From 9c76e0936c27bfbf74e2a89eb0fe2cba4177838a Mon Sep 17 00:00:00 2001
From: Alessandro Pogliaghi <apogliaghi@gmail.com>
Date: Thu, 30 Jul 2026 15:02:29 +0100
Subject: [PATCH] fix(tasks): recover resumes from missing branches

When a saved resume branch no longer exists in the task repository, clone its default branch instead. This lets the agent boot and restore the saved git checkpoint while keeping unrelated clone failures terminal.

Generated-By: PostHog Code
Task-Id: 3721ab47-bf20-4d0a-b474-8a622badccd2
---
 .../activities/provision_sandbox.py           | 27 +++++++++-
 .../tests/test_provision_sandbox.py           | 54 +++++++++++++++++++
 2 files changed, 80 insertions(+), 1 deletion(-)

diff --git a/products/tasks/backend/temporal/process_task/activities/provision_sandbox.py b/products/tasks/backend/temporal/process_task/activities/provision_sandbox.py
index 306d7b8f466d..15ccb706985e 100644
--- a/products/tasks/backend/temporal/process_task/activities/provision_sandbox.py
+++ b/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 (
@@ -677,12 +677,37 @@ 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:
diff --git a/products/tasks/backend/temporal/process_task/activities/tests/test_provision_sandbox.py b/products/tasks/backend/temporal/process_task/activities/tests/test_provision_sandbox.py
index 54de6b15a2d8..6af3e5e2c3ac 100644
--- a/products/tasks/backend/temporal/process_task/activities/tests/test_provision_sandbox.py
+++ b/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,
+        ),
+    ]