The Launch HTTP API

Every SDK speaks this API; if we do not ship an SDK for your language, these four endpoints are the whole integration. Base URL is https://api.e-volv.io/api/public/v1/flags. Every request carries Authorization: Bearer <key>; server keys send no Origin or x-evolve-app-id, client keys must send one of them. The normative contract is the Launch SDK contract.

GET /bootstrap?v=2 — server ruleset

Returns the environment’s full ruleset for server keys, with ETag. Repeat requests send If-None-Match and get an empty 304 when nothing changed. The SDK declares v=2, the ruleset shape version it understands.

curl -s "https://api.e-volv.io/api/public/v1/flags/bootstrap?v=2" \
  -H "Authorization: Bearer $EVOLVE_SERVER_KEY" \
  -H 'If-None-Match: "3f2a…"'

GET /bootstrap?context=… — client values

For client keys, returns evaluated values for one context — { flagKey: { value, variant, reason } } for every flag marked client-side available. The context is URL-encoded compact JSON of at most 4,096 characters; a larger or malformed context is read as {}. A flag absent from the response evaluates to the caller’s default with reason FLAG_NOT_FOUND. No rules are ever included.

const context = encodeURIComponent(
  JSON.stringify({ targetingKey: user.id, plan: user.plan })
);
const res = await fetch(
  `https://api.e-volv.io/api/public/v1/flags/bootstrap?context=${context}`,
  {
    headers: { Authorization: `Bearer ${EVOLVE_CLIENT_KEY}` },
  }
);
const { flags } = await res.json(); // { "checkout.new": { value: true, variant: "on", reason: "RULE:0" } }

GET /stream — server change notifications

A server-sent events stream for server SDKs. Events:

429 with Retry-After means the workspace is at its streaming cap: switch to polling and retry the stream afterwards. Client SDKs do not stream — they poll and re-fetch on focus.

POST /exposures

Records that subjects saw flags, for analytics and rollups. Batches of at most 1,000 exposures; always answered 202 — accepted: 0 means dropped (allowance or storage), which is not an error. Retries are idempotent on (ts, id). Each exposure carries:

curl -X POST "https://api.e-volv.io/api/public/v1/flags/exposures" \
  -H "Authorization: Bearer $EVOLVE_SERVER_KEY" \
  -H "Content-Type: application/json" \
  -d '{"exposures":[{"id":"9f1c…","ts":"2026-09-13T15:00:00.000Z","flagKey":"checkout.new","variant":"on","reason":"RULE:0","subject":"u_1","contextKind":"user"}]}'
# 202 { "accepted": 1 }

GET /ping

The install check behind flags.verify(), never a hot path:

curl -s "https://api.e-volv.io/api/public/v1/flags/ping" -H "Authorization: Bearer $EVOLVE_SERVER_KEY"
# 200 { "environment": "production", "keyKind": "server", "flags": 4, "etag": "…" }

Status codes

Next: SDKs by platform or back to Launch concepts.