refactor(sse): split handleChatCore into four response-path leaves

config/quality/file-size-baseline.json

@@ -523,7 +523,9 @@
     "open-sse/executors/codex.ts": 1584,
     "open-sse/executors/cursor.ts": 1868,
     "open-sse/executors/muse-spark-web.ts": 1405,
-    "open-sse/handlers/chatCore.ts": 6444,
+    "open-sse/handlers/chatCore.ts": 6426,
+    "open-sse/handlers/chatCore/nonStreamingResponse.ts": 1212,
+    "open-sse/handlers/chatCore/streamingResponse.ts": 1308,
     "open-sse/handlers/imageGeneration.ts": 3334,
     "open-sse/handlers/search.ts": 1789,
     "open-sse/mcp-server/schemas/tools.ts": 1621,
@@ -776,6 +778,7 @@
   "_rebaseline_2026_09_19_14162_native_codex_auto_resume": "PR #14162 (re-land of #13180, @mdigitalbh81 via @diegosouzapw): native Codex turn auto-resume. open-sse/services/combo/executeTargetAttempt.ts 1258->1273 (+15). Growth is 100% the PR's own, measured against the clean tip (1258 there, gate green): the pin step now advances the logical turn generation and logs the resumed provider/model when the attempt is an auto-resume dispatch, and the generation is passed into pinNativeCodexTurn — the branch has to sit at the pin site because that is the only place the winning target and effective connection are known. Covered by tests/unit/native-codex-auto-resume.test.ts + native-codex-auto-resume-guards.test.ts (15/15) and #13564's native-codex-turn-pin-model-scoped-fallback.test.ts (7/7).",
   "_rebaseline_2026_09_22_14405_freetier_observed_tools_retry": "Issue #14405 own growth: open-sse/executors/opencode.ts 1251->1303 (measured after merging release/v3.8.51, whose own drift entry _rebaseline_2026_09_22_opencode_train10c_drift had already moved the ceiling 1247->1251; the extra 5 lines over the original 1247->1294 measurement are the #14148 reconciliation: freeTierRetryCtx now reads the contract attempt back from the request body via attemptFor() instead of the removed shared _contractAttempt field) (+47 irreducible call-site wiring: freeTierRetryCtx builder + direct fast-path retry call + rotation-loop refusal arm delegating to handleLoopFreeTierRefusal + api-typecheck fixes (unknown-cast on stall-guard dispatch, callback-shaped loop handler keeping private finalize methods); the retry logic itself lives in the new module open-sse/executors/opencodeFreeTierRetry.ts (131 lines, under cap) and the merge helper in opencodeFreeTierContract.ts, so no logic was added to the frozen file beyond wiring two existing dispatch arms. Compaction attempts measured and reverted: loop-call wrapper (+22 net), fast-path/loop fusion (fragile: retry-403 vs original-403 share status). Covered by tests/unit/opencode-free-tier-refusal-rotation.test.ts (3 retry tests: union success, original refusal + store untouched, no retry without names) + tests/unit/opencode-free-tier-request-contract.test.ts (2 merge tests).",
   "_rebaseline_2026_09_24_14659_pool_reselect_per_attempt_growth": "PR #14659 (opt-in OPENCODE_POOL_RESELECT, default off): own growth at existing chokepoints, additive and flag-off inert, re-measured on the release tip post-#14620 merge. open-sse/executors/opencode.ts 1301->1355 (+54: flag/resolver hoist, reselect cell, 429-arm hunk after stop/park exits); open-sse/utils/proxyFetch.ts 1294->1311 (+17: reselectPoolMember field on AppliedProxySink + read-only currentAppliedProxySink getter on the shared store); src/sse/handlers/chat.ts 2563->2564 (+1: reselectPoolMember field on the sink literal); src/sse/handlers/chatHelpers.ts 1258->1303 (+45: publishPoolReselectResolver helper + one call at the capture site, resolver re-invokes pool selection). Covered by tests/unit/opencode-429-pool-reselect.test.ts (6/6 GREEN) + flag guards 58/58.",
+  "_rebaseline_2026_09_23_13065_chatcore_reextract": "Re-extract of #13065 onto the release/v3.8.51 tip (Diego's ask: each leaf must be an empty-diff lift of its chatCore.ts region, imports/exports aside). The two new leaves inherit the exact size of the blocks they carry out of the barrel: nonStreamingResponse.ts holds the if(!stream) leg plus the runNonStreamingProviderLeg/finalizeToolLoopError wrappers; streamingResponse.ts holds the if(stream) provider pipeline. Shrinking below the cap would mean re-modularizing beyond the approved extraction boundaries, which defeats the empty-diff review criterion. Frozen at current size: any further growth of these two files fails the gate.",
   "_rebaseline_2026_09_30_15186_stream_output_model_lockout": "Model-only lockout skipped for an isolated 5xx after the stream already relayed output (locked again once 3 such failures arrive in a row with no completed stream in between): open-sse/utils/stream.ts 3297->3298 (return registerStreamTiming(sseStream, timing)), open-sse/handlers/chatCore.ts 6441->6444 (hasEmittedOutput passed to createStreamFailureFinalizers + streak reset on a completed stream + its import) and src/sse/handlers/chatHelpers.ts 1285->1286 (streamOutputEmitted read from the failure payload) -- irreducible call-site wiring. The logic lives in new modules: open-sse/utils/streamTiming.ts (output registry), open-sse/services/accountFallback/postOutputFailureStreak.ts (streak) and src/sse/services/syntheticEmptyStream.ts (isRequestScopedServerFailure); src/sse/services/auth.ts stays under its ceiling because buildExhaustionOptions now reuses the markAccountUnavailable option type. Covered by tests/unit/stream-failure-after-output-no-model-lockout.test.ts.",
   "_rebaseline_2026_10_03_uniform_provider_regime_mount": "Own growth (uniform provider regime mount): src/app/(dashboard)/dashboard/settings/components/ProxyRegistryManager.tsx 1479->1483 (+4 = the PoolUpstreamRegimeLine import and its three-line conditional mount under the pool members label, next to PoolEgressObservation/PoolMemberEgressLines: rendered only when poolScope is 'provider' with a non-blank poolScopeId, which becomes the line's provider; nothing renders for other scopes or a blank id, so no conclusion without a provider). The regime itself lives outside the frozen file, all under cap: PoolUpstreamRegimeLine.tsx, the dedicated GET /api/settings/proxies/pool/uniform-egress route, readUniformEgressRegime/isUpstreamRegime in src/lib/proxyPoolEgressObservation.ts and getProviderUpstreamSummary in src/lib/db/proxies.ts. Only the mount point is irreducible. Covered by tests/unit/ui/proxy-registry-manager-regime-mount.test.tsx and tests/unit/ui/pool-upstream-regime-line.test.tsx.",
   "_rebaseline_2026_10_02_admission_rejection_call_log": "PR own growth (admission rejection call-log) after extraction of the rejection-logging logic into the new src/sse/handlers/admissionRejectionLog.ts (under cap): src/sse/handlers/chat.ts 2586->2597 (+11 = one import + 10 call-site lines at the single acquire() rejection site, irreducible — plancher +6 prouve, gate exige +0). Covered by tests/unit/admission-rejection-call-log.test.ts.",