fix(simulation): resume live provider builds

tests/test_simulation_projects.py

@@ -8,6 +8,7 @@ from fastapi import FastAPI
 from fastapi.testclient import TestClient
 
 from k1link.simulation.gaussian_pipeline_gateway import (
+    GaussianPipelineUnavailableError,
     GaussianSourceBundleUpload,
     GaussianSourceMemberUpload,
 )
@@ -281,6 +282,91 @@ def test_failed_project_retries_from_retained_source_and_releases_old_job(tmp_pa
     assert queued["source"]["uploaded_byte_length"] == queued["source"]["total_byte_length"]
 
 
+def test_failed_local_project_reattaches_to_live_provider_job_without_rebuild(
+    tmp_path: Path,
+) -> None:
+    store = SimulationProjectStore(tmp_path)
+    project = store.create(
+        name="Reconnect scene",
+        scene_type="outdoor",
+        source_kind="folder",
+        files=_folder_files(),
+    )
+    _upload_all(store, project)
+    store.begin_build(project["project_id"])
+    store.update_processing(
+        project["project_id"],
+        status="processing",
+        provider_job_id="gsp-20260826000000-deadbeef",
+        provider_state="building_streamed_sog",
+        progress={"completed_steps": 3, "total_steps": 5},
+        bundle_sha256="d" * 64,
+    )
+    store.fail(project["project_id"], "temporary provider transport failure")
+    provider = _ReadyProvider()
+    service = SimulationProjectService(
+        store,
+        provider_factory=lambda: provider,
+    )  # type: ignore[arg-type]
+
+    resumed = service.begin_build(project["project_id"])
+
+    assert resumed["status"] == "processing"
+    assert resumed["error"] is None
+    assert resumed["provider"]["job_id"] == "gsp-20260826000000-deadbeef"
+    assert resumed["provider"]["state"] == "ready"
+    assert provider.deleted == []
+    assert provider.upload_calls == 0
+    assert provider.submit_calls == 0
+
+
+def test_live_provider_reattach_retries_temporary_unavailability(
+    tmp_path: Path,
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    store = SimulationProjectStore(tmp_path)
+    project = store.create(
+        name="Flaky tunnel scene",
+        scene_type="outdoor",
+        source_kind="folder",
+        files=_folder_files(),
+    )
+    _upload_all(store, project)
+    store.begin_build(project["project_id"])
+    store.update_processing(
+        project["project_id"],
+        status="processing",
+        provider_job_id="gsp-20260826000000-deadbeef",
+        provider_state="building_collision",
+        bundle_sha256="d" * 64,
+    )
+    store.fail(project["project_id"], "temporary provider transport failure")
+
+    class _FlakyProvider(_ReadyProvider):
+        def __init__(self) -> None:
+            super().__init__()
+            self.get_job_calls = 0
+
+        def get_job(self, job_id: str) -> dict[str, object]:
+            self.get_job_calls += 1
+            if self.get_job_calls < 3:
+                raise GaussianPipelineUnavailableError("temporary tunnel failure")
+            return super().get_job(job_id)
+
+    provider = _FlakyProvider()
+    monkeypatch.setattr("k1link.simulation.projects.time.sleep", lambda _delay: None)
+    service = SimulationProjectService(
+        store,
+        provider_factory=lambda: provider,
+    )  # type: ignore[arg-type]
+
+    resumed = service.begin_build(project["project_id"])
+
+    assert resumed["status"] == "processing"
+    assert provider.get_job_calls == 3
+    assert provider.deleted == []
+
+
 def test_ready_project_rebuilds_from_retained_source_and_preserves_viewer_settings(
     tmp_path: Path,
 ) -> None: