# AGENTS.md — Build guide for ScreenshotOne

## Project scope
Render an approved public URL or supplied HTML through a bounded Chromium worker and return a cached image/PDF with inspectable request options.

Catalogue verdict: kinda. A competent coding agent can build a useful self-hosted screenshot endpoint around Playwright in a weekend. Matching ScreenshotOne's reliable browser fleet, proxy locations, stealth behavior, maintained blocking rules, videos, and production edge-case handling is a much larger infrastructure product.
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- Do not publish, spend money, contact customers, delete source data or run irreversible migrations without the project owner's authorization.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
- Runtime and tools: Node, Fastify, Playwright Chromium and better-sqlite3 with a bounded browser pool.
- Before starting: A provisioned Chromium runtime, an API key, cache storage and owned target pages; do not assume browser dependencies ship with Node.

## Stack and architecture
- Node, Fastify, Playwright Chromium and better-sqlite3 with a bounded browser pool
- Data design: Store RenderRequest, NormalizedOptions, CacheEntry and Attempt; cache keys include all rendering options and access scope, while failures never populate successful cache entries.
- Setup: A provisioned Chromium runtime, an API key, cache storage and owned target pages; do not assume browser dependencies ship with Node

## Security and data integrity
- Constrain navigation, redirects and subresource requests to allowed public targets; do not let a browser worker access private infrastructure. Bound render concurrency, size and duration.
- Limit dimensions, delay, concurrency and total bytes; start with one authenticated deployment. HTML input is active content, so browser network containment applies to it too; never claim filter lists reliably dismiss all cookie dialogs.
- Keep secrets outside client bundles and exported projects; document what leaves the device and make retention/deletion controls visible.

## Agent implementation rules
- Project rule — domain: Store RenderRequest, NormalizedOptions, CacheEntry and Attempt; cache keys include all rendering options and access scope, while failures never populate successful cache entries.
- Project rule — scope and recovery: Limit dimensions, delay, concurrency and total bytes; start with one authenticated deployment. HTML input is active content, so browser network containment applies to it too; never claim filter lists reliably dismiss all cookie dialogs.
- Project rule — acceptance: Request a page that redirects to a private IP and one with a private-network subresource; block both routes and preserve a clear failed job instead of returning a misleading screenshot.
- Project rule — delivery: document real setup commands and permissions; do not claim a build, accuracy level, performance result or security certification that has not been demonstrated.

## Optional agent skills and references
- Recommended skill: [agent-browser](https://github.com/vercel-labs/agent-browser/blob/main/skills/agent-browser/SKILL.md) — inspect the approved browser workflow and reproduce permitted page interactions; the CLI/browser runtime is a separate prerequisite. Follow the maintainer's installation instructions and match its requirements to the chosen runtime.
- Recommended skill: [sharp-edges](https://github.com/trailofbits/skills/blob/main/plugins/sharp-edges/skills/sharp-edges/SKILL.md) — review configuration and API defaults against the app-specific invariants and recovery boundaries above; this is not a security certification. Follow the maintainer's installation instructions and match its requirements to the chosen runtime.

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 this working slice using synthetic or explicitly authorized non-sensitive examples: Render an approved public URL or supplied HTML through a bounded Chromium worker and return a cached image/PDF with inspectable request options.
- Share a synthetic example export and the acceptance walkthrough; keep real customer, health, financial and source data private: Request a page that redirects to a private IP and one with a private-network subresource; block both routes and preserve a clear failed job instead of returning a misleading screenshot.
- State the limits before asking someone to replace their existing tool: Limit dimensions, delay, concurrency and total bytes; start with one authenticated deployment. HTML input is active content, so browser network containment applies to it too; never claim filter lists reliably dismiss all cookie dialogs.

## Engineering roadmap
1. Phase 1 — Pin the working slice and create its example input: Render an approved public URL or supplied HTML through a bounded Chromium worker and return a cached image/PDF with inspectable request options. Confirm setup: A provisioned Chromium runtime, an API key, cache storage and owned target pages; do not assume browser dependencies ship with Node.
2. Phase 2 — Implement persistence and write-time invariants before decorating the UI: Store RenderRequest, NormalizedOptions, CacheEntry and Attempt; cache keys include all rendering options and access scope, while failures never populate successful cache entries.
3. Phase 3 — Connect the working view to real saved state. Constrain navigation, redirects and subresource requests to allowed public targets; do not let a browser worker access private infrastructure. Bound render concurrency, size and duration.
4. Phase 4 — Expose the app-specific limits and recovery path in context: Limit dimensions, delay, concurrency and total bytes; start with one authenticated deployment. HTML input is active content, so browser network containment applies to it too; never claim filter lists reliably dismiss all cookie dialogs.
5. Phase 5 — Walk through this concrete acceptance case and preserve its exported evidence: Request a page that redirects to a private IP and one with a private-network subresource; block both routes and preserve a clear failed job instead of returning a misleading screenshot. Finish the README and backup/restore instructions; report unfinished capabilities explicitly.

## Paid-product capabilities outside this build
- managed browser capacity, rate limiting, and high availability
- maintained ad, cookie banner, chat widget, and popup blocking rules
- residential proxies, selectable IP locations, and stealth tuning
- scrolling screenshots, video generation, and GPU rendering
- production support for difficult sites and browser edge cases

## Implementation prompt
Build the following focused alternative to ScreenshotOne. This is a deliberately limited personal or small-team substitute, not parity with the paid service.

WORKING SLICE
Render an approved public URL or supplied HTML through a bounded Chromium worker and return a cached image/PDF with inspectable request options.

SETUP AND ARCHITECTURE
Use Node, Fastify, Playwright Chromium and better-sqlite3 with a bounded browser pool. Prerequisites: A provisioned Chromium runtime, an API key, cache storage and owned target pages; do not assume browser dependencies ship with Node. Before integrating anything, record actual versions and permissions, plus model files or provider limits only where used, in the README; make unavailable dependencies visible rather than simulating success.

DOMAIN MODEL AND INVARIANTS
Store RenderRequest, NormalizedOptions, CacheEntry and Attempt; cache keys include all rendering options and access scope, while failures never populate successful cache entries.

IMPLEMENTATION CONTRACT
Constrain navigation, redirects and subresource requests to allowed public targets; do not let a browser worker access private infrastructure. Bound render concurrency, size and duration. Provide an input/setup view, the main work view, and a review/export view appropriate to this workflow. Preserve the last saved state if a job or save fails. Include empty, loading, permission-denied, partial and retryable-error states. Log identifiers and error categories without secret values or unnecessary private content.

APP-SPECIFIC BOUNDARY AND RECOVERY
Limit dimensions, delay, concurrency and total bytes; start with one authenticated deployment. HTML input is active content, so browser network containment applies to it too; never claim filter lists reliably dismiss all cookie dialogs.

ACCEPTANCE SCENARIO
Request a page that redirects to a private IP and one with a private-network subresource; block both routes and preserve a clear failed job instead of returning a misleading screenshot. Also reopen the app after an interrupted operation, confirm the saved record/export remains inspectable, and document the recovery action. These are implementation acceptance requirements, not a claim that this guide has been tested.

DELIVERY
Deliver a runnable repository with migrations or project-format versioning, a non-sensitive example, environment/permission setup, the exact manual acceptance steps, and a backup/export-and-restore walkthrough. Implement the working slice before optional integrations; list any deferred paid-product capabilities honestly. Do not add capabilities outside the working slice just to resemble the original product.

PROJECT RULES FOR AGENTS.md
Keep the domain invariants above executable at the write boundary. Propose scope changes before adding providers or permissions. Never fabricate source evidence, publish results, identity matches or successful delivery. Preserve user originals and require an explicit confirmation for destructive changes or external publication.

## 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.