diff --git a/Sources/AnyLanguageModel/Models/SystemLanguageModel.swift b/Sources/AnyLanguageModel/Models/SystemLanguageModel.swift
index ff2e8f25..10cf4b30 100644
--- a/Sources/AnyLanguageModel/Models/SystemLanguageModel.swift
+++ b/Sources/AnyLanguageModel/Models/SystemLanguageModel.swift
@@ -78,7 +78,7 @@
             let fmSession = FoundationModels.LanguageModelSession(
                 model: systemModel,
                 tools: session.tools.toFoundationModels(),
-                transcript: session.transcript.toFoundationModels(
+                transcript: fmTranscriptDroppingDuplicatePrompt(session.transcript, prompt: prompt).toFoundationModels(
                     instructions: session.instructions,
                     toolDefinitions: session.tools
                         .filter(\.includesSchemaInInstructions)
@@ -159,7 +159,7 @@
             let fmSession = FoundationModels.LanguageModelSession(
                 model: systemModel,
                 tools: session.tools.toFoundationModels(),
-                transcript: session.transcript.toFoundationModels(
+                transcript: fmTranscriptDroppingDuplicatePrompt(session.transcript, prompt: prompt).toFoundationModels(
                     instructions: session.instructions,
                     toolDefinitions: session.tools
                         .filter(\.includesSchemaInInstructions)
@@ -367,6 +367,21 @@
 
     // MARK: - Helpers
 
+    @available(macOS 26.0, iOS 26.0, watchOS 26.0, tvOS 26.0, visionOS 26.0, *)
+    func fmTranscriptDroppingDuplicatePrompt(_ transcript: Transcript, prompt: Prompt) -> Transcript {
+        guard let lastEntry = transcript.last, case .prompt(let lastPrompt) = lastEntry else {
+            return transcript
+        }
+        let lastText = lastPrompt.segments.compactMap { segment -> String? in
+            if case .text(let textSegment) = segment { return textSegment.content }
+            return nil
+        }.joined()
+        guard lastText == prompt.description else {
+            return transcript
+        }
+        return Transcript(entries: transcript.dropLast())
+    }
+
     @available(macOS 26.0, iOS 26.0, watchOS 26.0, tvOS 26.0, visionOS 26.0, *)
     extension Prompt {
         fileprivate func toFoundationModels() -> FoundationModels.Prompt {