feat(no-sisyphus-gpt): allow Sisyphus with GPT-5.4 model

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-opencode)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

src/hooks/no-sisyphus-gpt/hook.ts

@@ -1,5 +1,5 @@
 import type { PluginInput } from "@opencode-ai/plugin"
-import { isGptModel } from "../../agents/types"
+import { isGptModel, isGpt5_4Model } from "../../agents/types"
 import { getSessionAgent, updateSessionAgent } from "../../features/claude-code-session-state"
 import { log } from "../../shared"
 import { getAgentConfigKey, getAgentDisplayName } from "../../shared/agent-display-names"
@@ -7,8 +7,8 @@ import { getAgentConfigKey, getAgentDisplayName } from "../../shared/agent-displ
 const TOAST_TITLE = "NEVER Use Sisyphus with GPT"
 const TOAST_MESSAGE = [
   "Sisyphus works best with Claude Opus, and works fine with Kimi/GLM models.",
-  "Do NOT use Sisyphus with GPT.",
+  "Do NOT use Sisyphus with GPT (except GPT-5.4 which has specialized support).",
-  "For GPT models, always use Hephaestus.",
+  "For GPT models (other than 5.4), always use Hephaestus.",
 ].join("\n")
 const HEPHAESTUS_DISPLAY = getAgentDisplayName("hephaestus")
 
@@ -41,7 +41,7 @@ export function createNoSisyphusGptHook(ctx: PluginInput) {
       const agentKey = getAgentConfigKey(rawAgent)
       const modelID = input.model?.modelID
 
-      if (agentKey === "sisyphus" && modelID && isGptModel(modelID)) {
+      if (agentKey === "sisyphus" && modelID && isGptModel(modelID) && !isGpt5_4Model(modelID)) {
         showToast(ctx, input.sessionID)
         input.agent = HEPHAESTUS_DISPLAY
         if (output?.message) {

src/hooks/no-sisyphus-gpt/index.test.ts

@@ -43,12 +43,33 @@ describe("no-sisyphus-gpt hook", () => {
     expect(showToast.mock.calls[0]?.[0]).toMatchObject({
       body: {
         title: "NEVER Use Sisyphus with GPT",
-        message: expect.stringContaining("For GPT models, always use Hephaestus."),
+        message: expect.stringContaining("For GPT models (other than 5.4), always use Hephaestus."),
         variant: "error",
       },
     })
   })
 
+  test("does not show toast for gpt-5.4 model (Sisyphus has specialized support)", async () => {
+    // given - sisyphus with gpt-5.4 model (should be allowed)
+    const showToast = spyOn({ fn: async () => ({}) }, "fn")
+    const hook = createNoSisyphusGptHook({
+      client: { tui: { showToast } },
+    } as any)
+
+    const output = createOutput()
+
+    // when - chat.message runs with gpt-5.4
+    await hook["chat.message"]?.({
+      sessionID: "ses_gpt54",
+      agent: SISYPHUS_DISPLAY,
+      model: { providerID: "openai", modelID: "gpt-5.4" },
+    }, output)
+
+    // then - no toast, agent NOT switched to Hephaestus
+    expect(showToast).toHaveBeenCalledTimes(0)
+    expect(output.message.agent).toBeUndefined()
+  })
+
   test("does not show toast for non-gpt model", async () => {
     // given - sisyphus with claude model
     const showToast = spyOn({ fn: async () => ({}) }, "fn")