Claude Code 1M Context (Opt-Out)

⚠️ This skill may become obsolete. The Opus 4.6 "1M context" mode is currently an Anthropic beta. Once it graduates to GA (or Anthropic changes the default back to 200K), everything documented here stops mattering. If you're reading this and the CLAUDE_CODE_DISABLE_1M_CONTEXT env var no longer does anything — or the "Opus 4.6 (with 1M context)" label no longer shows up in your Claude Code banner — this skill can probably be deleted from gallia. Check the Claude Code docs on extended context first.

The problem

Claude Code 2.1.x running inside the VS Code extension defaults to Opus 4.6 with the 1M-context beta when your account is entitled to it. The 1M window is great for massive codebase reads, but:

1. Every turn costs more. The 1M-context variant is a separate SKU with premium pricing — you burn through your token budget noticeably faster than the standard 200K Opus 4.6.
2. Most sessions don't need it. A typical Claude Code session (single-file edits, small refactors, debugging one bug) fits comfortably in 200K. Using 1M for those sessions is pure waste.
3. There's no obvious toggle in the UI. The VS Code extension's Claude Code: Select Model command lets you pick opus or sonnet, but the 1M variant is layered on top of "opus" via a separate beta opt-in that isn't exposed in the model picker.

Result: users notice their tokens draining faster than they expected and have no obvious way to stop it.

The fix

Set CLAUDE_CODE_DISABLE_1M_CONTEXT=1 in the environment Claude Code starts with. The Claude Code binary checks this env var at session start and, if set, pins the session to the standard 200K Opus context.

Canonical place to set it: the VS Code extension's claudeCode.environmentVariables setting in ~/.local/share/code-server/User/settings.json (code-server) or ~/.config/Code/User/settings.json (VS Code desktop). The extension reads that setting on every Claude Code process launch and injects the values into the child process env.

Step-by-step

1. Edit the VS Code user settings

# code-server (the usual Adom container setup)
$EDITOR ~/.local/share/code-server/User/settings.json

# VS Code desktop
$EDITOR ~/.config/Code/User/settings.json

Add (or merge into) the claudeCode.environmentVariables object:

{
  // ... your other settings ...
  "claudeCode.preferredLocation": "panel",
  "claudeCode.selectedModel": "opus",

  // NEW: pin to 200K standard context so sessions don't use the
  // expensive 1M beta variant.
  "claudeCode.environmentVariables": {
    "CLAUDE_CODE_DISABLE_1M_CONTEXT": "1"
  }
}

If there are already other env vars under claudeCode.environmentVariables, add CLAUDE_CODE_DISABLE_1M_CONTEXT as another key inside the existing object — don't wipe the others.

2. Restart the Claude Code panel

The env var is only read at Claude Code process launch, so the currently-running session keeps using whatever it was using. Close the Claude Code panel and reopen it (or Ctrl+Shift+P → Claude Code: Start New Conversation) for the change to take effect.

You do not need to reload the entire VS Code window — the Claude Code process is per-panel, so closing and reopening the panel is enough.

3. Verify

The first banner / system message in the fresh session should say Opus 4.6 without the "with 1M context" suffix. You can also confirm by asking Claude "what model are you running" — it should report claude-opus-4-6 (no [1m] tag).

You can also grep the running process env:

PID=$(pgrep -f 'resources/native-binary/claude' | head -1)
cat /proc/$PID/environ | tr '\0' '\n' | grep DISABLE_1M
# → CLAUDE_CODE_DISABLE_1M_CONTEXT=1

To re-enable 1M context

Just remove (or comment out) the CLAUDE_CODE_DISABLE_1M_CONTEXT entry from claudeCode.environmentVariables and restart the Claude Code panel. The extension will re-enable the beta on the next session launch (provided your account is still entitled).

If you want it only sometimes — e.g. for one long session reading a huge codebase — temporarily override it by launching the claude binary from a terminal with CLAUDE_CODE_DISABLE_1M_CONTEXT= (empty string) in front, or remove the setting, open one panel, then put the setting back and restart. The env var is evaluated per-process, so panels started under different env can coexist.

Other Claude Code settings worth knowing about

These also live under the claudeCode.* namespace in the VS Code user settings and are relevant when you're tuning cost/behavior:

Troubleshooting

"I restarted the panel but it's still on 1M context"

Double-check:

• Settings file path is correct (code-server vs VS Code desktop use different paths — see Step 1).
• JSON is syntactically valid after your edit (jq . < settings.json should parse cleanly — code-server and code both tolerate line comments but not trailing commas inside environmentVariables).
• You restarted the Claude Code panel, not just opened a new chat in the existing panel. New chats in the same panel reuse the existing process env.

"The setting vanishes when I restart"

VS Code / code-server reads the user settings file fresh on each launch. If your edit is missing after a restart, either:

• Another extension is rewriting the file (unlikely, but check git history on the settings file), or
• You edited workspace settings (.vscode/settings.json in a project folder) instead of user settings — workspace settings only apply when that workspace is open. Put the env var in user settings for a global pin.

"CLAUDE_CODE_DISABLE_1M_CONTEXT doesn't do anything"

Likely one of:

• You're on an older Claude Code version that didn't yet ship the kill switch. Update the extension (code-server --install-extension anthropic.claude-code or via the Extensions pane) and try again.
• Anthropic changed the env var name or retired the beta. Check the extended context docs and update this skill.

Why it's in gallia

This lives in gallia (not just in an individual user's local settings) because every Adom user running Claude Code inside their container hits the same problem: 1M context on by default, no obvious toggle, tokens burning faster than expected. Putting the fix in a gallia skill means any Claude Code session can discover and apply it via the standard /adom skill umbrella.

When the Anthropic beta graduates and the default changes back (or when Claude Code ships a proper in-UI context-window toggle), this skill becomes obsolete and can be removed.