diff --git a/Makefile b/Makefile
index 3af3df8..207384a 100644
--- a/Makefile
+++ b/Makefile
@@ -99,6 +99,18 @@ export-fixtures: ## Regenerate plan JSON for every tools/exporter/examples/*.sce
 examples: export-fixtures ## Regenerate fixtures from scenarios and run them through plan-runner against their oracles.
 	@cargo test -p plan-runner --test examples
 
+VIEWER_PORT ?= 8000
+
+.PHONY: viewer
+viewer: ## Serve the repository over HTTP for the plan viewer (override the port with VIEWER_PORT=...)
+	@if ! command -v python3 >/dev/null 2>&1; then \
+		echo "python3 not found. Enter the dev shell with 'make shell' (or 'nix develop') first."; \
+		exit 1; \
+	fi
+	@echo "Plan viewer: http://localhost:$(VIEWER_PORT)/tools/plan-viewer/index.html"
+	@echo "Example: http://localhost:$(VIEWER_PORT)/tools/plan-viewer/index.html?fixture=../../crates/plan-runner/fixtures/two_atom_join.json"
+	@python3 -m http.server $(VIEWER_PORT)
+
 .PHONY: shell
 shell: ## Enter the Nix dev shell defined in flake.nix
 	@nix develop
diff --git a/tools/plan-viewer/README.md b/tools/plan-viewer/README.md
index b1e2d51..5ab043c 100644
--- a/tools/plan-viewer/README.md
+++ b/tools/plan-viewer/README.md
@@ -1,17 +1,17 @@
-# Plan Viewer
+## Query Plan Viewer
 
-A static HTML viewer for `plan-runner` fixtures.
+A static HTML viewer for `plan-runner` JSON files (the fixtures).
 It renders the plan DAG, the input facts, and the relation computed at every plan node, so a fixture can be inspected without reading raw JSON.
 
-## Usage
+### Usag
 
 Open [`index.html`](index.html) in a browser, then drop a fixture from `crates/plan-runner/fixtures/` onto the page or pick one with the file input.
 
 When the repository is served over HTTP, a fixture can also be loaded through a query parameter:
 
 ```sh
-python3 -m http.server 8000
-# then open:
+make viewer  # Or `VIEWER_PORT=9000 make viewer`
+# Then open:
 # http://localhost:8000/tools/plan-viewer/index.html?fixture=../../crates/plan-runner/fixtures/two_atom_join.json
 ```
 
@@ -26,7 +26,7 @@ python3 -m http.server 8000
 
 The header badge reports whether the evaluated bindings match the fixture's `expected_bindings` as a multiset, mirroring `plan_runner::verify`.
 
-## Scope
+### Scope
 
 The viewer re-implements the scan, semijoin, and natural join semantics of `crates/query-ops` and the execution order of `crates/plan-runner` in JavaScript, for display only.
 The Rust crates and their tests remain the correctness oracle; if the two ever disagree, the Rust behavior wins and the viewer has a bug.