diff --git a/changelog/unreleased/qoder-history-reasoning-content.md b/changelog/unreleased/qoder-history-reasoning-content.md
new file mode 100644
index 00000000..0d2ad198
--- /dev/null
+++ b/changelog/unreleased/qoder-history-reasoning-content.md
@@ -0,0 +1,7 @@
+### English
+
+- Qoder requests now keep the `reasoning_content` of earlier assistant messages instead of silently dropping it.
+
+### 中文
+
+- Qoder 请求现在会保留历史 assistant 消息中的 `reasoning_content`，不再静默丢弃。
diff --git a/internal/providers/qoder/direct.go b/internal/providers/qoder/direct.go
index 5f063ed7..64741ba4 100644
--- a/internal/providers/qoder/direct.go
+++ b/internal/providers/qoder/direct.go
@@ -337,6 +337,9 @@ func BuildPlainChatBody(req translate.ChatRequest, now time.Time) map[string]any
 		if message.ToolCallID != "" {
 			item["tool_call_id"] = message.ToolCallID
 		}
+		if message.ReasoningContent != "" {
+			item["reasoning_content"] = message.ReasoningContent
+		}
 		if len(message.ToolCalls) > 0 {
 			item["tool_calls"] = json.RawMessage(message.ToolCalls)
 		}
diff --git a/internal/providers/qoder/history_reasoning_test.go b/internal/providers/qoder/history_reasoning_test.go
new file mode 100644
index 00000000..79d6a632
--- /dev/null
+++ b/internal/providers/qoder/history_reasoning_test.go
@@ -0,0 +1,26 @@
+package qoder
+
+import (
+	"testing"
+	"time"
+
+	"github.com/caigee-cmd/cli2api/internal/translate"
+)
+
+// Regression for #330: client-supplied historical reasoning must survive the
+// plaintext body rebuild.
+func TestBuildPlainChatBodyKeepsHistoricalReasoning(t *testing.T) {
+	req := translate.ChatRequest{Model: "dfmodel", Messages: []translate.ChatMessage{
+		{Role: "user", Content: "Use the synthetic snapshot."},
+		{Role: "assistant", Content: "Snapshot checked.", ReasoningContent: "Synthetic marker: M1"},
+		{Role: "user", Content: "Continue."},
+	}}
+	body := BuildPlainChatBody(req, time.Unix(1, 0))
+	messages := body["messages"].([]map[string]any)
+	if got := messages[1]["reasoning_content"]; got != "Synthetic marker: M1" {
+		t.Fatalf("historical reasoning lost: got %#v", got)
+	}
+	if _, ok := messages[0]["reasoning_content"]; ok {
+		t.Fatalf("empty reasoning_content should be omitted: %#v", messages[0])
+	}
+}