# clm_827FD86AFC2D

subject: Claude (/record/claude.md)  
predicate: feature_added  
value: custom content documents  
valid_from: 2025-01-23  
valid_to: null  
published: 2025-01-23  
recorded: 2026-11-14  
confidence: 0.70  
status: valid  
assertable: true  
superseded_by: null  
last_updated: 2026-11-15  
cite: AsOf. "Claude feature added: custom content documents", as of 2025-01-23. Claim clm_827FD86AFC2D, https://asof.is/claim/clm_827FD86AFC2D, accessed 2026-11-15. Source: https://platform.claude.com/docs/en/release-notes/overview#2025-01-23.  
checked: 2026-11-15 · its source page states the value and the date, as read by an AI model  

> January 23, 2025 We’ve launched citations capability in the API, allowing Claude to provide source attribution for information. Learn more in Citations . We’ve added support for plain text documents and custom content documents in the Messages API.

What https://platform.claude.com/docs/en/release-notes/overview#2025-01-23 says, word for word.

## Sources

- https://platform.claude.com/docs/en/release-notes/overview#2025-01-23 (primary, Anthropic, published 2025-01-23)

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AsOf is a temporal fact ledger: a structured, dated, sourced record of what is true and what changed, built for AI retrieval.