SyncValsverifier → artifact → classifier → verdict
SyncVals · Trajectory

dualmaster-membridge

claude-code claude-opus-4-8 ✓ resolved GOOD_SUCCESS ↑ 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
GOOD_SUCCESSLegitimate solve, implements the asked-for behavior; tests verify real functionality.
SubtypeLegitimate Solution
EvidenceInstruction specifies the exact bridge timing and arbitration: m_req_o/m_addr_o during E+1, m_data_i valid E+3, winner ack/data during E+4, and E+5 back-to-back fairness. The agent wrote /app/dut.sv with an IDLE/BUSY1..BUSY4 FSM, registered requests, and just_finished/last_win arbitration. Verifier output: TEST dut_forbidden: PASS, TEST dut_compiles: PASS, TEST simulation_completed: PASS (Mismatches: 0 in 3839 samples), TEST reference_equivalence: PASS (all 3839 samples matched reference). Trajectory shows only Write /app/dut.sv and a local compile command, with no evidence of reading hidden tests or solution files.
Root causeThe agent correctly inferred and implemented the specified registered timing and alternating arbitration behavior. The tests check behavioral equivalence against a reference over varied request patterns, so the pass reflects a real solution rather than test gaming.
RecommendationN/A - task is fine
Trajectory
Tool-by-tool agent trajectory
2 tool calls · 2 tool types · 6 steps
A bridge shares one read-only memory port between requesters A and B, keeping neither starved. Ports: clk, rst, a_req_i, a_addr_i (8), a_ack_o, a_data_o (16), b_req_i, b_addr_i (8), b_ack_o, b_data_o (16), m_req_o, m_addr_o (8), m_data_i (16). rst is synchronous active high, clearing all state and outputs to 0. All outputs are registered. A requester holds req and addr stable through the cycle after its ack. The bridge samples on the idle edge after a request first appears, calling that edge E; a freshly-arriving request is registered one idle cycle before it is sampled as E. One request finishes before the next is sampled. m_req_o and m_addr_o carry the chosen command during E+1 only. m_data_i is valid during E+3. The winner's ack and word are high during E+4 only, the other ack 0. E+4 is the last occupied cycle; the bridge is idle again at E+5, never earlier or later. A sample after a fully idle stretch favours A when both ask. The sample at E+5 directly after an operation instead takes the requester that did not just win if it asks, else the one that did; a later idle stretch resets this, so the next cold sample favours A again. edge E E+1 E+3 E+4 E+5 E+6 m_req_o 0 1 0 0 0 1 a_ack_o 0 0 0 1 0 0 a_data_o and b_data_o matter only while the matching ack is high. Write module TopModule to /app/dut.sv. Plain ASCII synthesizable SystemVerilog only: no define, include, ifdef, system tasks, force, release, bind.
I'll analyze the timing spec carefully, then write the module. Let me work through the timing model: - A request appearing at cycle T is registered (1-cycle delay), sampled at the idle cycle **E = T+1**. - Decision at edge E→E+1 drives `m_req_o`/`m_addr_o` during **E+1** only. - `m_data_i` is valid during **E+3**, captured at edge E+3→E+4. - Winner's `ack`/`data` high during **E+4** only; idle again at **E+5** (which is itself the next sample edge for back-to-back). - Arbitration: cold sample favors A; the sample at E+5 favors the requester that did *not* just win (else the one that did); an idle stretch resets to cold.
write · /app/dut.sv
module TopModule (
    input  logic        clk,
    input  logic        rst,
    input  logic        a_req_i,
    input  logic [7:0]  a_addr_i,
    output logic        a_ack_o,
    output logic [15:0] a_data_o,
    input  logic        b_req_i,
    input  logic [7:0]  b_addr_i,
    output logic        b_ack_o,
    output logic [15:0] b_data_o,
    output logic        m_req_o,
    output logic [7:0]  m_addr_o,
    input  logic [15:0] m_data_i
);

    // Busy-phase states (E+1 .. E+4)
    localparam logic [2:0] IDLE  = 3'd0,
                           BUSY1 = 3'd1,  // E+1: command driven
                           BUSY2 = 3'd2,  // E+2
                           BUSY3 = 3'd3,  // E+3: m_data_i valid
                           BUSY4 = 3'd4;   // E+4: ack + data

    logic [2:0] state;
    logic       win;           // current op winner: 0 = A, 1 = B
    logic       last_win;      // winner of previous op
    logic       just_finished; // this idle sample directly follows an op (E+5)

    // Registered requests / addresses (one-cycle registration before sampling)
    logic        a_req_r, b_req_r;
    logic [7:0]  a_addr_r, b_addr_r;

    // Combinational arbitration, consumed only while IDLE
    logic launch;
    logic sel;

    always_comb begin
        launch = 1'b0;
        sel    = 1'b0;
        if (just_finished) begin
            // sample directly after an operation: prefer the one that did not just win
            if (last_win == 1'b0) begin
                // A just won -> prefer B
                if (b_req_r)      begin launch = 1'b1; sel = 1'b1; end
                else if (a_req_r) begin launch = 1'b1; sel = 1'b0; end
            end else begin
                // B just won -> prefer A
                if (a_req_r)      begin launch = 1'b1; sel = 1'b0; end
                else if (b_req_r) begin launch = 1'b1; sel = 1'b1; end
            end
        end else begin
            // cold sample after an idle stretch: prefer A
            if (a_req_r)      begin launch = 1'b1; sel = 1'b0; end
            else if (b_req_r) begin launch = 1'b1; sel = 1'b1; end
        end
    end

    always_ff @(posedge clk) begin
        if (rst) begin
            state         <= IDLE;
            win           <= 1'b0;
            last_win      <= 1'b0;
            just_finished <= 1'b0;
            a_req_r       <= 1'b0;
            b_req_r       <= 1'b0;
            a_addr_r      <= 8'd0;
            b_addr_r      <= 8'd0;
            a_ack_o       <= 1'b0;
            b_ack_o       <= 1'b0;
            a_data_o      <= 16'd0;
            b_data_o      <= 16'd0;
            m_req_o       <= 1'b0;
            m_addr_o      <= 8'd0;
        end else begin
            // register requests/addresses every cycle
            a_req_r  <= a_req_i;
            b_req_r  <= b_req_i;
            a_addr_r <= a_addr_i;
            b_addr_r <= b_addr_i;

            // default output values
            a_ack_o  <= 1'b0;
            b_ack_o  <= 1'b0;
            m_req_o  <= 1'b0;
            m_addr_o <= 8'd0;

            case (state)
                IDLE: begin
                    if (launch) begin
                        state         <= BUSY1;
                        win           <= sel;
                        m_req_o       <= 1'b1;
                        m_addr_o      <= (sel == 1'b0) ? a_addr_r : b_addr_r;
                        just_finished <= 1'b0;
                    end else begin
                        state         <= IDLE;
                        just_finished <= 1'b0; // idle stretch resets fairness -> next is cold
                    end
                end

                BUSY1: state <= BUSY2;   // E+2

                BUSY2: state <= BUSY3;   // E+3 (m_data_i valid this cycle)

                BUSY3: begin             // capture data, raise ack for E+4
                    state <= BUSY4;
                    if (win == 1'b0) begin
                        a_ack_o  <= 1'b1;
                        a_data_o <= m_data_i;
                    end else begin
                        b_ack_o  <= 1'b1;
                        b_data_o <= m_data_i;
                    end
                end

                BUSY4: begin             // E+4 done -> idle at E+5
                    state         <= IDLE;
                    last_win      <= win;
                    just_finished <= 1'b1;
                    a_data_o      <= 16'd0;
                    b_data_o      <= 16'd0;
                end

                default: state <= IDLE;
            endcase
        end
    end

endmodule
Let me verify it compiles cleanly if a simulator is available.

Lint/compile the SystemVerilog module

shell
(command -v verilator >/dev/null && verilator --lint-only -Wall -Wno-DECLFILENAME dut.sv 2>&1 | head -40 || echo "verilator not found"); (command -v iverilog >/dev/null && iverilog -g2012 -o /tmp/dut.out dut.sv && echo "iverilog OK" || echo "iverilog not found or failed")
output
verilator not found
iverilog OK

[stdout]
verilator not found
iverilog OK
The module compiles cleanly (`iverilog -g2012 OK`). I wrote `/app/dut.sv` implementing the shared read-only memory bridge. Key design decisions matched to the spec: **Pipeline timing** , a small FSM (`IDLE → BUSY1..BUSY4 → IDLE`): - Requests are registered every cycle (`*_req_r`, `*_addr_r`), giving the "registered one idle cycle before it is sampled as E" behavior, so a request first seen at cycle T is sampled at **E = T+1**. - Launch decision at edge E→E+1 drives `m_req_o=1` and `m_addr_o` during **E+1 only**. - `m_data_i` (valid during **E+3**) is captured at the E+3→E+4 edge; the winner's `ack` and `data_o` are asserted during **E+4 only**, the loser's ack stays 0. - State returns to `IDLE` at **E+5**, which is itself the next sample edge , enabling the back-to-back `m_req_o=1` shown at E+6. **Arbitration** (`always_comb`, consumed only in `IDLE`): - `just_finished=0` (cold, after an idle stretch): prefer **A**. - `just_finished=1` (the E+5 sample right after an op): prefer the requester that did **not** just win (`last_win`), else the one that did. - Failing to launch during an idle cycle clears `just_finished`, so a later cold sample favors A again. **Reset**: synchronous, active-high, clears all state and registered outputs to 0. All outputs are registered; only ASCII synthesizable constructs used (no `define`/`include`/`ifdef`/system tasks/`force`/`release`/`bind`). Traced against the given waveform (`m_req_o`: 0,1,0,0,0,1 and `a_ack_o`: 0,0,0,1,0,0 across E…E+6) , it matches.
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
TEST dut_present: PASS (/app/dut.sv exists)
TEST dut_forbidden: PASS (no forbidden constructs)
TEST dut_compiles: PASS (compiled with held-back reference/testbench)
TEST simulation_completed: PASS (Mismatches: 0 in 3839 samples)
TEST reference_equivalence: PASS (all 3839 samples matched reference)
{"score": 1.000000, "results_file": "/tmp/h2t-grader-home.OXcB1I/runtime/cb_verifier_306-2748-29053-30772_306/results.jsonl"}

Reproduce this trial: git checkout 2f94510 && PYTHONPATH=src python3 scripts/build_site.py , then open trial/trial_b8a2eccb27cc4451. Re-running the agent live requires EVAL_PLATFORM_ENABLE_OAUTH_SMOKE=1 and is non-deterministic.

Trial trial_b8a2eccb27cc4451 · verifier authoritative; classifier explanatory.