From 6b904421b742bcfd45f2e605c0320b0ae5fffda7 Mon Sep 17 00:00:00 2001
From: Icewind52 <williamtang83@hotmail.com>
Date: Sun, 22 Feb 2026 03:30:49 -0800
Subject: [PATCH] feat: add /v1/responses endpoint for Codex CLI support

- Add passthrough proxy to Copilot's /responses backend
- Filter unsupported tools (e.g. web_search) before forwarding
- Register /v1/responses route in server.ts
- Enables models like gpt-5.3-codex that require the Responses API

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
---
 src/routes/responses/handler.ts | 85 +++++++++++++++++++++++++++++++++
 src/routes/responses/route.ts   | 15 ++++++
 src/server.ts                   |  4 ++
 3 files changed, 104 insertions(+)
 create mode 100644 src/routes/responses/handler.ts
 create mode 100644 src/routes/responses/route.ts

diff --git a/src/routes/responses/handler.ts b/src/routes/responses/handler.ts
new file mode 100644
index 000000000..bf944007b
--- /dev/null
+++ b/src/routes/responses/handler.ts
@@ -0,0 +1,85 @@
+import type { Context } from "hono"
+
+import consola from "consola"
+import { stream as honoStream } from "hono/streaming"
+
+import { copilotHeaders, copilotBaseUrl } from "~/lib/api-config"
+import { awaitApproval } from "~/lib/approval"
+import { HTTPError } from "~/lib/error"
+import { checkRateLimit } from "~/lib/rate-limit"
+import { state } from "~/lib/state"
+
+interface ResponsesTool {
+  type: string
+  [key: string]: unknown
+}
+
+interface ResponsesPayload {
+  model: string
+  input: unknown
+  stream?: boolean
+  tools?: Array<ResponsesTool>
+  [key: string]: unknown
+}
+
+export async function handleResponse(c: Context) {
+  await checkRateLimit(state)
+
+  if (!state.copilotToken) throw new Error("Copilot token not found")
+
+  const payload = await c.req.json<ResponsesPayload>()
+  consola.debug("Responses API payload:", JSON.stringify(payload).slice(-400))
+
+  if (state.manualApprove) {
+    await awaitApproval()
+  }
+
+  const headers: Record<string, string> = {
+    ...copilotHeaders(state),
+    "X-Initiator": "user",
+  }
+
+  // Strip tools not supported by Copilot backend (e.g. web_search)
+  if (Array.isArray(payload.tools)) {
+    payload.tools = payload.tools.filter((t) => t.type === "function")
+    if (payload.tools.length === 0) delete payload.tools
+  }
+
+  const response = await fetch(`${copilotBaseUrl(state)}/responses`, {
+    method: "POST",
+    headers,
+    body: JSON.stringify(payload),
+  })
+
+  if (!response.ok) {
+    consola.error("Failed to create response", response)
+    throw new HTTPError("Failed to create response", response)
+  }
+
+  // If streaming, pipe through the raw SSE stream
+  if (payload.stream) {
+    c.header("Content-Type", "text/event-stream")
+    c.header("Cache-Control", "no-cache")
+    c.header("Connection", "keep-alive")
+
+    return honoStream(c, async (stream) => {
+      const body = response.body as ReadableStream<Uint8Array> | null
+      const reader = body?.getReader()
+      if (!reader) return
+
+      try {
+        for (;;) {
+          const result = await reader.read()
+          if (result.done) break
+          await stream.write(result.value)
+        }
+      } finally {
+        reader.releaseLock()
+      }
+    })
+  }
+
+  // Non-streaming: return JSON directly
+  const result: unknown = await response.json()
+  return c.json(result as Record<string, unknown>)
+}
diff --git a/src/routes/responses/route.ts b/src/routes/responses/route.ts
new file mode 100644
index 000000000..e1f9d0b3c
--- /dev/null
+++ b/src/routes/responses/route.ts
@@ -0,0 +1,15 @@
+import { Hono } from "hono"
+
+import { forwardError } from "~/lib/error"
+
+import { handleResponse } from "./handler"
+
+export const responsesRoutes = new Hono()
+
+responsesRoutes.post("/", async (c) => {
+  try {
+    return await handleResponse(c)
+  } catch (error) {
+    return await forwardError(c, error)
+  }
+})
diff --git a/src/server.ts b/src/server.ts
index 462a278f3..d1fad2ecc 100644
--- a/src/server.ts
+++ b/src/server.ts
@@ -6,6 +6,7 @@ import { completionRoutes } from "./routes/chat-completions/route"
 import { embeddingRoutes } from "./routes/embeddings/route"
 import { messageRoutes } from "./routes/messages/route"
 import { modelRoutes } from "./routes/models/route"
+import { responsesRoutes } from "./routes/responses/route"
 import { tokenRoute } from "./routes/token/route"
 import { usageRoute } from "./routes/usage/route"
 
@@ -29,3 +30,6 @@ server.route("/v1/embeddings", embeddingRoutes)
 
 // Anthropic compatible endpoints
 server.route("/v1/messages", messageRoutes)
+
+// OpenAI Responses API compatible endpoint
+server.route("/v1/responses", responsesRoutes)