diff --git a/.github/workflows/cd-deploy-nodes-gcp.patch-external.yml b/.github/workflows/cd-deploy-nodes-gcp.patch-external.yml
new file mode 100644
index 00000000000..b990f9b915e
--- /dev/null
+++ b/.github/workflows/cd-deploy-nodes-gcp.patch-external.yml
@@ -0,0 +1,37 @@
+# Workflow patches for skipping Google Cloud CD deployments on PRs from external repositories.
+name: Deploy Nodes to GCP
+
+# Run on PRs from external repositories, let them pass, and then Mergify will check them.
+# GitHub doesn't support filtering workflows by source branch names, so we have to do it for each
+# job.
+on:
+  pull_request:
+
+# IMPORTANT
+#
+# These job names must be kept in sync with the `.patch.yml` and `.yml` files.
+jobs:
+  # We don't patch the testnet job, because testnet isn't required to merge (it's too unstable)
+  build:
+    name: Build CD Docker / Build images
+    # Only run on PRs from external repositories, skipping ZF branches and tags.
+    if: ${{ !contains(github.head_ref || github.ref, 'refs/heads/') && !contains(github.head_ref || github.ref, 'refs/tags/') }}
+    runs-on: ubuntu-latest
+    steps:
+      - run: 'echo "No build required"'
+
+  test-configuration-file:
+    name: Test CD default Docker config file / Test default-conf in Docker
+    # This dependency allows all these jobs to depend on a single condition, making it easier to
+    # change.
+    needs: build
+    runs-on: ubuntu-latest
+    steps:
+      - run: 'echo "No build required"'
+
+  test-zebra-conf-path:
+    name: Test CD custom Docker config file / Test custom-conf in Docker
+    needs: build
+    runs-on: ubuntu-latest
+    steps:
+      - run: 'echo "No build required"'
diff --git a/.github/workflows/cd-deploy-nodes-gcp.patch.yml b/.github/workflows/cd-deploy-nodes-gcp.patch.yml
index 457bedc2a3b..ed4c6afbc85 100644
--- a/.github/workflows/cd-deploy-nodes-gcp.patch.yml
+++ b/.github/workflows/cd-deploy-nodes-gcp.patch.yml
@@ -1,5 +1,8 @@
+# Workflow patches for skipping Google Cloud CD deployments, when Rust code or dependencies aren't
+# modified in a PR.
 name: Deploy Nodes to GCP
 
+# Run on PRs with unmodified code and dependency files.
 on:
   pull_request:
    paths-ignore:
@@ -19,7 +22,11 @@ on:
      - '.github/workflows/cd-deploy-nodes-gcp.yml'
      - '.github/workflows/sub-build-docker-image.yml'
 
+# IMPORTANT
+#
+# These job names must be kept in sync with the `.patch-external.yml` and `.yml` files.
 jobs:
+  # We don't patch the testnet job, because testnet isn't required to merge (it's too unstable)
   build:
     name: Build CD Docker / Build images
     runs-on: ubuntu-latest
@@ -36,4 +43,4 @@ jobs:
     name: Test CD custom Docker config file / Test custom-conf in Docker
     runs-on: ubuntu-latest
     steps:
-      - run: 'echo "No build required"'
\ No newline at end of file
+      - run: 'echo "No build required"'
diff --git a/.github/workflows/cd-deploy-nodes-gcp.yml b/.github/workflows/cd-deploy-nodes-gcp.yml
index 9cf6a274728..a6be4cbb4c4 100644
--- a/.github/workflows/cd-deploy-nodes-gcp.yml
+++ b/.github/workflows/cd-deploy-nodes-gcp.yml
@@ -1,3 +1,6 @@
+# Google Cloud node deployments and tests that run when Rust code or dependencies are modified,
+# but only on PRs from the ZcashFoundation/zebra repository.
+# (External PRs are tested/deployed by mergify.)
 name: Deploy Nodes to GCP
 
 # Ensures that only one workflow task will run at a time. Previous deployments, if
@@ -31,6 +34,7 @@ on:
 
   # TODO: Temporarily disabled to reduce network load, see #6894.
   #push:
+  #  # Skip main branch updates where Rust code and dependencies aren't modified.
   #  branches:
   #    - main
   #  paths:
@@ -52,6 +56,7 @@ on:
 
   # Only runs the Docker image tests, doesn't deploy any instances
   pull_request:
+    # Skip PRs where Rust code and dependencies aren't modified.
     paths:
       # code and tests
       - '**/*.rs'
@@ -73,6 +78,9 @@ on:
     types:
       - published
 
+# IMPORTANT
+#
+# These job names must be kept in sync with the `.patch.yml` and `.patch-external.yml` files.
 jobs:
   # If a release was made we want to extract the first part of the semver from the
   # tag_name
@@ -107,6 +115,9 @@ jobs:
   # The image will be commonly named `zebrad:<short-hash | github-ref | semver>`
   build:
     name: Build CD Docker
+    # Skip PRs from external repositories, let them pass, and then Mergify will check them.
+    # Since this workflow also runs on release tags, we need to check for them as well.
+    if: ${{ contains(github.head_ref || github.ref, 'refs/heads/') || contains(github.head_ref || github.ref, 'refs/tags/') }}
     uses: ./.github/workflows/sub-build-docker-image.yml
     with:
       dockerfile_path: ./docker/Dockerfile
diff --git a/.github/workflows/ci-integration-tests-gcp.patch-external.yml b/.github/workflows/ci-integration-tests-gcp.patch-external.yml
new file mode 100644
index 00000000000..5f95c4f6d41
--- /dev/null
+++ b/.github/workflows/ci-integration-tests-gcp.patch-external.yml
@@ -0,0 +1,101 @@
+# Workflow patches for skipping Google Cloud unit test CI on PRs from external repositories.
+name: Integration Tests on GCP
+
+# Run on PRs from external repositories, let them pass, and then Mergify will check them.
+# GitHub doesn't support filtering workflows by source branch names, so we have to do it for each
+# job.
+on:
+  pull_request:
+
+# IMPORTANT
+#
+# These job names must be kept in sync with the `.patch.yml` and `.yml` files.
+jobs:
+  # We don't patch the testnet job, because testnet isn't required to merge (it's too unstable)
+  get-available-disks:
+    name: Check if cached state disks exist for Mainnet / Check if cached state disks exist
+    # Only run on PRs from external repositories.
+    # (github.ref is always a local branch, so this check will skip non-PRs as well.)
+    if: ${{ !contains(github.head_ref || github.ref, 'refs/heads/') }}
+    runs-on: ubuntu-latest
+    steps:
+      - run: 'echo "No build required"'
+
+  build:
+    name: Build CI Docker / Build images
+    # This dependency allows all these jobs to depend on a single condition, making it easier to
+    # change.
+    needs: get-available-disks
+    runs-on: ubuntu-latest
+    steps:
+      - run: 'echo "No build required"'
+
+  test-stateful-sync:
+    name: Zebra checkpoint update / Run sync-past-checkpoint test
+    needs: get-available-disks
+    runs-on: ubuntu-latest
+    steps:
+      - run: 'echo "No build required"'
+
+  test-update-sync:
+    name: Zebra tip update / Run update-to-tip test
+    needs: get-available-disks
+    runs-on: ubuntu-latest
+    steps:
+      - run: 'echo "No build required"'
+
+  checkpoints-mainnet:
+    name: Generate checkpoints mainnet / Run checkpoints-mainnet test
+    needs: get-available-disks
+    runs-on: ubuntu-latest
+    steps:
+      - run: 'echo "No build required"'
+
+  lightwalletd-rpc-test:
+    name: Zebra tip JSON-RPC / Run fully-synced-rpc test
+    needs: get-available-disks
+    runs-on: ubuntu-latest
+    steps:
+      - run: 'echo "No build required"'
+
+  lightwalletd-transactions-test:
+    name: lightwalletd tip send / Run lwd-send-transactions test
+    needs: get-available-disks
+    runs-on: ubuntu-latest
+    steps:
+      - run: 'echo "No build required"'
+
+  get-block-template-test:
+    name: get block template / Run get-block-template test
+    needs: get-available-disks
+    runs-on: ubuntu-latest
+    steps:
+      - run: 'echo "No build required"'
+
+  submit-block-test:
+    name: submit block / Run submit-block test
+    needs: get-available-disks
+    runs-on: ubuntu-latest
+    steps:
+      - run: 'echo "No build required"'
+
+  lightwalletd-full-sync:
+    name: lightwalletd tip / Run lwd-full-sync test
+    needs: get-available-disks
+    runs-on: ubuntu-latest
+    steps:
+      - run: 'echo "No build required"'
+
+  lightwalletd-update-sync:
+    name: lightwalletd tip update / Run lwd-update-sync test
+    needs: get-available-disks
+    runs-on: ubuntu-latest
+    steps:
+      - run: 'echo "No build required"'
+
+  lightwalletd-grpc-test:
+    name: lightwalletd GRPC tests / Run lwd-grpc-wallet test
+    needs: get-available-disks
+    runs-on: ubuntu-latest
+    steps:
+      - run: 'echo "No build required"'
diff --git a/.github/workflows/ci-integration-tests-gcp.patch.yml b/.github/workflows/ci-integration-tests-gcp.patch.yml
index f671429b5bf..faef2491dde 100644
--- a/.github/workflows/ci-integration-tests-gcp.patch.yml
+++ b/.github/workflows/ci-integration-tests-gcp.patch.yml
@@ -1,7 +1,8 @@
+# Workflow patches for skipping Google Cloud integration test CI when Rust code or dependencies
+# aren't modified in a PR.
 name: Integration Tests on GCP
 
-# These jobs *don't* depend on cached Google Cloud state disks,
-# so they can be skipped when the modified files make the actual workflow run.
+# Run on PRs with unmodified code and dependency files.
 on:
   pull_request:
     paths-ignore:
@@ -25,6 +26,9 @@ on:
       - '.github/workflows/sub-find-cached-disks.yml'
       - '.github/workflows/sub-build-docker-image.yml'
 
+# IMPORTANT
+#
+# These job names must be kept in sync with the `.patch-external.yml` and `.yml` files.
 jobs:
   # We don't patch the testnet job, because testnet isn't required to merge (it's too unstable)
   get-available-disks:
diff --git a/.github/workflows/ci-integration-tests-gcp.yml b/.github/workflows/ci-integration-tests-gcp.yml
index 1132762c210..32556265bb5 100644
--- a/.github/workflows/ci-integration-tests-gcp.yml
+++ b/.github/workflows/ci-integration-tests-gcp.yml
@@ -1,3 +1,5 @@
+# Google Cloud integration tests that run when Rust code or dependencies are modified,
+# but only on PRs from the ZcashFoundation/zebra repository. (External PRs are tested by mergify.)
 name: Integration Tests on GCP
 
 # Ensures that only one workflow task will run at a time. Previous builds, if
@@ -47,6 +49,7 @@ on:
         default: false
 
   pull_request:
+    # Skip PRs where Rust code and dependencies aren't modified.
     paths:
       # code and tests
       - '**/*.rs'
@@ -68,6 +71,7 @@ on:
       - '.github/workflows/sub-find-cached-disks.yml'
 
   push:
+    # Skip main branch updates where Rust code and dependencies aren't modified.
     branches:
       - main
     paths:
@@ -91,6 +95,9 @@ on:
       - '.github/workflows/sub-find-cached-disks.yml'
       - '.github/workflows/sub-build-docker-image.yml'
 
+# IMPORTANT
+#
+# These job names must be kept in sync with the `.patch.yml` and `.patch-external.yml` files.
 jobs:
   # to also run a job on Mergify head branches,
   # add `|| (github.event_name == 'push' && startsWith(github.head_ref, 'mergify/merge-queue/'))`:
@@ -104,6 +111,8 @@ jobs:
   # The outputs for this job have the same names as the workflow outputs in sub-find-cached-disks.yml
   get-available-disks:
     name: Check if cached state disks exist for ${{ inputs.network || vars.ZCASH_NETWORK }}
+    # Skip PRs from external repositories, let them pass, and then Mergify will check them
+    if: ${{ contains(github.head_ref || github.ref, 'refs/heads/') }}
     uses: ./.github/workflows/sub-find-cached-disks.yml
     with:
       network: ${{ inputs.network || vars.ZCASH_NETWORK }}
@@ -114,6 +123,7 @@ jobs:
   # Some outputs are ignored, because we don't run those jobs on testnet.
   get-available-disks-testnet:
     name: Check if cached state disks exist for testnet
+    if: ${{ contains(github.head_ref || github.ref, 'refs/heads/') }}
     uses: ./.github/workflows/sub-find-cached-disks.yml
     with:
       network: 'Testnet'
@@ -125,6 +135,7 @@ jobs:
   # testnet when running the image.
   build:
     name: Build CI Docker
+    if: ${{ contains(github.head_ref || github.ref, 'refs/heads/') }}
     uses: ./.github/workflows/sub-build-docker-image.yml
     with:
       dockerfile_path: ./docker/Dockerfile
diff --git a/.github/workflows/ci-lint.yml b/.github/workflows/ci-lint.yml
index 12add6d2951..19eac034727 100644
--- a/.github/workflows/ci-lint.yml
+++ b/.github/workflows/ci-lint.yml
@@ -148,7 +148,11 @@ jobs:
         with:
           level: warning
           fail_on_error: false
+      # This gives an error when run on PRs from external repositories, so we skip it.
       - name: validate-dependabot
+        # If this is a PR, check that the PR source is from a local branch.
+        # (github.ref is always a local branch, so this check always passes for non-PRs.)
+        if: ${{ contains(github.head_ref || github.ref, 'refs/heads/') }}
         uses: marocchino/validate-dependabot@v2.1.0
 
   codespell:
diff --git a/.github/workflows/ci-unit-tests-docker.patch-external.yml b/.github/workflows/ci-unit-tests-docker.patch-external.yml
new file mode 100644
index 00000000000..759a484da2d
--- /dev/null
+++ b/.github/workflows/ci-unit-tests-docker.patch-external.yml
@@ -0,0 +1,65 @@
+# Workflow patches for skipping Google Cloud unit test CI on PRs from external repositories.
+name: Docker Unit Tests
+
+# Run on PRs from external repositories, let them pass, and then Mergify will check them.
+# GitHub doesn't support filtering workflows by source branch names, so we have to do it for each
+# job.
+on:
+  pull_request:
+
+# IMPORTANT
+#
+# These job names must be kept in sync with the `.patch.yml` and `.yml` files.
+jobs:
+  build:
+    name: Build CI Docker / Build images
+    # Only run on PRs from external repositories.
+    # (github.ref is always a local branch, so this check will skip non-PRs as well.)
+    if: ${{ !contains(github.head_ref || github.ref, 'refs/heads/') }}
+    runs-on: ubuntu-latest
+    steps:
+      - run: 'echo "No build required"'
+
+  test-all:
+    name: Test all
+    # This dependency allows all these jobs to depend on a single condition, making it easier to
+    # change.
+    needs: build
+    runs-on: ubuntu-latest
+    steps:
+      - run: 'echo "No build required"'
+
+  test-fake-activation-heights:
+    name: Test with fake activation heights
+    needs: build
+    runs-on: ubuntu-latest
+    steps:
+      - run: 'echo "No build required"'
+
+  test-empty-sync:
+    name: Test checkpoint sync from empty state
+    needs: build
+    runs-on: ubuntu-latest
+    steps:
+      - run: 'echo "No build required"'
+
+  test-lightwalletd-integration:
+    name: Test integration with lightwalletd
+    needs: build
+    runs-on: ubuntu-latest
+    steps:
+      - run: 'echo "No build required"'
+
+  test-configuration-file:
+    name: Test CI default Docker config file / Test default-conf in Docker
+    needs: build
+    runs-on: ubuntu-latest
+    steps:
+      - run: 'echo "No build required"'
+
+  test-zebra-conf-path:
+    name: Test CI custom Docker config file / Test custom-conf in Docker
+    needs: build
+    runs-on: ubuntu-latest
+    steps:
+      - run: 'echo "No build required"'
diff --git a/.github/workflows/ci-unit-tests-docker.patch.yml b/.github/workflows/ci-unit-tests-docker.patch.yml
index c9c69768f54..a485f3155a1 100644
--- a/.github/workflows/ci-unit-tests-docker.patch.yml
+++ b/.github/workflows/ci-unit-tests-docker.patch.yml
@@ -1,7 +1,7 @@
+# Workflow patches for skipping unit test CI when Rust code or dependencies aren't modified in a PR.
 name: Docker Unit Tests
 
-# These jobs *don't* depend on cached Google Cloud state disks,
-# so they can be skipped when the modified files make the actual workflow run.
+# Run on PRs with unmodified code and dependency files.
 on:
   pull_request:
     paths-ignore:
@@ -25,6 +25,9 @@ on:
       - '.github/workflows/sub-find-cached-disks.yml'
       - '.github/workflows/sub-build-docker-image.yml'
 
+# IMPORTANT
+#
+# These job names must be kept in sync with the `.patch-external.yml` and `.yml` files.
 jobs:
   build:
     name: Build CI Docker / Build images
diff --git a/.github/workflows/ci-unit-tests-docker.yml b/.github/workflows/ci-unit-tests-docker.yml
index 73834aa649f..309f05868d0 100644
--- a/.github/workflows/ci-unit-tests-docker.yml
+++ b/.github/workflows/ci-unit-tests-docker.yml
@@ -1,3 +1,5 @@
+# Google Cloud unit tests that run when Rust code or dependencies are modified,
+# but only on PRs from the ZcashFoundation/zebra repository. (External PRs are tested by mergify.)
 name: Docker Unit Tests
 
 # Ensures that only one workflow task will run at a time. Previous builds, if
@@ -21,6 +23,7 @@ on:
         default: false
 
   pull_request:
+    # Skip PRs where Rust code and dependencies aren't modified.
     paths:
       # code and tests
       - '**/*.rs'
@@ -44,6 +47,7 @@ on:
   push:
     branches:
       - main
+    # Skip main branch updates where Rust code and dependencies aren't modified.
     paths:
       # code and tests
       - '**/*.rs'
@@ -75,6 +79,9 @@ env:
   COLORBT_SHOW_HIDDEN: ${{ vars.COLORBT_SHOW_HIDDEN }}
   CARGO_INCREMENTAL: ${{ vars.CARGO_INCREMENTAL }}
 
+# IMPORTANT
+#
+# These job names must be kept in sync with the `.patch.yml` and `.patch-external.yml` files.
 jobs:
   # Build the docker image used by the tests.
   #
@@ -83,6 +90,8 @@ jobs:
   # testnet when running the image.
   build:
     name: Build CI Docker
+    # Skip PRs from external repositories, let them pass, and then Mergify will check them
+    if: ${{ contains(github.head_ref || github.ref, 'refs/heads/') }}
     uses: ./.github/workflows/sub-build-docker-image.yml
     with:
       dockerfile_path: ./docker/Dockerfile
diff --git a/.github/workflows/docs-deploy-firebase.patch-external.yml b/.github/workflows/docs-deploy-firebase.patch-external.yml
new file mode 100644
index 00000000000..706f24d694c
--- /dev/null
+++ b/.github/workflows/docs-deploy-firebase.patch-external.yml
@@ -0,0 +1,30 @@
+# Workflow patches for skipping Google Cloud docs updates on PRs from external repositories.
+name: Docs
+
+# Run on PRs from external repositories, let them pass, and then Mergify will check them.
+# GitHub doesn't support filtering workflows by source branch names, so we have to do it for each
+# job.
+on:
+  pull_request:
+
+# IMPORTANT
+#
+# These job names must be kept in sync with the `.patch.yml` and `.yml` files.
+jobs:
+  build-docs-book:
+    name: Build and Deploy Zebra Book Docs
+    # Only run on PRs from external repositories.
+    # (github.ref is always a local branch, so this check will skip non-PRs as well.)
+    if: ${{ !contains(github.head_ref || github.ref, 'refs/heads/') }}
+    runs-on: ubuntu-latest
+    steps:
+      - run: 'echo "No build required"'
+
+  build-docs-internal:
+    name: Build and Deploy Zebra Internal Docs
+    # This dependency allows all these jobs to depend on a single condition, making it easier to
+    # change.
+    needs: build-docs-book
+    runs-on: ubuntu-latest
+    steps:
+      - run: 'echo "No build required"'
diff --git a/.github/workflows/docs-deploy-firebase.patch.yml b/.github/workflows/docs-deploy-firebase.patch.yml
index 4f6a0c2db8f..ed8bba560b5 100644
--- a/.github/workflows/docs-deploy-firebase.patch.yml
+++ b/.github/workflows/docs-deploy-firebase.patch.yml
@@ -1,9 +1,10 @@
+# Workflow patches for skipping Google Cloud docs updates when docs, Rust code, or dependencies
+# aren't modified in a PR.
 name: Docs
 
+# Run on PRs with unmodified docs, code, and dependency files.
 on:
   pull_request:
-    branches:
-      - main
     paths-ignore:
       # doc source files
       - 'book/**'
@@ -20,6 +21,9 @@ on:
       # workflow definitions
       - '.github/workflows/docs-deploy-firebase.yml'
 
+# IMPORTANT
+#
+# These job names must be kept in sync with the `.patch-external.yml` and `.yml` files.
 jobs:
   build-docs-book:
     name: Build and Deploy Zebra Book Docs
@@ -29,7 +33,6 @@ jobs:
 
   build-docs-internal:
     name: Build and Deploy Zebra Internal Docs
-    timeout-minutes: 45
     runs-on: ubuntu-latest
     steps:
       - run: 'echo "No build required"'
diff --git a/.github/workflows/docs-deploy-firebase.yml b/.github/workflows/docs-deploy-firebase.yml
index e6d0220dcba..f81e48bc263 100644
--- a/.github/workflows/docs-deploy-firebase.yml
+++ b/.github/workflows/docs-deploy-firebase.yml
@@ -1,3 +1,5 @@
+# Google Cloud docs updates that run when docs, Rust code, or dependencies are modified,
+# but only on PRs from the ZcashFoundation/zebra repository. (External PRs are deployed by mergify.)
 name: Docs
 
 # Ensures that only one workflow task will run at a time. Previous deployments, if
@@ -9,7 +11,9 @@ concurrency:
 
 on:
   workflow_dispatch:
+
   push:
+    # Skip main branch updates where docs, Rust code, and dependencies aren't modified.
     branches:
       - main
     paths:
@@ -29,8 +33,7 @@ on:
       - '.github/workflows/docs-deploy-firebase.yml'
 
   pull_request:
-    branches:
-      - main
+    # Skip PRs where docs, Rust code, and dependencies aren't modified.
     paths:
       # doc source files
       - 'book/**'
@@ -60,9 +63,14 @@ env:
   # https://github.com/ZcashFoundation/zebra/blob/main/.cargo/config.toml#L87
   RUSTDOCFLAGS: --html-in-header katex-header.html -D warnings -A rustdoc::private_intra_doc_links
 
+# IMPORTANT
+#
+# These job names must be kept in sync with the `.patch.yml` and `.patch-external.yml` files.
 jobs:
   build-docs-book:
     name: Build and Deploy Zebra Book Docs
+    # Skip PRs from external repositories, let them pass, and then Mergify will check them
+    if: ${{ contains(github.head_ref || github.ref, 'refs/heads/') }}
     timeout-minutes: 5
     runs-on: ubuntu-latest
     permissions:
@@ -116,6 +124,7 @@ jobs:
 
   build-docs-internal:
     name: Build and Deploy Zebra Internal Docs
+    if: ${{ contains(github.head_ref || github.ref, 'refs/heads/') }}
     timeout-minutes: 45
     runs-on: ubuntu-latest
     permissions:
diff --git a/zebrad/src/application.rs b/zebrad/src/application.rs
index d8df9d3f009..f0ce1a204d8 100644
--- a/zebrad/src/application.rs
+++ b/zebrad/src/application.rs
@@ -1,4 +1,7 @@
 //! Zebrad Abscissa Application
+//!
+//! This is the code that starts `zebrad`, and launches its tasks and services.
+//! See [the crate docs](crate) and [the start docs](crate::commands::start) for more details.
 
 use std::{env, fmt::Write as _, io::Write as _, process, sync::Arc};
 
diff --git a/zebrad/src/commands.rs b/zebrad/src/commands.rs
index 70728ce9302..9751f8693e1 100644
--- a/zebrad/src/commands.rs
+++ b/zebrad/src/commands.rs
@@ -10,10 +10,11 @@ pub use self::{entry_point::EntryPoint, start::StartCmd};
 
 use self::{copy_state::CopyStateCmd, generate::GenerateCmd, tip_height::TipHeightCmd};
 
+pub mod start;
+
 mod copy_state;
 mod entry_point;
 mod generate;
-mod start;
 mod tip_height;
 
 #[cfg(test)]