# AGENTS.md — Build guide for PDF Expert

## Project scope
Build a Mac PDFKit viewer for highlighting, notes, form filling and page organization. Preserve originals and export a new document with an annotation summary for review.

Catalogue verdict: yes. The core loop is small enough for a capable coding agent to produce a useful local version in one sitting. For PDF Expert, annotate, fill, merge, and lightly edit PDFs in a polished local desktop app. The hard boundary is native apple polish, sync, reliable rendering, and mobile continuity, plus document fidelity, identity, and compliance.
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- Do not publish, spend money, contact customers, delete source data or run irreversible migrations without the project owner's authorization.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
- macOS, Xcode and a selected deployment target. Ask for each OS permission only when its feature is enabled; code signing and distribution are separate release tasks.
- Implementation components: Swift, SwiftUI and focused AppKit integrations for a macOS utility. SQLite or Codable files for local settings and history; macOS Keychain for credentials. PDFKit for supported viewing, annotations and forms; no Python service or browser frontend is needed.
- Scope boundary: Arbitrary PDF text editing, device sync and certified signing are deferred.

## Stack and architecture
- Swift, SwiftUI and focused AppKit integrations for a macOS utility.
- SQLite or Codable files for local settings and history; macOS Keychain for credentials.
- PDFKit for supported viewing, annotations and forms; no Python service or browser frontend is needed.
- Domain model: PDF documents, PDFKit annotations, form values, page selections and versioned export copies

## Security and data integrity
- Open only user-selected PDFs with scoped file access, bound document size and treat links/attachments as untrusted. Never run embedded actions automatically or overwrite the original. Warn when an edit invalidates an existing signature; no screen, clipboard or typing capture is required.
- Correctness boundary: Unsupported PDF forms and signatures are reported; a visual signature stamp is never labeled a verified digital signature.
- Keep UI state on the main actor, cancel obsolete background tasks, and avoid blocking system callbacks. Record only the selected feature scope, with clear retention controls.
- Export settings and explicitly selected history without secrets. Preserve the last working configuration and provide a reset that does not delete user source files.

## Agent implementation rules
- Project rule — data model: PDF documents, PDFKit annotations, form values, page selections and versioned export copies
- Project rule — preserve this invariant: Unsupported PDF forms and signatures are reported; a visual signature stamp is never labeled a verified digital signature.
- Project rule — acceptance evidence: Fill a supported form and reopen the exported copy with values intact; rotating a page preserves the source hash and warns about signature validity.

## Optional agent skills and references
- Optional external skill: [swiftui-expert-skill](https://github.com/AvdLee/SwiftUI-Agent-Skill/blob/main/skills/swiftui-expert-skill/SKILL.md) — Build and review native SwiftUI views, state management, navigation, accessibility and rendering performance. Review its instructions and compatibility before use; it does not grant deployment, data-access or publication permission.
- Optional external skill: [swift-concurrency](https://github.com/AvdLee/Swift-Concurrency-Agent-Skill/blob/main/skills/swift-concurrency/SKILL.md) — Design Swift async tasks, actors, isolation, cancellation and safe data sharing, including Swift 6 migration. 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.
- Optional external skill: [pdf](https://github.com/anthropics/skills/blob/main/skills/pdf/SKILL.md) — Process PDFs through extraction, generation, page operations, form filling and OCR workflows. 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 PDF Expert-inspired workflow with owned or clearly labeled sample data: Build a Mac PDFKit viewer for highlighting, notes, form filling and page organization. Preserve originals and export a new document with an annotation summary for review.
- Publish a reproducible walkthrough with this observable result: Fill a supported form and reopen the exported copy with values intact; rotating a page preserves the source hash and warns about signature validity.
- Explain who can operate this scoped tool, its setup and ongoing costs, and these remaining product gaps: Arbitrary PDF text editing, device sync and certified signing are deferred. Avoid guaranteed savings, performance scores or implied endorsement.

## Engineering roadmap
1. Phase 1 — Scope and fixtures. Implement this bounded workflow: Build a Mac PDFKit viewer for highlighting, notes, form filling and page organization. Preserve originals and export a new document with an annotation summary for review. Record prerequisites, select representative user-owned fixtures and document the unsupported features: Arbitrary PDF text editing, device sync and certified signing are deferred.
2. Phase 2 — Durable model. Model PDF documents, PDFKit annotations, form values, page selections and versioned export copies Add migrations or a versioned document format, explicit validation, stable IDs and a visible import-error report. Preserve this rule: Unsupported PDF forms and signatures are reported; a visual signature stamp is never labeled a verified digital signature.
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. Keep UI state on the main actor, cancel obsolete background tasks, and avoid blocking system callbacks. Record only the selected feature scope, with clear retention controls.
4. Phase 4 — Permissions and integration failure. Open only user-selected PDFs with scoped file access, bound document size and treat links/attachments as untrusted. Never run embedded actions automatically or overwrite the original. Warn when an edit invalidates an existing signature; no screen, clipboard or typing capture is required. Request integration credentials and permissions only for the enabled feature; show a disconnected state instead of mock results.
5. Phase 5 — Portable handoff. Export settings and explicitly selected history without secrets. Preserve the last working configuration and provide a reset that does not delete user source files. Include setup, operating limits, fixture walkthrough and shutdown/restart instructions in the README.
6. Phase 6 — Acceptance scenarios. Fill a supported form and reopen the exported copy with values intact; rotating a page preserves the source hash and warns about signature validity. 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
- native Apple polish, sync, reliable rendering, and mobile continuity
- pixel-perfect proprietary PDF engine
- identity verification
- qualified trust services
- large template and integration ecosystem

## Implementation prompt
WORKING SLICE
Build a Mac PDFKit viewer for highlighting, notes, form filling and page organization. Preserve originals and export a new document with an annotation summary for review.

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

Architecture
- Swift, SwiftUI and focused AppKit integrations for a macOS utility.
- SQLite or Codable files for local settings and history; macOS Keychain for credentials.
- PDFKit for supported viewing, annotations and forms; no Python service or browser frontend is needed.

Prerequisites and limits
macOS, Xcode and a selected deployment target. Ask for each OS permission only when its feature is enabled; code signing and distribution are separate release tasks.
Outside this release: Arbitrary PDF text editing, device sync and certified signing are deferred.

Data model and correctness
PDF documents, PDFKit annotations, form values, page selections and versioned export copies
Invariant: Unsupported PDF forms and signatures are reported; a visual signature stamp is never labeled a verified digital signature.
Keep UI state on the main actor, cancel obsolete background tasks, and avoid blocking system callbacks. Record only the selected feature scope, with clear retention controls.

Security and privacy
Open only user-selected PDFs with scoped file access, bound document size and treat links/attachments as untrusted. Never run embedded actions automatically or overwrite the original. Warn when an edit invalidates an existing signature; no screen, clipboard or typing capture is required.

Recovery and export
Export settings and explicitly selected history without secrets. Preserve the last working configuration and provide a reset that does not delete user source files.

Implementation order
1. Phase 1 — Scope and fixtures. Implement this bounded workflow: Build a Mac PDFKit viewer for highlighting, notes, form filling and page organization. Preserve originals and export a new document with an annotation summary for review. Record prerequisites, select representative user-owned fixtures and document the unsupported features: Arbitrary PDF text editing, device sync and certified signing are deferred.
2. Phase 2 — Durable model. Model PDF documents, PDFKit annotations, form values, page selections and versioned export copies Add migrations or a versioned document format, explicit validation, stable IDs and a visible import-error report. Preserve this rule: Unsupported PDF forms and signatures are reported; a visual signature stamp is never labeled a verified digital signature.
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. Keep UI state on the main actor, cancel obsolete background tasks, and avoid blocking system callbacks. Record only the selected feature scope, with clear retention controls.
4. Phase 4 — Permissions and integration failure. Open only user-selected PDFs with scoped file access, bound document size and treat links/attachments as untrusted. Never run embedded actions automatically or overwrite the original. Warn when an edit invalidates an existing signature; no screen, clipboard or typing capture is required. Request integration credentials and permissions only for the enabled feature; show a disconnected state instead of mock results.
5. Phase 5 — Portable handoff. Export settings and explicitly selected history without secrets. Preserve the last working configuration and provide a reset that does not delete user source files. Include setup, operating limits, fixture walkthrough and shutdown/restart instructions in the README.
6. Phase 6 — Acceptance scenarios. Fill a supported form and reopen the exported copy with values intact; rotating a page preserves the source hash and warns about signature validity. Repeat the workflow after restart and with a denied permission or unavailable dependency; show recoverable failure rather than a success placeholder.

Acceptance
Fill a supported form and reopen the exported copy with values intact; rotating a page preserves the source hash and warns about signature validity.
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: [swiftui-expert-skill](https://github.com/AvdLee/SwiftUI-Agent-Skill/blob/main/skills/swiftui-expert-skill/SKILL.md) — Build and review native SwiftUI views, state management, navigation, accessibility and rendering performance. Review its instructions and compatibility before use; it does not grant deployment, data-access or publication permission.
Optional external skill: [swift-concurrency](https://github.com/AvdLee/Swift-Concurrency-Agent-Skill/blob/main/skills/swift-concurrency/SKILL.md) — Design Swift async tasks, actors, isolation, cancellation and safe data sharing, including Swift 6 migration. 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.
Optional external skill: [pdf](https://github.com/anthropics/skills/blob/main/skills/pdf/SKILL.md) — Process PDFs through extraction, generation, page operations, form filling and OCR workflows. Review its instructions and compatibility before use; it does not grant deployment, data-access or publication permission.
Project rule — data model: PDF documents, PDFKit annotations, form values, page selections and versioned export copies
Project rule — preserve this invariant: Unsupported PDF forms and signatures are reported; a visual signature stamp is never labeled a verified digital signature.
Project rule — acceptance evidence: Fill a supported form and reopen the exported copy with values intact; rotating a page preserves the source hash and warns about signature validity.

## 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.