Daily Phantom 30-34% of my 5-hour limit before I send a single prompt / Mystery Sonnet 4.5 usage appearing

I’m trying to figure out whether Claude’s usage accounting is broken, or whether reading prior chats or Project Knowledge activity is consuming far more usage than I realized. Every day when I open Claude if I dont start a chat my usage meter just starts draining. Whether it is reading chats from yesterday or opening a chat in a folder to see where I left off, usage is drained. For instance this morning I opened Claude on the web with a fresh 5-hour session at 0%. For roughly the first 40 minutes, I did not send Claude a single prompt. I: opened and looked through a Project Knowledge it exists to do a single function and has 5 MD files I want to insert into my other projects to consolidate the workflow to avoid having to move chats later to the specific project folder after the chat ends to organize it; Anyways, I found the original MD file I created on my harddrive then uploaded it to the project knowledge into 5 other folders; and opened/read a chat from yesterday without asking Claude to do anything. By the time I actually started chatting on that chat, my Current Session usage had gone from 0% to 34%. So apparently just navigating Projects, reviewing existing material, and adding a handful of files to Project Knowledge consumed roughly one-third of my entire 5-hour allowance. I have noticed this “phantom draw” before too. Sometimes merely opening Claude on the web and moving around existing Projects/chats seems to make the usage meter climb even though I’m not generating responses. Then I resumed a long conversation from yesterday using Opus 5. My Current Session meter went from about 34% to about 60% almost immediately, which is at least understandable if Claude is reprocessing a huge existing context. But here is the stranger part: I log the usage-limit changes locally. While I was in that Opus 5 chat, the log suddenly started identifying claude-sonnet-4-5-20250929 as a chat model. I have not knowingly started or selected a Sonnet 4.5 conversation. The Sonnet entries sometimes appear within fractions of a second of identical Opus 5 usage-meter readings, so I cannot tell whether: Claude is silently falling back/downgrading from Opus; some background process is using Sonnet; an old/hidden chat session is active somewhere; the model identifier in the usage telemetry is wrong; or the whole usage meter is just being reconciled strangely. I’m not claiming the Sonnet entries represent additional usage because several of them mirror the exact same Opus meter changes. But I would really like to know why Sonnet 4.5 is appearing at all when I’m using Opus 5. The 0% → 34% draw before sending a prompt is the part that concerns me most. If uploading/browsing Project Knowledge consumes session quota, that needs to be documented much more clearly. If it isn’t supposed to, then something seems wrong with the usage accounting. Has anyone else with Claude Pro seen their 5-hour meter drain substantially just from working inside Projects/Project Knowledge or reading chats without actually prompting Claude? I do have Claude desktop installed but not running but had it logged out to focus on web usage. The chrome extension was logged out as well.