FA-11580 / Filesystem semantics / Member archive

Seeking an append descriptor causes an overwrite · case 05

Seeking an append descriptor causes an overwrite.

Member previewVariant 5 · 3 implementations · 6 checks per implementation

Case contract

Deterministic in-memory filesystem model. Open a character file in append mode, seek to nonnegative seek, then write payload. Return [contents,new offset]; zero-length payload leaves the sought offset unchanged in this controlled model.

Why this case matters

An offline semantic experiment for file API clients; it models only the stated operations, not a complete operating system.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
seek to beginning does not overwrite	`["5bc", 1]`	`["abc5", 4]`	Failed

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This record includes three runnable implementations, regression fixtures, execution results, and source hashes.

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