diff --git a/im/backend/internal/app/admin_ai.go b/im/backend/internal/app/admin_ai.go
index dc608e8..9f46e87 100644
--- a/im/backend/internal/app/admin_ai.go
+++ b/im/backend/internal/app/admin_ai.go
@@ -5,6 +5,7 @@ import (
 	"crypto/sha256"
 	"database/sql"
 	"encoding/hex"
+	"encoding/json"
 	"errors"
 	"fmt"
 	"net/http"
@@ -27,18 +28,44 @@ type aiModelRequest struct {
 	TimeoutMS   *int     `json:"timeoutMs"`
 	Status      *int     `json:"status"`
 	IsDefault   *bool    `json:"isDefault"`
+	// Raw provider fields merged into every call, e.g. {"thinking":{"type":"disabled"}}
+	// to stop a model that reasons by default from spending the budget thinking.
+	Extra *string `json:"extra"`
 }
 
-const aiModelColumns = `id,name,protocol,base_url,model_name,api_key_cipher,temperature,max_tokens,timeout_ms,status,is_default,created_at,updated_at`
+// The column is JSON, so an invalid value has to be refused before it is stored
+// and starts failing every call at read time instead.
+func aiModelExtra(value *string, fallback any) (any, error) {
+	if value == nil {
+		return fallback, nil
+	}
+	trimmed := strings.TrimSpace(*value)
+	if trimmed == "" {
+		return nil, nil
+	}
+	var parsed map[string]any
+	if err := json.Unmarshal([]byte(trimmed), &parsed); err != nil {
+		return nil, fmt.Errorf("扩展参数必须是 JSON 对象")
+	}
+	return trimmed, nil
+}
+
+const aiModelColumns = `id,name,protocol,base_url,model_name,api_key_cipher,temperature,max_tokens,timeout_ms,status,is_default,extra_json,created_at,updated_at`
 
 func (a *App) scanAIModel(scan func(dest ...any) error) (aiModel, error) {
 	var model aiModel
 	var cipher string
+	var extra sql.NullString
 	var created, updated time.Time
 	if err := scan(&model.ID, &model.Name, &model.Protocol, &model.BaseURL, &model.ModelName, &cipher,
-		&model.Temperature, &model.MaxTokens, &model.TimeoutMS, &model.Status, &model.IsDefault, &created, &updated); err != nil {
+		&model.Temperature, &model.MaxTokens, &model.TimeoutMS, &model.Status, &model.IsDefault, &extra, &created, &updated); err != nil {
 		return aiModel{}, err
 	}
+	if strings.TrimSpace(extra.String) != "" {
+		if err := json.Unmarshal([]byte(extra.String), &model.Extra); err != nil {
+			return model, fmt.Errorf("模型 %s 的扩展参数不是合法 JSON", model.Name)
+		}
+	}
 	model.HasAPIKey = cipher != ""
 	if cipher != "" {
 		plain, err := a.decryptSecret(cipher)
@@ -187,6 +214,11 @@ func (a *App) adminCreateAIModel(w http.ResponseWriter, r *http.Request) {
 		status = *req.Status
 	}
 	isDefault := req.IsDefault != nil && *req.IsDefault
+	extra, err := aiModelExtra(req.Extra, nil)
+	if err != nil {
+		fail(w, http.StatusBadRequest, 20001, err.Error())
+		return
+	}
 	tx, err := a.db.BeginTx(r.Context(), nil)
 	if err != nil {
 		fail(w, http.StatusInternalServerError, 50001, "保存模型失败")
@@ -200,9 +232,9 @@ func (a *App) adminCreateAIModel(w http.ResponseWriter, r *http.Request) {
 		}
 	}
 	result, err := tx.ExecContext(r.Context(), `INSERT INTO ai_models
-		(name,protocol,base_url,model_name,api_key_cipher,temperature,max_tokens,timeout_ms,status,is_default)
-		VALUES(?,?,?,?,?,?,?,?,?,?)`,
-		req.Name, req.Protocol, req.BaseURL, req.ModelName, cipher, temperature, maxTokens, timeout, status, btoi(isDefault))
+		(name,protocol,base_url,model_name,api_key_cipher,temperature,max_tokens,timeout_ms,status,is_default,extra_json)
+		VALUES(?,?,?,?,?,?,?,?,?,?,?)`,
+		req.Name, req.Protocol, req.BaseURL, req.ModelName, cipher, temperature, maxTokens, timeout, status, btoi(isDefault), extra)
 	if err != nil {
 		if isDuplicateAIModelName(err) {
 			fail(w, http.StatusBadRequest, 20001, "模型名称已存在")
@@ -270,6 +302,16 @@ func (a *App) adminUpdateAIModel(w http.ResponseWriter, r *http.Request) {
 	if req.IsDefault != nil {
 		isDefault = *req.IsDefault
 	}
+	var existingExtra any
+	if len(existing.Extra) > 0 {
+		encoded, _ := json.Marshal(existing.Extra)
+		existingExtra = string(encoded)
+	}
+	extra, err := aiModelExtra(req.Extra, existingExtra)
+	if err != nil {
+		fail(w, http.StatusBadRequest, 20001, err.Error())
+		return
+	}
 	tx, err := a.db.BeginTx(r.Context(), nil)
 	if err != nil {
 		fail(w, http.StatusInternalServerError, 50001, "保存模型失败")
@@ -282,9 +324,9 @@ func (a *App) adminUpdateAIModel(w http.ResponseWriter, r *http.Request) {
 			return
 		}
 	}
-	args := append([]any{req.Name, req.Protocol, req.BaseURL, req.ModelName, temperature, maxTokens, timeout, status, btoi(isDefault)}, cipherArgs...)
+	args := append([]any{req.Name, req.Protocol, req.BaseURL, req.ModelName, temperature, maxTokens, timeout, status, btoi(isDefault), extra}, cipherArgs...)
 	args = append(args, id)
-	if _, err = tx.ExecContext(r.Context(), `UPDATE ai_models SET name=?,protocol=?,base_url=?,model_name=?,temperature=?,max_tokens=?,timeout_ms=?,status=?,is_default=?`+cipherClause+` WHERE id=?`, args...); err != nil {
+	if _, err = tx.ExecContext(r.Context(), `UPDATE ai_models SET name=?,protocol=?,base_url=?,model_name=?,temperature=?,max_tokens=?,timeout_ms=?,status=?,is_default=?,extra_json=?`+cipherClause+` WHERE id=?`, args...); err != nil {
 		if isDuplicateAIModelName(err) {
 			fail(w, http.StatusBadRequest, 20001, "模型名称已存在")
 			return
diff --git a/im/backend/internal/app/ai_providers.go b/im/backend/internal/app/ai_providers.go
index cdae894..e2fb1b9 100644
--- a/im/backend/internal/app/ai_providers.go
+++ b/im/backend/internal/app/ai_providers.go
@@ -68,6 +68,10 @@ type aiModel struct {
 	IsDefault   bool    `json:"isDefault"`
 	APIKey      string  `json:"-"`
 	HasAPIKey   bool    `json:"hasApiKey"`
+	// Provider-specific request fields, merged into the call body. This is how a
+	// model that thinks by default is asked not to, without a code change:
+	// {"thinking":{"type":"disabled"}}.
+	Extra map[string]any `json:"extra,omitempty"`
 	CreatedAt   string  `json:"createdAt"`
 	UpdatedAt   string  `json:"updatedAt"`
 }
@@ -169,6 +173,19 @@ func aiRequestMaxTokens(req aiChatRequest, model aiModel) int {
 	return 256
 }
 
+// aiWithExtra adds the model's configured protocol fields to a request body.
+// It never overwrites what the caller set: the structural fields and the budget
+// this code reasons about stay under this code's control.
+func aiWithExtra(model aiModel, body map[string]any) map[string]any {
+	for key, value := range model.Extra {
+		if _, taken := body[key]; taken {
+			continue
+		}
+		body[key] = value
+	}
+	return body
+}
+
 // One retry, with enough room for the thinking plus a short answer, and a cap
 // so a misconfigured model cannot bill an unbounded completion.
 func aiRetryMaxTokens(current int) int {
@@ -242,13 +259,13 @@ func (p openAIProvider) Chat(ctx context.Context, req aiChatRequest) (aiChatResu
 	}
 	raw, err := aiPostJSON(ctx, p.client, aiEndpoint(p.base, "/chat/completions"),
 		map[string]string{"Authorization": "Bearer " + p.model.APIKey},
-		map[string]any{
+		aiWithExtra(p.model, map[string]any{
 			"model":       p.model.ModelName,
 			"messages":    messages,
 			"max_tokens":  aiRequestMaxTokens(req, p.model),
 			"temperature": aiRequestTemperature(req, p.model),
 			"stream":      false,
-		})
+		}))
 	if err != nil {
 		return aiChatResult{}, err
 	}
diff --git a/im/backend/internal/app/ai_providers_test.go b/im/backend/internal/app/ai_providers_test.go
index 6d1bf62..bd0b891 100644
--- a/im/backend/internal/app/ai_providers_test.go
+++ b/im/backend/internal/app/ai_providers_test.go
@@ -320,3 +320,51 @@ func TestTruncatedAnswerIsRetriedAndKeptIfItSurvives(t *testing.T) {
 		t.Fatalf("text = %q", result.Text)
 	}
 }
+
+// A model that reasons by default is told not to through its stored protocol
+// fields, without a code change and without a second model row.
+func TestModelExtraFieldsReachTheProviderWithoutOverridingTheCall(t *testing.T) {
+	server, body, _ := captureAIRequest(t, `{"id":"c","choices":[{"message":{"content":"在的"},"finish_reason":"stop"}],"usage":{}}`, 200)
+	model := testModel("openai", server.URL)
+	model.Extra = map[string]any{
+		"thinking": map[string]any{"type": "disabled"},
+		// Structural fields and the budget stay under this code's control.
+		"model":      "someone-elses-model",
+		"max_tokens": 999999,
+		"stream":     true,
+	}
+	provider, err := newAIProvider(model, false)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if _, err = provider.Chat(context.Background(), aiChatRequest{Messages: []aiChatMessage{{Role: "user", Text: "在吗"}}}); err != nil {
+		t.Fatal(err)
+	}
+	thinking, ok := (*body)["thinking"].(map[string]any)
+	if !ok || thinking["type"] != "disabled" {
+		t.Fatalf("thinking = %v", (*body)["thinking"])
+	}
+	if (*body)["model"] != "demo-model" || (*body)["max_tokens"] != float64(128) || (*body)["stream"] != false {
+		t.Fatalf("扩展参数不得覆盖调用本身: %v", *body)
+	}
+}
+
+func TestAIModelExtraIsValidatedBeforeItIsStored(t *testing.T) {
+	keep := "{\"thinking\":{\"type\":\"disabled\"}}"
+	value, err := aiModelExtra(&keep, nil)
+	if err != nil || value != keep {
+		t.Fatalf("value = %v err = %v", value, err)
+	}
+	blank := "  "
+	if value, err = aiModelExtra(&blank, "old"); err != nil || value != nil {
+		t.Fatalf("留空应清除扩展参数: %v %v", value, err)
+	}
+	broken := "{not json"
+	if _, err = aiModelExtra(&broken, nil); err == nil {
+		t.Fatal("非法 JSON 必须在写库前被拒绝")
+	}
+	// Omitted entirely: the stored value survives an edit that does not mention it.
+	if value, err = aiModelExtra(nil, "old"); err != nil || value != "old" {
+		t.Fatalf("value = %v err = %v", value, err)
+	}
+}