diff --git a/doc/plugins/PLUGIN_SPEC.md b/doc/plugins/PLUGIN_SPEC.md
index d1bd103486c..523aba36037 100644
--- a/doc/plugins/PLUGIN_SPEC.md
+++ b/doc/plugins/PLUGIN_SPEC.md
@@ -607,7 +607,11 @@ The plugin UI calls the host bridge, which forwards the request to the worker. T
 Input includes:
 
 - data key (plugin-defined, e.g. `"sync-health"`, `"issue-detail"`)
-- context (company id, project id, entity id, etc.)
+- browser-supplied context (company id, project id, entity id, etc.)
+- trusted actor context from the host, available to SDK handlers as the second
+  argument (`request.actor`). User-scoped plugins must compare any requested
+  `userId` with `request.actor.userId`; they must not trust a `userId` supplied
+  by the plugin UI request body.
 - optional query parameters
 
 ### 13.9 `performAction`
@@ -621,6 +625,10 @@ Examples:
 - "create branch from issue"
 - "restart process"
 
+Action handlers receive the same trusted host request context as data handlers
+as their second argument. User-scoped mutations must authorize against
+`request.actor.userId` rather than any caller-supplied `params.userId`.
+
 ### 13.10 `executeTool`
 
 Runs a plugin-contributed agent tool during a run.
diff --git a/packages/plugins/plugin-briefs/src/worker.ts b/packages/plugins/plugin-briefs/src/worker.ts
index 205d6dcc86d..526dea0b138 100644
--- a/packages/plugins/plugin-briefs/src/worker.ts
+++ b/packages/plugins/plugin-briefs/src/worker.ts
@@ -2,6 +2,7 @@ import {
   definePlugin,
   runWorker,
   type Issue,
+  type PluginBridgeRequestContext,
   type PluginContext,
   type PluginIssueRelationSummary,
   type ToolResult,
@@ -51,6 +52,16 @@ function stringParam(value: unknown, name: string): string {
   return value.trim();
 }
 
+function assertTrustedBridgeUserScope(userId: string, request?: PluginBridgeRequestContext): void {
+  const actorUserId = request?.actor?.userId;
+  if (!actorUserId) {
+    throw new Error("Briefs user-scoped UI calls require a signed-in user");
+  }
+  if (actorUserId !== userId) {
+    throw new Error("Briefs user scope mismatch");
+  }
+}
+
 function numberParam(value: unknown): number | null {
   return typeof value === "number" && Number.isFinite(value) ? Math.max(0, Math.trunc(value)) : null;
 }
@@ -280,26 +291,28 @@ const plugin = definePlugin({
   async setup(ctx) {
     const store = createBriefsStore(ctx.db);
 
-    ctx.data.register("cards", async (params) => {
+    ctx.data.register("cards", async (params, request) => {
       const input = listBriefCardsInputSchema.parse(params);
+      assertTrustedBridgeUserScope(input.userId, request);
       return {
         cards: await store.listCards(input),
       };
     });
 
-    ctx.data.register("preferences", async (params) => {
+    ctx.data.register("preferences", async (params, request) => {
       const input = objectParam(params, "params");
       const companyId = typeof input.companyId === "string" ? input.companyId : "";
       const userId = typeof input.userId === "string" ? input.userId : "";
       if (!companyId || !userId) {
         throw new Error("companyId and userId are required");
       }
+      assertTrustedBridgeUserScope(userId, request);
       return {
         preferences: await store.loadPreferences({ companyId, userId }),
       };
     });
 
-    ctx.data.register("page", async (params) => {
+    ctx.data.register("page", async (params, request) => {
       const input = objectParam(params, "params");
       const companyId = typeof input.companyId === "string" ? input.companyId : "";
       const userId = typeof input.userId === "string" ? input.userId : "";
@@ -307,6 +320,7 @@ const plugin = definePlugin({
       if (!companyId || !userId) {
         throw new Error("companyId and userId are required");
       }
+      assertTrustedBridgeUserScope(userId, request);
       const [cards, preferences] = await Promise.all([
         store.listCards({ companyId, userId, includeHidden }),
         store.loadPreferences({ companyId, userId }),
@@ -373,8 +387,9 @@ const plugin = definePlugin({
       return ctx.routines.managed.run(MANUAL_REFRESH_ROUTINE_KEY, stringParam(params.companyId, "companyId"));
     });
 
-    ctx.actions.register("pin-card", async (params) => {
+    ctx.actions.register("pin-card", async (params, request) => {
       const input = pinBriefCardInputSchema.parse(params);
+      assertTrustedBridgeUserScope(input.userId, request);
       await store.setPinned(input);
       await ctx.activity.log({
         companyId: input.companyId,
@@ -386,8 +401,9 @@ const plugin = definePlugin({
       return { ok: true };
     });
 
-    ctx.actions.register("update-preferences", async (params) => {
+    ctx.actions.register("update-preferences", async (params, request) => {
       const input = updateBriefPreferencesInputSchema.parse(params);
+      assertTrustedBridgeUserScope(input.userId, request);
       const preferences = briefPreferencesSchema.parse(input);
       await store.upsertPreferences(preferences);
       await ctx.activity.log({
diff --git a/packages/plugins/plugin-briefs/tests/managed-resources.spec.ts b/packages/plugins/plugin-briefs/tests/managed-resources.spec.ts
index ad7bae1f8ff..a62be2be1b6 100644
--- a/packages/plugins/plugin-briefs/tests/managed-resources.spec.ts
+++ b/packages/plugins/plugin-briefs/tests/managed-resources.spec.ts
@@ -11,6 +11,14 @@ import manifest, {
 import plugin from "../src/worker.js";
 
 const companyId = "11111111-1111-4111-8111-111111111111";
+const bridgeActor = {
+  actorType: "user" as const,
+  actorId: "signed-in-user",
+  userId: "signed-in-user",
+  agentId: null,
+  runId: null,
+  source: "session",
+};
 
 describe("Briefs managed resources", () => {
   it("declares the Briefing Analyst, skills, routines, and agent tools", () => {
@@ -71,4 +79,23 @@ describe("Briefs managed resources", () => {
       expect(routine.missingRefs).toEqual([]);
     }
   });
+
+  it("rejects user-scoped UI bridge calls for a different user", async () => {
+    const harness = createTestHarness({ manifest });
+    await plugin.definition.setup?.(harness.ctx);
+    const victimParams = { companyId, userId: "victim-user" };
+    const context = { actor: bridgeActor };
+
+    await expect(harness.getData("page", victimParams, context)).rejects.toThrow("Briefs user scope mismatch");
+    await expect(harness.getData("preferences", victimParams, context)).rejects.toThrow("Briefs user scope mismatch");
+    await expect(harness.performAction("pin-card", {
+      ...victimParams,
+      cardId: "card-1",
+      pinned: true,
+    }, context)).rejects.toThrow("Briefs user scope mismatch");
+    await expect(harness.performAction("update-preferences", {
+      ...victimParams,
+      cadence: "daily",
+    }, context)).rejects.toThrow("Briefs user scope mismatch");
+  });
 });
diff --git a/packages/plugins/sdk/README.md b/packages/plugins/sdk/README.md
index b9a02d5c149..51b1725c102 100644
--- a/packages/plugins/sdk/README.md
+++ b/packages/plugins/sdk/README.md
@@ -564,6 +564,8 @@ export function DashboardWidget() {
 
 Fetches data from the worker's registered `getData` handler. Re-fetches when `params` changes. Returns `{ data, loading, error, refresh }`.
 
+Worker handlers receive browser-supplied `params` as the first argument and trusted host context as the second argument. For user-scoped data, compare any requested `params.userId` with `request.actor.userId`; do not trust `params.userId` by itself.
+
 ```tsx
 import { usePluginData } from "@paperclipai/plugin-sdk/ui";
 
@@ -596,6 +598,8 @@ export function SyncStatusWidget({ context }: PluginWidgetProps) {
 
 Returns an async function that calls the worker's `performAction` handler. Throws `PluginBridgeError` on failure.
 
+Action handlers also receive trusted host context as their second argument. User-scoped mutations should authorize against `request.actor.userId`.
+
 ```tsx
 import { useState } from "react";
 import { usePluginAction, type PluginBridgeError } from "@paperclipai/plugin-sdk/ui";
diff --git a/packages/plugins/sdk/src/index.ts b/packages/plugins/sdk/src/index.ts
index 1fbf172b509..a8f35c98273 100644
--- a/packages/plugins/sdk/src/index.ts
+++ b/packages/plugins/sdk/src/index.ts
@@ -241,6 +241,10 @@ export type {
   AgentSessionEvent,
   AgentSessionSendResult,
   PluginGoalsClient,
+  PluginBridgeActorContext,
+  PluginBridgeRequestContext,
+  PluginDataHandler,
+  PluginActionHandler,
   PluginDataClient,
   PluginActionsClient,
   PluginStreamsClient,
diff --git a/packages/plugins/sdk/src/protocol.ts b/packages/plugins/sdk/src/protocol.ts
index 2c76beab23a..6180d5f117a 100644
--- a/packages/plugins/sdk/src/protocol.ts
+++ b/packages/plugins/sdk/src/protocol.ts
@@ -65,6 +65,7 @@ import type {
   PluginAuthorizationDecisionResult,
   PluginAuthorizationPolicyRecord,
   PluginAuthorizationPolicySummary,
+  PluginBridgeActorContext,
 } from "./types.js";
 import type {
   PluginHealthDiagnostics,
@@ -361,6 +362,8 @@ export interface GetDataParams {
   companyId?: string | null;
   /** Context and query parameters from the UI. */
   params: Record<string, unknown>;
+  /** Trusted actor context supplied by the host, never by the browser. */
+  actor?: PluginBridgeActorContext | null;
   /** Optional launcher/container metadata from the host render environment. */
   renderEnvironment?: PluginLauncherRenderContextSnapshot | null;
 }
@@ -401,6 +404,8 @@ export interface PerformActionParams {
   params: Record<string, unknown>;
   /** Authenticated actor context resolved by the host, never by caller params. */
   actorContext?: PluginPerformActionActorContext | null;
+  /** Trusted actor context supplied by the host, never by the browser. */
+  actor?: PluginBridgeActorContext | null;
   /** Optional launcher/container metadata from the host render environment. */
   renderEnvironment?: PluginLauncherRenderContextSnapshot | null;
 }
diff --git a/packages/plugins/sdk/src/testing.ts b/packages/plugins/sdk/src/testing.ts
index f8f1fc262aa..a0473d5b2ad 100644
--- a/packages/plugins/sdk/src/testing.ts
+++ b/packages/plugins/sdk/src/testing.ts
@@ -42,6 +42,9 @@ import type {
   PrincipalPermissionGrant,
   PermissionKey,
   PrincipalType,
+  PluginBridgeRequestContext,
+  PluginDataHandler,
+  PluginActionHandler,
 } from "./types.js";
 import type {
   PluginEnvironmentValidateConfigParams,
@@ -57,8 +60,6 @@ import type {
   PluginEnvironmentRealizeWorkspaceResult,
   PluginEnvironmentExecuteParams,
   PluginEnvironmentExecuteResult,
-  PluginPerformActionActorContext,
-  PluginPerformActionContext,
 } from "./protocol.js";
 
 export interface TestHarnessOptions {
@@ -78,10 +79,9 @@ export interface TestHarnessLogEntry {
 
 export interface TestHarnessPerformActionOptions {
   /**
-   * Authenticated actor context to expose to the action handler. Omitted fields
-   * default to null, and `type` defaults to `system`.
+   * Authenticated actor context to expose to the action handler.
    */
-  actor?: Partial<PluginPerformActionActorContext> | null;
+  actor?: Partial<NonNullable<PluginBridgeRequestContext["actor"]> & { type?: "user" | "agent" | "system"; companyId?: string | null }> | null;
   /**
    * Host-authorized company scope. When provided, this is injected into
    * `params.companyId` so tests match the production bridge's anti-spoofing
@@ -112,12 +112,12 @@ export interface TestHarness {
   /** Execute a previously-registered scheduled job handler. */
   runJob(jobKey: string, partial?: Partial<PluginJobContext>): Promise<void>;
   /** Invoke a `ctx.data.register(...)` handler by key. */
-  getData<T = unknown>(key: string, params?: Record<string, unknown>): Promise<T>;
+  getData<T = unknown>(key: string, params?: Record<string, unknown>, context?: Partial<PluginBridgeRequestContext>): Promise<T>;
   /** Invoke a `ctx.actions.register(...)` handler by key. */
   performAction<T = unknown>(
     key: string,
     params?: Record<string, unknown>,
-    options?: TestHarnessPerformActionOptions,
+    options?: TestHarnessPerformActionOptions | Partial<PluginBridgeRequestContext>,
   ): Promise<T>;
   /** Execute a registered tool handler via `ctx.tools.execute(...)`. */
   executeTool<T = ToolResult>(name: string, params: unknown, runCtx?: Partial<ToolRunContext>): Promise<T>;
@@ -510,11 +510,8 @@ export function createTestHarness(options: TestHarnessOptions): TestHarness {
   const events: EventRegistration[] = [];
   const jobs = new Map<string, (job: PluginJobContext) => Promise<void>>();
   const launchers = new Map<string, PluginLauncherRegistration>();
-  const dataHandlers = new Map<string, (params: Record<string, unknown>) => Promise<unknown>>();
-  const actionHandlers = new Map<
-    string,
-    (params: Record<string, unknown>, context: PluginPerformActionContext) => Promise<unknown>
-  >();
+  const dataHandlers = new Map<string, PluginDataHandler>();
+  const actionHandlers = new Map<string, PluginActionHandler>();
   const toolHandlers = new Map<string, (params: unknown, runCtx: ToolRunContext) => Promise<ToolResult>>();
 
   function localFolderKey(companyId: string, folderKey: string): string {
@@ -529,29 +526,29 @@ export function createTestHarness(options: TestHarnessOptions): TestHarness {
     return typeof value === "string" && value.trim().length > 0 ? value.trim() : null;
   }
 
-  function actorTypeOrSystem(value: unknown): PluginPerformActionActorContext["type"] {
-    return value === "user" || value === "agent" || value === "system" ? value : "system";
-  }
-
   function actionContextFor(
     params: Record<string, unknown>,
     options?: TestHarnessPerformActionOptions,
-  ): PluginPerformActionContext {
+  ): PluginBridgeRequestContext {
     const actorInput = options?.actor ?? null;
     const companyId = stringOrNull(options?.companyId) ?? stringOrNull(actorInput?.companyId) ?? stringOrNull(params.companyId);
+    const actorType = actorInput?.actorType === "agent" || actorInput?.type === "agent" ? "agent" : "user";
+    const userId = stringOrNull(actorInput?.userId);
+    const agentId = stringOrNull(actorInput?.agentId);
     const actor = Object.freeze({
-      type: actorTypeOrSystem(actorInput?.type),
-      userId: stringOrNull(actorInput?.userId),
-      agentId: stringOrNull(actorInput?.agentId),
+      actorType,
+      actorId: stringOrNull(actorInput?.actorId) ?? (actorType === "agent" ? agentId ?? "agent-test" : userId ?? "user-test"),
+      userId,
+      agentId,
       runId: stringOrNull(actorInput?.runId),
-      companyId,
+      source: stringOrNull(actorInput?.source),
     });
-    return Object.freeze({ actor, companyId });
+    return Object.freeze({ actor, companyId, renderEnvironment: null });
   }
 
   function paramsWithHostCompanyScope(
     params: Record<string, unknown>,
-    context: PluginPerformActionContext,
+    context: PluginBridgeRequestContext,
     options?: TestHarnessPerformActionOptions,
   ): Record<string, unknown> {
     if (Object.prototype.hasOwnProperty.call(options ?? {}, "companyId")) {
@@ -560,6 +557,17 @@ export function createTestHarness(options: TestHarnessOptions): TestHarness {
     return params;
   }
 
+  function isBridgeRequestContextOptions(
+    options: TestHarnessPerformActionOptions | Partial<PluginBridgeRequestContext> | undefined,
+  ): options is Partial<PluginBridgeRequestContext> {
+    if (!options || typeof options !== "object") return false;
+    const actor = (options as Partial<PluginBridgeRequestContext>).actor;
+    return Boolean(
+      "renderEnvironment" in options
+      || (actor && typeof actor === "object" && "actorType" in actor),
+    );
+  }
+
   function normalizeLocalFolderRelativePath(relativePath: string): string {
     const parts: string[] = [];
     for (const segment of relativePath.split(/[\\/]+/)) {
@@ -2355,20 +2363,33 @@ export function createTestHarness(options: TestHarnessOptions): TestHarness {
         scheduledAt: partial.scheduledAt ?? new Date().toISOString(),
       });
     },
-    async getData<T = unknown>(key: string, params: Record<string, unknown> = {}) {
+    async getData<T = unknown>(key: string, params: Record<string, unknown> = {}, context: Partial<PluginBridgeRequestContext> = {}) {
       const handler = dataHandlers.get(key);
       if (!handler) throw new Error(`No data handler registered for '${key}'`);
-      return await handler(params) as T;
+      return await handler(params, {
+        actor: context.actor ?? null,
+        companyId: context.companyId ?? null,
+        renderEnvironment: context.renderEnvironment ?? null,
+      }) as T;
     },
     async performAction<T = unknown>(
       key: string,
       params: Record<string, unknown> = {},
-      options?: TestHarnessPerformActionOptions,
+      options?: TestHarnessPerformActionOptions | Partial<PluginBridgeRequestContext>,
     ) {
       const handler = actionHandlers.get(key);
       if (!handler) throw new Error(`No action handler registered for '${key}'`);
-      const context = actionContextFor(params, options);
-      return await handler(paramsWithHostCompanyScope(params, context, options), context) as T;
+      const bridgeContext = isBridgeRequestContextOptions(options)
+        ? {
+            actor: options.actor ?? null,
+            companyId: options.companyId ?? null,
+            renderEnvironment: options.renderEnvironment ?? null,
+          }
+        : actionContextFor(params, options as TestHarnessPerformActionOptions | undefined);
+      return await handler(
+        paramsWithHostCompanyScope(params, bridgeContext, options as TestHarnessPerformActionOptions | undefined),
+        bridgeContext,
+      ) as T;
     },
     async executeTool<T = ToolResult>(name: string, params: unknown, runCtx: Partial<ToolRunContext> = {}) {
       const handler = toolHandlers.get(name);
diff --git a/packages/plugins/sdk/src/types.ts b/packages/plugins/sdk/src/types.ts
index 90af99b4803..7e9012d315c 100644
--- a/packages/plugins/sdk/src/types.ts
+++ b/packages/plugins/sdk/src/types.ts
@@ -46,8 +46,6 @@ import type {
   PrincipalPermissionGrant,
   PrincipalType,
 } from "@paperclipai/shared";
-import type { PluginPerformActionContext } from "./protocol.js";
-
 // ---------------------------------------------------------------------------
 // Re-exports from @paperclipai/shared (plugin authors import from one place)
 // ---------------------------------------------------------------------------
@@ -928,6 +926,31 @@ export interface PluginSkillsClient {
   };
 }
 
+export interface PluginBridgeActorContext {
+  actorType: "user" | "agent";
+  actorId: string;
+  userId: string | null;
+  agentId: string | null;
+  runId: string | null;
+  source: string | null;
+}
+
+export interface PluginBridgeRequestContext {
+  actor: PluginBridgeActorContext | null;
+  companyId: string | null;
+  renderEnvironment?: PluginLauncherRenderContextSnapshot | null;
+}
+
+export type PluginDataHandler = (
+  params: Record<string, unknown>,
+  context: PluginBridgeRequestContext,
+) => Promise<unknown>;
+
+export type PluginActionHandler = (
+  params: Record<string, unknown>,
+  context: PluginBridgeRequestContext,
+) => Promise<unknown>;
+
 /**
  * `ctx.data` — register `getData` handlers that back `usePluginData()` in the
  * plugin's frontend components.
@@ -942,9 +965,9 @@ export interface PluginDataClient {
    * Register a handler for a plugin-defined data key.
    *
    * @param key - Stable string identifier for this data type (e.g. `"sync-health"`)
-   * @param handler - Async function that receives request params and returns JSON-serializable data
+   * @param handler - Async function that receives request params plus trusted host context and returns JSON-serializable data
    */
-  register(key: string, handler: (params: Record<string, unknown>) => Promise<unknown>): void;
+  register(key: string, handler: PluginDataHandler): void;
 }
 
 /**
@@ -958,12 +981,9 @@ export interface PluginActionsClient {
    * Register a handler for a plugin-defined action key.
    *
    * @param key - Stable string identifier for this action (e.g. `"resync"`)
-   * @param handler - Async function that receives action params plus immutable host actor context and returns a result
+   * @param handler - Async function that receives action params plus trusted host context and returns a result
    */
-  register(
-    key: string,
-    handler: (params: Record<string, unknown>, context: PluginPerformActionContext) => Promise<unknown>,
-  ): void;
+  register(key: string, handler: PluginActionHandler): void;
 }
 
 /**
diff --git a/packages/plugins/sdk/src/worker-rpc-host.ts b/packages/plugins/sdk/src/worker-rpc-host.ts
index a135d1f0a9c..713bc00be3d 100644
--- a/packages/plugins/sdk/src/worker-rpc-host.ts
+++ b/packages/plugins/sdk/src/worker-rpc-host.ts
@@ -64,6 +64,10 @@ import type {
   ToolResult,
   EventFilter,
   AgentSessionEvent,
+  PluginDataHandler,
+  PluginActionHandler,
+  PluginBridgeActorContext,
+  PluginBridgeRequestContext,
 } from "./types.js";
 import type {
   JsonRpcId,
@@ -78,8 +82,6 @@ import type {
   RunJobParams,
   GetDataParams,
   PerformActionParams,
-  PluginPerformActionActorContext,
-  PluginPerformActionContext,
   ExecuteToolParams,
   PluginEnvironmentAcquireLeaseParams,
   PluginEnvironmentDestroyLeaseParams,
@@ -290,11 +292,8 @@ export function startWorkerRpcHost(options: WorkerRpcHostOptions): WorkerRpcHost
   const eventHandlers: EventRegistration[] = [];
   const jobHandlers = new Map<string, (job: PluginJobContext) => Promise<void>>();
   const launcherRegistrations = new Map<string, PluginLauncherRegistration>();
-  const dataHandlers = new Map<string, (params: Record<string, unknown>) => Promise<unknown>>();
-  const actionHandlers = new Map<
-    string,
-    (params: Record<string, unknown>, context: PluginPerformActionContext) => Promise<unknown>
-  >();
+  const dataHandlers = new Map<string, PluginDataHandler>();
+  const actionHandlers = new Map<string, PluginActionHandler>();
   const toolHandlers = new Map<string, {
     declaration: Pick<import("@paperclipai/shared").PluginToolDeclaration, "displayName" | "description" | "parametersSchema">;
     fn: (params: unknown, runCtx: ToolRunContext) => Promise<ToolResult>;
@@ -1189,10 +1188,7 @@ export function startWorkerRpcHost(options: WorkerRpcHostOptions): WorkerRpcHost
       },
 
       actions: {
-        register(
-          key: string,
-          handler: (params: Record<string, unknown>, context: PluginPerformActionContext) => Promise<unknown>,
-        ): void {
+        register(key: string, handler: PluginActionHandler): void {
           actionHandlers.set(key, handler);
         },
       },
@@ -1519,31 +1515,38 @@ export function startWorkerRpcHost(options: WorkerRpcHostOptions): WorkerRpcHost
       ...params.params,
       ...(params.companyId === undefined ? {} : { companyId: params.companyId }),
       ...(params.renderEnvironment === undefined ? {} : { renderEnvironment: params.renderEnvironment }),
-    });
+    }, bridgeRequestContextFromParams(params));
   }
 
   function stringOrNull(value: unknown): string | null {
     return typeof value === "string" && value.trim().length > 0 ? value.trim() : null;
   }
 
-  function actorTypeOrSystem(value: unknown): PluginPerformActionActorContext["type"] {
-    return value === "user" || value === "agent" || value === "system" ? value : "system";
+  function bridgeActorFromLegacyContext(value: unknown): PluginBridgeActorContext | null {
+    if (!value || typeof value !== "object" || Array.isArray(value)) return null;
+    const rawActor = value as Record<string, unknown>;
+    const actorType = rawActor.type === "agent" ? "agent" : "user";
+    const userId = stringOrNull(rawActor.userId);
+    const agentId = stringOrNull(rawActor.agentId);
+    return Object.freeze({
+      actorType,
+      actorId: actorType === "agent" ? agentId ?? "unknown-agent" : userId ?? "board",
+      userId,
+      agentId,
+      runId: stringOrNull(rawActor.runId),
+      source: null,
+    });
   }
 
-  function actionContextFromParams(params: PerformActionParams): PluginPerformActionContext {
-    const rawActor = params.actorContext && typeof params.actorContext === "object"
-      ? params.actorContext
-      : null;
-    const actor = Object.freeze({
-      type: actorTypeOrSystem(rawActor?.type),
-      userId: stringOrNull(rawActor?.userId),
-      agentId: stringOrNull(rawActor?.agentId),
-      runId: stringOrNull(rawActor?.runId),
-      companyId: stringOrNull(rawActor?.companyId),
-    });
+  function bridgeRequestContextFromParams(params: GetDataParams | PerformActionParams): PluginBridgeRequestContext {
+    const actor = params.actor ?? bridgeActorFromLegacyContext("actorContext" in params ? params.actorContext : null);
+    const companyId = stringOrNull(params.companyId)
+      ?? stringOrNull("actorContext" in params && params.actorContext ? params.actorContext.companyId : null);
+    const renderEnvironment = params.renderEnvironment ?? null;
     return Object.freeze({
-      actor,
-      companyId: actor.companyId,
+      actor: actor ? Object.freeze(actor) : null,
+      companyId,
+      renderEnvironment,
     });
   }
 
@@ -1558,7 +1561,7 @@ export function startWorkerRpcHost(options: WorkerRpcHostOptions): WorkerRpcHost
         ...(params.companyId === undefined ? {} : { companyId: params.companyId }),
         ...(params.renderEnvironment === undefined ? {} : { renderEnvironment: params.renderEnvironment }),
       },
-      actionContextFromParams(params),
+      bridgeRequestContextFromParams(params),
     );
   }
 
diff --git a/packages/plugins/sdk/tests/bridge-context.test.ts b/packages/plugins/sdk/tests/bridge-context.test.ts
new file mode 100644
index 00000000000..8159c1d302e
--- /dev/null
+++ b/packages/plugins/sdk/tests/bridge-context.test.ts
@@ -0,0 +1,44 @@
+import { describe, expect, it } from "vitest";
+
+import { createTestHarness } from "../src/testing.js";
+import { definePlugin } from "../src/define-plugin.js";
+import type { PaperclipPluginManifestV1 } from "../src/types.js";
+
+const manifest: PaperclipPluginManifestV1 = {
+  apiVersion: 1,
+  id: "paperclip.test.bridge-context",
+  displayName: "Bridge Context Test",
+  version: "0.0.0",
+  description: "Tests trusted bridge request context.",
+  author: "Paperclip",
+  categories: ["ui"],
+  capabilities: [],
+  entrypoints: {
+    worker: "./dist/worker.js",
+  },
+};
+
+describe("plugin bridge request context", () => {
+  it("makes trusted actor context available to data and action handlers", async () => {
+    const plugin = definePlugin({
+      async setup(ctx) {
+        ctx.data.register("whoami", async (_params, request) => request.actor);
+        ctx.actions.register("whoami", async (_params, request) => request.actor);
+      },
+    });
+    const harness = createTestHarness({ manifest });
+    await plugin.definition.setup?.(harness.ctx);
+
+    const actor = {
+      actorType: "user" as const,
+      actorId: "user-1",
+      userId: "user-1",
+      agentId: null,
+      runId: "run-1",
+      source: "session",
+    };
+
+    await expect(harness.getData("whoami", {}, { actor })).resolves.toEqual(actor);
+    await expect(harness.performAction("whoami", {}, { actor })).resolves.toEqual(actor);
+  });
+});
diff --git a/packages/plugins/sdk/tests/testing-actions.test.ts b/packages/plugins/sdk/tests/testing-actions.test.ts
index ab0026b283f..06ac308e52e 100644
--- a/packages/plugins/sdk/tests/testing-actions.test.ts
+++ b/packages/plugins/sdk/tests/testing-actions.test.ts
@@ -30,11 +30,12 @@ describe("createTestHarness action context", () => {
     const result = await harness.performAction<{
       paramsCompanyId: unknown;
       actor: {
-        type: string;
+        actorType: string;
+        actorId: string;
         userId: string | null;
         agentId: string | null;
         runId: string | null;
-        companyId: string | null;
+        source: string | null;
       };
       companyId: string | null;
       contextFrozen: boolean;
@@ -55,11 +56,12 @@ describe("createTestHarness action context", () => {
     expect(result.paramsCompanyId).toBe("host-company");
     expect(result.companyId).toBe("host-company");
     expect(result.actor).toEqual({
-      type: "user",
+      actorType: "user",
+      actorId: "board-user-1",
       userId: "board-user-1",
       agentId: null,
       runId: "run-1",
-      companyId: "host-company",
+      source: null,
     });
     expect(result.contextFrozen).toBe(true);
     expect(result.actorFrozen).toBe(true);
diff --git a/server/src/__tests__/plugin-routes-authz.test.ts b/server/src/__tests__/plugin-routes-authz.test.ts
index 272e20c3575..93f358ea393 100644
--- a/server/src/__tests__/plugin-routes-authz.test.ts
+++ b/server/src/__tests__/plugin-routes-authz.test.ts
@@ -642,6 +642,50 @@ describe.sequential("plugin tool and bridge authz", () => {
       key: "health",
       companyId: companyA,
       params: { view: "compact" },
+      actor: {
+        actorType: "user",
+        actorId: "user-1",
+        userId: "user-1",
+        agentId: null,
+        runId: null,
+        source: "session",
+      },
+      renderEnvironment: null,
+    });
+  });
+
+  it("passes trusted actor context to plugin data handlers without trusting caller user params", async () => {
+    readyPlugin();
+    const call = vi.fn().mockResolvedValue({ ok: true });
+    const { app } = await createApp(boardActor({
+      userId: "signed-in-user",
+      companyIds: [companyA],
+    }), {}, {
+      bridgeDeps: {
+        workerManager: { call },
+      },
+    });
+
+    const res = await request(app)
+      .post(`/api/plugins/${pluginId}/data/page`)
+      .send({
+        companyId: companyA,
+        params: { companyId: companyA, userId: "victim-user" },
+      });
+
+    expect(res.status).toBe(200);
+    expect(call).toHaveBeenCalledWith(pluginId, "getData", {
+      key: "page",
+      companyId: companyA,
+      params: { companyId: companyA, userId: "victim-user" },
+      actor: {
+        actorType: "user",
+        actorId: "signed-in-user",
+        userId: "signed-in-user",
+        agentId: null,
+        runId: null,
+        source: "session",
+      },
       renderEnvironment: null,
     });
   });
@@ -674,6 +718,14 @@ describe.sequential("plugin tool and bridge authz", () => {
         runId: null,
         companyId: null,
       },
+      actor: {
+        actorType: "user",
+        actorId: "admin-1",
+        userId: "admin-1",
+        agentId: null,
+        runId: null,
+        source: "session",
+      },
       renderEnvironment: null,
     });
   });
@@ -711,6 +763,14 @@ describe.sequential("plugin tool and bridge authz", () => {
         runId: runA,
         companyId: companyA,
       },
+      actor: {
+        actorType: "user",
+        actorId: "user-1",
+        userId: "user-1",
+        agentId: null,
+        runId: runA,
+        source: "session",
+      },
       renderEnvironment: null,
     });
   });
@@ -735,6 +795,11 @@ describe.sequential("plugin tool and bridge authz", () => {
         userId: null,
         companyId: companyA,
       }),
+      actor: expect.objectContaining({
+        actorType: "user",
+        actorId: "board",
+        userId: null,
+      }),
     }));
   });
 
@@ -771,6 +836,14 @@ describe.sequential("plugin tool and bridge authz", () => {
         runId: runA,
         companyId: companyA,
       },
+      actor: {
+        actorType: "agent",
+        actorId: agentA,
+        userId: null,
+        agentId: agentA,
+        runId: runA,
+        source: "agent_jwt",
+      },
       renderEnvironment: null,
     });
 
@@ -800,6 +873,14 @@ describe.sequential("plugin tool and bridge authz", () => {
         runId: runA,
         companyId: companyA,
       },
+      actor: {
+        actorType: "agent",
+        actorId: agentA,
+        userId: null,
+        agentId: agentA,
+        runId: runA,
+        source: "agent_jwt",
+      },
       renderEnvironment: null,
     });
   });
diff --git a/server/src/routes/plugins.ts b/server/src/routes/plugins.ts
index d572c90d6fa..57d1d26d865 100644
--- a/server/src/routes/plugins.ts
+++ b/server/src/routes/plugins.ts
@@ -55,7 +55,7 @@ import type { PluginJobStore } from "../services/plugin-job-store.js";
 import type { PluginWorkerManager } from "../services/plugin-worker-manager.js";
 import type { PluginStreamBus } from "../services/plugin-stream-bus.js";
 import type { PluginToolDispatcher } from "../services/plugin-tool-dispatcher.js";
-import type { PluginPerformActionActorContext, ToolRunContext } from "@paperclipai/plugin-sdk";
+import type { PluginBridgeActorContext, PluginPerformActionActorContext, ToolRunContext } from "@paperclipai/plugin-sdk";
 import { JsonRpcCallError, PLUGIN_RPC_ERROR_CODES } from "@paperclipai/plugin-sdk";
 import {
   assertAuthenticated,
@@ -601,6 +601,18 @@ export function pluginRoutes(
     };
   }
 
+  function trustedPluginBridgeActor(req: Request): PluginBridgeActorContext {
+    const actor = getActorInfo(req);
+    return {
+      actorType: actor.actorType,
+      actorId: actor.actorId,
+      userId: req.actor.type === "board" ? req.actor.userId ?? null : null,
+      agentId: req.actor.type === "agent" ? req.actor.agentId ?? null : null,
+      runId: actor.runId,
+      source: req.actor.source ?? null,
+    };
+  }
+
   function actionParamsWithAuthorizedCompanyScope(
     params: Record<string, unknown> | undefined,
     companyId: string | undefined,
@@ -1169,6 +1181,7 @@ export function pluginRoutes(
           key: body.key,
           ...(companyId ? { companyId } : {}),
           params: body.params ?? {},
+          actor: trustedPluginBridgeActor(req),
           renderEnvironment: body.renderEnvironment ?? null,
         },
       );
@@ -1262,6 +1275,7 @@ export function pluginRoutes(
           key: body.key,
           params: actionParamsWithAuthorizedCompanyScope(body.params, companyId),
           actorContext: performActionActorContext(req, companyId),
+          actor: trustedPluginBridgeActor(req),
           renderEnvironment: body.renderEnvironment ?? null,
         },
       );
@@ -1356,6 +1370,7 @@ export function pluginRoutes(
           key,
           ...(companyId ? { companyId } : {}),
           params: body?.params ?? {},
+          actor: trustedPluginBridgeActor(req),
           renderEnvironment: body?.renderEnvironment ?? null,
         },
       );
@@ -1446,6 +1461,7 @@ export function pluginRoutes(
           key,
           params: actionParamsWithAuthorizedCompanyScope(body?.params, companyId),
           actorContext: performActionActorContext(req, companyId),
+          actor: trustedPluginBridgeActor(req),
           renderEnvironment: body?.renderEnvironment ?? null,
         },
       );