# noCV engineering task library Content version 5 Fictional engineering practice briefs. Starter repositories, fixtures, automated grading, and verified ownership are not included. Tests, patches, and runbooks are requested deliverables. They become Outcome Evidence only through a qualified Mission and immutable Evidence IDs. Independent adaptation must be observed under a declared verification policy and cite immutable Evidence IDs. Completing a planning ticket establishes no Ownership Evidence. ## CBLOB — Reference-aware blob retention and deletion Fictional archive Moss deduplicates generated attachments across documents within each organization. Use local files and transactional metadata stubs. **Field:** Storage systems. **Suggested stack:** TypeScript, SQLite, Filesystem adapter, Vitest. **Engineer value:** Practice reclamation races and explicit data-lifecycle guarantees. **Company value:** Inspect whether storage cleanup avoids broken references and hidden retention. **Delivery agreement:** Operate only on a dedicated local fixture directory; no user folders are targeted. ### Setup prerequisites - Generate duplicate and unique local byte fixtures. - Create synthetic document references across two organizations. ### Model blob references Separate logical use from physical bytes. #### CBLOB-101 — Separate attachment display names from blob identities **Task · Medium priority · Foundational** noCV practice brief v5 · CBLOB-101 · Reference-aware blob retention and deletion Fictional engineering practice briefs. Starter repositories, fixtures, automated grading, and verified ownership are not included. Phase: Model blob references. Depends on: No preceding ticket. Difficulty: Foundational. Estimated focused work: 60 minutes; setup and prerequisite tickets are additional. Estimated field mix: Storage systems 60% · Database engineering 40%. Field percentages are editorial estimates of the ticket's engineering focus. They total 100%; they are not measured time, proficiency scores, or ownership evidence. Renaming an attachment currently moves its physical file and breaks another reference. Store display names on references. Acceptance criteria - Rename changes only reference metadata - Blob identity stays stable - Other references keep their names Implementation constraints - Content identity cannot depend on a user-facing filename. Verification - Rename shared attachment - Fail metadata write and inspect file identity Deliverables - Reference schema and rename cases Rollout and recovery: Disable rename if it touches physical blobs. Project prerequisites: Generate duplicate and unique local byte fixtures. Create synthetic document references across two organizations. Engineer value: Practice reclamation races and explicit data-lifecycle guarantees. Company value: Inspect whether storage cleanup avoids broken references and hidden retention. AI tools are welcome during implementation. Record assumptions, review the result, and verify its behavior. Planning status does not create Outcome Evidence or Ownership Evidence. #### CBLOB-102 — Scope blob deduplication to the owning organization **Bug · High priority · Intermediate** noCV practice brief v5 · CBLOB-102 · Reference-aware blob retention and deletion Fictional engineering practice briefs. Starter repositories, fixtures, automated grading, and verified ownership are not included. Phase: Model blob references. Depends on: CBLOB-101. Difficulty: Intermediate. Estimated focused work: 120 minutes; setup and prerequisite tickets are additional. Estimated field mix: Privacy engineering 40% · Security 40% · Storage systems 20%. Field percentages are editorial estimates of the ticket's engineering focus. They total 100%; they are not measured time, proficiency scores, or ownership evidence. Equal bytes across organizations share observable lookup results. Restrict deduplication to the tenant boundary. Acceptance criteria - Same-tenant duplicates reuse safely - Foreign existence is not disclosed - All reference reads include tenant scope Implementation constraints - Digest equality is not authorization. Verification - Deduplicate own fixtures - Probe matching foreign digest Deliverables - Scoped blob lookup and denial cases Rollout and recovery: Disable deduplication if scope isolation fails. Project prerequisites: Generate duplicate and unique local byte fixtures. Create synthetic document references across two organizations. Engineer value: Practice reclamation races and explicit data-lifecycle guarantees. Company value: Inspect whether storage cleanup avoids broken references and hidden retention. AI tools are welcome during implementation. Record assumptions, review the result, and verify its behavior. Planning status does not create Outcome Evidence or Ownership Evidence. #### CBLOB-103 — Reject references to incomplete synthetic blobs **Task · High priority · Foundational** noCV practice brief v5 · CBLOB-103 · Reference-aware blob retention and deletion Fictional engineering practice briefs. Starter repositories, fixtures, automated grading, and verified ownership are not included. Phase: Model blob references. Depends on: CBLOB-101, CBLOB-102. Difficulty: Foundational. Estimated focused work: 75 minutes; setup and prerequisite tickets are additional. Estimated field mix: Storage systems 50% · Database engineering 50%. Field percentages are editorial estimates of the ticket's engineering focus. They total 100%; they are not measured time, proficiency scores, or ownership evidence. Documents can attach blobs before upload verification ends. Require available status before creating a reference. Acceptance criteria - Available blob can attach - Incomplete blob cannot attach - Denied attachment creates no reference Implementation constraints - Status check and reference insertion share a transaction boundary. Verification - Attach verified fixture - Race verification failure with attach Deliverables - Attachment admission and cases Rollout and recovery: Pause attachments when availability cannot be established. Project prerequisites: Generate duplicate and unique local byte fixtures. Create synthetic document references across two organizations. Engineer value: Practice reclamation races and explicit data-lifecycle guarantees. Company value: Inspect whether storage cleanup avoids broken references and hidden retention. AI tools are welcome during implementation. Record assumptions, review the result, and verify its behavior. Planning status does not create Outcome Evidence or Ownership Evidence. ### Guard reclamation Handle races and failures safely. #### CBLOB-104 — Tombstone unreferenced blobs before physical deletion **Story · High priority · Advanced** noCV practice brief v5 · CBLOB-104 · Reference-aware blob retention and deletion Fictional engineering practice briefs. Starter repositories, fixtures, automated grading, and verified ownership are not included. Phase: Guard reclamation. Depends on: CBLOB-103. Difficulty: Advanced. Estimated focused work: 180 minutes; setup and prerequisite tickets are additional. Estimated field mix: Storage systems 60% · Database engineering 40%. Field percentages are editorial estimates of the ticket's engineering focus. They total 100%; they are not measured time, proficiency scores, or ownership evidence. Cleanup deletes bytes immediately when count reaches zero, leaving no recoverable decision record. Add a pending-deletion state. Acceptance criteria - Zero references create tombstone - Referenced blobs remain available - Tombstone records eligibility time Implementation constraints - Tombstones describe metadata, not proof of physical erasure. Verification - Remove final reference - Remove one of two references Deliverables - Tombstone transition and cases Rollout and recovery: Pause physical deletion while retaining tombstones. Project prerequisites: Generate duplicate and unique local byte fixtures. Create synthetic document references across two organizations. Engineer value: Practice reclamation races and explicit data-lifecycle guarantees. Company value: Inspect whether storage cleanup avoids broken references and hidden retention. AI tools are welcome during implementation. Record assumptions, review the result, and verify its behavior. Planning status does not create Outcome Evidence or Ownership Evidence. #### CBLOB-105 — Prevent a new blob reference racing with reclamation **Bug · High priority · Expert** noCV practice brief v5 · CBLOB-105 · Reference-aware blob retention and deletion Fictional engineering practice briefs. Starter repositories, fixtures, automated grading, and verified ownership are not included. Phase: Guard reclamation. Depends on: CBLOB-104. Difficulty: Expert. Estimated focused work: 240 minutes; setup and prerequisite tickets are additional. Estimated field mix: Database engineering 60% · Storage systems 40%. Field percentages are editorial estimates of the ticket's engineering focus. They total 100%; they are not measured time, proficiency scores, or ownership evidence. A document attaches a blob while cleanup deletes its file. Coordinate reference admission and deletion eligibility. Acceptance criteria - New reference either cancels eligibility or fails explicitly - Deletion cannot remove newly referenced bytes - Retried admission is safe Implementation constraints - Choose and document one atomic state protocol. Verification - Attach before claim - Race attachment against deletion claim Deliverables - Reclamation protocol and interleaving tests Rollout and recovery: Disable reclamation if the mutual-exclusion invariant fails. Project prerequisites: Generate duplicate and unique local byte fixtures. Create synthetic document references across two organizations. Engineer value: Practice reclamation races and explicit data-lifecycle guarantees. Company value: Inspect whether storage cleanup avoids broken references and hidden retention. AI tools are welcome during implementation. Record assumptions, review the result, and verify its behavior. Planning status does not create Outcome Evidence or Ownership Evidence. #### CBLOB-106 — Record physical blob deletion failures without claiming completion **Task · High priority · Intermediate** noCV practice brief v5 · CBLOB-106 · Reference-aware blob retention and deletion Fictional engineering practice briefs. Starter repositories, fixtures, automated grading, and verified ownership are not included. Phase: Guard reclamation. Depends on: CBLOB-104, CBLOB-105. Difficulty: Intermediate. Estimated focused work: 135 minutes; setup and prerequisite tickets are additional. Estimated field mix: Storage systems 70% · Site reliability 30%. Field percentages are editorial estimates of the ticket's engineering focus. They total 100%; they are not measured time, proficiency scores, or ownership evidence. Permission errors are swallowed and metadata says Deleted while bytes remain. Persist retryable failure state. Acceptance criteria - Successful deletion records acknowledgement - Failure remains pending - Already absent file is idempotent success Implementation constraints - Do not log attachment contents or paths outside fixture scope. Verification - Delete fixture - Inject permission failure Deliverables - Deletion result handling and cases Rollout and recovery: Pause retries on repeated provider faults. Project prerequisites: Generate duplicate and unique local byte fixtures. Create synthetic document references across two organizations. Engineer value: Practice reclamation races and explicit data-lifecycle guarantees. Company value: Inspect whether storage cleanup avoids broken references and hidden retention. AI tools are welcome during implementation. Record assumptions, review the result, and verify its behavior. Planning status does not create Outcome Evidence or Ownership Evidence. #### CBLOB-107 — Reconcile blob metadata after a crash during deletion **Bug · High priority · Advanced** noCV practice brief v5 · CBLOB-107 · Reference-aware blob retention and deletion Fictional engineering practice briefs. Starter repositories, fixtures, automated grading, and verified ownership are not included. Phase: Guard reclamation. Depends on: CBLOB-106. Difficulty: Advanced. Estimated focused work: 180 minutes; setup and prerequisite tickets are additional. Estimated field mix: Storage systems 60% · Database engineering 40%. Field percentages are editorial estimates of the ticket's engineering focus. They total 100%; they are not measured time, proficiency scores, or ownership evidence. A process dies after file removal but before metadata commit. Recovery must distinguish absent bytes from an untouched blob. Acceptance criteria - Missing claimed blob completes metadata - Existing claimed blob retries safely - Unclaimed blob is never deleted Implementation constraints - Recovery requires durable deletion claim identity. Verification - Crash after file removal - Restart with stale unrelated claim Deliverables - Deletion reconciliation and restart cases Rollout and recovery: Stop automatic recovery if claims cannot be verified. Project prerequisites: Generate duplicate and unique local byte fixtures. Create synthetic document references across two organizations. Engineer value: Practice reclamation races and explicit data-lifecycle guarantees. Company value: Inspect whether storage cleanup avoids broken references and hidden retention. AI tools are welcome during implementation. Record assumptions, review the result, and verify its behavior. Planning status does not create Outcome Evidence or Ownership Evidence. ### Operate retention Bound scanning and verify recovery. #### CBLOB-108 — Bound blob reclamation scans by eligibility cursor **Chore · Medium priority · Intermediate** noCV practice brief v5 · CBLOB-108 · Reference-aware blob retention and deletion Fictional engineering practice briefs. Starter repositories, fixtures, automated grading, and verified ownership are not included. Phase: Operate retention. Depends on: CBLOB-107. Difficulty: Intermediate. Estimated focused work: 120 minutes; setup and prerequisite tickets are additional. Estimated field mix: Database engineering 50% · Performance engineering 30% · Storage systems 20%. Field percentages are editorial estimates of the ticket's engineering focus. They total 100%; they are not measured time, proficiency scores, or ownership evidence. The sweeper repeatedly scans the full blob table. Add indexed bounded batches without skipping concurrent tombstones. Acceptance criteria - Batch size is capped - Cursor order is stable - New eligible rows appear on a subsequent pass Implementation constraints - Document cursor reset at end of pass. Verification - Sweep multiple pages - Insert eligible row during scan Deliverables - Sweep pagination and concurrency cases Rollout and recovery: Reduce to explicit small batches while cursor logic is repaired. Project prerequisites: Generate duplicate and unique local byte fixtures. Create synthetic document references across two organizations. Engineer value: Practice reclamation races and explicit data-lifecycle guarantees. Company value: Inspect whether storage cleanup avoids broken references and hidden retention. AI tools are welcome during implementation. Record assumptions, review the result, and verify its behavior. Planning status does not create Outcome Evidence or Ownership Evidence. #### CBLOB-109 — Protect retained document versions from blob cleanup **Bug · High priority · Advanced** noCV practice brief v5 · CBLOB-109 · Reference-aware blob retention and deletion Fictional engineering practice briefs. Starter repositories, fixtures, automated grading, and verified ownership are not included. Phase: Operate retention. Depends on: CBLOB-105, CBLOB-108. Difficulty: Advanced. Estimated focused work: 180 minutes; setup and prerequisite tickets are additional. Estimated field mix: Storage systems 60% · Database engineering 40%. Field percentages are editorial estimates of the ticket's engineering focus. They total 100%; they are not measured time, proficiency scores, or ownership evidence. Cleanup counts only current document references and breaks retained versions. Include every retained reference authority. Acceptance criteria - Retained versions preserve blobs - Expired versions release references - Cross-tenant records cannot affect counts Implementation constraints - Retention policy is a fixture contract, not a legal claim. Verification - Retain old version - Expire it and inspect eligibility Deliverables - Version-aware reference accounting Rollout and recovery: Pause cleanup until all reference sources reconcile. Project prerequisites: Generate duplicate and unique local byte fixtures. Create synthetic document references across two organizations. Engineer value: Practice reclamation races and explicit data-lifecycle guarantees. Company value: Inspect whether storage cleanup avoids broken references and hidden retention. AI tools are welcome during implementation. Record assumptions, review the result, and verify its behavior. Planning status does not create Outcome Evidence or Ownership Evidence. #### CBLOB-110 — Produce a blob-reclamation report that distinguishes planned and removed bytes **Story · Medium priority · Intermediate** noCV practice brief v5 · CBLOB-110 · Reference-aware blob retention and deletion Fictional engineering practice briefs. Starter repositories, fixtures, automated grading, and verified ownership are not included. Phase: Operate retention. Depends on: CBLOB-106, CBLOB-109. Difficulty: Intermediate. Estimated focused work: 105 minutes; setup and prerequisite tickets are additional. Estimated field mix: Storage systems 60% · Site reliability 40%. Field percentages are editorial estimates of the ticket's engineering focus. They total 100%; they are not measured time, proficiency scores, or ownership evidence. Operators report savings from tombstoned bytes that still exist. Separate eligible, attempted and acknowledged removal totals. Acceptance criteria - Planned bytes are labeled - Failures remain outstanding - Only acknowledged removals count as reclaimed Implementation constraints - State measurements are local fixture observations. Verification - Sweep successful fixture batch - Fail half the deletions Deliverables - Reclamation report projection Rollout and recovery: Hide savings totals if acknowledgements cannot be reconciled. Project prerequisites: Generate duplicate and unique local byte fixtures. Create synthetic document references across two organizations. Engineer value: Practice reclamation races and explicit data-lifecycle guarantees. Company value: Inspect whether storage cleanup avoids broken references and hidden retention. AI tools are welcome during implementation. Record assumptions, review the result, and verify its behavior. Planning status does not create Outcome Evidence or Ownership Evidence.