fix(scenarios): reject non-array changedFiles that bypasses the source-upload scan

[jeffrey701]

What

assertScenarioLocalBranchInputSafe is a safety-boundary validator — it exists to refuse
source content ("source contents are never uploaded") and oversized payloads
("metadata-only paths are required") in scenario local-branch inputs. But its changedFiles
handling was gated on Array.isArray(changedFiles): a present-but-non-array value (a
plain object like { diff: "…5000 chars of source…" }, or a bare string) fell through the
Array.isArray guard entirely, so the nested forbidden-key/oversize scan never ran and the
function returned normally — silently accepting exactly the kind of payload it exists to
reject. The outer top-level-key loop only inspects payload's own keys; it does not recurse
into a non-array changedFiles value, so nothing else caught it either.

Change

Reject a present, non-array changedFiles outright, before the Array.isArray block:

if (changedFiles !== undefined && !Array.isArray(changedFiles)) {
  throw new Error("Refusing non-array changedFiles; an array of file entries is required.");
}

Behavior for every already-correct case is unchanged: a valid array of entries (with or
without forbidden keys / oversized values) still runs the full scan, and an omitted /
undefined changedFiles is still allowed.

Validation

• New regression test in test/unit/scenario-input-model.test.ts: both
  assertScenarioLocalBranchInputSafe({ changedFiles: { diff: "x".repeat(5000) } }) and
  assertScenarioLocalBranchInputSafe({ changedFiles: "not-an-array" }) now throw, while a
  valid array and an omitted changedFiles still do not.
• npx vitest run test/unit/scenario-input-model.test.ts → all pass; 100% branch coverage on
  the new guard (both operands, both sides, verified via lcov).
• Full npm run test:changed net green (modulo the pre-existing Windows-only
  subprocess/symlink baseline failures that pass on Linux CI).

Closes #8328

[superagent-security]

Superagent didn't find any vulnerabilities or security issues in this PR.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.62%. Comparing base (6c25eb6) to head (4e4c5d1).
⚠️ Report is 18 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #8467      +/-   ##
==========================================
- Coverage   92.45%   89.62%   -2.84%     
==========================================
  Files         791       98     -693     
  Lines       79320    22790   -56530     
  Branches    23954     3898   -20056     
==========================================
- Hits        73335    20425   -52910     
+ Misses       4858     2187    -2671     
+ Partials     1127      178     -949     

Flag	Coverage Δ
shard-1	57.14% <0.00%> (-1.23%)	⬇️
shard-2	65.47% <0.00%> (+14.36%)	⬆️
shard-3	100.00% <100.00%> (+46.57%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
src/scenarios/input-model.ts	100.00% <100.00%> (ø)

... and 693 files with indirect coverage changes

[loopover-orb]

Tip

✅ LoopOver review result - approve/merge recommended

_{Review updated: 2026-07-24 14:51:38 UTC}

2 files · 1 AI reviewer · no blockers · readiness 93/100 · CI green · clean

✅ Suggested Action - Approve/Merge

• safe to merge

Review summary
This is a narrow, correctly-targeted security fix: `assertScenarioLocalBranchInputSafe` previously only scanned `changedFiles` when it was an array, so a plain object or string value bypassed the forbidden-key/oversize scan entirely and could smuggle source content past this safety boundary. The fix adds an explicit `Array.isArray` negative-case guard before the existing positive-case block, throwing on any present non-array value while leaving the array and undefined paths untouched. The regression test directly exercises both the object and string bypass shapes plus confirms the valid-array and omitted cases still pass, which is exactly the coverage this change needs.

Nits — 3 non-blocking

• src/scenarios/input-model.ts:199-204 — the new guard duplicates the `Array.isArray(changedFiles)` check as two separate `if` blocks; an `else` or a single branch (array vs non-undefined-non-array) would read more clearly, though this is purely stylistic.
• The inline comments in both the source and test files are fairly verbose for what the code already makes clear from the error message and test name.
• Consider consolidating the two adjacent `Array.isArray` checks in src/scenarios/input-model.ts into a single conditional (e.g. `if (changedFiles !== undefined) { if (!Array.isArray(changedFiles)) throw …; else { … } }`) for readability.

Decision drivers

• ✅ Code review — No blockers (1 reviewer)
• ✅ Gate result — Passing (No configured blocker found.)

Context & advisory signals — never blocks the verdict

Signal	Result	Evidence
Linked issue	✅ Linked	#8328
Related work	✅ No active overlap found	No same-issue or scoped active PR overlap found.
Change scope	✅ 20/20	Low review scope from cached public metadata (1 linked issue).
Validation posture	✅ 25/25	PR body includes validation/test evidence.
Contributor workload	✅ 10/10	Author activity: 66 registered-repo PR(s), 31 merged, 17 issue(s).
Contributor context	✅ Confirmed Gittensor contributor	jeffrey701; Gittensor profile; 66 PR(s), 17 issue(s).
Improvement	✅ Minor	risk: clean · value: minor · LLM: moderate

Linked issue satisfaction

Addressed
The diff adds the exact guard the issue requests (throw on present, non-array changedFiles) and includes regression tests for the object and string bypass cases plus confirmation that valid array and omitted changedFiles still pass.

Review context

• Author: jeffrey701
• Role context: outside_contributor
• Public audience mode: oss maintainer
• Lane context: Repository is configured for direct PR review.
• Public profile languages: not available
• Official Gittensor activity: 66 PR(s), 17 issue(s).
• PR-specific overlap: none found.

Contributor next steps

• Start here: Triage stale or unlinked PRs.

Signal definitions

• Related work = same linked issue, overlapping active PRs, or title/path similarity.
• Change scope = cached public metadata such as size labels, draft state, and review-burden hints.
• Validation posture = whether the PR provides enough public validation/test evidence for maintainer review.
• Contributor workload = public contributor activity and cleanup pressure, not a repo-wide quality failure.
• Contributor context = public GitHub/Gittensor identity context; non-Gittensor status is not a blocker.

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_{🟩 Safe / merged · 🟦 Advisory · 🟨 Held for review · 🟥 Blocked / closed}

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LoopOver approves — the gate is satisfied and CI is green.