Adopt an already-published PR instead of publishing again

Fixes counterexample 5 from specs/orchestrator.qnt. A crash after the
PR was opened but before PR_OPEN was recorded left the agent in
EXECUTING; the restart question's 'continue' and 'start' then published
again, Gitea refused a second PR, and there was no way back to PR_OPEN.
On the live run the executor model happened to notice the existing
work; recovery must not depend on that.

- Boot (A3 step 4): in EXECUTING, if Gitea shows the milestone's PR
  open, adopt it, watch it from the start, and resume in PR_OPEN with a
  notice. Gitea unreachable or the PR closed: the restart question, as
  before.
- MilestonePublisher.publish is idempotent: after pushing, an open PR
  for the branch is adopted (and so updated) rather than a second one
  opened. This also covers a PR opened whose response was lost.
- The model adopts too, gains the lost-response outcome, and now counts
  PRs opened per milestone (one_pr_per_milestone was a flag the fixed
  model could never set). A mutant without adoption fails the new
  scenario; the properties held over 200,000 traces each.

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/control.py

@@ -130,6 +130,8 @@ class MilestonePublisher(Protocol):
 
     def close_pull_request(self, index: int, note: str) -> None: ...
 
+    def published_pull_request(self, task_id: str, milestone: int) -> Any: ...
+
 
 class PlanBoard(Protocol):
     """The Gitea side of plan gating; the concrete one is in
@@ -323,6 +325,27 @@ class Orchestrator:
                 "restarted while waiting on you: "
                 + pending.get("prompt", "my last question still stands")
             )
+        elif state.state == EXECUTING and (published := self._published_pr()):
+            # A3 step 4: Gitea shows this milestone's PR open, so it was
+            # published and only PR_OPEN went unrecorded. Adopt the PR rather
+            # than ask, and never publish it again. Nothing watched it yet,
+            # so every comment on it is new.
+            milestone = int(self._data.get("milestone", 1))
+            self._data["pr"] = {
+                "number": published.number,
+                "url": published.url,
+                "milestone": milestone,
+                "last_comment": self._watch(
+                    "review", published.number, self.handle_review_comment, after=0
+                ),
+            }
+            self._unwatch("plan")
+            self._transition(PR_OPEN, cause=f"boot: milestone {milestone} published")
+            self._transport.send_message(
+                f"restarted after milestone {milestone} was published: PR "
+                f"#{published.number} is open ({published.url}); watching it for "
+                "review comments"
+            )
         elif state.state == PR_OPEN:
             # Waiting on review is a committed state like a gate (A3 step
             # 8): resume, and watch the PR again from its cursor.
@@ -980,6 +1003,20 @@ class Orchestrator:
             f"task on {project} abandoned{closed}. Say 'use <project>' to start another"
         )
 
+    def _published_pr(self) -> Any:
+        """The open PR for the current milestone, if Gitea shows one; None
+        when there is none or Gitea cannot say (then the restart question
+        is asked as before)."""
+        task_id = self._data.get("task_id")
+        if self._publisher is None or not task_id:
+            return None
+        try:
+            return self._publisher.published_pull_request(
+                str(task_id), int(self._data.get("milestone", 1))
+            )
+        except GiteaError:
+            return None
+
     def _return_to_pr_open(self, cause: str) -> None:
         self._transition(PR_OPEN, cause=cause)
         pr = self._data.get("pr") or {}

nisse-dev/src/nisse_dev/publish.py

@@ -84,6 +84,19 @@ class MilestonePublisher:
             cause=f"publishing milestone {milestone}",
         )
         self._git.push(self._remote, branch, token=self._token)
+        # Idempotent: if a PR for this branch is already open (a crash after
+        # opening it, or a response lost on the way back), the push above
+        # has updated it; adopt it rather than fail on a second.
+        existing = self.published_pull_request(task_id, milestone)
+        if existing is not None:
+            self._store.commit_intent(
+                intent_id, cause=f"adopted open PR #{existing.number}"
+            )
+            return PublishResult(
+                existing,
+                f"PR #{existing.number} was already open for this milestone; "
+                f"pushed to it: {existing.url}",
+            )
         pr = self._client.open_pull_request(
             self._repo,
             head=branch,
@@ -94,6 +107,17 @@ class MilestonePublisher:
         self._store.commit_intent(intent_id, cause=f"opened PR #{pr.number}")
         return PublishResult(pr, f"opened PR #{pr.number}: {pr.url}")
 
+    def published_pull_request(
+        self, task_id: str, milestone: int
+    ) -> PullRequest | None:
+        """The open PR for a milestone's branch, if there is one. A closed one
+        does not count: the operator closed it, so a new one may be opened.
+        Raises GiteaError when Gitea cannot say."""
+        pr = self._client.find_pull_request(
+            self._repo, self.branch_for(task_id, milestone)
+        )
+        return pr if pr is not None and pr.state == "open" else None
+
     def comment(self, index: int, body: str) -> None:
         """Reply on the PR. Courtesy only — the pushed commit is the real
         answer — so a failure here must not derail the review loop."""

nisse-dev/tests/test_publish.py

@@ -16,6 +16,7 @@ class FakeGitea:
     def __init__(self, *, fail: bool = False) -> None:
         self.opened: list[dict[str, Any]] = []
         self.existing: list[str] = []
+        self.closed: set[str] = set()
         self._fail = fail
 
     def open_pull_request(
@@ -33,7 +34,8 @@ class FakeGitea:
 
     def find_pull_request(self, repo: str, head: str) -> PullRequest | None:
         if head in self.existing:
-            return PullRequest(number=1, state="open", head=head, url="u")
+            state = "closed" if head in self.closed else "open"
+            return PullRequest(number=1, state=state, head=head, url="u")
         return None
 
 
@@ -212,3 +214,32 @@ def test_a_followup_the_executor_committed_itself_is_pushed(
     # 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
+
+
+def test_publishing_again_adopts_the_open_pr_instead_of_opening_another(
+    store: StateStore, tmp_path: Path
+) -> None:
+    # E.g. Gitea opened the PR but the response was lost, and the milestone
+    # was published again: the PR is adopted and updated, never duplicated.
+    git = FakeGit(tmp_path / "work")
+    client = FakeGitea()
+    publisher = build(store, git, client)
+    publisher.publish(task_id="t", milestone=1, project="demo", plan="p")
+    (tmp_path / "work" / "more.txt").write_text("more")
+    result = publisher.publish(task_id="t", milestone=1, project="demo", plan="p")
+    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 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")
+    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")
+    assert len(client.opened) == 1  # the operator closed it; a new one opens

nisse-dev/tests/test_quint_counterexamples.py

@@ -134,6 +134,12 @@ class Publisher:
             PullRequest(number=20, state="open", head=branch, url="u"), "opened PR #20"
         )
 
+    def published_pull_request(self, task_id: str, milestone: int) -> Any:
+        branch = f"{task_id}/milestone-{milestone}"
+        if branch in self._gitea.prs:
+            return PullRequest(number=20, state="open", head=branch, url="u")
+        return None
+
     def push_followup(self, **kwargs: Any) -> str | None:
         return "abc12345"
 
@@ -249,7 +255,6 @@ def test_an_afterthought_rejects_the_next_plan(tmp_path: Path) -> None:
     assert agent.gate().get("rev") == 2  # arch was rev-1; not re-planned
 
 
-@XFAIL
 def test_crash_after_opening_the_pr_publishes_again(tmp_path: Path) -> None:
     """crashAfterOpeningThePrPublishesAgainTest"""
     gitea = FakeGitea()
@@ -261,9 +266,11 @@ def test_crash_after_opening_the_pr_publishes_again(tmp_path: Path) -> None:
     assert agent.state == EXECUTING  # the PR exists; PR_OPEN was never recorded
 
     agent = Agent(tmp_path, gitea)  # restart: the intent is verified
-    agent.say("continue", "start milestone 1")
-    # There is a PR for this milestone: the agent must end up watching it,
-    # not trying to open another.
+    # There is a PR for this milestone: the agent adopts it on boot and ends
+    # up watching it, never trying to open another.
+    assert agent.state == PR_OPEN
+    assert "PR #20 is open" in agent.transport.outbound[-1].text
+    agent.say("continue", "start milestone 1")  # no longer means anything
     assert agent.publisher.attempts == 0
     assert agent.state == PR_OPEN
 
@@ -321,3 +328,22 @@ def test_the_harness_reaches_pr_open_without_faults(tmp_path: Path) -> None:
     assert agent.state == PR_OPEN
     assert agent.publisher.attempts == 1
     _ = (AWAIT_INPUT, MILESTONE_PLANNING)
+
+
+def test_boot_asks_as_before_when_gitea_cannot_say(
+    tmp_path: Path, monkeypatch: pytest.MonkeyPatch
+) -> None:
+    gitea = FakeGitea()
+    agent = Agent(tmp_path, gitea)
+    agent.say("use demo", "approve", "approve")
+    agent.publisher.crash_after_opening = True
+    with pytest.raises(SystemExit):
+        agent.say("start milestone 1")
+
+    def unreachable(self: Publisher, task_id: str, milestone: int) -> Any:
+        raise GiteaError("gitea is down")
+
+    monkeypatch.setattr(Publisher, "published_pull_request", unreachable)
+    agent = Agent(tmp_path, gitea)
+    assert agent.state == AWAIT_INPUT
+    assert "restarted mid-EXECUTING" in agent.transport.outbound[-1].text