diff --git a/backend/app/models/__init__.py b/backend/app/models/__init__.py
index 0697c07..f7a3c94 100644
--- a/backend/app/models/__init__.py
+++ b/backend/app/models/__init__.py
@@ -21,6 +21,7 @@ from .tag_alias import TagAlias
 from .tag_allowlist import TagAllowlist
 from .tag_reference_embedding import TagReferenceEmbedding
 from .tag_suggestion_rejection import TagSuggestionRejection
+from .task_run import TaskRun
 
 __all__ = [
     "Base",
@@ -46,4 +47,5 @@ __all__ = [
     "TagAllowlist",
     "TagReferenceEmbedding",
     "TagSuggestionRejection",
+    "TaskRun",
 ]
diff --git a/backend/app/models/task_run.py b/backend/app/models/task_run.py
new file mode 100644
index 0000000..e8eac05
--- /dev/null
+++ b/backend/app/models/task_run.py
@@ -0,0 +1,48 @@
+"""FC-3i: task_run — per-Celery-task lifecycle audit row.
+
+One row inserted by the task_prerun signal at task start, updated by
+task_postrun / task_failure / task_retry. The shape supports the
+SystemActivity dashboard's three panes: per-queue queue+worker summary,
+recent failures (24h, grouped by error_type), and full paginated
+activity history.
+
+Retention: ok rows pruned after 24h, error/timeout after 7d (see
+backend.app.tasks.maintenance.prune_task_runs).
+
+Recovery: rows stuck in 'running' for >5 min flipped to 'error' by
+backend.app.tasks.maintenance.recover_stalled_task_runs (Beat 5 min).
+"""
+
+from datetime import datetime
+
+from sqlalchemy import DateTime, Integer, String, Text
+from sqlalchemy.orm import Mapped, mapped_column
+
+from .base import Base
+
+
+class TaskRun(Base):
+    __tablename__ = "task_run"
+
+    id: Mapped[int] = mapped_column(Integer, primary_key=True)
+    celery_task_id: Mapped[str] = mapped_column(
+        String(64), nullable=False, index=True,
+    )
+    queue: Mapped[str] = mapped_column(String(32), nullable=False, index=True)
+    task_name: Mapped[str] = mapped_column(String(128), nullable=False, index=True)
+    target_id: Mapped[int | None] = mapped_column(Integer, nullable=True)
+    started_at: Mapped[datetime] = mapped_column(
+        DateTime(timezone=True), nullable=False, index=True,
+    )
+    finished_at: Mapped[datetime | None] = mapped_column(
+        DateTime(timezone=True), nullable=True, index=True,
+    )
+    duration_ms: Mapped[int | None] = mapped_column(Integer, nullable=True)
+    status: Mapped[str] = mapped_column(
+        String(16), nullable=False, default="running", index=True,
+    )
+    error_type: Mapped[str | None] = mapped_column(String(128), nullable=True)
+    error_message: Mapped[str | None] = mapped_column(Text, nullable=True)
+    retry_count: Mapped[int | None] = mapped_column(Integer, nullable=True)
+    worker_hostname: Mapped[str | None] = mapped_column(String(128), nullable=True)
+    args_summary: Mapped[str | None] = mapped_column(String(255), nullable=True)