fix(transcription): normalize chat-style apiBase to audio endpoint (#3637)

nanobot/providers/transcription.py

@@ -7,6 +7,25 @@ from pathlib import Path
 import httpx
 from loguru import logger
 
+_TRANSCRIPTIONS_PATH = "audio/transcriptions"
+
+
+def _resolve_transcription_url(api_base: str | None, default_url: str) -> str:
+    """Resolve the full transcription endpoint URL.
+
+    Accepts either a chat-style base (e.g. ``https://api.groq.com/openai/v1``)
+    or a complete URL already ending in ``/audio/transcriptions``. A chat-style
+    base — the form users naturally copy from their LLM provider config — gets
+    the path appended instead of being POSTed verbatim and 404ing (#3637).
+    """
+    if not api_base:
+        return default_url
+    base = api_base.rstrip("/")
+    if base.endswith(_TRANSCRIPTIONS_PATH):
+        return base
+    return f"{base}/{_TRANSCRIPTIONS_PATH}"
+
+
 # Up to 3 retries (4 attempts total) with exponential backoff on transient
 # failures. Whisper endpoints occasionally return 502/503 under load, and
 # mobile-network transcription callers hit sporadic connect/read errors.
@@ -127,12 +146,12 @@ class OpenAITranscriptionProvider:
         language: str | None = None,
     ):
         self.api_key = api_key or os.environ.get("OPENAI_API_KEY")
-        self.api_url = (
-            api_base
-            or os.environ.get("OPENAI_TRANSCRIPTION_BASE_URL")
-            or "https://api.openai.com/v1/audio/transcriptions"
+        self.api_url = _resolve_transcription_url(
+            api_base or os.environ.get("OPENAI_TRANSCRIPTION_BASE_URL"),
+            "https://api.openai.com/v1/audio/transcriptions",
         )
         self.language = language or None
+        logger.debug("OpenAI transcription endpoint: {}", self.api_url)
 
     async def transcribe(self, file_path: str | Path) -> str:
         if not self.api_key:
@@ -166,12 +185,12 @@ class GroqTranscriptionProvider:
         language: str | None = None,
     ):
         self.api_key = api_key or os.environ.get("GROQ_API_KEY")
-        self.api_url = (
-            api_base
-            or os.environ.get("GROQ_BASE_URL")
-            or "https://api.groq.com/openai/v1/audio/transcriptions"
+        self.api_url = _resolve_transcription_url(
+            api_base or os.environ.get("GROQ_BASE_URL"),
+            "https://api.groq.com/openai/v1/audio/transcriptions",
         )
         self.language = language or None
+        logger.debug("Groq transcription endpoint: {}", self.api_url)
 
     async def transcribe(self, file_path: str | Path) -> str:
         """

tests/providers/test_transcription.py

@@ -8,7 +8,11 @@ from unittest.mock import AsyncMock, patch
 import httpx
 import pytest
 
-from nanobot.providers.transcription import GroqTranscriptionProvider, OpenAITranscriptionProvider
+from nanobot.providers.transcription import (
+    GroqTranscriptionProvider,
+    OpenAITranscriptionProvider,
+    _resolve_transcription_url,
+)
 
 
 @pytest.fixture
@@ -290,3 +294,37 @@ async def test_retries_on_every_advertised_transient_exception(
         result = await provider.transcribe(audio_file)
     assert result == "recovered"
     assert post.await_count == 2
+
+
+# ---------------------------------------------------------------------------
+# apiBase normalization (#3637): a chat-style base must not be POSTed verbatim
+# ---------------------------------------------------------------------------
+
+
+def test_resolve_transcription_url_falls_back_to_default() -> None:
+    default = "https://api.openai.com/v1/audio/transcriptions"
+    assert _resolve_transcription_url(None, default) == default
+    assert _resolve_transcription_url("", default) == default
+
+
+def test_resolve_transcription_url_appends_path_to_chat_style_base() -> None:
+    assert (
+        _resolve_transcription_url("https://api.groq.com/openai/v1", "https://x/audio/transcriptions")
+        == "https://api.groq.com/openai/v1/audio/transcriptions"
+    )
+    # Trailing slash must not produce a doubled separator.
+    assert (
+        _resolve_transcription_url("https://api.groq.com/openai/v1/", "https://x/audio/transcriptions")
+        == "https://api.groq.com/openai/v1/audio/transcriptions"
+    )
+
+
+def test_resolve_transcription_url_keeps_full_endpoint() -> None:
+    full = "https://api.groq.com/openai/v1/audio/transcriptions"
+    assert _resolve_transcription_url(full, "https://x/audio/transcriptions") == full
+
+
+def test_groq_provider_normalizes_chat_style_api_base() -> None:
+    """Regression for #3637: apiBase set to the v1 base resolves to the audio endpoint."""
+    provider = GroqTranscriptionProvider(api_key="gsk-test", api_base="https://api.groq.com/openai/v1")
+    assert provider.api_url == "https://api.groq.com/openai/v1/audio/transcriptions"