[FEATURE]

Preflight Checklist

• [x] I have searched existing requests and this feature hasn't been requested yet
• [x] This is a single feature request (not multiple features)

Problem Statement

When a subagent is running in the TUI (or has just finished), there is no way to
see how much of its context window it is actually using.

The numbers that are shown — ↓ 33.9k tokens of running task, or 37.5k tokens
on completion of an agent — are cumulative input/output tokens across all the subagent's
API calls, not the current context-window size. These two metrics behave very
differently: cumulative tokens grow every turn (each turn re-reads prior context
as input), while the actual live context size is bounded by the model's window.

As a result, I cannot tell from the TUI whether a long-running subagent is at
30% or 90% of its context window.

Proposed Solution

Add the subagent's context-window usage to two existing TUI surfaces, in the <used>/<max> format.

Show current context size next to the elapsed timer

• For running task: Implementing Task 3: HomeViewModel… (25m 53s · 30k/1M · ↓ 33.9k tokens)
• For completed agent: Done (31 tool uses · 30k/1M · 37.5k tokens · 3m 41s)
• For the bottom with the list of sub-agent sessions: general-purpose <agent-session-name> 30k/1M · 8s

Alternative Solutions

_No response_

Priority

Medium - Would be very helpful

Feature Category

Interactive mode (TUI)

Use Case Example

_No response_

Additional Context

This is how it is currently, without context tokens:

<img width="1321" height="489" alt="Image" src="https://github.com/user-attachments/assets/04cf1663-b9ef-4592-acf5-5ef9c40f0752" />