fix(register): require explicit topic when ambiguous

Assistant: codex
Assistant-Model: gpt-5.6-sol
Assistant-Session: 01a06d83-1cbc-71f2-b0dc-e0f48cedae43

statehub_register.py

@@ -250,7 +250,14 @@ def run_register(args: argparse.Namespace) -> None:
     if domain not in domain_slugs:
         domain = _ask_for_domain(domain, domain_slugs)
 
-    topic = _find_or_create_topic(domain, snapshot.project_name, repo_slug, inference, args.api_base)
+    topic = _find_or_create_topic(
+        domain,
+        snapshot.project_name,
+        repo_slug,
+        inference,
+        args.api_base,
+        requested_topic_slug=getattr(args, "topic", None),
+    )
     topic_id = topic["id"]
     topic_slug = topic.get("slug") or domain
 
@@ -831,11 +838,54 @@ def _find_or_create_topic(
     repo_slug: str,
     inference: RegisterInference,
     api_base: str,
+    *,
+    requested_topic_slug: str | None = None,
 ) -> dict[str, Any]:
     topics = _api_get("/topics/?status=active", api_base)
-    existing = next((t for t in topics if t.get("domain_slug") == domain), None)
-    if existing:
-        return existing
+    domain_topics = [topic for topic in topics if topic.get("domain_slug") == domain]
+
+    explicit_slug = _slugify(requested_topic_slug or "") or None
+    inferred_slug = inference.topic_slug
+    preferred_slug = explicit_slug or inferred_slug
+    if preferred_slug:
+        existing = next(
+            (topic for topic in domain_topics if topic.get("slug") == preferred_slug),
+            None,
+        )
+        if existing:
+            return existing
+
+    if explicit_slug:
+        cross_domain = [
+            str(topic.get("domain_slug"))
+            for topic in topics
+            if topic.get("slug") == explicit_slug and topic.get("domain_slug") != domain
+        ]
+        if cross_domain:
+            domains = ", ".join(sorted(set(cross_domain)))
+            raise SystemExit(
+                f"ERROR: Topic '{explicit_slug}' belongs to domain(s) {domains}, "
+                f"not '{domain}'."
+            )
+        available = ", ".join(
+            sorted(str(topic.get("slug")) for topic in domain_topics if topic.get("slug"))
+        ) or "(none)"
+        raise SystemExit(
+            f"ERROR: Active topic '{explicit_slug}' was not found in domain '{domain}'. "
+            f"Available: {available}"
+        )
+
+    if len(domain_topics) == 1:
+        return domain_topics[0]
+    if len(domain_topics) > 1:
+        available = ", ".join(
+            sorted(str(topic.get("slug")) for topic in domain_topics if topic.get("slug"))
+        )
+        raise SystemExit(
+            f"ERROR: Domain '{domain}' has multiple active topics: {available}. "
+            "Pass --topic <slug>."
+        )
+
     slug = inference.topic_slug or repo_slug
     title = inference.topic_title or project_name
     print(f"==> Creating active topic '{slug}' for domain '{domain}'")