Pin the nested agent-intent to the U5 snapshot fix

Why: composition consistency - Dev pins agent-intent at 765a7e7; the
native container's nested copy must match (check-pins).
Evidence: pin only; intent library verified by verify-u5.
Impact: nested gitlink pointer change.
Refs: feature/agent-stack-audit-remediation-b1

adapters/native/backend.go

@@ -141,7 +141,7 @@ func (b *Backend) Close() {
 
 // Execute 运行一轮带工具的自研智能体循环，产出目标交付物。
 func (b *Backend) Execute(ctx context.Context, req exec.Request) (*exec.Result, error) {
-	if len(req.Targets) == 0 {
+	if len(req.Targets) == 0 && !allowEmptyTargets(ctx) {
 		req.Targets = []string{"output.md"}
 	}
 	profile := strings.TrimSpace(req.ToolProfile)
@@ -149,10 +149,10 @@ func (b *Backend) Execute(ctx context.Context, req exec.Request) (*exec.Result,
 		profile = exec.ToolProfileWorkspace
 	}
 	if profile != exec.ToolProfileWorkspace && profile != exec.ToolProfileReasoning {
-		return &exec.Result{Success: false, ErrorReason: "unknown tool profile: " + profile}, nil
+		return preflightFail("unknown tool profile: " + profile), nil
 	}
 	if b.opts.Stream == nil && (strings.TrimSpace(b.opts.APIBase) == "" || strings.TrimSpace(b.opts.APIKey) == "") {
-		return &exec.Result{Success: false, ErrorReason: "agent-native backend requires api base/key (or injected stream)"}, nil
+		return preflightFail("agent-native backend requires api base/key (or injected stream)"), nil
 	}
 	if b.opts.Ask != nil {
 		ctx = mcp.WithAsk(ctx, b.opts.Ask)
@@ -168,7 +168,7 @@ func (b *Backend) Execute(ctx context.Context, req exec.Request) (*exec.Result,
 		model = strings.TrimSpace(req.Model)
 	}
 	if model == "" {
-		return &exec.Result{Success: false, ErrorReason: "agent-native backend requires model"}, nil
+		return preflightFail("agent-native backend requires model"), nil
 	}
 
 	workDir := req.WorkDir
@@ -177,7 +177,7 @@ func (b *Backend) Execute(ctx context.Context, req exec.Request) (*exec.Result,
 		// 落一次性临时目录，不污染进程 CWD（契约套件即发此类请求）。
 		tmp, err := os.MkdirTemp("", "agent-native-run-*")
 		if err != nil {
-			return &exec.Result{Success: false, ErrorReason: err.Error()}, nil
+			return preflightFail(err.Error()), nil
 		}
 		workDir = tmp
 	} else if !filepath.IsAbs(workDir) {
@@ -185,7 +185,7 @@ func (b *Backend) Execute(ctx context.Context, req exec.Request) (*exec.Result,
 		workDir = filepath.Join(wd, workDir)
 	}
 	if err := os.MkdirAll(workDir, 0o755); err != nil {
-		return &exec.Result{Success: false, ErrorReason: err.Error()}, nil
+		return preflightFail(err.Error()), nil
 	}
 	if strings.TrimSpace(req.Instructions) != "" {
 		_ = os.WriteFile(filepath.Join(workDir, "INSTRUCTIONS.md"), []byte(req.Instructions), 0o644)
@@ -207,13 +207,28 @@ func (b *Backend) Execute(ctx context.Context, req exec.Request) (*exec.Result,
 	}
 	for _, name := range req.Skills {
 		if !indexSet[name] {
-			return &exec.Result{Success: false, ErrorReason: "declared skill not installed: " + name}, nil
+			return preflightFail("declared skill not installed: " + name), nil
 		}
 	}
 
+	writable := writableFrom(ctx)
+	// F02: a non-empty Writable cannot be enforced for exec/MCP/host tools —
+	// reject in preflight rather than pretend the write-set holds.
+	if len(writable) > 0 && profile == exec.ToolProfileWorkspace {
+		if b.opts.Exec != nil {
+			return preflightFail("writable write-set cannot be enforced when exec tools are enabled"), nil
+		}
+		if b.opts.MCP != nil {
+			return preflightFail("writable write-set cannot be enforced when MCP tools are enabled"), nil
+		}
+		if len(b.opts.HostTools) > 0 {
+			return preflightFail("writable write-set cannot be enforced when host tools are enabled"), nil
+		}
+	}
 	var reg *tools.Registry
 	if profile == exec.ToolProfileWorkspace {
 		reg = tools.WorkspaceToolsCheckpointed(workDir, filestate.New(), b.opts.Checkpoints, b.opts.CheckpointAnchor)
+		tools.ApplyWriteAllowlist(reg, writable)
 		skills.RegisterLoader(reg, skillStore)
 		if b.opts.Search != nil {
 			tools.RegisterSearch(reg, b.opts.Search)
@@ -237,7 +252,7 @@ func (b *Backend) Execute(ctx context.Context, req exec.Request) (*exec.Result,
 			switch {
 			case len(req.ToolAllowlist) > 0 || b.opts.MCP.Ready():
 				if err := b.opts.MCP.RegisterInto(ctx, reg); err != nil {
-					return &exec.Result{Success: false, ErrorReason: err.Error()}, nil
+					return preflightFail(err.Error()), nil
 				}
 			default:
 				b.opts.MCP.StartBackground(ctx, reg)
@@ -246,32 +261,31 @@ func (b *Backend) Execute(ctx context.Context, req exec.Request) (*exec.Result,
 		subagent.Register(reg, b.opts.Subagent)
 		for _, tool := range b.opts.HostTools {
 			if reg.Has(tool.Name()) {
-				return &exec.Result{Success: false, ErrorReason: "host tool name conflicts with a builtin: " + tool.Name()}, nil
+				return preflightFail("host tool name conflicts with a builtin: " + tool.Name()), nil
 			}
 			reg.Register(tool)
 		}
 		if err := reg.Restrict(req.ToolAllowlist); err != nil {
-			return &exec.Result{Success: false, ErrorReason: err.Error()}, nil
+			return preflightFail(err.Error()), nil
 		}
 	}
+	// Scope-keyed transcript: empty scope keeps the legacy fixed path.
+	transcript := transcriptPathForScope(workDir, req.SessionScope)
 	// 会话毒化轮转：上次失败属 resume-unsafe 时，把旧 transcript 归档，
 	// 本次以全新会话开始（续跑毒化会话只会复现同样的失败）。
-	b.rotateIfPoisoned(workDir)
-	store, err := session.Open(filepath.Join(workDir, ".agentx", "transcript.jsonl"))
+	b.rotateIfPoisoned(workDir, transcript)
+	store, err := session.Open(transcript)
 	if err != nil {
-		return &exec.Result{Success: false, ErrorReason: err.Error()}, nil
+		return preflightFail(err.Error()), nil
 	}
 	stream := b.opts.Stream
 	if stream == nil {
 		client := &llm.Client{BaseURL: b.opts.APIBase, APIKey: b.opts.APIKey}
 		stream = client.Stream
 	}
-	_ = store.SaveMeta(map[string]string{
-		"model":   model,
-		"scope":   req.SessionScope,
-		"exec_id": req.ExecutionID,
-		"updated": time.Now().UTC().Format(time.RFC3339),
-	})
+	if err := b.bindSessionScope(store, req.SessionScope, model, req.ExecutionID); err != nil {
+		return preflightFail(err.Error()), nil
+	}
 	b.maybeCompact(ctx, store, stream, model)
 
 	timeout := req.Timeout
@@ -317,36 +331,82 @@ func (b *Backend) Execute(ctx context.Context, req exec.Request) (*exec.Result,
 	onProcess := req.OnEvent
 	runRes, err := b.run(runCtx, model, runBudget, reg, store, stream, profile, req, workDir, skillIndex, &logs, onProcess)
 	if err != nil {
-		return &exec.Result{Success: false, ErrorReason: err.Error(), Logs: logs.String()}, nil
+		// Persist/session transport failure after the run started: outcome uncertain.
+		return &exec.Result{
+			Success: false, ErrorReason: err.Error(), Logs: logs.String(),
+			Unknown: true, SideEffects: exec.SideEffectPossible,
+		}, nil
 	}
 	_ = os.WriteFile(filepath.Join(workDir, "execution.log"), []byte(logs.String()), 0o644)
 
+	// CapText sink: always capture the final assistant text for contract mapping.
+	captureText(ctx, runRes.Text)
+
 	// reasoning 档无工具：把最终文本写入仍为空的目标文件。
+	// 先授权全部 target，任一拒绝则零写入（避免 ../、绝对路径、符号链接逃逸先落地）。
 	if profile == exec.ToolProfileReasoning && strings.TrimSpace(runRes.Text) != "" {
+		type reasoningTarget struct {
+			path string
+			skip bool
+		}
+		authorized := make([]reasoningTarget, 0, len(req.Targets))
 		for _, target := range req.Targets {
-			path := filepath.Join(workDir, filepath.FromSlash(target))
-			if b2, err := os.ReadFile(path); err == nil && len(strings.TrimSpace(string(b2))) > 0 {
+			if !pathInWriteSet(writable, target) {
+				return &exec.Result{
+					Success: false, ErrorReason: "target is outside the declared writable set: " + target,
+					Logs: logs.String(), SideEffects: sideEffectsForTools(runRes.ToolCalls),
+				}, nil
+			}
+			path, resolveErr := tools.Resolve(workDir, filepath.FromSlash(target))
+			if resolveErr != nil {
+				return &exec.Result{
+					Success: false, ErrorReason: resolveErr.Error(), Logs: logs.String(),
+					SideEffects: sideEffectsForTools(runRes.ToolCalls),
+				}, nil
+			}
+			skip := false
+			if b2, readErr := os.ReadFile(path); readErr == nil && len(strings.TrimSpace(string(b2))) > 0 {
+				skip = true
+			}
+			authorized = append(authorized, reasoningTarget{path: path, skip: skip})
+		}
+		for _, at := range authorized {
+			if at.skip {
 				continue
 			}
-			_ = os.MkdirAll(filepath.Dir(path), 0o755)
-			_ = os.WriteFile(path, []byte(runRes.Text), 0o644)
+			_ = os.MkdirAll(filepath.Dir(at.path), 0o755)
+			_ = os.WriteFile(at.path, []byte(runRes.Text), 0o644)
 		}
 	}
 
 	if runRes.Err != nil {
 		reason := runRes.Err.Error()
 		b.noteFailure(workDir, reason)
+		canceled := runRes.Canceled || runRes.StopReason == llm.StopAborted
+		retryable := runRes.Retryable && !canceled
 		assessment := exec.AssessStepFailure(exec.StepFailureSignals{
 			Err:     runRes.Err,
 			WorkDir: workDir,
-			Result:  &exec.Result{ErrorReason: reason, Retryable: runRes.Retryable, Logs: logs.String()},
+			Result:  &exec.Result{ErrorReason: reason, Retryable: retryable, Logs: logs.String()},
 		})
 		b.logger().Error("native step failure classified", runRes.Err,
 			"failure_class", assessment.Class.String(),
-			"work_dir", workDir)
-		res := &exec.Result{Success: false, ErrorReason: reason, Logs: logs.String(), Retryable: runRes.Retryable}
-		if runRes.StopReason == llm.StopAborted {
-			res.Retryable = true
+			"work_dir", workDir,
+			"canceled", canceled)
+		res := &exec.Result{
+			Success:     false,
+			ErrorReason: reason,
+			Logs:        logs.String(),
+			Retryable:   retryable,
+			Canceled:    canceled,
+			SideEffects: exec.SideEffectPossible,
+		}
+		if canceled {
+			// Aborted/canceled: never retryable; side effects may already exist.
+			res.Retryable = false
+			res.SideEffects = exec.SideEffectPossible
+		} else if runRes.ToolCalls == 0 {
+			res.SideEffects = exec.SideEffectNone
 		}
 		return res, nil
 	}
@@ -354,7 +414,14 @@ func (b *Backend) Execute(ctx context.Context, req exec.Request) (*exec.Result,
 
 	patches, matErr := exec.MaterializeTargets(workDir, req.Targets, nil)
 	if matErr != nil {
-		return &exec.Result{Success: false, ErrorReason: matErr.Error(), Patches: patches, Logs: logs.String()}, nil
+		return &exec.Result{
+			Success: false, ErrorReason: matErr.Error(), Patches: patches, Logs: logs.String(),
+			SideEffects: exec.SideEffectPossible,
+		}, nil
+	}
+	side := sideEffectsForTools(runRes.ToolCalls)
+	if len(patches) > 0 {
+		side = exec.SideEffectPossible
 	}
 	return &exec.Result{
 		Success:          true,
@@ -362,6 +429,7 @@ func (b *Backend) Execute(ctx context.Context, req exec.Request) (*exec.Result,
 		Logs:             logs.String(),
 		PromptTokens:     runRes.Usage.PromptTokens,
 		CompletionTokens: runRes.Usage.CompletionTokens,
+		SideEffects:      side,
 	}, nil
 }
 
@@ -522,6 +590,19 @@ type errString string
 
 func (e errString) Error() string { return string(e) }
 
+// preflightFail is a definitive rejection before any tool dispatch.
+func preflightFail(reason string) *exec.Result {
+	return &exec.Result{Success: false, ErrorReason: reason, SideEffects: exec.SideEffectNone}
+}
+
+// sideEffectsForTools maps dispatched tool count to a SideEffects qualifier.
+func sideEffectsForTools(toolCalls int) exec.SideEffects {
+	if toolCalls > 0 {
+		return exec.SideEffectPossible
+	}
+	return exec.SideEffectNone
+}
+
 // resumeUnsafeMarkers 续跑不安全的关键词（会话已被污染：上下文溢出/
 // 迭代上限/非法请求——重试必须换新会话而非续跑）。
 var resumeUnsafeMarkers = []string{
@@ -531,7 +612,7 @@ var resumeUnsafeMarkers = []string{
 }
 
 // rotateIfPoisoned 上次失败属 resume-unsafe 且存在旧会话时归档旧会话。
-func (b *Backend) rotateIfPoisoned(workDir string) {
+func (b *Backend) rotateIfPoisoned(workDir, transcript string) {
 	reason := strings.ToLower(b.failureReason(workDir))
 	if reason == "" {
 		return
@@ -546,7 +627,10 @@ func (b *Backend) rotateIfPoisoned(workDir string) {
 	if !unsafe {
 		return
 	}
-	path := filepath.Join(workDir, ".agentx", "transcript.jsonl")
+	path := transcript
+	if strings.TrimSpace(path) == "" {
+		path = filepath.Join(workDir, ".agentx", "transcript.jsonl")
+	}
 	if _, err := os.Stat(path); err != nil {
 		return
 	}
@@ -555,6 +639,36 @@ func (b *Backend) rotateIfPoisoned(workDir string) {
 		"transcript.poisoned."+time.Now().UTC().Format("20060102T150405.000000000")+".jsonl"))
 }
 
+// bindSessionScope records scope identity on the store and fail-closes when an
+// existing store's recorded identity differs or is absent for a non-empty scope
+// (do not auto-attribute old records to a new identity).
+func (b *Backend) bindSessionScope(store *session.Store, scopeID, model, execID string) error {
+	meta := store.ReadMeta()
+	if meta == nil {
+		meta = map[string]string{}
+	}
+	if scopeID != "" {
+		prev := strings.TrimSpace(meta["scope"])
+		if prev != "" && prev != scopeID {
+			return errString("session store scope identity mismatch: store has " + prev + ", request has " + scopeID)
+		}
+		if prev == "" {
+			entries, err := store.Entries()
+			if err != nil {
+				return err
+			}
+			if len(entries) > 0 {
+				return errString("session store lacks scope identity; refusing to adopt for scope " + scopeID)
+			}
+		}
+		meta["scope"] = scopeID
+	}
+	meta["model"] = model
+	meta["exec_id"] = execID
+	meta["updated"] = time.Now().UTC().Format(time.RFC3339)
+	return store.SaveMeta(meta)
+}
+
 func (b *Backend) logger() *logsys.Logger {
 	if b == nil || b.opts.Log == nil {
 		return logsys.Nop()

adapters/native/backend_test.go

@@ -111,6 +111,79 @@ func TestBackendReasoningProfileWritesText(t *testing.T) {
 	}
 }
 
+func TestBackendReasoningProfileRejectsPathEscape(t *testing.T) {
+	parent := t.TempDir()
+	dir := filepath.Join(parent, "work")
+	if err := os.MkdirAll(dir, 0o755); err != nil {
+		t.Fatal(err)
+	}
+	outside := filepath.Join(parent, "pwned.md")
+	leak := "SHOULD-NOT-ESCAPE"
+	b := New(Options{
+		ModelOptions: ModelOptions{
+			Model: "fake",
+			Stream: script(
+				llm.Message{Role: llm.RoleAssistant, Content: leak, StopReason: llm.StopEnd},
+			),
+		},
+	})
+
+	// Traversal: authorize-before-write must reject and leave zero target writes.
+	res, err := b.Execute(context.Background(), exec.Request{
+		WorkDir: dir, Prompt: "escape", ToolProfile: exec.ToolProfileReasoning,
+		Targets: []string{"safe.md", "../pwned.md"},
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if res.Success || !strings.Contains(res.ErrorReason, "escapes workspace") {
+		t.Fatalf("want path escape failure, got %+v", res)
+	}
+	if _, statErr := os.Stat(outside); !os.IsNotExist(statErr) {
+		t.Fatalf("traversal must not create outside file: %v", statErr)
+	}
+	if _, statErr := os.Stat(filepath.Join(dir, "safe.md")); !os.IsNotExist(statErr) {
+		t.Fatal("rejected batch must perform zero target writes")
+	}
+
+	// Absolute path outside workDir.
+	res, err = b.Execute(context.Background(), exec.Request{
+		WorkDir: dir, Prompt: "escape-abs", ToolProfile: exec.ToolProfileReasoning,
+		Targets: []string{outside},
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if res.Success || !strings.Contains(res.ErrorReason, "escapes workspace") {
+		t.Fatalf("want absolute escape failure, got %+v", res)
+	}
+	if _, statErr := os.Stat(outside); !os.IsNotExist(statErr) {
+		t.Fatalf("absolute escape must not create outside file: %v", statErr)
+	}
+
+	// Symlink component leaving the workspace.
+	outsideDir := filepath.Join(parent, "outside-dir")
+	if err := os.MkdirAll(outsideDir, 0o755); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.Symlink(outsideDir, filepath.Join(dir, "link")); err != nil {
+		t.Fatal(err)
+	}
+	res, err = b.Execute(context.Background(), exec.Request{
+		WorkDir: dir, Prompt: "escape-symlink", ToolProfile: exec.ToolProfileReasoning,
+		Targets: []string{"link/secret.md"},
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if res.Success || !strings.Contains(res.ErrorReason, "escapes workspace") {
+		t.Fatalf("want symlink escape failure, got %+v", res)
+	}
+	if _, statErr := os.Stat(filepath.Join(outsideDir, "secret.md")); !os.IsNotExist(statErr) {
+		t.Fatalf("symlink escape must not write outside: %v", statErr)
+	}
+}
+
 func TestBackendFailClosedWithoutConfig(t *testing.T) {
 	b := New(Options{})
 	res, err := b.Execute(context.Background(), exec.Request{WorkDir: t.TempDir(), Targets: []string{"x.md"}})

adapters/native/contract.go

@@ -39,6 +39,7 @@ func (c contractBackend) Execute(ctx context.Context, req exec.ContractRequest)
 	if profile == "" {
 		profile = exec.ToolProfileReasoning
 	}
+	scopeID := scopeIdentity(req.SessionScope)
 	old := exec.Request{
 		Prompt:        req.Prompt,
 		Instructions:  req.Instructions,
@@ -47,6 +48,7 @@ func (c contractBackend) Execute(ctx context.Context, req exec.ContractRequest)
 		ToolProfile:   profile,
 		ToolAllowlist: append([]string(nil), req.ToolPolicy.Allowlist...),
 		WorkDir:       req.Workspace.Root,
+		SessionScope:  scopeID,
 		OnEvent:       onEvent,
 	}
 	if b := req.ContractBudget; b.MaxPromptTokens > 0 || b.MaxCompletionTokens > 0 || !b.Deadline.IsZero() {
@@ -56,6 +58,15 @@ func (c contractBackend) Execute(ctx context.Context, req exec.ContractRequest)
 			Deadline:            b.Deadline,
 		}
 	}
+	// CapText / F15: pure-text contract tasks must not force implicit file delivery.
+	explicitTargets := len(req.Targets) > 0
+	if !explicitTargets && profile == exec.ToolProfileReasoning {
+		ctx = withAllowEmptyTargets(ctx)
+	}
+	ctx = withWritable(ctx, req.Workspace.Writable)
+	var finalText string
+	ctx = withTextSink(ctx, &finalText)
+
 	res, err := c.b.Execute(ctx, old)
 	if err != nil {
 		// 传输/实现级错误：按契约映射为 Unknown，不经 Go error 返回业务终态。
@@ -74,7 +85,16 @@ func (c contractBackend) Execute(ctx context.Context, req exec.ContractRequest)
 	switch {
 	case res.Success:
 		out.Outcome = exec.OutcomeSucceeded
-		out.Files = res.Patches
+		if explicitTargets {
+			out.Files = res.Patches
+		}
+		// CapText: surface the real assistant text for pure-text success.
+		out.Text = finalText
+		if out.Text == "" && len(res.Patches) == 1 {
+			for _, body := range res.Patches {
+				out.Text = string(body)
+			}
+		}
 	case errors.Is(ctx.Err(), context.Canceled):
 		out.Outcome = exec.OutcomeCanceled
 		out.Err = &exec.Error{Code: exec.ErrCanceled, Reason: res.ErrorReason, SideEffects: exec.SideEffectPossible}

adapters/native/contract_bind.go

@@ -0,0 +1,91 @@
+package native
+
+import (
+	"context"
+	"crypto/sha256"
+	"encoding/hex"
+	"path/filepath"
+	"strings"
+
+	"agent-native/exec"
+)
+
+// Contract-binding context keys: Writable / CapText / empty-target semantics
+// stay inside the adapter so exec.Request remains unchanged for the legacy facade.
+
+type ctxKey int
+
+const (
+	keyWritable ctxKey = iota
+	keyAllowEmptyTargets
+	keyTextSink
+)
+
+func withWritable(ctx context.Context, paths []string) context.Context {
+	if len(paths) == 0 {
+		return ctx
+	}
+	return context.WithValue(ctx, keyWritable, append([]string(nil), paths...))
+}
+
+func writableFrom(ctx context.Context) []string {
+	v, _ := ctx.Value(keyWritable).([]string)
+	return v
+}
+
+func withAllowEmptyTargets(ctx context.Context) context.Context {
+	return context.WithValue(ctx, keyAllowEmptyTargets, true)
+}
+
+func allowEmptyTargets(ctx context.Context) bool {
+	v, _ := ctx.Value(keyAllowEmptyTargets).(bool)
+	return v
+}
+
+func withTextSink(ctx context.Context, sink *string) context.Context {
+	if sink == nil {
+		return ctx
+	}
+	return context.WithValue(ctx, keyTextSink, sink)
+}
+
+func captureText(ctx context.Context, text string) {
+	if sink, ok := ctx.Value(keyTextSink).(*string); ok && sink != nil {
+		*sink = text
+	}
+}
+
+// scopeIdentity returns a stable non-empty identity string for a non-zero
+// SessionScope, or "" for the legacy one-shot / empty-scope path.
+func scopeIdentity(s exec.SessionScope) string {
+	t := strings.TrimSpace(s.Tenant)
+	p := strings.TrimSpace(s.Project)
+	sess := strings.TrimSpace(s.Session)
+	if t == "" && p == "" && sess == "" {
+		return ""
+	}
+	return t + "/" + p + "/" + sess
+}
+
+// transcriptPathForScope binds storage identity to SessionScope.
+// Empty scope keeps the historical fixed path under .agentx/transcript.jsonl.
+func transcriptPathForScope(workDir, scopeID string) string {
+	if strings.TrimSpace(scopeID) == "" {
+		return filepath.Join(workDir, ".agentx", "transcript.jsonl")
+	}
+	sum := sha256.Sum256([]byte(scopeID))
+	return filepath.Join(workDir, ".agentx", "transcript."+hex.EncodeToString(sum[:16])+".jsonl")
+}
+
+func pathInWriteSet(allow []string, rel string) bool {
+	if len(allow) == 0 {
+		return true
+	}
+	rel = filepath.ToSlash(filepath.Clean(strings.TrimSpace(rel)))
+	for _, a := range allow {
+		if filepath.ToSlash(filepath.Clean(strings.TrimSpace(a))) == rel {
+			return true
+		}
+	}
+	return false
+}

adapters/native/contract_regression_test.go

@@ -0,0 +1,291 @@
+package native
+
+import (
+	"context"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+
+	"agent-native/exec"
+	"agent-native/runtime/llm"
+	"agent-native/runtime/session"
+	"agent-native/runtime/tools"
+)
+
+func TestContractScopeIsolationNoSharedTranscript(t *testing.T) {
+	dir := t.TempDir()
+	b := New(Options{
+		ModelOptions: ModelOptions{
+			Model: "fake",
+			Stream: script(
+				llm.Message{Role: llm.RoleAssistant, Content: "from-a", StopReason: llm.StopEnd},
+			),
+		},
+	}).Contract()
+
+	scopeA := exec.SessionScope{Tenant: "t1", Project: "p1", Session: "s-a"}
+	scopeB := exec.SessionScope{Tenant: "t1", Project: "p1", Session: "s-b"}
+	resA, err := b.Execute(context.Background(), exec.ContractRequest{
+		ExecutionID:  "e-a",
+		Prompt:       "hello-a",
+		SessionScope: scopeA,
+		Workspace:    exec.WorkspaceHandle{Root: dir},
+	})
+	if err != nil || resA.Outcome != exec.OutcomeSucceeded {
+		t.Fatalf("scope A: %+v %v", resA, err)
+	}
+
+	// Fresh backend/stream for scope B so replies differ.
+	b2 := New(Options{
+		ModelOptions: ModelOptions{
+			Model: "fake",
+			Stream: script(
+				llm.Message{Role: llm.RoleAssistant, Content: "from-b", StopReason: llm.StopEnd},
+			),
+		},
+	}).Contract()
+	resB, err := b2.Execute(context.Background(), exec.ContractRequest{
+		ExecutionID:  "e-b",
+		Prompt:       "hello-b",
+		SessionScope: scopeB,
+		Workspace:    exec.WorkspaceHandle{Root: dir},
+	})
+	if err != nil || resB.Outcome != exec.OutcomeSucceeded {
+		t.Fatalf("scope B: %+v %v", resB, err)
+	}
+
+	pathA := transcriptPathForScope(dir, scopeIdentity(scopeA))
+	pathB := transcriptPathForScope(dir, scopeIdentity(scopeB))
+	if pathA == pathB {
+		t.Fatal("different scopes must not share a transcript path")
+	}
+	if pathA == filepath.Join(dir, ".agentx", "transcript.jsonl") {
+		t.Fatal("non-empty scope must not use the legacy fixed transcript path")
+	}
+	storeA, err := session.Open(pathA)
+	if err != nil {
+		t.Fatal(err)
+	}
+	storeB, err := session.Open(pathB)
+	if err != nil {
+		t.Fatal(err)
+	}
+	msgsA, err := storeA.Load()
+	if err != nil {
+		t.Fatal(err)
+	}
+	msgsB, err := storeB.Load()
+	if err != nil {
+		t.Fatal(err)
+	}
+	joinedA := messagesBlob(msgsA)
+	joinedB := messagesBlob(msgsB)
+	if strings.Contains(joinedA, "hello-b") || strings.Contains(joinedA, "from-b") {
+		t.Fatalf("scope A transcript leaked B context: %s", joinedA)
+	}
+	if strings.Contains(joinedB, "hello-a") || strings.Contains(joinedB, "from-a") {
+		t.Fatalf("scope B transcript leaked A context: %s", joinedB)
+	}
+}
+
+func TestContractMatchingScopeCanResume(t *testing.T) {
+	dir := t.TempDir()
+	scope := exec.SessionScope{Tenant: "t", Project: "p", Session: "resume-me"}
+	b1 := New(Options{
+		ModelOptions: ModelOptions{
+			Model:  "fake",
+			Stream: script(llm.Message{Role: llm.RoleAssistant, Content: "first", StopReason: llm.StopEnd}),
+		},
+	}).Contract()
+	if res, err := b1.Execute(context.Background(), exec.ContractRequest{
+		ExecutionID: "e1", Prompt: "turn-1", SessionScope: scope,
+		Workspace: exec.WorkspaceHandle{Root: dir},
+	}); err != nil || res.Outcome != exec.OutcomeSucceeded {
+		t.Fatalf("first turn: %+v %v", res, err)
+	}
+
+	var sawPrior bool
+	b2 := New(Options{
+		ModelOptions: ModelOptions{
+			Model: "fake",
+			Stream: func(ctx context.Context, model string, messages []llm.Message, decls []llm.ToolDecl, opts llm.StreamOptions) <-chan llm.Event {
+				for _, m := range messages {
+					if m.Role == llm.RoleUser && m.Content == "turn-1" {
+						sawPrior = true
+					}
+					if m.Role == llm.RoleAssistant && m.Content == "first" {
+						sawPrior = true
+					}
+				}
+				ch := make(chan llm.Event, 2)
+				go func() {
+					defer close(ch)
+					ch <- llm.Event{Kind: llm.KindTextDelta, Text: "second"}
+					ch <- llm.Event{Kind: llm.KindMessageEnd, Message: llm.Message{Role: llm.RoleAssistant, Content: "second", StopReason: llm.StopEnd}}
+				}()
+				return ch
+			},
+		},
+	}).Contract()
+	if res, err := b2.Execute(context.Background(), exec.ContractRequest{
+		ExecutionID: "e2", Prompt: "turn-2", SessionScope: scope,
+		Workspace: exec.WorkspaceHandle{Root: dir},
+	}); err != nil || res.Outcome != exec.OutcomeSucceeded {
+		t.Fatalf("resume turn: %+v %v", res, err)
+	}
+	if !sawPrior {
+		t.Fatal("matching scope must resume prior transcript context")
+	}
+}
+
+func TestContractOldStoreWithoutIdentityNotAdopted(t *testing.T) {
+	dir := t.TempDir()
+	scope := exec.SessionScope{Tenant: "t", Project: "p", Session: "orphan"}
+	path := transcriptPathForScope(dir, scopeIdentity(scope))
+	if err := os.MkdirAll(filepath.Dir(path), 0o755); err != nil {
+		t.Fatal(err)
+	}
+	// Pre-seed records with no scope identity in meta.
+	body := "{\"role\":\"user\",\"content\":\"old\"}\n{\"role\":\"assistant\",\"content\":\"ghost\"}\n"
+	if err := os.WriteFile(path, []byte(body), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	b := New(Options{
+		ModelOptions: ModelOptions{
+			Model:  "fake",
+			Stream: script(llm.Message{Role: llm.RoleAssistant, Content: "new", StopReason: llm.StopEnd}),
+		},
+	}).Contract()
+	res, err := b.Execute(context.Background(), exec.ContractRequest{
+		ExecutionID: "e-orphan", Prompt: "hi", SessionScope: scope,
+		Workspace: exec.WorkspaceHandle{Root: dir},
+	})
+	if err != nil {
+		t.Fatalf("transport: %v", err)
+	}
+	if res.Outcome == exec.OutcomeSucceeded {
+		t.Fatal("must not auto-adopt a store lacking scope identity")
+	}
+	if res.Err == nil || !strings.Contains(res.Err.Reason, "scope identity") {
+		t.Fatalf("want scope-identity refusal, got %+v", res.Err)
+	}
+}
+
+func TestContractWritableFileToolHonorsAllowlist(t *testing.T) {
+	dir := t.TempDir()
+	b := New(Options{
+		ModelOptions: ModelOptions{
+			Model: "fake",
+			Stream: script(
+				llm.Message{Role: llm.RoleAssistant, StopReason: llm.StopToolCalls, ToolCalls: []llm.ToolCall{{
+					ID: "c1", Name: "write_file", Arguments: `{"path":"allowed.md","content":"ok"}`,
+				}}},
+				llm.Message{Role: llm.RoleAssistant, StopReason: llm.StopToolCalls, ToolCalls: []llm.ToolCall{{
+					ID: "c2", Name: "write_file", Arguments: `{"path":"denied.md","content":"no"}`,
+				}}},
+				llm.Message{Role: llm.RoleAssistant, Content: "done", StopReason: llm.StopEnd},
+			),
+		},
+	}).Contract()
+	res, err := b.Execute(context.Background(), exec.ContractRequest{
+		ExecutionID: "e-w",
+		Prompt:      "write",
+		Workspace: exec.WorkspaceHandle{
+			Root:     dir,
+			Writable: []string{"allowed.md"},
+		},
+		ToolPolicy: exec.ToolPolicy{Profile: exec.ToolProfileWorkspace},
+		Targets:    []string{"allowed.md"},
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if res.Outcome != exec.OutcomeSucceeded {
+		// Tool denial is soft (IsError to model); run may still succeed if allowed.md exists.
+		t.Logf("outcome=%s err=%+v", res.Outcome, res.Err)
+	}
+	if _, err := os.Stat(filepath.Join(dir, "allowed.md")); err != nil {
+		t.Fatalf("allowed write missing: %v (outcome=%s)", err, res.Outcome)
+	}
+	if _, err := os.Stat(filepath.Join(dir, "denied.md")); !os.IsNotExist(err) {
+		t.Fatal("denied.md must not be written under Writable allowlist")
+	}
+}
+
+func TestContractWritableRejectsExecInPreflight(t *testing.T) {
+	dir := t.TempDir()
+	b := New(Options{
+		ModelOptions: ModelOptions{
+			Model:  "fake",
+			Stream: script(llm.Message{Role: llm.RoleAssistant, Content: "x", StopReason: llm.StopEnd}),
+		},
+		ToolOptions: ToolOptions{
+			Exec: &tools.ExecConfig{Bash: "/bin/bash"},
+		},
+	}).Contract()
+	res, err := b.Execute(context.Background(), exec.ContractRequest{
+		ExecutionID: "e-exec",
+		Prompt:      "x",
+		Workspace: exec.WorkspaceHandle{
+			Root:     dir,
+			Writable: []string{"a.md"},
+		},
+		ToolPolicy: exec.ToolPolicy{Profile: exec.ToolProfileWorkspace},
+		Targets:    []string{"a.md"},
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if res.Outcome == exec.OutcomeSucceeded {
+		t.Fatal("Writable + exec tools enabled must be rejected in preflight")
+	}
+	if res.Err == nil || !strings.Contains(res.Err.Reason, "writable") {
+		t.Fatalf("want writable preflight error, got %+v", res.Err)
+	}
+}
+
+func TestContractPureTextSuccessCarriesText(t *testing.T) {
+	dir := t.TempDir()
+	b := New(Options{
+		ModelOptions: ModelOptions{
+			Model:  "fake",
+			Stream: script(llm.Message{Role: llm.RoleAssistant, Content: "纯文本答复内容", StopReason: llm.StopEnd}),
+		},
+	}).Contract()
+	res, err := b.Execute(context.Background(), exec.ContractRequest{
+		ExecutionID: "e-text",
+		Prompt:      "说点什么",
+		Workspace:   exec.WorkspaceHandle{Root: dir},
+		// empty ToolPolicy → reasoning; empty Targets → CapText, no file delivery
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if res.Outcome != exec.OutcomeSucceeded {
+		t.Fatalf("outcome=%s err=%+v", res.Outcome, res.Err)
+	}
+	if strings.TrimSpace(res.Text) == "" {
+		t.Fatal("CapText pure-text success must carry non-empty Text")
+	}
+	if !strings.Contains(res.Text, "纯文本答复内容") {
+		t.Fatalf("Text=%q", res.Text)
+	}
+	if len(res.Files) != 0 {
+		t.Fatalf("pure-text must not force file delivery, Files=%v", res.Files)
+	}
+	if _, err := os.Stat(filepath.Join(dir, "output.md")); !os.IsNotExist(err) {
+		t.Fatal("pure-text must not implicitly write output.md")
+	}
+}
+
+func messagesBlob(msgs []llm.Message) string {
+	var b strings.Builder
+	for _, m := range msgs {
+		b.WriteString(string(m.Role))
+		b.WriteByte(':')
+		b.WriteString(m.Content)
+		b.WriteByte('\n')
+	}
+	return b.String()
+}

adapters/native/r2_regression_test.go

@@ -20,7 +20,7 @@ func TestR2PoisonMarkerSurvivesNewProcess(t *testing.T) {
 		t.Fatal(err)
 	}
 	b := New(Options{})
-	b.rotateIfPoisoned(dir)
+	b.rotateIfPoisoned(dir, transcript)
 	if _, err := os.Stat(transcript); !os.IsNotExist(err) {
 		t.Fatal("poisoned transcript still at the live path")
 	}

adapters/native/result_fidelity_test.go

@@ -0,0 +1,178 @@
+package native
+
+import (
+	"context"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+	"time"
+
+	"agent-native/exec"
+	"agent-native/runtime/llm"
+)
+
+// TestExecuteCanceledIsNotRetryable: aborted/canceled runs carry Canceled
+// semantics with Retryable=false and SideEffects=possible.
+func TestExecuteCanceledIsNotRetryable(t *testing.T) {
+	dir := t.TempDir()
+	b := New(Options{
+		ModelOptions: ModelOptions{
+			Model: "fake",
+			Stream: func(ctx context.Context, model string, messages []llm.Message, decls []llm.ToolDecl, opts llm.StreamOptions) <-chan llm.Event {
+				ch := make(chan llm.Event, 1)
+				go func() {
+					<-ctx.Done()
+					ch <- llm.Event{
+						Kind:      llm.KindError,
+						Err:       ctx.Err(),
+						Retryable: true, // provider may mark abort retryable; adapter must not.
+						Message:   llm.Message{Role: llm.RoleAssistant, StopReason: llm.StopAborted},
+					}
+					close(ch)
+				}()
+				return ch
+			},
+		},
+	})
+	ctx, cancel := context.WithTimeout(context.Background(), 30*time.Millisecond)
+	defer cancel()
+	res, err := b.Execute(ctx, exec.Request{
+		WorkDir: dir, Prompt: "cancel me", Targets: []string{"output.md"},
+	})
+	if err != nil {
+		t.Fatalf("transport error: %v", err)
+	}
+	if res.Success {
+		t.Fatalf("canceled run must not succeed: %+v", res)
+	}
+	if !res.Canceled {
+		t.Fatalf("want Canceled=true, got %+v", res)
+	}
+	if res.Retryable {
+		t.Fatalf("canceled must not be Retryable: %+v", res)
+	}
+	if res.EffectiveSideEffects() != exec.SideEffectPossible {
+		t.Fatalf("canceled SideEffects = %q, want possible", res.EffectiveSideEffects())
+	}
+}
+
+// TestExecuteToolFailureSideEffectsPossible: failure after tools may have run
+// reports SideEffects=possible.
+func TestExecuteToolFailureSideEffectsPossible(t *testing.T) {
+	dir := t.TempDir()
+	var call int
+	b := New(Options{
+		ModelOptions: ModelOptions{
+			Model: "fake",
+			Stream: func(ctx context.Context, model string, messages []llm.Message, decls []llm.ToolDecl, opts llm.StreamOptions) <-chan llm.Event {
+				ch := make(chan llm.Event, 2)
+				go func() {
+					defer close(ch)
+					call++
+					if call == 1 {
+						msg := llm.Message{Role: llm.RoleAssistant, StopReason: llm.StopToolCalls, ToolCalls: []llm.ToolCall{{
+							ID: "c1", Name: "write_file", Arguments: `{"path":"scratch.md","content":"side effect"}`,
+						}}}
+						ch <- llm.Event{Kind: llm.KindMessageEnd, Message: msg}
+						return
+					}
+					ch <- llm.Event{
+						Kind:    llm.KindError,
+						Err:     errString("provider failed after tools"),
+						Message: llm.Message{Role: llm.RoleAssistant, Content: "boom", StopReason: llm.StopError},
+					}
+				}()
+				return ch
+			},
+		},
+	})
+	res, err := b.Execute(context.Background(), exec.Request{
+		WorkDir: dir, Prompt: "write then fail", Targets: []string{"output.md"},
+	})
+	if err != nil {
+		t.Fatalf("transport error: %v", err)
+	}
+	if res.Success || res.Canceled {
+		t.Fatalf("want definitive failure after tools, got %+v", res)
+	}
+	if res.SideEffects != exec.SideEffectPossible {
+		t.Fatalf("SideEffects = %q, want possible", res.SideEffects)
+	}
+	if _, statErr := os.Stat(filepath.Join(dir, "scratch.md")); statErr != nil {
+		t.Fatalf("tool side effect missing: %v", statErr)
+	}
+}
+
+// TestExecutePreflightSideEffectsNone: validation rejection before tools
+// reports SideEffects=none.
+func TestExecutePreflightSideEffectsNone(t *testing.T) {
+	cases := []struct {
+		name string
+		opts Options
+		req  exec.Request
+		want string
+	}{
+		{
+			name: "missing-config",
+			opts: Options{},
+			req:  exec.Request{WorkDir: t.TempDir(), Targets: []string{"x.md"}},
+			want: "requires",
+		},
+		{
+			name: "bad-profile",
+			opts: Options{ModelOptions: ModelOptions{Stream: script(), Model: "fake"}},
+			req:  exec.Request{WorkDir: t.TempDir(), Targets: []string{"x.md"}, ToolProfile: "bogus"},
+			want: "tool profile",
+		},
+		{
+			name: "missing-model",
+			opts: Options{ModelOptions: ModelOptions{APIBase: "http://x", APIKey: "k"}},
+			req:  exec.Request{WorkDir: t.TempDir(), Targets: []string{"x.md"}},
+			want: "model",
+		},
+	}
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			res, err := New(tc.opts).Execute(context.Background(), tc.req)
+			if err != nil {
+				t.Fatalf("transport error: %v", err)
+			}
+			if res.Success || res.Canceled || res.Unknown || res.Retryable {
+				t.Fatalf("preflight must be definitive non-retry failure: %+v", res)
+			}
+			if res.SideEffects != exec.SideEffectNone {
+				t.Fatalf("SideEffects = %q, want none", res.SideEffects)
+			}
+			if !strings.Contains(res.ErrorReason, tc.want) {
+				t.Fatalf("ErrorReason = %q, want substring %q", res.ErrorReason, tc.want)
+			}
+		})
+	}
+}
+
+// TestExecuteSuccessSideEffectsReflectTools: success after tool dispatch
+// reports SideEffects=possible; patches also imply possible.
+func TestExecuteSuccessSideEffectsReflectTools(t *testing.T) {
+	dir := t.TempDir()
+	b := New(Options{
+		ModelOptions: ModelOptions{
+			Model: "fake",
+			Stream: script(
+				llm.Message{Role: llm.RoleAssistant, StopReason: llm.StopToolCalls, ToolCalls: []llm.ToolCall{{
+					ID: "c1", Name: "write_file", Arguments: `{"path":"output.md","content":"ok"}`,
+				}}},
+				llm.Message{Role: llm.RoleAssistant, Content: "done", StopReason: llm.StopEnd},
+			),
+		},
+	})
+	res, err := b.Execute(context.Background(), exec.Request{
+		WorkDir: dir, Prompt: "write", Targets: []string{"output.md"},
+	})
+	if err != nil || !res.Success {
+		t.Fatalf("want success, got err=%v res=%+v", err, res)
+	}
+	if res.SideEffects != exec.SideEffectPossible {
+		t.Fatalf("SideEffects = %q, want possible", res.SideEffects)
+	}
+}

exec/backend.go

@@ -76,10 +76,34 @@ type Result struct {
 	ErrorReason string            `json:"error_reason"`
 	// Retryable marks a provider-transient failure that may receive a
 	// fresh step invocation. Permanent missing deliverables stay false.
+	// Canceled and Unknown are never retryable; do not set Retryable with them.
 	Retryable bool `json:"retryable,omitempty"`
 	// PromptTokens and CompletionTokens are set by pi-native when the provider reports usage.
 	PromptTokens     int `json:"prompt_tokens,omitempty"`
 	CompletionTokens int `json:"completion_tokens,omitempty"`
+
+	// ---- terminal fidelity (optional; zero-value = legacy behavior) ----
+
+	// Canceled marks an aborted/canceled run. Distinct from Retryable:
+	// a canceled action must not be auto-retried (Retryable must stay false).
+	Canceled bool `json:"canceled,omitempty"`
+	// Unknown marks that execution reached the provider/tool stage and the
+	// terminal outcome could not be determined (side effects may exist).
+	// Unknown is not a retryable failure.
+	Unknown bool `json:"unknown,omitempty"`
+	// SideEffects qualifies external side-effect risk for retry/fallback.
+	// Empty means SideEffectPossible — the safe legacy reading. Set
+	// SideEffectNone only when no tool dispatch (or equivalent) is provable.
+	SideEffects SideEffects `json:"side_effects,omitempty"`
+}
+
+// EffectiveSideEffects returns the side-effect qualifier for retry decisions.
+// An empty SideEffects value means SideEffectPossible (backward compatible).
+func (r *Result) EffectiveSideEffects() SideEffects {
+	if r == nil || r.SideEffects == "" {
+		return SideEffectPossible
+	}
+	return r.SideEffects
 }
 
 type Backend interface {

exec/result_fidelity_test.go

@@ -0,0 +1,30 @@
+package exec_test
+
+import (
+	"testing"
+
+	"agent-native/exec"
+)
+
+// TestResultZeroValueKeepsLegacyMeaning pins backward compatibility:
+// empty SideEffects reads as possible; Canceled/Unknown stay false.
+func TestResultZeroValueKeepsLegacyMeaning(t *testing.T) {
+	var r exec.Result
+	if r.Success || r.Retryable || r.Canceled || r.Unknown {
+		t.Fatalf("zero Result must keep legacy false flags, got %+v", r)
+	}
+	if r.SideEffects != "" {
+		t.Fatalf("zero SideEffects must be empty (legacy), got %q", r.SideEffects)
+	}
+	if got := r.EffectiveSideEffects(); got != exec.SideEffectPossible {
+		t.Fatalf("EffectiveSideEffects() = %q, want %q", got, exec.SideEffectPossible)
+	}
+	r.SideEffects = exec.SideEffectNone
+	if got := r.EffectiveSideEffects(); got != exec.SideEffectNone {
+		t.Fatalf("explicit none: EffectiveSideEffects() = %q", got)
+	}
+	r.SideEffects = exec.SideEffectPossible
+	if got := r.EffectiveSideEffects(); got != exec.SideEffectPossible {
+		t.Fatalf("explicit possible: EffectiveSideEffects() = %q", got)
+	}
+}

runtime/loop.go

@@ -3,6 +3,7 @@ package runtime
 import (
 	"context"
 	"encoding/json"
+	"errors"
 	"fmt"
 	"strconv"
 	"strings"
@@ -198,6 +199,13 @@ type Result struct {
 	Notice     string
 	Err        error
 	Retryable  bool
+	// Canceled is true when the run stopped due to abort/cancel (StopAborted
+	// or context cancellation). Canceled runs are never retryable.
+	Canceled bool
+	// ToolCalls is the number of tool invocations dispatched during the run.
+	// Adapters use it to set SideEffects (0 before any dispatch => none where
+	// the failure is otherwise definitive; otherwise possible).
+	ToolCalls int
 }
 
 // Run executes the turn loop until the model stops, follow-ups drain, or the turn cap is hit.
@@ -332,19 +340,28 @@ func Run(ctx context.Context, cfg Config, user llm.Message) (Result, error) {
 	for turn := 0; turn < cfg.MaxTurns; turn++ {
 		if ctx.Err() != nil {
 			cfg.logger().Error("runtime turn aborted", ctx.Err())
-			return Result{Text: last.Content, Messages: messages, StopReason: llm.StopAborted, Err: ctx.Err()}, nil
+			return Result{
+				Text: last.Content, Messages: messages, StopReason: llm.StopAborted,
+				Err: ctx.Err(), Canceled: true, ToolCalls: toolCalls,
+			}, nil
 		}
 		if reason := budgetExceeded(cfg.Budget, usage, toolCalls, time.Now()); reason != "" {
-			return budgetStop(cfg, last, messages, usage, reason), nil
+			return budgetStop(cfg, last, messages, usage, toolCalls, reason), nil
 		}
 		emit(cfg, Event{Type: "turn_start"})
 		emit(cfg, Event{Type: "message_start"})
 		request := prepareRequest(cfg, messages, turn, &repeats, &lengthNudge)
 		end, errEv := consume(ctx, cfg, request)
 		if errEv != nil {
-			cfg.logger().Error("runtime turn failed", errEv, "retryable", end.Retryable)
+			canceled := end.Message.StopReason == llm.StopAborted ||
+				errors.Is(errEv, context.Canceled) || errors.Is(ctx.Err(), context.Canceled)
+			retryable := end.Retryable && !canceled
+			cfg.logger().Error("runtime turn failed", errEv, "retryable", retryable, "canceled", canceled)
 			emitUsage(cfg, usage)
-			return Result{Text: end.Message.Content, Messages: messages, StopReason: end.Message.StopReason, Err: errEv, Retryable: end.Retryable}, nil
+			return Result{
+				Text: end.Message.Content, Messages: messages, StopReason: end.Message.StopReason,
+				Err: errEv, Retryable: retryable, Canceled: canceled, ToolCalls: toolCalls,
+			}, nil
 		}
 		last = end.Message
 		usage.PromptTokens += end.Usage.PromptTokens
@@ -360,7 +377,7 @@ func Run(ctx context.Context, cfg Config, user llm.Message) (Result, error) {
 			cfg.logger().Error("runtime terminal stream failed", end.Err)
 			emitUsage(cfg, usage)
 			return Result{Text: last.Content, Messages: messages, StopReason: llm.StopError,
-				Usage: usage, Err: end.Err, Retryable: false}, nil
+				Usage: usage, Err: end.Err, Retryable: false, ToolCalls: toolCalls}, nil
 		}
 		if err := persist(cfg, last); err != nil {
 			return Result{}, err
@@ -375,7 +392,7 @@ func Run(ctx context.Context, cfg Config, user llm.Message) (Result, error) {
 				if err != nil {
 					return Result{}, err
 				}
-				return budgetStop(cfg, last, messages, usage, reason), nil
+				return budgetStop(cfg, last, messages, usage, toolCalls, reason), nil
 			}
 			if cfg.Budget != nil && cfg.Budget.MaxToolCalls > 0 && toolCalls+len(last.ToolCalls) > cfg.Budget.MaxToolCalls {
 				reason := fmt.Sprintf("budget_exceeded: tool calls %d+%d > max %d", toolCalls, len(last.ToolCalls), cfg.Budget.MaxToolCalls)
@@ -384,7 +401,7 @@ func Run(ctx context.Context, cfg Config, user llm.Message) (Result, error) {
 				if err != nil {
 					return Result{}, err
 				}
-				return budgetStop(cfg, last, messages, usage, reason), nil
+				return budgetStop(cfg, last, messages, usage, toolCalls, reason), nil
 			}
 			toolCalls += len(last.ToolCalls)
 			if cfg.RepeatGuard {
@@ -418,7 +435,8 @@ func Run(ctx context.Context, cfg Config, user llm.Message) (Result, error) {
 			if lengthCap > 0 && lengthContinues >= lengthCap {
 				errCap := errString("length continuation exceeded")
 				cfg.logger().Error("runtime length continuation exceeded", errCap)
-				return Result{Text: last.Content, Messages: messages, StopReason: llm.StopError, Usage: usage, Err: errCap}, nil
+				return Result{Text: last.Content, Messages: messages, StopReason: llm.StopError,
+					Usage: usage, Err: errCap, ToolCalls: toolCalls}, nil
 			}
 			lengthContinues++
 			lengthNudge = true
@@ -454,9 +472,9 @@ func Run(ctx context.Context, cfg Config, user llm.Message) (Result, error) {
 				}
 				continue
 			}
-			return settle(cfg, last, messages, usage, decision.Notice), nil
+			return settle(cfg, last, messages, usage, toolCalls, decision.Notice), nil
 		}
-		return settle(cfg, last, messages, usage, ""), nil
+		return settle(cfg, last, messages, usage, toolCalls, ""), nil
 	}
 	errCap := errString("max turns exceeded")
 	cfg.logger().Error("runtime turn cap hit", errCap)
@@ -466,6 +484,7 @@ func Run(ctx context.Context, cfg Config, user llm.Message) (Result, error) {
 		StopReason: llm.StopError,
 		Usage:      usage,
 		Err:        errCap,
+		ToolCalls:  toolCalls,
 	}, nil
 }
 
@@ -841,11 +860,11 @@ func runOne(ctx context.Context, cfg Config, call llm.ToolCall) llm.Message {
 	return msg
 }
 
-func settle(cfg Config, last llm.Message, messages []llm.Message, usage llm.Usage, notice string) Result {
+func settle(cfg Config, last llm.Message, messages []llm.Message, usage llm.Usage, toolCalls int, notice string) Result {
 	emit(cfg, Event{Type: "agent_end", Message: last})
 	emit(cfg, Event{Type: "agent_settled", Message: last})
 	emitUsage(cfg, usage)
-	return Result{Text: last.Content, Messages: messages, StopReason: last.StopReason, Usage: usage, Notice: notice}
+	return Result{Text: last.Content, Messages: messages, StopReason: last.StopReason, Usage: usage, Notice: notice, ToolCalls: toolCalls}
 }
 
 func prepareRequest(cfg Config, messages []llm.Message, turn int, repeats *repeatState, lengthNudge *bool) []llm.Message {
@@ -1200,12 +1219,12 @@ func budgetExceeded(b *Budget, usage llm.Usage, toolCalls int, now time.Time) st
 }
 
 // budgetStop 以预算超限收尾：发事件、留日志、按 StopError 返回（不可重试）。
-func budgetStop(cfg Config, last llm.Message, messages []llm.Message, usage llm.Usage, reason string) Result {
+func budgetStop(cfg Config, last llm.Message, messages []llm.Message, usage llm.Usage, toolCalls int, reason string) Result {
 	emit(cfg, Event{Type: "budget_exceeded", Text: reason})
 	emitUsage(cfg, usage)
 	err := errString(reason)
 	cfg.logger().Error("runtime budget exceeded", err)
-	return Result{Text: last.Content, Messages: messages, StopReason: llm.StopError, Usage: usage, Err: err}
+	return Result{Text: last.Content, Messages: messages, StopReason: llm.StopError, Usage: usage, Err: err, ToolCalls: toolCalls}
 }
 
 type errString string

runtime/session/tree.go

@@ -153,6 +153,11 @@ func (s *Store) Name() string {
 }
 
 func (s *Store) appendEntryLocked(e Entry) (Entry, error) {
+	// Exclusive-writer: repair a torn/missing-newline tail before append so the
+	// next load does not see mid-file JSON corruption from concatenated bytes.
+	if err := s.repairTailLocked(); err != nil {
+		return Entry{}, err
+	}
 	entries, err := s.readEntriesLocked()
 	if err != nil {
 		return Entry{}, err
@@ -191,6 +196,45 @@ func (s *Store) appendEntryLocked(e Entry) (Entry, error) {
 	return e, nil
 }
 
+// repairTailLocked fixes only the final line under exclusive-writer semantics:
+// truncate an invalid torn fragment, or append a missing newline after a valid
+// final record. Mid-file corruption is left untouched so the next read still
+// fails closed.
+func (s *Store) repairTailLocked() error {
+	raw, err := os.ReadFile(s.path)
+	if err != nil {
+		if os.IsNotExist(err) {
+			return nil
+		}
+		return err
+	}
+	if len(raw) == 0 || raw[len(raw)-1] == '\n' {
+		return nil
+	}
+	text := string(raw)
+	idx := strings.LastIndexByte(text, '\n')
+	var prefix, fragment string
+	if idx >= 0 {
+		prefix = text[:idx+1]
+		fragment = text[idx+1:]
+	} else {
+		fragment = text
+	}
+	if fragment == "" {
+		return nil
+	}
+	var fixed string
+	if json.Valid([]byte(fragment)) {
+		fixed = prefix + fragment + "\n"
+	} else {
+		fixed = prefix
+	}
+	if fixed == text {
+		return nil
+	}
+	return os.WriteFile(s.path, []byte(fixed), 0o644)
+}
+
 func (s *Store) readEntriesLocked() ([]Entry, error) {
 	raw, err := os.ReadFile(s.path)
 	if err != nil {

runtime/session/tree_test.go

@@ -81,6 +81,111 @@ func TestLegacyTranscriptStillLoads(t *testing.T) {
 	}
 }
 
+func TestRepairTornTailBeforeAppend(t *testing.T) {
+	dir := t.TempDir()
+	path := filepath.Join(dir, "torn.jsonl")
+	// Valid record + torn final fragment (no closing brace / newline).
+	body := "{\"role\":\"user\",\"content\":\"ok\"}\n{\"role\":\"assistant\",\"content\":\"tor"
+	if err := os.WriteFile(path, []byte(body), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	s, err := Open(path)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err := s.Append(llm.Message{Role: llm.RoleAssistant, Content: "repaired"}); err != nil {
+		t.Fatal(err)
+	}
+	msgs, err := s.Load()
+	if err != nil {
+		t.Fatalf("load after repair: %v", err)
+	}
+	if len(msgs) != 2 || msgs[0].Content != "ok" || msgs[1].Content != "repaired" {
+		t.Fatalf("msgs after torn repair: %+v", msgs)
+	}
+	raw, _ := os.ReadFile(path)
+	if !strings.HasSuffix(string(raw), "\n") {
+		t.Fatal("file must end with newline after repair-append")
+	}
+	if strings.Contains(string(raw), "tor\n{") || strings.Contains(string(raw), "tor{") {
+		t.Fatalf("torn fragment was concatenated: %s", raw)
+	}
+}
+
+func TestRepairMissingNewlineBeforeAppend(t *testing.T) {
+	dir := t.TempDir()
+	path := filepath.Join(dir, "nonewline.jsonl")
+	// Complete JSON record without trailing newline.
+	body := "{\"role\":\"user\",\"content\":\"hi\"}"
+	if err := os.WriteFile(path, []byte(body), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	s, err := Open(path)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err := s.Append(llm.Message{Role: llm.RoleAssistant, Content: "next"}); err != nil {
+		t.Fatal(err)
+	}
+	msgs, err := s.Load()
+	if err != nil {
+		t.Fatalf("load after newline repair: %v", err)
+	}
+	if len(msgs) != 2 || msgs[0].Content != "hi" || msgs[1].Content != "next" {
+		t.Fatalf("msgs: %+v", msgs)
+	}
+	raw, _ := os.ReadFile(path)
+	// Two separate JSON lines — not one concatenated object.
+	lines := strings.Split(strings.TrimSuffix(string(raw), "\n"), "\n")
+	if len(lines) != 2 {
+		t.Fatalf("want 2 lines, got %d in %q", len(lines), raw)
+	}
+}
+
+func TestMidFileCorruptionStillErrors(t *testing.T) {
+	dir := t.TempDir()
+	path := filepath.Join(dir, "mid.jsonl")
+	body := "{\"role\":\"user\",\"content\":\"a\"}\n{not-json}\n{\"role\":\"assistant\",\"content\":\"b\"}\n"
+	if err := os.WriteFile(path, []byte(body), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	s, err := Open(path)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if _, err := s.Load(); err == nil {
+		t.Fatal("mid-file corruption must be a hard error on load")
+	}
+	if err := s.Append(llm.Message{Role: llm.RoleUser, Content: "x"}); err == nil {
+		t.Fatal("mid-file corruption must be a hard error on append")
+	}
+}
+
+func TestRepairThenAppendThenLoad(t *testing.T) {
+	dir := t.TempDir()
+	path := filepath.Join(dir, "roundtrip.jsonl")
+	if err := os.WriteFile(path, []byte("{\"role\":\"user\",\"content\":\"one\"}\n{\"role\":\"as"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	s, err := Open(path)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err := s.Append(llm.Message{Role: llm.RoleAssistant, Content: "two"}); err != nil {
+		t.Fatal(err)
+	}
+	if err := s.Append(llm.Message{Role: llm.RoleUser, Content: "three"}); err != nil {
+		t.Fatal(err)
+	}
+	msgs, err := s.Load()
+	if err != nil || len(msgs) != 3 {
+		t.Fatalf("roundtrip load: %+v %v", msgs, err)
+	}
+	if msgs[0].Content != "one" || msgs[1].Content != "two" || msgs[2].Content != "three" {
+		t.Fatalf("contents: %+v", msgs)
+	}
+}
+
 func TestCatalogContinueResumeAndHTML(t *testing.T) {
 	dir := t.TempDir()
 	s, err := Open(filepath.Join(dir, "sess.jsonl"))

runtime/tools/builtin.go

@@ -78,9 +78,10 @@ func (t *readFile) Execute(_ context.Context, args json.RawMessage) (Result, err
 }
 
 type writeFile struct {
-	root  string
-	files *filestate.Tracker
-	mark  func(rel string, before []byte, existed bool, after []byte)
+	root     string
+	files    *filestate.Tracker
+	mark     func(rel string, before []byte, existed bool, after []byte)
+	writable []string // empty = unrestricted (product default)
 }
 
 func (t *writeFile) Name() string { return "write_file" }
@@ -102,6 +103,9 @@ func (t *writeFile) Execute(_ context.Context, args json.RawMessage) (Result, er
 	if err != nil {
 		return Result{Content: err.Error(), IsError: true}, nil
 	}
+	if msg := rejectOutsideWriteSet(t.writable, obj.Path); msg != "" {
+		return Result{Content: msg, IsError: true}, nil
+	}
 	if msg := rejectStaleWrite(t.files, path); msg != "" {
 		return Result{Content: msg, IsError: true}, nil
 	}
@@ -119,9 +123,10 @@ func (t *writeFile) Execute(_ context.Context, args json.RawMessage) (Result, er
 }
 
 type editFile struct {
-	root  string
-	files *filestate.Tracker
-	mark  func(rel string, before []byte, existed bool, after []byte)
+	root     string
+	files    *filestate.Tracker
+	mark     func(rel string, before []byte, existed bool, after []byte)
+	writable []string
 }
 
 func (t *editFile) Name() string { return "edit_file" }
@@ -147,6 +152,9 @@ func (t *editFile) Execute(_ context.Context, args json.RawMessage) (Result, err
 	if err != nil {
 		return Result{Content: err.Error(), IsError: true}, nil
 	}
+	if msg := rejectOutsideWriteSet(t.writable, obj.Path); msg != "" {
+		return Result{Content: msg, IsError: true}, nil
+	}
 	if msg := rejectStaleWrite(t.files, path); msg != "" {
 		return Result{Content: msg, IsError: true}, nil
 	}
@@ -294,9 +302,10 @@ func (t *grepTool) Execute(_ context.Context, args json.RawMessage) (Result, err
 
 // multiEditTool 一次多处替换：全部命中且互不冲突才落盘，任一失败即整体不动。
 type multiEditTool struct {
-	root  string
-	files *filestate.Tracker
-	mark  func(rel string, before []byte, existed bool, after []byte)
+	root     string
+	files    *filestate.Tracker
+	mark     func(rel string, before []byte, existed bool, after []byte)
+	writable []string
 }
 
 func (t *multiEditTool) Name() string { return "multi_edit" }
@@ -327,6 +336,9 @@ func (t *multiEditTool) Execute(_ context.Context, args json.RawMessage) (Result
 	if err != nil {
 		return Result{Content: err.Error(), IsError: true}, nil
 	}
+	if msg := rejectOutsideWriteSet(t.writable, obj.Path); msg != "" {
+		return Result{Content: msg, IsError: true}, nil
+	}
 	if msg := rejectStaleWrite(t.files, path); msg != "" {
 		return Result{Content: msg, IsError: true}, nil
 	}

runtime/tools/exec.go

@@ -9,6 +9,7 @@ import (
 	"os/exec"
 	"path/filepath"
 	"strings"
+	"sync"
 	"syscall"
 	"time"
 	"unicode/utf8"
@@ -23,6 +24,7 @@ type ExecConfig struct {
 	Bash   string
 	Python string
 	// Env 传给子进程的完整白名单环境（KEY=VALUE）；不含本进程任何隐式变量。
+	// nil 在注册/启动时归一为空白名单（不继承宿主环境）；显式空切片同样为空白名单。
 	Env []string
 	// ScriptDir 落盘脚本目录（相对 root，默认 .agent/scripts）；空用默认。
 	ScriptDir string
@@ -34,6 +36,16 @@ const (
 	execMaxOutput      = 64 << 10
 )
 
+// normalizeExecEnv maps a nil env to an empty whitelist baseline so os/exec
+// does not inherit the host environment. An explicit empty or non-nil slice
+// is returned unchanged.
+func normalizeExecEnv(env []string) []string {
+	if env == nil {
+		return []string{}
+	}
+	return env
+}
+
 // blockedCommandMarkers 最小命令黑名单：明显提权/自毁模式直接拒绝。
 // 这不是沙箱，只是防呆；真实隔离靠宿主环境。
 var blockedCommandMarkers = []string{
@@ -45,6 +57,7 @@ var blockedCommandMarkers = []string{
 
 // RegisterExecTools 注册 run_command / run_python（解释器未配置的项跳过注册）。
 func RegisterExecTools(r *Registry, root string, cfg ExecConfig) {
+	cfg.Env = normalizeExecEnv(cfg.Env)
 	if strings.TrimSpace(cfg.Bash) != "" {
 		r.Register(&runCommandTool{root: root, cfg: cfg})
 	}
@@ -81,8 +94,8 @@ func (t *runCommandTool) Execute(ctx context.Context, args json.RawMessage) (Res
 		return Result{Content: "command rejected by blocklist (sudo / destructive patterns are not allowed)", IsError: true}, nil
 	}
 	timeout := clampTimeout(obj.TimeoutSeconds)
-	out, timedOut, err := runProcess(ctx, t.cfg.Bash, []string{"-c", obj.Command}, t.root, t.cfg.Env, timeout)
-	content := formatProcessOutput(out, timedOut, err)
+	out, total, timedOut, err := runProcess(ctx, t.cfg.Bash, []string{"-c", obj.Command}, t.root, t.cfg.Env, timeout)
+	content := formatProcessOutput(out, total, timedOut, err)
 	return Result{Content: content, IsError: timedOut || err != nil}, nil
 }
 
@@ -124,19 +137,20 @@ func (t *runPythonTool) Execute(ctx context.Context, args json.RawMessage) (Resu
 		return Result{Content: err.Error(), IsError: true}, nil
 	}
 	timeout := clampTimeout(obj.TimeoutSeconds)
-	out, timedOut, err := runProcess(ctx, t.cfg.Python, []string{script}, t.root, t.cfg.Env, timeout)
-	content := formatProcessOutput(out, timedOut, err)
+	out, total, timedOut, err := runProcess(ctx, t.cfg.Python, []string{script}, t.root, t.cfg.Env, timeout)
+	content := formatProcessOutput(out, total, timedOut, err)
 	content = "script: " + filepath.ToSlash(filepath.Join(dir, name)) + "\n" + content
 	return Result{Content: content, IsError: timedOut || err != nil}, nil
 }
 
 // runProcess 启动独立进程组的子进程；ctx 取消或超时先到者杀整组（SIGKILL）。
-func runProcess(ctx context.Context, interpreter string, argv []string, dir string, env []string, timeout time.Duration) (out []byte, timedOut bool, err error) {
+// 合并输出持续排入有界头尾缓冲，避免 CombinedOutput 无界增长；Wait 回收子进程。
+func runProcess(ctx context.Context, interpreter string, argv []string, dir string, env []string, timeout time.Duration) (out []byte, total int, timedOut bool, err error) {
 	runCtx, cancel := context.WithTimeout(ctx, timeout)
 	defer cancel()
 	cmd := exec.CommandContext(runCtx, interpreter, argv...)
 	cmd.Dir = dir
-	cmd.Env = env
+	cmd.Env = normalizeExecEnv(env)
 	// 独立进程组：超时/取消时杀 -PGID，确保孙进程一并退出。
 	cmd.SysProcAttr = &syscall.SysProcAttr{Setpgid: true}
 	cmd.Cancel = func() error {
@@ -146,9 +160,13 @@ func runProcess(ctx context.Context, interpreter string, argv []string, dir stri
 		return nil
 	}
 	cmd.WaitDelay = 3 * time.Second
-	out, err = cmd.CombinedOutput()
+	buf := newHeadTailBuffer(execMaxOutput)
+	cmd.Stdout = buf
+	cmd.Stderr = buf
+	err = cmd.Run()
+	out, total = buf.Snapshot()
 	timedOut = runCtx.Err() != nil && (ctx.Err() == nil || runCtx.Err() != ctx.Err())
-	return out, timedOut, err
+	return out, total, timedOut, err
 }
 
 func clampTimeout(seconds int) time.Duration {
@@ -171,14 +189,108 @@ func blocked(command string) bool {
 	return false
 }
 
+// headTailBuffer keeps a fixed-size head and a ring-buffer tail while counting
+// all bytes written, so chatty children cannot grow memory without bound.
+type headTailBuffer struct {
+	mu         sync.Mutex
+	max        int
+	half       int
+	head       []byte
+	tail       []byte
+	tailPos    int
+	tailFilled int
+	total      int
+}
+
+func newHeadTailBuffer(max int) *headTailBuffer {
+	if max < 2 {
+		max = 2
+	}
+	half := max / 2
+	return &headTailBuffer{
+		max:  max,
+		half: half,
+		head: make([]byte, 0, half),
+		tail: make([]byte, half),
+	}
+}
+
+func (b *headTailBuffer) Write(p []byte) (int, error) {
+	b.mu.Lock()
+	defer b.mu.Unlock()
+	n := len(p)
+	for len(p) > 0 {
+		if len(b.head) < b.half {
+			take := b.half - len(b.head)
+			if take > len(p) {
+				take = len(p)
+			}
+			b.head = append(b.head, p[:take]...)
+			b.total += take
+			p = p[take:]
+			continue
+		}
+		// Head is full: remaining bytes rotate through the fixed tail ring.
+		for i := 0; i < len(p); i++ {
+			b.tail[b.tailPos] = p[i]
+			b.tailPos = (b.tailPos + 1) % b.half
+			if b.tailFilled < b.half {
+				b.tailFilled++
+			}
+		}
+		b.total += len(p)
+		break
+	}
+	return n, nil
+}
+
+// Snapshot returns retained bytes and the total byte count observed.
+// When total <= max the slice is the full stream; when truncated it is
+// head||tail of length max (callers use total for the dropped-bytes marker).
+func (b *headTailBuffer) Snapshot() ([]byte, int) {
+	b.mu.Lock()
+	defer b.mu.Unlock()
+	if b.total <= b.half {
+		out := make([]byte, len(b.head))
+		copy(out, b.head)
+		return out, b.total
+	}
+	tail := b.tailBytesLocked()
+	out := make([]byte, 0, len(b.head)+len(tail))
+	out = append(out, b.head...)
+	out = append(out, tail...)
+	return out, b.total
+}
+
+func (b *headTailBuffer) tailBytesLocked() []byte {
+	if b.tailFilled == 0 {
+		return nil
+	}
+	if b.tailFilled < b.half {
+		out := make([]byte, b.tailFilled)
+		copy(out, b.tail[:b.tailFilled])
+		return out
+	}
+	out := make([]byte, b.half)
+	n := copy(out, b.tail[b.tailPos:])
+	copy(out[n:], b.tail[:b.tailPos])
+	return out
+}
+
 // formatProcessOutput 截断为头尾各半（总上限 execMaxOutput）并标注退出状态。
-func formatProcessOutput(out []byte, timedOut bool, err error) string {
+// out 为有界捕获结果；total 为子进程实际写出字节数（可大于 len(out)）。
+func formatProcessOutput(out []byte, total int, timedOut bool, err error) string {
 	text := string(out)
-	if len(out) > execMaxOutput {
+	if total > execMaxOutput {
 		half := execMaxOutput / 2
-		dropped := len(out) - execMaxOutput
+		dropped := total - execMaxOutput
 		head := CutUTF8(string(out), half)
-		tail := string(out[len(out)-half:])
+		tail := ""
+		if len(out) > half {
+			tail = string(out[len(out)-half:])
+		} else if len(out) > len(head) {
+			tail = string(out[len(head):])
+		}
 		for len(tail) > 0 && !utf8.RuneStart(tail[0]) {
 			tail = tail[1:]
 		}

runtime/tools/exec_tools_test.go

@@ -54,6 +54,37 @@ func TestRunCommandEnvWhitelist(t *testing.T) {
 	}
 }
 
+func TestRunCommandNilEnvIsEmptyWhitelist(t *testing.T) {
+	bash := lookInterpreter(t, "bash")
+	t.Setenv("KERNEL_SECRET_LEAK", "must-not-leak")
+	root := t.TempDir()
+	reg := NewRegistry(root)
+	// Env left nil: must normalize to empty whitelist (not inherit host).
+	RegisterExecTools(reg, root, ExecConfig{Bash: bash})
+	res := runTool(t, reg, "run_command", `{"command":"echo secret=${KERNEL_SECRET_LEAK:-absent}"}`)
+	if res.IsError {
+		t.Fatal(res.Content)
+	}
+	if !strings.Contains(res.Content, "secret=absent") {
+		t.Fatalf("nil Env must not inherit host secrets, got:\n%s", res.Content)
+	}
+}
+
+func TestRunCommandExplicitEmptyEnvStaysEmpty(t *testing.T) {
+	bash := lookInterpreter(t, "bash")
+	t.Setenv("KERNEL_SECRET_LEAK", "must-not-leak")
+	root := t.TempDir()
+	reg := NewRegistry(root)
+	RegisterExecTools(reg, root, ExecConfig{Bash: bash, Env: []string{}})
+	res := runTool(t, reg, "run_command", `{"command":"echo secret=${KERNEL_SECRET_LEAK:-absent}"}`)
+	if res.IsError {
+		t.Fatal(res.Content)
+	}
+	if !strings.Contains(res.Content, "secret=absent") {
+		t.Fatalf("explicit empty Env must stay empty, got:\n%s", res.Content)
+	}
+}
+
 func TestRunCommandTimeoutKillsProcessGroup(t *testing.T) {
 	bash := lookInterpreter(t, "bash")
 	root := t.TempDir()
@@ -129,6 +160,71 @@ func TestRunCommandOutputTruncation(t *testing.T) {
 	}
 }
 
+func TestHeadTailBufferBoundsMemoryAndPreservesSmall(t *testing.T) {
+	buf := newHeadTailBuffer(64)
+	if _, err := buf.Write([]byte("hello")); err != nil {
+		t.Fatal(err)
+	}
+	out, total := buf.Snapshot()
+	if total != 5 || string(out) != "hello" {
+		t.Fatalf("small output must be unchanged, got %q total=%d", out, total)
+	}
+
+	buf = newHeadTailBuffer(64)
+	var payload strings.Builder
+	for i := 0; i < 200; i++ {
+		payload.WriteByte(byte('A' + (i % 26)))
+	}
+	if _, err := buf.Write([]byte(payload.String())); err != nil {
+		t.Fatal(err)
+	}
+	out, total = buf.Snapshot()
+	if total != 200 {
+		t.Fatalf("total must count all bytes, got %d", total)
+	}
+	if len(out) != 64 {
+		t.Fatalf("retained buffer must be capped at 64, got %d", len(out))
+	}
+	if string(out[:32]) != payload.String()[:32] {
+		t.Fatalf("head mismatch: %q", out[:32])
+	}
+	if string(out[32:]) != payload.String()[200-32:] {
+		t.Fatalf("tail mismatch: %q", out[32:])
+	}
+	// Internal retention stays O(max), not O(total).
+	if cap(buf.head)+cap(buf.tail) > 64+8 {
+		t.Fatalf("buffer capacity must stay near max, head=%d tail=%d", cap(buf.head), cap(buf.tail))
+	}
+}
+
+func TestRunCommandChattyOutputCancelDrains(t *testing.T) {
+	bash := lookInterpreter(t, "bash")
+	root := t.TempDir()
+	reg := NewRegistry(root)
+	RegisterExecTools(reg, root, ExecConfig{Bash: bash, Env: []string{"PATH=/usr/bin:/bin"}})
+
+	ctx, cancel := context.WithCancel(context.Background())
+	go func() {
+		time.Sleep(150 * time.Millisecond)
+		cancel()
+	}()
+	start := time.Now()
+	// Chatty child: continuous stdout until killed; capture must stay bounded and Wait must reap.
+	res := reg.Execute(ctx, "run_command", []byte(
+		`{"command":"while true; do head -c 8192 /dev/zero | tr '\\0' 'y'; done","timeout_seconds":60}`,
+	))
+	elapsed := time.Since(start)
+	if elapsed > 10*time.Second {
+		t.Fatalf("cancel must drain/reap promptly, took %s", elapsed)
+	}
+	if !res.IsError {
+		t.Fatalf("canceled chatty command must be an error result, got %+v", res)
+	}
+	if len(res.Content) > execMaxOutput+512 {
+		t.Fatalf("chatty cancel output must stay capped, got %d", len(res.Content))
+	}
+}
+
 func TestRunPythonPersistsScriptAndRuns(t *testing.T) {
 	python := lookInterpreter(t, "python3")
 	root := t.TempDir()

runtime/tools/registry.go

@@ -5,6 +5,7 @@ import (
 	"encoding/json"
 	"fmt"
 	"io"
+	"path/filepath"
 	"strings"
 	"sync"
 	"time"
@@ -352,6 +353,45 @@ func rejectStaleWrite(files *filestate.Tracker, path string) string {
 	return ""
 }
 
+// rejectOutsideWriteSet rejects rel when a non-empty write-set was declared and
+// rel is not one of the listed relative paths. Empty allow = unrestricted.
+func rejectOutsideWriteSet(allow []string, rel string) string {
+	if len(allow) == 0 {
+		return ""
+	}
+	rel = filepath.ToSlash(filepath.Clean(strings.TrimSpace(rel)))
+	if rel == "." || rel == "" {
+		return "path is outside the declared writable set"
+	}
+	for _, a := range allow {
+		if filepath.ToSlash(filepath.Clean(strings.TrimSpace(a))) == rel {
+			return ""
+		}
+	}
+	return "path is outside the declared writable set"
+}
+
+// ApplyWriteAllowlist threads a WorkspaceHandle.Writable set into document
+// write tools (write_file / edit_file / multi_edit). Empty allow is a no-op.
+func ApplyWriteAllowlist(r *Registry, allow []string) {
+	if r == nil || len(allow) == 0 {
+		return
+	}
+	cp := append([]string(nil), allow...)
+	r.mu.Lock()
+	defer r.mu.Unlock()
+	for _, t := range r.tools {
+		switch w := t.(type) {
+		case *writeFile:
+			w.writable = cp
+		case *editFile:
+			w.writable = cp
+		case *multiEditTool:
+			w.writable = cp
+		}
+	}
+}
+
 func mustPath(root, rel string) (string, error) {
 	return Resolve(root, rel)
 }

runtime/tools/writable_test.go

@@ -0,0 +1,26 @@
+package tools
+
+import (
+	"context"
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+func TestWriteAllowlistRestrictsDocumentTools(t *testing.T) {
+	root := t.TempDir()
+	reg := WorkspaceTools(root)
+	ApplyWriteAllowlist(reg, []string{"allowed.md"})
+
+	ok := reg.Execute(context.Background(), "write_file", []byte(`{"path":"allowed.md","content":"yes"}`))
+	if ok.IsError {
+		t.Fatalf("allowed write rejected: %s", ok.Content)
+	}
+	denied := reg.Execute(context.Background(), "write_file", []byte(`{"path":"other.md","content":"no"}`))
+	if !denied.IsError {
+		t.Fatal("write outside writable set must fail")
+	}
+	if _, err := os.Stat(filepath.Join(root, "other.md")); !os.IsNotExist(err) {
+		t.Fatal("denied path must not be created")
+	}
+}