GitNexus/MIGRATION.md

Migration Guide

impact tool may now return { status: 'ambiguous' } (PR #888, issue #470)

Before this change the impact MCP tool silently picked the first match when the target name hit multiple symbols (Class → Interface → Function → Method → Constructor priority UNION). This often produced analysis for the wrong symbol with no signal back to the caller.

After this change, when the resolver finds more than one viable match and the caller supplied none of target_uid / file_path / kind, impact returns a disambiguation response shaped like:

{
  "status": "ambiguous",
  "message": "Found N symbols matching '<target>'. Use target_uid, file_path, or kind to disambiguate.",
  "target": { "name": "<target>" },
  "direction": "upstream",
  "impactedCount": null,
  "risk": "UNKNOWN",
  "candidates": [
    { "uid": "...", "name": "...", "kind": "Function", "filePath": "...", "line": 42, "score": 0.76 }
  ]
}

impactedCount is null, not 0, on an ambiguous result (#2687): no single symbol was resolved, so the blast radius is undetermined. A numeric 0 was indistinguishable from a genuine "nothing depends on this", so a caller testing impactedCount === 0 read a false all-clear. Read maxImpactedCount (callgraph ambiguity) or the per-candidate counts in candidates[] for the real figure. Callers written as impactedCount || 0 are unaffected.

Do I need to migrate?

Probably not, but check for assumptions. Callers that unconditionally read result.byDepth / result.summary / result.affected_processes without first checking result.status will now see undefined in the ambiguous case. The fix is to branch on result.status === 'ambiguous' first and follow up with target_uid (preferred) or file_path / kind.

The context tool's ambiguous response is a strict superset of the existing shape — every candidate gains a score field, no existing field has changed. No migration required for context callers.

What happens on re-index?

Nothing — this is an MCP-surface change only. The graph schema, indexer, and stored data are untouched.

---

OVERRIDES → METHOD_OVERRIDES (PR #642)

The OVERRIDES relationship type has been renamed to METHOD_OVERRIDES for consistency with the new METHOD_IMPLEMENTS edge type.

Do I need to migrate?

No. Backward compatibility is handled automatically at runtime:

• local-backend.ts dual-reads both OVERRIDES and METHOD_OVERRIDES in all impact-analysis and context queries. Existing stored graphs with OVERRIDES edges continue to return correct results without any manual intervention.
• The REL_TYPES array in schema-constants.ts includes both names so Cypher queries that reference either will work.

What happens on re-index?

Running npx gitnexus analyze on a repository produces METHOD_OVERRIDES edges going forward. The old OVERRIDES edges are replaced as part of the normal full re-index.

When will the legacy alias be removed?

The OVERRIDES compat alias will remain until a future major version. Removal will be announced in this file and in the changelog before it happens.

meta.json → gitnexus.json (PR #2363)

The per-repo index metadata file's primary name changed from .gitnexus/meta.json to .gitnexus/gitnexus.json (and from branches/<slug>/meta.json to branches/<slug>/gitnexus.json for multi-branch indexes). This is purely a filename change — the JSON content and every field in it are identical.

Do I need to migrate?

No. Backward compatibility is handled automatically at runtime:

• saveMeta dual-writes both filenames on every analyze, so meta.json keeps existing and staying current. Older GitNexus binaries, still-running MCP servers, and the shipped editor hooks that read meta.json continue to work unchanged.
• loadMeta reads gitnexus.json first and falls back to meta.json when the primary file is absent, so a repo indexed by an older version works without re-analysis.
• Each analyze run also reconciles the two files (the fresher indexedAt wins and is written to both), so even a repo written by a mix of old and new versions converges. Nothing is ever deleted.

What happens on re-index?

Running npx gitnexus analyze writes both gitnexus.json and meta.json with identical content. A pre-existing repo that only has meta.json gets gitnexus.json bootstrapped from it on the first run.

What about rollback?

Downgrading to an older GitNexus version is safe: meta.json is always present and current, so the older binary sees the existing index (including the incrementalInProgress crash-recovery flag) instead of treating the repo as never analyzed.

When will the legacy mirror be removed?

The meta.json mirror will remain until a future major version. Removal will be announced in this file and in the changelog before it happens.

Ambiguous responses report the true match count (PR #2796, issue #2787)

The MCP symbol resolver returns at most 20 candidate rows. Every ambiguous response used to take its count from that capped window, so a name with 92 matches (constructor, in this repo's own index) reported 20. The same PR pinned the window with an ORDER BY, which turned that undercount from flaky into stable — and a stable wrong number reads as authoritative.

Three consumer-visible changes follow:

• impact's totalCandidates changed meaning. It was the length of the capped 20-row window; it is now the true COUNT(*) of matching symbols. Callers using totalCandidates === candidates.length as a "not truncated" proxy will now see the two diverge. This is a bug fix — the old number was wrong — but it is still a value change on a published field.
• totalCandidates and candidatesTruncated are new on other tools. They now also appear on context, trace, the explain / pdg_query block-anchor path, and on rename (which returns context's ambiguous payload verbatim). candidatesTruncated: true is present only when candidates[] is shorter than totalCandidates — absent otherwise, never false.
• The message template gained a (showing M) suffix. It follows the total — Found 92 symbols matching 'constructor' (showing 20). … — and appears only when the returned window is smaller than the total. impact uses the longer (showing M of N) form.

Do I need to migrate?

Only if you read totalCandidates or parse message. The last two changes are purely additive — no field was removed or renamed and candidates[] keeps its shape — so PR #888's "no existing field has changed. No migration required for context callers" still holds for context.

• Reading totalCandidates on impact: it is a true total now. Detect a shortened window with candidatesTruncated (or totalCandidates > candidates.length) rather than by comparing it to an array length.
• Parsing message for a count: the total is still the first number, but a (showing M) parenthetical may now follow it. Prefer the structured totalCandidates field over the string.

What happens on re-index?

Nothing — this is an MCP-surface change only. The graph schema, indexer, and stored data are untouched.

schemaVersion → schemaFingerprint (issue #2798)

The field that decides whether an existing index can be reused changed in .gitnexus/gitnexus.json (and in each branches/<slug>/gitnexus.json): schemaVersion?: number has been removed and schemaFingerprint?: string added. The new value is a 12-character digest of the graph DDL this build creates, so it describes the schema an index's tables were actually built from rather than asserting a number about it.

An absent fingerprint is treated as a mismatch, and that is the whole backward-compatibility story: every index written by an earlier GitNexus carries no fingerprint, so it is rebuilt exactly once.

Do I need to migrate?

No. There is nothing to run, edit, or pass. The first analyze after upgrading logs one line —

index schema changed (built by an unidentified GitNexus build, this build is <fingerprint>); forcing a full re-analyze so the database is recreated from the current schema.

— and then performs that full re-analyze itself. The same run stamps the fingerprint, and every run after it takes the normal incremental path again.

What happens on re-index?

One automatic full re-analyze, once per index. Nothing else changes; the resulting graph is what the current build would have produced anyway.

The scope of that one-time cost is worth knowing before you hit it. It is per index, not per machine or per repository — branch-scoped index slots (#2106) each keep their own gitnexus.json, so every slot pays for itself the first time it is analyzed after the upgrade. On a very large repository a full re-analyze is substantial, not a blip; plan the first post-upgrade run accordingly.

Why a digest instead of a version number?

schemaVersion was hand-incremented, and it had to predict something a number cannot know: whether the DDL an on-disk database was created from matches this build's. It collided with main eight times, twice exactly — and an exact clash was the quiet failure. Two builds stamp the same number over different DDL, the strict === reuse gate reads the index as current, the CREATE … TABLE statements are skipped as "already exists", and edges whose endpoint pair the live database cannot persist are dropped. A wrong graph, with no error anywhere.

A derived digest cannot fail that way: two builds agree exactly when their DDL agrees, so concurrent branches never need renumbering and a mismatch is always a real mismatch. The retired ladder's per-version rationale (v2 BasicBlock.callees through v35's generated relation cross-product) now lives only in git history: git show 561f913a3:gitnexus/src/storage/repo-manager.ts.

What about rollback?

Downgrading to an older GitNexus is safe. The older binary looks for schemaVersion, does not find one, treats the index as pre-versioning, and forces its own full rebuild — the same one-time cost in the other direction, never a stale or mismatched graph.

What if I alternate between an old and a new binary?

Every switch forces a rebuild. The end-of-run metadata is written as a fresh object literal rather than merged over the previous file, so a new build's write drops schemaVersion and an old build's write drops schemaFingerprint — neither field survives the other's run, and each binary then finds its own gate unsatisfied. This hits anyone running a pinned npx gitnexus@<version> alongside a local build, or an editor hook still on an older release. It is a cost, not a correctness problem: each run rebuilds against its own schema, and the graph it serves is correct for the binary that produced it. Pin one version per index to avoid the churn.