Fix #1280: chat tool-result details body renders the actual returned payload

ChatOutputHtmlRenderer.RenderToolResultBody now always emits the full payload via

RenderToolPayload, so opening the <details> shows the actual result string. The

compact "(N lines)" indicator remains in the <summary> for the collapsed state.

CopilotToolEventMapper.BuildSuccessResult now prefers DetailedContent over Content

so the renderer receives the full text rather than the short summary variant.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: JoshuaRowePhantom

Phantom.Workspaces.Agent.Gui.Tests/ChatOutputHtmlRendererTests.cs

@@ -1077,16 +1077,21 @@ public void RenderToolCallPair_WithLargeSingleLineResult_SummaryShowsCharacterCo
     }
 
     [Fact]
-    public void RenderToolCallPair_WithLargeResultJson_BodyDoesNotContainFullPayload()
+    public void RenderToolCallPair_WithLargeResultJson_BodyContainsFullPayload()
     {
+        // #1280: the <details> body now renders the FULL escaped payload so the user can inspect
+        // the actual returned text; the compact "(N lines)" header stays in <summary>. Replaces
+        // the earlier wrong-behavior test that asserted the body did NOT contain the payload.
         var lineCount = ChatOutputHtmlRenderer.MaxToolResultLines + 5;
         var lines = Enumerable.Range(0, lineCount).Select(i => $"line-{i}").ToList();
         lines[10] = "UNIQUE_PAYLOAD_MARKER_XYZ";
         var largeResult = string.Join("\n", lines);
 
         var html = ChatOutputHtmlRenderer.RenderToolCallPair("c0", "my_tool", "{}", largeResult);
 
-        Assert.DoesNotContain("UNIQUE_PAYLOAD_MARKER_XYZ", html, StringComparison.Ordinal);
+        Assert.Contains("UNIQUE_PAYLOAD_MARKER_XYZ", html, StringComparison.Ordinal);
+        // Summary line still shows the compact "(N lines)" header for the collapsed state.
+        Assert.Contains($"result  ({lineCount} lines)", html, StringComparison.Ordinal);
     }
 
     [Fact]

Phantom.Workspaces.Agent.Gui/ViewModels/DocumentModels/ChatOutputHtmlRenderer.cs

@@ -830,13 +830,15 @@ private static string SummarizeResult(string resultJson)
             ? ToolResultOverflowSummary(resultJson)
             : FirstLine(resultJson);
 
-    // Body for the tool RESULT block. Small results render in full; oversized results render only
-    // the short "(N lines)" / "(N characters)" summary instead of the fully-expanded payload tree
-    // (issue #1069). The full payload stays available via data-details-target.
+    // Body for the tool RESULT block. #1280: always render the full escaped payload inside the
+    // <details> body so the user can inspect the actual returned text; the compact "(N lines)" /
+    // "(N characters)" header lives in the collapsed <summary>. The full payload remains
+    // available via data-details-target for the modal inspector as well.
     private static (string Html, bool Overflowed) RenderToolResultBody(string resultJson)
-        => ToolResultOverflows(resultJson)
-            ? (HtmlEscape(ToolResultOverflowSummary(resultJson)), true)
-            : (RenderToolPayload(resultJson), false);
+    {
+        var overflowed = ToolResultOverflows(resultJson);
+        return (RenderToolPayload(resultJson), overflowed);
+    }
 
     private static string DiagnosticHeader(string text)
     {

Phantom.Workspaces.Llm.Core.Tests/CopilotToolEventMapperTests.cs

@@ -104,6 +104,56 @@ public void MapToolComplete_MapsSuccessfulTextResult_PairedByCallId()
         Assert.Equal("the result text", result.Result);
     }
 
+    // ── Issue #1280: prefer DetailedContent (SDK-full text) for UI/timeline rendering ────
+
+    [Fact]
+    public void MapToolComplete_WhenDetailedContentPresent_UsesDetailedContentAsResult()
+    {
+        // #1280: DetailedContent is documented by the SDK as the UI-oriented full text; Content
+        // is potentially truncated for LLM token efficiency. For the chat surface we want the
+        // full text — mapper prefers DetailedContent when both are present.
+        var completeEvent = new ToolExecutionCompleteEvent
+        {
+            Data = new ToolExecutionCompleteData
+            {
+                ToolCallId = "call-2",
+                Success = true,
+                Result = new ToolExecutionCompleteResult
+                {
+                    Content = "truncated-for-model",
+                    DetailedContent = "FULL UNTRUNCATED DETAIL FOR UI",
+                },
+            },
+        };
+
+        var result = CopilotToolEventMapper.MapToolComplete(completeEvent);
+
+        Assert.Equal("FULL UNTRUNCATED DETAIL FOR UI", result.Result);
+    }
+
+    [Fact]
+    public void MapToolComplete_WhenOnlyContentPresent_FallsBackToContent()
+    {
+        // Fallback path: no DetailedContent — use Content.
+        var completeEvent = new ToolExecutionCompleteEvent
+        {
+            Data = new ToolExecutionCompleteData
+            {
+                ToolCallId = "call-3",
+                Success = true,
+                Result = new ToolExecutionCompleteResult
+                {
+                    Content = "content-only",
+                    DetailedContent = null,
+                },
+            },
+        };
+
+        var result = CopilotToolEventMapper.MapToolComplete(completeEvent);
+
+        Assert.Equal("content-only", result.Result);
+    }
+
     [Fact]
     public void MapToolComplete_FallsBackToTextContent_WhenNoSummaryContent()
     {

Phantom.Workspaces.Llm.Core/CopilotToolEventMapper.cs

@@ -131,14 +131,14 @@ private static object BuildSuccessResult(ToolExecutionCompleteResult? result)
             return string.Empty;
         }
 
-        if (!string.IsNullOrEmpty(result.Content))
+        if (!string.IsNullOrEmpty(result.DetailedContent))
         {
-            return result.Content;
+            return result.DetailedContent;
         }
 
-        if (!string.IsNullOrEmpty(result.DetailedContent))
+        if (!string.IsNullOrEmpty(result.Content))
         {
-            return result.DetailedContent;
+            return result.Content;
         }
 
         if (result.Contents is { Length: > 0 })