fix(multimodal): image OOM guard, Feishu post media extraction, vision fallback

- Add file size pre-check via stat() before read_bytes() to prevent OOM
  on oversized images/audio/video
- Fix _extract_post_content to extract media tags (file_key) from Feishu
  post messages so videos are no longer silently dropped
- Add supports_vision=False guard to downgrade images to text placeholders
- Add video_mime_compat() for video format validation
- Use full file path in content_text so model read_file works if needed
- Pass input_limits to AgentLoop in nanobot.py facade
- Deduplicate _MEDIA_PLACEHOLDER_TYPES from LLMProvider constant
- Remove unused _extract_post_text legacy wrapper
- Add 14 new tests covering vision fallback, count limits, video compat

nanobot/agent/context.py

@@ -2,6 +2,7 @@
 
 import base64
 import mimetypes
+import os
 import platform
 from pathlib import Path
 from typing import Any
@@ -16,6 +17,7 @@ from nanobot.utils.helpers import (
     current_time_str,
     detect_audio_mime,
     detect_image_mime,
+    video_mime_compat,
 )
 from nanobot.utils.prompt_templates import render_template
 
@@ -33,6 +35,18 @@ class ContextBuilder:
         self.skills = SkillsLoader(workspace)
         self.input_limits = input_limits or InputLimitsConfig()
 
+    @staticmethod
+    def _file_size_ok(p: Path, max_bytes: int) -> bool | None:
+        """Check file size via stat without reading into memory.
+
+        Returns True if size is within limit, False if oversized,
+        None if file cannot be stat'd (caller should try read_bytes instead).
+        """
+        try:
+            return os.stat(p).st_size <= max_bytes
+        except OSError:
+            return None
+
     def build_system_prompt(self, skill_names: list[str] | None = None) -> str:
         """Build the system prompt from identity, bootstrap files, memory, and skills."""
         parts = [self._get_identity()]
@@ -171,7 +185,8 @@ class ContextBuilder:
             text: The user text message.
             media: List of file paths to media files.
             supports_vision: True=model supports images, False=use placeholder,
-                             None=unconfigured (send images as before).
+                             None=unconfigured (send images as before, let
+                             provider/retry handle degradation).
             supports_audio: True=model supports native audio, False/None=skip
                             (channel layer already transcribed).
             supports_video: True=model supports native video, False/None=use
@@ -210,15 +225,22 @@ class ContextBuilder:
         # Process images
         for path in image_media:
             p = Path(path)
+
+            # When explicitly marked as non-vision, downgrade to text placeholder
+            if supports_vision is False:
+                blocks.append({"type": "text", "text": f"[image: {p}]"})
+                continue
+
+            size_ok = self._file_size_ok(p, limits.max_input_image_bytes)
+            if size_ok is False:
+                size_mb = limits.max_input_image_bytes // (1024 * 1024)
+                notes.append(f"[Skipped image: file too large ({p.name}, limit {size_mb} MB)]")
+                continue
             try:
                 raw = p.read_bytes()
             except OSError:
                 notes.append(f"[Skipped image: unable to read ({p.name or path})]")
                 continue
-            if len(raw) > limits.max_input_image_bytes:
-                size_mb = limits.max_input_image_bytes // (1024 * 1024)
-                notes.append(f"[Skipped image: file too large ({p.name}, limit {size_mb} MB)]")
-                continue
             img_mime = detect_image_mime(raw[:32]) or mimetypes.guess_type(path)[0]
             if not img_mime or not img_mime.startswith("image/"):
                 notes.append(f"[Skipped image: unsupported or invalid image format ({p.name})]")
@@ -232,10 +254,24 @@ class ContextBuilder:
             p = Path(path)
             guessed_mime = mimetypes.guess_type(path)[0] or ""
             is_audio = guessed_mime.startswith("audio/")
+            is_video = guessed_mime.startswith("video/")
+
+            # Pre-check file size via stat to avoid reading oversized files into memory.
+            # Determine the relevant byte limit based on detected media type.
+            _size_limit = 0
+            if is_audio or is_video:
+                _size_limit = limits.max_input_audio_bytes if is_audio else limits.max_input_video_bytes
+            _stat_size_ok = self._file_size_ok(p, _size_limit) if _size_limit else None
+            if _stat_size_ok is False:
+                size_mb = _size_limit // (1024 * 1024)
+                label = "audio" if is_audio else "video"
+                notes.append(f"[Skipped {label}: file too large ({p.name}, limit {size_mb} MB)]")
+                continue
 
             try:
                 raw = p.read_bytes()
             except OSError:
+                notes.append(f"[Skipped file: unable to read ({p.name or path})]")
                 continue
 
             # Audio detection: by magic bytes or by filename
@@ -264,10 +300,9 @@ class ContextBuilder:
                     blocks.append({"type": "text", "text": f"[audio: {p}]"})
                 continue
 
-            # Video detection: by filename extension
-            is_video = guessed_mime.startswith("video/")
+            # Video detection (already classified above)
             if is_video:
-                if supports_video is True:
+                if supports_video is True and video_mime_compat(guessed_mime):
                     video_count += 1
                     if video_count > limits.max_input_videos:
                         if video_count == limits.max_input_videos + 1:

nanobot/agent/loop.py

@@ -632,7 +632,7 @@ class AgentLoop:
             metadata=meta,
         )
 
-    _MEDIA_PLACEHOLDER_TYPES = {"image_url", "input_audio", "video_url"}
+    _MEDIA_PLACEHOLDER_TYPES = LLMProvider._STRIP_MEDIA_TYPES
 
     def _sanitize_persisted_blocks(
         self,

nanobot/channels/feishu.py

@@ -169,19 +169,22 @@ def _extract_element_content(element: dict) -> list[str]:
     return parts
 
 
-def _extract_post_content(content_json: dict) -> tuple[str, list[str]]:
-    """Extract text and image keys from Feishu post (rich text) message.
+def _extract_post_content(content_json: dict) -> tuple[str, list[str], list[dict]]:
+    """Extract text and media info from Feishu post (rich text) message.
 
     Handles three payload shapes:
     - Direct:    {"title": "...", "content": [[...]]}
     - Localized: {"zh_cn": {"title": "...", "content": [...]}}
     - Wrapped:   {"post": {"zh_cn": {"title": "...", "content": [...]}}}
+
+    Returns (text, image_keys, media_items) where media_items is a list of
+    {"tag": "media", "file_key": "..."} dicts for video/file attachments.
     """
 
-    def _parse_block(block: dict) -> tuple[str | None, list[str]]:
+    def _parse_block(block: dict) -> tuple[str | None, list[str], list[dict]]:
         if not isinstance(block, dict) or not isinstance(block.get("content"), list):
-            return None, []
-        texts, images = [], []
+            return None, [], []
+        texts, images, medias = [], [], []
         if title := block.get("title"):
             texts.append(title)
         for row in block["content"]:
@@ -201,43 +204,36 @@ def _extract_post_content(content_json: dict) -> tuple[str, list[str]]:
                     texts.append(f"\n```{lang}\n{code_text}\n```\n")
                 elif tag == "img" and (key := el.get("image_key")):
                     images.append(key)
-        return (" ".join(texts).strip() or None), images
+                elif tag == "media" and el.get("file_key"):
+                    medias.append({"tag": "media", "file_key": el["file_key"]})
+        return (" ".join(texts).strip() or None), images, medias
 
     # Unwrap optional {"post": ...} envelope
     root = content_json
     if isinstance(root, dict) and isinstance(root.get("post"), dict):
         root = root["post"]
     if not isinstance(root, dict):
-        return "", []
+        return "", [], []
 
     # Direct format
     if "content" in root:
-        text, imgs = _parse_block(root)
-        if text or imgs:
-            return text or "", imgs
+        text, imgs, medias = _parse_block(root)
+        if text or imgs or medias:
+            return text or "", imgs, medias
 
     # Localized: prefer known locales, then fall back to any dict child
     for key in ("zh_cn", "en_us", "ja_jp"):
         if key in root:
-            text, imgs = _parse_block(root[key])
-            if text or imgs:
-                return text or "", imgs
+            text, imgs, medias = _parse_block(root[key])
+            if text or imgs or medias:
+                return text or "", imgs, medias
     for val in root.values():
         if isinstance(val, dict):
-            text, imgs = _parse_block(val)
-            if text or imgs:
-                return text or "", imgs
+            text, imgs, medias = _parse_block(val)
+            if text or imgs or medias:
+                return text or "", imgs, medias
 
-    return "", []
-
-
-def _extract_post_text(content_json: dict) -> str:
-    """Extract plain text from Feishu post (rich text) message content.
-
-    Legacy wrapper for _extract_post_content, returns only text.
-    """
-    text, _ = _extract_post_content(content_json)
-    return text
+    return "", [], []
 
 
 class FeishuConfig(Base):
@@ -1027,7 +1023,7 @@ class FeishuChannel(BaseChannel):
             file_path = media_dir / filename
             file_path.write_bytes(data)
             logger.debug("Downloaded {} to {}", msg_type, file_path)
-            return str(file_path), f"[{msg_type}: {filename}]"
+            return str(file_path), f"[{msg_type}: {file_path}]"
 
         return None, f"[{msg_type}: download failed]"
 
@@ -1067,7 +1063,7 @@ class FeishuChannel(BaseChannel):
             if msg_type == "text":
                 text = content_json.get("text", "").strip()
             elif msg_type == "post":
-                text, _ = _extract_post_content(content_json)
+                text, _, _ = _extract_post_content(content_json)
                 text = text.strip()
             else:
                 text = ""
@@ -1542,7 +1538,7 @@ class FeishuChannel(BaseChannel):
                     content_parts.append(text)
 
             elif msg_type == "post":
-                text, image_keys = _extract_post_content(content_json)
+                text, image_keys, media_items = _extract_post_content(content_json)
                 if text:
                     content_parts.append(text)
                 # Download images embedded in post
@@ -1553,6 +1549,14 @@ class FeishuChannel(BaseChannel):
                     if file_path:
                         media_paths.append(file_path)
                     content_parts.append(content_text)
+                # Download media (video/file) embedded in post
+                for media_item in media_items:
+                    file_path, content_text = await self._download_and_save_media(
+                        "media", media_item, message_id
+                    )
+                    if file_path:
+                        media_paths.append(file_path)
+                    content_parts.append(content_text)
 
             elif msg_type in ("image", "audio", "file", "media"):
                 file_path, content_text = await self._download_and_save_media(

nanobot/nanobot.py

@@ -78,6 +78,7 @@ class Nanobot:
             provider_retry_mode=defaults.provider_retry_mode,
             web_config=config.tools.web,
             exec_config=config.tools.exec,
+            input_limits=config.tools.input_limits,
             restrict_to_workspace=config.tools.restrict_to_workspace,
             mcp_servers=config.tools.mcp_servers,
             timezone=defaults.timezone,

nanobot/providers/base.py

@@ -369,7 +369,7 @@ class LLMProvider(ABC):
 
     @staticmethod
     def _strip_media_content(messages: list[dict[str, Any]]) -> list[dict[str, Any]] | None:
-        """Replace image_url and input_audio blocks with text placeholders.
+        """Replace image_url, input_audio, and video_url blocks with text placeholders.
 
         Returns None if no media blocks were found (no changes needed).
         """

nanobot/utils/helpers.py

@@ -93,6 +93,20 @@ def audio_format_for_api(mime: str) -> str:
     return _AUDIO_FORMAT_MAP.get(mime, mime.split("/")[-1])
 
 
+# Video formats commonly supported by LLM APIs (data URI inline)
+_VIDEO_MIME_COMPAT = {
+    "video/mp4", "video/quicktime", "video/x-m4v",
+    "video/webm", "video/x-matroska",
+}
+
+
+def video_mime_compat(mime: str | None) -> bool:
+    """Check if the video MIME is in the commonly-supported set."""
+    if not mime:
+        return False
+    return mime in _VIDEO_MIME_COMPAT
+
+
 def build_image_content_blocks(raw: bytes, mime: str, path: str, label: str) -> list[dict[str, Any]]:
     """Build native image blocks plus a short text label."""
     b64 = base64.b64encode(raw).decode()

tests/channels/test_feishu_post_content.py

@@ -27,10 +27,11 @@ def test_extract_post_content_supports_post_wrapper_shape() -> None:
         }
     }
 
-    text, image_keys = _extract_post_content(payload)
+    text, image_keys, media_items = _extract_post_content(payload)
 
     assert text == "日报 完成"
     assert image_keys == ["img_1"]
+    assert media_items == []
 
 
 def test_extract_post_content_keeps_direct_shape_behavior() -> None:
@@ -45,10 +46,38 @@ def test_extract_post_content_keeps_direct_shape_behavior() -> None:
         ],
     }
 
-    text, image_keys = _extract_post_content(payload)
+    text, image_keys, media_items = _extract_post_content(payload)
 
     assert text == "Daily report"
     assert image_keys == ["img_a", "img_b"]
+    assert media_items == []
+
+
+def test_extract_post_content_extracts_media_tags() -> None:
+    payload = {
+        "title": "",
+        "content": [
+            [{"tag": "img", "image_key": "img_1", "width": 345, "height": 34}],
+            [{"tag": "media", "file_key": "file_v3_0010j_abc", "image_key": "img_v3_0210j_xyz"}],
+        ],
+    }
+
+    text, image_keys, media_items = _extract_post_content(payload)
+
+    assert image_keys == ["img_1"]
+    assert media_items == [{"tag": "media", "file_key": "file_v3_0010j_abc"}]
+
+
+def test_extract_post_content_ignores_media_without_file_key() -> None:
+    payload = {
+        "content": [
+            [{"tag": "media"}],
+        ],
+    }
+
+    text, image_keys, media_items = _extract_post_content(payload)
+
+    assert media_items == []
 
 
 def test_register_optional_event_keeps_builder_when_method_missing() -> None:

tests/test_multimodal_capabilities.py

@@ -338,11 +338,10 @@ class TestInputLimitsAudioVideo:
         assert audio_blocks[0]["input_audio"]["format"] == "mp3"
 
     def test_missing_file_gracefully_skipped(self, ctx, tmp_path):
-        """Missing file should be gracefully skipped."""
+        """Missing file should be skipped with a visible note."""
         result = ctx._build_user_content("hello", [str(tmp_path / "ghost.wav")], supports_audio=True)
-        # Missing file is silently skipped (non-image path uses continue on OSError)
         assert isinstance(result, str)
-        assert result == "hello"
+        assert "[Skipped file: unable to read" in result
 
 
 # ── _strip_media_content ──────────────────────────────────────────────
@@ -495,3 +494,175 @@ class TestCodexAudioConversion:
         audio_items = [i for i in result["content"] if i.get("type") == "input_audio"]
         assert len(audio_items) == 1
         assert audio_items[0]["input_audio"]["data"] == "abc123"
+
+    def test_video_url_converted_to_text_placeholder(self):
+        from nanobot.providers.openai_codex_provider import _convert_user_message
+        content = [
+            {"type": "video_url", "video_url": {"url": "data:video/mp4;base64,abc"},
+             "_meta": {"path": "/video.mp4"}},
+            {"type": "text", "text": "watch"},
+        ]
+        result = _convert_user_message(content)
+        text_items = [i for i in result["content"] if i.get("type") == "input_text"]
+        assert any("[video:" in i.get("text", "") for i in text_items)
+
+
+# ── New tests for review fixes ──────────────────────────────────────────
+
+class TestSupportsVisionFalse:
+    """Tests for supports_vision=False (image downgrade to placeholder)."""
+
+    @pytest.fixture
+    def ctx(self, tmp_path):
+        return ContextBuilder(tmp_path, timezone="UTC")
+
+    def _make_png(self, size: int = 64) -> bytes:
+        import struct, zlib
+        header = b"\x89PNG\r\n\x1a\n"
+        ihdr_data = struct.pack(">IIBBBBB", 1, 1, 8, 2, 0, 0, 0)
+        ihdr_crc = zlib.crc32(b"IHDR" + ihdr_data) & 0xFFFFFFFF
+        ihdr = struct.pack(">I", 13) + b"IHDR" + ihdr_data + struct.pack(">I", ihdr_crc)
+        raw = b"\x00\x00\x00\x00"
+        idat_crc = zlib.crc32(b"IDAT" + raw) & 0xFFFFFFFF
+        idat = struct.pack(">I", len(raw)) + b"IDAT" + raw + struct.pack(">I", idat_crc)
+        iend_crc = zlib.crc32(b"IEND") & 0xFFFFFFFF
+        iend = struct.pack(">I", 0) + b"IEND" + struct.pack(">I", iend_crc)
+        return header + ihdr + idat + iend
+
+    def test_vision_false_downgrades_to_placeholder(self, ctx, tmp_path):
+        img_path = tmp_path / "test.png"
+        img_path.write_bytes(self._make_png())
+        result = ctx._build_user_content("look", [str(img_path)], supports_vision=False)
+        assert isinstance(result, list)
+        assert not any(b.get("type") == "image_url" for b in result)
+        assert any("[image:" in (b.get("text") or "") for b in result)
+
+    def test_vision_false_no_file_read(self, ctx, tmp_path):
+        """With supports_vision=False, file should not be read (no crash on missing)."""
+        missing = tmp_path / "nonexistent.png"
+        result = ctx._build_user_content("look", [str(missing)], supports_vision=False)
+        assert isinstance(result, list)
+        assert any("[image:" in (b.get("text") or "") for b in result)
+
+
+class TestAudioVideoCountLimits:
+    """Tests for max_input_audios / max_input_videos count enforcement."""
+
+    @pytest.fixture
+    def ctx(self, tmp_path):
+        return ContextBuilder(tmp_path, timezone="UTC",
+                              input_limits=InputLimitsConfig(
+                                  max_input_audios=1,
+                                  max_input_videos=1,
+                                  max_input_audio_bytes=10 * 1024 * 1024,
+                                  max_input_video_bytes=20 * 1024 * 1024,
+                              ))
+
+    def _make_wav(self) -> bytes:
+        data = b"\x00\x00"
+        fmt_chunk = (
+            b"\x01\x00" + (1).to_bytes(2, "little") + (44100).to_bytes(4, "little")
+            + (88200).to_bytes(4, "little") + (2).to_bytes(2, "little")
+            + (16).to_bytes(2, "little")
+        )
+        return (
+            b"RIFF" + (36 + len(data)).to_bytes(4, "little") + b"WAVE"
+            + b"fmt " + (16).to_bytes(4, "little") + fmt_chunk
+            + b"data" + len(data).to_bytes(4, "little") + data
+        )
+
+    def _make_mp4(self) -> bytes:
+        ftyp_data = b"isom" + b"\x00" * 12
+        return (8 + len(ftyp_data)).to_bytes(4, "big") + b"ftyp" + ftyp_data
+
+    def test_audio_count_limit_enforced(self, ctx, tmp_path):
+        """Only first audio should be accepted; second should be skipped."""
+        wav1 = tmp_path / "a1.wav"
+        wav1.write_bytes(self._make_wav())
+        wav2 = tmp_path / "a2.wav"
+        wav2.write_bytes(self._make_wav())
+        result = ctx._build_user_content("listen", [str(wav1), str(wav2)], supports_audio=True)
+        # Should have note about skip + one audio block
+        if isinstance(result, list):
+            audio_blocks = [b for b in result if b.get("type") == "input_audio"]
+            assert len(audio_blocks) == 1
+            text_blocks = [b for b in result if b.get("type") == "text"]
+            notes_text = " ".join(b.get("text", "") for b in text_blocks)
+            assert "Skipped audio" in notes_text
+        else:
+            # All skipped, result is string
+            assert "Skipped audio" in result
+
+    def test_video_count_limit_enforced(self, ctx, tmp_path):
+        """Only first video should be accepted; second should be skipped."""
+        mp4_1 = tmp_path / "v1.mp4"
+        mp4_1.write_bytes(self._make_mp4())
+        mp4_2 = tmp_path / "v2.mp4"
+        mp4_2.write_bytes(self._make_mp4())
+        result = ctx._build_user_content("watch", [str(mp4_1), str(mp4_2)], supports_video=True)
+        if isinstance(result, list):
+            video_blocks = [b for b in result if b.get("type") == "video_url"]
+            assert len(video_blocks) == 1
+            text_blocks = [b for b in result if b.get("type") == "text"]
+            notes_text = " ".join(b.get("text", "") for b in text_blocks)
+            assert "Skipped video" in notes_text
+        else:
+            assert "Skipped video" in result
+
+
+class TestVideoMimeCompat:
+    """Tests for video_mime_compat function."""
+
+    def test_compatible_mp4(self):
+        from nanobot.utils.helpers import video_mime_compat
+        assert video_mime_compat("video/mp4") is True
+
+    def test_compatible_webm(self):
+        from nanobot.utils.helpers import video_mime_compat
+        assert video_mime_compat("video/webm") is True
+
+    def test_compatible_quicktime(self):
+        from nanobot.utils.helpers import video_mime_compat
+        assert video_mime_compat("video/quicktime") is True
+
+    def test_incompatible_avi(self):
+        from nanobot.utils.helpers import video_mime_compat
+        assert video_mime_compat("video/x-msvideo") is False
+
+    def test_none(self):
+        from nanobot.utils.helpers import video_mime_compat
+        assert video_mime_compat(None) is False
+
+
+class TestSupportsAudioCaseInsensitive:
+    """Case insensitivity for supports_audio / supports_video."""
+
+    def test_audio_case_insensitive(self):
+        d = AgentDefaults(audio_models=["GPT-4o"])
+        assert d.supports_audio("openai/gpt-4o-audio") is True
+
+    def test_video_case_insensitive(self):
+        d = AgentDefaults(video_models=["GLM-5V"])
+        assert d.supports_video("zhipu/glm-5v-turbo") is True
+
+
+class TestNonImageOSErrorNote:
+    """Non-image media OSError should produce a visible note."""
+
+    @pytest.fixture
+    def ctx(self, tmp_path):
+        return ContextBuilder(tmp_path, timezone="UTC")
+
+    def test_missing_audio_produces_note(self, ctx, tmp_path):
+        result = ctx._build_user_content(
+            "hello", [str(tmp_path / "missing.wav")], supports_audio=True
+        )
+        assert isinstance(result, str)
+        assert "[Skipped file: unable to read" in result
+
+    def test_missing_video_produces_note(self, ctx, tmp_path):
+        result = ctx._build_user_content(
+            "hello", [str(tmp_path / "missing.mp4")], supports_video=True
+        )
+        assert isinstance(result, str)
+        assert "[Skipped file: unable to read" in result