fix(ai): use "(no tool output)" placeholder for empty tool results without images (#6290)

OpenAI Completions and Responses providers unconditionally replaced empty
tool result text with "(see attached image)", even when the result had no
image content. This caused the model to hallucinate image attachments for
commands that produce no output (e.g. curl -s with SSL errors, grep with
no matches, true/false).

Now matches the Google provider behavior: "(see attached image)" is only
used when images are actually present; empty results get "(no tool output)".

Co-authored-by: tzwm <tzwm@users.noreply.github.com>
Co-authored-by: Mario Zechner <badlogicgames@gmail.com>

packages/ai/CHANGELOG.md

@@ -11,6 +11,7 @@
 - Fixed Amazon Bedrock prompt-cache points for Claude Fable 5 and Claude Sonnet 5 ([#6235](https://github.com/earendil-works/pi/issues/6235)).
 - Fixed DS4 server context overflow detection for `Prompt has ... tokens, but the configured context size is ... tokens` errors ([#6262](https://github.com/earendil-works/pi/issues/6262)).
 - Fixed OpenAI Codex WebSocket sessions to rotate cached connections before the backend's 60-minute limit, avoiding connection-limit failures on long sessions ([#6268](https://github.com/earendil-works/pi/issues/6268)).
+- Fixed OpenAI Completions and Responses providers to send `(no tool output)` instead of `(see attached image)` when a tool result has empty text and no image content, preventing the model from hallucinating image attachments.
 - Fixed OpenAI Responses and Azure OpenAI Responses requests to avoid sending `max_output_tokens` values below the provider minimum ([#6265](https://github.com/earendil-works/pi/issues/6265)).
 - Fixed retry classification for Cloudflare 524 timeout responses ([#6239](https://github.com/earendil-works/pi/issues/6239)).
 

packages/ai/src/api/openai-completions.ts

@@ -1033,10 +1033,11 @@ export function convertMessages(
 
 				// Always send tool result with text (or placeholder if only images)
 				const hasText = textResult.length > 0;
+				const toolResultText = hasText ? textResult : hasImages ? "(see attached image)" : "(no tool output)";
 				// Some providers require the 'name' field in tool results
 				const toolResultMsg: ChatCompletionToolMessageParam = {
 					role: "tool",
-					content: sanitizeSurrogates(hasText ? textResult : "(see attached image)"),
+					content: sanitizeSurrogates(toolResultText),
 					tool_call_id: toolMsg.toolCallId,
 				};
 				if (compat.requiresToolResultName && toolMsg.toolName) {

packages/ai/src/api/openai-responses-shared.ts

@@ -251,7 +251,7 @@ export function convertResponsesMessages<TApi extends Api>(
 
 				output = contentParts;
 			} else {
-				output = sanitizeSurrogates(hasText ? textResult : "(see attached image)");
+				output = sanitizeSurrogates(hasText ? textResult : hasImages ? "(see attached image)" : "(no tool output)");
 			}
 
 			messages.push({

packages/ai/test/openai-completions-tool-result-images.test.ts

@@ -54,6 +54,17 @@ function buildToolResult(toolCallId: string, timestamp: number): ToolResultMessa
 	};
 }
 
+function buildEmptyToolResult(toolCallId: string, timestamp: number): ToolResultMessage {
+	return {
+		role: "toolResult",
+		toolCallId,
+		toolName: "bash",
+		content: [{ type: "text", text: "" }],
+		isError: false,
+		timestamp,
+	};
+}
+
 describe("openai-completions convertMessages", () => {
 	it("batches tool-result images after consecutive tool results", () => {
 		const { compat: _compat, ...baseModel } = getModel("openai", "gpt-4o-mini");
@@ -100,4 +111,39 @@ describe("openai-completions convertMessages", () => {
 		);
 		expect(imageParts.length).toBe(2);
 	});
+
+	it("uses '(no tool output)' placeholder for empty tool results without images", () => {
+		const { compat: _compat, ...baseModel } = getModel("openai", "gpt-4o-mini");
+		const model: Model<"openai-completions"> = {
+			...baseModel,
+			api: "openai-completions",
+			input: ["text", "image"],
+		};
+
+		const now = Date.now();
+		const assistantMessage: AssistantMessage = {
+			role: "assistant",
+			content: [{ type: "toolCall", id: "tool-1", name: "bash", arguments: { command: "true" } }],
+			api: model.api,
+			provider: model.provider,
+			model: model.id,
+			usage: emptyUsage,
+			stopReason: "toolUse",
+			timestamp: now,
+		};
+
+		const context: Context = {
+			messages: [
+				{ role: "user", content: "Run the command", timestamp: now - 1 },
+				assistantMessage,
+				buildEmptyToolResult("tool-1", now + 1),
+			],
+		};
+
+		const messages = convertMessages(model, context, compat);
+		const toolMessage = messages.find((m) => m.role === "tool") as { role: "tool"; content: string } | undefined;
+		expect(toolMessage).toBeTruthy();
+		expect(toolMessage?.content).toBe("(no tool output)");
+		expect(toolMessage?.content).not.toContain("see attached image");
+	});
 });

packages/ai/test/openai-responses-empty-tool-result.test.ts

@@ -0,0 +1,58 @@
+import { describe, expect, it } from "vitest";
+import { convertResponsesMessages } from "../src/api/openai-responses-shared.ts";
+import { getModel } from "../src/compat.ts";
+import type { AssistantMessage, Context, ToolResultMessage, Usage } from "../src/types.ts";
+
+const usage: Usage = {
+	input: 0,
+	output: 0,
+	cacheRead: 0,
+	cacheWrite: 0,
+	totalTokens: 0,
+	cost: { input: 0, output: 0, cacheRead: 0, cacheWrite: 0, total: 0 },
+};
+
+function buildEmptyToolResult(toolCallId: string, timestamp: number): ToolResultMessage {
+	return {
+		role: "toolResult",
+		toolCallId,
+		toolName: "bash",
+		content: [{ type: "text", text: "" }],
+		isError: false,
+		timestamp,
+	};
+}
+
+describe("OpenAI Responses convertResponsesMessages empty tool result", () => {
+	it("uses '(no tool output)' placeholder for empty tool results without images", () => {
+		const model = getModel("openai", "gpt-4o-mini");
+		const now = Date.now();
+		const assistant: AssistantMessage = {
+			role: "assistant",
+			content: [{ type: "toolCall", id: "tool-1", name: "bash", arguments: { command: "true" } }],
+			api: model.api,
+			provider: model.provider,
+			model: model.id,
+			usage,
+			stopReason: "toolUse",
+			timestamp: now,
+		};
+
+		const context: Context = {
+			messages: [
+				{ role: "user", content: "Run the command", timestamp: now - 1 },
+				assistant,
+				buildEmptyToolResult("tool-1", now + 1),
+			],
+		};
+
+		const input = convertResponsesMessages(model, context, new Set(["openai", "openai-codex", "opencode"]));
+		const functionCallOutput = input.find((item) => item.type === "function_call_output") as
+			| { type: "function_call_output"; output: string }
+			| undefined;
+
+		expect(functionCallOutput).toBeTruthy();
+		expect(functionCallOutput?.output).toBe("(no tool output)");
+		expect(functionCallOutput?.output).not.toContain("see attached image");
+	});
+});