diff --git a/.prettierignore b/.prettierignore
index 96ad364a..139038b2 100644
--- a/.prettierignore
+++ b/.prettierignore
@@ -2,7 +2,7 @@
 #
 # SPDX-License-Identifier: MIT
 
-# The releases up to 0.0.0-alpha.126 keep the formatting release-please wrote,
+# The releases up to 0.0.0-alpha.127 keep the formatting release-please wrote,
 # and prettier would rewrite every one of them. A released entry is not
 # rewritten.
 CHANGELOG.md
diff --git a/AGENTS.md b/AGENTS.md
index f0c74d6b..7c41ab53 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -39,10 +39,11 @@ To learn what the project _is_, read [docs/](docs/index.md), and
   </details>
   ```
 
-- **No compatibility promise on the `0.0.0-alphaN` stream.** Rename, move or
-  delete. No alias, deprecation cycle, `legacy_` path, or hand-written message
-  for the old spelling. A test asserting the old behaviour is not a blocker;
-  say in the PR where its coverage moved.
+- **No compatibility promise before 1.0.** Rename, move or delete. No alias,
+  deprecation cycle, `legacy_` path, or hand-written message for the old
+  spelling. A test asserting the old behaviour is not a blocker; say in the PR
+  where its coverage moved. A release that breaks a file or an import raises
+  the minor version, and its notes name the break.
 - **Every `feat`, `fix`, `perf`, `refactor`, `docs` or `revert` PR adds its
   title under `## Upcoming version` in `CHANGELOG.md`**, with a link to the PR.
   The label `no changelog` opts one out; only the user sets it.
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 3ec0bf49..e4dfa965 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -12,6 +12,14 @@ it releases that version ([RELEASING.md](https://github.com/energy-models/mathsp
 
 ## Upcoming version
 
+## 0.1.0rc1 (2026-09-25)
+
+The release candidate for 0.1.0, the first release on PyPI:
+`pip install mathspec==0.1.0rc1`. The package installs, imports and runs as
+`mathspec` since 0.0.0-alpha.127
+([#702](https://github.com/energy-models/mathspec/pull/702)). The
+`0.0.0-alpha.N` releases below were tags and GitHub releases only.
+
 - docs: a page says how the package version and the language version of a model file relate ([#711](https://github.com/energy-models/mathspec/pull/711))
 - docs: the installation page and the PyPI project page say `pip install mathspec`, and the README's links resolve on PyPI ([#707](https://github.com/energy-models/mathspec/pull/707))
 - docs: every link to the documentation points at mathspec.readthedocs.io ([#706](https://github.com/energy-models/mathspec/pull/706))