diff --git a/src/handler/db/repository.py b/src/handler/db/repository.py
index 450c9d5..da3fd4b 100644
--- a/src/handler/db/repository.py
+++ b/src/handler/db/repository.py
@@ -337,12 +337,59 @@ def update_project(conn: Connection, project_id: str, **fields: Any) -> dict | N
     return get_project(conn, project_id)
 
 
+def _purge_agent_dependents(conn: Connection, agent_ids: list[int]) -> None:
+    """Delete (or detach) everything that references the given agents, so the agent rows
+    themselves can be removed without tripping a foreign key.
+
+    ``shared_context`` is a *global* table keyed by ``key`` — its rows outlive any one
+    agent, so we only null the ``set_by_agent_id`` attribution rather than delete them.
+    ``checkmarks`` must go before ``log_entries`` (it carries an FK to ``log_entries`` via
+    the ``use_alter`` cycle). Approvals authored by these agents go with them.
+    """
+    if not agent_ids:
+        return
+    conn.execute(
+        shared_context.update()
+        .where(shared_context.c.set_by_agent_id.in_(agent_ids))
+        .values(set_by_agent_id=None)
+    )
+    conn.execute(approvals.delete().where(approvals.c.approved_by_agent_id.in_(agent_ids)))
+    conn.execute(checkmarks.delete().where(checkmarks.c.agent_id.in_(agent_ids)))
+    conn.execute(log_entries.delete().where(log_entries.c.agent_id.in_(agent_ids)))
+
+
 def delete_project(conn: Connection, project_id: str) -> bool:
+    """Remove a project and everything scoped to it.
+
+    Every project accumulates FK-referencing rows (at minimum the ``sync`` command queued
+    at registration, plus each agent's log/checkmark history), so the bare project delete
+    would violate ``commands``/``agents``/``approvals``/``schedules`` foreign keys. Clear
+    the dependents in FK-safe order first: agent-owned rows, then ``schedules`` (which
+    reference ``commands`` via ``last_command_id``), then the remaining project-scoped
+    rows, then the agents, then the project itself.
+    """
+    agent_ids = [
+        row[0]
+        for row in conn.execute(
+            select(agents.c.id).where(agents.c.project_id == project_id)
+        ).all()
+    ]
+    _purge_agent_dependents(conn, agent_ids)
+    conn.execute(schedules.delete().where(schedules.c.project_id == project_id))
+    conn.execute(approvals.delete().where(approvals.c.project_id == project_id))
+    conn.execute(commands.delete().where(commands.c.project_id == project_id))
+    conn.execute(agents.delete().where(agents.c.project_id == project_id))
     result = conn.execute(projects.delete().where(projects.c.id == project_id))
     return result.rowcount > 0
 
 
 def delete_agent(conn: Connection, project_id: str, name: str) -> bool:
+    """Remove a single agent row, first clearing its log/checkmark/approval history so the
+    ``log_entries``/``checkmarks``/``approvals`` foreign keys don't block the delete."""
+    agent = get_agent_by_name(conn, project_id, name)
+    if agent is None:
+        return False
+    _purge_agent_dependents(conn, [agent["id"]])
     result = conn.execute(
         agents.delete().where(agents.c.project_id == project_id, agents.c.name == name)
     )
diff --git a/tests/test_repository_web.py b/tests/test_repository_web.py
index 0d6255b..19661dc 100644
--- a/tests/test_repository_web.py
+++ b/tests/test_repository_web.py
@@ -24,6 +24,51 @@ def test_delete_agent_row(conn):
     assert repo.get_agent_by_name(conn, "p", "api") is None
 
 
+def test_delete_project_cascades_all_dependents(conn):
+    """A real project always has FK-referencing rows (the sync command, agent history,
+    approvals, schedules). Deleting it must clear them, not raise a ForeignKeyViolation."""
+    from datetime import UTC, datetime
+
+    repo.create_project(conn, "p", "/tmp/p", git_remote="https://github.com/me/p.git")
+    # The sync command queued at registration — the exact row that blocked the delete.
+    repo.enqueue_command(conn, "sync", project_id="p", requested_by="operator:web")
+    agent = repo.create_agent(conn, "p", "api", "/tmp/p/api")
+    repo.insert_log_entry(conn, agent_id=agent["id"], status="working", summary="did work")
+    repo.upsert_checkmark_row(conn, agent_id=agent["id"], status="working")
+    repo.set_shared_context(conn, "db", "postgres", agent["id"])
+    repo.record_approval(conn, "p", "feat/x", "approved", approved_by_agent_id=agent["id"])
+    repo.create_schedule(
+        conn, "p", "nightly", "run the thing", 3600, datetime.now(UTC)
+    )
+
+    assert repo.delete_project(conn, "p") is True
+
+    # Project and everything scoped to it are gone.
+    assert repo.get_project(conn, "p") is None
+    assert repo.get_agent_by_name(conn, "p", "api") is None
+    assert repo.list_commands(conn, project_id="p") == []
+    assert repo.list_approvals(conn, "p") == []
+    assert repo.list_schedules(conn) == []
+    # The global shared-context row survives, with its agent attribution cleared.
+    ctx = repo.get_shared_context_key(conn, "db")
+    assert ctx is not None and ctx["value"] == "postgres"
+    assert ctx["set_by_agent_id"] is None
+
+
+def test_delete_agent_cascades_log_and_checkmark(conn):
+    """Every spawned agent accrues a checkmark + log entries via the hooks; removing the
+    agent must clear them rather than trip the log_entries/checkmarks foreign keys."""
+    repo.create_project(conn, "p", "/tmp/p")
+    agent = repo.create_agent(conn, "p", "api", "/tmp/p/api")
+    repo.insert_log_entry(conn, agent_id=agent["id"], status="working", summary="x")
+    repo.upsert_checkmark_row(conn, agent_id=agent["id"], status="working")
+
+    assert repo.delete_agent(conn, "p", "api") is True
+    assert repo.get_agent_by_name(conn, "p", "api") is None
+    assert repo.get_checkmark(conn, agent["id"]) is None
+    assert repo.get_log(conn, agent["id"]) == []
+
+
 def test_enqueue_get_and_list_command(conn):
     repo.create_project(conn, "p", "/tmp/p")
     cmd = repo.enqueue_command(