Background

Alibaba Cloud OpenTelemetry documentation recommends writing traceId and spanId into application logs so that trace data and log data can be correlated in backends (e.g., SLS, Grafana). Currently, qwen-code debug log files (~/.qwen/debug/{sessionId}.txt) contain timestamps and log levels, but no trace context — making it impossible to join a log line to its corresponding OTel span.

Proposed Change

Inject [trace_id=xxx span_id=yyy] into every debug log line. Priority:

1. Active OTel span — if a real span is active (non-zero traceId), use its traceId/spanId
2. Session-derived fallback — if no active span, derive a deterministic traceId from sessionId via SHA-256 (same algorithm as LogToSpanProcessor), and generate a stable per-session spanId
3. No context — omit the trace fields entirely

Example output:

2026-01-24T10:30:00.000Z [DEBUG] [OTEL] [trace_id=aabb...8899 span_id=1122334455667788] OpenTelemetry SDK started successfully.
2026-01-24T10:30:01.123Z [DEBUG] [tool.Bash] [trace_id=aabb...8899 span_id=deadbeef12345678] Tool executed

Implementation

New files

• packages/core/src/telemetry/trace-id-utils.ts — shared deriveTraceId, randomSpanId, randomHexString; used by both LogToSpanProcessor and debugLogger to ensure consistent traceIds
• packages/core/src/telemetry/session-context.ts — neutral singleton module to pass session root context from sdk.ts to tracer.ts without circular dependency
• packages/core/src/telemetry/tracer.ts — withSpan (auto-lifecycle async wrapper), startSpanWithContext (manual lifecycle for async generators), createSessionRootContext

Modified files

• debugLogger.ts — getTraceContext() with OTel-first priority; buildLogLine includes trace fields; fallback spanId cached per session
• sdk.ts — call setSessionContext(createSessionRootContext(sessionId)) after SDK start; clear on shutdown
• log-to-span-processor.ts — remove local deriveTraceId/randomHexString, import from trace-id-utils
• loggingContentGenerator.ts — wrap generateContent in withSpan; use startSpanWithContext + runInContext for generateContentStream so the span covers the full stream lifetime
• client.ts — wrap generateContent in withSpan
• coreToolScheduler.ts — wrap executeSingleToolCall in withSpan; mark tool error/denial paths as SpanStatusCode.ERROR

Testing

All existing tests pass. New tests added for:

• Trace context injection in log lines
• OTel span priority over session fallback
• Zero-traceId fallback behavior
• Stable fallback spanId per session
• deriveTraceId determinism and format