diff --git a/packages/types/src/providers/openai-codex.ts b/packages/types/src/providers/openai-codex.ts
index f8d9bd25df..fd1d80198c 100644
--- a/packages/types/src/providers/openai-codex.ts
+++ b/packages/types/src/providers/openai-codex.ts
@@ -16,7 +16,7 @@ import type { ModelInfo } from "../model.js"
 
 export type OpenAiCodexModelId = keyof typeof openAiCodexModels
 
-export const openAiCodexDefaultModelId: OpenAiCodexModelId = "gpt-5.3-codex"
+export const openAiCodexDefaultModelId: OpenAiCodexModelId = "gpt-5.4"
 
 /**
  * Models available through the Codex OAuth flow.
@@ -24,6 +24,21 @@ export const openAiCodexDefaultModelId: OpenAiCodexModelId = "gpt-5.3-codex"
  * Costs are 0 as they are covered by the subscription.
  */
 export const openAiCodexModels = {
+	"gpt-5.4": {
+		maxTokens: 128000,
+		contextWindow: 1_050_000,
+		includedTools: ["apply_patch"],
+		excludedTools: ["apply_diff", "write_to_file"],
+		supportsImages: true,
+		supportsPromptCache: true,
+		supportsReasoningEffort: ["none", "low", "medium", "high", "xhigh"],
+		reasoningEffort: "none",
+		inputPrice: 0,
+		outputPrice: 0,
+		supportsVerbosity: true,
+		supportsTemperature: false,
+		description: "GPT-5.4: Most capable model with upfront planning and deep reasoning via ChatGPT subscription",
+	},
 	"gpt-5.1-codex-max": {
 		maxTokens: 128000,
 		contextWindow: 400000,
@@ -119,7 +134,7 @@ export const openAiCodexModels = {
 		excludedTools: ["apply_diff", "write_to_file"],
 		supportsImages: true,
 		supportsPromptCache: true,
-		supportsReasoningEffort: ["minimal", "low", "medium", "high"],
+		supportsReasoningEffort: ["none", "low", "medium", "high"],
 		reasoningEffort: "medium",
 		// Subscription-based: no per-token costs
 		inputPrice: 0,
diff --git a/src/api/providers/__tests__/openai-codex.spec.ts b/src/api/providers/__tests__/openai-codex.spec.ts
index 2e164fe469..2e4ad110dd 100644
--- a/src/api/providers/__tests__/openai-codex.spec.ts
+++ b/src/api/providers/__tests__/openai-codex.spec.ts
@@ -3,27 +3,42 @@
 import { OpenAiCodexHandler } from "../openai-codex"
 
 describe("OpenAiCodexHandler.getModel", () => {
-	it.each(["gpt-5.1", "gpt-5", "gpt-5.1-codex", "gpt-5-codex", "gpt-5-codex-mini", "gpt-5.3-codex-spark"])(
-		"should return specified model when a valid model id is provided: %s",
-		(apiModelId) => {
-			const handler = new OpenAiCodexHandler({ apiModelId })
-			const model = handler.getModel()
-
-			expect(model.id).toBe(apiModelId)
-			expect(model.info).toBeDefined()
-			// Default reasoning effort for GPT-5 family
-			expect(model.info.reasoningEffort).toBe("medium")
-		},
-	)
+	it.each([
+		"gpt-5.1",
+		"gpt-5",
+		"gpt-5.1-codex",
+		"gpt-5-codex",
+		"gpt-5-codex-mini",
+		"gpt-5.3-codex-spark",
+	])("should return specified model when a valid model id is provided: %s", (apiModelId) => {
+		const handler = new OpenAiCodexHandler({ apiModelId })
+		const model = handler.getModel()
+
+		expect(model.id).toBe(apiModelId)
+		expect(model.info).toBeDefined()
+		// Default reasoning effort for GPT-5 family
+		expect(model.info.reasoningEffort).toBe("medium")
+	})
 
 	it("should fall back to default model when an invalid model id is provided", () => {
 		const handler = new OpenAiCodexHandler({ apiModelId: "not-a-real-model" })
 		const model = handler.getModel()
 
-		expect(model.id).toBe("gpt-5.3-codex")
+		expect(model.id).toBe("gpt-5.4")
 		expect(model.info).toBeDefined()
 	})
 
+	it("should use GPT-5.4 with thinking/non-thinking reasoning effort levels", () => {
+		const handler = new OpenAiCodexHandler({ apiModelId: "gpt-5.4" })
+		const model = handler.getModel()
+
+		expect(model.id).toBe("gpt-5.4")
+		expect(model.info.contextWindow).toBe(1_050_000)
+		expect(model.info.supportsReasoningEffort).toContain("none")
+		expect(model.info.supportsReasoningEffort).toContain("xhigh")
+		expect(model.info.reasoningEffort).toBe("none")
+	})
+
 	it("should use Spark-specific limits and capabilities", () => {
 		const handler = new OpenAiCodexHandler({ apiModelId: "gpt-5.3-codex-spark" })
 		const model = handler.getModel()