diff --git a/examples/rec_gsm8k/README.md b/examples/rec_gsm8k/README.md
index b3a5673463..af1e71b086 100644
--- a/examples/rec_gsm8k/README.md
+++ b/examples/rec_gsm8k/README.md
@@ -83,11 +83,10 @@ algorithm:
     epsilon_high: 0.2
     clip_mode: "one-side"
     weight: "none"
-    temp: 1.0
-    regularizer: "none"
-    regularizer_coef: 0.0
   advantage_fn_args:
     std_normalize: false
+  kl_loss_fn_args:
+    kl_coef: 0.0
 ```
 
 **REC-OneSide-IS:**
@@ -100,11 +99,42 @@ algorithm:
     epsilon_high: 0.2
     clip_mode: "one-side"
     weight: "importance_sampling"
-    temp: 1.0
-    regularizer: "none"
-    regularizer_coef: 0.0
   advantage_fn_args:
     std_normalize: false
+  kl_loss_fn_args:
+    kl_coef: 0.0
+```
+
+**REC-GSPO-NoIS:**
+
+```
+algorithm:
+  algorithm_type: rec
+  policy_loss_fn_args:
+    epsilon_low: 3e-4
+    epsilon_high: 4e-4
+    clip_mode: "gspo-one-side"
+    weight: "none"
+  advantage_fn_args:
+    std_normalize: false
+  kl_loss_fn_args:
+    kl_coef: 0.0
+```
+
+**REC-GSPO-IS:**
+
+```
+algorithm:
+  algorithm_type: rec
+  policy_loss_fn_args:
+    epsilon_low: 3e-4
+    epsilon_high: 4e-4
+    clip_mode: "gspo-one-side"
+    weight: "gspo_importance_sampling"
+  advantage_fn_args:
+    std_normalize: false
+  kl_loss_fn_args:
+    kl_coef: 0.0
 ```
 
 **REC-TwoSide-IS:**
@@ -122,6 +152,8 @@ algorithm:
     regularizer_coef: 0.0
   advantage_fn_args:
     std_normalize: false
+  kl_loss_fn_args:
+    kl_coef: 0.0
 ```
 
 **REC-Ring-NoIS:**
@@ -141,6 +173,8 @@ algorithm:
     regularizer_coef: 0.0
   advantage_fn_args:
     std_normalize: false
+  kl_loss_fn_args:
+    kl_coef: 0.0
 ```
 
 ### REP family
@@ -159,6 +193,8 @@ algorithm:
     regularizer_coef: 0.1
   advantage_fn_args:
     std_normalize: false
+  kl_loss_fn_args:
+    kl_coef: 0.0
 ```
 
 
@@ -174,6 +210,8 @@ algorithm:
     regularizer_coef: 0.1
   advantage_fn_args:
     std_normalize: false
+  kl_loss_fn_args:
+    kl_coef: 0.0
 ```
 
 ### RED family
@@ -191,6 +229,8 @@ algorithm:
   advantage_fn_args:
     std_normalize: false
     drop: "balance"
+  kl_loss_fn_args:
+    kl_coef: 0.0
 ```
 
 
@@ -206,6 +246,8 @@ algorithm:
     temp: 1.0
   advantage_fn_args:
     std_normalize: false
+  kl_loss_fn_args:
+    kl_coef: 0.0
 ```
 
 ## Citation
diff --git a/examples/rec_gsm8k/gsm8k.yaml b/examples/rec_gsm8k/gsm8k.yaml
index c0dd6a3f07..209b0dfe05 100644
--- a/examples/rec_gsm8k/gsm8k.yaml
+++ b/examples/rec_gsm8k/gsm8k.yaml
@@ -16,16 +16,15 @@ algorithm:
     epsilon_high: 0.2
     clip_mode: "one-side"
     weight: "none"
-    temp: 1.0
-    regularizer: "none"
-    regularizer_coef: 0.0
   advantage_fn_args:
     std_normalize: false
+  kl_loss_fn_args:
+    kl_coef: 0.0
 cluster:
   node_num: 1
   gpu_per_node: 8
 buffer:
-  total_steps: 100
+  total_steps: 160
   batch_size: 96
   explorer_input:
     taskset:
diff --git a/trinity/algorithm/algorithm.py b/trinity/algorithm/algorithm.py
index cd8fce5f35..ebe5978a07 100644
--- a/trinity/algorithm/algorithm.py
+++ b/trinity/algorithm/algorithm.py
@@ -434,8 +434,8 @@ def default_config(cls) -> Dict:
             "policy_loss_fn": "rec",
             "advantage_fn": "rec",
             "kl_penalty_fn": "none",
-            "kl_loss_fn": "none",
-            "entropy_loss_fn": "none",
+            "kl_loss_fn": "k2",
+            "entropy_loss_fn": "default",
         }
 
 
diff --git a/trinity/algorithm/policy_loss_fn/gspo_policy_loss.py b/trinity/algorithm/policy_loss_fn/gspo_policy_loss.py
index 5b30a6a6af..7527603e03 100644
--- a/trinity/algorithm/policy_loss_fn/gspo_policy_loss.py
+++ b/trinity/algorithm/policy_loss_fn/gspo_policy_loss.py
@@ -30,6 +30,15 @@ def __init__(
         if _clip_range_high is None:
             raise ValueError("Either clip_range or clip_range_high must be specified.")
         self.clip_range_high = _clip_range_high
+
+        if loss_agg_mode != "seq-mean-token-mean":
+            from trinity.utils.log import get_logger
+
+            logger = get_logger(__name__)
+            logger.warning(
+                f"The original GSPO paper requires loss_agg_mode to be 'seq-mean-token-mean', but the current setting is '{loss_agg_mode}'."
+            )
+            # loss_agg_mode = "seq-mean-token-mean"
         self.loss_agg_mode = loss_agg_mode
 
     def __call__(  # type: ignore
diff --git a/trinity/algorithm/policy_loss_fn/rec_policy_loss.py b/trinity/algorithm/policy_loss_fn/rec_policy_loss.py
index 5d7c547e62..6f00ac86c1 100644
--- a/trinity/algorithm/policy_loss_fn/rec_policy_loss.py
+++ b/trinity/algorithm/policy_loss_fn/rec_policy_loss.py
@@ -6,7 +6,7 @@
 import torch
 
 from trinity.algorithm.policy_loss_fn.policy_loss_fn import PolicyLossFn
-from trinity.algorithm.utils import masked_mean
+from trinity.algorithm.utils import aggregate_loss, masked_mean
 
 
 class RECPolicyLossFn(PolicyLossFn):
@@ -41,6 +41,7 @@ def __init__(
         assert self.clip_mode in [
             "none",
             "one-side",
+            "gspo-one-side",
             "two-side",
             "ring",
         ], f"Invalid clip_mode: {self.clip_mode}"
@@ -48,6 +49,7 @@ def __init__(
         assert self.weight in [
             "none",
             "importance_sampling",
+            "gspo_importance_sampling",
             "advantage",
         ], f"Invalid weight: {self.weight}"
 
@@ -71,8 +73,8 @@ def __call__(  # type: ignore
         **kwargs,
     ) -> Tuple[torch.Tensor, Dict]:
         """Calculate REC loss."""
-        # token-wise
-        ratio = torch.exp(logprob - old_logprob).detach()
+
+        ratio = torch.exp(logprob - old_logprob).detach()  # token-wise prob ratio
 
         # clipping
         if self.clip_mode == "two-side":
@@ -81,6 +83,16 @@ def __call__(  # type: ignore
             is_in_range = (ratio <= (1 + self.epsilon_high)) * (advantages >= 0) + (
                 advantages <= 0
             ) * (ratio >= (1 - self.epsilon_low))
+        elif self.clip_mode == "gspo-one-side":
+            mean_log_prob_diff = masked_mean(
+                logprob - old_logprob, action_mask, axis=-1
+            ).detach()  # [batch_size]
+            normalized_seq_ratio = torch.exp(mean_log_prob_diff).unsqueeze(-1)  # [batch_size, 1]
+            is_in_range = (normalized_seq_ratio <= (1 + self.epsilon_high)) * (advantages >= 0) + (
+                normalized_seq_ratio >= (1 - self.epsilon_low)
+            ) * (
+                advantages <= 0
+            )  # [batch_size, seq_len]
         elif self.clip_mode == "ring":
             is_in_range = (
                 (ratio >= (1 - self.epsilon_low)) * (ratio <= (1 + self.epsilon_high))
@@ -93,6 +105,8 @@ def __call__(  # type: ignore
 
         if self.weight == "importance_sampling":
             advantages = advantages * ratio  # importance sampling
+        elif self.weight == "gspo_importance_sampling":
+            advantages = advantages * normalized_seq_ratio
         elif self.weight == "advantage":
             weight = torch.exp(advantages / self.temp)
             advantages = advantages * weight  # advantage weighting  (unnormalized version)
@@ -107,7 +121,15 @@ def __call__(  # type: ignore
             regularizer_losses = self.regularizer_coef * (logprob - old_logprob).square()
             pg_losses = pg_losses + regularizer_losses
 
-        pg_loss = masked_mean(pg_losses, action_mask)
+        if self.clip_mode == "gspo-one-side":
+            # [EXPERIMENTAL] specialized for gspo-style rec variant for now
+            pg_loss = aggregate_loss(
+                values=pg_losses,
+                mask=action_mask,
+                loss_agg_mode="seq-mean-token-mean",
+            )
+        else:
+            pg_loss = masked_mean(pg_losses, action_mask)
 
         pg_clipfrac = masked_mean(is_clipped_mask.float(), action_mask)
         metrics = {