diff --git a/studio/backend/core/inference/inference.py b/studio/backend/core/inference/inference.py
index 4dca4db7689..f113b7fe291 100644
--- a/studio/backend/core/inference/inference.py
+++ b/studio/backend/core/inference/inference.py
@@ -982,7 +982,23 @@ def _generate_chat_response_inner(
             formatted_prompt = self.format_chat_prompt(messages, system_prompt)
 
         # Step 3: generate
-        yield from self.generate_stream(
+
+        # Newer hybrid-thinking templates (Qwen3.5 / Qwen3.6 style) *prefill* the reasoning
+        # opener in the generation prompt (`...<|im_start|>assistant\n<think>\n`), so the
+        # model's own output stream is `reasoning...</think>answer` with no opening tag.
+        # The shared stream protocol marks reasoning with literal <think>...</think> tags
+        # (the harmony parser above emits them for gpt-oss, and llama-server handles the
+        # prefilled-opener convention natively on the GGUF path). Without re-emitting the
+        # opener here, everything the model thinks renders as answer text on the
+        # safetensors path (#6815). enable_thinking=False prompts end with an *empty*
+        # `<think>\n\n</think>` block, not the bare opener, so they are unaffected.
+        # This generator yields *cumulative* snapshots (consumers diff each value
+        # against the previous one), so the synthetic opener must remain part of
+        # every subsequent snapshot rather than be emitted once on its own.
+        think_prefix = "<think>" if formatted_prompt.rstrip().endswith("<think>") else ""
+        if think_prefix:
+            yield think_prefix
+        for cumulative in self.generate_stream(
             formatted_prompt,
             temperature,
             top_p,
@@ -992,7 +1008,8 @@ def _generate_chat_response_inner(
             repetition_penalty,
             cancel_event = cancel_event,
             _adapter_state = _adapter_state,
-        )
+        ):
+            yield think_prefix + cumulative
 
     def _generate_vision_response(
         self,