From 9f9978635c844fb78ea6ba81c5ce74a1f5cdbac3 Mon Sep 17 00:00:00 2001
From: Peter Steinberger <steipete@gmail.com>
Date: Sun, 15 Feb 2026 13:30:37 +0000
Subject: [PATCH] refactor(gateway): share rpc attachment normalization

---
 src/gateway/server-methods/agent.ts           | 20 ++----------
 .../attachment-normalize.test.ts              | 19 +++++++++++
 .../server-methods/attachment-normalize.ts    | 32 +++++++++++++++++++
 src/gateway/server-methods/chat.ts            | 20 ++----------
 4 files changed, 55 insertions(+), 36 deletions(-)
 create mode 100644 src/gateway/server-methods/attachment-normalize.test.ts
 create mode 100644 src/gateway/server-methods/attachment-normalize.ts

diff --git a/src/gateway/server-methods/agent.ts b/src/gateway/server-methods/agent.ts
index fed4d190f..5d4c8773f 100644
--- a/src/gateway/server-methods/agent.ts
+++ b/src/gateway/server-methods/agent.ts
@@ -48,6 +48,7 @@ import {
 import { formatForLog } from "../ws-log.js";
 import { waitForAgentJob } from "./agent-job.js";
 import { injectTimestamp, timestampOptsFromConfig } from "./agent-timestamp.js";
+import { normalizeRpcAttachmentsToChatAttachments } from "./attachment-normalize.js";
 import { sessionsHandlers } from "./sessions.js";
 
 const RESET_COMMAND_RE = /^\/(new|reset)(?:\s+([\s\S]*))?$/i;
@@ -213,24 +214,7 @@ export const agentHandlers: GatewayRequestHandlers = {
       });
       return;
     }
-    const normalizedAttachments =
-      request.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) ?? [];
+    const normalizedAttachments = normalizeRpcAttachmentsToChatAttachments(request.attachments);
 
     let message = request.message.trim();
     let images: Array<{ type: "image"; data: string; mimeType: string }> = [];
diff --git a/src/gateway/server-methods/attachment-normalize.test.ts b/src/gateway/server-methods/attachment-normalize.test.ts
new file mode 100644
index 000000000..159bae804
--- /dev/null
+++ b/src/gateway/server-methods/attachment-normalize.test.ts
@@ -0,0 +1,19 @@
+import { describe, expect, it } from "vitest";
+import { normalizeRpcAttachmentsToChatAttachments } from "./attachment-normalize.js";
+
+describe("normalizeRpcAttachmentsToChatAttachments", () => {
+  it("passes through string content", () => {
+    const res = normalizeRpcAttachmentsToChatAttachments([
+      { type: "file", mimeType: "image/png", fileName: "a.png", content: "Zm9v" },
+    ]);
+    expect(res).toEqual([
+      { type: "file", mimeType: "image/png", fileName: "a.png", content: "Zm9v" },
+    ]);
+  });
+
+  it("converts Uint8Array content to base64", () => {
+    const bytes = new TextEncoder().encode("foo");
+    const res = normalizeRpcAttachmentsToChatAttachments([{ content: bytes }]);
+    expect(res[0]?.content).toBe("Zm9v");
+  });
+});
diff --git a/src/gateway/server-methods/attachment-normalize.ts b/src/gateway/server-methods/attachment-normalize.ts
new file mode 100644
index 000000000..b8eb00926
--- /dev/null
+++ b/src/gateway/server-methods/attachment-normalize.ts
@@ -0,0 +1,32 @@
+import type { ChatAttachment } from "../chat-attachments.js";
+
+export type RpcAttachmentInput = {
+  type?: unknown;
+  mimeType?: unknown;
+  fileName?: unknown;
+  content?: unknown;
+};
+
+export function normalizeRpcAttachmentsToChatAttachments(
+  attachments: RpcAttachmentInput[] | undefined,
+): ChatAttachment[] {
+  return (
+    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",
+                )
+              : a?.content instanceof ArrayBuffer
+                ? Buffer.from(a.content).toString("base64")
+                : undefined,
+      }))
+      .filter((a) => a.content) ?? []
+  );
+}
diff --git a/src/gateway/server-methods/chat.ts b/src/gateway/server-methods/chat.ts
index d82511386..52225dc0b 100644
--- a/src/gateway/server-methods/chat.ts
+++ b/src/gateway/server-methods/chat.ts
@@ -39,6 +39,7 @@ import {
 } from "../session-utils.js";
 import { formatForLog } from "../ws-log.js";
 import { injectTimestamp, timestampOptsFromConfig } from "./agent-timestamp.js";
+import { normalizeRpcAttachmentsToChatAttachments } from "./attachment-normalize.js";
 
 type TranscriptAppendResult = {
   ok: boolean;
@@ -385,24 +386,7 @@ export const chatHandlers: GatewayRequestHandlers = {
     }
     const inboundMessage = sanitizedMessageResult.message;
     const stopCommand = isChatStopCommandText(inboundMessage);
-    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,
-        }))
-        .filter((a) => a.content) ?? [];
+    const normalizedAttachments = normalizeRpcAttachmentsToChatAttachments(p.attachments);
     const rawMessage = inboundMessage.trim();
     if (!rawMessage && normalizedAttachments.length === 0) {
       respond(