SyncValsverifier → artifact → classifier → verdict
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.
SubtypeEnvironment Issues
Evidenceverifier/test-stdout.txt: "FAIL: tampered GRADER_HOME/runtime detected -> failing closed (score 0)" and result.json reward=0.0. tests/test.sh runs detect_tamper before copying/compiling /app/dut.sv, so the verifier never reached iverilog or the randomized reference comparison. agent/trajectory.json shows the agent created /app/dut.sv and only ran "iverilog -g2012 -o /tmp/dut_compile dut.sv"; there is no evidence it modified H2T_GRADER_HOME, H2T_REWARD_JSON_PATH, /logs/verifier ownership/modes, or grader paths.
Root causeThe trial failed because the verifier's anti-tamper preflight detected an invalid grader/runtime filesystem state before evaluating the submitted SystemVerilog. This does not reveal an underspecification or brittle behavioral test in the task itself.
RecommendationN/A - task is fine
Trajectory
Tool-by-tool agent trajectory
2 tool calls · 2 tool types · 5 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.
Looking at this problem, I need to design a store-then-emit FSM: accept bytes into a memory, then generate MD5-style padded 64-bit blocks per lane and emit them in an interleaved order with proper handshakes. Let me work through the design and write it.
write · /app/dut.sv
// TopModule: splits a message byte stream across 4 lanes, pads each lane
// independently (0x80 marker + zero fill + 16-bit big-endian bit-length in the
// last two bytes of the lane's final block), packs 8 bytes per 64-bit block
// big-endian, and emits blocks in interleaved order (all lanes' block0, then
// all lanes' block1, ...) with valid/ready handshakes on both sides.
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 [1:0] ACCEPT = 2'd0,
                     LOAD   = 2'd1,
                     EMIT   = 2'd2;

    reg [1:0]  state;
    reg [13:0] k;        // count of accepted bytes so far (also next write index)
    reg [13:0] N;        // total message length in bytes (1..8191)
    reg [1:0]  curL;     // current lane being emitted
    reg [15:0] curJ;     // current block index being emitted
    reg [15:0] maxB;     // == B(lane0), the largest per-lane block count
    reg [1:0]  tlane;    // highest lane reaching the max block index

    // byte storage indexed by arrival order
    reg [7:0]  mem [0:8191];

    // ---- number of bytes routed to lane L ----
    function automatic [13:0] lane_n(input [1:0] L);
        reg [11:0] base;
        reg [1:0]  rem;
        begin
            base   = N[13:2];   // floor(N/4)
            rem    = N[1:0];    // N mod 4
            lane_n = {2'b00, base} + ((L < rem) ? 14'd1 : 14'd0);
        end
    endfunction

    // ---- number of 64-bit blocks emitted by lane L ----
    function automatic [15:0] lane_B(input [1:0] L);
        reg [13:0] nn;
        reg [10:0] q;
        reg [2:0]  r;
        begin
            nn      = lane_n(L);
            q       = nn[13:3];        // floor(n/8)
            r       = nn[2:0];         // n mod 8
            lane_B  = {5'd0, q} + ((r <= 3'd5) ? 16'd1 : 16'd2);
        end
    endfunction

    // ---- generate the 64-bit block value for lane L, block index jj ----
    function automatic [63:0] gen_block(input [1:0] L, input [15:0] jj);
        integer    b;
        reg [13:0] nlane;
        reg [15:0] lenb;
        reg [15:0] Blane;
        reg [15:0] jf;
        reg [15:0] pos;
        reg [15:0] addr;
        reg [7:0]  bv;
        reg [63:0] blk;
        begin
            nlane = lane_n(L);
            lenb  = {nlane[12:0], 3'b000};   // 8 * n  (bit length), 16-bit
            Blane = lane_B(L);
            jf    = Blane - 16'd1;           // final block index for this lane
            blk   = 64'd0;
            for (b = 0; b < 8; b = b + 1) begin
                pos = (jj << 3) + b[15:0];
                if ((jj == jf) && (b == 6))
                    bv = lenb[15:8];
                else if ((jj == jf) && (b == 7))
                    bv = lenb[7:0];
                else if (pos < {2'b00, nlane}) begin
                    addr = (pos << 2) + {14'd0, L};   // arrival index = pos*4 + L
                    bv   = mem[addr];
                end
                else if (pos == {2'b00, nlane})
                    bv = 8'h80;
                else
                    bv = 8'h00;
                blk[(7 - b) * 8 +: 8] = bv;   // earliest byte in [63:56]
            end
            gen_block = blk;
        end
    endfunction

    always @(posedge clk) begin
        if (rst) begin
            state         <= ACCEPT;
            byte_ready_o  <= 1'b1;
            block_valid_o <= 1'b0;
            done_o        <= 1'b0;
            busy_o        <= 1'b0;
            block_o       <= 64'd0;
            k             <= 14'd0;
            N             <= 14'd0;
            curL          <= 2'd0;
            curJ          <= 16'd0;
            maxB          <= 16'd0;
            tlane         <= 2'd0;
        end else begin
            case (state)
                ACCEPT: begin
                    if (byte_valid_i && byte_ready_o) begin
                        mem[k] <= byte_i;
                        if (k == 14'd0)
                            busy_o <= 1'b1;
                        if (last_i) begin
                            N             <= k + 14'd1;
                            byte_ready_o  <= 1'b0;
                            block_valid_o <= 1'b0;
                            done_o        <= 1'b0;
                            curL          <= 2'd0;
                            curJ          <= 16'd0;
                            state         <= LOAD;
                        end else begin
                            k <= k + 14'd1;
                        end
                    end
                end

                LOAD: begin
                    // N and mem are stable this cycle; present lane0 block0.
                    maxB    <= lane_B(2'd0);
                    tlane   <= (lane_B(2'd3) == lane_B(2'd0)) ? 2'd3 :
                               (lane_B(2'd2) == lane_B(2'd0)) ? 2'd2 :
                               (lane_B(2'd1) == lane_B(2'd0)) ? 2'd1 : 2'd0;
                    block_o       <= gen_block(2'd0, 16'd0);
                    block_valid_o <= 1'b1;
                    done_o        <= 1'b0;   // first block is never the final one
                    state         <= EMIT;
                end

                EMIT: begin
                    if (block_valid_o && block_ready_i) begin
                        if ((curL < 2'd3) && (lane_B(curL + 2'd1) > curJ)) begin
                            // next lane at same block index
                            curL          <= curL + 2'd1;
                            block_o       <= gen_block(curL + 2'd1, curJ);
                            done_o        <= ((curJ == maxB - 16'd1) &&
                                              ((curL + 2'd1) == tlane));
                            block_valid_o <= 1'b1;
                        end else if ((curJ + 16'd1) < maxB) begin
                            // wrap to lane0 at next block index
                            curL          <= 2'd0;
                            curJ          <= curJ + 16'd1;
                            block_o       <= gen_block(2'd0, curJ + 16'd1);
                            done_o        <= (((curJ + 16'd1) == maxB - 16'd1) &&
                                              (2'd0 == tlane));
                            block_valid_o <= 1'b1;
                        end else begin
                            // final block just accepted
                            block_valid_o <= 1'b0;
                            done_o        <= 1'b0;
                            busy_o        <= 1'b0;
                            byte_ready_o  <= 1'b1;
                            k             <= 14'd0;
                            state         <= ACCEPT;
                        end
                    end
                    // else: stalled -> hold all outputs
                end

                default: state <= ACCEPT;
            endcase
        end
    end

endmodule
Let me verify it compiles with iverilog and run a quick self-check against my model of the spec.

Compile dut.sv with iverilog

shell
iverilog -g2012 -o /tmp/dut_compile dut.sv 2>&1 | head -40 && echo "EXIT: ${PIPESTATUS[0]}"
output
EXIT: 0

[stdout]
EXIT: 0
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_679936a4820f466e. Re-running the agent live requires EVAL_PLATFORM_ENABLE_OAUTH_SMOKE=1 and is non-deterministic.

Trial trial_679936a4820f466e · verifier authoritative; classifier explanatory.