diff --git a/src/agents/utils.test.ts b/src/agents/utils.test.ts
index 87d6db761..b0280f52e 100644
--- a/src/agents/utils.test.ts
+++ b/src/agents/utils.test.ts
@@ -966,6 +966,28 @@ describe("createBuiltinAgents with requiresAnyModel gating (sisyphus)", () => {
       cacheSpy.mockRestore()
     }
   })
+
+  test("atlas and metis resolve to OpenAI in an OpenAI-only environment without a system default", async () => {
+    // #given
+    const fetchSpy = spyOn(shared, "fetchAvailableModels").mockResolvedValue(new Set(["openai/gpt-5.4"]))
+    const cacheSpy = spyOn(connectedProvidersCache, "readConnectedProvidersCache").mockReturnValue(["openai"])
+
+    try {
+      // #when
+      const agents = await createBuiltinAgents([], {}, undefined, undefined, undefined, undefined, [], {})
+
+      // #then
+      expect(agents.atlas).toBeDefined()
+      expect(agents.atlas.model).toBe("openai/gpt-5.4")
+      expect(agents.atlas.variant).toBe("medium")
+      expect(agents.metis).toBeDefined()
+      expect(agents.metis.model).toBe("openai/gpt-5.4")
+      expect(agents.metis.variant).toBe("high")
+    } finally {
+      fetchSpy.mockRestore()
+      cacheSpy.mockRestore()
+    }
+  })
 })
 
 describe("buildAgent with category and skills", () => {
diff --git a/src/cli/__snapshots__/model-fallback.test.ts.snap b/src/cli/__snapshots__/model-fallback.test.ts.snap
index 8602b7377..e20e589fc 100644
--- a/src/cli/__snapshots__/model-fallback.test.ts.snap
+++ b/src/cli/__snapshots__/model-fallback.test.ts.snap
@@ -69,7 +69,7 @@ exports[`generateModelConfig single native provider uses Claude models when only
   "$schema": "https://raw.githubusercontent.com/code-yeongyu/oh-my-openagent/dev/assets/oh-my-opencode.schema.json",
   "agents": {
     "atlas": {
-      "model": "anthropic/claude-sonnet-4-5",
+      "model": "anthropic/claude-sonnet-4-6",
     },
     "explore": {
       "model": "anthropic/claude-haiku-4-5",
@@ -110,17 +110,17 @@ exports[`generateModelConfig single native provider uses Claude models when only
       "variant": "max",
     },
     "unspecified-high": {
-      "model": "anthropic/claude-sonnet-4-5",
+      "model": "anthropic/claude-sonnet-4-6",
     },
     "unspecified-low": {
-      "model": "anthropic/claude-sonnet-4-5",
+      "model": "anthropic/claude-sonnet-4-6",
     },
     "visual-engineering": {
       "model": "anthropic/claude-opus-4-6",
       "variant": "max",
     },
     "writing": {
-      "model": "anthropic/claude-sonnet-4-5",
+      "model": "anthropic/claude-sonnet-4-6",
     },
   },
 }
@@ -131,7 +131,7 @@ exports[`generateModelConfig single native provider uses Claude models with isMa
   "$schema": "https://raw.githubusercontent.com/code-yeongyu/oh-my-openagent/dev/assets/oh-my-opencode.schema.json",
   "agents": {
     "atlas": {
-      "model": "anthropic/claude-sonnet-4-5",
+      "model": "anthropic/claude-sonnet-4-6",
     },
     "explore": {
       "model": "anthropic/claude-haiku-4-5",
@@ -176,14 +176,14 @@ exports[`generateModelConfig single native provider uses Claude models with isMa
       "variant": "max",
     },
     "unspecified-low": {
-      "model": "anthropic/claude-sonnet-4-5",
+      "model": "anthropic/claude-sonnet-4-6",
     },
     "visual-engineering": {
       "model": "anthropic/claude-opus-4-6",
       "variant": "max",
     },
     "writing": {
-      "model": "anthropic/claude-sonnet-4-5",
+      "model": "anthropic/claude-sonnet-4-6",
     },
   },
 }
@@ -194,7 +194,8 @@ exports[`generateModelConfig single native provider uses OpenAI models when only
   "$schema": "https://raw.githubusercontent.com/code-yeongyu/oh-my-openagent/dev/assets/oh-my-opencode.schema.json",
   "agents": {
     "atlas": {
-      "model": "opencode/glm-4.7-free",
+      "model": "openai/gpt-5.4",
+      "variant": "medium",
     },
     "explore": {
       "model": "openai/gpt-5.4",
@@ -209,7 +210,8 @@ exports[`generateModelConfig single native provider uses OpenAI models when only
       "variant": "medium",
     },
     "metis": {
-      "model": "opencode/glm-4.7-free",
+      "model": "openai/gpt-5.4",
+      "variant": "high",
     },
     "momus": {
       "model": "openai/gpt-5.4",
@@ -232,7 +234,8 @@ exports[`generateModelConfig single native provider uses OpenAI models when only
       "variant": "medium",
     },
     "sisyphus-junior": {
-      "model": "opencode/glm-4.7-free",
+      "model": "openai/gpt-5.4",
+      "variant": "medium",
     },
   },
   "categories": {
@@ -249,7 +252,7 @@ exports[`generateModelConfig single native provider uses OpenAI models when only
       "variant": "low",
     },
     "ultrabrain": {
-      "model": "openai/gpt-5.3-codex",
+      "model": "openai/gpt-5.4",
       "variant": "xhigh",
     },
     "unspecified-high": {
@@ -277,7 +280,8 @@ exports[`generateModelConfig single native provider uses OpenAI models with isMa
   "$schema": "https://raw.githubusercontent.com/code-yeongyu/oh-my-openagent/dev/assets/oh-my-opencode.schema.json",
   "agents": {
     "atlas": {
-      "model": "opencode/glm-4.7-free",
+      "model": "openai/gpt-5.4",
+      "variant": "medium",
     },
     "explore": {
       "model": "openai/gpt-5.4",
@@ -292,7 +296,8 @@ exports[`generateModelConfig single native provider uses OpenAI models with isMa
       "variant": "medium",
     },
     "metis": {
-      "model": "opencode/glm-4.7-free",
+      "model": "openai/gpt-5.4",
+      "variant": "high",
     },
     "momus": {
       "model": "openai/gpt-5.4",
@@ -315,7 +320,8 @@ exports[`generateModelConfig single native provider uses OpenAI models with isMa
       "variant": "medium",
     },
     "sisyphus-junior": {
-      "model": "opencode/glm-4.7-free",
+      "model": "openai/gpt-5.4",
+      "variant": "medium",
     },
   },
   "categories": {
@@ -332,7 +338,7 @@ exports[`generateModelConfig single native provider uses OpenAI models with isMa
       "variant": "low",
     },
     "ultrabrain": {
-      "model": "openai/gpt-5.3-codex",
+      "model": "openai/gpt-5.4",
       "variant": "xhigh",
     },
     "unspecified-high": {
@@ -480,7 +486,7 @@ exports[`generateModelConfig all native providers uses preferred models from fal
   "$schema": "https://raw.githubusercontent.com/code-yeongyu/oh-my-openagent/dev/assets/oh-my-opencode.schema.json",
   "agents": {
     "atlas": {
-      "model": "anthropic/claude-sonnet-4-5",
+      "model": "anthropic/claude-sonnet-4-6",
     },
     "explore": {
       "model": "anthropic/claude-haiku-4-5",
@@ -530,14 +536,14 @@ exports[`generateModelConfig all native providers uses preferred models from fal
       "model": "anthropic/claude-haiku-4-5",
     },
     "ultrabrain": {
-      "model": "openai/gpt-5.3-codex",
+      "model": "openai/gpt-5.4",
       "variant": "xhigh",
     },
     "unspecified-high": {
-      "model": "anthropic/claude-sonnet-4-5",
+      "model": "anthropic/claude-sonnet-4-6",
     },
     "unspecified-low": {
-      "model": "anthropic/claude-sonnet-4-5",
+      "model": "anthropic/claude-sonnet-4-6",
     },
     "visual-engineering": {
       "model": "google/gemini-3.1-pro-preview",
@@ -555,7 +561,7 @@ exports[`generateModelConfig all native providers uses preferred models with isM
   "$schema": "https://raw.githubusercontent.com/code-yeongyu/oh-my-openagent/dev/assets/oh-my-opencode.schema.json",
   "agents": {
     "atlas": {
-      "model": "anthropic/claude-sonnet-4-5",
+      "model": "anthropic/claude-sonnet-4-6",
     },
     "explore": {
       "model": "anthropic/claude-haiku-4-5",
@@ -605,15 +611,15 @@ exports[`generateModelConfig all native providers uses preferred models with isM
       "model": "anthropic/claude-haiku-4-5",
     },
     "ultrabrain": {
-      "model": "openai/gpt-5.3-codex",
+      "model": "openai/gpt-5.4",
       "variant": "xhigh",
     },
     "unspecified-high": {
-      "model": "openai/gpt-5.4",
-      "variant": "high",
+      "model": "anthropic/claude-opus-4-6",
+      "variant": "max",
     },
     "unspecified-low": {
-      "model": "anthropic/claude-sonnet-4-5",
+      "model": "anthropic/claude-sonnet-4-6",
     },
     "visual-engineering": {
       "model": "google/gemini-3.1-pro-preview",
@@ -631,7 +637,7 @@ exports[`generateModelConfig fallback providers uses OpenCode Zen models when on
   "$schema": "https://raw.githubusercontent.com/code-yeongyu/oh-my-openagent/dev/assets/oh-my-opencode.schema.json",
   "agents": {
     "atlas": {
-      "model": "opencode/claude-sonnet-4-5",
+      "model": "opencode/claude-sonnet-4-6",
     },
     "explore": {
       "model": "opencode/claude-haiku-4-5",
@@ -681,14 +687,14 @@ exports[`generateModelConfig fallback providers uses OpenCode Zen models when on
       "model": "opencode/claude-haiku-4-5",
     },
     "ultrabrain": {
-      "model": "opencode/gpt-5.3-codex",
+      "model": "opencode/gpt-5.4",
       "variant": "xhigh",
     },
     "unspecified-high": {
-      "model": "opencode/claude-sonnet-4-5",
+      "model": "opencode/claude-sonnet-4-6",
     },
     "unspecified-low": {
-      "model": "opencode/claude-sonnet-4-5",
+      "model": "opencode/claude-sonnet-4-6",
     },
     "visual-engineering": {
       "model": "opencode/gemini-3.1-pro",
@@ -706,7 +712,7 @@ exports[`generateModelConfig fallback providers uses OpenCode Zen models with is
   "$schema": "https://raw.githubusercontent.com/code-yeongyu/oh-my-openagent/dev/assets/oh-my-opencode.schema.json",
   "agents": {
     "atlas": {
-      "model": "opencode/claude-sonnet-4-5",
+      "model": "opencode/claude-sonnet-4-6",
     },
     "explore": {
       "model": "opencode/claude-haiku-4-5",
@@ -756,15 +762,15 @@ exports[`generateModelConfig fallback providers uses OpenCode Zen models with is
       "model": "opencode/claude-haiku-4-5",
     },
     "ultrabrain": {
-      "model": "opencode/gpt-5.3-codex",
+      "model": "opencode/gpt-5.4",
       "variant": "xhigh",
     },
     "unspecified-high": {
-      "model": "opencode/gpt-5.4",
-      "variant": "high",
+      "model": "opencode/claude-opus-4-6",
+      "variant": "max",
     },
     "unspecified-low": {
-      "model": "opencode/claude-sonnet-4-5",
+      "model": "opencode/claude-sonnet-4-6",
     },
     "visual-engineering": {
       "model": "opencode/gemini-3.1-pro",
@@ -782,11 +788,15 @@ exports[`generateModelConfig fallback providers uses GitHub Copilot models when
   "$schema": "https://raw.githubusercontent.com/code-yeongyu/oh-my-openagent/dev/assets/oh-my-opencode.schema.json",
   "agents": {
     "atlas": {
-      "model": "github-copilot/claude-sonnet-4.5",
+      "model": "github-copilot/claude-sonnet-4.6",
     },
     "explore": {
       "model": "github-copilot/gpt-5-mini",
     },
+    "hephaestus": {
+      "model": "github-copilot/gpt-5.4",
+      "variant": "medium",
+    },
     "metis": {
       "model": "github-copilot/claude-opus-4.6",
       "variant": "max",
@@ -796,7 +806,7 @@ exports[`generateModelConfig fallback providers uses GitHub Copilot models when
       "variant": "xhigh",
     },
     "multimodal-looker": {
-      "model": "opencode/glm-4.7-free",
+      "model": "github-copilot/gpt-5-nano",
     },
     "oracle": {
       "model": "github-copilot/gpt-5.4",
@@ -827,10 +837,10 @@ exports[`generateModelConfig fallback providers uses GitHub Copilot models when
       "variant": "high",
     },
     "unspecified-high": {
-      "model": "github-copilot/claude-sonnet-4.5",
+      "model": "github-copilot/claude-sonnet-4.6",
     },
     "unspecified-low": {
-      "model": "github-copilot/claude-sonnet-4.5",
+      "model": "github-copilot/claude-sonnet-4.6",
     },
     "visual-engineering": {
       "model": "github-copilot/gemini-3.1-pro-preview",
@@ -848,11 +858,15 @@ exports[`generateModelConfig fallback providers uses GitHub Copilot models with
   "$schema": "https://raw.githubusercontent.com/code-yeongyu/oh-my-openagent/dev/assets/oh-my-opencode.schema.json",
   "agents": {
     "atlas": {
-      "model": "github-copilot/claude-sonnet-4.5",
+      "model": "github-copilot/claude-sonnet-4.6",
     },
     "explore": {
       "model": "github-copilot/gpt-5-mini",
     },
+    "hephaestus": {
+      "model": "github-copilot/gpt-5.4",
+      "variant": "medium",
+    },
     "metis": {
       "model": "github-copilot/claude-opus-4.6",
       "variant": "max",
@@ -862,7 +876,7 @@ exports[`generateModelConfig fallback providers uses GitHub Copilot models with
       "variant": "xhigh",
     },
     "multimodal-looker": {
-      "model": "opencode/glm-4.7-free",
+      "model": "github-copilot/gpt-5-nano",
     },
     "oracle": {
       "model": "github-copilot/gpt-5.4",
@@ -893,11 +907,11 @@ exports[`generateModelConfig fallback providers uses GitHub Copilot models with
       "variant": "high",
     },
     "unspecified-high": {
-      "model": "github-copilot/gpt-5.4",
-      "variant": "high",
+      "model": "github-copilot/claude-opus-4.6",
+      "variant": "max",
     },
     "unspecified-low": {
-      "model": "github-copilot/claude-sonnet-4.5",
+      "model": "github-copilot/claude-sonnet-4.6",
     },
     "visual-engineering": {
       "model": "github-copilot/gemini-3.1-pro-preview",
@@ -1031,7 +1045,7 @@ exports[`generateModelConfig mixed provider scenarios uses Claude + OpenCode Zen
   "$schema": "https://raw.githubusercontent.com/code-yeongyu/oh-my-openagent/dev/assets/oh-my-opencode.schema.json",
   "agents": {
     "atlas": {
-      "model": "anthropic/claude-sonnet-4-5",
+      "model": "anthropic/claude-sonnet-4-6",
     },
     "explore": {
       "model": "anthropic/claude-haiku-4-5",
@@ -1081,14 +1095,14 @@ exports[`generateModelConfig mixed provider scenarios uses Claude + OpenCode Zen
       "model": "anthropic/claude-haiku-4-5",
     },
     "ultrabrain": {
-      "model": "opencode/gpt-5.3-codex",
+      "model": "opencode/gpt-5.4",
       "variant": "xhigh",
     },
     "unspecified-high": {
-      "model": "anthropic/claude-sonnet-4-5",
+      "model": "anthropic/claude-sonnet-4-6",
     },
     "unspecified-low": {
-      "model": "anthropic/claude-sonnet-4-5",
+      "model": "anthropic/claude-sonnet-4-6",
     },
     "visual-engineering": {
       "model": "opencode/gemini-3.1-pro",
@@ -1106,7 +1120,7 @@ exports[`generateModelConfig mixed provider scenarios uses OpenAI + Copilot comb
   "$schema": "https://raw.githubusercontent.com/code-yeongyu/oh-my-openagent/dev/assets/oh-my-opencode.schema.json",
   "agents": {
     "atlas": {
-      "model": "github-copilot/claude-sonnet-4.5",
+      "model": "github-copilot/claude-sonnet-4.6",
     },
     "explore": {
       "model": "github-copilot/gpt-5-mini",
@@ -1156,14 +1170,14 @@ exports[`generateModelConfig mixed provider scenarios uses OpenAI + Copilot comb
       "model": "github-copilot/claude-haiku-4.5",
     },
     "ultrabrain": {
-      "model": "openai/gpt-5.3-codex",
+      "model": "openai/gpt-5.4",
       "variant": "xhigh",
     },
     "unspecified-high": {
-      "model": "github-copilot/claude-sonnet-4.5",
+      "model": "github-copilot/claude-sonnet-4.6",
     },
     "unspecified-low": {
-      "model": "github-copilot/claude-sonnet-4.5",
+      "model": "github-copilot/claude-sonnet-4.6",
     },
     "visual-engineering": {
       "model": "github-copilot/gemini-3.1-pro-preview",
@@ -1181,7 +1195,7 @@ exports[`generateModelConfig mixed provider scenarios uses Claude + ZAI combinat
   "$schema": "https://raw.githubusercontent.com/code-yeongyu/oh-my-openagent/dev/assets/oh-my-opencode.schema.json",
   "agents": {
     "atlas": {
-      "model": "anthropic/claude-sonnet-4-5",
+      "model": "anthropic/claude-sonnet-4-6",
     },
     "explore": {
       "model": "anthropic/claude-haiku-4-5",
@@ -1225,16 +1239,16 @@ exports[`generateModelConfig mixed provider scenarios uses Claude + ZAI combinat
       "variant": "max",
     },
     "unspecified-high": {
-      "model": "anthropic/claude-sonnet-4-5",
+      "model": "anthropic/claude-sonnet-4-6",
     },
     "unspecified-low": {
-      "model": "anthropic/claude-sonnet-4-5",
+      "model": "anthropic/claude-sonnet-4-6",
     },
     "visual-engineering": {
       "model": "zai-coding-plan/glm-5",
     },
     "writing": {
-      "model": "anthropic/claude-sonnet-4-5",
+      "model": "anthropic/claude-sonnet-4-6",
     },
   },
 }
@@ -1245,7 +1259,7 @@ exports[`generateModelConfig mixed provider scenarios uses Gemini + Claude combi
   "$schema": "https://raw.githubusercontent.com/code-yeongyu/oh-my-openagent/dev/assets/oh-my-opencode.schema.json",
   "agents": {
     "atlas": {
-      "model": "anthropic/claude-sonnet-4-5",
+      "model": "anthropic/claude-sonnet-4-6",
     },
     "explore": {
       "model": "anthropic/claude-haiku-4-5",
@@ -1290,10 +1304,10 @@ exports[`generateModelConfig mixed provider scenarios uses Gemini + Claude combi
       "variant": "high",
     },
     "unspecified-high": {
-      "model": "anthropic/claude-sonnet-4-5",
+      "model": "anthropic/claude-sonnet-4-6",
     },
     "unspecified-low": {
-      "model": "anthropic/claude-sonnet-4-5",
+      "model": "anthropic/claude-sonnet-4-6",
     },
     "visual-engineering": {
       "model": "google/gemini-3.1-pro-preview",
@@ -1311,7 +1325,7 @@ exports[`generateModelConfig mixed provider scenarios uses all fallback provider
   "$schema": "https://raw.githubusercontent.com/code-yeongyu/oh-my-openagent/dev/assets/oh-my-opencode.schema.json",
   "agents": {
     "atlas": {
-      "model": "github-copilot/claude-sonnet-4.5",
+      "model": "github-copilot/claude-sonnet-4.6",
     },
     "explore": {
       "model": "opencode/claude-haiku-4-5",
@@ -1364,14 +1378,14 @@ exports[`generateModelConfig mixed provider scenarios uses all fallback provider
       "model": "github-copilot/claude-haiku-4.5",
     },
     "ultrabrain": {
-      "model": "opencode/gpt-5.3-codex",
+      "model": "opencode/gpt-5.4",
       "variant": "xhigh",
     },
     "unspecified-high": {
-      "model": "github-copilot/claude-sonnet-4.5",
+      "model": "github-copilot/claude-sonnet-4.6",
     },
     "unspecified-low": {
-      "model": "github-copilot/claude-sonnet-4.5",
+      "model": "github-copilot/claude-sonnet-4.6",
     },
     "visual-engineering": {
       "model": "github-copilot/gemini-3.1-pro-preview",
@@ -1389,7 +1403,7 @@ exports[`generateModelConfig mixed provider scenarios uses all providers togethe
   "$schema": "https://raw.githubusercontent.com/code-yeongyu/oh-my-openagent/dev/assets/oh-my-opencode.schema.json",
   "agents": {
     "atlas": {
-      "model": "anthropic/claude-sonnet-4-5",
+      "model": "anthropic/claude-sonnet-4-6",
     },
     "explore": {
       "model": "anthropic/claude-haiku-4-5",
@@ -1442,14 +1456,14 @@ exports[`generateModelConfig mixed provider scenarios uses all providers togethe
       "model": "anthropic/claude-haiku-4-5",
     },
     "ultrabrain": {
-      "model": "openai/gpt-5.3-codex",
+      "model": "openai/gpt-5.4",
       "variant": "xhigh",
     },
     "unspecified-high": {
-      "model": "anthropic/claude-sonnet-4-5",
+      "model": "anthropic/claude-sonnet-4-6",
     },
     "unspecified-low": {
-      "model": "anthropic/claude-sonnet-4-5",
+      "model": "anthropic/claude-sonnet-4-6",
     },
     "visual-engineering": {
       "model": "google/gemini-3.1-pro-preview",
@@ -1467,7 +1481,7 @@ exports[`generateModelConfig mixed provider scenarios uses all providers with is
   "$schema": "https://raw.githubusercontent.com/code-yeongyu/oh-my-openagent/dev/assets/oh-my-opencode.schema.json",
   "agents": {
     "atlas": {
-      "model": "anthropic/claude-sonnet-4-5",
+      "model": "anthropic/claude-sonnet-4-6",
     },
     "explore": {
       "model": "anthropic/claude-haiku-4-5",
@@ -1520,15 +1534,15 @@ exports[`generateModelConfig mixed provider scenarios uses all providers with is
       "model": "anthropic/claude-haiku-4-5",
     },
     "ultrabrain": {
-      "model": "openai/gpt-5.3-codex",
+      "model": "openai/gpt-5.4",
       "variant": "xhigh",
     },
     "unspecified-high": {
-      "model": "openai/gpt-5.4",
-      "variant": "high",
+      "model": "anthropic/claude-opus-4-6",
+      "variant": "max",
     },
     "unspecified-low": {
-      "model": "anthropic/claude-sonnet-4-5",
+      "model": "anthropic/claude-sonnet-4-6",
     },
     "visual-engineering": {
       "model": "google/gemini-3.1-pro-preview",
diff --git a/src/cli/model-fallback-requirements.test.ts b/src/cli/model-fallback-requirements.test.ts
new file mode 100644
index 000000000..4bcfd1511
--- /dev/null
+++ b/src/cli/model-fallback-requirements.test.ts
@@ -0,0 +1,31 @@
+import { describe, expect, test } from "bun:test"
+
+import {
+  CLI_AGENT_MODEL_REQUIREMENTS,
+  CLI_CATEGORY_MODEL_REQUIREMENTS,
+} from "./model-fallback-requirements"
+import { AGENT_MODEL_REQUIREMENTS, CATEGORY_MODEL_REQUIREMENTS } from "../shared/model-requirements"
+
+describe("CLI model fallback requirements", () => {
+  test("agent requirements stay aligned with runtime requirements", () => {
+    // #given
+    const runtimeAgents = AGENT_MODEL_REQUIREMENTS
+
+    // #when
+    const cliAgents = CLI_AGENT_MODEL_REQUIREMENTS
+
+    // #then
+    expect(cliAgents).toEqual(runtimeAgents)
+  })
+
+  test("category requirements stay aligned with runtime requirements", () => {
+    // #given
+    const runtimeCategories = CATEGORY_MODEL_REQUIREMENTS
+
+    // #when
+    const cliCategories = CLI_CATEGORY_MODEL_REQUIREMENTS
+
+    // #then
+    expect(cliCategories).toEqual(runtimeCategories)
+  })
+})
diff --git a/src/cli/model-fallback-requirements.ts b/src/cli/model-fallback-requirements.ts
index 2178aa920..a13b6f035 100644
--- a/src/cli/model-fallback-requirements.ts
+++ b/src/cli/model-fallback-requirements.ts
@@ -1,283 +1,9 @@
-import type { ModelRequirement } from "../shared/model-requirements";
+import {
+  AGENT_MODEL_REQUIREMENTS,
+  CATEGORY_MODEL_REQUIREMENTS,
+  type ModelRequirement,
+} from "../shared/model-requirements"
 
-// NOTE: These requirements are used by the CLI config generator (`generateModelConfig`).
-// They intentionally use "install-time" provider IDs (anthropic/openai/google/opencode/etc),
-// not runtime-only providers like `nvidia`.
+export const CLI_AGENT_MODEL_REQUIREMENTS: Record<string, ModelRequirement> = AGENT_MODEL_REQUIREMENTS
 
-export const CLI_AGENT_MODEL_REQUIREMENTS: Record<string, ModelRequirement> = {
-  sisyphus: {
-    fallbackChain: [
-      {
-        providers: ["anthropic", "github-copilot", "opencode"],
-        model: "claude-opus-4-6",
-        variant: "max",
-      },
-      { providers: ["opencode-go"], model: "kimi-k2.5" },
-      { providers: ["kimi-for-coding"], model: "k2p5" },
-      { providers: ["openai", "github-copilot", "opencode"], model: "gpt-5.4", variant: "medium" },
-      { providers: ["zai-coding-plan", "opencode"], model: "glm-5" },
-    ],
-    requiresAnyModel: true,
-  },
-  hephaestus: {
-    fallbackChain: [
-      {
-        providers: ["openai", "opencode"],
-        model: "gpt-5.3-codex",
-        variant: "medium",
-      },
-    ],
-    requiresProvider: ["openai", "opencode"],
-  },
-  oracle: {
-    fallbackChain: [
-      {
-        providers: ["openai", "github-copilot", "opencode"],
-        model: "gpt-5.4",
-        variant: "high",
-      },
-      {
-        providers: ["google", "github-copilot", "opencode"],
-        model: "gemini-3.1-pro",
-        variant: "high",
-      },
-      {
-        providers: ["anthropic", "github-copilot", "opencode"],
-        model: "claude-opus-4-6",
-        variant: "max",
-      },
-      { providers: ["opencode-go"], model: "glm-5" },
-    ],
-  },
-  librarian: {
-    fallbackChain: [
-      { providers: ["opencode-go"], model: "minimax-m2.5" },
-      { providers: ["opencode"], model: "minimax-m2.5-free" },
-      { providers: ["anthropic", "opencode"], model: "claude-haiku-4-5" },
-      { providers: ["opencode"], model: "gpt-5-nano" },
-    ],
-  },
-  explore: {
-    fallbackChain: [
-      { providers: ["github-copilot"], model: "grok-code-fast-1" },
-      { providers: ["opencode-go"], model: "minimax-m2.5" },
-      { providers: ["anthropic", "opencode"], model: "claude-haiku-4-5" },
-      { providers: ["opencode"], model: "gpt-5-nano" },
-    ],
-  },
-  "multimodal-looker": {
-    fallbackChain: [
-      { providers: ["openai", "opencode"], model: "gpt-5.4", variant: "medium" },
-      { providers: ["opencode-go"], model: "kimi-k2.5" },
-      { providers: ["zai-coding-plan"], model: "glm-4.6v" },
-      { providers: ["opencode"], model: "gpt-5-nano" },
-    ],
-  },
-  prometheus: {
-    fallbackChain: [
-      {
-        providers: ["anthropic", "github-copilot", "opencode"],
-        model: "claude-opus-4-6",
-        variant: "max",
-      },
-      { providers: ["kimi-for-coding"], model: "k2p5" },
-      {
-        providers: ["openai", "github-copilot", "opencode"],
-        model: "gpt-5.4",
-        variant: "high",
-      },
-      { providers: ["opencode-go"], model: "glm-5" },
-      {
-        providers: ["google", "github-copilot", "opencode"],
-        model: "gemini-3.1-pro",
-      },
-    ],
-  },
-  metis: {
-    fallbackChain: [
-      {
-        providers: ["anthropic", "github-copilot", "opencode"],
-        model: "claude-opus-4-6",
-        variant: "max",
-      },
-      { providers: ["opencode-go"], model: "glm-5" },
-      { providers: ["kimi-for-coding"], model: "k2p5" },
-    ],
-  },
-  momus: {
-    fallbackChain: [
-      {
-        providers: ["openai", "github-copilot", "opencode"],
-        model: "gpt-5.4",
-        variant: "xhigh",
-      },
-      {
-        providers: ["anthropic", "github-copilot", "opencode"],
-        model: "claude-opus-4-6",
-        variant: "max",
-      },
-      {
-        providers: ["google", "github-copilot", "opencode"],
-        model: "gemini-3.1-pro",
-        variant: "high",
-      },
-      { providers: ["opencode-go"], model: "glm-5" },
-    ],
-  },
-  atlas: {
-    fallbackChain: [
-      { providers: ["anthropic", "github-copilot", "opencode"], model: "claude-sonnet-4-5" },
-      { providers: ["opencode-go"], model: "kimi-k2.5" },
-    ],
-  },
-  "sisyphus-junior": {
-    fallbackChain: [
-      { providers: ["anthropic", "github-copilot", "opencode"], model: "claude-sonnet-4-6" },
-      { providers: ["opencode-go"], model: "kimi-k2.5" },
-      { providers: ["opencode"], model: "big-pickle" },
-    ],
-  },
-};
-
-export const CLI_CATEGORY_MODEL_REQUIREMENTS: Record<string, ModelRequirement> = {
-  "visual-engineering": {
-    fallbackChain: [
-      {
-        providers: ["google", "github-copilot", "opencode"],
-        model: "gemini-3.1-pro",
-        variant: "high",
-      },
-      { providers: ["zai-coding-plan", "opencode"], model: "glm-5" },
-      {
-        providers: ["anthropic", "github-copilot", "opencode"],
-        model: "claude-opus-4-6",
-        variant: "max",
-      },
-      { providers: ["kimi-for-coding"], model: "k2p5" },
-      { providers: ["opencode-go"], model: "glm-5" },
-    ],
-  },
-  ultrabrain: {
-    fallbackChain: [
-      {
-        providers: ["openai", "opencode"],
-        model: "gpt-5.3-codex",
-        variant: "xhigh",
-      },
-      {
-        providers: ["google", "github-copilot", "opencode"],
-        model: "gemini-3.1-pro",
-        variant: "high",
-      },
-      {
-        providers: ["anthropic", "github-copilot", "opencode"],
-        model: "claude-opus-4-6",
-        variant: "max",
-      },
-      { providers: ["opencode-go"], model: "glm-5" },
-    ],
-  },
-  deep: {
-    fallbackChain: [
-      {
-        providers: ["openai", "opencode"],
-        model: "gpt-5.3-codex",
-        variant: "medium",
-      },
-      {
-        providers: ["anthropic", "github-copilot", "opencode"],
-        model: "claude-opus-4-6",
-        variant: "max",
-      },
-      {
-        providers: ["google", "github-copilot", "opencode"],
-        model: "gemini-3.1-pro",
-        variant: "high",
-      },
-    ],
-    requiresModel: "gpt-5.3-codex",
-  },
-  artistry: {
-    fallbackChain: [
-      {
-        providers: ["google", "github-copilot", "opencode"],
-        model: "gemini-3.1-pro",
-        variant: "high",
-      },
-      {
-        providers: ["anthropic", "github-copilot", "opencode"],
-        model: "claude-opus-4-6",
-        variant: "max",
-      },
-      {
-        providers: ["openai", "github-copilot", "opencode"],
-        model: "gpt-5.4",
-      },
-    ],
-    requiresModel: "gemini-3.1-pro",
-  },
-  quick: {
-    fallbackChain: [
-      {
-        providers: ["anthropic", "github-copilot", "opencode"],
-        model: "claude-haiku-4-5",
-      },
-      {
-        providers: ["google", "github-copilot", "opencode"],
-        model: "gemini-3-flash",
-      },
-      { providers: ["opencode-go"], model: "minimax-m2.5" },
-      { providers: ["opencode"], model: "gpt-5-nano" },
-    ],
-  },
-  "unspecified-low": {
-    fallbackChain: [
-      {
-        providers: ["anthropic", "github-copilot", "opencode"],
-        model: "claude-sonnet-4-5",
-      },
-      {
-        providers: ["openai", "opencode"],
-        model: "gpt-5.3-codex",
-        variant: "medium",
-      },
-      { providers: ["opencode-go"], model: "kimi-k2.5" },
-      {
-        providers: ["google", "github-copilot", "opencode"],
-        model: "gemini-3-flash",
-      },
-    ],
-  },
-  "unspecified-high": {
-    fallbackChain: [
-      {
-        providers: ["openai", "github-copilot", "opencode"],
-        model: "gpt-5.4",
-        variant: "high",
-      },
-      {
-        providers: ["anthropic", "github-copilot", "opencode"],
-        model: "claude-opus-4-6",
-        variant: "max",
-      },
-      { providers: ["zai-coding-plan", "opencode"], model: "glm-5" },
-      { providers: ["kimi-for-coding"], model: "k2p5" },
-      { providers: ["opencode"], model: "kimi-k2.5" },
-      { providers: ["opencode-go"], model: "glm-5" },
-    ],
-  },
-  writing: {
-    fallbackChain: [
-      { providers: ["kimi-for-coding"], model: "k2p5" },
-      {
-        providers: ["google", "github-copilot", "opencode"],
-        model: "gemini-3-flash",
-      },
-      { providers: ["opencode-go"], model: "kimi-k2.5" },
-      {
-        providers: ["anthropic", "github-copilot", "opencode"],
-        model: "claude-sonnet-4-5",
-      },
-    ],
-  },
-};
+export const CLI_CATEGORY_MODEL_REQUIREMENTS: Record<string, ModelRequirement> = CATEGORY_MODEL_REQUIREMENTS
diff --git a/src/cli/model-fallback.test.ts b/src/cli/model-fallback.test.ts
index bd3e38447..cb6192f55 100644
--- a/src/cli/model-fallback.test.ts
+++ b/src/cli/model-fallback.test.ts
@@ -13,6 +13,7 @@ function createConfig(overrides: Partial<InstallConfig> = {}): InstallConfig {
     hasOpencodeZen: false,
     hasZaiCodingPlan: false,
     hasKimiForCoding: false,
+    hasOpencodeGo: false,
     ...overrides,
   }
 }
@@ -410,6 +411,44 @@ describe("generateModelConfig", () => {
     })
   })
 
+  describe("OpenAI fallback coverage", () => {
+    test("Atlas resolves to OpenAI when only OpenAI is available", () => {
+      // #given
+      const config = createConfig({ hasOpenAI: true })
+
+      // #when
+      const result = generateModelConfig(config)
+
+      // #then
+      expect(result.agents?.atlas?.model).toBe("openai/gpt-5.4")
+      expect(result.agents?.atlas?.variant).toBe("medium")
+    })
+
+    test("Metis resolves to OpenAI when only OpenAI is available", () => {
+      // #given
+      const config = createConfig({ hasOpenAI: true })
+
+      // #when
+      const result = generateModelConfig(config)
+
+      // #then
+      expect(result.agents?.metis?.model).toBe("openai/gpt-5.4")
+      expect(result.agents?.metis?.variant).toBe("high")
+    })
+
+    test("Sisyphus-Junior resolves to OpenAI when only OpenAI is available", () => {
+      // #given
+      const config = createConfig({ hasOpenAI: true })
+
+      // #when
+      const result = generateModelConfig(config)
+
+      // #then
+      expect(result.agents?.["sisyphus-junior"]?.model).toBe("openai/gpt-5.4")
+      expect(result.agents?.["sisyphus-junior"]?.variant).toBe("medium")
+    })
+  })
+
   describe("Hephaestus agent special cases", () => {
     test("Hephaestus is created when OpenAI is available (openai provider connected)", () => {
       // #given
@@ -423,15 +462,18 @@ describe("generateModelConfig", () => {
       expect(result.agents?.hephaestus?.variant).toBe("medium")
     })
 
-    test("Hephaestus is NOT created when only Copilot is available (gpt-5.3-codex unavailable on github-copilot)", () => {
+    test("Hephaestus falls back to Copilot GPT-5.4 when only Copilot is available", () => {
       // #given
       const config = createConfig({ hasCopilot: true })
 
       // #when
       const result = generateModelConfig(config)
 
-      // #then - hephaestus is omitted because gpt-5.3-codex is not available on github-copilot
-      expect(result.agents?.hephaestus).toBeUndefined()
+      // #then
+      expect(result.agents?.hephaestus).toEqual({
+        model: "github-copilot/gpt-5.4",
+        variant: "medium",
+      })
     })
 
     test("Hephaestus is created when OpenCode Zen is available (opencode provider connected)", () => {
diff --git a/src/cli/openai-only-model-catalog.test.ts b/src/cli/openai-only-model-catalog.test.ts
index ee56d2d06..eebb0e8fa 100644
--- a/src/cli/openai-only-model-catalog.test.ts
+++ b/src/cli/openai-only-model-catalog.test.ts
@@ -13,6 +13,7 @@ function createConfig(overrides: Partial<InstallConfig> = {}): InstallConfig {
     hasOpencodeZen: false,
     hasZaiCodingPlan: false,
     hasKimiForCoding: false,
+    hasOpencodeGo: false,
     ...overrides,
   }
 }
@@ -43,4 +44,17 @@ describe("generateModelConfig OpenAI-only model catalog", () => {
     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" })
   })
+
+  test("does not apply OpenAI-only overrides when OpenCode Go is also available", () => {
+    // #given
+    const config = createConfig({ hasOpenAI: true, hasOpencodeGo: true })
+
+    // #when
+    const result = generateModelConfig(config)
+
+    // #then
+    expect(result.agents?.explore).toEqual({ model: "opencode-go/minimax-m2.5" })
+    expect(result.agents?.librarian).toEqual({ model: "opencode-go/minimax-m2.5" })
+    expect(result.categories?.quick).toEqual({ model: "opencode-go/minimax-m2.5" })
+  })
 })
diff --git a/src/cli/openai-only-model-catalog.ts b/src/cli/openai-only-model-catalog.ts
index 52e8484e1..a6428a1ef 100644
--- a/src/cli/openai-only-model-catalog.ts
+++ b/src/cli/openai-only-model-catalog.ts
@@ -17,6 +17,7 @@ export function isOpenAiOnlyAvailability(availability: ProviderAvailability): bo
     availability.native.openai &&
     !availability.native.claude &&
     !availability.native.gemini &&
+    !availability.opencodeGo &&
     !availability.opencodeZen &&
     !availability.copilot &&
     !availability.zai &&
diff --git a/src/plugin-handlers/agent-config-handler.test.ts b/src/plugin-handlers/agent-config-handler.test.ts
index 064e86116..d0d01a897 100644
--- a/src/plugin-handlers/agent-config-handler.test.ts
+++ b/src/plugin-handlers/agent-config-handler.test.ts
@@ -74,6 +74,13 @@ describe("applyAgentConfig builtin override protection", () => {
     mode: "subagent",
   }
 
+  const builtinAtlasConfig: AgentConfig = {
+    name: "atlas",
+    prompt: "atlas prompt",
+    mode: "all",
+    model: "openai/gpt-5.4",
+  }
+
   const sisyphusJuniorConfig: AgentConfig = {
     name: "Sisyphus-Junior",
     prompt: "junior prompt",
@@ -85,6 +92,7 @@ describe("applyAgentConfig builtin override protection", () => {
       sisyphus: builtinSisyphusConfig,
       oracle: builtinOracleConfig,
       "multimodal-looker": builtinMultimodalLookerConfig,
+      atlas: builtinAtlasConfig,
     })
 
     createSisyphusJuniorAgentSpy = spyOn(
@@ -255,4 +263,19 @@ describe("applyAgentConfig builtin override protection", () => {
       })
     })
   })
+
+  test("passes the resolved Atlas model to Sisyphus-Junior as its fallback default", async () => {
+    // given
+
+    // when
+    await applyAgentConfig({
+      config: createBaseConfig(),
+      pluginConfig: createPluginConfig(),
+      ctx: { directory: "/tmp" },
+      pluginComponents: createPluginComponents(),
+    })
+
+    // then
+    expect(createSisyphusJuniorAgentSpy).toHaveBeenCalledWith(undefined, "openai/gpt-5.4", false)
+  })
 })
diff --git a/src/plugin-handlers/agent-config-handler.ts b/src/plugin-handlers/agent-config-handler.ts
index e078b0688..de316ffb7 100644
--- a/src/plugin-handlers/agent-config-handler.ts
+++ b/src/plugin-handlers/agent-config-handler.ts
@@ -158,7 +158,7 @@ export async function applyAgentConfig(params: {
 
     agentConfig["sisyphus-junior"] = createSisyphusJuniorAgentWithOverrides(
       params.pluginConfig.agents?.["sisyphus-junior"],
-      undefined,
+      (builtinAgents.atlas as { model?: string } | undefined)?.model,
       useTaskSystem,
     );
 
diff --git a/src/shared/model-requirements.test.ts b/src/shared/model-requirements.test.ts
index 45055ad62..63278e57f 100644
--- a/src/shared/model-requirements.test.ts
+++ b/src/shared/model-requirements.test.ts
@@ -178,6 +178,13 @@ describe("AGENT_MODEL_REQUIREMENTS", () => {
     expect(primary.model).toBe("claude-opus-4-6")
     expect(primary.providers).toEqual(["anthropic", "github-copilot", "opencode"])
     expect(primary.variant).toBe("max")
+
+    const openAiFallback = metis.fallbackChain.find((entry) => entry.providers.includes("openai"))
+    expect(openAiFallback).toEqual({
+      providers: ["openai", "github-copilot", "opencode"],
+      model: "gpt-5.4",
+      variant: "high",
+    })
   })
 
   test("momus has valid fallbackChain with gpt-5.4 as primary", () => {
@@ -213,6 +220,32 @@ describe("AGENT_MODEL_REQUIREMENTS", () => {
     const secondary = atlas.fallbackChain[1]
     expect(secondary.model).toBe("kimi-k2.5")
     expect(secondary.providers[0]).toBe("opencode-go")
+
+    const tertiary = atlas.fallbackChain[2]
+    expect(tertiary).toEqual({
+      providers: ["openai", "github-copilot", "opencode"],
+      model: "gpt-5.4",
+      variant: "medium",
+    })
+  })
+
+  test("sisyphus-junior has an OpenAI fallback before big-pickle", () => {
+    // given - sisyphus-junior agent requirement
+    const sisyphusJunior = AGENT_MODEL_REQUIREMENTS["sisyphus-junior"]
+
+    // when - locating the OpenAI fallback entry
+    const openAiFallback = sisyphusJunior.fallbackChain.find((entry) => entry.providers.includes("openai"))
+    const openAiFallbackIndex = sisyphusJunior.fallbackChain.findIndex((entry) => entry.providers.includes("openai"))
+    const bigPickleIndex = sisyphusJunior.fallbackChain.findIndex((entry) => entry.model === "big-pickle")
+
+    // then
+    expect(openAiFallback).toEqual({
+      providers: ["openai", "github-copilot", "opencode"],
+      model: "gpt-5.4",
+      variant: "medium",
+    })
+    expect(openAiFallbackIndex).toBeGreaterThan(-1)
+    expect(bigPickleIndex).toBeGreaterThan(openAiFallbackIndex)
   })
 
   test("hephaestus supports openai, github-copilot, venice, and opencode providers", () => {
diff --git a/src/shared/model-requirements.ts b/src/shared/model-requirements.ts
index 2e59eb3bf..56863e658 100644
--- a/src/shared/model-requirements.ts
+++ b/src/shared/model-requirements.ts
@@ -121,6 +121,11 @@ export const AGENT_MODEL_REQUIREMENTS: Record<string, ModelRequirement> = {
         model: "claude-opus-4-6",
         variant: "max",
       },
+      {
+        providers: ["openai", "github-copilot", "opencode"],
+        model: "gpt-5.4",
+        variant: "high",
+      },
       { providers: ["opencode-go"], model: "glm-5" },
       { providers: ["kimi-for-coding"], model: "k2p5" },
     ],
@@ -149,12 +154,22 @@ export const AGENT_MODEL_REQUIREMENTS: Record<string, ModelRequirement> = {
     fallbackChain: [
       { providers: ["anthropic", "github-copilot", "opencode"], model: "claude-sonnet-4-6" },
       { providers: ["opencode-go"], model: "kimi-k2.5" },
+      {
+        providers: ["openai", "github-copilot", "opencode"],
+        model: "gpt-5.4",
+        variant: "medium",
+      },
     ],
   },
   "sisyphus-junior": {
     fallbackChain: [
       { providers: ["anthropic", "github-copilot", "opencode"], model: "claude-sonnet-4-6" },
       { providers: ["opencode-go"], model: "kimi-k2.5" },
+      {
+        providers: ["openai", "github-copilot", "opencode"],
+        model: "gpt-5.4",
+        variant: "medium",
+      },
       { providers: ["opencode"], model: "big-pickle" },
     ],
   },