fix(coding-agent): allow session id for no-session runs

closes #6070

packages/coding-agent/CHANGELOG.md

@@ -4,6 +4,7 @@
 
 ### Fixed
 
+- Fixed `--no-session --session-id` so ephemeral CLI runs can use deterministic session IDs for provider cache affinity ([#6070](https://github.com/earendil-works/pi/issues/6070)).
 - Fixed disk BMP image files to be detected, converted to PNG, and attached through `read` and CLI `@file` inputs ([#6047](https://github.com/earendil-works/pi/issues/6047)).
 - Fixed auto-retry for provider stream errors that explicitly tell callers to retry the request ([#6019](https://github.com/earendil-works/pi/issues/6019)).
 

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

@@ -1431,8 +1431,8 @@ export class SessionManager {
 	}
 
 	/** Create an in-memory session (no file persistence) */
-	static inMemory(cwd: string = process.cwd()): SessionManager {
-		return new SessionManager(cwd, "", undefined, false);
+	static inMemory(cwd: string = process.cwd(), options?: NewSessionOptions): SessionManager {
+		return new SessionManager(cwd, "", undefined, false, options);
 	}
 
 	/**

packages/coding-agent/src/main.ts

@@ -225,7 +225,6 @@ function validateSessionIdFlags(parsed: Args): void {
 		parsed.session ? "--session" : undefined,
 		parsed.continue ? "--continue" : undefined,
 		parsed.resume ? "--resume" : undefined,
-		parsed.noSession ? "--no-session" : undefined,
 	].filter((flag): flag is string => flag !== undefined);
 
 	if (conflictingFlags.length > 0) {
@@ -259,7 +258,7 @@ async function createSessionManager(
 	settingsManager: SettingsManager,
 ): Promise<SessionManager> {
 	if (parsed.noSession || parsed.help || parsed.listModels !== undefined) {
-		return SessionManager.inMemory(cwd);
+		return SessionManager.inMemory(cwd, parsed.sessionId !== undefined ? { id: parsed.sessionId } : undefined);
 	}
 
 	if (parsed.fork) {

packages/coding-agent/test/session-id-readonly.test.ts

@@ -108,6 +108,13 @@ describe("--session-id read-only commands", () => {
 		expect(hasSessionWithId(join(result.agentDir, "sessions"), "read-only-help")).toBe(false);
 	});
 
+	it("allows --no-session with --session-id", async () => {
+		const result = await runCli(["--no-session", "--session-id", "ephemeral-id", "--help"]);
+
+		expect(result.code).toBe(0);
+		expect(hasSessionWithId(join(result.agentDir, "sessions"), "ephemeral-id")).toBe(false);
+	});
+
 	it("does not reserve a session for --list-models", async () => {
 		const result = await runCli(["--session-id", "read-only-models", "--list-models"]);
 

packages/coding-agent/test/session-manager/custom-session-id.test.ts

@@ -13,6 +13,13 @@ describe("SessionManager.newSession with custom id", () => {
 		expect(session.getSessionId()).toBe("my-custom-id");
 	});
 
+	it("uses the provided id when creating an in-memory session", () => {
+		const session = SessionManager.inMemory(process.cwd(), { id: "memory-session-id" });
+		expect(session.getSessionId()).toBe("memory-session-id");
+		expect(session.getHeader()!.id).toBe("memory-session-id");
+		expect(session.getSessionFile()).toBeUndefined();
+	});
+
 	it("allows alphanumeric session ids with interior punctuation", () => {
 		const session = SessionManager.inMemory();
 		session.newSession({ id: "abc-123_def.456" });