SyncValsverifier → artifact → classifier → verdict
SyncVals · Trajectory

open-drain-command-engine

codex gpt-5.5 ✓ 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
EvidenceTest output shows: 'MISMATCH_COUNTS cmd_ack=0 busy=0 al=0 bit_out=0 scl=0 sda=0' and 'mismatches=0 samples=2351'. Agent's implementation defines TopModule with required port list, instantiates I2CBitCommandController submodule, implements full FSM with 16 states covering start (cmd=0), stop (cmd=1), write (cmd=2), and read (cmd=3) commands with phased timing: setup → release SCL → wait for high → done. All outputs registered, reset synchronous active-high, `al` sticky arbitration flag asserts on start/write-1 when SDA observed low during high SCL. Compilation: iverilog -g2012 -s TopModule passed with exit code 0.
Root causeAgent correctly parsed complex timing-sensitive I2C protocol specification and implemented a well-structured FSM controller with explicit phase separation to avoid simultaneous input sampling and line-drive changes on the same clock edge, meeting all stated timing invariants.
RecommendationN/A - task is fine
Trajectory
Tool-by-tool agent trajectory
10 tool calls · 2 tool types · 20 steps
<permissions instructions> Filesystem sandboxing defines which files can be read or written. `sandbox_mode` is `danger-full-access`: No filesystem sandboxing - all commands are permitted. Network access is enabled. Approval policy is currently never. Do not provide the `sandbox_permissions` for any reason, commands will be rejected. </permissions instructions><apps_instructions> ## Apps (Connectors) Apps (Connectors) can be explicitly triggered in user messages in the format `[$app-name](app://{connector_id})`. Apps can also be implicitly triggered as long as the context suggests usage of available apps. An app is equivalent to a set of MCP tools within the `codex_apps` MCP. An installed app's MCP tools are either provided to you already, or can be lazy-loaded through the `tool_search` tool. If `tool_search` is available, the apps that are searchable by `tools_search` will be listed by it. Do not additionally call list_mcp_resources or list_mcp_resource_templates for apps. </apps_instructions><skills_instructions> ## Skills A skill is a set of instructions provided through a `SKILL.md` source. Below is the list of skills that can be used. Each entry includes a name, description, and source locator. `file` locators are on the host filesystem, `environment resource` locators are owned by an execution environment, `orchestrator resource` locators are opaque non-filesystem resources, and `custom resource` locators use their provider's access mechanism. ### Available skills - imagegen: Generate or edit raster images when the task benefits from AI-created bitmap visuals such as photos, illustrations, textures, sprites, mockups, or transparent-background cutouts. Use when Codex should create a brand-new image, transform an existing image, or derive visual variants from references, and the output should be a bitmap asset rather than repo-native code or vector. Do not use when the task is better handled by editing existing SVG/vector/code-native assets, extending an established icon or logo system, or building the visual directly in HTML/CSS/canvas. (file: /tmp/codex-home/skills/.system/imagegen/SKILL.md) - openai-docs: Use when the user asks how to build with OpenAI products or APIs, asks about Codex itself or choosing Codex surfaces, needs up-to-date official documentation with citations, help choosing the latest model for a use case, or model upgrade and prompt-upgrade guidance; use OpenAI docs MCP tools for non-Codex docs questions, use the Codex manual helper first for broad Codex self-knowledge, and restrict fallback browsing to official OpenAI domains. (file: /tmp/codex-home/skills/.system/openai-docs/SKILL.md) - plugin-creator: Create and scaffold plugin directories for Codex with a required `.codex-plugin/plugin.json`, optional plugin folders/files, valid manifest defaults, and personal-marketplace entries by default. Use when Codex needs to create a new personal plugin, add optional plugin structure, generate or update marketplace entries for plugin ordering and availability metadata, or update an existing local plugin during development with the CLI-driven cachebuster and reinstall flow. (file: /tmp/codex-home/skills/.system/plugin-creator/SKILL.md) - skill-creator: Guide for creating effective skills. This skill should be used when users want to create a new skill (or update an existing skill) that extends Codex's capabilities with specialized knowledge, workflows, or tool integrations. (file: /tmp/codex-home/skills/.system/skill-creator/SKILL.md) - skill-installer: Install Codex skills into $CODEX_HOME/skills from a curated list or a [code-host] repo path. Use when a user asks to list installable skills, install a curated skill, or install a skill from another repo (including private repos). (file: /tmp/codex-home/skills/.system/skill-installer/SKILL.md) ### How to use skills - Discovery: The list above is the skills available in this session (name + description + source locator). `file` entries live on the host filesystem, `environment resource` entries are owned by their execution environment, `orchestrator resource` entries must be accessed through `skills.list` and `skills.read`, and `custom resource` entries use their provider's access mechanism. - Trigger rules: If the user names a skill (with `$SkillName` or plain text) OR the task clearly matches a skill's description shown above, you must use that skill for that turn. Multiple mentions mean use them all. Do not carry skills across turns unless re-mentioned. - Missing/blocked: If a named skill isn't in the list or its source can't be read, say so briefly and continue with the best fallback. - How to use a skill (progressive disclosure): 1) After deciding to use a skill, the main agent must read its `SKILL.md` completely before taking task actions. For a `file` entry, open the listed path. For an `environment resource`, use the filesystem of the owning environment. For an `orchestrator resource`, call `skills.list` with `{"authority":{"kind":"orchestrator"}}`, select the matching package, and pass its `main_resource` to `skills.read`. If a read is truncated or paginated, continue until EOF. 2) When `SKILL.md` references another resource, use the same access mechanism. Resolve relative paths against a filesystem-backed skill directory. For orchestrator skills, pass the exact referenced resource identifier with the same authority and package to `skills.read`; do not treat `skill://` identifiers as filesystem paths. 3) If `SKILL.md` points to extra folders such as `references/`, use its routing instructions to identify the resources required for the task. The main agent must read each required instruction or reference file itself before acting on it. Do not delegate reading, summarizing, or interpreting skill instructions to a subagent. Subagents may still perform task work when the selected skill allows it. 4) For filesystem-backed skills, prefer running or patching provided scripts instead of retyping large code blocks. For orchestrator skills, use `skills.read` and the available tools; do not invent a local path. 5) Reuse provided assets or templates through the same source access mechanism instead of recreating them. - Coordination and sequencing: - If multiple skills apply, choose the minimal set that covers the request and state the order you'll use them. - Announce which skill(s) you're using and why (one short line). If you skip an obvious skill, say why. - Context hygiene: - Progressive disclosure applies to selecting relevant files, not partially reading a selected instruction file. Do not load unrelated references, scripts, or assets. - Avoid deep reference-chasing: prefer opening only files directly linked from `SKILL.md` unless you're blocked. - When variants exist (frameworks, providers, domains), pick only the relevant reference file(s) and note that choice. - Safety and fallback: If a skill can't be applied cleanly (missing files, unclear instructions), state the issue, pick the next-best approach, and continue. </skills_instructions>
<environment_context> <cwd>/app</cwd> <shell>bash</shell> <current_date>2026-06-20</current_date> <timezone>Etc/UTC</timezone> <filesystem><workspace_roots><root>/app</root></workspace_roots><permission_profile type="disabled"><file_system type="unrestricted" /></permission_profile></filesystem> </environment_context>
Implement `/app/dut.sv`. Define `TopModule` with this port list: `input clk, rst, cmd_valid, bit_in, scl_i, sda_i; input [1:0] cmd; output cmd_ack, busy, al, bit_out, scl_drive_low, sda_drive_low;`. Define another module and instantiate it from `TopModule`. `rst` is synchronous active high and clears outputs to 0. All outputs are registered. `cmd_ack` is a one-cycle completion pulse. Accept a command only when none is active; `cmd=0` may be accepted while idle or busy, and other commands only while `busy` is high. Illegal commands leave outputs unchanged and do not acknowledge. The line controls are open-drain: 1 pulls low, 0 releases. The command-accept edge only loads the first registered phase; it must not also consume `scl_i` or sample `sda_i` for phase completion. Because every output is registered, when a later phase says "until `scl_i` is high", the clock edge that observes high only records that fact; the next visible line-drive/ack phase appears on the following clock. Command acceptance itself is a visible registered phase: for stop, write, and read, the line-drive values loaded on the accept edge must be held through one additional full clocked setup cycle before the SCL-release phase begins. `cmd=0` starts or restarts ownership: release both lines on accept, then in following clocked wait phase keep both released until `scl_i` is high, keep SCL released while pulling SDA low for one full cycle, then pull SCL low and pulse `cmd_ack`; `busy` is set from the accept edge. `cmd=1` stops: drive both low on accept, keep both low for the following setup cycle, release SCL until `scl_i` is high, then release SDA, clear `busy`, and pulse `cmd_ack` on the following clock. `cmd=2` writes `bit_in`: on accept drive SCL low and drive SDA low for 0 or released for 1, keep those drive values for the following setup cycle, release SCL until `scl_i` is high, then pull SCL low and acknowledge on the following clock. `cmd=3` reads: on accept drive SCL low and release SDA, keep those drive values for the following setup cycle, release SCL until `scl_i` is high, sample `sda_i` on that high-SCL edge into `bit_out`, then pull SCL low and acknowledge on the following clock. `al` is sticky until reset and asserts only during start or write-1 high-SCL phases when released SDA is observed low.
I’ll inspect the workspace first so the implementation matches the expected file shape and any existing test harness.
shell
pwd && rg --files -g '!*node_modules*' -g '!*.vcd'
output
Chunk ID: 11b2ee
Wall time: 0.0000 seconds
Process exited with code 1
Original token count: 2
Output:
/app
shell
git status --short
output
Chunk ID: e4fee9
Wall time: 0.0000 seconds
Process exited with code 127
Original token count: 11
Output:
/bin/bash: line 1: git: command not found
The container is very small: `git` is not installed, and `rg --files` did not report any files. I’ll list the directory directly and then create the DUT if it is missing.
shell
ls -la
output
Chunk ID: 6b6cd0
Wall time: 0.0000 seconds
Process exited with code 0
Original token count: 24
Output:
total 8
drwxr-xr-x 2 root root 4096 Jun 19 22:02 .
drwxr-xr-x 1 root root 4096 Jun 20 16:48 ..
shell
find /app -maxdepth 3 -type f -print
output
Chunk ID: 5923d6
Wall time: 0.0000 seconds
Process exited with code 0
Original token count: 0
Output:
I’ve got an empty workspace, so I’m implementing `dut.sv` from the timing contract itself. The main design choice is to make the SCL-high wait phases explicitly registered so the edge that sees `scl_i=1` does not also change the line drives or acknowledge.
I’m going to add a small controller module and keep `TopModule` as a wrapper, as requested. The controller will store the write bit at accept time and split setup/release/wait/done phases so input sampling never happens on the same edge that makes a new line-drive phase visible.
apply_patch
*** Begin Patch
*** Add File: /app/dut.sv
+module TopModule(
+    input clk, rst, cmd_valid, bit_in, scl_i, sda_i,
+    input [1:0] cmd,
+    output cmd_ack, busy, al, bit_out, scl_drive_low, sda_drive_low
+);
+    I2CBitCommandController controller (
+        .clk(clk),
+        .rst(rst),
+        .cmd_valid(cmd_valid),
+        .bit_in(bit_in),
+        .scl_i(scl_i),
+        .sda_i(sda_i),
+        .cmd(cmd),
+        .cmd_ack(cmd_ack),
+        .busy(busy),
+        .al(al),
+        .bit_out(bit_out),
+        .scl_drive_low(scl_drive_low),
+        .sda_drive_low(sda_drive_low)
+    );
+endmodule
+
+module I2CBitCommandController(
+    input logic clk,
+    input logic rst,
+    input logic cmd_valid,
+    input logic bit_in,
+    input logic scl_i,
+    input logic sda_i,
+    input logic [1:0] cmd,
+    output logic cmd_ack,
+    output logic busy,
+    output logic al,
+    output logic bit_out,
+    output logic scl_drive_low,
+    output logic sda_drive_low
+);
+    typedef enum logic [3:0] {
+        ST_IDLE,
+        ST_START_WAIT_HIGH,
+        ST_START_SDA_LOW,
+        ST_START_DONE,
+        ST_STOP_SETUP,
+        ST_STOP_RELEASE_SCL,
+        ST_STOP_WAIT_HIGH,
+        ST_STOP_DONE,
+        ST_WRITE_SETUP,
+        ST_WRITE_RELEASE_SCL,
+        ST_WRITE_WAIT_HIGH,
+        ST_WRITE_DONE,
+        ST_READ_SETUP,
+        ST_READ_RELEASE_SCL,
+        ST_READ_WAIT_HIGH,
+        ST_READ_DONE
+    } state_t;
+
+    state_t state;
+    logic write_bit;
+
+    always_ff @(posedge clk) begin
+        if (rst) begin
+            state <= ST_IDLE;
+            write_bit <= 1'b0;
+            cmd_ack <= 1'b0;
+            busy <= 1'b0;
+            al <= 1'b0;
+            bit_out <= 1'b0;
+            scl_drive_low <= 1'b0;
+            sda_drive_low <= 1'b0;
+        end else begin
+            case (state)
+                ST_IDLE: begin
+                    cmd_ack <= 1'b0;
+
+                    if (cmd_valid && (cmd == 2'd0)) begin
+                        busy <= 1'b1;
+                        scl_drive_low <= 1'b0;
+                        sda_drive_low <= 1'b0;
+                        state <= ST_START_WAIT_HIGH;
+                    end else if (cmd_valid && busy && (cmd == 2'd1)) begin
+                        scl_drive_low <= 1'b1;
+                        sda_drive_low <= 1'b1;
+                        state <= ST_STOP_SETUP;
+                    end else if (cmd_valid && busy && (cmd == 2'd2)) begin
+                        write_bit <= bit_in;
+                        scl_drive_low <= 1'b1;
+                        sda_drive_low <= ~bit_in;
+                        state <= ST_WRITE_SETUP;
+                    end else if (cmd_valid && busy && (cmd == 2'd3)) begin
+                        scl_drive_low <= 1'b1;
+                        sda_drive_low <= 1'b0;
+                        state <= ST_READ_SETUP;
+                    end
+                end
+
+                ST_START_WAIT_HIGH: begin
+                    cmd_ack <= 1'b0;
+                    scl_drive_low <= 1'b0;
+                    sda_drive_low <= 1'b0;
+
+                    if (scl_i) begin
+                        if (!sda_i) begin
+                            al <= 1'b1;
+                        end
+                        state <= ST_START_SDA_LOW;
+                    end
+                end
+
+                ST_START_SDA_LOW: begin
+                    cmd_ack <= 1'b0;
+                    scl_drive_low <= 1'b0;
+                    sda_drive_low <= 1'b1;
+                    state <= ST_START_DONE;
+                end
+
+                ST_START_DONE: begin
+                    cmd_ack <= 1'b1;
+                    scl_drive_low <= 1'b1;
+                    sda_drive_low <= 1'b1;
+                    state <= ST_IDLE;
+                end
+
+                ST_STOP_SETUP: begin
+                    cmd_ack <= 1'b0;
+                    scl_drive_low <= 1'b1;
+                    sda_drive_low <= 1'b1;
+                    state <= ST_STOP_RELEASE_SCL;
+                end
+
+                ST_STOP_RELEASE_SCL: begin
+                    cmd_ack <= 1'b0;
+                    scl_drive_low <= 1'b0;
+                    sda_drive_low <= 1'b1;
+                    state <= ST_STOP_WAIT_HIGH;
+                end
+
+                ST_STOP_WAIT_HIGH: begin
+                    cmd_ack <= 1'b0;
+                    scl_drive_low <= 1'b0;
+                    sda_drive_low <= 1'b1;
+
+                    if (scl_i) begin
+                        state <= ST_STOP_DONE;
+                    end
+                end
+
+                ST_STOP_DONE: begin
+                    cmd_ack <= 1'b1;
+                    busy <= 1'b0;
+                    scl_drive_low <= 1'b0;
+                    sda_drive_low <= 1'b0;
+                    state <= ST_IDLE;
+                end
+
+                ST_WRITE_SETUP: begin
+                    cmd_ack <= 1'b0;
+                    scl_drive_low <= 1'b1;
+                    sda_drive_low <= ~write_bit;
+                    state <= ST_WRITE_RELEASE_SCL;
+                end
+
+                ST_WRITE_RELEASE_SCL: begin
+                    cmd_ack <= 1'b0;
+                    scl_drive_low <= 1'b0;
+                    sda_drive_low <= ~write_bit;
+                    state <= ST_WRITE_WAIT_HIGH;
+                end
+
+                ST_WRITE_WAIT_HIGH: begin
+                    cmd_ack <= 1'b0;
+                    scl_drive_low <= 1'b0;
+                    sda_drive_low <= ~write_bit;
+
+                    if (scl_i) begin
+                        if (write_bit && !sda_i) begin
+                            al <= 1'b1;
+                        end
+                        state <= ST_WRITE_DONE;
+                    end
+                end
+
+                ST_WRITE_DONE: begin
+                    cmd_ack <= 1'b1;
+                    scl_drive_low <= 1'b1;
+                    sda_drive_low <= ~write_bit;
+                    state <= ST_IDLE;
+                end
+
+                ST_READ_SETUP: begin
+                    cmd_ack <= 1'b0;
+                    scl_drive_low <= 1'b1;
+                    sda_drive_low <= 1'b0;
+                    state <= ST_READ_RELEASE_SCL;
+                end
+
+                ST_READ_RELEASE_SCL: begin
+                    cmd_ack <= 1'b0;
+                    scl_drive_low <= 1'b0;
+                    sda_drive_low <= 1'b0;
+                    state <= ST_READ_WAIT_HIGH;
+                end
+
+                ST_READ_WAIT_HIGH: begin
+                    cmd_ack <= 1'b0;
+                    scl_drive_low <= 1'b0;
+                    sda_drive_low <= 1'b0;
+
+                    if (scl_i) begin
+                        bit_out <= sda_i;
+                        state <= ST_READ_DONE;
+                    end
+                end
+
+                ST_READ_DONE: begin
+                    cmd_ack <= 1'b1;
+                    scl_drive_low <= 1'b1;
+                    sda_drive_low <= 1'b0;
+                    state <= ST_IDLE;
+                end
+
+                default: begin
+                    state <= ST_IDLE;
+                    cmd_ack <= 1'b0;
+                end
+            endcase
+        end
+    end
+endmodule
*** End Patch


Exit code: 0
Wall time: 0 seconds
Output:
Success. Updated the following files:
A /app/dut.sv
The implementation is in place. I’ll do a syntax check with whatever HDL tool is available in the container, and if none is present I’ll at least inspect the generated source.
shell
command -v iverilog
output
Chunk ID: f20e5f
Wall time: 0.0000 seconds
Process exited with code 0
Original token count: 5
Output:
/usr/bin/iverilog
shell
command -v verilator
output
Chunk ID: 8d07e6
Wall time: 0.0000 seconds
Process exited with code 1
Original token count: 0
Output:
shell
sed -n '1,260p' /app/dut.sv
output
Chunk ID: c66115
Wall time: 0.0000 seconds
Process exited with code 0
Original token count: 1749
Output:
module TopModule(
    input clk, rst, cmd_valid, bit_in, scl_i, sda_i,
    input [1:0] cmd,
    output cmd_ack, busy, al, bit_out, scl_drive_low, sda_drive_low
);
    I2CBitCommandController controller (
        .clk(clk),
        .rst(rst),
        .cmd_valid(cmd_valid),
        .bit_in(bit_in),
        .scl_i(scl_i),
        .sda_i(sda_i),
        .cmd(cmd),
        .cmd_ack(cmd_ack),
        .busy(busy),
        .al(al),
        .bit_out(bit_out),
        .scl_drive_low(scl_drive_low),
        .sda_drive_low(sda_drive_low)
    );
endmodule

module I2CBitCommandController(
    input logic clk,
    input logic rst,
    input logic cmd_valid,
    input logic bit_in,
    input logic scl_i,
    input logic sda_i,
    input logic [1:0] cmd,
    output logic cmd_ack,
    output logic busy,
    output logic al,
    output logic bit_out,
    output logic scl_drive_low,
    output logic sda_drive_low
);
    typedef enum logic [3:0] {
        ST_IDLE,
        ST_START_WAIT_HIGH,
        ST_START_SDA_LOW,
        ST_START_DONE,
        ST_STOP_SETUP,
        ST_STOP_RELEASE_SCL,
        ST_STOP_WAIT_HIGH,
        ST_STOP_DONE,
        ST_WRITE_SETUP,
        ST_WRITE_RELEASE_SCL,
        ST_WRITE_WAIT_HIGH,
        ST_WRITE_DONE,
        ST_READ_SETUP,
        ST_READ_RELEASE_SCL,
        ST_READ_WAIT_HIGH,
        ST_READ_DONE
    } state_t;

    state_t state;
    logic write_bit;

    always_ff @(posedge clk) begin
        if (rst) begin
            state <= ST_IDLE;
            write_bit <= 1'b0;
            cmd_ack <= 1'b0;
            busy <= 1'b0;
            al <= 1'b0;
            bit_out <= 1'b0;
            scl_drive_low <= 1'b0;
            sda_drive_low <= 1'b0;
        end else begin
            case (state)
                ST_IDLE: begin
                    cmd_ack <= 1'b0;

                    if (cmd_valid && (cmd == 2'd0)) begin
                        busy <= 1'b1;
                        scl_drive_low <= 1'b0;
                        sda_drive_low <= 1'b0;
                        state <= ST_START_WAIT_HIGH;
                    end else if (cmd_valid && busy && (cmd == 2'd1)) begin
                        scl_drive_low <= 1'b1;
                        sda_drive_low <= 1'b1;
                        state <= ST_STOP_SETUP;
                    end else if (cmd_valid && busy && (cmd == 2'd2)) begin
                        write_bit <= bit_in;
                        scl_drive_low <= 1'b1;
                        sda_drive_low <= ~bit_in;
                        state <= ST_WRITE_SETUP;
                    end else if (cmd_valid && busy && (cmd == 2'd3)) begin
                        scl_drive_low <= 1'b1;
                        sda_drive_low <= 1'b0;
                        state <= ST_READ_SETUP;
                    end
                end

                ST_START_WAIT_HIGH: begin
                    cmd_ack <= 1'b0;
                    scl_drive_low <= 1'b0;
                    sda_drive_low <= 1'b0;

                    if (scl_i) begin
                        if (!sda_i) begin
                            al <= 1'b1;
                        end
                        state <= ST_START_SDA_LOW;
                    end
                end

                ST_START_SDA_LOW: begin
                    cmd_ack <= 1'b0;
                    scl_drive_low <= 1'b0;
                    sda_drive_low <= 1'b1;
                    state <= ST_START_DONE;
                end

                ST_START_DONE: begin
                    cmd_ack <= 1'b1;
                    scl_drive_low <= 1'b1;
                    sda_drive_low <= 1'b1;
                    state <= ST_IDLE;
                end

                ST_STOP_SETUP: begin
                    cmd_ack <= 1'b0;
                    scl_drive_low <= 1'b1;
                    sda_drive_low <= 1'b1;
                    state <= ST_STOP_RELEASE_SCL;
                end

                ST_STOP_RELEASE_SCL: begin
                    cmd_ack <= 1'b0;
                    scl_drive_low <= 1'b0;
                    sda_drive_low <= 1'b1;
                    state <= ST_STOP_WAIT_HIGH;
                end

                ST_STOP_WAIT_HIGH: begin
                    cmd_ack <= 1'b0;
                    scl_drive_low <= 1'b0;
                    sda_drive_low <= 1'b1;

                    if (scl_i) begin
                        state <= ST_STOP_DONE;
                    end
                end

                ST_STOP_DONE: begin
                    cmd_ack <= 1'b1;
                    busy <= 1'b0;
                    scl_drive_low <= 1'b0;
                    sda_drive_low <= 1'b0;
                    state <= ST_IDLE;
                end

                ST_WRITE_SETUP: begin
                    cmd_ack <= 1'b0;
                    scl_drive_low <= 1'b1;
                    sda_drive_low <= ~write_bit;
                    state <= ST_WRITE_RELEASE_SCL;
                end

                ST_WRITE_RELEASE_SCL: begin
                    cmd_ack <= 1'b0;
                    scl_drive_low <= 1'b0;
                    sda_drive_low <= ~write_bit;
                    state <= ST_WRITE_WAIT_HIGH;
                end

                ST_WRITE_WAIT_HIGH: begin
                    cmd_ack <= 1'b0;
                    scl_drive_low <= 1'b0;
                    sda_drive_low <= ~write_bit;

                    if (scl_i) begin
                        if (write_bit && !sda_i) begin
                            al <= 1'b1;
                        end
                        state <= ST_WRITE_DONE;
                    end
                end

                ST_WRITE_DONE: begin
                    cmd_ack <= 1'b1;
                    scl_drive_low <= 1'b1;
                    sda_drive_low <= ~write_bit;
                    state <= ST_IDLE;
                end

                ST_READ_SETUP: begin
                    cmd_ack <= 1'b0;
                    scl_drive_low <= 1'b1;
                    sda_drive_low <= 1'b0;
                    state <= ST_READ_RELEASE_SCL;
                end

                ST_READ_RELEASE_SCL: begin
                    cmd_ack <= 1'b0;
                    scl_drive_low <= 1'b0;
                    sda_drive_low <= 1'b0;
                    state <= ST_READ_WAIT_HIGH;
                end

                ST_READ_WAIT_HIGH: begin
                    cmd_ack <= 1'b0;
                    scl_drive_low <= 1'b0;
                    sda_drive_low <= 1'b0;

                    if (scl_i) begin
                        bit_out <= sda_i;
                        state <= ST_READ_DONE;
                    end
                end

                ST_READ_DONE: begin
                    cmd_ack <= 1'b1;
                    scl_drive_low <= 1'b1;
                    sda_drive_low <= 1'b0;
                    state <= ST_IDLE;
                end

                default: begin
                    state <= ST_IDLE;
                    cmd_ack <= 1'b0;
                end
            endcase
        end
    end
endmodule
`iverilog` is available, so I’ll run a SystemVerilog syntax compile against `TopModule` now.
shell
iverilog -g2012 -s TopModule -o /tmp/dut_check.vvp /app/dut.sv
output
Chunk ID: 2b062b
Wall time: 0.0000 seconds
Process exited with code 0
Original token count: 0
Output:
shell
nl -ba /app/dut.sv | sed -n '1,240p'
output
Chunk ID: 1aab20
Wall time: 0.0001 seconds
Process exited with code 0
Original token count: 2148
Output:
     1	module TopModule(
     2	    input clk, rst, cmd_valid, bit_in, scl_i, sda_i,
     3	    input [1:0] cmd,
     4	    output cmd_ack, busy, al, bit_out, scl_drive_low, sda_drive_low
     5	);
     6	    I2CBitCommandController controller (
     7	        .clk(clk),
     8	        .rst(rst),
     9	        .cmd_valid(cmd_valid),
    10	        .bit_in(bit_in),
    11	        .scl_i(scl_i),
    12	        .sda_i(sda_i),
    13	        .cmd(cmd),
    14	        .cmd_ack(cmd_ack),
    15	        .busy(busy),
    16	        .al(al),
    17	        .bit_out(bit_out),
    18	        .scl_drive_low(scl_drive_low),
    19	        .sda_drive_low(sda_drive_low)
    20	    );
    21	endmodule
    22	
    23	module I2CBitCommandController(
    24	    input logic clk,
    25	    input logic rst,
    26	    input logic cmd_valid,
    27	    input logic bit_in,
    28	    input logic scl_i,
    29	    input logic sda_i,
    30	    input logic [1:0] cmd,
    31	    output logic cmd_ack,
    32	    output logic busy,
    33	    output logic al,
    34	    output logic bit_out,
    35	    output logic scl_drive_low,
    36	    output logic sda_drive_low
    37	);
    38	    typedef enum logic [3:0] {
    39	        ST_IDLE,
    40	        ST_START_WAIT_HIGH,
    41	        ST_START_SDA_LOW,
    42	        ST_START_DONE,
    43	        ST_STOP_SETUP,
    44	        ST_STOP_RELEASE_SCL,
    45	        ST_STOP_WAIT_HIGH,
    46	        ST_STOP_DONE,
    47	        ST_WRITE_SETUP,
    48	        ST_WRITE_RELEASE_SCL,
    49	        ST_WRITE_WAIT_HIGH,
    50	        ST_WRITE_DONE,
    51	        ST_READ_SETUP,
    52	        ST_READ_RELEASE_SCL,
    53	        ST_READ_WAIT_HIGH,
    54	        ST_READ_DONE
    55	    } state_t;
    56	
    57	    state_t state;
    58	    logic write_bit;
    59	
    60	    always_ff @(posedge clk) begin
    61	        if (rst) begin
    62	            state <= ST_IDLE;
    63	            write_bit <= 1'b0;
    64	            cmd_ack <= 1'b0;
    65	            busy <= 1'b0;
    66	            al <= 1'b0;
    67	            bit_out <= 1'b0;
    68	            scl_drive_low <= 1'b0;
    69	            sda_drive_low <= 1'b0;
    70	        end else begin
    71	            case (state)
    72	                ST_IDLE: begin
    73	                    cmd_ack <= 1'b0;
    74	
    75	                    if (cmd_valid && (cmd == 2'd0)) begin
    76	                        busy <= 1'b1;
    77	                        scl_drive_low <= 1'b0;
    78	                        sda_drive_low <= 1'b0;
    79	                        state <= ST_START_WAIT_HIGH;
    80	                    end else if (cmd_valid && busy && (cmd == 2'd1)) begin
    81	                        scl_drive_low <= 1'b1;
    82	                        sda_drive_low <= 1'b1;
    83	                        state <= ST_STOP_SETUP;
    84	                    end else if (cmd_valid && busy && (cmd == 2'd2)) begin
    85	                        write_bit <= bit_in;
    86	                        scl_drive_low <= 1'b1;
    87	                        sda_drive_low <= ~bit_in;
    88	                        state <= ST_WRITE_SETUP;
    89	                    end else if (cmd_valid && busy && (cmd == 2'd3)) begin
    90	                        scl_drive_low <= 1'b1;
    91	                        sda_drive_low <= 1'b0;
    92	                        state <= ST_READ_SETUP;
    93	                    end
    94	                end
    95	
    96	                ST_START_WAIT_HIGH: begin
    97	                    cmd_ack <= 1'b0;
    98	                    scl_drive_low <= 1'b0;
    99	                    sda_drive_low <= 1'b0;
   100	
   101	                    if (scl_i) begin
   102	                        if (!sda_i) begin
   103	                            al <= 1'b1;
   104	                        end
   105	                        state <= ST_START_SDA_LOW;
   106	                    end
   107	                end
   108	
   109	                ST_START_SDA_LOW: begin
   110	                    cmd_ack <= 1'b0;
   111	                    scl_drive_low <= 1'b0;
   112	                    sda_drive_low <= 1'b1;
   113	                    state <= ST_START_DONE;
   114	                end
   115	
   116	                ST_START_DONE: begin
   117	                    cmd_ack <= 1'b1;
   118	                    scl_drive_low <= 1'b1;
   119	                    sda_drive_low <= 1'b1;
   120	                    state <= ST_IDLE;
   121	                end
   122	
   123	                ST_STOP_SETUP: begin
   124	                    cmd_ack <= 1'b0;
   125	                    scl_drive_low <= 1'b1;
   126	                    sda_drive_low <= 1'b1;
   127	                    state <= ST_STOP_RELEASE_SCL;
   128	                end
   129	
   130	                ST_STOP_RELEASE_SCL: begin
   131	                    cmd_ack <= 1'b0;
   132	                    scl_drive_low <= 1'b0;
   133	                    sda_drive_low <= 1'b1;
   134	                    state <= ST_STOP_WAIT_HIGH;
   135	                end
   136	
   137	                ST_STOP_WAIT_HIGH: begin
   138	                    cmd_ack <= 1'b0;
   139	                    scl_drive_low <= 1'b0;
   140	                    sda_drive_low <= 1'b1;
   141	
   142	                    if (scl_i) begin
   143	                        state <= ST_STOP_DONE;
   144	                    end
   145	                end
   146	
   147	                ST_STOP_DONE: begin
   148	                    cmd_ack <= 1'b1;
   149	                    busy <= 1'b0;
   150	                    scl_drive_low <= 1'b0;
   151	                    sda_drive_low <= 1'b0;
   152	                    state <= ST_IDLE;
   153	                end
   154	
   155	                ST_WRITE_SETUP: begin
   156	                    cmd_ack <= 1'b0;
   157	                    scl_drive_low <= 1'b1;
   158	                    sda_drive_low <= ~write_bit;
   159	                    state <= ST_WRITE_RELEASE_SCL;
   160	                end
   161	
   162	                ST_WRITE_RELEASE_SCL: begin
   163	                    cmd_ack <= 1'b0;
   164	                    scl_drive_low <= 1'b0;
   165	                    sda_drive_low <= ~write_bit;
   166	                    state <= ST_WRITE_WAIT_HIGH;
   167	                end
   168	
   169	                ST_WRITE_WAIT_HIGH: begin
   170	                    cmd_ack <= 1'b0;
   171	                    scl_drive_low <= 1'b0;
   172	                    sda_drive_low <= ~write_bit;
   173	
   174	                    if (scl_i) begin
   175	                        if (write_bit && !sda_i) begin
   176	                            al <= 1'b1;
   177	                        end
   178	                        state <= ST_WRITE_DONE;
   179	                    end
   180	                end
   181	
   182	                ST_WRITE_DONE: begin
   183	                    cmd_ack <= 1'b1;
   184	                    scl_drive_low <= 1'b1;
   185	                    sda_drive_low <= ~write_bit;
   186	                    state <= ST_IDLE;
   187	                end
   188	
   189	                ST_READ_SETUP: begin
   190	                    cmd_ack <= 1'b0;
   191	                    scl_drive_low <= 1'b1;
   192	                    sda_drive_low <= 1'b0;
   193	                    state <= ST_READ_RELEASE_SCL;
   194	                end
   195	
   196	                ST_READ_RELEASE_SCL: begin
   197	                    cmd_ack <= 1'b0;
   198	                    scl_drive_low <= 1'b0;
   199	                    sda_drive_low <= 1'b0;
   200	                    state <= ST_READ_WAIT_HIGH;
   201	                end
   202	
   203	                ST_READ_WAIT_HIGH: begin
   204	                    cmd_ack <= 1'b0;
   205	                    scl_drive_low <= 1'b0;
   206	                    sda_drive_low <= 1'b0;
   207	
   208	                    if (scl_i) begin
   209	                        bit_out <= sda_i;
   210	                        state <= ST_READ_DONE;
   211	                    end
   212	                end
   213	
   214	                ST_READ_DONE: begin
   215	                    cmd_ack <= 1'b1;
   216	                    scl_drive_low <= 1'b1;
   217	                    sda_drive_low <= 1'b0;
   218	                    state <= ST_IDLE;
   219	                end
   220	
   221	                default: begin
   222	                    state <= ST_IDLE;
   223	                    cmd_ack <= 1'b0;
   224	                end
   225	            endcase
   226	        end
   227	    end
   228	endmodule
Implemented `/app/dut.sv`. `TopModule` now instantiates `I2CBitCommandController`, with registered outputs, synchronous active-high reset, legal command gating, sticky `al`, and the requested phased timing for start/stop/write/read. Verification run: ```bash iverilog -g2012 -s TopModule -o /tmp/dut_check.vvp /app/dut.sv ``` It compiles cleanly.
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
MISMATCH_COUNTS cmd_ack=0 busy=0 al=0 bit_out=0 scl=0 sda=0
__CHIPBENCH_MISMATCH_SUMMARY__: mismatches=0 samples=2351

Reproduce this trial: git checkout 2f94510 && PYTHONPATH=src python3 scripts/build_site.py , then open trial/trial_226d4f6a0fab461c. Re-running the agent live requires EVAL_PLATFORM_ENABLE_OAUTH_SMOKE=1 and is non-deterministic.

Trial trial_226d4f6a0fab461c · verifier authoritative; classifier explanatory.