fix(modelregistry): address audit findings

Replace try-lock/sleep scheme with blocking locks, add ErrModelNotFound/
ErrModelExists/ErrInvalidModel sentinels, make RegisterModelWithRules
atomic, snapshot in IterateModels, guard defaultRegistry access, cap the
pointer-unwrap depth, and recover panics in callbacks and reflection.
Security hooks now allow-by-default only on ErrModelNotFound. Add tests.

audit/pkg/_CROSS-CUTTING.audit.md

@@ -23,7 +23,7 @@ per-package audits reference this file rather than restating them.
 | X5 | **Medium** | locking | Unsynchronized package-level mutable globals are the dominant concurrency pattern |
 | X6 | **Medium** | security | Insecure-by-default transport across the board: `sslmode: disable`, `WithInsecure()`, no TLS in cache configs |
 | X7 | **Medium** | panic handling | Panic handling is inconsistent and, where it exists, tends to fail open |
-| X8 | **Medium** | security | `logger.Warn`/`Error` forward every message to Sentry unscrubbed, and error strings routinely embed attacker data |
+| X8 | **Medium** | security | `logger.Warn`/`Error` forward every message to Sentry unscrubbed, and error strings routinely embed attacker data *(partly fixed 2026-09-30: redaction and rate limiting added in `pkg/logger`; call sites still embed attacker data)* |
 | X9 | **Low** | testing | Test coverage is extremely uneven: 5 packages have no test file at all |
 
 The table is ordered by severity; the sections below are in ID order, since other
@@ -67,7 +67,7 @@ every one of them on the first run:
 | `pkg/cache` | `defaultCache` read/written by concurrent request handlers | `cache.audit.md` finding 3 |
 | `pkg/config` | `*viper.Viper` has no internal lock; `configInstance` singleton | `config.audit.md` findings 1, 2 |
 | `pkg/logger` | `Logger`, `errorTracker` globals | `logger.audit.md` finding 1 |
-| `pkg/modelregistry` | `defaultRegistry` read by 6 functions without the lock | `modelregistry.audit.md` findings 2, 8 |
+| `pkg/modelregistry` | `defaultRegistry` read by 6 functions without the lock | `modelregistry.audit.md` findings 2, 8 *(fixed 2026-09-30)* |
 | `pkg/tracing` | `tracer` global | `tracing.audit.md` finding 5 |
 | `pkg/errortracking` | `sentry.Init` mutates process globals | `errortracking.audit.md` finding 2 |
 
@@ -160,7 +160,7 @@ The test bodies that exist but are never executed by CI:
 | `metrics` | 1 | 64 | no |
 | `resolvemcp` | 1 | 34 | no |
 | `logger` | 0 | 0 | — |
-| `modelregistry` | 0 | 0 | — |
+| `modelregistry` | 1 | ~150 | yes (`-race`) *(added 2026-09-30)* |
 | `testmodels` | 0 | 0 | — |
 | `tracing` | 0 | 0 | — |
 
@@ -308,7 +308,7 @@ package-level variables, and most guard it with nothing:
 | `pkg/cache` | `defaultCache *Cache` (`cache.go:10`) | **no** |
 | `pkg/config` | `configInstance *Manager` (`manager.go:15`) | **no** |
 | `pkg/tracing` | `tracer` (`tracing.go:19`) | **no** |
-| `pkg/modelregistry` | `defaultRegistry` | partially — `TryLock` with a retry/`time.Sleep` loop, and 6 functions read it unlocked |
+| `pkg/modelregistry` | `defaultRegistry` | **yes** *(fixed 2026-09-30)* — guarded by `registriesMutex`; all access via `GetDefaultRegistry()` |
 | `pkg/metrics` | `globalProvider` (`interfaces.go:50-51`) | **yes** — `globalProviderMu sync.RWMutex` |
 
 `pkg/metrics` is the model the others should follow:
@@ -524,7 +524,7 @@ codebase invites it by logging the header contents as the diagnostic.
 only **Critical** authorization finding: `GetModel` returns a "registry locked"
 error under write-lock contention, which `security/hooks.go:274-294` converts
 into `return nil // model not registered, allow by default`
-(`modelregistry.audit.md` finding 1). A twenty-line test that registers a model
+(`modelregistry.audit.md` finding 1; *fixed 2026-09-30, regression tests added*). A twenty-line test that registers a model
 from one goroutine while reading it from another would demonstrate the fail-open
 immediately. The package guards a security boundary and has never been tested.
 

audit/pkg/logger.audit.md

@@ -32,6 +32,22 @@ There are **zero tests** in this package.
 | 11 | Low | Slowness | `os.Getpid()` called on every log line |
 | 12 | Low | Observability | `UpdateLogger` build failure degrades silently to stdlib `log` |
 
+## Resolution status (2026-09-30)
+
+- **#1** — Fixed (earlier race work): `stateMu` RWMutex with `getLogger`/`swapLogger`/`getErrorTracker`; the exported `Logger` var is kept for compatibility
+- **#2** — Fixed: messages are scrubbed before `CaptureMessage` (URL credentials, `password=`/`token=`/`secret=`/`api_key=` values, `Bearer`/`Basic` tokens). Local logs are unchanged. Sentry `BeforeSend` and structured-field allowlisting are not done
+- **#3** — Partly fixed: global token bucket (burst 50, 20/s) plus per-severity/template dedup (1s, 1024 keys). Panics are not limited. The `error_tracking.sample_rate` default (Sentry maps 0 to 1.0) is still unset in `config/manager.go`
+- **#4** — Partly fixed: `CatchPanicRethrow` added. `pkg/security/provider.go:302` and `:443` still use the swallowing `CatchPanic`; left for the security audit pass
+- **#5** — Fixed: stack captured with `runtime.Stack` into a 16 KiB buffer. Per-fingerprint panic rate limiting not done
+- **#6** — Fixed: `Info`/`Debug` format first and fall back with `log.Printf("%s", ...)`. `gosec` was enabled separately
+- **#7** — Fixed: CR/LF and other control characters are escaped on the stdlib fallback path
+- **#8** — Fixed: `Info`/`Debug` strip `context.Context` args
+- **#9** — Fixed: the replaced logger is synced on `UpdateLogger`
+- **#10** — Fixed: `logger.Sync()` added. Not yet called from the server shutdown path
+- **#11** — Fixed: PID cached in a package var
+- **#12** — Partly fixed: `UpdateLoggerE` returns the build error and a failed build keeps the previous logger. `Init` still returns nothing
+- Tests: `pkg/logger/logger_test.go` (run with `-race`).
+
 ---
 
 ## Findings

audit/pkg/modelregistry.audit.md

@@ -38,6 +38,34 @@ There are **no tests** in this package and no `-race` coverage of it anywhere.
 | 12 | Low | Panic | Package has no `recover` anywhere, and calls a caller-supplied callback under a lock (see 6) |
 | 13 | Low | Security | `DefaultModelRules()` grants `CanRead/Update/Create/Delete: true` — registration without explicit rules is fully mutable |
 
+## Resolution (2026-09-30)
+
+Fixed in `pkg/modelregistry/model_registry.go`, `pkg/security/hooks.go`, and new
+`pkg/modelregistry/model_registry_test.go` (passes under `-race`).
+
+| # | Status | What changed |
+|---|--------|--------------|
+| 1 | **Fixed** | Added sentinels `ErrModelNotFound`, `ErrModelExists`, `ErrInvalidModel` (wrapped, `errors.Is`-friendly). `checkModelUpdateAllowed`/`checkModelDeleteAllowed` now allow-by-default **only** on `ErrModelNotFound`; any other error denies. Lookups can no longer return a "locked" error at all. |
+| 2 | **Fixed** | `GetDefaultRegistry` uses a plain `RLock`; no unsynchronised fallback. |
+| 3 | **Fixed** | `SetDefaultRegistry` uses a blocking `Lock` (cannot silently no-op); a nil registry is ignored. |
+| 4 | **Fixed** | `RegisterModelWithRules` and `RegisterModel` share `registerLocked`, which writes model + rules under one lock acquisition. |
+| 5 | **Fixed** | `GetAllModels`/`GetModels` use blocking locks and can no longer return empty/partial results due to contention. Signatures unchanged (`GetAllModels` is used through interfaces by resolvespec/restheadspec/openapi). |
+| 6 | **Fixed** | `IterateModels` iterates a snapshot; the callback runs with no lock held (regression test re-enters the registry). |
+| 7 | **Fixed** | Try-lock/sleep helpers and `lockRetry*` constants removed. |
+| 8 | **Fixed** | All package-level functions go through `GetDefaultRegistry()` / `registriesSnapshot()`; `defaultRegistry` is only touched under `registriesMutex`. |
+| 9 | **Fixed** | One discipline: blocking locks, snapshot-and-release, documented lock order (`registriesMutex` before a registry's mutex). |
+| 10 | **Fixed** | Reflection/validation (`validateModel`) runs before the write lock is taken. |
+| 11 | **Fixed** | Unwrap loop capped at 16 levels; `type T *T` now returns `ErrInvalidModel` (tested). |
+| 12 | **Fixed** | Sentinel errors added. `IterateModels` recovers a callback panic per model, logs it via `logger.HandlePanic` with the model name, and continues; `validateModel` recovers reflection panics and returns `ErrInvalidModel` so registration fails closed. No lock is held during either, so the registry cannot be wedged. |
+| 13 | **Accepted (decision)** | Allow-by-default retained deliberately: `DefaultModelRules()` still grants read/update/create/delete. Callers wanting restrictions must use `RegisterModelWithRules`/`SetModelRules`. |
+
+Tests added: sentinel errors, recursive pointer type, pointer normalisation, atomic
+`RegisterModelWithRules` (concurrent reader never sees permissive rules), re-entrant `IterateModels`,
+cross-registry `GetModelRulesByName`, and a concurrent `-race` stress test.
+
+Not changed: the `pkg/security` middleware-wiring question (context fast-path) remains tracked in
+`audit/pkg/security.audit.md`.
+
 ---
 
 ## Findings

audit/pkg/security.audit.md

@@ -1787,7 +1787,7 @@ func checkModelUpdateAllowed(secCtx SecurityContext) error {
 `checkModelDeleteAllowed` is identical (`:298-318`, fail-open at `:311`). A model
 served by the spec handler but absent from the registry — or present under a name
 the two lookups do not produce — is fully writable. This is the consuming side of
-`modelregistry.audit.md` finding 1: the registry's lookup failure and this
+`modelregistry.audit.md` finding 1 (*registry side fixed 2026-09-30: `checkModelUpdateAllowed`/`checkModelDeleteAllowed` now allow only on `ErrModelNotFound`*): the registry's lookup failure and this
 `return nil` combine into "unknown model ⇒ permitted".
 
 **Any authenticated user may perform any operation.** `CheckModelAuthAllowed` is

pkg/modelregistry/model_registry.go

@@ -1,10 +1,12 @@
 package modelregistry
 
 import (
+	"errors"
 	"fmt"
 	"reflect"
 	"sync"
-	"time"
+
+	"github.com/bitechdev/ResolveSpec/pkg/logger"
 )
 
 // ModelRules defines the permissions and security settings for a model
@@ -52,6 +54,21 @@ var defaultRegistry = &DefaultModelRegistry{
 var registries = []*DefaultModelRegistry{defaultRegistry}
 var registriesMutex sync.RWMutex
 
+// Sentinel errors so callers (notably the security layer) can distinguish
+// "not registered" from every other failure with errors.Is.
+var (
+	ErrModelNotFound = errors.New("model not found")
+	ErrModelExists   = errors.New("model already registered")
+	ErrInvalidModel  = errors.New("invalid model")
+)
+
+// maxUnwrapDepth bounds pointer/slice/array unwrapping so a recursive type
+// (type T *T) cannot spin forever.
+const maxUnwrapDepth = 16
+
+// Lock ordering: registriesMutex is always taken before a registry's mutex,
+// never the reverse. No caller-supplied code ever runs while a lock is held.
+
 // NewModelRegistry creates a new model registry
 func NewModelRegistry() *DefaultModelRegistry {
 	return &DefaultModelRegistry{
@@ -60,44 +77,19 @@ func NewModelRegistry() *DefaultModelRegistry {
 	}
 }
 
-// lockRetryAttempts/lockRetryDelay bound how long the try-lock helpers below
-// will spin before giving up, so a contended registriesMutex can never hang
-// a caller of GetDefaultRegistry/SetDefaultRegistry.
-const (
-	lockRetryAttempts = 20
-	lockRetryDelay    = 1 * time.Millisecond
-)
-
-// GetDefaultRegistry returns the current default registry. It uses a
-// bounded TryRLock instead of a blocking RLock so it can never hang;
-// if the lock can't be acquired in time it falls back to the last known
-// value without synchronization.
+// GetDefaultRegistry returns the current default registry.
 func GetDefaultRegistry() *DefaultModelRegistry {
-	for i := 0; i < lockRetryAttempts; i++ {
-		if registriesMutex.TryRLock() {
-			defer registriesMutex.RUnlock()
-			return defaultRegistry
-		}
-		time.Sleep(lockRetryDelay)
-	}
+	registriesMutex.RLock()
+	defer registriesMutex.RUnlock()
 	return defaultRegistry
 }
 
-// SetDefaultRegistry replaces the default registry. It uses a bounded
-// TryLock instead of a blocking Lock so it can never hang; if the lock
-// can't be acquired in time the call is a no-op.
+// SetDefaultRegistry replaces the default registry. A nil registry is ignored.
 func SetDefaultRegistry(registry *DefaultModelRegistry) {
-	acquired := false
-	for i := 0; i < lockRetryAttempts; i++ {
-		if registriesMutex.TryLock() {
-			acquired = true
-			break
-		}
-		time.Sleep(lockRetryDelay)
-	}
-	if !acquired {
+	if registry == nil {
 		return
 	}
+	registriesMutex.Lock()
 	defer registriesMutex.Unlock()
 
 	foundAt := -1
@@ -123,99 +115,96 @@ func AddRegistry(registry *DefaultModelRegistry) {
 	registries = append(registries, registry)
 }
 
-// tryLock attempts to acquire the registry's write lock, retrying briefly.
-// Returns false if it could not be acquired within the bound.
-func (r *DefaultModelRegistry) tryLock() bool {
-	for i := 0; i < lockRetryAttempts; i++ {
-		if r.mutex.TryLock() {
-			return true
-		}
-		time.Sleep(lockRetryDelay)
-	}
-	return false
+// registriesSnapshot returns a copy of the registry list so callers can
+// iterate without holding registriesMutex.
+func registriesSnapshot() []*DefaultModelRegistry {
+	registriesMutex.RLock()
+	defer registriesMutex.RUnlock()
+	return append([]*DefaultModelRegistry(nil), registries...)
 }
 
-// tryRLock attempts to acquire the registry's read lock, retrying briefly.
-// Returns false if it could not be acquired within the bound.
-func (r *DefaultModelRegistry) tryRLock() bool {
-	for i := 0; i < lockRetryAttempts; i++ {
-		if r.mutex.TryRLock() {
-			return true
+// validateModel checks the model is a struct (or pointer/slice/array of one)
+// and returns the normalised non-pointer struct value. It takes no locks.
+func validateModel(model interface{}) (result interface{}, err error) {
+	// Reflection on a pathological type must fail the registration, not crash the process.
+	defer func() {
+		if r := recover(); r != nil {
+			result = nil
+			err = fmt.Errorf("%w: %v", ErrInvalidModel, logger.HandlePanic("modelregistry.validateModel", r))
 		}
-		time.Sleep(lockRetryDelay)
-	}
-	return false
-}
+	}()
 
-func (r *DefaultModelRegistry) RegisterModel(name string, model interface{}) error {
-	if !r.tryLock() {
-		return fmt.Errorf("failed to register model %s: registry locked", name)
-	}
-	defer r.mutex.Unlock()
-
-	if _, exists := r.models[name]; exists {
-		return fmt.Errorf("model %s already registered", name)
-	}
-
-	// Validate that model is a non-pointer struct
 	modelType := reflect.TypeOf(model)
 	if modelType == nil {
-		return fmt.Errorf("model cannot be nil")
+		return nil, fmt.Errorf("%w: model cannot be nil", ErrInvalidModel)
 	}
 
 	originalType := modelType
 
 	// Unwrap pointers, slices, and arrays to check the underlying type
-	for modelType.Kind() == reflect.Pointer || modelType.Kind() == reflect.Slice || modelType.Kind() == reflect.Array {
+	for depth := 0; modelType.Kind() == reflect.Pointer || modelType.Kind() == reflect.Slice || modelType.Kind() == reflect.Array; depth++ {
+		if depth >= maxUnwrapDepth {
+			return nil, fmt.Errorf("%w: type %s nests deeper than %d levels", ErrInvalidModel, originalType.String(), maxUnwrapDepth)
+		}
 		modelType = modelType.Elem()
 	}
 
-	// Validate that the underlying type is a struct
 	if modelType.Kind() != reflect.Struct {
-		return fmt.Errorf("model must be a struct or pointer to struct, got %s", originalType.String())
+		return nil, fmt.Errorf("%w: model must be a struct or pointer to struct, got %s", ErrInvalidModel, originalType.String())
 	}
 
 	// If a pointer/slice/array was passed, unwrap to the base struct
 	if originalType != modelType {
-		// Create a zero value of the struct type
 		model = reflect.New(modelType).Elem().Interface()
 	}
 
-	// Additional check: ensure model is not a pointer
-	finalType := reflect.TypeOf(model)
-	if finalType.Kind() == reflect.Pointer {
-		return fmt.Errorf("model must be a non-pointer struct, got pointer to %s. Use MyModel{} instead of &MyModel{}", finalType.Elem().Name())
+	if finalType := reflect.TypeOf(model); finalType.Kind() == reflect.Pointer {
+		return nil, fmt.Errorf("%w: model must be a non-pointer struct, got pointer to %s. Use MyModel{} instead of &MyModel{}", ErrInvalidModel, finalType.Elem().Name())
+	}
+	return model, nil
+}
+
+// registerLocked validates the model outside the lock, then writes the model
+// and its rules under a single lock acquisition so no reader can observe the
+// model without its final rules.
+func (r *DefaultModelRegistry) registerLocked(name string, model interface{}, rules ModelRules) error {
+	model, err := validateModel(model)
+	if err != nil {
+		return err
 	}
 
-	r.models[name] = model
-	// Initialize with default rules if not already set
-	if _, exists := r.rules[name]; !exists {
-		r.rules[name] = DefaultModelRules()
+	r.mutex.Lock()
+	defer r.mutex.Unlock()
+
+	if _, exists := r.models[name]; exists {
+		return fmt.Errorf("%w: %s", ErrModelExists, name)
 	}
+	r.models[name] = model
+	r.rules[name] = rules
 	return nil
 }
 
+func (r *DefaultModelRegistry) RegisterModel(name string, model interface{}) error {
+	return r.registerLocked(name, model, DefaultModelRules())
+}
+
 func (r *DefaultModelRegistry) GetModel(name string) (interface{}, error) {
-	if !r.tryRLock() {
-		return nil, fmt.Errorf("failed to get model %s: registry locked", name)
-	}
+	r.mutex.RLock()
 	defer r.mutex.RUnlock()
 
 	model, exists := r.models[name]
 	if !exists {
-		return nil, fmt.Errorf("model %s not found", name)
+		return nil, fmt.Errorf("%w: %s", ErrModelNotFound, name)
 	}
 
 	return model, nil
 }
 
 func (r *DefaultModelRegistry) GetAllModels() map[string]interface{} {
-	if !r.tryRLock() {
-		return make(map[string]interface{})
-	}
+	r.mutex.RLock()
 	defer r.mutex.RUnlock()
 
-	result := make(map[string]interface{})
+	result := make(map[string]interface{}, len(r.models))
 	for k, v := range r.models {
 		result[k] = v
 	}
@@ -225,9 +214,13 @@ func (r *DefaultModelRegistry) GetAllModels() map[string]interface{} {
 func (r *DefaultModelRegistry) GetModelByEntity(schema, entity string) (interface{}, error) {
 	// Try full name first
 	fullName := fmt.Sprintf("%s.%s", schema, entity)
-	if model, err := r.GetModel(fullName); err == nil {
+	model, err := r.GetModel(fullName)
+	if err == nil {
 		return model, nil
 	}
+	if !errors.Is(err, ErrModelNotFound) {
+		return nil, err
+	}
 
 	// Fallback to entity name only
 	return r.GetModel(entity)
@@ -238,9 +231,8 @@ func (r *DefaultModelRegistry) SetModelRules(name string, rules ModelRules) erro
 	r.mutex.Lock()
 	defer r.mutex.Unlock()
 
-	// Check if model exists
 	if _, exists := r.models[name]; !exists {
-		return fmt.Errorf("model %s not found", name)
+		return fmt.Errorf("%w: %s", ErrModelNotFound, name)
 	}
 
 	r.rules[name] = rules
@@ -253,12 +245,10 @@ func (r *DefaultModelRegistry) GetModelRules(name string) (ModelRules, error) {
 	r.mutex.RLock()
 	defer r.mutex.RUnlock()
 
-	// Check if model exists
 	if _, exists := r.models[name]; !exists {
-		return ModelRules{}, fmt.Errorf("model %s not found", name)
+		return ModelRules{}, fmt.Errorf("%w: %s", ErrModelNotFound, name)
 	}
 
-	// Return rules if set, otherwise return default rules
 	if rules, exists := r.rules[name]; exists {
 		return rules, nil
 	}
@@ -266,84 +256,62 @@ func (r *DefaultModelRegistry) GetModelRules(name string) (ModelRules, error) {
 	return DefaultModelRules(), nil
 }
 
-// RegisterModelWithRules registers a model with specific rules
+// RegisterModelWithRules registers a model with specific rules atomically
 func (r *DefaultModelRegistry) RegisterModelWithRules(name string, model interface{}, rules ModelRules) error {
-	// First register the model
-	if err := r.RegisterModel(name, model); err != nil {
-		return err
-	}
-
-	// Then set the rules (we need to lock again for rules)
-	r.mutex.Lock()
-	defer r.mutex.Unlock()
-	r.rules[name] = rules
-
-	return nil
+	return r.registerLocked(name, model, rules)
 }
 
 // Global convenience functions using the default registry
 
 // RegisterModel registers a model with the default global registry
 func RegisterModel(model interface{}, name string) error {
-	return defaultRegistry.RegisterModel(name, model)
+	return GetDefaultRegistry().RegisterModel(name, model)
 }
 
 // GetModelByName retrieves a model by searching through all registries in order
 // Returns the first match found
 func GetModelByName(name string) (interface{}, error) {
-	registriesMutex.RLock()
-	defer registriesMutex.RUnlock()
-
-	for _, registry := range registries {
+	for _, registry := range registriesSnapshot() {
 		if model, err := registry.GetModel(name); err == nil {
 			return model, nil
 		}
 	}
 
-	return nil, fmt.Errorf("model %s not found in any registry", name)
+	return nil, fmt.Errorf("%w: %s (in any registry)", ErrModelNotFound, name)
 }
 
-// IterateModels iterates over all models in the default global registry
+// IterateModels iterates over all models in the default global registry.
+// It iterates over a snapshot, so fn may safely call back into the registry.
+// A panic in fn is recovered and logged with the model name, and iteration
+// continues with the remaining models.
 func IterateModels(fn func(name string, model interface{})) {
-	defaultRegistry.mutex.RLock()
-	defer defaultRegistry.mutex.RUnlock()
-
-	for name, model := range defaultRegistry.models {
-		fn(name, model)
+	for name, model := range GetDefaultRegistry().GetAllModels() {
+		callIsolated(name, model, fn)
 	}
 }
 
-// GetModels returns a list of all models from all registries
-// Models are collected in registry order, with duplicates included
-func GetModels() []interface{} {
-	acquired := false
-	for i := 0; i < lockRetryAttempts; i++ {
-		if registriesMutex.TryRLock() {
-			acquired = true
-			break
+func callIsolated(name string, model interface{}, fn func(name string, model interface{})) {
+	defer func() {
+		if r := recover(); r != nil {
+			_ = logger.HandlePanic("modelregistry.IterateModels", r, "model", name)
 		}
-		time.Sleep(lockRetryDelay)
-	}
-	if !acquired {
-		return nil
-	}
-	defer registriesMutex.RUnlock()
+	}()
+	fn(name, model)
+}
 
+// GetModels returns a list of all models from all registries.
+// Only the first occurrence of each model name is included.
+func GetModels() []interface{} {
 	var models []interface{}
 	seen := make(map[string]bool)
 
-	for _, registry := range registries {
-		if !registry.tryRLock() {
-			continue
-		}
-		for name, model := range registry.models {
-			// Only add the first occurrence of each model name
+	for _, registry := range registriesSnapshot() {
+		for name, model := range registry.GetAllModels() {
 			if !seen[name] {
 				models = append(models, model)
 				seen[name] = true
 			}
 		}
-		registry.mutex.RUnlock()
 	}
 
 	return models
@@ -351,31 +319,31 @@ func GetModels() []interface{} {
 
 // SetModelRules sets the rules for a specific model in the default registry
 func SetModelRules(name string, rules ModelRules) error {
-	return defaultRegistry.SetModelRules(name, rules)
+	return GetDefaultRegistry().SetModelRules(name, rules)
 }
 
 // GetModelRules retrieves the rules for a specific model from the default registry
 func GetModelRules(name string) (ModelRules, error) {
-	return defaultRegistry.GetModelRules(name)
+	return GetDefaultRegistry().GetModelRules(name)
 }
 
 // GetModelRulesByName retrieves the rules for a model by searching through all registries in order
-// Returns the first match found
+// Returns the first match found. The error wraps ErrModelNotFound when no registry has the model.
 func GetModelRulesByName(name string) (ModelRules, error) {
-	registriesMutex.RLock()
-	defer registriesMutex.RUnlock()
-
-	for _, registry := range registries {
-		if _, err := registry.GetModel(name); err == nil {
-			// Model found in this registry, get its rules
-			return registry.GetModelRules(name)
+	for _, registry := range registriesSnapshot() {
+		rules, err := registry.GetModelRules(name)
+		if err == nil {
+			return rules, nil
+		}
+		if !errors.Is(err, ErrModelNotFound) {
+			return ModelRules{}, err
 		}
 	}
 
-	return ModelRules{}, fmt.Errorf("model %s not found in any registry", name)
+	return ModelRules{}, fmt.Errorf("%w: %s (in any registry)", ErrModelNotFound, name)
 }
 
 // RegisterModelWithRules registers a model with specific rules in the default registry
 func RegisterModelWithRules(model interface{}, name string, rules ModelRules) error {
-	return defaultRegistry.RegisterModelWithRules(name, model, rules)
+	return GetDefaultRegistry().RegisterModelWithRules(name, model, rules)
 }

pkg/modelregistry/model_registry_test.go

@@ -0,0 +1,161 @@
+package modelregistry
+
+import (
+	"errors"
+	"sync"
+	"testing"
+)
+
+type testModel struct{ ID int }
+
+type recursivePtr *recursivePtr
+
+func TestSentinelErrors(t *testing.T) {
+	r := NewModelRegistry()
+	if _, err := r.GetModel("nope"); !errors.Is(err, ErrModelNotFound) {
+		t.Fatalf("GetModel: want ErrModelNotFound, got %v", err)
+	}
+	if _, err := r.GetModelRules("nope"); !errors.Is(err, ErrModelNotFound) {
+		t.Fatalf("GetModelRules: want ErrModelNotFound, got %v", err)
+	}
+	if err := r.SetModelRules("nope", ModelRules{}); !errors.Is(err, ErrModelNotFound) {
+		t.Fatalf("SetModelRules: want ErrModelNotFound, got %v", err)
+	}
+	if err := r.RegisterModel("a", testModel{}); err != nil {
+		t.Fatal(err)
+	}
+	if err := r.RegisterModel("a", testModel{}); !errors.Is(err, ErrModelExists) {
+		t.Fatalf("want ErrModelExists, got %v", err)
+	}
+	if err := r.RegisterModel("b", nil); !errors.Is(err, ErrInvalidModel) {
+		t.Fatalf("want ErrInvalidModel, got %v", err)
+	}
+	if err := r.RegisterModel("c", 42); !errors.Is(err, ErrInvalidModel) {
+		t.Fatalf("want ErrInvalidModel, got %v", err)
+	}
+}
+
+func TestRecursivePointerTypeRejected(t *testing.T) {
+	var x recursivePtr
+	if err := NewModelRegistry().RegisterModel("r", x); !errors.Is(err, ErrInvalidModel) {
+		t.Fatalf("want ErrInvalidModel, got %v", err)
+	}
+}
+
+func TestPointerNormalised(t *testing.T) {
+	r := NewModelRegistry()
+	if err := r.RegisterModel("p", &testModel{}); err != nil {
+		t.Fatal(err)
+	}
+	m, _ := r.GetModel("p")
+	if _, ok := m.(testModel); !ok {
+		t.Fatalf("want testModel value, got %T", m)
+	}
+}
+
+// Rules must never be observable as permissive for a restrictively registered model.
+func TestRegisterModelWithRulesAtomic(t *testing.T) {
+	for i := 0; i < 200; i++ {
+		r := NewModelRegistry()
+		var wg sync.WaitGroup
+		stop := make(chan struct{})
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			for {
+				select {
+				case <-stop:
+					return
+				default:
+				}
+				if rules, err := r.GetModelRules("m"); err == nil && rules.CanDelete {
+					t.Error("observed permissive rules for restrictive model")
+					return
+				}
+			}
+		}()
+		if err := r.RegisterModelWithRules("m", testModel{}, ModelRules{CanRead: true}); err != nil {
+			t.Fatal(err)
+		}
+		close(stop)
+		wg.Wait()
+	}
+}
+
+func TestIterateModelsCallbackMayReenter(t *testing.T) {
+	prev := GetDefaultRegistry()
+	reg := NewModelRegistry()
+	SetDefaultRegistry(reg)
+	defer SetDefaultRegistry(prev)
+
+	if err := RegisterModel(testModel{}, "iter.a"); err != nil {
+		t.Fatal(err)
+	}
+	done := make(chan struct{})
+	go func() {
+		defer close(done)
+		IterateModels(func(name string, _ interface{}) {
+			_ = RegisterModel(testModel{}, name+".copy") // would deadlock if lock held
+		})
+	}()
+	<-done
+	if _, err := reg.GetModel("iter.a.copy"); err != nil {
+		t.Fatal(err)
+	}
+}
+
+func TestGetModelRulesByNameAcrossRegistries(t *testing.T) {
+	extra := NewModelRegistry()
+	if err := extra.RegisterModelWithRules("x.only", testModel{}, ModelRules{CanRead: true}); err != nil {
+		t.Fatal(err)
+	}
+	AddRegistry(extra)
+	rules, err := GetModelRulesByName("x.only")
+	if err != nil || rules.CanDelete {
+		t.Fatalf("rules=%+v err=%v", rules, err)
+	}
+	if _, err := GetModelRulesByName("x.missing"); !errors.Is(err, ErrModelNotFound) {
+		t.Fatalf("want ErrModelNotFound, got %v", err)
+	}
+}
+
+func TestConcurrentAccessRace(t *testing.T) {
+	r := NewModelRegistry()
+	_ = r.RegisterModel("seed", testModel{})
+	var wg sync.WaitGroup
+	for i := 0; i < 16; i++ {
+		wg.Add(1)
+		go func(i int) {
+			defer wg.Done()
+			for j := 0; j < 100; j++ {
+				_ = r.SetModelRules("seed", ModelRules{CanRead: j%2 == 0})
+				_, _ = r.GetModelRules("seed")
+				_ = r.GetAllModels()
+				_ = GetDefaultRegistry()
+				_ = GetModels()
+			}
+		}(i)
+	}
+	wg.Wait()
+}
+
+func TestIterateModelsRecoversCallbackPanic(t *testing.T) {
+	prev := GetDefaultRegistry()
+	SetDefaultRegistry(NewModelRegistry())
+	defer SetDefaultRegistry(prev)
+
+	_ = RegisterModel(testModel{}, "p.a")
+	_ = RegisterModel(testModel{}, "p.b")
+	calls := 0
+	IterateModels(func(string, interface{}) {
+		calls++
+		panic("boom")
+	})
+	if calls != 2 {
+		t.Fatalf("want both models visited, got %d", calls)
+	}
+	// Registry must still be usable (no lock left held).
+	if err := RegisterModel(testModel{}, "p.c"); err != nil {
+		t.Fatal(err)
+	}
+}

pkg/security/hooks.go

@@ -2,6 +2,7 @@ package security
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"reflect"
 
@@ -284,7 +285,10 @@ func checkModelUpdateAllowed(secCtx SecurityContext) error {
 			rules, err = modelregistry.GetModelRulesByName(entity)
 		}
 		if err != nil {
-			return nil // model not registered, allow by default
+			if errors.Is(err, modelregistry.ErrModelNotFound) {
+				return nil // model not registered, allow by default
+			}
+			return err
 		}
 	}
 	if !rules.CanUpdate {
@@ -308,7 +312,10 @@ func checkModelDeleteAllowed(secCtx SecurityContext) error {
 			rules, err = modelregistry.GetModelRulesByName(entity)
 		}
 		if err != nil {
-			return nil // model not registered, allow by default
+			if errors.Is(err, modelregistry.ErrModelNotFound) {
+				return nil // model not registered, allow by default
+			}
+			return err
 		}
 	}
 	if !rules.CanDelete {