[BUG] Unexpected high usage (49%) for minimal session work

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?

Description

Experiencing unexpectedly high usage consumption for a session with minimal actual work performed.

## Session Details

• Model: Claude Opus 4.5 (claude-opus-4-5-20251101)
• Session age: ~30 minutes since reset
• Usage reported: 49% of session quota

## Actual Work Performed in Session

The session was a continuation from a previous conversation (context was summarized). The actual work in the NEW session was:

1. Answered 3 short clarifying questions about a workflow plan
2. Updated one markdown plan file (~300 lines)
3. Created one YAML workflow file (~170 lines)
4. A few TodoWrite calls

Total: ~4-5 tool calls, minimal back-and-forth

What Should Happen?

## Expected Behavior

Given the minimal work (essentially creating one file after brief Q&A), usage should be significantly lower than 49%.

## Possible Factors

• Large context summary passed from previous session continuation
• Pre-loaded file contents in system reminders at session start
• Opus model pricing

Even accounting for these, 49% seems disproportionate for ~10-15 minutes of light work.

Error Messages/Logs

Steps to Reproduce

Steps to Reproduce

1. Start a Claude Code session with Opus model (--model opus)
2. Have a long/complex conversation that eventually hits context limits and gets compacted/summarized
3. Continue working in the same session after compaction (or the session auto-continues from the summary)
4. Perform minimal work in the new context window:

• A few Q&A exchanges (3-5 messages)
• Create/edit 1-2 small files

1. Check usage with /cost or observe the usage indicator

Observed: Usage shows ~49% consumed despite minimal actual work post-compaction

Expected: Usage should reflect only the work done, not disproportionately high for simple file creation

## Additional Context

The session continuation included:

• A <system-reminder> block with a long conversation summary (~500+ lines)
• Pre-loaded file contents from previous Read tool calls shown in system reminders
• An existing plan file (~300 lines) that was read and updated

It appears the large input context from the continuation may be getting counted repeatedly or disproportionately against the usage quota.

Question

Is this expected behavior for Opus with session continuations, or is there potentially a bug in usage calculation?

Claude Model

Opus

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.1.4 (Claude Code)

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

PowerShell

Additional Information

_No response_