feat: add boundary log forwarding from agent to coderd (#21345)

Add agent forwarding of boundary audit logs from workspaces to coderd
via agent API, and re-emission of boundary logs to coderd stderr. This
change adds a server to the workspace agent that always listens on a
unix socket for boundary to connect and send audit logs.

coderd log format example:
```
[API] 2025-12-23 18:31:46.755 [info] coderd.agentrpc: boundary_request owner=.. workspace_name=.. agent_name=.. decision=.. workspace_id=.. http_method=.. http_url=.. event_time=.. request_id=..
```

Corresponding boundary PR: https://github.com/coder/boundary/pull/124
RFC:
https://www.notion.so/coderhq/Agent-Boundary-Logs-2afd579be59280f29629fc9823ac41ba
https://github.com/coder/coder/issues/21280

agent/agent.go

@@ -43,6 +43,7 @@ import (
 	"github.com/coder/coder/v2/agent/agentscripts"
 	"github.com/coder/coder/v2/agent/agentsocket"
 	"github.com/coder/coder/v2/agent/agentssh"
+	"github.com/coder/coder/v2/agent/boundarylogproxy"
 	"github.com/coder/coder/v2/agent/proto"
 	"github.com/coder/coder/v2/agent/proto/resourcesmonitor"
 	"github.com/coder/coder/v2/agent/reconnectingpty"
@@ -102,6 +103,7 @@ type Options struct {
 	Clock                        quartz.Clock
 	SocketServerEnabled          bool
 	SocketPath                   string // Path for the agent socket server socket
+	BoundaryLogProxySocketPath   string
 }
 
 type Client interface {
@@ -205,10 +207,11 @@ func New(options Options) Agent {
 		metrics:            newAgentMetrics(prometheusRegistry),
 		execer:             options.Execer,
 
-		devcontainers:       options.Devcontainers,
-		containerAPIOptions: options.DevcontainerAPIOptions,
-		socketPath:          options.SocketPath,
-		socketServerEnabled: options.SocketServerEnabled,
+		devcontainers:              options.Devcontainers,
+		containerAPIOptions:        options.DevcontainerAPIOptions,
+		socketPath:                 options.SocketPath,
+		socketServerEnabled:        options.SocketServerEnabled,
+		boundaryLogProxySocketPath: options.BoundaryLogProxySocketPath,
 	}
 	// Initially, we have a closed channel, reflecting the fact that we are not initially connected.
 	// Each time we connect we replace the channel (while holding the closeMutex) with a new one
@@ -277,6 +280,11 @@ type agent struct {
 
 	logSender *agentsdk.LogSender
 
+	// boundaryLogProxy is a socket server that forwards boundary audit logs to coderd.
+	// It may be nil if there is a problem starting the server.
+	boundaryLogProxy           *boundarylogproxy.Server
+	boundaryLogProxySocketPath string
+
 	prometheusRegistry *prometheus.Registry
 	// metrics are prometheus registered metrics that will be collected and
 	// labeled in Coder with the agent + workspace.
@@ -371,6 +379,7 @@ func (a *agent) init() {
 	)
 
 	a.initSocketServer()
+	a.startBoundaryLogProxyServer()
 
 	go a.runLoop()
 }
@@ -395,6 +404,19 @@ func (a *agent) initSocketServer() {
 	a.logger.Debug(a.hardCtx, "socket server started", slog.F("path", a.socketPath))
 }
 
+// startBoundaryLogProxyServer starts the boundary log proxy socket server.
+func (a *agent) startBoundaryLogProxyServer() {
+	proxy := boundarylogproxy.NewServer(a.logger, a.boundaryLogProxySocketPath)
+	if err := proxy.Start(); err != nil {
+		a.logger.Warn(a.hardCtx, "failed to start boundary log proxy", slog.Error(err))
+		return
+	}
+
+	a.boundaryLogProxy = proxy
+	a.logger.Info(a.hardCtx, "boundary log proxy server started",
+		slog.F("socket_path", a.boundaryLogProxySocketPath))
+}
+
 // runLoop attempts to start the agent in a retry loop.
 // Coder may be offline temporarily, a connection issue
 // may be happening, but regardless after the intermittent
@@ -1012,6 +1034,15 @@ func (a *agent) run() (retErr error) {
 			return err
 		})
 
+	// Forward boundary audit logs to coderd if boundary log forwarding is enabled.
+	// These are audit logs so they should continue during graceful shutdown.
+	if a.boundaryLogProxy != nil {
+		proxyFunc := func(ctx context.Context, aAPI proto.DRPCAgentClient27) error {
+			return a.boundaryLogProxy.RunForwarder(ctx, aAPI)
+		}
+		connMan.startAgentAPI("boundary log proxy", gracefulShutdownBehaviorRemain, proxyFunc)
+	}
+
 	// part of graceful shut down is reporting the final lifecycle states, e.g "ShuttingDown" so the
 	// lifecycle reporting has to be via gracefulShutdownBehaviorRemain
 	connMan.startAgentAPI("report lifecycle", gracefulShutdownBehaviorRemain, a.reportLifecycle)
@@ -1982,6 +2013,13 @@ func (a *agent) Close() error {
 		a.logger.Error(a.hardCtx, "container API close", slog.Error(err))
 	}
 
+	if a.boundaryLogProxy != nil {
+		err = a.boundaryLogProxy.Close()
+		if err != nil {
+			a.logger.Warn(context.Background(), "close boundary log proxy", slog.Error(err))
+		}
+	}
+
 	// Wait for the graceful shutdown to complete, but don't wait forever so
 	// that we don't break user expectations.
 	go func() {

agent/boundary_logs_test.go

@@ -0,0 +1,165 @@
+//go:build linux || darwin
+
+package agent_test
+
+import (
+	"context"
+	"net"
+	"path/filepath"
+	"sync"
+	"testing"
+
+	"github.com/google/uuid"
+	"github.com/stretchr/testify/require"
+	"google.golang.org/protobuf/proto"
+	"google.golang.org/protobuf/types/known/timestamppb"
+
+	"cdr.dev/slog"
+
+	"github.com/coder/coder/v2/agent/boundarylogproxy"
+	"github.com/coder/coder/v2/agent/boundarylogproxy/codec"
+	agentproto "github.com/coder/coder/v2/agent/proto"
+	"github.com/coder/coder/v2/coderd/agentapi"
+	"github.com/coder/coder/v2/testutil"
+)
+
+// logSink captures structured log entries for testing.
+type logSink struct {
+	mu      sync.Mutex
+	entries []slog.SinkEntry
+}
+
+func (s *logSink) LogEntry(_ context.Context, e slog.SinkEntry) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	s.entries = append(s.entries, e)
+}
+
+func (*logSink) Sync() {}
+
+func (s *logSink) getEntries() []slog.SinkEntry {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	return append([]slog.SinkEntry{}, s.entries...)
+}
+
+// getField returns the value of a field by name from a slog.Map.
+func getField(fields slog.Map, name string) interface{} {
+	for _, f := range fields {
+		if f.Name == name {
+			return f.Value
+		}
+	}
+	return nil
+}
+
+func sendBoundaryLogsRequest(t *testing.T, conn net.Conn, req *agentproto.ReportBoundaryLogsRequest) {
+	t.Helper()
+
+	data, err := proto.Marshal(req)
+	require.NoError(t, err)
+
+	err = codec.WriteFrame(conn, codec.TagV1, data)
+	require.NoError(t, err)
+}
+
+// TestBoundaryLogs_EndToEnd is an end-to-end test that sends a protobuf
+// message over the agent's unix socket (as boundary would) and verifies
+// it is ultimately logged by coderd with the correct structured fields.
+func TestBoundaryLogs_EndToEnd(t *testing.T) {
+	t.Parallel()
+
+	socketPath := filepath.Join(testutil.TempDirUnixSocket(t), "boundary.sock")
+	srv := boundarylogproxy.NewServer(testutil.Logger(t), socketPath)
+
+	err := srv.Start()
+	require.NoError(t, err)
+	t.Cleanup(func() { require.NoError(t, srv.Close()) })
+
+	sink := &logSink{}
+	logger := slog.Make(sink)
+	workspaceID := uuid.New()
+	reporter := &agentapi.BoundaryLogsAPI{
+		Log:         logger,
+		WorkspaceID: workspaceID,
+	}
+
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+	forwarderDone := make(chan error, 1)
+	go func() {
+		forwarderDone <- srv.RunForwarder(ctx, reporter)
+	}()
+
+	conn, err := net.Dial("unix", socketPath)
+	require.NoError(t, err)
+	defer conn.Close()
+
+	// Allowed HTTP request.
+	req := &agentproto.ReportBoundaryLogsRequest{
+		Logs: []*agentproto.BoundaryLog{
+			{
+				Allowed: true,
+				Time:    timestamppb.Now(),
+				Resource: &agentproto.BoundaryLog_HttpRequest_{
+					HttpRequest: &agentproto.BoundaryLog_HttpRequest{
+						Method:      "GET",
+						Url:         "https://example.com/allowed",
+						MatchedRule: "*.example.com",
+					},
+				},
+			},
+		},
+	}
+	sendBoundaryLogsRequest(t, conn, req)
+
+	require.Eventually(t, func() bool {
+		return len(sink.getEntries()) >= 1
+	}, testutil.WaitShort, testutil.IntervalFast)
+
+	entries := sink.getEntries()
+	require.Len(t, entries, 1)
+	entry := entries[0]
+	require.Equal(t, slog.LevelInfo, entry.Level)
+	require.Equal(t, "boundary_request", entry.Message)
+	require.Equal(t, "allow", getField(entry.Fields, "decision"))
+	require.Equal(t, workspaceID.String(), getField(entry.Fields, "workspace_id"))
+	require.Equal(t, "GET", getField(entry.Fields, "http_method"))
+	require.Equal(t, "https://example.com/allowed", getField(entry.Fields, "http_url"))
+	require.Equal(t, "*.example.com", getField(entry.Fields, "matched_rule"))
+
+	// Denied HTTP request.
+	req2 := &agentproto.ReportBoundaryLogsRequest{
+		Logs: []*agentproto.BoundaryLog{
+			{
+				Allowed: false,
+				Time:    timestamppb.Now(),
+				Resource: &agentproto.BoundaryLog_HttpRequest_{
+					HttpRequest: &agentproto.BoundaryLog_HttpRequest{
+						Method: "POST",
+						Url:    "https://blocked.com/denied",
+					},
+				},
+			},
+		},
+	}
+	sendBoundaryLogsRequest(t, conn, req2)
+
+	require.Eventually(t, func() bool {
+		return len(sink.getEntries()) >= 2
+	}, testutil.WaitShort, testutil.IntervalFast)
+
+	entries = sink.getEntries()
+	entry = entries[1]
+	require.Len(t, entries, 2)
+	require.Equal(t, slog.LevelInfo, entry.Level)
+	require.Equal(t, "boundary_request", entry.Message)
+	require.Equal(t, "deny", getField(entry.Fields, "decision"))
+	require.Equal(t, workspaceID.String(), getField(entry.Fields, "workspace_id"))
+	require.Equal(t, "POST", getField(entry.Fields, "http_method"))
+	require.Equal(t, "https://blocked.com/denied", getField(entry.Fields, "http_url"))
+	require.Equal(t, nil, getField(entry.Fields, "matched_rule"))
+
+	cancel()
+	<-forwarderDone
+}

agent/boundarylogproxy/codec/codec.go

@@ -0,0 +1,127 @@
+// Package codec implements the wire format for agent <-> boundary communication.
+//
+// Wire Format:
+//   - 8 bits: big-endian tag
+//   - 24 bits: big-endian length of the protobuf data (bit usage depends on tag)
+//   - length bytes: encoded protobuf data
+//
+// Note that while there are 24 bits available for the length, the actual maximum
+// length depends on the tag. For TagV1, only 15 bits are used (MaxMessageSizeV1).
+package codec
+
+import (
+	"encoding/binary"
+	"io"
+
+	"golang.org/x/xerrors"
+)
+
+type Tag uint8
+
+const (
+	// TagV1 identifies the first revision of the protocol. This version has a maximum
+	// data length of MaxMessageSizeV1.
+	TagV1 Tag = 1
+)
+
+const (
+	// DataLength is the number of bits used for the length of encoded protobuf data.
+	DataLength = 24
+
+	// tagLength is the number of bits used for the tag.
+	tagLength = 8
+
+	// MaxMessageSizeV1 is the maximum size of the encoded protobuf messages sent
+	// over the wire for the TagV1 tag. While the wire format allows 24 bits for
+	// length, TagV1 only uses 15 bits.
+	MaxMessageSizeV1 uint32 = 1 << 15
+)
+
+var (
+	// ErrMessageTooLarge is returned when the message exceeds the maximum size
+	// allowed for the tag.
+	ErrMessageTooLarge = xerrors.New("message too large")
+	// ErrUnsupportedTag is returned when an unrecognized tag is encountered.
+	ErrUnsupportedTag = xerrors.New("unsupported tag")
+)
+
+// WriteFrame writes a framed message with the given tag and data. The data
+// must not exceed 2^DataLength in length.
+func WriteFrame(w io.Writer, tag Tag, data []byte) error {
+	var maxSize uint32
+	switch tag {
+	case TagV1:
+		maxSize = MaxMessageSizeV1
+	default:
+		return xerrors.Errorf("%w: %d", ErrUnsupportedTag, tag)
+	}
+
+	if len(data) > int(maxSize) {
+		return xerrors.Errorf("%w for tag %d: %d > %d", ErrMessageTooLarge, tag, len(data), maxSize)
+	}
+
+	var header uint32
+	//nolint:gosec // The length check above ensures there's no overflow.
+	header |= uint32(len(data))
+	header |= uint32(tag) << DataLength
+
+	if err := binary.Write(w, binary.BigEndian, header); err != nil {
+		return xerrors.Errorf("write header error: %w", err)
+	}
+	if _, err := w.Write(data); err != nil {
+		return xerrors.Errorf("write data error: %w", err)
+	}
+
+	return nil
+}
+
+// ReadFrame reads a framed message, returning the decoded tag and data. If the
+// message size exceeds MaxMessageSizeV1, ErrMessageTooLarge is returned. The
+// provided buf is used if it has sufficient capacity; otherwise a new buffer is
+// allocated. To reuse the buffer across calls, pass in the returned data slice:
+//
+//	buf := make([]byte, initialSize)
+//	for {
+//	    _, buf, _ = ReadFrame(r, buf)
+//	}
+func ReadFrame(r io.Reader, buf []byte) (Tag, []byte, error) {
+	var header uint32
+	if err := binary.Read(r, binary.BigEndian, &header); err != nil {
+		return 0, nil, xerrors.Errorf("read header error: %w", err)
+	}
+
+	const lengthMask = (1 << DataLength) - 1
+	length := header & lengthMask
+	const tagMask = (1 << tagLength) - 1 // 0xFF
+	shifted := (header >> DataLength) & tagMask
+	if shifted > tagMask {
+		// This is really only here to satisfy the gosec linter. We know from above that
+		// shifted <= tagMask.
+		return 0, nil, xerrors.Errorf("invalid tag: %d", shifted)
+	}
+	tag := Tag(shifted)
+
+	var maxSize uint32
+	switch tag {
+	case TagV1:
+		maxSize = MaxMessageSizeV1
+	default:
+		return 0, nil, xerrors.Errorf("%w: %d", ErrUnsupportedTag, tag)
+	}
+
+	if length > maxSize {
+		return 0, nil, ErrMessageTooLarge
+	}
+
+	if cap(buf) < int(length) {
+		buf = make([]byte, length)
+	} else {
+		buf = buf[:length:cap(buf)]
+	}
+
+	if _, err := io.ReadFull(r, buf[:length]); err != nil {
+		return 0, nil, xerrors.Errorf("read full error: %w", err)
+	}
+
+	return tag, buf[:length], nil
+}

agent/boundarylogproxy/codec/codec_test.go

@@ -0,0 +1,145 @@
+package codec_test
+
+import (
+	"bytes"
+	"encoding/binary"
+	"io"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+
+	"github.com/coder/coder/v2/agent/boundarylogproxy/codec"
+)
+
+func TestRoundTrip(t *testing.T) {
+	t.Parallel()
+
+	tests := []struct {
+		name string
+		tag  codec.Tag
+		data []byte
+	}{
+		{
+			name: "empty data",
+			tag:  codec.TagV1,
+			data: []byte{},
+		},
+		{
+			name: "simple data",
+			tag:  codec.TagV1,
+			data: []byte("hello world"),
+		},
+		{
+			name: "binary data",
+			tag:  codec.TagV1,
+			data: []byte{0x00, 0x01, 0x02, 0xff, 0xfe},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+
+			var buf bytes.Buffer
+			err := codec.WriteFrame(&buf, tt.tag, tt.data)
+			require.NoError(t, err)
+
+			readBuf := make([]byte, codec.MaxMessageSizeV1)
+			tag, data, err := codec.ReadFrame(&buf, readBuf)
+			require.NoError(t, err)
+			require.Equal(t, tt.tag, tag)
+			require.Equal(t, tt.data, data)
+		})
+	}
+}
+
+func TestReadFrameTooLarge(t *testing.T) {
+	t.Parallel()
+
+	// Hand construct a header that indicates the message size exceeds the maximum
+	// message size for codec.TagV1 by one. We just write the header to buf because
+	// we expect codec.ReadFrame to bail out when reading the invalid length.
+	header := uint32(codec.TagV1)<<codec.DataLength | (codec.MaxMessageSizeV1 + 1)
+	data := make([]byte, 4)
+	binary.BigEndian.PutUint32(data, header)
+
+	var buf bytes.Buffer
+	_, err := buf.Write(data)
+	require.NoError(t, err)
+
+	readBuf := make([]byte, 1)
+	_, _, err = codec.ReadFrame(&buf, readBuf)
+	require.ErrorIs(t, err, codec.ErrMessageTooLarge)
+}
+
+func TestReadFrameEmptyReader(t *testing.T) {
+	t.Parallel()
+
+	var buf bytes.Buffer
+	readBuf := make([]byte, codec.MaxMessageSizeV1)
+	_, _, err := codec.ReadFrame(&buf, readBuf)
+	require.ErrorIs(t, err, io.EOF)
+}
+
+func TestReadFrameInvalidTag(t *testing.T) {
+	t.Parallel()
+
+	// Hand construct a header that indicates a tag we don't know about. We just
+	// write the header to buf because we expect codec.ReadFrame to bail out when
+	// reading the invalid tag.
+	const (
+		dataLength uint32 = 10
+		bogusTag   uint32 = 2
+	)
+	header := bogusTag<<codec.DataLength | dataLength
+	data := make([]byte, 4)
+	binary.BigEndian.PutUint32(data, header)
+
+	var buf bytes.Buffer
+	_, err := buf.Write(data)
+	require.NoError(t, err)
+
+	readBuf := make([]byte, 1)
+	_, _, err = codec.ReadFrame(&buf, readBuf)
+	require.ErrorIs(t, err, codec.ErrUnsupportedTag)
+}
+
+func TestReadFrameAllocatesWhenNeeded(t *testing.T) {
+	t.Parallel()
+
+	var buf bytes.Buffer
+	data := []byte("this message is longer than the buffer")
+	err := codec.WriteFrame(&buf, codec.TagV1, data)
+	require.NoError(t, err)
+
+	// Buffer with insufficient capacity triggers allocation.
+	readBuf := make([]byte, 4)
+	tag, got, err := codec.ReadFrame(&buf, readBuf)
+	require.NoError(t, err)
+	require.Equal(t, codec.TagV1, tag)
+	require.Equal(t, data, got)
+}
+
+func TestWriteFrameDataSize(t *testing.T) {
+	t.Parallel()
+
+	var buf bytes.Buffer
+	data := make([]byte, codec.MaxMessageSizeV1)
+	err := codec.WriteFrame(&buf, codec.TagV1, data)
+	require.NoError(t, err)
+
+	//nolint: makezero // This intentionally increases the slice length.
+	data = append(data, 0) // One byte over the maximum
+	err = codec.WriteFrame(&buf, codec.TagV1, data)
+	require.ErrorIs(t, err, codec.ErrMessageTooLarge)
+}
+
+func TestWriteFrameInvalidTag(t *testing.T) {
+	t.Parallel()
+
+	var buf bytes.Buffer
+	data := make([]byte, 1)
+	const bogusTag = 2
+	err := codec.WriteFrame(&buf, codec.Tag(bogusTag), data)
+	require.ErrorIs(t, err, codec.ErrUnsupportedTag)
+}

agent/boundarylogproxy/proxy.go

@@ -2,6 +2,204 @@
 // audit logs and forwards them to coderd via the agent API.
 package boundarylogproxy
 
-// Server a placeholder for the server that will listen on a Unix socket for
-// boundary logs to be forwarded.
-type Server struct{}
+import (
+	"context"
+	"errors"
+	"io"
+	"net"
+	"os"
+	"path/filepath"
+	"sync"
+
+	"golang.org/x/xerrors"
+	"google.golang.org/protobuf/proto"
+
+	"cdr.dev/slog"
+	"github.com/coder/coder/v2/agent/boundarylogproxy/codec"
+	agentproto "github.com/coder/coder/v2/agent/proto"
+)
+
+const (
+	// logBufferSize is the size of the channel buffer for incoming log requests
+	// from workspaces. This buffer size is intended to handle short bursts of workspaces
+	// forwarding batches of logs in parallel.
+	logBufferSize = 100
+)
+
+// DefaultSocketPath returns the default path for the boundary audit log socket.
+func DefaultSocketPath() string {
+	return filepath.Join(os.TempDir(), "boundary-audit.sock")
+}
+
+// Reporter reports boundary logs from workspaces.
+type Reporter interface {
+	ReportBoundaryLogs(ctx context.Context, req *agentproto.ReportBoundaryLogsRequest) (*agentproto.ReportBoundaryLogsResponse, error)
+}
+
+// Server listens on a Unix socket for boundary log messages and buffers them
+// for forwarding to coderd. The socket server and the forwarder are decoupled:
+// - Start() creates the socket and accepts a connection from boundary
+// - RunForwarder() drains the buffer and sends logs to coderd via AgentAPI
+type Server struct {
+	logger     slog.Logger
+	socketPath string
+
+	listener net.Listener
+	cancel   context.CancelFunc
+	wg       sync.WaitGroup
+
+	// logs buffers incoming log requests for the forwarder to drain.
+	logs chan *agentproto.ReportBoundaryLogsRequest
+}
+
+// NewServer creates a new boundary log proxy server.
+func NewServer(logger slog.Logger, socketPath string) *Server {
+	return &Server{
+		logger:     logger.Named("boundary-log-proxy"),
+		socketPath: socketPath,
+		logs:       make(chan *agentproto.ReportBoundaryLogsRequest, logBufferSize),
+	}
+}
+
+// Start begins listening for connections on the Unix socket, and handles new
+// connections in a separate goroutine. Incoming logs from connections are
+// buffered until RunForwarder drains them.
+func (s *Server) Start() error {
+	if err := os.Remove(s.socketPath); err != nil && !os.IsNotExist(err) {
+		return xerrors.Errorf("remove existing socket: %w", err)
+	}
+
+	listener, err := net.Listen("unix", s.socketPath)
+	if err != nil {
+		return xerrors.Errorf("listen on socket: %w", err)
+	}
+
+	s.listener = listener
+	ctx, cancel := context.WithCancel(context.Background())
+	s.cancel = cancel
+
+	s.wg.Add(1)
+	go s.acceptLoop(ctx)
+
+	s.logger.Info(ctx, "boundary log proxy started", slog.F("socket_path", s.socketPath))
+	return nil
+}
+
+// RunForwarder drains the log buffer and forwards logs to coderd.
+// It blocks until ctx is canceled.
+func (s *Server) RunForwarder(ctx context.Context, sender Reporter) error {
+	s.logger.Debug(ctx, "boundary log forwarder started")
+
+	for {
+		select {
+		case <-ctx.Done():
+			return ctx.Err()
+		case req := <-s.logs:
+			_, err := sender.ReportBoundaryLogs(ctx, req)
+			if err != nil {
+				s.logger.Warn(ctx, "failed to forward boundary logs",
+					slog.Error(err),
+					slog.F("log_count", len(req.Logs)))
+				// Continue forwarding other logs. The current batch is lost,
+				// but the socket stays alive.
+			}
+		}
+	}
+}
+
+func (s *Server) acceptLoop(ctx context.Context) {
+	defer s.wg.Done()
+
+	for {
+		conn, err := s.listener.Accept()
+		if err != nil {
+			if ctx.Err() != nil {
+				s.logger.Warn(ctx, "accept loop terminated", slog.Error(ctx.Err()))
+				return
+			}
+			s.logger.Warn(ctx, "socket accept error", slog.Error(err))
+			continue
+		}
+
+		s.wg.Add(1)
+		go s.handleConnection(ctx, conn)
+	}
+}
+
+func (s *Server) handleConnection(ctx context.Context, conn net.Conn) {
+	defer s.wg.Done()
+
+	ctx, cancel := context.WithCancel(ctx)
+	defer cancel()
+
+	s.wg.Add(1)
+	go func() {
+		defer s.wg.Done()
+		<-ctx.Done()
+		_ = conn.Close()
+	}()
+
+	// This is intended to be a sane starting point for the read buffer size. It may be
+	// grown by codec.ReadFrame if necessary.
+	const initBufSize = 1 << 10
+	buf := make([]byte, initBufSize)
+
+	for {
+		select {
+		case <-ctx.Done():
+			return
+		default:
+		}
+
+		var (
+			tag codec.Tag
+			err error
+		)
+		tag, buf, err = codec.ReadFrame(conn, buf)
+		switch {
+		case errors.Is(err, io.EOF) || errors.Is(err, net.ErrClosed):
+			return
+		case err != nil:
+			s.logger.Warn(ctx, "read frame error", slog.Error(err))
+			return
+		}
+
+		if tag != codec.TagV1 {
+			s.logger.Warn(ctx, "invalid tag value", slog.F("tag", tag))
+			return
+		}
+
+		var req agentproto.ReportBoundaryLogsRequest
+		if err := proto.Unmarshal(buf, &req); err != nil {
+			s.logger.Warn(ctx, "proto unmarshal error", slog.Error(err))
+			continue
+		}
+
+		select {
+		case s.logs <- &req:
+		default:
+			s.logger.Warn(ctx, "dropping boundary logs, buffer full",
+				slog.F("log_count", len(req.Logs)))
+		}
+	}
+}
+
+// Close stops the server and blocks until resources have been cleaned up.
+// It must be called after Start.
+func (s *Server) Close() error {
+	if s.cancel != nil {
+		s.cancel()
+	}
+
+	if s.listener != nil {
+		_ = s.listener.Close()
+	}
+
+	s.wg.Wait()
+
+	err := os.Remove(s.socketPath)
+	if err != nil && !errors.Is(err, os.ErrNotExist) {
+		return err
+	}
+	return nil
+}

agent/boundarylogproxy/proxy_test.go

@@ -0,0 +1,578 @@
+//go:build linux || darwin
+
+package boundarylogproxy_test
+
+import (
+	"context"
+	"encoding/binary"
+	"net"
+	"path/filepath"
+	"sync"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/require"
+	"google.golang.org/protobuf/proto"
+	"google.golang.org/protobuf/types/known/timestamppb"
+
+	"github.com/coder/coder/v2/agent/boundarylogproxy"
+	"github.com/coder/coder/v2/agent/boundarylogproxy/codec"
+	agentproto "github.com/coder/coder/v2/agent/proto"
+	"github.com/coder/coder/v2/testutil"
+)
+
+// sendMessage writes a framed protobuf message to the connection.
+func sendMessage(t *testing.T, conn net.Conn, req *agentproto.ReportBoundaryLogsRequest) {
+	t.Helper()
+
+	data, err := proto.Marshal(req)
+	if err != nil {
+		//nolint:gocritic // In tests we're not worried about conn being nil.
+		t.Errorf("%s marshal req: %s", conn.LocalAddr().String(), err)
+	}
+
+	err = codec.WriteFrame(conn, codec.TagV1, data)
+	if err != nil {
+		//nolint:gocritic // In tests we're not worried about conn being nil.
+		t.Errorf("%s write frame: %s", conn.LocalAddr().String(), err)
+	}
+}
+
+// fakeReporter implements boundarylogproxy.Reporter for testing.
+type fakeReporter struct {
+	mu      sync.Mutex
+	logs    []*agentproto.ReportBoundaryLogsRequest
+	err     error
+	errOnce bool // only error once, then succeed
+
+	// reportCb is called when a ReportBoundaryLogsRequest is processed. It must not
+	// block.
+	reportCb func()
+}
+
+func (f *fakeReporter) ReportBoundaryLogs(_ context.Context, req *agentproto.ReportBoundaryLogsRequest) (*agentproto.ReportBoundaryLogsResponse, error) {
+	f.mu.Lock()
+	defer f.mu.Unlock()
+
+	if f.reportCb != nil {
+		f.reportCb()
+	}
+
+	if f.err != nil {
+		if f.errOnce {
+			err := f.err
+			f.err = nil
+			return nil, err
+		}
+		return nil, f.err
+	}
+	f.logs = append(f.logs, req)
+	return &agentproto.ReportBoundaryLogsResponse{}, nil
+}
+
+func (f *fakeReporter) getLogs() []*agentproto.ReportBoundaryLogsRequest {
+	f.mu.Lock()
+	defer f.mu.Unlock()
+	return append([]*agentproto.ReportBoundaryLogsRequest{}, f.logs...)
+}
+
+func TestServer_StartAndClose(t *testing.T) {
+	t.Parallel()
+
+	socketPath := filepath.Join(testutil.TempDirUnixSocket(t), "boundary.sock")
+	srv := boundarylogproxy.NewServer(testutil.Logger(t), socketPath)
+
+	err := srv.Start()
+	require.NoError(t, err)
+
+	// Verify socket exists and is connectable.
+	conn, err := net.Dial("unix", socketPath)
+	require.NoError(t, err)
+	err = conn.Close()
+	require.NoError(t, err)
+
+	err = srv.Close()
+	require.NoError(t, err)
+}
+
+func TestServer_ReceiveAndForwardLogs(t *testing.T) {
+	t.Parallel()
+
+	socketPath := filepath.Join(testutil.TempDirUnixSocket(t), "boundary.sock")
+	srv := boundarylogproxy.NewServer(testutil.Logger(t), socketPath)
+
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	err := srv.Start()
+	require.NoError(t, err)
+	t.Cleanup(func() { require.NoError(t, srv.Close()) })
+
+	reporter := &fakeReporter{}
+
+	// Start forwarder in background.
+	forwarderDone := make(chan error, 1)
+	go func() {
+		forwarderDone <- srv.RunForwarder(ctx, reporter)
+	}()
+
+	// Connect and send a log message.
+	conn, err := net.Dial("unix", socketPath)
+	require.NoError(t, err)
+	defer conn.Close()
+
+	req := &agentproto.ReportBoundaryLogsRequest{
+		Logs: []*agentproto.BoundaryLog{
+			{
+				Allowed: true,
+				Time:    timestamppb.Now(),
+				Resource: &agentproto.BoundaryLog_HttpRequest_{
+					HttpRequest: &agentproto.BoundaryLog_HttpRequest{
+						Method: "GET",
+						Url:    "https://example.com",
+					},
+				},
+			},
+		},
+	}
+
+	sendMessage(t, conn, req)
+
+	// Wait for the reporter to receive the log.
+	require.Eventually(t, func() bool {
+		logs := reporter.getLogs()
+		return len(logs) == 1
+	}, testutil.WaitShort, testutil.IntervalFast)
+
+	logs := reporter.getLogs()
+	require.Len(t, logs, 1)
+	require.Len(t, logs[0].Logs, 1)
+	require.True(t, logs[0].Logs[0].Allowed)
+	require.Equal(t, "GET", logs[0].Logs[0].GetHttpRequest().Method)
+	require.Equal(t, "https://example.com", logs[0].Logs[0].GetHttpRequest().Url)
+
+	cancel()
+	<-forwarderDone
+}
+
+func TestServer_MultipleMessages(t *testing.T) {
+	t.Parallel()
+
+	socketPath := filepath.Join(testutil.TempDirUnixSocket(t), "boundary.sock")
+	srv := boundarylogproxy.NewServer(testutil.Logger(t), socketPath)
+
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	err := srv.Start()
+	require.NoError(t, err)
+	defer srv.Close()
+
+	reporter := &fakeReporter{}
+
+	forwarderDone := make(chan error, 1)
+	go func() {
+		forwarderDone <- srv.RunForwarder(ctx, reporter)
+	}()
+
+	conn, err := net.Dial("unix", socketPath)
+	require.NoError(t, err)
+	defer conn.Close()
+
+	// Send multiple messages and verify they are all received.
+	for range 5 {
+		req := &agentproto.ReportBoundaryLogsRequest{
+			Logs: []*agentproto.BoundaryLog{
+				{
+					Allowed: true,
+					Time:    timestamppb.Now(),
+					Resource: &agentproto.BoundaryLog_HttpRequest_{
+						HttpRequest: &agentproto.BoundaryLog_HttpRequest{
+							Method: "POST",
+							Url:    "https://example.com/api",
+						},
+					},
+				},
+			},
+		}
+		sendMessage(t, conn, req)
+	}
+
+	require.Eventually(t, func() bool {
+		logs := reporter.getLogs()
+		return len(logs) == 5
+	}, testutil.WaitShort, testutil.IntervalFast)
+
+	cancel()
+	<-forwarderDone
+}
+
+func TestServer_MultipleConnections(t *testing.T) {
+	t.Parallel()
+
+	socketPath := filepath.Join(testutil.TempDirUnixSocket(t), "boundary.sock")
+	srv := boundarylogproxy.NewServer(testutil.Logger(t), socketPath)
+
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	err := srv.Start()
+	require.NoError(t, err)
+	t.Cleanup(func() { require.NoError(t, srv.Close()) })
+
+	reporter := &fakeReporter{}
+
+	forwarderDone := make(chan error, 1)
+	go func() {
+		forwarderDone <- srv.RunForwarder(ctx, reporter)
+	}()
+
+	// Create multiple connections and send from each.
+	const numConns = 3
+	var wg sync.WaitGroup
+	wg.Add(numConns)
+	for i := range numConns {
+		go func(connID int) {
+			defer wg.Done()
+			conn, err := net.Dial("unix", socketPath)
+			if err != nil {
+				t.Errorf("conn %d dial: %s", connID, err)
+			}
+			defer conn.Close()
+
+			req := &agentproto.ReportBoundaryLogsRequest{
+				Logs: []*agentproto.BoundaryLog{
+					{
+						Allowed: true,
+						Time:    timestamppb.Now(),
+						Resource: &agentproto.BoundaryLog_HttpRequest_{
+							HttpRequest: &agentproto.BoundaryLog_HttpRequest{
+								Method: "GET",
+								Url:    "https://example.com",
+							},
+						},
+					},
+				},
+			}
+			sendMessage(t, conn, req)
+		}(i)
+	}
+	wg.Wait()
+
+	require.Eventually(t, func() bool {
+		logs := reporter.getLogs()
+		return len(logs) == numConns
+	}, testutil.WaitShort, testutil.IntervalFast)
+
+	cancel()
+	<-forwarderDone
+}
+
+func TestServer_MessageTooLarge(t *testing.T) {
+	t.Parallel()
+
+	socketPath := filepath.Join(testutil.TempDirUnixSocket(t), "boundary.sock")
+	srv := boundarylogproxy.NewServer(testutil.Logger(t), socketPath)
+
+	err := srv.Start()
+	require.NoError(t, err)
+	t.Cleanup(func() { require.NoError(t, srv.Close()) })
+
+	conn, err := net.Dial("unix", socketPath)
+	require.NoError(t, err)
+	defer conn.Close()
+
+	// Send a message claiming to be larger than the max message size.
+	var length uint32 = codec.MaxMessageSizeV1 + 1
+	err = binary.Write(conn, binary.BigEndian, length)
+	require.NoError(t, err)
+
+	// The server should close the connection after receiving an oversized
+	// message length.
+	buf := make([]byte, 1)
+	err = conn.SetReadDeadline(time.Now().Add(time.Second))
+	require.NoError(t, err)
+	_, err = conn.Read(buf)
+	require.Error(t, err) // Should get EOF or closed connection.
+}
+
+func TestServer_ForwarderContinuesAfterError(t *testing.T) {
+	t.Parallel()
+
+	socketPath := filepath.Join(testutil.TempDirUnixSocket(t), "boundary.sock")
+	srv := boundarylogproxy.NewServer(testutil.Logger(t), socketPath)
+
+	err := srv.Start()
+	require.NoError(t, err)
+	t.Cleanup(func() { require.NoError(t, srv.Close()) })
+
+	reportNotify := make(chan struct{}, 1)
+	reporter := &fakeReporter{
+		// Simulate an error on the first call.
+		err:     context.DeadlineExceeded,
+		errOnce: true,
+		reportCb: func() {
+			reportNotify <- struct{}{}
+		},
+	}
+
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+	forwarderDone := make(chan error, 1)
+	go func() {
+		forwarderDone <- srv.RunForwarder(ctx, reporter)
+	}()
+
+	conn, err := net.Dial("unix", socketPath)
+	require.NoError(t, err)
+	defer conn.Close()
+
+	// Send the first message to be processed and wait for failure.
+	req1 := &agentproto.ReportBoundaryLogsRequest{
+		Logs: []*agentproto.BoundaryLog{
+			{
+				Allowed: true,
+				Time:    timestamppb.Now(),
+				Resource: &agentproto.BoundaryLog_HttpRequest_{
+					HttpRequest: &agentproto.BoundaryLog_HttpRequest{
+						Method: "GET",
+						Url:    "https://example.com/first",
+					},
+				},
+			},
+		},
+	}
+	sendMessage(t, conn, req1)
+
+	select {
+	case <-reportNotify:
+	case <-time.After(testutil.WaitShort):
+		t.Fatal("timed out waiting for first message to be processed")
+	}
+
+	// Send the second message, which should succeed.
+	req2 := &agentproto.ReportBoundaryLogsRequest{
+		Logs: []*agentproto.BoundaryLog{
+			{
+				Allowed: false,
+				Time:    timestamppb.Now(),
+				Resource: &agentproto.BoundaryLog_HttpRequest_{
+					HttpRequest: &agentproto.BoundaryLog_HttpRequest{
+						Method: "POST",
+						Url:    "https://example.com/second",
+					},
+				},
+			},
+		},
+	}
+	sendMessage(t, conn, req2)
+
+	// Only the second message should be recorded.
+	require.Eventually(t, func() bool {
+		logs := reporter.getLogs()
+		return len(logs) == 1
+	}, testutil.WaitShort, testutil.IntervalFast)
+
+	logs := reporter.getLogs()
+	require.Len(t, logs, 1)
+	require.Equal(t, "https://example.com/second", logs[0].Logs[0].GetHttpRequest().Url)
+
+	cancel()
+	<-forwarderDone
+}
+
+func TestServer_CloseStopsForwarder(t *testing.T) {
+	t.Parallel()
+
+	socketPath := filepath.Join(testutil.TempDirUnixSocket(t), "boundary.sock")
+	srv := boundarylogproxy.NewServer(testutil.Logger(t), socketPath)
+
+	err := srv.Start()
+	require.NoError(t, err)
+	t.Cleanup(func() { require.NoError(t, srv.Close()) })
+
+	reporter := &fakeReporter{}
+
+	forwarderCtx, forwarderCancel := context.WithCancel(context.Background())
+	forwarderDone := make(chan error, 1)
+	go func() {
+		forwarderDone <- srv.RunForwarder(forwarderCtx, reporter)
+	}()
+
+	// Cancel the forwarder context and verify it stops.
+	forwarderCancel()
+
+	select {
+	case err := <-forwarderDone:
+		require.ErrorIs(t, err, context.Canceled)
+	case <-time.After(testutil.WaitShort):
+		t.Fatal("forwarder did not stop")
+	}
+}
+
+func TestServer_InvalidProtobuf(t *testing.T) {
+	t.Parallel()
+
+	socketPath := filepath.Join(testutil.TempDirUnixSocket(t), "boundary.sock")
+	srv := boundarylogproxy.NewServer(testutil.Logger(t), socketPath)
+
+	err := srv.Start()
+	require.NoError(t, err)
+	t.Cleanup(func() { require.NoError(t, srv.Close()) })
+
+	reporter := &fakeReporter{}
+
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+	forwarderDone := make(chan error, 1)
+	go func() {
+		forwarderDone <- srv.RunForwarder(ctx, reporter)
+	}()
+
+	conn, err := net.Dial("unix", socketPath)
+	require.NoError(t, err)
+	defer conn.Close()
+
+	// Send a valid header with garbage protobuf data.
+	// The server should log an unmarshal error but continue processing.
+	invalidProto := []byte{0xFF, 0xFF, 0xFF, 0xFF, 0xFF}
+	//nolint: gosec // codec.DataLength is always less than the size of the header.
+	header := (uint32(codec.TagV1) << codec.DataLength) | uint32(len(invalidProto))
+	err = binary.Write(conn, binary.BigEndian, header)
+	require.NoError(t, err)
+	_, err = conn.Write(invalidProto)
+	require.NoError(t, err)
+
+	// Now send a valid message. The server should continue processing.
+	req := &agentproto.ReportBoundaryLogsRequest{
+		Logs: []*agentproto.BoundaryLog{
+			{
+				Allowed: true,
+				Time:    timestamppb.Now(),
+				Resource: &agentproto.BoundaryLog_HttpRequest_{
+					HttpRequest: &agentproto.BoundaryLog_HttpRequest{
+						Method: "GET",
+						Url:    "https://example.com/valid",
+					},
+				},
+			},
+		},
+	}
+	sendMessage(t, conn, req)
+
+	require.Eventually(t, func() bool {
+		logs := reporter.getLogs()
+		return len(logs) == 1
+	}, testutil.WaitShort, testutil.IntervalFast)
+
+	cancel()
+	<-forwarderDone
+}
+
+func TestServer_InvalidHeader(t *testing.T) {
+	t.Parallel()
+
+	socketPath := filepath.Join(testutil.TempDirUnixSocket(t), "boundary.sock")
+	srv := boundarylogproxy.NewServer(testutil.Logger(t), socketPath)
+
+	err := srv.Start()
+	require.NoError(t, err)
+	t.Cleanup(func() { require.NoError(t, srv.Close()) })
+
+	reporter := &fakeReporter{}
+
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+	forwarderDone := make(chan error, 1)
+	go func() {
+		forwarderDone <- srv.RunForwarder(ctx, reporter)
+	}()
+
+	// sendInvalidHeader sends a header and verifies the server closes the
+	// connection.
+	sendInvalidHeader := func(t *testing.T, name string, header uint32) {
+		t.Helper()
+
+		conn, err := net.Dial("unix", socketPath)
+		require.NoError(t, err)
+		defer conn.Close()
+
+		err = binary.Write(conn, binary.BigEndian, header)
+		require.NoError(t, err, name)
+
+		// The server closes the connection on invalid header, so the next
+		// write should fail with a broken pipe error.
+		require.Eventually(t, func() bool {
+			_, err := conn.Write([]byte{0x00})
+			return err != nil
+		}, testutil.WaitShort, testutil.IntervalFast, name)
+	}
+
+	// TagV1 with length exceeding MaxMessageSizeV1.
+	sendInvalidHeader(t, "v1 too large", (uint32(codec.TagV1)<<codec.DataLength)|(codec.MaxMessageSizeV1+1))
+
+	// Unknown tag.
+	const bogusTag = 0xFF
+	sendInvalidHeader(t, "unknown tag too large", (bogusTag<<codec.DataLength)|(codec.MaxMessageSizeV1+1))
+
+	cancel()
+	<-forwarderDone
+}
+
+func TestServer_AllowRequest(t *testing.T) {
+	t.Parallel()
+
+	socketPath := filepath.Join(testutil.TempDirUnixSocket(t), "boundary.sock")
+	srv := boundarylogproxy.NewServer(testutil.Logger(t), socketPath)
+
+	err := srv.Start()
+	require.NoError(t, err)
+	t.Cleanup(func() { require.NoError(t, srv.Close()) })
+
+	reporter := &fakeReporter{}
+
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+	forwarderDone := make(chan error, 1)
+	go func() {
+		forwarderDone <- srv.RunForwarder(ctx, reporter)
+	}()
+
+	conn, err := net.Dial("unix", socketPath)
+	require.NoError(t, err)
+	defer conn.Close()
+
+	// Send an allowed request with a matched rule.
+	logTime := timestamppb.Now()
+	req := &agentproto.ReportBoundaryLogsRequest{
+		Logs: []*agentproto.BoundaryLog{
+			{
+				Allowed: true,
+				Time:    logTime,
+				Resource: &agentproto.BoundaryLog_HttpRequest_{
+					HttpRequest: &agentproto.BoundaryLog_HttpRequest{
+						Method:      "GET",
+						Url:         "https://malicious.com/attack",
+						MatchedRule: "*.malicious.com",
+					},
+				},
+			},
+		},
+	}
+	sendMessage(t, conn, req)
+
+	require.Eventually(t, func() bool {
+		logs := reporter.getLogs()
+		return len(logs) == 1
+	}, testutil.WaitShort, testutil.IntervalFast)
+
+	logs := reporter.getLogs()
+	require.Len(t, logs, 1)
+	require.True(t, logs[0].Logs[0].Allowed)
+	require.Equal(t, logTime.Seconds, logs[0].Logs[0].Time.Seconds)
+	require.Equal(t, logTime.Nanos, logs[0].Logs[0].Time.Nanos)
+	require.Equal(t, "*.malicious.com", logs[0].Logs[0].GetHttpRequest().MatchedRule)
+
+	cancel()
+	<-forwarderDone
+}

cli/agent.go

@@ -31,6 +31,7 @@ import (
 	"github.com/coder/coder/v2/agent/agentcontainers"
 	"github.com/coder/coder/v2/agent/agentexec"
 	"github.com/coder/coder/v2/agent/agentssh"
+	"github.com/coder/coder/v2/agent/boundarylogproxy"
 	"github.com/coder/coder/v2/agent/reaper"
 	"github.com/coder/coder/v2/buildinfo"
 	"github.com/coder/coder/v2/cli/clilog"
@@ -59,6 +60,7 @@ func workspaceAgent() *serpent.Command {
 		devcontainerDiscoveryAutostart bool
 		socketServerEnabled            bool
 		socketPath                     string
+		boundaryLogProxySocketPath     string
 	)
 	agentAuth := &AgentAuth{}
 	cmd := &serpent.Command{
@@ -319,8 +321,9 @@ func workspaceAgent() *serpent.Command {
 						agentcontainers.WithProjectDiscovery(devcontainerProjectDiscovery),
 						agentcontainers.WithDiscoveryAutostart(devcontainerDiscoveryAutostart),
 					},
-					SocketPath:          socketPath,
-					SocketServerEnabled: socketServerEnabled,
+					SocketPath:                 socketPath,
+					SocketServerEnabled:        socketServerEnabled,
+					BoundaryLogProxySocketPath: boundaryLogProxySocketPath,
 				})
 
 				if debugAddress != "" {
@@ -494,6 +497,13 @@ func workspaceAgent() *serpent.Command {
 			Description: "Specify the path for the agent socket.",
 			Value:       serpent.StringOf(&socketPath),
 		},
+		{
+			Flag:        "boundary-log-proxy-socket-path",
+			Default:     boundarylogproxy.DefaultSocketPath(),
+			Env:         "CODER_AGENT_BOUNDARY_LOG_PROXY_SOCKET_PATH",
+			Description: "The path for the boundary log proxy server Unix socket. Boundary should write audit logs to this socket.",
+			Value:       serpent.StringOf(&boundaryLogProxySocketPath),
+		},
 	}
 	agentAuth.AttachOptions(cmd, false)
 	return cmd

cli/clitest/golden.go

@@ -138,6 +138,17 @@ func normalizeGoldenFile(t *testing.T, byt []byte) []byte {
 
 	// The home directory changes depending on the test environment.
 	byt = bytes.ReplaceAll(byt, []byte(homeDir), []byte("~"))
+
+	// Normalize the temp directory. os.TempDir() may include a trailing slash
+	// (macOS) or not (Linux/Windows), and the temp directory may be followed by
+	// more filepath elements with an OS-specific separator. We handle all cases
+	// by replacing tempdir+separator first, then tempdir alone.
+	tempDir := filepath.Clean(os.TempDir())
+	byt = bytes.ReplaceAll(byt, []byte(tempDir+string(filepath.Separator)), []byte("/tmp/"))
+	byt = bytes.ReplaceAll(byt, []byte(tempDir), []byte("/tmp"))
+	// Clean up trailing slash when temp dir is used standalone (e.g., "/tmp/)" -> "/tmp)").
+	byt = bytes.ReplaceAll(byt, []byte("/tmp/)"), []byte("/tmp)"))
+
 	for _, r := range []struct {
 		old string
 		new string
@@ -145,7 +156,6 @@ func normalizeGoldenFile(t *testing.T, byt []byte) []byte {
 		{"\r\n", "\n"},
 		{`~\.cache\coder`, "~/.cache/coder"},
 		{`C:\Users\RUNNER~1\AppData\Local\Temp`, "/tmp"},
-		{os.TempDir(), "/tmp"},
 	} {
 		byt = bytes.ReplaceAll(byt, []byte(r.old), []byte(r.new))
 	}

cli/testdata/coder_agent_--help.golden

@@ -39,6 +39,10 @@ OPTIONS:
       --block-file-transfer bool, $CODER_AGENT_BLOCK_FILE_TRANSFER (default: false)
           Block file transfer using known applications: nc,rsync,scp,sftp.
 
+      --boundary-log-proxy-socket-path string, $CODER_AGENT_BOUNDARY_LOG_PROXY_SOCKET_PATH (default: /tmp/boundary-audit.sock)
+          The path for the boundary log proxy server Unix socket. Boundary
+          should write audit logs to this socket.
+
       --debug-address string, $CODER_AGENT_DEBUG_ADDRESS (default: 127.0.0.1:2113)
           The bind address to serve a debug HTTP server.
 

coderd/agentapi/api.go

@@ -220,7 +220,10 @@ func New(opts Options, workspace database.Workspace) *API {
 		Database:       opts.Database,
 	}
 
-	api.BoundaryLogsAPI = &BoundaryLogsAPI{}
+	api.BoundaryLogsAPI = &BoundaryLogsAPI{
+		Log:         opts.Log,
+		WorkspaceID: opts.WorkspaceID,
+	}
 
 	// Start background cache refresh loop to handle workspace changes
 	// like prebuild claims where owner_id and other fields may be modified in the DB.

coderd/agentapi/boundary_logs.go

@@ -2,14 +2,60 @@ package agentapi
 
 import (
 	"context"
+	"time"
 
-	"golang.org/x/xerrors"
+	"github.com/google/uuid"
+
+	"cdr.dev/slog"
 
 	agentproto "github.com/coder/coder/v2/agent/proto"
 )
 
-type BoundaryLogsAPI struct{}
+type BoundaryLogsAPI struct {
+	Log         slog.Logger
+	WorkspaceID uuid.UUID
+}
 
-func (*BoundaryLogsAPI) ReportBoundaryLogs(context.Context, *agentproto.ReportBoundaryLogsRequest) (*agentproto.ReportBoundaryLogsResponse, error) {
-	return nil, xerrors.New("not implemented")
+func (a *BoundaryLogsAPI) ReportBoundaryLogs(ctx context.Context, req *agentproto.ReportBoundaryLogsRequest) (*agentproto.ReportBoundaryLogsResponse, error) {
+	for _, l := range req.Logs {
+		var logTime time.Time
+		if l.Time != nil {
+			logTime = l.Time.AsTime()
+		}
+
+		switch r := l.Resource.(type) {
+		case *agentproto.BoundaryLog_HttpRequest_:
+			if r.HttpRequest == nil {
+				a.Log.Warn(ctx, "empty http request resource",
+					slog.F("workspace_id", a.WorkspaceID.String()))
+				continue
+			}
+
+			fields := []slog.Field{
+				slog.F("decision", allowBoolToString(l.Allowed)),
+				slog.F("workspace_id", a.WorkspaceID.String()),
+				slog.F("http_method", r.HttpRequest.Method),
+				slog.F("http_url", r.HttpRequest.Url),
+				slog.F("event_time", logTime.Format(time.RFC3339Nano)),
+			}
+			if l.Allowed {
+				fields = append(fields, slog.F("matched_rule", r.HttpRequest.MatchedRule))
+			}
+
+			a.Log.With(fields...).Info(ctx, "boundary_request")
+		default:
+			a.Log.Warn(ctx, "unknown resource type",
+				slog.F("workspace_id", a.WorkspaceID.String()))
+		}
+	}
+
+	return &agentproto.ReportBoundaryLogsResponse{}, nil
+}
+
+//nolint:revive // This stringifies the boolean argument.
+func allowBoolToString(b bool) string {
+	if b {
+		return "allow"
+	}
+	return "deny"
 }