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Public story · 2026-07-25 · high
Max plan users get the new default automatically, and any harness that never pinned a specific model ID just started running a different model overnight.
Why now: Version 2.1.219 shipped July 24, and anyone running Claude Code on a schedule needs to check which model their next run will actually call.
Claude Code shipped v2.1.219 on July 24, and it makes claude-opus-5 the default Opus model with a 1M-token context window, per the release notes. Opus 4.7 drops out of fast mode entirely, so /fast now only applies to Opus 5 and Opus 4.8.
Pricing holds at $5 per million input tokens and $25 per million output, same as Opus 4.8. Fast mode still costs double the base price for roughly 2.5x speed. Nothing changed there.
What changed is who gets the new default without asking for it. Max plan users get claude-opus-5 automatically. If your harness never pins a specific model ID, it's now calling a different model than it was calling yesterday. You didn't touch your code, and your output changed anyway.
I've hit this failure mode before. A harness with no pinned model works fine for months. Then it starts producing different output, and you spend an afternoon convinced you broke something in your own code. The fix is boring: pin the model ID.
The release notes name this directly as the likely explanation when a harness changes behavior with no code changes on your end. That's a specific admission, not a vague warning.
Each link below shares sources, entities, or timing with this story.
Claude Code uses Opus / Shared entities / Same source / Shared topic / Earlier coverage / Tension
Linked by a graph relationship (Claude Code uses Opus); both cover Claude Code, Opus; cite the same source (Released July 24).
Claude Code uses Opus / Shared entities / Same source / Shared topic / Earlier coverage
Linked by a graph relationship (Claude Code uses Opus); both cover Claude Code, Opus; cite the same source (Released July 24).
Linked by a graph relationship (Claude Code uses Opus); both cover Claude Code, Opus; cite the same source (Released July 24).
Linked by a graph relationship (Claude Code uses Opus); both cover Claude Code, Opus; cite the same source (Released July 24).
Linked by a graph relationship (Claude Code uses Opus); both cover Claude Code, Opus; cite the same source (Released July 24).
Claude Code uses Opus / Shared entity: Claude Code / Same source / Shared topic / Earlier coverage / Tension
Linked by a graph relationship (Claude Code uses Opus); both cover Claude Code; cite the same source (Released July 24).
Claude Code uses Opus / Shared entity: Claude Code / Same source / Shared topic / Earlier coverage
Linked by a graph relationship (Claude Code uses Opus); both cover Claude Code; cite the same source (Released July 24).
Claude Code uses Opus / Shared entities / Shared topic / Earlier coverage / Tension
Linked by a graph relationship (Claude Code uses Opus); both cover Claude Code, Opus; overlapping topics (claude, code, context, opus).