Prediction share deep links: the payload-derived fallback is structurally broken

What happened

The record was created with no deepLinkPath in the request. The share service filled one in by itself, derived from the payload's ticker:

POST /share
{ "payload": { "kind": "new_position", "market": "prediction",
               "ticker": "KXFEDDECISION-26SEP-H0", ... } }     // no deepLinkPath sent

GET /share/sY8xsvmkqD
  "deepLinkPath": "predictions/event/KXFEDDECISION-26SEP-H0"   // service derived this

That path matches the resolver's allowed shape, so resolvePredictionDeepLink honours it verbatim and the app navigates. The route mounts correctly — and then the screen's data fetch 404s.

Fallback path
market ticker …-26SEP-H0 → error screen

Client-supplied path
event ticker …-26SEP → loads correctly

The API confirms the ticker distinction

Why it cannot be repaired downstream

Three plausible recovery routes were checked. None of them work.

The event ticker exists in exactly one place: the client's position.platformData.eventTicker. Any derivation that starts from the share payload is working from information that was already thrown away.

Current exposure

The live blast radius is small, but the only thing holding it closed is a truthiness check.

• The app's only prediction share builder is buildPredictionShareRequest, and it always emits kind: "existing_position" with predictions/event/<eventTicker> attached. The new_position prediction share used in this test is not something the app produces today.
• eventTicker is a required z.string() in the positions schema, so it is normally present.
• The gap: the guard is eventTicker ? `predictions/event/…` : undefined. An empty string passes schema validation, is falsy, silently drops the path, and mints a dead link — permanently, because records are immutable.

A second dead path found along the way

withDeepLinkPathFallback derives v1/predictions/<ticker> for prediction payloads. That shape is doubly useless: the resolver's PREDICTION_EVENT_PATH regex rejects it (so it is ignored in favour of the market-ticker derivation), and it does not route at all — firing phantom://v1/predictions/KXFEDDECISION-26SEP at the app leaves it on the home tab, verified live.

Recommendation

• Fail the create instead of minting a dead link. When eventTicker is missing or empty, a prediction share should not be created at all. A share that opens an error screen is worse than a share that never existed, and immutability means there is no second chance.
• Delete the prediction branch of withDeepLinkPathFallback. It advertises a safety net that cannot work, and its v1/predictions/<ticker> output routes nowhere.
• Longer term, carry the event ticker in the payload. Adding an eventTicker field alongside ticker is the only change that makes server-side derivation correct — and it would let the service stop guessing.

Record under test

{
    "shareId": "sY8xsvmkqD",
    "v": 2,
    "payload": {
        "chanceMultiplier": "1.42",
        "kind": "new_position",
        "market": "prediction",
        "outcome": "Fed maintains rate",
        "priceSeries": [
            "0.40000000",
            "0.42000000",
            "0.44000000",
            "0.46000000",
            "0.48000000",
            "0.50000000",
            "0.52000000",
            "0.54000000",
            "0.56000000",
            "0.58000000",
            "0.60000000",
            "0.62000000"
        ],
        "ticker": "KXFEDDECISION-26SEP-H0",
        "valueUsd": "50.00"
    },
    "sharer": {
        "avatarUrl": "https://api.phantom.app/image-proxy/?image=https%3A%2F%2Flh3.googleusercontent.com%2F9gT6FdrAgl-mlcrvvvsmpu4QGpwkvkUhtv92ARzHyLhS3unLQYlFJtCrNZX3MAElrcyKUYjftIA93td8B-XA0u5Fs3EreBHzFxY%3Ds250-k",
        "username": "mistystarmie"
    },
    "deepLinkPath": "predictions/event/KXFEDDECISION-26SEP-H0",
    "createdAt": "2026-08-14T16:00:46.042Z",
    "display": {
        "headerTitle": "Share Position",
        "title": "KXFEDDECISION-26SEP-H0",
        "subtitle": "Fed maintains rate",
        "badge": {
            "text": "Fed maintains rate",
            "color": "positive"
        },
        "icon": {
            "fallbackText": "K"
        },
        "headline": {
            "value": "$50.00",
            "amountUsd": "5