Session log

GET https://app.vern.so/api/v1/migrations/{migration_id}/log

Returns the settled record of a migration: the plan, the files that went in, who approved what and when, how many rows were written per sheet, and whether existing rows were replaced. It’s designed to be fetched once, after the migration finishes, and stored on your side — so months later you can answer your own customer’s “what did you do to my data?”. This is not the live feed. For a run in progress use Stream the thread; the log deliberately excludes the conversation and returns the outcome instead.

Available only once the migration has settled. While anything is still in flight the endpoint returns 409 rather than a partial log — see Availability.

Authentication

Requires an x-api-key header. See Authentication.

Query

string

default:"json"

json (default) for the structured log, or md / markdown for a human-readable transcript you can paste into a ticket or hand to a customer.

Availability

The log covers every run to date, so it’s a superset of anything you fetched earlier — a migration re-imported later returns a longer log. It’s gated on the migration being settled, which deliberately includes failures: a run can write rows and then fail validation, and that’s exactly when someone asks what happened. completed, failed and canceled all return a log. While a run is still going you get 409 with the current status, so a poller can tell “not yet” from “broken”:

{
  "error": "Migration is still in progress. The final log is available once it completes.",
  "status": "awaiting_approval",
  "retry_after_seconds": 30
}

Response

200 OK.

{
  "migration_id": "c0a8012e-...",
  "generated_at": "2026-08-21T10:02:11.000Z",
  "status": "completed",
  "covers": {
    "runs": 4,
    "from": "2026-08-21T09:02:00.000Z",
    "to": "2026-08-21T09:18:44.000Z"
  },
  "runs": [
    {
      "run_id": "e5d4c3b2-...",
      "kind": "execute",
      "status": "completed",
      "started_at": "2026-08-21T09:14:02.000Z",
      "completed_at": "2026-08-21T09:18:44.000Z",
      "started_by": null,
      "files": ["contacts.csv", "deals.xlsx"],
      "plan": "Map contacts.csv → Contacts…",
      "questions": [],
      "answers": {},
      "outcome": {
        "ok": true,
        "rows_written": 48213,
        "per_sheet": [{ "sheet": "Contacts", "rows": 48213 }],
        "invalid_rows": 27,
        "error": null,
        "replaced_existing_data": true
      },
      "audit": [
        { "at": "2026-08-21T09:14:02.000Z", "event": "started" },
        { "at": "2026-08-21T09:17:55.000Z", "event": "plan_approved" }
      ]
    }
  ]
}

Fields

string

When this log was produced. The log always covers everything up to this moment.

string

The migration’s settled state — completed, failed or canceled.

object

How much this log spans — { runs, from, to }, the number of runs and the timestamp range they fall in.

object[]

Every run, oldest first.

Show run

string

The run’s id — the same one Poll a run uses.

string

Which leg this run was: generate, update, reuse, clarify or execute. Only an execute writes rows.

string

How the run ended.

string | null

The dashboard user who started it, or null when it was started through this API.

string[]

The source files this run read.

string | null

The mapping plan as presented for approval.

object[]

Any questions the run asked, and answers the replies it received.

object | null

What the run did. null for runs that never reached an outcome.

Show outcome

boolean | null

Whether the run succeeded.

integer | null

Total rows written across all sheets.

object[]

Per-sheet counts — { sheet, rows }.

integer | null

Rows written with at least one cell that failed validation.

string | null

Why it failed, when it did.

boolean

true means this run emptied its destination sheets before writing — it replaced the previous import rather than adding to it. Worth surfacing to your customer; it’s the difference between “we added 48k rows” and “we swapped out everything that was there”.

object[]

Who did what, in order — { at, event, ... }. Covers the moments that matter for accountability: started, plan approved, templates adjusted.

Markdown

?format=md renders the same data as a readable transcript — run headings, the plan, an audit table, and the result. Labels mirror the History tab in the Vern dashboard, so an export you hand a customer and what your team sees in-app tell the same story.

curl "https://app.vern.so/api/v1/migrations/c0a8012e-.../log?format=md" \
  -H "x-api-key: $VERN_API_KEY" \
  -o migration-log.md

Errors

Status	Meaning
`401`	API key missing or invalid.
`404`	No migration with that id in your account.
`409`	Still in progress. Body carries `status` and `retry_after_seconds`.
`429`	Rate limit hit — back off and retry.
`500`	Server error.
`503`	The migration’s data region is unavailable.

What the log cannot tell you

Worth knowing before you build a compliance story on it:

No per-row lineage. The log says a run wrote 48,213 rows to Contacts. It cannot say output row 4,312 came from line 4,180 of contacts.csv.
“Failed” doesn’t mean “untouched”. A run can insert rows and then fail validation. Read outcome.rows_written, not just status.
It isn’t tamper-evident. The underlying run records are mutable by users in your account. Treat the log as a faithful report, not as an audit seal.
Retention is keyed to the workbook. Logs are swept with the migration’s data under your retention policy. This is the argument for fetching and storing the log yourself.

Example

curl "https://app.vern.so/api/v1/migrations/c0a8012e-.../log" \
  -H "x-api-key: $VERN_API_KEY"

Poll a run — confirm the migration settled before fetching.
Export CSV — get the data itself out.
Errors & limits — shared conventions.

Overview

Get started

API reference

Reference

Authentication

Query

Availability

Response

Fields

Markdown

Errors

What the log cannot tell you

Example

Next

​Authentication

​Query

​Availability

​Response

​Fields

​Markdown

​Errors

​What the log cannot tell you

​Example

​Next

Authentication

Query

Availability

Response

Fields

Markdown

Errors

What the log cannot tell you

Example

Next