feat(tui): expose subagent cost breakdown in sidebar

Author: Integralist

FORK.md

@@ -47,6 +47,7 @@ git push -u origin <your-custom-branch>
 
 ### 2026-07-17
 
+-**Exposed Sub-agent Cost Calculations in TUI Sidebar:** Added recursive cost-summing for sub-agent threads. Updates the TUI Context sidebar to display a detailed breakdown of Main Agent cost, Sub-agent total cost, and combined Total Cost under the active session ID.
 -**Ported PR #23262 (File Cycling in Permission Prompt):** Ported the file cycling feature from upstream PR #23262 to [packages/tui/src/routes/session/permission.tsx](file:///Users/mmcdonnell/code/opencode/packages/tui/src/routes/session/permission.tsx). This enables cycling through multiple files inside the TUI permission dialog using `[` and `]` keys.
 -**Added [FORK.md](file:///Users/mmcdonnell/code/opencode/FORK.md):** Outlines branching, syncing, and custom workspace strategy.
 -**Added [Makefile](file:///Users/mmcdonnell/code/opencode/Makefile):** Standard checkmake-compliant targets for building, cleaning, testing, and syncing with automatic Bun dependency management.

packages/opencode/test/fixture/tui-plugin.ts

@@ -314,6 +314,7 @@ export function createTuiPluginApi(opts: Opts = {}): HostPluginApi {
 },
 session: {
 count: opts.state?.session?.count??(()=>0),
+list: opts.state?.session?.list??(()=>[]),
 get: opts.state?.session?.get??(()=>undefined),
 diff: opts.state?.session?.diff??(()=>[]),
 todo: opts.state?.session?.todo??(()=>[]),

packages/plugin/src/tui.ts

@@ -385,6 +385,7 @@ export type TuiState = {
 readonlyvcs: {branch?: string;default_branch?: string}|undefined
 session: {
 count: ()=>number
+list: ()=>ReadonlyArray<Session>
 get: (sessionID: string)=>Session|undefined
 diff: (sessionID: string)=>ReadonlyArray<TuiSidebarFileItem>
 todo: (sessionID: string)=>ReadonlyArray<TuiSidebarTodoItem>

packages/tui/src/feature-plugins/sidebar/context.tsx

@@ -1,7 +1,7 @@
 importtype{AssistantMessage}from"@opencode-ai/sdk/v2"
 importtype{TuiPlugin,TuiPluginApi}from"@opencode-ai/plugin/tui"
 importtype{BuiltinTuiPlugin}from"../builtins"
-import{createMemo}from"solid-js"
+import{createMemo,Show}from"solid-js"
 
 constid="internal:sidebar-context"
 
@@ -15,6 +15,31 @@ function View(props: { api: TuiPluginApi; session_id: string }) {
 constmsg=createMemo(()=>props.api.state.session.messages(props.session_id))
 constsession=createMemo(()=>props.api.state.session.get(props.session_id))
 constcost=createMemo(()=>session()?.cost??0)
+constallSessions=createMemo(()=>props.api.state.session.list())
+
+constsubagentCost=createMemo(()=>{
+constlist=allSessions()
+lettotal=0
+constqueue=[props.session_id]
+constvisited=newSet<string>()
+
+while(queue.length>0){
+constcurrentID=queue.shift()!
+if(visited.has(currentID))continue
+visited.add(currentID)
+
+for(constsoflist){
+if(s.parentID===currentID&&s.id!==props.session_id){
+total+=s.cost??0
+queue.push(s.id)
+}
+}
+}
+returntotal
+})
+
+consthasSubagents=createMemo(()=>subagentCost()>0)
+consttotalCost=createMemo(()=>cost()+subagentCost())
 
 conststate=createMemo(()=>{
 constlast=msg().findLast((item): item is AssistantMessage=>item.role==="assistant"&&item.tokens.output>0)
@@ -41,7 +66,22 @@ function View(props: { api: TuiPluginApi; session_id: string }) {
 </text>
 <textfg={theme().textMuted}>{state().tokens.toLocaleString()} tokens</text>
 <textfg={theme().textMuted}>{state().percent??0}% used</text>
-<textfg={theme().textMuted}>{money.format(cost())} spent</text>
+<Show
+when={hasSubagents()}
+fallback={<textfg={theme().textMuted}>{money.format(cost())} spent</text>}
+>
+<boxmarginTop={1}>
+<textfg={theme().textMuted}>
+ Main Agent: <spanstyle={{fg: theme().text}}>{money.format(cost())}</span>
+</text>
+<textfg={theme().textMuted}>
+ Sub-agents: <spanstyle={{fg: theme().text}}>{money.format(subagentCost())}</span>
+</text>
+<textfg={theme().textMuted}>
+ Total Cost: <spanstyle={{fg: theme().warning}}>{money.format(totalCost())}</span>
+</text>
+</box>
+</Show>
 </box>
 )
 }

packages/tui/src/plugin/adapters.tsx

@@ -120,6 +120,9 @@ function stateApi(sync: ReturnType<typeof useSync>): TuiPluginApi["state"] {
 count(){
 returnsync.data.session.length
 },
+list(){
+returnsync.data.session
+},
 get(sessionID){
 returnsync.session.get(sessionID)
 },