diff --git a/aibridge/intercept/messages/reqpayload.go b/aibridge/intercept/messages/reqpayload.go
index 12f25758ae..ce5f0dfdb0 100644
--- a/aibridge/intercept/messages/reqpayload.go
+++ b/aibridge/intercept/messages/reqpayload.go
@@ -57,6 +57,7 @@ var (
 	constTool       = string(constant.ValueOf[constant.Tool]())
 	constToolResult = string(constant.ValueOf[constant.ToolResult]())
 	constUser       = string(anthropic.MessageParamRoleUser)
+	constSystem     = "system"
 
 	// bedrockUnsupportedFields are top-level fields present in the Anthropic Messages
 	// API that are absent from the Bedrock request body schema. Sending them results
@@ -166,6 +167,16 @@ func (p RequestPayload) lastUserPrompt() (string, bool, error) {
 	}
 
 	lastMessage := messageItems[len(messageItems)-1]
+	// Clients using the mid-conversation system beta (e.g. Claude Code with
+	// anthropic-beta: mid-conversation-system-*) append a trailing role=system
+	// message after the user's prompt, such as an injected skills list. When the
+	// last message is that system message, step back exactly one message to find
+	// the user's prompt. We only step back past a single trailing system message
+	// so we never re-record a stale prompt from an earlier turn that contained no
+	// new user input. See https://docs.claude.com/en/api/beta-headers.
+	if lastMessage.Get(messagesReqFieldRole).String() == constSystem && len(messageItems) >= 2 {
+		lastMessage = messageItems[len(messageItems)-2]
+	}
 	if lastMessage.Get(messagesReqFieldRole).String() != constUser {
 		return "", false, nil
 	}
diff --git a/aibridge/intercept/messages/reqpayload_internal_test.go b/aibridge/intercept/messages/reqpayload_internal_test.go
index 1ef50223c5..3dc5c1262f 100644
--- a/aibridge/intercept/messages/reqpayload_internal_test.go
+++ b/aibridge/intercept/messages/reqpayload_internal_test.go
@@ -202,6 +202,41 @@ func TestRequestPayloadLastUserPrompt(t *testing.T) {
 			expectedFound:  true,
 			expectError:    false,
 		},
+		{
+			name:           "trailing system message steps back to user prompt",
+			requestBody:    `{"model":"claude-opus-4-5","max_tokens":1024,"messages":[{"role":"user","content":"hello"},{"role":"system","content":"available skills: ..."}]}`,
+			expectedPrompt: "hello",
+			expectedFound:  true,
+			expectError:    false,
+		},
+		{
+			name:           "trailing system message with typed user content returns last text block",
+			requestBody:    `{"model":"claude-opus-4-5","max_tokens":1024,"messages":[{"role":"user","content":[{"type":"text","text":"first"},{"type":"text","text":"last"}]},{"role":"system","content":"available skills: ..."}]}`,
+			expectedPrompt: "last",
+			expectedFound:  true,
+			expectError:    false,
+		},
+		{
+			name:           "trailing system message after non user does not record",
+			requestBody:    `{"model":"claude-opus-4-5","max_tokens":1024,"messages":[{"role":"assistant","content":"response"},{"role":"system","content":"available skills: ..."}]}`,
+			expectedPrompt: "",
+			expectedFound:  false,
+			expectError:    false,
+		},
+		{
+			name:           "only system message does not step out of bounds",
+			requestBody:    `{"model":"claude-opus-4-5","max_tokens":1024,"messages":[{"role":"system","content":"available skills: ..."}]}`,
+			expectedPrompt: "",
+			expectedFound:  false,
+			expectError:    false,
+		},
+		{
+			name:           "two trailing system messages only steps back once",
+			requestBody:    `{"model":"claude-opus-4-5","max_tokens":1024,"messages":[{"role":"user","content":"hello"},{"role":"system","content":"a"},{"role":"system","content":"b"}]}`,
+			expectedPrompt: "",
+			expectedFound:  false,
+			expectError:    false,
+		},
 		{
 			name:           "messages wrong type returns error",
 			requestBody:    `{"model":"claude-opus-4-5","max_tokens":1024,"messages":{}}`,