TypeScript SDK

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LangChain

• Root output: Reasoning content blocks become the answer string on the root trace output. The generation span keeps the full block list. Tool-call payloads stay unchanged.

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LangChain

• Model name: When a chat model is not serializable, the handler reads ls_model_name from run metadata after invocation params.

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Tool calls

• Failure payloads: A tool result with success: false or status of error or failed is recorded as an error. The span uses structuredContent.error when that field is set.

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LangChain

• Callback handler: LemmaLangChainCallbackHandler accepts LangChain 1.x callback arguments and sets run_inline, raise_error, and the ignore_* flags.

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Vercel AI

• Telemetry types: The Vercel AI telemetry object is assignable to the AI SDK Telemetry type without a cast.

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Mastra

• Exporter types: exportTracingEvent accepts the framework event shape, so you can pass the exporter without a cast.

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Tracing

• One turn, two processes: startTurn, attachTurn, and apply record a host and a sandbox as one trace. The child keeps a journal and does not call ingest. The host sends once. turn.end() still raises on failure.

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Ingest

• Fail open: trace() and TraceHandle.end() catch HTTP and network errors, log them, and do not rethrow. ingest() still raises. A delivery failure does not replace your agent’s error.

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Generations

• Model identity: A typed generation span copies the model from the invocation, the response, or response metadata when params omit it. Completion text is not used as a model id.

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Vercel AI

• Provider system: A generation records the provider system when the call sets messages.

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Tool calls

• Encoded failures: A tool payload that encodes a failure is stored as a span error.

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Tracing

• OpenCode: codingAgentTurnTrace accepts the opencode harness id.

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Tracing

• Coding-agent turns: codingAgentTurnTrace builds one trace from a completed coding-agent turn: prompt, tool calls, and response.

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Generations

• Token usage: LangChain, OpenAI Agents, Vercel AI SDK, and Mastra record token usage, including cache and reasoning tokens from Agents SDK and AI SDK 7 shapes.
• Provider: Generation spans set the provider system from the model provider.

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Tracing

• Release: Pass release to the client, or set LEMMA_RELEASE, to stamp the running revision on each trace.
• Provenance: Spans record the SDK language and integration so missing usage is distinct from a real zero.

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Tracing

• Inputs and outputs: Prompts, tool inputs, tool outputs, model output, and error messages are always recorded. The recordInputs and recordOutputs options are removed. Redact sensitive values before they reach the agent.

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Tracing

• Error messages: Empty and missing failure text uses the same message in the TypeScript and Python SDKs. Serialized payloads use compact JSON.

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Tool calls

• User-facing text: Set userFacingMessage when a tool sends text directly to the person. Lemma shows that text as the message they received.

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Mastra

• Agent name: The trace name comes from the agent entity, then the entity name, then the id inside the run span name. An explicit agentName still wins.

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Vercel AI

• Trace contract: One integration owns one in-flight run. The root records the current turn, thread, and user, with wall-clock times and structured output.

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OpenAI Agents

• Trace contract: The processor records current-turn input and output, terminal errors, and span-bounded times. Soft tool errors match the Python SDK.

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LangChain

• Trace contract: Owned runs keep current-turn input, output, and errors. Tool calls stay nested under one root until the final answer. LangGraph uses the LangChain adapter.

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Mastra

• Exporter: LemmaMastraExporter maps agent and workflow spans to Lemma traces, with nested generations and tools. Soft tool failures and the current user turn are included.

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Tool calls

• MCP errors: A tool result with isError is recorded as an error, without an invented output.
• Child timing: A tool span no longer ends after its parent generation.

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Tracing

• Registry: An ended trace handle is released from the client registry.

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Ingest

• One delivery: The replace option is removed. Each execution sends one complete trace. Patching a trace over time is not supported.

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Ingest

• end() sends: TraceHandle.flush is removed. end() is how a trace handle is sent.

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Tracing

• Environment field: The undocumented environment client field is removed.

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Debug

• Ingest status: LEMMA_DEBUG_VERIFY and debugSmokeTest check GET /traces/ingest-status for up to 15 seconds, so a backlog does not look like a missed delivery.
• Debug flag: LEMMA_DEBUG=1 is the preferred value. true still works.

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Debug

• Delivery logs: Debug mode logs client config and ingest responses, including failure hints.
• Smoke test: debugSmokeTest checks that a trace reached Lemma.

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Ingest

• Send on end: Trace handles and the OpenAI Agents processor send a trace once, when it ends. They no longer send partial snapshots along the way.

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Tracing

• First public release: @uselemma/tracing sends traces to Lemma, with debug mode and experiment mode.

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LangChain

• Callback handler: A LangChain callback handler records chains, model calls, and tools.

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OpenAI Agents

• Processor: An OpenAI Agents processor records agent runs.

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Vercel AI

• Telemetry: A Vercel AI SDK telemetry integration records model and tool calls.