diff --git a/.github/workflows/main-golint.yml b/.github/workflows/main-golint.yml
index e9e78a5d..4ddd7930 100644
--- a/.github/workflows/main-golint.yml
+++ b/.github/workflows/main-golint.yml
@@ -85,3 +85,14 @@ jobs:
 
       - name: Check build of nexusd
         run: make service
+
+      - name: Run coverage and refresh README badge
+        if: matrix.os == 'ubuntu-latest'
+        run: make coverage
+
+      - name: Report coverage drift in README badge
+        if: matrix.os == 'ubuntu-latest'
+        run: |
+          if ! git diff --exit-code -- README.md; then
+            echo "::warning::README.md coverage badge differs from committed version. Run 'make coverage' locally and commit the result if you want the badge refreshed."
+          fi
diff --git a/Makefile b/Makefile
index ebdb0dbd..826a9a69 100644
--- a/Makefile
+++ b/Makefile
@@ -1,6 +1,6 @@
 SERVICE_DIR = nexusd
 
-.PHONY: all vet test service clean install uninstall
+.PHONY: all vet test service clean install uninstall test-coverage coverage-badge coverage
 
 all: vet test service
 
@@ -27,6 +27,34 @@ benchmark:
 	go test ./test -run=XXX -bench=. -scheme=tcps
 	go test ./test -run=XXX -bench=. -scheme=ws -compress
 
+# Run the full suite once with coverage instrumentation. The transport-matrix
+# variants in `test` are not re-run here — they exercise transport edge cases,
+# not different code paths in the router/wamp/client packages we measure.
+test-coverage:
+	go test -race -coverprofile=coverage.out -covermode=atomic ./...
+	go tool cover -func=coverage.out | tail -1 | awk '{print $$3}' > coverage.txt
+	@printf 'total coverage: %s\n' "$$(cat coverage.txt)"
+
+# Rewrite the README coverage badge line to a shields.io URL with the
+# current percentage and a color picked from the same thresholds shields.io
+# uses for its built-in coverage badges. shields.io renders the badge on
+# the fly, so no SVG file is committed. Idempotent: same percentage → no
+# diff. Cross-platform sed -i (works under BSD and GNU sed).
+coverage-badge: test-coverage
+	@PCT=$$(tr -d '%' < coverage.txt); \
+	COLOR=$$(awk -v p="$$PCT" 'BEGIN { \
+		if (p<50) print "red"; \
+		else if (p<70) print "orange"; \
+		else if (p<80) print "yellow"; \
+		else if (p<90) print "yellowgreen"; \
+		else print "brightgreen" }'); \
+	sed -i.bak -E "s|coverage-[0-9.]+%25-[a-z]+|coverage-$${PCT}%25-$${COLOR}|" README.md; \
+	rm -f README.md.bak; \
+	printf 'coverage badge: %s%% (%s)\n' "$$PCT" "$$COLOR"
+
+# Top-level: tests with coverage + badge regen. Run before pushing.
+coverage: coverage-badge
+
 service: $(SERVICE_DIR)/nexusd
 
 $(SERVICE_DIR)/nexusd:
diff --git a/README.md b/README.md
index 2ea544dc..615543e2 100644
--- a/README.md
+++ b/README.md
@@ -2,7 +2,8 @@
 
 # WAMP v2 router library, client library and router service
 
-[![Build Status](https://travis-ci.org/gammazero/nexus.svg)](https://travis-ci.org/gammazero/nexus)
+[![Main CI](https://github.com/gammazero/nexus/actions/workflows/main-golint.yml/badge.svg)](https://github.com/gammazero/nexus/actions/workflows/main-golint.yml)
+[![Coverage](https://img.shields.io/badge/coverage-56.1%25-orange)](https://github.com/gammazero/nexus/actions/workflows/main-golint.yml)
 [![License](https://img.shields.io/badge/License-MIT-blue.svg)](LICENSE)
 [![GoDoc](https://godoc.org/github.com/gammazero/nexus?status.svg)](https://godoc.org/github.com/gammazero/nexus)