From 4240984594ff9f4da6da45dd20093d697a98d201 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jo=C3=A3o=20Salavisa?= <joao.salavisa@gmail.com>
Date: Mon, 2 Feb 2026 22:53:29 +0000
Subject: [PATCH] Fix diff view not updating when agent modifies files (#157)

---
 .../internal/orchestrator/event_handlers.go   | 10 +++++--
 .../components/task/task-changes-panel.tsx    |  8 +++--
 .../session-runtime/session-runtime-slice.ts  | 30 ++-----------------
 3 files changed, 15 insertions(+), 33 deletions(-)

diff --git a/apps/backend/internal/orchestrator/event_handlers.go b/apps/backend/internal/orchestrator/event_handlers.go
index ec21d4844e..668b6158a6 100644
--- a/apps/backend/internal/orchestrator/event_handlers.go
+++ b/apps/backend/internal/orchestrator/event_handlers.go
@@ -1141,7 +1141,7 @@ func (s *Service) isSnapshotDuplicate(existing, new *models.GitSnapshot) bool {
 		return false
 	}
 
-	// Compare file paths, staged status, and line counts
+	// Compare file paths, staged status, line counts, and diff content
 	for path, newFileData := range new.Files {
 		existingFileData, exists := existing.Files[path]
 		if !exists {
@@ -1154,7 +1154,8 @@ func (s *Service) isSnapshotDuplicate(existing, new *models.GitSnapshot) bool {
 
 		if newInfo.staged != existingInfo.staged ||
 			newInfo.additions != existingInfo.additions ||
-			newInfo.deletions != existingInfo.deletions {
+			newInfo.deletions != existingInfo.deletions ||
+			newInfo.diff != existingInfo.diff {
 			return false
 		}
 	}
@@ -1167,6 +1168,7 @@ type fileInfoCompare struct {
 	staged    bool
 	additions int
 	deletions int
+	diff      string
 }
 
 // extractFileInfo extracts comparable fields from a file info interface
@@ -1190,6 +1192,10 @@ func extractFileInfo(fileData interface{}) fileInfoCompare {
 		} else if deletions, ok := fileMap["deletions"].(int); ok {
 			info.deletions = deletions
 		}
+		// Extract diff content for comparison
+		if diff, ok := fileMap["diff"].(string); ok {
+			info.diff = diff
+		}
 	}
 	return info
 }
diff --git a/apps/web/components/task/task-changes-panel.tsx b/apps/web/components/task/task-changes-panel.tsx
index 8dbfdaaf11..b0868c0979 100644
--- a/apps/web/components/task/task-changes-panel.tsx
+++ b/apps/web/components/task/task-changes-panel.tsx
@@ -99,8 +99,9 @@ const TaskChangesPanel = memo(function TaskChangesPanel({
   }, [cumulativeDiff]);
 
   const selectedFile = selectedDiffPath && gitStatus?.files ? gitStatus.files[selectedDiffPath] : null;
-  // Use provided content if available, otherwise fall back to git status
-  const selectedDiffContent = selectedDiff?.content ?? selectedFile?.diff ?? '';
+  // Prioritize current git status for uncommitted files, use provided content only for historical diffs
+  // This ensures that when a file is modified by the agent, we show the latest diff
+  const selectedDiffContent = selectedFile?.diff ?? selectedDiff?.content ?? '';
   const isSingleDiffSelected = Boolean(selectedDiffPath && (hasProvidedContent || selectedFile));
   // Discard only works for uncommitted changes (not committed/historical diffs)
   const canDiscard = Boolean(selectedDiffPath && selectedFile && !hasProvidedContent);
@@ -192,7 +193,8 @@ const TaskChangesPanel = memo(function TaskChangesPanel({
       <SessionPanelContent>
         {isSingleDiffSelected && selectedDiffContent ? (
           // Render single file diff (from commit, snapshot, or uncommitted)
-          <div key={`selected-${selectedDiffPath}-${selectedDiffContent.length}`} className="space-y-4">
+          // Use timestamp from git status to ensure re-render when file changes
+          <div key={`selected-${selectedDiffPath}-${gitStatus?.timestamp ?? ''}-${selectedDiffContent.length}`} className="space-y-4">
             <FileDiffViewer
               filePath={selectedDiffPath!}
               diff={normalizeDiffContent(selectedDiffContent)}
diff --git a/apps/web/lib/state/slices/session-runtime/session-runtime-slice.ts b/apps/web/lib/state/slices/session-runtime/session-runtime-slice.ts
index 367ac78d26..70fb159292 100644
--- a/apps/web/lib/state/slices/session-runtime/session-runtime-slice.ts
+++ b/apps/web/lib/state/slices/session-runtime/session-runtime-slice.ts
@@ -3,17 +3,6 @@ import type { SessionRuntimeSlice, SessionRuntimeSliceState } from './types';
 
 const maxProcessOutputBytes = 2 * 1024 * 1024;
 
-/** Helper to compare two string arrays for equality */
-function arraysEqual(a: string[] | undefined, b: string[] | undefined): boolean {
-  if (a === b) return true;
-  if (!a || !b) return false;
-  if (a.length !== b.length) return false;
-  for (let i = 0; i < a.length; i++) {
-    if (a[i] !== b[i]) return false;
-  }
-  return true;
-}
-
 function trimProcessOutput(value: string) {
   if (value.length <= maxProcessOutputBytes) {
     return value;
@@ -94,23 +83,8 @@ export const createSessionRuntimeSlice: StateCreator<
     }),
   setGitStatus: (sessionId, gitStatus) =>
     set((draft) => {
-      const existing = draft.gitStatus.bySessionId[sessionId];
-      // Skip update if git status content hasn't meaningfully changed
-      // Compare branch, file counts, and modified/added/deleted arrays
-      if (existing) {
-        const sameContent =
-          existing.branch === gitStatus.branch &&
-          existing.ahead === gitStatus.ahead &&
-          existing.behind === gitStatus.behind &&
-          arraysEqual(existing.modified, gitStatus.modified) &&
-          arraysEqual(existing.added, gitStatus.added) &&
-          arraysEqual(existing.deleted, gitStatus.deleted) &&
-          arraysEqual(existing.untracked, gitStatus.untracked) &&
-          arraysEqual(existing.renamed, gitStatus.renamed);
-        if (sameContent) {
-          return; // Skip update - no meaningful changes
-        }
-      }
+      // Always update git status - the timestamp and file diffs may have changed
+      // even if the file lists are the same. The backend sends updates when content changes.
       draft.gitStatus.bySessionId[sessionId] = gitStatus;
     }),
   clearGitStatus: (sessionId) =>