Case study: stabilize file browser on switch and add light preview

streamlit-client/app.py

@@ -456,6 +456,48 @@ def load_chat_from_file(chat_path: Path) -> list[dict]:
     return data.get("messages", [])
 
 
+def _render_case_file_preview(event: dict | None, root_path: Path):
+    """Render a light-theme preview for selected files from streamlit-file-browser."""
+    if not event or not isinstance(event, dict):
+        return
+    if event.get("type") != "SELECT_FILE":
+        return
+    target = (event.get("target") or {}).get("path")
+    if not target:
+        return
+    file_path = (root_path / target).resolve()
+    if not file_path.exists() or file_path.is_dir():
+        st.warning(f"File `{target}` not found under current workspace.")
+        return
+
+    st.markdown("#### File Preview")
+    suffix = file_path.suffix.lower()
+    if suffix in {".png", ".jpg", ".jpeg", ".gif", ".webp"}:
+        st.image(str(file_path))
+        return
+
+    # Text/code preview (light theme via existing CSS on st.code)
+    max_chars = 300_000
+    with open(file_path, "r", encoding="utf-8", errors="ignore") as f:
+        content = f.read(max_chars + 1)
+    if len(content) > max_chars:
+        content = content[:max_chars] + "\n\n... [truncated]"
+
+    lang_map = {
+        ".py": "python",
+        ".js": "javascript",
+        ".ts": "typescript",
+        ".json": "json",
+        ".md": "markdown",
+        ".sh": "bash",
+        ".yml": "yaml",
+        ".yaml": "yaml",
+        ".csv": "text",
+        ".txt": "text",
+    }
+    st.code(content, language=lang_map.get(suffix, "text"))
+
+
 def get_next_memo_number(memory_dir: Path) -> int:
     if not memory_dir.exists():
         return 1
@@ -578,21 +620,27 @@ if st.session_state.view_mode == "case_study":
     case_dir = selected_path.parent
     ws_dir = case_dir / "workspace"
     browse_path = ws_dir if ws_dir.exists() else case_dir
+    browse_root = str(browse_path.resolve())
+    # Force one rerun when case/workspace root changes to avoid first-empty browser state.
+    if st.session_state.get("case_fb_root") != browse_root:
+        st.session_state.case_fb_root = browse_root
+        st.rerun()
     # Use a case-specific key so switching case study resets browser state correctly
     fb_key = f"case_study_file_browser_{case_dir.name}"
     with st.expander("📂 Workspace Files (Agent Code)", expanded=False):
-        st.caption(f"Browsing: `{browse_path.resolve()}`")
+        st.caption(f"Browsing: `{browse_root}`")
         if st_file_browser is not None:
-            st_file_browser(
-                str(browse_path.resolve()),
+            fb_event = st_file_browser(
+                browse_root,
                 key=fb_key,
                 show_choose_file=True,
                 show_download_file=True,
                 show_delete_file=False,
                 show_new_folder=False,
                 show_upload_file=False,
-                show_preview=True,
+                show_preview=False,
             )
+            _render_case_file_preview(fb_event, browse_path.resolve())
         else:
             st.info("Install `streamlit-file-browser` to browse workspace files in Case Study mode.")
     st.stop()