The server read stdio lines and remote replies without any byte bound, answered batches of any size, and command_batch kept every step result: one faulty peer or batch could allocate and work without bound. Request lines are now read in bounded chunks (16 MiB; longer lines get a -32600 reply, are skipped, and framing continues), protocol batches hold at most 64 messages, control-channel replies past 256 MiB drop the connection with the usual uncertainty error, command_batch takes at most 256 steps and keeps at most 8 MiB of step results (past that the batch stops with the reason, still closing its atomic undo group). Eight new tests cover the line/batch/step/result caps and the atomic-group close; docs/mcp.md and the command_batch tool text document them. cargo test -p vectorcraft-mcp passes.
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