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claude-sonnet-4.5 retires on November 30, 2026, replaced by claude-sonnet-5.5

Anthropic lists November 30, 2026 as the retirement date of claude-sonnet-4.5 and names claude-sonnet-5.5 as its replacement, which leaves 30 days to move the calls that use it. This is for teams that call claude-sonnet-4.5 by name; the only seller in our prices is Anthropic, with the list prices of its own API verified on its public page on October 31, 2026, so any reseller price is outside our data.

RetirementsPublished 31 October 2026

claude-sonnet-4.5 stops on November 30, 2026, 30 days from today

November 30, 2026 | claude-sonnet-4-5-20250929 | claude-sonnet-5-5 |
Anthropic deprecations page read on

The official line gives the date, the dated identifier of claude-sonnet-4.5 and the identifier of claude-sonnet-5.5, and nothing else. Any request that pins that dated identifier is concerned. Search your code for it as well as for the short name claude-sonnet-4.5, because both forms point to the same retired model.

ModelRetired onAnnounced replacementBeforeAfter
Input, $/MOutput, $/MInput, $/MOutput, $/M
claude-sonnet-4.5claude-sonnet-5.53.0015.002.0010.00
claude-sonnet-4.5 is the only model in this notice, so November 30, 2026 is the one deadline every migration plan has to meet.

The status is official: the date comes from the Anthropic deprecations page, Anthropic deprecations page, read on October 19, 2026. It is not a rumour or a reseller notice, and it names its replacement explicitly, which removes the choice of a successor from the migration work.

30 days left before the retirement

Counted up to November 30, 2026, the date on the Anthropic page read on October 19, 2026

claude-sonnet-5.5 bills Output at $10.00 per million tokens

On the Anthropic price list checked on October 31, 2026, claude-sonnet-4.5 costs $15.00 per million Output tokens. Its replacement claude-sonnet-5.5, at $10.00 per million tokens, changes the Output line by −33%. Both prices are verified on the public Anthropic pricing page and are list prices for direct API calls.

Before

claude-sonnet-4.5

Input, $/M
3.00
Output, $/M
15.00

After

claude-sonnet-5.5

Input, $/M
2.00
Output, $/M
10.00

−33% on output

The Input price moves from claude-sonnet-4.5 at $3.00 to claude-sonnet-5.5 at $2.00 per million tokens. Cache reads go from claude-sonnet-4.5 at $0.30 to claude-sonnet-5.5 at $0.10 per million tokens. On every line of the list, claude-sonnet-5.5 costs less than claude-sonnet-4.5.

Output price per million tokens, retired model and replacementFor each retired model, its Output price and the Output price of its replacement, in US dollars per million tokens.claude-sonnet-4.5$15.00→ claude-sonnet-5.5$10.00Output price per million tokens, retired model and replacementFor each retired model, its Output price and the Output price of its replacement, in US dollars per million tokens.claude-sonnet-4.5$15.00→ claude-sonnet-5.5$10.00
At Anthropic, claude-sonnet-5.5 costs less than claude-sonnet-4.5 on Input, Output and cache read, so moving the calls lowers the list price of every token type.

A per-token price says nothing about how many tokens each answer uses with claude-sonnet-5.5. The total of an invoice depends on that count as much as on the list. Measure it on your own prompts during the trial phase, then compare the monthly total with the one you pay today for claude-sonnet-4.5.

ModelInput, $/MOutput, $/MCached input, $/MPrice checked on
claude-sonnet-4.53.0015.000.30
claude-sonnet-5.52.0010.000.10
At the Anthropic list price, the replacement is billed below the retired model on Input, Output and cache reads alike.

Direct API callers pay $10.00 per million Output tokens on claude-sonnet-5.5, reseller customers check their own price

If you call the Anthropic API directly, the date and the prices above are the ones that apply: the retirement sits on the official page and both prices on the Anthropic list. If you reach claude-sonnet-4.5 through a reseller or a cloud platform, its own calendar and its own price list are the ones to check before planning the move.

Teams whose prompts were tuned on claude-sonnet-4.5 carry the main risk. The official line names the replacement but describes no difference in behaviour, so answers, formats and refusals are worth checking on real traffic before the switch, not after.

Switch to claude-sonnet-5.5 in reversible phases before November 30, 2026

A rollback route to claude-sonnet-4.5 can stay in the plan only until November 30, 2026.

  1. Find every call

    Search code, configuration and logs for the short name claude-sonnet-4.5 and for the dated identifier shown in the official quote.

  2. Test on a sample

    Send a sample of real prompts to claude-sonnet-5.5 and compare answers, token counts and errors with those of claude-sonnet-4.5.

  3. Run both side by side

    Duplicate a slice of traffic to both models for a set period, and keep returning the answers of claude-sonnet-4.5 to users.

  4. Switch the traffic

    Route production calls to claude-sonnet-5.5 and track the bill per million tokens against the Anthropic list.

  5. Keep a way back

    Leave the route to claude-sonnet-4.5 in configuration so it can be restored at once if a regression appears.

  6. Remove the old route

    Delete every reference to claude-sonnet-4.5 before November 30, 2026.

  1. Retirement page read
  2. Retirement
Between the page reading and the retirement, the window has to hold the trial, the parallel run and the switch, with room left for a rollback.
Abstract illustration of particles moving from a fading band of light to a brighter one along curved, reversible paths

The Anthropic price list was checked on October 31, 2026; the deprecations page, Anthropic deprecations page, was read on October 19, 2026, and the date it gives for claude-sonnet-4.5 is November 30, 2026.