feat(model-requirements): add k2p5, kimi-k2.5, gpt-5.4 medium to Sisyphus fallback chain

Sisyphus can now fall back through Kimi and OpenAI models when Claude
is unavailable, enabling OpenAI-only users to use Sisyphus directly
instead of being redirected to Hephaestus.

Runtime chain: claude-opus-4-6 max → k2p5 → kimi-k2.5 → gpt-5.4 medium → glm-5 → big-pickle
CLI chain: claude-opus-4-6 max → k2p5 → gpt-5.4 medium → glm-5

docs/guide/agent-model-matching.md

@@ -64,7 +64,7 @@ These agents have Claude-optimized prompts — long, detailed, mechanics-driven.
 
 | Agent        | Role              | Fallback Chain                         | Notes                                                                                             |
 | ------------ | ----------------- | -------------------------------------- | ------------------------------------------------------------------------------------------------- |
-| **Sisyphus** | Main orchestrator | Claude Opus → GLM 5 → Big Pickle       | Claude-family first. GPT-5.4 has dedicated support, but Claude/Kimi/GLM remain the preferred fit. |
+| **Sisyphus** | Main orchestrator | Claude Opus → K2P5 → Kimi K2.5 → GPT-5.4 → GLM 5 → Big Pickle | Claude-family first. GPT-5.4 has dedicated prompt support. Kimi/GLM as intermediate fallbacks. |
 | **Metis**    | Plan gap analyzer | Claude Opus → GPT-5.4 → Gemini 3.1 Pro | Claude preferred, GPT acceptable fallback.                                                        |
 
 ### Dual-Prompt Agents → Claude preferred, GPT supported

src/agents/AGENTS.md

@@ -10,7 +10,7 @@ Agent factories following `createXXXAgent(model) → AgentConfig` pattern. Each
 
 | Agent | Model | Temp | Mode | Fallback Chain | Purpose |
 |-------|-------|------|------|----------------|---------|
-| **Sisyphus** | claude-opus-4-6 max | 0.1 | all | glm-5 → big-pickle | Main orchestrator, plans + delegates |
+| **Sisyphus** | claude-opus-4-6 max | 0.1 | all | k2p5 → kimi-k2.5 → gpt-5.4 medium → glm-5 → big-pickle | Main orchestrator, plans + delegates |
 | **Hephaestus** | gpt-5.3-codex medium | 0.1 | all | gpt-5.4 medium (copilot) | Autonomous deep worker |
 | **Oracle** | gpt-5.4 high | 0.1 | subagent | gemini-3.1-pro high → claude-opus-4-6 max | Read-only consultation |
 | **Librarian** | gemini-3-flash | 0.1 | subagent | minimax-m2.5-free → big-pickle | External docs/code search |

src/agents/utils.test.ts

@@ -891,9 +891,9 @@ describe("createBuiltinAgents with requiresAnyModel gating (sisyphus)", () => {
   })
 
   test("sisyphus is not created when no fallback model is available and provider not connected", async () => {
-    // #given - only openai/gpt-5.4 available, not in sisyphus fallback chain
+    // #given - only venice/deepseek-v3.2 available, not in sisyphus fallback chain
     const fetchSpy = spyOn(shared, "fetchAvailableModels").mockResolvedValue(
-      new Set(["openai/gpt-5.4"])
+      new Set(["venice/deepseek-v3.2"])
     )
     const cacheSpy = spyOn(connectedProvidersCache, "readConnectedProvidersCache").mockReturnValue([])
 

src/cli/__snapshots__/model-fallback.test.ts.snap

@@ -224,6 +224,10 @@ exports[`generateModelConfig single native provider uses OpenAI models when only
       "model": "openai/gpt-5.4",
       "variant": "high",
     },
+    "sisyphus": {
+      "model": "openai/gpt-5.4",
+      "variant": "medium",
+    },
   },
   "categories": {
     "deep": {
@@ -293,6 +297,10 @@ exports[`generateModelConfig single native provider uses OpenAI models with isMa
       "model": "openai/gpt-5.4",
       "variant": "high",
     },
+    "sisyphus": {
+      "model": "openai/gpt-5.4",
+      "variant": "medium",
+    },
   },
   "categories": {
     "deep": {

src/cli/config-manager.test.ts

@@ -249,8 +249,9 @@ describe("generateOmoConfig - model fallback system", () => {
     // #when generating config
     const result = generateOmoConfig(config)
 
-    // #then Sisyphus is omitted (requires all fallback providers)
-    expect((result.agents as Record<string, { model: string }>).sisyphus).toBeUndefined()
+    // #then Sisyphus resolves to gpt-5.4 medium (openai is now in sisyphus chain)
+    expect((result.agents as Record<string, { model: string; variant?: string }>).sisyphus.model).toBe("openai/gpt-5.4")
+    expect((result.agents as Record<string, { model: string; variant?: string }>).sisyphus.variant).toBe("medium")
     // #then Oracle should use native OpenAI (first fallback entry)
     expect((result.agents as Record<string, { model: string }>).oracle.model).toBe("openai/gpt-5.4")
     // #then multimodal-looker should use native OpenAI (first fallback entry is gpt-5.3-codex)

src/cli/model-fallback-requirements.ts

@@ -13,6 +13,7 @@ export const CLI_AGENT_MODEL_REQUIREMENTS: Record<string, ModelRequirement> = {
         variant: "max",
       },
       { 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,

src/cli/model-fallback.test.ts

@@ -396,7 +396,7 @@ describe("generateModelConfig", () => {
       expect(result.agents?.sisyphus?.model).toBe("anthropic/claude-opus-4-6")
     })
 
-    test("Sisyphus is omitted when no fallback provider is available (OpenAI not in chain)", () => {
+    test("Sisyphus resolves to gpt-5.4 medium when only OpenAI is available", () => {
       // #given
       const config = createConfig({ hasOpenAI: true })
 
@@ -404,7 +404,8 @@ describe("generateModelConfig", () => {
       const result = generateModelConfig(config)
 
       // #then
-      expect(result.agents?.sisyphus).toBeUndefined()
+      expect(result.agents?.sisyphus?.model).toBe("openai/gpt-5.4")
+      expect(result.agents?.sisyphus?.variant).toBe("medium")
     })
   })
 

src/hooks/model-fallback/hook.test.ts

@@ -134,8 +134,8 @@ describe("model fallback hook", () => {
 
     //#then - chain should progress to entry[1], not repeat entry[0]
     expect(secondOutput.message["model"]).toEqual({
-      providerID: "zai-coding-plan",
-      modelID: "glm-5",
+      providerID: "kimi-for-coding",
+      modelID: "k2p5",
     })
     expect(secondOutput.message["variant"]).toBeUndefined()
   })

src/plugin/event.model-fallback.test.ts

@@ -334,8 +334,8 @@ describe("createEventHandler - model fallback", () => {
 
     //#then - second fallback entry applied (chain advanced)
     expect(second.message["model"]).toEqual({
-      providerID: "zai-coding-plan",
-      modelID: "glm-5",
+      providerID: "kimi-for-coding",
+      modelID: "k2p5",
     })
     expect(second.message["variant"]).toBeUndefined()
     expect(abortCalls).toEqual([sessionID, sessionID])

src/shared/agent-variant.test.ts

@@ -124,8 +124,8 @@ describe("resolveVariantForModel", () => {
     expect(variant).toBe("medium")
   })
 
-  test("returns undefined for provider not in sisyphus chain", () => {
-    // #given openai is not in sisyphus fallback chain anymore
+  test("returns medium for openai/gpt-5.4 in sisyphus chain", () => {
+    // #given openai/gpt-5.4 is now in sisyphus fallback chain with variant medium
     const config = {} as OhMyOpenCodeConfig
     const model = { providerID: "openai", modelID: "gpt-5.4" }
 
@@ -133,7 +133,7 @@ describe("resolveVariantForModel", () => {
     const variant = resolveVariantForModel(config, "sisyphus", model)
 
     // then
-    expect(variant).toBeUndefined()
+    expect(variant).toBe("medium")
   })
 
   test("returns undefined for provider not in chain", () => {

src/shared/model-requirements.test.ts

@@ -23,15 +23,15 @@ describe("AGENT_MODEL_REQUIREMENTS", () => {
     expect(primary.variant).toBe("high")
   })
 
-  test("sisyphus has claude-opus-4-6 as primary and requiresAnyModel", () => {
+  test("sisyphus has claude-opus-4-6 as primary with k2p5, kimi-k2.5, gpt-5.4 medium fallbacks", () => {
     // #given - sisyphus agent requirement
     const sisyphus = AGENT_MODEL_REQUIREMENTS["sisyphus"]
 
     // #when - accessing Sisyphus requirement
-    // #then - fallbackChain has claude-opus-4-6 first, big-pickle last
+    // #then - fallbackChain has 6 entries with correct ordering
     expect(sisyphus).toBeDefined()
     expect(sisyphus.fallbackChain).toBeArray()
-    expect(sisyphus.fallbackChain).toHaveLength(3)
+    expect(sisyphus.fallbackChain).toHaveLength(6)
     expect(sisyphus.requiresAnyModel).toBe(true)
 
     const primary = sisyphus.fallbackChain[0]
@@ -39,7 +39,19 @@ describe("AGENT_MODEL_REQUIREMENTS", () => {
     expect(primary.model).toBe("claude-opus-4-6")
     expect(primary.variant).toBe("max")
 
-    const last = sisyphus.fallbackChain[2]
+    const second = sisyphus.fallbackChain[1]
+    expect(second.providers).toEqual(["kimi-for-coding"])
+    expect(second.model).toBe("k2p5")
+
+    const third = sisyphus.fallbackChain[2]
+    expect(third.model).toBe("kimi-k2.5")
+
+    const fourth = sisyphus.fallbackChain[3]
+    expect(fourth.providers).toContain("openai")
+    expect(fourth.model).toBe("gpt-5.4")
+    expect(fourth.variant).toBe("medium")
+
+    const last = sisyphus.fallbackChain[5]
     expect(last.providers[0]).toBe("opencode")
     expect(last.model).toBe("big-pickle")
   })

src/shared/model-requirements.ts

@@ -20,6 +20,19 @@ export const AGENT_MODEL_REQUIREMENTS: Record<string, ModelRequirement> = {
         model: "claude-opus-4-6",
         variant: "max",
       },
+      { providers: ["kimi-for-coding"], model: "k2p5" },
+      {
+        providers: [
+          "opencode",
+          "moonshotai",
+          "moonshotai-cn",
+          "firmware",
+          "ollama-cloud",
+          "aihubmix",
+        ],
+        model: "kimi-k2.5",
+      },
+      { providers: ["openai", "github-copilot", "opencode"], model: "gpt-5.4", variant: "medium" },
       { providers: ["zai-coding-plan", "opencode"], model: "glm-5" },
       { providers: ["opencode"], model: "big-pickle" },
     ],