LangSmith API + MCP vs Navige

LangSmith API + MCP

Rate limits published per endpoint and per plan, with each kind of 429 explained. Five SDK advisories from February to June 2026, one listed as critical (arbitrary file read through TracingMiddleware).

Navige

Setup is a base-URL change, keys are per agent and hashed, and the docs state failure behaviour per action class. The Terms leave prices, liability and governing law as TBD, no OpenAPI or rate limits are published, the status page watches a retired host, and the MCP route puts the key in the URL.

LangSmith API + MCP

1. Batch run reads. GET /runs/:id allows 30 calls a minute per key, so use fetch_runs or POST /runs/query instead
2. Pass trace_id or min_start_time to fetch_runs and keep limit low. Results page by a 25,000-character budget
3. Don't call create_dataset or run_experiment over MCP to make changes. They return how-to text, not results
4. Send X-Api-Key and point at the regional host (eu., apac. or aws.api.smith.langchain.com) that matches the workspace
5. Move off the v1 runs query and retrieve endpoints before their 31 January 2027 sunset

Navige

1. Send the Navige key in x-navige-key on the proxy. Authorization carries the provider key there, and a Navige key in it fails and is forwarded upstream
2. Act only on allow or approved from /enforce. Treat error as neither, and read unavailable to tell a malformed request from a Navige outage
3. Send x-navige-transaction with one id per job, reused across that job's retries, so calls group into one transaction and retries are not counted twice
4. On a 429 from the proxy, check for a blocking budget before retrying. Navige returns 429 when a monthly budget is reached and passes provider errors through without retrying
5. Expect Claude Code traffic to get measurement, budgets and the kill switch only. Context trimming, routing, the output ceiling and prompt caching are switched off for it