diff --git a/packages/opencode/src/session/system.ts b/packages/opencode/src/session/system.ts
index cd08986de6..fa9c126aa5 100644
--- a/packages/opencode/src/session/system.ts
+++ b/packages/opencode/src/session/system.ts
@@ -34,6 +34,23 @@ export namespace SystemPrompt {
   // kilocode_change end
 
   export function provider(model: Provider.Model) {
+    // kilocode_change start
+    switch (model.prompt) {
+      case "anthropic":
+        return [PROMPT_ANTHROPIC]
+      case "anthropic_without_todo":
+        return [PROMPT_DEFAULT]
+      case "beast":
+        return [PROMPT_BEAST]
+      case "codex":
+        return [PROMPT_CODEX]
+      case "gemini":
+        return [PROMPT_GEMINI]
+      case "trinity":
+        return [PROMPT_TRINITY]
+    }
+    // kilocode_change end
+
     if (model.api.id.includes("gpt-4") || model.api.id.includes("o1") || model.api.id.includes("o3"))
       return [PROMPT_BEAST]
     if (model.api.id.includes("gpt")) {
diff --git a/packages/opencode/test/kilocode/system-prompt.test.ts b/packages/opencode/test/kilocode/system-prompt.test.ts
new file mode 100644
index 0000000000..69b4b2ac1a
--- /dev/null
+++ b/packages/opencode/test/kilocode/system-prompt.test.ts
@@ -0,0 +1,70 @@
+import { describe, expect, test } from "bun:test"
+import { SystemPrompt } from "../../src/session/system"
+import { ProviderTest } from "../fake/provider"
+
+import PROMPT_ANTHROPIC from "../../src/session/prompt/anthropic.txt"
+import PROMPT_DEFAULT from "../../src/session/prompt/default.txt"
+import PROMPT_BEAST from "../../src/session/prompt/beast.txt"
+import PROMPT_CODEX from "../../src/session/prompt/codex.txt"
+import PROMPT_GEMINI from "../../src/session/prompt/gemini.txt"
+import PROMPT_TRINITY from "../../src/session/prompt/trinity.txt"
+
+describe("SystemPrompt.provider", () => {
+  describe("model.prompt override", () => {
+    test("anthropic prompt is selected when model.prompt is 'anthropic'", () => {
+      const model = ProviderTest.model({ prompt: "anthropic" })
+      const result = SystemPrompt.provider(model)
+      expect(result).toEqual([PROMPT_ANTHROPIC])
+    })
+
+    test("default prompt is selected when model.prompt is 'anthropic_without_todo'", () => {
+      const model = ProviderTest.model({ prompt: "anthropic_without_todo" })
+      const result = SystemPrompt.provider(model)
+      expect(result).toEqual([PROMPT_DEFAULT])
+    })
+
+    test("beast prompt is selected when model.prompt is 'beast'", () => {
+      const model = ProviderTest.model({ prompt: "beast" })
+      const result = SystemPrompt.provider(model)
+      expect(result).toEqual([PROMPT_BEAST])
+    })
+
+    test("codex prompt is selected when model.prompt is 'codex'", () => {
+      const model = ProviderTest.model({ prompt: "codex" })
+      const result = SystemPrompt.provider(model)
+      expect(result).toEqual([PROMPT_CODEX])
+    })
+
+    test("gemini prompt is selected when model.prompt is 'gemini'", () => {
+      const model = ProviderTest.model({ prompt: "gemini" })
+      const result = SystemPrompt.provider(model)
+      expect(result).toEqual([PROMPT_GEMINI])
+    })
+
+    test("trinity prompt is selected when model.prompt is 'trinity'", () => {
+      const model = ProviderTest.model({ prompt: "trinity" })
+      const result = SystemPrompt.provider(model)
+      expect(result).toEqual([PROMPT_TRINITY])
+    })
+
+    test("model.prompt takes precedence over model.api.id heuristic", () => {
+      // A model whose api.id contains "claude" (which would match anthropic via heuristic)
+      // but has prompt set to "beast" — prompt should win
+      const model = ProviderTest.model({
+        prompt: "beast",
+        api: { id: "anthropic/claude-4-opus", url: "https://example.com", npm: "@ai-sdk/anthropic" },
+      })
+      const result = SystemPrompt.provider(model)
+      expect(result).toEqual([PROMPT_BEAST])
+    })
+
+    test("model.api.id heuristic is used when model.prompt is undefined", () => {
+      const model = ProviderTest.model({
+        prompt: undefined,
+        api: { id: "anthropic/claude-4-opus", url: "https://example.com", npm: "@ai-sdk/anthropic" },
+      })
+      const result = SystemPrompt.provider(model)
+      expect(result).toEqual([PROMPT_ANTHROPIC])
+    })
+  })
+})