fix(store): isolate checkpoint file lists at write boundaries

[DeliciousBuding]

Summary

UpsertRunCheckpoint retains and returns the caller's Files backing array. GetRunCheckpoint and snapshot helpers already copy on read, but those copies cannot prevent a writer from changing the stored pre-run evidence after a successful upsert.

Reproduced on b091863506538543203344be8f5bc7aae41cbcc3 with production code unchanged:

• Input and result mutations change stored path/hash/size/content on Memory, FileStore and SQLiteStore (six backend/access cases).
• An unrelated settings write followed by a real close/reopen preserves the accidental edits on both durable backends.
• The real checkpoint-file handler returns changed after save / changed-hash instead of the originally saved evidence, including after replacing an existing checkpoint. These are local deterministic regressions, not a production incident or a real-model E2E claim.

Scope and ownership

One writer in an isolated task worktree. Allowed changes:

• edge-server/internal/store/store_domain.go: detach the checkpoint file list at the input and result boundary.
• edge-server/internal/store/checkpoint_ownership_test.go: repository isolation and durable-reopen regressions.
• edge-server/internal/api/checkpoint_test.go: user-visible preview behavior.

Owner contract: docs/architecture/02-edge-server.md, Checkpoint and restore semantics. No wire interface changes are intended.

Invariants / negative constraints

Preserve metadata, file order, timestamp stamping, upsert replacement, missing-run errors, empty-list return shape and existing read behavior. Do not change persistence error policy, SQL/schema, retention, checkpoint restore/write-back, filesystem access, authorization, deployment or runtime configuration. Do not broaden this into a new storage abstraction or verifier.

Acceptance

• Reproduce both writer ownership leaks on all three real backends and the real preview handler.
• The same tests pass after the smallest ownership fix, including File/SQLite close/reopen.
• Preserve nil/empty writer results and existing checkpoint/read/snapshot behavior.
• Complete store/API tests on Windows and Linux race; vet/staticcheck; existing lifecycle checkpoint tests.
• Required PR checks pass; merge, source-only documentation closeout and task branch/worktree cleanup.

Windows reproduction from edge-server:

CGO_ENABLED=0 go test -p 2 ./internal/store ./internal/api -run 'TestRunCheckpointWriteOwnsFiles|TestCheckpointPreviewRetainsSavedEvidence' -count=1 -v

The shell-specific environment assignment is separate on PowerShell. The checked-in regression source and red/green evidence are attached in the comments below. Fixed by #2342; source-only closeout does not imply a runtime rollout.

[DeliciousBuding]

Confirmed failing baseline

Regression source: 35469721dbf054e141f4953cee76183267ba9de4. Only the two test files differ from b091863506538543203344be8f5bc7aae41cbcc3; production code was unchanged. The command in the issue exited 1: both input/result cases failed on all three backends, durable edits survived File/SQLite reopen, and both real preview-handler cases returned changed evidence.

Red regression output (synthetic checkpoint data)

=== RUN   TestRunCheckpointWriteOwnsFiles
=== PAUSE TestRunCheckpointWriteOwnsFiles
=== CONT  TestRunCheckpointWriteOwnsFiles
=== RUN   TestRunCheckpointWriteOwnsFiles/memory
=== RUN   TestRunCheckpointWriteOwnsFiles/memory/input
    checkpoint_ownership_test.go:62: caller input changed stored checkpoint: got=store.RunCheckpoint{ID:"checkpoint", RunID:"run", WorkDir:"workspace", FileCount:2, TotalBytes:11, CreatedAt:"2026-09-06T10:51:58Z", Files:[]store.CheckpointFile{store.CheckpointFile{Path:"caller.txt", Size:1, Hash:"caller", Content:"x"}, store.CheckpointFile{Path:"a.txt", Size:5, Hash:"original-a", Content:"other"}}} want=store.RunCheckpoint{ID:"checkpoint", RunID:"run", WorkDir:"workspace", FileCount:2, TotalBytes:11, CreatedAt:"2026-09-06T10:51:58Z", Files:[]store.CheckpointFile{store.CheckpointFile{Path:"z.txt", Size:6, Hash:"original-z", Content:"before"}, store.CheckpointFile{Path:"a.txt", Size:5, Hash:"original-a", Content:"other"}}}
    checkpoint_ownership_test.go:69: checkpoint input and result share files: other=[]store.CheckpointFile{store.CheckpointFile{Path:"caller.txt", Size:1, Hash:"caller", Content:"x"}, store.CheckpointFile{Path:"a.txt", Size:5, Hash:"original-a", Content:"other"}}
=== RUN   TestRunCheckpointWriteOwnsFiles/memory/result
    checkpoint_ownership_test.go:62: caller result changed stored checkpoint: got=store.RunCheckpoint{ID:"checkpoint", RunID:"run", WorkDir:"workspace", FileCount:2, TotalBytes:11, CreatedAt:"2026-09-06T10:51:58Z", Files:[]store.CheckpointFile{store.CheckpointFile{Path:"caller.txt", Size:1, Hash:"caller", Content:"x"}, store.CheckpointFile{Path:"a.txt", Size:5, Hash:"original-a", Content:"other"}}} want=store.RunCheckpoint{ID:"checkpoint", RunID:"run", WorkDir:"workspace", FileCount:2, TotalBytes:11, CreatedAt:"2026-09-06T10:51:58Z", Files:[]store.CheckpointFile{store.CheckpointFile{Path:"z.txt", Size:6, Hash:"original-z", Content:"before"}, store.CheckpointFile{Path:"a.txt", Size:5, Hash:"original-a", Content:"other"}}}
    checkpoint_ownership_test.go:69: checkpoint input and result share files: other=[]store.CheckpointFile{store.CheckpointFile{Path:"caller.txt", Size:1, Hash:"caller", Content:"x"}, store.CheckpointFile{Path:"a.txt", Size:5, Hash:"original-a", Content:"other"}}
=== RUN   TestRunCheckpointWriteOwnsFiles/file
=== RUN   TestRunCheckpointWriteOwnsFiles/file/input
    checkpoint_ownership_test.go:62: caller input changed stored checkpoint: got=store.RunCheckpoint{ID:"checkpoint", RunID:"run", WorkDir:"workspace", FileCount:2, TotalBytes:11, CreatedAt:"2026-09-06T10:51:58Z", Files:[]store.CheckpointFile{store.CheckpointFile{Path:"caller.txt", Size:1, Hash:"caller", Content:"x"}, store.CheckpointFile{Path:"a.txt", Size:5, Hash:"original-a", Content:"other"}}} want=store.RunCheckpoint{ID:"checkpoint", RunID:"run", WorkDir:"workspace", FileCount:2, TotalBytes:11, CreatedAt:"2026-09-06T10:51:58Z", Files:[]store.CheckpointFile{store.CheckpointFile{Path:"z.txt", Size:6, Hash:"original-z", Content:"before"}, store.CheckpointFile{Path:"a.txt", Size:5, Hash:"original-a", Content:"other"}}}
    checkpoint_ownership_test.go:69: checkpoint input and result share files: other=[]store.CheckpointFile{store.CheckpointFile{Path:"caller.txt", Size:1, Hash:"caller", Content:"x"}, store.CheckpointFile{Path:"a.txt", Size:5, Hash:"original-a", Content:"other"}}
    checkpoint_ownership_test.go:90: caller input edits survived reopen: got=store.RunCheckpoint{ID:"checkpoint", RunID:"run", WorkDir:"workspace", FileCount:2, TotalBytes:11, CreatedAt:"2026-09-06T10:51:58Z", Files:[]store.CheckpointFile{store.CheckpointFile{Path:"caller.txt", Size:1, Hash:"caller", Content:"x"}, store.CheckpointFile{Path:"a.txt", Size:5, Hash:"original-a", Content:"other"}}} want=store.RunCheckpoint{ID:"checkpoint", RunID:"run", WorkDir:"workspace", FileCount:2, TotalBytes:11, CreatedAt:"2026-09-06T10:51:58Z", Files:[]store.CheckpointFile{store.CheckpointFile{Path:"z.txt", Size:6, Hash:"original-z", Content:"before"}, store.CheckpointFile{Path:"a.txt", Size:5, Hash:"original-a", Content:"other"}}}
=== RUN   TestRunCheckpointWriteOwnsFiles/file/result
    checkpoint_ownership_test.go:62: caller result changed stored checkpoint: got=store.RunCheckpoint{ID:"checkpoint", RunID:"run", WorkDir:"workspace", FileCount:2, TotalBytes:11, CreatedAt:"2026-09-06T10:51:58Z", Files:[]store.CheckpointFile{store.CheckpointFile{Path:"caller.txt", Size:1, Hash:"caller", Content:"x"}, store.CheckpointFile{Path:"a.txt", Size:5, Hash:"original-a", Content:"other"}}} want=store.RunCheckpoint{ID:"checkpoint", RunID:"run", WorkDir:"workspace", FileCount:2, TotalBytes:11, CreatedAt:"2026-09-06T10:51:58Z", Files:[]store.CheckpointFile{store.CheckpointFile{Path:"z.txt", Size:6, Hash:"original-z", Content:"before"}, store.CheckpointFile{Path:"a.txt", Size:5, Hash:"original-a", Content:"other"}}}
    checkpoint_ownership_test.go:69: checkpoint input and result share files: other=[]store.CheckpointFile{store.CheckpointFile{Path:"caller.txt", Size:1, Hash:"caller", Content:"x"}, store.CheckpointFile{Path:"a.txt", Size:5, Hash:"original-a", Content:"other"}}
    checkpoint_ownership_test.go:90: caller result edits survived reopen: got=store.RunCheckpoint{ID:"checkpoint", RunID:"run", WorkDir:"workspace", FileCount:2, TotalBytes:11, CreatedAt:"2026-09-06T10:51:58Z", Files:[]store.CheckpointFile{store.CheckpointFile{Path:"caller.txt", Size:1, Hash:"caller", Content:"x"}, store.CheckpointFile{Path:"a.txt", Size:5, Hash:"original-a", Content:"other"}}} want=store.RunCheckpoint{ID:"checkpoint", RunID:"run", WorkDir:"workspace", FileCount:2, TotalBytes:11, CreatedAt:"2026-09-06T10:51:58Z", Files:[]store.CheckpointFile{store.CheckpointFile{Path:"z.txt", Size:6, Hash:"original-z", Content:"before"}, store.CheckpointFile{Path:"a.txt", Size:5, Hash:"original-a", Content:"other"}}}
=== RUN   TestRunCheckpointWriteOwnsFiles/sqlite
=== RUN   TestRunCheckpointWriteOwnsFiles/sqlite/input
    checkpoint_ownership_test.go:62: caller input changed stored checkpoint: got=store.RunCheckpoint{ID:"checkpoint", RunID:"run", WorkDir:"workspace", FileCount:2, TotalBytes:11, CreatedAt:"2026-09-06T10:51:59Z", Files:[]store.CheckpointFile{store.CheckpointFile{Path:"caller.txt", Size:1, Hash:"caller", Content:"x"}, store.CheckpointFile{Path:"a.txt", Size:5, Hash:"original-a", Content:"other"}}} want=store.RunCheckpoint{ID:"checkpoint", RunID:"run", WorkDir:"workspace", FileCount:2, TotalBytes:11, CreatedAt:"2026-09-06T10:51:59Z", Files:[]store.CheckpointFile{store.CheckpointFile{Path:"z.txt", Size:6, Hash:"original-z", Content:"before"}, store.CheckpointFile{Path:"a.txt", Size:5, Hash:"original-a", Content:"other"}}}
    checkpoint_ownership_test.go:69: checkpoint input and result share files: other=[]store.CheckpointFile{store.CheckpointFile{Path:"caller.txt", Size:1, Hash:"caller", Content:"x"}, store.CheckpointFile{Path:"a.txt", Size:5, Hash:"original-a", Content:"other"}}
    checkpoint_ownership_test.go:90: caller input edits survived reopen: got=store.RunCheckpoint{ID:"checkpoint", RunID:"run", WorkDir:"workspace", FileCount:2, TotalBytes:11, CreatedAt:"2026-09-06T10:51:59Z", Files:[]store.CheckpointFile{store.CheckpointFile{Path:"caller.txt", Size:1, Hash:"caller", Content:"x"}, store.CheckpointFile{Path:"a.txt", Size:5, Hash:"original-a", Content:"other"}}} want=store.RunCheckpoint{ID:"checkpoint", RunID:"run", WorkDir:"workspace", FileCount:2, TotalBytes:11, CreatedAt:"2026-09-06T10:51:59Z", Files:[]store.CheckpointFile{store.CheckpointFile{Path:"z.txt", Size:6, Hash:"original-z", Content:"before"}, store.CheckpointFile{Path:"a.txt", Size:5, Hash:"original-a", Content:"other"}}}
=== RUN   TestRunCheckpointWriteOwnsFiles/sqlite/result
    checkpoint_ownership_test.go:62: caller result changed stored checkpoint: got=store.RunCheckpoint{ID:"checkpoint", RunID:"run", WorkDir:"workspace", FileCount:2, TotalBytes:11, CreatedAt:"2026-09-06T10:51:59Z", Files:[]store.CheckpointFile{store.CheckpointFile{Path:"caller.txt", Size:1, Hash:"caller", Content:"x"}, store.CheckpointFile{Path:"a.txt", Size:5, Hash:"original-a", Content:"other"}}} want=store.RunCheckpoint{ID:"checkpoint", RunID:"run", WorkDir:"workspace", FileCount:2, TotalBytes:11, CreatedAt:"2026-09-06T10:51:59Z", Files:[]store.CheckpointFile{store.CheckpointFile{Path:"z.txt", Size:6, Hash:"original-z", Content:"before"}, store.CheckpointFile{Path:"a.txt", Size:5, Hash:"original-a", Content:"other"}}}
    checkpoint_ownership_test.go:69: checkpoint input and result share files: other=[]store.CheckpointFile{store.CheckpointFile{Path:"caller.txt", Size:1, Hash:"caller", Content:"x"}, store.CheckpointFile{Path:"a.txt", Size:5, Hash:"original-a", Content:"other"}}
    checkpoint_ownership_test.go:90: caller result edits survived reopen: got=store.RunCheckpoint{ID:"checkpoint", RunID:"run", WorkDir:"workspace", FileCount:2, TotalBytes:11, CreatedAt:"2026-09-06T10:51:59Z", Files:[]store.CheckpointFile{store.CheckpointFile{Path:"caller.txt", Size:1, Hash:"caller", Content:"x"}, store.CheckpointFile{Path:"a.txt", Size:5, Hash:"original-a", Content:"other"}}} want=store.RunCheckpoint{ID:"checkpoint", RunID:"run", WorkDir:"workspace", FileCount:2, TotalBytes:11, CreatedAt:"2026-09-06T10:51:59Z", Files:[]store.CheckpointFile{store.CheckpointFile{Path:"z.txt", Size:6, Hash:"original-z", Content:"before"}, store.CheckpointFile{Path:"a.txt", Size:5, Hash:"original-a", Content:"other"}}}
--- FAIL: TestRunCheckpointWriteOwnsFiles (0.06s)
    --- FAIL: TestRunCheckpointWriteOwnsFiles/memory (0.00s)
        --- FAIL: TestRunCheckpointWriteOwnsFiles/memory/input (0.00s)
        --- FAIL: TestRunCheckpointWriteOwnsFiles/memory/result (0.00s)
    --- FAIL: TestRunCheckpointWriteOwnsFiles/file (0.01s)
        --- FAIL: TestRunCheckpointWriteOwnsFiles/file/input (0.01s)
        --- FAIL: TestRunCheckpointWriteOwnsFiles/file/result (0.00s)
    --- FAIL: TestRunCheckpointWriteOwnsFiles/sqlite (0.05s)
        --- FAIL: TestRunCheckpointWriteOwnsFiles/sqlite/input (0.02s)
        --- FAIL: TestRunCheckpointWriteOwnsFiles/sqlite/result (0.03s)
FAIL
FAIL	github.com/agenthub/edge-server/internal/store	0.093s
=== RUN   TestCheckpointPreviewRetainsSavedEvidence
=== RUN   TestCheckpointPreviewRetainsSavedEvidence/input
    checkpoint_test.go:181: caller input changed saved preview evidence: struct { Path string; Hash string; Content string; SizeBytes int }{Path:"src/a.ts", Hash:"changed-hash", Content:"changed after save", SizeBytes:12}
=== RUN   TestCheckpointPreviewRetainsSavedEvidence/result
    checkpoint_test.go:181: caller result changed saved preview evidence: struct { Path string; Hash string; Content string; SizeBytes int }{Path:"src/a.ts", Hash:"changed-hash", Content:"changed after save", SizeBytes:12}
--- FAIL: TestCheckpointPreviewRetainsSavedEvidence (0.00s)
    --- FAIL: TestCheckpointPreviewRetainsSavedEvidence/input (0.00s)
    --- FAIL: TestCheckpointPreviewRetainsSavedEvidence/result (0.00s)
FAIL
FAIL	github.com/agenthub/edge-server/internal/api	0.036s
FAIL

[DeliciousBuding]

Ownership fix and final local verification

Final head: 21745169df7f56b14a8583877deaa1bb3f5a624c. Production change is four added lines in store_domain.go: import slices and independently clone the incoming and outgoing checkpoint file lists. Existing Get/snapshot cloning and persistence semantics are unchanged.

The same six backend/access cases and both real preview-handler cases now pass. FileStore and SQLiteStore pass real close/reopen after an unrelated settings write. The nil/empty writer-result controls passed both before and after the fix; creation time, metadata and file ordering remain intact. Existing checkpoint lifecycle tests (event-before-start and honest absence without a workdir) pass.

Final local commands from edge-server:

• Windows: CGO_ENABLED=0, then go test -p 2 ./internal/store ./internal/api -count=1 -cpu=4 -timeout=10m — passed.
• Linux: CGO_ENABLED=1 go test -race -p 2 ./internal/store ./internal/api -count=1 -cpu=4 -timeout=10m — passed.
• go vet -p 2 ./internal/store ./internal/api — passed.
• staticcheck ./internal/store ./internal/api — passed.
• git diff --check — passed.

This is local real-repository/HTTP-handler evidence, not an actual model execution, live incident, remote stack E2E or packaged Desktop result. No runtime/configuration/authorization/restore changes were made. PR CI and merge are still pending.

Checkpoint regression and lifecycle outcomes (fixture diagnostic logs omitted)

=== RUN   TestRunCheckpointWriteOwnsFiles
=== RUN   TestRunCheckpointWritePreservesEmptyFileLists
=== RUN   TestRunCheckpointWritePreservesEmptyFileLists/nil
=== RUN   TestRunCheckpointWritePreservesEmptyFileLists/empty
--- PASS: TestRunCheckpointWritePreservesEmptyFileLists (0.00s)
    --- PASS: TestRunCheckpointWritePreservesEmptyFileLists/nil (0.00s)
    --- PASS: TestRunCheckpointWritePreservesEmptyFileLists/empty (0.00s)
=== RUN   TestSQLiteCheckpointDeltaSkipsUnchangedRows
--- PASS: TestSQLiteCheckpointDeltaSkipsUnchangedRows (0.02s)
=== RUN   TestSQLiteCheckpointDeltaRemovesRunEvidence
=== RUN   TestSQLiteCheckpointDeltaRemovesRunEvidence/terminal-cleanup
=== RUN   TestSQLiteCheckpointDeltaRemovesRunEvidence/delete-thread
--- PASS: TestSQLiteCheckpointDeltaRemovesRunEvidence (0.05s)
    --- PASS: TestSQLiteCheckpointDeltaRemovesRunEvidence/terminal-cleanup (0.02s)
    --- PASS: TestSQLiteCheckpointDeltaRemovesRunEvidence/delete-thread (0.02s)
=== RUN   TestSQLiteCheckpointSurvivesReopen
--- PASS: TestSQLiteCheckpointSurvivesReopen (0.03s)
=== RUN   TestSQLiteLegacyRowsAdoptsSettingsAndCheckpointsFromPayload
--- PASS: TestSQLiteLegacyRowsAdoptsSettingsAndCheckpointsFromPayload (0.04s)
=== RUN   TestStoreRunCheckpointUpsertAndGet
--- PASS: TestStoreRunCheckpointUpsertAndGet (0.00s)
=== RUN   TestStoreRunCheckpointSnapshotRoundTrip
--- PASS: TestStoreRunCheckpointSnapshotRoundTrip (0.00s)
=== RUN   TestRunCheckpointWriteOwnsFiles/memory
=== RUN   TestRunCheckpointWriteOwnsFiles/memory/input
=== RUN   TestRunCheckpointWriteOwnsFiles/memory/result
=== RUN   TestRunCheckpointWriteOwnsFiles/file
=== RUN   TestRunCheckpointWriteOwnsFiles/file/input
=== RUN   TestRunCheckpointWriteOwnsFiles/file/result
=== RUN   TestRunCheckpointWriteOwnsFiles/sqlite
=== RUN   TestRunCheckpointWriteOwnsFiles/sqlite/input
=== RUN   TestRunCheckpointWriteOwnsFiles/sqlite/result
--- PASS: TestRunCheckpointWriteOwnsFiles (0.06s)
    --- PASS: TestRunCheckpointWriteOwnsFiles/memory (0.00s)
        --- PASS: TestRunCheckpointWriteOwnsFiles/memory/input (0.00s)
        --- PASS: TestRunCheckpointWriteOwnsFiles/memory/result (0.00s)
    --- PASS: TestRunCheckpointWriteOwnsFiles/file (0.02s)
        --- PASS: TestRunCheckpointWriteOwnsFiles/file/input (0.01s)
        --- PASS: TestRunCheckpointWriteOwnsFiles/file/result (0.01s)
    --- PASS: TestRunCheckpointWriteOwnsFiles/sqlite (0.04s)
        --- PASS: TestRunCheckpointWriteOwnsFiles/sqlite/input (0.02s)
        --- PASS: TestRunCheckpointWriteOwnsFiles/sqlite/result (0.02s)
PASS
ok  	github.com/agenthub/edge-server/internal/store	0.224s
=== RUN   TestGetRunCheckpointMetadata
--- PASS: TestGetRunCheckpointMetadata (0.00s)
=== RUN   TestGetRunCheckpointHonestAbsence
--- PASS: TestGetRunCheckpointHonestAbsence (0.00s)
=== RUN   TestGetRunCheckpointFile
--- PASS: TestGetRunCheckpointFile (0.00s)
=== RUN   TestCheckpointPreviewRetainsSavedEvidence
=== RUN   TestCheckpointPreviewRetainsSavedEvidence/input
=== RUN   TestCheckpointPreviewRetainsSavedEvidence/result
--- PASS: TestCheckpointPreviewRetainsSavedEvidence (0.00s)
    --- PASS: TestCheckpointPreviewRetainsSavedEvidence/input (0.00s)
    --- PASS: TestCheckpointPreviewRetainsSavedEvidence/result (0.00s)
PASS
ok  	github.com/agenthub/edge-server/internal/api	0.039s
=== RUN   TestProcessExecutorEmitsRunCheckpointBeforeStart
--- PASS: TestProcessExecutorEmitsRunCheckpointBeforeStart (0.02s)
=== RUN   TestProcessExecutorNoCheckpointWithoutWorkDir
--- PASS: TestProcessExecutorNoCheckpointWithoutWorkDir (0.02s)
PASS
ok  	github.com/agenthub/edge-server/internal/lifecycle	0.064s

checkpoint-final-linux-race

ok  	github.com/agenthub/edge-server/internal/store	5.515s
ok  	github.com/agenthub/edge-server/internal/api	11.713s

checkpoint-final-windows

ok  	github.com/agenthub/edge-server/internal/store	2.042s
ok  	github.com/agenthub/edge-server/internal/api	1.131s

checkpoint-final-vet

(exit 0; no output)

checkpoint-final-staticcheck

(exit 0; no output)

[DeliciousBuding]

Merged and source-only closeout

• PR fix(store): isolate checkpoint file ownership #2342 was normally squash-merged as 49078e7adce93c8ed61108c6f427782f475cfc2c; the merged file tree matches tested head 21745169df7f56b14a8583877deaa1bb3f5a624c exactly.
• CI run 34029282680 completed successfully. All seven required checks passed under strict branch protection, including the backend integration/fixture lanes behind their aggregate checks. The preceding comment contains local Windows, Linux race and static-check results; skipped frontend/native/real-E2E jobs are not claimed as tested.
• The local source checkout is clean and synchronized to the merge commit. The completed local/remote task branch and worktree are removed; red/green evidence and unrelated work are preserved. Private operational owner documentation was committed and pushed, consolidating the related ownership-fix log rather than adding duplicate status entries.
• No remote source sync, runtime rebuild, restart, deployment, actual model execution or packaged Desktop validation was performed. Existing runtime verification snapshots remain historical; this fix does not add checkpoint restore/write-back.

All acceptance items for this bounded issue are now satisfied. #2304 and #1663 remain independent open follow-ups.