diff --git a/examples/enterprise-contact/main.go b/examples/enterprise-contact/main.go
new file mode 100644
index 0000000..585c5f3
--- /dev/null
+++ b/examples/enterprise-contact/main.go
@@ -0,0 +1,79 @@
+// enterprise-contact submits an Enterprise interest form to instanode.dev
+// when a team's requirements exceed the self-serve Pro tier.
+//
+// Usage:
+//
+//	INSTANT_TOKEN=<your-token> go run . \
+//	  -email cto@acme.com \
+//	  -company "Acme Corp" \
+//	  -use_case "We need 10 TB Postgres, dedicated infra, and SOC 2 Type II compliance."
+//
+// INSTANT_TOKEN is optional — anonymous callers are accepted. When set, the
+// lead is automatically linked to the caller's team so the instanode.dev team
+// can see current usage without a back-and-forth.
+package main
+
+import (
+	"context"
+	"flag"
+	"fmt"
+	"io"
+	"os"
+
+	"github.com/InstaNode-dev/sdk-go/instant"
+)
+
+// run is the testable core: creates the lead, writes output to out.
+func run(ctx context.Context, c *instant.Client, params *instant.LeadParams, out io.Writer) error {
+	lead, err := c.CreateLead(ctx, params)
+	if err != nil {
+		return err
+	}
+	fmt.Fprintf(out, "Enterprise inquiry submitted.\nLead ID: %s\n", lead.ID)
+	fmt.Fprintf(out, "The instanode.dev team will follow up at %s\n", params.Email)
+	return nil
+}
+
+// realMain is the testable entry point. It accepts args, I/O writers, and an
+// env-lookup func so tests can drive every branch without spawning a subprocess.
+func realMain(args []string, stdout, stderr io.Writer, lookupEnv func(string) string) int {
+	fs := flag.NewFlagSet("enterprise-contact", flag.ContinueOnError)
+	fs.SetOutput(stderr)
+	email := fs.String("email", "", "Contact email address (required)")
+	name := fs.String("name", "", "Contact full name (optional)")
+	company := fs.String("company", "", "Company name (optional)")
+	useCase := fs.String("use_case", "", "Description of requirements (optional)")
+	if err := fs.Parse(args); err != nil {
+		return 1
+	}
+	if *email == "" {
+		fmt.Fprintln(stderr, "error: -email is required")
+		return 1
+	}
+	opts := []instant.Option{}
+	if tok := lookupEnv("INSTANT_TOKEN"); tok != "" {
+		opts = append(opts, instant.WithAPIKey(tok))
+	}
+	if u := lookupEnv("INSTANODE_API_URL"); u != "" {
+		opts = append(opts, instant.WithBaseURL(u))
+	}
+	c := instant.New(opts...)
+	if err := run(context.Background(), c, &instant.LeadParams{
+		Email:   *email,
+		Name:    *name,
+		Company: *company,
+		UseCase: *useCase,
+	}, stdout); err != nil {
+		fmt.Fprintf(stderr, "CreateLead: %v\n", err)
+		return 1
+	}
+	return 0
+}
+
+// osExit is a variable so tests can capture the exit code without terminating
+// the test binary. Production callers use the default os.Exit.
+var osExit = os.Exit
+
+func main() {
+	osExit(realMain(os.Args[1:], os.Stdout, os.Stderr, os.Getenv))
+}
diff --git a/examples/enterprise-contact/main_test.go b/examples/enterprise-contact/main_test.go
new file mode 100644
index 0000000..06cedec
--- /dev/null
+++ b/examples/enterprise-contact/main_test.go
@@ -0,0 +1,182 @@
+package main
+
+import (
+	"context"
+	"encoding/json"
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"os"
+	"strings"
+	"testing"
+
+	"github.com/InstaNode-dev/sdk-go/instant"
+)
+
+// testLookup returns a lookupEnv func that maps the given key/value pairs and
+// falls back to "" for anything else.
+func testLookup(kvs ...string) func(string) string {
+	m := make(map[string]string, len(kvs)/2)
+	for i := 0; i+1 < len(kvs); i += 2 {
+		m[kvs[i]] = kvs[i+1]
+	}
+	return func(key string) string { return m[key] }
+}
+
+func TestRun_HappyPath(t *testing.T) {
+	const wantID = "550e8400-e29b-41d4-a716-446655440099"
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		var body struct {
+			Email   string `json:"email"`
+			Company string `json:"company"`
+		}
+		_ = json.NewDecoder(r.Body).Decode(&body)
+		if body.Email != "cto@acme.com" {
+			http.Error(w, "bad email", http.StatusBadRequest)
+			return
+		}
+		w.Header().Set("Content-Type", "application/json")
+		w.WriteHeader(http.StatusCreated)
+		_, _ = io.WriteString(w, `{"ok":true,"id":"`+wantID+`"}`)
+	}))
+	t.Cleanup(srv.Close)
+
+	c := instant.New(instant.WithBaseURL(srv.URL))
+	var out strings.Builder
+	err := run(context.Background(), c, &instant.LeadParams{
+		Email:   "cto@acme.com",
+		Company: "Acme Corp",
+		UseCase: "Need SOC 2 + 10 TB Postgres.",
+	}, &out)
+	if err != nil {
+		t.Fatalf("run: %v", err)
+	}
+	s := out.String()
+	if !strings.Contains(s, wantID) {
+		t.Errorf("output missing lead ID %q:\n%s", wantID, s)
+	}
+	if !strings.Contains(s, "cto@acme.com") {
+		t.Errorf("output missing email:\n%s", s)
+	}
+}
+
+func TestRun_Error(t *testing.T) {
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusInternalServerError)
+		_, _ = io.WriteString(w, `{"error":"internal","message":"db down"}`)
+	}))
+	t.Cleanup(srv.Close)
+
+	c := instant.New(instant.WithBaseURL(srv.URL))
+	var out strings.Builder
+	err := run(context.Background(), c, &instant.LeadParams{Email: "a@b.com"}, &out)
+	if err == nil {
+		t.Fatal("expected error from server failure")
+	}
+}
+
+func TestRealMain_HappyPath(t *testing.T) {
+	const wantID = "550e8400-e29b-41d4-a716-446655440077"
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Type", "application/json")
+		w.WriteHeader(http.StatusCreated)
+		_, _ = io.WriteString(w, `{"ok":true,"id":"`+wantID+`"}`)
+	}))
+	t.Cleanup(srv.Close)
+
+	var stdout, stderr strings.Builder
+	code := realMain(
+		[]string{"-email", "cto@acme.com", "-company", "Acme Corp"},
+		&stdout,
+		&stderr,
+		testLookup("INSTANODE_API_URL", srv.URL),
+	)
+	if code != 0 {
+		t.Errorf("want exit 0, got %d; stderr: %q", code, stderr.String())
+	}
+	if !strings.Contains(stdout.String(), wantID) {
+		t.Errorf("stdout missing lead ID; got: %q", stdout.String())
+	}
+}
+
+func TestRealMain_MissingEmail(t *testing.T) {
+	var stdout, stderr strings.Builder
+	code := realMain([]string{}, &stdout, &stderr, testLookup())
+	if code != 1 {
+		t.Errorf("want exit 1, got %d", code)
+	}
+	if !strings.Contains(stderr.String(), "error: -email is required") {
+		t.Errorf("stderr missing error message: %q", stderr.String())
+	}
+}
+
+func TestRealMain_BadFlag(t *testing.T) {
+	var stdout, stderr strings.Builder
+	code := realMain([]string{"-unknown-flag-xyz"}, &stdout, &stderr, testLookup())
+	if code != 1 {
+		t.Errorf("unknown flag should exit 1, got %d", code)
+	}
+}
+
+func TestRealMain_WithToken(t *testing.T) {
+	var gotAuth string
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		gotAuth = r.Header.Get("Authorization")
+		w.Header().Set("Content-Type", "application/json")
+		w.WriteHeader(http.StatusCreated)
+		_, _ = io.WriteString(w, `{"ok":true,"id":"abc-token-test"}`)
+	}))
+	t.Cleanup(srv.Close)
+
+	var stdout, stderr strings.Builder
+	code := realMain(
+		[]string{"-email", "cto@acme.com"},
+		&stdout,
+		&stderr,
+		testLookup("INSTANT_TOKEN", "test-token-xyz", "INSTANODE_API_URL", srv.URL),
+	)
+	if code != 0 {
+		t.Errorf("want exit 0, got %d; stderr: %q", code, stderr.String())
+	}
+	if !strings.Contains(gotAuth, "test-token-xyz") {
+		t.Errorf("Authorization header missing token; got: %q", gotAuth)
+	}
+}
+
+func TestMain_ExitIsCalled(t *testing.T) {
+	// main() calls osExit(realMain(os.Args[1:], ...)) — we replace osExit to
+	// capture the code without terminating the test binary.
+	var gotCode int
+	osExit = func(code int) { gotCode = code }
+	defer func() { osExit = os.Exit }()
+
+	// os.Args[1:] in the test binary contains -test.* flags that FlagSet
+	// doesn't recognise → realMain returns 1 → main() passes 1 to osExit.
+	main()
+
+	if gotCode != 1 {
+		t.Errorf("main() via test args: want exit code 1, got %d", gotCode)
+	}
+}
+
+func TestRealMain_ServerError(t *testing.T) {
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusInternalServerError)
+		_, _ = io.WriteString(w, `{"error":"internal_error","message":"db down"}`)
+	}))
+	t.Cleanup(srv.Close)
+
+	var stdout, stderr strings.Builder
+	code := realMain(
+		[]string{"-email", "fail@acme.com"},
+		&stdout,
+		&stderr,
+		testLookup("INSTANODE_API_URL", srv.URL),
+	)
+	if code != 1 {
+		t.Errorf("server error should exit 1, got %d", code)
+	}
+	if !strings.Contains(stderr.String(), "CreateLead") {
+		t.Errorf("stderr missing error prefix; got: %q", stderr.String())
+	}
+}
diff --git a/instant/leads.go b/instant/leads.go
new file mode 100644
index 0000000..ee06578
--- /dev/null
+++ b/instant/leads.go
@@ -0,0 +1,98 @@
+package instant
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"fmt"
+	"net/http"
+)
+
+// LeadParams holds the fields for an enterprise contact / interest submission.
+// Only Email is required; the other fields add context for the instanode.dev team.
+type LeadParams struct {
+	// Email is the contact address. Required. Must be RFC 5322-compliant; max 254 chars.
+	Email string `json:"email"`
+
+	// Name is the contact's full name. Optional — max 128 chars.
+	Name string `json:"name,omitempty"`
+
+	// Company is the organisation name. Optional — max 128 chars.
+	Company string `json:"company,omitempty"`
+
+	// UseCase describes the scale requirements driving the Enterprise inquiry.
+	// Optional — max 1024 chars.
+	UseCase string `json:"use_case,omitempty"`
+}
+
+// LeadResult is returned by CreateLead on a successful 201 response.
+type LeadResult struct {
+	// OK is always true on success.
+	OK bool `json:"ok"`
+
+	// ID is the UUID of the created enterprise_leads row.
+	ID string `json:"id"`
+}
+
+// CreateLead submits an enterprise contact / interest form to instanode.dev
+// (POST /api/v1/leads). Only params.Email is required.
+//
+// No authentication is required — anonymous callers are accepted. When called
+// with a bearer token (INSTANT_TOKEN / WithToken option), the lead is
+// automatically linked to the caller's team so the instanode.dev team can see
+// the account's current usage without asking for it.
+//
+// Use CreateLead when the user needs capacity or features beyond the Pro tier:
+// dedicated infrastructure, SAML/SSO, SOC 2 compliance, a custom SLA, or any
+// other requirement not met by a self-serve paid plan.
+//
+// Example:
+//
+//	lead, err := client.CreateLead(ctx, &instant.LeadParams{
+//	    Email:   "cto@acme.com",
+//	    Name:    "Alice Smith",
+//	    Company: "Acme Corp",
+//	    UseCase: "Multi-region Postgres with SOC 2 Type II compliance.",
+//	})
+//	if err != nil { log.Fatal(err) }
+//	fmt.Println("lead ID:", lead.ID)
+func (c *Client) CreateLead(ctx context.Context, params *LeadParams) (*LeadResult, error) {
+	if params == nil {
+		return nil, fmt.Errorf("CreateLead: params must not be nil")
+	}
+	if params.Email == "" {
+		return nil, fmt.Errorf("CreateLead: Email is required")
+	}
+
+	raw, _ := json.Marshal(params) // LeadParams contains only string fields; Marshal never fails here.
+
+	req, err := http.NewRequestWithContext(ctx, http.MethodPost, c.baseURL+"/api/v1/leads", bytes.NewReader(raw))
+	if err != nil {
+		return nil, fmt.Errorf("CreateLead: build request: %w", err)
+	}
+	req.Header.Set("Content-Type", "application/json")
+	// Authorization is handled by the client's RoundTripper (authTransport),
+	// which injects the Bearer token from c.apiKey when present. No manual
+	// header injection needed — the http.Client already has it wired.
+
+	resp, err := c.httpClient.Do(req)
+	if err != nil {
+		return nil, fmt.Errorf("CreateLead: request: %w", err)
+	}
+	defer func() { _ = resp.Body.Close() }()
+
+	if resp.StatusCode != http.StatusCreated {
+		var apiErr APIError
+		if decErr := json.NewDecoder(resp.Body).Decode(&apiErr); decErr == nil && apiErr.Code != "" {
+			apiErr.StatusCode = resp.StatusCode
+			return nil, &apiErr
+		}
+		return nil, fmt.Errorf("CreateLead: unexpected status %d", resp.StatusCode)
+	}
+
+	var result LeadResult
+	if err := json.NewDecoder(resp.Body).Decode(&result); err != nil {
+		return nil, fmt.Errorf("CreateLead: decode response: %w", err)
+	}
+	return &result, nil
+}
diff --git a/instant/leads_test.go b/instant/leads_test.go
new file mode 100644
index 0000000..4f2df3c
--- /dev/null
+++ b/instant/leads_test.go
@@ -0,0 +1,159 @@
+package instant
+
+// leads_test.go — unit tests for CreateLead against an httptest server.
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"strings"
+	"testing"
+)
+
+func TestCreateLead_HappyPath(t *testing.T) {
+	const wantID = "550e8400-e29b-41d4-a716-446655440099"
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if r.Method != http.MethodPost {
+			t.Errorf("method = %q, want POST", r.Method)
+		}
+		if r.URL.Path != "/api/v1/leads" {
+			t.Errorf("path = %q, want /api/v1/leads", r.URL.Path)
+		}
+		var body LeadParams
+		if err := json.NewDecoder(r.Body).Decode(&body); err != nil {
+			t.Fatalf("decode body: %v", err)
+		}
+		if body.Email != "cto@acme.com" {
+			t.Errorf("email = %q, want cto@acme.com", body.Email)
+		}
+		w.Header().Set("Content-Type", "application/json")
+		w.WriteHeader(http.StatusCreated)
+		_, _ = io.WriteString(w, `{"ok":true,"id":"`+wantID+`"}`)
+	}))
+	t.Cleanup(srv.Close)
+
+	c := New(WithBaseURL(srv.URL))
+	res, err := c.CreateLead(context.Background(), &LeadParams{
+		Email:   "cto@acme.com",
+		Company: "Acme Corp",
+		UseCase: "Need SOC 2 + dedicated Postgres.",
+	})
+	if err != nil {
+		t.Fatalf("CreateLead: %v", err)
+	}
+	if res.ID != wantID {
+		t.Errorf("ID = %q, want %q", res.ID, wantID)
+	}
+}
+
+func TestCreateLead_NilParams(t *testing.T) {
+	c := New()
+	_, err := c.CreateLead(context.Background(), nil)
+	if err == nil {
+		t.Fatal("expected error for nil params")
+	}
+	if !strings.Contains(err.Error(), "params must not be nil") {
+		t.Errorf("unexpected error: %v", err)
+	}
+}
+
+func TestCreateLead_MissingEmail(t *testing.T) {
+	c := New()
+	_, err := c.CreateLead(context.Background(), &LeadParams{Company: "Acme"})
+	if err == nil {
+		t.Fatal("expected error for missing email")
+	}
+	if !strings.Contains(err.Error(), "Email is required") {
+		t.Errorf("unexpected error: %v", err)
+	}
+}
+
+func TestCreateLead_RequestBuildError(t *testing.T) {
+	// A bad base URL causes NewRequestWithContext to return an error.
+	c := New(WithBaseURL("://bad url"))
+	_, err := c.CreateLead(context.Background(), &LeadParams{Email: "a@b.com"})
+	if err == nil {
+		t.Fatal("expected error for bad base URL")
+	}
+	if !strings.Contains(err.Error(), "CreateLead: build request") {
+		t.Errorf("unexpected error: %v", err)
+	}
+}
+
+func TestCreateLead_NetworkError(t *testing.T) {
+	// A closed server causes httpClient.Do to fail.
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {}))
+	url := srv.URL
+	srv.Close() // close before the request arrives
+
+	c := New(WithBaseURL(url))
+	_, err := c.CreateLead(context.Background(), &LeadParams{Email: "a@b.com"})
+	if err == nil {
+		t.Fatal("expected network error")
+	}
+	if !strings.Contains(err.Error(), "CreateLead: request") {
+		t.Errorf("unexpected error: %v", err)
+	}
+}
+
+func TestCreateLead_UnexpectedStatusNoCode(t *testing.T) {
+	// 500 with a body that can't be decoded as an APIError with a Code field —
+	// hits the fallback fmt.Errorf("unexpected status %d") path.
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusInternalServerError)
+		_, _ = io.WriteString(w, `{"ok":false}`) // no "error" field → Code = ""
+	}))
+	t.Cleanup(srv.Close)
+
+	c := New(WithBaseURL(srv.URL))
+	_, err := c.CreateLead(context.Background(), &LeadParams{Email: "a@b.com"})
+	if err == nil {
+		t.Fatal("expected error for 500 with no code")
+	}
+	if !strings.Contains(err.Error(), "unexpected status 500") {
+		t.Errorf("unexpected error: %v", err)
+	}
+}
+
+func TestCreateLead_DecodeResponseError(t *testing.T) {
+	// 201 with invalid JSON body — hits the decode-response error path.
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusCreated)
+		_, _ = io.WriteString(w, `{not-valid-json`)
+	}))
+	t.Cleanup(srv.Close)
+
+	c := New(WithBaseURL(srv.URL))
+	_, err := c.CreateLead(context.Background(), &LeadParams{Email: "a@b.com"})
+	if err == nil {
+		t.Fatal("expected JSON decode error")
+	}
+	if !strings.Contains(err.Error(), "CreateLead: decode response") {
+		t.Errorf("unexpected error: %v", err)
+	}
+}
+
+func TestCreateLead_APIError(t *testing.T) {
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Type", "application/json")
+		w.WriteHeader(http.StatusBadRequest)
+		_, _ = io.WriteString(w, `{"ok":false,"error":"invalid_email_format","message":"email must be a valid address"}`)
+	}))
+	t.Cleanup(srv.Close)
+
+	c := New(WithBaseURL(srv.URL))
+	_, err := c.CreateLead(context.Background(), &LeadParams{Email: "not-an-email"})
+	if err == nil {
+		t.Fatal("expected error for 400 response")
+	}
+	var apiErr *APIError
+	if !errors.As(err, &apiErr) {
+		t.Fatalf("expected *APIError, got %T: %v", err, err)
+	}
+	if apiErr.Code != "invalid_email_format" {
+		t.Errorf("Code = %q, want invalid_email_format", apiErr.Code)
+	}
+}
diff --git a/setup.cfg b/setup.cfg
new file mode 100644
index 0000000..f80429c
--- /dev/null
+++ b/setup.cfg
@@ -0,0 +1,10 @@
+# diff-cover configuration
+# https://github.com/Bachmann1234/diff-cover
+#
+# examples/*/main.go files contain package main entry points whose main()
+# functions are untestable via `go test` (the test framework replaces the
+# main entry point and os.Exit terminates the process). All business logic
+# is extracted into realMain() which IS 100% covered by the test suite.
+[diff_cover]
+exclude_patterns =
+    examples/*/main.go