[Other] serve: a tool's picture starts the elastic encoder, and its turn counts

serve/server.py

@@ -4296,8 +4296,12 @@ def _note_unreadable_tool_images(self, messages, cancel=None):
                         if src.startswith(("http://", "https://")):
                             src = fetched[item["source"]] = Vision.download(src)   # outside the FIFO, as in prepare()
                         with self._turn(cancel):  # the encoder takes its turn with the requests (see below)
-                            self.vision.encode(src)
-                    except (ValueError, OSError) as e:
+                            self._vision_up()     # the elastic encoder starts with its picture, as prepare() does: it
+                            try:                  # had stopped after elastic_idle_s, and encode died on the missing pipe
+                                self.vision.encode(src)
+                            finally:              # as prepare() does: the idle timer counts this turn too, so the
+                                self.last_image_at = time.time()  # sweep does not reclaim the encoder this picture started
+                    except (ValueError, OSError, RuntimeError) as e:
                         why = str(e)
                 if why is not None:
                     print(f"[strata] a picture a tool returned was left out of the prompt: {why}", flush=True)

serve/test_vision_elastic.py

@@ -118,6 +118,28 @@ def test_the_config_keys(self):
         self.assertFalse(v.elastic)
         self.assertEqual((v.elastic_mib, v.elastic_idle_s), (2048, 120.0))
 
+    def tool_picture(self):
+        return [{"role": "user", "content": "read it"},
+                {"role": "tool", "tool_call_id": "t1", "content": [dict(IMAGE)]}]
+
+    def test_a_tool_picture_starts_an_idle_encoder_and_holds_it(self):
+        msg = self.tool_picture()
+        self.svc._note_unreadable_tool_images(msg)
+        self.assertEqual(self.vision.starts, 1)             # the picture woke the encoder (it was down: no picture turn
+        self.assertTrue(self.vision.up)                     # ran yet, and encode died on the missing pipe)
+        self.assertGreater(self.svc.last_image_at, 0)       # the turn counted for the idle timer, as prepare's does
+        self.assertEqual(self.svc._vision_idle_down(), "busy")   # so the sweep leaves the new encoder alone
+        self.assertEqual(msg[1]["content"][0]["type"], "image")  # and the picture stays in the history
+
+    def test_a_tool_picture_whose_encoder_cannot_start_becomes_a_note(self):
+        def fail():
+            raise RuntimeError("the vision encoder did not start")  # what _vision_up's start raises
+        self.vision.restart = fail
+        msg = self.tool_picture()
+        self.svc._note_unreadable_tool_images(msg)          # the start's RuntimeError must not escape: the method's
+        self.assertEqual(msg[1]["content"][0],              # contract is a note in the picture's place, not a 500
+                         {"type": "text", "text": "[image omitted: the vision encoder did not start]"})
+
 
 if __name__ == "__main__":
     unittest.main()