diff --git a/apps/backend/internal/plugins/approval.go b/apps/backend/internal/plugins/approval.go
new file mode 100644
index 0000000000..836cf29b58
--- /dev/null
+++ b/apps/backend/internal/plugins/approval.go
@@ -0,0 +1,136 @@
+package plugins
+
+import (
+	"crypto/sha256"
+	"encoding/hex"
+	"errors"
+	"fmt"
+	"sort"
+	"strings"
+	"time"
+
+	"github.com/kandev/kandev/internal/plugins/manifest"
+)
+
+// ApprovalDecision is the typed allow/deny result for the generic plugin
+// authorization substrate. It is intentionally small and side-effect free:
+// no Host operation runs here.
+type ApprovalDecision struct {
+	Allowed bool
+	// Reason is stable and machine-readable when Allowed is false.
+	Reason ApprovalDenyReason
+	// AuditID is the immutable audit identity attached to the decision.
+	AuditID string
+	// Receipt contains the safe metadata a future exact Host adapter can use
+	// when persisting an audit/read receipt.
+	Receipt ApprovalReceipt
+}
+
+// ApprovalDenyReason is the stable typed denial vocabulary used by the
+// generic plugin approval layer.
+type ApprovalDenyReason string
+
+var ErrApprovalInvalidIdentifier = errors.New("plugins: approval identifier contains NUL")
+
+const (
+	maxCapabilityCount       = 1024
+	maxCapabilityIDLength    = 256
+	maxApprovalIDLength      = 1024
+	maxAuthorizationDataSize = 4096
+)
+
+// A foreign workspace (an installation with no approval in the requested
+// workspace) intentionally reuses ApprovalDenyMissingApproval rather than a
+// distinct reason: returning a different, more specific reason for "wrong
+// workspace" than for "no approval at all" would itself disclose that the
+// installation exists in another workspace, violating the fail-closed,
+// no-target-disclosure requirement for cross-workspace lookups.
+const (
+	ApprovalDenyMissingApproval       ApprovalDenyReason = "missing_capability_approval"
+	ApprovalDenyStaleRevision         ApprovalDenyReason = "stale_capability_revision"
+	ApprovalDenyRevokedApproval       ApprovalDenyReason = "capability_revoked"
+	ApprovalDenyHumanReserved         ApprovalDenyReason = "human_reserved"
+	ApprovalDenyForeignInstallation   ApprovalDenyReason = "foreign_installation"
+	ApprovalDenyUnsupportedCapability ApprovalDenyReason = "unsupported_capability"
+	ApprovalDenyUndeclaredCapability  ApprovalDenyReason = "undeclared_capability"
+	ApprovalDenyUnavailableCapability ApprovalDenyReason = "unavailable_capability"
+	ApprovalDenyMalformedRequest      ApprovalDenyReason = "malformed_request"
+)
+
+// ApprovalReceipt is the bounded, deterministic metadata future Host adapters
+// can attach to read/write receipts without carrying authority themselves.
+type ApprovalReceipt struct {
+	InstallationID string    `json:"installation_id"`
+	WorkspaceID    string    `json:"workspace_id"`
+	Revision       uint64    `json:"revision"`
+	CapabilityID   string    `json:"capability_id"`
+	RequestDigest  string    `json:"request_digest"`
+	MethodDigest   string    `json:"method_digest"`
+	AuditID        string    `json:"audit_id"`
+	Result         string    `json:"result"`
+	ObservedAt     time.Time `json:"observed_at"`
+}
+
+// CanonicalApprovalDigest returns a stable digest for receipt identity. The
+// inputs are normalized to keep the output deterministic and to avoid
+// accidentally treating whitespace as authority.
+func CanonicalApprovalDigest(parts ...string) string {
+	normalized := make([]string, len(parts))
+	for i, part := range parts {
+		normalized[i] = strings.TrimSpace(part)
+	}
+	sum := sha256.Sum256([]byte(strings.Join(normalized, "\x00")))
+	return hex.EncodeToString(sum[:])
+}
+
+// CanonicalCapabilityList returns a copy of caps sorted and deduplicated.
+func CanonicalCapabilityList(caps []string) ([]string, error) {
+	if len(caps) > maxCapabilityCount {
+		return nil, fmt.Errorf("plugins: too many capabilities")
+	}
+	out := make([]string, 0, len(caps))
+	seen := make(map[string]struct{}, len(caps))
+	for _, raw := range caps {
+		capability := strings.TrimSpace(raw)
+		if capability == "" || len(capability) > maxCapabilityIDLength || strings.ContainsRune(capability, '\x00') {
+			return nil, errors.New("plugins: empty capability")
+		}
+		if isHumanReservedCapability(capability) {
+			return nil, fmt.Errorf("plugins: Human-reserved capability %q cannot be approved", capability)
+		}
+		if !isExactHostV2Capability(capability) {
+			return nil, fmt.Errorf("plugins: capability %q is not an exact host.v2 capability", capability)
+		}
+		if _, ok := seen[capability]; ok {
+			continue
+		}
+		seen[capability] = struct{}{}
+		out = append(out, capability)
+	}
+	sort.Strings(out)
+	return out, nil
+}
+
+// ManifestCapabilityDigest is the canonical digest of the H6 capability set
+// derived from an installed manifest. Legacy v1 declarations retain their
+// original RPC behavior, but cannot themselves satisfy H6 authorization.
+func ManifestCapabilityDigest(m manifest.Manifest) string {
+	canonical, err := ManifestCapabilityIDs(m)
+	if err != nil {
+		return ""
+	}
+	return CanonicalApprovalDigest(canonical...)
+}
+
+// ManifestCapabilityIDs returns the exact capability IDs declared by an
+// installed manifest in canonical order.
+func ManifestCapabilityIDs(m manifest.Manifest) ([]string, error) {
+	caps := make([]string, 0, len(m.Capabilities.APIRead)+len(m.Capabilities.APIWrite))
+	for _, resource := range m.Capabilities.APIRead {
+		caps = append(caps, "host.v2.read:"+strings.TrimSpace(resource))
+	}
+	for _, resource := range m.Capabilities.APIWrite {
+		caps = append(caps, "host.v2.write:"+strings.TrimSpace(resource))
+	}
+	return CanonicalCapabilityList(caps)
+}
diff --git a/apps/backend/internal/plugins/approval_api.go b/apps/backend/internal/plugins/approval_api.go
new file mode 100644
index 0000000000..2e4eea86dc
--- /dev/null
+++ b/apps/backend/internal/plugins/approval_api.go
@@ -0,0 +1,59 @@
+package plugins
+
+import "time"
+
+// ListCapabilityApprovals returns the current approval rows for one installed
+// plugin identity.
+func (s *Service) ListCapabilityApprovals(installationID string) ([]CapabilityApprovalDTO, error) {
+	rows, err := s.approvalListByInstallation(installationID)
+	if err != nil {
+		return nil, err
+	}
+	out := make([]CapabilityApprovalDTO, 0, len(rows))
+	for _, row := range rows {
+		out = append(out, approvalDTOFromCurrent(row))
+	}
+	return out, nil
+}
+
+// GetCapabilityApproval returns the current approval row for an
+// installation/workspace pair.
+func (s *Service) GetCapabilityApproval(installationID, workspaceID string) (CapabilityApprovalDTO, bool, error) {
+	row, ok, err := s.approvalCurrent(installationID, workspaceID)
+	if err != nil || !ok {
+		return CapabilityApprovalDTO{}, ok, err
+	}
+	return approvalDTOFromCurrent(row), true, nil
+}
+
+// AuthorizeCapability evaluates a single exact capability request against the
+// current approval row and returns a typed allow/deny result.
+func (s *Service) AuthorizeCapability(
+	installationID, workspaceID, capabilityID string, requestedRevision uint64, requestDigest, methodDigest string,
+) ApprovalDecision {
+	return s.authorizePluginCapability(installationID, workspaceID, capabilityID, requestedRevision, requestDigest, methodDigest)
+}
+
+// GrantCapabilityApproval records a workspace-scoped approval. revision is
+// the exact next revision, and auditID is the stable idempotency identity.
+func (s *Service) GrantCapabilityApproval(installationID, workspaceID string, revision uint64, manifestDigest string, capabilityIDs []string, actor, reason, auditID string) (CapabilityApprovalDTO, error) {
+	row, err := s.approvalGrant(installationID, workspaceID, revision, manifestDigest, capabilityIDs, actor, reason, auditID)
+	if err != nil {
+		return CapabilityApprovalDTO{}, err
+	}
+	return approvalDTOFromCurrent(row), nil
+}
+
+// RevokeCapabilityApproval revokes only the supplied current revision. A
+// stale caller receives ErrApprovalRevisionConflict and must read back state.
+func (s *Service) RevokeCapabilityApproval(installationID, workspaceID string, expectedRevision uint64, actor, reason, auditID string) (CapabilityApprovalDTO, error) {
+	ledger := s.approvalLedger()
+	if ledger == nil {
+		return CapabilityApprovalDTO{}, ErrApprovalRevisionConflict
+	}
+	row, err := ledger.revokeIfRevision(installationID, workspaceID, expectedRevision, actor, reason, auditID, time.Now().UTC(), false)
+	if err != nil {
+		return CapabilityApprovalDTO{}, err
+	}
+	return approvalDTOFromCurrent(row), nil
+}
diff --git a/apps/backend/internal/plugins/approval_api_test.go b/apps/backend/internal/plugins/approval_api_test.go
new file mode 100644
index 0000000000..c89b347282
--- /dev/null
+++ b/apps/backend/internal/plugins/approval_api_test.go
@@ -0,0 +1,85 @@
+package plugins
+
+import (
+	"errors"
+	"testing"
+
+	"github.com/kandev/kandev/internal/plugins/manifest"
+	"github.com/kandev/kandev/internal/plugins/store"
+)
+
+func TestApprovalAPIExportsCurrentRowsAndDecision(t *testing.T) {
+	dir := t.TempDir()
+	svc := &Service{}
+	if err := svc.SetPluginsDir(dir); err != nil {
+		t.Fatalf("SetPluginsDir: %v", err)
+	}
+	t.Cleanup(func() { _ = svc.Close() })
+	if _, err := svc.approvalGrant("inst-1", "ws-1", 1, "digest-a", []string{"host.v2.read:tasks"}, "human", "grant", "audit-1"); err != nil {
+		t.Fatalf("grant: %v", err)
+	}
+
+	rows, err := svc.ListCapabilityApprovals("inst-1")
+	if err != nil {
+		t.Fatalf("ListCapabilityApprovals: %v", err)
+	}
+	if len(rows) != 1 || rows[0].WorkspaceID != "ws-1" {
+		t.Fatalf("rows = %#v", rows)
+	}
+
+	row, ok, err := svc.GetCapabilityApproval("inst-1", "ws-1")
+	if err != nil || !ok {
+		t.Fatalf("GetCapabilityApproval: ok=%v err=%v", ok, err)
+	}
+	if row.Revision != 1 {
+		t.Fatalf("row = %#v", row)
+	}
+
+	decision := svc.AuthorizeCapability("inst-1", "ws-1", "host.v2.read:tasks", 1, "req", "method")
+	if !decision.Allowed {
+		t.Fatalf("decision = %#v", decision)
+	}
+}
+
+func TestApprovalAPIRevokeRetryReplaysOriginalResult(t *testing.T) {
+	svc := &Service{}
+	if err := svc.SetPluginsDir(t.TempDir()); err != nil {
+		t.Fatalf("SetPluginsDir: %v", err)
+	}
+	t.Cleanup(func() { _ = svc.Close() })
+	if _, err := svc.GrantCapabilityApproval("inst-1", "ws-1", 1, "digest-a", []string{"host.v2.read:tasks"}, "human", "grant", "grant-1"); err != nil {
+		t.Fatalf("grant: %v", err)
+	}
+	first, err := svc.RevokeCapabilityApproval("inst-1", "ws-1", 1, "human", "revoke", "revoke-1")
+	if err != nil {
+		t.Fatalf("first revoke: %v", err)
+	}
+	replayed, err := svc.RevokeCapabilityApproval("inst-1", "ws-1", 1, "human", "revoke", "revoke-1")
+	if err != nil {
+		t.Fatalf("exact retry: %v", err)
+	}
+	if replayed.Revision != first.Revision || replayed.UpdatedAt != first.UpdatedAt {
+		t.Fatalf("retry changed original result: first=%#v replayed=%#v", first, replayed)
+	}
+	if _, err := svc.RevokeCapabilityApproval("inst-1", "ws-1", 2, "human", "revoke", "revoke-1"); !errors.Is(err, ErrApprovalIdempotencyConflict) {
+		t.Fatalf("changed expected revision error = %v, want idempotency conflict", err)
+	}
+}
+
+func TestGrantCapabilityApprovalRequiresInstalledManifestBinding(t *testing.T) {
+	svc := &Service{registry: NewRegistry()}
+	if err := svc.SetPluginsDir(t.TempDir()); err != nil {
+		t.Fatalf("SetPluginsDir: %v", err)
+	}
+	t.Cleanup(func() { _ = svc.Close() })
+	installed := &store.Record{
+		Manifest:       manifest.Manifest{ID: "plugin-a", Capabilities: manifest.Capabilities{APIRead: []string{"tasks"}}},
+		InstallationID: "inst-1",
+	}
+	svc.registry.Add(installed)
+
+	_, err := svc.GrantCapabilityApproval("inst-1", "ws-1", 1, ManifestCapabilityDigest(installed.Manifest), []string{"host.v2.read:messages"}, "human", "grant", "audit-1")
+	if err == nil {
+		t.Fatal("GrantCapabilityApproval accepted a capability outside the installed manifest")
+	}
+}
diff --git a/apps/backend/internal/plugins/approval_dto.go b/apps/backend/internal/plugins/approval_dto.go
new file mode 100644
index 0000000000..33e0ddd9de
--- /dev/null
+++ b/apps/backend/internal/plugins/approval_dto.go
@@ -0,0 +1,61 @@
+package plugins
+
+import "time"
+
+type CapabilityApprovalDTO struct {
+	InstallationID     string    `json:"installation_id"`
+	WorkspaceID        string    `json:"workspace_id"`
+	Revision           uint64    `json:"revision"`
+	ManifestDigest     string    `json:"manifest_digest"`
+	CapabilityIDs      []string  `json:"capability_ids"`
+	State              string    `json:"state"`
+	HumanActor         string    `json:"human_actor"`
+	HumanPolicyVersion string    `json:"human_policy_version"`
+	CreatedAt          time.Time `json:"created_at"`
+	UpdatedAt          time.Time `json:"updated_at"`
+}
+
+type CapabilityApprovalEventDTO struct {
+	AuditID        string    `json:"audit_id"`
+	InstallationID string    `json:"installation_id"`
+	WorkspaceID    string    `json:"workspace_id"`
+	BeforeRevision uint64    `json:"before_revision"`
+	AfterRevision  uint64    `json:"after_revision"`
+	BeforeDigest   string    `json:"before_digest"`
+	AfterDigest    string    `json:"after_digest"`
+	Actor          string    `json:"actor"`
+	Reason         string    `json:"reason"`
+	Type           string    `json:"type"`
+	ObservedAt     time.Time `json:"observed_at"`
+}
+
+func approvalDTOFromCurrent(current CapabilityApproval) CapabilityApprovalDTO {
+	return CapabilityApprovalDTO{
+		InstallationID:     current.InstallationID,
+		WorkspaceID:        current.WorkspaceID,
+		Revision:           current.Revision,
+		ManifestDigest:     current.ManifestDigest,
+		CapabilityIDs:      append([]string{}, current.CapabilityIDs...),
+		State:              string(current.State),
+		HumanActor:         current.HumanActor,
+		HumanPolicyVersion: current.HumanPolicyVersion,
+		CreatedAt:          current.CreatedAt,
+		UpdatedAt:          current.UpdatedAt,
+	}
+}
+
+func approvalEventDTOFromCurrent(event CapabilityApprovalEvent) CapabilityApprovalEventDTO {
+	return CapabilityApprovalEventDTO{
+		AuditID:        event.AuditID,
+		InstallationID: event.InstallationID,
+		WorkspaceID:    event.WorkspaceID,
+		BeforeRevision: event.BeforeRevision,
+		AfterRevision:  event.AfterRevision,
+		BeforeDigest:   event.BeforeDigest,
+		AfterDigest:    event.AfterDigest,
+		Actor:          event.Actor,
+		Reason:         event.Reason,
+		Type:           string(event.Type),
+		ObservedAt:     event.ObservedAt,
+	}
+}
diff --git a/apps/backend/internal/plugins/approval_dto_test.go b/apps/backend/internal/plugins/approval_dto_test.go
new file mode 100644
index 0000000000..3de4a19d62
--- /dev/null
+++ b/apps/backend/internal/plugins/approval_dto_test.go
@@ -0,0 +1,46 @@
+package plugins
+
+import (
+	"testing"
+	"time"
+)
+
+func TestApprovalDTOConversionCopiesState(t *testing.T) {
+	createdAt := time.Date(2026, time.August, 31, 1, 2, 3, 0, time.UTC)
+	updatedAt := createdAt.Add(time.Minute)
+	dto := approvalDTOFromCurrent(CapabilityApproval{
+		InstallationID:     "inst-1",
+		WorkspaceID:        "ws-1",
+		Revision:           7,
+		ManifestDigest:     "digest",
+		CapabilityIDs:      []string{"host.v2.read:tasks"},
+		State:              ApprovalStateActive,
+		HumanActor:         "human",
+		HumanPolicyVersion: "immutable",
+		CreatedAt:          createdAt,
+		UpdatedAt:          updatedAt,
+	})
+	if dto.InstallationID != "inst-1" || dto.WorkspaceID != "ws-1" || dto.Revision != 7 {
+		t.Fatalf("dto = %#v", dto)
+	}
+}
+
+func TestApprovalEventDTOConversionCopiesAuditIdentity(t *testing.T) {
+	when := time.Date(2026, time.August, 31, 1, 2, 3, 0, time.UTC)
+	dto := approvalEventDTOFromCurrent(CapabilityApprovalEvent{
+		AuditID:        "audit-1",
+		InstallationID: "inst-1",
+		WorkspaceID:    "ws-1",
+		BeforeRevision: 1,
+		AfterRevision:  2,
+		BeforeDigest:   "a",
+		AfterDigest:    "b",
+		Actor:          "human",
+		Reason:         "grant",
+		Type:           CapabilityApprovalEventGrant,
+		ObservedAt:     when,
+	})
+	if dto.AuditID != "audit-1" || dto.Type != string(CapabilityApprovalEventGrant) {
+		t.Fatalf("dto = %#v", dto)
+	}
+}
diff --git a/apps/backend/internal/plugins/approval_query_test.go b/apps/backend/internal/plugins/approval_query_test.go
new file mode 100644
index 0000000000..74e9d02568
--- /dev/null
+++ b/apps/backend/internal/plugins/approval_query_test.go
@@ -0,0 +1,117 @@
+package plugins
+
+import (
+	"testing"
+	"time"
+)
+
+func TestServiceApprovalQueriesReturnCurrentRows(t *testing.T) {
+	dir := t.TempDir()
+	svc := &Service{}
+	if err := svc.SetPluginsDir(dir); err != nil {
+		t.Fatalf("SetPluginsDir: %v", err)
+	}
+	t.Cleanup(func() { _ = svc.Close() })
+
+	if _, err := svc.approvalGrant("inst-1", "ws-1", 1, "digest-a", []string{"host.v2.read:tasks"}, "human", "grant", "audit-1"); err != nil {
+		t.Fatalf("grant ws-1: %v", err)
+	}
+	if _, err := svc.approvalGrant("inst-1", "ws-2", 1, "digest-b", []string{"host.v2.write:tasks"}, "human", "grant", "audit-2"); err != nil {
+		t.Fatalf("grant ws-2: %v", err)
+	}
+
+	rows, err := svc.approvalListByInstallation("inst-1")
+	if err != nil {
+		t.Fatalf("list: %v", err)
+	}
+	if len(rows) != 2 {
+		t.Fatalf("rows = %#v, want two workspace approvals", rows)
+	}
+}
+
+func TestServiceApprovalRevokeBumpsRevisionAndDenies(t *testing.T) {
+	dir := t.TempDir()
+	svc := &Service{}
+	if err := svc.SetPluginsDir(dir); err != nil {
+		t.Fatalf("SetPluginsDir: %v", err)
+	}
+	t.Cleanup(func() { _ = svc.Close() })
+	if _, err := svc.approvalGrant("inst-1", "ws-1", 1, "digest-a", []string{"host.v2.read:tasks"}, "human", "grant", "audit-1"); err != nil {
+		t.Fatalf("grant: %v", err)
+	}
+	if _, err := svc.approvalRevoke("inst-1", "ws-1", "human", "revoke", "audit-2"); err != nil {
+		t.Fatalf("revoke: %v", err)
+	}
+
+	decision := svc.authorizePluginCapability("inst-1", "ws-1", "host.v2.read:tasks", 2, "req", "method")
+	if decision.Allowed {
+		t.Fatalf("decision = %#v, want revoked approval denied", decision)
+	}
+	if decision.Reason != ApprovalDenyRevokedApproval {
+		t.Fatalf("reason = %q, want capability_revoked", decision.Reason)
+	}
+}
+
+func TestServiceApprovalRevokeRetryReplaysOriginalResult(t *testing.T) {
+	dir := t.TempDir()
+	svc := &Service{}
+	if err := svc.SetPluginsDir(dir); err != nil {
+		t.Fatalf("SetPluginsDir: %v", err)
+	}
+	t.Cleanup(func() { _ = svc.Close() })
+	if _, err := svc.approvalGrant("inst-1", "ws-1", 1, "digest-a", []string{"host.v2.read:tasks"}, "human", "grant", "audit-1"); err != nil {
+		t.Fatalf("grant: %v", err)
+	}
+	first, err := svc.approvalRevoke("inst-1", "ws-1", "human", "revoke", "revoke-1")
+	if err != nil {
+		t.Fatalf("first revoke: %v", err)
+	}
+	replayed, err := svc.approvalRevoke("inst-1", "ws-1", "human", "revoke", "revoke-1")
+	if err != nil {
+		t.Fatalf("retry revoke: %v", err)
+	}
+	if replayed.Revision != first.Revision || !replayed.UpdatedAt.Equal(first.UpdatedAt) {
+		t.Fatalf("retry changed the original result: first=%#v replayed=%#v", first, replayed)
+	}
+}
+
+func TestServiceApprovalTombstoneRetainsStateOnReinstall(t *testing.T) {
+	dir := t.TempDir()
+	svc := &Service{}
+	if err := svc.SetPluginsDir(dir); err != nil {
+		t.Fatalf("SetPluginsDir: %v", err)
+	}
+	t.Cleanup(func() { _ = svc.Close() })
+	if _, err := svc.approvalGrant("inst-1", "ws-1", 1, "digest-a", []string{"host.v2.read:tasks"}, "human", "grant", "audit-1"); err != nil {
+		t.Fatalf("grant: %v", err)
+	}
+	if err := svc.approvalTombstoneInstallation("inst-1"); err != nil {
+		t.Fatalf("tombstone: %v", err)
+	}
+	rows, err := svc.approvalListByInstallation("inst-1")
+	if err != nil {
+		t.Fatalf("list after tombstone: %v", err)
+	}
+	if len(rows) != 1 || rows[0].State != ApprovalStateRevoked {
+		t.Fatalf("rows after tombstone = %#v", rows)
+	}
+}
+
+func TestApprovalReceiptAuditIDIsDeterministic(t *testing.T) {
+	got := CanonicalApprovalDigest("inst", "ws", "cap", "req", "method", "1")
+	if got == "" {
+		t.Fatal("CanonicalApprovalDigest() returned empty audit id")
+	}
+}
+
+func TestApprovalLedgerGrantStoresCapabilitySnapshot(t *testing.T) {
+	dir := t.TempDir()
+	ledger := newApprovalLedger(dir)
+	approval, err := ledger.grant("inst-1", "ws-1", 1, "digest-a", []string{"host.v2.read:tasks", "host.v2.write:tasks"}, "human", "grant", "audit-1", time.Now().UTC())
+	if err != nil {
+		t.Fatalf("grant: %v", err)
+	}
+	if len(approval.CapabilityIDs) != 2 {
+		t.Fatalf("approval capability ids = %#v", approval.CapabilityIDs)
+	}
+}
diff --git a/apps/backend/internal/plugins/approval_service.go b/apps/backend/internal/plugins/approval_service.go
new file mode 100644
index 0000000000..ab2f1e7068
--- /dev/null
+++ b/apps/backend/internal/plugins/approval_service.go
@@ -0,0 +1,297 @@
+package plugins
+
+import (
+	"crypto/sha256"
+	"encoding/hex"
+	"fmt"
+	"strings"
+	"time"
+
+	"github.com/kandev/kandev/internal/plugins/store"
+)
+
+// approvalLedger returns the ledger wired by SetPluginsDir. Callers handle a
+// nil result (e.g. a Service constructed directly in tests without a plugins
+// directory).
+func (s *Service) approvalLedger() *approvalLedger {
+	return s.approvals
+}
+
+func (s *Service) approvalGrant(installationID, workspaceID string, revision uint64, manifestDigest string, capabilityIDs []string, actor, reason, auditID string) (CapabilityApproval, error) {
+	ledger := s.approvalLedger()
+	if ledger == nil {
+		return CapabilityApproval{}, fmt.Errorf("plugins: approval ledger not configured")
+	}
+	canonical, err := CanonicalCapabilityList(capabilityIDs)
+	if err != nil {
+		return CapabilityApproval{}, err
+	}
+	if err := s.validateApprovalManifest(installationID, manifestDigest, canonical); err != nil {
+		return CapabilityApproval{}, err
+	}
+	return ledger.grant(installationID, workspaceID, revision, manifestDigest, canonical, actor, reason, auditID, time.Now().UTC())
+}
+
+func (s *Service) validateApprovalManifest(installationID, manifestDigest string, capabilityIDs []string) error {
+	if s.registry == nil {
+		return nil
+	}
+	installed := s.installedRecordByInstallationID(installationID)
+	if installed == nil {
+		return fmt.Errorf("plugins: approval installation not found")
+	}
+	if manifestDigest != ManifestCapabilityDigest(installed.Manifest) {
+		return fmt.Errorf("plugins: approval manifest digest does not match installed manifest")
+	}
+	declared, err := ManifestCapabilityIDs(installed.Manifest)
+	if err != nil {
+		return err
+	}
+	declaredSet := make(map[string]struct{}, len(declared))
+	for _, capability := range declared {
+		declaredSet[capability] = struct{}{}
+	}
+	for _, capability := range capabilityIDs {
+		if _, ok := declaredSet[capability]; !ok {
+			return fmt.Errorf("plugins: capability %q is not declared by installed manifest", capability)
+		}
+	}
+	return nil
+}
+
+func (s *Service) approvalRevoke(installationID, workspaceID, actor, reason, auditID string) (CapabilityApproval, error) {
+	ledger := s.approvalLedger()
+	if ledger == nil {
+		return CapabilityApproval{}, fmt.Errorf("plugins: approval ledger not configured")
+	}
+	current, ok, err := ledger.get(installationID, workspaceID)
+	if err != nil || !ok {
+		if err != nil {
+			return CapabilityApproval{}, err
+		}
+		return CapabilityApproval{}, fmt.Errorf("plugins: approval not found")
+	}
+	return ledger.revokeIfRevision(installationID, workspaceID, current.Revision, actor, reason, auditID, time.Now().UTC(), true)
+}
+
+func (s *Service) approvalTombstoneInstallation(installationID string) error {
+	ledger := s.approvalLedger()
+	if ledger == nil {
+		return nil
+	}
+	return ledger.tombstoneInstallation(installationID, time.Now().UTC())
+}
+
+func (s *Service) approvalCurrent(installationID, workspaceID string) (CapabilityApproval, bool, error) {
+	ledger := s.approvalLedger()
+	if ledger == nil {
+		return CapabilityApproval{}, false, fmt.Errorf("plugins: approval ledger not configured")
+	}
+	return ledger.get(installationID, workspaceID)
+}
+
+func (s *Service) approvalListByInstallation(installationID string) ([]CapabilityApproval, error) {
+	ledger := s.approvalLedger()
+	if ledger == nil {
+		return nil, fmt.Errorf("plugins: approval ledger not configured")
+	}
+	return ledger.listByInstallation(installationID)
+}
+
+func (s *Service) authorizePluginCapability(installationID, workspaceID, capabilityID string, requestedRevision uint64, requestDigest, methodDigest string) ApprovalDecision {
+	reason, wellFormed := malformedAuthorizationRequestReason(installationID, workspaceID, capabilityID, requestDigest, methodDigest)
+	requestDigest = safeAuthorizationDigest(requestDigest)
+	methodDigest = safeAuthorizationDigest(methodDigest)
+	decision := ApprovalDecision{
+		Receipt: ApprovalReceipt{
+			InstallationID: safeReceiptIdentifier(installationID),
+			WorkspaceID:    safeReceiptIdentifier(workspaceID),
+			Revision:       requestedRevision,
+			CapabilityID:   safeReceiptCapabilityID(capabilityID),
+			RequestDigest:  requestDigest,
+			MethodDigest:   methodDigest,
+			AuditID:        CanonicalApprovalDigest(installationID, workspaceID, capabilityID, requestDigest, methodDigest, fmt.Sprint(requestedRevision)),
+			Result:         "denied",
+			ObservedAt:     time.Now().UTC(),
+		},
+	}
+	decision.AuditID = decision.Receipt.AuditID
+	if !wellFormed {
+		decision.Reason = reason
+		return decision
+	}
+	if isHumanReservedCapability(capabilityID) {
+		decision.Reason = ApprovalDenyHumanReserved
+		return decision
+	}
+	current, ok, err := s.approvalCurrent(installationID, workspaceID)
+	if err != nil {
+		decision.Reason = ApprovalDenyUnavailableCapability
+		return decision
+	}
+	if !ok {
+		decision.Reason = ApprovalDenyMissingApproval
+		return decision
+	}
+	if current.State != ApprovalStateActive || current.TombstonedAt != nil {
+		decision.Reason = ApprovalDenyRevokedApproval
+		return decision
+	}
+	if current.Revision != requestedRevision {
+		decision.Reason = ApprovalDenyStaleRevision
+		return decision
+	}
+	if reason, ok := s.manifestIntersectionDenyReason(installationID, capabilityID, current); !ok {
+		decision.Reason = reason
+		return decision
+	}
+	for _, allowed := range current.CapabilityIDs {
+		if allowed == capabilityID {
+			decision.Allowed = true
+			decision.Reason = ""
+			decision.Receipt.Result = "allowed"
+			decision.AuditID = decision.Receipt.AuditID
+			return decision
+		}
+	}
+	decision.Reason = ApprovalDenyUndeclaredCapability
+	return decision
+}
+
+// malformedAuthorizationRequestReason validates the structural shape of an
+// authorization request before any capability/approval semantics are
+// considered. ok is false when the request must be denied; reason is only
+// meaningful when ok is false.
+func malformedAuthorizationRequestReason(installationID, workspaceID, capabilityID, requestDigest, methodDigest string) (reason ApprovalDenyReason, ok bool) {
+	if !isBoundedApprovalIdentifier(installationID) || !isBoundedApprovalIdentifier(workspaceID) ||
+		!isBoundedAuthorizationData(requestDigest) || !isBoundedAuthorizationData(methodDigest) {
+		return ApprovalDenyMalformedRequest, false
+	}
+	if isUnsupportedCapabilityID(capabilityID) {
+		return ApprovalDenyUnsupportedCapability, false
+	}
+	return "", true
+}
+
+// manifestIntersectionDenyReason enforces that the current installed
+// manifest still declares capabilityID under the same digest the approval
+// was granted against. ok is false when the request must be denied; reason
+// is only meaningful when ok is false. A nil registry (e.g. a Service
+// constructed directly in tests) skips this check.
+func (s *Service) manifestIntersectionDenyReason(installationID, capabilityID string, current CapabilityApproval) (reason ApprovalDenyReason, ok bool) {
+	if s.registry == nil {
+		return "", true
+	}
+	installed := s.installedRecordByInstallationID(installationID)
+	if installed == nil {
+		return ApprovalDenyForeignInstallation, false
+	}
+	if current.ManifestDigest != ManifestCapabilityDigest(installed.Manifest) {
+		return ApprovalDenyUnavailableCapability, false
+	}
+	if !manifestDeclaresCapability(installed, capabilityID) {
+		return ApprovalDenyUndeclaredCapability, false
+	}
+	return "", true
+}
+
+func (s *Service) installedRecordByInstallationID(installationID string) *store.Record {
+	for _, record := range s.registry.List() {
+		if record.InstallationID == installationID {
+			return record
+		}
+	}
+	return nil
+}
+
+func manifestDeclaresCapability(record *store.Record, capabilityID string) bool {
+	for _, resource := range record.Capabilities.APIRead {
+		if capabilityID == "host.v2.read:"+resource {
+			return true
+		}
+	}
+	for _, resource := range record.Capabilities.APIWrite {
+		if capabilityID == "host.v2.write:"+resource {
+			return true
+		}
+	}
+	return false
+}
+
+// isUnsupportedCapabilityID reports whether capabilityID cannot be an exact
+// admitted capability class: empty, containing leading/trailing whitespace,
+// or a wildcard/broad alias. This mirrors the canonicalization rejected at
+// grant time (CanonicalCapabilityList) so an authorization request cannot
+// bypass the same rule by presenting a broad identity directly.
+func isUnsupportedCapabilityID(capabilityID string) bool {
+	return !isExactHostV2Capability(capabilityID) && !isHumanReservedCapability(capabilityID)
+}
+
+func isHumanReservedCapability(capabilityID string) bool {
+	resource := capabilityID
+	if _, suffix, ok := strings.Cut(capabilityID, ":"); ok {
+		resource = suffix
+	}
+	switch resource {
+	case "merge", "deploy", "release", "rewrite_history", "cross_workspace", "secret_scope_expand":
+		return true
+	default:
+		return false
+	}
+}
+
+func isExactHostV2Capability(capabilityID string) bool {
+	if len(capabilityID) == 0 || len(capabilityID) > maxCapabilityIDLength ||
+		strings.TrimSpace(capabilityID) != capabilityID || strings.ContainsAny(capabilityID, "*?\x00") {
+		return false
+	}
+	kind, resource, ok := strings.Cut(capabilityID, ":")
+	if !ok || !isHostV2CapabilityKind(kind) || !isExactCapabilityResource(resource) {
+		return false
+	}
+	return true
+}
+
+func isHostV2CapabilityKind(kind string) bool {
+	return kind == "host.v2.read" || kind == "host.v2.write"
+}
+
+func isExactCapabilityResource(resource string) bool {
+	if resource == "" || strings.Contains(resource, ":") {
+		return false
+	}
+	for _, r := range resource {
+		if (r < 'a' || r > 'z') && (r < '0' || r > '9') && r != '_' {
+			return false
+		}
+	}
+	return true
+}
+
+func isBoundedApprovalIdentifier(value string) bool {
+	return value != "" && len(value) <= maxApprovalIDLength && strings.TrimSpace(value) == value && !strings.ContainsRune(value, '\x00')
+}
+
+func isBoundedAuthorizationData(value string) bool {
+	return value != "" && len(value) <= maxAuthorizationDataSize && !strings.ContainsRune(value, '\x00')
+}
+
+func safeAuthorizationDigest(value string) string {
+	sum := sha256.Sum256([]byte(value))
+	return hex.EncodeToString(sum[:])
+}
+
+func safeReceiptIdentifier(value string) string {
+	if !isBoundedApprovalIdentifier(value) {
+		return ""
+	}
+	return value
+}
+
+func safeReceiptCapabilityID(value string) string {
+	if len(value) > maxCapabilityIDLength || strings.ContainsRune(value, '\x00') ||
+		(!isExactHostV2Capability(value) && !isHumanReservedCapability(value)) {
+		return ""
+	}
+	return value
+}
diff --git a/apps/backend/internal/plugins/approval_store.go b/apps/backend/internal/plugins/approval_store.go
new file mode 100644
index 0000000000..c24745ba79
--- /dev/null
+++ b/apps/backend/internal/plugins/approval_store.go
@@ -0,0 +1,477 @@
+package plugins
+
+import (
+	"encoding/json"
+	"errors"
+	"fmt"
+	"os"
+	"path/filepath"
+	"sort"
+	"strings"
+	"sync"
+	"time"
+)
+
+type ApprovalState string
+
+const (
+	ApprovalStateActive  ApprovalState = "active"
+	ApprovalStateRevoked ApprovalState = "revoked"
+)
+
+// HumanPolicyVersionImmutable is the only Human-policy version H6 currently
+// admits. H0 defines the Human-reserved deny intersection (merge, deploy,
+// release, history rewrite, cross-workspace access, secret-scope expansion)
+// as an immutable, singular policy with no versioned variants yet. The field
+// is stored on every approval row so a future policy revision has a stable
+// place to record which policy an approval was granted under; it is not a
+// caller-configurable input today.
+const HumanPolicyVersionImmutable = "immutable"
+
+type CapabilityApproval struct {
+	InstallationID     string        `json:"installation_id"`
+	WorkspaceID        string        `json:"workspace_id"`
+	Revision           uint64        `json:"revision"`
+	ManifestDigest     string        `json:"manifest_digest"`
+	CapabilityIDs      []string      `json:"capability_ids"`
+	State              ApprovalState `json:"state"`
+	HumanActor         string        `json:"human_actor"`
+	HumanPolicyVersion string        `json:"human_policy_version"`
+	CreatedAt          time.Time     `json:"created_at"`
+	UpdatedAt          time.Time     `json:"updated_at"`
+	TombstonedAt       *time.Time    `json:"tombstoned_at,omitempty"`
+}
+
+type CapabilityApprovalEventType string
+
+const (
+	CapabilityApprovalEventGrant         CapabilityApprovalEventType = "grant"
+	CapabilityApprovalEventNarrow        CapabilityApprovalEventType = "narrow"
+	CapabilityApprovalEventRevoke        CapabilityApprovalEventType = "revoke"
+	CapabilityApprovalEventUpgradeReview CapabilityApprovalEventType = "upgrade_review"
+)
+
+type CapabilityApprovalEvent struct {
+	AuditID        string                      `json:"audit_id"`
+	InstallationID string                      `json:"installation_id"`
+	WorkspaceID    string                      `json:"workspace_id"`
+	BeforeRevision uint64                      `json:"before_revision"`
+	AfterRevision  uint64                      `json:"after_revision"`
+	BeforeDigest   string                      `json:"before_digest"`
+	AfterDigest    string                      `json:"after_digest"`
+	Actor          string                      `json:"actor"`
+	Reason         string                      `json:"reason"`
+	Type           CapabilityApprovalEventType `json:"type"`
+	ObservedAt     time.Time                   `json:"observed_at"`
+}
+
+type approvalLedgerFile struct {
+	Approvals         map[string]CapabilityApproval       `json:"approvals"`
+	Events            []CapabilityApprovalEvent           `json:"events"`
+	Tombstones        map[string]time.Time                `json:"tombstones"`
+	Idempotency       map[string]CapabilityApproval       `json:"idempotency,omitempty"`
+	IdempotencyInputs map[string]approvalIdempotencyInput `json:"idempotency_inputs,omitempty"`
+}
+
+type approvalIdempotencyInput struct {
+	Revision       uint64   `json:"revision"`
+	ManifestDigest string   `json:"manifest_digest,omitempty"`
+	CapabilityIDs  []string `json:"capability_ids,omitempty"`
+	Actor          string   `json:"actor"`
+	Reason         string   `json:"reason"`
+}
+
+var (
+	ErrApprovalRevisionConflict       = errors.New("plugins: approval revision conflict")
+	ErrApprovalIdempotencyConflict    = errors.New("plugins: approval idempotency conflict")
+	ErrApprovalInstallationTombstoned = errors.New("plugins: installation approval tombstoned")
+)
+
+type approvalLedger struct {
+	dir string
+	mu  sync.Mutex
+}
+
+func newApprovalLedger(dir string) *approvalLedger {
+	return &approvalLedger{dir: dir}
+}
+
+func (l *approvalLedger) path() string {
+	return filepath.Join(l.dir, "approvals.json")
+}
+
+func (l *approvalLedger) load() (*approvalLedgerFile, error) {
+	data, err := os.ReadFile(l.path())
+	if err != nil {
+		if os.IsNotExist(err) {
+			return &approvalLedgerFile{
+				Approvals:         map[string]CapabilityApproval{},
+				Tombstones:        map[string]time.Time{},
+				Idempotency:       map[string]CapabilityApproval{},
+				IdempotencyInputs: map[string]approvalIdempotencyInput{},
+			}, nil
+		}
+		return nil, err
+	}
+	var file approvalLedgerFile
+	if err := json.Unmarshal(data, &file); err != nil {
+		return nil, err
+	}
+	if file.Approvals == nil {
+		file.Approvals = map[string]CapabilityApproval{}
+	}
+	if file.Tombstones == nil {
+		file.Tombstones = map[string]time.Time{}
+	}
+	if file.Idempotency == nil {
+		file.Idempotency = map[string]CapabilityApproval{}
+	}
+	if file.IdempotencyInputs == nil {
+		file.IdempotencyInputs = map[string]approvalIdempotencyInput{}
+	}
+	return &file, nil
+}
+
+func (l *approvalLedger) save(file *approvalLedgerFile) error {
+	if err := os.MkdirAll(l.dir, 0o755); err != nil {
+		return err
+	}
+	data, err := json.MarshalIndent(file, "", "  ")
+	if err != nil {
+		return err
+	}
+	tmp, err := os.CreateTemp(l.dir, ".approvals-*")
+	if err != nil {
+		return err
+	}
+	tmpPath := tmp.Name()
+	defer func() { _ = os.Remove(tmpPath) }()
+	if _, err := tmp.Write(data); err != nil {
+		_ = tmp.Close()
+		return err
+	}
+	if err := tmp.Sync(); err != nil {
+		_ = tmp.Close()
+		return err
+	}
+	if err := tmp.Close(); err != nil {
+		return err
+	}
+	if err := os.Rename(tmpPath, l.path()); err != nil {
+		return err
+	}
+	return syncApprovalLedgerDirectory(l.dir)
+}
+
+func approvalKey(installationID, workspaceID string) string {
+	return installationID + "\x00" + workspaceID
+}
+
+func approvalIdempotencyKey(eventType CapabilityApprovalEventType, auditID, installationID, workspaceID string) string {
+	return string(eventType) + "\x00" + auditID + "\x00" + installationID + "\x00" + workspaceID
+}
+
+func (l *approvalLedger) grant(installationID, workspaceID string, revision uint64, manifestDigest string, capabilityIDs []string, actor, reason, auditID string, at time.Time) (CapabilityApproval, error) {
+	if err := validateApprovalMutation(installationID, workspaceID, actor, reason, auditID); err != nil {
+		return CapabilityApproval{}, err
+	}
+	if revision == 0 {
+		return CapabilityApproval{}, ErrApprovalRevisionConflict
+	}
+	if strings.TrimSpace(auditID) == "" {
+		return CapabilityApproval{}, errors.New("plugins: approval audit id is required")
+	}
+	canonical, err := CanonicalCapabilityList(capabilityIDs)
+	if err != nil {
+		return CapabilityApproval{}, err
+	}
+	capabilityIDs = canonical
+	l.mu.Lock()
+	defer l.mu.Unlock()
+	file, err := l.load()
+	if err != nil {
+		return CapabilityApproval{}, err
+	}
+	key := approvalKey(installationID, workspaceID)
+	current := file.Approvals[key]
+	if _, tombstoned := file.Tombstones[installationID]; tombstoned {
+		return CapabilityApproval{}, ErrApprovalInstallationTombstoned
+	}
+	if replayed, found, err := approvalGrantReplay(file, installationID, workspaceID, revision, manifestDigest, capabilityIDs, actor, reason, auditID); found || err != nil {
+		return replayed, err
+	}
+	if !approvalRevisionFollows(current.Revision, revision) {
+		return CapabilityApproval{}, ErrApprovalRevisionConflict
+	}
+	approval := CapabilityApproval{
+		InstallationID:     installationID,
+		WorkspaceID:        workspaceID,
+		Revision:           revision,
+		ManifestDigest:     manifestDigest,
+		CapabilityIDs:      append([]string{}, capabilityIDs...),
+		State:              ApprovalStateActive,
+		HumanActor:         actor,
+		HumanPolicyVersion: HumanPolicyVersionImmutable,
+		CreatedAt:          at,
+		UpdatedAt:          at,
+	}
+	if current.Revision != 0 {
+		approval.CreatedAt = current.CreatedAt
+	}
+	eventType := CapabilityApprovalEventGrant
+	if isStrictSubset(capabilityIDs, current.CapabilityIDs) {
+		eventType = CapabilityApprovalEventNarrow
+	}
+	file.Approvals[key] = approval
+	file.Idempotency[approvalIdempotencyKey(CapabilityApprovalEventGrant, auditID, installationID, workspaceID)] = approval
+	file.IdempotencyInputs[approvalIdempotencyKey(CapabilityApprovalEventGrant, auditID, installationID, workspaceID)] = approvalIdempotencyInput{
+		Revision: revision, ManifestDigest: manifestDigest, CapabilityIDs: append([]string{}, capabilityIDs...), Actor: actor, Reason: reason,
+	}
+	file.Events = append(file.Events, CapabilityApprovalEvent{
+		AuditID: auditID, InstallationID: installationID, WorkspaceID: workspaceID,
+		BeforeRevision: current.Revision, AfterRevision: revision,
+		BeforeDigest: current.ManifestDigest, AfterDigest: manifestDigest,
+		Actor: actor, Reason: reason, Type: eventType, ObservedAt: at,
+	})
+	return approval, l.save(file)
+}
+
+func isStrictSubset(candidate, current []string) bool {
+	return len(candidate) < len(current) && equalStrings(intersectStrings(current, candidate), candidate)
+}
+
+func approvalGrantReplay(file *approvalLedgerFile, installationID, workspaceID string, revision uint64, manifestDigest string, capabilityIDs []string, actor, reason, auditID string) (CapabilityApproval, bool, error) {
+	key := approvalIdempotencyKey(CapabilityApprovalEventGrant, auditID, installationID, workspaceID)
+	replayed, ok := file.Idempotency[key]
+	if !ok {
+		return CapabilityApproval{}, false, nil
+	}
+	input, inputOK := file.IdempotencyInputs[key]
+	if inputOK && input.Revision == revision && input.ManifestDigest == manifestDigest && equalStrings(input.CapabilityIDs, capabilityIDs) && input.Actor == actor && input.Reason == reason {
+		return replayed, true, nil
+	}
+	return CapabilityApproval{}, true, ErrApprovalIdempotencyConflict
+}
+
+func approvalRevisionFollows(current, next uint64) bool {
+	if current == 0 {
+		return next == 1
+	}
+	return next == current+1
+}
+
+func (l *approvalLedger) revoke(installationID, workspaceID string, actor, reason, auditID string, at time.Time) (CapabilityApproval, error) {
+	return l.revokeIfRevision(installationID, workspaceID, 0, actor, reason, auditID, at, true)
+}
+
+func (l *approvalLedger) revokeIfRevision(installationID, workspaceID string, expectedRevision uint64, actor, reason, auditID string, at time.Time, allowCurrent bool) (CapabilityApproval, error) {
+	if err := validateApprovalMutation(installationID, workspaceID, actor, reason, auditID); err != nil {
+		return CapabilityApproval{}, err
+	}
+	if strings.TrimSpace(auditID) == "" {
+		return CapabilityApproval{}, errors.New("plugins: approval audit id is required")
+	}
+	l.mu.Lock()
+	defer l.mu.Unlock()
+	file, err := l.load()
+	if err != nil {
+		return CapabilityApproval{}, err
+	}
+	key := approvalKey(installationID, workspaceID)
+	current, ok := file.Approvals[key]
+	if !ok {
+		return CapabilityApproval{}, fmt.Errorf("plugins: approval not found")
+	}
+	effectiveExpectedRevision := expectedRevision
+	if allowCurrent {
+		effectiveExpectedRevision = current.Revision
+	}
+	if auditID != "" {
+		idempotencyKey := approvalIdempotencyKey(CapabilityApprovalEventRevoke, auditID, installationID, workspaceID)
+		if replayed, ok := file.Idempotency[idempotencyKey]; ok {
+			input, inputOK := file.IdempotencyInputs[idempotencyKey]
+			// Current-revision callers intentionally pass allowCurrent=true and
+			// do not retain the pre-mutation revision. Once the first revoke
+			// advances the row, the audit identity is the only stable lookup for
+			// an exact retry. Explicit-revision callers remain bound to the
+			// persisted pre-revoke revision.
+			if inputOK && (allowCurrent || input.Revision == expectedRevision) && input.Actor == actor && input.Reason == reason {
+				return replayed, nil
+			}
+			return CapabilityApproval{}, ErrApprovalIdempotencyConflict
+		}
+	}
+	expectedRevision = effectiveExpectedRevision
+	if current.Revision != expectedRevision {
+		return CapabilityApproval{}, ErrApprovalRevisionConflict
+	}
+	next := current
+	next.Revision++
+	next.State = ApprovalStateRevoked
+	next.HumanActor = actor
+	next.UpdatedAt = at
+	file.Approvals[key] = next
+	if auditID != "" {
+		idempotencyKey := approvalIdempotencyKey(CapabilityApprovalEventRevoke, auditID, installationID, workspaceID)
+		file.Idempotency[idempotencyKey] = next
+		file.IdempotencyInputs[idempotencyKey] = approvalIdempotencyInput{Revision: expectedRevision, Actor: actor, Reason: reason}
+	}
+	file.Events = append(file.Events, CapabilityApprovalEvent{
+		AuditID: auditID, InstallationID: installationID, WorkspaceID: workspaceID,
+		BeforeRevision: current.Revision, AfterRevision: next.Revision,
+		BeforeDigest: current.ManifestDigest, AfterDigest: current.ManifestDigest,
+		Actor: actor, Reason: reason, Type: CapabilityApprovalEventRevoke, ObservedAt: at,
+	})
+	return next, l.save(file)
+}
+
+func (l *approvalLedger) tombstoneInstallation(installationID string, at time.Time) error {
+	if err := validateApprovalIdentifiers(installationID, ""); err != nil {
+		return err
+	}
+	l.mu.Lock()
+	defer l.mu.Unlock()
+	file, err := l.load()
+	if err != nil {
+		return err
+	}
+	if _, ok := file.Tombstones[installationID]; !ok {
+		file.Tombstones[installationID] = at
+	}
+	for key, approval := range file.Approvals {
+		if approval.InstallationID != installationID {
+			continue
+		}
+		if approval.TombstonedAt != nil {
+			continue
+		}
+		approval.Revision++
+		approval.State = ApprovalStateRevoked
+		approval.UpdatedAt = at
+		tombstonedAt := at
+		approval.TombstonedAt = &tombstonedAt
+		file.Approvals[key] = approval
+		file.Events = append(file.Events, CapabilityApprovalEvent{
+			AuditID:        CanonicalApprovalDigest(installationID, approval.WorkspaceID, fmt.Sprint(approval.Revision), "uninstall"),
+			InstallationID: installationID, WorkspaceID: approval.WorkspaceID,
+			BeforeRevision: approval.Revision - 1, AfterRevision: approval.Revision,
+			BeforeDigest: approval.ManifestDigest, AfterDigest: approval.ManifestDigest,
+			Actor: "host", Reason: "installation uninstalled", Type: CapabilityApprovalEventRevoke, ObservedAt: at,
+		})
+	}
+	return l.save(file)
+}
+
+func (l *approvalLedger) reviewManifestChange(installationID, manifestDigest string, manifestCapabilities []string, at time.Time, force bool) error {
+	if err := validateApprovalIdentifiers(installationID, ""); err != nil {
+		return err
+	}
+	canonical, err := CanonicalCapabilityList(manifestCapabilities)
+	if err != nil {
+		return err
+	}
+	l.mu.Lock()
+	defer l.mu.Unlock()
+	file, err := l.load()
+	if err != nil {
+		return err
+	}
+	for key, approval := range file.Approvals {
+		if approval.InstallationID != installationID || (!force && approval.ManifestDigest == manifestDigest) || approval.TombstonedAt != nil {
+			continue
+		}
+		current := approval
+		approval.Revision++
+		approval.ManifestDigest = manifestDigest
+		approval.CapabilityIDs = intersectStrings(approval.CapabilityIDs, canonical)
+		approval.UpdatedAt = at
+		file.Approvals[key] = approval
+		file.Events = append(file.Events, CapabilityApprovalEvent{
+			AuditID:        CanonicalApprovalDigest(installationID, approval.WorkspaceID, fmt.Sprint(approval.Revision), manifestDigest, "manifest-review"),
+			InstallationID: installationID, WorkspaceID: approval.WorkspaceID,
+			BeforeRevision: current.Revision, AfterRevision: approval.Revision,
+			BeforeDigest: current.ManifestDigest, AfterDigest: manifestDigest,
+			Actor: "host", Reason: "installation manifest changed", Type: CapabilityApprovalEventUpgradeReview, ObservedAt: at,
+		})
+	}
+	return l.save(file)
+}
+
+func intersectStrings(a, b []string) []string {
+	if len(a) == 0 || len(b) == 0 {
+		return nil
+	}
+	allowed := make(map[string]struct{}, len(b))
+	for _, v := range b {
+		allowed[v] = struct{}{}
+	}
+	out := make([]string, 0, len(a))
+	for _, v := range a {
+		if _, ok := allowed[v]; ok {
+			out = append(out, v)
+		}
+	}
+	return out
+}
+
+func (l *approvalLedger) get(installationID, workspaceID string) (CapabilityApproval, bool, error) {
+	if err := validateApprovalIdentifiers(installationID, workspaceID); err != nil {
+		return CapabilityApproval{}, false, err
+	}
+	l.mu.Lock()
+	defer l.mu.Unlock()
+	file, err := l.load()
+	if err != nil {
+		return CapabilityApproval{}, false, err
+	}
+	approval, ok := file.Approvals[approvalKey(installationID, workspaceID)]
+	return approval, ok, nil
+}
+
+func (l *approvalLedger) listByInstallation(installationID string) ([]CapabilityApproval, error) {
+	if err := validateApprovalIdentifiers(installationID, ""); err != nil {
+		return nil, err
+	}
+	l.mu.Lock()
+	defer l.mu.Unlock()
+	file, err := l.load()
+	if err != nil {
+		return nil, err
+	}
+	var out []CapabilityApproval
+	for _, approval := range file.Approvals {
+		if approval.InstallationID == installationID {
+			out = append(out, approval)
+		}
+	}
+	sort.Slice(out, func(i, j int) bool {
+		if out[i].WorkspaceID == out[j].WorkspaceID {
+			return out[i].Revision < out[j].Revision
+		}
+		return out[i].WorkspaceID < out[j].WorkspaceID
+	})
+	return out, nil
+}
+
+func validateApprovalIdentifiers(installationID, workspaceID string) error {
+	if !isBoundedApprovalIdentifier(installationID) || (workspaceID != "" && !isBoundedApprovalIdentifier(workspaceID)) {
+		return ErrApprovalInvalidIdentifier
+	}
+	return nil
+}
+
+func validateApprovalAuditMetadata(actor, reason, auditID string) error {
+	for _, value := range []string{actor, reason, auditID} {
+		if value == "" || len(value) > maxApprovalIDLength || strings.ContainsRune(value, '\x00') {
+			return errors.New("plugins: approval audit metadata is malformed")
+		}
+	}
+	return nil
+}
+
+func validateApprovalMutation(installationID, workspaceID, actor, reason, auditID string) error {
+	if err := validateApprovalIdentifiers(installationID, workspaceID); err != nil {
+		return err
+	}
+	return validateApprovalAuditMetadata(actor, reason, auditID)
+}
diff --git a/apps/backend/internal/plugins/approval_store_sync_unix.go b/apps/backend/internal/plugins/approval_store_sync_unix.go
new file mode 100644
index 0000000000..ef03511816
--- /dev/null
+++ b/apps/backend/internal/plugins/approval_store_sync_unix.go
@@ -0,0 +1,17 @@
+//go:build !windows
+
+package plugins
+
+import "os"
+
+// syncApprovalLedgerDirectory flushes the rename metadata on platforms that
+// expose directory handles to fsync. The ledger file is already synced before
+// the rename.
+func syncApprovalLedgerDirectory(path string) error {
+	dir, err := os.Open(path)
+	if err != nil {
+		return err
+	}
+	defer func() { _ = dir.Close() }()
+	return dir.Sync()
+}
diff --git a/apps/backend/internal/plugins/approval_store_sync_windows.go b/apps/backend/internal/plugins/approval_store_sync_windows.go
new file mode 100644
index 0000000000..7594d0b35c
--- /dev/null
+++ b/apps/backend/internal/plugins/approval_store_sync_windows.go
@@ -0,0 +1,11 @@
+//go:build windows
+
+package plugins
+
+// Windows does not provide a usable directory fsync handle through Go's os
+// package. The ledger file is flushed before rename, so the replacement is
+// complete without attempting the read-only directory Sync that fails on
+// Windows.
+func syncApprovalLedgerDirectory(string) error {
+	return nil
+}
diff --git a/apps/backend/internal/plugins/approval_store_test.go b/apps/backend/internal/plugins/approval_store_test.go
new file mode 100644
index 0000000000..dd41ff05a0
--- /dev/null
+++ b/apps/backend/internal/plugins/approval_store_test.go
@@ -0,0 +1,511 @@
+package plugins
+
+import (
+	"errors"
+	"testing"
+	"time"
+
+	"github.com/kandev/kandev/internal/plugins/manifest"
+	"github.com/kandev/kandev/internal/plugins/store"
+)
+
+func TestApprovalLedgerGrantRevokeAndTombstone(t *testing.T) {
+	dir := t.TempDir()
+	ledger := newApprovalLedger(dir)
+
+	grantAt := time.Date(2026, time.August, 31, 12, 1, 0, 0, time.UTC)
+	approval, err := ledger.grant("inst-1", "ws-1", 1, "digest-a", []string{"host.v2.read:tasks"}, "human", "grant", "audit-1", grantAt)
+	if err != nil {
+		t.Fatalf("grant: %v", err)
+	}
+	if approval.State != ApprovalStateActive || approval.Revision != 1 {
+		t.Fatalf("grant approval = %#v", approval)
+	}
+
+	fetched, ok, err := ledger.get("inst-1", "ws-1")
+	if err != nil || !ok {
+		t.Fatalf("get: ok=%v err=%v", ok, err)
+	}
+	if fetched.ManifestDigest != "digest-a" || len(fetched.CapabilityIDs) != 1 {
+		t.Fatalf("fetched = %#v", fetched)
+	}
+
+	revoked, err := ledger.revoke("inst-1", "ws-1", "human", "revoke", "audit-2", grantAt.Add(time.Minute))
+	if err != nil {
+		t.Fatalf("revoke: %v", err)
+	}
+	if revoked.State != ApprovalStateRevoked || revoked.Revision != 2 {
+		t.Fatalf("revoked = %#v", revoked)
+	}
+
+	if err := ledger.tombstoneInstallation("inst-1", grantAt.Add(2*time.Minute)); err != nil {
+		t.Fatalf("tombstone: %v", err)
+	}
+	after, ok, err := ledger.get("inst-1", "ws-1")
+	if err != nil || !ok {
+		t.Fatalf("get after tombstone: ok=%v err=%v", ok, err)
+	}
+	if after.Revision != 3 || after.State != ApprovalStateRevoked {
+		t.Fatalf("after tombstone = %#v", after)
+	}
+}
+
+func TestAuthorizePluginCapabilityStableDenyReasons(t *testing.T) {
+	dir := t.TempDir()
+	svc := &Service{}
+	if err := svc.SetPluginsDir(dir); err != nil {
+		t.Fatalf("SetPluginsDir: %v", err)
+	}
+	t.Cleanup(func() { _ = svc.Close() })
+
+	decision := svc.authorizePluginCapability("inst-1", "ws-1", "host.v2.read:tasks", 1, "req", "method")
+	if decision.Allowed {
+		t.Fatal("decision unexpectedly allowed without approval")
+	}
+	if decision.Reason != ApprovalDenyMissingApproval {
+		t.Fatalf("reason = %q, want missing approval", decision.Reason)
+	}
+}
+
+func TestApprovalLedgerGrantRejectsRevisionRegression(t *testing.T) {
+	dir := t.TempDir()
+	ledger := newApprovalLedger(dir)
+
+	if _, err := ledger.grant("inst-1", "ws-1", 1, "digest-a", []string{"host.v2.read:tasks"}, "human", "grant", "audit-1", time.Now().UTC()); err != nil {
+		t.Fatalf("first grant: %v", err)
+	}
+	if _, err := ledger.grant("inst-1", "ws-1", 1, "digest-b", []string{"host.v2.read:tasks"}, "human", "grant", "audit-2", time.Now().UTC()); err == nil {
+		t.Fatal("grant accepted a non-incrementing revision")
+	}
+}
+
+func TestApprovalLedgerGrantRecordsHumanNarrowing(t *testing.T) {
+	dir := t.TempDir()
+	ledger := newApprovalLedger(dir)
+	at := time.Now().UTC()
+	if _, err := ledger.grant("inst-1", "ws-1", 1, "digest-a", []string{"host.v2.read:messages", "host.v2.read:tasks"}, "human", "grant", "audit-1", at); err != nil {
+		t.Fatalf("initial grant: %v", err)
+	}
+	if _, err := ledger.grant("inst-1", "ws-1", 2, "digest-a", []string{"host.v2.read:tasks"}, "human", "remove messages access", "audit-2", at.Add(time.Second)); err != nil {
+		t.Fatalf("narrow approval: %v", err)
+	}
+
+	file, err := ledger.load()
+	if err != nil {
+		t.Fatalf("load: %v", err)
+	}
+	if got := file.Events[1].Type; got != CapabilityApprovalEventNarrow {
+		t.Fatalf("narrowing event type = %q, want %q", got, CapabilityApprovalEventNarrow)
+	}
+}
+
+func TestApprovalLedgerGrantRejectsZeroRevision(t *testing.T) {
+	dir := t.TempDir()
+	ledger := newApprovalLedger(dir)
+
+	if _, err := ledger.grant("inst-1", "ws-1", 0, "digest-a", []string{"host.v2.read:tasks"}, "human", "grant", "audit-1", time.Now().UTC()); err == nil {
+		t.Fatal("grant accepted revision zero")
+	}
+	if _, ok, err := ledger.get("inst-1", "ws-1"); err != nil || ok {
+		t.Fatalf("grant persisted revision zero approval: ok=%v err=%v", ok, err)
+	}
+}
+
+func TestApprovalLedgerGrantRejectsNonInitialRevision(t *testing.T) {
+	dir := t.TempDir()
+	ledger := newApprovalLedger(dir)
+
+	if _, err := ledger.grant("inst-1", "ws-1", 2, "digest-a", []string{"host.v2.read:tasks"}, "human", "grant", "audit-1", time.Now().UTC()); err == nil {
+		t.Fatal("grant accepted non-initial revision")
+	}
+}
+
+func TestApprovalLedgerTombstonePersistsAcrossReload(t *testing.T) {
+	dir := t.TempDir()
+	ledger := newApprovalLedger(dir)
+
+	if _, err := ledger.grant("inst-1", "ws-1", 1, "digest-a", []string{"host.v2.read:tasks"}, "human", "grant", "audit-1", time.Now().UTC()); err != nil {
+		t.Fatalf("grant: %v", err)
+	}
+	if err := ledger.tombstoneInstallation("inst-1", time.Now().UTC()); err != nil {
+		t.Fatalf("tombstone: %v", err)
+	}
+	reloaded := newApprovalLedger(dir)
+	approval, ok, err := reloaded.get("inst-1", "ws-1")
+	if err != nil || !ok {
+		t.Fatalf("reloaded get: ok=%v err=%v", ok, err)
+	}
+	if approval.State != ApprovalStateRevoked || approval.Revision != 2 {
+		t.Fatalf("approval after reload = %#v", approval)
+	}
+}
+
+func TestAuthorizePluginCapabilityAllowsExactCurrentRevision(t *testing.T) {
+	dir := t.TempDir()
+	svc := &Service{}
+	if err := svc.SetPluginsDir(dir); err != nil {
+		t.Fatalf("SetPluginsDir: %v", err)
+	}
+	t.Cleanup(func() { _ = svc.Close() })
+	if _, err := svc.approvalGrant("inst-1", "ws-1", 1, "digest-a", []string{"host.v2.read:tasks"}, "human", "grant", "audit-1"); err != nil {
+		t.Fatalf("grant: %v", err)
+	}
+
+	decision := svc.authorizePluginCapability("inst-1", "ws-1", "host.v2.read:tasks", 1, "req", "method")
+	if !decision.Allowed {
+		t.Fatalf("decision = %#v, want allowed for exact current revision", decision)
+	}
+	if decision.Receipt.Result != "allowed" {
+		t.Fatalf("receipt result = %q, want allowed", decision.Receipt.Result)
+	}
+}
+
+func TestAuthorizePluginCapabilityDeniesStaleRevision(t *testing.T) {
+	dir := t.TempDir()
+	svc := &Service{}
+	if err := svc.SetPluginsDir(dir); err != nil {
+		t.Fatalf("SetPluginsDir: %v", err)
+	}
+	t.Cleanup(func() { _ = svc.Close() })
+	if _, err := svc.approvalGrant("inst-1", "ws-1", 1, "digest-a", []string{"host.v2.read:tasks"}, "human", "grant", "audit-1"); err != nil {
+		t.Fatalf("initial grant: %v", err)
+	}
+	if _, err := svc.approvalGrant("inst-1", "ws-1", 2, "digest-a", []string{"host.v2.read:tasks"}, "human", "grant", "audit-2"); err != nil {
+		t.Fatalf("second grant: %v", err)
+	}
+
+	decision := svc.authorizePluginCapability("inst-1", "ws-1", "host.v2.read:tasks", 1, "req", "method")
+	if decision.Allowed {
+		t.Fatalf("decision = %#v, want stale revision denied", decision)
+	}
+	if decision.Reason != ApprovalDenyStaleRevision {
+		t.Fatalf("reason = %q, want stale_capability_revision", decision.Reason)
+	}
+}
+
+func TestAuthorizePluginCapabilityDeniesHumanReservedCapability(t *testing.T) {
+	dir := t.TempDir()
+	svc := &Service{}
+	if err := svc.SetPluginsDir(dir); err != nil {
+		t.Fatalf("SetPluginsDir: %v", err)
+	}
+	t.Cleanup(func() { _ = svc.Close() })
+	if _, err := svc.approvalGrant("inst-1", "ws-1", 1, "digest-a", []string{"merge"}, "human", "grant", "audit-1"); err == nil {
+		t.Fatal("approvalGrant persisted a Human-reserved capability")
+	}
+
+	decision := svc.authorizePluginCapability("inst-1", "ws-1", "merge", 1, "req", "method")
+	if decision.Allowed {
+		t.Fatalf("decision = %#v, want human-reserved deny", decision)
+	}
+	if decision.Reason != ApprovalDenyHumanReserved {
+		t.Fatalf("reason = %q, want human_reserved", decision.Reason)
+	}
+}
+
+func TestAuthorizePluginCapabilityDeniesMalformedRequest(t *testing.T) {
+	dir := t.TempDir()
+	svc := &Service{}
+	if err := svc.SetPluginsDir(dir); err != nil {
+		t.Fatalf("SetPluginsDir: %v", err)
+	}
+	t.Cleanup(func() { _ = svc.Close() })
+
+	cases := []struct {
+		name           string
+		installationID string
+		workspaceID    string
+		requestDigest  string
+		methodDigest   string
+	}{
+		{"missing installation", "", "ws-1", "req", "method"},
+		{"missing workspace", "inst-1", "", "req", "method"},
+		{"missing request digest", "inst-1", "ws-1", "", "method"},
+		{"missing method digest", "inst-1", "ws-1", "req", ""},
+	}
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			decision := svc.authorizePluginCapability(tc.installationID, tc.workspaceID, "host.v2.read:tasks", 1, tc.requestDigest, tc.methodDigest)
+			if decision.Allowed {
+				t.Fatalf("decision unexpectedly allowed: %#v", decision)
+			}
+			if decision.Reason != ApprovalDenyMalformedRequest {
+				t.Fatalf("reason = %q, want malformed_request", decision.Reason)
+			}
+		})
+	}
+}
+
+func TestAuthorizePluginCapabilityDeniesUnsupportedCapabilityID(t *testing.T) {
+	dir := t.TempDir()
+	svc := &Service{}
+	if err := svc.SetPluginsDir(dir); err != nil {
+		t.Fatalf("SetPluginsDir: %v", err)
+	}
+	t.Cleanup(func() { _ = svc.Close() })
+	if _, err := svc.approvalGrant("inst-1", "ws-1", 1, "digest-a", []string{"host.v2.read:tasks"}, "human", "grant", "audit-1"); err != nil {
+		t.Fatalf("grant: %v", err)
+	}
+
+	for _, capabilityID := range []string{"", "host.v2.read:*", "host.v2.read:tas?s", " host.v2.read:tasks"} {
+		decision := svc.authorizePluginCapability("inst-1", "ws-1", capabilityID, 1, "req", "method")
+		if decision.Allowed {
+			t.Fatalf("capability %q unexpectedly allowed", capabilityID)
+		}
+		if decision.Reason != ApprovalDenyUnsupportedCapability {
+			t.Fatalf("capability %q reason = %q, want unsupported_capability", capabilityID, decision.Reason)
+		}
+	}
+}
+
+func TestApprovalGrantRetryIsIdempotent(t *testing.T) {
+	dir := t.TempDir()
+	ledger := newApprovalLedger(dir)
+	at := time.Now().UTC()
+	first, err := ledger.grant("inst-1", "ws-1", 1, "digest-a", []string{"host.v2.read:tasks"}, "human", "grant", "audit-1", at)
+	if err != nil {
+		t.Fatalf("first grant: %v", err)
+	}
+	second, err := ledger.grant("inst-1", "ws-1", 1, "digest-a", []string{"host.v2.read:tasks"}, "human", "grant", "audit-1", at.Add(time.Second))
+	if err != nil {
+		t.Fatalf("idempotent retry: %v", err)
+	}
+	if second.Revision != first.Revision || !second.UpdatedAt.Equal(first.UpdatedAt) {
+		t.Fatalf("retry changed approval: first=%#v second=%#v", first, second)
+	}
+	file, err := ledger.load()
+	if err != nil {
+		t.Fatalf("load: %v", err)
+	}
+	if len(file.Events) != 1 {
+		t.Fatalf("event count = %d, want one idempotent event", len(file.Events))
+	}
+}
+
+func TestApprovalGrantRetryRejectsChangedAuditPayload(t *testing.T) {
+	dir := t.TempDir()
+	ledger := newApprovalLedger(dir)
+	at := time.Now().UTC()
+	if _, err := ledger.grant("inst-1", "ws-1", 1, "digest-a", []string{"host.v2.read:tasks"}, "human", "grant", "audit-1", at); err != nil {
+		t.Fatalf("first grant: %v", err)
+	}
+
+	tests := []struct {
+		name   string
+		actor  string
+		reason string
+	}{
+		{name: "actor", actor: "other-human", reason: "grant"},
+		{name: "reason", actor: "human", reason: "different reason"},
+	}
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			if _, err := ledger.grant("inst-1", "ws-1", 1, "digest-a", []string{"host.v2.read:tasks"}, tc.actor, tc.reason, "audit-1", at.Add(time.Second)); !errors.Is(err, ErrApprovalIdempotencyConflict) {
+				t.Fatalf("changed grant payload error = %v, want idempotency conflict", err)
+			}
+		})
+	}
+}
+
+func TestApprovalRevokeRetryRejectsChangedAuditPayload(t *testing.T) {
+	dir := t.TempDir()
+	ledger := newApprovalLedger(dir)
+	at := time.Now().UTC()
+	if _, err := ledger.grant("inst-1", "ws-1", 1, "digest-a", []string{"host.v2.read:tasks"}, "human", "grant", "grant-1", at); err != nil {
+		t.Fatalf("grant: %v", err)
+	}
+	if _, err := ledger.revokeIfRevision("inst-1", "ws-1", 1, "human", "revoke", "revoke-1", at.Add(time.Second), false); err != nil {
+		t.Fatalf("first revoke: %v", err)
+	}
+
+	tests := []struct {
+		name             string
+		expectedRevision uint64
+		actor            string
+		reason           string
+	}{
+		{name: "revision", expectedRevision: 99, actor: "human", reason: "revoke"},
+		{name: "actor", expectedRevision: 1, actor: "other-human", reason: "revoke"},
+		{name: "reason", expectedRevision: 1, actor: "human", reason: "different reason"},
+	}
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			if _, err := ledger.revokeIfRevision("inst-1", "ws-1", tc.expectedRevision, tc.actor, tc.reason, "revoke-1", at.Add(2*time.Second), false); !errors.Is(err, ErrApprovalIdempotencyConflict) {
+				t.Fatalf("changed revoke payload error = %v, want idempotency conflict", err)
+			}
+		})
+	}
+}
+
+func TestApprovalRevokeRetryReplaysExactPayloadAfterRevisionAdvances(t *testing.T) {
+	dir := t.TempDir()
+	ledger := newApprovalLedger(dir)
+	at := time.Now().UTC()
+	if _, err := ledger.grant("inst-1", "ws-1", 1, "digest-a", []string{"host.v2.read:tasks"}, "human", "grant", "grant-1", at); err != nil {
+		t.Fatalf("grant: %v", err)
+	}
+	first, err := ledger.revokeIfRevision("inst-1", "ws-1", 1, "human", "revoke", "revoke-1", at.Add(time.Second), false)
+	if err != nil {
+		t.Fatalf("first revoke: %v", err)
+	}
+	file, err := ledger.load()
+	if err != nil {
+		t.Fatalf("load after revoke: %v", err)
+	}
+	current := file.Approvals[approvalKey("inst-1", "ws-1")]
+	if current.Revision != first.Revision {
+		t.Fatalf("loaded approval revision = %d, want %d", current.Revision, first.Revision)
+	}
+
+	replayed, err := ledger.revokeIfRevision("inst-1", "ws-1", 1, "human", "revoke", "revoke-1", at.Add(2*time.Second), false)
+	if err != nil {
+		t.Fatalf("exact replay revoke: %v", err)
+	}
+	if replayed.Revision != first.Revision || replayed.State != first.State || !replayed.UpdatedAt.Equal(first.UpdatedAt) {
+		t.Fatalf("retry did not replay original revoke: first=%#v replayed=%#v", first, replayed)
+	}
+
+	file, err = ledger.load()
+	if err != nil {
+		t.Fatalf("reload after replay: %v", err)
+	}
+	if len(file.Events) != 2 {
+		t.Fatalf("event count = %d, want grant and first revoke only", len(file.Events))
+	}
+}
+
+func TestApprovalGrantRetryReplaysAfterLaterRevision(t *testing.T) {
+	dir := t.TempDir()
+	ledger := newApprovalLedger(dir)
+	at := time.Now().UTC()
+	first, err := ledger.grant("inst-1", "ws-1", 1, "digest-a", []string{"host.v2.read:tasks"}, "human", "grant", "audit-1", at)
+	if err != nil {
+		t.Fatalf("first grant: %v", err)
+	}
+	if _, err := ledger.grant("inst-1", "ws-1", 2, "digest-b", []string{"host.v2.read:tasks"}, "human", "upgrade", "audit-2", at.Add(time.Second)); err != nil {
+		t.Fatalf("second grant: %v", err)
+	}
+
+	replayed, err := ledger.grant("inst-1", "ws-1", 1, "digest-a", []string{"host.v2.read:tasks"}, "human", "grant", "audit-1", at.Add(2*time.Second))
+	if err != nil {
+		t.Fatalf("retry original grant after later revision: %v", err)
+	}
+	if replayed.Revision != first.Revision || replayed.ManifestDigest != first.ManifestDigest || !replayed.UpdatedAt.Equal(first.UpdatedAt) {
+		t.Fatalf("retry did not replay original result: first=%#v replayed=%#v", first, replayed)
+	}
+	file, err := ledger.load()
+	if err != nil {
+		t.Fatalf("load: %v", err)
+	}
+	if len(file.Events) != 2 {
+		t.Fatalf("event count = %d, want original two events only", len(file.Events))
+	}
+}
+
+func TestApprovalTombstoneAppendsWorkspaceEventAndMarksRow(t *testing.T) {
+	dir := t.TempDir()
+	ledger := newApprovalLedger(dir)
+	at := time.Now().UTC()
+	if _, err := ledger.grant("inst-1", "ws-1", 1, "digest-a", []string{"host.v2.read:tasks"}, "human", "grant", "audit-1", at); err != nil {
+		t.Fatalf("grant: %v", err)
+	}
+	if err := ledger.tombstoneInstallation("inst-1", at.Add(time.Second)); err != nil {
+		t.Fatalf("tombstone: %v", err)
+	}
+	row, ok, err := ledger.get("inst-1", "ws-1")
+	if err != nil || !ok {
+		t.Fatalf("get: ok=%v err=%v", ok, err)
+	}
+	if row.TombstonedAt == nil {
+		t.Fatal("tombstone did not mark current approval")
+	}
+	file, err := ledger.load()
+	if err != nil {
+		t.Fatalf("load: %v", err)
+	}
+	if len(file.Events) != 2 || file.Events[1].Type != CapabilityApprovalEventRevoke || file.Events[1].AuditID == "" {
+		t.Fatalf("tombstone events = %#v", file.Events)
+	}
+}
+
+func TestApprovalTombstoneRetryDoesNotAdvanceRevisionOrDuplicateEvents(t *testing.T) {
+	dir := t.TempDir()
+	ledger := newApprovalLedger(dir)
+	at := time.Now().UTC()
+	if _, err := ledger.grant("inst-1", "ws-1", 1, "digest-a", []string{"host.v2.read:tasks"}, "human", "grant", "audit-1", at); err != nil {
+		t.Fatalf("grant: %v", err)
+	}
+	if err := ledger.tombstoneInstallation("inst-1", at.Add(time.Second)); err != nil {
+		t.Fatalf("first tombstone: %v", err)
+	}
+	first, ok, err := ledger.get("inst-1", "ws-1")
+	if err != nil || !ok {
+		t.Fatalf("get after first tombstone: ok=%v err=%v", ok, err)
+	}
+	if err := ledger.tombstoneInstallation("inst-1", at.Add(2*time.Second)); err != nil {
+		t.Fatalf("second tombstone: %v", err)
+	}
+	second, ok, err := ledger.get("inst-1", "ws-1")
+	if err != nil || !ok {
+		t.Fatalf("get after second tombstone: ok=%v err=%v", ok, err)
+	}
+	if second.Revision != first.Revision || !second.UpdatedAt.Equal(first.UpdatedAt) {
+		t.Fatalf("tombstone retry advanced row: first=%#v second=%#v", first, second)
+	}
+	file, err := ledger.load()
+	if err != nil {
+		t.Fatalf("load: %v", err)
+	}
+	if len(file.Events) != 2 {
+		t.Fatalf("event count = %d, want grant plus one tombstone revoke", len(file.Events))
+	}
+}
+
+func TestApprovalLedgerRejectsGrantForTombstonedInstallation(t *testing.T) {
+	dir := t.TempDir()
+	ledger := newApprovalLedger(dir)
+	if _, err := ledger.grant("inst-1", "ws-1", 1, "digest-a", []string{"host.v2.read:tasks"}, "human", "grant", "audit-1", time.Now().UTC()); err != nil {
+		t.Fatalf("grant: %v", err)
+	}
+	if err := ledger.tombstoneInstallation("inst-1", time.Now().UTC()); err != nil {
+		t.Fatalf("tombstone: %v", err)
+	}
+	if _, err := ledger.grant("inst-1", "ws-1", 3, "digest-b", []string{"host.v2.read:tasks"}, "human", "regrant", "audit-2", time.Now().UTC()); err == nil {
+		t.Fatal("grant accepted tombstoned installation")
+	}
+}
+
+func TestApprovalLedgerRejectsMissingAuditID(t *testing.T) {
+	dir := t.TempDir()
+	ledger := newApprovalLedger(dir)
+	if _, err := ledger.grant("inst-1", "ws-1", 1, "digest-a", []string{"host.v2.read:tasks"}, "human", "grant", "", time.Now().UTC()); err == nil {
+		t.Fatal("grant accepted empty audit id")
+	}
+}
+
+func TestAuthorizePluginCapabilityRequiresCurrentInstalledManifest(t *testing.T) {
+	dir := t.TempDir()
+	svc := &Service{registry: NewRegistry()}
+	if err := svc.SetPluginsDir(dir); err != nil {
+		t.Fatalf("SetPluginsDir: %v", err)
+	}
+	t.Cleanup(func() { _ = svc.Close() })
+	svc.registry.Add(&store.Record{
+		Manifest:       manifest.Manifest{ID: "plugin-a", Capabilities: manifest.Capabilities{APIRead: []string{"tasks"}}},
+		InstallationID: "inst-1",
+	})
+	if _, err := svc.approvalGrant("inst-1", "ws-1", 1, ManifestCapabilityDigest(svc.registry.List()[0].Manifest), []string{"host.v2.read:tasks"}, "human", "grant", "audit-1"); err != nil {
+		t.Fatalf("grant: %v", err)
+	}
+	decision := svc.authorizePluginCapability("inst-1", "ws-1", "host.v2.write:tasks", 1, "req", "method")
+	if decision.Allowed || decision.Reason != ApprovalDenyUndeclaredCapability {
+		t.Fatalf("decision = %#v, want manifest intersection denial", decision)
+	}
+}
+
+func TestApprovalLedgerRejectsNULIdentifiers(t *testing.T) {
+	ledger := newApprovalLedger(t.TempDir())
+	if _, err := ledger.grant("inst\x00-1", "ws-1", 1, "digest", []string{"host.v2.read:tasks"}, "human", "grant", "audit-1", time.Now().UTC()); !errors.Is(err, ErrApprovalInvalidIdentifier) {
+		t.Fatalf("grant error = %v, want invalid identifier", err)
+	}
+}
diff --git a/apps/backend/internal/plugins/approval_store_windows_test.go b/apps/backend/internal/plugins/approval_store_windows_test.go
new file mode 100644
index 0000000000..7d6e25c160
--- /dev/null
+++ b/apps/backend/internal/plugins/approval_store_windows_test.go
@@ -0,0 +1,15 @@
+//go:build windows
+
+package plugins
+
+import (
+	"testing"
+	"time"
+)
+
+func TestApprovalLedgerGrantWorksOnWindows(t *testing.T) {
+	ledger := newApprovalLedger(t.TempDir())
+	if _, err := ledger.grant("inst-1", "ws-1", 1, "digest-a", []string{"host.v2.read:tasks"}, "human", "grant", "audit-1", time.Now().UTC()); err != nil {
+		t.Fatalf("grant on Windows: %v", err)
+	}
+}
diff --git a/apps/backend/internal/plugins/approval_test.go b/apps/backend/internal/plugins/approval_test.go
new file mode 100644
index 0000000000..2d6c196812
--- /dev/null
+++ b/apps/backend/internal/plugins/approval_test.go
@@ -0,0 +1,236 @@
+package plugins
+
+import (
+	"strings"
+	"testing"
+	"time"
+)
+
+func TestCanonicalCapabilityListSortsDeduplicatesAndTrims(t *testing.T) {
+	got, err := CanonicalCapabilityList([]string{" host.v2.write:tasks ", "host.v2.read:tasks", "host.v2.write:tasks"})
+	if err != nil {
+		t.Fatalf("CanonicalCapabilityList() unexpected error: %v", err)
+	}
+	want := []string{"host.v2.read:tasks", "host.v2.write:tasks"}
+	if len(got) != len(want) {
+		t.Fatalf("len = %d, want %d", len(got), len(want))
+	}
+	for i := range want {
+		if got[i] != want[i] {
+			t.Fatalf("got[%d] = %q, want %q", i, got[i], want[i])
+		}
+	}
+}
+
+func TestCanonicalCapabilityListRejectsWildcards(t *testing.T) {
+	if _, err := CanonicalCapabilityList([]string{"host.v2.read:*"}); err == nil {
+		t.Fatal("CanonicalCapabilityList() accepted a wildcard capability")
+	}
+}
+
+func TestCanonicalCapabilityListRequiresExactHostV2Capabilities(t *testing.T) {
+	for _, capability := range []string{
+		"api_read:tasks",
+		"api_write:tasks",
+		"host.v2.read",
+		"host.v2.read:tasks:extra",
+		"host.v2.admin:tasks",
+	} {
+		if _, err := CanonicalCapabilityList([]string{capability}); err == nil {
+			t.Fatalf("CanonicalCapabilityList(%q) accepted a non-exact H6 capability", capability)
+		}
+	}
+
+	got, err := CanonicalCapabilityList([]string{"host.v2.write:tasks", "host.v2.read:tasks"})
+	if err != nil {
+		t.Fatalf("CanonicalCapabilityList() rejected exact H6 capabilities: %v", err)
+	}
+	want := []string{"host.v2.read:tasks", "host.v2.write:tasks"}
+	if !equalStrings(got, want) {
+		t.Fatalf("capabilities = %#v, want %#v", got, want)
+	}
+}
+
+func TestCanonicalCapabilityListRejectsNamespacedHumanReservedCapabilities(t *testing.T) {
+	for _, capability := range []string{
+		"api_write:merge",
+		"host.v2.write:merge",
+		"host.v2.write:deploy",
+		"host.v2.write:release",
+		"host.v2.write:rewrite_history",
+		"host.v2.write:cross_workspace",
+		"host.v2.write:secret_scope_expand",
+	} {
+		if _, err := CanonicalCapabilityList([]string{capability}); err == nil {
+			t.Fatalf("CanonicalCapabilityList(%q) accepted a Human-reserved capability", capability)
+		}
+	}
+}
+
+func TestAuthorizePluginCapabilityDoesNotTreatV1DeclarationsAsH6Authority(t *testing.T) {
+	svc := &Service{}
+	if err := svc.SetPluginsDir(t.TempDir()); err != nil {
+		t.Fatalf("SetPluginsDir: %v", err)
+	}
+	t.Cleanup(func() { _ = svc.Close() })
+	if _, err := svc.approvalGrant("inst-1", "ws-1", 1, "digest-a", []string{"host.v2.write:tasks"}, "human", "grant", "audit-1"); err != nil {
+		t.Fatalf("grant: %v", err)
+	}
+
+	for _, capabilityID := range []string{"api_read:tasks", "api_write:tasks"} {
+		decision := svc.authorizePluginCapability("inst-1", "ws-1", capabilityID, 1, "request", "method")
+		if decision.Allowed || decision.Reason != ApprovalDenyUnsupportedCapability {
+			t.Fatalf("legacy %q decision = %#v, want unsupported denial", capabilityID, decision)
+		}
+	}
+	for _, capabilityID := range []string{"api_write:merge", "host.v2.write:merge"} {
+		decision := svc.authorizePluginCapability("inst-1", "ws-1", capabilityID, 1, "request", "method")
+		if decision.Allowed || decision.Reason != ApprovalDenyHumanReserved {
+			t.Fatalf("reserved %q decision = %#v, want Human-policy denial", capabilityID, decision)
+		}
+	}
+}
+
+func TestCanonicalCapabilityListBoundsCapabilityInputs(t *testing.T) {
+	tooLong := "host.v2.read:" + strings.Repeat("a", 1024)
+	if _, err := CanonicalCapabilityList([]string{tooLong}); err == nil {
+		t.Fatal("CanonicalCapabilityList() accepted an oversized capability")
+	}
+
+	capabilities := make([]string, 1025)
+	for i := range capabilities {
+		capabilities[i] = "host.v2.read:tasks"
+	}
+	if _, err := CanonicalCapabilityList(capabilities); err == nil {
+		t.Fatal("CanonicalCapabilityList() accepted too many capability inputs")
+	}
+}
+
+func TestApprovalLedgerRejectsOversizedOrMalformedAuditMetadata(t *testing.T) {
+	ledger := newApprovalLedger(t.TempDir())
+	for _, tc := range []struct {
+		name   string
+		actor  string
+		reason string
+		audit  string
+	}{
+		{name: "oversized actor", actor: strings.Repeat("a", 1025), reason: "grant", audit: "audit-1"},
+		{name: "oversized reason", actor: "human", reason: strings.Repeat("a", 1025), audit: "audit-1"},
+		{name: "nul audit id", actor: "human", reason: "grant", audit: "audit\x00secret"},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			if _, err := ledger.grant("inst-1", "ws-1", 1, "digest-a", []string{"host.v2.read:tasks"}, tc.actor, tc.reason, tc.audit, time.Now().UTC()); err == nil {
+				t.Fatal("grant accepted unsafe audit metadata")
+			}
+		})
+	}
+}
+
+func TestCanonicalApprovalDigestIsStable(t *testing.T) {
+	got1 := CanonicalApprovalDigest(" installation ", "workspace", "7")
+	got2 := CanonicalApprovalDigest("installation", " workspace ", "7")
+	if got1 != got2 {
+		t.Fatalf("CanonicalApprovalDigest() is not stable: %q != %q", got1, got2)
+	}
+}
+
+func TestApprovalReceiptCarriesSafeMetadata(t *testing.T) {
+	when := time.Date(2026, time.August, 31, 12, 0, 0, 0, time.UTC)
+	receipt := ApprovalReceipt{
+		InstallationID: "inst-1",
+		WorkspaceID:    "ws-1",
+		Revision:       3,
+		CapabilityID:   "host.v2.read:tasks",
+		RequestDigest:  "req",
+		MethodDigest:   "method",
+		AuditID:        "audit-1",
+		Result:         "allowed",
+		ObservedAt:     when,
+	}
+	if receipt.InstallationID != "inst-1" || receipt.WorkspaceID != "ws-1" || receipt.Revision != 3 {
+		t.Fatalf("receipt = %#v, want safe identity fields preserved", receipt)
+	}
+	if receipt.ObservedAt != when {
+		t.Fatalf("ObservedAt = %v, want %v", receipt.ObservedAt, when)
+	}
+}
+
+func TestAuthorizePluginCapabilityCopiesAuditIDToDeniedDecision(t *testing.T) {
+	svc := &Service{}
+	if err := svc.SetPluginsDir(t.TempDir()); err != nil {
+		t.Fatalf("SetPluginsDir: %v", err)
+	}
+	t.Cleanup(func() { _ = svc.Close() })
+	decision := svc.authorizePluginCapability("inst-1", "ws-1", "host.v2.read:tasks", 1, "req", "method")
+	if decision.AuditID == "" || decision.AuditID != decision.Receipt.AuditID {
+		t.Fatalf("denied decision audit id = %q, receipt audit id = %q", decision.AuditID, decision.Receipt.AuditID)
+	}
+}
+
+func TestAuthorizePluginCapabilityBoundsAndDigestsReceiptInputs(t *testing.T) {
+	svc := &Service{}
+	if err := svc.SetPluginsDir(t.TempDir()); err != nil {
+		t.Fatalf("SetPluginsDir: %v", err)
+	}
+	t.Cleanup(func() { _ = svc.Close() })
+	secret := "token=super-secret-value"
+	decision := svc.authorizePluginCapability("inst-1", "ws-1", "host.v2.read:tasks", 1, secret, "method=secret")
+	if decision.Receipt.RequestDigest == secret || decision.Receipt.MethodDigest == "method=secret" {
+		t.Fatalf("receipt leaked request input: %#v", decision.Receipt)
+	}
+	if len(decision.Receipt.RequestDigest) != 64 || len(decision.Receipt.MethodDigest) != 64 {
+		t.Fatalf("receipt digest lengths = %d, %d; want SHA-256 hex", len(decision.Receipt.RequestDigest), len(decision.Receipt.MethodDigest))
+	}
+
+	tooLong := strings.Repeat("a", 1025)
+	for _, tc := range []struct {
+		name string
+		call func() ApprovalDecision
+	}{
+		{"installation", func() ApprovalDecision {
+			return svc.authorizePluginCapability(tooLong, "ws-1", "host.v2.read:tasks", 1, "request", "method")
+		}},
+		{"workspace", func() ApprovalDecision {
+			return svc.authorizePluginCapability("inst-1", tooLong, "host.v2.read:tasks", 1, "request", "method")
+		}},
+		{"request", func() ApprovalDecision {
+			return svc.authorizePluginCapability("inst-1", "ws-1", "host.v2.read:tasks", 1, strings.Repeat("a", 4097), "method")
+		}},
+		{"method", func() ApprovalDecision {
+			return svc.authorizePluginCapability("inst-1", "ws-1", "host.v2.read:tasks", 1, "request", strings.Repeat("a", 4097))
+		}},
+		{"nul request", func() ApprovalDecision {
+			return svc.authorizePluginCapability("inst-1", "ws-1", "host.v2.read:tasks", 1, "request\x00secret", "method")
+		}},
+		{"nul method", func() ApprovalDecision {
+			return svc.authorizePluginCapability("inst-1", "ws-1", "host.v2.read:tasks", 1, "request", "method\x00secret")
+		}},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			if decision := tc.call(); decision.Reason != ApprovalDenyMalformedRequest {
+				t.Fatalf("reason = %q, want malformed_request", decision.Reason)
+			}
+		})
+	}
+	malformed := svc.authorizePluginCapability(tooLong, "ws-1", "host.v2.read:tasks", 1, "request", "method")
+	if malformed.Receipt.InstallationID != "" {
+		t.Fatalf("receipt leaked malformed installation input: %#v", malformed.Receipt)
+	}
+}
+
+func TestAuthorizePluginCapabilityBoundsReservedCapabilityReceipt(t *testing.T) {
+	svc := &Service{}
+	if err := svc.SetPluginsDir(t.TempDir()); err != nil {
+		t.Fatalf("SetPluginsDir: %v", err)
+	}
+	t.Cleanup(func() { _ = svc.Close() })
+	tooLong := strings.Repeat("a", maxCapabilityIDLength) + ":merge"
+	for _, capabilityID := range []string{tooLong, "host.v2.read\x00:merge"} {
+		t.Run(capabilityID, func(t *testing.T) {
+			decision := svc.authorizePluginCapability("inst-1", "ws-1", capabilityID, 1, "request", "method")
+			if decision.Receipt.CapabilityID != "" {
+				t.Fatalf("receipt capability id = %q, want empty for unsafe input", decision.Receipt.CapabilityID)
+			}
+		})
+	}
+}
diff --git a/apps/backend/internal/plugins/provider.go b/apps/backend/internal/plugins/provider.go
index bbf7d74d21..a810f902b5 100644
--- a/apps/backend/internal/plugins/provider.go
+++ b/apps/backend/internal/plugins/provider.go
@@ -99,7 +99,7 @@ func ProvideWithStoreErrors(cfg *config.Config, dbPool *db.Pool, secrets SecretV
 
 	registry := NewRegistry()
 	if err := registry.Load(pluginStore); err != nil {
-		warnProvider(log, "Plugins registry load failed; starting with an empty registry", err)
+		warnProvider(log, "Plugins registry migration reported an error; continuing with loaded records", err)
 	}
 
 	svc := NewService(pluginStore, registry, eventBus, log)
diff --git a/apps/backend/internal/plugins/registry.go b/apps/backend/internal/plugins/registry.go
index 5e4a9de758..ea0ea44037 100644
--- a/apps/backend/internal/plugins/registry.go
+++ b/apps/backend/internal/plugins/registry.go
@@ -1,15 +1,23 @@
 package plugins
 
 import (
+	"errors"
 	"fmt"
 	"sort"
 	"strings"
 	"sync"
 	"time"
 
+	"github.com/google/uuid"
 	"github.com/kandev/kandev/internal/plugins/store"
 )
 
+// Registry is an in-memory, mutex-guarded index of installed plugins, keyed
+// by plugin id. It is loaded from the filesystem store at startup (Load)
+// and kept in sync as Service mutates installations, so read paths (List,
+// Get) never hit disk.
+//
+// Get and List return copies of the stored *store.Record so callers cannot
 // mutate registry state by holding onto a returned pointer; all writes go
 // through Add / Remove / SetStatus / SetRuntimeState / SetAutoUpdate /
 // SetRestartCount.
@@ -33,14 +41,24 @@ func (r *Registry) Load(s store.Store) error {
 	}
 
 	byID := make(map[string]*store.Record, len(records))
+	var migrationErrs []error
 	for _, rec := range records {
+		if rec.InstallationID == "" {
+			migrated := cloneRecord(rec)
+			migrated.InstallationID = uuid.NewString()
+			if err := s.Save(migrated); err != nil {
+				migrationErrs = append(migrationErrs, fmt.Errorf("migrate plugin installation id for %s: %w", rec.ID, err))
+			} else {
+				rec = migrated
+			}
+		}
 		byID[rec.ID] = cloneRecord(rec)
 	}
 
 	r.mu.Lock()
-	defer r.mu.Unlock()
 	r.byID = byID
-	return nil
+	r.mu.Unlock()
+	return errors.Join(migrationErrs...)
 }
 
 // Get returns a copy of the record for id, and whether it was found.
diff --git a/apps/backend/internal/plugins/registry_test.go b/apps/backend/internal/plugins/registry_test.go
index 1522fa881c..87a03a21e8 100644
--- a/apps/backend/internal/plugins/registry_test.go
+++ b/apps/backend/internal/plugins/registry_test.go
@@ -1,12 +1,35 @@
 package plugins
 
 import (
+	"context"
+	"errors"
+	"os"
+	"path/filepath"
 	"testing"
+	"time"
 
 	"github.com/kandev/kandev/internal/plugins/manifest"
 	"github.com/kandev/kandev/internal/plugins/store"
 )
 
+// migrationSaveErrorStore exposes both legacy and already-migrated records,
+// then fails the migration write. Registry.Load must still publish the full
+// List result so boot scans cannot treat valid records as sideloads.
+type migrationSaveErrorStore struct {
+	store.Store
+	records []*store.Record
+	saves   int
+}
+
+func (s *migrationSaveErrorStore) List() ([]*store.Record, error) {
+	return s.records, nil
+}
+
+func (s *migrationSaveErrorStore) Save(*store.Record) error {
+	s.saves++
+	return errors.New("simulated migration save failure")
+}
+
 // testManifest returns a minimal valid runtime-managed manifest for tests
 // that only need a store.Record, not a full installed package (see
 // service_test.go's testPackage for that).
@@ -44,6 +67,140 @@ func TestRegistryLoadPopulatesFromStore(t *testing.T) {
 	}
 }
 
+func TestRegistryLoadMigratesMissingInstallationIDOnce(t *testing.T) {
+	dir := t.TempDir()
+	fsStore := store.NewFSStore(dir)
+	if err := fsStore.Save(&store.Record{Manifest: *testManifest("kandev-plugin-slack"), Status: store.StatusRegistered}); err != nil {
+		t.Fatalf("Save: %v", err)
+	}
+
+	reg := NewRegistry()
+	if err := reg.Load(fsStore); err != nil {
+		t.Fatalf("Load() unexpected error: %v", err)
+	}
+
+	first, ok := reg.Get("kandev-plugin-slack")
+	if !ok {
+		t.Fatal("Get() expected record to be present after Load()")
+	}
+	if first.InstallationID == "" {
+		t.Fatal("Load() did not mint an installation id for a legacy record")
+	}
+
+	reloaded, err := fsStore.Get("kandev-plugin-slack")
+	if err != nil {
+		t.Fatalf("reloaded record: %v", err)
+	}
+	if reloaded.InstallationID != first.InstallationID {
+		t.Fatalf("installation id changed across migration/save: first=%q reloaded=%q", first.InstallationID, reloaded.InstallationID)
+	}
+
+	reg2 := NewRegistry()
+	if err := reg2.Load(fsStore); err != nil {
+		t.Fatalf("second Load() unexpected error: %v", err)
+	}
+	second, ok := reg2.Get("kandev-plugin-slack")
+	if !ok {
+		t.Fatal("Get() expected record to be present after second Load()")
+	}
+	if second.InstallationID != first.InstallationID {
+		t.Fatalf("installation id was regenerated on replay: first=%q second=%q", first.InstallationID, second.InstallationID)
+	}
+}
+
+func TestRegistryLoadRetainsRecordsWhenMigrationSaveFails(t *testing.T) {
+	legacy := &store.Record{Manifest: *testManifest("kandev-plugin-legacy"), Status: store.StatusDisabled}
+	migrated := &store.Record{
+		Manifest:       *testManifest("kandev-plugin-migrated"),
+		Status:         store.StatusActive,
+		InstallationID: "stable-installation",
+	}
+	registry := NewRegistry()
+	backend := &migrationSaveErrorStore{records: []*store.Record{legacy, migrated}}
+	err := registry.Load(backend)
+	if err == nil {
+		t.Fatal("Load() expected migration error")
+	}
+
+	for _, want := range []*store.Record{legacy, migrated} {
+		got, ok := registry.Get(want.ID)
+		if !ok {
+			t.Fatalf("Load() dropped %q after migration failure", want.ID)
+		}
+		if got.Status != want.Status {
+			t.Fatalf("Load() status for %q = %q, want %q", want.ID, got.Status, want.Status)
+		}
+	}
+	if got, _ := registry.Get(legacy.ID); got.InstallationID != "" {
+		t.Fatalf("Load() exposed an unpersisted installation id %q", got.InstallationID)
+	}
+
+	pluginsDir := t.TempDir()
+	manifestPath := filepath.Join(pluginsDir, legacy.ID, "1.0.0", manifestFileName)
+	if err := os.MkdirAll(filepath.Dir(manifestPath), 0o755); err != nil {
+		t.Fatalf("MkdirAll() = %v", err)
+	}
+	if err := os.WriteFile(manifestPath, []byte("id: kandev-plugin-legacy\napi_version: 1\nversion: 1.0.0\ndisplay_name: Legacy\nruntime:\n  type: binary\n  executables:\n    linux-amd64: server/plugin\n"), 0o644); err != nil {
+		t.Fatalf("WriteFile() = %v", err)
+	}
+
+	svc := &Service{store: backend, registry: registry, log: testLogger(t)}
+	if err := svc.SetPluginsDir(pluginsDir); err != nil {
+		t.Fatalf("SetPluginsDir: %v", err)
+	}
+	t.Cleanup(func() { _ = svc.Close() })
+	if _, err := svc.approvalLedger().grant("stable-installation", "workspace-1", 1, "digest", nil, "human", "grant", "audit-1", time.Now().UTC()); err != nil {
+		t.Fatalf("seed approval: %v", err)
+	}
+	result := svc.bootScan(context.Background())
+	if len(result.Added) != 0 {
+		t.Fatalf("boot scan registered an existing record as a sideload: %#v", result.Added)
+	}
+	if backend.saves != 1 {
+		t.Fatalf("boot scan performed %d store saves, want only the failed migration save", backend.saves)
+	}
+	if _, ok, err := svc.approvalCurrent("stable-installation", "workspace-1"); err != nil || !ok {
+		t.Fatalf("boot scan lost an unrelated approval: ok=%v err=%v", ok, err)
+	}
+}
+
+func TestServiceUninstallLegacyRecordAfterInstallationIDMigrationFails(t *testing.T) {
+	pluginsDir := t.TempDir()
+	fsStore := store.NewFSStore(pluginsDir)
+	legacy := &store.Record{
+		Manifest:    *testManifest("kandev-plugin-legacy"),
+		Status:      store.StatusDisabled,
+		InstallPath: filepath.Join(pluginsDir, "kandev-plugin-legacy", "1.0.0"),
+	}
+	if err := os.MkdirAll(legacy.InstallPath, 0o755); err != nil {
+		t.Fatalf("MkdirAll() = %v", err)
+	}
+	if err := fsStore.Save(legacy); err != nil {
+		t.Fatalf("Save() = %v", err)
+	}
+
+	registry := NewRegistry()
+	backend := &migrationSaveErrorStore{Store: fsStore, records: []*store.Record{legacy}}
+	if err := registry.Load(backend); err == nil {
+		t.Fatal("Load() expected migration error")
+	}
+	svc := NewService(backend, registry, nil, testLogger(t))
+	if err := svc.SetPluginsDir(pluginsDir); err != nil {
+		t.Fatalf("SetPluginsDir: %v", err)
+	}
+	t.Cleanup(func() { _ = svc.Close() })
+
+	if err := svc.Uninstall(t.Context(), legacy.ID); err != nil {
+		t.Fatalf("Uninstall() legacy record: %v", err)
+	}
+	if _, err := fsStore.Get(legacy.ID); !errors.Is(err, store.ErrNotFound) {
+		t.Fatalf("store.Get() after Uninstall() = %v, want store.ErrNotFound", err)
+	}
+	if _, ok := registry.Get(legacy.ID); ok {
+		t.Fatal("registry retained legacy record after Uninstall()")
+	}
+}
+
 func TestRegistryGetMissingReturnsNotOK(t *testing.T) {
 	reg := NewRegistry()
 	if _, ok := reg.Get("missing"); ok {
diff --git a/apps/backend/internal/plugins/service.go b/apps/backend/internal/plugins/service.go
index bf5089b784..55dbba6828 100644
--- a/apps/backend/internal/plugins/service.go
+++ b/apps/backend/internal/plugins/service.go
@@ -96,6 +96,7 @@ type Service struct {
 
 	pluginsDir          string
 	store               store.Store
+	approvals           *approvalLedger
 	registry            *Registry
 	state               *state.Store
 	userState           *state.UserStore
@@ -699,6 +700,7 @@ func (s *Service) SetPluginsDir(dir string) error {
 	// Keep package installation rooted correctly even when durable conversation
 	// state initialization fails and the caller continues in degraded mode.
 	s.pluginsDir = dir
+	s.approvals = newApprovalLedger(dir)
 	hostDir := filepath.Join(dir, ".host")
 	conversationTokens, err := loadOrCreateConversationTokenManager(
 		filepath.Join(hostDir, "conversation-token.key"),
diff --git a/apps/backend/internal/plugins/service_install.go b/apps/backend/internal/plugins/service_install.go
index 7c0ddc84d4..40e1b84e01 100644
--- a/apps/backend/internal/plugins/service_install.go
+++ b/apps/backend/internal/plugins/service_install.go
@@ -11,6 +11,7 @@ import (
 	"os"
 	"time"
 
+	"github.com/google/uuid"
 	"go.uber.org/zap"
 
 	"github.com/kandev/kandev/internal/plugins/manifest"
@@ -117,12 +118,33 @@ func (s *Service) Install(ctx context.Context, r io.Reader) (*store.Record, erro
 	// not a manifest fact) must be carried forward or an auto-update would
 	// silently reset the very toggle that triggered it.
 	if hadOldRec {
+		rec.InstallationID = oldRec.InstallationID
 		rec.AutoUpdate = oldRec.AutoUpdate
 	}
+	if rec.InstallationID == "" {
+		rec.InstallationID = uuid.NewString()
+	}
 	if err := s.store.Save(rec); err != nil {
 		s.rollbackFailedInstall(result.InstallPath, oldRec, hadOldRec && wasRunning)
 		return nil, fmt.Errorf("plugins: persist installed record: %w", err)
 	}
+	if err := s.reviewInstalledApprovals(rec); err != nil {
+		if hadOldRec {
+			if restoreErr := s.store.Save(oldRec); restoreErr != nil {
+				s.log.Warn("plugins: failed to restore old plugin record after approval review error",
+					zap.String("plugin_id", rec.ID), zap.Error(restoreErr))
+				s.registry.Add(rec)
+				return nil, errors.Join(err, fmt.Errorf("plugins: restore previous plugin record: %w", restoreErr))
+			}
+		} else if deleteErr := s.store.Delete(rec.ID); deleteErr != nil {
+			s.log.Warn("plugins: failed to delete plugin record after approval review error",
+				zap.String("plugin_id", rec.ID), zap.Error(deleteErr))
+			s.registry.Add(rec)
+			return nil, errors.Join(err, fmt.Errorf("plugins: remove failed plugin record: %w", deleteErr))
+		}
+		s.rollbackFailedInstall(result.InstallPath, oldRec, hadOldRec && wasRunning)
+		return nil, err
+	}
 	s.registry.Add(rec)
 	s.agentToolInstallMu.Unlock()
 	catalogLocked = false
@@ -146,6 +168,18 @@ func (s *Service) Install(ctx context.Context, r io.Reader) (*store.Record, erro
 	return installed, activateErr
 }
 
+func (s *Service) reviewInstalledApprovals(rec *store.Record) error {
+	ledger := s.approvalLedger()
+	if ledger == nil {
+		return nil
+	}
+	caps, err := ManifestCapabilityIDs(rec.Manifest)
+	if err != nil {
+		return err
+	}
+	return ledger.reviewManifestChange(rec.InstallationID, ManifestCapabilityDigest(rec.Manifest), caps, time.Now().UTC(), true)
+}
+
 // extractPackage runs pkgtar.Install and registers the extracted version
 // directory as an in-flight install, both under extractingMu so the directory
 // is never visible on disk without being marked. Install cannot take the
@@ -354,6 +388,12 @@ func (s *Service) Uninstall(ctx context.Context, id string) error {
 		s.runtime.Stop(id)
 	}
 	s.revokeGitCredentialProviderLeases(rec.RepositoryProviders)
+	if rec.InstallationID != "" {
+		if err := s.approvalTombstoneInstallation(rec.InstallationID); err != nil {
+			s.reconcileAbortedUninstall(id, wasRunning)
+			return fmt.Errorf("plugins: tombstone approval history: %w", err)
+		}
+	}
 	if err := s.deletePluginSecrets(ctx, id); err != nil {
 		s.reconcileAbortedUninstall(id, wasRunning)
 		return fmt.Errorf("plugins: uninstall aborted, could not purge plugin secrets: %w", err)
diff --git a/apps/backend/internal/plugins/service_install_test.go b/apps/backend/internal/plugins/service_install_test.go
index a5438ed3fd..3328eae75f 100644
--- a/apps/backend/internal/plugins/service_install_test.go
+++ b/apps/backend/internal/plugins/service_install_test.go
@@ -8,9 +8,11 @@ import (
 	"os"
 	"path/filepath"
 	goruntime "runtime"
+	"strings"
 	"sync"
 	"testing"
 
+	"github.com/kandev/kandev/internal/plugins/manifest"
 	"github.com/kandev/kandev/internal/plugins/pkgtar"
 	"github.com/kandev/kandev/internal/plugins/pkgtar/pkgtartest"
 	"github.com/kandev/kandev/internal/plugins/store"
@@ -108,6 +110,169 @@ func TestServiceInstallOverActivePluginRestartsWithNewVersion(t *testing.T) {
 	}
 }
 
+func TestServiceInstallUpgradeReviewsExistingCapabilityApprovals(t *testing.T) {
+	svc, _, _ := newTestService(t)
+	rec1, err := svc.Install(context.Background(), testPackageWithAPIRead(t, "kandev-plugin-slack", "1.0.0", "tasks", "messages"))
+	if err != nil {
+		t.Fatalf("install initial plugin: %v", err)
+	}
+	originalDigest := ManifestCapabilityDigest(rec1.Manifest)
+	if _, err := svc.approvalGrant(rec1.InstallationID, "ws-1", 1, originalDigest, []string{"host.v2.read:tasks", "host.v2.read:messages"}, "human", "grant", "audit-1"); err != nil {
+		t.Fatalf("grant initial approval: %v", err)
+	}
+
+	rec2, err := svc.Install(context.Background(), testPackageWithAPIRead(t, "kandev-plugin-slack", "1.1.0", "tasks"))
+	if err != nil {
+		t.Fatalf("upgrade plugin: %v", err)
+	}
+	if rec2.InstallationID != rec1.InstallationID {
+		t.Fatalf("installation id changed on upgrade: %q -> %q", rec1.InstallationID, rec2.InstallationID)
+	}
+
+	row, ok, err := svc.approvalCurrent(rec1.InstallationID, "ws-1")
+	if err != nil || !ok {
+		t.Fatalf("approvalCurrent after upgrade: ok=%v err=%v", ok, err)
+	}
+	if row.Revision != 2 {
+		t.Fatalf("revision after upgrade = %d, want 2", row.Revision)
+	}
+	if row.ManifestDigest != ManifestCapabilityDigest(rec2.Manifest) {
+		t.Fatalf("manifest digest after upgrade = %q, want %q", row.ManifestDigest, ManifestCapabilityDigest(rec2.Manifest))
+	}
+	if got, want := row.CapabilityIDs, []string{"host.v2.read:tasks"}; !equalStrings(got, want) {
+		t.Fatalf("capabilities after narrowing upgrade = %#v, want %#v", got, want)
+	}
+	if _, err := svc.approvalGrant(rec1.InstallationID, "ws-1", 3, row.ManifestDigest, []string{"host.v2.read:tasks"}, "human", "renew", "audit-2"); err != nil {
+		t.Fatalf("renew approval: %v", err)
+	}
+	rec3, err := svc.Install(context.Background(), testPackageWithAPIRead(t, "kandev-plugin-slack", "1.2.0", "tasks", "messages"))
+	if err != nil {
+		t.Fatalf("rollback-equivalent install: %v", err)
+	}
+	if rec3.InstallationID != rec1.InstallationID {
+		t.Fatalf("installation id changed on rollback-equivalent replacement: %q -> %q", rec1.InstallationID, rec3.InstallationID)
+	}
+	row, ok, err = svc.approvalCurrent(rec1.InstallationID, "ws-1")
+	if err != nil || !ok {
+		t.Fatalf("approvalCurrent after rollback-equivalent replacement: ok=%v err=%v", ok, err)
+	}
+	if row.Revision != 4 {
+		t.Fatalf("revision after rollback-equivalent replacement = %d, want 4", row.Revision)
+	}
+	if got, want := row.CapabilityIDs, []string{"host.v2.read:tasks"}; !equalStrings(got, want) {
+		t.Fatalf("capabilities after rollback-equivalent replacement = %#v, want %#v", got, want)
+	}
+	file, err := svc.approvalLedger().load()
+	if err != nil {
+		t.Fatalf("load approvals: %v", err)
+	}
+	if len(file.Events) != 4 || file.Events[1].Type != CapabilityApprovalEventUpgradeReview ||
+		file.Events[1].BeforeDigest != originalDigest || file.Events[1].AfterDigest != ManifestCapabilityDigest(rec2.Manifest) ||
+		file.Events[2].Type != CapabilityApprovalEventGrant || file.Events[3].Type != CapabilityApprovalEventUpgradeReview ||
+		file.Events[3].BeforeDigest != ManifestCapabilityDigest(rec2.Manifest) || file.Events[3].AfterDigest != ManifestCapabilityDigest(rec3.Manifest) {
+		t.Fatalf("approval events after upgrade = %#v", file.Events)
+	}
+}
+
+func TestServiceInstallUpgradeReviewFailureRestartsPreviousRuntime(t *testing.T) {
+	svc, _, rt := newTestService(t)
+	rec1, err := svc.Install(context.Background(), testPackageWithAPIRead(t, "kandev-plugin-slack", "1.0.0", "tasks"))
+	if err != nil {
+		t.Fatalf("install initial plugin: %v", err)
+	}
+	if _, err := svc.approvalGrant(rec1.InstallationID, "ws-1", 1, ManifestCapabilityDigest(rec1.Manifest), []string{"host.v2.read:tasks"}, "human", "grant", "audit-1"); err != nil {
+		t.Fatalf("grant approval: %v", err)
+	}
+
+	// An empty manifest resource is accepted by package extraction but is
+	// rejected while deriving the exact approval capability set. This fails
+	// after the old runtime has been stopped and the new record persisted.
+	_, err = svc.Install(context.Background(), testPackageWithAPIRead(t, "kandev-plugin-slack", "1.1.0", "*"))
+	if err == nil {
+		t.Fatal("upgrade with invalid capability expected an approval review error")
+	}
+	if !rt.Running("kandev-plugin-slack") {
+		t.Fatal("previous runtime was not restarted after approval review failure")
+	}
+	if got := rt.startCallCount("kandev-plugin-slack"); got != 2 {
+		t.Fatalf("runtime Start called %d times, want initial start plus rollback restart", got)
+	}
+	onDisk, err := svc.Get("kandev-plugin-slack")
+	if err != nil {
+		t.Fatalf("get restored plugin: %v", err)
+	}
+	if onDisk.Version != "1.0.0" {
+		t.Fatalf("restored plugin version = %q, want 1.0.0", onDisk.Version)
+	}
+}
+
+func TestServiceInstallUpgradeReviewRollbackFailureKeepsNewRecordCoherent(t *testing.T) {
+	dir := t.TempDir()
+	fsStore := store.NewFSStore(dir)
+	failing := &failMatchingSaveStore{
+		Store:   fsStore,
+		match:   func(rec *store.Record) bool { return rec.Version == "1.0.0" },
+		failErr: errors.New("simulated compensating save failure"),
+	}
+	svc := NewService(failing, NewRegistry(), nil, testLogger(t))
+	if err := svc.SetPluginsDir(dir); err != nil {
+		t.Fatalf("SetPluginsDir: %v", err)
+	}
+	svc.SetRuntime(newFakeRuntime())
+	t.Cleanup(func() { _ = svc.Close() })
+	if _, err := svc.Install(context.Background(), testPackageWithAPIRead(t, "kandev-plugin-slack", "1.0.0", "tasks")); err != nil {
+		t.Fatalf("install initial plugin: %v", err)
+	}
+	failing.arm()
+	_, err := svc.Install(context.Background(), testPackageWithAPIRead(t, "kandev-plugin-slack", "1.1.0", "*"))
+	if err == nil || !strings.Contains(err.Error(), "compensating save failure") {
+		t.Fatalf("upgrade error = %v, want compensating save failure", err)
+	}
+	onDisk, getErr := fsStore.Get("kandev-plugin-slack")
+	if getErr != nil {
+		t.Fatalf("store.Get(): %v", getErr)
+	}
+	if onDisk.Version != "1.1.0" {
+		t.Fatalf("persisted version = %q, want retained new version 1.1.0", onDisk.Version)
+	}
+	if _, statErr := os.Stat(onDisk.InstallPath); statErr != nil {
+		t.Fatalf("retained new install path missing: %v", statErr)
+	}
+	current, getErr := svc.Get("kandev-plugin-slack")
+	if getErr != nil || current.Version != "1.1.0" {
+		t.Fatalf("registry record = %#v, err=%v; want coherent new record", current, getErr)
+	}
+}
+
+func TestServiceInstallEquivalentUpgradeBumpsApprovalRevision(t *testing.T) {
+	svc, _, _ := newTestService(t)
+	rec1, err := svc.Install(context.Background(), testPackageWithAPIRead(t, "kandev-plugin-slack", "1.0.0", "tasks"))
+	if err != nil {
+		t.Fatalf("install initial plugin: %v", err)
+	}
+	digest := ManifestCapabilityDigest(rec1.Manifest)
+	if _, err := svc.approvalGrant(rec1.InstallationID, "ws-1", 1, digest, []string{"host.v2.read:tasks"}, "human", "grant", "audit-1"); err != nil {
+		t.Fatalf("grant: %v", err)
+	}
+	if _, err := svc.Install(context.Background(), testPackageWithAPIRead(t, "kandev-plugin-slack", "1.1.0", "tasks")); err != nil {
+		t.Fatalf("equivalent upgrade: %v", err)
+	}
+	row, ok, err := svc.approvalCurrent(rec1.InstallationID, "ws-1")
+	if err != nil || !ok {
+		t.Fatalf("approvalCurrent: ok=%v err=%v", ok, err)
+	}
+	if row.Revision != 2 {
+		t.Fatalf("revision = %d, want 2", row.Revision)
+	}
+	file, err := svc.approvalLedger().load()
+	if err != nil {
+		t.Fatalf("load approvals: %v", err)
+	}
+	if len(file.Events) != 2 || file.Events[1].Type != CapabilityApprovalEventUpgradeReview {
+		t.Fatalf("events = %#v, want grant and upgrade review", file.Events)
+	}
+}
+
 // failingSaveStore wraps a real store.Store, letting a test arm exactly one
 // Save call to fail with a simulated error — used to exercise Install's
 // cleanup-on-persist-failure path without a real disk-full/permission
@@ -118,6 +283,33 @@ type failingSaveStore struct {
 	failNext bool
 }
 
+type failMatchingSaveStore struct {
+	store.Store
+	mu      sync.Mutex
+	armed   bool
+	match   func(*store.Record) bool
+	failErr error
+}
+
+func (s *failMatchingSaveStore) Save(rec *store.Record) error {
+	s.mu.Lock()
+	fail := s.armed && s.match(rec)
+	if fail {
+		s.armed = false
+	}
+	s.mu.Unlock()
+	if fail {
+		return s.failErr
+	}
+	return s.Store.Save(rec)
+}
+
+func (s *failMatchingSaveStore) arm() {
+	s.mu.Lock()
+	s.armed = true
+	s.mu.Unlock()
+}
+
 func (s *failingSaveStore) Save(rec *store.Record) error {
 	s.mu.Lock()
 	fail := s.failNext
@@ -373,6 +565,44 @@ func TestServiceInstallFromURL_RejectsNonHTTPSchemeBeforeAnyRequest(t *testing.T
 	}
 }
 
+func testPackageWithAPIRead(t *testing.T, id, version string, resources ...string) *bytes.Buffer {
+	t.Helper()
+	platformKey := goruntime.GOOS + "-" + goruntime.GOARCH
+	quotedResources := make([]string, 0, len(resources))
+	for _, resource := range resources {
+		quotedResources = append(quotedResources, fmt.Sprintf("%q", resource))
+	}
+	minimumVersion := ""
+	for _, resource := range resources {
+		if resource == "messages" {
+			minimumVersion = fmt.Sprintf("min_kandev_version: %q\n", manifest.MinimumMessagesCapabilityVersion)
+			break
+		}
+	}
+	manifestYAML := fmt.Sprintf(`
+id: %s
+api_version: 1
+version: %s
+display_name: Test Plugin
+%s
+capabilities:
+  api_read: [%s]
+runtime:
+  type: binary
+  executables:
+    %s: server/plugin
+`, id, version, minimumVersion, strings.Join(quotedResources, ", "), platformKey)
+
+	var buf bytes.Buffer
+	if err := pkgtartest.WritePackage(&buf, map[string][]byte{
+		"manifest.yaml": []byte(manifestYAML),
+		"server/plugin": []byte("#!/bin/sh\necho fake\n"),
+	}); err != nil {
+		t.Fatalf("WritePackage: %v", err)
+	}
+	return &buf
+}
+
 // messagesMinKandevVersionPackage is like minKandevVersionPackage but
 // declares capabilities.api_read: messages, which subjects the manifest to
 // the capability minimum floor (MinimumMessagesCapabilityVersion).
diff --git a/apps/backend/internal/plugins/service_sync.go b/apps/backend/internal/plugins/service_sync.go
index 9a7052ff0a..a8716ad7ea 100644
--- a/apps/backend/internal/plugins/service_sync.go
+++ b/apps/backend/internal/plugins/service_sync.go
@@ -9,6 +9,7 @@ import (
 	"strings"
 	"time"
 
+	"github.com/google/uuid"
 	"go.uber.org/zap"
 
 	"github.com/kandev/kandev/internal/plugins/manifest"
@@ -198,11 +199,12 @@ func (s *Service) registerSideload(id, version string) error {
 	}
 
 	rec := &store.Record{
-		Manifest:    *m,
-		Status:      StatusDisabled,
-		InstallPath: versionDir,
-		Signed:      false,
-		InstalledAt: time.Now().UTC(),
+		Manifest:       *m,
+		Status:         StatusDisabled,
+		InstallationID: uuid.NewString(),
+		InstallPath:    versionDir,
+		Signed:         false,
+		InstalledAt:    time.Now().UTC(),
 	}
 	if err := s.store.Save(rec); err != nil {
 		return fmt.Errorf("persist sideloaded record: %w", err)
diff --git a/apps/backend/internal/plugins/service_test.go b/apps/backend/internal/plugins/service_test.go
index bb14b9e8dc..eda1e579ba 100644
--- a/apps/backend/internal/plugins/service_test.go
+++ b/apps/backend/internal/plugins/service_test.go
@@ -695,11 +695,17 @@ func TestServiceUninstallDeletesPluginUserStateForEveryUser(t *testing.T) {
 func TestServiceUninstallFailsClosedWhenUserStateCleanupFails(t *testing.T) {
 	svc, fsStore, rt := newTestService(t)
 	svc.SetUserState(newTestUserStateStore(t))
-	rec := installTestPlugin(t, svc, "kandev-plugin-notes")
 	ctx := context.Background()
+	rec, err := svc.Install(ctx, testPackageWithAPIRead(t, "kandev-plugin-notes", "1.0.0", "tasks"))
+	if err != nil {
+		t.Fatalf("install plugin: %v", err)
+	}
 	if _, err := svc.UserState().Set(ctx, rec.ID, "user_1", "task", "task_1", "note", json.RawMessage(`"a"`), nil); err != nil {
 		t.Fatalf("seed user state: %v", err)
 	}
+	if _, err := svc.approvalGrant(rec.InstallationID, "ws-1", 1, ManifestCapabilityDigest(rec.Manifest), []string{"host.v2.read:tasks"}, "human", "grant", "audit-1"); err != nil {
+		t.Fatalf("seed approval: %v", err)
+	}
 
 	cleanupErr := errors.New("user state database unavailable")
 	cleanup := &fakeUserStateCleanup{
@@ -710,7 +716,7 @@ func TestServiceUninstallFailsClosedWhenUserStateCleanupFails(t *testing.T) {
 	deliverer := &fakeDeliverer{}
 	svc.SetDeliverer(deliverer)
 
-	err := svc.Uninstall(ctx, rec.ID)
+	err = svc.Uninstall(ctx, rec.ID)
 	if err == nil || !strings.Contains(err.Error(), cleanupErr.Error()) {
 		t.Fatalf("Uninstall() error = %v, want user-state cleanup failure", err)
 	}
@@ -732,6 +738,14 @@ func TestServiceUninstallFailsClosedWhenUserStateCleanupFails(t *testing.T) {
 	if deliverer.refreshCount != 1 {
 		t.Fatalf("deliverer refreshes after failed uninstall = %d, want stopped-state reconciliation only", deliverer.refreshCount)
 	}
+	firstApproval, ok, err := svc.approvalCurrent(rec.InstallationID, "ws-1")
+	if err != nil || !ok {
+		t.Fatalf("approvalCurrent after failed uninstall: ok=%v err=%v", ok, err)
+	}
+	if firstApproval.Revision != 2 || firstApproval.TombstonedAt == nil {
+		t.Fatalf("approval after failed uninstall = %#v", firstApproval)
+	}
+	firstTombstone := *firstApproval.TombstonedAt
 
 	cleanup.deleteErr = nil
 	if err := svc.Uninstall(ctx, rec.ID); err != nil {
@@ -750,6 +764,75 @@ func TestServiceUninstallFailsClosedWhenUserStateCleanupFails(t *testing.T) {
 	if len(entries) != 0 {
 		t.Fatalf("user state rows after successful retry = %d, want 0", len(entries))
 	}
+	secondApproval, ok, err := svc.approvalCurrent(rec.InstallationID, "ws-1")
+	if err != nil || !ok {
+		t.Fatalf("approvalCurrent after successful retry: ok=%v err=%v", ok, err)
+	}
+	if secondApproval.Revision != firstApproval.Revision || secondApproval.TombstonedAt == nil || !secondApproval.TombstonedAt.Equal(firstTombstone) {
+		t.Fatalf("approval after uninstall retry changed tombstone state: first=%#v second=%#v", firstApproval, secondApproval)
+	}
+	ledger, err := svc.approvalLedger().load()
+	if err != nil {
+		t.Fatalf("load approvals after successful retry: %v", err)
+	}
+	if len(ledger.Events) != 2 {
+		t.Fatalf("approval event count after uninstall retry = %d, want grant plus single revoke", len(ledger.Events))
+	}
+}
+
+func TestServiceUninstallReconcilesRuntimeStateWhenApprovalTombstoneFails(t *testing.T) {
+	svc, _, rt := newTestService(t)
+	rec, err := svc.Install(context.Background(), testPackageWithAPIRead(t, "kandev-plugin-slack", "1.0.0", "tasks"))
+	if err != nil {
+		t.Fatalf("install plugin: %v", err)
+	}
+	if _, err := svc.approvalGrant(rec.InstallationID, "ws-1", 1, ManifestCapabilityDigest(rec.Manifest), []string{"host.v2.read:tasks"}, "human", "grant", "audit-1"); err != nil {
+		t.Fatalf("seed approval: %v", err)
+	}
+	if err := os.Remove(svc.approvalLedger().path()); err != nil {
+		t.Fatalf("remove approval ledger: %v", err)
+	}
+	if err := os.Mkdir(svc.approvalLedger().path(), 0o755); err != nil {
+		t.Fatalf("replace approval ledger with directory: %v", err)
+	}
+
+	err = svc.Uninstall(context.Background(), rec.ID)
+	if err == nil {
+		t.Fatal("Uninstall() expected tombstone failure")
+	}
+	if !rt.stopped(rec.ID) {
+		t.Fatal("Uninstall() did not stop the runtime before tombstone failure")
+	}
+	current, getErr := svc.Get(rec.ID)
+	if getErr != nil {
+		t.Fatalf("Get() after failed uninstall: %v", getErr)
+	}
+	if current.Status != StatusError {
+		t.Fatalf("status after failed tombstone = %q, want %q", current.Status, StatusError)
+	}
+}
+
+func TestServiceUninstallFencesOldApprovalAsRevokedAfterRegistryRemoval(t *testing.T) {
+	svc, _, _ := newTestService(t)
+	rec, err := svc.Install(context.Background(), testPackageWithAPIRead(t, "kandev-plugin-notes", "1.0.0", "tasks"))
+	if err != nil {
+		t.Fatalf("install: %v", err)
+	}
+	if _, err := svc.approvalGrant(rec.InstallationID, "ws-1", 1, ManifestCapabilityDigest(rec.Manifest), []string{"host.v2.read:tasks"}, "human", "grant", "audit-1"); err != nil {
+		t.Fatalf("grant approval: %v", err)
+	}
+
+	if err := svc.Uninstall(context.Background(), rec.ID); err != nil {
+		t.Fatalf("uninstall: %v", err)
+	}
+
+	decision := svc.AuthorizeCapability(rec.InstallationID, "ws-1", "host.v2.read:tasks", 1, "request-digest", "method-digest")
+	if decision.Allowed {
+		t.Fatalf("AuthorizeCapability() allowed tombstoned installation: %#v", decision)
+	}
+	if decision.Reason != ApprovalDenyRevokedApproval {
+		t.Fatalf("AuthorizeCapability() reason = %q, want %q", decision.Reason, ApprovalDenyRevokedApproval)
+	}
 }
 
 func TestServiceUninstallMissingReturnsNotFound(t *testing.T) {
diff --git a/apps/backend/internal/plugins/store/store.go b/apps/backend/internal/plugins/store/store.go
index beeed80fc6..84a7f0d633 100644
--- a/apps/backend/internal/plugins/store/store.go
+++ b/apps/backend/internal/plugins/store/store.go
@@ -39,9 +39,13 @@ var ErrNotFound = errors.New("plugin not found")
 type Record struct {
 	manifest.Manifest `yaml:",inline"`
 
-	Status      string `yaml:"status" json:"status"`
-	InstallPath string `yaml:"install_path" json:"install_path"`
-	Signed      bool   `yaml:"signed" json:"signed"`
+	Status string `yaml:"status" json:"status"`
+	// InstallationID is a Host-minted opaque principal for the installed
+	// plugin. It is persisted with the record and never derived from the
+	// plugin id, package digest, workspace, or install path.
+	InstallationID string `yaml:"installation_id,omitempty" json:"installation_id,omitempty"`
+	InstallPath    string `yaml:"install_path" json:"install_path"`
+	Signed         bool   `yaml:"signed" json:"signed"`
 	// AutoUpdate is the operator's per-plugin auto-update override. It is a
 	// tri-state: nil means "inherit the instance-wide default"
 	// (Service.AutoUpdateDefault), true forces auto-update on for this plugin,
diff --git a/docs/plans/plugins-capability-approval/plan.md b/docs/plans/plugins-capability-approval/plan.md
new file mode 100644
index 0000000000..8c8f523c44
--- /dev/null
+++ b/docs/plans/plugins-capability-approval/plan.md
@@ -0,0 +1,105 @@
+---
+created: 2026-09-07
+status: done
+requirements:
+  - REQ-PLUGINS-CAPABILITY-APPROVAL-001
+  - REQ-PLUGINS-CAPABILITY-APPROVAL-002
+  - REQ-PLUGINS-CAPABILITY-APPROVAL-003
+  - REQ-PLUGINS-CAPABILITY-APPROVAL-004
+  - REQ-PLUGINS-CAPABILITY-APPROVAL-005
+  - REQ-PLUGINS-CAPABILITY-APPROVAL-006
+system_design:
+  - ../../specs/plugins/system-design/capability-approval.md
+legacy_specs: []
+---
+
+# Implementation Plan: Generic Plugin Capability Approval and Audit (H6)
+
+## Overview
+
+Add the generic plugin capability-approval substrate as one vertical work
+order: host-minted installation identity, the workspace-scoped approval ledger
+with exact-revision admission, the append-only event trail, the fail-closed
+authorization decision with typed deny reasons, uninstall tombstones with
+reinstall identity, the legacy `v1` fence, and the audit receipt primitives.
+Scope is the substrate only: no approval UI, no coordinator surface, and no
+host receipt persistence.
+
+## Scope
+
+### In scope
+
+- `installation_id` minting and persistence on the plugin store record.
+- One current `CapabilityApproval` per `(installation_id, workspace_id)`.
+- Grant, narrow, revoke, and upgrade-review events in an append-only ledger.
+- Exact-revision admission and audit-id idempotency.
+- Fail-closed `AuthorizeCapability` with stable typed deny reasons.
+- Uninstall tombstone and reinstall identity mints.
+- The `host.v2` exact-capability fence for legacy `v1` declarations.
+- `ApprovalReceipt` and canonical digest primitives.
+
+### Out of scope
+
+- Approval or review UI, coordinator surfaces, dashboards.
+- Host adapter persistence of audit or read/write receipts.
+- Changes to legacy `v1` runtime behavior beyond fencing it from approval
+  authority.
+- H1-H5 plugin capabilities; this initiative is substrate only.
+
+### No UI changes
+
+This package does not create or change rendered UI, so no ASCII UI preview is
+included.
+
+## Technical approach
+
+The ledger (`approvals.json` under the plugins directory) owns approvals,
+events, tombstones, and idempotency inputs. One current approval per
+installation/workspace pair is stored keyed by the pair with exact next
+revision admission; every mutation appends an event carrying before/after
+revisions and digests. `installation_id` is minted at install time and
+attached to the store record; reinstall mints fresh identity and tombstones
+block the old identity permanently.
+
+The authorization path (`approval_service.go`) is a pure decision function
+that evaluates in a fixed order — malformed request, human-reserved, missing
+approval (including the foreign-workspace alias), revoked or tombstoned,
+stale revision, manifest intersection, approved list — and returns a typed
+decision carrying the audit identity and a bounded receipt. Legacy `v1`
+declarations keep their behavior but are fenced from approval admission and
+authorization.
+
+## Tests
+
+- `approval_test.go`, `approval_store_test.go`, `approval_service_test.go`:
+  canonicalization, exact-revision admission, idempotency, tombstone, and
+  reinstall-identity coverage.
+- `approval_api_test.go`, `approval_query_test.go`: API list/get, grant, and
+  revoke flows including conflict semantics.
+- `approval_dto_test.go`: DTO shape and receipt bounds.
+- Store install/sync tests: `installation_id` minting and persistence.
+
+## E2E tests
+
+No new E2E is required: the substrate exposes no UI surface. Go unit and
+integration tests exercise the full ledger and decision matrix; a browser
+duplicate of that matrix would add cost without observable UI coverage.
+
+## Work orders
+
+- [x] [Task 01: Capability approval substrate](task-01-capability-approval-substrate.md)
+
+## Verification results
+
+- `cd apps/backend && go build ./...` passed on the H6 head and was
+  re-verified on the merged head.
+- `cd apps/backend && go test ./internal/plugins/...` passed in 10 packages
+  on the H6 head and was re-verified on the merged head.
+
+## Risks
+
+- Ledger file corruption must not grant authority: unknown fields decode
+  forward-compatibly and missing maps initialize empty, but any decode failure
+  must fail closed at lookup.
+- A future policy revision must not silently reinterpret stored approvals:
+  the per-row human policy version is the stability point.
diff --git a/docs/plans/plugins-capability-approval/task-01-capability-approval-substrate.md b/docs/plans/plugins-capability-approval/task-01-capability-approval-substrate.md
new file mode 100644
index 0000000000..b73f63b6aa
--- /dev/null
+++ b/docs/plans/plugins-capability-approval/task-01-capability-approval-substrate.md
@@ -0,0 +1,146 @@
+---
+id: "01-capability-approval-substrate"
+title: "Capability approval substrate"
+status: done
+wave: 1
+depends_on: []
+plan: "plan.md"
+requirements:
+  - REQ-PLUGINS-CAPABILITY-APPROVAL-001
+  - REQ-PLUGINS-CAPABILITY-APPROVAL-002
+  - REQ-PLUGINS-CAPABILITY-APPROVAL-003
+  - REQ-PLUGINS-CAPABILITY-APPROVAL-004
+  - REQ-PLUGINS-CAPABILITY-APPROVAL-005
+  - REQ-PLUGINS-CAPABILITY-APPROVAL-006
+acceptance_criteria:
+  - AC-PLUGINS-CAPABILITY-APPROVAL-001.1
+  - AC-PLUGINS-CAPABILITY-APPROVAL-001.2
+  - AC-PLUGINS-CAPABILITY-APPROVAL-001.3
+  - AC-PLUGINS-CAPABILITY-APPROVAL-001.4
+  - AC-PLUGINS-CAPABILITY-APPROVAL-001.5
+  - AC-PLUGINS-CAPABILITY-APPROVAL-001.6
+  - AC-PLUGINS-CAPABILITY-APPROVAL-002.1
+  - AC-PLUGINS-CAPABILITY-APPROVAL-002.2
+  - AC-PLUGINS-CAPABILITY-APPROVAL-003.1
+  - AC-PLUGINS-CAPABILITY-APPROVAL-003.2
+  - AC-PLUGINS-CAPABILITY-APPROVAL-003.3
+  - AC-PLUGINS-CAPABILITY-APPROVAL-003.4
+  - AC-PLUGINS-CAPABILITY-APPROVAL-003.5
+  - AC-PLUGINS-CAPABILITY-APPROVAL-003.6
+  - AC-PLUGINS-CAPABILITY-APPROVAL-003.7
+  - AC-PLUGINS-CAPABILITY-APPROVAL-004.1
+  - AC-PLUGINS-CAPABILITY-APPROVAL-004.2
+  - AC-PLUGINS-CAPABILITY-APPROVAL-005.1
+  - AC-PLUGINS-CAPABILITY-APPROVAL-005.2
+  - AC-PLUGINS-CAPABILITY-APPROVAL-006.1
+  - AC-PLUGINS-CAPABILITY-APPROVAL-006.2
+  - AC-PLUGINS-CAPABILITY-APPROVAL-006.3
+system_design:
+  - ../../specs/plugins/system-design/capability-approval.md
+---
+
+# Task 01: Capability Approval Substrate
+
+## Summary
+
+Deliver the generic plugin capability-approval substrate: host-minted
+installation identity, one current approval per `(installation_id,
+workspace_id)`, append-only approval events, exact-revision admission, the
+fail-closed authorization decision with typed deny reasons, uninstall
+tombstones with fresh reinstall identity, the legacy `v1` fence, and the
+audit receipt primitives.
+
+## In scope
+
+- `InstallationID` minting and persistence on the plugin store record.
+- `CapabilityApproval` ledger with grant/narrow/revoke/upgrade-review events.
+- Exact next-revision admission and audit-id idempotency.
+- `AuthorizeCapability` fail-closed decision with stable deny vocabulary.
+- Tombstones on uninstall; fresh identity on reinstall.
+- `host.v2` exact-capability fence for legacy `v1` declarations.
+- `ApprovalReceipt` and canonical digest primitives.
+- Service and store APIs for list/get/grant/revoke.
+
+## Out of scope
+
+- Approval UI, coordinator surfaces, dashboards.
+- Host adapter persistence of receipts.
+- Legacy `v1` behavior changes beyond the fence.
+- H1-H5 capabilities.
+
+## Acceptance
+
+- Grants replace the current row for the installation/workspace pair and are
+  admitted only at the exact next revision with matching manifest digest and
+  manifest-declared capabilities.
+- Every mutation appends an event with before/after revisions and digests;
+  history is never rewritten.
+- Authorization denies missing, revoked, tombstoned, stale, human-reserved,
+  unavailable, undeclared, and malformed requests with distinct typed reasons;
+  foreign-workspace requests alias the missing-approval reason.
+- Uninstall tombstones the identity permanently; reinstall mints a new
+  identity, so no approval is inherited.
+- Legacy `v1` capabilities are rejected from approval lists and denied at
+  authorization as unsupported, while retaining their original runtime
+  behavior.
+
+## Verification
+
+```bash
+cd apps/backend && go build ./...
+cd apps/backend && go test ./internal/plugins/...
+```
+
+## Files likely touched
+
+- `apps/backend/internal/plugins/approval.go`
+- `apps/backend/internal/plugins/approval_api.go`
+- `apps/backend/internal/plugins/approval_dto.go`
+- `apps/backend/internal/plugins/approval_service.go`
+- `apps/backend/internal/plugins/approval_store.go`
+- `apps/backend/internal/plugins/registry.go`
+- `apps/backend/internal/plugins/service.go`
+- `apps/backend/internal/plugins/service_install.go`
+- `apps/backend/internal/plugins/service_sync.go`
+- `apps/backend/internal/plugins/store/store.go`
+- `apps/backend/internal/plugins/service_test.go`
+- `apps/backend/internal/plugins/store/store_test.go`
+
+## Dependencies
+
+None. This is the substrate initiative; no prior plugin capability wave is
+required.
+
+## Risks
+
+- Cross-workspace denial must not leak existence: the foreign-workspace path
+  intentionally reuses the missing-approval deny reason.
+- Ledger decode failures must fail closed at lookup rather than default to
+  allowing.
+
+## Parallelism
+
+`sequential` — single vertical work order owning the approval files.
+
+## Inputs
+
+- Requirements `REQ-PLUGINS-CAPABILITY-APPROVAL-001` through `-006`.
+- System design `docs/specs/plugins/system-design/capability-approval.md`.
+- Plan `plan.md`.
+- Existing manifest capability derivation (`ManifestCapabilityIDs`) and store
+  record patterns in `apps/backend/internal/plugins`.
+
+## Results
+
+Implemented the full substrate on the H6 head: installation id minting in the
+install path, the approval ledger with events/tombstones/idempotency, the
+fail-closed decision path with the typed deny vocabulary, reinstall identity
+mints, the `v1` fence, and receipt primitives. Verified with:
+
+```bash
+cd apps/backend && go test ./internal/plugins/...
+```
+
+Result: all 10 plugin packages pass, including the approval store, service,
+API, DTO, and query tests, on the H6 head and re-verified after the merge with
+current main.
diff --git a/docs/public/plugins-authoring.md b/docs/public/plugins-authoring.md
index 218fdaa58e..d148df3182 100644
--- a/docs/public/plugins-authoring.md
+++ b/docs/public/plugins-authoring.md
@@ -268,6 +268,12 @@ curated React, UI, and app-store surface.
 - capabilities.auth is the highest-risk capability. A webhook response may
   assert a verified external identity with X-Kandev-Auth-Login; only assert an
   email the IdP verified as owned by the subject. See [ADR 0050](../decisions/0050-plugin-external-auth-capability.md).
+- Plugin installations also carry a host-minted opaque installation identity
+  and a generic capability-approval ledger. That ledger records approval
+  history, exact approval revisions, and revocation tombstones for the host
+  boundary, but there is no public mutation UI in this release. Future exact
+  Host adapters consume the approval receipt/query surface; they do not derive
+  authority from plugin IDs, package digests, or workspace state.
 
 An isolated web app has a separate browser boundary. Kandev loads it in a
 sandboxed iframe with an opaque origin. It cannot use the host DOM, cookies,
diff --git a/docs/specs/plugins/requirements/capability-approval.md b/docs/specs/plugins/requirements/capability-approval.md
new file mode 100644
index 0000000000..8e184c4fcf
--- /dev/null
+++ b/docs/specs/plugins/requirements/capability-approval.md
@@ -0,0 +1,193 @@
+---
+status: active
+system: plugins
+created: 2026-09-07
+owners:
+  - kandev
+---
+
+# Plugin Capability Approval and Audit Requirements
+
+## Overview
+
+Installed plugins request host capabilities. Kandev must gate every capability
+request behind an explicit, workspace-scoped human approval, record an
+append-only audit trail of approval changes, and evaluate requests against the
+intersection of what the installed manifest declares, what the human approved,
+and what human policy reserves. This document defines that substrate for
+`host.v2` capabilities; it does not define approval UI, coordinator surfaces,
+or higher-level plugin features built on it.
+
+## Terminology
+
+- **Installation:** One installed plugin release, identified by a host-minted
+  opaque `installation_id`. The identity is never derived from the plugin id,
+  package digest, workspace, or install path.
+- **Approval:** One current capability approval row per
+  `(installation_id, workspace_id)` pair, associating an exact manifest digest
+  with a canonical list of approved capability ids.
+- **Effective authority:** The capability set obtained by intersecting the
+  installed manifest declaration, the current approval, and the human deny
+  policy. A capability is allowed only when all three admit it.
+- **Human deny policy:** The immutable set of human-reserved capabilities
+  (merge, deploy, release, history rewrite, cross-workspace access, and
+  secret-scope expansion) that no approval can ever grant.
+- **Tombstone:** The uninstall record that permanently blocks approvals for an
+  `installation_id` so a reinstall mints a new identity.
+
+## Requirements
+
+### REQ-PLUGINS-CAPABILITY-APPROVAL-001: Workspace-scoped capability approvals
+
+**Intent:** Give each workspace explicit, human-controlled authority over the
+capabilities an installed plugin may exercise inside that workspace, with one
+current approval per installation and workspace.
+
+**User story:** As a workspace operator, I want to approve exactly the
+capabilities a plugin may use in my workspace, so that plugin authority is
+explicit, auditable, and never broader than what the installed manifest
+declares.
+
+#### Acceptance criteria
+
+- **AC-PLUGINS-CAPABILITY-APPROVAL-001.1:** When a plugin installation is
+  recorded, the system shall assign it a host-minted opaque `installation_id`
+  that is not derived from the plugin id, package digest, workspace, or install
+  path.
+- **AC-PLUGINS-CAPABILITY-APPROVAL-001.2:** The system shall keep at most one
+  current approval per `(installation_id, workspace_id)` pair, and a grant on an
+  existing pair shall replace the previous current approval.
+- **AC-PLUGINS-CAPABILITY-APPROVAL-001.3:** When an approval is recorded, the
+  system shall reject it unless its manifest digest matches the installed
+  manifest and every requested capability id is declared by that manifest.
+- **AC-PLUGINS-CAPABILITY-APPROVAL-001.4:** When an approval is recorded, the
+  system shall reject any capability id that is human-reserved, malformed, or
+  not an exact `host.v2` capability.
+- **AC-PLUGINS-CAPABILITY-APPROVAL-001.5:** When a revision differs from the
+  current approval revision, the system shall reject the write with a revision
+  conflict and leave the stored approval unchanged.
+- **AC-PLUGINS-CAPABILITY-APPROVAL-001.6:** When a grant reuses an audit id with
+  different inputs, the system shall reject it without changing stored state.
+
+### REQ-PLUGINS-CAPABILITY-APPROVAL-002: Append-only approval events
+
+**Intent:** Preserve a complete, ordered audit trail of every approval change
+so authority changes can be reviewed after the fact.
+
+**User story:** As an auditor, I want every grant, narrow, revoke, and
+upgrade-review decision recorded with before/after revisions and digests, so
+that I can reconstruct how plugin authority changed over time.
+
+#### Acceptance criteria
+
+- **AC-PLUGINS-CAPABILITY-APPROVAL-002.1:** When the system changes an
+  approval, it shall append an event recording the installation, workspace,
+  before and after revisions and digests, actor, reason, event type, and an
+  observed timestamp, without rewriting or removing earlier events.
+- **AC-PLUGINS-CAPABILITY-APPROVAL-002.2:** The system shall support the event
+  types `grant`, `narrow`, `revoke`, and `upgrade_review`.
+
+### REQ-PLUGINS-CAPABILITY-APPROVAL-003: Fail-closed capability authorization
+
+**Intent:** Evaluate every capability request against the manifest ∩ approval
+∩ human deny-policy intersection, denying unless all three admit the request.
+
+**User story:** As a workspace operator, I want unauthorized capability requests
+to fail closed with a stable machine-readable deny reason, so that stale,
+revoked, cross-workspace, or undeclared requests can never succeed and can be
+diagnosed reliably.
+
+#### Acceptance criteria
+
+- **AC-PLUGINS-CAPABILITY-APPROVAL-003.1:** When a capability request arrives
+  whose approval is missing, revoked, or tombstoned, the system shall deny it
+  with the corresponding stable deny reason and no side effects.
+- **AC-PLUGINS-CAPABILITY-APPROVAL-003.2:** When a capability request names a
+  revision different from the current approval revision, the system shall deny
+  it as stale.
+- **AC-PLUGINS-CAPABILITY-APPROVAL-003.3:** When a capability request comes
+  from an installation with no approval in the requested workspace, the system
+  shall deny it with the same deny reason used for missing approvals, without
+  disclosing that the installation exists in another workspace.
+- **AC-PLUGINS-CAPABILITY-APPROVAL-003.4:** When a capability id is
+  human-reserved, the system shall deny it with the human-reserved deny reason.
+- **AC-PLUGINS-CAPABILITY-APPROVAL-003.5:** When the installed manifest no
+  longer declares the requested capability, or the approval digest no longer
+  matches the installed manifest, the system shall deny the request as
+  unavailable.
+- **AC-PLUGINS-CAPABILITY-APPROVAL-003.6:** When a request is structurally
+  malformed (unbounded or NUL-bearing identifiers, invalid digests, or an
+  unsupported capability form), the system shall deny it as malformed before
+  any approval lookup.
+- **AC-PLUGINS-CAPABILITY-APPROVAL-003.7:** When a request passes every gate,
+  the system shall allow it and attach the audit identity and a receipt
+  recording the bounded decision metadata.
+
+### REQ-PLUGINS-CAPABILITY-APPROVAL-004: Uninstall tombstones and reinstall identity
+
+**Intent:** Make uninstalled plugin authority permanently inert and force
+reinstalls to start from a fresh installation identity and fresh approvals.
+
+**User story:** As an operator, I want an uninstalled plugin's approvals to be
+permanently blocked and a reinstalled copy to require new approvals, so that
+stale authority can never be silently inherited.
+
+#### Acceptance criteria
+
+- **AC-PLUGINS-CAPABILITY-APPROVAL-004.1:** When a plugin is uninstalled, the
+  system shall tombstone the installation identity and deny every later
+  capability request for it.
+- **AC-PLUGINS-CAPABILITY-APPROVAL-004.2:** When a plugin is reinstalled, the
+  system shall mint a new `installation_id` so no prior approval can attach to
+  the new installation.
+
+### REQ-PLUGINS-CAPABILITY-APPROVAL-005: Legacy declaration fence
+
+**Intent:** Keep legacy `v1` capability declarations from being granted or
+exercised through the H6 approval substrate while preserving their original
+runtime behavior.
+
+**User story:** As a maintainer, I want legacy v1 capabilities fenced out of
+the approval substrate, so that only explicit `host.v2` capabilities can be
+approved and evaluated.
+
+#### Acceptance criteria
+
+- **AC-PLUGINS-CAPABILITY-APPROVAL-005.1:** When a capability id is not an
+  exact `host.v2` capability, the system shall reject it from approval lists
+  and deny it at authorization time as unsupported.
+- **AC-PLUGINS-CAPABILITY-APPROVAL-005.2:** Legacy `v1` declarations shall
+  retain their original runtime behavior without gaining H6 approval authority.
+
+### REQ-PLUGINS-CAPABILITY-APPROVAL-006: Generic audit receipts
+
+**Intent:** Give every authorization decision a bounded, deterministic receipt
+metadata shape that a future host adapter can persist without carrying
+authority.
+
+**User story:** As a host adapter author, I want a typed, bounded receipt on
+every decision, so that audit persistence can be added without redefining the
+decision contract.
+
+#### Acceptance criteria
+
+- **AC-PLUGINS-CAPABILITY-APPROVAL-006.1:** When the system produces a
+  decision, the decision shall carry a receipt with bounded installation,
+  workspace, revision, capability, request and method digests, audit id, and
+  result values.
+- **AC-PLUGINS-CAPABILITY-APPROVAL-006.2:** The receipt digests shall be
+  deterministic canonical digests of their normalized inputs.
+- **AC-PLUGINS-CAPABILITY-APPROVAL-006.3:** When any receipt field would
+  exceed its bound, the system shall truncate or redact it so the receipt
+  remains bounded.
+
+## Exclusions
+
+- No approval or review UI (settings pages, coordinator surfaces, or
+  dashboards) is in scope for this substrate.
+- No host adapter persistence of receipts is required; the receipt shape only
+  defines the metadata contract.
+- No changes to legacy `v1` runtime behavior are made beyond fencing it from
+  approval authority.
+- No cross-workspace disclosure surface exists: foreign-workspace requests are
+  indistinguishable from missing approvals.
diff --git a/docs/specs/plugins/system-design/capability-approval.md b/docs/specs/plugins/system-design/capability-approval.md
new file mode 100644
index 0000000000..910d499b5f
--- /dev/null
+++ b/docs/specs/plugins/system-design/capability-approval.md
@@ -0,0 +1,159 @@
+---
+status: current
+system: plugins
+requirements:
+  - REQ-PLUGINS-CAPABILITY-APPROVAL-001
+  - REQ-PLUGINS-CAPABILITY-APPROVAL-002
+  - REQ-PLUGINS-CAPABILITY-APPROVAL-003
+  - REQ-PLUGINS-CAPABILITY-APPROVAL-004
+  - REQ-PLUGINS-CAPABILITY-APPROVAL-005
+  - REQ-PLUGINS-CAPABILITY-APPROVAL-006
+created: 2026-09-07
+owners:
+  - kandev
+---
+
+# Plugin Capability Approval and Audit System Design
+
+## Purpose and boundaries
+
+This design describes the generic plugin capability-approval substrate in
+`apps/backend/internal/plugins`: the host-minted installation identity, the
+workspace-scoped approval ledger, the append-only event trail, the
+fail-closed authorization decision, uninstall tombstones, the legacy `v1`
+fence, and the audit receipt primitives. Higher-level surfaces (approval UI,
+coordinator flows, host receipt persistence) consume this substrate without
+being part of it.
+
+## Requirement mapping
+
+| Requirement | Design section |
+| --- | --- |
+| `REQ-PLUGINS-CAPABILITY-APPROVAL-001` | [Identity and approval ledger](#identity-and-approval-ledger) |
+| `REQ-PLUGINS-CAPABILITY-APPROVAL-002` | [Append-only event trail](#append-only-event-trail) |
+| `REQ-PLUGINS-CAPABILITY-APPROVAL-003` | [Fail-closed authorization](#fail-closed-authorization) |
+| `REQ-PLUGINS-CAPABILITY-APPROVAL-004` | [Tombstones and reinstall identity](#tombstones-and-reinstall-identity) |
+| `REQ-PLUGINS-CAPABILITY-APPROVAL-005` | [Legacy v1 fence](#legacy-v1-fence) |
+| `REQ-PLUGINS-CAPABILITY-APPROVAL-006` | [Audit receipts](#audit-receipts) |
+
+## Identity and approval ledger
+
+`store.Record.InstallationID` (`apps/backend/internal/plugins/store/store.go`)
+is the host-minted opaque principal for an installed plugin release. It is
+minted at install time and persisted with the record; it is never derived from
+the plugin id, package digest, workspace, or install path, so a reinstall
+necessarily produces a different identity.
+
+`CapabilityApproval` (`apps/backend/internal/plugins/approval_store.go`) is the
+current approval row: `(installation_id, workspace_id)` is the ledger key, and
+at most one current row exists per pair. A grant replaces the previous
+current row for its pair. The row stores the exact `manifest_digest` the
+approval was granted against, the canonically sorted and deduplicated
+`capability_ids`, the `active`/`revoked` state, the human actor, the immutable
+human policy version, and the audit revision. `HumanPolicyVersionImmutable`
+records that all current approvals are granted under the one unversioned
+human deny policy.
+
+Approval writes are admitted only at the exact next revision. A write naming
+any other revision fails with `ErrApprovalRevisionConflict` and leaves stored
+state unchanged (`revokeIfRevision` in `approval_store.go`). Reused audit ids
+are idempotent only for byte-identical inputs; a different input on the same
+audit id fails without changing stored state.
+
+`CanonicalCapabilityList` (`apps/backend/internal/plugins/approval.go`) is the
+single canonicalizer for capability lists: trim, bounded length, no NUL,
+deduplicate, sort. It rejects human-reserved capabilities and any id that is
+not an exact `host.v2` capability. `ManifestCapabilityIDs` derives the exact
+`host.v2.read:<resource>` / `host.v2.write:<resource>` capability set from an
+installed manifest, and `ManifestCapabilityDigest` derives its canonical
+digest. `Service.validateApprovalManifest` rejects a grant whose manifest
+digest does not match the installed manifest or that names capabilities the
+manifest does not declare: the approval can never be broader than the
+manifest.
+
+Ledger state persists as `approvals.json` under the plugins directory through
+the `approvalLedger` type (load/migrate semantics in `approval_store.go`).
+
+## Append-only event trail
+
+`CapabilityApprovalEvent` records every approval change after commit:
+installation, workspace, before/after revisions and digests, actor, reason, the
+`CapabilityApprovalEventType` (`grant`, `narrow`, `revoke`,
+`upgrade_review`), and the observed timestamp. Events are appended to the
+ledger; grants, narrows, revokes, and upgrade reviews never rewrite or remove
+earlier events. The API surface (`apps/backend/internal/plugins/approval_api.go`)
+exposes list/get so future audit consumers can replay authority history.
+
+## Fail-closed authorization
+
+`Service.authorizePluginCapability` (`approval_service.go`) is the single
+decision path for a capability request. It evaluates in a fixed order and
+returns a typed `ApprovalDecision` with a stable `ApprovalDenyReason`:
+
+1. Structural validation (`malformedAuthorizationRequestReason`): bounded
+   identifiers and digests, NUL-free, and an exact capability form. A
+   malformed request denies as `malformed_request` (or
+   `unsupported_capability` for a non-`host.v2` form) before any lookup.
+2. Human-reserved capability check denies as `human_reserved`.
+3. Ledger lookup. A missing row denies as `missing_capability_approval`; an
+   unavailable ledger denies as `unavailable_capability`. A foreign workspace
+   intentionally reuses the missing-approval reason: a more specific
+   cross-workspace reason would disclose that the installation exists in
+   another workspace.
+4. Revoked state or a non-nil tombstone denies as `capability_revoked`.
+5. A requested revision different from the current row denies as
+   `stale_capability_revision`.
+6. Manifest intersection (`manifestIntersectionDenyReason`): the installed
+   manifest must still declare the capability under the digest the approval
+   was granted against, otherwise `unavailable_capability`.
+7. The capability must appear in the approved list, otherwise
+   `undeclared_capability`. Otherwise the decision is allowed and carries the
+   audit identity.
+
+Every denial is side-effect free: no Host operation runs inside the approval
+layer. The deny vocabulary is typed (`ApprovalDenyReason` constants in
+`approval.go`) so callers can match reasons machine-readably.
+
+## Tombstones and reinstall identity
+
+`Service.approvalTombstoneInstallation` writes a tombstone for an
+installation identity at uninstall time. A tombstoned identity denies all
+later approvals and requests (`ErrApprovalInstallationTombstoned`,
+`capability_revoked`), permanently. Because the reinstall mints a new
+`installation_id`, no prior approval can attach to the new installation:
+authority cannot be silently inherited across an uninstall/reinstall cycle.
+
+## Legacy v1 fence
+
+`isExactHostV2Capability` gates both grant admission and authorization. A
+capability id that is not an exact `host.v2` capability is rejected from
+approval lists (`CanonicalCapabilityList`) and denied at authorization time as
+`unsupported_capability`. Legacy `v1` manifest declarations keep their original
+runtime behavior but cannot be granted or exercised through this substrate.
+
+## Audit receipts
+
+`ApprovalReceipt` (`approval.go`) is the bounded, deterministic metadata a
+future host adapter can persist on read or write receipts without carrying
+authority: installation, workspace, revision, capability id, request and
+method digests, audit id, result, and observed time. `CanonicalApprovalDigest`
+builds stable digest identities from trimmed, NUL-joined inputs. Receipt
+fields pass through the same safe-bounds helpers as the decision inputs, so a
+hostile identifier is truncated or redacted rather than propagated: the
+receipt is always bounded and cannot be coerced into authority.
+
+## Persistence and compatibility
+
+The approval ledger file carries approvals, events, tombstones, and idempotency
+inputs with forward-compatible JSON decoding (missing maps initialize empty).
+Optional fields on `store.Record` (installation id) decode on older records
+without migration; a missing installation identity simply has no approvals.
+The substrate admits only `HumanPolicyVersionImmutable` today; the stored
+per-row policy version is the stable extension point for a future policy
+revision.
+
+## Observability
+
+Decisions are pure typed results; the audit id and receipt give future
+adapters the exact metadata to persist. Events themselves are the observable
+authority history; there is no separate metric emission in this substrate.