Task-graph generation takes a collection of parameters as input, in the form of a JSON or YAML file.

During decision-task processing, some of these parameters are supplied on the command line or by environment variables. The decision task helpfully produces a full parameters file as one of its output artifacts. The other mach taskgraph commands can take this file as input. This can be very helpful when working on a change to the task graph.

When experimenting with local runs of the task-graph generation, it is always best to find a recent decision task’s parameters.yml file, and modify that file if necessary, rather than starting from scratch. This ensures you have a complete set of parameters.

The properties of the parameters object are described here, divided roughly by topic.

Push Information


Whether or not this push is a “backstop” push. That is a push where all builds and tests should run to ensure regressions aren’t accidentally missed.


The repository from which to do an initial clone, utilizing any available caching.


The repository containing the changeset to be built. This may differ from base_repository in cases where base_repository is likely to be cached and only a few additional commits are needed from head_repository.


The previous revision before head_rev got merged into. This can be a short revision string.


The revision to check out; this can be a short revision string


Reference where head_rev got merged into. It is usually a branch or a tag.


For Mercurial repositories, this is the same as head_rev. For git repositories, which do not allow pulling explicit revisions, this gives the symbolic ref containing head_rev that should be pulled from head_repository.


The tag attached to the revision, if any.


The list of all files added or modified by the push.


Email address indicating the person who made the push. Note that this value may be forged and must not be relied on for authentication.


The try syntax in the commit message, if any.


The ID from the pushlog


The timestamp of the push to the repository that triggered this decision task. Expressed as an integer seconds since the UNIX epoch.


The mercurial branch where the revision lives in.


The timestamp of the build date. Defaults to pushdate and falls back to present time of taskgraph invocation. Expressed as an integer seconds since the UNIX epoch.


A formatted timestamp of build_date. Expressed as a string with the following format: %Y%m%d%H%M%S


The type of repository, either hg or git.


The tasks_for value used to generate the decision task.

Tree Information


Another name for what may otherwise be called tree or branch or repository. This is the unqualified name, such as mozilla-central or cedar.


The SCM level associated with this tree. This dictates the names of resources used in the generated tasks, and those tasks will fail if it is incorrect.

Try Configuration


The mode in which a try push is operating. This can be one of:

  • "try_task_config" - Used to configure the taskgraph.

  • "try_option_syntax" - Used when pushing to try with legacy try syntax.

  • "try_auto" - Used to make try pushes behave more like a push on autoland.

  • "try_select" - Used by mach try to build a list of tasks locally.

  • None - Not a try push or mach try release.


The arguments given as try syntax (as a dictionary), or None if try_mode is not try_option_syntax.


The contents of the try_task_config.json file, or {} if try_mode is not try_task_config.

Test Configuration


The test manifest loader to use as defined in taskgraph.util.chunking.manifest_loaders.

Target Set

The “target set” is the set of task labels which must be included in a task graph. The task graph generation process will include any tasks required by those in the target set, recursively. In a decision task, this set can be specified programmatically using one of a variety of methods (e.g., parsing try syntax or reading a project-specific configuration file).


Can either be a boolean or a list of kinds.

When True, any task with the always_target attribute will be included in the target_task_graph regardless of whether they were filtered out by the target_tasks_method or not. Because they are not part of the target_set, they will still be eligible for optimization when the optimize_target_tasks parameter is False.

When specified as a list of kinds, only tasks with a matching kind will be eligible for addition to the graph.


List of filter functions (from taskcluster/gecko_taskgraph/ to apply. This is usually defined internally, as filters are typically global.


The method to use to determine the target task set. This is the suffix of one of the functions in taskcluster/gecko_taskgraph/


History of recent releases by platform and locale, used when generating partial updates for nightly releases. Suitable contents can be generated with mach release-history, which will print to the console by default.



A python path of the form <module>:<object> containing a dictionary of optimization strategies to use, overwriting the defaults.


If true, then target tasks are eligible for optimization.


Specify tasks to not optimize out of the graph. This is a list of labels. Any tasks in the graph matching one of the labels will not be optimized out of the graph.


Specify tasks to optimize out of the graph. This is a dictionary of label to taskId. Any tasks in the graph matching one of the labels will use the previously-run taskId rather than submitting a new task.

Release Promotion


Specify the release promotion build number.


Specify the version for release tasks.


Specify the application version for release tasks. For releases, this is often a less specific version number than version.


Specify the next version for version bump tasks.


The type of release being promoted. One of “nightly”, “beta”, “esr115”, “release-rc”, or “release”.


The time and date when a release is scheduled to live. This value is passed to Balrog.


Boolean which controls repacking vanilla Firefox builds for partners.


Boolean which controls adding attribution to vanilla Firefox builds for partners.


Boolean which controls repacking vanilla Firefox builds into EME-free builds.


List of partners to repack or attribute if a subset of the whole config. A null value defaults to all.


Configuration for partner repacks & attribution, as well as EME-free repacks.


The build number for partner repacks. We sometimes have multiple partner build numbers per release build number; this parameter lets us bump them independently. Defaults to 1.


The product that is being released.


A list of signoffs that are required for this release promotion flavor. If specified, and if the corresponding signoff_urls url isn’t specified, tasks that require these signoffs will not be scheduled.


A dictionary of signoff keys to url values. These are the urls marking the corresponding required_signoffs as signed off.

Repository Merge Day


Merge config describes the repository merge behaviour, using an alias to cover which set of file replacements and version increments are required, along with overrides for the source and target repository URIs.


The clone/push URI of the source repository, such as


The clone/push URI of the target repository, such as


The firefoxtree alias of the source branch, such as ‘central’, ‘beta’


The firefoxtree alias of the target branch, such as ‘beta’, ‘release’


Don’t push any results to target repositories.

Code Review


The code review process needs to know the Phabricator Differential diff that started the analysis. This parameter must start with PHID-DIFF-

Local configuration


Generate only the given kinds and their kind-dependencies. This is used for local inspection of the graph and is not supported at run-time.