Replacement map
| Old model or family | Status in official ledger | Named replacement | Action |
|---|---|---|---|
| Claude 1 and Claude Instant IDs | Retired November 6, 2024 | claude-haiku-4-5-20251001 | Replace hard-coded IDs and re-test prompts. |
| Claude 2.0 / 2.1 | Retired July 21, 2025 | claude-opus-4-8 | Re-baseline quality, latency, and cost. Context and behavior differ materially. |
| Claude Sonnet 3.5 IDs | Retired October 28, 2025 | claude-sonnet-4-6 | Apply Sonnet 4.6 migration notes, especially around assistant prefilling and tool versions where relevant. |
| Claude 3.7 Sonnet | Retired February 19, 2026 | claude-sonnet-4-6 | Move to Sonnet 4.6 or newer and account for reasoning/tool behavior changes. |
| Claude Opus 3 | Retired January 5, 2026 | claude-opus-4-8 | Re-test high-capability workflows and cost assumptions. |
| Claude Opus 4.1 | Deprecated June 5, 2026; retirement August 5, 2026 | claude-opus-4-8 | Migrate before retirement; verify parameter compatibility. |
Sonnet 5 migration notes
The official migration guide calls Sonnet 5 a drop-in upgrade from Sonnet 4.6 at the standard $3/$15 per MTok price, with introductory $2/$10 pricing through August 31, 2026. It also calls out breaking API changes for manual extended thinking and non-default sampling parameters.
The same guide says Sonnet 5 uses a new tokenizer, so token counts for the same text can be higher. That makes pre-migration cost checks part of the migration, not an afterthought.
Audit method for old codebases
Search for literal model IDs, not only visible model names. Then classify each ID as active, deprecated, retired, or partner-platform-specific. The deprecation page recommends using console usage exports to locate remaining deprecated-model usage.
For large engineering migrations, keep implementation practice out of this archive and use Claude Ships Code. This page is for historical and source-backed migration facts.
Parameter deprecations
The model deprecations page also records request-parameter deprecations. It says temperature, top_p, and top_k set to non-default values return a 400 error on Claude Opus 4.7 and later, including Opus 4.8, and on Claude Sonnet 5. That is a model-history detail with direct production consequences.
Questions this page answers
What replaced Claude 3.5 Sonnet?
The official deprecation ledger recommends Claude Sonnet 4.6 for the retired Claude 3.5 Sonnet model IDs.
What replaced Claude 2?
The official deprecation ledger recommends Claude Opus 4.8 for Claude 2.0 and Claude 2.1.
What should developers check before moving to Sonnet 5?
Check tokenizer-driven cost changes, manual extended thinking, non-default sampling parameters, max output sizing, and refusal handling for cybersecurity-sensitive workloads.