package agentworkspace

import (
	"context"
	"encoding/base64"
	"encoding/json"
	"errors"
	"io"
	"os"
	"os/exec"
	"path/filepath"
	"runtime"
	"strings"
	"sync"
	"syscall"
	"testing"
	"time"

	"golang.org/x/sys/unix"

	"iop/packages/go/agentconfig"
	"iop/packages/go/agentguard"
	"iop/packages/go/agenttask"
)

const confinementHelperEnvironment = "IOP_AGENTWORKSPACE_TEST_CONFINEMENT_HELPER"

type confinementHelperPlan struct {
	Allowed         []string `json:"allowed"`
	Denied          []string `json:"denied"`
	AllowedMetadata []string `json:"allowed_metadata"`
	DeniedMetadata  []string `json:"denied_metadata"`
}

func TestConfinementWriteHelper(t *testing.T) {
	encoded := os.Getenv(confinementHelperEnvironment)
	if encoded == "" {
		return
	}
	raw, err := base64.RawURLEncoding.DecodeString(encoded)
	if err != nil {
		t.Fatalf("decode helper plan: %v", err)
	}
	var plan confinementHelperPlan
	if err := json.Unmarshal(raw, &plan); err != nil {
		t.Fatalf("parse helper plan: %v", err)
	}
	for _, path := range plan.Allowed {
		if err := os.WriteFile(path, []byte("allowed\n"), 0o600); err != nil {
			t.Fatalf("allowed write %s: %v", path, err)
		}
		t.Logf("allowed write: %s", filepath.Base(path))
	}
	for _, path := range plan.Denied {
		err := os.WriteFile(path, []byte("denied\n"), 0o600)
		if err == nil {
			t.Fatalf("denied write unexpectedly succeeded: %s", path)
		}
		if !errors.Is(err, syscall.EACCES) &&
			!errors.Is(err, syscall.EPERM) &&
			!errors.Is(err, syscall.EROFS) {
			t.Fatalf("denied write returned an unexpected error for %s: %v", path, err)
		}
		t.Logf("denied write: %s: %v", filepath.Base(path), err)
	}
	for _, path := range plan.AllowedMetadata {
		for _, mutation := range confinementMetadataMutations(path) {
			if err := mutation.apply(); err != nil {
				if mutation.name == "setxattr" && xattrUnsupported(err) {
					t.Logf("allowed metadata %s unsupported: %v", mutation.name, err)
					continue
				}
				t.Fatalf("allowed metadata %s %s: %v", mutation.name, path, err)
			}
			t.Logf("allowed metadata %s: %s", mutation.name, filepath.Base(path))
		}
	}
	for _, path := range plan.DeniedMetadata {
		for _, mutation := range confinementMetadataMutations(path) {
			err := mutation.apply()
			if mutation.name == "setxattr" && xattrUnsupported(err) {
				t.Logf("denied metadata %s unsupported: %v", mutation.name, err)
				continue
			}
			if err == nil {
				t.Fatalf("denied metadata %s unexpectedly succeeded: %s", mutation.name, path)
			}
			if !confinementMutationDenied(err) {
				t.Fatalf(
					"denied metadata %s returned an unexpected error for %s: %v",
					mutation.name,
					path,
					err,
				)
			}
			t.Logf("denied metadata %s: %s: %v", mutation.name, filepath.Base(path), err)
		}
	}
}

type confinementMetadataMutation struct {
	name  string
	apply func() error
}

func confinementMetadataMutations(path string) []confinementMetadataMutation {
	timestamp := time.Unix(123456789, 0)
	return []confinementMetadataMutation{
		{name: "chmod", apply: func() error { return os.Chmod(path, 0o640) }},
		{name: "utime", apply: func() error { return os.Chtimes(path, timestamp, timestamp) }},
		{name: "chown", apply: func() error { return os.Chown(path, os.Getuid(), os.Getgid()) }},
		{name: "setxattr", apply: func() error {
			return unix.Setxattr(path, "user.iop_agentworkspace_test", []byte("metadata"), 0)
		}},
	}
}

func confinementMutationDenied(err error) bool {
	return errors.Is(err, syscall.EACCES) ||
		errors.Is(err, syscall.EPERM) ||
		errors.Is(err, syscall.EROFS)
}

func xattrUnsupported(err error) bool {
	return errors.Is(err, unix.ENOTSUP) || errors.Is(err, unix.EOPNOTSUPP)
}

func TestOverlayBackendConfinementDeniesActualAbsoluteWrites(t *testing.T) {
	if runtime.GOOS != "linux" && runtime.GOOS != "darwin" {
		t.Skip("executable confinement is implemented on Linux and macOS")
	}
	baseRoot, localRoot := newWorkspaceFixture(t)
	initializeDirtyGitFixture(t, baseRoot)
	protectedDescriptorPath := filepath.Join(baseRoot, "descriptor-protected.txt")
	writeFile(t, protectedDescriptorPath, "descriptor protected\n", 0o600)
	beforeSnapshot, err := captureWorkspaceSnapshot(
		context.Background(),
		baseRoot,
		"",
		"config-r1",
		"grant-r1",
	)
	if err != nil {
		t.Fatalf("capture before snapshot: %v", err)
	}
	beforeStatus := gitOutput(t, baseRoot, "status", "--porcelain=v1", "--untracked-files=all")
	beforeGitConfig, err := os.ReadFile(filepath.Join(baseRoot, ".git", "config"))
	if err != nil {
		t.Fatalf("read canonical Git config: %v", err)
	}

	backend := newTestBackend(t, localRoot, baseRoot)
	first, err := backend.Prepare(
		context.Background(),
		testIsolationRequest("task-a", "task-a#1"),
	)
	if err != nil {
		t.Fatalf("Prepare(first): %v", err)
	}
	second, err := backend.Prepare(
		context.Background(),
		testIsolationRequest("task-b", "task-b#1"),
	)
	if err != nil {
		t.Fatalf("Prepare(second): %v", err)
	}
	firstRecord, err := backend.LoadRecord(*first.Descriptor)
	if err != nil {
		t.Fatalf("LoadRecord(first): %v", err)
	}
	secondRecord, err := backend.LoadRecord(*second.Descriptor)
	if err != nil {
		t.Fatalf("LoadRecord(second): %v", err)
	}
	beforeSnapshotRecord, err := os.ReadFile(firstRecord.Locator.SnapshotRecord)
	if err != nil {
		t.Fatalf("read snapshot record: %v", err)
	}

	allowed := []string{
		filepath.Join(firstRecord.Locator.ViewRoot, "child-view.txt"),
		filepath.Join(firstRecord.Locator.TempRoot, "child-temp.txt"),
		filepath.Join(firstRecord.Locator.CacheRoot, "child-cache.txt"),
	}
	denied := []string{
		filepath.Join(baseRoot, "canonical-child.txt"),
		protectedDescriptorPath,
		filepath.Join(secondRecord.Locator.ViewRoot, "sibling-child.txt"),
		filepath.Join(firstRecord.Locator.SnapshotRoot, "snapshot-child.txt"),
		filepath.Join(baseRoot, ".git", "confinement-child"),
	}
	deniedMetadata := []string{
		filepath.Join(baseRoot, "shared.txt"),
		protectedDescriptorPath,
		filepath.Join(secondRecord.Locator.ViewRoot, "shared.txt"),
		firstRecord.Locator.SnapshotRecord,
		firstRecord.Locator.OverlayRecord,
		filepath.Join(baseRoot, ".git", "config"),
	}
	beforeMetadata := make(map[string]fileMetadata, len(deniedMetadata))
	for _, path := range deniedMetadata {
		beforeMetadata[path] = captureFileMetadata(t, path)
	}
	encodedPlan, err := json.Marshal(confinementHelperPlan{
		Allowed:         allowed,
		Denied:          denied,
		AllowedMetadata: allowed,
		DeniedMetadata:  deniedMetadata,
	})
	if err != nil {
		t.Fatalf("encode helper plan: %v", err)
	}
	protectedDescriptor, err := os.OpenFile(
		protectedDescriptorPath,
		os.O_WRONLY|os.O_APPEND,
		0,
	)
	if err != nil {
		t.Fatalf("open protected host descriptor: %v", err)
	}
	defer protectedDescriptor.Close()
	started, err := first.Confinement.Start(
		context.Background(),
		agenttask.ConfinementCommand{
			Name: os.Args[0],
			Args: []string{
				"-test.run=^TestConfinementWriteHelper$",
				"-test.v",
			},
			Env: append(
				os.Environ(),
				confinementHelperEnvironment+"="+
					base64.RawURLEncoding.EncodeToString(encodedPlan),
			),
		},
	)
	if err != nil {
		t.Fatalf("start confined child: %v", err)
	}
	stdoutFile, stdoutIsFile := started.Stdout().(*os.File)
	stderrFile, stderrIsFile := started.Stderr().(*os.File)
	if !stdoutIsFile || !stderrIsFile ||
		stdoutFile.Fd() == protectedDescriptor.Fd() ||
		stderrFile.Fd() == protectedDescriptor.Fd() {
		t.Fatal("proof-owned child output reused the protected host descriptor")
	}
	type pipeResult struct {
		content string
		err     error
	}
	stdoutResult := make(chan pipeResult, 1)
	stderrResult := make(chan pipeResult, 1)
	go func() {
		content, err := io.ReadAll(started.Stdout())
		stdoutResult <- pipeResult{content: string(content), err: err}
	}()
	go func() {
		content, err := io.ReadAll(started.Stderr())
		stderrResult <- pipeResult{content: string(content), err: err}
	}()
	if err := started.Stdin().Close(); err != nil {
		t.Fatalf("close confined child stdin: %v", err)
	}
	waitErr := started.Child().Wait()
	stdout := <-stdoutResult
	stderr := <-stderrResult
	if stdout.err != nil || stderr.err != nil {
		t.Fatalf("read confined helper output: stdout=%v stderr=%v", stdout.err, stderr.err)
	}
	output := stdout.content + stderr.content
	if waitErr != nil {
		t.Fatalf("confined helper: %v\n%s", waitErr, output)
	}
	if err := started.Abort(); err != nil {
		t.Fatalf("cleanup confined helper: %v", err)
	}
	t.Logf("confined child output:\n%s", output)
	if !strings.Contains(output, "allowed write") ||
		!strings.Contains(output, "denied write") ||
		!strings.Contains(output, "allowed metadata") ||
		!strings.Contains(output, "denied metadata") {
		t.Fatalf("confined helper did not report both outcomes:\n%s", output)
	}

	for _, path := range allowed {
		assertFileContent(t, path, "allowed\n")
	}
	for _, path := range denied {
		if path == protectedDescriptorPath {
			assertFileContent(t, path, "descriptor protected\n")
			continue
		}
		assertNotExist(t, path)
	}
	for path, before := range beforeMetadata {
		if after := captureFileMetadata(t, path); after != before {
			t.Fatalf("confined child changed protected metadata at %s: before=%#v after=%#v", path, before, after)
		}
	}
	afterSnapshotRecord, err := os.ReadFile(firstRecord.Locator.SnapshotRecord)
	if err != nil {
		t.Fatalf("read snapshot record after child: %v", err)
	}
	if string(afterSnapshotRecord) != string(beforeSnapshotRecord) {
		t.Fatal("confined child changed the immutable snapshot record")
	}
	afterGitConfig, err := os.ReadFile(filepath.Join(baseRoot, ".git", "config"))
	if err != nil {
		t.Fatalf("read canonical Git config after child: %v", err)
	}
	if string(afterGitConfig) != string(beforeGitConfig) {
		t.Fatal("confined child changed shared Git metadata")
	}
	afterStatus := gitOutput(t, baseRoot, "status", "--porcelain=v1", "--untracked-files=all")
	if afterStatus != beforeStatus {
		t.Fatalf("canonical Git status changed:\nbefore=%q\nafter=%q", beforeStatus, afterStatus)
	}
	afterSnapshot, err := captureWorkspaceSnapshot(
		context.Background(),
		baseRoot,
		"",
		"config-r1",
		"grant-r1",
	)
	if err != nil {
		t.Fatalf("capture after snapshot: %v", err)
	}
	if afterSnapshot.Revision != beforeSnapshot.Revision {
		t.Fatalf(
			"canonical fingerprint changed: %q != %q",
			afterSnapshot.Revision,
			beforeSnapshot.Revision,
		)
	}
}

type fileMetadata struct {
	Mode    os.FileMode
	ModTime time.Time
}

func captureFileMetadata(t *testing.T, path string) fileMetadata {
	t.Helper()
	info, err := os.Lstat(path)
	if err != nil {
		t.Fatalf("stat %s: %v", path, err)
	}
	return fileMetadata{Mode: info.Mode(), ModTime: info.ModTime()}
}

func TestOverlayBackendConcurrentTasksSharePinnedDirtyBaseAndIsolateWrites(t *testing.T) {
	if runtime.GOOS == "windows" {
		t.Skip("mode and symlink fixtures require Unix filesystem semantics")
	}
	baseRoot, localRoot := newWorkspaceFixture(t)
	initializeDirtyGitFixture(t, baseRoot)
	beforeStatus := gitOutput(t, baseRoot, "status", "--porcelain=v1", "--untracked-files=all")

	backend := newTestBackend(t, localRoot, baseRoot)
	requests := []agenttask.IsolationRequest{
		testIsolationRequest("task-a", "task-a#1"),
		testIsolationRequest("task-b", "task-b#1"),
	}
	prepared := make([]agenttask.PreparedIsolation, len(requests))
	errorsByIndex := make([]error, len(requests))
	var wait sync.WaitGroup
	for index := range requests {
		index := index
		wait.Add(1)
		go func() {
			defer wait.Done()
			prepared[index], errorsByIndex[index] = backend.Prepare(
				context.Background(),
				requests[index],
			)
		}()
	}
	wait.Wait()
	for index, err := range errorsByIndex {
		if err != nil {
			t.Fatalf("Prepare task %d: %v", index, err)
		}
	}

	first := prepared[0].Descriptor
	second := prepared[1].Descriptor
	if first.PinnedBaseRevision != second.PinnedBaseRevision {
		t.Fatalf(
			"pinned base revisions differ: %q != %q",
			first.PinnedBaseRevision,
			second.PinnedBaseRevision,
		)
	}
	if first.TaskRoot == second.TaskRoot || first.WorkingDir == second.WorkingDir {
		t.Fatalf("task roots are not isolated: %#v %#v", first, second)
	}
	for _, result := range prepared {
		admission := agentguard.Admit(agentguard.AdmissionRequest{
			Grant: result.Grant, Isolation: result.Descriptor, Profile: result.Profile,
		})
		if !admission.Allowed() {
			t.Fatalf("prepared overlay was not admissible: %#v", admission.Blocker)
		}
	}

	firstRecord, err := backend.LoadRecord(*first)
	if err != nil {
		t.Fatalf("LoadRecord(first): %v", err)
	}
	secondRecord, err := backend.LoadRecord(*second)
	if err != nil {
		t.Fatalf("LoadRecord(second): %v", err)
	}
	if firstRecord.Locator.SnapshotRoot != secondRecord.Locator.SnapshotRoot {
		t.Fatalf(
			"snapshot roots differ: %q != %q",
			firstRecord.Locator.SnapshotRoot,
			secondRecord.Locator.SnapshotRoot,
		)
	}
	assertSnapshotEvidence(t, firstRecord.Locator.SnapshotRecord)
	assertFileContent(t, filepath.Join(first.WorkingDir, "shared.txt"), "dirty base\n")
	assertFileContent(t, filepath.Join(second.WorkingDir, "shared.txt"), "dirty base\n")
	assertFileContent(t, filepath.Join(first.WorkingDir, "untracked.txt"), "untracked base\n")
	assertFileContent(t, filepath.Join(second.WorkingDir, "untracked.txt"), "untracked base\n")
	assertSymlink(t, filepath.Join(first.WorkingDir, "shared-link"), "shared.txt")
	assertExecutable(t, filepath.Join(first.WorkingDir, "script.sh"))

	writeFile(t, filepath.Join(first.WorkingDir, "shared.txt"), "task a\n", 0o644)
	writeFile(t, filepath.Join(second.WorkingDir, "shared.txt"), "task b\n", 0o644)
	writeFile(t, filepath.Join(first.WorkingDir, "only-a.txt"), "a\n", 0o644)
	writeFile(t, filepath.Join(second.WorkingDir, "only-b.txt"), "b\n", 0o644)
	writeFile(t, filepath.Join(firstRecord.Locator.TempRoot, "build.tmp"), "a temp\n", 0o600)
	writeFile(t, filepath.Join(secondRecord.Locator.TempRoot, "build.tmp"), "b temp\n", 0o600)
	writeFile(t, filepath.Join(firstRecord.Locator.CacheRoot, "cache"), "a cache\n", 0o600)
	writeFile(t, filepath.Join(secondRecord.Locator.CacheRoot, "cache"), "b cache\n", 0o600)
	writeFile(t, filepath.Join(firstRecord.Locator.GitMetadata, "task-owned"), "a git\n", 0o600)

	assertFileContent(t, filepath.Join(first.WorkingDir, "shared.txt"), "task a\n")
	assertFileContent(t, filepath.Join(second.WorkingDir, "shared.txt"), "task b\n")
	assertFileContent(t, filepath.Join(baseRoot, "shared.txt"), "dirty base\n")
	assertNotExist(t, filepath.Join(baseRoot, "only-a.txt"))
	assertNotExist(t, filepath.Join(baseRoot, "only-b.txt"))
	assertNotExist(t, filepath.Join(second.WorkingDir, "only-a.txt"))
	assertNotExist(t, filepath.Join(first.WorkingDir, "only-b.txt"))
	assertFileContent(t, filepath.Join(firstRecord.Locator.TempRoot, "build.tmp"), "a temp\n")
	assertFileContent(t, filepath.Join(secondRecord.Locator.TempRoot, "build.tmp"), "b temp\n")
	assertFileContent(t, filepath.Join(firstRecord.Locator.CacheRoot, "cache"), "a cache\n")
	assertFileContent(t, filepath.Join(secondRecord.Locator.CacheRoot, "cache"), "b cache\n")
	assertNotExist(t, filepath.Join(baseRoot, ".git", "task-owned"))
	assertNotExist(t, filepath.Join(secondRecord.Locator.GitMetadata, "task-owned"))

	afterStatus := gitOutput(t, baseRoot, "status", "--porcelain=v1", "--untracked-files=all")
	if beforeStatus != afterStatus {
		t.Fatalf("canonical Git state changed:\nbefore=%q\nafter=%q", beforeStatus, afterStatus)
	}

	assertWritableRootDenied(t, prepared[0], baseRoot, agentguard.BlockerCodeWritableRootEscape)
	assertWritableRootDenied(
		t,
		prepared[0],
		secondRecord.Locator.ViewRoot,
		agentguard.BlockerCodeWritableRootEscape,
	)
	canonicalLink := filepath.Join(firstRecord.Locator.TempRoot, "canonical-link")
	if err := os.Symlink(baseRoot, canonicalLink); err != nil {
		t.Fatalf("create canonical link: %v", err)
	}
	assertWritableRootDenied(
		t,
		prepared[0],
		canonicalLink,
		agentguard.BlockerCodeWritableRootEscape,
	)
}

func TestOverlayBackendIdempotencyAndFailureRetention(t *testing.T) {
	baseRoot, localRoot := newWorkspaceFixture(t)
	writeFile(t, filepath.Join(baseRoot, "input.txt"), "base\n", 0o644)
	backend := newTestBackend(t, localRoot, baseRoot)
	request := testIsolationRequest("task", "task#1")

	first, err := backend.Prepare(context.Background(), request)
	if err != nil {
		t.Fatalf("Prepare(first): %v", err)
	}
	writeFile(t, filepath.Join(first.Descriptor.WorkingDir, "partial.txt"), "retained\n", 0o600)
	writeFile(t, filepath.Join(baseRoot, "input.txt"), "base drift\n", 0o644)
	second, err := backend.Prepare(context.Background(), request)
	if err != nil {
		t.Fatalf("Prepare(second): %v", err)
	}
	if first.Descriptor.ID != second.Descriptor.ID ||
		first.Descriptor.Revision != second.Descriptor.Revision ||
		first.Descriptor.TaskRoot != second.Descriptor.TaskRoot {
		t.Fatalf("idempotent prepare changed identity: %#v != %#v", first.Descriptor, second.Descriptor)
	}
	assertFileContent(t, filepath.Join(second.Descriptor.WorkingDir, "input.txt"), "base\n")

	conflicting := request
	conflicting.Work.Unit.ID = "other-task"
	conflicting.Work.AttemptID = "other-task#1"
	if _, err := backend.Prepare(context.Background(), conflicting); err == nil ||
		!strings.Contains(err.Error(), "does not match the request") {
		t.Fatalf("conflicting idempotency key error = %v", err)
	}

	freshRequest := testIsolationRequest("fresh-task", "fresh-task#1")
	fresh, err := backend.Prepare(context.Background(), freshRequest)
	if err != nil {
		t.Fatalf("Prepare(fresh): %v", err)
	}
	if fresh.Descriptor.PinnedBaseRevision == first.Descriptor.PinnedBaseRevision {
		t.Fatal("fresh task reused a stale base revision")
	}
	assertFileContent(t, filepath.Join(fresh.Descriptor.WorkingDir, "input.txt"), "base drift\n")

	blockedProfile := second.Profile
	blockedProfile.ApprovalBypass = false
	admission := agentguard.Admit(agentguard.AdmissionRequest{
		Grant: second.Grant, Isolation: second.Descriptor, Profile: blockedProfile,
	})
	if admission.Allowed() ||
		admission.Blocker == nil ||
		admission.Blocker.Code != agentguard.BlockerCodeProviderApprovalBypassUnavailable {
		t.Fatalf("unexpected blocked admission: %#v", admission)
	}
	record, err := backend.LoadRecord(*second.Descriptor)
	if err != nil {
		t.Fatalf("LoadRecord after admission failure: %v", err)
	}
	if record.Retention != RetentionStateActive {
		t.Fatalf("retention state = %q, want %q", record.Retention, RetentionStateActive)
	}
	if record.RetentionPolicy.BlockedDays != 14 {
		t.Fatalf("blocked retention days = %d, want 14", record.RetentionPolicy.BlockedDays)
	}
	assertFileContent(t, filepath.Join(second.Descriptor.WorkingDir, "partial.txt"), "retained\n")
	assertFileContent(t, filepath.Join(baseRoot, "input.txt"), "base drift\n")
}

func TestOverlayBackendRejectsRetainedIdentityRebinding(t *testing.T) {
	baseRootA, localRoot := newWorkspaceFixture(t)
	baseRootB := filepath.Join(filepath.Dir(baseRootA), "workspace-b")
	if err := os.MkdirAll(baseRootB, 0o700); err != nil {
		t.Fatalf("create root B: %v", err)
	}
	writeFile(t, filepath.Join(baseRootA, "identity.txt"), "root A\n", 0o600)
	writeFile(t, filepath.Join(baseRootB, "identity.txt"), "root B\n", 0o600)

	resolvedRoot := baseRootA
	resolver := InputResolverFunc(func(
		_ context.Context,
		request agenttask.IsolationRequest,
	) (ResolvedInputs, error) {
		return ResolvedInputs{
			Grant: agentguard.WorkspaceGrant{
				ProjectID:   string(request.Project.ProjectID),
				WorkspaceID: string(request.Project.WorkspaceID),
				Root:        resolvedRoot,
				Revision:    string(request.Project.Intent.GrantRevision),
			},
			Profile: agentguard.ProviderProfile{
				ProviderID:              request.Target.ProviderID,
				ModelID:                 request.Target.ModelID,
				ProfileID:               request.Target.ProfileID,
				Revision:                request.Target.ProfileRevision,
				Unattended:              true,
				ApprovalBypass:          true,
				WritableRootConfinement: true,
			},
		}, nil
	})
	backend, err := NewBackend(BackendConfig{LocalRoot: localRoot}, resolver)
	if err != nil {
		t.Fatalf("NewBackend: %v", err)
	}
	request := testIsolationRequest("task", "task#1")
	first, err := backend.Prepare(context.Background(), request)
	if err != nil {
		t.Fatalf("Prepare(first): %v", err)
	}
	record, err := backend.LoadRecord(*first.Descriptor)
	if err != nil {
		t.Fatalf("LoadRecord(first): %v", err)
	}
	beforeRecord, err := os.ReadFile(record.Locator.OverlayRecord)
	if err != nil {
		t.Fatalf("read retained record: %v", err)
	}
	snapshot, err := readWorkspaceSnapshot(record.Locator.SnapshotRecord)
	if err != nil {
		t.Fatalf("read retained snapshot: %v", err)
	}
	if snapshot.CanonicalRoot != baseRootA ||
		snapshot.ConfigRevision != "config-r1" ||
		snapshot.GrantRevision != "grant-r1" {
		t.Fatalf("snapshot identity = %#v", snapshot)
	}

	resolvedRoot = baseRootB
	if _, err := backend.Prepare(context.Background(), request); err == nil ||
		!strings.Contains(err.Error(), "identity does not match") {
		t.Fatalf("root rebinding error = %v", err)
	}
	resolvedRoot = baseRootA

	configRebind := request
	configIntent := *request.Project.Intent
	configIntent.ConfigRevision = "config-r2"
	configRebind.Project.Intent = &configIntent
	configRebind.Target.ConfigRevision = "config-r2"
	if _, err := backend.Prepare(context.Background(), configRebind); err == nil ||
		!strings.Contains(err.Error(), "identity does not match") {
		t.Fatalf("config rebinding error = %v", err)
	}

	grantRebind := request
	grantIntent := *request.Project.Intent
	grantIntent.GrantRevision = "grant-r2"
	grantRebind.Project.Intent = &grantIntent
	if _, err := backend.Prepare(context.Background(), grantRebind); err == nil ||
		!strings.Contains(err.Error(), "identity does not match") {
		t.Fatalf("grant rebinding error = %v", err)
	}

	afterRecord, err := os.ReadFile(record.Locator.OverlayRecord)
	if err != nil {
		t.Fatalf("read retained record after rejection: %v", err)
	}
	if string(afterRecord) != string(beforeRecord) {
		t.Fatal("identity rebinding changed the retained overlay record")
	}
	exact, err := backend.Prepare(context.Background(), request)
	if err != nil {
		t.Fatalf("Prepare(exact replay): %v", err)
	}
	if exact.Descriptor.ID != first.Descriptor.ID ||
		exact.Descriptor.Revision != first.Descriptor.Revision ||
		exact.Descriptor.ConfinementRevision != first.Descriptor.ConfinementRevision {
		t.Fatalf("exact replay changed identity: %#v != %#v", exact.Descriptor, first.Descriptor)
	}
	assertFileContent(t, filepath.Join(exact.Descriptor.WorkingDir, "identity.txt"), "root A\n")
}

func TestOverlayBackendRejectsCanonicalSymlinkEscapeBeforeCreatingTask(t *testing.T) {
	if runtime.GOOS == "windows" {
		t.Skip("symlink fixture requires Unix filesystem semantics")
	}
	baseRoot, localRoot := newWorkspaceFixture(t)
	outside := filepath.Join(filepath.Dir(baseRoot), "outside.txt")
	writeFile(t, outside, "outside\n", 0o600)
	if err := os.Symlink(outside, filepath.Join(baseRoot, "escape")); err != nil {
		t.Fatalf("create escaping symlink: %v", err)
	}
	backend := newTestBackend(t, localRoot, baseRoot)
	_, err := backend.Prepare(
		context.Background(),
		testIsolationRequest("task", "task#1"),
	)
	if err == nil || !strings.Contains(err.Error(), "absolute symlink") {
		t.Fatalf("Prepare error = %v, want absolute symlink confinement failure", err)
	}
	entries, readErr := os.ReadDir(filepath.Join(localRoot, "tasks"))
	if readErr != nil {
		t.Fatalf("ReadDir tasks: %v", readErr)
	}
	if len(entries) != 0 {
		t.Fatalf("failed preparation left task artifacts: %v", entries)
	}
}

func TestOverlayBackendRejectsNestedSharedGitMetadata(t *testing.T) {
	baseRoot, localRoot := newWorkspaceFixture(t)
	writeFile(t, filepath.Join(baseRoot, "nested", ".git", "config"), "[core]\n", 0o600)
	backend := newTestBackend(t, localRoot, baseRoot)
	_, err := backend.Prepare(
		context.Background(),
		testIsolationRequest("task", "task#1"),
	)
	if err == nil || !strings.Contains(err.Error(), "nested Git metadata") {
		t.Fatalf("Prepare error = %v, want nested Git metadata failure", err)
	}
	entries, readErr := os.ReadDir(filepath.Join(localRoot, "tasks"))
	if readErr != nil {
		t.Fatalf("ReadDir tasks: %v", readErr)
	}
	if len(entries) != 0 {
		t.Fatalf("failed preparation left task artifacts: %v", entries)
	}
}

func newTestBackend(t *testing.T, localRoot, baseRoot string) *Backend {
	t.Helper()
	resolver := InputResolverFunc(func(
		_ context.Context,
		request agenttask.IsolationRequest,
	) (ResolvedInputs, error) {
		return ResolvedInputs{
			Grant: agentguard.WorkspaceGrant{
				ProjectID:   string(request.Project.ProjectID),
				WorkspaceID: string(request.Project.WorkspaceID),
				Root:        baseRoot,
				Revision:    string(request.Project.Intent.GrantRevision),
			},
			Profile: agentguard.ProviderProfile{
				ProviderID:              request.Target.ProviderID,
				ModelID:                 request.Target.ModelID,
				ProfileID:               request.Target.ProfileID,
				Revision:                request.Target.ProfileRevision,
				Unattended:              true,
				ApprovalBypass:          true,
				WritableRootConfinement: true,
			},
		}, nil
	})
	backend, err := NewBackend(BackendConfig{
		LocalRoot: localRoot,
		Retention: agentconfig.RetentionPolicy{
			CompletedDays: 7,
			BlockedDays:   14,
		},
	}, resolver)
	if err != nil {
		t.Fatalf("NewBackend: %v", err)
	}
	return backend
}

func testIsolationRequest(workID agenttask.WorkUnitID, attemptID agenttask.AttemptID) agenttask.IsolationRequest {
	projectID := agenttask.ProjectID("project")
	workspaceID := agenttask.WorkspaceID("workspace")
	return agenttask.IsolationRequest{
		Project: agenttask.ProjectRecord{
			ProjectID:   projectID,
			WorkspaceID: workspaceID,
			Intent: &agenttask.StartIntent{
				ProjectID: projectID, WorkspaceID: workspaceID,
				GrantRevision: "grant-r1", ConfigRevision: "config-r1",
			},
		},
		Work: agenttask.WorkRecord{
			Unit: agenttask.WorkUnit{
				ID: workID, IsolationMode: agentguard.IsolationModeOverlay,
			},
			AttemptID: attemptID,
		},
		Target: agenttask.ExecutionTarget{
			ProviderID: "provider", ModelID: "model", ProfileID: "profile",
			ProfileRevision: "profile-r1", ConfigRevision: "config-r1", Capacity: 2,
		},
		IdempotencyKey: "dispatch/" + string(workID) + "/" + string(attemptID) + "/isolation",
	}
}

func newWorkspaceFixture(t *testing.T) (string, string) {
	t.Helper()
	root, err := filepath.EvalSymlinks(t.TempDir())
	if err != nil {
		t.Fatalf("EvalSymlinks: %v", err)
	}
	baseRoot := filepath.Join(root, "workspace")
	localRoot := filepath.Join(root, "runtime")
	for _, directory := range []string{baseRoot, localRoot} {
		if err := os.MkdirAll(directory, 0o700); err != nil {
			t.Fatalf("MkdirAll %s: %v", directory, err)
		}
	}
	return baseRoot, localRoot
}

func initializeDirtyGitFixture(t *testing.T, root string) {
	t.Helper()
	if _, err := exec.LookPath("git"); err != nil {
		t.Skip("git is required for the workspace snapshot fixture")
	}
	gitRun(t, root, "init", "-q")
	gitRun(t, root, "config", "user.email", "agentworkspace@example.invalid")
	gitRun(t, root, "config", "user.name", "Agent Workspace Test")
	writeFile(t, filepath.Join(root, "shared.txt"), "committed\n", 0o644)
	writeFile(t, filepath.Join(root, "script.sh"), "#!/bin/sh\nexit 0\n", 0o755)
	if err := os.Symlink("shared.txt", filepath.Join(root, "shared-link")); err != nil {
		t.Fatalf("create internal symlink: %v", err)
	}
	gitRun(t, root, "add", "shared.txt", "script.sh", "shared-link")
	gitRun(t, root, "commit", "-q", "-m", "fixture")
	writeFile(t, filepath.Join(root, "shared.txt"), "dirty base\n", 0o644)
	writeFile(t, filepath.Join(root, "untracked.txt"), "untracked base\n", 0o644)
}

func assertSnapshotEvidence(t *testing.T, recordPath string) {
	t.Helper()
	snapshot, err := readWorkspaceSnapshot(recordPath)
	if err != nil {
		t.Fatalf("readWorkspaceSnapshot: %v", err)
	}
	entries := make(map[string]SnapshotEntry, len(snapshot.Entries))
	for _, entry := range snapshot.Entries {
		entries[entry.Path] = entry
	}
	shared := entries["shared.txt"]
	if shared.GitState != SnapshotGitStateTracked || !shared.Dirty ||
		shared.ContentDigest == "" {
		t.Fatalf("tracked dirty entry = %#v", shared)
	}
	untracked := entries["untracked.txt"]
	if untracked.GitState != SnapshotGitStateUntracked || untracked.Dirty ||
		untracked.ContentDigest == "" {
		t.Fatalf("untracked entry = %#v", untracked)
	}
	script := entries["script.sh"]
	if os.FileMode(script.Mode).Perm()&0o100 == 0 {
		t.Fatalf("script mode was not fingerprinted: %#o", script.Mode)
	}
	link := entries["shared-link"]
	if link.Kind != SnapshotEntrySymlink || link.SymlinkTarget != "shared.txt" ||
		link.ContentDigest == "" {
		t.Fatalf("symlink entry = %#v", link)
	}
}

func assertWritableRootDenied(
	t *testing.T,
	prepared agenttask.PreparedIsolation,
	root string,
	want agentguard.BlockerCode,
) {
	t.Helper()
	descriptor := *prepared.Descriptor
	descriptor.WritableRoots = append(append([]string(nil), descriptor.WritableRoots...), root)
	result := agentguard.Admit(agentguard.AdmissionRequest{
		Grant: prepared.Grant, Isolation: &descriptor, Profile: prepared.Profile,
	})
	if result.Allowed() || result.Blocker == nil || result.Blocker.Code != want {
		t.Fatalf("tampered writable root result = %#v, want %q", result, want)
	}
}

func assertFileContent(t *testing.T, path, want string) {
	t.Helper()
	content, err := os.ReadFile(path)
	if err != nil {
		t.Fatalf("ReadFile %s: %v", path, err)
	}
	if string(content) != want {
		t.Fatalf("content %s = %q, want %q", path, content, want)
	}
}

func assertNotExist(t *testing.T, path string) {
	t.Helper()
	if _, err := os.Lstat(path); !os.IsNotExist(err) {
		t.Fatalf("path %s exists or returned unexpected error: %v", path, err)
	}
}

func assertSymlink(t *testing.T, path, want string) {
	t.Helper()
	target, err := os.Readlink(path)
	if err != nil {
		t.Fatalf("Readlink %s: %v", path, err)
	}
	if target != want {
		t.Fatalf("symlink target %s = %q, want %q", path, target, want)
	}
}

func assertExecutable(t *testing.T, path string) {
	t.Helper()
	info, err := os.Stat(path)
	if err != nil {
		t.Fatalf("Stat %s: %v", path, err)
	}
	if info.Mode().Perm()&0o100 == 0 {
		t.Fatalf("%s is not executable: %s", path, info.Mode())
	}
}

func writeFile(t *testing.T, path, content string, mode os.FileMode) {
	t.Helper()
	if err := os.MkdirAll(filepath.Dir(path), 0o700); err != nil {
		t.Fatalf("MkdirAll %s: %v", filepath.Dir(path), err)
	}
	if err := os.WriteFile(path, []byte(content), mode); err != nil {
		t.Fatalf("WriteFile %s: %v", path, err)
	}
	if err := os.Chmod(path, mode); err != nil {
		t.Fatalf("Chmod %s: %v", path, err)
	}
}

func gitRun(t *testing.T, root string, args ...string) {
	t.Helper()
	command := exec.Command("git", append([]string{"-C", root}, args...)...)
	command.Env = append(os.Environ(), "LC_ALL=C")
	if output, err := command.CombinedOutput(); err != nil {
		t.Fatalf("git %v: %v\n%s", args, err, output)
	}
}

func gitOutput(t *testing.T, root string, args ...string) string {
	t.Helper()
	command := exec.Command("git", append([]string{"-C", root}, args...)...)
	command.Env = append(os.Environ(), "GIT_OPTIONAL_LOCKS=0", "LC_ALL=C")
	output, err := command.CombinedOutput()
	if err != nil {
		t.Fatalf("git %v: %v\n%s", args, err, output)
	}
	return string(output)
}