diff --git a/packages/ai/CHANGELOG.md b/packages/ai/CHANGELOG.md
index 2a035edf3..2570bac1d 100644
--- a/packages/ai/CHANGELOG.md
+++ b/packages/ai/CHANGELOG.md
@@ -2,6 +2,10 @@
 
 ## [Unreleased]
 
+### Fixed
+
+- Fixed OpenAI-compatible Chat Completions requests sending `tool_choice` without tools, which gateways can reject during compaction ([#8607](https://github.com/earendil-works/pi/issues/8607)).
+
 ## [0.84.3] - 2026-08-24
 
 ### Breaking Changes
diff --git a/packages/ai/src/api/openai-completions.ts b/packages/ai/src/api/openai-completions.ts
index 04326ca2f..0529db628 100644
--- a/packages/ai/src/api/openai-completions.ts
+++ b/packages/ai/src/api/openai-completions.ts
@@ -835,7 +835,7 @@ function buildParams(
 		applyAnthropicCacheControl(messages, params.tools, cacheControl);
 	}
 
-	if (options?.toolChoice) {
+	if (options?.toolChoice && params.tools?.length) {
 		params.tool_choice = options.toolChoice;
 	}
 
diff --git a/packages/ai/test/openai-completions-tool-choice.test.ts b/packages/ai/test/openai-completions-tool-choice.test.ts
index c453f3d54..35be54538 100644
--- a/packages/ai/test/openai-completions-tool-choice.test.ts
+++ b/packages/ai/test/openai-completions-tool-choice.test.ts
@@ -150,6 +150,30 @@ describe("openai-completions tool_choice", () => {
 		expect(params.tools?.length ?? 0).toBeGreaterThan(0);
 	});
 
+	it("omits toolChoice when no tools are provided", async () => {
+		const { compat: _compat, ...baseModel } = getModel("openai", "gpt-4o-mini")!;
+		const model = { ...baseModel, api: "openai-completions" } as const;
+		let payload: unknown;
+
+		await streamSimple(
+			model,
+			{
+				messages: [{ role: "user", content: "Summarize the conversation", timestamp: Date.now() }],
+			},
+			{
+				apiKey: "test",
+				toolChoice: "none",
+				onPayload: (params: unknown) => {
+					payload = params;
+				},
+			},
+		).result();
+
+		const params = (payload ?? mockState.lastParams) as { tool_choice?: string; tools?: unknown[] };
+		expect(params).not.toHaveProperty("tool_choice");
+		expect(params).not.toHaveProperty("tools");
+	});
+
 	it("omits strict when compat disables strict mode", async () => {
 		const { compat: _compat, ...baseModel } = getModel("openai", "gpt-4o-mini")!;
 		const model = {