diff --git a/src/resources/extensions/gsd/gsd-db.ts b/src/resources/extensions/gsd/gsd-db.ts
index d0120b65d..f6d379048 100644
--- a/src/resources/extensions/gsd/gsd-db.ts
+++ b/src/resources/extensions/gsd/gsd-db.ts
@@ -163,6 +163,29 @@ function openRawDb(path: string): unknown {
 
 const SCHEMA_VERSION = 14;
 
+function indexExists(db: DbAdapter, name: string): boolean {
+  return !!db.prepare(
+    "SELECT 1 as present FROM sqlite_master WHERE type = 'index' AND name = ?",
+  ).get(name);
+}
+
+function dedupeVerificationEvidenceRows(db: DbAdapter): void {
+  db.exec(`
+    DELETE FROM verification_evidence
+    WHERE rowid NOT IN (
+      SELECT MIN(rowid)
+      FROM verification_evidence
+      GROUP BY task_id, slice_id, milestone_id, command, verdict
+    )
+  `);
+}
+
+function ensureVerificationEvidenceDedupIndex(db: DbAdapter): void {
+  if (indexExists(db, "idx_verification_evidence_dedup")) return;
+  dedupeVerificationEvidenceRows(db);
+  db.exec("CREATE UNIQUE INDEX IF NOT EXISTS idx_verification_evidence_dedup ON verification_evidence(task_id, slice_id, milestone_id, command, verdict)");
+}
+
 function initSchema(db: DbAdapter, fileBacked: boolean): void {
   if (fileBacked) db.exec("PRAGMA journal_mode=WAL");
   if (fileBacked) db.exec("PRAGMA busy_timeout = 5000");
@@ -410,7 +433,7 @@ function initSchema(db: DbAdapter, fileBacked: boolean): void {
     db.exec("CREATE INDEX IF NOT EXISTS idx_milestones_status ON milestones(status)");
     db.exec("CREATE INDEX IF NOT EXISTS idx_quality_gates_pending ON quality_gates(milestone_id, slice_id, status)");
     db.exec("CREATE INDEX IF NOT EXISTS idx_verification_evidence_task ON verification_evidence(milestone_id, slice_id, task_id)");
-    db.exec("CREATE UNIQUE INDEX IF NOT EXISTS idx_verification_evidence_dedup ON verification_evidence(task_id, slice_id, milestone_id, command, verdict)");
+    ensureVerificationEvidenceDedupIndex(db);
 
     // v14 index — slice dependency lookups
     db.exec("CREATE INDEX IF NOT EXISTS idx_slice_deps_target ON slice_dependencies(milestone_id, depends_on_slice_id)");
@@ -743,7 +766,7 @@ function migrateSchema(db: DbAdapter): void {
       db.exec("CREATE INDEX IF NOT EXISTS idx_milestones_status ON milestones(status)");
       db.exec("CREATE INDEX IF NOT EXISTS idx_quality_gates_pending ON quality_gates(milestone_id, slice_id, status)");
       db.exec("CREATE INDEX IF NOT EXISTS idx_verification_evidence_task ON verification_evidence(milestone_id, slice_id, task_id)");
-      db.exec("CREATE UNIQUE INDEX IF NOT EXISTS idx_verification_evidence_dedup ON verification_evidence(task_id, slice_id, milestone_id, command, verdict)");
+      ensureVerificationEvidenceDedupIndex(db);
       db.prepare("INSERT INTO schema_version (version, applied_at) VALUES (:version, :applied_at)").run({
         ":version": 13,
         ":applied_at": new Date().toISOString(),
@@ -1542,6 +1565,30 @@ export interface TaskRow {
 }
 
 function rowToTask(row: Record<string, unknown>): TaskRow {
+  const parseTaskArray = (value: unknown): string[] => {
+    if (Array.isArray(value)) {
+      return value.filter((entry): entry is string => typeof entry === "string");
+    }
+    if (typeof value !== "string") return [];
+
+    const trimmed = value.trim();
+    if (!trimmed) return [];
+
+    try {
+      const parsed = JSON.parse(trimmed);
+      if (Array.isArray(parsed)) {
+        return parsed.filter((entry): entry is string => typeof entry === "string");
+      }
+      if (typeof parsed === "string" && parsed.trim()) {
+        return [parsed.trim()];
+      }
+    } catch {
+      // Older/corrupt DB rows may contain raw comma-separated paths instead of JSON arrays.
+    }
+
+    return trimmed.split(",").map((entry) => entry.trim()).filter(Boolean);
+  };
+
   return {
     milestone_id: row["milestone_id"] as string,
     slice_id: row["slice_id"] as string,
@@ -1561,10 +1608,10 @@ function rowToTask(row: Record<string, unknown>): TaskRow {
     full_summary_md: row["full_summary_md"] as string,
     description: (row["description"] as string) ?? "",
     estimate: (row["estimate"] as string) ?? "",
-    files: JSON.parse((row["files"] as string) || "[]"),
+    files: parseTaskArray(row["files"]),
     verify: (row["verify"] as string) ?? "",
-    inputs: JSON.parse((row["inputs"] as string) || "[]"),
-    expected_output: JSON.parse((row["expected_output"] as string) || "[]"),
+    inputs: parseTaskArray(row["inputs"]),
+    expected_output: parseTaskArray(row["expected_output"]),
     observability_impact: (row["observability_impact"] as string) ?? "",
     full_plan_md: (row["full_plan_md"] as string) ?? "",
     sequence: (row["sequence"] as number) ?? 0,
diff --git a/src/resources/extensions/gsd/tests/gsd-db.test.ts b/src/resources/extensions/gsd/tests/gsd-db.test.ts
index 557b5830c..097ea7151 100644
--- a/src/resources/extensions/gsd/tests/gsd-db.test.ts
+++ b/src/resources/extensions/gsd/tests/gsd-db.test.ts
@@ -15,6 +15,7 @@ import {
   getRequirementById,
   getActiveDecisions,
   getActiveRequirements,
+  getTask,
   transaction,
   _getAdapter,
   _resetProvider,
@@ -359,6 +360,79 @@ describe('gsd-db', () => {
     closeDatabase();
   });
 
+  test('gsd-db: recreates missing verification evidence dedup index after removing duplicate rows', () => {
+    const dbPath = tempDbPath();
+    openDatabase(dbPath);
+
+    let adapter = _getAdapter()!;
+    adapter.prepare("INSERT INTO milestones (id, created_at) VALUES (?, '')").run('M001');
+    adapter.prepare("INSERT INTO slices (milestone_id, id, created_at) VALUES (?, ?, '')").run('M001', 'S01');
+    adapter.prepare("INSERT INTO tasks (milestone_id, slice_id, id) VALUES (?, ?, ?)").run('M001', 'S01', 'T01');
+    adapter.exec('DROP INDEX IF EXISTS idx_verification_evidence_dedup');
+
+    const insertEvidence = adapter.prepare(
+      `INSERT INTO verification_evidence (
+        task_id, slice_id, milestone_id, command, exit_code, verdict, duration_ms, created_at
+      ) VALUES (?, ?, ?, ?, ?, ?, ?, ?)`,
+    );
+    insertEvidence.run('T01', 'S01', 'M001', 'npm test', 1, 'fail', 125, '2026-04-12T00:00:00.000Z');
+    insertEvidence.run('T01', 'S01', 'M001', 'npm test', 1, 'fail', 125, '2026-04-12T00:00:01.000Z');
+    insertEvidence.run('T01', 'S01', 'M001', 'npm run lint', 0, 'pass', 90, '2026-04-12T00:00:02.000Z');
+
+    closeDatabase();
+
+    assert.equal(openDatabase(dbPath), true, 'openDatabase should repair legacy duplicate evidence rows');
+
+    adapter = _getAdapter()!;
+    const countRow = adapter.prepare(
+      `SELECT count(*) as cnt
+       FROM verification_evidence
+       WHERE task_id = ? AND slice_id = ? AND milestone_id = ? AND command = ? AND verdict = ?`,
+    ).get('T01', 'S01', 'M001', 'npm test', 'fail');
+    assert.equal(countRow?.['cnt'], 1, 'duplicate verification evidence rows should be deduplicated before index creation');
+
+    const indexRow = adapter.prepare(
+      "SELECT name FROM sqlite_master WHERE type = 'index' AND name = 'idx_verification_evidence_dedup'",
+    ).get();
+    assert.equal(indexRow?.['name'], 'idx_verification_evidence_dedup', 'dedup index should be recreated on reopen');
+
+    cleanup(dbPath);
+  });
+
+  test('gsd-db: rowToTask tolerates legacy comma-separated task arrays', () => {
+    openDatabase(':memory:');
+
+    const adapter = _getAdapter()!;
+    adapter.prepare("INSERT INTO milestones (id, created_at) VALUES (?, '')").run('M001');
+    adapter.prepare("INSERT INTO slices (milestone_id, id, created_at) VALUES (?, ?, '')").run('M001', 'S01');
+    adapter.prepare(
+      `INSERT INTO tasks (
+        milestone_id, slice_id, id, key_files, key_decisions, files, inputs, expected_output
+      ) VALUES (?, ?, ?, ?, ?, ?, ?, ?)`,
+    ).run(
+      'M001',
+      'S01',
+      'T01',
+      '[]',
+      '[]',
+      'tests/test_verify.py, config.yaml, configs/roster_2026-05-11.yaml',
+      'tests/test_verify.py',
+      'reports/summary.md, artifacts/output.json',
+    );
+
+    const task = getTask('M001', 'S01', 'T01');
+    assert.ok(task, 'task should load successfully from DB');
+    assert.deepEqual(task?.files, [
+      'tests/test_verify.py',
+      'config.yaml',
+      'configs/roster_2026-05-11.yaml',
+    ]);
+    assert.deepEqual(task?.inputs, ['tests/test_verify.py']);
+    assert.deepEqual(task?.expected_output, ['reports/summary.md', 'artifacts/output.json']);
+
+    closeDatabase();
+  });
+
   test('gsd-db: query wrappers return null/empty when DB unavailable', () => {
     // Ensure DB is closed
     closeDatabase();