feat(server): add HTTP API response compression (#26440)

packages/opencode/src/server/routes/instance/httpapi/middleware/compression.ts

@@ -0,0 +1,64 @@
+import { deflateSync, gzipSync } from "node:zlib"
+import { Effect } from "effect"
+import { HttpBody, HttpRouter, HttpServerRequest, HttpServerResponse } from "effect/unstable/http"
+
+// Mirror of Hono's compressible content-type set so wire behavior matches.
+const COMPRESSIBLE_CONTENT_TYPE_REGEX =
+  /^\s*(?:text\/(?!event-stream(?:[;\s]|$))[^;\s]+|application\/(?:javascript|json|xml|xml-dtd|ecmascript|dart|postscript|rtf|tar|toml|vnd\.dart|vnd\.ms-fontobject|vnd\.ms-opentype|wasm|x-httpd-php|x-javascript|x-ns-proxy-autoconfig|x-sh|x-tar|x-www-form-urlencoded)|font\/(?:otf|ttf)|image\/(?:bmp|vnd\.adobe\.photoshop|vnd\.microsoft\.icon|vnd\.ms-dds|x-icon|x-ms-bmp)|message\/rfc822|model\/gltf-binary|x-shader\/x-fragment|x-shader\/x-vertex|[^;\s]+?\+(?:json|text|xml|yaml))(?:[;\s]|$)/i
+
+const NO_TRANSFORM_REGEX = /(?:^|,)\s*?no-transform\s*?(?:,|$)/i
+
+const STREAMING_PATHS = new Set(["/event", "/global/event"])
+const STREAMING_POST_REGEX = /^\/session\/[^/]+\/(?:message|prompt_async)$/
+
+const THRESHOLD_BYTES = 1024
+
+type Encoding = "gzip" | "deflate"
+
+function pickEncoding(acceptEncoding: string | undefined): Encoding | undefined {
+  if (!acceptEncoding) return undefined
+  const lower = acceptEncoding.toLowerCase()
+  if (lower.includes("gzip")) return "gzip"
+  if (lower.includes("deflate")) return "deflate"
+  return undefined
+}
+
+function pathOf(url: string): string {
+  const queryIndex = url.indexOf("?")
+  return queryIndex === -1 ? url : url.slice(0, queryIndex)
+}
+
+export const compressionLayer = HttpRouter.middleware<{ handles: unknown }>()((effect) =>
+  Effect.gen(function* () {
+    const response = yield* effect
+    const request = yield* HttpServerRequest.HttpServerRequest
+
+    if (request.method === "HEAD") return response
+    if (response.headers["content-encoding"]) return response
+    if (response.headers["transfer-encoding"]) return response
+
+    const body = response.body
+    if (body._tag !== "Uint8Array") return response
+    if (body.body.byteLength < THRESHOLD_BYTES) return response
+
+    const cacheControl = response.headers["cache-control"]
+    if (cacheControl && NO_TRANSFORM_REGEX.test(cacheControl)) return response
+
+    const path = pathOf(request.url)
+    if (STREAMING_PATHS.has(path)) return response
+    if (request.method === "POST" && STREAMING_POST_REGEX.test(path)) return response
+
+    const contentType = body.contentType
+    if (!COMPRESSIBLE_CONTENT_TYPE_REGEX.test(contentType)) return response
+
+    const encoding = pickEncoding(request.headers["accept-encoding"])
+    if (!encoding) return response
+
+    const compressed = encoding === "gzip" ? gzipSync(body.body) : deflateSync(body.body)
+    return HttpServerResponse.setHeader(
+      HttpServerResponse.setBody(response, HttpBody.uint8Array(compressed, contentType)),
+      "content-encoding",
+      encoding,
+    )
+  }),
+).layer

packages/opencode/src/server/routes/instance/httpapi/server.ts

@@ -81,6 +81,7 @@ import { workspaceRouterMiddleware, workspaceRoutingLayer } from "./middleware/w
 import { disposeMiddleware } from "./lifecycle"
 import { memoMap } from "@opencode-ai/core/effect/memo-map"
 import * as ServerBackend from "@/server/backend"
+import { compressionLayer } from "./middleware/compression"
 import { errorLayer } from "./middleware/error"
 import { fenceLayer } from "./middleware/fence"
 
@@ -174,6 +175,7 @@ export function createRoutes(corsOptions?: CorsOptions) {
   return Layer.mergeAll(rootApiRoutes, eventApiRoutes, instanceRoutes, docRoute, uiRoute).pipe(
     Layer.provide([
       errorLayer,
+      compressionLayer,
       fenceLayer,
       cors(corsOptions),
       runtime,

packages/opencode/test/server/httpapi-compression.test.ts

@@ -0,0 +1,159 @@
+import { afterEach, describe, expect, test } from "bun:test"
+import { gunzipSync, inflateSync } from "node:zlib"
+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, tmpdir } 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() {
+  Flag.OPENCODE_EXPERIMENTAL_HTTPAPI = true
+  return Server.Default().app
+}
+
+// /config echoes the config back. Padding the config pushes the response body
+// well past the 1024 B threshold so we can observe compression behavior.
+function fatConfig() {
+  const instructions: string[] = []
+  for (let i = 0; i < 50; i++) {
+    instructions.push(`padding-instruction-${i}-${"x".repeat(40)}`)
+  }
+  return {
+    formatter: false,
+    lsp: false,
+    username: "compression-test-user",
+    instructions,
+  }
+}
+
+describe("HttpApi compression", () => {
+  describe("encodes responses", () => {
+    test("gzips JSON when Accept-Encoding includes gzip and body exceeds threshold", async () => {
+      await using tmp = await tmpdir({ config: fatConfig() })
+      const response = await app().request("/config", {
+        headers: { "x-opencode-directory": tmp.path, "accept-encoding": "gzip" },
+      })
+      expect(response.status).toBe(200)
+      expect(response.headers.get("content-encoding")).toBe("gzip")
+      const compressed = new Uint8Array(await response.arrayBuffer())
+      const decompressed = gunzipSync(compressed)
+      const json = JSON.parse(new TextDecoder().decode(decompressed))
+      expect(json).toMatchObject({ username: "compression-test-user" })
+      expect(compressed.byteLength).toBeLessThan(decompressed.byteLength)
+    })
+
+    test("uses deflate when only deflate is acceptable", async () => {
+      await using tmp = await tmpdir({ config: fatConfig() })
+      const response = await app().request("/config", {
+        headers: { "x-opencode-directory": tmp.path, "accept-encoding": "deflate" },
+      })
+      expect(response.status).toBe(200)
+      expect(response.headers.get("content-encoding")).toBe("deflate")
+      const compressed = new Uint8Array(await response.arrayBuffer())
+      const decompressed = inflateSync(compressed)
+      const json = JSON.parse(new TextDecoder().decode(decompressed))
+      expect(json).toMatchObject({ username: "compression-test-user" })
+    })
+
+    test("prefers gzip when both gzip and deflate are acceptable", async () => {
+      await using tmp = await tmpdir({ config: fatConfig() })
+      const response = await app().request("/config", {
+        headers: { "x-opencode-directory": tmp.path, "accept-encoding": "gzip, deflate" },
+      })
+      expect(response.headers.get("content-encoding")).toBe("gzip")
+    })
+
+    test("does not include the original Content-Length when compressed", async () => {
+      await using tmp = await tmpdir({ config: fatConfig() })
+      const response = await app().request("/config", {
+        headers: { "x-opencode-directory": tmp.path, "accept-encoding": "gzip" },
+      })
+      const compressed = new Uint8Array(await response.arrayBuffer())
+      const declared = response.headers.get("content-length")
+      // Either absent (transfer-encoding chunked) or matches the compressed length.
+      if (declared !== null) expect(Number(declared)).toBe(compressed.byteLength)
+    })
+  })
+
+  describe("skips", () => {
+    test("when no Accept-Encoding header is present", async () => {
+      await using tmp = await tmpdir({ config: fatConfig() })
+      const response = await app().request("/config", {
+        headers: { "x-opencode-directory": tmp.path },
+      })
+      expect(response.headers.get("content-encoding")).toBeNull()
+    })
+
+    test("when Accept-Encoding only allows unsupported encodings", async () => {
+      await using tmp = await tmpdir({ config: fatConfig() })
+      const response = await app().request("/config", {
+        headers: { "x-opencode-directory": tmp.path, "accept-encoding": "br" },
+      })
+      expect(response.headers.get("content-encoding")).toBeNull()
+    })
+
+    test("when the response body is below the 1024-byte threshold", async () => {
+      // A bare config produces a tiny response (~few hundred bytes).
+      await using tmp = await tmpdir({ config: { formatter: false, lsp: false } })
+      const response = await app().request("/config", {
+        headers: { "x-opencode-directory": tmp.path, "accept-encoding": "gzip" },
+      })
+      expect(response.status).toBe(200)
+      const body = new Uint8Array(await response.arrayBuffer())
+      expect(body.byteLength).toBeLessThan(1024)
+      expect(response.headers.get("content-encoding")).toBeNull()
+    })
+
+    test("HEAD requests", async () => {
+      await using tmp = await tmpdir({ config: fatConfig() })
+      const response = await app().request("/config", {
+        method: "HEAD",
+        headers: { "x-opencode-directory": tmp.path, "accept-encoding": "gzip" },
+      })
+      expect(response.headers.get("content-encoding")).toBeNull()
+    })
+  })
+
+  describe("streaming exclusions", () => {
+    test("/event SSE is not compressed", async () => {
+      await using tmp = await tmpdir({ config: { formatter: false, lsp: false } })
+      const controller = new AbortController()
+      const response = await app().request("/event", {
+        headers: { "x-opencode-directory": tmp.path, "accept-encoding": "gzip" },
+        signal: controller.signal,
+      })
+      try {
+        expect(response.status).toBe(200)
+        expect(response.headers.get("content-encoding")).toBeNull()
+      } finally {
+        controller.abort()
+        await response.body?.cancel().catch(() => {})
+      }
+    })
+
+    test("/global/event SSE is not compressed", async () => {
+      const controller = new AbortController()
+      const response = await app().request("/global/event", {
+        headers: { "accept-encoding": "gzip" },
+        signal: controller.signal,
+      })
+      try {
+        expect(response.status).toBe(200)
+        expect(response.headers.get("content-encoding")).toBeNull()
+      } finally {
+        controller.abort()
+        await response.body?.cancel().catch(() => {})
+      }
+    })
+  })
+})