Implements the Replicate API backend (FLUX schnell / FLUX dev) per ImaGen
issue #3:
- internal/backend/replicate.go — Backend adapter. Supports model
refs as "owner/name" (uses /v1/models/{owner}/{name}/predictions) and
"owner/name:hash" (uses /v1/predictions with explicit version). Polls
/v1/predictions/{id} every 500ms with model-aware timeout (60s schnell,
120s dev). Resilience: 401 names api_token_env, 429 with exp backoff
up to 3 retries (honours Retry-After), 5xx retries once, image
download retries once on transient failure.
- internal/backend/replicate_pricing.go — hardcoded per-image USD rates
for known FLUX models, snapshotted from replicate.com/pricing with a
refresh TODO.
- internal/backend/replicate_test.go — mocked-HTTP unit tests covering
happy path (model + version-pinned), 401, 429 retry policy, failed
prediction, poll timeout, image-download retry, ctx cancel, BackendOpts
passthrough, default_steps, aspect-ratio reduction, sha256 prompt hash.
- internal/usage/usage.go — Supabase REST sink + read-side query for
mai.imagen_usage. Adapter writes are best-effort: failures warn but
the image still lands.
- cmd/imagen/usage.go — `imagen usage [--since DATE] [--raw]` reads
the table and prints a tab-aligned grouped or raw table with totals.
- cmd/imagen/backends.go — instances of type=replicate now report
"ok" or "not configured (set REPLICATE_API_TOKEN)" depending on env.
- internal/config/config.go — sample adds flux-schnell-replicate +
flux-dev-replicate; default_backend stays flux-schnell-local.
- Supabase migration mai.imagen_usage (id, created_at, backend, model,
seed, prompt_hash, latency_ms, cost_usd_estimate, caller) + indexes
on (created_at DESC) and (caller). The raw prompt is never stored.
Caller identity resolves from MAI_FROM_ID, then the tmux pane's
@mai-name option, mirroring the maimcp identity logic. Prompt hash is
sha256 of the user-facing prompt; raw prompt never reaches the table.
