[BUG] Anthropic backend silently overwrites ~/.claude.json on every launch — tengu_hawthorn_window restored to 200000 immediately after manual edit on Max plan account

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?

Describe the bug

~/.claude.json is a local config file on the user's machine. Anthropic's backend is silently overwriting values in this file on every launch without user knowledge, consent, or any documentation that this behavior exists.

Specifically: tengu_hawthorn_window is set to 200000 in ~/.claude.json. The user manually edited it to 1000000. On next launch, Anthropic's backend overwrote the value back to 200000 immediately. The edit did not survive a single session. /context continued showing the 200k cap.

This is a separate issue from the context cap regression itself. The unauthorized write behavior exists independently and affects every subscriber running Claude Code.

Steps to reproduce

Open ~/.claude.json and locate tengu_hawthorn_window
Change the value to anything other than the server-pushed value and save
Launch Claude Code
Immediately check ~/.claude.json — value has been silently restored to the server-pushed value
Check /context — cap unchanged
Expected behavior

User edits to local config files persist. If Anthropic requires certain values to be server-controlled, this must be disclosed and documented. Users must be informed that cachedGrowthBookFeatures in ~/.claude.json is a remotely managed block that overwrites local edits on every launch.

Actual behavior

Server silently restores tengu_hawthorn_window: 200000 on every launch regardless of local edits. No warning. No notification. No documentation. No user recourse.

Evidence

Manual edit confirmed overwritten immediately on next launch. Issue #53872 documents identical behavior with cachedExtraUsageDisabledReason — that reporter confirmed the value persisted across fresh install on a separate machine with a new login, proving this is account-bound on Anthropic's servers and not a local cache artifact.

Why this matters independently of the context cap

Users have no way to know their local config is being remotely managed. There is no documentation that cachedGrowthBookFeatures is a server-controlled block. Users attempting to work around entitlement bugs by editing config cannot do so. The same mechanism that enforces tengu_hawthorn_window: 200000 on this account could push any value to any subscriber's machine silently. This is a consent and transparency issue that exists regardless of whether the pushed values are harmful or neutral.

Is this a regression?

Unknown — the behavior may have always existed but was undetectable until the May 22 entitlement regression made the server-pushed values harmful rather than neutral.

Related issues

#62898 — the context cap this flag is enforcing
#53872 — identical server-overwrite behavior documented on cachedExtraUsageDisabledReason
#46331 — prior tengu_amber_redwood GrowthBook experiment silently reducing autocompact

Environment

Claude Code version: 2.1.116
Platform: macOS, Apple Silicon M3 Ultra
Plan: Claude Max
Labels: bug area:core area:cost platform:macos

What Should Happen?

Expected behavior

User edits to local config files persist. If Anthropic requires certain values to be server-controlled, this must be disclosed and documented. Users must be informed that cachedGrowthBookFeatures in ~/.claude.json is a remotely managed block that overwrites local edits on every launch.

Error Messages/Logs

Steps to Reproduce

Open ~/.claude.json and locate tengu_hawthorn_window
Change the value to anything other than the server-pushed value and save
Launch Claude Code
Immediately check ~/.claude.json — value has been silently restored to the server-pushed value
Check /context — cap unchanged

Claude Model

Sonnet (default)

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

v2.1.152

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_