Error Rosetta

Universal translator for cryptic error messages, stack traces, and log output. Takes the hieroglyphics your toolchain throws at you and produces plain-language diagnosis, root cause, and the exact fix — in your codebase, not some generic Stack Overflow answer from 2019.

"The Rosetta Stone let scholars read Egyptian hieroglyphics by providing the same text in three languages. Your compiler already speaks three languages — the error code, the stack trace, and the actual problem. It just refuses to use the third one."

What It Does

You see this:

text

TypeError: Cannot read properties of undefined (reading 'map')
    at UserList (webpack-internal:///./src/components/UserList.tsx:14:23)
    at renderWithHooks (webpack-internal:///./node_modules/react-dom/cjs/react-dom.development.js:14985:18)
    at mountIndeterminateComponent (webpack-internal:///./node_modules/react-dom/cjs/react-dom.development.js:17811:13)

Error Rosetta gives you this:

text

PLAIN ENGLISH: Your UserList component is trying to call .map() on
something that doesn't exist yet. On line 14, you're accessing a
property that is undefined — probably because the data hasn't loaded
from the API when the component first renders.

ROOT CAUSE: src/components/UserList.tsx:14 accesses `users.map()`
but `users` is undefined on first render. Your useEffect that fetches
users hasn't completed yet.

FIX: Add a guard before mapping:
  {users?.map(...)}  or  {users && users.map(...)}

  Better: Initialize your state with an empty array:
  const [users, setUsers] = useState([]);

The Translation Layers

Layer 1: Error Identification

Every error message, no matter how cryptic, contains these decodable components:

Component	What It Tells You	Example
Error Type	Category of problem	TypeError, ENOENT, HTTP 422, SegFault
Error Message	What went wrong (usually poorly)	"Cannot read properties of undefined"
Location	Where it happened	File path + line number
Stack Trace	How it got there	Call chain from entry point to error
Error Code	Machine-readable identifier	E0308, TS2345, EPERM

Layer 2: Context Enrichment

Raw error → enriched with your codebase context:

text

ENRICHMENT PROCESS:
├── Read the file + line referenced in the error
├── Understand what the code is TRYING to do (not just what failed)
├── Check the data flow: where does the undefined/null/wrong-type value come from?
├── Check recent changes: did a recent commit introduce this?
├── Check patterns: does this error match a known pattern for this framework/language?
└── Check siblings: are similar errors happening elsewhere?

Layer 3: Plain Language Translation

The enriched error is translated into three outputs:

text

1. WHAT HAPPENED (one sentence, no jargon)
   "Your code tried to use a list of users before the list was loaded."

2. WHY IT HAPPENED (root cause, in your codebase)
   "useState(undefined) + useEffect(async fetch) = undefined on first render."

3. HOW TO FIX IT (specific to your code, not generic advice)
   "Line 8: Change useState() to useState([])"

Error Pattern Library

JavaScript/TypeScript

Cryptic Error	Plain Translation	Common Fix
Cannot read properties of undefined (reading 'x')	You're accessing .x on something that doesn't exist	Add optional chaining ?.x or check for null/undefined first
x is not a function	You're calling something that isn't callable — it's a value, not a function	Check: did you forget () on a prior call? Is the import correct?
Maximum call stack size exceeded	Infinite recursion — a function calls itself forever	Find the recursive call missing its base case
Cannot assign to 'x' because it is a read-only property	You're mutating something that shouldn't be mutated	Use spread/Object.assign to create a new object instead
Module not found: Can't resolve 'x'	Import path is wrong or package isn't installed	Check spelling, check node_modules, run npm install
TS2345: Argument of type 'X' is not assignable to parameter of type 'Y'	Type mismatch — you're passing the wrong shape of data	Check what the function expects vs. what you're giving it

Python

Cryptic Error	Plain Translation	Common Fix
AttributeError: 'NoneType' object has no attribute 'x'	A function returned None when you expected an object	The function upstream returned nothing — check its return paths
IndentationError: unexpected indent	Whitespace is wrong (tabs vs. spaces or wrong level)	Fix indentation — use consistent spaces
RecursionError: maximum recursion depth exceeded	Infinite recursion	Find the missing base case in your recursive function
KeyError: 'x'	You're accessing a dictionary key that doesn't exist	Use .get('x', default) or check if 'x' in dict first
ImportError: cannot import name 'x' from 'y'	The thing you're importing doesn't exist in that module	Check spelling, check the module's __init__.py, check version

Rust

Cryptic Error	Plain Translation	Common Fix
E0382: borrow of moved value: 'x'	You used a value after giving ownership to something else	Clone it, use a reference, or restructure to avoid the move
E0308: mismatched types	Expected one type, got another	Check your function signatures and return types
E0502: cannot borrow 'x' as mutable because it is also borrowed as immutable	You have a read reference and are trying to write	Restructure to not hold both borrows simultaneously
E0106: missing lifetime specifier	Rust can't figure out how long a reference should live	Add explicit lifetime annotations

Go

Cryptic Error	Plain Translation	Common Fix
cannot use x (type Y) as type Z	Type mismatch in assignment or function call	Check the expected type and convert
undefined: x	Using a name that doesn't exist in this scope	Check import, check spelling, check scope
fatal error: all goroutines are asleep - deadlock!	Every goroutine is waiting for something and nothing can proceed	Check channel operations — something isn't sending or receiving
panic: runtime error: index out of range	Array/slice access beyond its length	Check bounds before accessing

System/OS Errors

Cryptic Error	Plain Translation	Common Fix
ENOENT: no such file or directory	File or directory doesn't exist at that path	Check the path — typo? Missing directory? Relative vs absolute?
EACCES: permission denied	You don't have permission to access this	Check file permissions, check if you need sudo/admin
EADDRINUSE: address already in use	Another process is already using that port	Kill the other process or use a different port
ENOMEM: not enough memory	System is out of memory	Check for memory leaks, increase available memory, or reduce consumption
ETIMEDOUT: connection timed out	The remote host didn't respond in time	Check network, check if the service is running, check firewall

HTTP Errors

Code	What The Server Actually Means	Developer Action
400 Bad Request	"Your request is malformed — I can't even parse it"	Check request body format, content-type header, required fields
401 Unauthorized	"Who are you? I don't see valid credentials"	Check auth token, check if it's expired, check the auth header format
403 Forbidden	"I know who you are. You're not allowed"	Check permissions/roles, check if the resource requires different access
404 Not Found	"That URL doesn't point to anything"	Check the URL path, check if the resource exists, check API version
409 Conflict	"This conflicts with the current state"	Check for duplicate resources, check version/ETag conflicts
422 Unprocessable Entity	"I can read your request but the data doesn't make sense"	Check validation rules, check field values against API docs
429 Too Many Requests	"Slow down. You're hitting the rate limit"	Add backoff/retry logic, check rate limit headers
500 Internal Server Error	"Something broke on my end, not your fault"	Check server logs, it's a bug in the backend
502 Bad Gateway	"I'm a proxy and the server behind me is broken"	Check the upstream service, check proxy config
503 Service Unavailable	"I'm overloaded or doing maintenance"	Retry with backoff, check status page

The Translation Process

text

INPUT: Error message, stack trace, or log output (paste the whole thing)

Phase 1: PARSE
├── Identify error type, code, message, and location
├── Extract stack trace frames
├── Identify the framework/language/tool that produced the error
└── Separate signal from noise (framework internals vs. your code)

Phase 2: LOCATE
├── Find YOUR code in the stack trace (skip framework frames)
├── Read the file and line where the error originated
├── Read the surrounding context (function, class, module)
└── Trace the data flow to the error point

Phase 3: DIAGNOSE
├── Match against known error patterns for this language/framework
├── Analyze the specific code context (not generic advice)
├── Identify the root cause (not the symptom)
├── Check: is this a new bug or a recurring pattern?
└── Check: did a recent change introduce this?

Phase 4: PRESCRIBE
├── Plain English explanation (one sentence)
├── Root cause in your code (specific file, line, variable)
├── Exact fix (code change, not concept)
├── Prevention (how to avoid this class of error in the future)
└── Confidence level (how certain is this diagnosis)

Output Format

text

╔══════════════════════════════════════════════════════════════╗
║                    ERROR ROSETTA                            ║
╠══════════════════════════════════════════════════════════════╣
║                                                              ║
║  ERROR: TypeError: Cannot read properties of undefined       ║
║         (reading 'map')                                      ║
║                                                              ║
║  TRANSLATION:                                                ║
║  Your UserList component renders before the API response     ║
║  arrives. On the first render, `users` is undefined, and     ║
║  you're calling .map() on undefined.                         ║
║                                                              ║
║  ROOT CAUSE:                                                 ║
║  src/components/UserList.tsx:8                                ║
║    const [users, setUsers] = useState();  ← initialized as  ║
║    undefined, not as empty array                             ║
║                                                              ║
║  FIX:                                                        ║
║  Line 8: useState()  →  useState([])                         ║
║                                                              ║
║  PREVENTION:                                                 ║
║  Always initialize state with the correct empty type:        ║
║    Arrays: useState([])                                      ║
║    Objects: useState(null) with explicit null check           ║
║    Strings: useState('')                                     ║
║                                                              ║
║  CONFIDENCE: 95% (matches React uninitialized-state pattern) ║
╚══════════════════════════════════════════════════════════════╝

When to Invoke

• Every time you see an error you don't immediately understand. That's the whole point.
• When onboarding in a new language or framework (the error messages are a new dialect)
• When the error is in a dependency's code and you need to understand what YOU did wrong
• When debugging a CI failure with a wall of log output
• When a user reports an error and you need to decode it fast

Why It Matters

Developers spend 35-50% of their time debugging. A significant portion of that time is spent understanding what the error message is telling them — not fixing the actual bug. The faster you decode the message, the faster you fix the problem.

Error Rosetta doesn't fix bugs. It removes the translation step between seeing the error and understanding the error. Everything after that is just typing.

Zero external dependencies. Zero API calls. Pure pattern matching and code analysis.