{"schema_version":"secwatch.filing_event.v1","accession":"0001819438-26-000022","form_type":"8-K","ticker":"GWH","cik":"0001819438","company_name":"ESS Tech, Inc.","filed_at":"2026-04-15T23:59:59+00:00","discovered_at":"2026-05-14T18:02:32.993373+00:00","generated_at":"2026-05-15T06:09:11.978540+00:00","sec_items":["5.02"],"event_type":"leadership","sentiment":"neutral","materiality_score":0.25,"calibrated_materiality_score":0.25,"confidence":"high","headline":"Director Michael Niggli resigns from ESS Tech board, effective May 29, 2026","bullets":["Michael Niggli notified resignation from Board, Audit Committee, and Nominating and Corporate Governance Committee.","Resignation effective as of the date of the 2026 annual meeting of stockholders on May 29, 2026.","Resignation not due to any disagreement with the Company regarding operations, policies, or practices.","Niggli served as Founding Chairman of the Company."],"urls":{"canonical":"https://secwatch.observer/filing/0001819438-26-000022","json":"https://secwatch.observer/filing/0001819438-26-000022.json","markdown":"https://secwatch.observer/filing/0001819438-26-000022.md","text":"https://secwatch.observer/filing/0001819438-26-000022.txt","edgar_index":"https://www.sec.gov/Archives/edgar/data/1819438/000181943826000022/0001819438-26-000022-index.htm","edgar_primary_document":"https://www.sec.gov/Archives/edgar/data/1819438/000181943826000022/wk-20260410.htm"},"model":{"generated_by":"deepseek-v4-flash:cloud@v2","generated_at":"2026-05-15T06:09:11.978540+00:00"},"review":{"review_status":"machine_generated","human_reviewed":false,"corrected":false,"correction_note":null,"correction_timestamp":null,"superseded_by":null,"related_filings":[]},"source_grounded_claims":[],"license":"Source filings: public domain (SEC EDGAR). Summaries (headline + bullets): CC-BY-4.0; attribute https://secwatch.observer"}