diff --git a/apps/host-cloudflare/src/auth/cloudflare-access.test.ts b/apps/host-cloudflare/src/auth/cloudflare-access.test.ts
index cf1952f114..3c6507d0c0 100644
--- a/apps/host-cloudflare/src/auth/cloudflare-access.test.ts
+++ b/apps/host-cloudflare/src/auth/cloudflare-access.test.ts
@@ -209,6 +209,53 @@ describe("internalPrincipal", () => {
   });
 });
 
+describe("principal origin", () => {
+  const internal: CloudflareConfig = { ...delegating, trustedInternal: true };
+
+  it("marks a person who reached Access with their own client as direct", () => {
+    const p = principalFromAccessClaims({ sub: "u", email: "person@example.com" }, config);
+    expect(p.origin).toBe("direct");
+  });
+
+  it("marks a service token as service", () => {
+    const p = principalFromAccessClaims({ common_name: "agent-token.access" }, config);
+    expect(p.origin).toBe("service");
+  });
+
+  it("marks a delegated run as service even though it acts as a person", () => {
+    const p = applyDelegatedSubject(delegatorPrincipal(), delegating, {
+      subject: "alice@example.com",
+      email: "alice@example.com",
+    });
+    expect(p?.origin).toBe("service");
+  });
+
+  it("marks the internal door as service, with or without a named person", () => {
+    const own = internalPrincipal(internal, { subject: null, email: null });
+    const named = internalPrincipal(internal, {
+      subject: "alice@example.com",
+      email: "alice@example.com",
+    });
+    expect([own?.origin, named?.origin]).toEqual(["service", "service"]);
+  });
+
+  it.effect("ignores an x-executor-origin header on the request", () =>
+    Effect.gen(function* () {
+      const { verify } = makeAccessVerifier(internal);
+      const p = yield* verify(
+        new Request("https://executor.test/mcp", {
+          headers: {
+            "X-Executor-Subject": "alice@example.com",
+            "X-Executor-Subject-Email": "alice@example.com",
+            "X-Executor-Origin": "direct",
+          },
+        }),
+      );
+      expect(p?.origin).toBe("service");
+    }),
+  );
+});
+
 describe("makeAccessVerifier doors", () => {
   const delegatedRequest = () =>
     new Request("https://executor.test/mcp", {
diff --git a/apps/host-cloudflare/src/auth/cloudflare-access.ts b/apps/host-cloudflare/src/auth/cloudflare-access.ts
index 6ace3c650a..9b403ca41c 100644
--- a/apps/host-cloudflare/src/auth/cloudflare-access.ts
+++ b/apps/host-cloudflare/src/auth/cloudflare-access.ts
@@ -63,6 +63,7 @@ export const principalFromAccessClaims = (
     name: typeof nameClaim === "string" ? nameClaim : commonName || null,
     avatarUrl: null,
     roles: isAdmin ? ["admin", ...groups] : groups.length > 0 ? groups : ["member"],
+    origin: email.length > 0 ? "direct" : "service",
     orgRoleModel: "organization",
     orgRole: isAdmin ? "admin" : "member",
   };
@@ -144,6 +145,7 @@ const bindSubject = (
     accountId: identityKey(subject),
     email,
     name: email.length > 0 ? email : subject,
+    origin: "service",
     roles: isAdmin ? ["admin"] : ["member"],
     // Restated rather than left to the spread: `Principal` discriminates `orgRole`
     // on `orgRoleModel`, so the spread alone leaves the union open and `orgRole`
@@ -171,10 +173,13 @@ export const internalPrincipal = (
   config: CloudflareConfig,
   delegated: DelegatedIdentity,
 ): Principal | null => {
-  const service = principalFromAccessClaims(
-    { common_name: config.accessDelegationCommonName ?? INTERNAL_BINDING_COMMON_NAME },
-    config,
-  );
+  const service: Principal = {
+    ...principalFromAccessClaims(
+      { common_name: config.accessDelegationCommonName ?? INTERNAL_BINDING_COMMON_NAME },
+      config,
+    ),
+    origin: "service",
+  };
   const subject = delegated.subject?.trim() ?? "";
   const email = delegated.email?.trim() ?? "";
   if (subject.length === 0 && email.length === 0) return service;
@@ -210,6 +215,7 @@ export const makeAccessVerifier = (config: CloudflareConfig) => {
     name: "Dev",
     avatarUrl: null,
     roles: ["admin"],
+    origin: "direct",
     orgRoleModel: "organization",
     orgRole: "admin",
   };
diff --git a/apps/host-cloudflare/src/mcp/agent-handler.ts b/apps/host-cloudflare/src/mcp/agent-handler.ts
index afd469b0c0..06bcf00d35 100644
--- a/apps/host-cloudflare/src/mcp/agent-handler.ts
+++ b/apps/host-cloudflare/src/mcp/agent-handler.ts
@@ -92,6 +92,7 @@ const propsForPrincipal = (
         toolMode: readToolMode(request),
         resource,
         webOrigin: new URL(request.url).origin,
+        origin: principal.origin ?? "service",
       },
       propagation,
     };
diff --git a/apps/host-cloudflare/src/mcp/session-durable-object.ts b/apps/host-cloudflare/src/mcp/session-durable-object.ts
index 92f8f263c6..ceaeb3f552 100644
--- a/apps/host-cloudflare/src/mcp/session-durable-object.ts
+++ b/apps/host-cloudflare/src/mcp/session-durable-object.ts
@@ -135,6 +135,7 @@ export class McpSessionDO extends McpAgentSessionDOBase<CloudflareEnv, CfSession
       artifactsEnabled: token.artifactsEnabled,
       searchToolsEnabled: token.searchToolsEnabled,
       toolMode: token.toolMode,
+      origin: token.origin,
     } satisfies SessionMeta);
   }
 
@@ -152,7 +153,7 @@ export class McpSessionDO extends McpAgentSessionDOBase<CloudflareEnv, CfSession
         sessionMeta.userId,
         sessionMeta.organizationId,
         sessionMeta.organizationName,
-        { mcpResource: sessionMeta.resource, orgWrites: "request" },
+        { mcpResource: sessionMeta.resource, orgWrites: "request", origin: sessionMeta.origin },
       ).pipe(Effect.provide(makeCloudflareExecutionStackLayer(config, dbHandle)));
       // Browser elicitation mode (the base owns the approval store + the HTTP
       // approval RPCs): a gated execution pauses and returns an approvalUrl into
diff --git a/packages/core/api/src/server/execution-stack-middleware.ts b/packages/core/api/src/server/execution-stack-middleware.ts
index df3b0d9341..afe0b45958 100644
--- a/packages/core/api/src/server/execution-stack-middleware.ts
+++ b/packages/core/api/src/server/execution-stack-middleware.ts
@@ -251,6 +251,7 @@ export const makeExecutionStackMiddleware = <
                 resolved.orgRoleModel === "none" || resolved.orgRole === "admin"
                   ? "allowed"
                   : "denied",
+              origin: resolved.origin,
             },
           ).pipe(
             Effect.provide(options.stackLayer, { local: true }),
diff --git a/packages/core/api/src/server/execution-stack.ts b/packages/core/api/src/server/execution-stack.ts
index 72837e83f2..8c2b6f7332 100644
--- a/packages/core/api/src/server/execution-stack.ts
+++ b/packages/core/api/src/server/execution-stack.ts
@@ -118,6 +118,8 @@ export const makeExecutionStack = <
     /** Workspace-settings permission for this binding (see
      *  `ExecutorConfig.orgWrites`), derived from the acting member's role. */
     readonly orgWrites?: ExecutorConfig<TPlugins>["orgWrites"];
+    /** How the acting account reached the executor (see `makeScopedExecutor`). */
+    readonly origin?: "direct" | "service";
   },
 ): Effect.Effect<
   { readonly executor: Executor<TPlugins>; readonly engine: ExecutionEngine<Cause.YieldableError> },
@@ -132,6 +134,7 @@ export const makeExecutionStack = <
       {
         plugins: { mcpResource: options?.mcpResource },
         ...(options?.orgWrites === undefined ? {} : { orgWrites: options.orgWrites }),
+        ...(options?.origin === undefined ? {} : { origin: options.origin }),
       },
     ).pipe(Effect.withSpan("executor.stack.scoped_executor"));
     const codeExecutor = yield* CodeExecutorProvider.asEffect().pipe(
diff --git a/packages/core/api/src/server/identity.ts b/packages/core/api/src/server/identity.ts
index 4c88040a96..4f7f924b97 100644
--- a/packages/core/api/src/server/identity.ts
+++ b/packages/core/api/src/server/identity.ts
@@ -48,6 +48,10 @@ interface PrincipalBase {
   readonly name: string | null;
   readonly avatarUrl: string | null;
   readonly roles: readonly string[];
+  /** How this identity reached the executor, as the host decided from
+   *  server-side facts: `direct` is a person's own client, `service` is
+   *  everything else. Absent is treated as `service`. */
+  readonly origin?: "direct" | "service";
 }
 
 /**
diff --git a/packages/core/api/src/server/scoped-executor.ts b/packages/core/api/src/server/scoped-executor.ts
index 0da4a36133..9c0caf8ebb 100644
--- a/packages/core/api/src/server/scoped-executor.ts
+++ b/packages/core/api/src/server/scoped-executor.ts
@@ -50,6 +50,7 @@ import {
   makeHostedHttpClientLayer,
   touchSubject,
   type HostedInternalHosts,
+  type InternalOrigin,
 } from "@executor-js/sdk/host-internal";
 
 import { DbProvider } from "./executor-fuma-db";
@@ -285,6 +286,9 @@ export const makeScopedExecutor = <
      *  `ExecutorConfig.orgWrites`). Hosts derive it from the acting member's
      *  role; omitted -> allowed (hosts with no role model). */
     readonly orgWrites?: ExecutorConfig<TPlugins>["orgWrites"];
+    /** How the acting account reached the executor, stamped on internal-host
+     *  calls. Omitted -> `service`. */
+    readonly origin?: InternalOrigin;
   },
 ): Effect.Effect<Executor<TPlugins>, StorageFailure, DbProvider | PluginsProvider | HostConfig> =>
   Effect.gen(function* () {
@@ -340,6 +344,7 @@ export const makeScopedExecutor = <
       requireTls: config.requireTls,
       internalHosts: config.internalHosts,
       internalCaller: accountId,
+      internalOrigin: options?.origin ?? "service",
     };
     const httpClientLayer = makeHostedHttpClientLayer(hostedHttpOptions);
     const hostedFetch = makeHostedFetch(hostedHttpOptions);
diff --git a/packages/core/sdk/src/host-internal.ts b/packages/core/sdk/src/host-internal.ts
index 824b13cc14..0c119e2e0b 100644
--- a/packages/core/sdk/src/host-internal.ts
+++ b/packages/core/sdk/src/host-internal.ts
@@ -39,6 +39,7 @@ export {
   type HostedHttpClientOptions,
   type HostedInternalFetcher,
   type HostedInternalHosts,
+  type InternalOrigin,
 } from "./hosted-http-client";
 
 export {
diff --git a/packages/core/sdk/src/hosted-http-client.test.ts b/packages/core/sdk/src/hosted-http-client.test.ts
index f21b440fab..723a0969c8 100644
--- a/packages/core/sdk/src/hosted-http-client.test.ts
+++ b/packages/core/sdk/src/hosted-http-client.test.ts
@@ -532,6 +532,32 @@ describe("internal host routing", () => {
     expect(external.urls).toEqual(["https://api.example/openapi.json"]);
   });
 
+  it("stamps the origin on internal hosts, replacing any value the request carried", async () => {
+    const seen: Array<string | null> = [];
+    const binding = {
+      fetch: async (request: Request) => {
+        seen.push(request.headers.get("x-executor-origin"));
+        return new Response("ok");
+      },
+    };
+    const external = externalStub();
+    const make = (internalOrigin?: "direct" | "service") =>
+      makeHostedFetch({
+        fetch: external.fetch,
+        resolveHostname: publicResolver,
+        internalHosts: { "tools.internal": binding },
+        ...(internalOrigin === undefined ? {} : { internalOrigin }),
+      });
+    const forged = { headers: { "x-executor-origin": "direct" } };
+
+    await make("direct")("https://tools.internal/mcp/websearch");
+    await make("service")("https://tools.internal/mcp/websearch");
+    await make("service")("https://tools.internal/mcp/websearch", forged);
+    await make()("https://tools.internal/mcp/websearch", forged);
+
+    expect(seen).toEqual(["direct", "service", "service", null]);
+  });
+
   it("hands the binding a manual-redirect request and returns its redirect untouched", async () => {
     const seen: string[] = [];
     const binding = {
diff --git a/packages/core/sdk/src/hosted-http-client.ts b/packages/core/sdk/src/hosted-http-client.ts
index 04346f5086..7de00f6244 100644
--- a/packages/core/sdk/src/hosted-http-client.ts
+++ b/packages/core/sdk/src/hosted-http-client.ts
@@ -26,6 +26,9 @@ export interface HostedInternalFetcher {
 /** Exact lowercase hostname to the fetcher that serves it, e.g. `tools.internal`. */
 export type HostedInternalHosts = Readonly<Record<string, HostedInternalFetcher>>;
 
+/** `direct`: a person's own client. `service`: everything else, delegated runs included. */
+export type InternalOrigin = "direct" | "service";
+
 export interface HostedHttpClientOptions {
   /**
    * Private hosts served by a service binding instead of the network. A request
@@ -41,6 +44,13 @@ export interface HostedHttpClientOptions {
    * means the header is removed.
    */
   readonly internalCaller?: string;
+  /**
+   * How the acting account reached this executor, sent to internal hosts only as
+   * `x-executor-origin`. Decided by the host from server-side facts; any value
+   * the request already carried is replaced, and absent means the header is
+   * removed.
+   */
+  readonly internalOrigin?: InternalOrigin;
   readonly allowLocalNetwork?: boolean;
   /** Require HTTPS, except private addresses explicitly allowed for local development. */
   readonly requireTls?: boolean;
@@ -307,6 +317,9 @@ const guardFetch = (
 /** Carries `HostedHttpClientOptions.internalCaller` to an internal host. */
 export const INTERNAL_CALLER_HEADER = "x-executor-account-id";
 
+/** Carries `HostedHttpClientOptions.internalOrigin` to an internal host. */
+export const INTERNAL_ORIGIN_HEADER = "x-executor-origin";
+
 // The router sits OUTSIDE the guard: a configured internal host goes straight to
 // its binding, everything else takes the guarded path unchanged.
 const routeInternalHosts = (
@@ -329,6 +342,10 @@ const routeInternalHosts = (
       if (options.internalCaller) {
         request.headers.set(INTERNAL_CALLER_HEADER, options.internalCaller);
       }
+      request.headers.delete(INTERNAL_ORIGIN_HEADER);
+      if (options.internalOrigin) {
+        request.headers.set(INTERNAL_ORIGIN_HEADER, options.internalOrigin);
+      }
       return await target.fetch(request);
     }
     if (isInternalHostname(hostname)) {
diff --git a/packages/hosts/cloudflare/src/mcp/agent-session-durable-object.ts b/packages/hosts/cloudflare/src/mcp/agent-session-durable-object.ts
index 805dd14d16..6c8f6db6d3 100644
--- a/packages/hosts/cloudflare/src/mcp/agent-session-durable-object.ts
+++ b/packages/hosts/cloudflare/src/mcp/agent-session-durable-object.ts
@@ -88,6 +88,9 @@ interface McpSessionInitBase {
    *  `/mcp/toolkits/<slug>` toolkit), so the tool catalog is scoped to it. */
   readonly resource: McpResource;
   readonly webOrigin?: string;
+  /** How the principal reached the executor, decided server-side at connect
+   *  time (see `Principal.origin`). Absent means `service`. */
+  readonly origin?: "direct" | "service";
 }
 
 /** Live session initialization metadata from an authenticated principal. */
@@ -173,6 +176,9 @@ interface SessionMetaBase {
    *  `buildMcpServer` scopes the tool catalog to it. */
   readonly resource: McpResource;
   readonly webOrigin?: string;
+  /** The origin carried from {@link McpSessionInit}. Absent, including for
+   *  sessions persisted before the field existed, means `service`. */
+  readonly origin?: "direct" | "service";
   /**
    * Whether this session's client advertised MCP-Apps support at `initialize`.
    *
diff --git a/packages/hosts/mcp/src/seams.ts b/packages/hosts/mcp/src/seams.ts
index 01d0994db0..3b6cd28e6a 100644
--- a/packages/hosts/mcp/src/seams.ts
+++ b/packages/hosts/mcp/src/seams.ts
@@ -50,6 +50,9 @@ const PrincipalFields = {
   name: Schema.NullOr(Schema.String),
   avatarUrl: Schema.NullOr(Schema.String),
   roles: Schema.Array(Schema.String),
+  /** How the principal reached the executor, decided by the host from
+   *  server-side facts. Absent is treated as `service`. */
+  origin: Schema.optional(Schema.Literals(["direct", "service"])),
 } as const;
 
 export const Principal = Schema.Union([