diff --git a/README.md b/README.md
index 1c302b8..0eab13c 100644
--- a/README.md
+++ b/README.md
@@ -96,6 +96,7 @@ they configure.
 | --- | --- | --- |
 | `config-dir` | empty | `--config-dir` |
 | `profile` | empty | `--profile` |
+| `debug` | `false` | `--debug` |
 
 ### Review Target
 
diff --git a/action.yml b/action.yml
index cb85b19..a251970 100644
--- a/action.yml
+++ b/action.yml
@@ -75,6 +75,10 @@ inputs:
     description: Path to additional review instructions.
     required: false
     default: ""
+  debug:
+    description: Pass --debug to DiffPal.
+    required: false
+    default: ""
 runs:
   using: composite
   steps:
@@ -104,4 +108,5 @@ runs:
         INPUT_LANGUAGE: ${{ inputs.language }}
         INPUT_INSTRUCTIONS: ${{ inputs.instructions }}
         INPUT_INSTRUCTIONS_FILE: ${{ inputs.instructions-file }}
+        INPUT_DEBUG: ${{ inputs.debug }}
       run: ${{ github.action_path }}/scripts/run-diffpal-review.sh
diff --git a/scripts/run-diffpal-review.sh b/scripts/run-diffpal-review.sh
index 1829a9c..d9fc21e 100755
--- a/scripts/run-diffpal-review.sh
+++ b/scripts/run-diffpal-review.sh
@@ -43,6 +43,9 @@ fi
 if [[ -n "${INPUT_PROFILE:-}" ]]; then
   argv+=(--profile "$INPUT_PROFILE")
 fi
+if truthy "${INPUT_DEBUG:-false}"; then
+  argv+=(--debug)
+fi
 
 argv+=(review github --base "$INPUT_BASE" --head "$INPUT_HEAD")
 
diff --git a/scripts/smoke-test.sh b/scripts/smoke-test.sh
index 3519e7e..6e250cf 100755
--- a/scripts/smoke-test.sh
+++ b/scripts/smoke-test.sh
@@ -153,6 +153,24 @@ test_wrapper_uses_installed_binary_and_feedback() {
   assert_contains "$argv" "diffpal-dev"
 }
 
+test_wrapper_forwards_debug_input() {
+  local dir="$1"
+  local bin_dir="$dir/debug-bin"
+  local argv="$dir/argv-debug"
+  mkdir -p "$bin_dir"
+  make_fake_diffpal "$bin_dir"
+
+  PATH="$bin_dir:$PATH" \
+    DIFFPAL_ARGV_FILE="$argv" \
+    DIFFPAL_BIN=diffpal \
+    INPUT_BASE=base-sha \
+    INPUT_HEAD=head-sha \
+    INPUT_DEBUG=true \
+    "$repo_root/scripts/run-diffpal-review.sh"
+
+  assert_contains "$argv" "--debug"
+}
+
 test_wrapper_can_disable_summary_overview() {
   local dir="$1"
   local bin_dir="$dir/overview-bin"
@@ -235,6 +253,7 @@ test_installer_installs_requested_version "$tmpdir/install"
 test_installer_selects_custom_path "$tmpdir/custom"
 test_installer_selects_path_when_install_disabled "$tmpdir/disabled"
 test_wrapper_uses_installed_binary_and_feedback "$tmpdir/wrapper-installed"
+test_wrapper_forwards_debug_input "$tmpdir/wrapper-debug"
 test_wrapper_can_disable_summary_overview "$tmpdir/wrapper-overview"
 test_wrapper_prints_gate_annotation_for_blocked_exit_code "$tmpdir/wrapper-gate"
 test_wrapper_keeps_non_gate_failures_generic "$tmpdir/wrapper-generic"