eduos-board-update-partial-write-header-json-spacing

Answer

Solution written to /workspace/solution.md.

Root cause: board-update-exec-tick.py persists the appended task/events before patching the header. The keeper's patch_field hard-coded a spaced fragment ("last_tick": "t100"), so on compact board.jsonl ("last_tick":"t100") it found 0 matches, asserted, and died after the append — leaving a partial write.

Fix: rebuild the search fragment with json.dumps, try both "k": "v" and "k":"v", require exactly one match, then replace. This also fixes escaping for values containing quotes.

def patch_field(text, key, old_value, new_value):
    jkey, jold, jnew = json.dumps(key), json.dumps(old_value), json.dumps(new_value)
    candidates = [f"{jkey}: {jold}", f"{jkey}:{jold}"]  # spaced, compact
    hits = []
    for cand in candidates:
        start = 0
        while (i := text.find(cand, start)) != -1:
            hits.append((i, len(cand))); start = i + len(cand)
    if len(hits) != 1:
        raise AssertionError(f"expected exactly one fragment for {key!r}, found {len(hits)}")
    i, n = hits[0]
    return text[:i] + f"{jkey}: {jnew}" + text[i + n:]

Recovery: confirm the diff is exactly one task row + two events, then git checkout HEAD -- board.jsonl (explicit paths; never git checkout ./reset --hard), apply the keeper fix, and rerun the updater.

Verified end-to-end in /tmp/repro: the buggy keeper reproduces found 0 after append; the fixed keeper accepts compact and spaced headers, rejects 0/>1 matches, escapes values via json.dumps, and a single rerun yields T1 complete, sequential event ids [1,2,3,4], header t101/def456, test-state 7→8, and git diff --check clean.