diff --git a/src/plugin-sdk/provider-tools.test.ts b/src/plugin-sdk/provider-tools.test.ts
index 0297446a960..d39774706e7 100644
--- a/src/plugin-sdk/provider-tools.test.ts
+++ b/src/plugin-sdk/provider-tools.test.ts
@@ -119,6 +119,90 @@ describe("buildProviderToolCompatFamilyHooks", () => {
     ).toStrictEqual([]);
   });
 
+  it("preserves string-const unions as a flat enum for the deepseek family", () => {
+    // Regression for https://github.com/openclaw/openclaw/issues/86468 —
+    // Typebox `Type.Union([Type.Literal(...)])` collapses to anyOf of consts;
+    // the previous normalizer kept only the first const, hiding every other
+    // literal from the model.
+    const hooks = buildProviderToolCompatFamilyHooks("deepseek");
+    const tools = [
+      {
+        name: "feishu_update_doc",
+        description: "",
+        parameters: {
+          type: "object",
+          properties: {
+            mode: {
+              description: "更新模式（必填）",
+              anyOf: [
+                { const: "overwrite", type: "string" },
+                { const: "append", type: "string" },
+                { const: "replace_range", type: "string" },
+              ],
+            },
+            optional_mode: {
+              anyOf: [
+                { const: "a", type: "string" },
+                { const: "b", type: "string" },
+                { type: "null" },
+              ],
+            },
+            single_const: {
+              anyOf: [{ const: "only", type: "string" }],
+            },
+          },
+          required: ["mode"],
+        },
+      },
+    ] as never;
+
+    const normalized = hooks.normalizeToolSchemas({
+      provider: "deepseek",
+      modelId: "deepseek-v4-pro",
+      modelApi: "openai-completions",
+      model: {
+        provider: "deepseek",
+        api: "openai-completions",
+        id: "deepseek-v4-pro",
+      } as never,
+      tools,
+    });
+
+    expect(normalized[0]?.parameters).toEqual({
+      type: "object",
+      properties: {
+        mode: {
+          description: "更新模式（必填）",
+          type: "string",
+          enum: ["overwrite", "append", "replace_range"],
+        },
+        optional_mode: {
+          type: "string",
+          enum: ["a", "b"],
+          nullable: true,
+        },
+        single_const: {
+          const: "only",
+          type: "string",
+        },
+      },
+      required: ["mode"],
+    });
+    expect(
+      hooks.inspectToolSchemas({
+        provider: "deepseek",
+        modelId: "deepseek-v4-pro",
+        modelApi: "openai-completions",
+        model: {
+          provider: "deepseek",
+          api: "openai-completions",
+          id: "deepseek-v4-pro",
+        } as never,
+        tools: normalized,
+      }),
+    ).toStrictEqual([]);
+  });
+
   it("normalizes parameter-free and typed-object schemas for the openai family", () => {
     const hooks = buildProviderToolCompatFamilyHooks("openai");
     const tools = [
diff --git a/src/plugin-sdk/provider-tools.ts b/src/plugin-sdk/provider-tools.ts
index fdf988a080b..c999786759c 100644
--- a/src/plugin-sdk/provider-tools.ts
+++ b/src/plugin-sdk/provider-tools.ts
@@ -455,6 +455,25 @@ function normalizeDeepSeekSchema(schema: unknown): unknown {
   const variants = record[unionKey] as unknown[];
   const normalizedVariants = variants.map((entry) => normalizeDeepSeekSchema(entry));
   const nonNullVariants = normalizedVariants.filter((entry) => !isNullSchemaVariant(entry));
+  const hasNullVariant = nonNullVariants.length < normalizedVariants.length;
+
+  // Preserve string-const unions as a flat string enum so DeepSeek tool
+  // callers still see every allowed literal. Without this, a Typebox
+  // `Type.Union([Type.Literal("a"), Type.Literal("b"), ...])` collapses to
+  // only the first const and the model can never pick any other value.
+  if (nonNullVariants.length > 1 && nonNullVariants.every((entry) => isStringConstVariant(entry))) {
+    const enumValues = nonNullVariants.map((entry) => (entry as { const: string }).const);
+    const merged: Record<string, unknown> = {
+      ...normalized,
+      type: "string",
+      enum: enumValues,
+    };
+    if (hasNullVariant) {
+      merged.nullable = true;
+    }
+    return merged;
+  }
+
   const selected = nonNullVariants[0] ?? normalizedVariants[0];
   if (!selected || typeof selected !== "object" || Array.isArray(selected)) {
     return normalized;
@@ -464,12 +483,20 @@ function normalizeDeepSeekSchema(schema: unknown): unknown {
     ...(selected as Record<string, unknown>),
     ...normalized,
   };
-  if (nonNullVariants.length < normalizedVariants.length) {
+  if (hasNullVariant) {
     merged.nullable = true;
   }
   return merged;
 }
 
+function isStringConstVariant(entry: unknown): entry is { const: string } {
+  if (!entry || typeof entry !== "object" || Array.isArray(entry)) {
+    return false;
+  }
+  const record = entry as Record<string, unknown>;
+  return typeof record.const === "string";
+}
+
 export function normalizeDeepSeekToolSchemas(
   ctx: ProviderNormalizeToolSchemasContext,
 ): AnyAgentTool[] {