move spoof prompt to support anthropic with custom modes (#1031)

packages/opencode/src/session/index.ts

@@ -17,6 +17,7 @@ import {
 
 import PROMPT_INITIALIZE from "../session/prompt/initialize.txt"
 import PROMPT_PLAN from "../session/prompt/plan.txt"
+import PROMPT_ANTHROPIC_SPOOF from "../session/prompt/anthropic_spoof.txt"
 
 import { App } from "../app/app"
 import { Bus } from "../bus"
@@ -546,7 +547,8 @@ export namespace Session {
     msgs.push({ info: userMsg, parts: userParts })
 
     const mode = await Mode.get(input.mode ?? "build")
-    let system = mode.prompt ? [mode.prompt] : SystemPrompt.provider(input.providerID, input.modelID)
+    let system = input.providerID === "anthropic" ? [PROMPT_ANTHROPIC_SPOOF.trim()] : []
+    system.push(...(mode.prompt ? [mode.prompt] : SystemPrompt.provider(input.modelID)))
     system.push(...(await SystemPrompt.environment()))
     system.push(...(await SystemPrompt.custom()))
     // max 2 system prompt messages for caching purposes

packages/opencode/src/session/system.ts

@@ -14,8 +14,7 @@ import PROMPT_SUMMARIZE from "./prompt/summarize.txt"
 import PROMPT_TITLE from "./prompt/title.txt"
 
 export namespace SystemPrompt {
-  export function provider(providerID: string, modelID: string) {
-    if (providerID === "anthropic") return [PROMPT_ANTHROPIC_SPOOF.trim(), PROMPT_ANTHROPIC]
+  export function provider(modelID: string) {
     if (modelID.includes("gpt-") || modelID.includes("o1") || modelID.includes("o3")) return [PROMPT_BEAST]
     if (modelID.includes("gemini-")) return [PROMPT_GEMINI]
     return [PROMPT_ANTHROPIC]