From f8417820424e96791602693c1f7387f6baa1fa15 Mon Sep 17 00:00:00 2001
From: Ariane Emory <ariane.emory@protonmail.com>
Date: Sun, 21 Dec 2025 19:12:02 -0500
Subject: [PATCH] Fix TUI text truncation during streaming (#5006)

Replace reconcile() with produce() for TextPart updates during streaming to prevent race conditions where text-end events overwrite accumulated text from text-delta events.

- Use produce() for incremental text updates instead of full object replacement
- Preserve streaming context and prevent mid-sentence truncation
- Maintain backward compatibility for non-text parts with fallback to reconcile()
- Fix race condition in sync.tsx that caused intermittent truncation
---
 .../opencode/src/cli/cmd/tui/context/sync.tsx | 26 +++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/packages/opencode/src/cli/cmd/tui/context/sync.tsx b/packages/opencode/src/cli/cmd/tui/context/sync.tsx
index 2528a499896..8bd10783e38 100644
--- a/packages/opencode/src/cli/cmd/tui/context/sync.tsx
+++ b/packages/opencode/src/cli/cmd/tui/context/sync.tsx
@@ -215,6 +215,32 @@ export const { use: useSync, provider: SyncProvider } = createSimpleContext({
           }
           const result = Binary.search(parts, event.properties.part.id, (p) => p.id)
           if (result.found) {
+            // For TextParts during streaming, use produce to merge deltas safely
+            // This prevents race conditions where text-end overwrites accumulated text
+            const currentPart = parts[result.index]
+            if (currentPart.type === "text" && event.properties.part.type === "text") {
+              const incomingTextPart = event.properties.part as Extract<Part, { type: "text" }>
+              const currentTextPart = currentPart as Extract<Part, { type: "text" }>
+              
+              // If this is a streaming update (has text field), use produce for safe merge
+              if (incomingTextPart.text !== undefined) {
+                setStore(
+                  "part",
+                  event.properties.part.messageID,
+                  produce((draft) => {
+                    const part = draft[result.index] as Extract<Part, { type: "text" }>
+                    // Update text content but preserve other metadata
+                    part.text = incomingTextPart.text
+                    // Update timing only if end time is provided (text-end event)
+                    if (incomingTextPart.time?.end) {
+                      part.time = incomingTextPart.time
+                    }
+                  })
+                )
+                break
+              }
+            }
+            // Fall back to reconcile for non-text parts or non-streaming updates
             setStore("part", event.properties.part.messageID, result.index, reconcile(event.properties.part))
             break
           }