chore: release 0.2.1

[FBumann]

Prompt: fix the message, then cut 0.3.0

Prompt: Im not sure if those are breaking, or only docs fixes … And yes, push the edit

Prompt: make it 0.2.1 and add the rule to AGENTS.md

Note

The following content was generated by AI.

What this changes

## Upcoming version becomes ## 0.2.1 (2026-10-01), edited into release notes. Merging this PR releases 0.2.1 (RELEASING.md). AGENTS.md now states that a release with no break raises the patch version, features included.

Why

Composition is finished: merge, override, adds_to: and one objective (#732, #761, #763). Nothing in the release breaks a 0.2.0 file or import, so by the version rule it is a patch release. The relation-syntax work (#596, #664, #665) is a separate break, and masks: (#803) is additive. Both come later.

What the notes do, the version rule, gate output, what is not done

The notes.

• A top paragraph says what the release is: a spec written as several files.
• A second paragraph says that nothing a 0.2.0 file or call does stops working, and names two rules of the language that are now stated exactly:
  • feat(language): a parameter value that is null or NaN is refused when the data is attached #788: a consumer that attaches data refuses a null or NaN parameter value.
  • fix(language): dual(c) is the rate at which the optimal objective rises with the right side of c, so an equality has a sign too #751: dual(c) is the rate in the right side, which is what engines return.
  • Each of those PRs changed only documentation and a docstring. mathspec neither attaches data nor computes duals, so neither breaks a file or an import. An earlier head of this PR called them breaks.
• The lines are grouped as Composition, Language, Typesetting and advice, and Documentation, in the 0.2.0 notes' shape.
• The feat(language): a sum other files add terms to is declared as an expression with empty: true #742 line (empty: true) is left out. feat(language): a term names the sum it adds to with adds_to:, and no file marks a sum as open #763 replaced it before any release carried it. Every other line is kept. A script compared the PR links of the old section with the new one: only feat(language): a sum other files add terms to is declared as an expression with empty: true #742 is missing, and nothing is added.
• The feat(language): a term names the sum it adds to with adds_to:, and no file marks a sum as open #763 line about adds_to: is reworded. "No file marks a sum as open" contrasts with empty: true, which no release had. It now says what the release has.

The version rule. AGENTS.md said that a release that breaks a file or an import raises the minor version, and did not say what any other release raises. It now says: "Every other release raises the patch version, features included." This is the usual reading before 1.0: ~=0.2.0 and ^0.2.0 both take 0.2.x. A changed message is not counted as a break, since the rule names files and imports only. The 0.2.0 notes counted one; this rule does not.

Checked against v0.2.0.

• The public API (__all__) only adds merge and override.
• The schema loses no key: its two removed lines are description strings.
• SUPPORTED_VERSIONS is unchanged, so the release reads the same language versions.
• Composition is not in 0.2.0, so no composition change is a break against it.

Gates.

• pixi run python -m tools.changelog check: "releases 0.2.1 on merge".
• pixi run lint: clean.
• pixi run test: 2618 passed, on the first head. The later commits change CHANGELOG.md and AGENTS.md only.
• pixi run ci not run, for the same reasons as on feat(language): a term names the sum it adds to with adds_to:, and no file marks a sum as open #763 (proxy, tectonic bundle).

Branch. This branch is main (69f673d) merged in, plus the release commits. Its diff against main is CHANGELOG.md and AGENTS.md.

Departed from. One issue, one PR: the AGENTS.md rule rides on the release PR, since this release is the one it decides. It is a chore and owes no changelog line.

Not done. No empty ## Upcoming version above the release. The next PR adds one.

🤖 Generated with Claude Code

https://claude.ai/code/session_01PBmqeqBrqpQC6MVoSrguHK

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