diff --git a/AGENTS.md b/AGENTS.md
index a8abf26..f9efc90 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -42,7 +42,9 @@ Layout (each directory's justfile module in parentheses):
   upstream commit) which must agree on the `@deltic/runtime` version
   (deltic's `wasi-shims` imports `@deltic/runtime/embedder` by bare
   specifier internally, so a drift would load the embedder module twice
-  and break `instanceof ComponentException` across the boundary); the root
+  and split the runtime/translator plan-format pairing; value recognition
+  itself is brand-based — deltic's `@deltic/protocol` predicates, not
+  `instanceof` — and survives a multi-copy graph); the root
   justfile's `exam-deltic` recipe (CI-wired) asserts one version
   repo-wide. Bump procedure: `conformance/driver-ct/deltic/README.md`.
 - `js/componentize/` (`just wpt::…`) — `websocket.js`, the WHATWG-API
diff --git a/conformance/driver-ct/deltic/README.md b/conformance/driver-ct/deltic/README.md
index 2859008..a591971 100644
--- a/conformance/driver-ct/deltic/README.md
+++ b/conformance/driver-ct/deltic/README.md
@@ -36,8 +36,9 @@ prereleases"). It is pinned in **two** places, both required to agree:
   SAME `@deltic/runtime` version (the module-identity constraint: deltic's
   `wasi-shims` imports `@deltic/runtime/embedder` by bare specifier
   internally, so every config resolving it must agree, or the embedder
-  module loads twice and `instanceof ComponentException` stops holding across the
-  boundary).
+  module loads twice — the host module's brand-based value recognition
+  survives that, but a second copy splits the runtime/translator
+  plan-format pairing).
 
 `@deltic/translator` ships the translator wasm asset **for the same
 commit** as `@deltic/runtime`, so the plan-format coupling is
diff --git a/conformance/driver-ct/deltic/browser/worker-entry.ts b/conformance/driver-ct/deltic/browser/worker-entry.ts
index 434cea2..ea84a82 100644
--- a/conformance/driver-ct/deltic/browser/worker-entry.ts
+++ b/conformance/driver-ct/deltic/browser/worker-entry.ts
@@ -2,11 +2,10 @@
 // surface (the local browser-bundle-entry.ts, re-exporting the pinned
 // JSR packages' public surface), the upstream worker message loop, and
 // this repo's deltic host module, resolved through ONE import map so the
-// emitted bundle carries exactly one embedder module instance — which is
-// what keeps `instanceof ComponentException` true when the host module throws
-// across the component boundary (workers resolve no import maps, so
-// bundling is the only sound shape; see @jsr/polymorph__test's
-// runner-deltic README).
+// emitted bundle carries exactly one embedder module instance — one
+// runtime/translator plan-format pairing, one copy on the runtime's
+// copy census (workers resolve no import maps, so bundling is the only
+// sound shape; see @jsr/polymorph__test's runner-deltic README).
 //
 // Built by `just conformance-ct::run-deltic-browser` with
 // `deno bundle --platform browser` into target/deltic-browser/, and
diff --git a/conformance/driver-ct/deltic/deno.json b/conformance/driver-ct/deltic/deno.json
index 238eaf5..231551e 100644
--- a/conformance/driver-ct/deltic/deno.json
+++ b/conformance/driver-ct/deltic/deno.json
@@ -1,5 +1,5 @@
 {
-  "//": "MODULE-IDENTITY CONSTRAINT: deltic's wasi module imports @deltic/runtime/embedder by bare specifier internally. The @deltic/runtime/embedder entry here must map to the IDENTICAL exact-pinned JSR version as ../../../js/deltic/deno.json's entry, or the embedder module loads twice and `instanceof ComponentException` stops holding across the module boundary. Pin story: exact-pinned JSR releases (caret-honest upstream: within a minor line releases stay compatible, breaking bumps the minor; per-commit `<next>-pre.g<hash>` prereleases exist between releases — pin exactly); @deltic/translator ships the translator wasm for that SAME commit; deno.lock carries integrity, --frozen enforced everywhere; one version repo-wide is asserted by the pin gate (justfile: exam-deltic).",
+  "//": "MODULE-IDENTITY CONSTRAINT: deltic's wasi module imports @deltic/runtime/embedder by bare specifier internally. The @deltic/runtime/embedder entry here must resolve to the IDENTICAL @deltic/runtime version as ../../../js/deltic/deno.json's caret range (in both deno.locks), or the embedder module loads twice: value recognition survives that (websocket.ts recognizes deltic values by @deltic/protocol brand predicates, not instanceof), but a second copy splits the runtime/translator plan-format pairing, and stateful handles (streams/futures) minted by one copy are refused by the other. Pin story: exact-pinned JSR releases (caret-honest upstream: within a minor line releases stay compatible, breaking bumps the minor; per-commit `<next>-pre.g<hash>` prereleases exist between releases — pin exactly); @deltic/translator ships the translator wasm for that SAME commit; deno.lock carries integrity, --frozen enforced everywhere; one version repo-wide is asserted by the pin gate (justfile: exam-deltic).",
   "imports": {
     "@deltic/ct-runner": "jsr:@deltic/ct-runner@0.1.0",
     "@deltic/runtime/embedder": "jsr:@deltic/runtime@0.1.0/embedder",
diff --git a/conformance/driver-ct/deltic/run.ts b/conformance/driver-ct/deltic/run.ts
index d58626b..4a882e4 100644
--- a/conformance/driver-ct/deltic/run.ts
+++ b/conformance/driver-ct/deltic/run.ts
@@ -31,7 +31,8 @@
 // `@deltic/runtime/embedder` by bare specifier internally; this leg's
 // `deno.json` AND `js/deltic/deno.json` must map that specifier to the
 // IDENTICAL exact-pinned JSR version, or the embedder module loads twice
-// and `instanceof ComponentException` stops holding across the module boundary.
+// and the graph carries two runtime/translator plan-format pairings (the
+// host module's value recognition is brand-based and survives that).
 //
 // The translator comes from the packaged `@deltic/translator` JSR
 // prerelease (defaultTranslator()) by default — no fetch step, no
diff --git a/examples/deltic-demo/run.ts b/examples/deltic-demo/run.ts
index 857343c..7b3e060 100644
--- a/examples/deltic-demo/run.ts
+++ b/examples/deltic-demo/run.ts
@@ -16,13 +16,13 @@
 // conformance/driver-ct/deltic/deno.json. The translator comes from the
 // packaged `@deltic/translator` JSR prerelease by default (no fetch
 // step); `--translator <path>` remains as an optional override for a
-// locally-built translator shim. The same import map is what keeps
-// `instanceof ComponentException` holding across the host-module boundary (see
-// that deno.json's MODULE-IDENTITY note).
+// locally-built translator shim. The same import map keeps one embedder
+// instance — one runtime/translator plan-format pairing — in the graph
+// (see that deno.json's MODULE-IDENTITY note).
 
 import { Translator } from "@deltic/runtime/shim";
 import type { ComponentArtifacts } from "@deltic/runtime/embedder";
-import { ComponentException, instantiate } from "@deltic/runtime/embedder";
+import { instantiate, isComponentException } from "@deltic/runtime/embedder";
 import { defaultTranslator } from "@deltic/translator";
 import { wasi } from "@deltic/wasi";
 import { websocketImports } from "../../js/deltic/websocket.ts";
@@ -126,7 +126,7 @@ async function main() {
       const received = await demo.run(`${echod.base}/echo`, cli.count);
       console.log(`round-tripped ${received}/${cli.count} messages`);
     } catch (err) {
-      const detail = err instanceof ComponentException ? err.payload : err;
+      const detail = isComponentException(err) ? err.payload : err;
       console.error(`demo failed: ${detail}`);
       Deno.exitCode = 1;
     }
diff --git a/js/componentize/wpt/parity/deltic-carrier.ts b/js/componentize/wpt/parity/deltic-carrier.ts
index a47ef78..000de1f 100644
--- a/js/componentize/wpt/parity/deltic-carrier.ts
+++ b/js/componentize/wpt/parity/deltic-carrier.ts
@@ -23,9 +23,10 @@
 // the bundle recipe runs `deno bundle` from that directory) and the
 // translator asset is extracted from the packaged `@deltic/translator`
 // JSR package's lock-pinned module cache (no fetch step). Bundling from
-// there is also what keeps `@deltic/runtime/embedder` a single module
-// instance across this bundle and js/deltic/websocket.ts, so
-// `instanceof ComponentException` holds.
+// there also keeps `@deltic/runtime/embedder` a single module instance
+// across this bundle and js/deltic/websocket.ts — one runtime/translator
+// plan-format pairing (value recognition is brand-based and would
+// survive a multi-copy bundle; the pairing would not).
 
 import { Translator } from "@deltic/runtime/shim";
 import { instantiate } from "@deltic/runtime/embedder";
diff --git a/js/deltic/README.md b/js/deltic/README.md
index dc3fc39..0e41064 100644
--- a/js/deltic/README.md
+++ b/js/deltic/README.md
@@ -35,8 +35,12 @@ identically on Deno.
 `deno.json`'s `@deltic/runtime/embedder` import maps to the exact same
 pinned URL as `conformance/driver-ct/deltic/deno.json`. deltic's
 `wasi-shims` module imports that specifier by bare name internally; if the
-two configs ever disagreed, the embedder module would load twice and
-`instanceof ComponentException` would stop holding across the boundary. Keep both
+two configs ever disagreed, the embedder module would load twice. This
+module recognizes deltic values by `@deltic/protocol` brand predicates
+(`isComponentException`, the `STREAM` brand), so recognition holds even in
+a multi-copy graph — but a duplicated embedder still splits the
+runtime/translator plan-format pairing, and stateful handles
+(streams/futures) minted by one copy are refused by the other. Keep both
 import maps byte-identical for that one entry.
 
 ## Unit tests
diff --git a/js/deltic/deno.json b/js/deltic/deno.json
index 096d0c2..90af8d9 100644
--- a/js/deltic/deno.json
+++ b/js/deltic/deno.json
@@ -3,7 +3,7 @@
   "version": "0.1.0",
   "license": "Apache-2.0",
   "exports": "./websocket.ts",
-  "//": "MODULE-IDENTITY CONSTRAINT: deltic's wasi module imports @deltic/runtime/embedder by bare specifier internally. This file's @deltic/runtime range and conformance/driver-ct/deltic/deno.json's exact pin must resolve to the IDENTICAL @deltic/runtime version in both deno.locks, or the embedder module loads twice and `instanceof ComponentException` stops holding across the module boundary. Pin story: this published package takes a caret range (caret-honest upstream: within a minor line releases stay compatible, breaking bumps the minor); the repo-internal conformance harness exact-pins instead so its lock is the single source of truth for the resolved version; deno.lock carries integrity, --frozen enforced everywhere; one RESOLVED version repo-wide (across both locks) is asserted by the pin gate (justfile: exam-deltic).",
+  "//": "MODULE-IDENTITY CONSTRAINT: deltic's wasi module imports @deltic/runtime/embedder by bare specifier internally. This file's @deltic/runtime range and conformance/driver-ct/deltic/deno.json's exact pin must resolve to the IDENTICAL @deltic/runtime version in both deno.locks, or the embedder module loads twice: value recognition survives that (websocket.ts recognizes deltic values by @deltic/protocol brand predicates, not instanceof), but a second copy splits the runtime/translator plan-format pairing, and stateful handles (streams/futures) minted by one copy are refused by the other. Pin story: this published package takes a caret range (caret-honest upstream: within a minor line releases stay compatible, breaking bumps the minor); the repo-internal conformance harness exact-pins instead so its lock is the single source of truth for the resolved version; deno.lock carries integrity, --frozen enforced everywhere; one RESOLVED version repo-wide (across both locks) is asserted by the pin gate (justfile: exam-deltic).",
   "imports": {
     "@deltic/runtime/embedder": "jsr:@deltic/runtime@^0.1.0/embedder"
   },
diff --git a/js/deltic/tests/websocket_test.ts b/js/deltic/tests/websocket_test.ts
index 4d36b17..0f4d686 100644
--- a/js/deltic/tests/websocket_test.ts
+++ b/js/deltic/tests/websocket_test.ts
@@ -13,6 +13,7 @@ import { ComponentException } from "@deltic/runtime/embedder";
 import {
   currentConfig,
   resetConfig,
+  type SendViaStreamError,
   setConnectTimeoutMs,
   setMaxInboundBufferBytes,
   type StreamMessage,
@@ -212,6 +213,69 @@ Deno.test("receive-via-stream: single-use; pending receive is rejected", async (
   });
 });
 
+// The two tests below hand-roll deltic values from nothing but the
+// @deltic/protocol registry brands (`Symbol.for` keys pinned by upstream's
+// own tests): per the protocol contract, an object carrying the brand is a
+// legal value from ANY runtime copy, so these prove the module's
+// recognition sites work without class identity — the multi-copy exposure
+// #48 closes. The literal keys are deliberate: a brand-generation bump
+// upstream must fail here and force the recognition sites to be
+// revisited. (Key spellings are stable across upstream renames: the
+// `ComponentException` brand is still `deltic.witError/1`.)
+
+Deno.test("send-via-stream: a foreign-copy ComponentException's payload passes through the error wrap", async () => {
+  await withServer(async (s) => {
+    const ws = await Websocket.connect(`${s.base}/echo`, []);
+    const foreign = Object.assign(new Error("minted elsewhere"), {
+      [Symbol.for("deltic.witError/1")]: true,
+      payload: { kind: "invalid-argument", value: "minted by another copy" },
+    });
+    const producer = (async function* () {
+      throw foreign;
+    })();
+    const e = await assertRejects(
+      () => ws.sendViaStream(producer as unknown as Parameters<Websocket["sendViaStream"]>[0]),
+      ComponentException,
+    ) as ComponentException<SendViaStreamError>;
+    // The structured payload must pass through, not be flattened to
+    // `{ kind: "other", value: String(error) }` as an unrecognized throw is.
+    assertEquals(e.payload.error, {
+      kind: "invalid-argument",
+      value: "minted by another copy",
+    } as WebsocketError);
+    assertEquals(e.payload.sent, 0n);
+    ws.close(1000, "");
+    await ws.waitClosed();
+  });
+});
+
+Deno.test("send-via-stream: a hand-rolled branded byte stream takes the batched-read path", async () => {
+  await withServer(async (s) => {
+    const ws = await Websocket.connect(`${s.base}/echo`, []);
+    const payload = new Uint8Array([104, 101, 121]);
+    // A minimal branded `Stream<u8>`: the brand plus the conventions'
+    // `read(max)` (empty chunk = end-of-stream). Deliberately neither a
+    // `ReadableStream` nor async-iterable, so only brand recognition can
+    // route it to the batched-read branch.
+    let reads = 0;
+    const data = {
+      [Symbol.for("deltic.stream/1")]: true,
+      read(_max: number): Promise<Uint8Array> {
+        reads += 1;
+        return Promise.resolve(reads === 1 ? payload : new Uint8Array(0));
+      },
+    };
+    const producer = (async function* () {
+      yield { kind: "binary", length: payload.length, data };
+    })();
+    await ws.sendViaStream(producer as unknown as Parameters<Websocket["sendViaStream"]>[0]);
+    const echoed = await ws.receive();
+    assertEquals(echoed, { kind: "binary", value: payload });
+    ws.close(1000, "");
+    await ws.waitClosed();
+  });
+});
+
 Deno.test("flow control: overflow closes, backlog stays receivable, then overflow error", async () => {
   await withServer(async (s) => {
     // A shrunk bound so a modest burst overflows it deterministically.
diff --git a/js/deltic/websocket.ts b/js/deltic/websocket.ts
index 7b4250e..e68cf30 100644
--- a/js/deltic/websocket.ts
+++ b/js/deltic/websocket.ts
@@ -28,7 +28,10 @@
 
 import {
   ComponentException,
-  Stream,
+  hasBrand,
+  isComponentException,
+  STREAM,
+  type Stream,
   type StreamSource,
 } from "@deltic/runtime/embedder";
 
@@ -521,9 +524,11 @@ export class Websocket {
         sent += 1n;
       }
     } catch (error) {
-      // A WIT error variant passes through; anything else is a host-side
-      // failure and must not masquerade as a normal close. websocket.js:370-378.
-      const payload: WebsocketError = error instanceof ComponentException
+      // A WIT error variant passes through — recognized by its
+      // process-global brand, so a `ComponentException` minted by any
+      // runtime copy counts; anything else is a host-side failure and must
+      // not masquerade as a normal close. websocket.js:370-378.
+      const payload: WebsocketError = isComponentException(error)
         ? error.payload as WebsocketError
         : { kind: "other", value: String(error) };
       throw new ComponentException<SendViaStreamError>(
@@ -894,12 +899,15 @@ async function collectByteStream(
     } finally {
       reader.releaseLock();
     }
-  } else if (stream instanceof Stream) {
-    // The conventions' `Stream<u8>`: `read(max)` yields a `Uint8Array`, and
-    // an EMPTY chunk means end-of-stream (contracts/embedder-api.md
-    // §"Streams and futures"). Read in batches rather than per element.
+  } else if (hasBrand(stream, STREAM)) {
+    // The conventions' `Stream<u8>`, recognized by its process-global brand
+    // (a handle minted by any runtime copy dispatches here): `read(max)`
+    // yields a `Uint8Array`, and an EMPTY chunk means end-of-stream
+    // (contracts/embedder-api.md §"Streams and futures"). Read in batches
+    // rather than per element.
+    const handle = stream as Stream<number>;
     for (;;) {
-      const chunk = await stream.read(READ_BATCH);
+      const chunk = await handle.read(READ_BATCH);
       if ((chunk as Uint8Array).length === 0) break;
       push(chunk);
     }