Large project brochures can fail on mobile connections. A resume button is not enough: appending bytes from a changed file can silently corrupt the result. Commission a version-aware download check that distinguishes a partial continuation from a complete replacement response.
Source-bound fact
A conditional range can return 206 when its validator matches, or a full 200 response when it does not. Official reference · Checked 17 October 2026.
Filled synthetic acceptance example
Synthetic teaching example, not a client case or a real-platform assessment. On narrow screens, scroll to read the complete table.
| Input | Check basis | Expected |
|---|---|---|
| Have bytes 0–39/100 ofv1; request40–99 | 206; v1; correct range | append60 bytes |
| Same request; server nowv2 | 200 full replacement | replace, never append |
| 206 starts50 instead of 40 | range discontinuity | reject the proposed append |
Supplier acceptance procedure
- Record file identity, validator, total size and the precise retained byte count.
- Ask the supplier to demonstrate interruption, matching continuation and a file revision between attempts.
- Compare the final file checksum and open the resulting document; an HTTP status alone cannot establish a valid PDF.
Interpret the output
The finite model accepts a60-byte continuation only at the expected offset with the expected version. It models the handover rule, not an HTTP server. A full response is treated as replacement even when the user pressed resume, preventing mixed-version concatenation.
Explicit limits
Single uncompressed byte-range model only; not multipart ranges, proxies, encrypted media or production PDF validation. Existing download-permission rules still apply.
Replay the finite teaching model
Save both files in one folder and use Node22 or newer. JSON contains inputs and expected results. The script processes synthetic data only, with no network, credentials, payment or paid API calls. Passing is not evidence that a real integration passed acceptance.
Filled inputs and expectations · Inspectable teaching script
node check.mjs resumable-brochure-version-boundary.json