diff --git a/packages/shared/src/contracts/generated/LlmModelSummary.ts b/packages/shared/src/contracts/generated/LlmModelSummary.ts
index be2e3c30c..97c5e6ad6 100644
--- a/packages/shared/src/contracts/generated/LlmModelSummary.ts
+++ b/packages/shared/src/contracts/generated/LlmModelSummary.ts
@@ -11,6 +11,6 @@ export type LlmModelSummary = { displayName: string, id: string,
  */
 agentMode: AgcAgentMode, 
 /**
- * 上游线协议；旧服务端缺字段时按 `openai_responses` 兼容。
+ * 上游线协议；旧服务端缺字段时按 `agent_mode` 的默认协议兼容。
  */
 protocol: AgcModelProtocol, };
diff --git a/packages/shared/src/contracts/generated/LlmUnavailableModel.ts b/packages/shared/src/contracts/generated/LlmUnavailableModel.ts
index f41401bbc..119e03dc7 100644
--- a/packages/shared/src/contracts/generated/LlmUnavailableModel.ts
+++ b/packages/shared/src/contracts/generated/LlmUnavailableModel.ts
@@ -6,4 +6,8 @@ import type { LlmModelUnavailableReason } from "./LlmModelUnavailableReason";
 /**
  * 目录里存在、但当前账号不可用的一条模型。字段与 [`LlmModelSummary`] 对齐，另带原因。
  */
-export type LlmUnavailableModel = { displayName: string, id: string, agentMode: AgcAgentMode, protocol: AgcModelProtocol, reason: LlmModelUnavailableReason, };
+export type LlmUnavailableModel = { displayName: string, id: string, agentMode: AgcAgentMode, 
+/**
+ * 上游线协议；旧服务端缺字段时按 `agent_mode` 的默认协议兼容。
+ */
+protocol: AgcModelProtocol, reason: LlmModelUnavailableReason, };
diff --git a/server-rs/crates/shared-contracts/src/llm_catalog.rs b/server-rs/crates/shared-contracts/src/llm_catalog.rs
index 72a79bfce..e25478082 100644
--- a/server-rs/crates/shared-contracts/src/llm_catalog.rs
+++ b/server-rs/crates/shared-contracts/src/llm_catalog.rs
@@ -124,9 +124,35 @@ impl AgcModelProtocol {
     }
 }
 
+/// 反序列化中间态：`protocol` 缺失时按 `agent_mode` 的默认协议补齐（见 `From` 实现）。
+#[derive(Deserialize)]
+#[serde(rename_all = "camelCase")]
+struct LlmModelSummaryWire {
+    display_name: String,
+    id: String,
+    #[serde(default)]
+    agent_mode: AgcAgentMode,
+    #[serde(default)]
+    protocol: Option<AgcModelProtocol>,
+}
+
+impl From<LlmModelSummaryWire> for LlmModelSummary {
+    fn from(wire: LlmModelSummaryWire) -> Self {
+        let protocol = wire
+            .protocol
+            .unwrap_or_else(|| wire.agent_mode.default_protocol());
+        Self {
+            display_name: wire.display_name,
+            id: wire.id,
+            agent_mode: wire.agent_mode,
+            protocol,
+        }
+    }
+}
+
 /// 本档可用的一条模型摘要。不包含上游真实模型名。
 #[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize)]
-#[serde(rename_all = "camelCase")]
+#[serde(rename_all = "camelCase", from = "LlmModelSummaryWire")]
 #[cfg_attr(feature = "ts-bindings", derive(ts_rs::TS))]
 #[cfg_attr(
     feature = "ts-bindings",
@@ -144,14 +170,42 @@ pub struct LlmModelSummary {
     /// 执行器；旧服务端缺字段时按 `codex` 兼容。
     #[serde(default)]
     pub agent_mode: AgcAgentMode,
-    /// 上游线协议；旧服务端缺字段时按 `openai_responses` 兼容。
+    /// 上游线协议；旧服务端缺字段时按 `agent_mode` 的默认协议兼容。
     #[serde(default)]
     pub protocol: AgcModelProtocol,
 }
 
+/// 反序列化中间态：与 [`LlmModelSummaryWire`] 同规则，额外携带 `reason`。
+#[derive(Deserialize)]
+#[serde(rename_all = "camelCase")]
+struct LlmUnavailableModelWire {
+    display_name: String,
+    id: String,
+    #[serde(default)]
+    agent_mode: AgcAgentMode,
+    #[serde(default)]
+    protocol: Option<AgcModelProtocol>,
+    reason: LlmModelUnavailableReason,
+}
+
+impl From<LlmUnavailableModelWire> for LlmUnavailableModel {
+    fn from(wire: LlmUnavailableModelWire) -> Self {
+        let protocol = wire
+            .protocol
+            .unwrap_or_else(|| wire.agent_mode.default_protocol());
+        Self {
+            display_name: wire.display_name,
+            id: wire.id,
+            agent_mode: wire.agent_mode,
+            protocol,
+            reason: wire.reason,
+        }
+    }
+}
+
 /// 目录里存在、但当前账号不可用的一条模型。字段与 [`LlmModelSummary`] 对齐，另带原因。
 #[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize)]
-#[serde(rename_all = "camelCase")]
+#[serde(rename_all = "camelCase", from = "LlmUnavailableModelWire")]
 #[cfg_attr(feature = "ts-bindings", derive(ts_rs::TS))]
 #[cfg_attr(
     feature = "ts-bindings",
@@ -168,6 +222,7 @@ pub struct LlmUnavailableModel {
     pub id: String,
     #[serde(default)]
     pub agent_mode: AgcAgentMode,
+    /// 上游线协议；旧服务端缺字段时按 `agent_mode` 的默认协议兼容。
     #[serde(default)]
     pub protocol: AgcModelProtocol,
     pub reason: LlmModelUnavailableReason,
@@ -224,3 +279,45 @@ pub struct LlmModelsResponse {
     #[cfg_attr(feature = "ts-bindings", ts(type = "number"))]
     pub revision: u64,
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn missing_protocol_follows_agent_mode() {
+        let cc: LlmModelSummary =
+            serde_json::from_str(r#"{"displayName":"Claude","id":"model-a","agentMode":"cc"}"#)
+                .unwrap();
+        assert_eq!(cc.protocol, AgcModelProtocol::Anthropic);
+
+        let legacy_alias: LlmModelSummary = serde_json::from_str(
+            r#"{"displayName":"Claude","id":"model-a","agentMode":"anthropic"}"#,
+        )
+        .unwrap();
+        assert_eq!(legacy_alias.agent_mode, AgcAgentMode::Cc);
+        assert_eq!(legacy_alias.protocol, AgcModelProtocol::Anthropic);
+
+        let codex: LlmModelSummary =
+            serde_json::from_str(r#"{"displayName":"GPT","id":"model-b"}"#).unwrap();
+        assert_eq!(codex.agent_mode, AgcAgentMode::Codex);
+        assert_eq!(codex.protocol, AgcModelProtocol::OpenAiResponses);
+
+        // 显式 protocol 优先，不被 agent_mode 覆盖。
+        let explicit: LlmModelSummary = serde_json::from_str(
+            r#"{"displayName":"GPT","id":"model-c","agentMode":"codex","protocol":"openai_chat"}"#,
+        )
+        .unwrap();
+        assert_eq!(explicit.protocol, AgcModelProtocol::OpenAiChat);
+    }
+
+    #[test]
+    fn unavailable_model_missing_protocol_follows_agent_mode() {
+        let cc: LlmUnavailableModel = serde_json::from_str(
+            r#"{"displayName":"Claude","id":"model-a","agentMode":"cc","reason":"disabled"}"#,
+        )
+        .unwrap();
+        assert_eq!(cc.protocol, AgcModelProtocol::Anthropic);
+        assert_eq!(cc.reason, LlmModelUnavailableReason::Disabled);
+    }
+}