Claude Code 3.0: What Nested Sessions and Idle Compaction Actually Do
Anthropic's Claude Code update adds nested sessions, idle compaction, and follow-up suggestions. Here's how the parallel workflow works and where it breaks.
What is new in the Claude Code 3.0 update?
Anthropic updated the Claude Code desktop app to make running multiple sessions at once less chaotic. The core additions are nested sessions (subtasks that spin off their own session and report results back to a main one), idle compaction (which summarizes long idle conversations before the prompt cache expires, saving on reprocessing costs), follow-up suggestions (one-click tasks Claude proposes while it works), a /btedu command for side questions that don’t interrupt the main session, and a sidebar that groups sessions by status instead of just listing them.
TL;DR
- Nested sessions let Claude split a task into subtasks that each run in their own session, then send only the final result back to the main chat instead of flooding it with output.
- Idle compaction summarizes a long conversation right before the hourly prompt cache expires, so resuming an idle session costs less than reprocessing the whole thread from scratch.
- Follow-up suggestions appear while Claude works and let you launch a new session for a related task (like fixing a bug Claude noticed but didn’t address) without stopping the current one.
- The sidebar now sorts sessions into three groups (needs input, working, completed) instead of one flat list, and each session shows a live to-do list, a recap card, and a side rail with context usage and changed files.
- Environments let you save a combination of folders, SSH hosts, or cloud setups so you don’t have to reconfigure the same workspace every time you start a session.
- The update is built for people running many sessions in parallel, which means it leans hard on usage limits, and Anthropic has not announced any changes to those limits alongside this release.
- Some previously available controls, including an effort slider, appear to be missing or hidden in the redesign, and several users report the GitHub PR buttons are harder to find.
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How do nested sessions work?
When you ask Claude Code to handle several tasks at once, it now starts a separate nested session for each one instead of running everything inline in the main chat. Each nested session works independently on its piece of the job. Once a nested session finishes, it reports its result back to the parent session, and that result is what shows up in the main conversation. The nested sessions themselves still appear in the sidebar, nested under the parent task, so you can open any of them individually to see the full detail if you need it.
This solves a specific annoyance: before this change, parallel work dumped all its output into the main chat, making long sessions hard to follow. Now the main thread stays readable, showing only the summarized outcome of each subtask, while the raw work is tucked away in its own session you can inspect on demand.
A concrete example from Anthropic’s demo: a main session titled “fix product grid layout shift” spawned two nested sessions, one to make images lazy-load on scroll and another to set explicit width and height on cart images. Both ran separately and reported their results back once done.
How does idle compaction reduce usage?
Claude Code relies on a prompt cache to avoid reprocessing an entire conversation every time you send a new message. That cache typically expires after about an hour. If you step away from a long session and come back later, the cache is gone, and Claude has to reprocess the full conversation history before it can respond, which eats into your usage limit.
Idle compaction addresses this by compacting a long session right before its cache would expire. Compacting turns the conversation into a condensed summary. When you return to that session, Claude only has to process the summary rather than the entire original thread. In the terminal, this shows up as a line noting the session was “compacted while idle before the prompt cache expired.”
Anthropic hasn’t published a specific figure for how much this saves, but the logic fits the broader update: if you’re running many sessions in parallel, some of them will inevitably sit idle while you focus on others, and compaction limits the cost of returning to those idle threads later.
What do follow-up suggestions and /btedu add?
While Claude works on a task, it can now surface follow-up suggestions, additional work it noticed but didn’t address in the current task. Clicking one starts it as its own independent session while your original task keeps running. In Anthropic’s demo, after fixing a layout shift bug, Claude flagged three related issues it hadn’t touched (cart image sizing, lazy loading below the fold, and missing labels on a checkout form), then offered to spin up a new session to fix the checkout form labels specifically.
The /btedu command handles a different problem: side questions that come up mid-session. Typing /btedu followed by a question opens it in a new tab rather than injecting it into your current conversation. This keeps tangential questions from slowing down or cluttering the main session you’re actually trying to finish.
How does the new sidebar organize sessions?
Instead of one flat list, sessions are now grouped into three categories: needs input, working, and completed. A session that needs your attention gets a small warning icon and moves into the “needs input” group automatically. Completed sessions also show an icon indicating where they ran, locally on your machine or in the cloud. The idea is that a glance at the sidebar tells you which sessions are waiting on you without opening each one.
Inside an individual session, three more additions aim at the same goal of visibility: a live to-do list that tracks Claude’s plan and checks off steps as it completes them, a recap card that summarizes what happened in the most recent turn so you don’t have to scroll back to find context, and a side rail showing where the session is running, how much context it has used, and which files it has changed.
Anthropic also added environments, which are saved combinations of folders, SSH hosts, or cloud setups you can launch a new session into without re-specifying everything each time. You can also give a folder its own work tree, meaning a separate copy of the repo, so that two sessions working in the same folder don’t collide on the same files.
Is Claude Code 3.0 worth using right now?
It depends heavily on which plan you’re on and how many sessions you actually want running simultaneously. Nested sessions and /btedu solve a real and common problem: long Claude Code sessions becoming unreadable once multiple things happen in parallel. Idle compaction is a sensible efficiency fix that should help anyone who leaves sessions open between work blocks.
The catch is usage limits. Running more parallel sessions means consuming more usage overall, and nested sessions add further consumption on top of that. Anthropic has not announced any changes to usage limits alongside this release, which means the feature set is realistically built for people on higher-tier (max) plans rather than the standard pro tier. Users on more limited plans may hit their caps quickly if they lean into running many sessions at once.
Feedback on the update has also been mixed on a few specific points. Several users want the effort slider back, since it appears to have been removed or hidden in the redesign. Some report that GitHub PR buttons are now harder to find. Others dislike that sessions move between sidebar groups automatically, since tracking ten-plus sessions that shuffle position on their own can be more confusing than helpful. Requests for grouping sessions by project, supporting multiple accounts in one app, and viewing all sessions from a phone without remote control setup remain unaddressed.
Frequently Asked Questions
What are nested sessions in Claude Code?
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Nested sessions are subtasks that Claude runs as their own separate sessions when handling multiple pieces of work at once. Each nested session works independently and sends its result back to the main session when finished, keeping the main chat free of detailed intermediate output.
What does idle compaction actually save?
It saves on reprocessing cost. Claude Code’s prompt cache expires after about an hour of inactivity. Idle compaction summarizes a long session right before that expiration, so when you return, Claude processes a short summary instead of the full conversation history. Anthropic has not published an exact savings figure.
Does Claude Code 3.0 change usage limits?
No. Anthropic has not announced any change to usage limits with this update. Since nested sessions and parallel workflows increase overall usage, this is being called out as a likely barrier for users on lower-tier plans.
What is the /btedu command for?
It lets you ask a side question in the middle of a session without interrupting the main task. The question opens in a new tab and runs separately while your original session keeps working.
Did Anthropic remove the effort slider?
It appears to be missing or hidden in the redesigned interface. This has been a common complaint in user feedback following the update, alongside reports that GitHub PR buttons are less discoverable than before.
