fix(agent): expose Gemini diff snapshot directories

internal/agent/codex.go

@@ -7,10 +7,7 @@ import (
 	"fmt"
 	"io"
 	"log"
-	"os"
 	"os/exec"
-	"path/filepath"
-	"regexp"
 	"strings"
 	"sync"
 )
@@ -128,7 +125,7 @@ func (a *CodexAgent) buildArgs(
 		agenticMode:   agenticMode,
 		autoApprove:   autoApprove,
 		sandboxBroken: sandboxBroken,
-		addDirs:       codexDiffSnapshotDirs(prompt),
+		addDirs:       diffSnapshotDirs(prompt),
 	})
 }
 
@@ -185,44 +182,6 @@ 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

internal/agent/gemini.go

@@ -90,17 +90,17 @@ func (a *GeminiAgent) CommandName() string {
 
 func (a *GeminiAgent) CommandLine() string {
 	agenticMode := a.Agentic || AllowUnsafeAgents()
-	args := a.buildArgs(agenticMode)
+	args := a.buildArgs(agenticMode, "")
 	return a.Command + " " + strings.Join(args, " ")
 }
 
-func (a *GeminiAgent) buildArgs(agenticMode bool) []string {
-	return a.buildArgsWithModel(a.Model, agenticMode)
+func (a *GeminiAgent) buildArgs(agenticMode bool, prompt string) []string {
+	return a.buildArgsWithModel(a.Model, agenticMode, prompt)
 }
 
 func (a *GeminiAgent) Review(ctx context.Context, repoPath, commitSHA, prompt string, output io.Writer) (string, error) {
 	agenticMode := a.Agentic || AllowUnsafeAgents()
-	args := a.buildArgs(agenticMode)
+	args := a.buildArgs(agenticMode, prompt)
 
 	result, stderrStr, err := a.runGemini(ctx, repoPath, prompt, args, output)
 	if err != nil && a.Model == defaultGeminiModel && isModelNotFoundError(stderrStr) {
@@ -109,15 +109,15 @@ func (a *GeminiAgent) Review(ctx context.Context, repoPath, commitSHA, prompt st
 		// its own default. Non-default models (set via WithModel /
 		// config) fail fast so config errors are surfaced.
 		log.Printf("gemini: model %q not found, retrying without -m flag", a.Model)
-		noModelArgs := a.buildArgsWithModel("", agenticMode)
+		noModelArgs := a.buildArgsWithModel("", agenticMode, prompt)
 		result, _, err = a.runGemini(ctx, repoPath, prompt, noModelArgs, output)
 	}
 	return result, err
 }
 
 // buildArgsWithModel builds CLI args with an explicit model override
 // (empty string omits the -m flag entirely).
-func (a *GeminiAgent) buildArgsWithModel(model string, agenticMode bool) []string {
+func (a *GeminiAgent) buildArgsWithModel(model string, agenticMode bool, prompt string) []string {
 	args := []string{"--output-format", "stream-json"}
 
 	if model != "" {
@@ -129,6 +129,12 @@ func (a *GeminiAgent) buildArgsWithModel(model string, agenticMode bool) []strin
 	} else {
 		args = append(args, "--approval-mode", "plan")
 	}
+
+	// Expose roborev diff snapshot dirs referenced in the prompt so
+	// gemini can read large diff files that live outside the repo.
+	for _, dir := range diffSnapshotDirs(prompt) {
+		args = append(args, "--include-directories", dir)
+	}
 	return args
 }
 

internal/agent/gemini_test.go

@@ -69,7 +69,7 @@ func TestGeminiBuildArgs(t *testing.T) {
 			assert := assert.New(t)
 
 			a := NewGeminiAgent("gemini")
-			args := a.buildArgs(tc.agentic)
+			args := a.buildArgs(tc.agentic, "")
 
 			// Check standalone boolean flags
 			for _, flag := range tc.wantFlags {
@@ -89,6 +89,33 @@ func TestGeminiBuildArgs(t *testing.T) {
 	}
 }
 
+func TestGeminiBuildArgsAddsDiffSnapshotDirectory(t *testing.T) {
+	a := NewGeminiAgent("gemini")
+	snapshotDir, err := os.MkdirTemp("", "roborev-snapshot-*")
+	require.NoError(t, err)
+	t.Cleanup(func() { os.RemoveAll(snapshotDir) })
+	diffFile := filepath.Join(snapshotDir, "roborev-snapshot-content.diff")
+	require.NoError(t, os.WriteFile(diffFile, []byte("diff --git a/x b/x\n"), 0o600))
+
+	args := a.buildArgs(false, "Read the diff from: `"+diffFile+"`")
+
+	idx := slices.Index(args, "--include-directories")
+	require.NotEqual(t, -1, idx, "expected --include-directories in args: %v", args)
+	require.Less(t, idx+1, len(args), "expected --include-directories value in args: %v", args)
+	assert.Equal(t, snapshotDir, args[idx+1])
+}
+
+func TestGeminiBuildArgsIgnoresDiffSnapshotOutsidePrivateDirectory(t *testing.T) {
+	a := NewGeminiAgent("gemini")
+	diffFile, err := os.CreateTemp("", "roborev-snapshot-*.diff")
+	require.NoError(t, err)
+	t.Cleanup(func() { os.Remove(diffFile.Name()) })
+
+	args := a.buildArgs(false, "Read the diff from: `"+diffFile.Name()+"`")
+
+	assert.NotContains(t, args, "--include-directories")
+}
+
 func assertFlagValue(t *testing.T, args []string, flag, expectedVal string) {
 	t.Helper()
 	assert := assert.New(t)

internal/agent/snapshot_dirs.go

@@ -0,0 +1,51 @@
+package agent
+
+import (
+	"os"
+	"path/filepath"
+	"regexp"
+	"strings"
+)
+
+var diffSnapshotRE = regexp.MustCompile("`([^`]*roborev-snapshot-[^`]*\\.diff)`")
+
+// diffSnapshotDirs scans a review prompt for backtick-quoted paths to
+// roborev diff snapshots and returns the unique parent directories.
+// Only paths that point to an existing file inside a "roborev-snapshot-"
+// directory are returned, so sandboxed agents can expose just those
+// private directories instead of the whole system temp dir.
+func diffSnapshotDirs(reviewPrompt string) []string {
+	matches := diffSnapshotRE.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
+}