fix(coding-agent): clear tree navigation compaction state

closes #3688

packages/coding-agent/CHANGELOG.md

@@ -8,6 +8,7 @@
 
 ### Fixed
 
+- Fixed `/tree` cancellation via `session_before_tree` leaving the session stuck in compaction state ([#3688](https://github.com/badlogic/pi-mono/issues/3688))
 - Fixed Escape interrupt handling when extensions hide the built-in working loader row ([#3674](https://github.com/badlogic/pi-mono/issues/3674))
 - Fixed coding-agent test expectations for current default models and missing-auth guidance.
 

packages/coding-agent/src/core/agent-session.ts

@@ -2711,6 +2711,8 @@ export class AgentSession {
 
 		// Set up abort controller for summarization
 		this._branchSummaryAbortController = new AbortController();
+
+		try {
 			let extensionSummary: { summary: string; details?: unknown } | undefined;
 			let fromExtension = false;
 
@@ -2759,7 +2761,6 @@ export class AgentSession {
 					replaceInstructions,
 					reserveTokens: branchSummarySettings.reserveTokens,
 				});
-			this._branchSummaryAbortController = undefined;
 				if (result.aborted) {
 					return { cancelled: true, aborted: true };
 				}
@@ -2804,7 +2805,12 @@ export class AgentSession {
 			let summaryEntry: BranchSummaryEntry | undefined;
 			if (summaryText) {
 				// Create summary at target position (can be null for root)
-			const summaryId = this.sessionManager.branchWithSummary(newLeafId, summaryText, summaryDetails, fromExtension);
+				const summaryId = this.sessionManager.branchWithSummary(
+					newLeafId,
+					summaryText,
+					summaryDetails,
+					fromExtension,
+				);
 				summaryEntry = this.sessionManager.getEntry(summaryId) as BranchSummaryEntry;
 
 				// Attach label to the summary entry
@@ -2839,8 +2845,10 @@ export class AgentSession {
 
 			// Emit to custom tools
 
-		this._branchSummaryAbortController = undefined;
 			return { editorText, cancelled: false, summaryEntry };
+		} finally {
+			this._branchSummaryAbortController = undefined;
+		}
 	}
 
 	/**

packages/coding-agent/test/suite/regressions/3688-tree-cancel-compacting.test.ts

@@ -0,0 +1,36 @@
+import { afterEach, describe, expect, it } from "vitest";
+import { assistantMsg, userMsg } from "../../utilities.js";
+import { createHarness, type Harness } from "../harness.js";
+
+describe("issue #3688 tree cancellation compaction state", () => {
+	const harnesses: Harness[] = [];
+
+	afterEach(() => {
+		while (harnesses.length > 0) {
+			harnesses.pop()?.cleanup();
+		}
+	});
+
+	it("clears branch summary state when session_before_tree cancels navigation", async () => {
+		const harness = await createHarness({
+			extensionFactories: [
+				(pi) => {
+					pi.on("session_before_tree", () => ({ cancel: true }));
+				},
+			],
+		});
+		harnesses.push(harness);
+
+		const targetId = harness.sessionManager.appendMessage(userMsg("first"));
+		harness.sessionManager.appendMessage(assistantMsg("reply"));
+		const currentLeafId = harness.sessionManager.appendMessage(userMsg("second"));
+
+		expect(harness.sessionManager.getLeafId()).toBe(currentLeafId);
+
+		const result = await harness.session.navigateTree(targetId, { summarize: false });
+
+		expect(result).toEqual({ cancelled: true });
+		expect(harness.session.isCompacting).toBe(false);
+		expect(harness.sessionManager.getLeafId()).toBe(currentLeafId);
+	});
+});