diff --git a/.github/workflows/platform_quality.yaml b/.github/workflows/platform_quality.yaml
new file mode 100644
index 000000000..97cff3d33
--- /dev/null
+++ b/.github/workflows/platform_quality.yaml
@@ -0,0 +1,23 @@
+name: Platform SDK quality gate (C#)
+
+on:
+  pull_request:
+    paths:
+      - platform/**
+      - .github/workflows/platform_quality.yaml
+      - .github/workflows/sdk_quality.yaml
+  workflow_dispatch:
+
+permissions:
+  contents: read
+
+concurrency:
+  group: platform-quality-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  quality:
+    uses: ./.github/workflows/sdk_quality.yaml
+    with:
+      target: platform
+      artifact_name: platform-quality
diff --git a/.github/workflows/sdk_quality.yaml b/.github/workflows/sdk_quality.yaml
new file mode 100644
index 000000000..910dc9da0
--- /dev/null
+++ b/.github/workflows/sdk_quality.yaml
@@ -0,0 +1,39 @@
+name: SDK quality (reusable)
+
+on:
+  workflow_call:
+    inputs:
+      target:
+        description: SDK target directory (e.g. platform)
+        required: true
+        type: string
+      artifact_name:
+        description: Name for the uploaded results artifact
+        required: true
+        type: string
+
+permissions:
+  contents: read
+
+jobs:
+  sdk-quality:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4
+
+      - uses: actions/setup-dotnet@67a3573c9a986a3f9c594539f4ab511d57bb3ce9 # v4
+        with:
+          dotnet-version: 8.0.x
+
+      - name: Check (build + test)
+        run: pwsh ./check.ps1 -Target ${{ inputs.target }}
+
+      - name: Publish results
+        if: always()
+        uses: actions/upload-artifact@ea165f8d65b6e75b540449e92b4886f43607fa02 # v4
+        with:
+          name: ${{ inputs.artifact_name }}
+          path: |
+            **/*.received.txt
+            **/test-results/**
+          if-no-files-found: ignore
diff --git a/.gitignore b/.gitignore
index ccd534821..5b6056421 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,2 +1,5 @@
 # Ignore Speakeasy regen change logs
 .speakeasy/logs/changes/
+
+# Local test run output (uploaded as a CI artifact, never committed)
+**/test-results/
diff --git a/check.ps1 b/check.ps1
new file mode 100644
index 000000000..4c4219608
--- /dev/null
+++ b/check.ps1
@@ -0,0 +1,44 @@
+#requires -Version 7
+[CmdletBinding()]
+param(
+    [string]$Target = ''
+)
+
+$ErrorActionPreference = 'Stop'
+$repoRoot = $PSScriptRoot
+
+$testProjects = Get-ChildItem -Path $repoRoot -Recurse -Filter '*.csproj' |
+    Where-Object { $_.FullName -match '[\\/]tests[\\/]' }
+
+if ($Target) {
+    $prefix = (Join-Path $repoRoot $Target)
+    $testProjects = $testProjects | Where-Object { $_.FullName.StartsWith($prefix, [System.StringComparison]::OrdinalIgnoreCase) }
+}
+
+if (-not $testProjects) {
+    Write-Error "No test projects found$(if ($Target) { " for target '$Target'" })."
+    exit 1
+}
+
+$failed = @()
+
+foreach ($proj in $testProjects) {
+    Write-Host "==> $($proj.FullName)" -ForegroundColor Cyan
+
+    dotnet build $proj.FullName -c Release --nologo
+    if ($LASTEXITCODE -ne 0) { $failed += "build: $($proj.Name)"; continue }
+
+    $env:DiffEngine_Disabled = 'true'
+    $env:CI = 'true'
+    dotnet test $proj.FullName -c Release --no-build `
+        --logger 'trx;LogFileName=results.trx' `
+        --results-directory (Join-Path $proj.Directory.FullName 'test-results')
+    if ($LASTEXITCODE -ne 0) { $failed += "test: $($proj.Name)" }
+}
+
+if ($failed) {
+    Write-Host "FAILED: $($failed -join ', ')" -ForegroundColor Red
+    exit 1
+}
+
+Write-Host 'OK' -ForegroundColor Green