Version skew protection

Your app and your tasks are deployed separately, so they are never live at exactly the same instant. In the window between them, an app running new code can trigger tasks built from old code — or the other way around. That’s version skew. Version skew protection closes the window. You give a deployment an external deployment id, your app sends the same id when it triggers, and Trigger.dev pins the run to the deployment carrying that id.

Version skew protection requires @trigger.dev/sdk and the trigger.dev CLI on v4.5.12 or later, the release that introduced external deployment ids. On an older version no id is sent, and runs execute on the current version with no warning.

The guarantee

Once your app is sending an external deployment id, a triggered run has one of four outcomes:

Situation	What happens
A deployment with that id is live	The run is pinned to it and executes immediately.
A deployment with that id is still building	The run waits, then executes pinned to it once the build lands.
No deployment with that id ever arrives	The run waits up to 1 hour, then expires.
No id was sent at all	Nothing changes — the run executes on the current version.

The id is the contract. There is no dashboard setting and nothing to switch on: if a trigger carries an external deployment id, that id is honoured. If it doesn’t, behaviour is exactly what it is today. This works identically in production, staging and preview (including per-branch preview deployments), with no per-environment configuration.

Quick start

The id is free-form and opaque to Trigger.dev — a commit SHA, a release tag, a CI run id, anything up to 128 characters. The only rule is that both halves carry the same value.

Deploy your tasks with an external id

npx trigger.dev@latest deploy --external-id "$(git rev-parse HEAD)"

Give your running app the same value

Set this in your hosting platform’s runtime environment variables, alongside TRIGGER_SECRET_KEY:

TRIGGER_EXTERNAL_DEPLOYMENT_ID=<the-same-commit-sha>

Whatever you use on both sides, make sure it can’t expand to an empty string. An unset shell variable deploys with no id at all, which silently gives you no protection rather than an error.

That’s it. Every task triggered by that release of your app now runs on the deployment you built for it. This recipe works on every platform, needs no integration, and is not git-specific. If you deploy to Vercel with the Vercel integration, both halves are filled in for you — see Automatic skew protection on Vercel.

Deploying with an external id

npx trigger.dev@latest deploy --external-id <value>

The value is stored on the deployment. It is never interpreted, parsed or validated beyond its length — the only constraint is 128 characters or fewer.

Reusing an id

Because deploys are often retried, redeployed and re-run by CI, repeating an id is a normal thing to do rather than an error. What happens depends on the state of the deployment that already holds it:

Existing deployment for this id	Default behaviour	With `--force`
Deployed	No build. The CLI reports the existing version, sets the same outputs, and exits successfully.	Builds a new one.
Building (a deploy is in flight)	Error, naming the version that is already building. Two builds racing for one id is almost always an accident.	Cancels the in-flight build, then starts a new one.
Failed, cancelled or timed out	Rebuilds. No flag needed — builds fail for reasons that have nothing to do with your code.	Rebuilds.
None	Builds.	Builds.

Deploying an id that is already live prints the existing version and stops:

Version 20250228.1 was already deployed for --external-id abc123 — nothing to build

Deploying an id that is mid-build fails, telling you which version is already building:

A deployment for external id "abc123" is already in progress (version 20250228.1). Wait for it to finish, or deploy again with --force to cancel it and start a new one.

The short-circuit on an already-deployed id makes --external-id useful on its own as deploy idempotency: a CI job that runs twice for the same commit builds once — provided the second run starts after the first has finished — and the short-circuited run still gets the version number in its output. A second run that starts while the first is still building hits the Building row above and errors. Only in the brief window before the first run has registered its build do both see “nothing deployed yet”; then both build, and the higher version wins.

In GitHub Actions, the short-circuited run sets the same step outputs (such as deploymentVersion) as a real build, so downstream steps work unchanged. One exception: needsPromotion is always false on a short-circuit, because a reused version is never promoted — so a workflow that gates a promote step on that output will skip promotion on the repeat run.

--force starts a new build for an id that already has one. It is non-destructive with respect to deployments that already succeeded — both remain, and the newer version wins. It is destructive to a build still in flight, which it cancels, because one id should not have two live builds racing to define it. It requires --external-id: on its own there is no previous deployment for it to build over, so it errors.

A cancelled deployment can never be deployed, so the build it replaces can’t land. The build itself is signalled to stop and usually does within seconds — but one running elsewhere (a --local-build, or a deploy from someone else’s machine) can keep going for a few minutes before it notices.

Redeploying the same commit

The short-circuit is keyed on the id alone, not on what went into the build. If you use the commit SHA as your id and then change something the commit doesn’t capture — a synced environment variable, a secret, a dependency resolved at build time — redeploying that commit produces no new build, and the deployed image keeps the older inputs. Three ways out, in order of preference:

Make a new commit. git commit --allow-empty -m "redeploy" gives you a new SHA, which is a new id, which builds. This is the only remedy that also works for the Vercel and GitHub integrations, which never pass --force.
Pass --force, if you drive deploys yourself.
Use an id that captures more than the commit — ${GITHUB_SHA}-${GITHUB_RUN_ID}, say — if your builds legitimately depend on inputs outside the tree. You lose idempotency in exchange.

See the deploy command reference for all deploy flags.

Automatic discovery

Setting the id yourself is the explicit path, and it always works. The SDK can also discover an id from the variables your hosting platform or CI system already injects, so you don’t have to wire anything up. Discovery happens at runtime, on each trigger call — never at module load — so a prebuilt bundle can’t pin a stale value. The SDK takes the first of these that yields a value:

externalDeploymentId passed to the trigger call — always honoured.
externalDeploymentId passed to configure() — always honoured.
TRIGGER_EXTERNAL_DEPLOYMENT_ID — always honoured.
Platform and CI variables — read only when TRIGGER_AUTOMATIC_SKEW_VERSION_PROTECTION is set to 1 or true.

The first three are explicit acts on your part, so they need no opt-in. Only the fourth — reading a commit SHA your platform injected on its own — requires one, because that value is there whether or not anyone asked for this feature.

TRIGGER_AUTOMATIC_SKEW_VERSION_PROTECTION=1

The value is trimmed and matched case-insensitively, so true, TRUE and True are all the same thing. Any other value — including 0, an empty string, or the variable being absent — leaves automatic discovery off. The variable gates discovery only; an id you set explicitly is always honoured either way.

Most platforms expose the commit SHA to the build, not to the running process. Discovery reads process.env inside your live application, so a variable that only exists during the build is a variable the SDK cannot see. On those platforms nothing is discovered and nothing breaks — your runs simply execute on the current version, silently, as they do today. If your platform is marked “Build only” below, use the manual recipe instead.

Hosting platforms

Read first, because a hosting variable describes the deployment that is running.

Platform	Variable	Available in the running app?
Vercel	`VERCEL_GIT_COMMIT_SHA`	Yes — build and runtime, provided “Automatically expose System Environment Variables” is on for the project.
Railway	`RAILWAY_GIT_COMMIT_SHA`	Yes — injected at build and runtime, no configuration.
Render	`RENDER_GIT_COMMIT`	Yes — exposed in both build and runtime environments.
Cloudflare Pages	`CF_PAGES_COMMIT_SHA`	Yes for Pages Functions; also present during the build.
Cloudflare Workers Builds	`WORKERS_CI_COMMIT_SHA`	Build only — not injected into the deployed Worker. Must be forwarded.
Netlify	`COMMIT_REF`	Build only in the general case. Must be forwarded. (`CACHED_COMMIT_REF` is the previous build’s SHA and is not read.)
AWS Amplify Hosting	`AWS_COMMIT_ID`	Build only. Must be forwarded.
Heroku	`HEROKU_BUILD_COMMIT`, then `HEROKU_SLUG_COMMIT`	Runtime, opt-in — requires dyno metadata.
Koyeb	`KOYEB_GIT_SHA`	Runtime only (not available during the build).
DigitalOcean App Platform	—	No fixed variable. Bind `${_self.COMMIT_HASH}` to a variable named `COMMIT_HASH` and the generic tier below picks it up.
Fly.io	—	Nothing is injected. Set one of the generic names below at deploy time.

CI systems

Read second. These are correct when your application is the CI job, and they are the natural source for --external-id in a pipeline. Once the job has ended they no longer exist, so they cannot be discovered from a long-running app.

System	Variable
GitHub Actions	`GITHUB_SHA`
GitLab CI	`CI_COMMIT_SHA`
CircleCI	`CIRCLE_SHA1`
Bitbucket Pipelines	`BITBUCKET_COMMIT`
Buildkite	`BUILDKITE_COMMIT`
Azure Pipelines	`BUILD_SOURCEVERSION`
Google Cloud Build	`COMMIT_SHA`
Drone / Woodpecker	`DRONE_COMMIT_SHA`
Jenkins (git plugin)	`GIT_COMMIT`
TeamCity	`BUILD_VCS_NUMBER`
Travis CI	`TRAVIS_COMMIT`

Generic fallbacks

Read last, after every named source above is exhausted:

COMMIT_SHA  →  COMMIT_HASH  →  GIT_COMMIT  →  GIT_SHA  →  GIT_HASH

These are the answer for any platform not listed: set one of them and you get pinning with no other changes. They go last precisely because they are unnamespaced and could plausibly be set by something other than your deploy. Empty and whitespace-only values are skipped rather than treated as a match, and a value longer than 128 characters is skipped rather than sent — so a generic name holding something that isn’t a deployment id degrades to “no id discovered” instead of an error.

If a generic name means something else in your environment, you have two clean escapes: set TRIGGER_EXTERNAL_DEPLOYMENT_ID explicitly (it outranks all discovery), or leave TRIGGER_AUTOMATIC_SKEW_VERSION_PROTECTION off and use the manual recipe.

The manual recipe

If your platform only exposes the commit at build time — or injects nothing at all — set the id yourself. This is not a lesser mode: it is the same mechanism, and the same code path the Vercel integration uses with both halves filled in automatically. Read the commit in the place where it is available, and write it into both halves:

# 1. Deploy side — name the deployment after the commit.
npx trigger.dev@latest deploy --external-id "$(git rev-parse HEAD)"

# 2. Application side — give the running app the same value.
TRIGGER_EXTERNAL_DEPLOYMENT_ID=<the-same-commit-sha>

Substitute a real value on both sides — and prefer something that fails loudly over a bare shell variable. On the platforms this section is about, the platform’s own commit variable is usually not set in the shell you are deploying from, so --external-id "$COMMIT_SHA" would quietly deploy with no id and leave you unprotected. Whatever your platform calls its build-time commit variable — COMMIT_REF on Netlify, AWS_COMMIT_ID on Amplify, WORKERS_CI_COMMIT_SHA on Cloudflare Workers Builds, $(git rev-parse HEAD) in a bespoke pipeline — read it there and forward it. Half two can be a runtime environment variable set in your platform’s configuration, or a build-time constant inlined into your bundle. Either works. Three things are worth knowing:

It needs no TRIGGER_AUTOMATIC_SKEW_VERSION_PROTECTION. That variable gates discovery, not pinning, and an explicitly set id is always honoured.
It is not Vercel-specific, or even git-specific. A release tag or CI run id is fine — the value only has to match on both sides.
Any name the SDK reads works. TRIGGER_EXTERNAL_DEPLOYMENT_ID is the clearest, but one of the generic fallbacks does the same job.

Example: Netlify

Netlify exposes COMMIT_REF to the build only, so forward it:

# In your build command or CI step
npx trigger.dev@latest deploy --external-id "$COMMIT_REF"

Then set TRIGGER_EXTERNAL_DEPLOYMENT_ID to the same commit in your site’s runtime environment variables — for example by writing it during the build, or by having your deploy pipeline set it through the Netlify API.

Setting the id in code

Environment variables are the usual way, but you can also pass the id directly. Both forms always win over discovery. Per trigger call:

import { myTask } from "./trigger/tasks";

await myTask.trigger(
  { foo: "bar" },
  { externalDeploymentId: process.env.VERCEL_GIT_COMMIT_SHA }
);

Or once, for every trigger made by the process:

import { configure } from "@trigger.dev/sdk";

configure({
  externalDeploymentId: process.env.MY_RELEASE_ID,
});

An empty or whitespace-only value counts as “not supplied” rather than an error, so wiring up a variable that isn’t always present is safe. Batch triggers carry the id too. batchTrigger resolves it per item exactly as trigger does, and it survives the asynchronous materialisation of batch items — so a large batch triggered during a deploy waits and releases item by item, each pinned to the deployment its calling code came from.

Waiting and expiry

When a run arrives with an id that isn’t deployed yet, it doesn’t fail — it waits. This is the ordinary case, not an edge case: your app frequently goes live a few seconds before your task build finishes. A waiting run shows in the dashboard with the status Pending version and the reason “Waiting for a deployment with this run’s external deployment id”. As soon as a deployment carrying that id is deployed, the run is released and executes pinned to it. An unknown id waits too, for the same reason: “we haven’t seen this deployment” and “this deployment hasn’t been created yet” look identical from the outside, and the second is common — your app often goes live before your deploy pipeline has even claimed a runner.

A run waiting on an external deployment id that never arrives expires after 1 hour. It moves to EXPIRED with a message naming the id it waited for — Run expired because no deployment with external id 'abc123' became available. This bounds — but does not diagnose — the configuration mistakes that produce a deployment which never lands. See When nothing ever lands.

A shorter run-level ttl that you set yourself still wins — the one-hour deadline is a backstop, not an extension. Note that the run still expires as an external-deployment expiry: the status reason and message name the id it was waiting for, not the ttl.

This deadline applies only to runs waiting on an external deployment id. Runs that wait for the reasons that already exist — such as triggering a task before your first deploy — keep waiting indefinitely, unchanged.

When nothing ever lands

Waiting is the right answer to a race and the wrong answer to a misconfiguration, and for the first hour the two look identical. Three setups produce an id that will never be deployed, and each expires every run from the affected release.

The commit didn’t build any tasks

The most damaging one, and the easiest to create by accident. If your deploy workflow is filtered on paths — paths: ['trigger/**'] in a monorepo is the usual shape — a commit that only touches your application produces no Trigger.dev deployment at all. Your app still sends that commit’s SHA, nothing ever holds it, and every run from that release waits an hour and expires. If you filter deploys by path, derive the id from the same filter on both sides — the SHA of the last commit that touched your task directory, not the commit being deployed:

TASK_ID=$(git log -1 --format=%H -- trigger/)
npx trigger.dev@latest deploy --external-id "$TASK_ID"

Compute the same value where you set your app’s variable. In GitHub Actions this needs fetch-depth: 0 on actions/checkout — the default shallow clone can’t see far enough back.

Two applications, one Trigger.dev project

If two deployables share one Trigger.dev project and only one of them deploys tasks, the other still sends its own commit SHA — an id nothing will ever hold. Give the application that doesn’t build tasks either no id, or the id of the deployment it should run against.

A preview deployment promoted to production

Ids resolve within a single environment. An id deployed to a preview branch does not exist in production, so promoting that preview build in your hosting platform — without a production deploy carrying the same id — parks and expires every production run. Deploy to production the normal way rather than promoting a preview artifact.

A run that hit one of these shows as EXPIRED with Run expired because no deployment with external id '…' became available. An environment producing nothing but that message has a configuration problem, not a timing problem.

Precedence

Several things can pin a run. The SDK sends an explicit version — the version option if you passed one, otherwise TRIGGER_VERSION — and the external deployment id, whenever it has them. The server then prefers the explicit version, then the id, then the current version:

explicit version (version option, else TRIGGER_VERSION)  >  external deployment id  >  current version

An explicit version passed to trigger() always wins. Because the SDK folds the option and the variable into a single value before sending, the version option overrides TRIGGER_VERSION on the client, and the server only ever sees the winner.
An explicit version therefore beats an external deployment id. This is what makes migration from atomic deploys safe: the legacy pin keeps governing until you remove the variable.
An external deployment id sent alongside an explicit version is ignored, not an error.
A trigger carrying neither runs on the current version.

Don’t leave a stale TRIGGER_VERSION behind. A TRIGGER_VERSION naming a version that doesn’t exist in the environment being triggered is not a soft failure and not a fallback — every trigger fails with a 422, wherever the trigger came from. It also suppresses the external deployment id, so skew protection can’t rescue it.The usual way to hit this is setting TRIGGER_VERSION at the project level on your hosting platform: a version built in production doesn’t exist in preview, so every preview trigger fails. Remove the variable once you’ve confirmed skew protection is working.

// Explicit version wins, even if an external deployment id is discovered.
await myTask.trigger({ foo: "bar" }, { version: "20250228.1" });

Automatic skew protection on Vercel

If you use the Vercel integration, version skew protection is set up for you and both halves are automatic:

The integration sets TRIGGER_AUTOMATIC_SKEW_VERSION_PROTECTION=1 on your Vercel project when you connect it, and adds it on the next build if it is missing — so projects connected before this existed pick it up without reconnecting. It only ever adds the variable, never overwrites one that is already there.
The integration passes your commit SHA as the deploy’s external id.
VERCEL_GIT_COMMIT_SHA is available at runtime on Vercel, so the SDK discovers the matching id with no work from you.

This covers production, staging and preview alike.

Opting out

Set TRIGGER_AUTOMATIC_SKEW_VERSION_PROTECTION to 0 on your Vercel project. A 0 you set today stays 0 through every subsequent build. Opting out only disables automatic discovery. You can still pin explicitly at any time by setting TRIGGER_EXTERNAL_DEPLOYMENT_ID yourself.

Replacing automatic atomic deployments

Automatic atomic deployments are deprecated. The setting still exists in your Vercel integration settings, is labelled Deprecated, and keeps working — nothing is being switched off for you. New connections have it off by default. Version skew protection is the supported mechanism.

Atomic deployments solved the same problem by gating your Vercel deployment on the Trigger.dev build, then spawning a second Vercel deployment with TRIGGER_VERSION baked in and promoting it. Version skew protection replaces it and is strictly less invasive:

	Automatic atomic deployments	Version skew protection
Vercel deployments per release	Two — the original, then a redeploy	One
Blocks your Vercel deployment	Yes, until the task build finishes	Never
`Auto-assign Custom Production Domains`	Must be disabled	Untouched
Environments covered	Production only	Production, staging and preview
Configuration	A setting on the production environment	None — the id is the contract
Runs triggered before the build lands	Run on the previous version	Wait, then run on the right version

Migrating

Make sure your app and your deploys are on v4.5.12 or later — the release that introduced external deployment ids. The CLI (trigger.dev) and the SDK (@trigger.dev/sdk) version together, so npx trigger.dev@latest update moves both; see the v4.5.12 release notes.
Confirm skew protection is working — deploy, then check that runs triggered by the new release are pinned to the new version.
Turn Atomic deployments off in your project’s Vercel settings.
Remove the TRIGGER_VERSION variable from your Vercel project. Until you do, it outranks the external deployment id and keeps governing.
Decide who promotes. Under atomic deployments Trigger.dev promoted for you; without it, either re-enable Auto-assign Custom Production Domains in Vercel or promote deliberately from your own pipeline.

Both mechanisms can run at the same time without conflict while the variable still names a live version — TRIGGER_VERSION simply keeps winning — so there is no broken intermediate state and no need to do all of this at once.

Step 4 is not optional, and don’t do it before step 2. While TRIGGER_VERSION names a version that exists in the environment being triggered, it simply keeps winning — safe, and why the two mechanisms coexist. The moment it names a version that environment doesn’t have, every trigger fails outright with a 422, and the external deployment id it suppresses can’t catch it.

If you want your Vercel deployment to stay gated on the Trigger.dev build, atomic deployments remain the way to do that. Version skew protection never blocks a deployment; it makes blocking unnecessary by making runs wait instead.

Deployment overview — versions, current version and version locking
Deploy CLI command — every deploy flag
Vercel integration
Preview branches
Atomic deploys (deprecated for Vercel)

Getting started

Fundamentals

Building with AI

Writing tasks

Agents

Configuration

Deployment

Private networking

Realtime

CLI

Observability

Using the Dashboard

Troubleshooting

Self-hosting

Open source

Help

Version skew protection

The guarantee

Quick start

Deploying with an external id

Reusing an id

Redeploying the same commit

Automatic discovery

Hosting platforms

CI systems

Generic fallbacks

The manual recipe

Example: Netlify

Setting the id in code

Waiting and expiry

When nothing ever lands

The commit didn’t build any tasks

Two applications, one Trigger.dev project

A preview deployment promoted to production

Precedence

Automatic skew protection on Vercel

Opting out

Replacing automatic atomic deployments

Migrating

​The guarantee

​Quick start

​Deploying with an external id

​Reusing an id

​Redeploying the same commit

​Automatic discovery

​Hosting platforms

​CI systems

​Generic fallbacks

​The manual recipe

​Example: Netlify

​Setting the id in code

​Waiting and expiry

​When nothing ever lands

​The commit didn’t build any tasks

​Two applications, one Trigger.dev project

​A preview deployment promoted to production

​Precedence

​Automatic skew protection on Vercel

​Opting out

​Replacing automatic atomic deployments

​Migrating

​Related

The guarantee

Quick start

Deploying with an external id

Reusing an id

Redeploying the same commit

Automatic discovery

Hosting platforms

CI systems

Generic fallbacks

The manual recipe

Example: Netlify

Setting the id in code

Waiting and expiry

When nothing ever lands

The commit didn’t build any tasks

Two applications, one Trigger.dev project

A preview deployment promoted to production

Precedence

Automatic skew protection on Vercel

Opting out

Replacing automatic atomic deployments

Migrating

Related