fix(sync): report accurate key counts in --frozen drift message

`deepl sync --frozen` previously reported `Sync drift detected: 0 new,
0 stale keys.` whenever the drift was caused by a newly-added target
locale (the `hasNewLocale` branch) — even though `--dry-run` against
the same state correctly reported the backfill count. The frozen branch
in `processBucket` short-circuited via `driftDetected = true` before
promoting current-status keys missing a target-locale translation into
`newKeysDelta`. The dry-run branch a few lines below already does this
promotion; the frozen path now mirrors it.

The drift message in `displayResult` also dropped `deletedKeys` entirely
even though `processBucket` populates that count correctly under frozen
drift (covered by an existing integration test). The message now uses
the same nonzero-only join pattern as the success-path summary
formatter, surfacing `new`, `stale`, and `deleted` counts when present.

The drift exit code (10) is unchanged. The dry-run output is unchanged.

Tests:
- New integration test exercising the hasNewLocale frozen branch
- Two new unit tests covering the broadened message format
- Full unit (4294) and integration (804) suites pass; lint + type-check
  clean

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: sjsyrek

CHANGELOG.md

@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Fixed
+
+- **sync**: `deepl sync --frozen` now reports an accurate key count when drift is caused by a newly-added target locale. Previously the message read `Sync drift detected: 0 new, 0 stale keys.` because the frozen branch in `processBucket` short-circuited before promoting current-status keys missing a target-locale translation into `newKeys` — even though `--dry-run` against the same state correctly reported the backfill count. The drift exit code (10) is unchanged. The drift message now also surfaces `deletedKeys` and only mentions nonzero categories, mirroring the success-path summary format.
+
 ## [1.2.0] - 2026-04-25
 
 ### Added

src/cli/commands/sync-command.ts

@@ -547,7 +547,12 @@ export class SyncCommand {
     }
 
     if (result.driftDetected) {
-      Logger.info(`Sync drift detected: ${result.newKeys} new, ${result.staleKeys} stale keys.`);
+      const driftParts: string[] = [];
+      if (result.newKeys > 0) driftParts.push(`${result.newKeys} new`);
+      if (result.staleKeys > 0) driftParts.push(`${result.staleKeys} stale`);
+      if (result.deletedKeys > 0) driftParts.push(`${result.deletedKeys} deleted`);
+      const driftSummary = driftParts.length > 0 ? driftParts.join(', ') : 'no key-level diffs surfaced';
+      Logger.info(`Sync drift detected: ${driftSummary} keys.`);
       return;
     }
 

src/sync/sync-process-bucket.ts

@@ -108,6 +108,12 @@ export async function processBucket(
     const hasNew = toTranslate.some(d => d.status === 'new') || hasNewLocale;
     const hasStale = toTranslate.some(d => d.status === 'stale');
     if ((failMissing && (hasNew || deletedDiffs.length > 0)) || (failStale && hasStale)) {
+      // Promote current keys missing a target-locale translation into newKeysDelta
+      // so the displayed count matches dry-run for the same input state.
+      if (hasNewLocale) {
+        const currentDiffs = diffs.filter(d => d.status === 'current');
+        out.newKeysDelta += currentDiffs.length;
+      }
       out.driftDetected = true;
       return out;
     }

tests/integration/sync.integration.test.ts

@@ -416,6 +416,49 @@ buckets:
       expect(result.deletedKeys).toBeGreaterThanOrEqual(1);
       expect(result.success).toBe(false);
     });
+
+    it('should report newKeys for a newly-added target locale needing backfill', async () => {
+      // Regression: previously the frozen branch detected drift via hasNewLocale
+      // but returned without promoting current-status keys into newKeysDelta,
+      // so displayResult printed "0 new, 0 stale" even though N keys needed
+      // translation for the new locale. Mirrors the dry-run promotion at
+      // sync-process-bucket.ts lines 124-127.
+      writeYamlConfig(tmpDir, BASIC_CONFIG_YAML);
+      writeSourceFile(tmpDir, 'locales/en.json', SOURCE_JSON);
+
+      nock(DEEPL_FREE_API_URL)
+        .post('/v2/translate')
+        .reply(200, {
+          translations: [
+            { text: 'Auf Wiedersehen', detected_source_language: 'EN', billed_characters: 15 },
+            { text: 'Hallo', detected_source_language: 'EN', billed_characters: 5 },
+            { text: 'Willkommen', detected_source_language: 'EN', billed_characters: 10 },
+          ],
+        });
+
+      const configInitial = await loadSyncConfig(tmpDir);
+      await syncService.sync(configInitial);
+
+      // Add a second target locale (fr) without touching the source file.
+      const expandedConfigYaml = `version: 1
+source_locale: en
+target_locales:
+  - de
+  - fr
+buckets:
+  json:
+    include:
+      - "locales/en.json"
+`;
+      writeYamlConfig(tmpDir, expandedConfigYaml);
+
+      const configAfter = await loadSyncConfig(tmpDir);
+      const result = await syncService.sync(configAfter, { frozen: true });
+
+      expect(result.driftDetected).toBe(true);
+      expect(result.success).toBe(false);
+      expect(result.newKeys).toBeGreaterThan(0);
+    });
   });
 
   describe('dry run', () => {

tests/unit/sync/sync-command.test.ts

@@ -127,6 +127,42 @@ describe('SyncCommand', () => {
       expect(infoOutput.toLowerCase()).toContain('drift');
     });
 
+    it('should include new and deleted counts in drift message when both are nonzero', async () => {
+      const result = makeResult({
+        driftDetected: true,
+        success: false,
+        newKeys: 5,
+        staleKeys: 0,
+        deletedKeys: 2,
+      });
+      const mockService = createMockSyncService(result);
+      const command = new SyncCommand(mockService);
+
+      await command.run({});
+
+      const infoOutput = logInfoSpy.mock.calls.map(c => String(c[0])).join('\n');
+      expect(infoOutput).toContain('Sync drift detected: 5 new, 2 deleted keys.');
+    });
+
+    it('should only mention nonzero categories in drift message', async () => {
+      const result = makeResult({
+        driftDetected: true,
+        success: false,
+        newKeys: 0,
+        staleKeys: 0,
+        deletedKeys: 3,
+      });
+      const mockService = createMockSyncService(result);
+      const command = new SyncCommand(mockService);
+
+      await command.run({});
+
+      const infoOutput = logInfoSpy.mock.calls.map(c => String(c[0])).join('\n');
+      expect(infoOutput).toContain('Sync drift detected: 3 deleted keys.');
+      expect(infoOutput).not.toMatch(/\bnew\b/);
+      expect(infoOutput).not.toMatch(/\bstale\b/);
+    });
+
     it('should output valid JSON to stdout when format is json', async () => {
       const result = makeResult();
       const mockService = createMockSyncService(result);