diff --git a/src/agents/types.test.ts b/src/agents/types.test.ts
new file mode 100644
index 00000000..186eddd1
--- /dev/null
+++ b/src/agents/types.test.ts
@@ -0,0 +1,49 @@
+import { describe, test, expect } from "bun:test";
+import { isGptModel } from "./types";
+
+describe("isGptModel", () => {
+  test("standard openai provider models", () => {
+    expect(isGptModel("openai/gpt-5.2")).toBe(true);
+    expect(isGptModel("openai/gpt-4o")).toBe(true);
+    expect(isGptModel("openai/o1")).toBe(true);
+    expect(isGptModel("openai/o3-mini")).toBe(true);
+  });
+
+  test("github copilot gpt models", () => {
+    expect(isGptModel("github-copilot/gpt-5.2")).toBe(true);
+    expect(isGptModel("github-copilot/gpt-4o")).toBe(true);
+  });
+
+  test("litellm proxied gpt models", () => {
+    expect(isGptModel("litellm/gpt-5.2")).toBe(true);
+    expect(isGptModel("litellm/gpt-4o")).toBe(true);
+    expect(isGptModel("litellm/o1")).toBe(true);
+    expect(isGptModel("litellm/o3-mini")).toBe(true);
+    expect(isGptModel("litellm/o4-mini")).toBe(true);
+  });
+
+  test("other proxied gpt models", () => {
+    expect(isGptModel("ollama/gpt-4o")).toBe(true);
+    expect(isGptModel("custom-provider/gpt-5.2")).toBe(true);
+  });
+
+  test("gpt4 prefix without hyphen (legacy naming)", () => {
+    expect(isGptModel("litellm/gpt4o")).toBe(true);
+    expect(isGptModel("ollama/gpt4")).toBe(true);
+  });
+
+  test("claude models are not gpt", () => {
+    expect(isGptModel("anthropic/claude-opus-4-6")).toBe(false);
+    expect(isGptModel("anthropic/claude-sonnet-4-5")).toBe(false);
+    expect(isGptModel("litellm/anthropic.claude-opus-4-5")).toBe(false);
+  });
+
+  test("gemini models are not gpt", () => {
+    expect(isGptModel("google/gemini-3-pro")).toBe(false);
+    expect(isGptModel("litellm/gemini-3-pro")).toBe(false);
+  });
+
+  test("opencode provider is not gpt", () => {
+    expect(isGptModel("opencode/claude-opus-4-6")).toBe(false);
+  });
+});
diff --git a/src/agents/types.ts b/src/agents/types.ts
index 14da69a1..92834883 100644
--- a/src/agents/types.ts
+++ b/src/agents/types.ts
@@ -66,8 +66,18 @@ export interface AgentPromptMetadata {
   keyTrigger?: string
 }
 
+function extractModelName(model: string): string {
+  return model.includes("/") ? model.split("/").pop() ?? model : model
+}
+
+const GPT_MODEL_PREFIXES = ["gpt-", "gpt4", "o1", "o3", "o4"]
+
 export function isGptModel(model: string): boolean {
-  return model.startsWith("openai/") || model.startsWith("github-copilot/gpt-")
+  if (model.startsWith("openai/") || model.startsWith("github-copilot/gpt-"))
+    return true
+
+  const modelName = extractModelName(model).toLowerCase()
+  return GPT_MODEL_PREFIXES.some((prefix) => modelName.startsWith(prefix))
 }
 
 export type BuiltinAgentName =
diff --git a/src/hooks/keyword-detector/ultrawork/source-detector.ts b/src/hooks/keyword-detector/ultrawork/source-detector.ts
index 2f0a897e..d49b8685 100644
--- a/src/hooks/keyword-detector/ultrawork/source-detector.ts
+++ b/src/hooks/keyword-detector/ultrawork/source-detector.ts
@@ -7,6 +7,8 @@
  * 3. Everything else (Claude, etc.) → default.ts
  */
 
+import { isGptModel } from "../../../agents/types"
+
 /**
  * Checks if agent is a planner-type agent.
  * Planners don't need ultrawork injection (they ARE the planner).
@@ -20,15 +22,7 @@ export function isPlannerAgent(agentName?: string): boolean {
   return /\bplan\b/.test(normalized)
 }
 
-/**
- * Checks if model is GPT 5.2 series.
- * GPT models benefit from specific prompting patterns.
- */
-export function isGptModel(modelID?: string): boolean {
-  if (!modelID) return false
-  const lowerModel = modelID.toLowerCase()
-  return lowerModel.includes("gpt")
-}
+export { isGptModel }
 
 /** Ultrawork message source type */
 export type UltraworkSource = "planner" | "gpt" | "default"
@@ -45,8 +39,8 @@ export function getUltraworkSource(
     return "planner"
   }
 
-  // Priority 2: GPT 5.2 models
-  if (isGptModel(modelID)) {
+  // Priority 2: GPT models
+  if (modelID && isGptModel(modelID)) {
     return "gpt"
   }