fix: prevent duplicate tool results on provider disconnect/fallback

src/query.ts

@@ -124,13 +124,25 @@ function* yieldMissingToolResultBlocks(
   assistantMessages: AssistantMessage[],
   errorMessage: string,
 ) {
-  for (const assistantMessage of assistantMessages) {
+  // Filter out duplicate tool use blocks within the same message to prevent duplicate tool results
+  const uniqueAssistantMessages = assistantMessages.map(assistantMessage => {
+    const content = assistantMessage.message.content
+    const uniqueContent = content.filter((item, index, self) => {
+      if (item.type !== 'tool_use') return true
+      return index === self.findIndex(other =>
+        other.type === 'tool_use' && other.id === item.id
+      )
+    })
+    return { ...assistantMessage, message: { ...assistantMessage.message, content: uniqueContent } }
+  })
+
+  for (const assistantMessage of uniqueAssistantMessages) {
     // Extract all tool use blocks from this assistant message
     const toolUseBlocks = assistantMessage.message.content.filter(
       content => content.type === 'tool_use',
     ) as ToolUseBlock[]
 
-    // Emit an interruption message for each tool use
+    // Emit an interruption message for each unique tool use
     for (const toolUse of toolUseBlocks) {
       yield createUserMessage({
         content: [

src/services/tools/StreamingToolExecutor.ts

@@ -74,6 +74,12 @@ export class StreamingToolExecutor {
    * Add a tool to the execution queue. Will start executing immediately if conditions allow.
    */
   addTool(block: ToolUseBlock, assistantMessage: AssistantMessage): void {
+    // Prevent duplicate tool additions - if a tool with this ID already exists, skip it.
+    // This can happen when provider disconnects/reconnects and resends the same tool_use block.
+    if (this.tools.some(t => t.id === block.id)) {
+      return
+    }
+
     const toolDefinition = findToolByName(this.toolDefinitions, block.name)
     if (!toolDefinition) {
       this.tools.push({