refactor(mattermost): deduplicate draft stream tests (#118215)

extensions/mattermost/src/mattermost/draft-stream.test.ts

@@ -12,11 +12,20 @@ type RequestRecord = {
   init?: RequestInit;
 };
 
-function createMockClient(): {
+type DraftStreamOptions = Omit<
+  Parameters<typeof createMattermostDraftStream>[0],
+  "client" | "channelId"
+> & {
+  request?: MattermostClient["request"];
+};
+
+function createDraftStreamFixture(options: DraftStreamOptions = {}): {
   client: MattermostClient;
   calls: RequestRecord[];
   requestMock: ReturnType<typeof vi.fn<MattermostClient["request"]>>;
+  stream: ReturnType<typeof createMattermostDraftStream>;
 } {
+  const { request, ...streamOptions } = options;
   const calls: RequestRecord[] = [];
   let nextId = 1;
   const requestImpl: MattermostClient["request"] = async <T>(
@@ -32,7 +41,7 @@ function createMockClient(): {
     }
     return {} as T;
   };
-  const requestMock = vi.fn(requestImpl);
+  const requestMock = vi.fn(request ?? requestImpl);
   const client: MattermostClient = {
     baseUrl: "https://chat.example.com",
     apiBaseUrl: "https://chat.example.com/api/v4",
@@ -40,7 +49,13 @@ function createMockClient(): {
     request: requestMock as MattermostClient["request"],
     fetchImpl: vi.fn() as MattermostClient["fetchImpl"],
   };
-  return { client, calls, requestMock };
+  const stream = createMattermostDraftStream({
+    client,
+    channelId: "channel-1",
+    throttleMs: 0,
+    ...streamOptions,
+  });
+  return { client, calls, requestMock, stream };
 }
 
 function parseRequestJson(init: RequestInit | undefined): Record<string, unknown> {
@@ -56,13 +71,7 @@ function parseRequestJson(init: RequestInit | undefined): Record<string, unknown
 
 describe("createMattermostDraftStream", () => {
   it("creates a preview post and updates it on later changes", async () => {
-    const { client, calls } = createMockClient();
-    const stream = createMattermostDraftStream({
-      client,
-      channelId: "channel-1",
-      rootId: "root-1",
-      throttleMs: 0,
-    });
+    const { calls, stream } = createDraftStreamFixture({ rootId: "root-1" });
 
     stream.update("Running `read`…");
     await stream.flush();
@@ -81,12 +90,7 @@ describe("createMattermostDraftStream", () => {
   });
 
   it("does not resend identical updates", async () => {
-    const { client, calls } = createMockClient();
-    const stream = createMattermostDraftStream({
-      client,
-      channelId: "channel-1",
-      throttleMs: 0,
-    });
+    const { calls, stream } = createDraftStreamFixture();
 
     stream.update("Working...");
     await stream.flush();
@@ -97,13 +101,7 @@ describe("createMattermostDraftStream", () => {
   });
 
   it("clears the preview post when no final reply is delivered", async () => {
-    const { client, calls } = createMockClient();
-    const stream = createMattermostDraftStream({
-      client,
-      channelId: "channel-1",
-      rootId: "root-1",
-      throttleMs: 0,
-    });
+    const { calls, stream } = createDraftStreamFixture({ rootId: "root-1" });
 
     stream.update("Working...");
     await stream.flush();
@@ -116,13 +114,7 @@ describe("createMattermostDraftStream", () => {
   });
 
   it("discardPending keeps the preview post but ignores later updates", async () => {
-    const { client, calls } = createMockClient();
-    const stream = createMattermostDraftStream({
-      client,
-      channelId: "channel-1",
-      rootId: "root-1",
-      throttleMs: 0,
-    });
+    const { calls, stream } = createDraftStreamFixture({ rootId: "root-1" });
 
     stream.update("Working...");
     await stream.flush();
@@ -136,13 +128,7 @@ describe("createMattermostDraftStream", () => {
   });
 
   it("seal keeps the preview post and cancels pending final overwrites", async () => {
-    const { client, calls } = createMockClient();
-    const stream = createMattermostDraftStream({
-      client,
-      channelId: "channel-1",
-      rootId: "root-1",
-      throttleMs: 0,
-    });
+    const { calls, stream } = createDraftStreamFixture({ rootId: "root-1" });
 
     stream.update("Working...");
     await stream.flush();
@@ -156,13 +142,7 @@ describe("createMattermostDraftStream", () => {
   });
 
   it("stop flushes the last pending update and ignores later ones", async () => {
-    const { client, calls } = createMockClient();
-    const stream = createMattermostDraftStream({
-      client,
-      channelId: "channel-1",
-      rootId: "root-1",
-      throttleMs: 1000,
-    });
+    const { calls, stream } = createDraftStreamFixture({ rootId: "root-1", throttleMs: 1000 });
 
     stream.update("Working...");
     await stream.flush();
@@ -185,20 +165,7 @@ describe("createMattermostDraftStream", () => {
     const requestImpl: MattermostClient["request"] = async () => {
       throw new Error("boom");
     };
-    const requestMock = vi.fn(requestImpl);
-    const client: MattermostClient = {
-      baseUrl: "https://chat.example.com",
-      apiBaseUrl: "https://chat.example.com/api/v4",
-      token: "token",
-      request: requestMock as MattermostClient["request"],
-      fetchImpl: vi.fn() as MattermostClient["fetchImpl"],
-    };
-    const stream = createMattermostDraftStream({
-      client,
-      channelId: "channel-1",
-      throttleMs: 0,
-      warn,
-    });
+    const { requestMock, stream } = createDraftStreamFixture({ request: requestImpl, warn });
 
     stream.update("Working...");
     await stream.flush();
@@ -212,14 +179,8 @@ describe("createMattermostDraftStream", () => {
 
   it("retains an accepted preview failure after its background flush has settled", async () => {
     const warn = vi.fn();
-    const { client, requestMock } = createMockClient();
+    const { requestMock, stream } = createDraftStreamFixture({ warn });
     requestMock.mockResolvedValueOnce({ message: "already visible" });
-    const stream = createMattermostDraftStream({
-      client,
-      channelId: "channel-1",
-      throttleMs: 0,
-      warn,
-    });
 
     stream.update("Already delivered");
     await vi.waitFor(() => expect(warn).toHaveBeenCalledOnce());
@@ -250,16 +211,10 @@ describe("createMattermostDraftStream", () => {
   });
 
   it("truncates on a code-point boundary so a straddling emoji is dropped whole", async () => {
-    const { client, calls } = createMockClient();
     // maxChars=12 => cut point is maxChars-3=9. The emoji 😀 occupies UTF-16
     // indices 8-9, so a raw slice(0,9) would keep the lone high surrogate at
     // index 8 and drop its low surrogate at index 9, leaking a dangling half.
-    const stream = createMattermostDraftStream({
-      client,
-      channelId: "channel-1",
-      throttleMs: 0,
-      maxChars: 12,
-    });
+    const { calls, stream } = createDraftStreamFixture({ maxChars: 12 });
 
     const input = `${"a".repeat(8)}\u{1F600}${"b".repeat(5)}`;
     stream.update(input);
@@ -296,20 +251,7 @@ describe("createMattermostDraftStream", () => {
       }
       return {} as T;
     };
-    const requestMock = vi.fn(requestImpl);
-    const client: MattermostClient = {
-      baseUrl: "https://chat.example.com",
-      apiBaseUrl: "https://chat.example.com/api/v4",
-      token: "token",
-      request: requestMock as MattermostClient["request"],
-      fetchImpl: vi.fn() as MattermostClient["fetchImpl"],
-    };
-    const stream = createMattermostDraftStream({
-      client,
-      channelId: "channel-1",
-      throttleMs: 1000,
-      warn,
-    });
+    const { stream } = createDraftStreamFixture({ request: requestImpl, throttleMs: 1000, warn });
 
     stream.update("Working...");
     await stream.flush();
@@ -326,11 +268,7 @@ describe("createMattermostDraftStream", () => {
 
 describe("createMattermostDraftStream forceNewMessage", () => {
   it("propagates a provider-accepted boundary post without an identity", async () => {
-    const { client, requestMock } = createMockClient();
-    const stream = createMattermostDraftStream({
-      client,
-      channelId: "channel-1",
-      throttleMs: 0,
+    const { requestMock, stream } = createDraftStreamFixture({
       maxChars: 10,
       chunkText: () => ["aaaaaaaaaa", "bbbbbbbbbb"],
     });
@@ -347,17 +285,13 @@ describe("createMattermostDraftStream forceNewMessage", () => {
   });
 
   it("retains accepted boundary failures before synchronous warning callbacks re-enter", async () => {
-    const { client, requestMock } = createMockClient();
     let reenteredBoundary: Promise<void> | undefined;
     const warn = vi.fn(() => {
       stream.update("must not publish twice");
       reenteredBoundary = stream.forceNewMessage();
       void reenteredBoundary.catch(() => {});
     });
-    const stream = createMattermostDraftStream({
-      client,
-      channelId: "channel-1",
-      throttleMs: 0,
+    const { requestMock, stream } = createDraftStreamFixture({
       maxChars: 10,
       chunkText: () => ["aaaaaaaaaa", "bbbbbbbbbb"],
       warn,
@@ -376,7 +310,7 @@ describe("createMattermostDraftStream forceNewMessage", () => {
   });
 
   it("propagates an accepted background failure that settles during boundary rotation", async () => {
-    const { client, requestMock } = createMockClient();
+    const { requestMock, stream } = createDraftStreamFixture();
     let releaseCreate: (() => void) | undefined;
     const createReady = new Promise<void>((resolve) => {
       releaseCreate = resolve;
@@ -385,11 +319,6 @@ describe("createMattermostDraftStream forceNewMessage", () => {
       await createReady;
       return { message: "already visible" };
     });
-    const stream = createMattermostDraftStream({
-      client,
-      channelId: "channel-1",
-      throttleMs: 0,
-    });
 
     stream.update("Accepted background preview");
     await vi.waitFor(() => expect(requestMock).toHaveBeenCalledOnce());
@@ -402,13 +331,7 @@ describe("createMattermostDraftStream forceNewMessage", () => {
   });
 
   it("creates a new post on the next update after forceNewMessage", async () => {
-    const { client, calls } = createMockClient();
-    const stream = createMattermostDraftStream({
-      client,
-      channelId: "channel-1",
-      rootId: "root-1",
-      throttleMs: 0,
-    });
+    const { calls, stream } = createDraftStreamFixture({ rootId: "root-1" });
 
     stream.update("Running `read`…");
     await stream.flush();
@@ -436,14 +359,10 @@ describe("createMattermostDraftStream forceNewMessage", () => {
   });
 
   it("restores and chunks an already-flushed over-limit block before rotating", async () => {
-    const { client, calls } = createMockClient();
     const firstChunk = "a".repeat(10);
     const secondChunk = "b".repeat(10);
     const chunkText = vi.fn(() => [firstChunk, secondChunk]);
-    const configuredStream = createMattermostDraftStream({
-      client,
-      channelId: "channel-1",
-      throttleMs: 0,
+    const { calls, stream: configuredStream } = createDraftStreamFixture({
       maxChars: 10,
       chunkText,
     });
@@ -507,19 +426,7 @@ describe("createMattermostDraftStream forceNewMessage", () => {
       }
       return {} as T;
     };
-    const requestMock = vi.fn(requestImpl);
-    const client: MattermostClient = {
-      baseUrl: "https://chat.example.com",
-      apiBaseUrl: "https://chat.example.com/api/v4",
-      token: "token",
-      request: requestMock as MattermostClient["request"],
-      fetchImpl: vi.fn() as MattermostClient["fetchImpl"],
-    };
-    const stream = createMattermostDraftStream({
-      client,
-      channelId: "channel-1",
-      throttleMs: 0,
-    });
+    const { stream } = createDraftStreamFixture({ request: requestImpl });
 
     stream.update("tool start");
     stream.update("tool complete");
@@ -573,19 +480,7 @@ describe("createMattermostDraftStream forceNewMessage", () => {
       }
       return {} as T;
     };
-    const requestMock = vi.fn(requestImpl);
-    const client: MattermostClient = {
-      baseUrl: "https://chat.example.com",
-      apiBaseUrl: "https://chat.example.com/api/v4",
-      token: "token",
-      request: requestMock as MattermostClient["request"],
-      fetchImpl: vi.fn() as MattermostClient["fetchImpl"],
-    };
-    const stream = createMattermostDraftStream({
-      client,
-      channelId: "channel-1",
-      throttleMs: 0,
-    });
+    const { stream } = createDraftStreamFixture({ request: requestImpl });
 
     stream.update("Looking into the logs");
     stream.update("Looking into the logs now");
@@ -600,12 +495,7 @@ describe("createMattermostDraftStream forceNewMessage", () => {
   });
 
   it("opens a fresh post for a partial that arrives before a fire-and-forget boundary settles", async () => {
-    const { client, calls } = createMockClient();
-    const stream = createMattermostDraftStream({
-      client,
-      channelId: "channel-1",
-      throttleMs: 0,
-    });
+    const { calls, stream } = createDraftStreamFixture();
 
     stream.update("block A");
     await stream.flush();
@@ -624,12 +514,7 @@ describe("createMattermostDraftStream forceNewMessage", () => {
   });
 
   it("resolves a cumulative terminal reply to the current confirmed generation", async () => {
-    const { client } = createMockClient();
-    const stream = createMattermostDraftStream({
-      client,
-      channelId: "channel-1",
-      throttleMs: 0,
-    });
+    const { stream } = createDraftStreamFixture();
 
     stream.updateAssistantText("First block");
     await stream.flush();
@@ -655,12 +540,7 @@ describe("createMattermostDraftStream forceNewMessage", () => {
   });
 
   it("strips confirmed assistant blocks but not transient progress generations", async () => {
-    const { client } = createMockClient();
-    const stream = createMattermostDraftStream({
-      client,
-      channelId: "channel-1",
-      throttleMs: 0,
-    });
+    const { stream } = createDraftStreamFixture();
 
     stream.updateAssistantText("First block");
     await stream.flush();
@@ -692,12 +572,7 @@ describe("createMattermostDraftStream forceNewMessage", () => {
   });
 
   it("uses provider-finalized content from a boundary edit", async () => {
-    const { client, requestMock } = createMockClient();
-    const stream = createMattermostDraftStream({
-      client,
-      channelId: "channel-1",
-      throttleMs: 0,
-    });
+    const { requestMock, stream } = createDraftStreamFixture();
 
     stream.updateAssistantText("Draft block");
     await stream.flush();
@@ -712,12 +587,7 @@ describe("createMattermostDraftStream forceNewMessage", () => {
   });
 
   it("keeps the canonical final when an assistant boundary fails to publish", async () => {
-    const { client, requestMock } = createMockClient();
-    const stream = createMattermostDraftStream({
-      client,
-      channelId: "channel-1",
-      throttleMs: 0,
-    });
+    const { requestMock, stream } = createDraftStreamFixture();
 
     stream.updateAssistantText("First block");
     await stream.flush();
@@ -734,11 +604,7 @@ describe("createMattermostDraftStream forceNewMessage", () => {
   });
 
   it("retains posts published before a later boundary chunk fails", async () => {
-    const { client, requestMock } = createMockClient();
-    const stream = createMattermostDraftStream({
-      client,
-      channelId: "channel-1",
-      throttleMs: 0,
+    const { requestMock, stream } = createDraftStreamFixture({
       chunkText: () => ["First half", "Second half"],
     });
 
@@ -758,11 +624,7 @@ describe("createMattermostDraftStream forceNewMessage", () => {
   });
 
   it("does not strip a requested prefix rewritten by the provider", async () => {
-    const { client, requestMock } = createMockClient();
-    const stream = createMattermostDraftStream({
-      client,
-      channelId: "channel-1",
-      throttleMs: 0,
+    const { requestMock, stream } = createDraftStreamFixture({
       chunkText: () => ["First half", "Second half"],
     });
 

extensions/mattermost/src/mattermost/monitor-draft-delivery.test.ts

@@ -23,6 +23,23 @@ function createMattermostClientMock(): MattermostClient {
   };
 }
 
+function createMattermostReceipt(messageId: string, kind: "text" | "preview" | "media") {
+  return createMessageReceiptFromOutboundResults({
+    results: [{ channel: "mattermost", messageId }],
+    kind,
+  });
+}
+
+function createConfirmedPreviewDelivery(messageId: string, content: string) {
+  return {
+    outcome: "text" as const,
+    messageIds: [messageId],
+    receipt: createMattermostReceipt(messageId, "preview"),
+    visibleReplySent: true,
+    content,
+  };
+}
+
 function createDraftStreamMock(postId: string | null | undefined = "preview-post-1") {
   return {
     flush: vi.fn(async () => {}),
@@ -37,10 +54,7 @@ function createDeliverFinalMock() {
   return vi.fn(async (payload: { text?: string }) => ({
     outcome: "text" as const,
     messageIds: ["delivered-post-1"],
-    receipt: createMessageReceiptFromOutboundResults({
-      results: [{ channel: "mattermost", messageId: "delivered-post-1" }],
-      kind: "text",
-    }),
+    receipt: createMattermostReceipt("delivered-post-1", "text"),
     visibleReplySent: true,
     content: payload.text ?? "",
   }));
@@ -51,6 +65,23 @@ function resolvePreviewFinalText(text?: string) {
   return editText ? { editText, alreadyDelivered: false } : undefined;
 }
 
+type DraftDeliveryParams = Parameters<typeof deliverMattermostReplyWithDraftPreview>[0];
+
+function deliverDraftPreview(
+  params: Pick<DraftDeliveryParams, "payload" | "draftStream" | "deliverPayload"> &
+    Partial<Omit<DraftDeliveryParams, "payload" | "draftStream" | "deliverPayload">>,
+) {
+  return deliverMattermostReplyWithDraftPreview({
+    info: { kind: "final" },
+    kind: "channel",
+    client: createMattermostClientMock(),
+    resolvePreviewFinalText,
+    previewState: { finalizedViaPreviewPost: false },
+    logVerboseMessage: vi.fn(),
+    ...params,
+  });
+}
+
 function mockCall(mock: { mock: { calls: unknown[][] } }, index: number, label: string): unknown[] {
   const resolvedIndex = index < 0 ? mock.mock.calls.length + index : index;
   const call = mock.mock.calls[resolvedIndex];
@@ -71,16 +102,10 @@ describe("deliverMattermostReplyWithDraftPreview", () => {
     const deliverFinal = createDeliverFinalMock();
     const recordThreadParticipation = vi.fn();
 
-    await deliverMattermostReplyWithDraftPreview({
+    await deliverDraftPreview({
       payload: { text: "  \n > Reasoning:\n> _hidden_" } as never,
-      info: { kind: "final" },
-      kind: "channel",
-      client: createMattermostClientMock(),
       draftStream,
       effectiveReplyToId: "thread-root-1",
-      resolvePreviewFinalText,
-      previewState: { finalizedViaPreviewPost: false },
-      logVerboseMessage: vi.fn(),
       recordThreadParticipation,
       deliverPayload: deliverFinal,
     });
@@ -99,16 +124,10 @@ describe("deliverMattermostReplyWithDraftPreview", () => {
     const deliverFinal = createDeliverFinalMock();
     const recordThreadParticipation = vi.fn();
 
-    const result = await deliverMattermostReplyWithDraftPreview({
+    const result = await deliverDraftPreview({
       payload: { text: "All good" } as never,
-      info: { kind: "final" },
-      kind: "channel",
-      client: createMattermostClientMock(),
       draftStream,
       effectiveReplyToId: "thread-root-1",
-      resolvePreviewFinalText,
-      previewState: { finalizedViaPreviewPost: false },
-      logVerboseMessage: vi.fn(),
       recordThreadParticipation,
       deliverPayload: deliverFinal,
     });
@@ -131,30 +150,16 @@ describe("deliverMattermostReplyWithDraftPreview", () => {
   it("reports a final already published in a sealed preview generation", async () => {
     const draftStream = createDraftStreamMock(null);
     const deliverFinal = createDeliverFinalMock();
-    const confirmedReceipt = createMessageReceiptFromOutboundResults({
-      results: [{ channel: "mattermost", messageId: "sealed-post-1" }],
-      kind: "preview",
-    });
+    const confirmedDelivery = createConfirmedPreviewDelivery("sealed-post-1", "Already visible");
 
-    const result = await deliverMattermostReplyWithDraftPreview({
+    const result = await deliverDraftPreview({
       payload: { text: "Already visible" } as never,
-      info: { kind: "final" },
-      kind: "channel",
-      client: createMattermostClientMock(),
       draftStream,
       effectiveReplyToId: "thread-root-1",
       resolvePreviewFinalText: () => ({
         alreadyDelivered: true,
-        confirmedDelivery: {
-          outcome: "text",
-          messageIds: ["sealed-post-1"],
-          receipt: confirmedReceipt,
-          visibleReplySent: true,
-          content: "Already visible",
-        },
+        confirmedDelivery,
       }),
-      previewState: { finalizedViaPreviewPost: false },
-      logVerboseMessage: vi.fn(),
       deliverPayload: deliverFinal,
     });
 
@@ -171,14 +176,8 @@ describe("deliverMattermostReplyWithDraftPreview", () => {
 
   it("still delivers media when the text is already published", async () => {
     const draftStream = createDraftStreamMock(null);
-    const confirmedReceipt = createMessageReceiptFromOutboundResults({
-      results: [{ channel: "mattermost", messageId: "sealed-post-1" }],
-      kind: "preview",
-    });
-    const mediaReceipt = createMessageReceiptFromOutboundResults({
-      results: [{ channel: "mattermost", messageId: "media-post-1" }],
-      kind: "media",
-    });
+    const confirmedDelivery = createConfirmedPreviewDelivery("sealed-post-1", "Already visible");
+    const mediaReceipt = createMattermostReceipt("media-post-1", "media");
     const deliverFinal = vi.fn(async () => ({
       outcome: "media" as const,
       messageIds: ["media-post-1"],
@@ -187,25 +186,14 @@ describe("deliverMattermostReplyWithDraftPreview", () => {
       content: "",
     }));
 
-    const result = await deliverMattermostReplyWithDraftPreview({
+    const result = await deliverDraftPreview({
       payload: { text: "Already visible", mediaUrl: "https://example.com/image.png" } as never,
-      info: { kind: "final" },
-      kind: "channel",
-      client: createMattermostClientMock(),
       draftStream,
       effectiveReplyToId: "thread-root-1",
       resolvePreviewFinalText: () => ({
         alreadyDelivered: true,
-        confirmedDelivery: {
-          outcome: "text",
-          messageIds: ["sealed-post-1"],
-          receipt: confirmedReceipt,
-          visibleReplySent: true,
-          content: "Already visible",
-        },
+        confirmedDelivery,
       }),
-      previewState: { finalizedViaPreviewPost: false },
-      logVerboseMessage: vi.fn(),
       deliverPayload: deliverFinal,
     });
 
@@ -224,31 +212,17 @@ describe("deliverMattermostReplyWithDraftPreview", () => {
   it("aggregates sealed and current preview posts into one terminal result", async () => {
     const draftStream = createDraftStreamMock("current-preview");
     const deliverFinal = createDeliverFinalMock();
-    const confirmedReceipt = createMessageReceiptFromOutboundResults({
-      results: [{ channel: "mattermost", messageId: "sealed-post-1" }],
-      kind: "preview",
-    });
+    const confirmedDelivery = createConfirmedPreviewDelivery("sealed-post-1", "First block");
 
-    const result = await deliverMattermostReplyWithDraftPreview({
+    const result = await deliverDraftPreview({
       payload: { text: "First block\n\nSecond block" } as never,
-      info: { kind: "final" },
-      kind: "channel",
-      client: createMattermostClientMock(),
       draftStream,
       effectiveReplyToId: "thread-root-1",
       resolvePreviewFinalText: () => ({
         editText: "Second block",
         alreadyDelivered: false,
-        confirmedDelivery: {
-          outcome: "text",
-          messageIds: ["sealed-post-1"],
-          receipt: confirmedReceipt,
-          visibleReplySent: true,
-          content: "First block",
-        },
+        confirmedDelivery,
       }),
-      previewState: { finalizedViaPreviewPost: false },
-      logVerboseMessage: vi.fn(),
       deliverPayload: deliverFinal,
     });
 
@@ -268,32 +242,18 @@ describe("deliverMattermostReplyWithDraftPreview", () => {
   it("sends only the remaining suffix after a partial boundary publish", async () => {
     const draftStream = createDraftStreamMock(null);
     const deliverFinal = createDeliverFinalMock();
-    const confirmedReceipt = createMessageReceiptFromOutboundResults({
-      results: [{ channel: "mattermost", messageId: "partial-post-1" }],
-      kind: "preview",
-    });
+    const confirmedDelivery = createConfirmedPreviewDelivery("partial-post-1", "First half");
 
-    const result = await deliverMattermostReplyWithDraftPreview({
+    const result = await deliverDraftPreview({
       payload: { text: "First half Second half" } as never,
-      info: { kind: "final" },
-      kind: "channel",
-      client: createMattermostClientMock(),
       draftStream,
       effectiveReplyToId: "thread-root-1",
       resolvePreviewFinalText: () => ({
         editText: "Second half",
         deliveryText: "Second half",
         alreadyDelivered: false,
-        confirmedDelivery: {
-          outcome: "text",
-          messageIds: ["partial-post-1"],
-          receipt: confirmedReceipt,
-          visibleReplySent: true,
-          content: "First half",
-        },
+        confirmedDelivery,
       }),
-      previewState: { finalizedViaPreviewPost: false },
-      logVerboseMessage: vi.fn(),
       deliverPayload: deliverFinal,
     });
 
@@ -343,15 +303,9 @@ describe("deliverMattermostReplyWithDraftPreview", () => {
     const draftStream = createDraftStreamMock();
     const deliverFinal = createDeliverFinalMock();
 
-    await deliverMattermostReplyWithDraftPreview({
+    await deliverDraftPreview({
       payload: { text: "All good", replyToId: "reply-1" } as never,
-      info: { kind: "final" },
-      kind: "channel",
-      client: createMattermostClientMock(),
       draftStream,
-      resolvePreviewFinalText,
-      previewState: { finalizedViaPreviewPost: false },
-      logVerboseMessage: vi.fn(),
       deliverPayload: deliverFinal,
     });
 
@@ -369,15 +323,9 @@ describe("deliverMattermostReplyWithDraftPreview", () => {
 
     let caught: unknown;
     try {
-      await deliverMattermostReplyWithDraftPreview({
+      await deliverDraftPreview({
         payload: { text: "Already visible", replyToId: "reply-1" } as never,
-        info: { kind: "final" },
-        kind: "channel",
-        client: createMattermostClientMock(),
         draftStream,
-        resolvePreviewFinalText,
-        previewState: { finalizedViaPreviewPost: false },
-        logVerboseMessage: vi.fn(),
         deliverPayload: deliverFinal,
       });
     } catch (error: unknown) {
@@ -401,20 +349,14 @@ describe("deliverMattermostReplyWithDraftPreview", () => {
     const draftStream = createDraftStreamMock();
     const deliverFinal = createDeliverFinalMock();
 
-    await deliverMattermostReplyWithDraftPreview({
+    await deliverDraftPreview({
       payload: {
         text: "Photo",
         replyToId: "reply-1",
         mediaUrl: "https://example.com/a.png",
       } as never,
-      info: { kind: "final" },
-      kind: "channel",
-      client: createMattermostClientMock(),
       draftStream,
       effectiveReplyToId: "thread-root-1",
-      resolvePreviewFinalText,
-      previewState: { finalizedViaPreviewPost: false },
-      logVerboseMessage: vi.fn(),
       deliverPayload: deliverFinal,
     });
 
@@ -428,21 +370,15 @@ describe("deliverMattermostReplyWithDraftPreview", () => {
     const draftStream = createDraftStreamMock();
     const deliverFinal = createDeliverFinalMock();
 
-    await deliverMattermostReplyWithDraftPreview({
+    await deliverDraftPreview({
       payload: {
         mediaUrl: "https://example.com/tts.mp3",
         audioAsVoice: true,
         spokenText: "Spoken answer",
         ttsSupplement: { spokenText: "Spoken answer" },
       } as never,
-      info: { kind: "final" },
-      kind: "channel",
-      client: createMattermostClientMock(),
       draftStream,
       effectiveReplyToId: "thread-root-1",
-      resolvePreviewFinalText,
-      previewState: { finalizedViaPreviewPost: false },
-      logVerboseMessage: vi.fn(),
       deliverPayload: deliverFinal,
     });
 
@@ -474,30 +410,21 @@ describe("deliverMattermostReplyWithDraftPreview", () => {
       return {
         outcome: "text" as const,
         messageIds: ["supplement-post-1"],
-        receipt: createMessageReceiptFromOutboundResults({
-          results: [{ channel: "mattermost", messageId: "supplement-post-1" }],
-          kind: "media",
-        }),
+        receipt: createMattermostReceipt("supplement-post-1", "media"),
         visibleReplySent: true,
         content: payload.text ?? "",
       };
     });
 
-    const result = await deliverMattermostReplyWithDraftPreview({
+    const result = await deliverDraftPreview({
       payload: {
         mediaUrl: "https://example.com/tts.mp3",
         audioAsVoice: true,
         spokenText: "Spoken answer",
         ttsSupplement: { spokenText: "Spoken answer" },
       } as never,
-      info: { kind: "final" },
-      kind: "channel",
-      client: createMattermostClientMock(),
       draftStream,
       effectiveReplyToId: "thread-root-1",
-      resolvePreviewFinalText,
-      previewState: { finalizedViaPreviewPost: false },
-      logVerboseMessage: vi.fn(),
       deliverPayload: deliverFinal,
     });
 
@@ -512,10 +439,7 @@ describe("deliverMattermostReplyWithDraftPreview", () => {
 
   it("preserves the finalized preview receipt when its supplement fails after sending", async () => {
     const draftStream = createDraftStreamMock();
-    const mediaReceipt = createMessageReceiptFromOutboundResults({
-      results: [{ channel: "mattermost", messageId: "media-post-1" }],
-      kind: "media",
-    });
+    const mediaReceipt = createMattermostReceipt("media-post-1", "media");
     const deliverFinal = vi.fn(async () => {
       throw createChannelPartialDeliveryError(new Error("supplement bookkeeping failed"), {
         messageIds: ["media-post-1"],
@@ -527,21 +451,15 @@ describe("deliverMattermostReplyWithDraftPreview", () => {
 
     let caught: unknown;
     try {
-      await deliverMattermostReplyWithDraftPreview({
+      await deliverDraftPreview({
         payload: {
           mediaUrl: "https://example.com/tts.mp3",
           audioAsVoice: true,
           spokenText: "Spoken answer",
           ttsSupplement: { spokenText: "Spoken answer" },
         } as never,
-        info: { kind: "final" },
-        kind: "channel",
-        client: createMattermostClientMock(),
         draftStream,
         effectiveReplyToId: "thread-root-1",
-        resolvePreviewFinalText,
-        previewState: { finalizedViaPreviewPost: false },
-        logVerboseMessage: vi.fn(),
         deliverPayload: deliverFinal,
       });
     } catch (error: unknown) {
@@ -564,16 +482,13 @@ describe("deliverMattermostReplyWithDraftPreview", () => {
     const deliverFinal = createDeliverFinalMock();
     updateMattermostPostSpy.mockRejectedValueOnce(new Error("edit failed"));
 
-    await deliverMattermostReplyWithDraftPreview({
+    await deliverDraftPreview({
       payload: {
         mediaUrl: "https://example.com/tts.mp3",
         audioAsVoice: true,
         spokenText: "Spoken answer",
         ttsSupplement: { spokenText: "Spoken answer" },
       } as never,
-      info: { kind: "final" },
-      kind: "channel",
-      client: createMattermostClientMock(),
       draftStream,
       effectiveReplyToId: "thread-root-1",
       resolvePreviewFinalText: (text) => ({
@@ -581,8 +496,6 @@ describe("deliverMattermostReplyWithDraftPreview", () => {
         deliveryText: "",
         alreadyDelivered: false,
       }),
-      previewState: { finalizedViaPreviewPost: false },
-      logVerboseMessage: vi.fn(),
       deliverPayload: deliverFinal,
     });
 
@@ -603,7 +516,7 @@ describe("deliverMattermostReplyWithDraftPreview", () => {
     const deliverFinal = createDeliverFinalMock();
     updateMattermostPostSpy.mockRejectedValueOnce(new Error("edit failed"));
 
-    await deliverMattermostReplyWithDraftPreview({
+    await deliverDraftPreview({
       payload: {
         mediaUrl: "https://example.com/tts.mp3",
         audioAsVoice: true,
@@ -613,9 +526,6 @@ describe("deliverMattermostReplyWithDraftPreview", () => {
           visibleTextAlreadyDelivered: true,
         },
       } as never,
-      info: { kind: "final" },
-      kind: "channel",
-      client: createMattermostClientMock(),
       draftStream,
       effectiveReplyToId: "thread-root-1",
       resolvePreviewFinalText: (text) => ({
@@ -623,8 +533,6 @@ describe("deliverMattermostReplyWithDraftPreview", () => {
         deliveryText: text?.trim(),
         alreadyDelivered: false,
       }),
-      previewState: { finalizedViaPreviewPost: false },
-      logVerboseMessage: vi.fn(),
       deliverPayload: deliverFinal,
     });
 
@@ -643,34 +551,20 @@ describe("deliverMattermostReplyWithDraftPreview", () => {
     const draftStream = createDraftStreamMock();
     const deliverFinal = createDeliverFinalMock();
 
-    await deliverMattermostReplyWithDraftPreview({
+    await deliverDraftPreview({
       payload: {
         mediaUrl: "https://example.com/tts.mp3",
         audioAsVoice: true,
         spokenText: "Spoken answer",
         ttsSupplement: { spokenText: "Spoken answer" },
       } as never,
-      info: { kind: "final" },
-      kind: "channel",
-      client: createMattermostClientMock(),
       draftStream,
       effectiveReplyToId: "thread-root-1",
       resolvePreviewFinalText: () => ({
         deliveryText: "",
-        confirmedDelivery: {
-          outcome: "text",
-          messageIds: ["preview-post-1"],
-          receipt: createMessageReceiptFromOutboundResults({
-            results: [{ channel: "mattermost", messageId: "preview-post-1" }],
-            kind: "preview",
-          }),
-          visibleReplySent: true,
-          content: "Spoken answer",
-        },
+        confirmedDelivery: createConfirmedPreviewDelivery("preview-post-1", "Spoken answer"),
         alreadyDelivered: true,
       }),
-      previewState: { finalizedViaPreviewPost: false },
-      logVerboseMessage: vi.fn(),
       deliverPayload: deliverFinal,
     });
 
@@ -686,16 +580,10 @@ describe("deliverMattermostReplyWithDraftPreview", () => {
     const draftStream = createDraftStreamMock();
     const deliverFinal = createDeliverFinalMock();
 
-    await deliverMattermostReplyWithDraftPreview({
+    await deliverDraftPreview({
       payload: { text: "Error", isError: true } as never,
-      info: { kind: "final" },
-      kind: "channel",
-      client: createMattermostClientMock(),
       draftStream,
       effectiveReplyToId: "thread-root-1",
-      resolvePreviewFinalText,
-      previewState: { finalizedViaPreviewPost: false },
-      logVerboseMessage: vi.fn(),
       deliverPayload: deliverFinal,
     });
 
@@ -709,16 +597,11 @@ describe("deliverMattermostReplyWithDraftPreview", () => {
     const deliverFinal = createDeliverFinalMock();
     const client = createMattermostClientMock();
 
-    await deliverMattermostReplyWithDraftPreview({
+    await deliverDraftPreview({
       payload: { text: "Final answer", replyToId: "child-post-789" } as never,
-      info: { kind: "final" },
-      kind: "channel",
       client,
       draftStream,
       effectiveReplyToId: "thread-root-456",
-      resolvePreviewFinalText,
-      previewState: { finalizedViaPreviewPost: false },
-      logVerboseMessage: vi.fn(),
       deliverPayload: deliverFinal,
     });
 
@@ -747,15 +630,9 @@ describe("deliverMattermostReplyWithDraftPreview", () => {
     });
 
     await expect(
-      deliverMattermostReplyWithDraftPreview({
+      deliverDraftPreview({
         payload: { text: "Broken", replyToId: "reply-1" } as never,
-        info: { kind: "final" },
-        kind: "channel",
-        client: createMattermostClientMock(),
         draftStream,
-        resolvePreviewFinalText,
-        previewState: { finalizedViaPreviewPost: false },
-        logVerboseMessage: vi.fn(),
         deliverPayload: deliverFinal,
       }),
     ).rejects.toThrow("send failed");