feat: auto-detect model provider and apply appropriate options (#146)

When overriding an agent's model to a different provider, the agent
now automatically gets provider-appropriate reasoning options:

- GPT models: `reasoningEffort`, `textVerbosity`
- Anthropic models: `thinking` with `budgetTokens`

## Why utils.ts changes are required

The original flow merges overrides onto pre-built agent configs:

    mergeAgentConfig(sisyphusAgent, { model: "gpt-5.2" })
    // Result: { model: "gpt-5.2", thinking: {...} }

The `thinking` config persists because it exists in the pre-built
`sisyphusAgent`. GPT models ignore `thinking` and need `reasoningEffort`.

The fix: call the agent factory with the resolved model, so the factory
can return the correct provider-specific config:

    buildAgent(createSisyphusAgent, "gpt-5.2")
    // Result: { model: "gpt-5.2", reasoningEffort: "medium" }

Closes #144

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

src/agents/oracle.ts

@@ -1,15 +1,9 @@
 import type { AgentConfig } from "@opencode-ai/sdk"
+import { isGptModel } from "./types"
 
-export const oracleAgent: AgentConfig = {
-  description:
-    "Expert technical advisor with deep reasoning for architecture decisions, code analysis, and engineering guidance.",
-  mode: "subagent",
-  model: "openai/gpt-5.2",
-  temperature: 0.1,
-  reasoningEffort: "medium",
-  textVerbosity: "high",
-  tools: { write: false, edit: false, task: false, background_task: false },
-  prompt: `You are a strategic technical advisor with deep reasoning capabilities, operating as a specialized consultant within an AI-assisted development environment.
+const DEFAULT_MODEL = "openai/gpt-5.2"
+
+const ORACLE_SYSTEM_PROMPT = `You are a strategic technical advisor with deep reasoning capabilities, operating as a specialized consultant within an AI-assisted development environment.
 
 ## Context
 
@@ -73,5 +67,24 @@ Organize your final answer in three tiers:
 
 ## Critical Note
 
-Your response goes directly to the user with no intermediate processing. Make your final message self-contained: a clear recommendation they can act on immediately, covering both what to do and why.`,
+Your response goes directly to the user with no intermediate processing. Make your final message self-contained: a clear recommendation they can act on immediately, covering both what to do and why.`
+
+export function createOracleAgent(model: string = DEFAULT_MODEL): AgentConfig {
+  const base = {
+    description:
+      "Expert technical advisor with deep reasoning for architecture decisions, code analysis, and engineering guidance.",
+    mode: "subagent" as const,
+    model,
+    temperature: 0.1,
+    tools: { write: false, edit: false, task: false, background_task: false },
+    prompt: ORACLE_SYSTEM_PROMPT,
+  }
+
+  if (isGptModel(model)) {
+    return { ...base, reasoningEffort: "medium", textVerbosity: "high" }
+  }
+
+  return { ...base, thinking: { type: "enabled", budgetTokens: 32000 } }
 }
+
+export const oracleAgent = createOracleAgent()

src/agents/sisyphus.ts

@@ -1,4 +1,7 @@
 import type { AgentConfig } from "@opencode-ai/sdk"
+import { isGptModel } from "./types"
+
+const DEFAULT_MODEL = "anthropic/claude-opus-4-5"
 
 const SISYPHUS_SYSTEM_PROMPT = `<Role>
 You are "Sisyphus" - Powerful AI Agent with orchestration capabilities from OhMyOpenCode.
@@ -452,16 +455,22 @@ If the user's approach seems problematic:
 
 `
 
-export const sisyphusAgent: AgentConfig = {
+export function createSisyphusAgent(model: string = DEFAULT_MODEL): AgentConfig {
+  const base = {
     description:
       "Sisyphus - Powerful AI orchestrator from OhMyOpenCode. Plans obsessively with todos, assesses search complexity before exploration, delegates strategically to specialized agents. Uses explore for internal code (parallel-friendly), librarian only for external docs, and always delegates UI work to frontend engineer.",
-  mode: "primary",
-  model: "anthropic/claude-opus-4-5",
-  thinking: {
-    type: "enabled",
-    budgetTokens: 32000,
-  },
+    mode: "primary" as const,
+    model,
     maxTokens: 64000,
     prompt: SISYPHUS_SYSTEM_PROMPT,
     color: "#00CED1",
+  }
+
+  if (isGptModel(model)) {
+    return { ...base, reasoningEffort: "medium" }
+  }
+
+  return { ...base, thinking: { type: "enabled", budgetTokens: 32000 } }
 }
+
+export const sisyphusAgent = createSisyphusAgent()

src/agents/types.ts

@@ -1,5 +1,11 @@
 import type { AgentConfig } from "@opencode-ai/sdk"
 
+export type AgentFactory = (model?: string) => AgentConfig
+
+export function isGptModel(model: string): boolean {
+  return model.startsWith("openai/") || model.startsWith("github-copilot/gpt-")
+}
+
 export type BuiltinAgentName =
   | "Sisyphus"
   | "oracle"

src/agents/utils.test.ts

@@ -0,0 +1,87 @@
+import { describe, test, expect } from "bun:test"
+import { createBuiltinAgents } from "./utils"
+
+describe("createBuiltinAgents with model overrides", () => {
+  test("Sisyphus with default model has thinking config", () => {
+    // #given - no overrides
+
+    // #when
+    const agents = createBuiltinAgents()
+
+    // #then
+    expect(agents.Sisyphus.model).toBe("anthropic/claude-opus-4-5")
+    expect(agents.Sisyphus.thinking).toEqual({ type: "enabled", budgetTokens: 32000 })
+    expect(agents.Sisyphus.reasoningEffort).toBeUndefined()
+  })
+
+  test("Sisyphus with GPT model override has reasoningEffort, no thinking", () => {
+    // #given
+    const overrides = {
+      Sisyphus: { model: "github-copilot/gpt-5.2" },
+    }
+
+    // #when
+    const agents = createBuiltinAgents([], overrides)
+
+    // #then
+    expect(agents.Sisyphus.model).toBe("github-copilot/gpt-5.2")
+    expect(agents.Sisyphus.reasoningEffort).toBe("medium")
+    expect(agents.Sisyphus.thinking).toBeUndefined()
+  })
+
+  test("Sisyphus with systemDefaultModel GPT has reasoningEffort, no thinking", () => {
+    // #given
+    const systemDefaultModel = "openai/gpt-5.2"
+
+    // #when
+    const agents = createBuiltinAgents([], {}, undefined, systemDefaultModel)
+
+    // #then
+    expect(agents.Sisyphus.model).toBe("openai/gpt-5.2")
+    expect(agents.Sisyphus.reasoningEffort).toBe("medium")
+    expect(agents.Sisyphus.thinking).toBeUndefined()
+  })
+
+  test("Oracle with default model has reasoningEffort", () => {
+    // #given - no overrides
+
+    // #when
+    const agents = createBuiltinAgents()
+
+    // #then
+    expect(agents.oracle.model).toBe("openai/gpt-5.2")
+    expect(agents.oracle.reasoningEffort).toBe("medium")
+    expect(agents.oracle.textVerbosity).toBe("high")
+    expect(agents.oracle.thinking).toBeUndefined()
+  })
+
+  test("Oracle with Claude model override has thinking, no reasoningEffort", () => {
+    // #given
+    const overrides = {
+      oracle: { model: "anthropic/claude-sonnet-4" },
+    }
+
+    // #when
+    const agents = createBuiltinAgents([], overrides)
+
+    // #then
+    expect(agents.oracle.model).toBe("anthropic/claude-sonnet-4")
+    expect(agents.oracle.thinking).toEqual({ type: "enabled", budgetTokens: 32000 })
+    expect(agents.oracle.reasoningEffort).toBeUndefined()
+    expect(agents.oracle.textVerbosity).toBeUndefined()
+  })
+
+  test("non-model overrides are still applied after factory rebuild", () => {
+    // #given
+    const overrides = {
+      Sisyphus: { model: "github-copilot/gpt-5.2", temperature: 0.5 },
+    }
+
+    // #when
+    const agents = createBuiltinAgents([], overrides)
+
+    // #then
+    expect(agents.Sisyphus.model).toBe("github-copilot/gpt-5.2")
+    expect(agents.Sisyphus.temperature).toBe(0.5)
+  })
+})

src/agents/utils.ts

@@ -1,7 +1,7 @@
 import type { AgentConfig } from "@opencode-ai/sdk"
-import type { BuiltinAgentName, AgentOverrideConfig, AgentOverrides } from "./types"
-import { sisyphusAgent } from "./sisyphus"
-import { oracleAgent } from "./oracle"
+import type { BuiltinAgentName, AgentOverrideConfig, AgentOverrides, AgentFactory } from "./types"
+import { createSisyphusAgent } from "./sisyphus"
+import { createOracleAgent } from "./oracle"
 import { librarianAgent } from "./librarian"
 import { exploreAgent } from "./explore"
 import { frontendUiUxEngineerAgent } from "./frontend-ui-ux-engineer"
@@ -9,9 +9,11 @@ import { documentWriterAgent } from "./document-writer"
 import { multimodalLookerAgent } from "./multimodal-looker"
 import { deepMerge } from "../shared"
 
-const allBuiltinAgents: Record<BuiltinAgentName, AgentConfig> = {
-  Sisyphus: sisyphusAgent,
-  oracle: oracleAgent,
+type AgentSource = AgentFactory | AgentConfig
+
+const agentSources: Record<BuiltinAgentName, AgentSource> = {
+  Sisyphus: createSisyphusAgent,
+  oracle: createOracleAgent,
   librarian: librarianAgent,
   explore: exploreAgent,
   "frontend-ui-ux-engineer": frontendUiUxEngineerAgent,
@@ -19,6 +21,14 @@ const allBuiltinAgents: Record<BuiltinAgentName, AgentConfig> = {
   "multimodal-looker": multimodalLookerAgent,
 }
 
+function isFactory(source: AgentSource): source is AgentFactory {
+  return typeof source === "function"
+}
+
+function buildAgent(source: AgentSource, model?: string): AgentConfig {
+  return isFactory(source) ? source(model) : source
+}
+
 export function createEnvContext(directory: string): string {
   const now = new Date()
   const timezone = Intl.DateTimeFormat().resolvedOptions().timeZone
@@ -67,37 +77,29 @@ export function createBuiltinAgents(
 ): Record<string, AgentConfig> {
   const result: Record<string, AgentConfig> = {}
 
-  for (const [name, config] of Object.entries(allBuiltinAgents)) {
+  for (const [name, source] of Object.entries(agentSources)) {
     const agentName = name as BuiltinAgentName
 
     if (disabledAgents.includes(agentName)) {
       continue
     }
 
-    let finalConfig = config
+    const override = agentOverrides[agentName]
+    const model = override?.model ?? (agentName === "Sisyphus" ? systemDefaultModel : undefined)
+
+    let config = buildAgent(source, model)
 
     if ((agentName === "Sisyphus" || agentName === "librarian") && directory && config.prompt) {
       const envContext = createEnvContext(directory)
-      finalConfig = {
-        ...config,
-        prompt: config.prompt + envContext,
-      }
-    }
-
-    const override = agentOverrides[agentName]
-
-    if (agentName === "Sisyphus" && systemDefaultModel && !override?.model) {
-      finalConfig = {
-        ...finalConfig,
-        model: systemDefaultModel,
-      }
+      config = { ...config, prompt: config.prompt + envContext }
     }
 
     if (override) {
-      result[name] = mergeAgentConfig(finalConfig, override)
-    } else {
-      result[name] = finalConfig
+      const { model: _, ...restOverride } = override
+      config = mergeAgentConfig(config, restOverride)
     }
+
+    result[name] = config
   }
 
   return result