Flatten harness branch names so a model's branch can't block them

Live run 3: the executor ran `git checkout -b <task id>` itself, and
publishing then failed, because git can't create '<task>/milestone-1'
while a branch named '<task>' exists. Milestone and delegation branches
are now '<task>-milestone-N' and 'delegation-milestone-N-F'. D4's
harness-owned branches (M2.1) remove the cause; this removes the
collision on the current loop.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PPQ14L3LikyefCMFBqEbKE

nisse-dev/src/nisse_dev/executor.py

@@ -134,7 +134,7 @@ class LLMExecutor:
         result = self._delegate.run(
             transcript.as_actor("helper"),
             brief=brief,
-            branch=f"delegation/milestone-{milestone}-{failures}",
+            branch=f"delegation-milestone-{milestone}-{failures}",
         )
         if result.usable:
             return None

nisse-dev/src/nisse_dev/publish.py

@@ -55,8 +55,10 @@ class MilestonePublisher:
 
     def branch_for(self, task_id: str, milestone: int) -> str:
         # Namespaced by task so re-running a project against the same repo
-        # cannot collide with an earlier run's branch.
-        return f"{task_id}/milestone-{milestone}"
+        # cannot collide with an earlier run's branch. Flat, with no "/":
+        # git stores branch names as paths, so a branch named after the task
+        # (which a model did make, live) would block "<task>/milestone-1".
+        return f"{task_id}-milestone-{milestone}"
 
     def publish(
         self,

nisse-dev/tests/test_publish.py

@@ -124,14 +124,29 @@ def test_publish_commits_pushes_and_opens_a_pr(
         task_id="demo-abc", milestone=2, project="demo", plan="the plan"
     )
 
-    assert git.pushed == ["demo-abc/milestone-2"]
-    assert client.opened[0]["head"] == "demo-abc/milestone-2"
+    assert git.pushed == ["demo-abc-milestone-2"]
+    assert client.opened[0]["head"] == "demo-abc-milestone-2"
     assert client.opened[0]["base"] == "main"
     assert "the plan" in client.opened[0]["body"]
     assert result.pull_request is not None
     assert "opened PR #1" in result.note
 
 
+def test_a_branch_named_after_the_task_does_not_block_publishing(
+    store: StateStore, tmp_path: Path
+) -> None:
+    # Live run 3: the executor ran `git checkout -b <task id>` itself. With
+    # "<task>/milestone-1" as the harness's branch, git refused it, since a
+    # branch name can't also be a directory of other branch names.
+    git = FakeGit(tmp_path / "work")
+    git.repo.checkout_new_branch("demo-abc")
+    result = build(store, git, FakeGitea()).publish(
+        task_id="demo-abc", milestone=1, project="demo", plan="p"
+    )
+    assert result.pull_request is not None
+    assert git.pushed == ["demo-abc-milestone-1"]
+
+
 def test_intent_is_recorded_then_committed(store: StateStore, tmp_path: Path) -> None:
     build(store, FakeGit(tmp_path / "work"), FakeGitea()).publish(
         task_id="t", milestone=1, project="demo", plan="p"
@@ -150,7 +165,7 @@ def test_failure_after_intent_leaves_it_pending_for_reconciliation(
 
     [pending] = store.pending_intents()
     assert pending.kind == OPEN_PR_INTENT
-    assert pending.payload["branch"] == "t/milestone-1"
+    assert pending.payload["branch"] == "t-milestone-1"
     assert pending.payload["sha"]
 
 
@@ -171,7 +186,7 @@ def test_nothing_to_commit_is_reported_not_raised(
 
 def test_branch_is_namespaced_by_task(store: StateStore, tmp_path: Path) -> None:
     publisher = build(store, FakeGit(tmp_path / "work"), FakeGitea())
-    assert publisher.branch_for("greet-9f2", 3) == "greet-9f2/milestone-3"
+    assert publisher.branch_for("greet-9f2", 3) == "greet-9f2-milestone-3"
 
 
 def test_reconciler_settles_an_intent_left_by_a_crash(
@@ -183,9 +198,9 @@ def test_reconciler_settles_an_intent_left_by_a_crash(
     client = FakeGitea()
     publisher = build(store, FakeGit(tmp_path / "work"), client)
     intent_id = store.begin_intent(
-        OPEN_PR_INTENT, {"branch": "t/milestone-1"}, cause="crash simulation"
+        OPEN_PR_INTENT, {"branch": "t-milestone-1"}, cause="crash simulation"
     )
-    client.existing.append("t/milestone-1")
+    client.existing.append("t-milestone-1")
 
     reconcilers = publisher.reconcilers()
     assert set(reconcilers) == {OPEN_PR_INTENT}
@@ -205,8 +220,8 @@ def test_work_the_executor_committed_itself_is_published(
         task_id="t", milestone=1, project="demo", plan="p"
     )
     assert result.pull_request is not None
-    assert git.pushed == ["t/milestone-1"]
-    assert git.remote["t/milestone-1"] == git.head_sha()
+    assert git.pushed == ["t-milestone-1"]
+    assert git.remote["t-milestone-1"] == git.head_sha()
 
 
 def test_a_followup_the_executor_committed_itself_is_pushed(
@@ -219,7 +234,7 @@ def test_a_followup_the_executor_committed_itself_is_pushed(
     git.repo.commit_all("Address review")
     sha = publisher.push_followup(task_id="t", milestone=1, message="m")
     assert sha == git.head_sha()
-    assert git.pushed == ["t/milestone-1", "t/milestone-1"]
+    assert git.pushed == ["t-milestone-1", "t-milestone-1"]
     # Nothing new since that push: no second push, and it says so.
     assert publisher.push_followup(task_id="t", milestone=1, message="m") is None
     assert len(git.pushed) == 2
@@ -239,15 +254,15 @@ def test_publishing_again_adopts_the_open_pr_instead_of_opening_another(
     assert len(client.opened) == 1
     assert result.pull_request is not None and result.pull_request.number == 1
     assert "already open" in result.note
-    assert git.pushed == ["t/milestone-1", "t/milestone-1"]  # updated it
+    assert git.pushed == ["t-milestone-1", "t-milestone-1"]  # updated it
     assert store.pending_intents() == []
 
 
 def test_a_closed_pr_is_not_adopted(store: StateStore, tmp_path: Path) -> None:
     git = FakeGit(tmp_path / "work")
     client = FakeGitea()
-    client.existing.append("t/milestone-1")
-    client.closed.add("t/milestone-1")
+    client.existing.append("t-milestone-1")
+    client.closed.add("t-milestone-1")
     publisher = build(store, git, client)
     assert publisher.published_pull_request("t", 1) is None
     publisher.publish(task_id="t", milestone=1, project="demo", plan="p")

nisse-dev/tests/test_quint_counterexamples.py

@@ -121,7 +121,7 @@ class Publisher:
         return {"open_pr": lambda intent: intent.payload["branch"] in self._gitea.prs}
 
     def publish(self, **kwargs: Any) -> PublishResult:
-        branch = f"{kwargs['task_id']}/milestone-{kwargs['milestone']}"
+        branch = f"{kwargs['task_id']}-milestone-{kwargs['milestone']}"
         self.attempts += 1
         intent = self._store.begin_intent("open_pr", {"branch": branch}, cause="t")
         if branch in self._gitea.prs:
@@ -135,7 +135,7 @@ class Publisher:
         )
 
     def published_pull_request(self, task_id: str, milestone: int) -> Any:
-        branch = f"{task_id}/milestone-{milestone}"
+        branch = f"{task_id}-milestone-{milestone}"
         if branch in self._gitea.prs:
             return PullRequest(number=20, state="open", head=branch, url="u")
         return None