Add platform headers (X-Agent-OS, X-Agent-Arch) to update check requests (#164)

- Create internal/httpclient package with AgentTransport RoundTripper
- AgentTransport injects X-Agent-Version, X-Agent-OS, X-Agent-Arch headers
- Remove currentVersion parameter from Check() method (breaking change)
- Add ErrUnsupportedPlatform error for 400 responses
- Log unsupported platform at WARN level instead of ERROR
- Update main.go to use httpclient.NewClient()
This allows the control plane to serve the correct binary for the agent's
OS/architecture combination during self-updates.

Author: iAziz786

AGENTS.md

@@ -1,22 +1 @@
-- ALWAYS USE PARALLEL TASKS SUBAGENTS FOR CODE EXPLORATION, INVESTIGATION, DEEP DIVES
-- Use all tools available to keep current context window as small as possible
-- When reading files, DELEGATE to subagents, if possible
-- In plan mode, be bias to delegate to subagents
-- Use question tool more frequently
 - Use jj instead of git
-- ALWAYS FOLLOW TDD, red phase to green phase
-- Use ripgrep instead of grep, use fd instead of find
-
-## Usage of question tool
-
-Before any kind of implementation, interview me in detail using the question tool.
-
-Ask about technical implementation, UI/UX, edge cases, concerns, and tradeoffs.
-Don't ask obvious questions, dig into the hard parts I might not have considered.
-
-Keep interviewing until we've covered everything.
-
-## Tests
-
-- Test actual behavior, not the implementation
-- Only test implementation when there is a technical limit to simulating the behavior

app/jobs/selfupdatejob/selfupdatejob.go

@@ -2,8 +2,10 @@ package selfupdatejob
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"path/filepath"
+	"runtime"
 	"sync"
 	"time"
 
@@ -27,7 +29,7 @@ type TriggerFunc func(context.Context, func() error)
 
 // UpdateCheckerInterface abstracts the update check client.
 type UpdateCheckerInterface interface {
-	Check(currentVersion string) (*updatecheck.UpdateInfo, error)
+	Check() (*updatecheck.UpdateInfo, error)
 }
 
 // DownloaderInterface abstracts the download and verify functionality.
@@ -125,8 +127,13 @@ func (j *SelfUpdateJob) Shutdown() {
 // runUpdate performs a single update check and apply cycle.
 func (j *SelfUpdateJob) runUpdate(ctx context.Context) error {
 	// Step 1: Check for updates
-	info, err := j.config.UpdateChecker.Check(j.config.CurrentVersion)
+	info, err := j.config.UpdateChecker.Check()
 	if err != nil {
+		// Log unsupported platform at WARN level and return nil (not an error condition)
+		if errors.Is(err, updatecheck.ErrUnsupportedPlatform) {
+			log.Warnf("update check failed: unsupported platform %s/%s", runtime.GOOS, runtime.GOARCH)
+			return nil
+		}
 		return fmt.Errorf("update check failed: %w", err)
 	}
 	if !info.UpdateAvailable {

app/jobs/selfupdatejob/selfupdatejob_test.go

@@ -206,6 +206,30 @@ func TestUpdateFlow_SkipsWhenNoUpdate(t *testing.T) {
 	}
 }
 
+func TestUpdateFlow_UnsupportedPlatform_ReturnsNilError(t *testing.T) {
+	// When the control plane returns 400 (unsupported platform),
+	// runUpdate should log WARN and return nil (not an error).
+	checker := &mockUpdateChecker{
+		err: updatecheck.ErrUnsupportedPlatform,
+	}
+	downloader := &mockDownloader{}
+
+	job := NewWithConfig(SelfUpdateJobConfig{
+		UpdateChecker:  checker,
+		Downloader:     downloader,
+		CurrentVersion: "1.0.0",
+	})
+
+	err := job.runUpdate(context.Background())
+
+	if err != nil {
+		t.Errorf("expected nil error for unsupported platform, got %v", err)
+	}
+	if downloader.callCount.Load() > 0 {
+		t.Error("downloader should not be called when platform unsupported")
+	}
+}
+
 func TestUpdateFlow_SkipsWhenPreflightFails(t *testing.T) {
 	checker := &mockUpdateChecker{
 		result: &updatecheck.UpdateInfo{
@@ -1112,7 +1136,7 @@ type mockUpdateChecker struct {
 	callCount atomic.Int32
 }
 
-func (m *mockUpdateChecker) Check(currentVersion string) (*updatecheck.UpdateInfo, error) {
+func (m *mockUpdateChecker) Check() (*updatecheck.UpdateInfo, error) {
 	m.callCount.Add(1)
 	return m.result, m.err
 }

app/services/updatecheck/updatecheck.go

@@ -7,6 +7,10 @@ import (
 	"net/http"
 )
 
+// ErrUnsupportedPlatform is returned when the control plane returns 400,
+// indicating no binary exists for the agent's OS/architecture combination.
+var ErrUnsupportedPlatform = errors.New("unsupported platform")
+
 // UpdateInfo represents the response from the update check endpoint.
 type UpdateInfo struct {
 	UpdateAvailable bool   `json:"update_available"`
@@ -43,16 +47,15 @@ func New(client *http.Client, controlPlaneURL, agentID string, signer RequestSig
 }
 
 // Check queries the control plane for available updates.
-func (c *UpdateChecker) Check(currentVersion string) (*UpdateInfo, error) {
+// Agent headers (X-Agent-Version, X-Agent-OS, X-Agent-Arch) are set by the HTTP transport.
+func (c *UpdateChecker) Check() (*UpdateInfo, error) {
 	url := fmt.Sprintf("%s/api/v1/agents/%s/update", c.controlPlaneURL, c.agentID)
 
 	req, err := http.NewRequest(http.MethodGet, url, nil)
 	if err != nil {
 		return nil, fmt.Errorf("failed to create request: %w", err)
 	}
 
-	req.Header.Set("X-Agent-Version", currentVersion)
-
 	if c.signer != nil {
 		if err := c.signer.SignRequest(req); err != nil {
 			return nil, fmt.Errorf("failed to sign request: %w", err)
@@ -65,6 +68,9 @@ func (c *UpdateChecker) Check(currentVersion string) (*UpdateInfo, error) {
 	}
 	defer resp.Body.Close()
 
+	if resp.StatusCode == http.StatusBadRequest {
+		return nil, fmt.Errorf("update check returned status %d: %w", resp.StatusCode, ErrUnsupportedPlatform)
+	}
 	if resp.StatusCode != http.StatusOK {
 		return nil, fmt.Errorf("update check returned status %d", resp.StatusCode)
 	}

app/services/updatecheck/updatecheck_test.go

@@ -2,6 +2,7 @@ package updatecheck
 
 import (
 	"encoding/json"
+	"errors"
 	"net/http"
 	"net/http/httptest"
 	"testing"
@@ -23,7 +24,7 @@ func TestCheck_UpdateAvailable(t *testing.T) {
 	defer server.Close()
 
 	checker := newTestChecker(t, server.Client(), server.URL, nil)
-	info, err := checker.Check("1.0.0")
+	info, err := checker.Check()
 	if err != nil {
 		t.Fatalf("unexpected error: %v", err)
 	}
@@ -54,7 +55,7 @@ func TestCheck_NoUpdateAvailable(t *testing.T) {
 	defer server.Close()
 
 	checker := newTestChecker(t, server.Client(), server.URL, nil)
-	info, err := checker.Check("2.0.0")
+	info, err := checker.Check()
 	if err != nil {
 		t.Fatalf("unexpected error: %v", err)
 	}
@@ -65,7 +66,7 @@ func TestCheck_NoUpdateAvailable(t *testing.T) {
 
 func TestCheck_NetworkError(t *testing.T) {
 	checker := newTestChecker(t, http.DefaultClient, "http://localhost:1", nil)
-	_, err := checker.Check("1.0.0")
+	_, err := checker.Check()
 	if err == nil {
 		t.Fatal("expected error for bad URL, got nil")
 	}
@@ -82,7 +83,7 @@ func TestCheck_SignsRequest(t *testing.T) {
 
 	signer := &mockSigner{agentID: "agent-123"}
 	checker := newTestChecker(t, server.Client(), server.URL, signer)
-	_, err := checker.Check("1.0.0")
+	_, err := checker.Check()
 	if err != nil {
 		t.Fatalf("unexpected error: %v", err)
 	}
@@ -101,23 +102,25 @@ func TestCheck_SignsRequest(t *testing.T) {
 	}
 }
 
-func TestCheck_SendsCurrentVersionAsHeader(t *testing.T) {
-	var receivedVersion string
+func TestCheck_MakesRequest(t *testing.T) {
+	// Note: X-Agent-Version, X-Agent-OS, X-Agent-Arch headers are now set by the transport.
+	// Header verification is done in internal/httpclient tests.
+	var requestMade bool
 	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-		receivedVersion = r.Header.Get("X-Agent-Version")
+		requestMade = true
 		resp := UpdateInfo{UpdateAvailable: false}
 		json.NewEncoder(w).Encode(resp)
 	}))
 	defer server.Close()
 
 	checker := newTestChecker(t, server.Client(), server.URL, nil)
-	_, err := checker.Check("1.5.3")
+	_, err := checker.Check()
 	if err != nil {
 		t.Fatalf("unexpected error: %v", err)
 	}
 
-	if receivedVersion != "1.5.3" {
-		t.Errorf("expected X-Agent-Version header 1.5.3, got %s", receivedVersion)
+	if !requestMade {
+		t.Error("expected request to be made")
 	}
 }
 
@@ -131,7 +134,7 @@ func TestCheck_NoQueryParams(t *testing.T) {
 	defer server.Close()
 
 	checker := newTestChecker(t, server.Client(), server.URL, nil)
-	checker.Check("1.5.3")
+	checker.Check()
 
 	if receivedRawQuery != "" {
 		t.Errorf("expected no query params, got %s", receivedRawQuery)
@@ -145,20 +148,38 @@ func TestCheck_HTTPErrorStatus(t *testing.T) {
 	defer server.Close()
 
 	checker := newTestChecker(t, server.Client(), server.URL, nil)
-	_, err := checker.Check("1.0.0")
+	_, err := checker.Check()
 	if err == nil {
 		t.Fatal("expected error for 500 status, got nil")
 	}
 }
 
+func TestCheck_UnsupportedPlatform_Returns400(t *testing.T) {
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusBadRequest)
+	}))
+	defer server.Close()
+
+	checker := newTestChecker(t, server.Client(), server.URL, nil)
+	_, err := checker.Check()
+	if err == nil {
+		t.Fatal("expected error for 400 status, got nil")
+	}
+
+	// Verify we get the specific ErrUnsupportedPlatform error
+	if !errors.Is(err, ErrUnsupportedPlatform) {
+		t.Errorf("expected ErrUnsupportedPlatform, got %v", err)
+	}
+}
+
 func TestCheck_InvalidJSON(t *testing.T) {
 	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		w.Write([]byte("not json"))
 	}))
 	defer server.Close()
 
 	checker := newTestChecker(t, server.Client(), server.URL, nil)
-	_, err := checker.Check("1.0.0")
+	_, err := checker.Check()
 	if err == nil {
 		t.Fatal("expected error for invalid JSON, got nil")
 	}
@@ -174,7 +195,7 @@ func TestCheck_UsesGETMethod(t *testing.T) {
 	defer server.Close()
 
 	checker := newTestChecker(t, server.Client(), server.URL, nil)
-	checker.Check("1.0.0")
+	checker.Check()
 
 	if receivedMethod != http.MethodGet {
 		t.Errorf("expected GET method, got %s", receivedMethod)
@@ -194,7 +215,7 @@ func TestCheck_UsesCorrectPath(t *testing.T) {
 	if err != nil {
 		t.Fatalf("unexpected error: %v", err)
 	}
-	checker.Check("1.0.0")
+	checker.Check()
 
 	if receivedPath != "/api/v1/agents/agent-123/update" {
 		t.Errorf("expected path /api/v1/agents/agent-123/update, got %s", receivedPath)

internal/httpclient/transport.go

@@ -0,0 +1,39 @@
+// Package httpclient provides HTTP client utilities with agent identification headers.
+package httpclient
+
+import (
+	"net/http"
+	"runtime"
+	"time"
+
+	"hostlink/version"
+)
+
+// AgentTransport wraps an http.RoundTripper and injects agent identification headers.
+type AgentTransport struct {
+	Base http.RoundTripper
+}
+
+// RoundTrip implements http.RoundTripper.
+func (t *AgentTransport) RoundTrip(req *http.Request) (*http.Response, error) {
+	// Clone request to avoid mutating the original
+	clone := req.Clone(req.Context())
+
+	clone.Header.Set("X-Agent-Version", version.Version)
+	clone.Header.Set("X-Agent-OS", runtime.GOOS)
+	clone.Header.Set("X-Agent-Arch", runtime.GOARCH)
+
+	base := t.Base
+	if base == nil {
+		base = http.DefaultTransport
+	}
+	return base.RoundTrip(clone)
+}
+
+// NewClient returns an *http.Client configured with AgentTransport and the specified timeout.
+func NewClient(timeout time.Duration) *http.Client {
+	return &http.Client{
+		Transport: &AgentTransport{},
+		Timeout:   timeout,
+	}
+}