osgrep

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name: osgrep description: Semantic code search using natural language queries. Use when users ask "where is X implemented", "how does Y work", "find the logic for Z", or need to locate code by concept rather than exact text. Returns file paths with line numbers and code snippets. allowed-tools: "Bash(osgrep:*), Read" license: Apache-2.0

When to Use

Use this to find code by concept or behavior (e.g., "where is auth validated", "how are plugins loaded"). Note: This tool prioritizes finding the right files and locations in the code. Snippets are truncated (max 16 lines) and are often just previews.

Example:

osgrep "how are plugins loaded"
osgrep "how are plugins loaded" packages/transformers.js/src

Strategy for Different Query Types

For Architectural/System-Level Questions (auth, LSP integration, file watching)

1. Search Broadly First: Use a conceptual query to map the landscape.
   • osgrep "authentication authorization checks"
2. Survey the Results: Look for patterns across multiple files:
   • Are checks in middleware? Decorators? Multiple services?
   • Do file paths suggest different layers (gateway, handlers, utils)?
3. Read Strategically: Pick 2-4 files that represent different aspects:
   • Read the main entry point
   • Read representative middleware/util files
   • Follow imports if architecture is unclear
4. Refine with Specific Searches: If one aspect is unclear:
   • osgrep "session validation logic"
   • osgrep "API authentication middleware"

For Targeted Implementation Details (specific function, algorithm)

1. Search Specifically: Ask about the precise logic.
   • osgrep "logic for merging user and default configuration"
2. Evaluate the Semantic Match:
   • Does the snippet look relevant?
   • Crucial: If it ends in ... or cuts off mid-logic, read the file.
3. One Search, One Read: Use osgrep to pinpoint the best file, then read it fully.

Hybrid Search Strategy (Semantic + Grep)

Combining semantic search with grep is 31% more effective than either alone.

Decision Heuristic:

• osgrep: Exploration. You don't know exact names/patterns.
• rg (ripgrep): Precision. You know the symbol/pattern to find.

Two-Stage Workflow:

1. Discover with osgrep: Find the right files conceptually

   • osgrep "authentication validation logic"
   • → Returns src/auth/middleware.ts:45, src/utils/jwt.ts:12

2. Pinpoint with ripgrep: Find exact matches in those files

   • rg "verifyToken|validateJWT" src/auth/ src/utils/
   • → Returns exact line numbers with context

Example: Finding rate limiting implementation

# Step 1: Conceptual discovery
osgrep "rate limiting throttling"
# → src/middleware/rateLimit.ts:23, src/api/limiter.ts:8

# Step 2: Exact symbols/patterns
rg "RateLimiter|throttle" src/middleware/ src/api/

Why this works: Semantic search narrows to the right files. Grep pinpoints exact locations within those files. Together = faster, more accurate results.

Output Format

Returns: path/to/file:line [Tags] Code Snippet

Example:

ORCHESTRATION src/auth/handler.ts:45
Defines: handleAuth | Calls: validate, checkRole, respond | Score: .94

export async function handleAuth(req: Request) {
  const token = req.headers.get("Authorization");
  ...

Tags:

• ORCHESTRATION: Contains logic, coordinates other code. Prioritize these.
• DEFINITION: Types, interfaces, classes.

Metadata:

• Defines: What this code defines
• Calls: What this code calls (helps trace flow)
• Score: Relevance (1 = best match)

Markers:

• ...: Truncation marker. Snippet is incomplete—use Read for full context.

Other Commands

# Trace call graph (who calls X, what X calls)
osgrep trace handleAuth

# Skeleton of a huge file (find which ranges to read)
osgrep skeleton src/giant-2000-line-file.ts

# Just file paths when you only need locations
osgrep "authentication" --compact

Tips

• More Words = Better: "auth" is vague. "where does the server validate JWT tokens" is specific.
• Prioritize ORCH Results: ORCHESTRATION results contain the logic—start there.
• Trust the Semantics: You don't need exact names. osgrep "how does the server start" works better than guessing osgrep "server.init".
• Watch for Distributed Patterns: If results span 5+ files in different directories, the feature is likely architectural—survey before diving deep.
• Scope When Possible: Use path constraints to focus: osgrep "auth" src/server/
• Use Line Ranges: Don't read entire files. Use the line ranges osgrep gives you.
• Rephrase If Needed: If results seem off, rephrase your query like you'd ask a teammate.

If Index is Building

If you see "Indexing", "Building", or "Syncing": STOP. Alert the user that the index is building. Ask if they want to wait or proceed with partial results.