diff --git a/00-META/checks/cycle_test.go b/00-META/checks/cycle_test.go
new file mode 100644
index 00000000..f7b2bd10
--- /dev/null
+++ b/00-META/checks/cycle_test.go
@@ -0,0 +1,169 @@
+package checks
+
+import (
+	"fmt"
+	"io/fs"
+	"path"
+	"sort"
+	"strings"
+	"testing"
+	"testing/fstest"
+)
+
+// The development cycle, checked (cycle.py until ADR 0527; ADR 0080). Everything here reads frontmatter only,
+// because a status this repository holds lives in frontmatter and nowhere else. The decision records and research
+// efforts live in the knowledge base (ADR 0290), whose rules judge them.
+
+var designStatuses = map[string]bool{"proposed": true, "designed": true, "in-progress": true, "implemented": true, "abandoned": true}
+
+// The keys an issue report carried while its status lived here. The issue tracker holds them now (ADR 0275), and
+// `issue-tracker.move` enforces the cycle's rules at the write. A report carrying one is a status in two places.
+var trackerKeys = []string{"status", "located-in", "fixed-by", "amended-design", "replay", "replay-none", "resolved"}
+
+// checkDesigns: every design parses, carries `layer:` matching its folder and a known `status:`; a to-be design
+// names a decision, and once in-progress or implemented names its owning code. As-is designs need no decisions.
+func checkDesigns(fsys fs.FS) []string {
+	var out []string
+	for _, layer := range []struct{ folder, name string }{{"00-as-is", "as-is"}, {"01-to-be", "to-be"}} {
+		entries, _ := fs.ReadDir(fsys, "03-DESIGN/"+layer.folder)
+		for _, e := range entries {
+			if e.IsDir() || !strings.HasSuffix(e.Name(), ".md") || e.Name() == "README.md" {
+				continue
+			}
+			p := path.Join("03-DESIGN", layer.folder, e.Name())
+			front := frontmatter(readFile(fsys, p))
+			if front == nil {
+				out = append(out, "cycle: "+p+": no frontmatter")
+				continue
+			}
+			if front.scalar("layer") != layer.name {
+				out = append(out, fmt.Sprintf("cycle: %s: layer is %q; this directory is %s", p, front.scalar("layer"), layer.name))
+			}
+			status := front.scalar("status")
+			if !designStatuses[status] {
+				var known []string
+				for s := range designStatuses {
+					known = append(known, s)
+				}
+				sort.Strings(known)
+				out = append(out, fmt.Sprintf("cycle: %s: status %q is not one of %v", p, status, known))
+			}
+			if layer.name == "to-be" {
+				if len(front.list("decisions")) == 0 {
+					out = append(out, "cycle: "+p+": names no decisions -- no design without a decision")
+				}
+				if (status == "in-progress" || status == "implemented") && len(front.list("code")) == 0 {
+					out = append(out, fmt.Sprintf("cycle: %s: status %s but code: names no owner -- no development without a design that says where", p, status))
+				}
+			}
+		}
+	}
+	return out
+}
+
+// checkIssues: no two issue folders share a number (issue 155: the number is how a record is cited), every report
+// has frontmatter with `opened:`, and none carries a key the tracker holds.
+func checkIssues(fsys fs.FS) []string {
+	var out []string
+	entries, _ := fs.ReadDir(fsys, "04-ISSUES")
+	seen := map[string]string{}
+	for _, e := range entries {
+		if !e.IsDir() {
+			continue
+		}
+		number := strings.SplitN(e.Name(), "-", 2)[0]
+		if number == "" || strings.Trim(number, "0123456789") != "" {
+			continue
+		}
+		if first, ok := seen[number]; ok {
+			out = append(out, fmt.Sprintf("cycle: 04-ISSUES/%s: is numbered %s, and so is %s -- an issue number is how it is cited, and two records "+
+				"answering to one means a citation that resolves to whichever the reader opened. Take the next free number across main AND every open pull request", e.Name(), number, first))
+		} else {
+			seen[number] = e.Name()
+		}
+	}
+	for _, e := range entries {
+		p := path.Join("04-ISSUES", e.Name(), "00-report.md")
+		if !e.IsDir() {
+			continue
+		}
+		if _, err := fs.Stat(fsys, p); err != nil {
+			continue
+		}
+		front := frontmatter(readFile(fsys, p))
+		if front == nil {
+			out = append(out, "cycle: "+p+": no frontmatter")
+			continue
+		}
+		if front.scalar("opened") == "" {
+			out = append(out, "cycle: "+p+": opened: says nothing -- the day the issue was opened, YYYY-MM-DD")
+			continue
+		}
+		var carried []string
+		for _, k := range trackerKeys {
+			if _, ok := front[k]; ok {
+				carried = append(carried, "`"+k+":`")
+			}
+		}
+		if len(carried) > 0 {
+			out = append(out, fmt.Sprintf("cycle: %s: carries %s, but an issue's status, owner, fix and replay live in the issue tracker (ADR 0275): "+
+				"move it with `issue-tracker.move`, and keep no copy here", p, strings.Join(carried, ", ")))
+		}
+	}
+	return out
+}
+
+func TestCycleDesignsHoldTheChain(t *testing.T) { expectNone(t, checkDesigns(rootFS())) }
+func TestCycleIssuesHoldTheChain(t *testing.T)  { expectNone(t, checkIssues(rootFS())) }
+
+func design(layer, status, extra string) *fstest.MapFile {
+	return doc("---\nlayer: " + layer + "\nstatus: " + status + "\n" + extra + "---\nbody\n")
+}
+
+func TestCycleDesignsCatchesEachBreak(t *testing.T) {
+	broken := fstest.MapFS{
+		"03-DESIGN/00-as-is/a-nofront.md":    doc("no frontmatter"),
+		"03-DESIGN/00-as-is/b-wronglayer.md": design("to-be", "implemented", ""),
+		"03-DESIGN/00-as-is/c-badstatus.md":  design("as-is", "done", ""),
+		"03-DESIGN/01-to-be/d-nodecision.md": design("to-be", "designed", ""),
+		"03-DESIGN/01-to-be/e-nocode.md":     design("to-be", "in-progress", "decisions: [ADR 0001]\n"),
+		"03-DESIGN/01-to-be/README.md":       doc("not a design"),
+	}
+	got := checkDesigns(broken)
+	expectProblem(t, got, "a-nofront.md: no frontmatter")
+	expectProblem(t, got, `b-wronglayer.md: layer is "to-be"; this directory is as-is`)
+	expectProblem(t, got, `c-badstatus.md: status "done" is not one of`)
+	expectProblem(t, got, "d-nodecision.md: names no decisions")
+	expectProblem(t, got, "e-nocode.md: status in-progress but code: names no owner")
+	if len(got) != 5 {
+		t.Errorf("exactly the five breaks, as-is needs no decisions and a README is no design: %q", got)
+	}
+}
+
+func TestCycleDesignsAcceptsASoundPair(t *testing.T) {
+	sound := fstest.MapFS{
+		"03-DESIGN/00-as-is/a.md": design("as-is", "implemented", ""),
+		"03-DESIGN/01-to-be/b.md": design("to-be", "in-progress", "decisions: [ADR 0001]\ncode: [mesh-sdk]\n"),
+	}
+	expectNone(t, checkDesigns(sound))
+}
+
+func TestCycleIssuesCatchesEachBreak(t *testing.T) {
+	report := func(front string) *fstest.MapFile { return doc("---\n" + front + "---\nbody\n") }
+	broken := fstest.MapFS{
+		"04-ISSUES/100-a/00-report.md":        report("opened: 2026-10-01\n"),
+		"04-ISSUES/100-b/00-report.md":        report("opened: 2026-10-01\n"),
+		"04-ISSUES/101-noopened/00-report.md": report("title: x\n"),
+		"04-ISSUES/102-tracker/00-report.md":  report("opened: 2026-10-01\nstatus: open\nreplay: none\n"),
+		"04-ISSUES/103-nofront/00-report.md":  doc("plain"),
+		"04-ISSUES/notes/readme.md":           doc("not an issue"),
+	}
+	got := checkIssues(broken)
+	expectProblem(t, got, "04-ISSUES/100-b: is numbered 100, and so is 100-a")
+	expectProblem(t, got, "101-noopened/00-report.md: opened: says nothing")
+	expectProblem(t, got, "102-tracker/00-report.md: carries `status:`, `replay:`")
+	expectProblem(t, got, "103-nofront/00-report.md: no frontmatter")
+	if len(got) != 4 {
+		t.Errorf("exactly the four breaks: %q", got)
+	}
+}