claude-sonnet-4-5-20250929
API: not sooner than 2026-09-29 · Copilot: 2026-09-01
Anthropic’s model-deprecations page (fetched 2026-08-30) still lists claude-sonnet-4-5-20250929 as Active, tentative retirement not sooner than 2026-09-29 — it is not Deprecated yet. GitHub Copilot’s 2026-07-31 changelog removes Claude Sonnet 4.5 / 4.6 (and others) from every Copilot surface on 2026-09-01. Do not collapse those calendars.
Four dates and ids you can quote
Anthropic API: not sooner than
Official table: claude-sonnet-4-5-20250929 is Active; tentative retirement is Not sooner than September 29, 2026. That is a lower bound, not an already-retired model.
GitHub Copilot removal
GitHub changelog 2026-07-31: Copilot Chat, inline edits, ask/agent, and completions drop Claude Sonnet 4.5 (and 4.6, among others) on 2026-09-01. That is Copilot’s catalog, not the Messages API.
The snapshot id to audit
The bare alias claude-sonnet-4-5 often shows no usage. Hunt the dated snapshot in code. Replacements that are still Active: claude-sonnet-5 or claude-sonnet-4-6.
API has not entered Deprecated
Anthropic’s lifecycle: Active → Legacy → Deprecated (still works, replacement + retirement date) → Retired (requests fail). The 4.5 snapshot is still Active today. Public models get at least 60 days’ email notice.
“Retirement” is not one switch
Anthropic’s deprecation page covers the Claude API, Claude Platform on AWS, and Microsoft Foundry. Bedrock and Vertex set their own dates. GitHub Copilot is a separate catalog: the 2026-07-31 changelog names 2026-09-01 for Gemini 3.1 Pro, Opus 4.5/4.6, Sonnet 4.5/4.6, and Raptor Mini across all Copilot experiences. Same model family, two clocks, about four weeks apart.
Why both dates show up in late August
Today is 2026-08-30. Copilot’s 09-01 is one day away; Anthropic’s “not sooner than 09-29” is about four weeks out. Reading Copilot removal as “the Sonnet 4.5 API dies tomorrow” shrinks the real API window. Ignoring Copilot while hard-coding 4.5 there breaks on 09-01. Split the product, then migrate.
Timeline
GitHub changelog: Upcoming August 2026 model deprecations in GitHub Copilot. Sonnet 4.5 → Claude Sonnet 5; Opus 4.5/4.6 → Opus 4.7 / 4.8 / 5. Individual annual Copilot subscribers keep Sonnet 4.6; monthly and enterprise do not.
platform.claude.com/docs/en/about-claude/model-deprecations: claude-sonnet-4-5-20250929 still Active, not sooner than 2026-09-29. claude-sonnet-5 not sooner than 2027-06-30; claude-sonnet-4-6 not sooner than 2027-02-17.
09-01: Copilot drops the listed models. 09-29: API lower bound; the real retirement date is whatever notice says, with ≥60 days for public models. Requests to retired models fail.
Confirmed vs rumor
Confirmed
Both primaries exist: Anthropic’s table (Active, not sooner than 2026-09-29) and GitHub’s Copilot changelog (2026-09-01 for Sonnet 4.5 et al.). API replacements follow the deprecation page; Copilot replacements follow Suggested alternative. The annual-individual Sonnet 4.6 carve-out is GitHub’s sentence, not a rumor.
Rumor / misread
“Sonnet 4.5 is already gone from the API” — the row is still Active. “09-01 is Anthropic’s retirement day” — that is Copilot. “Every Copilot user loses Sonnet 4.6 on 09-01” — annual individual plans are exempted. A third-party calendar saying “0 upcoming Anthropic shutdowns” does not freeze Copilot.
Migrate per product
Messages API / SDK: audit the snapshot id
Export Console Usage CSV and search claude-sonnet-4-5-20250929. Regression-test claude-sonnet-5 or claude-sonnet-4-6 before the 09-29 bound. Partner clouds may differ — read those tables.
GitHub Copilot: change model policy by 09-01
Enterprise admins may need to enable Sonnet 5 / Opus 4.7+ in Copilot model policies. Changelog: no action is required to remove models once deprecated. Annual individuals who still need Sonnet 4.6 should confirm plan type.
Migration order (official mechanism)
Decide whether the request is Anthropic API or Copilot. API: find hard-coded snapshots in Usage CSV and regress replacements before the bound. Copilot: move workflows to changelog alternatives before 09-01; enterprises check policy toggles. This page does not describe bypassing Copilot model policy or spoofing client identifiers.
What this means on QCode
QCode sells API access; it does not host GitHub Copilot. Copilot’s 09-01 drop does not by itself change the Messages API lifecycle. If you leave Copilot for your own API, pick ids that actually take traffic (for example claude-sonnet-5, claude-sonnet-4-6) at official price × service fee. This is not a Sonnet 4.5 product guide and does not treat “not sooner than 09-29” as already retired.
FAQ
Is claude-sonnet-4-5-20250929 already Deprecated?
No. On 2026-08-30 the official row is Active, retirement lower bound not sooner than 2026-09-29. Deprecated is a later state: still callable, not recommended, with a replacement and a date.
Why is Copilot four weeks earlier?
GitHub schedules the Copilot catalog. The 2026-07-31 changelog sets 09-01 across Copilot surfaces. Anthropic’s page covers its API and named clouds. The dates are allowed to diverge.
Which API id should I move to?
On the same table, claude-sonnet-5 and claude-sonnet-4-6 are Active, bounds 2027-06-30 and 2027-02-17. Pick after your own evals; do not only rewrite the string.
Do annual Copilot individuals keep Sonnet 4.6 after 09-01?
GitHub’s words: Claude Sonnet 4.6 remains available to individual GitHub Copilot subscribers on annual plans. Monthly and enterprise are outside that sentence. Sonnet 4.5 has no matching exception.
Do Bedrock / Vertex share 09-29?
Not necessarily. The page says partner-operated platforms set their own schedules. Use the Amazon Bedrock and Google Cloud model tables.
Will QCode turn off Sonnet 4.5 on 09-01?
09-01 is Copilot’s date, not the Anthropic API retirement. QCode follows upstream API lifecycle and whatever actually answers. Still migrate hard-coded ids before the API bound; do not bet on the Copilot calendar.
Sources
API status and “not sooner than September 29, 2026”: platform.claude.com/docs/en/about-claude/model-deprecations (fetched 2026-08-30). Copilot 09-01 table: github.blog/changelog/2026-07-31-upcoming-august-2026-model-deprecations-in-github-copilot. 60-day notice and failed requests after Retired: same Anthropic page.
Copilot’s catalog is moving; the API clock is the official table
Keep 09-01 and “not sooner than 09-29” apart. If you need your own API, official price × service fee on models that are actually sold.
Related
Claude Sonnet 5 guide
Copilot’s suggested alternative for Sonnet 4.5, and still Active on the API table.
Sonnet 5 vs Sonnet 4.6
Two Active Sonnet lines — change behavior, not only the id.
Claude Haiku 4.5
Another dated row on the same table: Haiku 4.5 not sooner than 2026-10-15.
Reading of Anthropic and GitHub public deprecation docs, not a statement by either vendor. Status is whatever the table and changelog say on the day you fetch them. QCode does not bypass vendor retirements or product policy.