From d77d152a4494f1690e1f9e870f8961e30b841e6b Mon Sep 17 00:00:00 2001
From: webtecnica <75556242+webtecnica@users.noreply.github.com>
Date: Sat, 4 Jul 2026 15:51:58 -0300
Subject: [PATCH 1/2] fix: classify OpenRouter 'no tool use' 404 as
 model_not_found with fallback

When OpenRouter routes to an endpoint that does not support tool/function
calling, it returns HTTP 404 with the message 'No endpoints found that
support tool use. Try disabling "browser_back".'

The raw error body does not contain 'model not found' or any other
_MODEL_NOT_FOUND_PATTERNS entry, so it falls through to FailoverReason.unknown
with retryable=True. The retry loop wastes 3-5 attempts on the same
deterministic rejection, then surfaces a confusing generic error instead of
automatically failing over to a fallback model or provider.

Adding the OpenRouter phrase to _MODEL_NOT_FOUND_PATTERNS classifies it as
model_not_found (retryable=False, should_fallback=True), which triggers the
client-error fast-fallback path in conversation_loop.py: the agent switches
to a configured fallback model/provider before the user sees the error.

Existing buffered guidance in conversation_loop.py (the 'support tool use'
hint at line ~2967) remains intact and surfaces only if every fallback
exhausts.
---
 agent/error_classifier.py | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/agent/error_classifier.py b/agent/error_classifier.py
index 3489c66c949b1..27311609de669 100644
--- a/agent/error_classifier.py
+++ b/agent/error_classifier.py
@@ -279,6 +279,15 @@ def is_auth(self) -> bool:
     "no such model",
     "unknown model",
     "unsupported model",
+    # OpenRouter returns 404 with this message when none of the candidate
+    # endpoints for the selected model support tool/function calling.
+    # Classifying this as model_not_found triggers fallback to a different
+    # model or provider that does support tools.  Without this entry the
+    # pattern falls through to ``unknown`` with ``retryable=True``, the
+    # retry loop burns all attempts on the same deterministic rejection,
+    # and the error surfaces as a confusing "model not found" message
+    # instead of automatically failing over.  See PR #58446.
+    "no endpoints found that support tool use",
 ]
 
 # Request-validation patterns — the request is malformed and will fail

From 48590ca396e022b4826c5e34e3c415ee0b1f3c44 Mon Sep 17 00:00:00 2001
From: webtecnica <75556242+webtecnica@users.noreply.github.com>
Date: Sat, 4 Jul 2026 19:33:07 -0300
Subject: [PATCH 2/2] test: add regression test for OpenRouter tool-use 404
 classification

---
 tests/agent/test_error_classifier.py | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/tests/agent/test_error_classifier.py b/tests/agent/test_error_classifier.py
index 6c533089986ce..7c266a5ad633a 100644
--- a/tests/agent/test_error_classifier.py
+++ b/tests/agent/test_error_classifier.py
@@ -516,6 +516,21 @@ def test_404_model_not_found(self):
         assert result.should_fallback is True
         assert result.retryable is False
 
+    def test_404_openrouter_tool_use_not_supported(self):
+        # OpenRouter returns 404 with this message when none of the
+        # candidate endpoints for the selected model support tool/function
+        # calling.  Classify as model_not_found so the agent fast-fallbacks
+        # to a model/provider that does support tools.
+        e = MockAPIError(
+            "No endpoints found that support tool use. "
+            "Try disabling \"browser_back\".",
+            status_code=404,
+        )
+        result = classify_api_error(e)
+        assert result.reason == FailoverReason.model_not_found
+        assert result.should_fallback is True
+        assert result.retryable is False
+
     def test_404_generic(self):
         # Generic 404 with no "model not found" signal — common for local
         # llama.cpp/Ollama/vLLM endpoints with slightly wrong paths.  Treat