support gpt 5.5

Author: betaHi

README.md

@@ -215,6 +215,7 @@ New endpoints for monitoring your Copilot usage and quotas.
 | Model | Status | Notes |
 | ----- | ------ | ----- |
 | `gpt-5.4` | Supported | Uses the standard GPT-5 chat/completions path. |
+| `gpt-5.5` | Supported | Uses the standard GPT-5 chat/completions path and resolves upstream snapshots such as `gpt-5.5-2026-04-23`. |
 | `gpt-5.3-codex` | Supported | Uses the Responses API bridge internally. |
 | `gpt-5.4-mini` | Supported | Uses the Responses API bridge internally. |
 | `claude-opus-4.7` | Supported | Snapshot aliases such as `claude-opus-4-7-20260417` resolve to this model, with `low`, `medium`, `high`, `xhigh`, and `max` effort support. |
@@ -230,6 +231,7 @@ Reasoning effort is model-specific.
 | Model | Supported values | Default |
 | ----- | ---------------- | ------- |
 | `gpt-5.4` | `low`, `medium`, `high`, `xhigh` | `medium` |
+| `gpt-5.5` | `none`, `low`, `medium`, `high`, `xhigh` | `medium` |
 | `gpt-5.3-codex` | `low`, `medium`, `high`, `xhigh` | `medium` |
 | `gpt-5.4-mini` | `none`, `low`, `medium` | `medium` |
 | `claude-opus-4.7` | `low`, `medium`, `high`, `xhigh`, `max` | `medium` |

src/services/copilot/create-chat-completions.ts

@@ -38,6 +38,10 @@ const getAllowedReasoningEfforts = (
 ): Array<
   Exclude<ChatCompletionsPayload["reasoning_effort"], null | undefined>
 > => {
+  if (modelId.startsWith("gpt-5.5")) {
+    return ["none", "low", "medium", "high", "xhigh"]
+  }
+
   if (modelId.startsWith("gpt-5.4-mini")) {
     return ["none", "low", "medium"]
   }

tests/anthropic-request.test.ts

@@ -122,6 +122,23 @@ describe("Anthropic model resolution", () => {
     expect(openAIPayload.model).toBe("gpt-5")
   })
 
+  test("should resolve GPT-5.5 aliases to the GPT-5 Copilot model", () => {
+    state.models = {
+      object: "list",
+      data: [createModel("gpt-5"), createModel("gpt-5-mini")],
+    }
+
+    const anthropicPayload: AnthropicMessagesPayload = {
+      model: "gpt-5.5",
+      messages: [{ role: "user", content: "Hello!" }],
+      max_tokens: 0,
+    }
+
+    const openAIPayload = translateToOpenAI(anthropicPayload)
+
+    expect(openAIPayload.model).toBe("gpt-5")
+  })
+
   test("should resolve Claude snapshot aliases to the base Copilot model", () => {
     state.models = {
       object: "list",

tests/create-chat-completions.test.ts

@@ -13,6 +13,10 @@ state.copilotToken = "test-token"
 state.vsCodeVersion = "1.0.0"
 state.accountType = "individual"
 
+const isolatedHome = path.join(os.tmpdir(), "copilot-api-test-home")
+await mkdir(isolatedHome, { recursive: true })
+process.env.HOME = isolatedHome
+
 const createMockResponse = (jsonBody: unknown, ok: boolean = true) => ({
   ok,
   status: ok ? 200 : 400,
@@ -41,11 +45,9 @@ const fetchMock = mock(
 afterEach(() => {
   fetchMock.mockClear()
   delete process.env.COPILOT_REASONING_EFFORT
-  process.env.HOME = originalHome
+  process.env.HOME = isolatedHome
 })
 
-const originalHome = process.env.HOME
-
 test("sets X-Initiator to agent if tool/assistant present", async () => {
   const payload: ChatCompletionsPayload = {
     messages: [
@@ -96,6 +98,45 @@ test("uses max_completion_tokens for GPT-5 family models", async () => {
   expect(body.max_tokens).toBeUndefined()
 })
 
+test("uses max_completion_tokens for gpt-5.5 with explicit reasoning effort", async () => {
+  const payload: ChatCompletionsPayload = {
+    messages: [{ role: "user", content: "hi" }],
+    model: "gpt-5.5",
+    max_tokens: 384,
+    reasoning_effort: "high",
+  }
+
+  await createChatCompletions(payload)
+
+  expect(fetchMock).toHaveBeenCalled()
+  const body = JSON.parse(
+    (fetchMock.mock.calls[0][1] as { body: string }).body,
+  ) as Record<string, unknown>
+
+  expect(body.max_completion_tokens).toBe(384)
+  expect(body.max_tokens).toBeUndefined()
+  expect(body.reasoning_effort).toBe("high")
+})
+
+test("passes through reasoning_effort none for gpt-5.5", async () => {
+  const payload: ChatCompletionsPayload = {
+    messages: [{ role: "user", content: "hi" }],
+    model: "gpt-5.5",
+    max_tokens: 128,
+    reasoning_effort: "none",
+  }
+
+  await createChatCompletions(payload)
+
+  expect(fetchMock).toHaveBeenCalled()
+  const body = JSON.parse(
+    (fetchMock.mock.calls[0][1] as { body: string }).body,
+  ) as Record<string, unknown>
+
+  expect(body.max_completion_tokens).toBe(128)
+  expect(body.reasoning_effort).toBe("none")
+})
+
 test("uses max_completion_tokens for gpt-5.3-codex", async () => {
   fetchMock.mockImplementationOnce(
     (_url: string, opts: { headers: Record<string, string>; body?: string }) =>
@@ -271,6 +312,42 @@ test("keeps max_tokens for non GPT-5 models", async () => {
   expect(body.max_completion_tokens).toBeUndefined()
 })
 
+test("keeps max_tokens and omits reasoning_effort for gemini-3.1-pro-preview", async () => {
+  const payload: ChatCompletionsPayload = {
+    messages: [{ role: "user", content: "hi" }],
+    model: "gemini-3.1-pro-preview",
+    max_tokens: 256,
+  }
+
+  await createChatCompletions(payload)
+
+  const body = JSON.parse(
+    (fetchMock.mock.calls[0][1] as { body: string }).body,
+  ) as Record<string, unknown>
+
+  expect(body.max_tokens).toBe(256)
+  expect(body.max_completion_tokens).toBeUndefined()
+  expect(body.reasoning_effort).toBeUndefined()
+})
+
+test("keeps max_tokens and omits reasoning_effort for gemini-3-flash-preview", async () => {
+  const payload: ChatCompletionsPayload = {
+    messages: [{ role: "user", content: "hi" }],
+    model: "gemini-3-flash-preview",
+    max_tokens: 256,
+  }
+
+  await createChatCompletions(payload)
+
+  const body = JSON.parse(
+    (fetchMock.mock.calls[0][1] as { body: string }).body,
+  ) as Record<string, unknown>
+
+  expect(body.max_tokens).toBe(256)
+  expect(body.max_completion_tokens).toBeUndefined()
+  expect(body.reasoning_effort).toBeUndefined()
+})
+
 test("passes through explicit reasoning_effort for GPT-5 family models", async () => {
   const payload: ChatCompletionsPayload = {
     messages: [{ role: "user", content: "hi" }],
@@ -559,6 +636,42 @@ test("uses COPILOT_REASONING_EFFORT from Claude settings.json", async () => {
   }
 })
 
+test("uses COPILOT_REASONING_EFFORT from Claude settings.json for gpt-5.5", async () => {
+  const tempHome = await mkdtemp(path.join(os.tmpdir(), "claude-settings-"))
+  const claudeDirectory = path.join(tempHome, ".claude")
+
+  try {
+    await mkdir(claudeDirectory, { recursive: true })
+    await writeFile(
+      path.join(claudeDirectory, "settings.json"),
+      JSON.stringify({
+        env: {
+          COPILOT_REASONING_EFFORT: "none",
+        },
+      }),
+    )
+
+    process.env.HOME = tempHome
+
+    const payload: ChatCompletionsPayload = {
+      messages: [{ role: "user", content: "hi" }],
+      model: "gpt-5.5",
+      max_tokens: 128,
+    }
+
+    await createChatCompletions(payload)
+
+    const body = JSON.parse(
+      (fetchMock.mock.calls[0][1] as { body: string }).body,
+    ) as Record<string, unknown>
+
+    expect(body.max_completion_tokens).toBe(128)
+    expect(body.reasoning_effort).toBe("none")
+  } finally {
+    await rm(tempHome, { recursive: true, force: true })
+  }
+})
+
 test("uses COPILOT_REASONING_EFFORT from Claude settings.json for claude-opus-4.7", async () => {
   const tempHome = await mkdtemp(path.join(os.tmpdir(), "claude-settings-"))
   const claudeDirectory = path.join(tempHome, ".claude")