fix(opencode-zen): add current free-tier models to registry to enable combo context pre-filtering (#8841)

Co-authored-by: diegosouzapw <diegosouzapw@users.noreply.github.com>

changelog.d/fixes/8841-fix.plan.md

@@ -0,0 +1 @@
+- fix(opencode-zen): add current free-tier models to registry to enable combo context pre-filtering (#8841)

open-sse/config/providers/registry/opencode/zen/index.ts

@@ -85,14 +85,13 @@ export const opencode_zenProvider: RegistryEntry = {
     { id: "qwen3.6-plus", name: "Qwen3.6 Plus", targetFormat: "claude", supportsVision: false },
 
     // ── Free Tier ──────────────────────────────────────────────
+    // #6998 (2026-07-14): upstream free tier rotated — minimax-m2.5-free,
+    // nemotron-3-super-free and qwen3.6-plus-free were delisted (401). Replaced
+    // by the 4 entries below with upstream-verified limits.
     { id: "deepseek-v4-flash-free", name: "DeepSeek V4 Flash Free", supportsReasoning: true },
-    { id: "minimax-m2.5-free", name: "MiniMax M2.5 Free", contextLength: 204800 },
-    { id: "nemotron-3-super-free", name: "Nemotron 3 Super Free", contextLength: 1000000 },
-    {
-      id: "qwen3.6-plus-free",
-      name: "Qwen3.6 Plus Free",
-      targetFormat: "claude",
-      contextLength: 200000,
-    },
+    { id: "mimo-v2.5-free", name: "MiMo V2.5 Free", contextLength: 200000 },
+    { id: "hy3-free", name: "HY3 Free", contextLength: 200000 },
+    { id: "nemotron-3-ultra-free", name: "Nemotron 3 Ultra Free", contextLength: 1000000 },
+    { id: "north-mini-code-free", name: "North Mini Code Free", contextLength: 200000 },
   ],
 };

tests/unit/repro-8841-context-overflow-opencode.test.ts

@@ -0,0 +1,117 @@
+import test from "node:test";
+import assert from "node:assert/strict";
+import fs from "node:fs";
+import os from "node:os";
+import path from "node:path";
+
+const TEST_DATA_DIR = fs.mkdtempSync(
+  path.join(os.tmpdir(), "omniroute-repro-8841-")
+);
+const ORIGINAL_DATA_DIR = process.env.DATA_DIR;
+process.env.DATA_DIR = TEST_DATA_DIR;
+
+const { getResolvedModelCapabilities } = await import(
+  "../../src/lib/modelCapabilities.ts"
+);
+const { getKnownContextOverflow, handleComboChat } = await import(
+  "../../open-sse/services/combo.ts"
+);
+const { getTokenLimit } = await import(
+  "../../open-sse/services/contextManager.ts"
+);
+const core = await import("../../src/lib/db/core.ts");
+
+test.after(() => {
+  core.resetDbInstance();
+  if (ORIGINAL_DATA_DIR === undefined) delete process.env.DATA_DIR;
+  else process.env.DATA_DIR = ORIGINAL_DATA_DIR;
+  fs.rmSync(TEST_DATA_DIR, { recursive: true, force: true });
+});
+
+const noopLog = {
+  info() {},
+  warn() {},
+  error() {},
+  debug() {},
+};
+
+const target = (m) => ({
+  kind: "model",
+  stepId: m,
+  executionKey: m,
+  modelStr: m,
+  provider: "opencode-zen",
+  providerId: null,
+  connectionId: null,
+  weight: 1,
+  label: null,
+});
+
+function largeBody() {
+  return {
+    messages: [{ role: "user", content: "x".repeat(840_000) }],
+    max_tokens: 8192,
+  };
+}
+
+function upstreamContextOverflowResponse() {
+  return new Response(
+    JSON.stringify({
+      error: {
+        code: "context_length_exceeded",
+        message:
+          "Input exceeds the context window for opencode/north-mini-code-free: estimated 210724 input tokens, limit 200000. Reduce the prompt or route to a model with a larger context window.",
+      },
+    }),
+    {
+      status: 400,
+      headers: { "Content-Type": "application/json" },
+    }
+  );
+}
+
+test("#8841 advertised vs compat-filter limit agree", () => {
+  const advertised = getTokenLimit("opencode-zen", "north-mini-code-free");
+  const caps = getResolvedModelCapabilities("opencode/north-mini-code-free");
+  assert.ok(advertised > 0);
+  assert.ok(
+    caps.contextWindow != null && caps.contextWindow > 0,
+    `contextWindow known (got ${caps.contextWindow})`
+  );
+});
+
+test("#8841 oversized request rejected up front (no dispatch)", async () => {
+  const body = largeBody();
+  const pool = [
+    target("opencode/north-mini-code-free"),
+    target("opencode/hy3-free"),
+  ];
+
+  assert.ok(getKnownContextOverflow(pool, body), "overflow before dispatch");
+
+  let dispatches = 0;
+  const result = await handleComboChat({
+    body,
+    combo: {
+      name: "pro-coding-repro-8841",
+      strategy: "priority",
+      models: [
+        "opencode/north-mini-code-free",
+        "opencode/hy3-free",
+      ],
+    },
+    handleSingleModel: async () => {
+      dispatches += 1;
+      return upstreamContextOverflowResponse();
+    },
+    log: noopLog,
+    settings: {},
+    allCombos: [],
+  });
+
+  assert.equal(dispatches, 0, `no upstream dispatch (got ${dispatches})`);
+  assert.equal(result.status, 400);
+  const json = await result.json();
+  assert.equal(json.error?.code, "context_length_exceeded");
+  assert.equal(json.diagnostics?.attempted, 0);
+});