diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 40e5c18dc..e6eccb8dd 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -92,3 +92,10 @@ repos:
         language: system
         pass_filenames: false
         always_run: true
+
+      - id: lint-workflow-size
+        name: lint workflow file size
+        entry: ./hack/lint-workflow-size
+        language: script
+        files: ^internal/scaffold/fullsend-repo/(\.github/workflows/|templates/)
+        pass_filenames: false
diff --git a/hack/lint-workflow-size b/hack/lint-workflow-size
new file mode 100755
index 000000000..3c7a6a907
--- /dev/null
+++ b/hack/lint-workflow-size
@@ -0,0 +1,76 @@
+#!/bin/bash
+
+# lint-workflow-size - Guard against logic accumulating in workflow YAML files
+#
+# Workflow files are GitHub-specific glue. Business logic, shell scripts, and
+# agent plumbing should live in scripts/ where they can be tested, reused, and
+# ported to other forges.
+#
+# See:
+#   ADR-0005  Forge abstraction layer
+#   ADR-0008  workflow_dispatch for cross-repo agent dispatch
+#
+# Default cap: 200 lines per workflow file. To raise the cap for a specific
+# file, add a comment anywhere in the YAML:
+#
+#   # lint-workflow-size: max-lines=350
+#
+# This forces an intentional, reviewable decision rather than silent growth.
+
+set -euo pipefail
+
+DEFAULT_MAX=200
+errors=0
+
+check_files() {
+  local dir="$1"
+
+  if [[ ! -d "${dir}" ]]; then
+    return
+  fi
+
+  for file in "${dir}"/*.yml "${dir}"/*.yaml; do
+    [[ -e "${file}" ]] || continue
+
+    lines=$(wc -l < "${file}")
+    filename=$(basename "${file}")
+    relpath="${file}"
+
+    # Check for per-file override
+    max="${DEFAULT_MAX}"
+    override=$(grep -o 'max-lines=[0-9]*' "${file}" 2>/dev/null | grep -o '[0-9]*' | tail -1 || true)
+    if [[ -n "${override}" ]]; then
+      max="${override}"
+    fi
+
+    if [[ "${lines}" -gt "${max}" ]]; then
+      echo "ERROR: ${relpath} is ${lines} lines (max ${max})" >&2
+      echo "" >&2
+      echo "  Workflow files are GitHub-specific glue — keep logic in scripts/" >&2
+      echo "  where it can be tested and ported to other forges." >&2
+      echo "  See ADR-0005 (forge abstraction layer)." >&2
+      echo "" >&2
+      echo "  To fix: extract inline shell into scripts/ and call with" >&2
+      echo "    run: bash scripts/your-script.sh" >&2
+      echo "" >&2
+      echo "  To raise the cap (if the size is justified), add this comment" >&2
+      echo "  to the file:" >&2
+      echo "    # lint-workflow-size: max-lines=<new-limit>" >&2
+      echo "" >&2
+      errors=$((errors + 1))
+    fi
+  done
+}
+
+# Agent workflow files in the .fullsend repo scaffold
+check_files "internal/scaffold/fullsend-repo/.github/workflows"
+
+# Shim workflow template (deployed to enrolled repos)
+check_files "internal/scaffold/fullsend-repo/templates"
+
+if [[ "${errors}" -gt 0 ]]; then
+  echo "FAILED: ${errors} workflow file(s) exceed size limit" >&2
+  exit 1
+else
+  echo "OK: All workflow files within size limits"
+fi
diff --git a/internal/scaffold/fullsend-repo/.github/workflows/fix.yml b/internal/scaffold/fullsend-repo/.github/workflows/fix.yml
index 33a02082c..298b02086 100644
--- a/internal/scaffold/fullsend-repo/.github/workflows/fix.yml
+++ b/internal/scaffold/fullsend-repo/.github/workflows/fix.yml
@@ -1,4 +1,5 @@
 # fullsend-stage: fix
+# lint-workflow-size: max-lines=310
 name: Fix
 
 on:
diff --git a/internal/scaffold/fullsend-repo/.github/workflows/prioritize-scheduler.yml b/internal/scaffold/fullsend-repo/.github/workflows/prioritize-scheduler.yml
index 8592db785..27c65247c 100644
--- a/internal/scaffold/fullsend-repo/.github/workflows/prioritize-scheduler.yml
+++ b/internal/scaffold/fullsend-repo/.github/workflows/prioritize-scheduler.yml
@@ -1,3 +1,4 @@
+# lint-workflow-size: max-lines=220
 name: Prioritize Scheduler
 
 on:
diff --git a/internal/scaffold/fullsend-repo/templates/shim-workflow.yaml b/internal/scaffold/fullsend-repo/templates/shim-workflow.yaml
index c5ff9ee39..e3767087e 100644
--- a/internal/scaffold/fullsend-repo/templates/shim-workflow.yaml
+++ b/internal/scaffold/fullsend-repo/templates/shim-workflow.yaml
@@ -1,3 +1,4 @@
+# lint-workflow-size: max-lines=535
 # fullsend shim workflow
 # Routes events to agent workflows in .fullsend via the dispatch.yml workflow.
 #