Adds level-B agent attribution: every MCP tool call can identify itself
with a `client` (e.g. cursor-ide, codex, echodo-orchestrator) and `model`
(e.g. claude-4.6-sonnet) string. Both optional, both stored in
agent_runs.metadata as JSONB so the schema doesn't move.
- claim_task: new optional `client` + `model` args. Written into the
inserted agent_runs row's metadata, and mirrored into the audit log
entry. On idempotent re-claim, incoming values are merged into
existing metadata (existing keys override only when explicit), so a
mid-session model switch updates attribution without losing earlier
context.
- complete_task: same optional args, with merge-on-close semantics —
late-bound values override the earlier claim's values so the run row
reflects whichever model actually closed the session. Audit row also
carries the merged identity.
- /settings/runs UI: stack the client/model under the actor name in the
table so attribution is visible at a glance without adding a column.
Smoke-tested: claim with {cursor-ide, claude-4.6-sonnet} then complete
with only model={claude-4.6-sonnet-medium-thinking} yields final
metadata {client: cursor-ide, model: claude-4.6-sonnet-medium-thinking}
on both the run row and the task.completed audit entry.
Co-authored-by: Cursor <cursoragent@cursor.com>
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