fix(rerank): harden web_search rerank fallback and correct stale docs

list()-materialize the reranker's output inside the guarded block so a
None / non-iterable / lazily-raising reranker falls back to native order
instead of raising out of web_search, and reject bool indices (an int
subclass) the same way _parse_hits already does.

Drop leftover web_fetch references from the rerank settings and Reranker
role help (reranking is wired into web_search only), and document both
endpoint paths (tools.reranker_alias and tools.rerank_url).

tests/test_web_search.py

@@ -359,6 +359,25 @@ class TestWebSearchReranking:
         out = _format_searxng(_results("A", "B"), "q", reranker=boom)
         assert out.index("[A]") < out.index("[B]")  # native order preserved
 
+    def test_none_order_falls_back_to_native_order(self):
+        # A reranker that returns None (or any non-iterable) must fall back, not
+        # raise — list() materializes it inside the guarded block.
+        out = _format_searxng(_results("A", "B"), "q", reranker=lambda q, d: None)
+        assert out.index("[A]") < out.index("[B]")  # native order preserved
+
+    def test_non_int_indices_ignored(self):
+        # bool is an int subclass; True/False must not be honored as indices 1/0.
+        # Junk entries are skipped while valid ints still apply: only 2 and 0 here.
+        out = _format_searxng(
+            _results("A", "B", "C"),
+            "q",
+            max_results=3,
+            reranker=lambda q, d: [True, "1", 2, 0],
+        )
+        # 2 -> C, 0 -> A; B (no valid index) is kept after. If True were honored
+        # as index 1, B would jump to the front — this pins it last.
+        assert out.index("[C]") < out.index("[A]") < out.index("[B]")
+
     def test_skipped_for_single_result(self):
         called = {"n": 0}
 

turnstone/console/static/admin.js

@@ -5205,7 +5205,7 @@ const MODEL_ROLES = [
   {
     label: "Reranker",
     description:
-      "Reranks web_search results and selects the most relevant chunks of large web_fetch pages. Point at a model whose base_url is a Cohere/Jina-compatible /rerank endpoint and whose capabilities include supports_rerank. Empty falls back to the tools.rerank_url setting (if set).",
+      "Reranks web_search results. Point at a model whose base_url is a Cohere/Jina-compatible /rerank endpoint and whose capabilities include supports_rerank. Empty falls back to the tools.rerank_url setting (if set).",
     aliasKey: "tools.reranker_alias",
     fallbackKind: "disabled",
     mediaCapability: "supports_rerank",

turnstone/core/session.py

@@ -1359,7 +1359,7 @@ class ChatSession:
         )
 
     def _rerank_enabled_for(self, tool: str) -> bool:
-        """Whether reranking is enabled for ``tool`` ('web_search' | 'web_fetch').
+        """Whether reranking is enabled for ``tool`` (currently: 'web_search').
 
         The per-tool toggles default on; the operative gate is whether an
         endpoint is configured (``_resolve_rerank_client`` returns None when

turnstone/core/settings_registry.py

@@ -259,9 +259,9 @@ def _build_registry() -> dict[str, SettingDef]:
             help="Full URL of a Cohere/Jina-compatible rerank endpoint, including the path "
             "(e.g. 'http://vllm:8000/rerank', 'http://tei:8080/rerank', or "
             "'https://api.cohere.com/v2/rerank'). Turnstone runs no rerank model itself: "
-            "web_search results and large web_fetch pages are reranked by POSTing to this "
-            "endpoint. Empty disables reranking entirely. Overrides config.toml [tools] "
-            "rerank_url and $TURNSTONE_RERANK_URL.",
+            "web_search results are reranked by POSTing to this endpoint. Empty disables "
+            "reranking entirely. Overrides config.toml [tools] rerank_url and "
+            "$TURNSTONE_RERANK_URL.",
         ),
         SettingDef(
             "tools.rerank_model",
@@ -291,9 +291,10 @@ def _build_registry() -> dict[str, SettingDef]:
             True,
             "Rerank web_search results when a rerank endpoint is configured",
             "tools",
-            help="When a rerank endpoint is set (tools.rerank_url), re-order web_search "
-            "results by query relevance before returning the top hits. No effect when no "
-            "endpoint is configured. Disable to keep the search backend's native ranking.",
+            help="When a rerank endpoint is configured (via tools.reranker_alias or "
+            "tools.rerank_url), re-order web_search results by query relevance before "
+            "returning the top hits. No effect when no endpoint is configured. Disable to "
+            "keep the search backend's native ranking.",
         ),
         SettingDef(
             "tools.reranker_alias",

turnstone/core/web_search.py

@@ -173,14 +173,22 @@ def _rerank_results(
     tail = results[_RERANK_POOL:]
     try:
         docs = [f"{r.get('title', '')}\n{r.get('content') or ''}".strip() for r in pool]
-        order = reranker(query, docs)
+        # Materialize inside the try so a None / non-iterable / lazily-raising
+        # reranker falls back here instead of exploding the splice loop below.
+        order = list(reranker(query, docs))
     except Exception as e:
         log.warning("rerank failed; using native result order: %s", e)
         return results
     seen: set[int] = set()
     reordered: list[dict[str, Any]] = []
     for idx in order:
-        if isinstance(idx, int) and 0 <= idx < len(pool) and idx not in seen:
+        # bool is an int subclass — reject a stray True/False posing as index 1/0.
+        if (
+            isinstance(idx, int)
+            and not isinstance(idx, bool)
+            and 0 <= idx < len(pool)
+            and idx not in seen
+        ):
             seen.add(idx)
             reordered.append(pool[idx])
     if not reordered: