evals(v4): OTEL o11y UX (doctor/welcome + cli shutdown)

[miguelg719]

Why

Stack 6/6.

What

• doctor + welcomeStatus surface the LangSmith key.
• cli.ts flushes/shuts down the tracer on SIGINT/SIGTERM (otel-gated, error-swallowing).

Testing

typecheck + unit + build green.

Base: #2761

---

Summary by cubic

Surfaces the LangSmith API key in doctor/welcome and flushes OTEL traces on CLI shutdown to improve observability. Previously these views omitted LangSmith and the CLI exited without flushing spans; now, when trace transport is "otel", the CLI waits for tracer shutdown on SIGINT/SIGTERM and ignores shutdown errors.

• doctor and welcome show the LangSmith API key, preferring LANGSMITH_API_KEY and falling back to LANGCHAIN_API_KEY; welcomeStatus records which var was used and doctor labels it.
• On SIGINT/SIGTERM, if transport is "otel", the CLI awaits shutdownTracing() before exit; errors are swallowed. Non-OTEL behavior is unchanged.
• No migration required.

^{Written for commit e601252. Summary will update on new commits.}

[changeset-bot]

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Latest commit: e601252

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[cubic-dev-ai]

All reported issues were addressed across 3 files

Architecture diagram

sequenceDiagram
    participant CLI as CLI Entry (cli.ts)
    participant Doctor as Doctor Command (tui/commands/doctor.ts)
    participant Welcome as Welcome Status (tui/welcomeStatus.ts)
    participant Env as Environment Snapshot
    participant OTEL as OTEL Framework (framework/otel.ts)
    participant Tracer as Tracer (shutdown/flush)
    participant Langsmith as LangSmith Provider

    Note over CLI,Welcome: OTEL Observability UX

    Welcome->>Env: snapshotEnv()
    Env->>Env: langSmithEntry() - resolve LANGSMITH_API_KEY first
    alt LANGSMITH_API_KEY set
        Env-->>Welcome: ProviderKeyEntry (set)
    else LANGSMITH_API_KEY not set
        Env->>Env: fallback to LANGCHAIN_API_KEY
        Env-->>Welcome: ProviderKeyEntry (set/optional)
    end
    Welcome-->>CLI: env snapshot with langsmith entry

    Doctor->>Doctor: renderHuman(report)
    Doctor->>Doctor: keyRow("LANGSMITH_API_KEY", ...)
    Doctor-->>CLI: displays LangSmith key status

    Note over CLI,OTEL: CLI Shutdown Signal Handling

    alt SIGINT/SIGTERM received
        CLI->>CLI: handleSignal(code)
        CLI->>CLI: try resolveTraceTransport()
        alt trace transport is "otel"
            CLI->>OTEL: import shutdownTracing()
            OTEL->>Tracer: await shutdown()
            Tracer-->>OTEL: completed/flushed
            OTEL-->>CLI: done
        else non-OTEL transport
            CLI->>CLI: no tracer shutdown (unchanged)
        end
        CLI->>CLI: process.exit(code)
    else normal exit
        CLI->>CLI: continue execution
    end

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