diff --git a/electron.vite.config.ts b/electron.vite.config.ts
index c02e9a5b..4b564663 100644
--- a/electron.vite.config.ts
+++ b/electron.vite.config.ts
@@ -22,7 +22,7 @@ export default defineConfig({
     },
   },
   preload: {
-    plugins: [externalizeDepsPlugin()],
+    plugins: [externalizeDepsPlugin({ exclude: ["zod"] })],
     resolve: {
       alias: {
         "@shared": resolve("src/shared"),
diff --git a/src/main/ipc-core-admin-handlers.ts b/src/main/ipc-core-admin-handlers.ts
index fdd4bde6..e2ea3e85 100644
--- a/src/main/ipc-core-admin-handlers.ts
+++ b/src/main/ipc-core-admin-handlers.ts
@@ -1,6 +1,7 @@
 import { execFile } from "node:child_process";
 import {
   IPC_CHANNELS,
+  companyIdSchema,
   companyInputSchema,
   connectorDisabledModelsSchema,
   connectorInputSchema,
@@ -73,13 +74,11 @@ export function registerCoreAdminHandlers({
   });
 
   registerHandle(IPC_CHANNELS.setCurrentCompany, async (_event, companyId) => {
-    if (typeof companyId !== "string" || !companyId) {
-      return fail("INVALID_COMPANY_ID", "A valid company id is required.");
-    }
-    if (!db.core.settings.hasCompany(companyId)) {
+    const parsed = companyIdSchema.parse(companyId);
+    if (!db.core.settings.hasCompany(parsed)) {
       return fail("COMPANY_NOT_FOUND", "The selected company does not exist.");
     }
-    db.core.settings.setCurrentCompany(companyId);
+    db.core.settings.setCurrentCompany(parsed);
     publishDomainChanged();
     return ok(true);
   });
@@ -153,13 +152,11 @@ export function registerCoreAdminHandlers({
   });
 
   registerHandle(IPC_CHANNELS.deleteCompany, async (_event, companyId) => {
-    if (typeof companyId !== "string" || companyId.length === 0) {
-      return fail("INVALID_INPUT", "Company ID is required.");
-    }
-    if (!db.core.settings.hasCompany(companyId)) {
+    const parsed = companyIdSchema.parse(companyId);
+    if (!db.core.settings.hasCompany(parsed)) {
       return fail("COMPANY_NOT_FOUND", "Company not found.");
     }
-    db.core.company.deleteCompany(companyId);
+    db.core.company.deleteCompany(parsed);
     publishDomainChanged();
     return ok(true);
   });
diff --git a/src/main/ipc-recovery-handlers.ts b/src/main/ipc-recovery-handlers.ts
index d5158f3d..0a6c9281 100644
--- a/src/main/ipc-recovery-handlers.ts
+++ b/src/main/ipc-recovery-handlers.ts
@@ -1,18 +1,6 @@
-import { z } from "zod";
-import { IPC_CHANNELS } from "@shared/contracts";
+import { IPC_CHANNELS, recoveryRetrySchema, recoveryTaskSchema } from "@shared/contracts";
 import { fail, ok, type RegisterDomainHandlersDependencies } from "./ipc-domain-common";
 
-const recoveryRetrySchema = z.object({
-  taskId: z.string(),
-  agentId: z.string(),
-  companyId: z.string(),
-});
-
-const recoveryTaskSchema = z.object({
-  taskId: z.string(),
-  companyId: z.string(),
-});
-
 export function registerRecoveryHandlers({
   registerHandle,
   db,
diff --git a/src/preload/index.ts b/src/preload/index.ts
index a8fea974..8c1cf30a 100644
--- a/src/preload/index.ts
+++ b/src/preload/index.ts
@@ -3,19 +3,23 @@ import { IPC_CHANNELS } from "@shared/contracts/channels";
 import type { DesktopApi } from "@shared/contracts/desktop-api";
 import {
   PRELOAD_FORWARDERS,
+  PRELOAD_INPUT_SCHEMAS,
   mapPreloadInvokeArgs,
   type PreloadForwardedApi,
 } from "@shared/contracts/preload-forwarders";
 import type { DesktopEvent } from "@shared/types";
 
 function createForwardedApi(): PreloadForwardedApi {
-  const forwardedEntries = PRELOAD_FORWARDERS.map(({ api, channel, payload }) => [
-    api,
-    (...args: unknown[]) => ipcRenderer.invoke(
-      IPC_CHANNELS[channel],
-      ...mapPreloadInvokeArgs(payload, args),
-    ),
-  ]);
+  const forwardedEntries = PRELOAD_FORWARDERS.map(({ api, channel, payload }) => {
+    const schema = PRELOAD_INPUT_SCHEMAS[api];
+    return [
+      api,
+      (...args: unknown[]) => ipcRenderer.invoke(
+        IPC_CHANNELS[channel],
+        ...mapPreloadInvokeArgs(payload, args, schema),
+      ),
+    ];
+  });
 
   return Object.fromEntries(forwardedEntries) as PreloadForwardedApi;
 }
diff --git a/src/shared/contracts/preload-forwarders.ts b/src/shared/contracts/preload-forwarders.ts
index 2112a21f..d25390be 100644
--- a/src/shared/contracts/preload-forwarders.ts
+++ b/src/shared/contracts/preload-forwarders.ts
@@ -1,5 +1,80 @@
+import { z } from "zod";
 import { IPC_CHANNELS } from "./channels";
 import type { DesktopApi } from "./desktop-api";
+import {
+  agentInputSchema,
+  heartbeatSettingsSchema,
+  hireRequestSchema,
+  triggerHeartbeatSchema,
+} from "./schemas-agents";
+import {
+  approvalDecisionSchema,
+  approvalInputSchema,
+} from "./schemas-approvals";
+import {
+  automationRuleInputSchema,
+  toggleAutomationRuleSchema,
+} from "./schemas-automation";
+import {
+  deleteEntitySchema,
+  entityGetterSchema,
+} from "./schemas-badges";
+import {
+  budgetPolicyInputSchema,
+  deleteBudgetPolicySchema,
+  resolveBudgetIncidentSchema,
+} from "./schemas-budget";
+import {
+  bootstrapOnboardingSchema,
+  companyIdSchema,
+  companyInputSchema,
+  connectorDisabledModelsSchema,
+  connectorInputSchema,
+  socialAccountInputSchema,
+  settingsSchema,
+  workspaceInputSchema,
+} from "./schemas-company";
+import {
+  removeCredentialInputSchema,
+  saveCredentialInputSchema,
+  testCredentialInputSchema,
+} from "./schemas-credentials";
+import {
+  assignSkillToAgentSchema,
+  cancelBrowserActionSchema,
+  cancelRunSchema,
+  checkSkillUpdateSchema,
+  deleteSkillSchema,
+  importSkillSchema,
+  openTerminalCommandSchema,
+  recoveryRetrySchema,
+  recoveryTaskSchema,
+  removeSkillFromAgentSchema,
+  runWorkflowSchema,
+  startRunSchema,
+  triggerBrowserLoginSchema,
+  workflowInputSchema,
+} from "./schemas-execution";
+import {
+  agentMessageInputSchema,
+  commentInputSchema,
+  documentInputSchema,
+  knowledgeEntryInputSchema,
+  markMessageReadSchema,
+  meetingInputSchema,
+} from "./schemas-messages";
+import {
+  oauthCancelInputSchema,
+  oauthManualCodeResponseSchema,
+  oauthPromptResponseSchema,
+  oauthStartInputSchema,
+} from "./schemas-oauth";
+import {
+  goalInputSchema,
+  projectInputSchema,
+  sprintInputSchema,
+  taskInputSchema,
+} from "./schemas-tasks";
 
 type DesktopFunctionKey = {
   [Key in keyof DesktopApi]: DesktopApi[Key] extends (...args: infer _Args) => unknown ? Key : never;
@@ -138,9 +213,83 @@ export const PRELOAD_FORWARDERS = [
 export type PreloadForwardedMethod = (typeof PRELOAD_FORWARDERS)[number]["api"];
 export type PreloadForwardedApi = Pick<DesktopApi, PreloadForwardedMethod>;
 
+const managedPathSchema = z.string().min(1);
+
+export const PRELOAD_INPUT_SCHEMAS: Partial<Record<PreloadForwardedMethod, z.ZodType<unknown>>> = {
+  openPath: managedPathSchema,
+  openWorkProduct: entityGetterSchema,
+  saveCompany: companyInputSchema,
+  setCurrentCompany: companyIdSchema,
+  saveConnector: connectorInputSchema,
+  testConnector: connectorInputSchema.shape.id,
+  saveWorkspace: workspaceInputSchema,
+  saveAgent: agentInputSchema,
+  requestHire: hireRequestSchema,
+  saveGoal: goalInputSchema,
+  saveProject: projectInputSchema,
+  saveTask: taskInputSchema,
+  requestApproval: approvalInputSchema,
+  decideApproval: approvalDecisionSchema,
+  startTaskRun: startRunSchema,
+  cancelRun: cancelRunSchema,
+  updateSettings: settingsSchema,
+  deleteCompany: companyIdSchema,
+  deleteAgent: deleteEntitySchema,
+  deleteTask: deleteEntitySchema,
+  deleteGoal: deleteEntitySchema,
+  deleteProject: deleteEntitySchema,
+  deleteWorkspace: deleteEntitySchema,
+  deleteApproval: deleteEntitySchema,
+  deleteSecret: deleteEntitySchema,
+  setConnectorDisabledModels: connectorDisabledModelsSchema,
+  addComment: commentInputSchema,
+  setHeartbeat: heartbeatSettingsSchema,
+  triggerHeartbeat: triggerHeartbeatSchema,
+  bootstrapOnboarding: bootstrapOnboardingSchema,
+  openTerminalCommand: openTerminalCommandSchema,
+  saveSocialAccount: socialAccountInputSchema,
+  deleteSocialAccount: deleteEntitySchema,
+  cancelBrowserAction: cancelBrowserActionSchema,
+  triggerBrowserLogin: triggerBrowserLoginSchema,
+  saveMeeting: meetingInputSchema,
+  deleteMeeting: deleteEntitySchema,
+  saveDocument: documentInputSchema,
+  deleteDocument: deleteEntitySchema,
+  saveKnowledgeEntry: knowledgeEntryInputSchema,
+  deleteKnowledgeEntry: deleteEntitySchema,
+  saveSprint: sprintInputSchema,
+  deleteSprint: deleteEntitySchema,
+  saveAutomationRule: automationRuleInputSchema,
+  deleteAutomationRule: deleteEntitySchema,
+  toggleAutomationRule: toggleAutomationRuleSchema,
+  sendAgentMessage: agentMessageInputSchema,
+  markMessageRead: markMessageReadSchema,
+  saveWorkflow: workflowInputSchema,
+  deleteWorkflow: deleteEntitySchema,
+  runWorkflow: runWorkflowSchema,
+  importSkill: importSkillSchema,
+  deleteSkill: deleteSkillSchema,
+  assignSkillToAgent: assignSkillToAgentSchema,
+  removeSkillFromAgent: removeSkillFromAgentSchema,
+  checkSkillUpdate: checkSkillUpdateSchema,
+  saveBudgetPolicy: budgetPolicyInputSchema,
+  deleteBudgetPolicy: deleteBudgetPolicySchema,
+  resolveBudgetIncident: resolveBudgetIncidentSchema,
+  recoveryRetry: recoveryRetrySchema,
+  recoveryFail: recoveryTaskSchema,
+  saveCredential: saveCredentialInputSchema,
+  removeCredential: removeCredentialInputSchema,
+  testCredential: testCredentialInputSchema,
+  startOAuth: oauthStartInputSchema,
+  cancelOAuth: oauthCancelInputSchema,
+  submitOAuthPrompt: oauthPromptResponseSchema,
+  submitOAuthManualCode: oauthManualCodeResponseSchema,
+};
+
 export function mapPreloadInvokeArgs(
   payload: PreloadPayloadSpec,
   args: readonly unknown[],
+  schema?: z.ZodType<unknown>,
 ): readonly unknown[] {
   if (payload.kind === "none") {
     assertArgCount(payload.kind, args.length, 0);
@@ -149,11 +298,12 @@ export function mapPreloadInvokeArgs(
 
   if (payload.kind === "single") {
     assertArgCount(payload.kind, args.length, 1);
-    return [args[0]];
+    return [schema ? schema.parse(args[0]) : args[0]];
   }
 
   assertArgCount(payload.kind, args.length, payload.keys.length);
-  return [Object.fromEntries(payload.keys.map((key, index) => [key, args[index]]))];
+  const objectPayload = Object.fromEntries(payload.keys.map((key, index) => [key, args[index]]));
+  return [schema ? schema.parse(objectPayload) : objectPayload];
 }
 
 function assertArgCount(kind: PreloadPayloadSpec["kind"], actual: number, expected: number): void {
diff --git a/src/shared/contracts/schemas-company.ts b/src/shared/contracts/schemas-company.ts
index eedf89db..7d3a15ee 100644
--- a/src/shared/contracts/schemas-company.ts
+++ b/src/shared/contracts/schemas-company.ts
@@ -1,6 +1,8 @@
 import { z } from "zod";
 import { optionalId } from "./helpers";
 
+export const companyIdSchema = z.string().uuid();
+
 export const companyInputSchema = z.object({
   id: optionalId,
   name: z.string().min(2).max(80),
diff --git a/src/shared/contracts/schemas-execution.ts b/src/shared/contracts/schemas-execution.ts
index b6ade778..e148d2f1 100644
--- a/src/shared/contracts/schemas-execution.ts
+++ b/src/shared/contracts/schemas-execution.ts
@@ -11,6 +11,17 @@ export const cancelRunSchema = z.object({
   runId: z.string().uuid(),
 });
 
+export const recoveryRetrySchema = z.object({
+  taskId: z.string().uuid(),
+  agentId: z.string().uuid(),
+  companyId: z.string().uuid(),
+});
+
+export const recoveryTaskSchema = z.object({
+  taskId: z.string().uuid(),
+  companyId: z.string().uuid(),
+});
+
 export const runLogSchema = z.object({
   companyId: z.string().uuid(),
   runId: z.string().uuid(),
diff --git a/tests/unit/preload-bundling-contract.test.ts b/tests/unit/preload-bundling-contract.test.ts
index 214ef016..6d7cd557 100644
--- a/tests/unit/preload-bundling-contract.test.ts
+++ b/tests/unit/preload-bundling-contract.test.ts
@@ -3,11 +3,12 @@ import { join } from "node:path";
 import { describe, expect, it } from "vitest";
 
 describe("preload bundling contract", () => {
-  it("keeps Zod validation on the main-process IPC boundary", () => {
+  it("delegates preload IPC validation through the shared forwarder registry", () => {
     const configSource = readFileSync(join(process.cwd(), "electron.vite.config.ts"), "utf8");
     const preloadSource = readFileSync(join(process.cwd(), "src/preload/index.ts"), "utf8");
 
-    expect(configSource).not.toContain('exclude: ["zod"]');
+    expect(configSource).toContain('exclude: ["zod"]');
+    expect(preloadSource).toContain("PRELOAD_INPUT_SCHEMAS");
     expect(preloadSource).not.toContain('from "@shared/contracts"');
     expect(preloadSource).not.toMatch(/from ["']zod["']|require\(["']zod["']\)/);
   });
diff --git a/tests/unit/preload-forwarders.test.ts b/tests/unit/preload-forwarders.test.ts
index 8a21556a..45540e82 100644
--- a/tests/unit/preload-forwarders.test.ts
+++ b/tests/unit/preload-forwarders.test.ts
@@ -4,10 +4,82 @@ import { describe, expect, it } from "vitest";
 import {
   IPC_CHANNELS,
   PRELOAD_FORWARDERS,
+  PRELOAD_INPUT_SCHEMAS,
   mapPreloadInvokeArgs,
   type PreloadPayloadSpec,
 } from "../../src/shared/contracts";
 
+const validatedInputMethods = [
+  "addComment",
+  "assignSkillToAgent",
+  "bootstrapOnboarding",
+  "cancelBrowserAction",
+  "cancelOAuth",
+  "cancelRun",
+  "checkSkillUpdate",
+  "decideApproval",
+  "deleteAgent",
+  "deleteApproval",
+  "deleteAutomationRule",
+  "deleteBudgetPolicy",
+  "deleteCompany",
+  "deleteDocument",
+  "deleteGoal",
+  "deleteKnowledgeEntry",
+  "deleteMeeting",
+  "deleteProject",
+  "deleteSecret",
+  "deleteSkill",
+  "deleteSocialAccount",
+  "deleteSprint",
+  "deleteTask",
+  "deleteWorkflow",
+  "deleteWorkspace",
+  "importSkill",
+  "markMessageRead",
+  "openPath",
+  "openTerminalCommand",
+  "openWorkProduct",
+  "recoveryFail",
+  "recoveryRetry",
+  "removeCredential",
+  "removeSkillFromAgent",
+  "requestApproval",
+  "requestHire",
+  "resolveBudgetIncident",
+  "runWorkflow",
+  "saveAgent",
+  "saveAutomationRule",
+  "saveBudgetPolicy",
+  "saveCompany",
+  "saveConnector",
+  "saveCredential",
+  "saveDocument",
+  "saveGoal",
+  "saveKnowledgeEntry",
+  "saveMeeting",
+  "saveProject",
+  "saveSocialAccount",
+  "saveSprint",
+  "saveTask",
+  "saveWorkflow",
+  "saveWorkspace",
+  "sendAgentMessage",
+  "setConnectorDisabledModels",
+  "setCurrentCompany",
+  "setHeartbeat",
+  "startOAuth",
+  "startTaskRun",
+  "submitOAuthManualCode",
+  "submitOAuthPrompt",
+  "testConnector",
+  "testCredential",
+  "toggleAutomationRule",
+  "triggerBrowserLogin",
+  "triggerHeartbeat",
+  "updateSettings",
+] as const;
+
 describe("preload forwarders", () => {
   it("keeps API methods and IPC channels unique", () => {
     const apiNames = new Set<string>();
@@ -47,6 +119,48 @@ describe("preload forwarders", () => {
     );
   });
 
+  it("validates write and action payloads before invoking main", () => {
+    const startRun = PRELOAD_FORWARDERS.find((forwarder) => forwarder.api === "startTaskRun");
+    const importSkill = PRELOAD_FORWARDERS.find((forwarder) => forwarder.api === "importSkill");
+
+    expect(startRun).toBeDefined();
+    expect(importSkill).toBeDefined();
+
+    expect(() =>
+      mapPreloadInvokeArgs(startRun!.payload, [{ companyId: "bad", taskId: "bad" }], PRELOAD_INPUT_SCHEMAS.startTaskRun)
+    ).toThrow();
+    expect(() =>
+      mapPreloadInvokeArgs(importSkill!.payload, ["company-1", ""], PRELOAD_INPUT_SCHEMAS.importSkill)
+    ).toThrow();
+  });
+
+  it("keeps every preload input schema attached to a registered forwarder", () => {
+    const apiNames = new Set<string>(PRELOAD_FORWARDERS.map((forwarder) => forwarder.api));
+
+    for (const method of Object.keys(PRELOAD_INPUT_SCHEMAS)) {
+      expect(apiNames.has(method)).toBe(true);
+    }
+  });
+
+  it("keeps write and action preload inputs behind schemas", () => {
+    expect(Object.keys(PRELOAD_INPUT_SCHEMAS).sort()).toEqual([...validatedInputMethods].sort());
+  });
+
+  it("samples read-path payload mapping without runtime schemas", () => {
+    const readPathSamples = [
+      { api: "getRunLog", args: [{ companyId: "bad", runId: "bad" }] },
+      { api: "listSkills", args: ["bad-company"] },
+      { api: "getBudgetStatus", args: ["bad-company"] },
+    ] as const;
+
+    for (const sample of readPathSamples) {
+      const forwarder = PRELOAD_FORWARDERS.find((candidate) => candidate.api === sample.api);
+      expect(forwarder).toBeDefined();
+      expect(PRELOAD_INPUT_SCHEMAS[sample.api]).toBeUndefined();
+      expect(mapPreloadInvokeArgs(forwarder!.payload, sample.args)).toHaveLength(1);
+    }
+  });
+
   it("keeps preload invoking through the shared registry", () => {
     const preloadSource = readFileSync(join(process.cwd(), "src/preload/index.ts"), "utf8");
     const staticChannelAccesses = [...preloadSource.matchAll(/IPC_CHANNELS\.([A-Za-z0-9_]+)/g)]