diff --git a/src/anthropic/lib/streaming/_beta_messages.py b/src/anthropic/lib/streaming/_beta_messages.py
index 7736b6bd..a4a16da1 100644
--- a/src/anthropic/lib/streaming/_beta_messages.py
+++ b/src/anthropic/lib/streaming/_beta_messages.py
@@ -525,7 +525,7 @@ def accumulate_event(
                 content.signature = event.delta.signature
         elif event.delta.type == "compaction_delta":
             if content.type == "compaction":
-                content.content = event.delta.content
+                content.content = (content.content or "") + (event.delta.content or "")
                 content.encrypted_content = event.delta.encrypted_content
         else:
             # we only want exhaustive checking for linters, not at runtime
diff --git a/src/anthropic/lib/streaming/_messages.py b/src/anthropic/lib/streaming/_messages.py
index 5c0da999..004182e6 100644
--- a/src/anthropic/lib/streaming/_messages.py
+++ b/src/anthropic/lib/streaming/_messages.py
@@ -477,7 +477,12 @@ def accumulate_event(
                 json_buf += bytes(event.delta.partial_json, "utf-8")
 
                 if json_buf:
-                    content.input = from_json(json_buf, partial_mode=True)
+                    try:
+                        content.input = from_json(json_buf, partial_mode=True)
+                    except ValueError as e:
+                        raise ValueError(
+                            f"Unable to parse tool parameter JSON from model. Please retry your request or adjust your prompt. Error: {e}. JSON: {json_buf.decode('utf-8')}"
+                        ) from e
 
                 setattr(content, JSON_BUF_PROPERTY, json_buf)
         elif event.delta.type == "citations_delta":