Remove the duo_workflow_incremental_checkpoints feature flag

Eduardo Bonetrequested to merge
629085-remove-the-duo-workflow-incremental-checkpoin into master

What does this MR do and why?

Every new Duo Agent Platform session now stores incremental checkpoints, and the incremental_checkpoints server capability is always advertised. The duo_workflow_incremental_checkpoints flag has been enabled on GitLab.com since 2026-07-30 with no incidents, so this MR deletes it. Workflows created before this change keep using the legacy checkpoint path, since the column is a per-workflow snapshot and switching one mid-flight would break its checkpoint chain.

Design notes
  • The incremental_checkpoints_enabled column is a per-workflow snapshot, set once at creation. Workflows created before this change with the column false continue on the legacy checkpoint path; nothing re-evaluates them. This is intentional: incremental checkpoint blobs are deltas, and switching a workflow mid-flight would leave an unreconstructable chain.
  • No gateway (AI Gateway / Duo Workflow Service) change is needed. The gateway reads the column and the server capability, never the Rails flag.
  • The incremental_checkpoints server capability stays (it's not removed), because older gateway versions decide whether to send checkpoint blobs based on it.
  • Merging starts the 30-day window after which every live workflow has incremental_checkpoints_enabled = true, a prerequisite for #627332.
  • This is the first of three flag-removal MRs. Next are the read-gate flags, then duo_workflow_write_incremental_only.
  • Changelog: other, since the flag was already enabled and there's no user-facing behavior change.

References

Screenshots or screen recordings

No UI change.

How to set up and validate locally

  1. Open the GraphQL explorer at http://gdk.test:3000/-/graphql-explorer.
  2. Run the query { aiFlowsMetadata { capabilities { name } } }. Expect: the list includes incremental_checkpoints alongside job_trace_pagination and tool_call_approval_source, with no feature flag enabled.
  3. Optionally repeat with a namespace: { aiFlowsMetadata(namespaceId: "gid://gitlab/Group/<id>") { capabilities { name } } }. Expect: same result.
  4. Start a new Duo Agent Platform session from any project (for example via the Duo Agent Platform panel in the Web IDE or the project's Automate > Sessions page) or via the Duo CLI.
  5. In bin/rails console, run Ai::DuoWorkflows::Workflow.last.incremental_checkpoints_enabled. Expect: true.
Negative check

In bin/rails console, run Feature.enabled?(:duo_workflow_incremental_checkpoints). Expect: it raises, because the flag definition no longer exists (development and test environments raise on unknown flags).

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