CDOWN-105 · Handle transfer boundaries

Verify downloaded course bytes before exposing Open

Practice briefTaskAdvanced

A truncated transfer is marked complete because the connection closed normally. Verify length and declared digest.

Focused work estimate: 3h + prerequisites
Priority in the scenario: High
Engineering practice: Hashing · Data integrity

Estimated field mix

Storage systems60%
Mobile40%

Field percentages are editorial estimates of the ticket's engineering focus. They total 100%; they are not measured time, proficiency scores, or ownership evidence.

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Project context

Fictional learning app Birch offers synthetic text and small local media fixtures through a loopback adapter. No copyrighted course assets or network accounts are needed.

Setup prerequisites

Create small local byte fixtures and a range-response stub.
Simulate low storage, interruptions and stale manifests.

Preceding work

Complete these dependencies, or supply their agreed outputs before taking this ticket.

Acceptance criteria

Completed means both checks pass
Mismatch stays unavailable
Bad partial bytes can be removed

Implementation constraints

Digest metadata comes from the local trusted manifest.

Verification to include

Download valid fixture
Truncate or flip one byte

Deliverables

Completion verifier and corruption cases

Rollout and recovery

Disable Open for unverified content.

Value of the work

For the engineer: Practice mobile file lifecycles and background state recovery.

For the team: Inspect predictable resource usage and truthful download status.

Evidence boundaries

Outcome Evidence: Tests, patches, and runbooks are requested deliverables. They become Outcome Evidence only through a qualified Mission and immutable Evidence IDs.

Ownership Evidence: Independent adaptation must be observed under a declared verification policy and cite immutable Evidence IDs. Completing a planning ticket establishes no Ownership Evidence.