@cfxlabsinc/b2b-services
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    Variable WRITE_CHUNK_SIZEConst

    WRITE_CHUNK_SIZE: 1000

    Payload bytes per Write.

    This is not a tunable, and it is coupled to WRITE_CU in the activities. Both values were measured against a real validator rather than reasoned about, because the ceiling lives in the validator and no amount of mocking reaches it. test/programDeployBuffer.surfnet.test.ts is that measurement:

    • the conventional 1012 with the service's default compute budget encoded to 1716 bytes against a 1644 ceiling — two compute-budget instructions plus the ComputeBudget program key;
    • dropping those (see WRITE_CU) brought it to 1648, still 4 bytes over;
    • 1000 leaves ~32 bytes of headroom, which is the margin this keeps.

    Both failures would have hit on the first chunk of a real deploy, after the buffer's ~6.3 SOL of rent had already been spent. The margin is deliberate: the exact fit is 1008, and a constant sitting precisely on a limit fails the day anything in the message grows by a byte.