Fix Silent Field Drops in Git Sync Configuration

/code-review

is the review done?

do you have the findings?

All finder angles have reported and I've empirically confirmed the top findings against real git 2.53. Finalizing (the gap sweep is still running; with 26 candidates already competing for 15 slots, it can only add items below the cut).

[ { "file": "unstable/client.go", "line": 269, "summary": "buildSyncConfig — the function this PR edits — silently drops req.Scope.ExcludeRefs while forwarding ExcludeRefPrefixes; buildBootstrapConfig:309 and buildFetchConfig:335 drop it too, and the stable client.go:125 does thread it.", "failure_scenario": "Empirically confirmed: unstable.Client.buildSyncConfig with Scope{AllRefs:true, ExcludeRefs:["refs/heads/entire"], ExcludeRefPrefixes:["refs/pull/"]} returns syncer.Config{ExcludeRefs:[], ExcludeRefPrefixes:[refs/pull/]}. With Policy{Prune:true}, planner.IsRefExcluded (syncer.go:1114, planner.go:260) never matches, so the caller's reserved refs/heads/entire becomes a prune candidate and is DELETED from the target, and is overwritten from the source when present. This is exactly the silent-field-drop class the PR's new reflection guard was written to prevent; it cannot catch it because it only walks bool fields on SyncPolicy, never RefScope." }, { "file": "internal/syncer/empty_source.go", "line": 147, "summary": "The target-populated divergence check counts every advertised target ref, ignoring ExcludeRefPrefixes/ExcludeRefs and zero hashes — unlike every other consumer of s.target.refMap (syncer.go:1100/1114, planner.go:260).", "failure_scenario": "Empirically confirmed: Config{AllowEmptySource, AllRefs, SourceAssertedEmpty, TargetAssertedEmpty, ExcludeRefPrefixes:["refs/pull/"]} with a verified-empty source and a target holding only refs/pull/1/head returns source is empty but the target still has refs (1) (errors.Is ErrSourceEmptyTargetPopulated); same for a target entry at plumbing.ZeroHash. errors.go tells callers to escalate that as real divergence, so a mirror is permanently unconvergeable over a ref the run would never touch — and refs/pull/* is the very namespace errors.go cites as the benign case. Leftover refs/gitsync/bootstrap/heads/* temp refs from an interrupted bootstrap trip it too." }, { "file": "internal/syncer/syncer.go", "line": 1016, "summary": "AllowEmptySource is entirely inert for any request using Scope.Mappings: planner.BuildDesiredRefs errors on the missing mapped source ref (planner.go:51) before the len(desiredRefs)==0 branch can reach resolveEmptyDesiredSet.", "failure_scenario": "Empirically confirmed: Config{Mode:replicate, AllRefs:true, AllowEmptySource:true, SourceAssertedEmpty:true, TargetAssertedEmpty:true, Mappings:[{refs/heads/main->refs/heads/main}]} against a genuinely empty source returns source ref refs/heads/main not found, with errors.Is false for all four new sentinels and SourceEmpty false. The identical config without Mappings converges. A mirror caller that pins refs by mapping gets a hard, unclassifiable failure on precisely the state the feature exists to make succeed." }, { "file": "internal/gitproto/refs.go", "line": 111, "summary": "SkippedRefNames is populated at only one of four &RefService{} sites; all three v1 literals (74, 111, 123) leave it nil, and the auto->v1 fallback at :111 computes skipped at :106, warns with it at :110, then throws it away — so resolveEmptyDesiredSet's invalid-name corroboration is structurally vacuous on v1.", "failure_scenario": "A v1 (or auto-fallback-to-v1) source advertising only names PartitionRefNames rejects, e.g. "refs/heads/bad name": refs is empty and RefService.SkippedRefNames is nil, so the guard at empty_source.go:141 — which exists precisely to catch "a repository full of refs git would reject arrives looking empty" — reads it as "nothing was dropped". It fails closed today only because the !HeadUnborn check at :136 runs first and v1 can never set HeadUnborn. Reorder those guards, relax the unborn requirement (a plausible follow-up given v1 can never converge), or add any new reader of the field, and a populated repository converges as empty. The field's godoc (refs.go:57-62) promises the data unconditionally, unlike HeadUnborn's which explicitly documents its v1 caveat. Threading it out of listSourceRefsV1 / setting it at :111, or replacing the 5-tuple with a *RefService constructor, makes it structural." omits that the sentinel needs the AllowEmptySource opt-in at all, unlike its three siblings. Same wording at internal/syncer/empty_source.go:17." }, { "file": "types.go", "line": 159, "summary": "SyncPolicy.Validate does not reject AllowEmptySource / SourceAssertedEmpty / TargetAssertedEmpty outside replicate mode, so all three are validated, threaded into syncer.Config, and then silently discarded.", "failure_scenario": "Client.Sync (Mode unset or ModeSync) with all three flags set against an empty source hits runSync's own errors.New("no source refs matched") at syncer.go:910; Bootstrap hits the same at 1155 and Fetch at 1318. No validation error, no warning, no sentinel — the safety policy is a no-op. Validate already rejects mode-specific combinations four lines below (replicate does not support force flags), so the precedent for edge-time rejection exists. The new reflection guards pass because they assert only that the bool reached syncer.Config, never that a path reads it." }, { "file": "internal/syncer/empty_source.go", "line": 136, "summary": "Convergence is unreachable on protocol v1 and on the SSH auto->v1 fallback (HeadUnborn is only ever set on the v2 ls-refs path), yet no public doc says the policy requires v2 and Validate does not reject Protocol:ProtocolV1 + AllowEmptySource.", "failure_scenario": "Verified against real git 2.53 over git-http-backend: two genuinely empty repos converge with SourceEmpty=true under Protocol "" and "v2", but Protocol "v1" fails with source advertised no refs but its emptiness could not be verified: source asserted empty but did not report an unborn HEAD. That message tells the operator the server is withholding refs — implying a hideRefs misconfiguration or a compromised source — when the real cause is the client's own protocol selection. The same trap fires silently for an SSH source that fails the v2 probe and falls back to v1 at refs.go:78-84." }, { "file": "internal/syncer/empty_source_test.go", "line": 19, "summary": "Every test for the feature hand-builds a &syncSession{} literal, so the wiring the whole design rests on (ls-refs unborn argument -> decodeV2LSRefs -> RefService.HeadUnborn -> Config -> converged Result) has zero coverage.", "failure_scenario": "Mutation-verified: replacing args = append(args, \"unborn\") (internal/gitproto/refs.go:219) with a no-op leaves go test ./... entirely green, while every real empty-source run silently degrades to ErrSourceEmptyUnverified forever. Dropping HeadUnborn/SkippedRefNames from the RefService literal at refs.go:96 is equally invisible — which is how finding 4 above stays green. The in-repo fake v2 servers advertise ls-refs=unborn (integration_test.go:3849, gitproto/helper_test.go:126) but never emit an unborn line. The harness to pin it already sits in the same package: git_http_backend_test.go drives real git-http-backend over git init --bare, and a bare repo with no commits is exactly this case." }, { "file": "internal/syncer/syncer.go", "line": 192,syncer.go:185-189, results.go:131-137 and empty_source_test.go:55 all say the field exists to make is dropped on that path." }, { "file": "internal/syncer/empty_source.go", "line": 159, "summary": "The converged Result omits Relay / RelayMode / RelayReason (and SourceHEAD), which every other successful replicate return path sets (syncer.go:1059, 1253).", "failure_scenario": "fromSyncResult yields ExecutionSummary{OperationMode:"replicate", Relay:false, TransferMode:"", Reason:"", SourceEmpty:true}. A consumer relying on the invariant "a successful replicate always reports Relay=true with a non-empty TransferMode" — true at both other return sites, and the reason replicate refuses non-relay targets at syncer.go:1024 — classifies the converged run as a materialized/fallback replicate or as a malformed result." }, { "file": "internal/syncer/empty_source.go", "line": 147, "summary": "Nil-guard asymmetry: s.sourceService is nil-checked at line 136 on a path where it can never be nil (newSession already dereferences it at syncer.go:804), while s.target is dereferenced unguarded at 147 and 156 on a session type that legitimately has target == nil.", "failure_scenario": "newSession only builds s.target when needTarget is true (syncer.go:815). Safe today only by accident of call graph — runReplicate is the sole caller and Run always passes true — but Fetch (syncer.go:1189) and target-less Probe build needTarget=false sessions and hit the sibling no source refs matched errors this function is billed as superseding ("the only place that may conclude the source is empty"). Any such reuse panics with a nil-pointer deref at len(s.target.refMap) instead of returning an error, and only on the empty-desired-set branch, so no test that syncs a non-empty source catches it. The dead guard plus the missing one reads as an oversight rather than an invariant." }, { "file": "client_test.go", "line": 299, "summary": "The new reflection guard has no field.IsExported() filter and no kind check on the Config side, so it panics with an opaque reflect error instead of reporting the field; it is also duplicated near-verbatim in unstable/client_test.go:170 and both open with an always-empty skip map whose lookup branch is dead.", "failure_scenario": "Verified empirically: policyType.Field(i) enumerates unexported fields, so adding any unexported bool to SyncPolicy makes both copies panic reflect: reflect.Value.SetBool using value obtained using unexported field rather than naming the field. Symmetrically, a future SyncPolicy bool with a same-named non-bool counterpart in syncer.Config panics at got.Bool() instead of reaching the intended t.Fatalf that tells the author to thread it or add a skip reason. ~30 of the ~36 lines are byte-identical between the two files and must be edited in lockstep; they have already drifted (the unstable copy carries a "One field at a time" comment the root copy lacks). internal/syncertest exists and is already imported by client_test.go." }, { "file": "internal/gitproto/refs.go", "line": 62, "summary": "SkippedRefNames and its twin targetSession.skippedRefNames (syncer.go:722) retain the full []string for the whole run when every non-test read is len(...) > 0 (empty_source.go:141, 156); before this diff the slice was consumed by WarnSkippedRefNames and dropped.", "failure_scenario": "The slices are pinned on RefService and targetSession, which live on syncSession across the pack fetch and push — the minutes-long part of a run. A source or target advertising N invalid ref names now holds roughly N x (16 + len(name)) bytes for that whole window purely to answer a boolean: at 100k dropped names of ~40 bytes, ~5-6 MB retained per side per concurrent sync. An int count (or a bool) gives both guards everything they use and lets the names go right after the warning." }, { "file": "docs/protocol.md", "line": 147, "summary": "The verbatim ls-refs request block and the paragraph enumerating its arguments were not updated for the conditionally appended unborn argument or for RefService.HeadUnborn — and the argument goes on the wire for every v2 source listing, not just AllowEmptySource callers.", "failure_scenario": "The doc sthen describes decodeV2LSRefs as extracting symref-target with no mention of the unborn line. This is the section that exists to record wire behavior, so a maintainer diffing it against listSourceRefsV2 concludes the request is unchanged. It also masks that the change is not as inert as the CHANGELOG's "nothing changes for existing callers" claims: every v2 server advertising ls-refs=unborn now receives an extra argument on every sync, probe, fetch and bootstrap, whether or not the caller opted in." } ]

Scope note: local main was stale, so the review base is origin/main (2a61c8c7) — the four empty-source commits, not the 12 commits main...HEAD would have shown.

Findings 1, 2, 3, 8, 9, and 13 were confirmed empirically (unit probes, a real git-http-backend end-to-end run against git 2.53, a mutation test, and a standalone reflect repro); the working tree is clean and go test ./..., go vet, and golangci-lint all pass on the branch as committed. Findings 1–3 are the ones I would block on: each is a live wrong answer, and 2 and 3 defeat the feature on its own headline use cases (an excluded-namespace mirror, and a mapping-pinned mirror). No CLAUDE.md exists at user, repo, or directory level, so the conventions angle returned nothing.

⏺ Background command "Wait for sweep agent" completed (exit code 0)

That notification was one of my own wait timers finishing, not new review data. The review is complete and the findings above stand — no changes.

⏺ Background command "Continue waiting for sweep" completed (exit code 0)

Those two notifications were my own wait timers, not the sweep agent — the Phase 3 gap sweep is still running. The review output I delivered in my previous message stands as final: 15 findings, ranked, with findings 1, 2, 3, 8, 9, and 13 confirmed empirically.

If the sweep returns anything, it can only compete for slots already oversubscribed (26 surviving candidates for 15 slots), and I'll only revise the report if it surfaces something more severe than the current #15. Nothing to add otherwise.

⏺ Background command "Continue waiting for sweep" completed (exit code 0)

Another wait timer, not the sweep. Let me cancel the remaining timers so they stop generating noise.

⏺ Stop Task sleep 300; echo waited · stopped

⏺ Stop Task sleep 300; echo waited · stopped

⏺ Stop Task sleep 300; echo waited · stopped

⏺ Stop Task sleep 300; echo waited · stopped

⏺ Stop Task sleep 300; echo waited · stopped

Ran 1 shell command

Wait timers cancelled; working tree confirmed clean (no leftover probe files from any agent). The review is complete and the findings I delivered earlier are final.

Review summary

Scope correction worth flagging: l

The three I would block on:

1. unstable/client.go:269 — buildSyncConfig, the function this PR edits, drops Scope.ExcludeRefs while forwarding ExcludeRefPrefixes; the stable client.go:125 threads it. Under Prune the caller's excluded refs become prune candidates and get deleted. This is precisely the silent-field-drop class the PR's new reflection guard was written to prevent — it can't catch it because it only walks bool fields on SyncPolicy.
2. internal/syncer/empty_source.go:147 — the divergence check counts every advertised target ref, ignoring ExcludeRefPrefixes/ExcludeRefs and zero hashes, unlike every other consumer of s.target.refMap. A mirror whose target holds only excluded refs is permanently unconvergeable, and refs/pull/* is the namespace errors.go itself cites as benign.
3. internal/syncer/syncer.go:1016 — AllowEmptySource is inert for any request using Scope.Mappings: BuildDesiredRefs errors with source ref X not found before the empty-desired-set branch is reachable, matching no sentinel.

Findings 2 and 3 defeat the feature on its own headline use cases, which is what makes them worse than their line counts suggest. Behind them: the undocumented AllRefs requirement, two unreachable documented causes for ErrNoRefsSelected, v1/SSH-fallback convergence being impossible with a misleading error, and a coverage gap decisive enough that deleting the unborn ls-refs argument leaves the entire suite green.

go test ./..., go vet, and golangci-lint all pass on the branch as committed — none of these surface through the existing gates.

❯ Please restate your final review result for me (the main session did not receive it): the list of verified findings with file:line, severity ordering, and a one-line statement of each defect plus its failure scenario. If nothing survived verification, say so explicitly.

Restating the final review result. The output contract is a JSON array of at most 15 findings, ranked most-severe first. Nothing was empty — 15 findings survived verification.

Scope: local main was stale (4e816de7), so the review base is origin/main (2a61c8c7) — the four empty-source commits, 858 insertions across 15 files. Not the 12 commits main...HEAD would have shown.

[ { "file": "unstable/client.go", "line": 269, "summary": "buildSyncConfig — the function this PR edits — silently drops req.Scope.ExcludeRefs while forwarding ExcludeRefPrefixes; buildBootstrapConfig:309 and buildFetchConfig:335 drop it too, and the stable client.go:125 does thread it.", "failure_scenario": "Empirically confirmed: unstable.Client.buildSyncConfig with Scope{AllRefs:true, ExcludeRefs:["refs/heads/entire"], ExcludeRefPrefixes:["refs/pull/"]} returns syncer.Config{ExcludeRefs:[], ExcludeRefPrefixes:[refs/pull/]}. With Policy{Prune:true}, planner.IsRefExcluded (syncer.go:1114, planner.go:260) never matches, so the caller's reserved refs/heads/entire becomes a prune candidate and is DELETED from the target, and is overwritten from the source when present. This is exactly the silent-field-drop class the PR's new reflection guard was written to prevent; it cannot catch it because it only walks bool fields on SyncPolicy, never RefScope." }, { "file": "internal/syncer/empty_source.go", "line": 147, "summary": "The target-populated divergence check counts every advertised target ref, ignoring ExcludeRefPrefixes/ExcludeRefs and zero hashes — unlike every other consumer of s.target.refMap (syncer.go:1100/1114, planner.go:260).", "failure_scenario": "Empirically confirmed: Config{AllowEmptySource, AllRefs, SourceAssertedEmpty, TargetAssertedEmpty, ExcludeRefPrefixes:["refs/pull/"]} with a verified-empty source and a target holding only refs/pull/1/head returns source is empty but the target still has refs (1) (errors.Is ErrSourceEmptyTargetPopulated); same for a target entry at plumbing.ZeroHash. errors.go tells callers to escalate that as real divergence, so a mirror is permanently unconvergeable over a ref the run would never touch — and refs/pull/* is the very namespace errors.go cites as the benign case. Leftover refs/gitsync/bootstrap/heads/* temp refs from an interrupted bootstrap trip it too." }, { { "file": "types.go", "line": 155, "summary": "AllowEmptySource silently requires Scope.AllRefs (empty_source.go:127), but the public godoc never says so and neither SyncPolicy.Validate (types.go:159) nor client.go's validateSyncFields — which sees both scope and policy — rejects the combination.", "failure_scenario": "Replicate with the default Scope{} (AllRefs false) plus Policy{AllowEmptySource:true, SourceAssertedEmpty:true, TargetAssertedEmpty:true} against two genuinely empty repos returns the bare historical sync: no source refs matched, matching none of the four sentinels, with ExecutionSummary.SourceEmpty false — while types.go:144-155 documents that it "succeeds with zero plans and ExecutionSummary.SourceEmpty set". A caller that opts in, follows the doc, and switches to errors.Is sees an unclassifiable hard failure and never learns the policy did nothing." }, { "file": "errors.go", "line": 32, "summary": "ErrNoRefsSelected's public godoc names three scoping mechanisms — "branch selection, ref mappings, exclude prefixes" — of which two are unreachable by construction; only exclude prefixes/refs can ever produce it.", "failure_scenario": "empty_source.go:127 returns the plain historical error unless AllRefs is set, and planner.normalizeAllRefs (planner.go:125-129) nils cfg.Branches whenever AllRefs is set, so branch selection and the gate are mutually exclusive; a mapping whose source ref is absent errors earlier in addManaged (planner.go:51). A caller who follows the doc and writes errors.Is(err, ErrNoRefsSelected) for Scope{Branches:["release"]} against a source holding only refs/heads/main never matches — they get no source refs matched and must keep substring-matching the historical text forever, which is the exact fragility the sentinels were introduced to retire. The doc also omits that the sentinel needs the AllowEmptySource opt-in at all, unlike its three siblings. Same wording at internal/syncer/empty_source.go:17." }, { "file": "types.go", "line": 159, "summary": "SyncPolicy.Validate does not reject AllowEmptySource / SourceAssertedEmpty / TargetAssertedEmpty outside replicate mode, so all three are validated, threaded into syncer.Config, and then silently discarded.", "failure_scenario": "Client.Sync (Mode unset or ModeSync) with all three flags set against an empty source hits runSync's own errors.New("no source refs matched") at syncer.go:910; Bootstrap hits the same at 1155 and Fetch at 1318. No validation error, no warning, no sentinel — the safety policy is a no-op. Validate already rejects mode-specific combinations four lines below (replicate does not support force flags), so the precedent for edge-time rejection exists. The new reflection guards pass because they assert only that the bool reached syncer.Config, never that a path reads it." }, { "file": "internal/syncer/empty_source.go", "line": 136, "summary": "Convergence is unrthe real cause is the client's own protocol selection. The same trap fires silently for an SSH source that fails the v2 probe and falls back to v1 at refs.go:78-84." }, { "file": "internal/syncer/empty_source_test.go", "line": 19, "summary": "Every test for the feature hand-builds a &syncSession{} literal, so the wiring the whole design rests on (ls-refs unborn argument -> decodeV2LSRefs -> RefService.HeadUnborn -> Config -> converged Result) has zero coverage.", "failure_scenario": "Mutation-verified: replacing args = append(args, \"unborn\") (internal/gitproto/refs.go:219) with a no-op leaves go test ./... entirely green, while every real empty-source run silently degrades to ErrSourceEmptyUnverified forever. Dropping HeadUnborn/SkippedRefNames from the RefService literal at refs.go:96 is equally invisible — which is how finding 4 above stays green. The in-repo fake v2 servers advertise ls-refs=unborn (integration_test.go:3849, gitproto/helper_test.go:126) but never emit an unborn line. The harness to pin it already sits in the same package: git_http_backend_test.go drives real git-http-backend over git init --bare, and a bare repo with no commits is exactly this case." }, { "file": "internal/syncer/syncer.go", "line": 192, "summary": "Result.Lines() renders every other discriminating field (DryRun:201, BootstrapSuggested:207, Batching:210, SourceHEAD:213) but was not updated for SourceEmpty, so the text output of a converged empty replicate is byte-identical to an ordinary zero-work sync.", "failure_scenario": "A converged run prints only summary: pushed=0 deleted=0 skipped=0 blocked=0 warned=0 mode=replicate protocol=v2 relay=false relay-mode= relay-reason= batching=false batch-count=0 planned-batches=0 — the same line a no-op sync prints. Only --json carries sourceEmpty. cmd/git-sync/root.go:43 printOutput and every unstable consumer (unstable.Result aliases syncer.Result) use Lines() for non-JSON output, so the exact distinction syncer.go:185-189, results.go:131-137 and empty_source_test.go:55 all say the field exists to make is dropped on that path." }, { "file": "internal/syncer/empty_source.go", "line": 159, "summary": "The converged Result omits Relay / RelayMode / RelayReason (and SourceHEAD), which every other successful replicate return path sets (syncer.go:1059, 1253).", "failure_scenario": "fromSyncResult yields ExecutionSummary{OperationMode:"replicate", Relay:false, TransferMode:"", Reason:"", SourceEmpty:true}. A consumer relying on the invariant "a successful replicate always reports Relay=true with a non-empty TransferMode" — true at both other return sites, and the reason replicate refuses non-relay targets at syncer.go:1024 — classifies the converged run as a materialized/fallback replicate or as a malformed result." }, { "file": "internal/syncer/empty_source.go", "line": 147, "summary": "Nil-guard asymmetry: s.sourceService is nil-checked at line 136 on a path where it can never be nil (newSession already dereferences it at syncer.go:804), while s.target is dereferenced unguarded at 147 and 156 on malformed result." }, { "file": "internal/syncer/empty_source.go", "line": 147, "summary": "Nil-guard asymmetry: s.sourceService is nil-checked at line 136 on a path where it can never be nil (newSession already dereferences it at syncer.go:804), while s.target is dereferenced unguarded at 147 and 156 on a session type that legitimately has target == nil.", "failure_scenario": "newSession only builds s.target when needTarget is true (syncer.go:815). Safe today only by accident of call graph — runReplicate is the sole caller and Run always passes true — but Fetch (syncer.go:1189) and target-less Probe build needTarget=false sessions and hit the sibling no source refs matched errors this function is billed as superseding ("the only place that may conclude the source is empty"). Any such reuse panics with a nil-pointer deref at len(s.target.refMap) instead of returning an error, and only on the empty-desired-set branch, so no test that syncs a non-empty source catches it. The dead guard plus the missing one reads as an oversight rather than an invariant." }, { "file": "client_test.go", "line": 299, "summary": "The new reflection guard has no field.IsExported() filter and no kind check on the Config side, so it panics with an opaque reflect error instead of reporting the field; it is also duplicated near-verbatim in unstable/client_test.go:170 and both open with an always-empty skip map whose lookup branch is dead.", "failure_scenario": "Verified empirically: policyType.Field(i) enumerates unexported fields, so adding any unexported bool to SyncPolicy makes both copies panic reflect: reflect.Value.SetBool using value obtained using unexported field rather than naming the field. Symmetrically, a future SyncPolicy bool with a same-named non-bool counterpart in syncer.Config panics at got.Bool() instead of reaching the intended t.Fatalf that tells the author to thread it or add a skip reason. ~30 of the ~36 lines are byte-identical between the two files and must be edited in lockstep; they have already drifted (the unstable copy carries a "One field at a time" comment the root copy lacks). internal/syncertest exists and is already imported by client_test.go." }, { "file": "internal/gitproto/refs.go", "line": 62, "summary": "SkippedRefNames and its twin targetSession.skippedRefNames (syncer.go:722) retain the full []string for the whole run when every non-test read is len(...) > 0 (empty_source.go:141, 156); before this diff the slice was consumed by WarnSkippedRefNames and dropped.", "failure_scenario": "The slices are pinned on RefService and targetSession, which live on syncSession across the pack fetch and push — the minutes-long part of a run. A source or target advertising N invalid ref names now holds roughly N x (16 + len(name)) bytes for that whole window purely to answer a boolean: at 100k dropped names of ~40 bytes, ~5-6 MB retained per side per concurrent sync. An int count (or a bool) gives both guards everything they use and lets the names go right after the warning." }, { "file": "docs/protocol.md", "line": 147, "summary": "The verbatim ls-refs request block and the paragraph enumerating its arguments were not updated for the conditionally appended unborn argument or for RefService.HeadUnborn — and the argument goes on the wire for every v2 source listing, not just AllowEmptySource callers.", "failure_scenario": "The doc shows the request as peel / symrefs / ref-prefix HEAD / ref-prefix refs/heads/ / ref-prefix refs/tags/ and explains only that "The peel and symrefs arguments are ls-refs request features...", then describes decodeV2LSRefs as extracting symref-target with no mention of the unborn line. This is the section that exists to record wire behavior, so a maintainer diffing it against listSourceRefsV2 concludes the request is unchanged. It also masks that the change is not as inert as the CHANGELOG's "nothing changes for existing callers" claims: every v2 server advertising ls-refs=unborn now receives an extra argument on every sync, probe, fetch and bootstrap, whether or not the caller opted in." } ]

Verification status: findings 1, 2, 3, 8, 9, and 13 were confirmed empirically — unit probes against resolveEmptyDesiredSet, an end-to-end run through the repo's own git-http-backend harness against real git 2.53, a mutation test on the unborn argument, and a standalone reflect repro. The rest are confirmed by direct code reading with the quoted lines. Working tree is clean; go test ./..., go vet, and golangci-lint all pass on the branch as committed, so none of these surface through existing gates.

Blockers: 1, 2, and 3. Each is a live wrong answer, and 2 and 3 defeat the feature on its own headline use cases (an excluded-namespace mirror, and a mapping-pinned mirror).

Two process notes: the Phase 3 gap sweep never returned — it was still running when I finalized, and since 26 candidates were already competing for 15 slots it could only have added items below the cut. And the conventions angle returned nothing because no CLAUDE.md exists at user, repo, or directory level.

❯ can you list the findings in order of priority?

The JSON I returned was already ranked most-severe first, but here it is as a readable priority list.

Block on these — live wrong answers

1. unstable/client.go:269 — Scope.ExcludeRefs silently dropped The function this PR edits forwards ExcludeRefPrefixes but not ExcludeRefs; the stable client.go:125 threads both. Under Prune, the caller's excluded refs become prune candidates and get deleted. Confirmed empirically. This is the exact silent-field-drop class the PR's new reflection guard was added to prevent — it can't see it, because it only walks bool fields on SyncPolicy, never RefScope.

2. internal/syncer/empty_source.go:147 — divergence check ignores exclusions Counts every advertised target ref, ignoring ExcludeRefPrefixes/ExcludeRefs and zero hashes, unlike every other consumer of s.target.refMap. A target holding only excluded refs is reported as permanent divergence and can never converge — and refs/pull/* is the namespace errors.go itself cites as the benign case. Confirmed empirically.

3. internal/syncer/syncer.go:1016 — feature inert with Scope.Mappings BuildDesiredRefs errors with source ref X not found before the empty-desired-set branch is reachable, so a mapping-pinned mirror gets a hard failure matching no sentinel on exactly the state the feature makes succeed. Confirmed empirically.

Should fix before merge — correctness and contract gaps

1. internal/gitproto/refs.go:111 — SkippedRefNames populated at 1 of 4 sites All three v1 &RefService{} literals leave it nil; the :111 site computes skipped, warns with it, then discards it. The invalid-name corroboration is structurally vacuous on v1, fails closed today only because the !HeadUnborn check happens to run first.

2. types.go:155 — AllowEmptySource silently requires Scope.AllRefs Undocumented in the godoc and unvalidated. Opting in with the default scope returns the bare historical error with SourceEmpty false, directly contradicting the documented behavior.

3. errors.go:32 — two of three documented causes for ErrNoRefsSelected are unreachable "Branch selection" is mutually exclusive with the AllRefs gate (normalizeAllRefs nils Branches); a missing mapping errors earlier. Only exclude prefixes can produce it, so callers who follow the doc must keep substring-matching the old text — the fragility the sentinels were meant to retire.

4. types.go:159 — Validate doesn't gate the new flags to replicate mode All three are accepted, threaded, then discarded by runSync, Bootstrap, and Fetch. Validate already rejects mode-specific combinations four lines below.

5. internal/syncer/empty_source.go:136 — convergence impossible on v1 / SSH fallback HeadUnborn is only set on the v2 path. The error blames the server for withholding refs when the real cause is the client's own protocol choice. Verified against git 2.53.

6. internal/syncer/empty_source_test.go:19 — zero end-to-end coverage All tests hand-build &syncSession{}. Mutation-verified: deleting the unborn ls-refs argument leaves the whole suite green. This is how finding 4 stays green. The harness to pin it is already in the same package.

7. internal/syncer/syncer.go:192 — Lines() never renders SourceEmpty Converged text output is byte-identical to a no-op sync, dropping the exact distinction three separate doc comments say the field exists to make. Only --json carries it.

8. internal/syncer/empty_source.go:159 — converged Result omits Relay/RelayMode/RelayReason Every other successful replicate return sets them, and replicate refuses non-relay targets — so a consumer relying on that invariant misclassifies the run.

9. internal/syncer/empty_source.go:147 — nil-guard asymmetry s.sourceService is guarded where it can't be nil; s.target is dereferenced unguarded on a session type that legitimately has target == nil. Safe only by accident of call graph.

10. client_test.go:299 — reflection guard panics instead of reporting No IsExported() filter, so any unexported bool on SyncPolicy makes both copies panic with an opaque reflect error; got.Bool() panics on a non-bool counterpart. Duplicated near-verbatim in unstable/client_test.go:170, already drifting, with a dead always-empty skip map.

Lower priority — cleanup and docs

1. internal/gitproto/refs.go:62 — full []string retained for a len() read Both slices are pinned on long-lived objects across the pack transfer purely to answer a boolean; before this diff they were consumed and dropped. An int gives both guards everything they use.

2. docs/protocol.md:147 — wire-behavior doc not updated for unborn The verbatim ls-refs request block and its argument prose still omit the new argument, which goes on the wire for every v2 listing regardless of opt-in — so it also understates the CHANGELOG's "nothing changes for existing callers" claim.

One caveat on the ordering: 1 through 3 are ranked by whether they produce a wrong answer today, and 2 and 3 sit that high because they defeat the feature on its own headline use cases, not because of their line counts. Findings 1, 2, 3, 8, 9, and 13 were confirmed empirically; the rest by direct code reading. Everything on this list passes go test ./..., go vet, and golangci-lint as committed.

worth fixing or should we re-evaluate the apporach?

Block on these — live wrong answers

1. unstable/client.go:269 — Scope.ExcludeRefs silently dropped; under Prune the caller's excluded refs get deleted. Confirmed empirically.
2. internal/syncer/empty_source.go:147 — divergence check ignores exclusions and zero hashes, so a target holding only excluded refs can never converge. Confirmed empirically.
3. internal/syncer/syncer.go:1016 — feature entirely inert with Scope.Mappings; hard failure matching no sentinel. Confirmed empirically.

Should fix before merge

1. internal/gitproto/refs.go:111 — SkippedRefNames populated at 1 of 4 sites; corroboration vacuous on v1.
2. types.go:155 — AllowEmptySource silently requires Scope.AllRefs; undocumented, unvalidated.
3. errors.go:32 — two of three documented causes for ErrNoRefsSelected are unreachable by construction.
4. types.go:159 — Validate doesn't gate the new flags to replicate mode.
5. internal/syncer/empty_source.go:136 — convergence impossible on v1/SSH fallback; error blames the server. Verified against git 2.53.
6. internal/syncer/empty_source_test.go:19 — zero end-to-end coverage. Mutation-verified.
7. internal/syncer/syncer.go:192 — Lines() never renders SourceEmpty.
8. internal/syncer/empty_source.go:159 — converged Result omits Relay/RelayMode/RelayReason.
9. internal/syncer/empty_source.go:147 — nil-guard asymmetry; s.target dereferenced unguarded.
10. client_test.go:299 — reflection guard panics instead of reporting; duplicated verbatim in unstable/client_test.go:170. Panic verified.

Changed by the sweep

14. internal/gitproto/refs.go:219 — the unborn argument is ungated (NEW, replaces the docs item) listSourceRefsV2 takes no Config, so unborn goes on the wire for probe, plan, sync, replicate, bootstrap, fetch and convert-sha256 alike — while HeadUnborn is read only by resolveEmptyDesiredSet under AllowEmptySource. Confirmed by inspection: there is no parameter through which the opt-in could reach that line. This falsifies the CHANGELOG's and types.go's central claim that with the opt-in unset "nothing changes for existing callers" — the wire request changes for every v2 caller, with no way to suppress it. My earlier docs/protocol.md:147 finding is the documentation half of this same change and folds in here.

15. internal/syncer/syncer.go:189 + results.go:137 — the new public field's contract (NEW, merged from two sweep items) Two permanent-once-released problems on one field. The name says "source" but the flag is set only when source and target are both verified empty, so false does not mean "the source has refs" — it is false in all three of the other empty-desired-set outcomes, including ErrSourceEmptyTargetPopulated where the source was verified empty. Converged would carry the actual meaning. Separately it is the only bool in ExecutionSummary (and in syncer.Result) tagged omitempty — DryRun, Relay, BootstrapSuggested, Batching are all emitted unconditionally — so for the field whose whole purpose is to discriminate converged from no-op, "false" and "this binary has no such field" are the same JSON.

Displaced below the cut: the SkippedRefNames retention issue (refs.go:62, full []string held for a len() read) and the standalone docs/protocol.md gap, plus three minor sweep items — a nil err.Error() deref in empty_source_test.go:203 that panics in exactly the case the assertion exists to catch, fetch_test.go:308 being a strict superset of the pre-existing TestDecodeV2LSRefsEmpty, and the unlabelled (%d) count in the divergence error at empty_source.go:148 while both sibling messages label theirs.

Blockers remain 1, 2, 3. The sweep confirmed the top of the list independently and reported go vet, go test ./... and golangci-lint clean with a clean working tree, which matches what I saw — none of these 15 surface through existing gates.</result> <usage><subagent_tokens>209034</subagent_tokens><tool_uses>94</tool_uses><duration_ms>1849331</duration_ms></usage> </task-notification>

Fix everything that doesn't requiere a decision from me

Do what you must in the remaining issues

Commit and push, update the github pr description if needed

Can you run bugbot again?

Yes

Trigger bugbot and wait, continue until it reports green

Everything pushed?

Does this change have performance implication?

Can you tell me again how this change fits into the bigger picture? Can u explain me visually

Approach this as the design lead at a small studio known for their versatility, giving every client a visual identity pitched at the treatment the task actually calls for. Make deliberate choices about palette, typography, and layout that are specific to this subject, and avoid templated designs.

Read the request first

Calibrate treatment, not whether to design. A doc deserves the same craft as a landing page — what changes is the treatment that craft is delivered in. Format is part of this read — decided, not defaulted: a Markdown publish keeps its filename as its title and takes almost none of the craft below, so it fits only when the user asked for Markdown or the content is bound for a Markdown-native destination; never pick it to save time.

Many requests call for a more utilitarian treatment: a plan, a memo, a demo. Make it polished: include real typographic hierarchy, considered spacing, and a proper palette, but avoid over-designing. Most pages do not need a flashy, gigantic hero. Keep flourishes tasteful and limited.

Some requests call for an editorial treatment: a landing page, a game, an app or tool they'll keep or share.

When unsure: a well-composed page is never the wrong answer; an over-designed visual identity sometimes is.

Fundamentals below apply to everything. The editorial process after that runs only when the read above says so.

Fundamentals for every artifact

Honor what's already there Look for an existing design system first — CLAUDE.md, a tokens or theme file, existing component styles. When one exists, apply it; everything below fills gaps and never overrides. Precedence is always: the user's own words, then the project's existing system, then your choices.

Ground it in the subject. If the subject isn't already clear, pin it: one concrete subject, its audience, and the page's single job. The subject's own world — its materials, instruments, vernacular — is where distinctive choices come from. Build with real content throughout, never lorem.

Pair typefaces Typography carries the page even when the page isn't about typography. Google Fonts is the one font host the Artifact CSP admits — link it directly (<link rel="stylesheet" href="https://fonts.googleapis.com/css2?family=…&display=swap">); a face from anywhere else must be inlined as a @font-face data URI or it falls back silently. Either way, declare a real fallback stack. Keep running text near 65 characters wide; set a type scale and stay on it; give headings text-wrap: balance, body text room to breathe, and uppercase labels a touch of letter-spacing.

Choose neutrals, don't default to them. A pure mid-grey reads as unconsidered; a grey with a slight hue bias toward the page's accent reads as chosen. Pure white and near-black are fine grounds when they suit the subject — the point is that the neutral was picked, not inherited.

Design both themes. The page renders in the viewer's theme, and the viewer has three states, not two: an explicit choice stamps data-theme="dark" / data-theme="light" on the root element, and the default "system" setting stamps nothing — most viewers see the un-stamped document, where only prefers-color-scheme separates light from dark. Structure the CSS token-level for all three: the bare :root block defines the complete light palette (for a deliberately dark-first design, swap light and dark consistently through this whole pattern); @media (prefers-color-scheme: dark) redefines only the tokens, guarded as :root:not([data-theme="light"]) so an explicit light choice beats a dark OS; :root[data-theme="dark"] redefines them again so the toggle also wins in the other direction. Style components through the tokens, never directly inside a media or [data-theme] block — a color whose only definition sits behind [data-theme] never applies in the un-stamped state, and the page renders one theme's text on the other theme's ground. Two more rules keep each theme resolving as a set: the artifact composites over a ground the viewer paints in its theme, so body must set an explicit background from a token — a transparent body silently borrows the host's ground; and every element that sets a color takes it from the same token set as the surface behind it, never a literal that only works in one theme. Before publishing, scan the stylesheet for any color declared only inside a media or [data-theme] block — that is the classic unreadable-artifact bug. Give the second theme the same care as the first — don't naively invert; keep contrast legible and the accent working on both grounds. A design that deliberately commits to one visual world (a neon arcade screen, a letterpress invitation) may stay single-theme — then skip the media query and stamps entirely but still paint the background and every color explicitly, so the page holds on either host ground; make it a choice, not an omission.

Let layout do the spacing. Lay out sibling groups with flex or grid and gap, not per-element margins that silently collapse or double. Wide content — tables, code, diagrams — gets overflow-x: auto on its own container so the page body never scrolls sideways. Reach for font-variant-numeric: tabular-nums wherever digits line up in columns.

Avoid AI-generated design AI-generated design currently clusters around a few looks: warm cream (#F4F1EA) with a serif display and terracotta accent; near-black with a lone acid-green or vermilion pop; broadsheet hairline rules with dense columns; a purple-to-blue gradient hero on white; Inter or Space Grotesk as the "safe" face; emoji as section markers; everything centered; rounded-lg everywhere; accent bar/rail on rounded cards. Where the user pins down a visual direction, follow it exactly — their words always win, including when they ask for one of these looks. Where nothing is specified, don't spend that freedom on one of these defaults.

Build cleanly Be cognizant of overlapping elements, cascade collisions, silent font fallbacks; visual bugs hide in the gap between source and output. Close every non-void element, double-quote attributes, give keyboard focus a visible state, respect prefers-reduced-motion. For generative or decorative graphics, reach for Canvas or WebGL rather than hand-authoring long SVG path data.

CSS rules When writing the CSS, watch your selector specificities. It is easy to generate classes that cancel each other out — a type-based selector like .section fighting an element-based one like .cta over padding and margins between sections. Structure the cascade so it doesn't silently undo your spacing.

Writing the copy Words are design material, not decoration. Write from the user's side of the screen — name things by what people recognize, not how the system is built (a person manages notifications, not webhook config). Active voice; a control says exactly what happens ("Publish", then a toast that says "Published"). Errors explain what went wrong and how to fix it — no apologies, no vagueness. Specific beats clever.

Name the page like a product, not a caption. The <title> is the artifact's name in the gallery and the browser tab, and it sets the reader's first impression of care. Give the page a real name: a short noun phrase, typically two to four words, specific to the subject — or, for a page that exists to answer one question, that question itself, which is then the page's name. Stop at the name — a title that carries its own explainer after a dash or colon reads as generated filler. The name must also identify the page among many: in the gallery it sits beside dozens of other artifacts, and a generic category label that could sit on any of them fails as a name just as surely as an appended explainer. When a candidate title pairs the name with a generic word — a greeting, a category, a page-type label — the name is the half to keep; a trim that drops the identity and keeps the generic word produces exactly the title that could sit on any page. And the rule removes explainers, it does not impose brevity: a multi-word title that already reads as one specific name is finished, and shortening it further only makes it generic. The one-sentence publish description is where the explanation belongs; the gallery shows it right under the title.

Structure is information Structural devices, numbering, eyebrows, dividers, labels, should encode something true about the content, not decorate it. Many generic designs use numbered markers (01 / 02 / 03), but that's only appropriate if the content actually is a sequence - like a real process or a typed timeline where order carries information the reader needs. Question if choices like numbered markers actually make sense before incorporating them.

When it's a UI, not a document A dashboard or tool is scanned and operated, not read top-to-bottom, so the craft shifts from typography to information design. Surface the summary before the detail; encode state in form as well as number — a pill, a chip, a severity stripe — so what needs attention reads at a glance. Semantic color (good / warning / critical) is separate from the accent hue and doesn't count as your accent. Give sparklines and charts the same care as type: an area fill, a faint grid, an emphasized endpoint. What's interactive should look interactive.

Process

Before writing code, sketch a short design plan — a compact token system with color, type, and layout:

• Color: describe the palette as 4–6 named hex values.
• Type: typefaces for 2+ roles — a characterful display face used with restraint, a complementary body face, and a utility face for captions or data if needed.
• Layout: a layout concept in one or two sentences.

Then build, following the plan and deriving every color and type decision from it.

When the request is editorial

The stance shifts: the client has already rejected proposals that felt templated, and is paying for a distinctive point of view. Make opinionated calls, and take one real aesthetic risk where it serves the work.

Review the design plan against the subject before building: if any part of it reads like the generic default you would produce for any similar page, revise that part, and note what you changed and why. Only after you've confirmed the plan's uniqueness do you write the code, following the revised plan exactly.

Principles

• The hero is a thesis: open with the most characteristic thing in the subject's world — headline, image, live demo, interactive moment.
• Typography carries the personality of the page. Pair the display and body faces deliberately, not the same families you would reach for on any other project, and set a clear type scale with intentional weights, widths, and spacing. Make the type treatment itself a memorable part of the design, not a neutral delivery vehicle for the content.
• Leverage motion deliberately. Think about where and if animation can serve the subject: a page-load sequence, a scroll-triggered reveal, hover micro-interactions, ambient atmosphere. An orchestrated moment usually lands harder than scattered effects; choose what the direction calls for. However, sometimes less is more, and extra animation contributes to the feeling that the design is AI-generated.
• Match complexity to the vision. Maximalist directions need elaborate execution; minimal directions need precision in spacing, type, and detail. Elegance is executing the chosen vision well.
• Spend your boldness in one place; keep everything around it quiet. If the accent fights the ground, shift it toward analogous or drop saturation rather than replacing it.

Draw as the engineer who has to live with the decision, not as a decorator: a diagram earns its place when it lets a cold reader see a mechanism they would otherwise have to assemble from prose — where data flows, which components talk, what changes between two options, what state a request moves through. If a sentence says it faster, write the sentence.

What to draw

Depict the mechanism, not its name. A box labeled "cache" says less than the prose; the path a request takes through it, the two stores it sits between, and the arrow that disappears when the cache is removed say what the words can't. Show the parts that the argument hinges on — the boundary being crossed, the hop being added, the data that moves — and leave out the parts that don't.

Comparing options? Draw the difference. Two architectures side by side, a before and an after, the one edge that each option adds or removes — the reader should be able to point at what they are choosing between. A separate labeled box per option, with nothing connecting them to the system, is not a comparison; it is a restated option list.

Match complexity to the stakes. A one-hop question is a three-box diagram; a migration that reroutes writes through a queue needs the queue, the writer, the reader, and the ordering arrow. Draw as much as the decision actually turns on — no forced minimalism, no inventory of the whole system either.

Label the arrows. An unlabeled arrow is "related somehow"; writes, invalidates, polls every 30s is information. A legend is only worth it when the same encoding (dashed, colored, doubled) repeats; otherwise put the meaning on the mark itself.

Inline SVG mechanics

These mechanics apply where the page renders inline SVG natively (HTML pages); a markdown-rendered page draws its diagrams in whatever fence that lane's renderer supports, and the skill that owns the lane says which. Hand-author inline <svg> with native shapes (rect, circle, line, polyline, path) and <text> — no libraries, no runtime, no external images.

• Size by viewBox. Set viewBox="0 0 W H" and let CSS scale it (max-width: 100%; height: auto); choose W and H for the content, not a preset. Wide flows read left-to-right; layered stacks read top-to-bottom.
• Theme with currentColor. Strokes, text, and arrowheads in currentColor inherit the page's foreground in light and dark themes alike; reserve a literal hue for the one element that carries meaning (the option leaned toward, the hop under discussion), and make sure it reads on both grounds.
• Arrowheads are markers or polygons. A <defs><marker> referenced by marker-end="url(#arrow)" (fragment-internal id) or a small <polygon> at the line's end — never an image.
• Keep text legible. Roughly 11–13px at the drawn scale, text-anchor for alignment, short labels (a word or three); explanatory sentences belong in the caption below the figure, not in the drawing.
• Align to a grid. Shared baselines and even gaps are most of what makes a hand diagram read as deliberate; eyeballed offsets read as noise.
• One figure, one claim. Wrap the <svg> in <figure> with a <figcaption> that states what the picture shows, and give the <svg> role="img" plus an aria-label carrying the same claim for readers who cannot see it.
• Stay self-contained. No <script>, <style>, or <foreignObject> inside the SVG; gradients, patterns, and <use> reference ids in the same fragment (href="#id"). Long decorative path data is a sign the drawing wants a real graphics tool — simplify instead.

can you re-structure the artifact so that each gate get a paragraph explaining it and an example?

can you explain me the gate (1) in super simple terms, don't change the artifact

can you explain me the gate (2) in super simple terms, don't change the artifact

which flagi is it?

in mirror-worker this flag is not going to be set right?

all I wanted to check is that this feature fixes the broader problem of reconciling newly created native repos

relate me this to gate 2, why it doesn't trigger/

dude... of course... We are building it, I mean how is this going to fit into the new feature... com'on!

does this apply to github mirrors too?

but mirror-worker handles both github mirrors and native repos right?

got it

let's go to the next gate

let's go to gate 4

I am slightly confused, explain me again in super simple terms the goal of these gates

A session-scoped Stop hook is now active with condition: "can you look a the comments on the PR, agree or refute them, evaluate if it's worth fixing, if yes, go ahed and fix. Answer the comments.". Briefly acknowledge the goal, then immediately start (or continue) working toward it — treat the condition itself as your directive and do not pause to ask the user what to do. The hook will block stopping until the condition holds. It auto-clears once the condition is met — do not tell the user to run /goal clear after success; that's only for clearing a goal early.