Impacted Targets

What are Impacted Targets?

Impacted targets are metadata about a pull request that defines the logical changes made by a pull request. They're a list of strings: for example, PR 123 which changes to the user service may have the following list of impacted targets: [backend, user-service, integration-tests]. Anytime two PRs have an overlap in the list of impacted target strings, Trunk Merge will ensure those PRs pass tests when based off of one another.

Generating Impacted Targets

The repo using the Merge Graph is required to generate impacted targets for every pull request. Some build systems (e.g. Bazel, Buck, Gradle, Turborepo, ...) define targets, which can be uploaded to the Merge Graph. Alternatively, a glob-based pattern approach could be used, where filepaths map to a target (e.g. files in src/backend upload the backend target.)
We offer out of the box CI solutions for uploading impacted targets based on the flavor of your repo (see below). If none of the solutions work, please let us know at our Slack; we are happy to help build out something for your use case. Alternatively, we are accepting contributions to our open-sourced repository.

Custom Impacted Targets

Impacted Targets should be computed for every PR. The list of impacted targets should be computed by comparing two different SHAs: the head of the target branch, and the merge commit of the pr.
From In this diagram, we want to compare the merge commit and the main tip.
Our reference implementation may be useful in guiding your implementation.
After they are computed, upload them to our services. Our HTTP POST endpoint can be found at We expect the following headers/body:
Content-Type: application/json,
x-api-token: <repo API token>
repo: {
host: "",
owner: <repo owner>, <!--- For example, "trunk-io" --->
name: <repo name>, <!--- For example, "merge-action" --->
pr: {
number: <pr number>, <!-- For example, 5 -->
sha: <pr sha>, <!-- For example, "07fc773f16c0353bc3820fed65d89afddb9f81c3" -->
targetBranch: <merge instance branch>, <!-- For example, "main" -->
impactedTargets: ["target-1", "target-2", ...] OR "ALL" <!--- see notes on "ALL" below --->
impactedTargets allows specifying either an array of strings representing the impacted targets from the PR or the string "ALL". Specifying "ALL" is the equivalent of saying that everything that comes into the graph after this PR should be based off of this one, which is useful when your PR contains changes that affect the whole repo (such as editing trunk.yaml or a GitHub workflow).

Impacted Targets Generation: Bazel + GitHub Actions

  1. 1.
    Grab your repository's API token from, in the settings > repo-name page.
  2. 2.
    Store the repository's API token as a GitHub action secret.
  3. 3.
    Use the trunk-io/merge-action action, as defined here.