fix(acp): resolve session/load across legacy session directories

session/load and session/resume resolved a session only within the
directory re-derived from cwd (SessionManager.list(cwd)), so sessions
stored under the legacy/hashed project-directory scheme (17.2.5+,
reverted in #7656) were unreachable and threw "ACP session not found"
despite existing on disk.

#findStoredSession now falls back to a global by-id scan (listAll,
already used by the fork path) when the cwd-scoped lookup misses. The
session id is globally unique and #openStoredSession reopens the file
with the request cwd, so no directory-scheme knowledge is needed.

Fixes #7779

packages/coding-agent/CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## [Unreleased]
 
+### Fixed
+
+- Fixed ACP `session/load` and `session/resume` failing with `ACP session not found` for sessions created under the legacy/hashed project-directory scheme (17.2.5+, reverted in #7656): the lookup only scanned the directory re-derived from `cwd`, so sessions stored under a differently-named directory were unreachable. It now falls back to a global by-id scan (the same one the fork path already uses) when the cwd-scoped lookup misses ([#7779](https://github.com/can1357/oh-my-pi/issues/7779)).
+
 ## [17.2.9] - 2026-08-05
 
 ### Breaking Changes

packages/coding-agent/src/modes/acp/acp-agent.ts

@@ -2019,7 +2019,16 @@ export class AcpAgent implements Agent {
 
 	async #findStoredSession(sessionId: string, cwd: string): Promise<StoredSessionInfo | undefined> {
 		const sessions = await this.#listStoredSessions(cwd);
-		return sessions.find(session => session.id === sessionId);
+		const scoped = sessions.find(session => session.id === sessionId);
+		if (scoped) {
+			return scoped;
+		}
+		// The cwd-derived directory only covers sessions stored under the current
+		// naming scheme. Sessions written under a legacy/hashed project directory
+		// (the 17.2.5+ scheme reverted in #7656) live elsewhere, so fall back to a
+		// global by-id scan: the session id is globally unique, and
+		// #openStoredSession reopens the file with the request cwd. See #7779.
+		return this.#findStoredSessionById(sessionId);
 	}
 
 	async #findStoredSessionById(sessionId: string): Promise<StoredSessionInfo | undefined> {

packages/coding-agent/test/acp-agent.test.ts

@@ -1104,6 +1104,48 @@ describe("ACP agent", () => {
 		await Bun.sleep(0);
 	});
 
+	it("loads a session stored under a legacy/hashed project directory (#7779)", async () => {
+		const harness = await createHarness();
+		const stored = new FakeAgentSession(harness.cwdA);
+		harness.sessions.push(stored);
+		stored.sessionManager.appendMessage({ role: "user", content: "legacy hello", timestamp: Date.now() });
+		stored.sessionManager.appendMessage(makeAssistantMessage("legacy reply"));
+		await stored.sessionManager.ensureOnDisk();
+		await stored.sessionManager.flush();
+
+		const sessionFile = stored.sessionManager.getSessionFile();
+		if (!sessionFile) throw new Error("session file not persisted");
+		const sessionId = stored.sessionId;
+		// Release the writer so the directory can be renamed out from under it.
+		await stored.dispose();
+
+		// Simulate the hashed-directory era (#7397, reverted in #7656): the
+		// session file lives under a project directory whose name the current
+		// cwd->dir scheme would never produce, so the cwd-scoped scan misses it.
+		const cwdDerivedDir = path.dirname(sessionFile);
+		const sessionsRoot = path.dirname(cwdDerivedDir);
+		const hashedDir = path.join(sessionsRoot, `home-cwd-a-${"a".repeat(64)}`);
+		await fs.promises.rename(cwdDerivedDir, hashedDir);
+
+		const loaded = await harness.agent.loadSession({
+			sessionId,
+			cwd: harness.cwdA,
+			mcpServers: [],
+		});
+		expectAcpStructure(zLoadSessionResponse, loaded);
+
+		const replayChunks = harness.updates.filter(
+			update =>
+				update.sessionId === sessionId &&
+				(update.update.sessionUpdate === "user_message_chunk" ||
+					update.update.sessionUpdate === "agent_message_chunk"),
+		);
+		expect(replayChunks.length).toBeGreaterThan(0);
+
+		harness.abortController.abort();
+		await Bun.sleep(0);
+	});
+
 	it("delivers the final visible answer when agent_end overtakes the assistant message_end (#4902)", async () => {
 		const harness = await createHarness();
 		const created = await harness.agent.newSession({ cwd: harness.cwdA, mcpServers: [] });