feat: add agent default variant handling in TUI and desktop

- Resolve variants via selected/configured/current helper flow in both clients
- Allow agent-configured variants across models when the active model supports that variant key
- Update TUI hydration to avoid promoting configured defaults into explicit overrides
- Add and adjust variant tests for app, TUI, and agent config
- Add a triage agent variant example

Closes #7138

Author: CasualDeveloper

.opencode/agent/triage.md

@@ -3,6 +3,7 @@ mode: primary
 hidden: true
 model: opencode/minimax-m2.5
 color: "#44BA81"
+variant: "high"
 tools:
   "*": false
   "github-triage": true

packages/app/src/context/local.tsx

@@ -206,6 +206,9 @@ export const { use: useLocal, provider: LocalProvider } = createSimpleContext({
               configured: this.configured(),
             })
           },
+          effective() {
+            return this.current()
+          },
           list() {
             const m = current()
             if (!m) return []

packages/app/src/context/model-variant.test.ts

@@ -2,23 +2,23 @@ import { describe, expect, test } from "bun:test"
 import { cycleModelVariant, getConfiguredAgentVariant, resolveModelVariant } from "./model-variant"
 
 describe("model variant", () => {
-  test("resolves configured agent variant when model matches", () => {
+  test("resolves configured agent variant when model supports variant", () => {
     const value = getConfiguredAgentVariant({
       agent: {
         model: { providerID: "openai", modelID: "gpt-5.2" },
         variant: "xhigh",
       },
       model: {
-        providerID: "openai",
-        modelID: "gpt-5.2",
+        providerID: "anthropic",
+        modelID: "claude-sonnet-4",
         variants: { low: {}, high: {}, xhigh: {} },
       },
     })
 
     expect(value).toBe("xhigh")
   })
 
-  test("ignores configured variant when model does not match", () => {
+  test("ignores configured variant when model does not support it", () => {
     const value = getConfiguredAgentVariant({
       agent: {
         model: { providerID: "openai", modelID: "gpt-5.2" },
@@ -27,7 +27,7 @@ describe("model variant", () => {
       model: {
         providerID: "anthropic",
         modelID: "claude-sonnet-4",
-        variants: { low: {}, high: {}, xhigh: {} },
+        variants: { low: {}, high: {} },
       },
     })
 
@@ -44,17 +44,17 @@ describe("model variant", () => {
     expect(value).toBe("high")
   })
 
-  test("cycles from configured variant to next", () => {
+  test("starts cycling from first variant when no explicit selection", () => {
     const value = cycleModelVariant({
       variants: ["low", "high", "xhigh"],
       selected: undefined,
       configured: "high",
     })
 
-    expect(value).toBe("xhigh")
+    expect(value).toBe("low")
   })
 
-  test("wraps from configured last variant to first", () => {
+  test("starts from first even when configured is last", () => {
     const value = cycleModelVariant({
       variants: ["low", "high", "xhigh"],
       selected: undefined,
@@ -63,4 +63,17 @@ describe("model variant", () => {
 
     expect(value).toBe("low")
   })
+
+  test("cycles through all variants from explicit selection", () => {
+    const variants = ["low", "high", "xhigh"]
+    const first = cycleModelVariant({ variants, selected: undefined, configured: "high" })
+    const second = cycleModelVariant({ variants, selected: first, configured: "high" })
+    const third = cycleModelVariant({ variants, selected: second, configured: "high" })
+    const fourth = cycleModelVariant({ variants, selected: third, configured: "high" })
+
+    expect(first).toBe("low")
+    expect(second).toBe("high")
+    expect(third).toBe("xhigh")
+    expect(fourth).toBeUndefined()
+  })
 })

packages/app/src/context/model-variant.ts

@@ -20,10 +20,7 @@ type VariantInput = {
 
 export function getConfiguredAgentVariant(input: { agent: Agent | undefined; model: Model | undefined }) {
   if (!input.agent?.variant) return undefined
-  if (!input.agent.model) return undefined
   if (!input.model?.variants) return undefined
-  if (input.agent.model.providerID !== input.model.providerID) return undefined
-  if (input.agent.model.modelID !== input.model.modelID) return undefined
   if (!(input.agent.variant in input.model.variants)) return undefined
   return input.agent.variant
 }
@@ -41,10 +38,5 @@ export function cycleModelVariant(input: VariantInput) {
     if (index === input.variants.length - 1) return undefined
     return input.variants[index + 1]
   }
-  if (input.configured && input.variants.includes(input.configured)) {
-    const index = input.variants.indexOf(input.configured)
-    if (index === input.variants.length - 1) return input.variants[0]
-    return input.variants[index + 1]
-  }
   return input.variants[0]
 }

packages/opencode/src/cli/cmd/tui/component/prompt/index.tsx

@@ -32,6 +32,7 @@ import { useToast } from "../../ui/toast"
 import { useKV } from "../../context/kv"
 import { useTextareaKeybindings } from "../textarea-keybindings"
 import { DialogSkill } from "../dialog-skill"
+import { getConfiguredAgentVariant } from "@tui/context/model-variant"
 
 export type PromptProps = {
   sessionID?: string
@@ -161,7 +162,17 @@ export function Prompt(props: PromptProps) {
       if (msg.agent && isPrimaryAgent) {
         local.agent.set(msg.agent)
         if (msg.model) local.model.set(msg.model)
-        if (msg.variant) local.model.variant.set(msg.variant)
+        if (msg.variant) {
+          const info = local.agent.list().find((x) => x.name === msg.agent)
+          const provider = msg.model ? sync.data.provider.find((x) => x.id === msg.model.providerID) : undefined
+          const model = msg.model ? provider?.models[msg.model.modelID] : undefined
+          const configured = getConfiguredAgentVariant({
+            agent: { variant: info?.variant },
+            model: { variants: model?.variants },
+          })
+          if (msg.variant === configured) local.model.variant.set(undefined)
+          if (msg.variant !== configured) local.model.variant.set(msg.variant)
+        }
       }
     }
   })
@@ -743,8 +754,8 @@ export function Prompt(props: PromptProps) {
   const showVariant = createMemo(() => {
     const variants = local.model.variant.list()
     if (variants.length === 0) return false
-    const current = local.model.variant.current()
-    return !!current
+    const effective = local.model.variant.effective()
+    return !!effective
   })
 
   const placeholderText = createMemo(() => {
@@ -1007,7 +1018,7 @@ export function Prompt(props: PromptProps) {
                   <Show when={showVariant()}>
                     <text fg={theme.textMuted}>·</text>
                     <text>
-                      <span style={{ fg: theme.warning, bold: true }}>{local.model.variant.current()}</span>
+                      <span style={{ fg: theme.warning, bold: true }}>{local.model.variant.effective()}</span>
                     </text>
                   </Show>
                 </box>

packages/opencode/src/cli/cmd/tui/context/local.tsx

@@ -12,6 +12,7 @@ import { Provider } from "@/provider/provider"
 import { useArgs } from "./args"
 import { useSDK } from "./sdk"
 import { RGBA } from "@opentui/core"
+import { cycleModelVariant, getConfiguredAgentVariant, resolveModelVariant } from "./model-variant"
 
 export const { use: useLocal, provider: LocalProvider } = createSimpleContext({
   name: "Local",
@@ -324,12 +325,33 @@ export const { use: useLocal, provider: LocalProvider } = createSimpleContext({
           })
         },
         variant: {
-          current() {
+          configured() {
+            const a = agent.current()
+            const m = currentModel()
+            if (!m) return undefined
+            const provider = sync.data.provider.find((x) => x.id === m.providerID)
+            const info = provider?.models[m.modelID]
+            return getConfiguredAgentVariant({
+              agent: { variant: a.variant },
+              model: { variants: info?.variants },
+            })
+          },
+          selected() {
             const m = currentModel()
             if (!m) return undefined
             const key = `${m.providerID}/${m.modelID}`
             return modelStore.variant[key]
           },
+          current() {
+            return resolveModelVariant({
+              variants: this.list(),
+              selected: this.selected(),
+              configured: this.configured(),
+            })
+          },
+          effective() {
+            return this.current()
+          },
           list() {
             const m = currentModel()
             if (!m) return []
@@ -348,17 +370,13 @@ export const { use: useLocal, provider: LocalProvider } = createSimpleContext({
           cycle() {
             const variants = this.list()
             if (variants.length === 0) return
-            const current = this.current()
-            if (!current) {
-              this.set(variants[0])
-              return
-            }
-            const index = variants.indexOf(current)
-            if (index === -1 || index === variants.length - 1) {
-              this.set(undefined)
-              return
-            }
-            this.set(variants[index + 1])
+            this.set(
+              cycleModelVariant({
+                variants,
+                selected: this.selected(),
+                configured: this.configured(),
+              }),
+            )
           },
         },
       }

packages/opencode/src/cli/cmd/tui/context/model-variant.ts

@@ -0,0 +1,36 @@
+type Agent = {
+  variant?: string
+}
+
+type Model = {
+  variants?: Record<string, unknown>
+}
+
+type VariantInput = {
+  variants: string[]
+  selected: string | undefined
+  configured: string | undefined
+}
+
+export function getConfiguredAgentVariant(input: { agent: Agent | undefined; model: Model | undefined }) {
+  if (!input.agent?.variant) return undefined
+  if (!input.model?.variants) return undefined
+  if (!(input.agent.variant in input.model.variants)) return undefined
+  return input.agent.variant
+}
+
+export function resolveModelVariant(input: VariantInput) {
+  if (input.selected && input.variants.includes(input.selected)) return input.selected
+  if (input.configured && input.variants.includes(input.configured)) return input.configured
+  return undefined
+}
+
+export function cycleModelVariant(input: VariantInput) {
+  if (input.variants.length === 0) return undefined
+  if (input.selected && input.variants.includes(input.selected)) {
+    const index = input.variants.indexOf(input.selected)
+    if (index === input.variants.length - 1) return undefined
+    return input.variants[index + 1]
+  }
+  return input.variants[0]
+}

packages/opencode/test/agent/agent.test.ts

@@ -687,3 +687,31 @@ test("defaultAgent throws when all primary agents are disabled", async () => {
     },
   })
 })
+
+test("agent variant can be set from config", async () => {
+  await using tmp = await tmpdir({
+    config: {
+      agent: {
+        build: { variant: "high" },
+      },
+    },
+  })
+  await Instance.provide({
+    directory: tmp.path,
+    fn: async () => {
+      const build = await Agent.get("build")
+      expect(build?.variant).toBe("high")
+    },
+  })
+})
+
+test("agent variant defaults to undefined when not set", async () => {
+  await using tmp = await tmpdir()
+  await Instance.provide({
+    directory: tmp.path,
+    fn: async () => {
+      const build = await Agent.get("build")
+      expect(build?.variant).toBeUndefined()
+    },
+  })
+})

packages/opencode/test/cli/tui/model-variant.test.ts

@@ -0,0 +1,40 @@
+import { describe, expect, test } from "bun:test"
+import {
+  cycleModelVariant,
+  getConfiguredAgentVariant,
+  resolveModelVariant,
+} from "../../../src/cli/cmd/tui/context/model-variant"
+
+describe("tui model variant", () => {
+  test("resolves configured variant when active model supports it", () => {
+    const value = getConfiguredAgentVariant({
+      agent: { variant: "high" },
+      model: { variants: { low: {}, high: {} } },
+    })
+
+    expect(value).toBe("high")
+  })
+
+  test("prefers selected variant over configured variant", () => {
+    const value = resolveModelVariant({
+      variants: ["low", "high", "xhigh"],
+      selected: "xhigh",
+      configured: "high",
+    })
+
+    expect(value).toBe("xhigh")
+  })
+
+  test("cycles through all variants from explicit selection", () => {
+    const variants = ["low", "high", "xhigh"]
+    const first = cycleModelVariant({ variants, selected: undefined, configured: "high" })
+    const second = cycleModelVariant({ variants, selected: first, configured: "high" })
+    const third = cycleModelVariant({ variants, selected: second, configured: "high" })
+    const fourth = cycleModelVariant({ variants, selected: third, configured: "high" })
+
+    expect(first).toBe("low")
+    expect(second).toBe("high")
+    expect(third).toBe("xhigh")
+    expect(fourth).toBeUndefined()
+  })
+})