[BUG] Stale tasks persist in system-reminder context throughout entire session

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

Tasks created early in a conversation (e.g., "Implement Tier 1 callbacks",
"Implement Tier 2 callbacks") continue appearing in <system-reminder> tags
for the rest of the session, even after the work has moved on to completely
unrelated features. The reminders say "The task tools haven't been used
recently" and list old tasks with stale statuses (in_progress, pending),
which is confusing when the conversation has long moved past that work.

Expected: Tasks from completed/abandoned work streams should either
auto-expire, or the system should stop injecting reminders about them after
a period of inactivity.

Observed: Tasks from the very start of the session
(hours/context-compactions ago) keep appearing in every other tool result,
cluttering the context and creating confusion about what's actually in
progress.

---
The root issue is that the task system injects reminders into tool results
but has no concept of task staleness or session phase changes.

What Should Happen?

After tasks are done, this task list should check off while working on project, once fully done, task list should disappear from terminal persistent text above input

Error Messages/Logs

Steps to Reproduce

• Requested plan to code with steps
• Steps displayed and then told to implement
• All steps implemented, but plan with steps and check boxes persisted no matter how work scope changed.

On windows 11, using git bash terminal

Claude Model

None

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

v2.1.76

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

Other

Additional Information

windows terminal, but using git bash terminal from generic github suite