Merge PR #8688: fix(mcp): preserve image tool results (@roboomp)

packages/coding-agent/CHANGELOG.md

@@ -94,6 +94,10 @@
 - Fixed external thinking being offered on xAI reasoning-only Responses models (grok-4 family) that reject `reasoning.effort`, where the private scratchpad ran alongside native reasoning instead of replacing it.
 - Fixed the extension tool-call handler timeout rendering outside a titled section in `/settings` by registering its Extensions group on the Tools tab.
 
+### Fixed
+
+- Preserved MCP `ImageContent` tool-result blocks so vision-capable models and the TUI can inspect returned images instead of receiving only a text placeholder ([#8687](https://github.com/can1357/oh-my-pi/issues/8687)).
+
 ## [17.3.4] - 2026-08-14
 
 ### Changed

packages/coding-agent/src/mcp/tool-bridge.ts

@@ -4,7 +4,7 @@
  * Converts MCP tool definitions to CustomTool format for the agent.
  */
 import type { AgentToolUpdateCallback } from "@oh-my-pi/pi-agent-core";
-import type { TSchema } from "@oh-my-pi/pi-ai";
+import type { ImageContent, TextContent, TSchema } from "@oh-my-pi/pi-ai";
 import { normalizeSchemaForMCP } from "@oh-my-pi/pi-ai/utils/schema";
 import { logger, untilAborted } from "@oh-my-pi/pi-utils";
 import { INTENT_FIELD } from "@oh-my-pi/pi-wire";
@@ -191,30 +191,40 @@ export interface MCPToolDetails {
 	meta?: OutputMeta;
 }
 /**
- * Format MCP content for LLM consumption.
+ * Convert MCP content to agent content while retaining image payloads.
  */
-function formatMCPContent(content: MCPContent[]): string {
-	const parts: string[] = [];
+function formatMCPContent(content: MCPContent[]): Array<TextContent | ImageContent> {
+	const blocks: Array<TextContent | ImageContent> = [];
+	let text = "";
+	const flushText = () => {
+		if (!text) return;
+		blocks.push({ type: "text", text });
+		text = "";
+	};
+	const appendText = (value: string) => {
+		text += text ? `\n\n${value}` : value;
+	};
 
 	for (const item of content) {
 		switch (item.type) {
 			case "text":
-				parts.push(item.text);
+				appendText(item.text);
 				break;
 			case "image":
-				parts.push(`[Image: ${item.mimeType}]`);
+				flushText();
+				blocks.push(item);
 				break;
 			case "resource":
-				if (item.resource.text) {
-					parts.push(`[Resource: ${item.resource.uri}]\n${item.resource.text}`);
-				} else {
-					parts.push(`[Resource: ${item.resource.uri}]`);
-				}
+				appendText(
+					item.resource.text
+						? `[Resource: ${item.resource.uri}]\n${item.resource.text}`
+						: `[Resource: ${item.resource.uri}]`,
+				);
 				break;
 		}
 	}
-
-	return parts.join("\n\n");
+	flushText();
+	return blocks.length > 0 ? blocks : [{ type: "text", text: "" }];
 }
 
 /** Build a CustomToolResult from a callTool response. */
@@ -225,7 +235,7 @@ function buildResult(
 	provider?: string,
 	providerName?: string,
 ): CustomToolResult<MCPToolDetails> {
-	const text = formatMCPContent(result.content);
+	const content = formatMCPContent(result.content);
 	const details: MCPToolDetails = {
 		serverName,
 		mcpToolName,
@@ -235,8 +245,14 @@ function buildResult(
 		provider,
 		providerName,
 	};
-	const contentText = result.isError ? `Error: ${text}` : text;
-	const toolResult: CustomToolResult<MCPToolDetails> = { content: [{ type: "text", text: contentText }], details };
+	if (result.isError) {
+		if (content[0]?.type === "text") {
+			content[0] = { type: "text", text: `Error: ${content[0].text}` };
+		} else {
+			content.unshift({ type: "text", text: "Error:" });
+		}
+	}
+	const toolResult: CustomToolResult<MCPToolDetails> = { content, details };
 	if (result.isError) {
 		toolResult.isError = true;
 	}

packages/coding-agent/test/mcp-reconnect.test.ts

@@ -6,7 +6,12 @@ import {
 	isRetriableConnectionError,
 	MCPTool,
 } from "@oh-my-pi/pi-coding-agent/mcp/tool-bridge";
-import type { MCPServerConnection, MCPToolCallResult, MCPTransport } from "@oh-my-pi/pi-coding-agent/mcp/types";
+import type {
+	MCPImageContent,
+	MCPServerConnection,
+	MCPToolCallResult,
+	MCPTransport,
+} from "@oh-my-pi/pi-coding-agent/mcp/types";
 import { ToolAbortError } from "@oh-my-pi/pi-coding-agent/tools/tool-errors";
 import { logger } from "@oh-my-pi/pi-utils";
 
@@ -146,6 +151,18 @@ describe("MCPTool.execute retry on connection error", () => {
 		expect(result.content[0]).toEqual({ type: "text", text: "ok" });
 	});
 
+	it("preserves image blocks returned by MCP tools", async () => {
+		const image: MCPImageContent = { type: "image", data: "iVBORw0KGgo=", mimeType: "image/png" };
+		const transport = mockTransport(async () => ({
+			content: [{ type: "text", text: "Screenshot captured" }, image],
+		}));
+		const tool = new MCPTool(makeConnection(transport), TOOL_DEF);
+
+		const result = await tool.execute("call-1", {}, noop, noCtx);
+
+		expect(result.content).toEqual([{ type: "text", text: "Screenshot captured" }, image]);
+	});
+
 	it("retries on transport closed and rebinding succeeds", async () => {
 		let oldCalls = 0;
 		let newCalls = 0;