fix(server): include Origin in CORS preflight Vary header (#26445)

packages/opencode/test/server/httpapi-cors-vary.test.ts

@@ -0,0 +1,82 @@
+import { afterEach, describe, expect, test } from "bun:test"
+import { Flag } from "@opencode-ai/core/flag/flag"
+import * as Log from "@opencode-ai/core/util/log"
+import { Server } from "../../src/server/server"
+import { resetDatabase } from "../fixture/db"
+import { disposeAllInstances } from "../fixture/fixture"
+
+void Log.init({ print: false })
+
+const original = Flag.OPENCODE_EXPERIMENTAL_HTTPAPI
+
+afterEach(async () => {
+  Flag.OPENCODE_EXPERIMENTAL_HTTPAPI = original
+  await disposeAllInstances()
+  await resetDatabase()
+})
+
+function app(experimental: boolean) {
+  Flag.OPENCODE_EXPERIMENTAL_HTTPAPI = experimental
+  return experimental ? Server.Default().app : Server.Legacy().app
+}
+
+const PREFLIGHT_HEADERS = {
+  origin: "http://localhost:3000",
+  "access-control-request-method": "POST",
+  "access-control-request-headers": "content-type, x-opencode-directory",
+}
+
+// effect-smol's HttpMiddleware.cors overwrites `Vary: Origin` with
+// `Vary: Access-Control-Request-Headers` on OPTIONS preflight responses
+// (the two share the same record key during the spread). With dynamic
+// origin echoing, missing Vary: Origin lets shared caches serve a preflight
+// cached for one origin against a different origin. corsVaryFixLayer
+// restores the merged form.
+describe("CORS preflight Vary header", () => {
+  test("Hono backend preflight Vary contains Origin", async () => {
+    const response = await app(false).request("/global/config", {
+      method: "OPTIONS",
+      headers: PREFLIGHT_HEADERS,
+    })
+
+    expect([200, 204]).toContain(response.status)
+    expect(response.headers.get("access-control-allow-origin")).toBe("http://localhost:3000")
+    expect((response.headers.get("vary") ?? "").toLowerCase()).toContain("origin")
+  })
+
+  test("HTTP API backend preflight Vary contains Origin", async () => {
+    const response = await app(true).request("/global/config", {
+      method: "OPTIONS",
+      headers: PREFLIGHT_HEADERS,
+    })
+
+    expect([200, 204]).toContain(response.status)
+    expect(response.headers.get("access-control-allow-origin")).toBe("http://localhost:3000")
+    expect((response.headers.get("vary") ?? "").toLowerCase()).toContain("origin")
+  })
+
+  test("HTTP API backend preflight Vary still preserves Access-Control-Request-Headers", async () => {
+    const response = await app(true).request("/global/config", {
+      method: "OPTIONS",
+      headers: PREFLIGHT_HEADERS,
+    })
+
+    const vary = (response.headers.get("vary") ?? "").toLowerCase()
+    expect(vary).toContain("origin")
+    expect(vary).toContain("access-control-request-headers")
+  })
+
+  test("HTTP API backend does not duplicate Origin in Vary", async () => {
+    const response = await app(true).request("/global/config", {
+      method: "OPTIONS",
+      headers: PREFLIGHT_HEADERS,
+    })
+
+    const vary = response.headers.get("vary") ?? ""
+    const originCount = vary
+      .split(",")
+      .map((s) => s.trim().toLowerCase())
+      .filter((s) => s === "origin").length
+    expect(originCount).toBe(1)
+  })
+})