diff --git a/.github/workflows/codeql.yml b/.github/workflows/codeql.yml
index 4b963e015..1d3f825ff 100644
--- a/.github/workflows/codeql.yml
+++ b/.github/workflows/codeql.yml
@@ -19,6 +19,17 @@ on:
   schedule:
     - cron: "42 6 * * 0"
 
+# A newer push to a pull request cancels that PR's superseded run. Each job
+# then joins a per-author queue for that job (its own `concurrency` block), so
+# one person opening many PRs runs one copy of each job at a time and cannot
+# fill the runner pool ahead of everyone else. Queued jobs start in the order they began waiting; GitHub
+# keeps up to 100 pending per queue and cancels arrivals past that. Every job
+# has a timeout so a hung job cannot hold its queue for hours. Bot-authored
+# PRs and non-PR events key on the run ID and never wait on a queue.
+concurrency:
+  group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.run_id }}
+  cancel-in-progress: true
+
 jobs:
   analyze:
     name: Analyze (${{ matrix.language }})
@@ -28,6 +39,10 @@ jobs:
     #   - https://gh.io/using-larger-runners (GitHub.com only)
     # Consider using larger runners or machines with greater resources for possible analysis time improvements.
     runs-on: ${{ (matrix.language == 'swift' && 'macos-latest') || 'ubuntu-latest' }}
+    timeout-minutes: 45
+    concurrency:
+      group: ${{ github.workflow }}-analyze-${{ matrix.language }}-${{ github.event_name == 'pull_request' && github.event.pull_request.user.type != 'Bot' && github.event.pull_request.user.login || github.run_id }}
+      queue: max
     permissions:
       # required for all workflows
       security-events: write
diff --git a/.github/workflows/format.yml b/.github/workflows/format.yml
index f458572eb..037909389 100644
--- a/.github/workflows/format.yml
+++ b/.github/workflows/format.yml
@@ -8,10 +8,25 @@ on:
 permissions:
   contents: read
 
+# A newer push to a pull request cancels that PR's superseded run. Each job
+# then joins a per-author queue for that job (its own `concurrency` block), so
+# one person opening many PRs runs one copy of each job at a time and cannot
+# fill the runner pool ahead of everyone else. Queued jobs start in the order they began waiting; GitHub
+# keeps up to 100 pending per queue and cancels arrivals past that. Every job
+# has a timeout so a hung job cannot hold its queue for hours. Bot-authored
+# PRs and non-PR events key on the run ID and never wait on a queue.
+concurrency:
+  group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.run_id }}
+  cancel-in-progress: true
+
 jobs:
   check-claude-md-symlink:
     name: CLAUDE.md symlink guard
     runs-on: ubuntu-latest
+    timeout-minutes: 5
+    concurrency:
+      group: ${{ github.workflow }}-check-claude-md-symlink-${{ github.event_name == 'pull_request' && github.event.pull_request.user.type != 'Bot' && github.event.pull_request.user.login || github.run_id }}
+      queue: max
     steps:
       - uses: actions/checkout@v4
 
@@ -42,9 +57,55 @@ jobs:
   format-rust:
     name: cargo fmt
     runs-on: ubuntu-latest
+    timeout-minutes: 25
+    concurrency:
+      group: ${{ github.workflow }}-format-rust-${{ github.event_name == 'pull_request' && github.event.pull_request.user.type != 'Bot' && github.event.pull_request.user.login || github.run_id }}
+      queue: max
     steps:
       - uses: actions/checkout@v4
 
+      # A hung job, a PR-triggered workflow without per-PR cancellation, or a
+      # job outside its per-author queue brings back the runner pile-up that
+      # the concurrency blocks prevent. Every PR-triggered workflow must carry
+      # test.yml's workflow-level block, and every job must set timeout-minutes
+      # and a per-author queue (keyed on the matrix too, for matrix jobs).
+      # Jobs that call a reusable workflow are skipped: they cannot set these.
+      - name: Require per-PR cancellation, per-author job queues and timeouts
+        shell: bash
+        run: |
+          reference=.github/workflows/test.yml
+          if [ "$(yq '.concurrency."cancel-in-progress" == true and (.concurrency.group // "" | test("pull_request\.number"))' "$reference")" != true ]; then
+            echo "::error file=$reference::test.yml must cancel superseded runs per pull request."
+            exit 1
+          fi
+          expected=$(yq -o=json -I=0 '.concurrency' "$reference")
+          status=0
+          for f in .github/workflows/*.yml .github/workflows/*.yaml; do
+            [ -f "$f" ] || continue
+            on_pr=$(yq '.on | ((tag == "!!map" and has("pull_request")) or (tag == "!!str" and . == "pull_request") or (tag == "!!seq" and ([.[] | select(. == "pull_request")] | length > 0)))' "$f")
+            [ "$on_pr" = true ] || continue
+            if [ "$(yq -o=json -I=0 '.concurrency' "$f")" != "$expected" ]; then
+              echo "::error file=$f::PR-triggered workflows must use the workflow-level concurrency block from test.yml."
+              status=1
+            fi
+            while read -r job; do
+              [ -n "$job" ] || continue
+              echo "::error file=$f::Job '$job' must set timeout-minutes."
+              status=1
+            done < <(yq '.jobs | to_entries[] | select(.value.uses == null and .value["timeout-minutes"] == null) | .key' "$f")
+            while read -r job; do
+              [ -n "$job" ] || continue
+              echo "::error file=$f::Job '$job' must join a per-author queue: concurrency.group keyed on pull_request.user.login and queue: max."
+              status=1
+            done < <(yq '.jobs | to_entries[] | select(.value.uses == null and (.value.concurrency.queue != "max" or (.value.concurrency.group // "" | test("pull_request\.user\.login") | not))) | .key' "$f")
+            while read -r job; do
+              [ -n "$job" ] || continue
+              echo "::error file=$f::Matrix job '$job' must include the matrix in its concurrency group so its legs do not queue behind each other."
+              status=1
+            done < <(yq '.jobs | to_entries[] | select(.value.strategy.matrix != null and (.value.concurrency.group // "" | test("matrix\.") | not)) | .key' "$f")
+          done
+          exit "$status"
+
       # Rust jobs must set up the toolchain through ./.github/actions/setup-rust,
       # which removes the image's stable and only saves caches from main. A
       # direct setup-rust-toolchain or rust-cache step skips both silently.
@@ -103,6 +164,10 @@ jobs:
 
   format-typescript:
     runs-on: ubuntu-latest
+    timeout-minutes: 10
+    concurrency:
+      group: ${{ github.workflow }}-format-typescript-${{ github.event_name == 'pull_request' && github.event.pull_request.user.type != 'Bot' && github.event.pull_request.user.login || github.run_id }}
+      queue: max
     defaults:
       run:
         working-directory: crates/trusted-server-js/lib
@@ -134,6 +199,10 @@ jobs:
 
   format-docs:
     runs-on: ubuntu-latest
+    timeout-minutes: 10
+    concurrency:
+      group: ${{ github.workflow }}-format-docs-${{ github.event_name == 'pull_request' && github.event.pull_request.user.type != 'Bot' && github.event.pull_request.user.login || github.run_id }}
+      queue: max
     defaults:
       run:
         working-directory: docs
@@ -175,6 +244,10 @@ jobs:
   docs-proposal-scripts:
     name: docs-proposal scripts
     runs-on: ubuntu-latest
+    timeout-minutes: 10
+    concurrency:
+      group: ${{ github.workflow }}-docs-proposal-scripts-${{ github.event_name == 'pull_request' && github.event.pull_request.user.type != 'Bot' && github.event.pull_request.user.login || github.run_id }}
+      queue: max
     steps:
       - uses: actions/checkout@v4
 
diff --git a/.github/workflows/integration-tests.yml b/.github/workflows/integration-tests.yml
index e3f2b3334..a276d23ec 100644
--- a/.github/workflows/integration-tests.yml
+++ b/.github/workflows/integration-tests.yml
@@ -10,6 +10,17 @@ on:
     types: [opened, synchronize, reopened]
   workflow_dispatch:
 
+# A newer push to a pull request cancels that PR's superseded run. Each job
+# then joins a per-author queue for that job (its own `concurrency` block), so
+# one person opening many PRs runs one copy of each job at a time and cannot
+# fill the runner pool ahead of everyone else. Queued jobs start in the order they began waiting; GitHub
+# keeps up to 100 pending per queue and cancels arrivals past that. Every job
+# has a timeout so a hung job cannot hold its queue for hours. Bot-authored
+# PRs and non-PR events key on the run ID and never wait on a queue.
+concurrency:
+  group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.run_id }}
+  cancel-in-progress: true
+
 env:
   ORIGIN_PORT: 8888
   ARTIFACTS_DIR: /tmp/integration-test-artifacts
@@ -23,6 +34,9 @@ jobs:
     name: prepare integration artifacts
     runs-on: ubuntu-latest
     timeout-minutes: 30
+    concurrency:
+      group: ${{ github.workflow }}-prepare-artifacts-${{ github.event_name == 'pull_request' && github.event.pull_request.user.type != 'Bot' && github.event.pull_request.user.login || github.run_id }}
+      queue: max
     steps:
       - uses: actions/checkout@v4
 
@@ -60,6 +74,9 @@ jobs:
     needs: prepare-artifacts
     runs-on: ubuntu-latest
     timeout-minutes: 20
+    concurrency:
+      group: ${{ github.workflow }}-integration-tests-${{ github.event_name == 'pull_request' && github.event.pull_request.user.type != 'Bot' && github.event.pull_request.user.login || github.run_id }}
+      queue: max
     steps:
       - uses: actions/checkout@v4
 
@@ -119,6 +136,9 @@ jobs:
     needs: prepare-artifacts
     runs-on: ubuntu-latest
     timeout-minutes: 15
+    concurrency:
+      group: ${{ github.workflow }}-integration-tests-fastly-ec-${{ github.event_name == 'pull_request' && github.event.pull_request.user.type != 'Bot' && github.event.pull_request.user.login || github.run_id }}
+      queue: max
     steps:
       - uses: actions/checkout@v4
 
@@ -163,6 +183,9 @@ jobs:
     # once the pinned Playwright version supports the newer image.
     runs-on: ubuntu-24.04
     timeout-minutes: 15
+    concurrency:
+      group: ${{ github.workflow }}-browser-tests-${{ github.event_name == 'pull_request' && github.event.pull_request.user.type != 'Bot' && github.event.pull_request.user.login || github.run_id }}
+      queue: max
     steps:
       - uses: actions/checkout@v4
 
diff --git a/.github/workflows/pbs-example.yml b/.github/workflows/pbs-example.yml
index dced0c7b6..d61072867 100644
--- a/.github/workflows/pbs-example.yml
+++ b/.github/workflows/pbs-example.yml
@@ -17,11 +17,25 @@ on:
 permissions:
   contents: read
 
+# A newer push to a pull request cancels that PR's superseded run. Each job
+# then joins a per-author queue for that job (its own `concurrency` block), so
+# one person opening many PRs runs one copy of each job at a time and cannot
+# fill the runner pool ahead of everyone else. Queued jobs start in the order they began waiting; GitHub
+# keeps up to 100 pending per queue and cancels arrivals past that. Every job
+# has a timeout so a hung job cannot hold its queue for hours. Bot-authored
+# PRs and non-PR events key on the run ID and never wait on a queue.
+concurrency:
+  group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.run_id }}
+  cancel-in-progress: true
+
 jobs:
   local-checks:
     name: PBS Terraform and Compose checks
     runs-on: ubuntu-latest
     timeout-minutes: 20
+    concurrency:
+      group: ${{ github.workflow }}-local-checks-${{ github.event_name == 'pull_request' && github.event.pull_request.user.type != 'Bot' && github.event.pull_request.user.login || github.run_id }}
+      queue: max
     env:
       TF_IN_AUTOMATION: 'true'
       AWS_EC2_METADATA_DISABLED: 'true'
diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 6cd995328..a5c669f83 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -8,11 +8,25 @@ on:
     branches: [main]
   pull_request:
 
+# A newer push to a pull request cancels that PR's superseded run. Each job
+# then joins a per-author queue for that job (its own `concurrency` block), so
+# one person opening many PRs runs one copy of each job at a time and cannot
+# fill the runner pool ahead of everyone else. Queued jobs start in the order they began waiting; GitHub
+# keeps up to 100 pending per queue and cancels arrivals past that. Every job
+# has a timeout so a hung job cannot hold its queue for hours. Bot-authored
+# PRs and non-PR events key on the run ID and never wait on a queue.
+concurrency:
+  group: ${{ github.workflow }}-${{ github.event.pull_request.number || github.run_id }}
+  cancel-in-progress: true
+
 jobs:
   test-rust:
     name: cargo test
     runs-on: ubuntu-latest
     timeout-minutes: 45
+    concurrency:
+      group: ${{ github.workflow }}-test-rust-${{ github.event_name == 'pull_request' && github.event.pull_request.user.type != 'Bot' && github.event.pull_request.user.login || github.run_id }}
+      queue: max
     steps:
       - uses: actions/checkout@v4
 
@@ -69,6 +83,9 @@ jobs:
     name: HTML EOF runtime (Fastly)
     runs-on: ubuntu-latest
     timeout-minutes: 25
+    concurrency:
+      group: ${{ github.workflow }}-test-fastly-eof-${{ github.event_name == 'pull_request' && github.event.pull_request.user.type != 'Bot' && github.event.pull_request.user.login || github.run_id }}
+      queue: max
     steps:
       - uses: actions/checkout@v4
 
@@ -117,6 +134,10 @@ jobs:
   test-axum:
     name: cargo test (axum native)
     runs-on: ubuntu-latest
+    timeout-minutes: 30
+    concurrency:
+      group: ${{ github.workflow }}-test-axum-${{ github.event_name == 'pull_request' && github.event.pull_request.user.type != 'Bot' && github.event.pull_request.user.login || github.run_id }}
+      queue: max
     steps:
       - uses: actions/checkout@v4
 
@@ -187,6 +208,10 @@ jobs:
   test-cloudflare:
     name: cargo check (cloudflare native + wasm32-unknown-unknown)
     runs-on: ubuntu-latest
+    timeout-minutes: 15
+    concurrency:
+      group: ${{ github.workflow }}-test-cloudflare-${{ github.event_name == 'pull_request' && github.event.pull_request.user.type != 'Bot' && github.event.pull_request.user.login || github.run_id }}
+      queue: max
     steps:
       - uses: actions/checkout@v4
 
@@ -212,6 +237,10 @@ jobs:
   test-spin:
     name: cargo check/build/test (spin native + wasm32-wasip1)
     runs-on: ubuntu-latest
+    timeout-minutes: 20
+    concurrency:
+      group: ${{ github.workflow }}-test-spin-${{ github.event_name == 'pull_request' && github.event.pull_request.user.type != 'Bot' && github.event.pull_request.user.login || github.run_id }}
+      queue: max
     steps:
       - uses: actions/checkout@v4
 
@@ -249,6 +278,10 @@ jobs:
   test-parity:
     name: cargo test (cross-adapter parity)
     runs-on: ubuntu-latest
+    timeout-minutes: 15
+    concurrency:
+      group: ${{ github.workflow }}-test-parity-${{ github.event_name == 'pull_request' && github.event.pull_request.user.type != 'Bot' && github.event.pull_request.user.login || github.run_id }}
+      queue: max
     steps:
       - uses: actions/checkout@v4
 
@@ -274,6 +307,10 @@ jobs:
       matrix:
         os: [ubuntu-latest, macos-latest]
     runs-on: ${{ matrix.os }}
+    timeout-minutes: 45
+    concurrency:
+      group: ${{ github.workflow }}-test-cli-${{ matrix.os }}-${{ github.event_name == 'pull_request' && github.event.pull_request.user.type != 'Bot' && github.event.pull_request.user.login || github.run_id }}
+      queue: max
     steps:
       - uses: actions/checkout@v4
 
@@ -338,6 +375,10 @@ jobs:
   test-typescript:
     name: vitest
     runs-on: ubuntu-latest
+    timeout-minutes: 10
+    concurrency:
+      group: ${{ github.workflow }}-test-typescript-${{ github.event_name == 'pull_request' && github.event.pull_request.user.type != 'Bot' && github.event.pull_request.user.login || github.run_id }}
+      queue: max
     defaults:
       run:
         working-directory: crates/trusted-server-js/lib