diff --git a/nanobot/providers/transcription.py b/nanobot/providers/transcription.py
index 9df6a6a8d..426f0088e 100644
--- a/nanobot/providers/transcription.py
+++ b/nanobot/providers/transcription.py
@@ -20,6 +20,7 @@ from loguru import logger
 
 _CHAT_COMPLETIONS_PATH = "chat/completions"
 _TRANSCRIPTIONS_PATH = "audio/transcriptions"
+_STEPFUN_ASR_PATH = "audio/asr/sse"
 _ASSEMBLYAI_DEFAULT_API_BASE = "https://api.assemblyai.com/v2"
 _ASSEMBLYAI_POLL_ATTEMPTS = 60
 _ASSEMBLYAI_POLL_INTERVAL_S = 2.0
@@ -72,6 +73,13 @@ def _resolve_api_path(api_base: str | None, default_base: str, path: str) -> str
     return f"{base}/{path.lstrip('/')}"
 
 
+def _resolve_stepfun_asr_url(api_base: str | None) -> str:
+    base = (api_base or "https://api.stepfun.com/v1").rstrip("/")
+    if base.endswith(_STEPFUN_ASR_PATH):
+        return base
+    return f"{base}/{_STEPFUN_ASR_PATH}"
+
+
 def _audio_mime_type(path: Path) -> str:
     return (
         _AUDIO_MIME_OVERRIDES.get(path.suffix.lower())
@@ -401,14 +409,15 @@ async def _post_stepfun_asr_with_retry(
                         _MAX_RETRIES + 1,
                     )
                     return ""
-            except httpx.HTTPStatusError:
-                if attempt < _MAX_RETRIES:
+            except httpx.HTTPStatusError as e:
+                if e.response.status_code in _RETRYABLE_STATUS and attempt < _MAX_RETRIES:
                     await asyncio.sleep(_BACKOFF_S[attempt])
                     continue
-                logger.exception(
-                    "{} transcription failed after {} attempts",
+                logger.error(
+                    "{} transcription HTTP {}{}",
                     provider_label,
-                    _MAX_RETRIES + 1,
+                    e.response.status_code,
+                    f" {e.response.reason_phrase}" if e.response.reason_phrase else "",
                 )
                 return ""
             except (httpx.RequestError, Exception):
@@ -792,10 +801,8 @@ class StepFunTranscriptionProvider:
         model: str | None = None,
     ):
         self.api_key = api_key or os.environ.get("STEPFUN_API_KEY")
-        # api_base is used verbatim; users can point to the Plan endpoint
-        # (https://api.stepfun.com/step_plan/v1/audio/asr/sse) or any
-        # compatible proxy.
-        self.api_url = api_base or self._DEFAULT_URL
+        # api_base accepts either a StepFun base URL or the full SSE endpoint.
+        self.api_url = _resolve_stepfun_asr_url(api_base)
         self.language = language or None
         self.model = model or "stepaudio-2.5-asr"
         logger.debug("StepFun transcription endpoint: {}", self.api_url)
diff --git a/tests/providers/test_stepfun_asr.py b/tests/providers/test_stepfun_asr.py
index 3056fad01..4074f0a7e 100644
--- a/tests/providers/test_stepfun_asr.py
+++ b/tests/providers/test_stepfun_asr.py
@@ -4,6 +4,7 @@ from __future__ import annotations
 
 import json
 from pathlib import Path
+from typing import Any
 from unittest.mock import AsyncMock, MagicMock, patch
 
 import httpx
@@ -43,6 +44,14 @@ def test_stepfun_api_base_overrides_url() -> None:
     assert provider.api_url == "https://api.stepfun.com/step_plan/v1/audio/asr/sse"
 
 
+def test_stepfun_api_base_appends_asr_path() -> None:
+    provider = StepFunTranscriptionProvider(
+        api_key="sk-test",
+        api_base="https://api.stepfun.com/step_plan/v1",
+    )
+    assert provider.api_url == "https://api.stepfun.com/step_plan/v1/audio/asr/sse"
+
+
 def test_stepfun_custom_model() -> None:
     provider = StepFunTranscriptionProvider(api_key="sk-test", model="stepaudio-2-asr-pro")
     assert provider.model == "stepaudio-2-asr-pro"
@@ -229,18 +238,18 @@ async def test_sse_empty_text_done_returns_empty(audio_file: Path) -> None:
 
 
 @pytest.mark.asyncio
-async def test_401_returns_empty_after_retries(audio_file: Path) -> None:
-    """401 is not in the retryable set but HTTPStatusError still triggers
-    the retry loop; all attempts exhaust and return ""."""
+async def test_401_returns_empty_without_retry(audio_file: Path) -> None:
+    """401 is not retryable; bad credentials should fail immediately."""
     stream_cm = _make_stream_cm(401, [])
+    sleep = AsyncMock()
 
     provider = StepFunTranscriptionProvider(api_key="sk-test")
-    with patch("httpx.AsyncClient.stream", stream_cm), patch(
-        "asyncio.sleep", AsyncMock()
-    ):
+    with patch("httpx.AsyncClient.stream", stream_cm), patch("asyncio.sleep", sleep):
         result = await provider.transcribe(audio_file)
 
     assert result == ""
+    assert stream_cm.call_count == 1
+    sleep.assert_not_awaited()
 
 
 @pytest.mark.asyncio