fix: clear stale build paths on idea changes

Co-authored-by: Codex <noreply@openai.com>

hackathon_advisor/agent.py

@@ -419,6 +419,8 @@ class AdvisorEngine:
         state["trace"] = trace[-12:]
         if plan:
             state["last_plan"] = list(plan)
+        else:
+            state.pop("last_plan", None)
         if artifact:
             state["last_artifact"] = artifact
 

static/app.js

@@ -427,7 +427,8 @@ function renderRestoredSession(data) {
     renderProjectReferenceState();
     renderProjects(session.last_projects || [], "No project page matched this request.");
     renderIdeas(session.ideas || []);
-    renderPlan(session.last_plan || []);
+    delete session.last_plan;
+    renderPlan([]);
     setCommandDisabled(false);
     restoreSessionCopy();
     return;
@@ -713,6 +714,7 @@ function selectIdea(ideaId) {
   if (!ideaId || !Array.isArray(session.ideas)) return;
   const idea = session.ideas.find((item) => item.id === ideaId);
   if (!idea) return;
+  const changedIdea = idea.id !== session.current_idea_id;
   bumpSessionRevision();
   session.current_idea_id = idea.id;
   if (Array.isArray(idea.goals) && idea.goals.length) {
@@ -722,7 +724,8 @@ function selectIdea(ideaId) {
   renderSelectedIdeaArtifact(idea);
   renderGoals(session.goals || []);
   renderIdeas(session.ideas);
-  renderPlan([]);
+  if (changedIdea) delete session.last_plan;
+  renderPlan(changedIdea ? [] : session.last_plan || []);
   session.ui_status = `selected: ${idea.title}`;
   corrections.textContent = session.ui_status;
   saveSession();

tests/test_agent.py

@@ -88,6 +88,20 @@ def test_plan_command_uses_current_idea() -> None:
     assert planned.state["ideas"][0]["title"] == first.artifact["title"]
 
 
+def test_non_plan_turns_clear_stale_build_plan() -> None:
+    index = ProjectIndex.from_files(Path("data/projects.json"), Path("data/project_index.json"))
+    engine = AdvisorEngine(index)
+
+    first = engine.turn("A local-first archive cartographer for family photos", {})
+    planned = engine.turn("make a build plan", first.state)
+    project = engine.turn("read project lolaby", planned.state)
+    second = engine.turn("A hands-on science coach for kitchen experiments", planned.state)
+
+    assert planned.state["last_plan"]
+    assert "last_plan" not in project.state
+    assert "last_plan" not in second.state
+
+
 def test_plan_and_rank_do_not_create_placeholder_ideas() -> None:
     index = ProjectIndex.from_files(Path("data/projects.json"), Path("data/project_index.json"))
     engine = AdvisorEngine(index)