fix: align OpenAI cache affinity and use uuidv7 session ids

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

@@ -1,6 +1,11 @@
+import { mkdtempSync, writeFileSync } from "node:fs";
+import { tmpdir } from "node:os";
+import { join } from "node:path";
 import { describe, expect, it } from "vitest";
 import { SessionManager } from "../../src/core/session-manager.js";
 
+const UUID_V7_RE = /^[0-9a-f]{8}-[0-9a-f]{4}-7[0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-9a-f]{12}$/;
+
 describe("SessionManager.newSession with custom id", () => {
 	it("uses the provided id instead of generating one", () => {
 		const session = SessionManager.inMemory();
@@ -8,20 +13,22 @@ describe("SessionManager.newSession with custom id", () => {
 		expect(session.getSessionId()).toBe("my-custom-id");
 	});
 
-	it("generates a random id when no id is provided", () => {
+	it("generates a UUIDv7 id when no id is provided", () => {
 		const session = SessionManager.inMemory();
 		session.newSession();
 		const id = session.getSessionId();
 		expect(id).toBeDefined();
 		expect(id).not.toBe("");
+		expect(id).toMatch(UUID_V7_RE);
 	});
 
-	it("generates a random id when options is provided without id", () => {
+	it("generates a UUIDv7 id when options is provided without id", () => {
 		const session = SessionManager.inMemory();
 		session.newSession({ parentSession: "parent.jsonl" });
 		const id = session.getSessionId();
 		expect(id).toBeDefined();
 		expect(id).not.toBe("");
+		expect(id).toMatch(UUID_V7_RE);
 	});
 
 	it("includes the custom id in the session header", () => {
@@ -32,4 +39,71 @@ describe("SessionManager.newSession with custom id", () => {
 		expect(header).not.toBeNull();
 		expect(header!.id).toBe("header-test-id");
 	});
+
+	it("generates a UUIDv7 id when constructed without an explicit id", () => {
+		const session = SessionManager.inMemory();
+		expect(session.getSessionId()).toMatch(UUID_V7_RE);
+		expect(session.getHeader()!.id).toBe(session.getSessionId());
+	});
+
+	it("generates a UUIDv7 id when creating a branched session", () => {
+		const session = SessionManager.inMemory();
+		const firstId = session.appendMessage({
+			role: "user",
+			content: [{ type: "text", text: "hello" }],
+			timestamp: Date.now(),
+		});
+
+		session.createBranchedSession(firstId);
+
+		expect(session.getSessionId()).toMatch(UUID_V7_RE);
+		expect(session.getHeader()!.id).toBe(session.getSessionId());
+	});
+
+	it("generates a UUIDv7 id when forking from another session file", () => {
+		const tempDir = mkdtempSync(join(tmpdir(), "pi-session-manager-"));
+		const sourcePath = join(tempDir, "source.jsonl");
+		writeFileSync(
+			sourcePath,
+			`${[
+				JSON.stringify({
+					type: "session",
+					version: 3,
+					id: "legacy-session-id",
+					timestamp: new Date().toISOString(),
+					cwd: tempDir,
+				}),
+				JSON.stringify({
+					type: "message",
+					id: "entry-1",
+					parentId: null,
+					timestamp: new Date().toISOString(),
+					message: {
+						role: "assistant",
+						content: [{ type: "text", text: "hello" }],
+						api: "openai-responses",
+						provider: "openai",
+						model: "gpt-5.4",
+						usage: {
+							input: 0,
+							output: 0,
+							cacheRead: 0,
+							cacheWrite: 0,
+							totalTokens: 0,
+							cost: { input: 0, output: 0, cacheRead: 0, cacheWrite: 0, total: 0 },
+						},
+						stopReason: "stop",
+						timestamp: Date.now(),
+					},
+				}),
+			].join("\n")}
+`,
+		);
+
+		const forked = SessionManager.forkFrom(sourcePath, tempDir, tempDir);
+		const header = forked.getHeader();
+		expect(header).not.toBeNull();
+		expect(header!.id).toMatch(UUID_V7_RE);
+		expect(header!.parentSession).toBe(sourcePath);
+	});
 });