The Sage Repository on GitHub#

The center of Sage development is the SageMath organization on GitHub, which consists of many repositories related with Sage. The most important one among them is of course the Sage repository, which we call “the Sage repo” for short.

Obtaining a GitHub account#

To share your work on Sage, you need a GitHub account. If you do not have one yet, choose a username and create an account. In the following, we assume your username “alice”. So you always read your own username if you see “alice”.

Using the GitHub CLI#

GitHub provides a command-line interface, the GitHub CLI, that can be used instead of the web interface. The central component of the GitHub CLI is the gh command that you can use in your terminal.


The page github_cli: Command-line interface for GitHub documents how to install the gh command for your platform. Or see GitHub CLI from GitHub.


You have to authenticate to your GitHub account to allow gh command to interact with GitHub. Typically the authorization proceeds as follows:

[alice@localhost sage]$ gh auth login
? What is your preferred protocol for Git operations? HTTPS
? Authenticate Git with your GitHub credentials? Yes
? How would you like to authenticate GitHub CLI? Login with a web browser

! First copy your one-time code: 3DA8-5ADA
Press Enter to open in your browser...
✓ Authentication complete.
- gh config set -h git_protocol https
✓ Configured git protocol
✓ Logged in as sage

where a web browser is used to enter credentials. You can also use an authentication token instead, in which case you must first generate a Personal Access Token here.

Next set the default repo for the gh command:

[alice@localhost sage]$ gh repo set-default sagemath/sage

and check:

[alice@localhost sage]$ gh repo view

which will show the default repo along with its readme, which is quite long.

Linking Git to your GitHub account#

In order for your Git to work with GitHub, your GitHub account needs to be linked with your Git. No action is needed if you have already contributed to any other project on GitHub and set up Git credentials or SSH keys for this.

The above dialogue from gh auth login linked your Git to GitHub by HTTPS protocol using your GitHub credentials. Alternatively you may like to use popular Git Credential Manager which stores your credentials natively to your platform. For more information, see Caching your GitHub credentials in Git.

If you prefer SSH to HTTPS for authenticating Git to GitHub, then you follow Git authentication through SSH to generate an SSH keypair and add the SSH public key to your GitHub account. A simple way to upload the public key is to choose SSH protocol for Git operations in the dialogue from gh auth login command above. For more details, see Connecting to GitHub with SSH.

We assume HTTPS protocol in the rest of this guide.

Forking the Sage repository#

The first step is to create your personal fork of the Sage repo on GitHub. After logging in to your GitHub account, visit the Sage repo, and simply click “Fork” on the Sage repo. Then your fork of the Sage repo is created at

Next if you don’t have a local Git repo of Sage, then start afresh cloning your fork:

[alice@localhost ~]$ git clone
Cloning into 'sage'...
remote: Enumerating objects: 914565, done.
remote: Counting objects: 100% (2738/2738), done.
remote: Compressing objects: 100% (855/855), done.
remote: Total 914565 (delta 1950), reused 2493 (delta 1875), pack-reused 911827
Receiving objects: 100% (914565/914565), 331.09 MiB | 11.22 MiB/s, done.
Resolving deltas: 100% (725438/725438), done.
Updating files: 100% (9936/9936), done.
[alice@localhost ~]$ cd sage
[alice@localhost sage]$ git remote -v
origin (fetch)
origin (push)

If you already have a local Git repo and only want to link your fork as origin remote, then do:

[alice@localhost sage]$ git remote add origin
[alice@localhost sage]$ git remote -v
origin (fetch)
origin (push)
[alice@localhost sage]$ git fetch origin
remote: Enumerating objects: 1136, done.
remote: Counting objects: 100% (1084/1084), done.
remote: Compressing objects: 100% (308/308), done.
remote: Total 1136 (delta 825), reused 982 (delta 776), pack-reused 52
Receiving objects: 100% (1136/1136), 2.62 MiB | 5.30 MiB/s, done.
Resolving deltas: 100% (838/838), completed with 145 local objects.
 * [new branch]      develop     -> origin/develop

You also add the Sage repo sagemath/sage as your remote upstream:

[alice@localhost sage]$ git remote add upstream
[alice@localhost sage]$ git remote -v
origin (fetch)
origin (push)
upstream (fetch)
upstream (push)


If you linked your Git to GitHub by SSH protocol, then do the following instead to set up remotes:

[alice@localhost sage]$ git remote add origin [email protected]:alice/sage.git
[alice@localhost sage]$ git remote add upstream [email protected]:sagemath/sage.git
[alice@localhost sage]$ git remote -v
origin  [email protected]:alice/sage.git (fetch)
origin  [email protected]:alice/sage.git (push)
upstream    [email protected]:sagemath/sage.git (fetch)
upstream    [email protected]:sagemath/sage.git (push)

To prevent accidental pushes to upstream (instead of origin), you may want to disable it by running:

[alice@localhost sage]$ git remote set-url --push upstream DISABLE

Of course, you can give arbitrary names to your Git remotes, but origin and upstream are the established defaults, which will make it easier to use tools such as the GitHub CLI.

Reporting bugs#

If you think you have found a bug in Sage, here is the procedure:

  • Search through our Google groups sage-devel, sage-support for postings related to your possible bug (it may have been fixed/reported already). You also search the GitHub issues to see if anyone else has already opened an issue about your bug.

  • If you do not find anything but you are not sure that you have found a bug, ask about it on sage-devel.

  • If you are sure that you have found a bug, then create on GitHub a new issue about the bug.

    A bug report should contain:

    • An explicit and reproducible example illustrating your bug (and/or the steps required to reproduce the buggy behavior). It also helps to describe what behaviour is expected.

    • The version of Sage you run, as well as the version of the optional packages that may be involved in the bug.

    • If relevant, describe your operating system as accurately as you can and the architecture of your CPU (32 bit, 64 bit, …).

Follow Opening an issue for further guide. Thank you in advance for reporting bugs to improve Sage!

Planning an enhancement#

In addition to bug reports, you should also open an issue if you have some new code or an idea that makes Sage better. If you have a feature request, start a discussion on sage-devel first, and then if there seems to be a general agreement that you have a good idea, open an issue describing the idea.

Before opening a new issue, consider the following points:

  • Make sure that nobody else has opened an issue (or a PR) about the same or closely related issue. Search through the existing issues and PRs with some key words.

  • It is much better to open several specific issues than one that is very broad. Indeed, a single issue which deals with lots of different issues can be quite problematic, and should be avoided.

  • Be precise: If foo does not work on macOS but is fine on Linux, mention that in the title. Use the keyword option so that searches will pick up the issue.

  • The problem described in the issue must be solvable. For example, it would be silly to open an issue whose purpose was “Make Sage the best mathematical software in the world”. There is no metric to measure this properly and it is highly subjective.

  • If appropriate, provide URLs to background information or sage-devel conversation relevant to the issue you are reporting.

Opening an issue#

Whether it’s reporting a bug or planning an enhancement, issue should be opened on our Sage repo sagemath/sage on GitHub.

  • Think of an apt title. People scan through the titles of issues to decide which ones to look into further. So write a title that concisely describes what the issue is about.

  • Describe the issue in detail in the issue body. What is the issue? How can we solve the issue? Add links to relevant issues/PRs, and other resources.

    You may use GitHub mention @USERNAME to get attention from the people who would be interested in the issue or has expertise in this issue.

  • Add appropriate labels to the created issue:

    • Type labels with prefix t: such as t: bug, t: enhancement, t: feature, t: performance, t: refactoring, t: tests

    • Component labels with prefix c: such as c: basic arithmetic, c: linear algebra, c: geometry, etc.

    • Priority labels with prefix p: such as p: trivial / 5, p: minor / 4, p: major / 3, p: critical / 2, and p: blocker / 1

    If the issue is not expected to be solved in the near future, you may add wishlist item label.

Creating a Pull Request#

If you worked on an issue, and prepared a fix for a bug or wrote code for enhancing Sage, then you create a PR on the Sage repo sagemath/sage.

In addition to what were said about opening an issue, the following applies:

  • The title should concisely describe what the PR does. If the PR solves an issue, describe briefly what the PR solves (do not simply put the issue number in the title).

  • Explain what the PR solves in detail in the body. If the PR solves an issue, you may mention the issue here.

  • Add type, component, and priority labels. If this PR solves an existing issue, please duplicate the labels of the issue to this PR.

  • Dependencies: Use the phrase - Depends on, followed by the issue or PR reference. Repeat this in separate lines if there is more than one dependency. This format is understood by various dependency managers.

If you are working on a PR and the PR is not yet quite ready for review, then open the PR as draft.

The status of a PR#

If a PR is in the state of draft, the review process does not start. Otherwise, review process will start for the PR as soon as a reviewer gets interested with the PR, and the status of the PR will be indicated by status labels with prefix s:.

  • s: needs review: The code is ready to be peer-reviewed. If the code is not yours, then you can review it. See Reviewing Code.

  • s: needs work: Something needs to be changed in the code. The reason should appear in the comments.

  • s: needs info: The author of the PR or someone else should answer to a question or provide information to proceed the review process.

  • s: positive review: The PR has been reviewed positively, and the release manager will merge it to the develop branch of the Sage repo in due time.

If the PR does not get positive review and it is decided to close the PR, then the PR will get one of resolution labels: r: duplicate, r: invalid, r: wontfix, r: worksforme.

The stopgap#

When Sage returns wrong results, an issue and a PR should be created:

The stopgap PR does not fix the problem but adds a warning that will be printed whenever anyone uses the relevant code, until the problem is finally fixed.

To produce the warning message, use code like the following:

from sage.misc.stopgap import stopgap
stopgap("This code contains bugs and may be mathematically unreliable.",

Replace ISSUE_NUM by the reference number for the stopgap issue. On the stopgap issue, enter the reference number for the stopgap PR. Stopgap issues and PRs should be marked as critical.


If mathematically valid code causes Sage to raise an error or crash, for example, there is no need for a stopgap. Rather, stopgaps are to warn users that they may be using buggy code; if Sage crashes, this is not an issue.

Commenting issues and PRs#

Anyone can comment on an issue or a PR. If a PR is linked to an issue, you may not be sure where the comment should go. Then

  • Comments on the reported issue should go on the issue.

  • Comments on the submitted code should go on the PR.

Checks on PRs#

If you manage to fix a bug or enhance Sage, you are our hero. See Development Walk-through for making changes to the Sage source code and Creating a Pull Request to create a PR for the changes.

For each push to a PR, automated tests for the branch of the PR run on GitHub Actions.

  • A linting workflow checks that the code of the current branch adheres to the style guidelines using Pycodestyle (in the pycodestyle-minimal configuration) and Relint.

    In order to see details when it fails, you can click on the check and then select the most recent workflow run.

  • The build and test workflow on GitHub Actions builds Sage for the current branch (incrementally on top of an installation of the develop branch) and runs the test. Details are again available by clicking on the check.

    The automatic workflow runs on a container based on ubuntu-focal-standard. To request a run of the workflow on a different platform, you can issue a workflow dispatch. You can select any of the platforms for which a prebuilt container image exists.

  • The build documentation workflow on GitHub Actions builds the HTML documentation for the current branch.

    A link to the built doc is added in a comment, and so you can easily inspect changes to the documentation without the need to locally rebuild the docs yourself.

    If the doc build fails, you can go to Actions tab and examine documentation build workflow and choose the particular branch to see what went wrong.

Final notes#

  • Every bug fixed should result in a doctest.

  • There are many enhancements possible for Sage and too few developers to implement all the good ideas.

  • If you are a developer, be nice and try to solve a stale/old issue every once in a while.

  • Some people regularly do triage. In this context, this means that we look at new bugs and classify them according to our perceived priority. It is very likely that different people will see priorities of bugs very differently from us, so please let us know if you see a problem with specific PRs.