T001 Prepare the isolated checkout and doctor proof in target/verification/.
T002 Complete spec, clarified assumptions, plan, and contract in specs/057-idempotent-task-reports/.

US1: Recover the acknowledgment

T003 [US1] Add a failing identical-report core regression in crates/signaltty-core/src/model.rs.
T004 [US1] Return whether a report mutates the task in crates/signaltty-core/src/model.rs, excluding acceptance time from content matching.
T005 [US1] Add failing reconnect/event IPC regression in crates/signaltty-server/tests/orchestrator_tasks.rs.
T006 [US1] Suppress duplicate paired events and persistence requests in crates/signaltty-server/src/store.rs and crates/signaltty-server/src/tasks.rs.
T007 [US1] Verify concurrent identical reports and saved-result retries in crates/signaltty-server/tests/orchestrator_tasks.rs.

US2: Preserve the outcome

T008 [US2] Verify each content mismatch and terminal tasks without results in crates/signaltty-core/src/model.rs and crates/signaltty-server/tests/orchestrator_tasks.rs. Retain limits: summary 1 byte … 8 KiB; at most 32 artifacts.
T009 [US2] Record immutable retry semantics in docs/02-data-model.md, docs/08-ipc.md, and docs/adr/0035-idempotent-task-reports.md.

Delivery

T010 Run the full gate and record actual proof and limits in specs/057-idempotent-task-reports/verification.md.
T011 Review Standards and Spec, then final Gemini 3.8 Flash High on Antigravity; record findings and responses in specs/057-idempotent-task-reports/verification.md.
T012 Commit and open a linked PR; update specs/057-idempotent-task-reports/handoff.md.

Dependencies: T001 → T002 → T003 → T004 → T005 → T006 → T007 → T008 → T009 → T010 → T011 → T012. US1 is the MVP; US2 locks down refusals before delivery. Tests precede each implementation slice. Documentation and read-only review can run independently after implementation; source edits have one owner.