@@ -26,7 +26,7 @@ storage of its own, or scheduling (`@corbits/cron`).
   its own run principal, `deriveRunPrincipalId(tenantId, runId)`, through
   Interchange's mail-triggered grant path, never as the credential owner.
 - Trigger mail is signed by the durable per-tenant system sender
-  (`webhook@domain`), whose key is co-delivered on the run-grants barrier.
+  (`webhook@domain`), whose key is co-delivered with the run grants in the single `routeMail` call.
 - No unsigned mode: a credential without a verifier matches no hook.
 - Unknown hooks and name collisions both answer `404`.
 - `exactOptionalPropertyTypes` is on: omit optional keys, never assign
 
@@ -61,9 +61,9 @@ Signatures are checked over the raw request bytes, and the body is forwarded unc
 | `createRunTriggerDeliverer(opts)`                     | Delivers trigger mail to a live run as its run principal.                  |
 | `createTenantSystemSender({ db, principalKeyStore })` | Durable per-tenant sender (`<localPart>@domain`) that signs trigger mail.  |
 | `isRunTriggerUnroutable(error)`                       | Narrows to `{ code, address, runId }` when the router has no route.        |
-| `RUN_GRANTS_NOT_ROUTABLE`, `RUN_MAIL_NOT_ROUTABLE`    | The two `code` values.                                                     |
+| `RUN_MAIL_NOT_ROUTABLE`                               | The error `code`.                                                          |
 | `RunTriggerUnroutableError`                           | The error `isRunTriggerUnroutable` matches.                                |
-| `HookMailRouter`                                      | Router type the host passes in: `routeMail` and `sendRunGrants`.           |
+| `HookRouter`                                          | `Pick<SidecarRouter, "routeMail">`, the router the host passes in.         |
 | `MailDeliverer`                                       | `{ to(address, content, tenantId, subject) }`, what the deliverer returns. |
 
 ### `runWebhookMigrations(dbConfig, { schema })`
@@ -78,7 +78,7 @@ Run `runWebhookMigrations` at hub start, after `runMigrations`, then build the r
 import { createEnvKeyCredentialCipher } from "@intx/crypto";
 import { createDB, createPrincipalKeyStore, runMigrations } from "@intx/db";
 import { hexDecode } from "@intx/types";
-import { createHookRoutes, type HookMailRouter } from "@corbits/webhooks";
+import { createHookRoutes, type HookRouter } from "@corbits/webhooks";
 import { runWebhookMigrations } from "@corbits/webhooks/migrations";
 
 const dbConfig = {
@@ -93,7 +93,7 @@ await runWebhookMigrations(dbConfig, { schema: "public" });
 
 const { db } = createDB(dbConfig);
 
-export const hookRoutes = (router: HookMailRouter) =>
+export const hookRoutes = (router: HookRouter) =>
   createHookRoutes({
     db,
     credentialCipher: createEnvKeyCredentialCipher(
@@ -143,6 +143,13 @@ curl -X POST "$HUB/api/hooks/crd_…" \
 
 The hub answers `202 { "ok": true, "to": "run_…@acme.example" }` and the run starts.
 
+## Upgrading from 0.2
+
+- `HookMailRouter` is replaced by `HookRouter`, `Pick<SidecarRouter, "routeMail">` from `@intx/hub-sessions`. Pass the hub's sidecar router as before; `sendRunGrants` is no longer used.
+- Run grants and trigger mail go out in one `routeMail` call, so `RUN_GRANTS_NOT_ROUTABLE` and `RunTriggerUnroutableCode` are removed. Every unroutable delivery throws `RunTriggerUnroutableError` with `code` `RUN_MAIL_NOT_ROUTABLE`, and `new RunTriggerUnroutableError(address, runId)` no longer takes a code.
+- `isRunTriggerUnroutable` uses `instanceof`; every consumer must resolve one copy of `@corbits/webhooks`.
+- `@intx/hub-sessions` is a new peer dependency.
+
 ## Upgrading from 0.1
 
 - `installWebhooks(opts)` is removed. Call `app.route("/api/hooks", createHookRoutes(deps))` with the same `db`, `credentialCipher`, `principalKeyStore` and `router`; drop `app` from the options.
 
@@ -10,7 +10,7 @@ import {
 import { createEnvKeyCredentialCipher } from "@intx/crypto";
 import { principal, tenant } from "@intx/db/schema";
 
-import { createHookRoutes, type HookMailRouter } from "../src/index.js";
+import { createHookRoutes, type HookRouter } from "../src/index.js";
 import { runWebhookMigrations } from "../src/migrations.js";
 
 const PG_ENV = [
@@ -95,21 +95,16 @@ export const testCredentialCipher = createEnvKeyCredentialCipher(
   new Uint8Array(32).fill(7),
 );
 
-/** A sidecar router that records every frame and routes all of them. */
+/** A sidecar router that records every call and routes all of them. */
 export function recordingRouter() {
-  const grants: Parameters<HookMailRouter["sendRunGrants"]>[] = [];
-  const mail: Parameters<HookMailRouter["routeMail"]>[] = [];
-  const router: HookMailRouter = {
-    sendRunGrants: (...args) => {
-      grants.push(args);
-      return true;
-    },
+  const mail: Parameters<HookRouter["routeMail"]>[] = [];
+  const router: HookRouter = {
     routeMail: (...args) => {
       mail.push(args);
       return true;
     },
   };
-  return { router, grants, mail };
+  return { router, mail };
 }
 
 /**
@@ -118,7 +113,7 @@ export function recordingRouter() {
  */
 export function mountHookRoutes(opts: {
   db: TestDb["db"];
-  router: HookMailRouter;
+  router: HookRouter;
 }): Hono {
   const app = new Hono();
   app.route(
 
@@ -172,7 +172,7 @@ describe.skipIf(!harnessDbAvailable())(
       });
 
       expect(res.status).toBe(401);
-      expect(recorded.grants).toEqual([]);
+      expect(recorded.mail).toEqual([]);
       expect(recorded.mail).toEqual([]);
       const { runPrincipals, grants } = await runGrants(db());
       expect(runPrincipals).toEqual([]);
@@ -198,10 +198,10 @@ describe.skipIf(!harnessDbAvailable())(
       expect(grants.map((g) => [g.principalId, g.resource, g.action])).toEqual([
         [runPrincipal?.id ?? "", "tool:read_file", "invoke"],
       ]);
-      const [frame] = recorded.grants;
-      expect(frame?.[0]).toBe(ADDRESS);
-      expect(frame?.[2]).toHaveLength(1);
       expect(recorded.mail).toHaveLength(1);
+      const [call] = recorded.mail;
+      expect(call?.[0]).toBe(ADDRESS);
+      expect(call?.[4]?.stepGrants).toHaveLength(1);
     });
 
     test("a replayed delivery is 409 on every replica", async () => {
 
@@ -57,6 +57,7 @@
     "@intx/db": "0.4.0",
     "@intx/hub-api": "0.4.0",
     "@intx/hub-common": "0.4.0",
+    "@intx/hub-sessions": "0.4.0",
     "@intx/mime": "0.4.0",
     "@intx/types": "0.4.0",
     "@types/bun": "1.3.9",
@@ -72,6 +73,7 @@
     "@intx/db": "^0.4.0",
     "@intx/hub-api": "^0.4.0",
     "@intx/hub-common": "^0.4.0",
+    "@intx/hub-sessions": "^0.4.0",
     "@intx/mime": "^0.4.0",
     "@intx/types": "^0.4.0",
     "drizzle-orm": "^0.45.1",
 
@@ -5,9 +5,10 @@ import { hexEncode } from "@intx/types";
 import {
   createRunTriggerDeliverer,
   isRunTriggerUnroutable,
+  RUN_MAIL_NOT_ROUTABLE,
+  RunTriggerUnroutableError,
 } from "./deliver.js";
-import { RUN_GRANTS_NOT_ROUTABLE, RUN_MAIL_NOT_ROUTABLE } from "./deliver.js";
-import type { HookMailRouter } from "./deliver.js";
+import type { HookRouter } from "./deliver.js";
 import type { SystemSender } from "./system-sender.js";
 
 const ADDRESS = "run_0123456789abcdef@localhost";
@@ -39,40 +40,17 @@ async function durableSystemSender() {
 }
 
 function recordingRouter() {
-  const grants: {
-    address: string;
-    senderIdentities: Parameters<HookMailRouter["sendRunGrants"]>[3];
-  }[] = [];
-  const mail: { authenticatedSender: string; rawMessage: string }[] = [];
-  return {
-    grants,
-    mail,
-    router: {
-      routeMail: (
-        _address: string,
-        rawMessage: string,
-        authenticatedSender: string,
-      ) => {
-        mail.push({ authenticatedSender, rawMessage });
-        return true;
-      },
-      sendRunGrants: (
-        address: string,
-        _runId: string,
-        _stepGrants: Parameters<HookMailRouter["sendRunGrants"]>[2],
-        senderIdentities: Parameters<HookMailRouter["sendRunGrants"]>[3],
-      ) => {
-        grants.push({ address, senderIdentities });
-        return true;
-      },
+  const calls: Parameters<HookRouter["routeMail"]>[] = [];
+  const router: HookRouter = {
+    routeMail: (...args) => {
+      calls.push(args);
+      return true;
     },
   };
+  return { calls, router };
 }
 
-function deliverer(
-  router: ReturnType<typeof recordingRouter>["router"],
-  systemSender: SystemSender,
-) {
+function deliverer(router: HookRouter, systemSender: SystemSender) {
   return createRunTriggerDeliverer({
     router,
     materialize: async () => ({ outcome: "materialized", stepGrants: [] }),
@@ -93,9 +71,9 @@ describe("createRunTriggerDeliverer", () => {
       "cron",
     );
 
-    const [frame] = recorded.mail;
-    expect(frame?.authenticatedSender).toBe("cron@localhost");
-    const raw = Buffer.from(frame?.rawMessage ?? "", "base64").toString("utf8");
+    const [call] = recorded.calls;
+    expect(call?.[2]).toBe("cron@localhost");
+    const raw = Buffer.from(call?.[1] ?? "", "base64").toString("utf8");
     // The recipient rejects a valid signature worn under a different From.
     expect(raw).toContain("From: cron@localhost");
   });
@@ -110,9 +88,9 @@ describe("createRunTriggerDeliverer", () => {
       undefined,
     );
 
-    const [barrier] = recorded.grants;
-    expect(barrier?.address).toBe(ADDRESS);
-    expect(barrier?.senderIdentities).toEqual([
+    const [call] = recorded.calls;
+    expect(call?.[0]).toBe(ADDRESS);
+    expect(call?.[4]?.senderIdentities).toEqual([
       {
         address: "cron@localhost",
         publicKey: hexEncode(sender.keyPair.publicKey),
@@ -137,12 +115,12 @@ describe("createRunTriggerDeliverer", () => {
     await deliver.to(ADDRESS, "two", "tnt_1", undefined);
 
     expect(sender.resolveCount()).toBe(2);
-    const keys = recorded.grants.map((g) => g.senderIdentities?.[0]?.publicKey);
+    const keys = recorded.calls.map(
+      (c) => c[4]?.senderIdentities?.[0]?.publicKey,
+    );
     expect(keys[0]).toBe(hexEncode(sender.keyPair.publicKey));
     expect(keys[1]).toBe(keys[0]);
-    expect(
-      recorded.mail.every((m) => m.authenticatedSender === "cron@localhost"),
-    ).toBe(true);
+    expect(recorded.calls.every((c) => c[2] === "cron@localhost")).toBe(true);
   });
 
   test("rejects a destination that is not a run address", async () => {
@@ -158,31 +136,33 @@ describe("createRunTriggerDeliverer", () => {
     ).rejects.toThrow("not a live run address");
   });
 
-  test("a dead run address fails with its run identity, not a bare string", async () => {
+  test("hands the run grants to the router in the one routeMail call", async () => {
     const sender = await durableSystemSender();
     const recorded = recordingRouter();
-    recorded.router.sendRunGrants = () => false;
-    const error = await deliverer(recorded.router, sender.sender)
-      .to(ADDRESS, "tick", "tnt_1", undefined)
-      .then(
-        () => {
-          throw new Error("the dead run delivered");
+    const stepGrants = [{ stepId: "s1" }] as never;
+    const deliver = createRunTriggerDeliverer({
+      router: recorded.router,
+      materialize: async () => ({ outcome: "materialized", stepGrants }),
+      tenantDomain: async () => "localhost",
+      senderLocalPart: "cron",
+      systemSender: sender.sender,
+    });
+    await deliver.to(ADDRESS, "tick", "tnt_1", undefined);
+
+    expect(recorded.calls).toHaveLength(1);
+    expect(recorded.calls[0]?.[4]).toEqual({
+      runId: "run_0123456789abcdef",
+      stepGrants,
+      senderIdentities: [
+        {
+          address: "cron@localhost",
+          publicKey: hexEncode(sender.keyPair.publicKey),
         },
-        (e: unknown) => e,
-      );
-
-    expect(isRunTriggerUnroutable(error)).toBe(true);
-    expect((error as { code: string }).code).toBe(RUN_GRANTS_NOT_ROUTABLE);
-    expect((error as { address: string }).address).toBe(ADDRESS);
-    expect((error as { runId: string }).runId).toBe("run_0123456789abcdef");
-    expect(String((error as Error).message)).toContain(
-      "run grants not routable",
-    );
-    // The grants barrier never went out, so no mail follows it.
-    expect(recorded.mail).toEqual([]);
+      ],
+    });
   });
 
-  test("unroutable mail after delivered grants names the run too", async () => {
+  test("a dead run address fails with its run identity, not a bare string", async () => {
     const sender = await durableSystemSender();
     const recorded = recordingRouter();
     recorded.router.routeMail = () => false;
@@ -195,12 +175,12 @@ describe("createRunTriggerDeliverer", () => {
         (e: unknown) => e,
       );
 
+    expect(error).toBeInstanceOf(RunTriggerUnroutableError);
     expect(isRunTriggerUnroutable(error)).toBe(true);
     expect((error as { code: string }).code).toBe(RUN_MAIL_NOT_ROUTABLE);
     expect((error as { address: string }).address).toBe(ADDRESS);
     expect((error as { runId: string }).runId).toBe("run_0123456789abcdef");
-    // The grants barrier went out before the mail leg failed.
-    expect(recorded.grants).toHaveLength(1);
+    expect(String((error as Error).message)).toContain("run mail not routable");
   });
 
   test("rejected grants deliver nothing", async () => {
@@ -222,7 +202,6 @@ describe("createRunTriggerDeliverer", () => {
     await expect(
       deliver.to(ADDRESS, "tick", "tnt_1", undefined),
     ).rejects.toThrow("run grants denied");
-    expect(recorded.grants).toEqual([]);
-    expect(recorded.mail).toEqual([]);
+    expect(recorded.calls).toEqual([]);
   });
 });