Time travel

Time travel gives operators and agents three separate controls over durable Loop history: diff reads what changed, rerun opens a new generation in the same run, and fork creates a linked run without changing its source.

Compare history

Compare two generations of one run:

compozy loop diff --run-id <run-id> --generation 1 --against-generation 2

Use --against-run to compare runs of the same Loop. Run comparisons include changed inputs and mark different pinned definitions. A live side is labeled as-of its current settled generation. Large values return their byte size and SHA-256 content hash instead of an oversized inline payload.

Diff is a workspace-scoped read and needs no additional agent capability.

In the web UI, open Inspect on a run and use Compare… on any generation row. The comparison view is its own deep-linkable page: node rows are grouped by change kind using the same changed / rerun / skipped / carried / verdict vocabulary the CLI prints, a value the daemon summarized shows its size and content hash with a link to the full content, run comparisons add an input block, a banner appears when the two runs pin different definition versions, and a still-executing side is labelled as such. Two identical generations render an explicit "nothing changed" state rather than an empty page. Pickers are scoped to the same Loop, so the UI never offers a cross-Loop comparison the daemon would reject.

Rerun from a node

compozy loop rerun --run-id <run-id> --from-node verify --reason "retry verification"

Rerun opens a generation with origin operator_rerun. The selected node and its transitive dependents run again; unrelated settled cells carry forward. Add --item <index> to address one fan-out lane.

The source run must have a settled generation, and the target cell cannot be pending or parked. Agents need loops.timetravel. An agent cannot rerun its own executing run, but it may rerun its own terminal run.

Fork a linked run

From the web UI, Fork from here on an Inspect generation row opens a dialog that defaults to that generation and pre-fills the source run's declared inputs. Submitting starts the fork and takes you to the new run; input errors render exactly as they do on the run form. Once forked, each run's Inspect sheet links the other — the source lists its forks, the fork names where it came from.

compozy loop fork --run-id <run-id> --generation 2 --input service=payments

Fork creates a new run that pins the source run's executed definition. Generation 1 is a settled fork_seed baseline; generation 2 executes the full body with the source inputs plus any validated overrides. The source stays unchanged. Run status exposes forked_from on the child and forks on the source.

Fork uses the Loop's normal concurrency policy. Agents need loops.timetravel, and the same executing-run self-operation rule applies.

Safe retries

Pass --request-id to rerun or fork when retrying a request after a transport failure. Reusing the same key with identical inputs returns the committed result; changing the request while reusing the key returns timetravel_key_reuse. Omitting the key means each accepted call is a new operation.