fix: expose Codex diff snapshot directories

internal/agent/codex.go

@@ -7,7 +7,10 @@ import (
 	"fmt"
 	"io"
 	"log"
+	"os"
 	"os/exec"
+	"path/filepath"
+	"regexp"
 	"strings"
 	"sync"
 )
@@ -118,12 +121,14 @@ func (a *CodexAgent) CommandLine() string {
 func (a *CodexAgent) buildArgs(
 	repoPath string,
 	agenticMode, autoApprove, sandboxBroken bool,
+	prompt string,
 ) []string {
 	return a.commandArgs(codexArgOptions{
 		repoPath:      repoPath,
 		agenticMode:   agenticMode,
 		autoApprove:   autoApprove,
 		sandboxBroken: sandboxBroken,
+		addDirs:       codexDiffSnapshotDirs(prompt),
 	})
 }
 
@@ -132,6 +137,7 @@ type codexArgOptions struct {
 	agenticMode   bool
 	autoApprove   bool
 	sandboxBroken bool
+	addDirs       []string
 	preview       bool
 }
 
@@ -159,6 +165,9 @@ func (a *CodexAgent) commandArgs(opts codexArgOptions) []string {
 	if !opts.preview {
 		args = append(args, "-C", opts.repoPath)
 	}
+	for _, dir := range opts.addDirs {
+		args = append(args, "--add-dir", dir)
+	}
 	if a.Model != "" {
 		args = append(args, "-m", a.Model)
 	}
@@ -176,6 +185,44 @@ func (a *CodexAgent) commandArgs(opts codexArgOptions) []string {
 	return args
 }
 
+var codexDiffSnapshotRE = regexp.MustCompile("`([^`]*roborev-snapshot-[^`]*\\.diff)`")
+
+func codexDiffSnapshotDirs(reviewPrompt string) []string {
+	matches := codexDiffSnapshotRE.FindAllStringSubmatch(reviewPrompt, -1)
+	if len(matches) == 0 {
+		return nil
+	}
+	seen := make(map[string]struct{}, len(matches))
+	var dirs []string
+	for _, match := range matches {
+		if len(match) < 2 {
+			continue
+		}
+		path := filepath.Clean(match[1])
+		if !filepath.IsAbs(path) {
+			continue
+		}
+		base := filepath.Base(path)
+		if !strings.HasPrefix(base, "roborev-snapshot-") || filepath.Ext(base) != ".diff" {
+			continue
+		}
+		dir := filepath.Dir(path)
+		if !strings.HasPrefix(filepath.Base(dir), "roborev-snapshot-") {
+			continue
+		}
+		info, err := os.Stat(path)
+		if err != nil || info.IsDir() {
+			continue
+		}
+		if _, ok := seen[dir]; ok {
+			continue
+		}
+		seen[dir] = struct{}{}
+		dirs = append(dirs, dir)
+	}
+	return dirs
+}
+
 func codexSupportsDangerousFlag(ctx context.Context, command string) (bool, error) {
 	if cached, ok := codexDangerousSupport.Load(command); ok {
 		return cached.(bool), nil
@@ -240,7 +287,7 @@ func (a *CodexAgent) Review(ctx context.Context, repoPath, commitSHA, prompt str
 	if sandboxBroken && autoApprove {
 		log.Printf("codex: sandbox disabled via config, using %s", codexAutoApproveFlag)
 	}
-	args := a.buildArgs(repoPath, agenticMode, autoApprove, sandboxBroken)
+	args := a.buildArgs(repoPath, agenticMode, autoApprove, sandboxBroken, prompt)
 
 	runResult, runErr := runStreamingCLI(ctx, streamingCLISpec{
 		Name:         "codex",

internal/agent/codex_test.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"errors"
 	"os"
+	"slices"
 	"strings"
 	"testing"
 	"time"
@@ -59,7 +60,7 @@ func TestCodex_buildArgs(t *testing.T) {
 
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
-			args := a.buildArgs("/repo", tt.agentic, tt.autoApprove, tt.sandboxBroken)
+			args := a.buildArgs("/repo", tt.agentic, tt.autoApprove, tt.sandboxBroken, "")
 
 			for _, flag := range tt.wantFlags {
 				assert.Contains(t, args, flag, "buildArgs() missing expected flag %q, args: %v", flag, args)
@@ -77,7 +78,7 @@ func TestCodex_buildArgs(t *testing.T) {
 func TestCodexBuildArgsWithSessionResume(t *testing.T) {
 	a := NewCodexAgent("codex").WithSessionID("session-123").(*CodexAgent)
 
-	args := a.buildArgs("/repo", false, true, false)
+	args := a.buildArgs("/repo", false, true, false, "")
 
 	require.GreaterOrEqual(t, len(args), 3)
 	assert.Equal(t, "exec", args[0])
@@ -87,10 +88,51 @@ func TestCodexBuildArgsWithSessionResume(t *testing.T) {
 	assert.Equal(t, "-", args[len(args)-1], "expected stdin marker '-' at end of args, got %v", args)
 }
 
+func TestCodexBuildArgsAddsDiffSnapshotDirectory(t *testing.T) {
+	a := NewCodexAgent("codex")
+	snapshotDir, err := os.MkdirTemp("", "roborev-snapshot-*")
+	require.NoError(t, err)
+	t.Cleanup(func() { os.RemoveAll(snapshotDir) })
+	diffFile := snapshotDir + string(os.PathSeparator) + "roborev-snapshot-content.diff"
+	require.NoError(t, os.WriteFile(diffFile, []byte("diff --git a/x b/x\n"), 0o600))
+
+	args := a.buildArgs(
+		"/repo",
+		false,
+		true,
+		false,
+		"Read the diff from: `"+diffFile+"`",
+	)
+
+	addDirIndex := slices.Index(args, "--add-dir")
+	require.NotEqual(t, -1, addDirIndex, "expected --add-dir in args: %v", args)
+	require.Less(t, addDirIndex+1, len(args), "expected --add-dir value in args: %v", args)
+	assert.Equal(t, snapshotDir, args[addDirIndex+1])
+	assert.Less(t, addDirIndex, len(args)-1, "--add-dir must appear before stdin marker: %v", args)
+	assert.Equal(t, "-", args[len(args)-1], "expected stdin marker '-' at end of args, got %v", args)
+}
+
+func TestCodexBuildArgsIgnoresDiffSnapshotOutsidePrivateDirectory(t *testing.T) {
+	a := NewCodexAgent("codex")
+	diffFile, err := os.CreateTemp("", "roborev-snapshot-*.diff")
+	require.NoError(t, err)
+	t.Cleanup(func() { os.Remove(diffFile.Name()) })
+
+	args := a.buildArgs(
+		"/repo",
+		false,
+		true,
+		false,
+		"Read the diff from: `"+diffFile.Name()+"`",
+	)
+
+	assert.NotContains(t, args, "--add-dir")
+}
+
 func TestCodexBuildArgsRejectsInvalidSessionResume(t *testing.T) {
 	a := NewCodexAgent("codex").WithSessionID("-bad-session").(*CodexAgent)
 
-	args := a.buildArgs("/repo", false, true, false)
+	args := a.buildArgs("/repo", false, true, false, "")
 
 	require.GreaterOrEqual(t, len(args), 2)
 	assert.Equal(t, "exec", args[0])

internal/daemon/worker_test.go

@@ -556,6 +556,9 @@ func TestWriteDiffSnapshot_WritesExternalReadableTempFile(t *testing.T) {
 	assert.False(t,
 		strings.HasPrefix(filepath.Clean(diffFile), filepath.Clean(gitDir)),
 		"snapshot should not live in git dir: got %s, git dir %s", diffFile, gitDir)
+	assert.True(t,
+		strings.HasPrefix(filepath.Base(filepath.Dir(diffFile)), "roborev-snapshot-"),
+		"snapshot should live in a private roborev temp dir, got %s", diffFile)
 	data, err := os.ReadFile(diffFile)
 	require.NoError(t, err)
 	assert.Contains(t, string(data), "diff --git")

internal/prompt/prompt.go

@@ -189,21 +189,26 @@ func WriteDiffSnapshot(repoPath, gitRef string, excludes []string) (string, func
 }
 
 func writeExternalDiffSnapshot(diff string) (string, func(), error) {
-	f, err := os.CreateTemp("", "roborev-snapshot-*.diff")
+	dir, err := os.MkdirTemp("", "roborev-snapshot-*")
 	if err != nil {
+		return "", nil, fmt.Errorf("create snapshot dir: %w", err)
+	}
+	diffFile := dir + string(os.PathSeparator) + "roborev-snapshot-content.diff"
+	f, err := os.OpenFile(diffFile, os.O_WRONLY|os.O_CREATE|os.O_EXCL, 0o600)
+	if err != nil {
+		os.RemoveAll(dir)
 		return "", nil, fmt.Errorf("create snapshot: %w", err)
 	}
-	diffFile := f.Name()
 	_, writeErr := f.WriteString(diff)
 	closeErr := f.Close()
 	if writeErr != nil || closeErr != nil {
-		os.Remove(diffFile)
+		os.RemoveAll(dir)
 		if writeErr != nil {
 			return "", nil, fmt.Errorf("write snapshot: %w", writeErr)
 		}
 		return "", nil, fmt.Errorf("close snapshot: %w", closeErr)
 	}
-	return diffFile, func() { os.Remove(diffFile) }, nil
+	return diffFile, func() { os.RemoveAll(dir) }, nil
 }
 
 // BuildDirtyWithSnapshot builds a dirty review prompt, writing the diff to a snapshot file