feat: support subagent reasoning overrides

.changeset/bright-subagents-reason.md

@@ -0,0 +1,6 @@
+---
+"@kilocode/cli": patch
+"kilo-code": patch
+---
+
+Support model-specific reasoning overrides for task subagents, including custom subagents with their own model and variant settings.

packages/kilo-vscode/tests/unit/settings-io.test.ts

@@ -168,12 +168,23 @@ describe("parseImport", () => {
   })
 
   it("preserves task subagent model and variant settings", () => {
-    const json = JSON.stringify({ subagent_model: "anthropic/claude-sonnet-4", subagent_variant: "high" })
+    const json = JSON.stringify({
+      subagent_model: "anthropic/claude-sonnet-4",
+      subagent_variant: "high",
+      subagent_variant_overrides: {
+        "anthropic/claude-sonnet-4": "max",
+        "openai/gpt-5": "xhigh",
+      },
+    })
     const result = parseImport(json)
     expect(result.ok).toBe(true)
     if (result.ok) {
       expect(result.config.subagent_model).toBe("anthropic/claude-sonnet-4")
       expect(result.config.subagent_variant).toBe("high")
+      expect(result.config.subagent_variant_overrides).toEqual({
+        "anthropic/claude-sonnet-4": "max",
+        "openai/gpt-5": "xhigh",
+      })
     }
   })
 

packages/kilo-vscode/webview-ui/src/components/settings/ModelsTab.tsx

@@ -1,4 +1,4 @@
-import { Component, For, createMemo } from "solid-js"
+import { Component, For, Show, createMemo } from "solid-js"
 import { Card } from "@kilocode/kilo-ui/card"
 import { useConfig } from "../../context/config"
 import { useLanguage } from "../../context/language"
@@ -36,32 +36,35 @@ const ModelsTab: Component = () => {
   }
 
   const subagentModel = createMemo(() => parseModelString(config().subagent_model ?? undefined))
-  const subagentVariants = createMemo(() => {
-    const model = provider.findModel(subagentModel())
-    return model?.variants ? Object.keys(model.variants) : []
-  })
+  const variantKey = createMemo(() => config().subagent_model ?? undefined)
+  const subagentVariants = createMemo(() => Object.keys(provider.findModel(subagentModel())?.variants ?? {}))
   const subagentVariant = createMemo(() => {
-    const list = subagentVariants()
-    if (list.length === 0) return undefined
-    const value = config().subagent_variant ?? undefined
-    return value && list.includes(value) ? value : undefined
+    const key = variantKey()
+    if (!key) return undefined
+    const value = config().subagent_variant_overrides?.[key]
+    if (value) return value
+    return config().subagent_model === key ? (config().subagent_variant ?? undefined) : undefined
   })
 
   function handleSubagentModelSelect(providerID: string, modelID: string) {
     if (!providerID || !modelID) {
       updateConfig({ subagent_model: null, subagent_variant: null })
       return
     }
-    const model = { providerID, modelID }
-    const variants = provider.findModel(model)?.variants
-    const list = variants ? Object.keys(variants) : []
-    const value = config().subagent_model === `${providerID}/${modelID}` ? config().subagent_variant : undefined
-    const variant = value && list.includes(value) ? value : list[0]
-    updateConfig({ subagent_model: `${providerID}/${modelID}`, subagent_variant: variant ?? null })
+    const value = `${providerID}/${modelID}`
+    updateConfig({
+      subagent_model: value,
+      ...(config().subagent_model === value ? {} : { subagent_variant: null }),
+    })
   }
 
-  function handleSubagentVariantSelect(value: string) {
-    updateConfig({ subagent_variant: value })
+  function updateSubagentVariant(value: string | null) {
+    const key = variantKey()
+    if (!key) return
+    updateConfig({
+      subagent_variant_overrides: { [key]: value },
+      ...(config().subagent_model === key ? { subagent_variant: null } : {}),
+    })
   }
 
   const allAgents = createMemo(() => session.agents())
@@ -124,7 +127,7 @@ const ModelsTab: Component = () => {
           title={language.t("settings.providers.subagentModel.title")}
           description={language.t("settings.providers.subagentModel.description")}
         >
-          <div style={{ display: "flex", "align-items": "center", gap: "8px", "flex-wrap": "wrap" }}>
+          <div style={{ display: "flex", "flex-direction": "column", "align-items": "flex-end", gap: "8px" }}>
             <ModelSelectorBase
               value={subagentModel()}
               onSelect={handleSubagentModelSelect}
@@ -134,12 +137,18 @@ const ModelsTab: Component = () => {
               label={language.t("settings.providers.subagentModel.title")}
               description={language.t("settings.providers.subagentModel.description")}
             />
-            <ThinkingSelectorBase
-              variants={subagentVariants()}
-              value={subagentVariant()}
-              onSelect={handleSubagentVariantSelect}
-              placement="bottom-start"
-            />
+            <Show when={subagentVariants().length > 0}>
+              <ThinkingSelectorBase
+                variants={subagentVariants()}
+                value={subagentVariant()}
+                onSelect={(value) => updateSubagentVariant(value)}
+                onClear={() => updateSubagentVariant(null)}
+                allowClear
+                clearLabel={language.t("settings.providers.notSet")}
+                placement="bottom-start"
+                globalTrigger={false}
+              />
+            </Show>
           </div>
         </SettingsRow>
         <SettingsRow

packages/kilo-vscode/webview-ui/src/components/settings/settings-io.ts

@@ -14,6 +14,7 @@ export const KNOWN_KEYS: ReadonlyArray<string> = [
   "small_model",
   "subagent_model",
   "subagent_variant",
+  "subagent_variant_overrides",
   "default_agent",
   "agent",
   "provider",

packages/kilo-vscode/webview-ui/src/styles/settings.css

@@ -107,6 +107,11 @@
     & > * {
       max-width: 100%;
     }
+
+    [data-slot="popover-trigger"] {
+      min-width: 0;
+      max-width: 100%;
+    }
   }
 }
 

packages/kilo-vscode/webview-ui/src/types/messages/config.ts

@@ -116,6 +116,7 @@ export interface Config {
   small_model?: string | null
   subagent_model?: string | null
   subagent_variant?: string | null
+  subagent_variant_overrides?: Record<string, string | null> | null
   default_agent?: string | null
   agent?: Record<string, AgentConfig>
   provider?: Record<string, ProviderConfig>

packages/opencode/src/config/config.ts

@@ -237,6 +237,12 @@ export const Info = Schema.Struct({
   subagent_variant: Schema.optional(Schema.NullOr(Schema.String)).annotate({
     description: "Default model variant for task-tool subagents when subagent_model is configured.",
   }),
+  subagent_variant_overrides: Schema.optional(
+    Schema.NullOr(Schema.Record(Schema.String, Schema.NullOr(Schema.String))),
+  ).annotate({
+    description:
+      "Model-specific variant overrides for task-tool subagents, keyed by provider/model. Valid overrides take precedence over saved, agent-specific, and inherited variants.",
+  }),
   default_agent: Schema.optional(Schema.NullOr(Schema.String)).annotate({
     description:
       "Default agent to use when none is specified. Must be a primary agent. Falls back to 'code' if not set or if the specified agent is invalid.",

packages/opencode/src/kilocode/tool/task.ts

@@ -84,6 +84,10 @@ export namespace KiloTask {
   type Saved = Model & { variant?: string }
   type Choice = { model: Model; variant?: string; sticky?: boolean; direct?: boolean }
 
+  function key(model: Model) {
+    return `${model.providerID}/${model.modelID}`
+  }
+
   function parse(value: string | null | undefined): Model | undefined {
     if (!value) return undefined
     const [providerID, ...parts] = value.split("/")
@@ -117,13 +121,14 @@ export namespace KiloTask {
   export const resolveModel = Effect.fn("KiloTask.resolveModel")(function* (input: {
     name: string
     agent: Pick<Agent.Info, "model" | "variant">
-    config: Pick<Config.Info, "subagent_model" | "subagent_variant">
+    config: Pick<Config.Info, "subagent_model" | "subagent_variant" | "subagent_variant_overrides">
     parent: Model
     variant?: string
     provider: Provider.Interface
   }) {
     const state = yield* saved(input.name)
     const cfg = parse(input.config.subagent_model)
+    const override = (model: Model) => input.config.subagent_variant_overrides?.[key(model)] ?? undefined
     const choices: Array<Choice | undefined> = [
       state
         ? {
@@ -138,7 +143,13 @@ export namespace KiloTask {
 
     for (const choice of choices) {
       if (!choice) continue
-      if (choice.direct) return { model: choice.model, variant: choice.variant }
+      if (choice.direct) {
+        const value = override(choice.model)
+        if (!value) return { model: choice.model, variant: choice.variant }
+        const full = yield* input.provider.getModel(choice.model.providerID, choice.model.modelID)
+        const variant = full.variants?.[value] ? value : choice.variant
+        return { model: choice.model, variant }
+      }
       const full = yield* input.provider.getModel(choice.model.providerID, choice.model.modelID).pipe(
         Effect.catchTag("ProviderModelNotFoundError", (err) =>
           Effect.sync(() => {
@@ -152,13 +163,21 @@ export namespace KiloTask {
         ),
       )
       if (!full) continue
-      const variant = choice.variant && full.variants?.[choice.variant] ? choice.variant : undefined
+      const fallback = choice.variant && full.variants?.[choice.variant] ? choice.variant : undefined
+      const value = override(choice.model)
+      const variant = value && full.variants?.[value] ? value : fallback
       return {
         model: choice.sticky && variant ? { ...choice.model, variant } : choice.model,
         variant,
       }
     }
 
-    return { model: input.parent, variant: input.variant }
+    const value = override(input.parent)
+    if (!value) return { model: input.parent, variant: input.variant }
+    const full = yield* input.provider
+      .getModel(input.parent.providerID, input.parent.modelID)
+      .pipe(Effect.catchTag("ProviderModelNotFoundError", () => Effect.succeed(undefined)))
+    const variant = full?.variants?.[value] ? value : input.variant
+    return { model: input.parent, variant }
   })
 }

packages/opencode/test/kilocode/config/config.test.ts

@@ -234,6 +234,43 @@ describe("kilocode indexing config", () => {
   })
 })
 
+describe("subagent variant overrides", () => {
+  test("removes one model override without removing sibling models", () => {
+    const patch = decode({
+      subagent_variant_overrides: {
+        "anthropic/claude-sonnet-4-6": null,
+      },
+    })
+    const merged = KilocodeConfig.mergeConfig(
+      {
+        subagent_variant_overrides: {
+          "anthropic/claude-sonnet-4-6": "high",
+          "openai/gpt-5": "xhigh",
+        },
+      },
+      patch,
+    )
+
+    expect(patch.subagent_variant_overrides?.["anthropic/claude-sonnet-4-6"]).toBeNull()
+    expect(merged.subagent_variant_overrides).toEqual({ "openai/gpt-5": "xhigh" })
+  })
+
+  test("accepts a delete sentinel for the complete override map", () => {
+    const patch = decode({ subagent_variant_overrides: null })
+    const merged = KilocodeConfig.mergeConfig(
+      {
+        subagent_variant_overrides: {
+          "anthropic/claude-sonnet-4-6": "high",
+        },
+      },
+      patch,
+    )
+
+    expect(patch.subagent_variant_overrides).toBeNull()
+    expect(merged.subagent_variant_overrides).toBeUndefined()
+  })
+})
+
 describe("agent config", () => {
   test("accepts delete sentinels for agent model and variant overrides", () => {
     const patch = decode({ agent: { explore: { model: null, variant: null } } })