diff --git a/.github/workflows/migrate.yml b/.github/workflows/migrate.yml
index ff2be697a12..4975ca60334 100644
--- a/.github/workflows/migrate.yml
+++ b/.github/workflows/migrate.yml
@@ -48,6 +48,31 @@ jobs:
       cancel-in-progress: false
 
     steps:
+      # An environment only migrates from its own branch, so a manual dispatch
+      # from a feature branch cannot apply that branch's migrations to a shared
+      # database. Under workflow_call github.ref is the caller's ref (ci.yml's
+      # push to main/staging/dev). This fails rather than skips: ci.yml's
+      # promote gates on migrate succeeding, and a skipped run must never read
+      # as a migration that happened. It runs before any secret is read.
+      - name: Require the environment's own branch
+        env:
+          ENVIRONMENT: ${{ inputs.environment }}
+          REF: ${{ github.ref }}
+        run: |
+          case "${ENVIRONMENT}" in
+            production) expected=refs/heads/main ;;
+            staging) expected=refs/heads/staging ;;
+            dev) expected=refs/heads/dev ;;
+            *)
+              echo "::error::Unknown migrate environment '${ENVIRONMENT}'"
+              exit 1
+              ;;
+          esac
+          if [ "${REF}" != "${expected}" ]; then
+            echo "::error::Refusing to migrate ${ENVIRONMENT} from ${REF}; ${ENVIRONMENT} migrates only from ${expected}"
+            exit 1
+          fi
+
       - name: Checkout code
         uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v6
         with:
diff --git a/scripts/migrations-workflow.test.ts b/scripts/migrations-workflow.test.ts
index ce25ddd7058..d3e1494e37c 100644
--- a/scripts/migrations-workflow.test.ts
+++ b/scripts/migrations-workflow.test.ts
@@ -3,7 +3,9 @@ import { readFileSync } from 'node:fs'
 import { describe, expect, it } from 'vitest'
 
 const workflow = readFileSync(new URL('../.github/workflows/migrate.yml', import.meta.url), 'utf8')
-const step = workflow.match(/^ {8}run: \|\r?\n((?: {10}.*(?:\r?\n|$)|\r?\n)+)/m)?.[1]
+const step = workflow.match(
+  /^ {6}- name: Apply database schema changes\r?\n(?: {8}.*\r?\n)*? {8}run: \|\r?\n((?: {10}.*(?:\r?\n|$)|\r?\n)+)/m
+)?.[1]
 if (!step) throw new Error('Migration workflow must contain its schema application shell step')
 const script = step.replace(/^ {10}/gm, '')