diff --git a/.github/copilot-instructions.md b/.github/copilot-instructions.md
index aca62f32..9f7ef737 100644
--- a/.github/copilot-instructions.md
+++ b/.github/copilot-instructions.md
@@ -17,3 +17,4 @@ Read and follow the CONTRIBUTING.md file in this repository for all code style c
 - Install toolchain before running tests: `rustup toolchain install "$(< rust-toolchain)" && rustup component add --toolchain "$(< rust-toolchain)" rustfmt clippy`
 - Run `FMT=true LINT=true BUILD=true TEST=true DOC=true ./test.sh` to validate changes. If a test fails with a hint about `RUSTFLAGS` and `--cfg pdu_test_skip_*`, follow the hint and rerun with the suggested flags.
 - **ALWAYS run the full test suite** (`FMT=true LINT=true BUILD=true TEST=true DOC=true ./test.sh`) before committing, regardless of how trivial the change seems — this includes documentation-only changes, comment edits, config changes, and refactors. The test suite checks formatting, linting, building, tests, and docs across multiple feature combinations; any type of change can break any of these checks.
+- Set `PDU_NO_FAIL_FAST=true` to run all checks instead of stopping at the first failure — this lets you see which checks pass and which fail
diff --git a/AGENTS.md b/AGENTS.md
index aca62f32..9f7ef737 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -17,3 +17,4 @@ Read and follow the CONTRIBUTING.md file in this repository for all code style c
 - Install toolchain before running tests: `rustup toolchain install "$(< rust-toolchain)" && rustup component add --toolchain "$(< rust-toolchain)" rustfmt clippy`
 - Run `FMT=true LINT=true BUILD=true TEST=true DOC=true ./test.sh` to validate changes. If a test fails with a hint about `RUSTFLAGS` and `--cfg pdu_test_skip_*`, follow the hint and rerun with the suggested flags.
 - **ALWAYS run the full test suite** (`FMT=true LINT=true BUILD=true TEST=true DOC=true ./test.sh`) before committing, regardless of how trivial the change seems — this includes documentation-only changes, comment edits, config changes, and refactors. The test suite checks formatting, linting, building, tests, and docs across multiple feature combinations; any type of change can break any of these checks.
+- Set `PDU_NO_FAIL_FAST=true` to run all checks instead of stopping at the first failure — this lets you see which checks pass and which fail
diff --git a/CLAUDE.md b/CLAUDE.md
index 13c391ce..9046ee2a 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -17,4 +17,5 @@ Read and follow the CONTRIBUTING.md file in this repository for all code style c
 - Install toolchain before running tests: `rustup toolchain install "$(< rust-toolchain)" && rustup component add --toolchain "$(< rust-toolchain)" rustfmt clippy`
 - Run `FMT=true LINT=true BUILD=true TEST=true DOC=true ./test.sh` to validate changes. If a test fails with a hint about `RUSTFLAGS` and `--cfg pdu_test_skip_*`, follow the hint and rerun with the suggested flags.
 - **ALWAYS run the full test suite** (`FMT=true LINT=true BUILD=true TEST=true DOC=true ./test.sh`) before committing, regardless of how trivial the change seems — this includes documentation-only changes, comment edits, config changes, and refactors. The test suite checks formatting, linting, building, tests, and docs across multiple feature combinations; any type of change can break any of these checks.
+- Set `PDU_NO_FAIL_FAST=true` to run all checks instead of stopping at the first failure — this lets you see which checks pass and which fail
 - `gh` (GitHub CLI) is not installed — do not attempt to use it
diff --git a/template/ai-instructions/shared.md b/template/ai-instructions/shared.md
index aca62f32..9f7ef737 100644
--- a/template/ai-instructions/shared.md
+++ b/template/ai-instructions/shared.md
@@ -17,3 +17,4 @@ Read and follow the CONTRIBUTING.md file in this repository for all code style c
 - Install toolchain before running tests: `rustup toolchain install "$(< rust-toolchain)" && rustup component add --toolchain "$(< rust-toolchain)" rustfmt clippy`
 - Run `FMT=true LINT=true BUILD=true TEST=true DOC=true ./test.sh` to validate changes. If a test fails with a hint about `RUSTFLAGS` and `--cfg pdu_test_skip_*`, follow the hint and rerun with the suggested flags.
 - **ALWAYS run the full test suite** (`FMT=true LINT=true BUILD=true TEST=true DOC=true ./test.sh`) before committing, regardless of how trivial the change seems — this includes documentation-only changes, comment edits, config changes, and refactors. The test suite checks formatting, linting, building, tests, and docs across multiple feature combinations; any type of change can break any of these checks.
+- Set `PDU_NO_FAIL_FAST=true` to run all checks instead of stopping at the first failure — this lets you see which checks pass and which fail
diff --git a/test.sh b/test.sh
index dbb69fdf..6c027b36 100755
--- a/test.sh
+++ b/test.sh
@@ -1,6 +1,22 @@
 #! /bin/bash
 set -o errexit -o pipefail -o nounset
 
+# Validate PDU_NO_FAIL_FAST
+no_fail_fast="${PDU_NO_FAIL_FAST:-false}"
+case "$no_fail_fast" in
+true | false) ;;
+*)
+  echo "error: Invalid value for PDU_NO_FAIL_FAST: $no_fail_fast (expected 'true' or 'false')" >&2
+  exit 1
+  ;;
+esac
+
+# A temporary file is used instead of a variable because run_if and unit are
+# subshells, so variable assignments inside them don't propagate to the parent.
+failure_dir=$(mktemp -d)
+trap 'rm -rf "$failure_dir"' EXIT
+failure_marker="$failure_dir/failed"
+
 run() (
   echo >&2
   echo "exec> $*" >&2
@@ -16,7 +32,19 @@ run_if() (
   condition="$1"
   shift
   case "$condition" in
-  true) run "$@" ;;
+  true)
+    if [[ $no_fail_fast == 'true' ]]; then
+      run "$@" || {
+        exit_status=$?
+        printf 'error: Command failed with exit code %d: ' "$exit_status" >&2
+        printf '%q ' "$@" >&2
+        printf '\n' >&2
+        touch "$failure_marker"
+      }
+    else
+      run "$@"
+    fi
+    ;;
   false) skip "$@" ;;
   *)
     echo "error: Invalid condition: $condition" >&2
@@ -39,3 +67,9 @@ unit --all-features "$@"
 unit --features cli "$@"
 unit --features cli-completions "$@"
 unit --features ai-instructions "$@"
+
+if [[ -f "$failure_marker" ]]; then
+  echo >&2
+  echo 'error: Some checks have failed. Review the output above for details.' >&2
+  exit 1
+fi