Smoke v2 (#1283)

## Braintrust JS SDK Smoke Tests v2

### Design Principles

1. **Well-Known Tarball Paths**: Uses version-agnostic paths like
`braintrust-latest.tgz` so package.json never changes
2. **Build Before Install**: Ensures artifacts exist before npm tries to
install them
3. **Track Lock Files**: Commits lock files to catch transitive
dependency issues
4. **Makefile as Source of Truth**: Single clear interface (`make test`)
for every scenario
5. **Expected Failures Support**: Uses `xfail` status to document known
platform limitations without failing tests

### Quick Start

```bash
# Run all scenarios
make test

# Run specific scenario
make test otel-v1

# List available scenarios
make list
```

### What's Improved from v1

- ✅ No version-specific tarballs (eliminates package.json churn)
- ✅ Peer dependencies fully specified (no `--legacy-peer-deps`
workaround)
- ✅ Auto-discovery (no manual registration)
- ✅ Shared test package for DRY test logic
- ✅ Lock files tracked (surfaces packaging issues early)

This infrastructure ensures the Braintrust SDK "just works" across the
JavaScript ecosystem's diverse runtime landscape.

Author: ibolmo

.github/workflows/js.yaml

@@ -0,0 +1,129 @@
+# Auto-discover scenarios (any folder in scenarios/ with a Makefile)
+SCENARIOS := $(shell find scenarios -mindepth 1 -maxdepth 1 -type d -exec test -f {}/Makefile \; -print | sed 's|scenarios/||' | sort)
+
+.PHONY: help setup test list clean
+
+# =============================================================================
+# Help
+# =============================================================================
+
+help:
+	@echo "Smoke Test Infrastructure"
+	@echo ""
+	@echo "Available targets:"
+	@echo "  make test            - Run all scenarios (builds SDK once if needed)"
+	@echo "  make test <scenario> - Run specific scenario (e.g., make test otel-v1)"
+	@echo "  make setup           - Ensure SDK artifacts + shared package are ready"
+	@echo "  make clean           - Remove all build artifacts (force rebuild)"
+	@echo "  make list            - List discovered scenarios"
+	@echo ""
+	@echo "Environment variables:"
+	@echo "  BRAINTRUST_TAR           - Path to braintrust tarball (auto-set by parent when running locally)"
+	@echo "  BRAINTRUST_OTEL_TAR      - Path to otel tarball (auto-set by parent when running locally)"
+	@echo "  SMOKE_V2_SHARED_DIST     - Path to shared package dist (auto-set by parent when running locally)"
+	@echo ""
+	@echo "Running individual scenarios:"
+	@echo "  cd scenarios/otel-v1 && make test   - Runs standalone, builds if needed"
+	@echo ""
+	@echo "Discovered scenarios:"
+	@for scenario in $(SCENARIOS); do echo "  - $$scenario"; done
+
+# =============================================================================
+# Setup - Build SDK + shared package
+# =============================================================================
+
+setup:
+	@echo "==> Setting up smoke"
+	@mkdir -p ../artifacts
+
+	@# Build SDK and create tarball if not provided
+	@if [ -n "$(BRAINTRUST_TAR)" ] && [ -f "$(BRAINTRUST_TAR)" ]; then \
+		echo "==> Using provided BRAINTRUST_TAR: $(BRAINTRUST_TAR)"; \
+	else \
+		echo "==> Building SDK and creating tarball"; \
+		cd ../../.. && pnpm exec turbo build --filter=braintrust && pnpm --filter=braintrust pack --pack-destination sdk/js/artifacts; \
+		\
+		for f in sdk/js/artifacts/braintrust-*.tgz; do \
+			if [ "$$(basename $$f)" != "braintrust-latest.tgz" ] && \
+			   [ "$$(basename $$f)" != "braintrust-otel-latest.tgz" ]; then \
+				cp "$$f" sdk/js/artifacts/braintrust-latest.tgz; \
+				break; \
+			fi; \
+		done; \
+	fi
+
+	@# Build shared package if not provided
+	@if [ -n "$(SMOKE_V2_SHARED_DIST)" ] && [ -d "$(SMOKE_V2_SHARED_DIST)" ]; then \
+		echo "==> Using provided SMOKE_V2_SHARED_DIST: $(SMOKE_V2_SHARED_DIST)"; \
+	else \
+		if [ ! -d shared/dist ]; then \
+			echo "==> Building shared package"; \
+			cd shared && npm ci && npm run build; \
+		else \
+			echo "==> Shared package already built"; \
+		fi; \
+	fi
+
+# =============================================================================
+# Clean - Remove all build artifacts
+# =============================================================================
+
+clean:
+	@echo "==> Cleaning smoke artifacts"
+	rm -rf ../artifacts/*.tgz
+	rm -rf shared/dist shared/node_modules
+
+# =============================================================================
+# Test - Run scenarios
+# =============================================================================
+
+test:
+	@REQUESTED="$(filter-out test,$(MAKECMDGOALS))"; \
+	\
+	if [ -z "$$REQUESTED" ]; then \
+		SCENARIOS_TO_RUN="$(SCENARIOS)"; \
+		echo "==> Running all scenarios"; \
+	else \
+		SCENARIOS_TO_RUN=""; \
+		for scenario in $$REQUESTED; do \
+			if [ ! -d "scenarios/$$scenario" ]; then \
+				echo "Error: Scenario '$$scenario' not found"; \
+				echo "Available scenarios:"; \
+				for s in $(SCENARIOS); do echo "  - $$s"; done; \
+				exit 1; \
+			fi; \
+			SCENARIOS_TO_RUN="$$SCENARIOS_TO_RUN $$scenario"; \
+		done; \
+		echo "==> Running scenarios:$$SCENARIOS_TO_RUN"; \
+	fi; \
+	\
+	$(MAKE) setup; \
+	\
+	: $${BRAINTRUST_TAR:=../artifacts/braintrust-latest.tgz}; \
+	: $${BRAINTRUST_OTEL_TAR:=../artifacts/braintrust-otel-latest.tgz}; \
+	: $${SMOKE_V2_SHARED_DIST:=shared/dist}; \
+	export BRAINTRUST_TAR BRAINTRUST_OTEL_TAR SMOKE_V2_SHARED_DIST; \
+	\
+	for scenario in $$SCENARIOS_TO_RUN; do \
+		echo ""; \
+		echo "=== Testing $$scenario ==="; \
+		$(MAKE) -C scenarios/$$scenario test || exit 1; \
+	done; \
+	\
+	echo ""; \
+	echo "✓ All requested scenarios passed"
+
+# =============================================================================
+# List - Show discovered scenarios
+# =============================================================================
+
+list:
+	@echo "Discovered scenarios:"
+	@for scenario in $(SCENARIOS); do echo "  - $$scenario"; done
+
+# =============================================================================
+# Make scenario names valid targets (no-ops to support "make test otel-v1")
+# =============================================================================
+
+$(SCENARIOS):
+	@: