json({ error: err.message || 'Failed to update bank sync config' });
+    // 4xx setter validation messages are user-facing; 5xx internals are not.
+    if (err.status && err.status < 500) {
+      return res.status(err.status).json({ error: err.message });
+    }
+    log.error('[admin/bank-sync-config]', err);
+    res.status(500).json({ error: 'Failed to update bank sync config' });
   }
 });
 
@@ -552,7 +555,9 @@ router.post('/migrations/rollback', async (req: Req, res: Res) => {
     if (err.code === 'ROLLBACK_NOT_SUPPORTED') {
       return res.status(422).json({ error: err.message });
     }
-    res.status(500).json({ error: 'Rollback failed', details: err.message });
+    // Unknown failure: the audit log (above) keeps err.message; the response must not.
+    log.error('[admin/migrations/rollback]', err);
+    res.status(500).json({ error: 'Rollback failed' });
   }
 });
 
diff --git a/routes/import.cts b/routes/import.cts
index c98ccae..4ac11cf 100644
--- a/routes/import.cts
+++ b/routes/import.cts
@@ -39,7 +39,9 @@ function makeErrorId() {
 }
 
 function sendImportError(res, err, fallback, defaultCode) {
-  if (err.status) {
+  // Only 4xx service errors carry a user-facing message; a thrown error with
+  // an explicit 5xx status must fall through to the masked error-id branch.
+  if (err.status && err.status < 500) {
     return res.status(err.status).json({
       error: fallback,
       message: err.message,
diff --git a/routes/notifications.cts b/routes/notifications.cts
index 6c76f77..1bed038 100644
--- a/routes/notifications.cts
+++ b/routes/notifications.cts
@@ -9,6 +9,7 @@ const { sendTestEmail } = require('../services/notificationService.cts');
 const { sendTestPush } = require('../services/notificationService.cts')._push || {};
 const { decryptSecret } = require('../services/encryptionService.cts');
 const { encryptSecret } = require('../services/encryptionService.cts');
+const { ApiError, ValidationError } = require('../utils/apiError.cts');
 
 // ── Admin: SMTP configuration ─────────────────────────────────────────────────
 
@@ -74,13 +75,16 @@ router.put('/admin', requireAuth, requireAdmin, (req: Req, res: Res) => {
 // POST /api/notifications/test — send a test email
 router.post('/test', requireAuth, requireAdmin, async (req: Req, res: Res) => {
   const { to } = req.body;
-  if (!to) return res.status(400).json({ error: 'Recipient address required' });
+  if (!to) throw ValidationError('Recipient address required', 'to');
   try {
     await sendTestEmail(to);
-    res.json({ success: true });
   } catch (err) {
-    res.status(500).json({ error: err.message });
+    // Deliberate pass-through: the SMTP error text is the admin's own config
+    // feedback (bad host/auth/TLS). ApiError messages survive formatError;
+    // anything not wrapped would be masked as a generic 5xx.
+    throw new ApiError('NOTIFICATION_TEST_FAILED', err.message || 'Test email failed', 502);
   }
+  res.json({ success: true });
 });
 
 // ── User: notification preferences ───────────────────────────────────────────
@@ -164,7 +168,7 @@ router.post('/test-push', requireAuth, requireUser, async (req: Req, res: Res) =
     .get(req.user.id);
 
   if (!user?.push_channel || !user?.push_url) {
-    return res.status(400).json({ error: 'Push notification channel not configured' });
+    throw ValidationError('Push notification channel not configured', 'push_channel');
   }
 
   // Decrypt for sending
@@ -185,10 +189,12 @@ router.post('/test-push', requireAuth, requireUser, async (req: Req, res: Res) =
   try {
     if (!sendTestPush) throw new Error('Push service not initialised');
     await sendTestPush(userForPush);
-    res.json({ success: true });
   } catch (err) {
-    res.status(500).json({ error: err.message });
+    // Deliberate pass-through: the push-provider error is the user's own
+    // channel-config feedback (bad URL/token) — same rationale as /test above.
+    throw new ApiError('NOTIFICATION_TEST_FAILED', err.message || 'Test push failed', 502);
   }
+  res.json({ success: true });
 });
 
 module.exports = router;
diff --git a/routes/spending.cts b/routes/spending.cts
index 842ae14..0cf8444 100644
--- a/routes/spending.cts
+++ b/routes/spending.cts
@@ -3,9 +3,9 @@ import type { Req, Res, Next } from '../types/http';
 ('use strict');
 
 const express = require('express');
-const { log } = require('../utils/logger.cts');
 const router = express.Router();
 const { getDb } = require('../db/database.cts');
+const { ValidationError } = require('../utils/apiError.cts');
 const {
   getSpendingSummary,
   getSpendingTransactions,
@@ -18,31 +18,27 @@ const {
   getIncomeTransactions,
 } = require('../services/spendingService.cts');
 
+// Throws ValidationError on bad input; service errors propagate to the
+// terminal handler (4xx with .status pass their message through, 5xx are
+// masked + logged there — no per-route try/catch, per CODE_STANDARDS.md).
 function parseYM(source) {
   const now = new Date();
   const year = parseInt(source.year || now.getFullYear(), 10);
   const month = parseInt(source.month || now.getMonth() + 1, 10);
-  if (isNaN(year) || year < 2000 || year > 2100) return { error: 'Invalid year' };
-  if (isNaN(month) || month < 1 || month > 12) return { error: 'Invalid month' };
+  if (isNaN(year) || year < 2000 || year > 2100) throw ValidationError('Invalid year', 'year');
+  if (isNaN(month) || month < 1 || month > 12) throw ValidationError('Invalid month', 'month');
   return { year, month };
 }
 
 // GET /api/spending/summary?year=&month=
 router.get('/summary', (req: Req, res: Res) => {
   const ym = parseYM(req.query);
-  if (ym.error) return res.status(400).json({ error: ym.error });
-  try {
-    res.json(getSpendingSummary(getDb(), req.user.id, ym.year, ym.month));
-  } catch (err) {
-    log.error('[spending/summary]', err.message);
-    res.status(500).json({ error: 'Failed to load spending summary' });
-  }
+  res.json(getSpendingSummary(getDb(), req.user.id, ym.year, ym.month));
 });
 
 // GET /api/spending/transactions?year=&month=&category_id=&page=&limit=
 router.get('/transactions', (req: Req, res: Res) => {
   const ym = parseYM(req.query);
-  if (ym.error) return res.status(400).json({ error: ym.error });
 
   const { category_id, page, limit } = req.query;
   const categoryId =
@@ -52,56 +48,38 @@ router.get('/transactions', (req: Req, res: Res) => {
         ? parseInt(category_id, 10)
         : undefined;
 
-  try {
-    res.json(
-      getSpendingTransactions(getDb(), req.user.id, ym.year, ym.month, {
-        categoryId,
-        uncategorizedOnly: category_id === 'null',
-        page: parseInt(page || '1', 10),
-        limit: Math.min(parseInt(limit || '50', 10), 200),
-      }),
-    );
-  } catch (err) {
-    log.error('[spending/transactions]', err.message);
-    res.status(500).json({ error: 'Failed to load transactions' });
-  }
+  res.json(
+    getSpendingTransactions(getDb(), req.user.id, ym.year, ym.month, {
+      categoryId,
+      uncategorizedOnly: category_id === 'null',
+      page: parseInt(page || '1', 10),
+      limit: Math.min(parseInt(limit || '50', 10), 200),
+    }),
+  );
 });
 
 // PATCH /api/spending/transactions/:id/category
 router.patch('/transactions/:id/category', (req: Req, res: Res) => {
   const txId = parseInt(req.params.id, 10);
-  if (isNaN(txId)) return res.status(400).json({ error: 'Invalid transaction ID' });
+  if (isNaN(txId)) throw ValidationError('Invalid transaction ID', 'id');
 
   const { category_id, save_rule } = req.body || {};
   const categoryId =
     category_id === null || category_id === undefined ? null : parseInt(category_id, 10);
 
-  try {
-    categorizeTransaction(getDb(), req.user.id, txId, categoryId, !!save_rule);
-    res.json({ ok: true });
-  } catch (err) {
-    res
-      .status(err.status || 500)
-      .json({ error: err.message || 'Failed to categorize transaction' });
-  }
+  categorizeTransaction(getDb(), req.user.id, txId, categoryId, !!save_rule);
+  res.json({ ok: true });
 });
 
 // GET /api/spending/budgets?year=&month=
 router.get('/budgets', (req: Req, res: Res) => {
   const ym = parseYM(req.query);
-  if (ym.error) return res.status(400).json({ error: ym.error });
-  try {
-    res.json({ budgets: getSpendingBudgets(getDb(), req.user.id, ym.year, ym.month) });
-  } catch (err) {
-    log.error('[spending/budgets GET]', err.message);
-    res.status(500).json({ error: 'Failed to load budgets' });
-  }
+  res.json({ budgets: getSpendingBudgets(getDb(), req.user.id, ym.year, ym.month) });
 });
 
 // POST /api/spending/budgets/copy — copy all budgets from previous month into target month
 router.post('/budgets/copy', (req: Req, res: Res) => {
   const ym = parseYM(req.body || {});
-  if (ym.error) return res.status(400).json({ error: ym.error });
 
   // Previous month
   let prevYear = ym.year,
@@ -111,25 +89,24 @@ router.post('/budgets/copy', (req: Req, res: Res) => {
     prevYear--;
   }
 
-  try {
-    const db = getDb();
-    const prev = db
-      .prepare(
-        `
+  const db = getDb();
+  const prev = db
+    .prepare(
+      `
       SELECT category_id, amount FROM spending_budgets
       WHERE user_id = ? AND year = ? AND month = ?
     `,
-      )
-      .all(req.user.id, prevYear, prevMonth);
+    )
+    .all(req.user.id, prevYear, prevMonth);
 
-    if (prev.length === 0) {
-      return res.json({
-        copied: 0,
-        budgets: getSpendingBudgets(db, req.user.id, ym.year, ym.month),
-      });
-    }
+  if (prev.length === 0) {
+    return res.json({
+      copied: 0,
+      budgets: getSpendingBudgets(db, req.user.id, ym.year, ym.month),
+    });
+  }
 
-    const upsert = db.prepare(`
+  const upsert = db.prepare(`
       INSERT INTO spending_budgets (user_id, category_id, year, month, amount, updated_at)
       VALUES (?, ?, ?, ?, ?, datetime('now'))
       ON CONFLICT(user_id, category_id, year, month) DO UPDATE SET
@@ -137,95 +114,66 @@ router.post('/budgets/copy', (req: Req, res: Res) => {
         updated_at = datetime('now')
     `);
 
-    db.transaction(() => {
-      for (const row of prev)
-        upsert.run(req.user.id, row.category_id, ym.year, ym.month, row.amount);
-    })();
+  db.transaction(() => {
+    for (const row of prev) upsert.run(req.user.id, row.category_id, ym.year, ym.month, row.amount);
+  })();
 
-    res.json({
-      copied: prev.length,
-      budgets: getSpendingBudgets(db, req.user.id, ym.year, ym.month),
-    });
-  } catch (err) {
-    log.error('[spending/budgets/copy]', err.message);
-    res.status(500).json({ error: 'Failed to copy budgets' });
-  }
+  res.json({
+    copied: prev.length,
+    budgets: getSpendingBudgets(db, req.user.id, ym.year, ym.month),
+  });
 });
 
 // PUT /api/spending/budgets — { category_id, year, month, amount }
 router.put('/budgets', (req: Req, res: Res) => {
   const { category_id, year, month, amount } = req.body || {};
-  if (!category_id) return res.status(400).json({ error: 'category_id required' });
+  if (!category_id) throw ValidationError('category_id required', 'category_id');
   const ym = parseYM({ year, month });
-  if (ym.error) return res.status(400).json({ error: ym.error });
 
-  try {
-    setSpendingBudget(
-      getDb(),
-      req.user.id,
-      parseInt(category_id, 10),
-      ym.year,
-      ym.month,
-      amount ?? null,
-    );
-    res.json({ ok: true });
-  } catch (err) {
-    log.error('[spending/budgets PUT]', err.message);
-    res.status(500).json({ error: 'Failed to save budget' });
-  }
+  setSpendingBudget(
+    getDb(),
+    req.user.id,
+    parseInt(category_id, 10),
+    ym.year,
+    ym.month,
+    amount ?? null,
+  );
+  res.json({ ok: true });
 });
 
 // GET /api/spending/category-rules
 router.get('/category-rules', (req: Req, res: Res) => {
-  try {
-    res.json({ rules: getSpendingCategoryRules(getDb(), req.user.id) });
-  } catch (err) {
-    log.error('[spending/category-rules GET]', err.message);
-    res.status(500).json({ error: 'Failed to load rules' });
-  }
+  res.json({ rules: getSpendingCategoryRules(getDb(), req.user.id) });
 });
 
 // POST /api/spending/category-rules — { category_id, merchant }
 router.post('/category-rules', (req: Req, res: Res) => {
   const { category_id, merchant } = req.body || {};
   if (!category_id || !merchant)
-    return res.status(400).json({ error: 'category_id and merchant required' });
-  try {
-    addSpendingCategoryRule(getDb(), req.user.id, parseInt(category_id, 10), merchant);
-    res.json({ ok: true });
-  } catch (err) {
-    log.error('[spending/category-rules POST]', err.message);
-    res.status(err.status || 500).json({ error: err.message || 'Failed to save rule' });
-  }
+    throw ValidationError(
+      'category_id and merchant required',
+      !category_id ? 'category_id' : 'merchant',
+    );
+  addSpendingCategoryRule(getDb(), req.user.id, parseInt(category_id, 10), merchant);
+  res.json({ ok: true });
 });
 
 // DELETE /api/spending/category-rules/:id
 router.delete('/category-rules/:id', (req: Req, res: Res) => {
-  try {
-    deleteSpendingCategoryRule(getDb(), req.user.id, parseInt(req.params.id, 10));
-    res.json({ ok: true });
-  } catch (err) {
-    log.error('[spending/category-rules DELETE]', err.message);
-    res.status(500).json({ error: 'Failed to delete rule' });
-  }
+  deleteSpendingCategoryRule(getDb(), req.user.id, parseInt(req.params.id, 10));
+  res.json({ ok: true });
 });
 
 // GET /api/spending/income?year=&month=&page=
 router.get('/income', (req: Req, res: Res) => {
   const ym = parseYM(req.query);
-  if (ym.error) return res.status(400).json({ error: ym.error });
-  try {
-    res.json(
-      getIncomeTransactions(getDb(), req.user.id, ym.year, ym.month, {
-        page: parseInt(req.query.page || '1', 10),
-        limit: Math.min(parseInt(req.query.limit || '50', 10), 200),
-        includeIgnored: req.query.include_ignored === 'true',
-      }),
-    );
-  } catch (err) {
-    log.error('[spending/income]', err.message);
-    res.status(500).json({ error: 'Failed to load income transactions' });
-  }
+  res.json(
+    getIncomeTransactions(getDb(), req.user.id, ym.year, ym.month, {
+      page: parseInt(req.query.page || '1', 10),
+      limit: Math.min(parseInt(req.query.limit || '50', 10), 200),
+      includeIgnored: req.query.include_ignored === 'true',
+    }),
+  );
 });
 
 module.exports = router;
diff --git a/routes/transactions.cts b/routes/transactions.cts
index 4013b3c..1f5e929 100644
--- a/routes/transactions.cts
+++ b/routes/transactions.cts
@@ -996,7 +996,10 @@ router.post('/unmatch-bulk', (req: Req, res: Res) => {
           results.push({ transaction_id: txId, ok: true });
         }
       } catch (err) {
-        results.push({ transaction_id: txId, ok: false, error: err.message });
+        // Per-item feedback: service 4xx messages are user-facing; anything
+        // else is masked — 500-class internals must not leak into the results.
+        const msg = err.status && err.status < 500 ? err.message : 'Unmatch failed';
+        results.push({ transaction_id: txId, ok: false, error: msg });
       }
     }
   })();