fix(gateway): verbose tool progress no longer truncates args when tool_preview_length is 0 (#8735)

When tool_preview_length is 0 (default for platforms without a tier
default, like Session), verbose mode was truncating args JSON to 200
characters.  Since the user explicitly opted into verbose mode, they
expect full tool call detail — the 200-char cap defeated the purpose.

Now: tool_preview_length=0 means no truncation in verbose mode.
Positive values still cap as before.  Platform message-length limits
handle overflow naturally.

gateway/run.py

@@ -7411,9 +7411,11 @@ class GatewayRunner:
                     _pl = get_tool_preview_max_len()
                     import json as _json
                     args_str = _json.dumps(args, ensure_ascii=False, default=str)
-                    _cap = _pl if _pl > 0 else 200
-                    if len(args_str) > _cap:
-                        args_str = args_str[:_cap - 3] + "..."
+                    # When tool_preview_length is 0 (default), don't truncate
+                    # in verbose mode — the user explicitly asked for full
+                    # detail.  Platform message-length limits handle the rest.
+                    if _pl > 0 and len(args_str) > _pl:
+                        args_str = args_str[:_pl - 3] + "..."
                     msg = f"{emoji} {tool_name}({list(args.keys())})\n{args_str}"
                 elif preview:
                     msg = f"{emoji} {tool_name}: \"{preview}\""

tests/gateway/test_run_progress_topics.py

@@ -396,6 +396,27 @@ class QueuedCommentaryAgent:
         }
 
 
+class VerboseAgent:
+    """Agent that emits a tool call with args whose JSON exceeds 200 chars."""
+    LONG_CODE = "x" * 300
+
+    def __init__(self, **kwargs):
+        self.tool_progress_callback = kwargs.get("tool_progress_callback")
+        self.tools = []
+
+    def run_conversation(self, message, conversation_history=None, task_id=None):
+        self.tool_progress_callback(
+            "tool.started", "execute_code", None,
+            {"code": self.LONG_CODE},
+        )
+        time.sleep(0.35)
+        return {
+            "final_response": "done",
+            "messages": [],
+            "api_calls": 1,
+        }
+
+
 async def _run_with_agent(
     monkeypatch,
     tmp_path,
@@ -575,3 +596,45 @@ async def test_run_agent_queued_message_does_not_treat_commentary_as_final(monke
     assert result["final_response"] == "final response 2"
     assert "I'll inspect the repo first." in sent_texts
     assert "final response 1" in sent_texts
+
+
+@pytest.mark.asyncio
+async def test_verbose_mode_does_not_truncate_args_by_default(monkeypatch, tmp_path):
+    """Verbose mode with default tool_preview_length (0) should NOT truncate args.
+
+    Previously, verbose mode capped args at 200 chars when tool_preview_length
+    was 0 (default).  The user explicitly opted into verbose — show full detail.
+    """
+    adapter, result = await _run_with_agent(
+        monkeypatch,
+        tmp_path,
+        VerboseAgent,
+        session_id="sess-verbose-no-truncate",
+        config_data={"display": {"tool_progress": "verbose", "tool_preview_length": 0}},
+    )
+
+    assert result["final_response"] == "done"
+    # The full 300-char 'x' string should be present, not truncated to 200
+    all_content = " ".join(call["content"] for call in adapter.sent)
+    all_content += " ".join(call["content"] for call in adapter.edits)
+    assert VerboseAgent.LONG_CODE in all_content
+
+
+@pytest.mark.asyncio
+async def test_verbose_mode_respects_explicit_tool_preview_length(monkeypatch, tmp_path):
+    """When tool_preview_length is set to a positive value, verbose truncates to that."""
+    adapter, result = await _run_with_agent(
+        monkeypatch,
+        tmp_path,
+        VerboseAgent,
+        session_id="sess-verbose-explicit-cap",
+        config_data={"display": {"tool_progress": "verbose", "tool_preview_length": 50}},
+    )
+
+    assert result["final_response"] == "done"
+    all_content = " ".join(call["content"] for call in adapter.sent)
+    all_content += " ".join(call["content"] for call in adapter.edits)
+    # Should be truncated — full 300-char string NOT present
+    assert VerboseAgent.LONG_CODE not in all_content
+    # But should still contain the truncated portion with "..."
+    assert "..." in all_content