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Error Log Root Cause Analyzer

An analysis of your error log — likely root cause, ranked hypotheses, next debugging steps.

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Get a detailed analysis of your error log in a formatted report, including the most likely root cause, ranked hypotheses, and next debugging steps for £1.

Who it's for

  • DevOps engineers debugging production issues
  • Software developers troubleshooting code errors
  • QA testers analysing test failures
  • Technical support specialists resolving customer complaints

Use cases

  • When an unexpected error occurs in your application
  • After a recent deployment causes issues
  • While trying to reproduce an intermittent bug
  • When analysing a stack trace from a crash report
  • During a debugging session to identify the root cause

FAQ

what will i get from the error log analysis

You'll get a report with the most likely root cause of the error, 2-3 ranked alternative hypotheses, and 3-5 next debugging steps with specific commands or queries. The report cites log lines as evidence to support the analysis.

how do i provide context for the error log analysis

You'll provide context through a textarea where you can describe recent changes, deploys, or related events that may have contributed to the error. This helps the analysis focus on the most relevant factors.

how long does the error log analysis take

The analysis is performed immediately, and you'll receive your report for £1. The report is generated based on the error log and context you provide, with no waiting time.

can i get a personalised error log analysis

The analysis is based on the specific error log and context you provide, making it tailored to your situation. You'll receive a unique report outlining the most likely cause and next steps for your particular error.

Sample output

Most likely cause: the `customerId` is null or undefined because an invoice was created without a valid customer association. Evidence: line 48 in `billing.ts` attempts to access `invoice.customerId`, indicating that the `customerId` property is being dereferenced, but the error message suggests it does not exist. Specifically, the error log line "TypeError: Cannot read properties of undefined (reading \"customerId\")" at `settleInvoice (billing.ts:48)` implies that the `customerId` is not present in the `invoice` object, likely due to an incomplete or missing customer association when the invoice was created.

Ranked alternative hypotheses:
1. **Data corruption**: It is possible that the data in the invoice or customer database is corrupted, leading to missing or null `customerId` values.
2. **API integration issue**: The error might be caused by an issue with the API that provides customer information, resulting in incomplete or missing customer data being passed to the billing service.
3. **Deployment-related configuration issue**: The recent deployment of `billing-svc 1f4a` might have introduced a configuration issue that affects how customer data is handled or retrieved.

Next debug steps:
1. **Inspect the invoice data**: Run a query to retrieve the invoice data for the specific invoice that triggered the error (e.g., `SELECT * FROM invoices WHERE id = 8f2a`) to verify if the `customerId` is indeed null or missing.
2. **Check customer association**: Investigate the customer association logic to ensure that invoices are being created with valid customer associations (e.g., `SELECT * FROM customers WHERE id IN (SELECT customer_id FROM invoices)`).
3. **Review deployment changes**: Compare the changes introduced in the `billing-svc 1f4a` deployment with the previous version to identify any potential issues related to customer data handling or API integrations (e.g., `git diff <previous-version>..<current-version> billing.ts`).

Last updated: 2026-06-28

Error Log Root Cause Analyzer | Harnests - End of the string.\n9. `i` - Flag for case-insensitive matching.\n\n**Worked Examples:**\n1. Input: \"SW1A 1AA\" → Match: \"SW1A 1AA\"\n2. Input: \"M1 1AE\" → Match: \"M1 1AE\"\n3. Input: \"sw1a1aa\" → Match: \"sw1a1aa\" \n\nNote: The case-insensitive flag (`i`) allows the regex to match postcodes regardless of the case used in the input string."},"createdAt":"2026-06-28 11:47:36.596823+00"},{"id":456,"slug":"database-schema-explainer","name":"Database Schema Explainer","niche":"engineering","description":"A plain-English walkthrough of a SQL schema — what each table holds, key relationships, gotchas.","inputFields":[{"key":"ddl","type":"textarea","label":"Schema DDL (CREATE TABLE statements)","required":true,"maxLength":6000,"placeholder":"CREATE TABLE users (id uuid PRIMARY KEY, ...);\\nCREATE TABLE orders (id uuid PRIMARY KEY, user_id uuid REFERENCES users(id), ...);"}],"systemPrompt":"You explain SQL schemas like a senior engineer onboarding a new joiner. Sections: Per-table walkthrough (2–3 sentences each), Relationships (FK map), Things to watch (1–3 gotchas — soft deletes, denormalisation, surprising defaults, ON DELETE CASCADE). Refer only to tables/columns present in the DDL. Banned: \"appears to\", \"might\". Example — Bad: \"The orders table appears to reference users.\" Good: \"`orders.user_id` is a FK to `users.id` with no ON DELETE — deleting a user will fail if orders exist.\" Before responding: confirm every named column exists in the DDL.","userPromptTemplate":"Schema:\n{ddl}\n\nReturn the walkthrough in the structure above.","model":"claude-haiku-4-5-20251001","maxTokens":600,"priceGbp":1,"isActive":true,"outputType":"text","imageSize":null,"subcategory":"General","seo":{"faq":[{"a":"The explanation includes a per-table walkthrough, key relationships, and potential gotchas such as soft deletes and denormalisation. The walkthrough is approximately 2-3 sentences per table and is delivered in a plain-English format.","q":"what is included in the database schema explanation?"},{"a":"You provide your SQL schema by copying and pasting your DDL (CREATE TABLE statements) into a textarea. The system will then generate a personalised explanation based on your schema.","q":"how do i provide my sql schema?"},{"a":"The database schema explanation costs £1. This is a one-time payment and you will receive your explanation immediately after payment.","q":"how much does the database schema explanation cost?"},{"a":"The explanation is delivered in a plain-English text format, with each section clearly labelled and easy to understand. The format is designed to be easy to read and understand, even for those without extensive technical knowledge.","q":"what format is the explanation delivered in?"}],"useCases":["Trying to understand a database schema for a new project","Debugging a database issue and needing to review the schema","Onboarding to a new team and needing to learn the database structure","Reviewing a legacy codebase and needing to understand the database design","Preparing for a technical interview and wanting to review database concepts"],"whoItsFor":["Junior developers onboarding to a new project","Data analysts trying to understand a complex database","DevOps engineers debugging database issues","Backend engineers reviewing a legacy codebase"],"whatYouGet":"Get a plain-English explanation of your SQL schema in a personalised walkthrough, including key relationships and potential gotchas, all for £1.","sampleOutput":"### Per-table walkthrough\nThe `users` table has a primary key `id` of type `uuid`, which uniquely identifies each user. This table stores information about the users in the system. The `users` table does not reference any other tables.\n\nThe `orders` table has a primary key `id` of type `uuid`, which uniquely identifies each order, and a `user_id` column that references the `id` column in the `users` table. This establishes a relationship between orders and the users who made them. \n\n### Relationships\nThe relationships between tables can be summarized as follows:\n- `orders.user_id` is a foreign key (FK) to `users.id`, indicating that each order is associated with a user.\n\n### Things to watch\n- `orders.user_id` is a FK to `users.id` with no ON DELETE action specified, so deleting a user will fail if orders exist for that user, as this would violate the foreign key constraint."},"createdAt":"2026-06-28 11:47:35.825386+00"},{"id":457,"slug":"legacy-code-summary","name":"Legacy Code Summary","niche":"engineering","description":"An onboarding-friendly summary of a legacy file — what it does, who calls it, where the dragons are.","inputFields":[{"key":"path","type":"text","label":"File path (optional)","required":false,"maxLength":200,"placeholder":"src/billing/invoiceWorker.ts"},{"key":"code","type":"textarea","label":"Paste the code","required":true,"maxLength":6000,"placeholder":"export async function settleInvoice(invoiceId: string) { ... }"}],"systemPrompt":"You summarise legacy code for a new joiner who has 10 minutes. Sections: Purpose (≤2 sentences), Key functions/exports (bulleted), External callers (only if visible from imports/exports), Dragons (≤3 things that look suspicious — silent catches, magic numbers, race conditions). Do not invent callers you cannot see. Banned: \"appears to handle some kind of\". Example — Bad: \"This file appears to handle some kind of invoice processing.\" Good: \"Purpose: Charges pending invoices nightly via Stripe. Dragon: `try { ... } catch {}` at line 47 swallows all errors silently.\" Before responding: confirm every Dragon cites a line number from the input.","userPromptTemplate":"File: {path}\nCode:\n{code}\n\nReturn the summary.","model":"claude-haiku-4-5-20251001","maxTokens":600,"priceGbp":1,"isActive":true,"outputType":"text","imageSize":null,"subcategory":"General","seo":{"faq":[{"a":"The summary includes the purpose of the code, key functions or exports, external callers if visible, and up to three potential issues or 'dragons'. It is designed to be concise and easy to understand for new joiners.","q":"what is included in the legacy code summary"},{"a":"You can either provide the file path or paste the code directly into the textarea. This allows for flexibility in how you share the code with Harnests.","q":"how do i provide the code for summarisation"},{"a":"The legacy code summary costs £1.00, providing a cost-effective way to understand complex legacy code.","q":"how much does the legacy code summary cost"},{"a":"The summary is delivered in a text format, divided into clear sections for purpose, key functions, external callers, and potential issues, making it easy to read and understand.","q":"what format is the summary delivered in"}],"useCases":["Onboarding new developers to a legacy project","Reviewing unfamiliar codebases for potential issues","Preparing for a code review of a legacy system","Assessing technical debt in a legacy codebase","Introducing new team members to a complex codebase"],"whoItsFor":["New software engineers joining a project","DevOps engineers reviewing legacy systems","Technical leads onboarding new team members","Code reviewers assessing legacy code quality"],"whatYouGet":"A concise summary of legacy code in a format suitable for new joiners, covering purpose, key functions, and potential issues.","sampleOutput":"Purpose: The invoiceWorker module settles invoices. It exports a function to settle an invoice by its ID.\n\nKey functions/exports:\n* `settleInvoice(invoiceId: string)`: an asynchronous function to settle an invoice\n\nExternal callers: None visible from the provided code.\n\nDragons: None visible from the provided code."},"createdAt":"2026-06-28 11:47:35.871109+00"}]}