Trace Capture

Workflow tracing records which steps ran via StepTransition. Trace capture goes deeper — it records what happened inside each step: every tool call, thinking block, token count, and cost. The trace is written to a JSONL file during execution, and the file path flows through the workflow journal so analysis tools can find it.

When you need trace capture

Markov analysis — fingerprint an agent’s behavioral patterns across runs
Cost attribution — break down per-step token usage and cost
Debugging — replay exactly what the agent saw, thought, and did
Regression detection — compare traces across code changes

Setup

Trace capture requires two things: an agent model that writes trace files, and a workflow client that propagates the path.

1. Configure traceDir on ClaudeAgentModel

The ClaudeAgentModel from agent-client writes a JSONL trace file per call() when traceDir is set:

ClaudeAgentModel model = ClaudeAgentModel.builder()
        .traceDir(Path.of("traces"))
        .build();

Each call produces a file like traces/agent-run-20260528-143000-a1b2c3d4.jsonl containing every message in the session.

2. Bridge to a trace-aware AgentClient

The workflow-flows AgentClient is a @FunctionalInterface that returns text. To carry trace metadata, override executeForResult():

var coreClient = AgentClient.create(model);

io.github.markpollack.workflow.flows.steps.AgentClient workflowClient =
    new io.github.markpollack.workflow.flows.steps.AgentClient() {

        @Override
        public String execute(String prompt, AgentContext ctx) {
            return executeForResult(prompt, ctx).text();
        }

        @Override
        public ExecutionResult executeForResult(String prompt, AgentContext ctx) {
            AgentClientResponse response = coreClient.run(prompt);
            String tracePath = (String) response.getMetadata().get("tracePath");
            return new ExecutionResult(response.getResult(), tracePath);
        }
    };

Plain lambdas still work — executeForResult() defaults to calling execute() with a null trace path.

3. Use AgentClientStep in a workflow

AgentClientStep fixStep = AgentClientStep.of(workflowClient, "Fix: {input}");
AgentClientStep verifyStep = AgentClientStep.of(workflowClient, "Verify the fix: {input}");

TraceRecorder recorder = TraceRecorder.inMemory();
WorkflowExecutor executor = new WorkflowExecutor(recorder);

String result = Workflow.<String, String>define("remediate")
        .withExecutor(executor)
        .step(fixStep)
        .then(verifyStep)
        .run("failing test in AuthService");

Each AgentClientStep gets its own trace file. The path flows through to StepTransition:

List<StepTransition> trace = recorder.getTrace(runId);
for (StepTransition t : trace) {
    if (t.tracePath() != null) {
        System.out.println(t.toStep() + " → " + t.tracePath());
    }
}
// AgentClientStep → /abs/path/traces/agent-run-20260528-143000-a1b2c3d4.jsonl
// AgentClientStep → /abs/path/traces/agent-run-20260528-143500-e5f6g7h8.jsonl

How it works

The trace path flows through four layers:

AgentClient.executeForResult()        → ExecutionResult(text, tracePath)
  AgentClientStep.updateContext()     → sets AgentContext.TRACE_PATH
    WorkflowExecutor.recordTransition() → reads TRACE_PATH, clears it, records StepTransition
      TraceRecorder                   → stores/persists the transition

The executor clears TRACE_PATH from context after each step so deterministic steps don’t inherit a stale path.

Journal integration

When using workflow-journal, trace paths appear in WorkflowStepEvent and are included in the journal’s JSON output:

Journal.configure(new JsonFileStorage(journalDir));
WorkflowJournal.registerEventType();

try (Run run = Journal.run("remediate-experiment").start()) {
    WorkflowExecutor executor = new WorkflowExecutor(
            new LocalStepRunner(),
            WorkflowJournal.forRun(run));
    // ... run workflow
}

The journal event includes tracePath when present:

{
  "type": "workflow_step",
  "stepName": "AgentClientStep",
  "nodeType": "AGENT",
  "stepDurationMs": 12000,
  "tokensUsed": 3200,
  "costUsd": 0.048,
  "tracePath": "/abs/path/traces/agent-run-20260528-143000-a1b2c3d4.jsonl"
}

JDBC persistence

JdbcTraceRecorder stores trace paths in the trace_path column of step_transitions:

JdbcTraceRecorder recorder = new JdbcTraceRecorder(dataSource);
List<StepTransition> trace = recorder.getTrace("run-1");

// Find all trace files for a run
List<String> traceFiles = trace.stream()
        .map(StepTransition::tracePath)
        .filter(Objects::nonNull)
        .toList();

ClaudeStep vs AgentClientStep

	ClaudeStep	AgentClientStep
Execution	CLI subprocess (`claude -p`)	In-process via `ClaudeAgentModel`
Trace capture	Not available (text-only output)	Full JSONL trace files
Token/cost data	Discarded at process boundary	Available in `providerFields`
Use case	Quick scripts, prototyping	Experiments, production workflows

For any workflow where you need to analyze what the agent did — use AgentClientStep.

Maven coordinates

<!-- workflow-flows (always needed) -->
<dependency>
    <groupId>io.github.markpollack</groupId>
    <artifactId>workflow-flows</artifactId>
    <version>0.10.0</version>
</dependency>

<!-- agent-client + Claude model (for trace-aware client) -->
<dependency>
    <groupId>io.github.markpollack</groupId>
    <artifactId>agent-client-core</artifactId>
    <version>0.25.0</version>
</dependency>
<dependency>
    <groupId>io.github.markpollack</groupId>
    <artifactId>agent-claude</artifactId>
    <version>0.25.0</version>
</dependency>

Or use the AgentWorks BOM (1.1.0+) for managed versions.

Durability

JdbcTraceRecorder, CheckpointingStepRunner

API Reference

StepTransition, TraceRecorder, WorkflowExecutor

Projects

AgentWorks

Agento

Supporting Projects

Migration

When you need trace capture

Setup

1. Configure traceDir on ClaudeAgentModel

2. Bridge to a trace-aware AgentClient

3. Use AgentClientStep in a workflow

How it works

Journal integration

JDBC persistence

ClaudeStep vs AgentClientStep

Maven coordinates

Durability

API Reference

​When you need trace capture

​Setup

​1. Configure traceDir on ClaudeAgentModel

​2. Bridge to a trace-aware AgentClient

​3. Use AgentClientStep in a workflow

​How it works

​Journal integration

​JDBC persistence

​ClaudeStep vs AgentClientStep

​Maven coordinates

​Related

Durability

API Reference

When you need trace capture

Setup

1. Configure traceDir on ClaudeAgentModel

2. Bridge to a trace-aware AgentClient

3. Use AgentClientStep in a workflow

How it works

Journal integration

JDBC persistence

ClaudeStep vs AgentClientStep

Maven coordinates

Related