fix(discord): surface final reply permission context

extensions/discord/src/monitor/message-handler.process.ts

@@ -98,6 +98,21 @@ function isProcessAborted(abortSignal?: AbortSignal): boolean {
   return Boolean(abortSignal?.aborted);
 }
 
+function formatDiscordReplyDeliveryFailure(params: {
+  kind: string;
+  err: unknown;
+  target: string;
+  sessionKey?: string;
+}) {
+  const context = [
+    `target=${params.target}`,
+    params.sessionKey ? `session=${params.sessionKey}` : undefined,
+  ]
+    .filter(Boolean)
+    .join(" ");
+  return `discord ${params.kind} reply failed (${context}): ${String(params.err)}`;
+}
+
 type DiscordMessageProcessObserver = {
   onFinalReplyStart?: () => void;
   onFinalReplyDelivered?: () => void;
@@ -889,7 +904,16 @@ export async function processDiscordMessage(
         }
       },
       onError: (err, info) => {
-        runtime.error?.(danger(`discord ${info.kind} reply failed: ${String(err)}`));
+        runtime.error?.(
+          danger(
+            formatDiscordReplyDeliveryFailure({
+              kind: info.kind,
+              err,
+              target: deliverTarget,
+              sessionKey: ctxPayload.SessionKey,
+            }),
+          ),
+        );
       },
       onReplyStart: async () => {
         if (isProcessAborted(abortSignal)) {

extensions/discord/src/monitor/reply-delivery.test.ts

@@ -10,6 +10,9 @@ const sendMessageDiscordMock = vi.hoisted(() => vi.fn());
 const sendVoiceMessageDiscordMock = vi.hoisted(() => vi.fn());
 const sendWebhookMessageDiscordMock = vi.hoisted(() => vi.fn());
 const sendDiscordTextMock = vi.hoisted(() => vi.fn());
+const buildDiscordSendErrorMock = vi.hoisted(() =>
+  vi.fn<(err: unknown, ctx?: unknown) => Promise<unknown>>(async (err: unknown) => err),
+);
 const retryAsyncMock = vi.hoisted(() =>
   vi.fn(
     async (
@@ -47,6 +50,7 @@ vi.mock("../send.js", async () => {
 });
 
 vi.mock("../send.shared.js", () => ({
+  buildDiscordSendError: (err: unknown, ctx: unknown) => buildDiscordSendErrorMock(err, ctx),
   sendDiscordText: (...args: unknown[]) => sendDiscordTextMock(...args),
 }));
 
@@ -135,6 +139,7 @@ describe("deliverDiscordReply", () => {
       id: "msg-direct-1",
       channel_id: "channel-1",
     });
+    buildDiscordSendErrorMock.mockClear().mockImplementation(async (err: unknown) => err);
     retryAsyncMock.mockClear();
     threadBindingTesting.resetThreadBindingsForTests();
   });
@@ -485,6 +490,40 @@ describe("deliverDiscordReply", () => {
     expect(sendMessageDiscordMock).toHaveBeenCalledTimes(1);
   });
 
+  it("wraps direct REST permission errors with channel context", async () => {
+    const apiErr = Object.assign(new Error("Missing Permissions"), {
+      code: 50013,
+      status: 403,
+    });
+    const wrappedErr = new Error(
+      "discord missing permissions in channel 789; permission probe did not identify missing ViewChannel/SendMessages (code=50013 status=403)",
+    );
+    sendDiscordTextMock.mockRejectedValueOnce(apiErr);
+    buildDiscordSendErrorMock.mockResolvedValueOnce(wrappedErr);
+
+    const fakeRest = {
+      post: vi.fn(),
+      get: vi.fn(),
+    } as unknown as import("@buape/carbon").RequestClient;
+
+    await expect(
+      deliverDiscordReply({
+        replies: [{ text: "fail" }],
+        target: "channel:789",
+        token: "token",
+        rest: fakeRest,
+        runtime,
+        cfg,
+        textLimit: 2000,
+      }),
+    ).rejects.toThrow("discord missing permissions in channel 789");
+
+    expect(buildDiscordSendErrorMock).toHaveBeenCalledWith(
+      apiErr,
+      expect.objectContaining({ channelId: "789", hasMedia: false }),
+    );
+  });
+
   it("throws after exhausting retry attempts", async () => {
     const rateLimitErr = Object.assign(new Error("rate limited"), { status: 429 });
     sendMessageDiscordMock.mockRejectedValue(rateLimitErr);

extensions/discord/src/monitor/reply-delivery.ts

@@ -23,7 +23,7 @@ import { chunkDiscordTextWithMode } from "../chunk.js";
 import { isLikelyDiscordVideoMedia } from "../media-detection.js";
 import { createDiscordRetryRunner } from "../retry.js";
 import { sendMessageDiscord, sendVoiceMessageDiscord, sendWebhookMessageDiscord } from "../send.js";
-import { sendDiscordText } from "../send.shared.js";
+import { buildDiscordSendError, sendDiscordText } from "../send.shared.js";
 
 export type DiscordThreadBindingLookupRecord = {
   accountId: string;
@@ -322,21 +322,31 @@ async function sendDiscordChunkWithFallback(params: {
   // that can cause ordering issues under queue contention or rate limiting.
   if (params.channelId && params.request && params.rest) {
     const { channelId, request, rest } = params;
-    await sendWithRetry(
-      () =>
-        sendDiscordText(
-          rest,
-          channelId,
-          text,
-          params.replyTo,
-          request,
-          params.maxLinesPerMessage,
-          undefined,
-          undefined,
-          params.chunkMode,
-        ),
-      params.retryConfig,
-    );
+    try {
+      await sendWithRetry(
+        () =>
+          sendDiscordText(
+            rest,
+            channelId,
+            text,
+            params.replyTo,
+            request,
+            params.maxLinesPerMessage,
+            undefined,
+            undefined,
+            params.chunkMode,
+          ),
+        params.retryConfig,
+      );
+    } catch (err) {
+      throw await buildDiscordSendError(err, {
+        channelId,
+        cfg: params.cfg,
+        rest,
+        token: params.token,
+        hasMedia: false,
+      });
+    }
     return;
   }
   await sendWithRetry(

extensions/discord/src/send.sends-basic-channel-messages.test.ts

@@ -355,6 +355,41 @@ describe("sendMessageDiscord", () => {
     expect(String(error)).toMatch(/SendMessages/);
   });
 
+  it("keeps 50013 context when permission probe finds baseline permissions", async () => {
+    const { rest, postMock, getMock } = makeDiscordRest();
+    const perms = PermissionFlagsBits.ViewChannel | PermissionFlagsBits.SendMessages;
+    const apiError = Object.assign(new Error("Missing Permissions"), {
+      code: 50013,
+      status: 403,
+    });
+    postMock.mockRejectedValueOnce(apiError);
+    getMock
+      .mockResolvedValueOnce({ type: ChannelType.GuildText })
+      .mockResolvedValueOnce({
+        id: "789",
+        guild_id: "guild1",
+        type: 0,
+        permission_overwrites: [],
+      })
+      .mockResolvedValueOnce({ id: "bot1" })
+      .mockResolvedValueOnce({
+        id: "guild1",
+        roles: [{ id: "guild1", permissions: perms.toString() }],
+      })
+      .mockResolvedValueOnce({ roles: [] });
+
+    let error: unknown;
+    try {
+      await sendMessageDiscord("channel:789", "hello", { rest, token: "t", cfg: DISCORD_TEST_CFG });
+    } catch (err) {
+      error = err;
+    }
+    expect(String(error)).toMatch(
+      /permission probe did not identify missing ViewChannel\/SendMessages/,
+    );
+    expect(String(error)).toMatch(/code=50013 status=403/);
+  });
+
   it("uploads media attachments", async () => {
     const { rest, postMock } = makeDiscordRest();
     postMock.mockResolvedValue({ id: "msg", channel_id: "789" });

extensions/discord/src/send.shared.ts

@@ -116,6 +116,25 @@ function getDiscordErrorCode(err: unknown) {
   return undefined;
 }
 
+function getDiscordErrorStatus(err: unknown) {
+  if (!err || typeof err !== "object") {
+    return undefined;
+  }
+  const candidate =
+    "status" in err && err.status !== undefined
+      ? err.status
+      : "statusCode" in err && err.statusCode !== undefined
+        ? err.statusCode
+        : undefined;
+  if (typeof candidate === "number" && Number.isFinite(candidate)) {
+    return candidate;
+  }
+  if (typeof candidate === "string" && /^\d+$/.test(candidate)) {
+    return Number(candidate);
+  }
+  return undefined;
+}
+
 async function buildDiscordSendError(
   err: unknown,
   ctx: {
@@ -132,8 +151,8 @@ async function buildDiscordSendError(
   const code = getDiscordErrorCode(err);
   if (code === DISCORD_CANNOT_DM) {
     return new DiscordSendError(
-      "discord dm failed: user blocks dms or privacy settings disallow it",
-      { kind: "dm-blocked" },
+      `discord dm failed: user blocks dms or privacy settings disallow it (code=${code})`,
+      { kind: "dm-blocked", discordCode: code, status: getDiscordErrorStatus(err) },
     );
   }
   if (code !== DISCORD_MISSING_PERMISSIONS) {
@@ -141,15 +160,17 @@ async function buildDiscordSendError(
   }
 
   let missing: string[] = [];
+  let probedChannelType: number | undefined;
   try {
     const permissions = await fetchChannelPermissionsDiscord(ctx.channelId, {
       rest: ctx.rest,
       token: ctx.token,
       cfg: ctx.cfg,
     });
+    probedChannelType = permissions.channelType;
     const current = new Set(permissions.permissions);
     const required = ["ViewChannel", "SendMessages"];
-    if (isThreadChannelType(permissions.channelType)) {
+    if (isThreadChannelType(probedChannelType)) {
       required.push("SendMessagesInThreads");
     }
     if (ctx.hasMedia) {
@@ -160,15 +181,29 @@ async function buildDiscordSendError(
     /* ignore permission probe errors */
   }
 
+  const status = getDiscordErrorStatus(err);
+  const apiDetails = [`code=${code}`, status != null ? `status=${status}` : undefined]
+    .filter(Boolean)
+    .join(" ");
+  const probedPermissions = ["ViewChannel", "SendMessages"];
+  if (isThreadChannelType(probedChannelType)) {
+    probedPermissions.push("SendMessagesInThreads");
+  }
+  if (ctx.hasMedia) {
+    probedPermissions.push("AttachFiles");
+  }
+  const probeSummary = probedPermissions.join("/");
   const missingLabel = missing.length
-    ? `missing permissions in channel ${ctx.channelId}: ${missing.join(", ")}`
-    : `missing permissions in channel ${ctx.channelId}`;
+    ? `discord missing permissions in channel ${ctx.channelId}: ${missing.join(", ")}`
+    : `discord missing permissions in channel ${ctx.channelId}; permission probe did not identify missing ${probeSummary}`;
   return new DiscordSendError(
-    `${missingLabel}. bot might be muted or blocked by role/channel overrides`,
+    `${missingLabel} (${apiDetails}). bot might be blocked by channel/thread overrides, archived thread state, reply target visibility, or app-role position`,
     {
       kind: "missing-permissions",
       channelId: ctx.channelId,
       missingPermissions: missing,
+      discordCode: code,
+      status,
     },
   );
 }

extensions/discord/src/send.types.ts

@@ -6,6 +6,8 @@ export class DiscordSendError extends Error {
   kind?: "missing-permissions" | "dm-blocked";
   channelId?: string;
   missingPermissions?: string[];
+  discordCode?: number;
+  status?: number;
 
   constructor(message: string, opts?: Partial<DiscordSendError>) {
     super(message);