feat(hooks): add no-hephaestus-non-gpt hook to enforce GPT-only for Hephaestus

src/hooks/no-hephaestus-non-gpt/hook.ts

@@ -0,0 +1,54 @@
+import type { PluginInput } from "@opencode-ai/plugin"
+import { isGptModel } from "../../agents/types"
+import { getSessionAgent, updateSessionAgent } from "../../features/claude-code-session-state"
+import { log } from "../../shared"
+import { getAgentConfigKey, getAgentDisplayName } from "../../shared/agent-display-names"
+
+const TOAST_TITLE = "NEVER Use Hephaestus with Non-GPT"
+const TOAST_MESSAGE = [
+  "Hephaestus is designed exclusively for GPT models.",
+  "Hephaestus + non-GPT performs worse than vanilla Sisyphus.",
+  "For Claude/Kimi/GLM models, always use Sisyphus.",
+].join("\n")
+const SISYPHUS_DISPLAY = getAgentDisplayName("sisyphus")
+
+function showToast(ctx: PluginInput, sessionID: string): void {
+  ctx.client.tui.showToast({
+    body: {
+      title: TOAST_TITLE,
+      message: TOAST_MESSAGE,
+      variant: "error",
+      duration: 10000,
+    },
+  }).catch((error) => {
+    log("[no-hephaestus-non-gpt] Failed to show toast", {
+      sessionID,
+      error,
+    })
+  })
+}
+
+export function createNoHephaestusNonGptHook(ctx: PluginInput) {
+  return {
+    "chat.message": async (input: {
+      sessionID: string
+      agent?: string
+      model?: { providerID: string; modelID: string }
+    }, output?: {
+      message?: { agent?: string; [key: string]: unknown }
+    }): Promise<void> => {
+      const rawAgent = input.agent ?? getSessionAgent(input.sessionID) ?? ""
+      const agentKey = getAgentConfigKey(rawAgent)
+      const modelID = input.model?.modelID
+
+      if (agentKey === "hephaestus" && modelID && !isGptModel(modelID)) {
+        showToast(ctx, input.sessionID)
+        input.agent = SISYPHUS_DISPLAY
+        if (output?.message) {
+          output.message.agent = SISYPHUS_DISPLAY
+        }
+        updateSessionAgent(input.sessionID, SISYPHUS_DISPLAY)
+      }
+    },
+  }
+}