MCP SERVERWork out which tests a change really affects, by following the import graph instead of guessing from filenames.
LABSCO SUMMARY
Matching auth.ts to auth.test.ts misses the test that reaches it three imports away, and running everything is slow. The import graph gives an exact answer plus the chain that explains it — and the same graph then answers the questions nobody schedules time for: dead files, untested files, cycles.
An AST and dependency-graph analyser for TypeScript and JavaScript: it parses the project with ts-morph, builds a bidirectional import graph, and answers which tests a set of changed files reaches.
A TypeScript or JavaScript project root, and git for the branch-diff tools — they run git diff --name-only internally. Published on npm as ast-impact-mapper-mcp. After switching branches, refresh_project clears the cached AST so the next call re-parses.
One command — npx -y ast-impact-mapper-mcp
USE CASES
Get the affected tests for the files you touched, then the exact command to run just those in your runner.
The import chain shows the path from your change to that test — usually through a fixture nobody remembers.
Take the affected set from the branch diff, then drop the tests that only see a type-only change.
Compare a file against its HEAD version and get the change classified rather than eyeballing the diff for removed exports.
Coverage gaps list source files no test reaches; unreachable modules list files nothing imports at all.
Get the cycle itself, then the symbol-level graph to see which declaration creates it.
Counted once with only startup setup. Other versions, modes or optional credentials may expose a different list.
analyze_api_surface_mutationCompares a file against its HEAD version and classifies the change as breaking_api_change (exported function signature changed, parameter removed/added, interface field removed) or internal_refactor (only implementation body changed). Use to answer: is this PR a breaking change or a safe refactor?
detect_architectural_cyclesDetects circular import dependencies — A imports B which imports C which imports A. Cycles cause unpredictable module initialization order and indicate tight coupling. Use to answer: are there circular dependencies I need to break before refactoring?
differentiate_type_impactClassifies each changed file as type-only or runtime, then splits affected tests into "must run" vs "skippable". A test is skippable when the changed file contains only TypeScript type declarations (interfaces/type aliases) or the test imports it via import type. Use to answer: which tests can I skip after a type-only refactor?
explain_impactFinds the exact import chain that connects a changed source file to a test file. Use to answer: why does changing file X cause test Y to be affected? Returns the step-by-step import path from the test to the changed file.
generate_skeleton_viewGenerates a token-optimized representation of a source file by stripping function and method bodies, keeping only JSDocs and declarations with line numbers.
generate_test_commandOutputs the optimal test execution command for Jest, Vitest, or Playwright based on changed files.
get_affected_testsGiven a list of changed source files, returns which test files are affected — directly or transitively through the import graph. Use to answer: which tests should I run after this code change?
get_affected_tests_by_branchRuns git diff --name-only <base_branch>...HEAD internally and returns affected test files. Use instead of get_affected_tests when you want the server to handle the git diff automatically.
get_coverage_gapsFinds source files that are not reachable from any test file through the import graph — i.e. completely untested code. Use to answer: which parts of the codebase have zero test coverage?
get_dependency_graphReturns the direct import graph for a specific file: what it imports, and what imports it. Use to answer: what depends on this file? What does this file depend on?
get_rename_aware_diffLike get_affected_tests_by_branch, but correctly handles renamed and moved files. Uses --find-renames to detect file moves and --ignore-all-space to skip whitespace-only changes. Use instead of get_affected_tests_by_branch when the branch contains refactors or file moves.
get_symbol_dependency_graphRetrieves a bidirectional or directed dependency graph mapped to individual declarations, functions, and variables.
get_test_summaryReturns a bird's-eye view of the project's test structure: coverage rate, most-imported source files (highest risk to change), and tests with the deepest import chains. Use to answer: what is the overall test health of this project?
identify_unreachable_modulesFinds source files that are never imported by any other file — dead code candidates safe to delete. Automatically excludes known entry points (index.ts, main.ts, pages/, routes/, app/, api/, bin/). Use to answer: which files in this codebase are orphaned and can be safely removed?
refresh_projectClears the cached AST for a project root, forcing a full re-parse on the next call. Use after switching branches, running git pull, or adding/removing files.
BEFORE YOU INSTALL
15 tools when we connected.
npx on PATH
CONTEXT COST
Rated by the size of the 15 tool definitions that ride along on every turn, not by how many there are
INSTALLATION
Add the block to your client, or run the command directly.
{
"mcpServers": {
"ast-impact-mapper-mcp": {
"command": "npx",
"args": [
"-y",
"ast-impact-mapper-mcp"
]
}
}
}npx -y ast-impact-mapper-mcpMCP servers
khalomsky
pratik7368patil
depwire
jgravelle