Crashdx README | AllMCPs

crashdx

A crash diagnosis engine for Apple platforms: parses .ips crash reports, symbolicates them against dSYMs, and produces an evidence-cited, ranked diagnosis, not just a symbolicated stack trace.

Ships as a dependency-free Swift library (CrashDXCore imports only Foundation), a CLI (crashdx), and an MCP server (crashdx-mcp), so agents and humans use the same engine.

Why

A symbolicated stack trace tells you where a process died, not why. crashdx adds a second stage on top of symbolication: deterministic, rule-based evidence extraction (watchdog budgets, jetsam tables, register and memory state, lastExceptionBacktrace/asi) feeding a ranked set of competing hypotheses, each citing the specific facts that support it and pointing back into the raw report.

Two properties it holds onto deliberately:

Every claim is traceable. Facts carry a JSON path into the original report, so any verdict can be checked rather than trusted.
It says "inconclusive" when it is. A verdict requires the leading hypothesis to be strongly supported and clearly ahead of the runner-up; otherwise you get the ranked candidates and what would settle it.

There are no LLM calls in the engine: it produces verifiable facts and ranked interpretations, and leaves the narrative to whatever consumes them. See docs/DESIGN.md for the full architecture.

Example output

Everything below is real, unedited output from fixtures in this repo (elisions are marked). Paths are relative to the repo root, and the --dsym flags point at dSYMs the repo ships, so these reproduce as-is; use swift run crashdx ... if you have not installed the binary.

A verdict

Code

$ crashdx analyze Tests/CrashDXCoreTests/Fixtures/nsexcrash.ips \
      --dsym Tests/CrashDXCoreTests/Fixtures/nsexcrash.dSYM

process:    nsexcrash
bug_type:   309
os:         macOS 26.3.1 (25D2128)
exception:  EXC_CRASH (SIGABRT)
terminated: Abort trap: 6
faulting thread (15 frames):
  libsystem_kernel.dylib  __pthread_kill
  libsystem_pthread.dylib  pthread_kill
  libsystem_c.dylib  abort
  libc++abi.dylib  __abort_message
  libc++abi.dylib  demangling_terminate_handler()
  libobjc.A.dylib  _objc_terminate()
  libc++abi.dylib  std::__terminate(void (*)())
  libc++abi.dylib  __cxxabiv1::failed_throw(__cxxabiv1::__cxa_exception*)
  libc++abi.dylib  __cxa_throw
  libobjc.A.dylib  objc_exception_throw
  CoreFoundation  -[NSException raise]
  nsexcrash  throwingHelper() (main.swift:8)
  nsexcrash  doWork() (main.swift:12)
  nsexcrash  main (main.swift:15)
  dyld  start
last exception backtrace (7 frames):
  CoreFoundation  __exceptionPreprocess
  libobjc.A.dylib  objc_exception_throw
  CoreFoundation  -[NSException raise]
  nsexcrash  throwingHelper() (main.swift:8)
  nsexcrash  doWork() (main.swift:12)
  nsexcrash  main (main.swift:15)
  dyld  start
symbolication (engine: crashSymbolicator):
  nsexcrash  symbolicated
  libsystem_kernel.dylib  no_dsym
  libsystem_pthread.dylib  no_dsym
  ...
DIAGNOSIS: Uncaught Objective-C exception (NSException)   (strong, score 5)
  A lastExceptionBacktrace is present and an objc_exception_throw frame appears in it (or on the
  faulting thread) — together these are pathognomonic for an uncaught NSException: `-raise` walked up
  through objc_exception_throw and was never caught, so the runtime called terminate and aborted. The
  asi "Terminating app due to uncaught exception" message is only corroboration when present; plain
  CLI/Foundation processes never write it, so its absence is not evidence against this hypothesis.
  evidence: lastExceptionBacktrace is present with 7 frame(s); lastExceptionBacktrace frame 1 matches
            sentinel 'objc-exception-throw': objc_exception_throw; Faulting thread frame 9 matches
            sentinel 'objc-exception-throw': objc_exception_throw
  inspect:  nsexcrash throwingHelper() (main.swift:8)
  confirm:  Symbolicate the app frames in lastExceptionBacktrace to find the throw site; Check the
            asi/console log for the exception name and reason, if available
  also considered: cxx-terminate (moderate, 2), abort-generic (weak, 1)

The evidence line cites the supporting facts the rule scored on, up to four, with a running total when there are more; each fact carries a path back into the original report, which --json --tier standard exposes. also considered is the full remainder of the ranked list, so you can see what the verdict beat and by how much.

An inconclusive result

When the leading hypothesis is not strongly supported and clearly ahead, you get the candidates instead of a label:

Code

$ crashdx analyze Tests/CrashDXCoreTests/Fixtures/synthetic/wild-address.ips \
      --dsym corpus/fixtures/nullderef/nullderef.dSYM

process:    synthetic-wild-address
bug_type:   309
os:         macOS 26.3.1 (25D2128)
exception:  EXC_BAD_ACCESS (SIGSEGV)
terminated: Segmentation fault: 11
faulting thread (4 frames):
  nullderef  readThroughNullPointer() (main.swift:9)
  nullderef  run() (main.swift:13)
  nullderef  main (main.swift:16)
  dyld  start
symbolication (engine: crashSymbolicator):
  nullderef  symbolicated
  dyld  no_dsym
DIAGNOSIS: INCONCLUSIVE — competing hypotheses:
  1. Wild pointer or use-after-free [wild-or-uaf-address]   (moderate, score 3)
     The faulting address is outside the null page, and vmregioninfo reports it is not inside any known
     VM region at all — consistent with either a WILD pointer (an uninitialized or garbage value used as
     an address) or a USE-AFTER-FREE into memory the OS has since unmapped. This is deliberately a
     lower-confidence hypothesis than null-dereference: absence of region information doesn't distinguish
     between these two causes.
     evidence: Faulting address: 0x1deadbeef; Exception type: EXC_BAD_ACCESS
     inspect:  nullderef readThroughNullPointer() (main.swift:9)
     confirm:  Re-run with Address Sanitizer enabled to catch the use-after-free at the free/access site;
               Enable NSZombies (Malloc Scribble/Guard Malloc) to turn this into an immediate,
               informative crash; Profile with Instruments' Allocations tool, recording reference counts

Other crash families

The same shape applies across the rule set. Verdict and evidence lines from four more fixtures, with the explanation and follow-up steps elided:

Code

# synthetic/watchdog-scene-create.ips
DIAGNOSIS: Watchdog timeout (main thread stall)   (strong, score 6)
  evidence: Termination code: 2343432205 (0x8badf00d); Termination namespace: FRONTBOARD; Watchdog
            event: scene-create, allowance 19.97s

# synthetic/jetsam-per-process-limit.ips
DIAGNOSIS: Jetsam memory kill   (strong, score 5)
  evidence: Exception subtype: RESOURCE_TYPE_MEMORY; Jetsam per-process-limit indicator:
            per-process-limit 350808KB exceeds task limit 335872KB

# synthetic/stack-overflow.ips
DIAGNOSIS: Stack overflow   (strong, score 5)
  evidence: Faulting address 0x3000 is near the stack region: vmregioninfo names a STACK GUARD region;
            within 500 bytes of sp (0x31f4); Faulting thread has 5 consecutive frames with identical
            symbol 'recurse(_:)' starting at frame 0 — a recursion signature

# crashspike-unsymbolicated.ips, with --dsym Tests/CrashDXCoreTests/Fixtures/crashspike.dSYM
DIAGNOSIS: Swift runtime fatal trap   (strong, score 6)
  evidence: Exception type: EXC_BREAKPOINT; Signal: SIGTRAP; Faulting thread frame 0 matches sentinel
            'assertion-failure': _assertionFailure(_:_:file:line:flags:)

Each of those also prints the full explanation, inspect point, and confirm steps shown in the first example.

JSON

--json emits the same analysis as a structured AnalysisReport, which is what the MCP server returns and what you would parse in CI. Below is the same crash as the first example, abridged (/* ... */ marks elisions). The real output is a single minified line with sorted keys, so pipe it through jq or python3 -m json.tool; it is pretty-printed and reordered here for readability:

JSON Config

{
  "schemaVersion": "0.2",
  "tier": "summary",
  "diagnosis": {
    "status": "verdict",
    "verdict": {
      "id": "uncaught-objc-exception",
      "title": "Uncaught Objective-C exception (NSException)",
      "category": "objc-exception",
      "explanation": "A lastExceptionBacktrace is present and an objc_exception_throw frame ...",
      "supporting": [
        { "factID": "leb.present", "weight": 1 },
        { "factID": "leb.sentinel.objc-exception-throw", "weight": 3 },
        { "factID": "frames.sentinel.objc-exception-throw", "weight": 1 }
      ],
      "contradicting": [],
      "inspect": [
        { "frameIndex": 3, "leb": true, "symbol": "throwingHelper()",
          "sourceFile": "main.swift", "sourceLine": 8 }
      ],
      "confirmFurtherBy": [ /* ... */ ]
    },
    "hypotheses": [ /* all 3, each with its band + score */ ]
  },
  "event": {
    "bugType": "309", "exceptionType": "EXC_CRASH", "signal": "SIGABRT",
    "terminationIndicator": "Abort trap: 6", "terminationNamespace": "SIGNAL"
  },
  "faultingThread": { "index": 0, "queue": "com.apple.main-thread", "triggered": true,
                      "frames": [ /* ... */ ] },
  "symbolication": { "engine": "crashSymbolicator", "images": [ /* per-image outcome + uuid */ ] },
  "process": { "name": "nsexcrash", "osVersion": "macOS 26.3.1 (25D2128)",
               "captureTime": "2026-07-23 00:22:01.2793 +0000" }
}

Note "leb": true on the inspect point: the throw site was recovered from lastExceptionBacktrace rather than the faulting thread, and the report says so instead of flattening the distinction.

--tier standard (see Report tiers) adds diagnosis.factsConsidered, which resolves every factID to its human-readable statement and its sourcePath into the raw report:

JSON Config

{ "id": "leb.sentinel.objc-exception-throw",
  "statement": "lastExceptionBacktrace frame 1 matches sentinel 'objc-exception-throw': objc_exception_throw",
  "sourcePath": "lastExceptionBacktrace[1]" }

sourcePath is not optional on a Fact, so every fact the diagnosis cites can be walked back to the part of the report it was read from.

Committed golden snapshots of both tiers live in Tests/CrashDXCoreTests/Fixtures/ (nsexcrash-summary-golden.json, nullderef-standard-golden.json) if you want the complete, unabridged shape.

Requirements

macOS 14+
Swift 6.2+ toolchain. The manifest itself is swift-tools-version:6.0, but the MCP server's pinned dependencies declare up to 6.2, and SwiftPM resolves the whole package graph, so 6.2 is the real floor for every target, including CrashDXCore.
Xcode (not just Command Line Tools): symbolication drives Apple's CrashSymbolicator.py from Xcode's CoreSymbolicationDT.framework, located via xcode-select -p. Without it, crashdx falls back to atos, which resolves fewer source locations. Parsing and diagnosis work either way.
/usr/bin/python3 and /usr/bin/dwarfdump (both provided by Xcode's command line tools), used to run CrashSymbolicator.py and to verify dSYM UUIDs.

Supported reports

Honest scope, because a crash diagnoser that quietly does worse on your platform is worse than one that says so:

arm64 crash reports are fully supported: Apple silicon Macs, iOS/iPadOS/watchOS/ tvOS devices, and Simulators hosted on Apple silicon. This is what the fixture corpus covers.
x86_64 reports (Intel Macs, Rosetta-translated processes, Simulators on Intel) parse and symbolicate, and the engine reads x86_THREAD_STATE registers and the 4 KB page size. There is no Intel fixture in the corpus, so this path is reasoned-about rather than exercised against a real report.
Only crash reports (bug_type 309/109). Jetsam event reports (JetsamEvent-*.ips, bug_type 298) and hang/stackshot reports (bug_type 288) use a different payload shape with no threads or exception object; crashdx parses them without error but has no facts to work from and will report inconclusive.

Privacy

crashdx runs entirely on your machine and makes no network calls of any kind. Crash reports, dSYMs, and everything derived from them stay local. This matters because .ips files contain identifying data (crashReporterKey, boot/sleep-wake UUIDs, device model, and usernames in paths), so if you attach one to a bug report, scrub it first.

Install / build

git clone https://github.com/r00tify/crashdx.git
cd crashdx
swift build -c release

The binaries land in .build/release/. To put them on your PATH:

sudo mkdir -p /usr/local/bin
sudo cp .build/release/crashdx .build/release/crashdx-mcp /usr/local/bin/

(Or copy them somewhere you already own, such as ~/.local/bin.)

Usage

Crash reports live in ~/Library/Logs/DiagnosticReports/ on macOS (or Console.app → Crash Reports); on iOS, Settings → Privacy & Security → Analytics & Improvements → Analytics Data, and Xcode's Organizer for TestFlight/App Store crashes.

crashdx analyze report.ips                           # human-readable summary + diagnosis
crashdx analyze report.ips --json                    # structured AnalysisReport JSON
crashdx analyze report.ips --json --tier full        # ...with every thread included
crashdx symbolicate report.ips --dsym path/to.dSYM   # just symbolicate, print enriched .ips
crashdx --version

--dsym accepts a .dSYM bundle, an .xcarchive, or a directory to search recursively (repeatable), and --no-spotlight skips Spotlight-based discovery while --no-archives skips Xcode's archive directory. Run crashdx <subcommand> --help for the full option list. Note that --json and --tier apply to analyze only; symbolicate always emits a complete .ips.

Both subcommands search Spotlight and Xcode's archives for a matching dSYM automatically. For foreign reports (user-submitted, TestFlight, CI artifacts) pass the build's dSYM explicitly with --dsym.

Strings taken from the report (process name, symbols, paths, exception text) are escaped before the human-readable summary prints them: C0 controls, DEL, and bidi overrides render as \x0A / \u{202E} instead of being emitted, so a crafted report cannot forge a DIAGNOSIS: line or repaint your terminal. --json and symbolicate emit the report's strings verbatim; treat their output as data, not as terminal text.

A dSYM from a different build is refused rather than used: a stale dSYM produces confidently wrong symbols, which is worse than none. That case is reported as uuid_mismatch (with the offending path in reason), kept distinct from no_dsym because the fix is different: find the archive matching the report's build UUID, rather than go looking for a file you may already have.

Report tiers

--tier controls how much of the report is emitted; it never changes the diagnosis, which is always computed from the full report:

Tier	Contents
`summary` (default)	Faulting thread (capped at 15 frames), `lastExceptionBacktrace`, and the diagnosis verdict + ranked hypotheses
`standard`	Lifts the frame cap, and adds the binary images, other threads that contain app frames, and `factsConsidered` (the evidence behind each hypothesis)
`full`	Adds every remaining thread, including those with no app frames

Exit codes

0 success · 64 usage error · 65 the input could not be parsed as an .ips report, or symbolication failed · 66 file not found or unreadable.

Diagnostics go to stderr; stdout carries report output (and --help/--version).

MCP server

crashdx-mcp exposes the same pipeline over stdio (newline-delimited JSON-RPC) as the crashdx_analyze and crashdx_symbolicate tools. With Claude Code:

Terminal

claude mcp add crashdx /usr/local/bin/crashdx-mcp

A matching crash-triage Agent Skill ships in .claude/skills/crash-triage/, covering how to read the diagnosis and the interpretation pitfalls specific to each crash family.

As a library

Add https://github.com/r00tify/crashdx.git to your Package.swift, depend on the CrashDXCore product, and call AnalyzePipeline.analyze(path:tier:dsymPaths:useSpotlight:searchArchives:), the same entry point both binaries use.

CrashDXCore imports nothing but Foundation, but two limitations are worth knowing before you depend on it:

It is macOS-only. Symbolication shells out to atos/dwarfdump/mdfind through Foundation.Process, which does not exist on iOS. Adding this package to an iOS target fails during dependency resolution, before anything compiles.
SwiftPM resolves the whole package graph rather than a single product, so depending on this package pins the MCP server's dependencies (swift-sdk and its transitive NIO/ collections/log packages) in your Package.resolved even if you never import them.

AnalysisReport and the diagnosis model are Sendable, so analysing a directory of reports concurrently works as you would expect.

Project layout

Code

Sources/CrashDXCore/   Parsing, symbolication, and the diagnosis engine (imports only Foundation)
Sources/crashdx/       CLI
Sources/crashdx-mcp/   MCP server (depends on swift-sdk)
Tests/                 Unit + integration tests, golden snapshots, crash fixtures
corpus/                Ground-truth crash fixtures and their verified findings
docs/DESIGN.md         Diagnosis engine architecture
Scripts/               Fixture scrubbing and the CI privacy guard

Testing

swift test

Contributing

See CONTRIBUTING.md. One rule matters more than the rest: crash reports and dSYMs must be scrubbed before they are committed. They carry device identifiers and your username. Scripts/scrub-fixture.py handles .ips files and Scripts/check-fixtures-scrubbed.sh (also run in CI) will tell you if anything slipped through.

Security and privacy

crashdx makes no network calls; nothing leaves your machine. See SECURITY.md for vulnerability reporting and for what a .ips file actually contains before you share one.

License

MIT. See LICENSE.