Index and query a codebase as a structural graph — build the code graph, trace blast radius of a change, find callers/callees/inheritors, semantic code search by meaning, assemble PR review context, and detect what changed since last index. Use when the user asks how code connects, what breaks if X changes, what calls a function, what a class inherits from, how to navigate an unfamiliar codebase, or to understand risk before editing.
Index and query a codebase as a structural graph — build the code graph, trace blast radius of a change, find callers/callees/inheritors, semantic code search by meaning, assemble PR review context, and detect what changed since last index. Use when the user asks how code connects, what breaks if X changes, what calls a function, what a class inherits from, how to navigate an unfamiliar codebase, or to understand risk before editing.
when_to_use
- what calls X
- what breaks if I change Y
- what does Z inherit from
- find code that handles authentication
- impact analysis before editing
- code navigation in unfamiliar repos
- blast radius before a PR
- pre-commit change detection
Index any repo as a code knowledge graph and answer structural questions about it: callers, callees, impact radius, semantic search, and review context. Requires the code MCP profile (set SLM_MCP_PROFILE=code in your plugin .mcp.json).
Prerequisite rule: every tool except build_code_graph self-guards — if the graph is not built it returns {"success": false, "error": "Code graph not built. Run build_code_graph first."}. Always index first.
Parses all supported source files, extracts functions/classes/imports, builds the call graph, detects execution flows, and identifies code communities. Replaces any previous index for the same repo.
repo_path — absolute path to the repository root. Must exist.
languages — comma-separated language filter, e.g. "python,typescript". Empty string = index all supported languages.
exclude_patterns — comma-separated glob patterns to exclude, e.g. "**/node_modules/**,**/.venv/**". Empty = no exclusions.
When to (re)build:
Before using any other graph tool for the first time on a repo.
After significant changes to the codebase (pull, merge, large refactor).
When detect_changes or query_graph returns stale/unexpected results.
Rebuild is safe and idempotent — it replaces the previous index atomically per file.
# Index the full repo
build_code_graph(repo_path="/abs/path/to/myrepo")
# Index only Python, skip tests and generated code
build_code_graph(
repo_path="/abs/path/to/myrepo",
languages="python",
exclude_patterns="**/tests/**,**/generated/**"
)
Query the graph for structural relationships. pattern is required and must be one of the eight valid values below. target is a qualified name, partial name, or node ID — matched with exact-then-LIKE fallback.
Valid patterns:
pattern
returns
callers_of
functions/methods that call target
callees_of
functions/methods that target calls
imports_of
modules/symbols that target imports
imported_by
who imports target
tests_for
test nodes associated with target
inherits_from
base classes of target
inherited_by
subclasses of target
contains
symbols defined inside target (e.g. methods in a class)
# Who calls the auth handler?
query_graph(pattern="callers_of", target="authenticate_user")
# What does the payment processor import?
query_graph(pattern="imports_of", target="PaymentProcessor", limit=30)
# What classes inherit from BaseModel?
query_graph(pattern="inherited_by", target="BaseModel")
3. get_blast_radius — impact analysis
get_blast_radius(
changed_files: str,
max_depth: int = 2,
max_nodes: int = 500,
) -> {success, changed_nodes, impacted_nodes, impacted_files, edges, depth_reached, truncated}
Computes the full impact radius for one or more changed files using bidirectional BFS (callers and callees). Returns every node and file reachable within max_depth hops. Use this before editing to understand risk surface.
changed_files — comma-separated file paths relative to the repo root, e.g. "src/auth/handler.py,src/auth/models.py".
max_depth — BFS depth. Default 2. Increase to 3–4 for deep call chains; lower to 1 for a quick first-degree check.
max_nodes — caps the result set. If truncated=true in the response, the real blast radius is larger.
# What breaks if I change the auth handler?
get_blast_radius(changed_files="src/auth/handler.py")
# Deeper analysis across two files
get_blast_radius(
changed_files="src/payments/gateway.py,src/payments/models.py",
max_depth=3,
max_nodes=200
)
If truncated is true, narrow the scope with max_nodes or reduce max_depth to get a reliable result.
Hybrid FTS5 + vector search over all indexed code entities. Use when you know what the code does but not what it's called.
query — natural language description, e.g. "retry logic for HTTP requests" or "parse JWT token from header".
kind — optional filter: "Function", "Class", "File", or "Test". Empty = all kinds. Case-insensitive match in the engine.
limit — max results. Default 20.
Results include a score field (higher = more relevant).
# Find where authentication is handled
semantic_search_code(query="authenticate user from request token")
# Find only test functions that cover database writes
semantic_search_code(query="database write transaction rollback", kind="Test")
# Find the rate limiter class
semantic_search_code(query="rate limiting middleware", kind="Class", limit=5)
Produces a token-optimized review package for a set of changed files: a plain-language summary, a ranked list of review items with per-node risk scores, and a list of changed symbols that have no associated test coverage.
changed_files — comma-separated file paths relative to the repo root.
include_source — whether to include source code snippets in the context (default True). Set False to reduce token usage when you only need the risk analysis.
risk_score is a float 0–1 on the overall changeset. review_items[].risk_score is per-node.
# Get review context for a PR touching two files
get_review_context(changed_files="src/auth/handler.py,src/auth/utils.py")
# Risk summary only, no source snippets
get_review_context(
changed_files="src/payments/gateway.py",
include_source=False
)
Runs git diff against base, maps the changed hunks to graph nodes, and returns a risk-scored list of changed functions, test gaps, and review priorities. Requires the repo to be a git repository.
base — git ref to diff against. Default "HEAD~1" (one commit back). Any valid git ref works: "main", "v3.6.13", a commit SHA, etc.
# What changed in the last commit?
detect_changes()
# What changed since the release branch?
detect_changes(base="release/v3.6.13")
# What changed relative to main?
detect_changes(base="main")
Returns error if the repo root is not a git repository or if git is not available.
Realistic Workflow
Explore an unfamiliar codebase
# 1. Index it
build_code_graph(repo_path="/abs/path/to/repo")
# 2. Find the entry point by meaning
semantic_search_code(query="request router entry point", kind="Function")
# 3. Trace what it calls
query_graph(pattern="callees_of", target="handle_request")
# 4. See who else calls the same core function
query_graph(pattern="callers_of", target="authenticate_user")
Before editing a function
# 1. Know what you are touching
semantic_search_code(query="retry HTTP requests with backoff")
# 2. Understand blast radius before making the change
get_blast_radius(changed_files="src/http/client.py")
# 3. Check test gaps
get_review_context(changed_files="src/http/client.py")
Pre-commit / PR review
# 1. What changed in this branch vs main?
detect_changes(base="main")
# 2. Full impact analysis for the changed files
get_blast_radius(changed_files="src/auth/handler.py,src/auth/models.py")
# 3. Assemble review context
get_review_context(changed_files="src/auth/handler.py,src/auth/models.py")
Error Handling
All tools return {"success": false, "error": "<message>"} on failure — they never raise.
Error message
Cause
Fix
Code graph not built. Run build_code_graph first.
No index exists
Call build_code_graph(repo_path=...) first
Repository path does not exist: <path>
Bad repo_path in build
Pass an absolute path that exists
Git not available or not a git repository: ...
detect_changes needs git
Only works in git repos with git installed
Invalid pattern '...'
Wrong pattern in query_graph
Use one of the 8 valid pattern strings
No node found matching '<target>'
Target not in index
Rebuild or check the qualified name via semantic_search_code
If build_code_graph returns files_parsed: 0, no supported source files were found — check repo_path and exclude_patterns.
Profile Requirement
This skill uses graph tools that are only active under the code MCP profile
(or full / power). Your plugin .mcp.json must include:
Without this, the six graph tools are not registered and will appear as unknown
tools. Run slm status to confirm the active profile.
Switching profiles at runtime (v3.8.0+): Use switch_profile("code") via
MCP to activate the code profile in a session that started with a different
profile. See slm-profile for the full profile switching workflow.
Related skills
slm-profile — workspace isolation and profile switching (required for code tools)
slm-recall — retrieve architectural decisions before graph queries
slm-status — confirm the active profile and graph index health
