diff --git a/workspace-server/cmd/memory-plugin-postgres/E2E.md b/workspace-server/cmd/memory-plugin-postgres/E2E.md
new file mode 100644
index 00000000..23ad9d07
--- /dev/null
+++ b/workspace-server/cmd/memory-plugin-postgres/E2E.md
@@ -0,0 +1,68 @@
+# Real-subprocess E2E for memory-plugin-postgres
+
+The default `go test ./...` suite covers the plugin via in-process
+sqlmock tests (PR-3). This directory ALSO ships build-tag-gated tests
+that spawn the real binary against a live postgres — to catch
+classes of bug in-process tests can't see:
+
+- Boot-path regressions (env var typos, panic-on-startup)
+- Wire-format bugs sqlmock smooths over (the `pq.Array` issue we
+  hit during PR-3 development)
+- HTTP/socket encoding edge cases
+- C1 idempotency (real upsert against real postgres)
+
+## Running
+
+The tests skip silently unless an operator opts in with both:
+- The `memory_plugin_e2e` build tag
+- `MEMORY_PLUGIN_E2E_DB` env var pointing at a writable postgres
+
+### Quick local run (with docker)
+
+```bash
+docker run --rm -d --name memory-plugin-e2e-pg \
+  -e POSTGRES_PASSWORD=test -e POSTGRES_USER=test -e POSTGRES_DB=test \
+  -p 5432:5432 \
+  pgvector/pgvector:pg16
+
+# Wait a few seconds for postgres to accept connections
+until docker exec memory-plugin-e2e-pg pg_isready -U test >/dev/null 2>&1; do sleep 0.5; done
+
+MEMORY_PLUGIN_E2E_DB=postgres://test:test@localhost:5432/test?sslmode=disable \
+  go test -tags memory_plugin_e2e -v -count=1 ./cmd/memory-plugin-postgres/
+
+docker stop memory-plugin-e2e-pg
+```
+
+### CI integration
+
+These tests are NOT in the default required-checks set. Operators
+gating cutover on the suite should add a separate workflow step:
+
+```yaml
+- name: Memory plugin E2E
+  if: ${{ contains(github.event.pull_request.labels.*.name, 'memory-v2') }}
+  run: |
+    MEMORY_PLUGIN_E2E_DB=${{ secrets.MEMORY_PLUGIN_TEST_DSN }} \
+      go test -tags memory_plugin_e2e -v -count=1 ./cmd/memory-plugin-postgres/
+```
+
+## What each test pins
+
+| Test | Covers |
+|---|---|
+| `TestE2E_BootAndHealth` | Binary builds, starts, advertises all 5 capabilities |
+| `TestE2E_FullCommitSearchForgetRoundTrip` | Real wire encoding (no sqlmock), full agent flow |
+| `TestE2E_IdempotencyKey` | C1 fix end-to-end — upserts against real postgres |
+
+## What's still NOT covered
+
+- Migration drift (assumes the migrations dir is at the conventional
+  path; operator-customized layouts need their own test)
+- Plugin-internal recovery (kill backing store mid-request, etc.)
+- Concurrent commits with id collisions across processes
+- TTL eviction (would need to extend test runtime past `expires_at`)
+
+These gaps apply equally to forks of this binary; they're listed in
+[`testing-your-plugin.md`](../../../docs/memory-plugins/testing-your-plugin.md)
+under "what the harness does NOT cover".
diff --git a/workspace-server/cmd/memory-plugin-postgres/boot_e2e_test.go b/workspace-server/cmd/memory-plugin-postgres/boot_e2e_test.go
new file mode 100644
index 00000000..b8b76543
--- /dev/null
+++ b/workspace-server/cmd/memory-plugin-postgres/boot_e2e_test.go
@@ -0,0 +1,289 @@
+//go:build memory_plugin_e2e
+
+// Package main's real-subprocess boot test (#293 fixup, RFC #2728).
+//
+// Build-tag gated so it only runs when an operator explicitly opts in:
+//
+//   MEMORY_PLUGIN_E2E_DB=postgres://test:test@localhost:5432/test?sslmode=disable \
+//     go test -tags memory_plugin_e2e -v ./cmd/memory-plugin-postgres/
+//
+// Why a separate build tag:
+//   - The default `go test ./...` run shouldn't require docker or a
+//     live postgres
+//   - CI gates that DO want to run this can set the env var + tag
+//   - Operators verifying a custom plugin against the contract can
+//     copy this file as the template (replace the binary build step
+//     with their own)
+//
+// What this exercises that PR-11's swap test doesn't:
+//   - Real `go build` of cmd/memory-plugin-postgres/
+//   - Real binary boot via os/exec — catches mixed-key panics, missing
+//     env vars, crash-on-startup issues that in-process tests skip
+//   - Real postgres connection — catches wire-format bugs (e.g. the
+//     pq.Array regression we hit during PR-3)
+//   - Real HTTP round-trip with a TCP socket — catches encoding edge
+//     cases sqlmock + httptest can't see
+//
+// What this does NOT cover:
+//   - Schema migration drift (assumes the migrations dir is at the
+//     conventional path; operator-customized layouts need their own
+//     test)
+//   - Plugin-internal recovery (kill backing store mid-request, etc.)
+
+package main
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"runtime"
+	"testing"
+	"time"
+
+	mclient "github.com/Molecule-AI/molecule-monorepo/platform/internal/memory/client"
+	"github.com/Molecule-AI/molecule-monorepo/platform/internal/memory/contract"
+)
+
+const (
+	bootProbeTimeout = 30 * time.Second
+	bootProbeStep   = 500 * time.Millisecond
+)
+
+// requireE2EDB returns the test DSN. Skips the test (not fails) when
+// the env var is unset — keeps `-tags memory_plugin_e2e` runs from
+// crashing on dev machines without postgres.
+func requireE2EDB(t *testing.T) string {
+	t.Helper()
+	dsn := os.Getenv("MEMORY_PLUGIN_E2E_DB")
+	if dsn == "" {
+		t.Skip("MEMORY_PLUGIN_E2E_DB not set — skipping real-subprocess boot test")
+	}
+	return dsn
+}
+
+// buildBinary compiles cmd/memory-plugin-postgres/ to a temp dir.
+// Returns the path of the built binary. Test cleanup deletes it.
+func buildBinary(t *testing.T) string {
+	t.Helper()
+	dir := t.TempDir()
+	out := filepath.Join(dir, "memory-plugin-postgres")
+	if runtime.GOOS == "windows" {
+		out += ".exe"
+	}
+	// Find the cmd dir relative to this file.
+	_, thisFile, _, _ := runtime.Caller(0)
+	cmdDir := filepath.Dir(thisFile)
+	build := exec.Command("go", "build", "-o", out, ".")
+	build.Dir = cmdDir
+	build.Env = os.Environ()
+	if outErr, err := build.CombinedOutput(); err != nil {
+		t.Fatalf("go build failed: %v\n%s", err, outErr)
+	}
+	return out
+}
+
+// startBinary launches the built binary with the supplied env. Returns
+// the *exec.Cmd (test cleanup kills it) and the http URL it's listening
+// on. Polls /v1/health until ready or times out.
+func startBinary(t *testing.T, binary, dsn, listen string) (*exec.Cmd, string) {
+	t.Helper()
+	url := "http://" + listen
+	cmd := exec.Command(binary)
+	cmd.Env = append(os.Environ(),
+		"MEMORY_PLUGIN_DATABASE_URL="+dsn,
+		"MEMORY_PLUGIN_LISTEN_ADDR="+listen,
+		// Migrations dir lives next to the cmd source. The binary
+		// reads it relative to cwd by default; we set the env var
+		// override so the test doesn't depend on cwd.
+		"MEMORY_PLUGIN_MIGRATIONS_DIR="+migrationsDirForTest(t),
+	)
+	stdout := &bytes.Buffer{}
+	stderr := &bytes.Buffer{}
+	cmd.Stdout = stdout
+	cmd.Stderr = stderr
+	if err := cmd.Start(); err != nil {
+		t.Fatalf("start binary: %v", err)
+	}
+	t.Cleanup(func() {
+		if cmd.Process != nil {
+			_ = cmd.Process.Kill()
+			_ = cmd.Wait()
+		}
+		if t.Failed() {
+			t.Logf("binary stdout:\n%s", stdout.String())
+			t.Logf("binary stderr:\n%s", stderr.String())
+		}
+	})
+
+	deadline := time.Now().Add(bootProbeTimeout)
+	for time.Now().Before(deadline) {
+		resp, err := http.Get(url + "/v1/health")
+		if err == nil {
+			_ = resp.Body.Close()
+			if resp.StatusCode == 200 {
+				return cmd, url
+			}
+		}
+		// Bail early if the binary already exited.
+		if cmd.ProcessState != nil && cmd.ProcessState.Exited() {
+			t.Fatalf("binary exited during boot: stderr:\n%s", stderr.String())
+		}
+		time.Sleep(bootProbeStep)
+	}
+	t.Fatalf("binary did not become ready within %v", bootProbeTimeout)
+	return nil, ""
+}
+
+func migrationsDirForTest(t *testing.T) string {
+	t.Helper()
+	_, thisFile, _, _ := runtime.Caller(0)
+	return filepath.Join(filepath.Dir(thisFile), "migrations")
+}
+
+// TestE2E_BootAndHealth: build + start the real binary, hit /v1/health,
+// confirm capabilities match what the built-in plugin declares. Catches
+// "binary doesn't start" / "wrong env var name" / "panics on first
+// request" classes that in-process tests miss.
+func TestE2E_BootAndHealth(t *testing.T) {
+	dsn := requireE2EDB(t)
+	binary := buildBinary(t)
+	_, url := startBinary(t, binary, dsn, "127.0.0.1:19100")
+	cl := mclient.New(mclient.Config{BaseURL: url})
+
+	hr, err := cl.Boot(context.Background())
+	if err != nil {
+		t.Fatalf("Boot: %v", err)
+	}
+	if hr.Status != "ok" {
+		t.Errorf("status = %q", hr.Status)
+	}
+	wantCaps := map[string]bool{"fts": true, "embedding": true, "ttl": true, "pin": true, "propagation": true}
+	gotCaps := map[string]bool{}
+	for _, c := range hr.Capabilities {
+		gotCaps[c] = true
+	}
+	for c := range wantCaps {
+		if !gotCaps[c] {
+			t.Errorf("capability %q missing — built-in plugin should declare all 5", c)
+		}
+	}
+}
+
+// TestE2E_FullCommitSearchForgetRoundTrip: the full agent flow against
+// real postgres + real HTTP. Catches wire-format regressions (the
+// pq.Array bug we hit during PR-3 development) and contract-level
+// drift between Go bindings and the spec.
+func TestE2E_FullCommitSearchForgetRoundTrip(t *testing.T) {
+	dsn := requireE2EDB(t)
+	binary := buildBinary(t)
+	_, url := startBinary(t, binary, dsn, "127.0.0.1:19101")
+	cl := mclient.New(mclient.Config{BaseURL: url})
+
+	ctx := context.Background()
+	ns := fmt.Sprintf("workspace:e2e-%d", time.Now().UnixNano())
+
+	// 1. Upsert namespace.
+	if _, err := cl.UpsertNamespace(ctx, ns, contract.NamespaceUpsert{Kind: contract.NamespaceKindWorkspace}); err != nil {
+		t.Fatalf("UpsertNamespace: %v", err)
+	}
+	t.Cleanup(func() { _ = cl.DeleteNamespace(context.Background(), ns) })
+
+	// 2. Commit a memory.
+	resp, err := cl.CommitMemory(ctx, ns, contract.MemoryWrite{
+		Content: "user prefers tabs over spaces",
+		Kind:    contract.MemoryKindFact,
+		Source:  contract.MemorySourceAgent,
+	})
+	if err != nil {
+		t.Fatalf("CommitMemory: %v", err)
+	}
+	if resp.ID == "" {
+		t.Fatal("plugin returned empty memory id")
+	}
+
+	// 3. Search and find the memory we just wrote.
+	sresp, err := cl.Search(ctx, contract.SearchRequest{Namespaces: []string{ns}, Query: "tabs"})
+	if err != nil {
+		t.Fatalf("Search: %v", err)
+	}
+	if len(sresp.Memories) == 0 {
+		t.Errorf("Search returned 0 memories, want at least 1")
+	}
+	found := false
+	for _, m := range sresp.Memories {
+		if m.ID == resp.ID && m.Content == "user prefers tabs over spaces" {
+			found = true
+			break
+		}
+	}
+	if !found {
+		got, _ := json.Marshal(sresp.Memories)
+		t.Errorf("committed memory not found in search results: %s", got)
+	}
+
+	// 4. Forget the memory.
+	if err := cl.ForgetMemory(ctx, resp.ID, contract.ForgetRequest{RequestedByNamespace: ns}); err != nil {
+		t.Fatalf("ForgetMemory: %v", err)
+	}
+
+	// 5. Search again — gone.
+	sresp, err = cl.Search(ctx, contract.SearchRequest{Namespaces: []string{ns}, Query: "tabs"})
+	if err != nil {
+		t.Fatalf("Search after forget: %v", err)
+	}
+	for _, m := range sresp.Memories {
+		if m.ID == resp.ID {
+			t.Errorf("forgotten memory still in search results")
+		}
+	}
+}
+
+// TestE2E_IdempotencyKey covers the C1 fix end-to-end: same id passed
+// twice should upsert (one row, updated content), not duplicate.
+func TestE2E_IdempotencyKey(t *testing.T) {
+	dsn := requireE2EDB(t)
+	binary := buildBinary(t)
+	_, url := startBinary(t, binary, dsn, "127.0.0.1:19102")
+	cl := mclient.New(mclient.Config{BaseURL: url})
+
+	ctx := context.Background()
+	ns := fmt.Sprintf("workspace:e2e-idem-%d", time.Now().UnixNano())
+	if _, err := cl.UpsertNamespace(ctx, ns, contract.NamespaceUpsert{Kind: contract.NamespaceKindWorkspace}); err != nil {
+		t.Fatalf("UpsertNamespace: %v", err)
+	}
+	t.Cleanup(func() { _ = cl.DeleteNamespace(context.Background(), ns) })
+
+	fixedID := "11111111-2222-3333-4444-555555555555"
+	for i, content := range []string{"first version", "second version (updated)"} {
+		if _, err := cl.CommitMemory(ctx, ns, contract.MemoryWrite{
+			ID:      fixedID,
+			Content: content,
+			Kind:    contract.MemoryKindFact,
+			Source:  contract.MemorySourceAgent,
+		}); err != nil {
+			t.Fatalf("commit %d: %v", i, err)
+		}
+	}
+
+	sresp, err := cl.Search(ctx, contract.SearchRequest{Namespaces: []string{ns}})
+	if err != nil {
+		t.Fatalf("Search: %v", err)
+	}
+	matches := 0
+	for _, m := range sresp.Memories {
+		if m.ID == fixedID {
+			matches++
+			if m.Content != "second version (updated)" {
+				t.Errorf("upsert did not update content: got %q", m.Content)
+			}
+		}
+	}
+	if matches != 1 {
+		t.Errorf("upsert produced %d rows for id=%s, want 1", matches, fixedID)
+	}
+}