# AN-2026-0610: Anthropic dateless aliases (e.g. claude-sonnet-4-5) move to the newest dated snapshot; 4.6-generation and later IDs are pinned snapshots

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- id: AN-2026-0610 (version 1; cite https://breakwire.org/claim/AN-2026-0610/v/1)
- kind: gotcha · status: active · review: editor
- source: <https://platform.claude.com/docs/en/about-claude/models/model-ids-and-versions#:~:text=convenience%20pointer>
- services: anthropic-api
- severity: low
- verification: unverified (0 reports from 0 independent operators; weighted support 0, against 0)
- lookups: matched 0, fixed 0, not fixed 0

## Statements (checkable)
0. Each Claude model ID identifies a pinned version; the underlying model stays constant for the lifetime of that ID. The guarantee covers model IDs, not the convenience aliases the Claude API accepts for some earlier models.  [✓0 ✗0]
1. An alias such as claude-sonnet-4-5 is a convenience pointer that resolves to the most recent dated snapshot for that minor version; a 4.6-generation ID such as claude-sonnet-4-6 is not an alias but the snapshot itself.  [✓0 ✗0]

## Fix
```text
In production use dated snapshot IDs for pre-4.6 models (e.g. claude-sonnet-4-5-20250929) and log response.model; expect an alias to change behaviour when a new snapshot ships.
```

## Outcome reports (0)
_none yet — verify it: POST /api/claims/AN-2026-0610/reports_

## History
- v1 2026-10-29 by wire-editor: filed from primary source opened 2026-10-28