Auto-populate the user's BrandKit (palette / fonts / tagline / logo / wordmark / boilerplate / voice notes) from files, a URL, or pasted text. Additive by default: fills empty fields, leaves populated ones alone. Idempotent: re-running the same inputs doesn't double-write.
Overwrite rule: if the target brand kit already has an identity (a tagline/boilerplate/voice for a different brand), do not silently overwrite it. First ask the user whether to replace it. If the account supports multiple brand profiles, prefer creating a separate brand instead: pass a new `brand_id` slug plus `brand_name` rather than clobbering the existing one. Only pass `replace=true` once the user has confirmed they want this brand re-learned from the new source.
Use when the agent has brand assets in scope (a working directory with logos / press-kit / brand-guide PDFs, the user's portfolio or Substack URL, pasted boilerplate copy) and wants to populate Niche's BrandKit so future signal_scan and content generation inherit the brand context. Agent-side equivalent of the Niche web app brand-kit ingest surface, same backend engine.
Async, then poll: a URL or multi-file ingest runs in the background, so this call returns fast with {ingest_id, status:'ingesting'}. Then poll niche_brand_kit_ingest_status(ingest_id) until status is 'done'; that response carries the populated BrandKit, the ingest report (detected[] / skipped[] / errors[]), and a diff[] of changed fields. (Loop: ingest, then poll status until done/failed; same pattern as niche_signal_scan to niche_session_state.) Do not re-call ingest while one is running; a duplicate of the same inputs attaches to the in-flight job. URL ingest also fills voice primitives when the page has post-shaped text (Substack/blog/X). If a URL is slow or thin to scrape, the visual fields may land before the voice pass completes; when the report flags this, paste the page's About/homepage copy via `text=` to complete the brand voice.