diff --git a/CHANGELOG.md b/CHANGELOG.md
index 25a1392ac..5054c3542 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -21,6 +21,7 @@
 - Onboarding/Gateway: persist non-interactive gateway token auth in config; add WS wizard + gateway tool-calling regression coverage.
 - Gateway/Control UI: make `chat.send` non-blocking, wire Stop to `chat.abort`, and treat `/stop` as an out-of-band abort. (#653)
 - Gateway/Control UI: allow `chat.abort` without `runId` (abort active runs), suppress post-abort chat streaming, and prune stuck chat runs. (#653)
+- Gateway/Control UI: sniff image attachments for chat.send, drop non-images, and log mismatches. (#670) — thanks @cristip73.
 - CLI: `clawdbot sessions` now includes `elev:*` + `usage:*` flags in the table output.
 - CLI/Pairing: accept positional provider for `pairing list|approve` (npm-run compatible); update docs/bot hints.
 - Branding: normalize user-facing “ClawdBot”/“CLAWDBOT” → “Clawdbot” (CLI, status, docs).
diff --git a/src/agents/pi-embedded-runner.ts b/src/agents/pi-embedded-runner.ts
index 48cd2cf06..55c9219b2 100644
--- a/src/agents/pi-embedded-runner.ts
+++ b/src/agents/pi-embedded-runner.ts
@@ -8,7 +8,12 @@ import type {
   AgentTool,
   ThinkingLevel,
 } from "@mariozechner/pi-agent-core";
-import type { Api, AssistantMessage, Model } from "@mariozechner/pi-ai";
+import type {
+  Api,
+  AssistantMessage,
+  ImageContent,
+  Model,
+} from "@mariozechner/pi-ai";
 import {
   createAgentSession,
   discoverAuthStorage,
@@ -1009,6 +1014,8 @@ export async function runEmbeddedPiAgent(params: {
   config?: ClawdbotConfig;
   skillsSnapshot?: SkillSnapshot;
   prompt: string;
+  /** Optional image attachments for multimodal messages. */
+  images?: ImageContent[];
   provider?: string;
   model?: string;
   authProfileId?: string;
@@ -1434,7 +1441,9 @@ export async function runEmbeddedPiAgent(params: {
               `embedded run prompt start: runId=${params.runId} sessionId=${params.sessionId}`,
             );
             try {
-              await session.prompt(params.prompt);
+              await session.prompt(params.prompt, {
+                images: params.images,
+              });
             } catch (err) {
               promptError = err;
             } finally {
diff --git a/src/commands/agent.ts b/src/commands/agent.ts
index 485324828..cf7eb6ab7 100644
--- a/src/commands/agent.ts
+++ b/src/commands/agent.ts
@@ -66,8 +66,17 @@ import {
 } from "../utils/message-provider.js";
 import { normalizeE164 } from "../utils.js";
 
+/** Image content block for Claude API multimodal messages. */
+type ImageContent = {
+  type: "image";
+  data: string;
+  mimeType: string;
+};
+
 type AgentCommandOpts = {
   message: string;
+  /** Optional image attachments for multimodal messages. */
+  images?: ImageContent[];
   to?: string;
   sessionId?: string;
   sessionKey?: string;
@@ -450,6 +459,7 @@ export async function agentCommand(
           config: cfg,
           skillsSnapshot,
           prompt: body,
+          images: opts.images,
           provider: providerOverride,
           model: modelOverride,
           authProfileId: sessionEntry?.authProfileOverride,
diff --git a/src/gateway/chat-attachments.test.ts b/src/gateway/chat-attachments.test.ts
index e07116636..2cc47fb48 100644
--- a/src/gateway/chat-attachments.test.ts
+++ b/src/gateway/chat-attachments.test.ts
@@ -3,6 +3,7 @@ import { describe, expect, it } from "vitest";
 import {
   buildMessageWithAttachments,
   type ChatAttachment,
+  parseMessageWithAttachments,
 } from "./chat-attachments.js";
 
 const PNG_1x1 =
@@ -56,3 +57,65 @@ describe("buildMessageWithAttachments", () => {
     ).toThrow(/exceeds size limit/i);
   });
 });
+
+describe("parseMessageWithAttachments", () => {
+  it("sniffs mime when missing", async () => {
+    const logs: string[] = [];
+    const parsed = await parseMessageWithAttachments(
+      "see this",
+      [
+        {
+          type: "image",
+          fileName: "dot.png",
+          content: PNG_1x1,
+        },
+      ],
+      { log: { warn: (message) => logs.push(message) } },
+    );
+    expect(parsed.message).toBe("see this");
+    expect(parsed.images).toHaveLength(1);
+    expect(parsed.images[0]?.mimeType).toBe("image/png");
+    expect(parsed.images[0]?.data).toBe(PNG_1x1);
+    expect(logs).toHaveLength(0);
+  });
+
+  it("drops non-image payloads and logs", async () => {
+    const logs: string[] = [];
+    const pdf = Buffer.from("%PDF-1.4\n").toString("base64");
+    const parsed = await parseMessageWithAttachments(
+      "x",
+      [
+        {
+          type: "file",
+          mimeType: "image/png",
+          fileName: "not-image.pdf",
+          content: pdf,
+        },
+      ],
+      { log: { warn: (message) => logs.push(message) } },
+    );
+    expect(parsed.images).toHaveLength(0);
+    expect(logs).toHaveLength(1);
+    expect(logs[0]).toMatch(/non-image/i);
+  });
+
+  it("prefers sniffed mime type and logs mismatch", async () => {
+    const logs: string[] = [];
+    const parsed = await parseMessageWithAttachments(
+      "x",
+      [
+        {
+          type: "image",
+          mimeType: "image/jpeg",
+          fileName: "dot.png",
+          content: PNG_1x1,
+        },
+      ],
+      { log: { warn: (message) => logs.push(message) } },
+    );
+    expect(parsed.images).toHaveLength(1);
+    expect(parsed.images[0]?.mimeType).toBe("image/png");
+    expect(logs).toHaveLength(1);
+    expect(logs[0]).toMatch(/mime mismatch/i);
+  });
+});
diff --git a/src/gateway/chat-attachments.ts b/src/gateway/chat-attachments.ts
index 523da182d..e24fc4e2c 100644
--- a/src/gateway/chat-attachments.ts
+++ b/src/gateway/chat-attachments.ts
@@ -1,3 +1,5 @@
+import { detectMime } from "../media/mime.js";
+
 export type ChatAttachment = {
   type?: string;
   mimeType?: string;
@@ -5,6 +7,133 @@ export type ChatAttachment = {
   content?: unknown;
 };
 
+export type ChatImageContent = {
+  type: "image";
+  data: string;
+  mimeType: string;
+};
+
+export type ParsedMessageWithImages = {
+  message: string;
+  images: ChatImageContent[];
+};
+
+type AttachmentLog = {
+  warn: (message: string) => void;
+};
+
+function normalizeMime(mime?: string): string | undefined {
+  if (!mime) return undefined;
+  const cleaned = mime.split(";")[0]?.trim().toLowerCase();
+  return cleaned || undefined;
+}
+
+async function sniffMimeFromBase64(
+  base64: string,
+): Promise<string | undefined> {
+  const trimmed = base64.trim();
+  if (!trimmed) return undefined;
+
+  const take = Math.min(256, trimmed.length);
+  const sliceLen = take - (take % 4);
+  if (sliceLen < 8) return undefined;
+
+  try {
+    const head = Buffer.from(trimmed.slice(0, sliceLen), "base64");
+    return await detectMime({ buffer: head });
+  } catch {
+    return undefined;
+  }
+}
+
+function isImageMime(mime?: string): boolean {
+  return typeof mime === "string" && mime.startsWith("image/");
+}
+
+/**
+ * Parse attachments and extract images as structured content blocks.
+ * Returns the message text and an array of image content blocks
+ * compatible with Claude API's image format.
+ */
+export async function parseMessageWithAttachments(
+  message: string,
+  attachments: ChatAttachment[] | undefined,
+  opts?: { maxBytes?: number; log?: AttachmentLog },
+): Promise<ParsedMessageWithImages> {
+  const maxBytes = opts?.maxBytes ?? 5_000_000; // 5 MB
+  const log = opts?.log;
+  if (!attachments || attachments.length === 0) {
+    return { message, images: [] };
+  }
+
+  const images: ChatImageContent[] = [];
+
+  for (const [idx, att] of attachments.entries()) {
+    if (!att) continue;
+    const mime = att.mimeType ?? "";
+    const content = att.content;
+    const label = att.fileName || att.type || `attachment-${idx + 1}`;
+
+    if (typeof content !== "string") {
+      throw new Error(`attachment ${label}: content must be base64 string`);
+    }
+
+    let sizeBytes = 0;
+    let b64 = content.trim();
+    // Strip data URL prefix if present (e.g., "data:image/jpeg;base64,...")
+    const dataUrlMatch = /^data:[^;]+;base64,(.*)$/.exec(b64);
+    if (dataUrlMatch) {
+      b64 = dataUrlMatch[1];
+    }
+    // Basic base64 sanity: length multiple of 4 and charset check.
+    if (b64.length % 4 !== 0 || /[^A-Za-z0-9+/=]/.test(b64)) {
+      throw new Error(`attachment ${label}: invalid base64 content`);
+    }
+    try {
+      sizeBytes = Buffer.from(b64, "base64").byteLength;
+    } catch {
+      throw new Error(`attachment ${label}: invalid base64 content`);
+    }
+    if (sizeBytes <= 0 || sizeBytes > maxBytes) {
+      throw new Error(
+        `attachment ${label}: exceeds size limit (${sizeBytes} > ${maxBytes} bytes)`,
+      );
+    }
+
+    const providedMime = normalizeMime(mime);
+    const sniffedMime = normalizeMime(await sniffMimeFromBase64(b64));
+    if (sniffedMime && !isImageMime(sniffedMime)) {
+      log?.warn(
+        `attachment ${label}: detected non-image (${sniffedMime}), dropping`,
+      );
+      continue;
+    }
+    if (!sniffedMime && !isImageMime(providedMime)) {
+      log?.warn(
+        `attachment ${label}: unable to detect image mime type, dropping`,
+      );
+      continue;
+    }
+    if (sniffedMime && providedMime && sniffedMime !== providedMime) {
+      log?.warn(
+        `attachment ${label}: mime mismatch (${providedMime} -> ${sniffedMime}), using sniffed`,
+      );
+    }
+
+    images.push({
+      type: "image",
+      data: b64,
+      mimeType: sniffedMime ?? providedMime ?? mime,
+    });
+  }
+
+  return { message, images };
+}
+
+/**
+ * @deprecated Use parseMessageWithAttachments instead.
+ * This function converts images to markdown data URLs which Claude API cannot process as images.
+ */
 export function buildMessageWithAttachments(
   message: string,
   attachments: ChatAttachment[] | undefined,
diff --git a/src/gateway/server-bridge.ts b/src/gateway/server-bridge.ts
index 1de965f9a..87ac5a955 100644
--- a/src/gateway/server-bridge.ts
+++ b/src/gateway/server-bridge.ts
@@ -43,7 +43,10 @@ import {
   isChatStopCommandText,
   resolveChatRunExpiresAtMs,
 } from "./chat-abort.js";
-import { buildMessageWithAttachments } from "./chat-attachments.js";
+import {
+  type ChatImageContent,
+  parseMessageWithAttachments,
+} from "./chat-attachments.js";
 import {
   ErrorCodes,
   errorShape,
@@ -793,32 +796,37 @@ export function createBridgeHandlers(ctx: BridgeHandlersContext) {
           };
           const stopCommand = isChatStopCommandText(p.message);
           const normalizedAttachments =
-            p.attachments?.map((a) => ({
-              type: typeof a?.type === "string" ? a.type : undefined,
-              mimeType:
-                typeof a?.mimeType === "string" ? a.mimeType : undefined,
-              fileName:
-                typeof a?.fileName === "string" ? a.fileName : undefined,
-              content:
-                typeof a?.content === "string"
-                  ? a.content
-                  : ArrayBuffer.isView(a?.content)
-                    ? Buffer.from(
-                        a.content.buffer,
-                        a.content.byteOffset,
-                        a.content.byteLength,
-                      ).toString("base64")
-                    : undefined,
-            })) ?? [];
+            p.attachments
+              ?.map((a) => ({
+                type: typeof a?.type === "string" ? a.type : undefined,
+                mimeType:
+                  typeof a?.mimeType === "string" ? a.mimeType : undefined,
+                fileName:
+                  typeof a?.fileName === "string" ? a.fileName : undefined,
+                content:
+                  typeof a?.content === "string"
+                    ? a.content
+                    : ArrayBuffer.isView(a?.content)
+                      ? Buffer.from(
+                          a.content.buffer,
+                          a.content.byteOffset,
+                          a.content.byteLength,
+                        ).toString("base64")
+                      : undefined,
+              }))
+              .filter((a) => a.content) ?? [];
 
-          let messageWithAttachments = p.message;
+          let parsedMessage = p.message;
+          let parsedImages: ChatImageContent[] = [];
           if (normalizedAttachments.length > 0) {
             try {
-              messageWithAttachments = buildMessageWithAttachments(
+              const parsed = await parseMessageWithAttachments(
                 p.message,
                 normalizedAttachments,
-                { maxBytes: 5_000_000 },
+                { maxBytes: 5_000_000, log: ctx.logBridge },
               );
+              parsedMessage = parsed.message;
+              parsedImages = parsed.images;
             } catch (err) {
               return {
                 ok: false,
@@ -922,7 +930,8 @@ export function createBridgeHandlers(ctx: BridgeHandlersContext) {
             };
             void agentCommand(
               {
-                message: messageWithAttachments,
+                message: parsedMessage,
+                images: parsedImages.length > 0 ? parsedImages : undefined,
                 sessionId,
                 sessionKey: p.sessionKey,
                 runId: clientRunId,
diff --git a/src/gateway/server-methods/chat.ts b/src/gateway/server-methods/chat.ts
index e2c5db37b..c3afb65d4 100644
--- a/src/gateway/server-methods/chat.ts
+++ b/src/gateway/server-methods/chat.ts
@@ -13,7 +13,10 @@ import {
   isChatStopCommandText,
   resolveChatRunExpiresAtMs,
 } from "../chat-abort.js";
-import { buildMessageWithAttachments } from "../chat-attachments.js";
+import {
+  type ChatImageContent,
+  parseMessageWithAttachments,
+} from "../chat-attachments.js";
 import {
   ErrorCodes,
   errorShape,
@@ -181,29 +184,34 @@ export const chatHandlers: GatewayRequestHandlers = {
     };
     const stopCommand = isChatStopCommandText(p.message);
     const normalizedAttachments =
-      p.attachments?.map((a) => ({
-        type: typeof a?.type === "string" ? a.type : undefined,
-        mimeType: typeof a?.mimeType === "string" ? a.mimeType : undefined,
-        fileName: typeof a?.fileName === "string" ? a.fileName : undefined,
-        content:
-          typeof a?.content === "string"
-            ? a.content
-            : ArrayBuffer.isView(a?.content)
-              ? Buffer.from(
-                  a.content.buffer,
-                  a.content.byteOffset,
-                  a.content.byteLength,
-                ).toString("base64")
-              : undefined,
-      })) ?? [];
-    let messageWithAttachments = p.message;
+      p.attachments
+        ?.map((a) => ({
+          type: typeof a?.type === "string" ? a.type : undefined,
+          mimeType: typeof a?.mimeType === "string" ? a.mimeType : undefined,
+          fileName: typeof a?.fileName === "string" ? a.fileName : undefined,
+          content:
+            typeof a?.content === "string"
+              ? a.content
+              : ArrayBuffer.isView(a?.content)
+                ? Buffer.from(
+                    a.content.buffer,
+                    a.content.byteOffset,
+                    a.content.byteLength,
+                  ).toString("base64")
+                : undefined,
+        }))
+        .filter((a) => a.content) ?? [];
+    let parsedMessage = p.message;
+    let parsedImages: ChatImageContent[] = [];
     if (normalizedAttachments.length > 0) {
       try {
-        messageWithAttachments = buildMessageWithAttachments(
+        const parsed = await parseMessageWithAttachments(
           p.message,
           normalizedAttachments,
-          { maxBytes: 5_000_000 },
+          { maxBytes: 5_000_000, log: context.logGateway },
         );
+        parsedMessage = parsed.message;
+        parsedImages = parsed.images;
       } catch (err) {
         respond(
           false,
@@ -312,7 +320,8 @@ export const chatHandlers: GatewayRequestHandlers = {
 
       void agentCommand(
         {
-          message: messageWithAttachments,
+          message: parsedMessage,
+          images: parsedImages.length > 0 ? parsedImages : undefined,
           sessionId,
           sessionKey: p.sessionKey,
           runId: clientRunId,
diff --git a/src/gateway/server-methods/types.ts b/src/gateway/server-methods/types.ts
index 79545fe80..613faa32a 100644
--- a/src/gateway/server-methods/types.ts
+++ b/src/gateway/server-methods/types.ts
@@ -32,6 +32,7 @@ export type GatewayRequestContext = {
   getHealthCache: () => HealthSummary | null;
   refreshHealthSnapshot: (opts?: { probe?: boolean }) => Promise<HealthSummary>;
   logHealth: { error: (message: string) => void };
+  logGateway: { warn: (message: string) => void };
   incrementPresenceVersion: () => number;
   getHealthVersion: () => number;
   broadcast: (
diff --git a/src/gateway/server.ts b/src/gateway/server.ts
index a56f07605..2f77446bc 100644
--- a/src/gateway/server.ts
+++ b/src/gateway/server.ts
@@ -1674,6 +1674,7 @@ export async function startGatewayServer(
               getHealthCache: () => healthCache,
               refreshHealthSnapshot,
               logHealth,
+              logGateway: log,
               incrementPresenceVersion: () => {
                 presenceVersion += 1;
                 return presenceVersion;