diff --git a/packages/coding-agent/src/core/custom-tools/loader.ts b/packages/coding-agent/src/core/custom-tools/loader.ts
index 095f41c8..3772e0d7 100644
--- a/packages/coding-agent/src/core/custom-tools/loader.ts
+++ b/packages/coding-agent/src/core/custom-tools/loader.ts
@@ -298,7 +298,8 @@ export async function loadCustomTools(
 	// Shared API object - all tools get the same instance
 	const sharedApi: ToolAPI = {
 		cwd,
-		exec: (command: string, args: string[], options?: ExecOptions) => execCommand(command, args, cwd, options),
+		exec: (command: string, args: string[], options?: ExecOptions) =>
+			execCommand(command, args, options?.cwd ?? cwd, options),
 		ui: createNoOpUIContext(),
 		hasUI: false,
 	};
diff --git a/packages/coding-agent/src/core/custom-tools/types.ts b/packages/coding-agent/src/core/custom-tools/types.ts
index b5ccc591..d9e3297d 100644
--- a/packages/coding-agent/src/core/custom-tools/types.ts
+++ b/packages/coding-agent/src/core/custom-tools/types.ts
@@ -31,6 +31,8 @@ export interface ExecOptions {
 	signal?: AbortSignal;
 	/** Timeout in milliseconds */
 	timeout?: number;
+	/** Working directory */
+	cwd?: string;
 }
 
 /** API passed to custom tool factory (stable across session changes) */
diff --git a/packages/coding-agent/test/compaction-hooks-example.test.ts b/packages/coding-agent/test/compaction-hooks-example.test.ts
index 0d200702..126cb1a6 100644
--- a/packages/coding-agent/test/compaction-hooks-example.test.ts
+++ b/packages/coding-agent/test/compaction-hooks-example.test.ts
@@ -9,11 +9,13 @@ describe("Documentation example", () => {
 	it("custom compaction example should type-check correctly", () => {
 		// This is the example from hooks.md - verify it compiles
 		const exampleHook = (pi: HookAPI) => {
-			pi.on("session", async (event, _ctx) => {
+			pi.on("session", async (event, ctx) => {
 				if (event.reason !== "before_compact") return;
 
 				// After narrowing, these should all be accessible
-				const { preparation, previousCompactions, sessionManager, modelRegistry, model } = event;
+				// sessionManager and modelRegistry come from ctx, not event
+				const { preparation, previousCompactions, model } = event;
+				const { sessionManager, modelRegistry } = ctx;
 				const { messagesToSummarize, messagesToKeep, tokensBefore, firstKeptEntryId, cutPoint } = preparation;
 
 				// Get previous summary from most recent compaction
diff --git a/packages/coding-agent/test/compaction-hooks.test.ts b/packages/coding-agent/test/compaction-hooks.test.ts
index 6e9a071d..66d21b3d 100644
--- a/packages/coding-agent/test/compaction-hooks.test.ts
+++ b/packages/coding-agent/test/compaction-hooks.test.ts
@@ -91,7 +91,7 @@ describe.skipIf(!API_KEY)("Compaction hooks", () => {
 		const authStorage = new AuthStorage(join(tempDir, "auth.json"));
 		const modelRegistry = new ModelRegistry(authStorage);
 
-		hookRunner = new HookRunner(hooks, tempDir);
+		hookRunner = new HookRunner(hooks, tempDir, sessionManager, modelRegistry);
 		hookRunner.setUIContext(
 			{
 				select: async () => null,
@@ -101,7 +101,6 @@ describe.skipIf(!API_KEY)("Compaction hooks", () => {
 			},
 			false,
 		);
-		hookRunner.setSessionFile(sessionManager.getSessionFile() ?? null);
 
 		session = new AgentSession({
 			agent,
@@ -140,8 +139,7 @@ describe.skipIf(!API_KEY)("Compaction hooks", () => {
 			expect(beforeEvent.preparation.messagesToKeep).toBeDefined();
 			expect(beforeEvent.preparation.tokensBefore).toBeGreaterThanOrEqual(0);
 			expect(beforeEvent.model).toBeDefined();
-			expect(beforeEvent.sessionManager).toBeDefined();
-			expect(beforeEvent.modelRegistry).toBeDefined();
+			// sessionManager and modelRegistry are now on ctx, not event
 		}
 
 		const afterEvent = compactEvents[0];
@@ -217,8 +215,9 @@ describe.skipIf(!API_KEY)("Compaction hooks", () => {
 
 		const afterEvent = compactEvents[0];
 		if (afterEvent.reason === "compact") {
-			const entries = afterEvent.sessionManager.getEntries();
-			const hasCompactionEntry = entries.some((e) => e.type === "compaction");
+			// sessionManager is now on ctx, use session.sessionManager directly
+			const entries = session.sessionManager.getEntries();
+			const hasCompactionEntry = entries.some((e: { type: string }) => e.type === "compaction");
 			expect(hasCompactionEntry).toBe(true);
 		}
 	}, 120000);
@@ -361,9 +360,12 @@ describe.skipIf(!API_KEY)("Compaction hooks", () => {
 		expect(event.model).toHaveProperty("provider");
 		expect(event.model).toHaveProperty("id");
 
-		expect(typeof event.modelRegistry.getApiKey).toBe("function");
+		// sessionManager and modelRegistry are now on ctx, not event
+		// Verify they're accessible via session
+		expect(typeof session.sessionManager.getEntries).toBe("function");
+		expect(typeof session.modelRegistry.getApiKey).toBe("function");
 
-		const entries = event.sessionManager.getEntries();
+		const entries = session.sessionManager.getEntries();
 		expect(Array.isArray(entries)).toBe(true);
 		expect(entries.length).toBeGreaterThan(0);
 	}, 120000);