This is purely operational plumbing: a `fetchWithRetry` helper for vendor seat HTTP calls, wired into `callVendor` and the panel's inline caller, plus unit tests. It touches no content, citations, provenance, assessments, or AGENTS.md. It does not weaken §3.15 checks — retries fire only on network-level errors, HTTP 429, and 5xx, never on a completed reply, so a seat's substantive judgment (including a refusal or empty reply, still handled by the caller) is never re-rolled until it agrees; if anything it makes multi-model concurrence more likely to actually be obtained rather than a seat being silently lost. Non-transient 4xx pass through untouched so existing error handling and messages remain, and exhaustion surfaces the last response or throws rather than fabricating success. Tests pin the contract, and the diff is complete with no omitted files. No epistemic rule is implicated.

The change only affects internal scripting for vendor API calls and adds tests; it does not touch content, citations, provenance records, assessments, or AGENTS.md. The new fetchWithRetry helper adds network-level robustness (retries for 5xx/429 and network errors) and is used by callVendor in both the shared vendor library and the cross-model-check script. This strengthens reliability of the multi-model ratification process without altering or weakening any epistemic or governance checks in §3. No rules about real citations, provenance, independence, or append-only assessments are implicated. Therefore, the modification is compatible with the constitution and does not introduce any violations.

The change introduces a well-scoped retry mechanism for transient network failures (5xx, 429, and socket errors) in the scripts that contact vendor models. It does not weaken the multi-model concurrence checks (§3.15); rather, it makes the execution of those checks more robust against edge infrastructure flakiness. The implementation passes through real HTTP errors and timeouts to maintain the existing failure and validation logic, and includes appropriate tests as required by §8.

The diff only adds fetchWithRetry in scripts/lib/vendors.mjs, wires it into callVendor in vendors.mjs and the panel caller in cross-model-check.mjs, and pins the contract with seven tests. It retries network-level fetch errors, HTTP 429, and HTTP 5xx with bounded backoff, and deliberately does not retry other 4xx or deadline timeouts, so existing res.ok handling and fail-closed behavior stay intact. No content, citations, assessments, provenance, or AGENTS.md are touched, and nothing reclassifies or weakens §3.15 ratification, CI, or independence checks. This is operational reliability for paid seat calls, not an epistemic or check-dodging change. Omitted-files is empty, so the full change is in view.

This is infrastructure hardening, not a content or epistemic change: it adds a fetchWithRetry helper used by the panel's vendor seat callers, retrying only transient classes (network-level fetch errors, HTTP 429, HTTP 5xx) with backoff, while deliberately passing through 4xx responses to the caller's existing res.ok handling and rethrowing timeout/abort errors. It does not weaken the §3.15 checks — the fail-closed behavior is preserved (persistent failure still throws after exhaustion; genuine HTTP errors keep their existing messages), no change is reclassified, and no ratification path is bypassed. Retrying only occurs when no usable response was received, so no successful seat output is discarded or double-counted. The change touches no content, citations, provenance, assessments, or AGENTS.md, and it ships with 7 tests pinning the retry contract, consistent with the code rules (§8) on testing important behavior. Nothing in the diff fabricates a record or exposes confidence material.