diff --git a/nerve/agent/tools/handlers/tasks.py b/nerve/agent/tools/handlers/tasks.py
index cc7eea23..541b8825 100644
--- a/nerve/agent/tools/handlers/tasks.py
+++ b/nerve/agent/tools/handlers/tasks.py
@@ -474,6 +474,10 @@ def _move_to_done() -> None:
                     file_path=rel_path,
                     title=task["title"],
                     status="done",
+                    source=task.get("source"),
+                    source_url=task.get("source_url"),
+                    deadline=task.get("deadline"),
+                    tags=task.get("tags") or "",
                     content=content,
                 )
 
diff --git a/nerve/tasks/manager.py b/nerve/tasks/manager.py
index 7c00e721..25d64a56 100644
--- a/nerve/tasks/manager.py
+++ b/nerve/tasks/manager.py
@@ -101,6 +101,10 @@ def _move_to_done() -> None:
                 file_path=rel_path,
                 title=row["title"],
                 status="done",
+                source=row.get("source"),
+                source_url=row.get("source_url"),
+                deadline=row.get("deadline"),
+                tags=row.get("tags") or "",
                 content=content,
             )
 
diff --git a/tests/test_task_completion.py b/tests/test_task_completion.py
new file mode 100644
index 00000000..6cb15150
--- /dev/null
+++ b/tests/test_task_completion.py
@@ -0,0 +1,69 @@
+"""Regression tests for completing tasks."""
+
+from __future__ import annotations
+
+import pytest
+
+from nerve.agent.tools.handlers.tasks import task_done_handler
+from nerve.agent.tools.registry import ToolContext
+from nerve.db import Database
+from nerve.tasks.manager import TaskManager
+
+
+TASK_METADATA = {
+    "source": "github",
+    "source_url": "https://github.com/example/project/issues/123",
+    "deadline": "2026-08-02",
+    "tags": "bug,github,urgent",
+}
+
+
+async def _create_task(db: Database, tmp_path, task_id: str) -> None:
+    active_dir = tmp_path / "memory" / "tasks" / "active"
+    active_dir.mkdir(parents=True, exist_ok=True)
+    task_file = active_dir / f"{task_id}.md"
+    content = "# Preserve metadata\n\nInvestigate source synchronization.\n"
+    task_file.write_text(content, encoding="utf-8")
+    await db.upsert_task(
+        task_id=task_id,
+        file_path=str(task_file.relative_to(tmp_path)),
+        title="Preserve metadata",
+        status="pending",
+        content=content,
+        **TASK_METADATA,
+    )
+
+
+async def _assert_metadata_preserved(db: Database, task_id: str) -> None:
+    task = await db.get_task(task_id)
+    assert task is not None
+    assert task["status"] == "done"
+    assert {field: task[field] for field in TASK_METADATA} == TASK_METADATA
+    assert task["file_path"].startswith("memory/tasks/done/")
+
+    matches = await db.search_tasks(
+        query="source synchronization", status="all", tag="urgent",
+    )
+    assert [match["id"] for match in matches] == [task_id]
+
+
+@pytest.mark.asyncio
+async def test_task_done_handler_preserves_metadata(db: Database, tmp_path):
+    task_id = "2026-07-30-handler-metadata"
+    await _create_task(db, tmp_path, task_id)
+
+    ctx = ToolContext(session_id="test", db=db, workspace=tmp_path)
+    await task_done_handler(ctx, {"task_id": task_id})
+
+    await _assert_metadata_preserved(db, task_id)
+
+
+@pytest.mark.asyncio
+async def test_task_manager_mark_done_preserves_metadata(db: Database, tmp_path):
+    task_id = "2026-07-30-manager-metadata"
+    await _create_task(db, tmp_path, task_id)
+
+    manager = TaskManager(tmp_path, db)
+    assert await manager.mark_done(task_id)
+
+    await _assert_metadata_preserved(db, task_id)