paramSupport.js

import { getCapabilitiesForModel } from "../../providers/capabilities.js";

// Strip request params a given provider/model rejects upstream (e.g. HTTP 400).
// Config-driven: add a rule instead of scattering `delete body.x` across executors.

// Each rule: optional provider, regex match on model, list of params to drop.
// A param is removed only when it is present (!== undefined).
const STRIP_RULES = [
  // All Claude models: temperature deprecated/rejected upstream (Anthropic 400). #1748
  { match: /claude/i, drop: ["temperature"] },
  // GitHub Copilot gpt-5.4: temperature unsupported.
  { provider: "github", match: /gpt-5\.4/i, drop: ["temperature"] },
  // GitHub Copilot Claude (except opus/sonnet 4.6): thinking + reasoning_effort rejected. #713
  { provider: "github", match: (m) => /claude/i.test(m) && !/claude.*(opus|sonnet).*4\.6/i.test(m), drop: ["thinking", "reasoning_effort"] },
  // Cloudflare Workers AI: content must be plain string, rejects OpenAI content-part array (#1926)
  { provider: "cloudflare-ai", flattenContent: true },
  { provider: "volcengine-ark", match: /glm-5/i, clampToModelMaxOutput: true },
  // VolcEngine Ark caps the Kimi family at max_tokens <= 32768, but the model's
  // advertised ceiling is far higher (Kimi-K2.7-Code resolves to maxOutput 262144),
  // so clampToModelMaxOutput alone leaves it uncapped and the request 400s with
  // "integer above maximum value, expected <= 32768". Pin an explicit endpoint cap;
  // min() with the model ceiling still applies if a variant's own limit is lower.
  { provider: "volcengine-ark", match: /kimi/i, maxOutputCap: 32768, clampToModelMaxOutput: true },
  // OpenAI gpt-5 family + o-series reject `max_tokens` upstream (HTTP 400:
  // "Use 'max_completion_tokens' instead.") — rename so the output cap survives.
  // Provider-agnostic: the OpenAI API contract applies to resellers/proxies too
  // (openai, github copilot, azure, openrouter, ...). #2742
  { match: /(^|[^a-z0-9])(gpt-5|o[134])([^a-z0-9]|$)/i, rename: { max_tokens: "max_completion_tokens" } },
];

// Test a rule's match (regex or predicate) against the model id.
function matches(rule, model) {
  if (!rule.match) return true;
  return typeof rule.match === "function" ? rule.match(model) : rule.match.test(model);
}

function clampNumber(body, key, ceiling) {
  if (typeof body[key] === "number" && Number.isFinite(body[key]) && body[key] > ceiling) {
    body[key] = ceiling;
  }
}

// Remove unsupported params from body in place; returns body.
export function stripUnsupportedParams(provider, model, body) {
  if (!model || !body || typeof body !== "object") return body;
  for (const rule of STRIP_RULES) {
    if (rule.provider && rule.provider !== provider) continue;
    if (!matches(rule, model)) continue;
    for (const key of rule.drop || []) {
      if (body[key] !== undefined) delete body[key];
    }
    // CF Workers AI oneOf root schema only accepts content as plain string (#1926)
    if (rule.flattenContent && Array.isArray(body.messages)) {
      for (const msg of body.messages) {
        if (msg && Array.isArray(msg.content)) {
          msg.content = msg.content
            .map(b => (b?.type === "text" && typeof b.text === "string") ? b.text : "")
            .join("");
        }
      }
    }
    if (rule.clampToModelMaxOutput || Number.isFinite(rule.maxOutputCap)) {
      const modelCeiling = getCapabilitiesForModel(provider, model).maxOutput;
      const candidates = [];
      if (rule.clampToModelMaxOutput && Number.isFinite(modelCeiling) && modelCeiling > 0) {
        candidates.push(modelCeiling);
      }
      if (Number.isFinite(rule.maxOutputCap) && rule.maxOutputCap > 0) {
        candidates.push(rule.maxOutputCap);
      }
      if (candidates.length > 0) {
        const ceiling = Math.min(...candidates);
        clampNumber(body, "max_tokens", ceiling);
        clampNumber(body, "max_completion_tokens", ceiling);
        clampNumber(body, "max_output_tokens", ceiling);
      }
    }
    // Rename params the upstream rejects under their old name (e.g. OpenAI
    // gpt-5/o-series: max_tokens → max_completion_tokens). Prefer keeping an
    // already-present target name, then drop the rejected one.
    if (rule.rename) {
      for (const [from, to] of Object.entries(rule.rename)) {
        if (body[from] === undefined) continue;
        if (body[to] === undefined) body[to] = body[from];
        delete body[from];
      }
    }
  }
  return body;
}