diff --git a/src/cli/__snapshots__/model-fallback.test.ts.snap b/src/cli/__snapshots__/model-fallback.test.ts.snap
index 819e1b79c..47dba5ebc 100644
--- a/src/cli/__snapshots__/model-fallback.test.ts.snap
+++ b/src/cli/__snapshots__/model-fallback.test.ts.snap
@@ -195,14 +195,16 @@ exports[`generateModelConfig single native provider uses OpenAI models when only
       "variant": "medium",
     },
     "explore": {
-      "model": "opencode/gpt-5-nano",
+      "model": "openai/gpt-5.4",
+      "variant": "medium",
     },
     "hephaestus": {
       "model": "openai/gpt-5.3-codex",
       "variant": "medium",
     },
     "librarian": {
-      "model": "opencode/glm-4.7-free",
+      "model": "openai/gpt-5.4",
+      "variant": "medium",
     },
     "metis": {
       "model": "openai/gpt-5.4",
@@ -230,12 +232,17 @@ exports[`generateModelConfig single native provider uses OpenAI models when only
     },
   },
   "categories": {
+    "artistry": {
+      "model": "openai/gpt-5.4",
+      "variant": "xhigh",
+    },
     "deep": {
       "model": "openai/gpt-5.3-codex",
       "variant": "medium",
     },
     "quick": {
-      "model": "opencode/glm-4.7-free",
+      "model": "openai/gpt-5.3-codex",
+      "variant": "low",
     },
     "ultrabrain": {
       "model": "openai/gpt-5.3-codex",
@@ -250,10 +257,12 @@ exports[`generateModelConfig single native provider uses OpenAI models when only
       "variant": "medium",
     },
     "visual-engineering": {
-      "model": "opencode/glm-4.7-free",
+      "model": "openai/gpt-5.4",
+      "variant": "high",
     },
     "writing": {
-      "model": "opencode/glm-4.7-free",
+      "model": "openai/gpt-5.4",
+      "variant": "medium",
     },
   },
 }
@@ -268,14 +277,16 @@ exports[`generateModelConfig single native provider uses OpenAI models with isMa
       "variant": "medium",
     },
     "explore": {
-      "model": "opencode/gpt-5-nano",
+      "model": "openai/gpt-5.4",
+      "variant": "medium",
     },
     "hephaestus": {
       "model": "openai/gpt-5.3-codex",
       "variant": "medium",
     },
     "librarian": {
-      "model": "opencode/glm-4.7-free",
+      "model": "openai/gpt-5.4",
+      "variant": "medium",
     },
     "metis": {
       "model": "openai/gpt-5.4",
@@ -303,12 +314,17 @@ exports[`generateModelConfig single native provider uses OpenAI models with isMa
     },
   },
   "categories": {
+    "artistry": {
+      "model": "openai/gpt-5.4",
+      "variant": "xhigh",
+    },
     "deep": {
       "model": "openai/gpt-5.3-codex",
       "variant": "medium",
     },
     "quick": {
-      "model": "opencode/glm-4.7-free",
+      "model": "openai/gpt-5.3-codex",
+      "variant": "low",
     },
     "ultrabrain": {
       "model": "openai/gpt-5.3-codex",
@@ -323,10 +339,12 @@ exports[`generateModelConfig single native provider uses OpenAI models with isMa
       "variant": "medium",
     },
     "visual-engineering": {
-      "model": "opencode/glm-4.7-free",
+      "model": "openai/gpt-5.4",
+      "variant": "high",
     },
     "writing": {
-      "model": "opencode/glm-4.7-free",
+      "model": "openai/gpt-5.4",
+      "variant": "medium",
     },
   },
 }
diff --git a/src/cli/model-fallback.test.ts b/src/cli/model-fallback.test.ts
index dcc83e023..39bc73f50 100644
--- a/src/cli/model-fallback.test.ts
+++ b/src/cli/model-fallback.test.ts
@@ -344,15 +344,16 @@ describe("generateModelConfig", () => {
       expect(result.agents?.explore?.model).toBe("anthropic/claude-haiku-4-5")
     })
 
-    test("explore uses gpt-5-nano when only OpenAI available", () => {
+    test("explore uses OpenAI model when only OpenAI available", () => {
       // #given only OpenAI is available
       const config = createConfig({ hasOpenAI: true })
 
       // #when generateModelConfig is called
       const result = generateModelConfig(config)
 
-      // #then explore should use gpt-5-nano (fallback)
-      expect(result.agents?.explore?.model).toBe("opencode/gpt-5-nano")
+      // #then explore should use native OpenAI model
+      expect(result.agents?.explore?.model).toBe("openai/gpt-5.4")
+      expect(result.agents?.explore?.variant).toBe("medium")
     })
 
     test("explore uses gpt-5-mini when only Copilot available", () => {
diff --git a/src/cli/model-fallback.ts b/src/cli/model-fallback.ts
index ffa9925d8..3b9c917ef 100644
--- a/src/cli/model-fallback.ts
+++ b/src/cli/model-fallback.ts
@@ -5,6 +5,7 @@ import {
 import type { InstallConfig } from "./types"
 
 import type { AgentConfig, CategoryConfig, GeneratedOmoConfig } from "./model-fallback-types"
+import { applyOpenAiOnlyModelCatalog, isOpenAiOnlyAvailability } from "./openai-only-model-catalog"
 import { toProviderAvailability } from "./provider-availability"
 import {
 	getSisyphusFallbackChain,
@@ -122,11 +123,15 @@ export function generateModelConfig(config: InstallConfig): GeneratedOmoConfig {
     }
   }
 
-  return {
+  const generatedConfig: GeneratedOmoConfig = {
     $schema: SCHEMA_URL,
     agents,
     categories,
   }
+
+  return isOpenAiOnlyAvailability(avail)
+    ? applyOpenAiOnlyModelCatalog(generatedConfig)
+    : generatedConfig
 }
 
 export function shouldShowChatGPTOnlyWarning(config: InstallConfig): boolean {
diff --git a/src/cli/openai-only-model-catalog.test.ts b/src/cli/openai-only-model-catalog.test.ts
new file mode 100644
index 000000000..ee56d2d06
--- /dev/null
+++ b/src/cli/openai-only-model-catalog.test.ts
@@ -0,0 +1,46 @@
+import { describe, expect, test } from "bun:test"
+
+import { generateModelConfig } from "./model-fallback"
+import type { InstallConfig } from "./types"
+
+function createConfig(overrides: Partial<InstallConfig> = {}): InstallConfig {
+  return {
+    hasClaude: false,
+    isMax20: false,
+    hasOpenAI: false,
+    hasGemini: false,
+    hasCopilot: false,
+    hasOpencodeZen: false,
+    hasZaiCodingPlan: false,
+    hasKimiForCoding: false,
+    ...overrides,
+  }
+}
+
+describe("generateModelConfig OpenAI-only model catalog", () => {
+  test("fills remaining OpenAI-only agent gaps with OpenAI models", () => {
+    // #given
+    const config = createConfig({ hasOpenAI: true })
+
+    // #when
+    const result = generateModelConfig(config)
+
+    // #then
+    expect(result.agents?.explore).toEqual({ model: "openai/gpt-5.4", variant: "medium" })
+    expect(result.agents?.librarian).toEqual({ model: "openai/gpt-5.4", variant: "medium" })
+  })
+
+  test("fills remaining OpenAI-only category gaps with OpenAI models", () => {
+    // #given
+    const config = createConfig({ hasOpenAI: true })
+
+    // #when
+    const result = generateModelConfig(config)
+
+    // #then
+    expect(result.categories?.artistry).toEqual({ model: "openai/gpt-5.4", variant: "xhigh" })
+    expect(result.categories?.quick).toEqual({ model: "openai/gpt-5.3-codex", variant: "low" })
+    expect(result.categories?.["visual-engineering"]).toEqual({ model: "openai/gpt-5.4", variant: "high" })
+    expect(result.categories?.writing).toEqual({ model: "openai/gpt-5.4", variant: "medium" })
+  })
+})
diff --git a/src/cli/openai-only-model-catalog.ts b/src/cli/openai-only-model-catalog.ts
new file mode 100644
index 000000000..52e8484e1
--- /dev/null
+++ b/src/cli/openai-only-model-catalog.ts
@@ -0,0 +1,39 @@
+import type { AgentConfig, CategoryConfig, GeneratedOmoConfig, ProviderAvailability } from "./model-fallback-types"
+
+const OPENAI_ONLY_AGENT_OVERRIDES: Record<string, AgentConfig> = {
+  explore: { model: "openai/gpt-5.4", variant: "medium" },
+  librarian: { model: "openai/gpt-5.4", variant: "medium" },
+}
+
+const OPENAI_ONLY_CATEGORY_OVERRIDES: Record<string, CategoryConfig> = {
+  artistry: { model: "openai/gpt-5.4", variant: "xhigh" },
+  quick: { model: "openai/gpt-5.3-codex", variant: "low" },
+  "visual-engineering": { model: "openai/gpt-5.4", variant: "high" },
+  writing: { model: "openai/gpt-5.4", variant: "medium" },
+}
+
+export function isOpenAiOnlyAvailability(availability: ProviderAvailability): boolean {
+  return (
+    availability.native.openai &&
+    !availability.native.claude &&
+    !availability.native.gemini &&
+    !availability.opencodeZen &&
+    !availability.copilot &&
+    !availability.zai &&
+    !availability.kimiForCoding
+  )
+}
+
+export function applyOpenAiOnlyModelCatalog(config: GeneratedOmoConfig): GeneratedOmoConfig {
+  return {
+    ...config,
+    agents: {
+      ...config.agents,
+      ...OPENAI_ONLY_AGENT_OVERRIDES,
+    },
+    categories: {
+      ...config.categories,
+      ...OPENAI_ONLY_CATEGORY_OVERRIDES,
+    },
+  }
+}