diff --git a/test/registered/spec/test_ngram_speculative_decoding.py b/test/registered/spec/test_ngram_speculative_decoding.py
index 690e6ec45f8f..f80b1e646dea 100644
--- a/test/registered/spec/test_ngram_speculative_decoding.py
+++ b/test/registered/spec/test_ngram_speculative_decoding.py
@@ -1,6 +1,3 @@
-import json
-import os
-import tempfile
 import unittest
 
 import requests
@@ -35,21 +32,6 @@
     0.8,
 ]
 
-EXTERNAL_SAM_CORPUS_RECORDS = [
-    "The capital of France is Paris.",
-    "The answer to life, the universe, and everything is 42.",
-]
-
-
-def _safe_remove(path: str):
-    if os.path.exists(path):
-        os.remove(path)
-
-
-def _safe_kill_process(process):
-    if process is not None and process.poll() is None:
-        kill_process_tree(process.pid)
-
 
 class TestNgramSpeculativeDecodingBase(GSM8KMixin, CustomTestCase):
     model = DEFAULT_TARGET_MODEL_NGRAM
@@ -91,7 +73,78 @@ def get_server_args(cls):
 class TestNgramSpeculativeDecodingFlashinfer(TestNgramSpeculativeDecodingBase):
     @classmethod
     def get_server_args(cls):
-        return DEFAULT_SERVER_ARGS + ["--attention-backend", "flashinfer"]
+        return DEFAULT_SERVER_ARGS + [
+            "--attention-backend",
+            "flashinfer",
+            "--speculative-ngram-external-sam-budget",
+            "8",
+        ]
+
+    def test_output_as_corpus_boosts_accept_length(self):
+        """Baseline → HTTP add corpus → verify accept length boost."""
+        prompts = [
+            "The capital of France is",
+            "In mathematics, the Pythagorean theorem states that",
+            "The speed of light in a vacuum is approximately",
+            "Water boils at a temperature of",
+            "The largest planet in our solar system is",
+        ]
+        max_new_tokens = 128
+        num_rounds = 3
+
+        def generate_batch():
+            outputs = []
+            for prompt in prompts:
+                resp = requests.post(
+                    self.base_url + "/generate",
+                    json={
+                        "text": prompt,
+                        "sampling_params": {
+                            "temperature": 0,
+                            "max_new_tokens": max_new_tokens,
+                        },
+                    },
+                    timeout=120,
+                )
+                self.assertEqual(resp.status_code, 200, resp.text)
+                outputs.append(resp.json()["text"])
+            return outputs
+
+        def get_accept_length():
+            info = requests.get(self.base_url + "/get_server_info").json()
+            return info["internal_states"][0]["avg_spec_accept_length"]
+
+        # Phase 1: baseline — no SAM corpus loaded, only trie
+        generated_outputs = []
+        for _ in range(num_rounds):
+            generated_outputs = generate_batch()
+        baseline_accept_len = get_accept_length()
+        print(f"\n  Baseline accept length (no SAM): {baseline_accept_len:.2f}")
+
+        # Flush cache so phase 2 starts clean
+        requests.post(self.base_url + "/flush_cache", timeout=30)
+
+        # Phase 2: add generated outputs as corpus via HTTP API
+        resp = requests.post(
+            self.base_url + "/add_external_corpus",
+            json={"corpus_id": "bench", "documents": generated_outputs},
+            timeout=120,
+        )
+        self.assertEqual(resp.status_code, 200, resp.text)
+        self.assertTrue(resp.json()["success"], resp.json().get("message"))
+
+        for _ in range(num_rounds):
+            generate_batch()
+        sam_accept_len = get_accept_length()
+        print(f"  SAM accept length (output as corpus): {sam_accept_len:.2f}")
+        print(f"  Speedup: {sam_accept_len / baseline_accept_len:.2f}x")
+
+        self.assertGreater(
+            sam_accept_len,
+            baseline_accept_len * 2.0,
+            f"SAM accept length ({sam_accept_len:.2f}) should be at least 2x "
+            f"baseline ({baseline_accept_len:.2f}) when corpus matches output",
+        )
 
 
 class TestNgramSpeculativeDecodingPaged(TestNgramSpeculativeDecodingBase):
@@ -106,66 +159,5 @@ def get_server_args(cls):
         ]
 
 
-class TestNgramExternalSamSmoke(CustomTestCase):
-    model = DEFAULT_TARGET_MODEL_NGRAM
-    base_url = DEFAULT_URL_FOR_TEST
-    attention_backends = ("triton", "flashinfer")
-
-    def get_server_args(self, attention_backend):
-        return DEFAULT_SERVER_ARGS + [
-            "--attention-backend",
-            attention_backend,
-            "--speculative-ngram-external-corpus-path",
-            self.external_corpus_path,
-            "--speculative-ngram-external-sam-budget",
-            "4",
-        ]
-
-    @classmethod
-    def setUpClass(cls):
-        envs.SGLANG_JIT_DEEPGEMM_PRECOMPILE.set(False)
-        envs.SGLANG_ENABLE_JIT_DEEPGEMM.set(False)
-        with tempfile.NamedTemporaryFile(
-            mode="w", suffix=".jsonl", prefix="ngram_external_sam_", delete=False
-        ) as f:
-            for record in EXTERNAL_SAM_CORPUS_RECORDS:
-                f.write(json.dumps(record))
-                f.write("\n")
-            cls.external_corpus_path = f.name
-        cls.addClassCleanup(_safe_remove, cls.external_corpus_path)
-
-    def _run_external_sam_smoke(self, attention_backend):
-        process = popen_launch_server(
-            self.model,
-            self.base_url,
-            timeout=DEFAULT_TIMEOUT_FOR_SERVER_LAUNCH,
-            other_args=self.get_server_args(attention_backend),
-        )
-        try:
-            response = requests.post(
-                self.base_url + "/generate",
-                json={
-                    "text": "The capital of France is",
-                    "sampling_params": {
-                        "temperature": 0,
-                        "max_new_tokens": 8,
-                    },
-                },
-                timeout=120,
-            )
-            self.assertEqual(response.status_code, 200, response.text)
-            response_json = response.json()
-            self.assertIn("text", response_json)
-            self.assertIn("meta_info", response_json)
-            self.assertGreater(response_json["meta_info"]["completion_tokens"], 0)
-        finally:
-            _safe_kill_process(process)
-
-    def test_generate_with_external_sam(self):
-        for attention_backend in self.attention_backends:
-            with self.subTest(attention_backend=attention_backend):
-                self._run_external_sam_smoke(attention_backend)
-
-
 if __name__ == "__main__":
     unittest.main()