📊 Full opportunity report: Disk Is the Contract: Inside Threlmark’s Local-First Architecture on ThorstenMeyerAI.com — validation score, market gap, and execution plan.
TL;DR
Threlmark introduces a local-first, file-based architecture where JSON files on disk serve as the single source of truth. This design simplifies data portability, interoperability, and resilience, with no reliance on servers or databases.
Threlmark has implemented a novel architecture where project data is stored exclusively in JSON files on disk, making the filesystem the single source of truth and eliminating the need for a server or database. This approach allows users to manage multi-project roadmaps with open, portable, and restartable data, directly impacting how project tools can interoperate and scale.
The core design choice is that the on-disk layout functions as the API, with each project, card, and artifact represented as individual JSON files within a structured directory. This setup enables external tools to read, write, and participate in project management without permission barriers or proprietary databases. The system defaults to a home directory (~/.threlmark), with a manifest file (threlmark.json), dependency graph (links.json), and individual project folders containing metadata, lane configurations, and one file per roadmap card.
To ensure safety and consistency, Threlmark employs atomic file writes—writing to a temporary file and then renaming it atomically—and uses read-merge-write patterns that preserve unknown fields, allowing for forward compatibility. The architecture supports concurrent external edits without conflicts, as each card is stored in a separate file, preventing race conditions common in monolithic JSON arrays. The self-healing board logic reconciles the actual files against the lane order, automatically adding missing cards and removing orphaned IDs, ensuring data integrity.
Disk is the contract: inside a local-first roadmap hub
A Next.js app on top of plain JSON files — no database, no cloud, no accounts. The key decision: the on-disk layout IS the API. Everything else cascades from taking that seriously.
There is no server-of-record — the files are the record
The UI and any external tool reach the same files through the same discipline. The data root defaults to ~/.threlmark — home-based, because it’s a shared hub every one of your apps points at.
Inspectable
Every artifact is a file you can cat, diff, grep, commit.
Portable · no lock-in
Back up with cp, sync with Dropbox / git, migrate trivially.
Interoperable
Any tool in any language joins by reading / writing files.
Restartable
No in-memory state to lose — stateless over the files.
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Intuitive interface of a conventional FTP client
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Two disciplined patterns instead of a database
“Just use files” is easy to get wrong. These two patterns — ported from a battle-tested sibling app — are what make file-based state sound rather than reckless.
Atomic writes
Write to a temp file in the same dir, then rename() over the target. Rename is atomic on one filesystem — a crash mid-write leaves the complete old file or the complete new one, never a half.
The board heals itself
A single roadmap.json array races when two tools write at once. One file per card makes writes collision-free. Lane order lives in board.json and reconciles on read.
board.json. It writes an item file — the board fixes itself on Threlmark’s next read. Unknown keys are preserved, so the contract is forward-compatible.
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The numbers can’t drift from the files
Anything computable from item state is computed — so the displayed numbers can never disagree with the underlying JSON. Priority is the clearest example: it’s calculated on read, never persisted.
priority — computed on read
Impact weighted heaviest; effort the only axis that subtracts. Reused verbatim from the original tool, so imported cards rank identically.
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A handoff is a first-class flow event
The genuinely 2026-shaped part: most building is done by AI agents, so Threlmark closes the loop. Watch a card go from ranked to Done without anyone dragging it.
Handoff → report → self-move
The brief carries a reporting protocol. The agent reports through REST or the filesystem — and a done report moves the card itself.
POST /api/projects/:id/
items/:itemId/reportDirect call. Applied immediately.
drop reports/.json
→ ingested on read Robust even if the server’s down at finish time.
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A small formula, and an honest hosting caveat
Because items are globally addressable (
Portfolio ranking — status-weighted
In-flight work floats to the top; bottlenecks cost the most, so blockers get nudged up.
Static read-only demo
Seeded data, writes to localStorage. Try-before-you-clone.
Personal Node instance
Password-gated, persistent backed-up THRELMARK_DATA_DIR.
Multi-tenant SaaS
Add accounts + per-tenant isolation. A separate build.
src/lib/*/store.ts is the natural seam — the same boundary that keeps the local tool simple is the one you’d extend for multi-tenancy. The architecture doesn’t fight that future; it just doesn’t pay for it until you need it.
Implications of a Serverless, File-Based Data Model
This architecture fundamentally alters traditional project management tools by removing the reliance on centralized servers or databases. It enhances data portability, allowing users to back up, migrate, and integrate with other tools seamlessly. The approach also improves resilience, as all data is stored locally and can be recovered or inspected directly via the filesystem. For developers and power users, this model simplifies integration, debugging, and customization, fostering an ecosystem of interoperable, open-source tools that can participate without permission barriers.
The Evolution of Local-First Project Management Tools
Traditional project management systems often rely on cloud-based databases, creating dependencies on specific platforms and risking data lock-in. Threlmark’s design builds on a growing trend toward local-first applications, emphasizing user control and data portability. Its architecture echoes principles seen in other open-source projects that prioritize filesystem-based data storage, but it distinguishes itself through its focus on multi-project workflows and AI integration. The decision to make the filesystem the contract addresses longstanding issues around data fragmentation, lock-in, and external tool integration.
Previously, tools like Notion or Trello stored data in proprietary formats or cloud servers, limiting offline access and interoperability. Threlmark’s approach aims to overcome these limitations by making each artifact inspectable, editable, and portable through simple file operations, aligning with the needs of developers, power users, and teams seeking more control over their project data.
“The on-disk layout is the API. That choice cascades into how concurrency is handled, why there’s one file per card, and how external tools can participate without permission.”
— Thorsten Meyer
Remaining Questions About Threlmark’s Architecture
While the architecture’s principles are clear, it is not yet confirmed how well this approach scales with very large projects or complex workflows involving numerous external tools. For more details, see Disk Is the Contract. The impact on real-time collaboration and multi-user scenarios remains to be tested, as does integration with existing project management ecosystems. Additionally, the user experience of managing files directly versus traditional interfaces is still evolving, and the potential for conflicts or data loss in edge cases has not been fully explored.
Next Steps for Adoption and Development
Threlmark plans to release an open-source version of its architecture, encouraging community testing and integration with other tools. Future updates may include enhanced automation, better conflict resolution, and user-friendly interfaces for managing files. Developers and users will likely monitor how well the system handles scaling and collaboration, with potential improvements aimed at balancing local control with cloud-like features.
Key Questions
How does Threlmark handle concurrent edits from external tools?
It uses atomic file writes and a self-healing board that reconciles the actual files with the lane order on each read, minimizing conflicts and ensuring consistency.
Is this approach compatible with existing project management tools?
Since it relies on reading and writing JSON files, external tools can participate easily, but full integration with proprietary platforms may require additional development.
Can this system support multi-user collaboration?
While designed for local and single-user workflows, multi-user scenarios are still being explored, especially regarding simultaneous external edits and conflict resolution.
What are the advantages of a file-based system over a database?
It offers greater data portability, no lock-in, easier debugging, and straightforward backups, while eliminating server dependencies and simplifying interoperability.
Source: ThorstenMeyerAI.com
