Best possible solution:

Keep the current main classifier implementation and close this superseded branch rather than merging an older assistant-only variant.

Do we have a high-confidence way to reproduce the issue?

Yes at source level for the original bug: the released v2026.6.11 classifier still drops server/upstream embedded payload reasons, while current main now has regression coverage and the fixed classifier path.

Is this the best way to solve the issue?

Yes for current main: the implemented fix is the better shape because it covers both structured assistant error types and embedded provider payload classification, not only this PR's assistant-stage mapping.

Security review:

Security review cleared: The PR diff changes internal TypeScript fallback classification and focused tests only; no secrets, dependencies, workflows, package scripts, or supply-chain surfaces are touched.

AGENTS.md: found and applied where relevant.

What I checked:

• Current main shared error-type classifier: Current main maps structured errorType values server_error and upstream_error to the canonical server_error failover reason, then feeds that classification into classifyFailoverSignal. (src/agents/embedded-agent-helpers/errors.ts:925, 9f98b6e174d1)
• Current main embedded payload classifier: Current main accepts server_error and overloaded provider payload classifications and returns an embedded_error_payload fallback classification, covering the gateway/embedded payload route from the linked bug. (src/agents/embedded-agent-runner/result-fallback-classifier.ts:154, 9f98b6e174d1)
• Current regression coverage: Current main has regression coverage for the reported JSON upstream_error payload returning reason server_error through the embedded result classifier. (src/agents/embedded-agent-runner/result-fallback-classifier.test.ts:53, 16b275a0fba7)
• Git-history provenance: Current checked-out line history for the implemented classifier/test lines is carried by 16b275a; the canonical merged PR for the same bug is fix #95519: [Bug]: Fallback should trigger on provider upstream_error / LLM request failed #95542 with landed commit cfd8ba8. (src/agents/embedded-agent-runner/result-fallback-classifier.ts:154, 16b275a0fba7)
• Release provenance: The implementation is current-main-only in this checkout: v2026.6.11 still has the older business-denial-only provider payload helper and does not contain 16b275a. (src/agents/embedded-agent-runner/result-fallback-classifier.ts:150, 16b275a0fba7)
• Related item status: The linked bug is closed, and GitHub shows fix #95519: [Bug]: Fallback should trigger on provider upstream_error / LLM request failed #95542 as the merged closing PR for the same upstream_error fallback problem. (cfd8ba8fc81d)

Likely related people:

• mikasa0818: Authored the merged canonical PR that implements the upstream_error/server_error classifier and embedded payload fallback coverage for the same bug. (role: canonical fix author; confidence: high; commits: cfd8ba8fc81d; files: src/agents/embedded-agent-helpers/errors.ts, src/agents/embedded-agent-runner/result-fallback-classifier.ts, src/agents/embedded-agent-runner/result-fallback-classifier.test.ts)
• altaywtf: The canonical merged PR discussion records the squash merge and notes the prepared and landed SHAs; the landed commit also carries Altay co-author context. (role: merger and follow-up owner; confidence: medium; commits: cfd8ba8fc81d; files: src/agents/embedded-agent-helpers/errors.ts, src/agents/embedded-agent-runner/result-fallback-classifier.ts)
• Yzx: Current-main blame for the implemented classifier and regression-test lines points to the later commit that carries the implementation in this checkout, though that commit is broad and not specific to this fallback bug. (role: current line-history carrier; confidence: low; commits: 16b275a0fba7; files: src/agents/embedded-agent-helpers/errors.ts, src/agents/embedded-agent-runner/result-fallback-classifier.ts, src/agents/embedded-agent-runner/result-fallback-classifier.test.ts)

Codex review notes: model internal, reasoning high; reviewed against 9f98b6e174d1; fix evidence: commit 16b275a0fba7, main fix timestamp 2026-06-30T17:43:10-07:00.