SyncVals · Trajectory

hash-message-padder

claude-code claude-opus-4-8 ✗ failed HARNESS_ERROR ↑ View task

Solved from the instruction alone, tests/ and solution/ were withheld from the agent's workspace and restored only for grading.

Reward = tests/test.sh exit code (0 → resolved); the classification below is post-hoc and cannot change it.

Classification , post-hoc; cannot change the reward

HARNESS_ERRORInfrastructure failure, the agent never ran properly. Not a signal about agent or task.

SubtypeVerifier runtime tamper detection

Root causeThe failure was caused by the verifier/runtime integrity check, not by the task specification or by a behavioral mismatch in the agent's SystemVerilog solution. The actual randomized RefModule comparison never ran.

RecommendationN/A - infrastructure/runtime issue, not a task-specification problem

Trajectory

Tool-by-tool agent trajectory

3 tool calls · 2 tool types · 7 steps

Design a SystemVerilog module named TopModule that splits a stream of message bytes across four parallel lanes, pads each lane independently, and frames the result into 64-bit blocks, with valid/ready handshakes on both the byte input and the block output. Ports, one bit each unless noted: inputs clk, rst, start_i, byte_i [7:0], byte_valid_i, last_i, block_ready_i; outputs block_o [63:0], block_valid_o, byte_ready_o, done_o, busy_o. All five outputs are registered. rst is synchronous active high: every output clears to 0 except byte_ready_o which clears to 1. block_o is compared only while block_valid_o is high. A byte is accepted on a rising edge where byte_valid_i and byte_ready_o are both high. start_i accompanies the first accepted byte, last_i the final one. The message length is its accepted-byte count, 1 to 8191. Number the accepted bytes from zero in arrival order. Byte k belongs to lane k mod 4. Within a lane the bytes keep their arrival order and pack eight per block, big-endian, the earliest byte in block_o[63:56]. Each lane is padded on its own byte stream. Append 0x80 in the byte position immediately after that lane's last byte, fill the rest with zero, and place that lane's length in bits, which is eight times the number of bytes routed to the lane, as a 16-bit big-endian value in byte6 and byte7 of the lane's final block. Emit the fewest blocks per lane that hold the lane's bytes, the marker, the fill and the length. When a lane's byte count is a multiple of eight, its 0x80 and length occupy one additional all-padding block. When the block holding a lane's last byte has six or seven byte positions filled, the length does not share it: that block carries the bytes, 0x80 and zero fill, and a following block holds only the length. A lane with no bytes still emits one block holding 0x80, zero fill and a zero length. Index the blocks of each lane from zero. Emit all four lanes' block 0, then all four lanes' block 1, and so on; within an index emit lane 0 first through lane 3. Skip a lane at indices beyond its block count. block_valid_o is high while a block is presented and a block is accepted on a rising edge where block_valid_o and block_ready_i are both high; while it is stalled block_o and block_valid_o hold. Present one block at a time. byte_ready_o is high while bytes are accepted and low while blocks are leaving. busy_o is high from the first accepted byte until the final block is accepted, low otherwise. The final block is the highest index reached by any lane, taken in the highest-numbered lane that reaches it. done_o is high for the cycles that block is presented, so on its accepting edge block_valid_o, block_ready_i and done_o are all high. Put the implementation in /app/dut.sv with the module named TopModule and exactly this port list. It is compiled with iverilog -g2012 against a held-back reference and simulated under randomized stimulus that drives the byte side and randomly stalls the block side; the design must match the reference on every output on every clock edge for every sample. Use plain synthesizable SystemVerilog: module/endmodule, always/assign, localparam, reg, wire, logic and functions. Do not use preprocessor directives (include, define, ifdef, ifndef, undef, the token-paste operator), do not call simulator system tasks ($display, $write, $finish, $stop, $system, $fopen, $fwrite, $fdisplay, $fread, $fgets, $feof, $readmem, $writemem, $dumpfile, $dumpvars, $fatal, $exit, $error, $warning, $assert), do not use force or release, and do not import DPI-C; the verifier rejects the submission before simulation if any of these appear in /app/dut.sv.

I'll design this carefully. This is a buffer-then-emit pipeline: accept all bytes, split into 4 lanes, apply MD-style padding per lane, then emit interleaved 64-bit blocks. Let me reason through the key facts and then implement. Key derivations: - Lane L byte count: `cnt[L] = (N + 3 - L) / 4` (counts are non-increasing across lanes). - Blocks per lane: `blk[L] = (cnt[L] + 10) / 8` (= ceil((cnt+3)/8), handles the "+1 block when multiple of 8" and "length spills to next block when 6/7 filled" rules automatically). - Since counts are non-increasing, valid lanes at any index form a prefix `{0..m}`, so `maxIndex = blk[0]-1` and the final/last-emitted block is the highest lane whose `blk == blk[0]`. - A one-cycle "prep" gap after the last byte is forced by the registered output + memory-write race (block 0 can need the just-stored last byte for small N). Let me write it:

write · /app/dut.sv

module TopModule(
  input  wire        clk,
  input  wire        rst,
  input  wire        start_i,
  input  wire [7:0]  byte_i,
  input  wire        byte_valid_i,
  input  wire        last_i,
  input  wire        block_ready_i,
  output reg  [63:0] block_o,
  output reg         block_valid_o,
  output reg         byte_ready_o,
  output reg         done_o,
  output reg         busy_o
);

  localparam RECV = 1'b0;
  localparam SEND = 1'b1;

  reg        state;
  reg [12:0] wcnt;              // bytes accepted so far (0..8191)
  reg [7:0]  mem [0:8191];      // bytes stored in arrival order
  reg [12:0] cnt [0:3];         // per-lane byte count
  reg [8:0]  blk [0:3];         // per-lane block count
  reg [8:0]  maxIndex;          // highest block index reached (blk[0]-1)
  reg [1:0]  lastLane;          // highest lane reaching maxIndex
  reg [8:0]  idx;               // current block index being emitted
  reg [1:0]  lane;              // current lane being emitted

  // combinational temporaries
  reg [13:0] Ntmp;
  reg [13:0] c0,c1,c2,c3;
  reg [8:0]  b0,b1,b2,b3;
  reg [8:0]  nidx;
  reg [1:0]  nlane;

  // Compute the 64-bit block value for a given (index, lane).
  function [63:0] block_val(input [8:0] bidx, input [1:0] blane);
    reg [63:0] r;
    integer    bb;
    reg [12:0] c;
    reg [15:0] len;
    reg        is_final;
    reg [13:0] p;
    reg [15:0] addr;
    reg [7:0]  bv;
    begin
      c        = cnt[blane];
      len      = c << 3;                      // length in bits
      is_final = (bidx == (blk[blane] - 9'd1));
      r        = 64'b0;
      for (bb = 0; bb < 8; bb = bb + 1) begin
        p = bidx * 8 + bb;                    // byte position within the lane stream
        if (is_final && bb == 6)      bv = len[15:8];
        else if (is_final && bb == 7) bv = len[7:0];
        else if (p < c) begin
          addr = p * 4 + blane;               // arrival index of this lane byte
          bv   = mem[addr];
        end
        else if (p == c)              bv = 8'h80;   // padding marker
        else                          bv = 8'h00;   // zero fill
        r[(7-bb)*8 +: 8] = bv;                // byte 0 -> [63:56]
      end
      block_val = r;
    end
  endfunction

  always @(posedge clk) begin
    if (rst) begin
      byte_ready_o  <= 1'b1;
      block_valid_o <= 1'b0;
      done_o        <= 1'b0;
      busy_o        <= 1'b0;
      block_o       <= 64'b0;
      state         <= RECV;
      wcnt          <= 13'd0;
      idx           <= 9'd0;
      lane          <= 2'd0;
    end else begin
      case (state)
        RECV: begin
          if (byte_valid_i && byte_ready_o) begin
            mem[wcnt] <= byte_i;
            wcnt      <= wcnt + 13'd1;
            busy_o    <= 1'b1;
            if (last_i) begin
              // Finalize per-lane geometry from N = wcnt+1.
              Ntmp = wcnt + 13'd1;
              c0 = (Ntmp + 14'd3) >> 2;
              c1 = (Ntmp + 14'd2) >> 2;
              c2 = (Ntmp + 14'd1) >> 2;
              c3 = Ntmp >> 2;
              b0 = (c0 + 14'd10) >> 3;
              b1 = (c1 + 14'd10) >> 3;
              b2 = (c2 + 14'd10) >> 3;
              b3 = (c3 + 14'd10) >> 3;
              cnt[0] <= c0; cnt[1] <= c1; cnt[2] <= c2; cnt[3] <= c3;
              blk[0] <= b0; blk[1] <= b1; blk[2] <= b2; blk[3] <= b3;
              maxIndex <= b0 - 9'd1;
              lastLane <= (b3==b0) ? 2'd3 :
                          (b2==b0) ? 2'd2 :
                          (b1==b0) ? 2'd1 : 2'd0;
              byte_ready_o  <= 1'b0;
              block_valid_o <= 1'b0;   // one prep cycle before first block
              idx           <= 9'd0;
              lane          <= 2'd0;
              state         <= SEND;
            end
          end
        end

        SEND: begin
          if (!block_valid_o) begin
            // Present the first block (mem/cnt/blk now settled).
            block_o       <= block_val(idx, lane);
            block_valid_o <= 1'b1;
            done_o        <= (idx==maxIndex) && (lane==lastLane);
          end else if (block_ready_i) begin
            if ((idx==maxIndex) && (lane==lastLane)) begin
              // Final block accepted: return to receive.
              block_valid_o <= 1'b0;
              done_o        <= 1'b0;
              busy_o        <= 1'b0;
              byte_ready_o  <= 1'b1;
              wcnt          <= 13'd0;
              state         <= RECV;
            end else begin
              // Advance to next block in emission order.
              if (lane < 2'd3 && idx < blk[lane + 2'd1]) begin
                nidx  = idx;
                nlane = lane + 2'd1;
              end else begin
                nidx  = idx + 9'd1;
                nlane = 2'd0;
              end
              idx     <= nidx;
              lane    <= nlane;
              block_o <= block_val(nidx, nlane);
              done_o  <= (nidx==maxIndex) && (nlane==lastLane);
            end
          end
        end
      endcase
    end
  end
endmodule

Now let me verify it compiles and passes a self-checking testbench against a behavioral golden model I'll write from the spec.

Compile dut.sv for syntax check

shell

iverilog -g2012 -o /tmp/dut_syntax dut.sv 2>&1 | head -40 && echo "EXIT=$?"

output

EXIT=0

[stdout]
EXIT=0

Compiles. Now let me build a self-checking testbench with an **independent** golden model (computing the expected block sequence from arrays, not reusing DUT logic) to validate content, ordering, padding, and length across many randomized runs with byte gaps and block stalls.

write · /tmp/tb.sv

module tb;
  reg clk=0, rst=1, start_i=0, byte_valid_i=0, last_i=0, block_ready_i=0;
  reg [7:0] byte_i=0;
  wire [63:0] block_o;
  wire block_valid_o, byte_ready_o, done_o, busy_o;

  TopModule dut(.clk(clk),.rst(rst),.start_i(start_i),.byte_i(byte_i),
    .byte_valid_i(byte_valid_i),.last_i(last_i),.block_ready_i(block_ready_i),
    .block_o(block_o),.block_valid_o(block_valid_o),.byte_ready_o(byte_ready_o),
    .done_o(done_o),.busy_o(busy_o));

  always #5 clk = ~clk;

  integer errors = 0;

  // ---- independent golden model ----
  // Given a message (msg array, length N), produce expected block list.
  task automatic gen_expected(input integer msg[], input integer N,
                              output longint exp[$]);
    integer cntL[0:3];
    integer blkL[0:3];
    integer L, maxIdx, lastL, i, j, p, bpos, addr, len, cval, isf;
    longint blk;
    reg [7:0] bv;
    begin
      exp = {};
      for (L=0;L<4;L=L+1) begin
        cntL[L] = (N + 3 - L) / 4;
        blkL[L] = (cntL[L] + 10) / 8;
      end
      maxIdx = blkL[0]-1;
      lastL = (blkL[3]==blkL[0])?3:(blkL[2]==blkL[0])?2:(blkL[1]==blkL[0])?1:0;
      // emission order: index outer, lane inner, skip if idx>=blk
      for (i=0;i<=maxIdx;i=i+1) begin
        for (L=0;L<4;L=L+1) begin
          if (i < blkL[L]) begin
            cval = cntL[L];
            len = cval*8;
            isf = (i == blkL[L]-1);
            blk = 0;
            for (j=0;j<8;j=j+1) begin
              p = i*8+j;
              if (isf && j==6) bv = (len>>8) & 8'hff;
              else if (isf && j==7) bv = len & 8'hff;
              else if (p < cval) begin addr = p*4+L; bv = msg[addr]; end
              else if (p == cval) bv = 8'h80;
              else bv = 8'h00;
              blk = (blk << 8) | bv;
            end
            exp.push_back(blk);
          end
        end
      end
    end
  endtask

  integer msg[0:8191];
  longint exp[$];
  integer N, k, seed;
  longint got;
  integer collected;
  integer expDoneIdx;

  task automatic run_msg(input integer N_in);
    integer gap;
    begin
      N = N_in;
      for (k=0;k<N;k=k+1) msg[k] = $random & 8'hff;
      gen_expected(msg, N, exp);

      // drive bytes
      k = 0;
      while (k < N) begin
        // random gap: sometimes deassert valid
        gap = ($random % 3);
        if (gap==0) begin
          byte_valid_i = 0; @(posedge clk); #1;
        end else begin
          byte_valid_i = 1;
          byte_i = msg[k];
          start_i = (k==0);
          last_i  = (k==N-1);
          @(posedge clk); #1;
          if (byte_ready_o===1'b1) begin
            k = k + 1;
          end
        end
      end
      byte_valid_i = 0; start_i=0; last_i=0;

      // receive blocks with random stalls; check
      collected = 0;
      while (collected < exp.size()) begin
        block_ready_i = ($random % 2);
        @(posedge clk); #1;
        if (block_valid_o===1'b1 && block_ready_i===1'b1) begin
          got = block_o;
          if (got !== exp[collected]) begin
            errors = errors + 1;
            $display("MISMATCH N=%0d blk#%0d got=%h exp=%h", N, collected, got, exp[collected]);
          end
          // done_o must be high exactly on the last block
          if (collected == exp.size()-1) begin
            if (done_o !== 1'b1) begin errors=errors+1; $display("done low on final N=%0d",N); end
          end else begin
            if (done_o !== 1'b0) begin errors=errors+1; $display("done high early N=%0d blk%0d",N,collected); end
          end
          collected = collected + 1;
        end
      end
      block_ready_i = 0;
      // after final accept, busy should drop within a cycle
      @(posedge clk); #1;
      if (busy_o !== 1'b0) begin errors=errors+1; $display("busy stuck N=%0d",N); end
      if (byte_ready_o !== 1'b1) begin errors=errors+1; $display("ready not restored N=%0d",N); end
    end
  endtask

  integer t, rN;
  initial begin
    rst = 1; block_ready_i=0;
    @(posedge clk); @(posedge clk); #1;
    rst = 0; @(posedge clk); #1;

    // targeted small lengths (edge cases)
    for (rN=1; rN<=40; rN=rN+1) run_msg(rN);
    // multiples of 8 lane counts etc.
    run_msg(32); run_msg(64); run_msg(24); run_msg(48);
    // random larger
    for (t=0;t<60;t=t+1) begin
      rN = ($unsigned($random) % 300) + 1;
      run_msg(rN);
    end
    // a couple big ones
    run_msg(2000); run_msg(8191); run_msg(4096);

    if (errors==0) $display("ALL TESTS PASSED");
    else $display("TOTAL ERRORS=%0d", errors);
    $finish;
  end
endmodule

Final diff , what the agent changed

No file changes, the agent left the workspace untouched.

Verifier output , the proof behind the reward

tests/test.sh

FAIL: tampered GRADER_HOME/runtime detected -> failing closed (score 0)

Reproduce this trial: git checkout 2f94510 && PYTHONPATH=src python3 scripts/build_site.py , then open trial/trial_a805e1636f754bb6. Re-running the agent live requires EVAL_PLATFORM_ENABLE_OAUTH_SMOKE=1 and is non-deterministic.

Trial trial_a805e1636f754bb6 · verifier authoritative; classifier explanatory.