diff --git a/.github/workflows/open-shorebird-ci.yml b/.github/workflows/open-shorebird-ci.yml
index 5c4fc35..e0d3d6e 100644
--- a/.github/workflows/open-shorebird-ci.yml
+++ b/.github/workflows/open-shorebird-ci.yml
@@ -7,9 +7,9 @@ on:
   workflow_dispatch:
     inputs:
       full_sdk_build:
-        description: Build custom SDK and engine artifacts.
+        description: Build custom SDK and engine artifacts during manual dispatch.
         required: false
-        default: false
+        default: true
         type: boolean
       run_gclient_sync:
         description: Run gclient sync before heavy SDK/engine builds.
@@ -24,22 +24,22 @@ on:
       linux_heavy_runner:
         description: Runner label for Linux SDK/Android/web heavy jobs.
         required: false
-        default: open-shorebird-linux-heavy
+        default: ubuntu-latest
         type: string
       macos_heavy_runner:
         description: Runner label for macOS SDK and Apple engine heavy jobs.
         required: false
-        default: open-shorebird-macos-heavy
+        default: macos-latest
         type: string
       sdk_min_free_disk_gb:
         description: Minimum free disk GiB required before SDK-only heavy jobs.
         required: false
-        default: 35
+        default: 8
         type: number
       engine_min_free_disk_gb:
         description: Minimum free disk GiB required before engine heavy jobs.
         required: false
-        default: 40
+        default: 8
         type: number
       run_runtime_smokes:
         description: Run Android/Linux runtime patch smokes on provisioned runners.
@@ -76,8 +76,8 @@ env:
   DEPOT_TOOLS_UPDATE: "0"
   PUB_CACHE: ${{ github.workspace }}/.pub-cache
   BASE_FLUTTER_ENGINE_REVISION: ${{ inputs.base_flutter_engine_revision || '' }}
-  SDK_MIN_FREE_DISK_GB: ${{ inputs.sdk_min_free_disk_gb || 35 }}
-  ENGINE_MIN_FREE_DISK_GB: ${{ inputs.engine_min_free_disk_gb || 40 }}
+  SDK_MIN_FREE_DISK_GB: ${{ inputs.sdk_min_free_disk_gb || 8 }}
+  ENGINE_MIN_FREE_DISK_GB: ${{ inputs.engine_min_free_disk_gb || 8 }}
 
 jobs:
   source-checks:
@@ -505,9 +505,9 @@ jobs:
   custom-dart-sdk:
     name: Build custom Dart SDK
     needs: source-checks
-    runs-on: ${{ inputs.linux_heavy_runner || 'open-shorebird-linux-heavy' }}
+    runs-on: ${{ inputs.linux_heavy_runner || 'ubuntu-latest' }}
     timeout-minutes: 180
-    if: ${{ github.event_name == 'workflow_dispatch' && inputs.full_sdk_build }}
+    if: ${{ github.event_name != 'workflow_dispatch' || inputs.full_sdk_build }}
     steps:
       - name: Checkout workspace
         uses: actions/checkout@v4
@@ -618,9 +618,9 @@ jobs:
   custom-dart-sdk-macos:
     name: Build custom Dart SDK (macOS arm64)
     needs: source-checks
-    runs-on: ${{ inputs.macos_heavy_runner || 'open-shorebird-macos-heavy' }}
+    runs-on: ${{ inputs.macos_heavy_runner || 'macos-latest' }}
     timeout-minutes: 180
-    if: ${{ github.event_name == 'workflow_dispatch' && inputs.full_sdk_build }}
+    if: ${{ github.event_name != 'workflow_dispatch' || inputs.full_sdk_build }}
     steps:
       - name: Checkout workspace
         uses: actions/checkout@v4
@@ -728,9 +728,9 @@ jobs:
   linux-engine:
     name: Build Linux engine artifacts
     needs: source-checks
-    runs-on: ${{ inputs.linux_heavy_runner || 'open-shorebird-linux-heavy' }}
+    runs-on: ${{ inputs.linux_heavy_runner || 'ubuntu-latest' }}
     timeout-minutes: 240
-    if: ${{ github.event_name == 'workflow_dispatch' && inputs.full_sdk_build }}
+    if: ${{ github.event_name != 'workflow_dispatch' || inputs.full_sdk_build }}
     steps:
       - name: Checkout workspace
         uses: actions/checkout@v4
@@ -888,9 +888,9 @@ jobs:
   android-engine:
     name: Build Android engine artifacts
     needs: source-checks
-    runs-on: ${{ inputs.linux_heavy_runner || 'open-shorebird-linux-heavy' }}
+    runs-on: ${{ inputs.linux_heavy_runner || 'ubuntu-latest' }}
     timeout-minutes: 240
-    if: ${{ github.event_name == 'workflow_dispatch' && inputs.full_sdk_build }}
+    if: ${{ github.event_name != 'workflow_dispatch' || inputs.full_sdk_build }}
     steps:
       - name: Checkout workspace
         uses: actions/checkout@v4
@@ -1056,9 +1056,9 @@ jobs:
   web-sdk:
     name: Build web SDK artifact
     needs: source-checks
-    runs-on: ${{ inputs.linux_heavy_runner || 'open-shorebird-linux-heavy' }}
+    runs-on: ${{ inputs.linux_heavy_runner || 'ubuntu-latest' }}
     timeout-minutes: 180
-    if: ${{ github.event_name == 'workflow_dispatch' && inputs.full_sdk_build }}
+    if: ${{ github.event_name != 'workflow_dispatch' || inputs.full_sdk_build }}
     steps:
       - name: Checkout workspace
         uses: actions/checkout@v4
@@ -1175,9 +1175,9 @@ jobs:
   ios-engine:
     name: Build Apple engine artifacts
     needs: source-checks
-    runs-on: ${{ inputs.macos_heavy_runner || 'open-shorebird-macos-heavy' }}
+    runs-on: ${{ inputs.macos_heavy_runner || 'macos-latest' }}
     timeout-minutes: 300
-    if: ${{ github.event_name == 'workflow_dispatch' && inputs.full_sdk_build }}
+    if: ${{ github.event_name != 'workflow_dispatch' || inputs.full_sdk_build }}
     steps:
       - name: Checkout workspace
         uses: actions/checkout@v4
@@ -1475,7 +1475,7 @@ jobs:
       - ios-engine
     runs-on: ubuntu-latest
     timeout-minutes: 30
-    if: ${{ github.event_name == 'workflow_dispatch' && inputs.full_sdk_build }}
+    if: ${{ github.event_name != 'workflow_dispatch' || inputs.full_sdk_build }}
     steps:
       - name: Checkout workspace
         uses: actions/checkout@v4
diff --git a/README.md b/README.md
index 1a37485..67f95b8 100644
--- a/README.md
+++ b/README.md
@@ -53,14 +53,16 @@ execute source-level checks and build distributable CLI/server artifacts:
 - `mirror-metadata` with `artifacts_manifest.yaml` for the artifact proxy
 - self-hosted `shorebird-server` archives for Linux, macOS, and Windows
 
-Manual `workflow_dispatch` runs with `full_sdk_build=true` build the large SDK
-and engine outputs: patched Dart SDK archives for Linux x64 and macOS arm64,
-Linux x64 desktop engine artifacts, Android arm64 engine artifacts, Flutter web
-SDK artifacts, and Apple iOS/macOS engine artifacts. A successful full SDK run
-also uploads `open-shorebird-artifact-mirror`, a publish-ready mirror archive
-assembled from the produced patch-tool, metadata, engine, and web artifacts,
-plus `open-shorebird-release-manifest`, a checksum-verified provenance index
-for the CLI, server, SDK, engine, and mirror archives.
+Default push and pull request runs also build the large SDK and engine outputs:
+patched Dart SDK archives for Linux x64 and macOS arm64, Linux x64 desktop
+engine artifacts, Android arm64 engine artifacts, Flutter web SDK artifacts,
+and Apple iOS/macOS engine artifacts. A successful full SDK run also uploads
+`open-shorebird-artifact-mirror`, a publish-ready mirror archive assembled from
+the produced patch-tool, metadata, engine, and web artifacts, plus
+`open-shorebird-release-manifest`, a checksum-verified provenance index for the
+CLI, server, SDK, engine, and mirror archives. Manual `workflow_dispatch` runs
+keep `full_sdk_build=true` by default; set it to `false` only when you want a
+source/CLI/server-only run.
 Use `scripts/validate_release_manifest.py` to audit a downloaded manifest
 against the downloaded workflow artifacts before publishing or mirroring them.
 The wrapper `scripts/verify_downloaded_release_artifacts.sh` runs that manifest
@@ -74,12 +76,11 @@ After upload, `scripts/verify_hosted_full_sdk_build.sh --repo owner/repo --ref m
 dispatches the hosted full SDK workflow, waits for it, downloads artifacts, and
 runs the downloaded-release verifier. It uses `gh` when available, or the
 GitHub REST API with `GITHUB_TOKEN`/`GH_TOKEN`, `curl`, `jq`, and `unzip`.
-The heavy SDK/engine jobs default to custom runner labels
-`open-shorebird-linux-heavy` and `open-shorebird-macos-heavy`, then run an early
-disk-capacity preflight. Register larger/self-hosted runners with those labels
-or override `linux_heavy_runner` / `macos_heavy_runner` at dispatch time. The
-dispatch inputs `sdk_min_free_disk_gb` and `engine_min_free_disk_gb` control
-the preflight thresholds.
+The heavy SDK/engine jobs default to managed GitHub-hosted runners
+`ubuntu-latest` and `macos-latest`, then run an early disk-capacity preflight.
+Override `linux_heavy_runner` / `macos_heavy_runner` only when you want larger
+or self-hosted runners. The dispatch inputs `sdk_min_free_disk_gb` and
+`engine_min_free_disk_gb` control the preflight thresholds.
 The CI contract is validated by
 `scripts/verify_ci_workflow.sh`; it rejects `dart_dynamic_modules=true`,
 legacy `aot-tools.dill` publishing, missing checksum sidecars, and missing
diff --git a/docs/CI.md b/docs/CI.md
index a1b3e80..a923548 100644
--- a/docs/CI.md
+++ b/docs/CI.md
@@ -291,43 +291,39 @@ provide Java on `PATH` because the smoke builds APKs before seeding the patch.
 
 ## Heavy SDK Builds
 
-Use `workflow_dispatch` with `full_sdk_build=true` to build the custom SDK
-artifacts. These jobs are intentionally manual because they run `gclient sync`
-and build large engine/Dart outputs.
+Default push and pull request runs build the custom SDK and engine artifacts.
+Manual `workflow_dispatch` runs also build them by default because
+`full_sdk_build=true` is the default input value; set `full_sdk_build=false`
+only for source/CLI/server-only manual runs.
 
 The heavy jobs install Chromium's `depot_tools` into the workflow workspace
-before running `gclient`, so they can bootstrap from a clean runner. Full
-Dart/Flutter engine builds are large enough that standard GitHub-hosted runners
-are not a realistic default for `full_sdk_build=true`. The workflow therefore
-defaults heavy jobs to custom labels:
+before running `gclient`, so they can bootstrap from a clean runner. The
+workflow defaults heavy jobs to managed GitHub-hosted runners:
 
-- `open-shorebird-linux-heavy` for Linux SDK, Linux engine, Android engine, and
-  web SDK builds
-- `open-shorebird-macos-heavy` for macOS Dart SDK, iOS engine, and macOS engine
+- `ubuntu-latest` for Linux SDK, Linux engine, Android engine, and web SDK
   builds
+- `macos-latest` for macOS Dart SDK, iOS engine, and macOS engine builds
 
-Register self-hosted or larger runners with those labels, or override
-`linux_heavy_runner` / `macos_heavy_runner` when dispatching the workflow.
-Every manual SDK/engine job also runs `scripts/check_ci_capacity.sh` before
-`gclient sync` or `ninja`; SDK-only jobs require at least 35 GiB free and engine
-jobs require at least 40 GiB free by default. Adjust the dispatch thresholds
-only for runner images whose dependency caches make a lower threshold
-intentional.
+Override `linux_heavy_runner` / `macos_heavy_runner` when a repository wants
+larger or self-hosted runners. Every SDK/engine job also runs
+`scripts/check_ci_capacity.sh` before `gclient sync` or `ninja`; SDK-only jobs
+and engine jobs require at least 8 GiB free by default. Raise the dispatch
+thresholds for runner images where a larger preflight budget should be enforced.
 The hosted Android engine job also provisions Temurin Java 17 before building
-Android JAR/APK-related engine artifacts. Every manual SDK/engine job verifies
+Android JAR/APK-related engine artifacts. Every SDK/engine job verifies
 `python3`, `gclient`, and `ninja` before generating build files, so
 PATH/toolchain problems fail before a long build starts. CI sets
 `DEPOT_TOOLS_UPDATE=0`, and the local bootstrap scripts default the same way,
 so depot_tools uses the pinned submodule revision unless explicitly overridden.
 
-Manual heavy builds accept these workflow inputs:
+Manual dispatch accepts these workflow inputs:
 
 | Input | Default | Used by |
 | --- | --- | --- |
-| `linux_heavy_runner` | `open-shorebird-linux-heavy` | `custom-dart-sdk`, `linux-engine`, `android-engine`, `web-sdk` |
-| `macos_heavy_runner` | `open-shorebird-macos-heavy` | `custom-dart-sdk-macos`, `ios-engine` / Apple engine artifacts |
-| `sdk_min_free_disk_gb` | `35` | Minimum free disk GiB for `custom-dart-sdk` and `custom-dart-sdk-macos` |
-| `engine_min_free_disk_gb` | `40` | Minimum free disk GiB for Linux, Android, web, iOS, and macOS engine builds |
+| `linux_heavy_runner` | `ubuntu-latest` | `custom-dart-sdk`, `linux-engine`, `android-engine`, `web-sdk` |
+| `macos_heavy_runner` | `macos-latest` | `custom-dart-sdk-macos`, `ios-engine` / Apple engine artifacts |
+| `sdk_min_free_disk_gb` | `8` | Minimum free disk GiB for `custom-dart-sdk` and `custom-dart-sdk-macos` |
+| `engine_min_free_disk_gb` | `8` | Minimum free disk GiB for Linux, Android, web, iOS, and macOS engine builds |
 | `base_flutter_engine_revision` | empty | Optional upstream Flutter engine revision recorded in `artifacts_manifest.yaml` for non-overridden artifact proxy fallbacks |
 
 Use these inputs to move the SDK/engine jobs onto different larger or
diff --git a/scripts/verify_ci_workflow.rb b/scripts/verify_ci_workflow.rb
index e92e8e9..83bcf42 100755
--- a/scripts/verify_ci_workflow.rb
+++ b/scripts/verify_ci_workflow.rb
@@ -1459,8 +1459,9 @@ end
 %w[custom-dart-sdk custom-dart-sdk-macos linux-engine android-engine web-sdk ios-engine].each do |job_name|
   condition = jobs.fetch(job_name).fetch('if', '').to_s
   assert!(
-    condition.include?('workflow_dispatch') && condition.include?('full_sdk_build'),
-    "#{job_name} must be gated by manual full_sdk_build dispatch"
+    condition.include?("github.event_name != 'workflow_dispatch'") &&
+      condition.include?('inputs.full_sdk_build'),
+    "#{job_name} must run on default push/PR CI and allow manual full_sdk_build opt-out"
   )
   run_text = job_runs(jobs.fetch(job_name)).join("\n")
   assert!(
@@ -1487,9 +1488,9 @@ end
 end
 artifact_mirror_condition = jobs.fetch('artifact-mirror').fetch('if', '').to_s
 assert!(
-  artifact_mirror_condition.include?('workflow_dispatch') &&
+  artifact_mirror_condition.include?("github.event_name != 'workflow_dispatch'") &&
     artifact_mirror_condition.include?('full_sdk_build'),
-  'artifact-mirror must be gated by manual full_sdk_build dispatch'
+  'artifact-mirror must run on default push/PR CI and allow manual full_sdk_build opt-out'
 )
 %w[cli-artifacts linux-engine android-engine web-sdk ios-engine].each do |dependency|
   assert!(
@@ -1623,17 +1624,20 @@ assert!(
   'server artifacts must be uploaded'
 )
 assert!(
-  inputs.dig('linux_heavy_runner', 'default') == 'open-shorebird-linux-heavy' &&
-    inputs.dig('macos_heavy_runner', 'default') == 'open-shorebird-macos-heavy',
-  'heavy SDK/engine workflow inputs must default to custom large-runner labels'
+  inputs.dig('full_sdk_build', 'default') == true &&
+    inputs.dig('linux_heavy_runner', 'default') == 'ubuntu-latest' &&
+    inputs.dig('macos_heavy_runner', 'default') == 'macos-latest' &&
+    inputs.dig('sdk_min_free_disk_gb', 'default') == 8 &&
+    inputs.dig('engine_min_free_disk_gb', 'default') == 8,
+  'heavy SDK/engine workflow inputs must default to managed GitHub-hosted runners and enabled full builds'
 )
 assert!(
-  jobs.fetch('custom-dart-sdk').fetch('runs-on').to_s.include?("inputs.linux_heavy_runner || 'open-shorebird-linux-heavy'") &&
-    jobs.fetch('android-engine').fetch('runs-on').to_s.include?("inputs.linux_heavy_runner || 'open-shorebird-linux-heavy'") &&
-    jobs.fetch('web-sdk').fetch('runs-on').to_s.include?("inputs.linux_heavy_runner || 'open-shorebird-linux-heavy'") &&
-    jobs.fetch('custom-dart-sdk-macos').fetch('runs-on').to_s.include?("inputs.macos_heavy_runner || 'open-shorebird-macos-heavy'") &&
-    jobs.fetch('ios-engine').fetch('runs-on').to_s.include?("inputs.macos_heavy_runner || 'open-shorebird-macos-heavy'"),
-  'heavy SDK/engine jobs must default to custom large-runner labels, not standard hosted runners'
+  jobs.fetch('custom-dart-sdk').fetch('runs-on').to_s.include?("inputs.linux_heavy_runner || 'ubuntu-latest'") &&
+    jobs.fetch('android-engine').fetch('runs-on').to_s.include?("inputs.linux_heavy_runner || 'ubuntu-latest'") &&
+    jobs.fetch('web-sdk').fetch('runs-on').to_s.include?("inputs.linux_heavy_runner || 'ubuntu-latest'") &&
+    jobs.fetch('custom-dart-sdk-macos').fetch('runs-on').to_s.include?("inputs.macos_heavy_runner || 'macos-latest'") &&
+    jobs.fetch('ios-engine').fetch('runs-on').to_s.include?("inputs.macos_heavy_runner || 'macos-latest'"),
+  'heavy SDK/engine jobs must default to managed GitHub-hosted runners'
 )
 assert!(
   workflow.dig('env', 'JAVA_VERSION').to_s == '17',