Startup warning when CLAUDE_CODE_DISABLE_1M

Startup warning when CLAUDE_CODE_DISABLE_1M_CONTEXT can't actually be enforced

If your 1M-context disable flag has no effect on your model, startup now tells you and points at the real setting.

You'll notice Notable Improvements

JSON All of v2.1.223

You'll noticeTier: how much it should matter to you

3Useful: my rating, 1 to 5

0Signal: worth watching, 1 to 5

Context LimitsArea: what it touches

ImprovementsKind: in v2.1.223, 05 Aug 26

What probably matters to youSection of the release

What

A second startup notice fires when the 1M-context disable flag is set but the limit is not enforced for the current model.

Details

the notice points you at CLAUDE_CODE_AUTO_COMPACT_WINDOW, or the autoCompactWindow setting, as the thing that will actually take effect
gated on CLAUDE_CODE_DISABLE_1M_CONTEXT being set
both this and the existing notice are printed at startup, except under json or stream-json output or a background session, where they are written to the log as warnings instead

Evidence

CLAUDE_CODE_DISABLE_1M_CONTEXT is set, but the

Strings lifted out of the shipped bundle, so the claim above can be checked against them.

Read from

Names in the bundleCLAUDE_CODE_DISABLE_1M_CONTEXTCLAUDE_CODE_AUTO_COMPACT_WINDOWautoCompactWindow

How sure we are

One source agreesOne thing we can check says the same as this entry.

Anthropic's release notes agreeChanged CLAUDE_CODE_DISABLE_1M_CONTEXT to hold every Claude model with a native 1M window to 200K via auto-compaction, not just a fixed…

See this entry in the whole of v2.1.223 →

The build it came inv2.1.223

5 Aug 2026 · 201 entries, this one is #47.

Use it now26
You'll notice99
Nothing to try yet21
Under the hood55

Either side of it

v2.1.222Older
v2.1.224Newer

Open the release →

Names in this entry

envCLAUDE_CODE_DISABLE_1M_CONTEXT
Set to 1 to disable 1M context window support. When set, 1M model variants are unavailable in the model picker, and Claude Code holds sessions on models with a native 1M window, such as Sonnet 5.5 and the Fable models, to a 200K window; see Extended context for how the hold is enforced. Useful for enterprise environments with compliance requirements. For its role in correcting the window for an unrecognized [1m] model ID, see Correct the window for a gateway or custom model ID
envCLAUDE_CODE_AUTO_COMPACT_WINDOW
Set the auto-compact window in tokens, from 100000 to 1000000. Accepts a plain integer such as 500000 only: a value like 500k reads as 500 and clamps to the 100K minimum. The effective window is also capped at the model's context window. Takes precedence over the /autocompact command, the --autocompact flag, and the autoCompactWindow setting. The status line's used_percentage always measures against the model's full context window, so once this variable is set, that percentage no longer indicates when compaction will run
settingautoCompactWindow
Set how full the context gets before Claude Code compacts

Anthropic's note

Upstream's own release notes for v2.1.223 name something this entry names, so the two are probably about the same change. Probably: the pairing is made on a shared name rather than on the words around it.

Changed CLAUDE_CODE_DISABLE_1M_CONTEXT to hold every Claude model with a native 1M window to 200K via auto-compaction, not just a fixed list; a startup warning now appears when auto-compaction isn't holding the session to 200K

Is this right?

Other releases about the same thing. Found by shared names or similar wording; neither means one caused the other.

v2.1.235 Context-limit banner now tells you auto-compact is switched off
Both mention compact
v2.1.235 Assorted smaller additions
Both mention compact
v2.1.267 Compaction can now be intercepted and rewritten by a session.compact plugin hook
Both mention compact