diff --git a/docs/cli/message.md b/docs/cli/message.md
index 77dc8025ee46..c7799991afc6 100644
--- a/docs/cli/message.md
+++ b/docs/cli/message.md
@@ -98,8 +98,9 @@ true}`. `--pin` is shorthand for pinned delivery when the channel supports
   it.
 - `--reply-to <id>`, `--thread-id <id>` (Telegram forum topic; Slack thread
   timestamp, same field as `--reply-to`).
-- `--force-document` (Telegram, WhatsApp): send images/GIFs/videos as
-  documents to avoid channel compression.
+- `--force-document`: preserve original image bytes on Slack, or send
+  images/GIFs/videos as documents on Telegram and WhatsApp, to avoid channel
+  compression.
 - `--silent` (Telegram, Discord): send without a notification.
 - `--gif-playback` (WhatsApp only): treat video media as GIF playback.
 
diff --git a/docs/nodes/images.md b/docs/nodes/images.md
index fe77964adf6c..d32a4fcff9f7 100644
--- a/docs/nodes/images.md
+++ b/docs/nodes/images.md
@@ -23,7 +23,7 @@ portable formats, byte limits, and lazy transcoding, see
 
 - `--media <path-or-url>` — attach media (image/audio/video/document); accepts local paths or URLs. Optional; caption can be empty for media-only sends.
 - `--gif-playback` — treat video media as GIF playback (WhatsApp only).
-- `--force-document` — send media as a document to avoid channel compression (Telegram, WhatsApp); applies to images, GIFs, and videos.
+- `--force-document` — preserve original image bytes on Slack, or send images, GIFs, and videos as documents on Telegram and WhatsApp, to avoid channel compression.
 - `--reply-to <id>`, `--thread-id <id>`, `--pin`, `--silent` — delivery/threading options shared with text-only sends.
 - `--dry-run` — print the resolved payload and skip sending.
 - `--json` — print the result as JSON: `{ action, channel, dryRun, handledBy, messageId?, payload }` (`payload` carries the channel-specific send result, including any media reference).
diff --git a/extensions/slack/src/action-runtime.test.ts b/extensions/slack/src/action-runtime.test.ts
index 8226dd1a3764..ddc1f560f05c 100644
--- a/extensions/slack/src/action-runtime.test.ts
+++ b/extensions/slack/src/action-runtime.test.ts
@@ -973,6 +973,37 @@ describe("handleSlackAction", () => {
     });
   });
 
+  it.each([
+    {
+      name: "sendMessage",
+      params: {
+        action: "sendMessage",
+        to: "channel:C123",
+        content: "original image",
+        mediaUrl: "/tmp/original.png",
+        forceDocument: true,
+      },
+      expectedTarget: "channel:C123",
+    },
+    {
+      name: "workspace-qualified uploadFile",
+      params: {
+        action: "uploadFile",
+        to: "team:T123:channel:C123",
+        filePath: "/tmp/original.png",
+        initialComment: "original image",
+        forceDocument: true,
+      },
+      expectedTarget: "team:T123:channel:C123",
+    },
+  ] as const)("forwards forced-media intent for $name", async ({ params, expectedTarget }) => {
+    await handleSlackAction(params, slackConfig());
+
+    expectSlackSendCall(0, expectedTarget, "original image", {
+      forceDocument: true,
+    });
+  });
+
   it.each([
     {
       action: "sendMessage",
diff --git a/extensions/slack/src/action-runtime.ts b/extensions/slack/src/action-runtime.ts
index e6cb787549df..d8bd5f7372ae 100644
--- a/extensions/slack/src/action-runtime.ts
+++ b/extensions/slack/src/action-runtime.ts
@@ -673,6 +673,7 @@ export async function handleSlackAction(
         const replyBroadcast = readBooleanParam(params, "replyBroadcast");
         const textIsSlackMrkdwn = readBooleanParam(params, "textIsSlackMrkdwn");
         const textIsSlackPlainText = readBooleanParam(params, "textIsSlackPlainText");
+        const forceDocument = readBooleanParam(params, "forceDocument") === true;
         const preparedMessages = context?.preparedMessages;
         const authoredTextPlacement = readStringParam(params, "authoredTextPlacement") as
           | "none"
@@ -712,6 +713,7 @@ export async function handleSlackAction(
           mediaLocalRoots: context?.mediaLocalRoots,
           mediaReadFile: context?.mediaReadFile,
           threadTs: threadTs ?? undefined,
+          ...(forceDocument ? { forceDocument: true } : {}),
         };
         const sendOpts = {
           ...baseSendOpts,
@@ -807,6 +809,7 @@ export async function handleSlackAction(
         });
         const filename = readStringParam(params, "filename");
         const title = readStringParam(params, "title");
+        const forceDocument = readBooleanParam(params, "forceDocument") === true;
         const replyBroadcast = readBooleanParam(params, "replyBroadcast");
         if (replyBroadcast) {
           throw new Error(
@@ -831,6 +834,7 @@ export async function handleSlackAction(
             mediaLocalRoots: context?.mediaLocalRoots,
             mediaReadFile: context?.mediaReadFile,
             threadTs: threadTs ?? undefined,
+            ...(forceDocument ? { forceDocument: true } : {}),
             ...(filename ? { uploadFileName: filename } : {}),
             ...(title ? { uploadTitle: title } : {}),
           },
diff --git a/extensions/slack/src/actions.ts b/extensions/slack/src/actions.ts
index 4964e0e3fdd6..04c7fbb5dfdb 100644
--- a/extensions/slack/src/actions.ts
+++ b/extensions/slack/src/actions.ts
@@ -334,6 +334,7 @@ export async function sendSlackMessage(
   opts: Omit<SlackActionClientOpts, "cfg"> & {
     cfg: OpenClawConfig;
     mediaUrl?: string;
+    forceDocument?: boolean;
     mediaAccess?: {
       localRoots?: readonly string[];
       readFile?: (filePath: string) => Promise<Buffer>;
@@ -356,6 +357,7 @@ export async function sendSlackMessage(
     cfg: opts.cfg,
     token: opts.token,
     mediaUrl: opts.mediaUrl,
+    ...(opts.forceDocument ? { forceDocument: true } : {}),
     mediaAccess: opts.mediaAccess,
     mediaLocalRoots: opts.mediaLocalRoots,
     mediaReadFile: opts.mediaReadFile,
diff --git a/extensions/slack/src/client-delivery.ts b/extensions/slack/src/client-delivery.ts
index 79d9713dc3f9..f2555d541cd8 100644
--- a/extensions/slack/src/client-delivery.ts
+++ b/extensions/slack/src/client-delivery.ts
@@ -250,6 +250,7 @@ export async function uploadSlackFile(params: {
   uploadTitle?: string;
   mediaLocalRoots?: readonly string[];
   mediaReadFile?: (filePath: string) => Promise<Buffer>;
+  optimizeImages?: boolean;
   caption?: string;
   threadTs?: string;
   maxBytes?: number;
@@ -261,6 +262,7 @@ export async function uploadSlackFile(params: {
     mediaAccess: params.mediaAccess,
     mediaLocalRoots: params.mediaLocalRoots,
     mediaReadFile: params.mediaReadFile,
+    ...(params.optimizeImages !== undefined ? { optimizeImages: params.optimizeImages } : {}),
   });
   // Slack classifies previews by filename even when the upload body has a MIME type.
   const uploadFileName =
diff --git a/extensions/slack/src/message-action-dispatch.test.ts b/extensions/slack/src/message-action-dispatch.test.ts
index 74e0f650c14d..9f2182d14e84 100644
--- a/extensions/slack/src/message-action-dispatch.test.ts
+++ b/extensions/slack/src/message-action-dispatch.test.ts
@@ -751,6 +751,49 @@ describe("handleSlackMessageAction", () => {
     expectNoForwardedToolContext(invoke);
   });
 
+  it.each(["forceDocument", "asDocument"] as const)(
+    "normalizes %s for Slack send and upload-file",
+    async (propertyName) => {
+      const sendInvoke = createInvokeSpy();
+      await handleSlackMessageAction({
+        providerId: "slack",
+        ctx: {
+          action: "send",
+          cfg: slackConfig(),
+          params: {
+            to: "channel:C1",
+            media: "/tmp/original.png",
+            [propertyName]: true,
+          },
+        } as never,
+        invoke: sendInvoke as never,
+      });
+      expect(firstAction(sendInvoke)).toMatchObject({
+        action: "sendMessage",
+        forceDocument: true,
+      });
+
+      const uploadInvoke = createInvokeSpy();
+      await handleSlackMessageAction({
+        providerId: "slack",
+        ctx: {
+          action: "upload-file",
+          cfg: slackConfig(),
+          params: {
+            to: "channel:C1",
+            filePath: "/tmp/original.png",
+            [propertyName]: true,
+          },
+        } as never,
+        invoke: uploadInvoke as never,
+      });
+      expect(firstAction(uploadInvoke)).toMatchObject({
+        action: "uploadFile",
+        forceDocument: true,
+      });
+    },
+  );
+
   it("rejects replyBroadcast for upload-file", async () => {
     await expect(
       handleSlackMessageAction({
diff --git a/extensions/slack/src/message-action-dispatch.ts b/extensions/slack/src/message-action-dispatch.ts
index b2c65c5666a2..6e04d82d132c 100644
--- a/extensions/slack/src/message-action-dispatch.ts
+++ b/extensions/slack/src/message-action-dispatch.ts
@@ -31,6 +31,12 @@ type SlackActionInvoke = (
   toolContext?: ChannelMessageActionContext["toolContext"],
 ) => Promise<AgentToolResult<unknown>>;
 
+function readSlackForceDocument(params: Record<string, unknown>): boolean {
+  return (
+    readBooleanParam(params, "forceDocument") ?? readBooleanParam(params, "asDocument") ?? false
+  );
+}
+
 function resolveSlackPresentationText(
   content: string | undefined,
   presentation: ReturnType<typeof normalizeMessagePresentation>,
@@ -131,6 +137,7 @@ export async function handleSlackMessageAction(params: {
         to,
         content: content ?? "",
         mediaUrl: mediaUrl ?? undefined,
+        ...(readSlackForceDocument(actionParams) ? { forceDocument: true } : {}),
         accountId,
         threadTs: threadId ?? replyTo ?? undefined,
         ...(topLevel ? { topLevel: true } : {}),
@@ -355,6 +362,7 @@ export async function handleSlackMessageAction(params: {
         filename: readStringParam(actionParams, "filename"),
         title: readStringParam(actionParams, "title"),
         threadTs: threadId ?? undefined,
+        ...(readSlackForceDocument(actionParams) ? { forceDocument: true } : {}),
         ...(topLevel ? { topLevel: true } : {}),
         accountId,
       },
diff --git a/extensions/slack/src/message-tool-api.ts b/extensions/slack/src/message-tool-api.ts
index 7a4092201a9c..bb296fc30ad2 100644
--- a/extensions/slack/src/message-tool-api.ts
+++ b/extensions/slack/src/message-tool-api.ts
@@ -32,6 +32,17 @@ function createSlackReactionEmojiSchema(): Record<string, TSchema> {
   };
 }
 
+function createSlackForcedMediaSchema(): Record<string, TSchema> {
+  const description =
+    "Preserve original image bytes without image optimization. Slack still uploads a regular file; this does not convert it into a Slack document.";
+  return {
+    forceDocument: Type.Optional(Type.Boolean({ description })),
+    asDocument: Type.Optional(
+      Type.Boolean({ description: `Alias for forceDocument. ${description}` }),
+    ),
+  };
+}
+
 function createSlackMessageIdActionSchema(): Record<string, TSchema> {
   const description =
     'Slack message timestamp/message id (for example "1777423717.666499"). Used by react, reactions, edit, delete, pin, and unpin actions. React defaults to the current inbound message when available. Not used by download-file, which requires fileId from event.files[].id.';
@@ -43,6 +54,7 @@ function createSlackMessageIdActionSchema(): Record<string, TSchema> {
 
 function createSlackSendActionSchema(): Record<string, TSchema> {
   return {
+    ...createSlackForcedMediaSchema(),
     topLevel: Type.Optional(
       Type.Boolean({
         description:
@@ -60,6 +72,7 @@ function createSlackSendActionSchema(): Record<string, TSchema> {
 
 function createSlackTopLevelActionSchema(): Record<string, TSchema> {
   return {
+    ...createSlackForcedMediaSchema(),
     topLevel: Type.Optional(
       Type.Boolean({
         description:
diff --git a/extensions/slack/src/message-tools.test.ts b/extensions/slack/src/message-tools.test.ts
index 1e64d7f4afdc..eccffca34940 100644
--- a/extensions/slack/src/message-tools.test.ts
+++ b/extensions/slack/src/message-tools.test.ts
@@ -220,6 +220,18 @@ describe("Slack message tools", () => {
     ]);
     expect(discovery.capabilities).toEqual(["presentation"]);
     expect(Array.isArray(discovery.schema)).toBe(true);
+    const schemas = Array.isArray(discovery.schema) ? discovery.schema : [];
+    for (const propertyName of ["forceDocument", "asDocument"]) {
+      const entries = schemas.filter((entry) => propertyName in entry.properties);
+      expect(entries.map((entry) => entry.actions)).toEqual([["send"], ["upload-file"]]);
+      for (const entry of entries) {
+        const description = (entry.properties[propertyName] as { description?: string })
+          .description;
+        expect(description).toMatch(/preserve original image bytes/i);
+        expect(description).toMatch(/without image optimization/i);
+        expect(description).toMatch(/not.*Slack document/i);
+      }
+    }
   });
 
   it("honors account-scoped action gates", () => {
diff --git a/extensions/slack/src/outbound-adapter.test.ts b/extensions/slack/src/outbound-adapter.test.ts
index 8e04732943c6..6c1776c2d04c 100644
--- a/extensions/slack/src/outbound-adapter.test.ts
+++ b/extensions/slack/src/outbound-adapter.test.ts
@@ -92,6 +92,28 @@ describe("slackOutbound", () => {
     expect(result).toEqual({ channel: "slack", messageId: "m-final" });
   });
 
+  it("forwards forced-media intent through the core outbound adapter", async () => {
+    sendMessageSlackMock.mockResolvedValueOnce({ messageId: "m-media" });
+
+    await slackOutbound.sendMedia!({
+      cfg,
+      to: "C123",
+      text: "original image",
+      mediaUrl: "https://example.com/original.png",
+      forceDocument: true,
+      accountId: "default",
+    });
+
+    expect(sendMessageSlackMock).toHaveBeenCalledWith(
+      "C123",
+      "original image",
+      expect.objectContaining({
+        mediaUrl: "https://example.com/original.png",
+        forceDocument: true,
+      }),
+    );
+  });
+
   it("renders channelData Slack blocks on payload sends", async () => {
     sendMessageSlackMock.mockResolvedValueOnce({ messageId: "m-blocks" });
 
diff --git a/extensions/slack/src/outbound-adapter.ts b/extensions/slack/src/outbound-adapter.ts
index fee9d2b9ee04..bc4530c69a77 100644
--- a/extensions/slack/src/outbound-adapter.ts
+++ b/extensions/slack/src/outbound-adapter.ts
@@ -182,6 +182,7 @@ async function sendSlackOutboundMessage(params: {
   to: string;
   text: string;
   mediaUrl?: string;
+  forceDocument?: boolean;
   mediaAccess?: {
     localRoots?: readonly string[];
     readFile?: (filePath: string) => Promise<Buffer>;
@@ -227,6 +228,7 @@ async function sendSlackOutboundMessage(params: {
           mediaAccess: params.mediaAccess,
           mediaLocalRoots: params.mediaLocalRoots,
           mediaReadFile: params.mediaReadFile,
+          ...(params.forceDocument ? { forceDocument: true } : {}),
         }
       : {}),
     ...(params.blocks ? { blocks: params.blocks } : {}),
diff --git a/extensions/slack/src/send.ts b/extensions/slack/src/send.ts
index b8bf565f28e3..a1191a31faaa 100644
--- a/extensions/slack/src/send.ts
+++ b/extensions/slack/src/send.ts
@@ -113,6 +113,7 @@ type SlackSendOpts = {
   token?: string;
   accountId?: string;
   mediaUrl?: string;
+  forceDocument?: boolean;
   mediaAccess?: {
     localRoots?: readonly string[];
     readFile?: (filePath: string) => Promise<Buffer>;
@@ -1418,6 +1419,7 @@ async function sendMessageSlackQueuedInner(params: {
       caption: firstChunk,
       threadTs: opts.threadTs,
       maxBytes: mediaMaxBytes,
+      ...(opts.forceDocument ? { optimizeImages: false } : {}),
       onPlatformSendDispatch: dispatchOnce,
       ...(delivery.upload ? { auditContext: delivery.upload.auditContext } : {}),
     });
diff --git a/extensions/slack/src/send.upload.test.ts b/extensions/slack/src/send.upload.test.ts
index 81790c15cbab..d3aa4436fbe8 100644
--- a/extensions/slack/src/send.upload.test.ts
+++ b/extensions/slack/src/send.upload.test.ts
@@ -276,6 +276,36 @@ describe("sendMessageSlack file upload with user IDs", () => {
     vi.restoreAllMocks();
   });
 
+  it("disables image optimization for forced-media uploads", async () => {
+    await sendUpload(client, {
+      mediaUrl: "/tmp/original.png",
+      forceDocument: true,
+    });
+
+    expect(loadOutboundMediaFromUrlMock).toHaveBeenCalledWith(
+      "/tmp/original.png",
+      expect.objectContaining({ optimizeImages: false }),
+    );
+  });
+
+  it.each([
+    ["absent", undefined],
+    ["false", false],
+  ] as const)(
+    "keeps default image optimization when forced-media intent is %s",
+    async (_name, forceDocument) => {
+      await sendUpload(client, {
+        mediaUrl: "/tmp/optimized.png",
+        ...(forceDocument !== undefined ? { forceDocument } : {}),
+      });
+
+      const loadOptions = loadOutboundMediaFromUrlMock.mock.calls[0]?.[1] as
+        | { optimizeImages?: boolean }
+        | undefined;
+      expect(loadOptions?.optimizeImages).toBeUndefined();
+    },
+  );
+
   it.each([
     {
       name: "resolves bare user ID to DM channel before completing upload",
diff --git a/src/cli/program/message/register.send.ts b/src/cli/program/message/register.send.ts
index cd7683f014ed..3835631fa72b 100644
--- a/src/cli/program/message/register.send.ts
+++ b/src/cli/program/message/register.send.ts
@@ -31,7 +31,7 @@ export function registerMessageSendCommand(message: Command, helpers: MessageCli
         .option("--gif-playback", "Treat video media as GIF playback (WhatsApp only).", false)
         .option(
           "--force-document",
-          "Send media as document to avoid channel compression (Telegram, WhatsApp). Applies to images, GIFs, and videos.",
+          "Preserve original image bytes on Slack, or send images, GIFs, and videos as documents on Telegram and WhatsApp, to avoid channel compression.",
           false,
         )
         .option(