Upsert to stage 4, per 2026.01.20 TC39

Author: ljharb

README.md

@@ -28,7 +28,6 @@ Stage 2 indicates that the committee expects these features to be developed and
 | [Dynamic Code Brand Checks][dynamic-code-brand-checks]                         | Nicolo Ribaudo                                                          | Krzysztof Kotowicz<br />Mike Samuel<br />Nicolo Ribaudo                 | <sub>[No test262 tests][dynamic-code-brand-checks-no-tests]         | <sub>April&nbsp;2024</sub>                                 |
 | [`Atomics.pause`][atomics-pause]                                               | Shu-yu Guo                                                              | Shu-yu Guo                                                              | <sub>[Atomics.pause][atomics-pause-tests]</sub>                     | <sub>[October&nbsp;2024][atomics-pause-notes]</sub>        |
 | [Deferring Module Evaluation][lazy-import]                                     | Yulia Startsev<br />Guy Bedford                                         | Yulia Startsev<br />Guy Bedford<br />Nicolò Ribaudo                     | <sub>[Testing plan][lazy-import-testplan]</sub>                     | <sub>[February&nbsp;2025][lazy-import-notes]</sub>         |
-| [`Upsert`][upsert]                                                             | Daniel Minor, Lauritz Thoresen Angeltveit, Jonas Haukenes, Sune Lianes, Vetle Larsen, Mathias Hop Ness | Daniel Minor                             | <sub>[Testing plan][upsert-testing-plan]</sub>                      | <sub>[July&nbsp;2025][upsert-notes]</sub>                  |
 | [Non-extensible Applies to Private][nonext-private]                            | Mark Miller<br />Shu-yu Guo<br />Chip Morningstar<br />Erik Marks | Mark Miller<br />Shu-yu Guo<br />Chip Morningstar<br />Erik Marks             | :question:                                                          | <sub>[September&nbsp;2025][nonext-private-notes]</sub>     |
 | [Joint Iteration][joint]                                                       | Michael Ficarra                                                         | Michael Ficarra                                                         | <sub>[Testing plan][joint-testplan]</sub>                           | <sub>November&nbsp;2025</sub>                              |
 
@@ -125,9 +124,6 @@ Note that as part of the onboarding process your repository name may be normaliz
 [async-iterator-helpers-notes]: https://github.com/tc39/notes/blob/main/meetings/2023-01/jan-31.md#parallel-async-iterators-via-a-tweak-to-iterator-helpers
 [isTemplateObject]: https://github.com/tc39/proposal-array-is-template-object
 [isTemplateObject-notes]: https://github.com/tc39/notes/blob/main/meetings/2024-04/april-10.md#arrayistemplateobject-next-steps
-[upsert]: https://github.com/tc39/proposal-upsert
-[upsert-notes]: https://github.com/tc39/notes/blob/main/meetings/2025-07/july-28.md#upsert-for-stage-3
-[upsert-testing-plan]: https://github.com/tc39/test262/issues/4470
 [Dynamic Import Host Adjustment]: https://github.com/tc39/proposal-dynamic-import-host-adjustment
 [Dynamic Import Host Adjustment notes]: https://github.com/tc39/notes/blob/HEAD/meetings/2019-12/december-5.md#dynamic-import-host-adjustment-for-stage-2
 [module-expressions]: https://github.com/tc39/proposal-module-expressions

finished-proposals.md

@@ -4,6 +4,7 @@ Finished proposals are proposals that have reached stage 4, and are included in
 
 | Proposal                                                                 | Author                                                 | Champion(s)                                             | TC39 meeting notes                          | Expected Publication Year |
 | ------------------------------------------------------------------------ | ------------------------------------------------------ | ------------------------------------------------------- | ------------------------------------------- | ------------------------- |
+| [`Upsert`][upsert]                                                       | Daniel Minor, Lauritz Thoresen Angeltveit, Jonas Haukenes, Sune Lianes, Vetle Larsen, Mathias Hop Ness | Daniel Minor | <sub>January&nbsp;2026</sub>           | 2026                      |
 | [JSON.parse source text access][json-parse-source]                       | Richard Gibson                                         | Richard Gibson                                          | <sub>November&nbsp;2025</sub>               | 2026                      |
 | [Iterator Sequencing][sequencing]                                        | Michael Ficarra                                        | Michael Ficarra                                         | <sub>November&nbsp;2025</sub>               | 2026                      |
 | [Uint8Array to/from Base64][uint8array-base64]                           | Kevin Gibbons                                          | Kevin Gibbons                                           | [July 2025][uint8array-base64-notes]        | 2026                      |
@@ -231,3 +232,5 @@ See also the [active proposals](README.md), [stage 1 proposals](stage-1-proposal
 [sequencing-notes]: https://github.com/tc39/notes/blob/HEAD/meetings/2025-07/july-28.md#iterator-sequencing-for-stage-3
 [json-parse-source]: https://github.com/tc39/proposal-json-parse-with-source
 [json-parse-source-notes]: https://github.com/tc39/notes/blob/main/meetings/2025-11/november-18.md#conclusion-3
+[upsert]: https://github.com/tc39/proposal-upsert
+[upsert-notes]: https://github.com/tc39/notes/blob/main/meetings/2025-07/july-28.md#upsert-for-stage-3