diff --git a/CHANGELOG.md b/CHANGELOG.md
index 0c67944..f7f7397 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,6 +4,19 @@ All notable changes to this project will be documented in this file.
 
 ## [Unreleased]
 
+- **Fixed: auto-compaction (and manual `/compact`) failed with `Tool call not
+  allowed while generating summary` whenever the Cursor agent used a tool while
+  summarizing.** opencode declares zero tools on a compaction/summary turn, but
+  the Cursor agent runs its own tools regardless; the provider forwarded that
+  activity as provider-executed `tool-call` parts, which opencode's summary
+  guard rejects. The provider now routes no-tools turns through the existing
+  `"reasoning"` tool-display path, so Cursor's tool activity surfaces as
+  reasoning text instead of crossing the tool-execution boundary. Manual
+  `/compact` was affected all along; **auto**-compaction became reachable only
+  in 0.7.1-next.0, because #89 published real per-model context windows —
+  pre-0.7.1 opencode saw `limit.context: 0` for every Cursor model, and a zero
+  context limit structurally disables the auto-compaction trigger.
+
 ## [0.7.1-next.0] — 2026-08-03 (pre-release)
 
 Pre-release of the skills bridge (#90) and per-model context limits + pricing
diff --git a/README.md b/README.md
index c5c2626..f540d02 100644
--- a/README.md
+++ b/README.md
@@ -413,6 +413,10 @@ open a PR.
 - **`"reasoning"`** — compact inline lines (`[tool] write {"path":…}`). Works on any host; use
   this on older opencode versions.
 
+Turns where the host declares no tools at all — compaction/summary and title generation — always
+use `"reasoning"` regardless of this setting. opencode rejects tool parts on a summary turn, so
+Cursor's tool activity is folded into reasoning text there instead.
+
 To force the fallback:
 
 ```json
diff --git a/src/provider/language-model.ts b/src/provider/language-model.ts
index dee2813..be1d7aa 100644
--- a/src/provider/language-model.ts
+++ b/src/provider/language-model.ts
@@ -34,6 +34,7 @@ import {
 import {
 	cursorEventsToContent,
 	cursorEventsToStream,
+	effectiveToolDisplay,
 	type ToolDisplay,
 } from "./stream-map.js";
 import { resolveControls } from "./controls.js";
@@ -549,9 +550,11 @@ export class CursorLanguageModel implements LanguageModelV3 {
 				? (po["sessionID"] as string)
 				: undefined;
 		return {
-			stream: cursorEventsToStream(this.agentRun(options), this.config.toolDisplay, {
-				sessionID,
-			}),
+			stream: cursorEventsToStream(
+				this.agentRun(options),
+				effectiveToolDisplay(this.config.toolDisplay, options.tools),
+				{ sessionID },
+			),
 		};
 	}
 
@@ -563,7 +566,7 @@ export class CursorLanguageModel implements LanguageModelV3 {
 	}> {
 		const result = await cursorEventsToContent(
 			this.agentRun(options),
-			this.config.toolDisplay,
+			effectiveToolDisplay(this.config.toolDisplay, options.tools),
 		);
 		return { ...result, warnings: [] };
 	}
diff --git a/src/provider/stream-map.ts b/src/provider/stream-map.ts
index 1cbf241..59a847c 100644
--- a/src/provider/stream-map.ts
+++ b/src/provider/stream-map.ts
@@ -1,4 +1,5 @@
 import type {
+	LanguageModelV3CallOptions,
 	LanguageModelV3Content,
 	LanguageModelV3FinishReason,
 	LanguageModelV3StreamPart,
@@ -55,6 +56,24 @@ function injectSubagentSessionId(
  */
 export type ToolDisplay = "reasoning" | "blocks";
 
+/**
+ * A host that declared no tools cannot accept tool parts — opencode's summary
+ * guard throws on them (`Tool call not allowed while generating summary`).
+ * Cursor's agent runs its own tools regardless, so fold that activity into
+ * reasoning text for those turns. Returns the configured mode otherwise.
+ */
+export function effectiveToolDisplay(
+	configured: ToolDisplay | undefined,
+	tools: LanguageModelV3CallOptions["tools"],
+): ToolDisplay {
+	// `Array.isArray` rather than a null check: opencode passes tools as a
+	// Record at its own layer and the ai-sdk converts it to an array (an empty
+	// Record short-circuits to `undefined`), so a raw record never reaches us
+	// today — but this way the guard holds even if that conversion changes.
+	if (!Array.isArray(tools) || tools.length === 0) return "reasoning";
+	return configured ?? "blocks";
+}
+
 const FINISH_STOP: LanguageModelV3FinishReason = {
 	unified: "stop",
 	raw: undefined,
diff --git a/test/language-model.test.ts b/test/language-model.test.ts
index b4f651e..6101f95 100644
--- a/test/language-model.test.ts
+++ b/test/language-model.test.ts
@@ -456,4 +456,123 @@ describe("CursorLanguageModel doStream — resume-aware retry", () => {
 		// Original resume failure preserved as the cause for diagnosability.
 		expect((error.cause as Error)?.message).toContain("error");
 	});
+});
+
+// Regression for "Tool call not allowed while generating summary" on turns
+// where opencode declares no tools (compaction/summary, title generation).
+// The Cursor agent runs its own tools regardless; the provider must fold that
+// activity into reasoning text rather than emitting provider-executed
+// tool-call parts the host cannot accept.
+describe("CursorLanguageModel — no-tools turns fold tool activity into reasoning", () => {
+	const TOOL_TYPES = [
+		"tool-input-start",
+		"tool-input-delta",
+		"tool-input-end",
+		"tool-call",
+		"tool-result",
+	] as const;
+
+	// A Cursor tool-call for an MCP tool (the shape that produced the reported
+	// `cursor_context-mode_ctx_search` part).
+	const mcpToolCallUpdate = {
+		type: "tool-call-started",
+		callId: "c1",
+		toolCall: { type: "mcp", args: { toolName: "context-mode_ctx_search", providerIdentifier: "context-mode" } },
+	};
+	const mcpToolResultUpdate = {
+		type: "tool-call-completed",
+		callId: "c1",
+		toolCall: { type: "mcp", result: { content: [{ type: "text", text: "ok" }] } },
+	};
+
+	it("doStream: a no-tools turn emits no tool parts", async () => {
+		const model = makeModel();
+		create.mockResolvedValueOnce(
+			fakeAgent({
+				agentId: "a1",
+				updates: [mcpToolCallUpdate, mcpToolResultUpdate, { type: "text-delta", text: "summary" }],
+			}),
+		);
+
+		const parts = await collectStream(
+			streamCall(model, {
+				prompt: [user("summarize")],
+				// tools intentionally omitted — mirrors opencode's compaction turn
+				providerOptions: { cursor: { sessionID: "s1" } },
+			} as never),
+		);
+
+		for (const t of TOOL_TYPES) {
+			expect(eventTypes(parts)).not.toContain(t);
+		}
+
+		// Absence alone would also hold if the stream emitted nothing, so assert
+		// the activity was FOLDED INTO reasoning rather than dropped.
+		const reasoning = parts
+			.filter(
+				(p): p is Extract<LanguageModelV3StreamPart, { type: "reasoning-delta" }> =>
+					p.type === "reasoning-delta",
+			)
+			.map((p) => p.delta)
+			.join("");
+		expect(reasoning).toContain("context-mode_ctx_search");
+		// The summary text itself still reaches the host.
+		const text = parts
+			.filter(
+				(p): p is Extract<LanguageModelV3StreamPart, { type: "text-delta" }> =>
+					p.type === "text-delta",
+			)
+			.map((p) => p.delta)
+			.join("");
+		expect(text).toBe("summary");
+	});
+
+	it("doStream: a turn WITH tools still emits tool-call parts", async () => {
+		const model = makeModel();
+		create.mockResolvedValueOnce(
+			fakeAgent({
+				agentId: "a1",
+				updates: [mcpToolCallUpdate, mcpToolResultUpdate, { type: "text-delta", text: "done" }],
+			}),
+		);
+
+		const parts = await collectStream(
+			streamCall(model, {
+				prompt: [sys("S"), user("hi")],
+				tools: [{ type: "function", name: "read", inputSchema: {} }],
+				providerOptions: { cursor: { sessionID: "s1" } },
+			} as never),
+		);
+
+		// Normal tool blocks are preserved — the suppression is no-tools-only.
+		expect(eventTypes(parts)).toContain("tool-call");
+	});
+
+	it("doGenerate: a no-tools turn carries no tool-call in content", async () => {
+		const model = makeModel();
+		create.mockResolvedValueOnce(
+			fakeAgent({
+				agentId: "a1",
+				updates: [mcpToolCallUpdate, mcpToolResultUpdate, { type: "text-delta", text: "summary" }],
+			}),
+		);
+
+		const result = await model.doGenerate({
+			prompt: [user("summarize")],
+			providerOptions: { cursor: { sessionID: "s1" } },
+		} as never);
+
+		const toolContent = result.content.filter((c) => c.type === "tool-call");
+		expect(toolContent).toHaveLength(0);
+
+		// Folded into reasoning, not dropped.
+		const reasoning = result.content
+			.filter(
+				(c): c is Extract<typeof c, { type: "reasoning" }> =>
+					c.type === "reasoning",
+			)
+			.map((c) => c.text)
+			.join("");
+		expect(reasoning).toContain("context-mode_ctx_search");
+	});
 });
\ No newline at end of file
diff --git a/test/stream-map.test.ts b/test/stream-map.test.ts
index aec64f6..dd9aa80 100644
--- a/test/stream-map.test.ts
+++ b/test/stream-map.test.ts
@@ -4,6 +4,7 @@ import type { CursorEvent } from "../src/provider/agent-events.js";
 import {
 	cursorEventsToContent,
 	cursorEventsToStream,
+	effectiveToolDisplay,
 	mapUsage,
 } from "../src/provider/stream-map.js";
 import {
@@ -1696,3 +1697,25 @@ describe("subagent child-session linking (blocks)", () => {
 		expect(foldedMetadata(result)["sessionId"]).toBeUndefined();
 	});
 });
+
+describe("effectiveToolDisplay", () => {
+	it("returns \"reasoning\" when tools are undefined", () => {
+		expect(effectiveToolDisplay("blocks", undefined)).toBe("reasoning");
+	});
+
+	it("returns \"reasoning\" when tools are an empty array", () => {
+		expect(effectiveToolDisplay("blocks", [])).toBe("reasoning");
+	});
+
+	it("returns the configured mode when tools are present", () => {
+		expect(effectiveToolDisplay("blocks", [{ type: "function", name: "read" } as never])).toBe(
+			"blocks",
+		);
+	});
+
+	it("defaults to \"blocks\" when configured is undefined and tools are present", () => {
+		expect(
+			effectiveToolDisplay(undefined, [{ type: "function", name: "read" } as never]),
+		).toBe("blocks");
+	});
+});