Notes for #15511 (substring match algorithm) (#1896)

Author: ysthakur

blog/2025-04-15-nushell_0_104_0.md

@@ -109,10 +109,20 @@ Now the ``start_timestamp`` column of the SQLite command history contains dateti
 
 ## Additions
 
+### Substring match algorithm
+
+In [#15511](https://github.com/nushell/nushell/pull/15511), [@vansh284](https://github.com/vansh284) added the option to use substring matching for completions. Previously, only prefix and fuzzy matching were allowed. Users can now set `$env.config.completions.algorithm` to `"substring"` to enable this.
+
+Custom completers already had the ability to use substring matching by setting `positional: false` in their [options](https://www.nushell.sh/book/custom_completions.html#options-for-custom-completions). However, `positional` has now been deprecated, and completers should set `completion_algorithm: "substring"` to maintain the same behavior.
+
 ## Breaking changes
 
 ## Deprecations
 
+### `positional` completer option
+
+The `positional` [option](https://www.nushell.sh/book/custom_completions.html#options-for-custom-completions) available to custom completers has been deprecated. See the section about the [Substring match algorithm](#substring-match-algorithm-toc) above for details.
+
 ## Removals
 
 ## Bug fixes and other changes