fix(agent): correct within-turn duplicate tool call ID pairing in sanitizeHistory

Replace single-value idRemap with queue-based idQueue so multiple tool
results sharing the same original ID pair correctly in encounter order.
Previously the map overwrote on duplicates, causing the second result to
be dropped and a synthetic placeholder to be emitted instead.

internal/agent/loop_history.go

@@ -408,9 +408,10 @@ func sanitizeHistory(msgs []providers.Message) ([]providers.Message, int) {
 			msg.ToolCalls = make([]providers.ToolCall, len(oldCalls))
 			copy(msg.ToolCalls, oldCalls)
 
-			// Dedup: rewrite any ID that was already seen in an earlier turn.
-			// Maps original ID → rewritten ID for pairing with tool results below.
-			idRemap := make(map[string]string, len(msg.ToolCalls))
+			// Dedup: rewrite any ID that was already seen in an earlier turn or
+			// within the same turn. Uses a queue per original ID so multiple tool
+			// results with the same raw ID pair correctly in encounter order.
+			idQueue := make(map[string][]string, len(msg.ToolCalls)) // origID → []newID
 			expectedIDs := make(map[string]bool, len(msg.ToolCalls))
 			for j := range msg.ToolCalls {
 				origID := msg.ToolCalls[j].ID
@@ -421,7 +422,7 @@ func sanitizeHistory(msgs []providers.Message) ([]providers.Message, int) {
 				}
 				msg.ToolCalls[j].ID = newID
 				globalSeen[newID] = true
-				idRemap[origID] = newID
+				idQueue[origID] = append(idQueue[origID], newID)
 				expectedIDs[newID] = true
 			}
 
@@ -431,7 +432,9 @@ func sanitizeHistory(msgs []providers.Message) ([]providers.Message, int) {
 			for i+1 < len(msgs) && msgs[i+1].Role == "tool" {
 				i++
 				toolMsg := msgs[i]
-				if newID, ok := idRemap[toolMsg.ToolCallID]; ok && expectedIDs[newID] {
+				if queue, ok := idQueue[toolMsg.ToolCallID]; ok && len(queue) > 0 {
+					newID := queue[0]
+					idQueue[toolMsg.ToolCallID] = queue[1:]
 					toolMsg.ToolCallID = newID
 					result = append(result, toolMsg)
 					delete(expectedIDs, newID)

internal/agent/loop_history_test.go

@@ -243,6 +243,58 @@ func TestSanitizeHistory_DedupsDuplicateIDsAcrossTurns(t *testing.T) {
 	}
 }
 
+func TestSanitizeHistory_DedupsDuplicateIDsWithinTurn(t *testing.T) {
+	msgs := []providers.Message{
+		{Role: "user", Content: "do two things"},
+		{Role: "assistant", Content: "", ToolCalls: []providers.ToolCall{
+			{ID: "call_abc", Name: "read_file"},
+			{ID: "call_abc", Name: "write_file"}, // same ID within turn
+		}},
+		{Role: "tool", Content: "result1", ToolCallID: "call_abc"},
+		{Role: "tool", Content: "result2", ToolCallID: "call_abc"},
+		{Role: "assistant", Content: "done"},
+	}
+	got, dropped := sanitizeHistory(msgs)
+	if dropped != 0 {
+		t.Errorf("expected 0 dropped, got %d", dropped)
+	}
+
+	// Both tool results must be present and paired correctly
+	toolResults := 0
+	for _, m := range got {
+		if m.Role == "tool" {
+			toolResults++
+		}
+	}
+	if toolResults != 2 {
+		t.Errorf("expected 2 tool results, got %d", toolResults)
+	}
+
+	// All tool call IDs must be unique
+	seen := make(map[string]bool)
+	for _, m := range got {
+		for _, tc := range m.ToolCalls {
+			if seen[tc.ID] {
+				t.Errorf("duplicate tool call ID: %s", tc.ID)
+			}
+			seen[tc.ID] = true
+		}
+	}
+
+	// Each tool result ID must match a tool call ID
+	callIDs := make(map[string]bool)
+	for _, m := range got {
+		for _, tc := range m.ToolCalls {
+			callIDs[tc.ID] = true
+		}
+	}
+	for _, m := range got {
+		if m.Role == "tool" && !callIDs[m.ToolCallID] {
+			t.Errorf("tool result ID %s has no matching tool call", m.ToolCallID)
+		}
+	}
+}
+
 func TestSanitizeHistory_NoDedupWhenIDsUnique(t *testing.T) {
 	msgs := []providers.Message{
 		{Role: "user", Content: "hello"},