docs: Vercel integration – marketplace link, Build options, Root Directory warning (#3097)

Adds a direct Vercel Marketplace link, documents configuring build
options via the project config page, and adds a warning and workaround
for projects using a Vercel Root Directory

Author: isshaddad

docs/vercel-integration.mdx

@@ -10,7 +10,8 @@ The Vercel integration connects your Vercel project to your Trigger.dev project
 This eliminates the need to manually run the `trigger.dev deploy` command or maintain custom CI/CD workflows for Vercel-based projects.
 
 <Note>
-  The Vercel integration requires the [GitHub integration](/github-integration) to be connected as well, since Trigger.dev builds your tasks from your GitHub repository.
+  The Vercel integration requires the [GitHub integration](/github-integration) to be connected as
+  well, since Trigger.dev builds your tasks from your GitHub repository.
 </Note>
 
 ## Installation
@@ -22,23 +23,27 @@ You can connect Vercel from two entry points:
 <Steps>
 
 <Step title="Connect Vercel">
-  Go to your project's **Settings** page and click **Connect Vercel**. This will redirect you to Vercel to authorize the Trigger.dev app.
+  Go to your project's **Settings** page and click **Connect Vercel**. This will redirect you to
+  Vercel to authorize the Trigger.dev app.
 </Step>
 
 <Step title="Select a Vercel project">
   Choose which Vercel project to connect to your Trigger.dev project.
 </Step>
 
 <Step title="Map environments">
-  If your Vercel project has custom environments, choose which one maps to your Trigger.dev staging environment.
+  If your Vercel project has custom environments, choose which one maps to your Trigger.dev staging
+  environment.
 </Step>
 
 <Step title="Sync environment variables">
-  Review the environment variables that will be pulled from Vercel into Trigger.dev. You can deselect any variables you don't want to sync.
+  Review the environment variables that will be pulled from Vercel into Trigger.dev. You can
+  deselect any variables you don't want to sync.
 </Step>
 
-<Step title="Configure build settings">
-  Optionally adjust [build settings](#build-settings) for atomic deployments, env var pulling, and new env var discovery.
+<Step title="Configure build options">
+  Optionally adjust [build options](#build-options) for atomic deployments, env var pulling, and new
+  env var discovery.
 </Step>
 
 <Step title="Connect GitHub">
@@ -52,11 +57,14 @@ You can connect Vercel from two entry points:
 <Steps>
 
 <Step title="Install the integration">
-  Find Trigger.dev on the Vercel Marketplace and install it. This will redirect you to Trigger.dev to complete setup.
+  Install the [Trigger.dev integration from the Vercel
+  Marketplace](https://vercel.com/marketplace/trigger). This will redirect you to Trigger.dev to
+  complete setup.
 </Step>
 
 <Step title="Select your Trigger.dev organization and project">
-  Choose which Trigger.dev organization and project to connect. If you're new to Trigger.dev, you'll be guided through creating an organization and project.
+  Choose which Trigger.dev organization and project to connect. If you're new to Trigger.dev, you'll
+  be guided through creating an organization and project.
 </Step>
 
 <Step title="Connect GitHub">
@@ -66,9 +74,21 @@ You can connect Vercel from two entry points:
 </Steps>
 
 <Note>
-  When installing from the Vercel Marketplace, default build settings are applied automatically. You can adjust them later in your project settings.
+  When installing from the Vercel Marketplace, default Build options are applied automatically. You
+  can adjust them later in your project settings.
 </Note>
 
+<Warning>
+  **Vercel Root Directory:** If your Vercel project uses a **Root Directory** (e.g. you deploy a
+  single subfolder such as `app` or `web`), you may see "The specified Root Directory does not
+  exist" after connecting the integration. If you see this error, try using the **repository root**
+  (leave Root Directory empty) in your Vercel project settings. If your Vercel frontend build
+  requires a Root Directory (e.g. in a monorepo), keep that setting in Vercel and instead point
+  Trigger.dev to the subfolder by setting the **Trigger config file** path (and other [Build
+  options](#build-options)) in your Trigger.dev project configuration. Trigger.dev always builds
+  from the repo root.
+</Warning>
+
 ## Environment variable sync
 
 The integration syncs environment variables in both directions:
@@ -78,13 +98,15 @@ The integration syncs environment variables in both directions:
 **Trigger.dev → Vercel**: Trigger.dev syncs API keys (like `TRIGGER_SECRET_KEY`) to your Vercel project so your app can communicate with Trigger.dev.
 
 The following variables are excluded from the Vercel → Trigger.dev sync:
+
 - `TRIGGER_SECRET_KEY`, `TRIGGER_VERSION`, `TRIGGER_PREVIEW_BRANCH` (managed by Trigger.dev)
 - Sensitive/secret-type variables (Vercel API limitation)
 
 You can control sync behavior per-variable from your project's Vercel settings. Deselecting a variable prevents its value from being updated during future syncs.
 
 <Tip>
-  For dynamic environment variables (e.g., from NeonDB branching), use the `syncEnvVars` build extension instead. Learn more about [environment variables](/deploy-environment-variables).
+  For dynamic environment variables (e.g., from NeonDB branching), use the `syncEnvVars` build
+  extension instead. Learn more about [environment variables](/deploy-environment-variables).
 </Tip>
 
 ## Atomic deployments
@@ -94,7 +116,9 @@ Atomic deployments ensure your Vercel app and Trigger.dev tasks are deployed in
 Atomic deployments are enabled for the production environment by default.
 
 <Note>
-  When atomic deployments are enabled, the integration automatically disables `Auto-assign Custom Production Domains` on your Vercel project. This is required so that Vercel doesn't promote a deployment before the Trigger.dev build is ready.
+  When atomic deployments are enabled, the integration automatically disables `Auto-assign Custom
+  Production Domains` on your Vercel project. This is required so that Vercel doesn't promote a
+  deployment before the Trigger.dev build is ready.
 </Note>
 
 Previously, setting up atomic deployments with Vercel required custom GitHub Actions workflows. The Vercel integration automates this entirely. For more details on how atomic deployments work, see [Atomic deploys](/deployment/atomic-deployment).
@@ -103,27 +127,30 @@ Previously, setting up atomic deployments with Vercel required custom GitHub Act
 
 The integration maps Vercel environments to Trigger.dev environments:
 
-| Vercel environment | Trigger.dev environment |
-| --- | --- |
-| Production | Production |
+| Vercel environment | Trigger.dev environment        |
+| ------------------ | ------------------------------ |
+| Production         | Production                     |
 | Custom environment | Staging (you choose which one) |
-| Preview | Preview |
-| Development | Development |
+| Preview            | Preview                        |
+| Development        | Development                    |
 
 If your Vercel project has a custom environment, you can select which one maps to your Trigger.dev staging environment during setup or in your project settings.
 
 <Note>
-  Preview deployments require the preview environment to be enabled on your project. Learn more about [preview branches](/deployment/preview-branches).
+  Preview deployments require the preview environment to be enabled on your project. Learn more
+  about [preview branches](/deployment/preview-branches).
 </Note>
 
-## Build settings
+## Build options
 
 You can configure the following settings per-environment from your project's Vercel settings:
 
 - **Atomic deployments**: Controls whether Trigger.dev and Vercel deployments are synchronized. Enabled for production by default.
 - **Pull env vars before build**: When enabled, Trigger.dev pulls the latest environment variables from Vercel before each build. Enabled for production, staging, and preview by default.
 - **Discover new env vars**: When enabled, new environment variables found in Vercel that don't yet exist in Trigger.dev are created automatically during builds. Only available for environments that also have env var pulling enabled. Enabled for production, staging, and preview by default.
 
+To change build options that would normally go in `trigger.config.ts` (such as [extensions](/config/config-file#extensions) or other build configuration), use **Build options** on your project's configuration page in the Trigger.dev dashboard.
+
 ## Disconnecting
 
 You can disconnect the Vercel integration from either side: