core: add Model service for v2 system to track AI providers and capabilities

Adds the AuthV2 layer to the application runtime so the v2 authentication
system is available throughout the app. This ensures auth state is properly
managed and accessible to all components that depend on it.

packages/core/src/global.ts

@@ -71,6 +71,8 @@ export const layer = Layer.effect(
   Effect.sync(() => Service.of(make())),
 )
 
+export const defaultLayer = layer
+
 export const layerWith = (input: Partial<Interface>) =>
   Layer.effect(
     Service,

packages/opencode/src/cli/cmd/tui/context/sync-v2.tsx

@@ -11,21 +11,21 @@ import { createSimpleContext } from "./helper"
 import { useSDK } from "./sdk"
 
 function activeAssistant(messages: SessionMessage[]) {
-  const index = messages.findLastIndex((message) => message.type === "assistant" && !message.time.completed)
+  const index = messages.findIndex((message) => message.type === "assistant" && !message.time.completed)
   if (index < 0) return
   const assistant = messages[index]
   return assistant?.type === "assistant" ? assistant : undefined
 }
 
 function activeCompaction(messages: SessionMessage[]) {
-  const index = messages.findLastIndex((message) => message.type === "compaction")
+  const index = messages.findIndex((message) => message.type === "compaction")
   if (index < 0) return
   const compaction = messages[index]
   return compaction?.type === "compaction" ? compaction : undefined
 }
 
 function activeShell(messages: SessionMessage[], callID: string) {
-  const index = messages.findLastIndex((message) => message.type === "shell" && message.callID === callID)
+  const index = messages.findIndex((message) => message.type === "shell" && message.callID === callID)
   if (index < 0) return
   const shell = messages[index]
   return shell?.type === "shell" ? shell : undefined
@@ -74,7 +74,7 @@ export const { use: useSyncV2, provider: SyncProviderV2 } = createSimpleContext(
       switch (event.type) {
         case "session.next.prompted": {
           update(event.properties.sessionID, (draft) => {
-            draft.push({
+            draft.unshift({
               id: event.id,
               type: "user",
               text: event.properties.prompt.text,
@@ -87,7 +87,7 @@ export const { use: useSyncV2, provider: SyncProviderV2 } = createSimpleContext(
         }
         case "session.next.synthetic":
           update(event.properties.sessionID, (draft) => {
-            draft.push({
+            draft.unshift({
               id: event.id,
               type: "synthetic",
               sessionID: event.properties.sessionID,
@@ -98,7 +98,7 @@ export const { use: useSyncV2, provider: SyncProviderV2 } = createSimpleContext(
           break
         case "session.next.shell.started":
           update(event.properties.sessionID, (draft) => {
-            draft.push({
+            draft.unshift({
               id: event.id,
               type: "shell",
               callID: event.properties.callID,
@@ -120,7 +120,7 @@ export const { use: useSyncV2, provider: SyncProviderV2 } = createSimpleContext(
           update(event.properties.sessionID, (draft) => {
             const currentAssistant = activeAssistant(draft)
             if (currentAssistant) currentAssistant.time.completed = event.properties.timestamp
-            draft.push({
+            draft.unshift({
               id: event.id,
               type: "assistant",
               agent: event.properties.agent,
@@ -259,7 +259,7 @@ export const { use: useSyncV2, provider: SyncProviderV2 } = createSimpleContext(
           break
         case "session.next.compaction.started":
           update(event.properties.sessionID, (draft) => {
-            draft.push({
+            draft.unshift({
               id: event.id,
               type: "compaction",
               reason: event.properties.reason,

packages/opencode/src/cli/cmd/tui/feature-plugins/system/session-v2.tsx

@@ -5,7 +5,7 @@ import { Spinner } from "@tui/component/spinner"
 import { useTheme } from "@tui/context/theme"
 import { useLocal } from "@tui/context/local"
 import { useKeyboard, useRenderer, useTerminalDimensions, type JSX } from "@opentui/solid"
-import type { SyntaxStyle } from "@opentui/core"
+import { TextAttributes, type BoxRenderable, type SyntaxStyle } from "@opentui/core"
 import { Locale } from "@/util/locale"
 import { LANGUAGE_EXTENSIONS } from "@/lsp/language"
 import path from "path"
@@ -44,6 +44,10 @@ function View(props: { api: TuiPluginApi; sessionID: string }) {
   const messages = createMemo(() => sync.data.messages[props.sessionID] ?? [])
   const renderedMessages = createMemo(() => messages().toReversed())
   const lastAssistant = createMemo(() => renderedMessages().findLast((message) => message.type === "assistant"))
+  const lastUserCreated = (index: number) =>
+    renderedMessages()
+      .slice(0, index)
+      .findLast((message) => message.type === "user")?.time.created
 
   createEffect(() => {
     void sync.session.message.sync(props.sessionID)
@@ -83,10 +87,11 @@ function View(props: { api: TuiPluginApi; sessionID: string }) {
                       last={lastAssistant()?.id === message.id}
                       syntax={syntax()}
                       subtleSyntax={subtleSyntax()}
+                      start={lastUserCreated(index())}
                     />
                   </Match>
                   <Match when={message.type === "synthetic"}>
-                    <SyntheticMessage message={message as SessionMessageSynthetic} index={index()} />
+                    <></>
                   </Match>
                   <Match when={message.type === "shell"}>
                     <ShellMessage message={message as SessionMessageShell} />
@@ -146,63 +151,36 @@ function UserMessage(props: { message: SessionMessageUser; index: number }) {
     <box
       id={props.message.id}
       border={["left"]}
-      borderColor={theme.primary}
+      borderColor={theme.secondary}
       customBorderChars={SplitBorder.customBorderChars}
       marginTop={props.index === 0 ? 0 : 1}
       flexShrink={0}
-    >
-      <box paddingTop={1} paddingBottom={1} paddingLeft={2} backgroundColor={theme.backgroundPanel}>
-        <Show
-          when={props.message.text.trim()}
-          fallback={
-            <MissingData label="User message text" detail={`Message ${props.message.id} has no text field content.`} />
-          }
-        >
-          <text fg={theme.text}>{props.message.text}</text>
-        </Show>
-        <Show when={attachments().length}>
-          <box flexDirection="row" paddingTop={1} gap={1} flexWrap="wrap">
-            <For each={props.message.files ?? []}>
-              {(file) => (
-                <text fg={theme.text}>
-                  <span style={{ bg: theme.secondary, fg: theme.background }}> {file.mime} </span>
-                  <span style={{ bg: theme.backgroundElement, fg: theme.textMuted }}> {file.name ?? file.uri} </span>
-                </text>
-              )}
-            </For>
-            <For each={props.message.agents ?? []}>
-              {(agent) => (
-                <text fg={theme.text}>
-                  <span style={{ bg: theme.accent, fg: theme.background }}> agent </span>
-                  <span style={{ bg: theme.backgroundElement, fg: theme.textMuted }}> {agent.name} </span>
-                </text>
-              )}
-            </For>
-          </box>
-        </Show>
-        <text fg={theme.textMuted}>{Locale.todayTimeOrDateTime(props.message.time.created)}</text>
-      </box>
-    </box>
-  )
-}
-
-function SyntheticMessage(props: { message: SessionMessageSynthetic; index: number }) {
-  const { theme } = useTheme()
-  return (
-    <box
-      id={props.message.id}
-      border={["left"]}
-      borderColor={theme.backgroundElement}
-      customBorderChars={SplitBorder.customBorderChars}
-      marginTop={props.index === 0 ? 0 : 1}
-      paddingLeft={2}
       paddingTop={1}
       paddingBottom={1}
+      paddingLeft={2}
       backgroundColor={theme.backgroundPanel}
-      flexShrink={0}
     >
-      <text fg={theme.textMuted}>Synthetic</text>
       <text fg={theme.text}>{props.message.text}</text>
+      <Show when={attachments().length}>
+        <box flexDirection="row" paddingTop={1} gap={1} flexWrap="wrap">
+          <For each={props.message.files ?? []}>
+            {(file) => (
+              <text fg={theme.text}>
+                <span style={{ bg: theme.secondary, fg: theme.background }}> {file.mime} </span>
+                <span style={{ bg: theme.backgroundElement, fg: theme.textMuted }}> {file.name ?? file.uri} </span>
+              </text>
+            )}
+          </For>
+          <For each={props.message.agents ?? []}>
+            {(agent) => (
+              <text fg={theme.text}>
+                <span style={{ bg: theme.accent, fg: theme.background }}> agent </span>
+                <span style={{ bg: theme.backgroundElement, fg: theme.textMuted }}> {agent.name} </span>
+              </text>
+            )}
+          </For>
+        </box>
+      </Show>
     </box>
   )
 }
@@ -237,7 +215,7 @@ function ShellMessage(props: { message: SessionMessageShell }) {
 }
 
 function CompactionMessage(props: { message: SessionMessageCompaction }) {
-  const { theme } = useTheme()
+  const { theme, syntax } = useTheme()
   return (
     <box
       marginTop={1}
@@ -248,7 +226,19 @@ function CompactionMessage(props: { message: SessionMessageCompaction }) {
       flexShrink={0}
     >
       <Show when={props.message.summary}>
-        <text fg={theme.textMuted}>{props.message.summary}</text>
+        {(summary) => (
+          <box paddingLeft={3} paddingTop={1}>
+            <code
+              filetype="markdown"
+              drawUnstyledText={false}
+              streaming={false}
+              syntaxStyle={syntax()}
+              content={summary().trim()}
+              conceal={true}
+              fg={theme.text}
+            />
+          </box>
+        )}
       </Show>
     </box>
   )
@@ -294,12 +284,13 @@ function AssistantMessage(props: {
   last: boolean
   syntax: SyntaxStyle
   subtleSyntax: SyntaxStyle
+  start?: number
 }) {
   const { theme } = useTheme()
   const local = useLocal()
   const duration = createMemo(() => {
     if (!props.message.time.completed) return 0
-    return props.message.time.completed - props.message.time.created
+    return props.message.time.completed - (props.start ?? props.message.time.created)
   })
   const model = createMemo(() => {
     const variant = props.message.model.variant ? `/${props.message.model.variant}` : ""
@@ -361,7 +352,7 @@ function AssistantText(props: { part: SessionMessageAssistantText; syntax: Synta
   const { theme } = useTheme()
   return (
     <Show when={props.part.text.trim()}>
-      <box paddingLeft={3} marginTop={1} flexShrink={0}>
+      <box paddingLeft={3} marginTop={1} flexShrink={0} id="text">
         <code
           filetype="markdown"
           drawUnstyledText={false}
@@ -521,33 +512,93 @@ function InlineTool(props: {
   part: SessionMessageAssistantTool
 }) {
   const { theme } = useTheme()
+  const renderer = useRenderer()
+  const [margin, setMargin] = createSignal(0)
+  const [hover, setHover] = createSignal(false)
+  const [showError, setShowError] = createSignal(false)
   const error = createMemo(() => (props.part.state.status === "error" ? props.part.state.error.message : undefined))
+  const complete = createMemo(() => !!props.complete)
   const denied = createMemo(() => {
     const message = error()
     if (!message) return false
     return (
       message.includes("QuestionRejectedError") ||
       message.includes("rejected permission") ||
+      message.includes("specified a rule") ||
       message.includes("user dismissed")
     )
   })
+  const fg = createMemo(() => {
+    if (error()) return theme.error
+    if (complete()) return theme.textMuted
+    return theme.text
+  })
+  const attributes = createMemo(() => (denied() ? TextAttributes.STRIKETHROUGH : undefined))
   return (
-    <box marginTop={1} paddingLeft={3} flexShrink={0}>
-      <Switch>
-        <Match when={props.spinner}>
-          <Spinner color={theme.text}>{props.children}</Spinner>
-        </Match>
-        <Match when={true}>
-          <text paddingLeft={3} fg={props.complete ? theme.textMuted : theme.text}>
-            <Show fallback={<>~ {props.pending}</>} when={props.complete}>
-              {props.icon} {props.children}
-            </Show>
-          </text>
-        </Match>
-      </Switch>
-      <Show when={error() && !denied()}>
-        <text fg={theme.error}>{error()}</text>
-      </Show>
+    <box
+      marginTop={margin()}
+      paddingLeft={3}
+      flexShrink={0}
+      flexDirection="row"
+      gap={1}
+      backgroundColor={hover() && error() ? theme.backgroundMenu : undefined}
+      onMouseOver={() => error() && setHover(true)}
+      onMouseOut={() => setHover(false)}
+      onMouseUp={() => {
+        if (!error()) return
+        if (renderer.getSelection()?.getSelectedText()) return
+        setShowError((prev) => !prev)
+      }}
+      renderBefore={function () {
+        const el = this as BoxRenderable
+        const parent = el.parent
+        if (!parent) return
+        const previous = parent.getChildren()[parent.getChildren().indexOf(el) - 1]
+        if (!previous) {
+          setMargin(0)
+          return
+        }
+        if (previous.id.startsWith("text")) setMargin(1)
+      }}
+    >
+      <box flexShrink={0}>
+        <Switch>
+          <Match when={props.spinner}>
+            <Spinner color={theme.text} />
+          </Match>
+          <Match when={complete()}>
+            <text fg={fg()} attributes={attributes()}>
+              {props.icon}
+            </text>
+          </Match>
+          <Match when={true}>
+            <text fg={fg()} attributes={attributes()}>
+              ~
+            </text>
+          </Match>
+        </Switch>
+      </box>
+      <box flexGrow={1}>
+        <box>
+          <Switch>
+            <Match when={complete()}>
+              <text fg={fg()} attributes={attributes()}>
+                {props.children}
+              </text>
+            </Match>
+            <Match when={true}>
+              <text fg={fg()} attributes={attributes()}>
+                {props.pending}
+              </text>
+            </Match>
+          </Switch>
+        </box>
+        <Show when={showError() && error()}>
+          <box>
+            <text fg={theme.error}>{error()}</text>
+          </box>
+        </Show>
+      </box>
     </box>
   )
 }

packages/opencode/src/id/id.ts

@@ -13,6 +13,7 @@ const prefixes = {
   tool: "tool",
   workspace: "wrk",
   entry: "ent",
+  account: "act",
 } as const
 
 export function schema(prefix: keyof typeof prefixes) {

packages/opencode/src/session/processor.ts

@@ -655,7 +655,7 @@ export const layer: Layer.Layer<
           EventV2.run(SessionEvent.Step.Failed.Sync, {
             sessionID: ctx.sessionID,
             error: {
-              type: error.name,
+              type: "unknown",
               message: errorMessage(e),
             },
             timestamp: DateTime.makeUnsafe(Date.now()),

packages/opencode/src/v2/auth.ts

@@ -0,0 +1,246 @@
+import path from "path"
+import { Effect, Layer, Option, Schema, Context, SynchronizedRef } from "effect"
+import { Identifier } from "@opencode-ai/core/util/identifier"
+import { NonNegativeInt, withStatics } from "@/util/schema"
+import { Global } from "@opencode-ai/core/global"
+import { AppFileSystem } from "@opencode-ai/core/filesystem"
+
+export const OAUTH_DUMMY_KEY = "opencode-oauth-dummy-key"
+
+const AccountID = Schema.String.pipe(
+  Schema.brand("AccountID"),
+  withStatics((schema) => ({ create: () => schema.make("acc_" + Identifier.ascending()) })),
+)
+export type AccountID = typeof AccountID.Type
+
+export const ServiceID = Schema.String.pipe(Schema.brand("ServiceID"))
+export type ServiceID = typeof ServiceID.Type
+
+export class OAuthCredential extends Schema.Class<OAuthCredential>("AuthV2.OAuthCredential")({
+  type: Schema.Literal("oauth"),
+  refresh: Schema.String,
+  access: Schema.String,
+  expires: NonNegativeInt,
+}) {}
+
+export class ApiKeyCredential extends Schema.Class<ApiKeyCredential>("AuthV2.ApiKeyCredential")({
+  type: Schema.Literal("api"),
+  key: Schema.String,
+  metadata: Schema.optional(Schema.Record(Schema.String, Schema.String)),
+}) {}
+
+export const Credential = Schema.Union([OAuthCredential, ApiKeyCredential])
+  .pipe(Schema.toTaggedUnion("type"))
+  .annotate({
+    identifier: "AuthV2.Credential",
+  })
+export type Credential = Schema.Schema.Type<typeof Credential>
+
+export class Account extends Schema.Class<Account>("AuthV2.Account")({
+  id: AccountID,
+  serviceID: ServiceID,
+  description: Schema.String,
+  credential: Credential,
+}) {}
+
+export class AuthFileWriteError extends Schema.TaggedErrorClass<AuthFileWriteError>()("AuthV2.FileWriteError", {
+  operation: Schema.Union([Schema.Literal("migrate"), Schema.Literal("write")]),
+  cause: Schema.Defect,
+}) {}
+
+export type AuthError = AuthFileWriteError
+
+interface Writable {
+  version: 2
+  accounts: Record<string, Account>
+  active: Record<string, AccountID>
+}
+
+const decodeV1 = Schema.decodeUnknownOption(Schema.Record(Schema.String, Credential))
+
+function migrate(old: Record<string, unknown>): Writable {
+  const accounts: Record<string, Account> = {}
+  const active: Record<string, AccountID> = {}
+  for (const [serviceID, value] of Object.entries(old)) {
+    const decoded = Option.getOrElse(decodeV1({ [serviceID]: value }), () => ({}))
+    const parsed = (decoded as Record<string, Credential>)[serviceID]
+    if (!parsed) continue
+    const id = Identifier.ascending()
+    const accountID = AccountID.make(id)
+    const brandedServiceID = ServiceID.make(serviceID)
+    accounts[id] = new Account({
+      id: accountID,
+      serviceID: brandedServiceID,
+      description: "default",
+      credential: parsed,
+    })
+    active[brandedServiceID] = accountID
+  }
+  return { version: 2, accounts, active }
+}
+
+export interface Interface {
+  readonly get: (accountID: AccountID) => Effect.Effect<Account | undefined, AuthError>
+  readonly all: () => Effect.Effect<Account[], AuthError>
+  readonly create: (input: {
+    serviceID: ServiceID
+    credential: Credential
+    description?: string
+    active?: boolean
+  }) => Effect.Effect<Account, AuthError>
+  readonly update: (
+    accountID: AccountID,
+    updates: Partial<Pick<Account, "description" | "credential">>,
+  ) => Effect.Effect<void, AuthError>
+  readonly remove: (accountID: AccountID) => Effect.Effect<void, AuthError>
+  readonly activate: (accountID: AccountID) => Effect.Effect<void, AuthError>
+  readonly active: (serviceID: ServiceID) => Effect.Effect<Account | undefined, AuthError>
+  readonly forService: (serviceID: ServiceID) => Effect.Effect<Account[], AuthError>
+}
+
+export class Service extends Context.Service<Service, Interface>()("@opencode/v2/Auth") {}
+
+export const layer = Layer.effect(
+  Service,
+  Effect.gen(function* () {
+    const fsys = yield* AppFileSystem.Service
+    const global = yield* Global.Service
+    const file = path.join(global.data, "auth-v2.json")
+
+    const load: () => Effect.Effect<Writable, AuthError> = Effect.fnUntraced(function* () {
+      if (process.env.OPENCODE_AUTH_CONTENT) {
+        try {
+          return JSON.parse(process.env.OPENCODE_AUTH_CONTENT)
+        } catch {}
+      }
+
+      const raw = yield* fsys.readJson(file).pipe(Effect.orElseSucceed(() => null))
+
+      if (!raw || typeof raw !== "object") return { version: 2, accounts: {}, active: {} }
+
+      if ("version" in raw && raw.version === 2) return raw as Writable
+
+      const migrated = migrate(raw as Record<string, unknown>)
+      yield* fsys
+        .writeJson(file, migrated, 0o600)
+        .pipe(Effect.mapError((cause) => new AuthFileWriteError({ operation: "migrate", cause })))
+      return migrated
+    })
+
+    const write = (data: Writable) =>
+      fsys
+        .writeJson(file, data, 0o600)
+        .pipe(Effect.mapError((cause) => new AuthFileWriteError({ operation: "write", cause })))
+
+    const state = SynchronizedRef.makeUnsafe(yield* load())
+
+    const result: Interface = {
+      get: Effect.fn("AuthV2.get")(function* (accountID) {
+        return (yield* SynchronizedRef.get(state)).accounts[accountID]
+      }),
+
+      all: Effect.fn("AuthV2.all")(function* () {
+        return Object.values((yield* SynchronizedRef.get(state)).accounts)
+      }),
+
+      active: Effect.fn("AuthV2.active")(function* (serviceID) {
+        const data = yield* SynchronizedRef.get(state)
+        return (
+          data.accounts[data.active[serviceID]] ?? Object.values(data.accounts).find((a) => a.serviceID === serviceID)
+        )
+      }),
+
+      forService: Effect.fn("AuthV2.list")(function* (serviceID) {
+        return Object.values((yield* SynchronizedRef.get(state)).accounts).filter((a) => a.serviceID === serviceID)
+      }),
+
+      create: Effect.fn("AuthV2.add")(function* (input) {
+        return yield* SynchronizedRef.modifyEffect(
+          state,
+          Effect.fnUntraced(function* (data) {
+            const account = new Account({
+              id: AccountID.make(Identifier.ascending()),
+              serviceID: input.serviceID,
+              description: input.description ?? "default",
+              credential: input.credential,
+            })
+            const next = {
+              ...data,
+              accounts: { ...data.accounts, [account.id]: account },
+              active:
+                (input.active ?? Object.values(data.accounts).every((a) => a.serviceID !== input.serviceID))
+                  ? { ...data.active, [input.serviceID]: account.id }
+                  : data.active,
+            }
+
+            yield* write(next)
+            return [account, next] as const
+          }),
+        )
+      }),
+
+      update: Effect.fn("AuthV2.update")(function* (accountID, updates) {
+        yield* SynchronizedRef.modifyEffect(
+          state,
+          Effect.fnUntraced(function* (data) {
+            const existing = data.accounts[accountID]
+            if (!existing) return [undefined, data] as const
+
+            const next = {
+              ...data,
+              accounts: {
+                ...data.accounts,
+                [accountID]: new Account({
+                  id: accountID,
+                  serviceID: existing.serviceID,
+                  description: updates.description ?? existing.description,
+                  credential: updates.credential ?? existing.credential,
+                }),
+              },
+            }
+
+            yield* write(next)
+            return [undefined, next] as const
+          }),
+        )
+      }),
+
+      remove: Effect.fn("AuthV2.remove")(function* (accountID) {
+        yield* SynchronizedRef.modifyEffect(
+          state,
+          Effect.fnUntraced(function* (data) {
+            const accounts = { ...data.accounts }
+            const active = { ...data.active }
+            if (accounts[accountID] && active[accounts[accountID].serviceID] === accountID)
+              delete active[accounts[accountID].serviceID]
+            delete accounts[accountID]
+
+            const next = { ...data, accounts, active }
+            yield* write(next)
+            return [undefined, next] as const
+          }),
+        )
+      }),
+
+      activate: Effect.fn("AuthV2.activate")(function* (accountID) {
+        yield* SynchronizedRef.modifyEffect(
+          state,
+          Effect.fnUntraced(function* (data) {
+            const account = data.accounts[accountID]
+            if (!account) return [undefined, data] as const
+
+            const next = { ...data, active: { ...data.active, [account.serviceID]: accountID } }
+            yield* write(next)
+            return [undefined, next] as const
+          }),
+        )
+      }),
+    }
+
+    return Service.of(result)
+  }),
+)
+
+export const defaultLayer = layer.pipe(Layer.provide(AppFileSystem.defaultLayer), Layer.provide(Global.defaultLayer))
+
+export * as AuthV2 from "./auth"

packages/opencode/src/v2/model.ts

@@ -0,0 +1,135 @@
+import { withStatics } from "@/util/schema"
+import { Array, Context, Effect, HashMap, Layer, Option, Order, pipe, Schema } from "effect"
+import { DateTimeUtcFromMillis } from "effect/Schema"
+
+export const ID = Schema.String.pipe(Schema.brand("Model.ID"))
+export type ID = typeof ID.Type
+
+export const ProviderID = Schema.String.pipe(
+  Schema.brand("Model.ProviderID"),
+  withStatics((schema) => ({
+    // Well-known providers
+    opencode: schema.make("opencode"),
+    anthropic: schema.make("anthropic"),
+    openai: schema.make("openai"),
+    google: schema.make("google"),
+    googleVertex: schema.make("google-vertex"),
+    githubCopilot: schema.make("github-copilot"),
+    amazonBedrock: schema.make("amazon-bedrock"),
+    azure: schema.make("azure"),
+    openrouter: schema.make("openrouter"),
+    mistral: schema.make("mistral"),
+    gitlab: schema.make("gitlab"),
+  })),
+)
+export type ProviderID = typeof ProviderID.Type
+
+export const ApiFormat = Schema.Union([
+  Schema.Literal("openai/responses"),
+  Schema.Literal("openai/completions"),
+  Schema.Literal("anthropic"),
+])
+
+const Modalities = Schema.Struct({
+  text: Schema.Boolean,
+  audio: Schema.Boolean,
+  image: Schema.Boolean,
+  video: Schema.Boolean,
+  pdf: Schema.Boolean,
+})
+
+export const Capabilities = Schema.Struct({
+  temperature: Schema.Boolean,
+  reasoning: Schema.Boolean,
+  attachment: Schema.Boolean,
+  toolcall: Schema.Boolean,
+  small: Schema.Boolean,
+  input: Modalities,
+  output: Modalities,
+})
+
+export class Info extends Schema.Class<Info>("Model.Info")({
+  id: ID,
+  providerID: ProviderID,
+  api: Schema.Struct({
+    format: ApiFormat,
+    url: Schema.String,
+    headers: Schema.Record(Schema.String, Schema.String),
+  }),
+  capabilities: Capabilities,
+  name: Schema.String,
+  family: Schema.optional(Schema.String),
+  variants: Schema.Record(Schema.String, Schema.Record(Schema.String, Schema.Any)),
+  time: Schema.Struct({
+    released: DateTimeUtcFromMillis,
+  }),
+}) {}
+
+export function parse(input: string): { providerID: ProviderID; modelID: ID } {
+  const [providerID, ...modelID] = input.split("/")
+  return {
+    providerID: ProviderID.make(providerID),
+    modelID: ID.make(modelID.join("/")),
+  }
+}
+
+export interface Interface {
+  readonly get: (providerID: ProviderID, modelID: ID) => Effect.Effect<Option.Option<Info>>
+  readonly add: (model: Info) => Effect.Effect<void>
+  readonly remove: (providerID: ProviderID, modelID: ID) => Effect.Effect<void>
+  readonly all: () => Effect.Effect<Info[]>
+  readonly default: () => Effect.Effect<Option.Option<Info>>
+  readonly small: (provider: ProviderID) => Effect.Effect<Option.Option<Info>>
+}
+
+export class Service extends Context.Service<Service, Interface>()("@opencode/v2/Model") {}
+
+export const layer = Layer.effect(
+  Service,
+  Effect.gen(function* () {
+    let models = HashMap.empty<string, Info>()
+
+    function key(providerID: ProviderID, modelID: ID) {
+      return `${providerID}/${modelID}`
+    }
+
+    const result: Interface = {
+      get: Effect.fn("V2Model.get")(function* (providerID, modelID) {
+        return HashMap.get(models, key(providerID, modelID))
+      }),
+
+      add: Effect.fn("V2Model.add")(function* (model) {
+        models = HashMap.set(models, key(model.providerID, model.id), model)
+      }),
+
+      remove: Effect.fn("V2Model.remove")(function* (providerID, modelID) {
+        models = HashMap.remove(models, key(providerID, modelID))
+      }),
+
+      all: Effect.fn("V2Model.all")(function* () {
+        return pipe(
+          models,
+          HashMap.toValues,
+          Array.sortWith((item) => item.time.released.epochMilliseconds, Order.flip(Order.Number)),
+        )
+      }),
+
+      default: Effect.fn("V2Model.default")(function* () {
+        const all = yield* result.all()
+        return Option.fromUndefinedOr(all[0])
+      }),
+
+      small: Effect.fn("V2Model.small")(function* (providerID) {
+        const all = yield* result.all()
+        const match = all.find((model) => model.capabilities.small && model.providerID === providerID)
+        return Option.fromUndefinedOr(match)
+      }),
+    }
+
+    return Service.of(result)
+  }),
+)
+
+export const defaultLayer = layer
+
+export * as Modelv2 from "./model"

packages/opencode/src/v2/session-event.ts

@@ -22,10 +22,13 @@ const Base = {
   sessionID: SessionID,
 }
 
-const Error = Schema.Struct({
-  type: Schema.String,
+export const UnknownError = Schema.Struct({
+  type: Schema.Literal("unknown"),
   message: Schema.String,
+}).annotate({
+  identifier: "Session.Error.Unknown",
 })
+export type UnknownError = Schema.Schema.Type<typeof UnknownError>
 
 export const AgentSwitched = EventV2.define({
   type: "session.next.agent.switched",
@@ -139,7 +142,7 @@ export namespace Step {
     aggregate: "sessionID",
     schema: {
       ...Base,
-      error: Error,
+      error: UnknownError,
     },
   })
   export type Failed = Schema.Schema.Type<typeof Failed>
@@ -296,7 +299,7 @@ export namespace Tool {
     schema: {
       ...Base,
       callID: Schema.String,
-      error: Error,
+      error: UnknownError,
       provider: Schema.Struct({
         executed: Schema.Boolean,
         metadata: Schema.Record(Schema.String, Schema.Unknown).pipe(Schema.optional),

packages/opencode/src/v2/session-message.ts

@@ -87,10 +87,7 @@ export class ToolStateError extends Schema.Class<ToolStateError>("Session.Messag
   input: Schema.Record(Schema.String, Schema.Unknown),
   content: ToolOutput.Content.pipe(Schema.Array),
   structured: ToolOutput.Structured,
-  error: Schema.Struct({
-    type: Schema.String,
-    message: Schema.String,
-  }),
+  error: SessionEvent.UnknownError,
 }) {}
 
 export const ToolState = Schema.Union([ToolStatePending, ToolStateRunning, ToolStateCompleted, ToolStateError]).pipe(