diff --git a/src/agents/pi-tools.test.ts b/src/agents/pi-tools.test.ts
index 0c61fc555..77463f33d 100644
--- a/src/agents/pi-tools.test.ts
+++ b/src/agents/pi-tools.test.ts
@@ -18,4 +18,51 @@ describe("createClawdisCodingTools", () => {
     expect(parameters.properties?.request).toBeDefined();
     expect(parameters.required ?? []).toContain("action");
   });
+
+  it("preserves union action values in merged schema", () => {
+    const tools = createClawdisCodingTools();
+    const toolNames = tools
+      .filter((tool) => tool.name.startsWith("clawdis_"))
+      .map((tool) => tool.name);
+
+    for (const name of toolNames) {
+      const tool = tools.find((candidate) => candidate.name === name);
+      expect(tool).toBeDefined();
+      const parameters = tool?.parameters as {
+        anyOf?: Array<{ properties?: Record<string, unknown> }>;
+        properties?: Record<string, unknown>;
+      };
+      const actionValues = new Set<string>();
+      for (const variant of parameters.anyOf ?? []) {
+        const action = variant?.properties?.action as
+          | { const?: unknown; enum?: unknown[] }
+          | undefined;
+        if (typeof action?.const === "string") actionValues.add(action.const);
+        if (Array.isArray(action?.enum)) {
+          for (const value of action.enum) {
+            if (typeof value === "string") actionValues.add(value);
+          }
+        }
+      }
+
+      const mergedAction = parameters.properties?.action as
+        | { const?: unknown; enum?: unknown[] }
+        | undefined;
+      const mergedValues = new Set<string>();
+      if (typeof mergedAction?.const === "string") {
+        mergedValues.add(mergedAction.const);
+      }
+      if (Array.isArray(mergedAction?.enum)) {
+        for (const value of mergedAction.enum) {
+          if (typeof value === "string") mergedValues.add(value);
+        }
+      }
+
+      expect(actionValues.size).toBeGreaterThan(1);
+      expect(mergedValues.size).toBe(actionValues.size);
+      for (const value of actionValues) {
+        expect(mergedValues.has(value)).toBe(true);
+      }
+    }
+  });
 });
diff --git a/src/agents/pi-tools.ts b/src/agents/pi-tools.ts
index a0aa68539..273641ffb 100644
--- a/src/agents/pi-tools.ts
+++ b/src/agents/pi-tools.ts
@@ -99,6 +99,41 @@ async function normalizeReadImageResult(
 
 type AnyAgentTool = AgentTool<TSchema, unknown>;
 
+function extractEnumValues(schema: unknown): unknown[] | undefined {
+  if (!schema || typeof schema !== "object") return undefined;
+  const record = schema as Record<string, unknown>;
+  if (Array.isArray(record.enum)) return record.enum;
+  if ("const" in record) return [record.const];
+  return undefined;
+}
+
+function mergePropertySchemas(existing: unknown, incoming: unknown): unknown {
+  if (!existing) return incoming;
+  if (!incoming) return existing;
+
+  const existingEnum = extractEnumValues(existing);
+  const incomingEnum = extractEnumValues(incoming);
+  if (existingEnum || incomingEnum) {
+    const values = Array.from(
+      new Set([...(existingEnum ?? []), ...(incomingEnum ?? [])]),
+    );
+    const merged: Record<string, unknown> = {};
+    for (const source of [existing, incoming]) {
+      if (!source || typeof source !== "object") continue;
+      const record = source as Record<string, unknown>;
+      for (const key of ["title", "description", "default"]) {
+        if (!(key in merged) && key in record) merged[key] = record[key];
+      }
+    }
+    const types = new Set(values.map((value) => typeof value));
+    if (types.size === 1) merged.type = Array.from(types)[0];
+    merged.enum = values;
+    return merged;
+  }
+
+  return existing;
+}
+
 function normalizeToolParameters(tool: AnyAgentTool): AnyAgentTool {
   const schema =
     tool.parameters && typeof tool.parameters === "object"
@@ -119,7 +154,14 @@ function normalizeToolParameters(tool: AnyAgentTool): AnyAgentTool {
     for (const [key, value] of Object.entries(
       props as Record<string, unknown>,
     )) {
-      if (!(key in mergedProperties)) mergedProperties[key] = value;
+      if (!(key in mergedProperties)) {
+        mergedProperties[key] = value;
+        continue;
+      }
+      mergedProperties[key] = mergePropertySchemas(
+        mergedProperties[key],
+        value,
+      );
     }
     const required = Array.isArray((entry as { required?: unknown }).required)
       ? (entry as { required: unknown[] }).required