How Much Does It Cost to Fix an AI-Built App in the UK?

Why you cannot get a reliable quote without a diagnostic

AI-generated codebases are not predictably scoped from the outside. A Lovable application that looks like a simple authentication fix may have Supabase RLS misconfigurations that affect every table in the database. A Bolt.new application with a straightforward deployment failure may have circular-fix debt in the underlying codebase that makes the deployment issue a symptom rather than the root cause.

Any engineer who provides a reliable fixed-price remediation quote for an AI-generated application without first reviewing the codebase is either guessing or including a large contingency buffer that you are paying for whether the complexity materialises or not. The correct sequence is: diagnostic audit first, remediation quote based on actual findings.

This article sets out the UK price ranges for each remediation tier, what each covers, what drives costs up within the tier, and the cost benchmarks that provide context for the prices.

The price tiers

Diagnostic Audit — £495 (launch price; standard £750)

The diagnostic audit is not a remediation service. It is an assessment that produces a written report with a fix, refactor, or rebuild recommendation and a scoped quote for the recommended next step. Three to five working days. Read-only repository access only.

At the current launch price of £495, this is below the cost of a single day of senior developer time in the UK (average £438; £600 to £700 or above for specialists per YunoJuno 2024 data). The distinction from an open-ended day rate engagement is that the audit delivers a specific, bounded output — a written report and a scoped recommendation — rather than billable hours spent exploring the codebase.

Add Jam's traditional code review starts at £750; a senior developer hired directly at £500 per day would spend most of the first day simply reading the codebase. At £495 for a dedicated senior assessment of an AI-generated codebase by engineers who understand the specific failure patterns, the diagnostic audit is the cheapest available way to know what you are actually dealing with.

Quick Fix — £350 to £750

A quick fix addresses a single, named, clearly scoped issue. Examples: adding the correct environment variables to Vercel, updating the Supabase authentication redirect URL for the production domain, enabling Stripe live mode and configuring the production webhook endpoint.

A quick fix does not require the diagnostic audit as a prerequisite — provided the issue is genuinely single and clearly defined, which requires confirmation in a free 20-minute triage call. If the intake call reveals that the "single issue" is one symptom of a more complex underlying problem, the quick fix route is not appropriate.

The price range reflects complexity: a 20-minute configuration change with a one-hour verification process is at the lower end; a fix that requires understanding the existing code to implement correctly, and has potential side effects that require testing, is at the upper end.

Deployment Rescue — £1,250 to £3,500

A deployment rescue takes an application that works in the tool's preview environment and gets it live and stable on the target production hosting platform. The work covers environment configuration, domain and SSL setup, hosting platform settings, and the specific configuration changes required for the application's backend and authentication to function under the production domain.

This tier assumes the application is fundamentally sound — the code works, the backend is correctly configured for development, and the remaining issues are deployment and environment configuration. It does not cover code-level architectural problems or security hardening beyond the standard configuration work.

The price range reflects the hosting stack complexity. A simple Next.js application deploying to Vercel with a Supabase backend is at the lower end. An application with a custom domain, multiple backend services, a payment integration requiring webhook configuration, and an OAuth provider requiring redirect URI updates across multiple services is toward the upper end.

Production-Ready Upgrade — £3,500 to £8,000

A production-ready upgrade takes a working prototype to a secure, deployable application. It covers authentication hardening, database security review and RLS configuration, payments integration in live mode with webhook verification, hosting and monitoring setup, and a handover package with documentation. The 14-day post-delivery support window is included.

This is the correct tier for applications preparing to launch to real users, particularly in regulated sectors. The work is more extensive than a deployment rescue because it addresses security posture — not just whether the application runs, but whether it is safe for users to interact with.

The price range reflects the depth of security issues found in the diagnostic audit. An application with correctly structured code and primarily configuration-level security gaps is at the lower end. An application with RLS misconfigurations across multiple tables, authentication gaps requiring code-level changes, and exposed secrets requiring rotation and code remediation is toward the upper end.

Refactor — £8,000 to £25,000

A refactor rewrites the internal structure of the application while preserving its functionality from the user's perspective. The UI remains the same; the underlying implementation is rebuilt to a maintainable and secure standard. This tier is appropriate for applications where the codebase has accumulated circular-fix debt to the point where targeted patching is no longer cost-effective, but the user-facing product — the screens, the workflows, the business logic — is worth preserving.

The wide price range reflects codebase size and complexity. A small application of 2,000 to 5,000 lines that requires a structural refactor of its database access layer and authentication module is toward the lower end. A larger application with multiple user roles, complex business logic, and accumulated debt across the full stack is toward the upper end.

A refactor requires a statement of work with an explicit scope and a clear description of what is being preserved and what is being rewritten. A refactor without a defined scope is effectively an open-ended rebuild.

Rebuild — £8,000 to £25,000+

A rebuild starts from scratch. The existing codebase is used as requirements documentation — it shows what the application needs to do — but not as the starting point for the new code. A rebuild is appropriate when the existing codebase is architecturally unsalvageable: when the data model has no coherent design, when the authentication layer cannot be made secure without rewriting it from the first line, or when accumulated circular-fix debt has produced a codebase that a senior engineer cannot confidently extend without introducing new faults.

The cost of a rebuild has fallen substantially because AI tools — used as construction aids under human engineering oversight, rather than as autonomous authors — can implement a well-designed architecture faster than a traditional manual build. The rebuild cost in the range above assumes this model: a human architect designs the structure, defines the data model, and reviews every significant component; an AI tool accelerates implementation within that structure.

The lower end of the rebuild range (£8,000 to £12,000) covers a straightforward application of modest scope. The upper end (£20,000 to £25,000+) covers a complex application with multiple user roles, integrations, and business logic that requires careful re-implementation. Applications above this complexity are scoped individually after the diagnostic audit.

What drives the price up within each tier

Several factors consistently push remediation costs toward the upper end of each range:

• Regulated sectors. Financial services, healthcare, and legal applications require additional security review, regulatory documentation, and sometimes external legal review of the GDPR and sector-specific compliance position. This adds time and cost at every tier.
• Live applications with existing users. An application that already has users and live data requires more careful remediation — staging environments, gradual rollouts, and user-facing communication planning. The work is the same; the risk management overhead is higher.
• Circular-fix debt in the codebase. An application that has been through many rounds of AI-prompted fixes has accumulated regressions and inconsistencies throughout the codebase. Understanding what is there before changing anything takes longer and costs more than working with a straightforward first-generation codebase.
• Multiple backend integrations. Applications with several third-party integrations — Stripe, Supabase, a CRM, an email provider, a third-party API — require configuration verification across each integration, not just the primary backend.

The cost of not fixing it

The cost of an AI app fix is more legible than the cost of not fixing it, but the latter is often higher.

A personal data breach triggered by an exposed Supabase service role key or permissive RLS configuration requires ICO notification within 72 hours, potential notification to affected individuals, and the cost of the breach investigation and remediation. ICO enforcement action for serious breaches can reach 4% of global annual turnover under UK GDPR. The remediation cost for the security vulnerability that caused the breach is typically a small fraction of the total cost of the breach.

For applications in the fundraising pipeline, technical due diligence will identify the security and architecture issues that the Diagnostic Audit would have found. A post-due-diligence remediation negotiation, with an investor who has identified the problems rather than the founder who has disclosed them proactively, is a less favourable position than a pre-due-diligence audit and a clean technical disclosure.

The £495 Diagnostic Audit is the least expensive way to know what you are dealing with. The alternative is discovering it at a less convenient moment.