Branches — Trip Planner

Problem

Branches is a mobile trip planner I’m building outside work, where the itinerary is a notebook of cells and an LLM turns text into real places on the map. Trip planning usually ends up split across a notes app, a map, and a camera roll, and nothing connects them.

I wanted one surface where the plan and the map are the same data: write “dinner at a place in a neighborhood at 8pm” and get a pin, without copying it over by hand.

Approach

I started from a written steering spec in the README that records the decisions, data model, and milestones before any code. The core idea is an itinerary that behaves like a Jupyter notebook.

• Cells. An itinerary is an ordered list of typed cells: note, place, media, transit, ai, and day. Each has a JSON payload, an optional cached output, and a staleAt timestamp. An AI cell shows Run, or Re-run once it is stale or has output, the way a notebook cell does.
• Text → map. A note cell can be scanned for places. A server action makes a forced tool call to the model to pull out concrete place mentions, and each candidate is geocoded through MapTiler. Accepting the inline chip appends a place cell, and the pin shows up on the map through Convex’s reactive queries.
• AI cells. A prompt runs in a Convex action with one tool, add_place. The server geocodes the name and appends a sibling place cell, so the model’s suggestions land on the map as real records.
• Swappable map. A MapProvider interface (camera, markers, routes, bounds, events) sits between the app and the renderer. MapLibre is the v1 implementation. A Felt provider is committed as a stub, because Felt has no native iOS SDK and a WebView map would compromise the main view.
• Backend. Convex handles the schema, auth, file storage, and realtime. Photos upload to Convex storage. API keys live in Convex environment variables, not the client.

Result

A v1 scaffold. It covers email/password auth, a tab shell (Map, Explore, Media, Feed), trip creation, the itinerary editor, text → map, AI cells, and photo upload. The README lists the known gaps:

• Cells aren’t grouped by day in the UI yet. The model supports it.
• Explore is static mock data, and the Felt integration is a stub.
• Apple and Google sign-in aren’t wired up.
• There are no tests yet.

Notes

• The spec describes AI output as streamed. The current action writes a start marker and then the final text in one update, so true incremental streaming is still to do.
• The repo name is branches. The spec’s working title is different, and the product name isn’t settled.
• Deferred on purpose: offline tiles, real social features, transit routing, and CRDT-style concurrent editing.