# AGENTS.md — Build guide for Mailbird ## Project scope Connect one existing mailbox through its supported authentication method, synchronize a bounded local cache and provide a unified-style inbox with a composer. Render email in a sanitized viewer with remote images off by default. Catalogue verdict: kinda. The core loop is buildable, but a dependable replacement becomes a real weekend or multi-day project. For Mailbird, build a Windows email client with unified inbox, local search, and simple integrations. The hard boundary is windows polish, provider compatibility, app integrations, sync, and support, plus mail infrastructure, integrations, and client polish. 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 - Do not publish, spend money, contact customers, delete source data or run irreversible migrations without the project owner's authorization.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 and the Rust toolchain, a supported desktop build environment and an explicitly selected data folder. Remote sync is outside the initial scope. An existing mailbox with supported IMAP/SMTP or OAuth access. Provider app registration may be required. - Implementation components: Tauri, React and TypeScript for the desktop interface with a narrowly scoped Rust filesystem bridge. SQLite for structured state and search; user-owned files for original documents and attachments. A server-side/local-process IMAP/SMTP adapter and platform credential store; sanitized sandboxed message rendering. - Scope boundary: Provider OAuth approval, hosted email delivery and universal attachment rendering remain separate. ## Stack and architecture - Tauri, React and TypeScript for the desktop interface with a narrowly scoped Rust filesystem bridge. - SQLite for structured state and search; user-owned files for original documents and attachments. - A server-side/local-process IMAP/SMTP adapter and platform credential store; sanitized sandboxed message rendering. - Domain model: mail accounts, IMAP UIDs and UIDVALIDITY, folders, thread references, draft revisions and SMTP receipts ## Security and data integrity - Limit Tauri capabilities to selected folders and commands. Render imported content without executable HTML, and never expose arbitrary shell execution to the webview. - Correctness boundary: A mailbox UID is meaningful only with its UIDVALIDITY; uncertain SMTP delivery cannot be retried blindly and secrets belong in the OS credential store. - Save edits atomically with stable IDs and revision history. Detect external file changes and offer a conflict copy instead of last-write-wins data loss. - Provide a portable folder export with a JSON manifest and original files. Restore to a separate folder; rebuild disposable indexes from sources. ## Agent implementation rules - Project rule — data model: mail accounts, IMAP UIDs and UIDVALIDITY, folders, thread references, draft revisions and SMTP receipts - Project rule — preserve this invariant: A mailbox UID is meaningful only with its UIDVALIDITY; uncertain SMTP delivery cannot be retried blindly and secrets belong in the OS credential store. - Project rule — acceptance evidence: A UIDVALIDITY reset rebuilds the cache without deleting server mail; a malicious HTML message cannot run script or make authenticated local requests. ## Optional agent skills and references - Optional external skill: [vercel-react-best-practices](https://github.com/vercel-labs/agent-skills/blob/main/skills/react-best-practices/SKILL.md) — Improve React and Next.js data fetching, rendering, bundle size and server performance. Review its instructions and compatibility before use; it does not grant deployment, data-access or publication permission. - 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 Mailbird-inspired workflow with owned or clearly labeled sample data: Connect one existing mailbox through its supported authentication method, synchronize a bounded local cache and provide a unified-style inbox with a composer. Render email in a sanitized viewer with remote images off by default. - Publish a reproducible walkthrough with this observable result: A UIDVALIDITY reset rebuilds the cache without deleting server mail; a malicious HTML message cannot run script or make authenticated local requests. - Explain who can operate this scoped tool, its setup and ongoing costs, and these remaining product gaps: Provider OAuth approval, hosted email delivery and universal attachment rendering remain separate. Avoid guaranteed savings, performance scores or implied endorsement. ## Engineering roadmap 1. Phase 1 — Scope and fixtures. Implement this bounded workflow: Connect one existing mailbox through its supported authentication method, synchronize a bounded local cache and provide a unified-style inbox with a composer. Render email in a sanitized viewer with remote images off by default. Record prerequisites, select representative user-owned fixtures and document the unsupported features: Provider OAuth approval, hosted email delivery and universal attachment rendering remain separate. 2. Phase 2 — Durable model. Model mail accounts, IMAP UIDs and UIDVALIDITY, folders, thread references, draft revisions and SMTP receipts Add migrations or a versioned document format, explicit validation, stable IDs and a visible import-error report. Preserve this rule: A mailbox UID is meaningful only with its UIDVALIDITY; uncertain SMTP delivery cannot be retried blindly and secrets belong in the OS credential store. 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. Save edits atomically with stable IDs and revision history. Detect external file changes and offer a conflict copy instead of last-write-wins data loss. 4. Phase 4 — Permissions and integration failure. Limit Tauri capabilities to selected folders and commands. Render imported content without executable HTML, and never expose arbitrary shell execution to the webview. Request integration credentials and permissions only for the enabled feature; show a disconnected state instead of mock results. 5. Phase 5 — Portable handoff. Provide a portable folder export with a JSON manifest and original files. Restore to a separate folder; rebuild disposable indexes from sources. Include setup, operating limits, fixture walkthrough and shutdown/restart instructions in the README. 6. Phase 6 — Acceptance scenarios. A UIDVALIDITY reset rebuilds the cache without deleting server mail; a malicious HTML message cannot run script or make authenticated local requests. 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 - Windows polish, provider compatibility, app integrations, sync, and support - mail hosting and deliverability - push on every platform - advanced team collaboration - provider-specific AI and search ## Implementation prompt WORKING SLICE Connect one existing mailbox through its supported authentication method, synchronize a bounded local cache and provide a unified-style inbox with a composer. Render email in a sanitized viewer with remote images off by default. Build this scoped Mailbird-inspired workflow with a documented data model and visible failure states. Architecture - Tauri, React and TypeScript for the desktop interface with a narrowly scoped Rust filesystem bridge. - SQLite for structured state and search; user-owned files for original documents and attachments. - A server-side/local-process IMAP/SMTP adapter and platform credential store; sanitized sandboxed message rendering. Prerequisites and limits Node and the Rust toolchain, a supported desktop build environment and an explicitly selected data folder. Remote sync is outside the initial scope. An existing mailbox with supported IMAP/SMTP or OAuth access. Provider app registration may be required. Outside this release: Provider OAuth approval, hosted email delivery and universal attachment rendering remain separate. Data model and correctness mail accounts, IMAP UIDs and UIDVALIDITY, folders, thread references, draft revisions and SMTP receipts Invariant: A mailbox UID is meaningful only with its UIDVALIDITY; uncertain SMTP delivery cannot be retried blindly and secrets belong in the OS credential store. Save edits atomically with stable IDs and revision history. Detect external file changes and offer a conflict copy instead of last-write-wins data loss. Security and privacy Limit Tauri capabilities to selected folders and commands. Render imported content without executable HTML, and never expose arbitrary shell execution to the webview. Recovery and export Provide a portable folder export with a JSON manifest and original files. Restore to a separate folder; rebuild disposable indexes from sources. Implementation order 1. Phase 1 — Scope and fixtures. Implement this bounded workflow: Connect one existing mailbox through its supported authentication method, synchronize a bounded local cache and provide a unified-style inbox with a composer. Render email in a sanitized viewer with remote images off by default. Record prerequisites, select representative user-owned fixtures and document the unsupported features: Provider OAuth approval, hosted email delivery and universal attachment rendering remain separate. 2. Phase 2 — Durable model. Model mail accounts, IMAP UIDs and UIDVALIDITY, folders, thread references, draft revisions and SMTP receipts Add migrations or a versioned document format, explicit validation, stable IDs and a visible import-error report. Preserve this rule: A mailbox UID is meaningful only with its UIDVALIDITY; uncertain SMTP delivery cannot be retried blindly and secrets belong in the OS credential store. 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. Save edits atomically with stable IDs and revision history. Detect external file changes and offer a conflict copy instead of last-write-wins data loss. 4. Phase 4 — Permissions and integration failure. Limit Tauri capabilities to selected folders and commands. Render imported content without executable HTML, and never expose arbitrary shell execution to the webview. Request integration credentials and permissions only for the enabled feature; show a disconnected state instead of mock results. 5. Phase 5 — Portable handoff. Provide a portable folder export with a JSON manifest and original files. Restore to a separate folder; rebuild disposable indexes from sources. Include setup, operating limits, fixture walkthrough and shutdown/restart instructions in the README. 6. Phase 6 — Acceptance scenarios. A UIDVALIDITY reset rebuilds the cache without deleting server mail; a malicious HTML message cannot run script or make authenticated local requests. Repeat the workflow after restart and with a denied permission or unavailable dependency; show recoverable failure rather than a success placeholder. Acceptance A UIDVALIDITY reset rebuilds the cache without deleting server mail; a malicious HTML message cannot run script or make authenticated local requests. 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: [vercel-react-best-practices](https://github.com/vercel-labs/agent-skills/blob/main/skills/react-best-practices/SKILL.md) — Improve React and Next.js data fetching, rendering, bundle size and server performance. Review its instructions and compatibility before use; it does not grant deployment, data-access or publication permission. 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: mail accounts, IMAP UIDs and UIDVALIDITY, folders, thread references, draft revisions and SMTP receipts Project rule — preserve this invariant: A mailbox UID is meaningful only with its UIDVALIDITY; uncertain SMTP delivery cannot be retried blindly and secrets belong in the OS credential store. Project rule — acceptance evidence: A UIDVALIDITY reset rebuilds the cache without deleting server mail; a malicious HTML message cannot run script or make authenticated local requests. ## 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.