fix(acp): keep read-file starts compact

acp_adapter/tools.py

@@ -960,18 +960,11 @@ def build_tool_start(
         )
 
     if tool_name == "read_file":
-        path = arguments.get("path", "")
-        offset = arguments.get("offset")
-        limit = arguments.get("limit")
-        bits = []
-        if offset:
-            bits.append(f"from line {offset}")
-        if limit:
-            bits.append(f"limit {limit}")
-        suffix = f" ({', '.join(bits)})" if bits else ""
-        content = [_text(f"Reading {path}{suffix}")]
+        # The title and location already identify the file. Sending a synthetic
+        # "Reading ..." content block makes Zed render an unhelpful Output
+        # section before the real file contents arrive on completion.
         return acp.start_tool_call(
-            tool_call_id, title, kind=kind, content=content, locations=locations,
+            tool_call_id, title, kind=kind, content=None, locations=locations,
         )
 
     if tool_name == "search_files":

tests/acp/test_tools.py

@@ -189,15 +189,13 @@ class TestBuildToolStart:
         assert "ls -la /tmp" in text
 
     def test_build_tool_start_for_read_file(self):
-        """read_file should include the path in content."""
+        """read_file start should stay compact; completion carries file contents."""
         args = {"path": "/etc/hosts", "offset": 1, "limit": 50}
         result = build_tool_start("tc-3", "read_file", args)
         assert isinstance(result, ToolCallStart)
         assert result.kind == "read"
-        assert len(result.content) >= 1
-        content_item = result.content[0]
-        assert isinstance(content_item, ContentToolCallContent)
-        assert "/etc/hosts" in content_item.content.text
+        assert result.content is None
+        assert result.raw_input is None
 
     def test_build_tool_start_for_search(self):
         """search_files should include pattern in content."""