# AGENTS.md — Build guide for QR Tiger

## Project scope
Generate QR codes that point to stable user-owned short URLs, preview contrast/quiet zone and export SVG or PNG. Let the owner edit the destination without changing the printed code.

Catalogue verdict: yes. A library call with a UI. Peak "why is this a subscription."
Use the implementation prompt below to define the deliverable. Complete each phase's acceptance checks before extending the scope.

## Working agreement
- Inspect the repository and its existing instructions before choosing paths, dependencies or commands. Keep one coherent stack and explain changes to the proposed architecture.
- Plan a vertical slice that accepts a real input and produces the useful output described below. Persist only the state the prompt calls for; respect memory-only and upstream-managed workflows. Use fixtures only when they are clearly labelled.
- After scaffolding, document the actual install, development, check and build commands in README and keep them synchronized with the package or project manifest. Do not report commands as successful unless they ran.
- Work in small steps. At handoff, list implemented flows, checks actually performed, remaining blockers, and any credentials or provider setup the owner must supply.
- Do not publish, spend money, contact customers, delete source data or run irreversible migrations without the project owner's authorization.

## Prerequisites
- Node, SQLite on persistent disk, a stable public HTTPS origin and authenticated owner access. The domain must remain under the owner’s control for printed dynamic codes to keep working.
- Implementation components: Node.js, TypeScript and Express with server-rendered HTML and small browser modules. SQLite through better-sqlite3 with migrations, prepared statements and a single background worker. qr-code-styling for QR rendering, with an explicit public HTTPS origin and non-recycled redirect slugs.
- Scope boundary: Tracking depends on maintaining the domain and hosting; no lifetime availability claim.

## Stack and architecture
- Node.js, TypeScript and Express with server-rendered HTML and small browser modules.
- SQLite through better-sqlite3 with migrations, prepared statements and a single background worker.
- qr-code-styling for QR rendering, with an explicit public HTTPS origin and non-recycled redirect slugs.
- Domain model: QR designs, stable redirect slugs, destinations, revision history and export dimensions

## Security and data integrity
- Public routes accept only their documented inputs with rate/size limits. Protect every owner/customer action with authenticated authorization and CSRF checks; keep secrets outside exports and redact personal data from logs.
- Correctness boundary: Scan reliability cannot be guaranteed from appearance alone; slugs are unique and destination edits accept only approved HTTP/HTTPS URLs.
- Use short SQLite transactions and persist job state before starting work. Give retries stable operation IDs; report incomplete or unknown results instead of silently repeating them.
- Use a consistent SQLite backup and an attachment manifest. Export portable JSON/CSV, then restore to a new directory without overwriting the original data.

## Agent implementation rules
- Project rule — data model: QR designs, stable redirect slugs, destinations, revision history and export dimensions
- Project rule — preserve this invariant: Scan reliability cannot be guaranteed from appearance alone; slugs are unique and destination edits accept only approved HTTP/HTTPS URLs.
- Project rule — acceptance evidence: Print or scan a fixture at the intended size, change its destination and keep the code valid; deleting a slug shows a deliberate inactive page rather than reassigning it.

## Optional agent skills and references
- Optional external skill: [web-design-guidelines](https://github.com/vercel-labs/agent-skills/blob/main/skills/web-design-guidelines/SKILL.md) — Review web interfaces for accessibility, keyboard focus, forms, navigation and interaction quality. Review its instructions and compatibility before use; it does not grant deployment, data-access or publication permission.
- Optional external skill: [sharp-edges](https://github.com/trailofbits/skills/blob/main/plugins/sharp-edges/skills/sharp-edges/SKILL.md) — Review security-sensitive APIs and configuration for dangerous defaults and easy-to-misuse interfaces. Review its instructions and compatibility before use; it does not grant deployment, data-access or publication permission.

Read the linked SKILL.md and its dependencies before adding a skill. Select only the skills matching this project's runtime and task; their documentation does not supply API access, credentials or approval to perform external actions. Pin the reviewed revision where the tool supports it. Follow the chosen agent's documented project-level installation mechanism.

## Distribution ideas
These are optional planning notes. Obtain the owner's approval before publishing or contacting anyone.
- Demonstrate the actual QR Tiger-inspired workflow with owned or clearly labeled sample data: Generate QR codes that point to stable user-owned short URLs, preview contrast/quiet zone and export SVG or PNG. Let the owner edit the destination without changing the printed code.
- Publish a reproducible walkthrough with this observable result: Print or scan a fixture at the intended size, change its destination and keep the code valid; deleting a slug shows a deliberate inactive page rather than reassigning it.
- Explain who can operate this scoped tool, its setup and ongoing costs, and these remaining product gaps: Tracking depends on maintaining the domain and hosting; no lifetime availability claim. Avoid guaranteed savings, performance scores or implied endorsement.

## Engineering roadmap
1. Phase 1 — Scope and fixtures. Implement this bounded workflow: Generate QR codes that point to stable user-owned short URLs, preview contrast/quiet zone and export SVG or PNG. Let the owner edit the destination without changing the printed code. Record prerequisites, select representative user-owned fixtures and document the unsupported features: Tracking depends on maintaining the domain and hosting; no lifetime availability claim.
2. Phase 2 — Durable model. Model QR designs, stable redirect slugs, destinations, revision history and export dimensions Add migrations or a versioned document format, explicit validation, stable IDs and a visible import-error report. Preserve this rule: Scan reliability cannot be guaranteed from appearance alone; slugs are unique and destination edits accept only approved HTTP/HTTPS URLs.
3. Phase 3 — Complete the first useful path. Implement the workflow's input, review and output interface, with clear controls and explicit empty/error states. Use short SQLite transactions and persist job state before starting work. Give retries stable operation IDs; report incomplete or unknown results instead of silently repeating them.
4. Phase 4 — Permissions and integration failure. Public routes accept only their documented inputs with rate/size limits. Protect every owner/customer action with authenticated authorization and CSRF checks; keep secrets outside exports and redact personal data from logs. Request integration credentials and permissions only for the enabled feature; show a disconnected state instead of mock results.
5. Phase 5 — Portable handoff. Use a consistent SQLite backup and an attachment manifest. Export portable JSON/CSV, then restore to a new directory without overwriting the original data. Include setup, operating limits, fixture walkthrough and shutdown/restart instructions in the README.
6. Phase 6 — Acceptance scenarios. Print or scan a fixture at the intended size, change its destination and keep the code valid; deleting a slug shows a deliberate inactive page rather than reassigning it. Repeat the workflow after restart and with a denied permission or unavailable dependency; show recoverable failure rather than a success placeholder.

## Paid-product capabilities outside this build
- hosted dynamic-QR redirects on their domain
- their scan-analytics dashboard
- bulk generation UI

## Implementation prompt
WORKING SLICE
Generate QR codes that point to stable user-owned short URLs, preview contrast/quiet zone and export SVG or PNG. Let the owner edit the destination without changing the printed code.

Build this scoped QR Tiger-inspired workflow with a documented data model and visible failure states.

Architecture
- Node.js, TypeScript and Express with server-rendered HTML and small browser modules.
- SQLite through better-sqlite3 with migrations, prepared statements and a single background worker.
- qr-code-styling for QR rendering, with an explicit public HTTPS origin and non-recycled redirect slugs.

Prerequisites and limits
Node, SQLite on persistent disk, a stable public HTTPS origin and authenticated owner access. The domain must remain under the owner’s control for printed dynamic codes to keep working.
Outside this release: Tracking depends on maintaining the domain and hosting; no lifetime availability claim.

Data model and correctness
QR designs, stable redirect slugs, destinations, revision history and export dimensions
Invariant: Scan reliability cannot be guaranteed from appearance alone; slugs are unique and destination edits accept only approved HTTP/HTTPS URLs.
Use short SQLite transactions and persist job state before starting work. Give retries stable operation IDs; report incomplete or unknown results instead of silently repeating them.

Security and privacy
Public routes accept only their documented inputs with rate/size limits. Protect every owner/customer action with authenticated authorization and CSRF checks; keep secrets outside exports and redact personal data from logs.

Recovery and export
Use a consistent SQLite backup and an attachment manifest. Export portable JSON/CSV, then restore to a new directory without overwriting the original data.

Implementation order
1. Phase 1 — Scope and fixtures. Implement this bounded workflow: Generate QR codes that point to stable user-owned short URLs, preview contrast/quiet zone and export SVG or PNG. Let the owner edit the destination without changing the printed code. Record prerequisites, select representative user-owned fixtures and document the unsupported features: Tracking depends on maintaining the domain and hosting; no lifetime availability claim.
2. Phase 2 — Durable model. Model QR designs, stable redirect slugs, destinations, revision history and export dimensions Add migrations or a versioned document format, explicit validation, stable IDs and a visible import-error report. Preserve this rule: Scan reliability cannot be guaranteed from appearance alone; slugs are unique and destination edits accept only approved HTTP/HTTPS URLs.
3. Phase 3 — Complete the first useful path. Implement the workflow's input, review and output interface, with clear controls and explicit empty/error states. Use short SQLite transactions and persist job state before starting work. Give retries stable operation IDs; report incomplete or unknown results instead of silently repeating them.
4. Phase 4 — Permissions and integration failure. Public routes accept only their documented inputs with rate/size limits. Protect every owner/customer action with authenticated authorization and CSRF checks; keep secrets outside exports and redact personal data from logs. Request integration credentials and permissions only for the enabled feature; show a disconnected state instead of mock results.
5. Phase 5 — Portable handoff. Use a consistent SQLite backup and an attachment manifest. Export portable JSON/CSV, then restore to a new directory without overwriting the original data. Include setup, operating limits, fixture walkthrough and shutdown/restart instructions in the README.
6. Phase 6 — Acceptance scenarios. Print or scan a fixture at the intended size, change its destination and keep the code valid; deleting a slug shows a deliberate inactive page rather than reassigning it. Repeat the workflow after restart and with a denied permission or unavailable dependency; show recoverable failure rather than a success placeholder.

Acceptance
Print or scan a fixture at the intended size, change its destination and keep the code valid; deleting a slug shows a deliberate inactive page rather than reassigning it.
Use real source data or clearly labeled fixtures. Explain unsupported input and provider failures; do not fabricate analytics, delivery receipts, accuracy claims or security guarantees.

Optional agent guidance
Optional external skill: [web-design-guidelines](https://github.com/vercel-labs/agent-skills/blob/main/skills/web-design-guidelines/SKILL.md) — Review web interfaces for accessibility, keyboard focus, forms, navigation and interaction quality. Review its instructions and compatibility before use; it does not grant deployment, data-access or publication permission.
Optional external skill: [sharp-edges](https://github.com/trailofbits/skills/blob/main/plugins/sharp-edges/skills/sharp-edges/SKILL.md) — Review security-sensitive APIs and configuration for dangerous defaults and easy-to-misuse interfaces. Review its instructions and compatibility before use; it does not grant deployment, data-access or publication permission.
Project rule — data model: QR designs, stable redirect slugs, destinations, revision history and export dimensions
Project rule — preserve this invariant: Scan reliability cannot be guaranteed from appearance alone; slugs are unique and destination edits accept only approved HTTP/HTTPS URLs.
Project rule — acceptance evidence: Print or scan a fixture at the intended size, change its destination and keep the code valid; deleting a slug shows a deliberate inactive page rather than reassigning it.

## Completion evidence
Demonstrate the prompt's acceptance scenarios against the scoped workflow. Include setup from a clean checkout and failure recovery. Check persistence across restart and export/restore only for the state the prompt says to store; for memory-only tools, confirm that temporary content is discarded as specified. Record actual results and remaining limitations. A detailed plan alone does not establish a working replacement.