diff --git a/.secrets.baseline b/.secrets.baseline
index f93f324a6..4bd3270a7 100644
--- a/.secrets.baseline
+++ b/.secrets.baseline
@@ -151,7 +151,7 @@
         "filename": "atroposlib/envs/eval.py",
         "hashed_secret": "829c3804401b0727f70f73d4415e162400cbe57b",
         "is_verified": false,
-        "line_number": 218
+        "line_number": 225
       }
     ],
     "atroposlib/tests/test_reasoning_models.py": [
diff --git a/atroposlib/envs/base.py b/atroposlib/envs/base.py
index 3d3b6c207..11499cad6 100644
--- a/atroposlib/envs/base.py
+++ b/atroposlib/envs/base.py
@@ -791,6 +791,30 @@ async def evaluate_log(
                     writer.write(sample)
             logger.info("Evaluation samples saved to %s", samples_filepath)
 
+            try:
+                from atroposlib.frontend.jsonl2html import generate_eval_html
+
+                generate_eval_html(samples_filepath)
+            except Exception as e:
+                logger.warning("Failed to generate eval HTML viewer: %s", e)
+
+    def log_eval_sample(self, sample):
+        """Stream-write a single eval sample to samples.jsonl.
+
+        Lazy-initializes the writer on first call. Use this inside evaluate()
+        to write samples as they complete rather than batching at the end.
+        If using this, omit the samples= parameter from evaluate_log().
+        """
+        if self._eval_sample_writer is None:
+            if self.config.data_dir_to_save_evals is None:
+                return
+            os.makedirs(self.config.data_dir_to_save_evals, exist_ok=True)
+            self._eval_samples_path = os.path.join(
+                self.config.data_dir_to_save_evals, "samples.jsonl"
+            )
+            self._eval_sample_writer = jsonlines.open(self._eval_samples_path, "w")
+        self._eval_sample_writer.write(sample)
+
     @retry(
         stop=stop_after_attempt(3),
         wait=wait_random_exponential(multiplier=1, max=10),
@@ -1336,8 +1360,32 @@ async def _run_evaluate(self):
         """
         Internal method to run evaluation with proper setup.
         """
+        self._eval_sample_writer = None
+        self._eval_samples_path = None
         await self.setup()
-        await self.evaluate()
+        try:
+            await self.evaluate()
+        finally:
+            # Close streaming eval sample writer if it was used
+            if self._eval_sample_writer is not None:
+                self._eval_sample_writer.close()
+                if self._eval_samples_path:
+                    try:
+                        from atroposlib.frontend.jsonl2html import generate_eval_html
+
+                        generate_eval_html(self._eval_samples_path)
+                    except Exception as e:
+                        logger.warning("Failed to generate eval HTML: %s", e)
+            # Close JSONL trajectory writer if it was used
+            if self.jsonl_writer is not None:
+                self.jsonl_writer.close()
+                if self.config.data_path_to_save_groups:
+                    try:
+                        from atroposlib.frontend.jsonl2html import generate_html
+
+                        generate_html(self.config.data_path_to_save_groups)
+                    except Exception as e:
+                        logger.warning("Failed to generate trajectory HTML: %s", e)
 
     @classmethod
     def cli(cls):
@@ -1928,6 +1976,10 @@ def run(self) -> None:
                 env_config_dict_base = default_env_config_from_init.model_dump()
                 # Apply specific overrides for evaluate mode that are generally useful
                 env_config_dict_base["use_wandb"] = True
+                if env_config_dict_base.get("data_dir_to_save_evals") is None:
+                    env_config_dict_base["data_dir_to_save_evals"] = (
+                        f"eval_results/{cls.name or 'eval'}"
+                    )
 
                 env_config_dict = merge_dicts(
                     env_config_dict_base,  # `config_init` defaults with evaluate adjustments
diff --git a/atroposlib/envs/eval.py b/atroposlib/envs/eval.py
index 21090b03f..0760c128a 100644
--- a/atroposlib/envs/eval.py
+++ b/atroposlib/envs/eval.py
@@ -104,6 +104,13 @@ def evaluate_log(
                 writer.write(sample)
         print(f"Evaluation samples saved to {samples_filepath}")
 
+        try:
+            from atroposlib.frontend.jsonl2html import generate_eval_html
+
+            generate_eval_html(samples_filepath)
+        except Exception as e:
+            print(f"Warning: Failed to generate eval HTML viewer: {e}")
+
 
 class EvalBase(ABC):
     """ """
diff --git a/atroposlib/frontend/jsonl2html.py b/atroposlib/frontend/jsonl2html.py
index 264dbb64a..57e8c9741 100644
--- a/atroposlib/frontend/jsonl2html.py
+++ b/atroposlib/frontend/jsonl2html.py
@@ -117,6 +117,117 @@ def create_html_for_group(group_data, index):
     return group_html
 
 
+# --- Eval Sample Conversion ---
+
+
+def _eval_sample_to_viewable(sample):
+    """Convert a single eval sample dict to {messages, scores} format for the HTML viewer."""
+    # Extract score
+    score = sample.get("score")
+    if score is None:
+        is_correct = sample.get("is_correct")
+        if is_correct is not None:
+            score = 1.0 if is_correct else 0.0
+        else:
+            grade = sample.get("grade", "")
+            score = 1.0 if grade == "CORRECT" else 0.0
+
+    # Build conversation from available fields
+    if "messages" in sample and isinstance(sample["messages"], list):
+        conversation = sample["messages"]
+    else:
+        conversation = []
+        question = sample.get("question") or sample.get("problem") or ""
+        if question:
+            conversation.append({"role": "user", "content": str(question)})
+
+        response = sample.get("model_response") or sample.get("response") or ""
+        if response:
+            conversation.append({"role": "assistant", "content": str(response)})
+
+        gold = sample.get("gold_answer") or sample.get("answer") or ""
+        if gold:
+            conversation.append({"role": "system", "content": f"[Gold Answer]: {gold}"})
+
+    if not conversation:
+        return None
+
+    return {"messages": [conversation], "scores": [score]}
+
+
+def generate_eval_html(input_path, output_path=None):
+    """Generate an HTML viewer from eval-format samples.jsonl.
+
+    Each line is a flat dict with task-specific fields (question, model_response, score, etc.).
+    Converts them to the {messages, scores} format used by the existing HTML template.
+    """
+    input_filepath = Path(input_path)
+    if not input_filepath.is_file():
+        print(f"Error: Input file not found: {input_filepath}", file=sys.stderr)
+        return
+
+    if output_path is None:
+        output_filepath = input_filepath.with_suffix(".html")
+    else:
+        output_filepath = Path(output_path)
+
+    output_filepath.parent.mkdir(parents=True, exist_ok=True)
+
+    try:
+        with open(TEMPLATE_FILE, "r", encoding="utf-8") as f_template:
+            html_template_content = f_template.read()
+    except FileNotFoundError:
+        print(f"Error: Template file not found: {TEMPLATE_FILE}", file=sys.stderr)
+        return
+
+    all_groups_html = []
+    group_index = 0
+    with open(input_filepath, "r", encoding="utf-8") as f:
+        for line_num, line in enumerate(f, 1):
+            line = line.strip()
+            if not line:
+                continue
+            try:
+                sample = json.loads(line)
+            except json.JSONDecodeError:
+                print(
+                    f"Warning: Skipping line {line_num}. Invalid JSON.",
+                    file=sys.stderr,
+                )
+                continue
+
+            viewable = _eval_sample_to_viewable(sample)
+            if viewable is None:
+                continue
+
+            group_html = create_html_for_group(viewable, group_index)
+            if group_html:
+                all_groups_html.append(group_html)
+                group_index += 1
+
+    if not all_groups_html:
+        print("Warning: No valid eval samples to render.", file=sys.stderr)
+        groups_content = "<p>No data to display.</p>"
+    else:
+        groups_content = "\n".join(all_groups_html)
+
+    title = f"Eval Results - {input_filepath.name}"
+    try:
+        final_html = html_template_content.format(
+            title=html.escape(title), groups_html=groups_content
+        )
+    except KeyError as e:
+        print(
+            f"Error: Template missing placeholder: {{{e}}}",
+            file=sys.stderr,
+        )
+        return
+
+    with open(output_filepath, "w", encoding="utf-8") as f:
+        f.write(final_html)
+    print(f"Generated eval HTML viewer: {output_filepath.absolute()}")
+
+
 # --- Main Function ---
 
 
diff --git a/environments/gsm8k_server.py b/environments/gsm8k_server.py
index 87823526e..09eca7c5b 100644
--- a/environments/gsm8k_server.py
+++ b/environments/gsm8k_server.py
@@ -189,17 +189,18 @@ async def rollout_and_score_eval(self, question: str, answer: str) -> dict:
     async def evaluate(self, *args, **kwargs):
         start_time = time.time()
 
-        eval_tasks = []
-        for item in self.test:
-            eval_tasks.append(
-                self.rollout_and_score_eval(item["question"], item["gold_answer"])
+        async def rollout_and_log(item):
+            result = await self.rollout_and_score_eval(
+                item["question"], item["gold_answer"]
             )
+            if result is not None:
+                self.log_eval_sample(result.get("sample", result))
+            return result
+
+        eval_tasks = [rollout_and_log(item) for item in self.test]
         results = await tqdm_asyncio.gather(*eval_tasks)
 
-        # Extract scores and samples
         scores = [result["score"] for result in results]
-        samples = [result["sample"] for result in results]
-
         percent_correct = sum(scores) / len(scores)
 
         end_time = time.time()
@@ -207,14 +208,8 @@ async def evaluate(self, *args, **kwargs):
         # Add to existing metrics for wandb
         self.eval_metrics.append(("eval/percent_correct", percent_correct))
 
-        # Log evaluation results
-        eval_metrics = {
-            "eval/percent_correct": percent_correct,
-        }
-
         await self.evaluate_log(
-            metrics=eval_metrics,
-            samples=samples,
+            metrics={"eval/percent_correct": percent_correct},
             start_time=start_time,
             end_time=end_time,
             generation_parameters={