<table border="1" cellspacing="0" cellpadding="8">
<tr>
<th>Issue</th>
<td>
<a href=https://github.com/llvm/llvm-project/issues/148139>148139</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>
P3641R0: Rename `std::observable` to `std::observable_checkpoint`, and add a feature-test macro
</td>
</tr>
<tr>
<th>Labels</th>
<td>
libc++,
c++26,
wg21 paper
</td>
</tr>
<tr>
<th>Assignees</th>
<td>
</td>
</tr>
<tr>
<th>Reporter</th>
<td>
frederick-vs-ja
</td>
</tr>
</table>
<pre>
**Link:** https://wg21.link/P3641R0
Feature-test macro:
```c++
#define __cpp_lib_observable_checkpoint 202506L // freestanding, also in <utility>
```
This should be probably simultaneously implemented with [P1494R5](https://wg21.link/P1494R5) (#127869).
</pre>
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