diff --git a/browser-host/relay-broker-live.test.mjs b/browser-host/relay-broker-live.test.mjs
index acf0b8e956..54f8b803f4 100644
--- a/browser-host/relay-broker-live.test.mjs
+++ b/browser-host/relay-broker-live.test.mjs
@@ -1054,6 +1054,11 @@ test("production interest controls preserve socket/global routes and pending wri
 
 test.each([
   ["restricted: not a member", true, "Relay request failed (503)"],
+  [
+    'invalid: an open channel named "Launch" already exists',
+    true,
+    'An open channel named "Launch" already exists',
+  ],
   [
     "error: internal server error",
     false,
@@ -1828,13 +1833,20 @@ test.each([
       ]);
       await h.sockets[0].receive(["OK", event.id, false, reason]);
       const response = await result;
-      expect(response.status).toBe(503);
-      expect(await response.json()).toEqual({
-        error: summary.startsWith("rate-limited:")
-          ? summary
-          : "Socket publication could not be confirmed",
-        ...(!sent ? { sent: false } : {}),
-      });
+      // A proven validation refusal answers this client as the relay's HTTP
+      // API does, with its own text; the log keeps only the safe summary.
+      const validation = !sent && reason.startsWith("invalid:");
+      expect(response.status).toBe(validation ? 400 : 503);
+      expect(await response.json()).toEqual(
+        validation
+          ? { error: reason }
+          : {
+              error: summary.startsWith("rate-limited:")
+                ? summary
+                : "Socket publication could not be confirmed",
+              ...(!sent ? { sent: false } : {}),
+            },
+      );
       expect(lines).toContain(
         `publication id=${event.id} kind=9000 stage=socket sent=${sent} reason=Relay publication not confirmed refusal=${summary}`,
       );
diff --git a/browser-host/relay-broker.mjs b/browser-host/relay-broker.mjs
index 62449caf3b..d9df5ae464 100644
--- a/browser-host/relay-broker.mjs
+++ b/browser-host/relay-broker.mjs
@@ -2809,6 +2809,18 @@ export function relayBrokerPlugin({
               const conflict =
                 failure?.sent === false &&
                 failure.refusal?.startsWith("conflict:");
+              // Answer a proven validation refusal as the relay's HTTP API does,
+              // 400 with its bounded text, so every publish path shows the same
+              // reason. The text goes to this client only, never to the log.
+              if (
+                failure?.sent === false &&
+                failure.reason?.startsWith("invalid:") &&
+                !(
+                  readPublishing &&
+                  failure.refusal === READ_STATE_TIMESTAMP_REFUSAL
+                )
+              )
+                return json(res, 400, { error: failure.reason });
               return json(res, conflict ? 409 : 503, {
                 error:
                   failure?.sent === false &&
diff --git a/src/features/relay/http-admission.ts b/src/features/relay/http-admission.ts
index 2f4a46c64d..97c12c5eda 100644
--- a/src/features/relay/http-admission.ts
+++ b/src/features/relay/http-admission.ts
@@ -84,7 +84,7 @@ export function apiFailure(status: number, value: unknown): ApiFailure {
  * `reason` may keep an exact, caller-allowed upstream refusal from that body. */
 export async function readApiFailure(
   response: Response,
-  reason?: (body: unknown) => string | undefined,
+  reason?: (body: unknown, status: number) => string | undefined,
 ): Promise<ApiFailure> {
   if (!response.body) return apiFailure(response.status, undefined);
   const reader = response.body.getReader();
@@ -108,7 +108,7 @@ export async function readApiFailure(
       return apiFailure(response.status, undefined);
     }
     const failure = apiFailure(response.status, body);
-    const allowed = failure.quota ? undefined : reason?.(body);
+    const allowed = failure.quota ? undefined : reason?.(body, response.status);
     return allowed ? { ...failure, error: allowed } : failure;
   } finally {
     await reader.cancel().catch(() => {});
@@ -248,7 +248,7 @@ export async function admittedApiRequest(
   request: () => Promise<Response>,
   signal?: AbortSignal,
   priority: Ticket["priority"] = "foreground",
-  reason?: (body: unknown) => string | undefined,
+  reason?: (body: unknown, status: number) => string | undefined,
 ): Promise<Response> {
   return lane.run(
     async () => {
diff --git a/src/features/relay/native.test.ts b/src/features/relay/native.test.ts
index 3130ee6ee4..4247be7bd7 100644
--- a/src/features/relay/native.test.ts
+++ b/src/features/relay/native.test.ts
@@ -342,7 +342,7 @@ it.each([true, false])(
         status: accepted ? 200 : 403,
         body: accepted
           ? { accepted: true, event_id: JSON.parse(request.body ?? "{}").id }
-          : { error: "Registration denied" },
+          : { error: "restricted: registration denied" },
       });
       expect(outbox.supports(30177)).toBe(true);
       const id = outbox.send({ kind: 30177, tags: [["d", agent]], content });
@@ -351,7 +351,7 @@ it.each([true, false])(
           outbox.snapshot().find((item) => item.event.id === id),
         ).toMatchObject({
           delivery: accepted ? "accepted" : "failed",
-          ...(accepted ? {} : { error: "Relay rejected the message (403)" }),
+          ...(accepted ? {} : { error: "Registration denied" }),
         }),
       );
       const publishes = requests.filter(
diff --git a/src/features/relay/socket-requests.ts b/src/features/relay/socket-requests.ts
index b43e489528..4e2e7ee91b 100644
--- a/src/features/relay/socket-requests.ts
+++ b/src/features/relay/socket-requests.ts
@@ -6,12 +6,15 @@ import {
   MAX_EVENT_BYTES as CATALOG_EVENT_BYTES,
 } from "../agents/catalog-envelope.ts";
 
-/** False means proven non-delivery, not merely a negative or missing OK. */
+/** False means proven non-delivery, not merely a negative or missing OK.
+ * `refusal` is the log-safe summary; `reason` is the relay's own bounded text
+ * for a proven refusal, for the client only and never for logs. */
 export class SocketRequestError extends Error {
   constructor(
     message: string,
     readonly sent: boolean,
     readonly refusal?: string,
+    readonly reason?: string,
   ) {
     super(message);
   }
@@ -126,6 +129,7 @@ export function createSocketPublications(wake: () => void) {
             "Relay publication not confirmed",
             !rejected,
             publicationRefusal(data[3]),
+            rejected ? data[3] : undefined,
           ),
         );
       }
diff --git a/src/features/relay/transport.test.ts b/src/features/relay/transport.test.ts
index 3f0be4ea99..c3082ae4bb 100644
--- a/src/features/relay/transport.test.ts
+++ b/src/features/relay/transport.test.ts
@@ -2,6 +2,7 @@ import { assert, afterEach, expect, it, vi } from "vitest";
 import {
   connectBrokerTransport,
   connectSignedTransport,
+  acceptPublish,
   acceptReadStatePublish,
 } from "./transport";
 import {
@@ -136,6 +137,120 @@ it("distinguishes explicit rejection from invalid or missing delivery receipts",
     transport.writer.publish(event, new AbortController().signal),
   ).rejects.toBeInstanceOf(PublishRejected);
 });
+const refusal = (status: number, body: unknown) =>
+  acceptPublish(Response.json(body, { status }), "id").catch(
+    (reason: unknown) => reason,
+  );
+it.each([
+  [
+    'invalid: an open channel named "Launch" already exists',
+    'An open channel named "Launch" already exists',
+  ],
+  ["blocked:   you are banned", "You are banned"],
+  ["restricted: not a channel member", "Not a channel member"],
+  ["error: internal failure", "Internal failure"],
+  ["pow: difficulty too low", "Difficulty too low"],
+  ["duplicate: already accepted", "Already accepted"],
+  ["invalid:  ", "Relay rejected the message (400)"],
+  // Prefixes writers match on carry meaning: left as sent.
+  ["conflict: stale prev", "conflict: stale prev"],
+  ["rate-limited: slow down", "rate-limited: slow down"],
+  ["auth-required: sign in", "auth-required: sign in"],
+])(
+  "shows the relay's refusal text without its NIP-01 prefix: %s",
+  async (error, message) => {
+    const result = await refusal(400, { error });
+    expect(result).toBeInstanceOf(PublishRejected);
+    expect(result).toMatchObject({ message, reason: error });
+  },
+);
+it.each([
+  [400, {}],
+  [403, { error: 7 }],
+  [422, { error: "" }],
+  [404, "not an object"],
+  // A gateway or VPN edge can answer these statuses with JSON `{error}`; text
+  // without a NIP-01 prefix is not the relay's, so it is never shown.
+  [403, { error: "Forbidden by proxy" }],
+  [400, { error: "Plain relay text" }],
+  [401, { error: "Relay request failed (401)" }],
+])(
+  "falls back to the status summary when a %s refusal has no relay text: %j",
+  async (status, body) => {
+    const result = await refusal(status, body);
+    expect(result).toBeInstanceOf(PublishRejected);
+    expect(result).toHaveProperty(
+      "message",
+      `Relay rejected the message (${status})`,
+    );
+  },
+);
+it("carries the relay's refusal text through both publish transports", async () => {
+  const error = 'invalid: an open channel named "Launch" already exists';
+  const shown = 'An open channel named "Launch" already exists';
+  const event = signed(key, { kind: 9, content: "hello", tags: [["h", "c"]] });
+  const publishes = async (
+    transport: Awaited<ReturnType<typeof connectSignedTransport>>,
+  ) => {
+    assert.exists(transport.writer);
+    return transport.writer
+      .publish(event, new AbortController().signal)
+      .catch((reason: unknown) => reason);
+  };
+  // Admission reduces an upstream body to a status summary unless the
+  // publish keeps the relay's refusal.
+  const signedTransport = await connectSignedTransport(
+    hostSigner(key),
+    "https://relay.test",
+    "relay",
+  );
+  vi.stubGlobal("fetch", async () => Response.json({ error }, { status: 400 }));
+  expect(await publishes(signedTransport)).toMatchObject({
+    message: shown,
+    reason: error,
+  });
+  // Without relay text, admission's own summary must not replace the
+  // status summary `acceptPublish` shows.
+  for (const [status, body] of [
+    [400, {}],
+    [400, { error: 7 }],
+    [403, { error: "Forbidden by proxy" }],
+  ] as const) {
+    vi.stubGlobal("fetch", async () => Response.json(body, { status }));
+    expect(await publishes(signedTransport)).toHaveProperty(
+      "message",
+      `Relay rejected the message (${status})`,
+    );
+  }
+  // Other statuses stay a status summary, never upstream text.
+  vi.stubGlobal("fetch", async () => Response.json({ error }, { status: 500 }));
+  expect(await publishes(signedTransport)).toHaveProperty(
+    "message",
+    "Relay delivery could not be confirmed (500)",
+  );
+  vi.stubGlobal("fetch", async (url: string) =>
+    url.endsWith("/session")
+      ? Response.json({
+          viewer: key.pubkey,
+          relayAuthor: "relay",
+          writeKinds: [9],
+        })
+      : Response.json({ error }, { status: 400 }),
+  );
+  expect(await publishes(await connectBrokerTransport())).toMatchObject({
+    message: shown,
+    reason: error,
+  });
+});
+it("keeps the conflict refusal and the raw reason for classifying writers", async () => {
+  const conflict = await refusal(409, { error: "invalid: whatever" });
+  expect(conflict).toHaveProperty(
+    "message",
+    "conflict: the relay state changed; reload before writing again",
+  );
+  const refused = await refusal(400, { error: "restricted: nope" });
+  expect(refused).toHaveProperty("reason", "restricted: nope");
+});
 it.each([
   [
     "rate-limited: quota exceeded; retry in 17s",
diff --git a/src/features/relay/transport.ts b/src/features/relay/transport.ts
index b9c231369b..785b5f63c5 100644
--- a/src/features/relay/transport.ts
+++ b/src/features/relay/transport.ts
@@ -1424,6 +1424,9 @@ export async function connectSignedTransport(
             profiling,
             event.id,
             principal().api,
+            "foreground",
+            false,
+            refusalText,
           ).catch((error) => {
             if (error instanceof ApiPaused || error instanceof ApiNotSent)
               throw new PublishNotSent(error.message);
@@ -1491,11 +1494,12 @@ async function signedPost(
   admission: Parameters<typeof admittedApiRequest>[0],
   priority: "foreground" | "background" = "foreground",
   optionalPresence = false,
+  reason?: (body: unknown, status: number) => string | undefined,
 ) {
   const dispatch = (request: () => Promise<Response>) =>
     optionalPresence
       ? admission.prepare(request)
-      : admittedApiRequest(admission, request, signal, priority);
+      : admittedApiRequest(admission, request, signal, priority, reason);
   signal?.throwIfAborted();
   return admission.prepare(async () => {
     const body = JSON.stringify(value);
@@ -1530,6 +1534,39 @@ export async function acceptReadStatePublish(response: Response, id: string) {
   return acceptPublish(response, id);
 }
 
+const REFUSAL_STATUSES = [400, 401, 403, 404, 413, 422];
+/** NIP-01 machine-readable prefixes: the shape of a relay's own refusal. */
+const NIP01_PREFIX =
+  /^(invalid|blocked|restricted|error|pow|duplicate|rate-limited|conflict|auth-required):\s*/;
+/** Prefixes writers match on, so the text is shown as sent. */
+const KEPT_PREFIXES = new Set(["rate-limited", "conflict", "auth-required"]);
+/** The relay's own `{error}` text for a refused write. Admission otherwise
+ * reduces every upstream body to a status summary, so a signed publish asks
+ * it to keep this one, bounded by `readApiFailure`. A gateway or VPN edge
+ * can answer the same statuses with JSON `{error}`, so only relay-shaped
+ * text (a NIP-01 prefix) is kept. The prefix is a shape, not proof of origin. */
+const refusalText = (body: unknown, status: number) => {
+  const error = (body as { error?: unknown } | null)?.error;
+  return REFUSAL_STATUSES.includes(status) &&
+    typeof error === "string" &&
+    NIP01_PREFIX.test(error)
+    ? error
+    : undefined;
+};
+
+/** The display text for an HTTP refusal: the relay's own words without their
+ * NIP-01 machine prefix. `reason` keeps the raw text for classification. Text
+ * with a prefix writers match on (`conflict:`, `rate-limited:`) is shown as
+ * sent. Text without a prefix is not relay-shaped, so the status summary stays. */
+function refusalMessage(status: number, reason: string | undefined) {
+  const prefix = reason ? NIP01_PREFIX.exec(reason) : null;
+  if (!reason || !prefix) return `Relay rejected the message (${status})`;
+  if (KEPT_PREFIXES.has(prefix[1] ?? "")) return reason.trim();
+  const text = reason.slice(prefix[0].length).trim();
+  if (!text) return `Relay rejected the message (${status})`;
+  return text.charAt(0).toUpperCase() + text.slice(1);
+}
+
 /** A transport failure is an unknown outcome; only a definitive rejection is a failed write. */
 export async function acceptPublish(response: Response, id: string) {
   if (!response.ok) {
@@ -1540,7 +1577,7 @@ export async function acceptPublish(response: Response, id: string) {
       throw new PublishRejected(
         "conflict: the relay state changed; reload before writing again",
       );
-    if ([400, 401, 403, 404, 413, 422].includes(response.status)) {
+    if (REFUSAL_STATUSES.includes(response.status)) {
       // Keep the relay's bounded `{error}` text for writers that classify it.
       let reason: string | undefined;
       await readApiFailure(response, (value) => {
@@ -1549,7 +1586,7 @@ export async function acceptPublish(response: Response, id: string) {
         return undefined;
       });
       throw new PublishRejected(
-        `Relay rejected the message (${response.status})`,
+        refusalMessage(response.status, reason),
         reason,
       );
     }