Anthropic: Claude Haiku 4.5

Every other current Anthropic tier runs at a million-token context window. This row doesn't: it lists 200000tokensopenrouter-models, last checked 2026-09-14, the same ceiling 200000tokensopenrouter-models, last checked 2026-09-14 carried on anthropic/claude-3-haiku, a model old enough that its own catalog row carries no recorded benchmark index at all. Nothing about the Haiku line's context window has moved since.

The other tiers reached the ceiling by two different routes, and only one of them was a climb. Sonnet was never below it: anthropic/claude-sonnet-4 is the oldest Sonnet row in the catalog and it already listed 1000000tokensopenrouter-models, last checked 2026-09-14 — on essentially the same day anthropic/claude-opus-4 launched at 200000tokensopenrouter-models, last checked 2026-09-14, a fifth of the size; the two rows were added to the catalog within fifteen minutes of each other. Opus is the tier that actually moved, at 4.6, to 1000000tokensopenrouter-models, last checked 2026-09-14, and it has held there ever since.

Haiku 4.5 landed in between, which is the part that makes it interesting. It was listed on 15 October 2025 — 146 days after Sonnet was already running at a million, and 112 days before Opus got there on 4 February 2026. So the 200k ceiling is not a decision taken against a settled house standard; it is a row nobody has been back to. In the snapshot of 31 August 2026, five further Opus revisions, two Sonnets and a Fable have been listed since that date, and not one new Haiku.