fix(tasks): recover resumes from missing branches

products/tasks/backend/temporal/process_task/activities/provision_sandbox.py

@@ -24,7 +24,7 @@
     get_primary_sandbox_jwt_kid,
     get_sandbox_jwt_public_key,
 )
-from products.tasks.backend.logic.services.sandbox import Sandbox, SandboxConfig, SandboxTemplate
+from products.tasks.backend.logic.services.sandbox import ExecutionResult, Sandbox, SandboxConfig, SandboxTemplate
 from products.tasks.backend.logic.services.sandbox_usage import open_sandbox_session
 from products.tasks.backend.models import SandboxSnapshot, Task, TaskRun
 from products.tasks.backend.temporal.metrics import (
@@ -689,12 +689,37 @@ def clone_repository_in_sandbox(input: CloneRepositoryInSandboxInput) -> CloneRe
                 branch=ctx.branch if is_resume else None,
             )
 
+            if is_resume and ctx.branch and _is_missing_remote_branch_clone_error(clone_result):
+                emit_agent_log(
+                    ctx.run_id,
+                    "debug",
+                    f"Resume branch {ctx.branch} is unavailable; cloning the repository default branch so the agent can restore its git checkpoint",
+                )
+                clone_result = sandbox.clone_repository(
+                    input.repository,
+                    github_token=input.github_token,
+                    shallow=input.shallow_clone,
+                    branch=None,
+                )
+
         if clone_result.exit_code != 0:
             raise RuntimeError(f"Failed to clone repository {input.repository}: {clone_result.stderr}")
 
         return CloneRepositoryInSandboxOutput(clone_ms=clone_timer.elapsed_ms)
 
 
+def _is_missing_remote_branch_clone_error(result: ExecutionResult) -> bool:
+    if result.exit_code == 0:
+        return False
+
+    output = f"{result.stdout}\n{result.stderr}".casefold()
+    return (
+        "could not find remote branch" in output
+        or ("remote branch" in output and "not found in upstream origin" in output)
+        or "couldn't find remote ref" in output
+    )
+
+
 @activity.defn
 @asyncify
 def checkout_branch_in_sandbox(input: CheckoutBranchInSandboxInput) -> CheckoutBranchInSandboxOutput:

products/tasks/backend/temporal/process_task/activities/tests/test_provision_sandbox.py

@@ -52,3 +52,57 @@ def test_clone_repository_uses_saved_branch_only_for_resumes(mocker, activity_en
         shallow=True,
         branch=expected_branch,
     )
+
+
+def test_resume_clone_falls_back_to_default_branch_when_saved_branch_is_missing(mocker, activity_environment):
+    context = TaskProcessingContext(
+        task_id="task-id",
+        run_id="run-id",
+        team_id=1,
+        team_uuid="team-uuid",
+        organization_id="organization-id",
+        github_integration_id=123,
+        repository="posthog/posthog",
+        distinct_id="distinct-id",
+        state={"resume_from_run_id": "previous-run-id"},
+        _branch="branch-from-a-sibling-repository",
+    )
+    sandbox = mocker.Mock()
+    sandbox.clone_repository.side_effect = [
+        ExecutionResult(
+            stdout="",
+            stderr=(
+                "warning: Could not find remote branch branch-from-a-sibling-repository to clone.\n"
+                "fatal: Remote branch branch-from-a-sibling-repository not found in upstream origin"
+            ),
+            exit_code=128,
+        ),
+        ExecutionResult(stdout="", stderr="", exit_code=0),
+    ]
+    mocker.patch.object(Sandbox, "get_by_id", return_value=sandbox)
+
+    async_to_sync(activity_environment.run)(
+        clone_repository_in_sandbox,
+        CloneRepositoryInSandboxInput(
+            context=context,
+            sandbox_id="sandbox-id",
+            repository="posthog/posthog",
+            github_token="github-token",
+            shallow_clone=True,
+        ),
+    )
+
+    assert sandbox.clone_repository.call_args_list == [
+        mocker.call(
+            "posthog/posthog",
+            github_token="github-token",
+            shallow=True,
+            branch="branch-from-a-sibling-repository",
+        ),
+        mocker.call(
+            "posthog/posthog",
+            github_token="github-token",
+            shallow=True,
+            branch=None,
+        ),
+    ]