diff --git a/CHANGELOG.md b/CHANGELOG.md
index 00643f0a4f..2e6be28923 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -14,6 +14,7 @@
 ### 🔧 Bug Fixes
 
 - **tests(cli):** stabilize `setup-claude.test.ts` (#5959) — the dry-run path printed a multi-byte "──" heading to the test child's stdout, corrupting the node:test runner's V8-serialized event stream in ~50% of runs ("Unable to deserialize cloned data due to invalid or unsupported version") and randomly failing the PR→release queue. `syncClaudeProfilesFromModels` now accepts an injectable `log` sink (CLI default unchanged: `console.log`); the test injects a collector and gains assertions on the dry-run report. Validated 0/30 failures post-fix vs 5/10 on the pristine base.
+- **tests(cli):** deflake `cli-setup-opencode.test.ts` preemptively — same #5959 class: the command under test prints multi-byte "✔"/"✖" CLI glyphs to the test child's stdout, which can corrupt the node:test V8 report stream. Console silenced for the file (pattern of #6019/#6021); no test asserts on stdout. 0/20 failures, stdout clean.
 - **tests(ci):** collect the orphaned `tests/unit/executors/` directory (created by #5800 outside every runner glob — its 2 test files never ran anywhere). Added `executors` to the unit-runner brace globs (package.json, ci.yml shards, quality.yml TIA, test-impact map, test-discovery gate); both files pass (10/10).
 
 ### 📝 Maintenance
diff --git a/tests/unit/cli-setup-opencode.test.ts b/tests/unit/cli-setup-opencode.test.ts
index 714e901db8..ca5425e9d5 100644
--- a/tests/unit/cli-setup-opencode.test.ts
+++ b/tests/unit/cli-setup-opencode.test.ts
@@ -40,12 +40,27 @@ function readConfig() {
   return JSON.parse(fs.readFileSync(path.join(CONFIG_DIR, "opencode.json"), "utf8"));
 }
 
+// #5959-class deflake: the command under test prints CLI progress with multi-byte
+// glyphs (printInfo/printSuccess "✔"/printError "✖" via console.log). Under the
+// node:test runner those stdout writes interleave with the child's V8-serialized
+// report frames and can corrupt the stream ("Unable to deserialize cloned data
+// due to invalid or unsupported version"). No test here asserts on stdout, so
+// silence the stdout-writing console methods for the duration of this file
+// (same pattern as tests/unit/cli/setup-claude.test.ts, #6019/#6021).
+const _console = { log: console.log, info: console.info, warn: console.warn };
+
 describe("omniroute setup opencode", () => {
   before(() => {
+    console.log = () => {};
+    console.info = () => {};
+    console.warn = () => {};
     makeFakePluginDist();
   });
 
   after(() => {
+    console.log = _console.log;
+    console.info = _console.info;
+    console.warn = _console.warn;
     try {
       fs.rmSync(FIXTURE_ROOT, { recursive: true, force: true });
     } catch {
@@ -72,7 +87,11 @@ describe("omniroute setup opencode", () => {
     const [modulePath, options] = cfg.plugin[0];
     assert.equal(modulePath, "./plugins/omniroute/dist/index.js");
     assert.equal(options.providerId, "omniroute");
-    assert.equal(options.baseURL, "http://10.0.0.5:20128", "--base-url flag must reach the registered entry");
+    assert.equal(
+      options.baseURL,
+      "http://10.0.0.5:20128",
+      "--base-url flag must reach the registered entry"
+    );
   });
 
   it("is idempotent: re-running updates the entry in place instead of duplicating it", async () => {
@@ -85,10 +104,15 @@ describe("omniroute setup opencode", () => {
 
     const cfg = readConfig();
     const omniEntries = cfg.plugin.filter(
-      (p: unknown) => Array.isArray(p) && (p[1] as { providerId?: string })?.providerId === "omniroute"
+      (p: unknown) =>
+        Array.isArray(p) && (p[1] as { providerId?: string })?.providerId === "omniroute"
     );
     assert.equal(omniEntries.length, 1, "re-run must not duplicate the entry");
-    assert.equal(omniEntries[0][1].baseURL, "http://10.0.0.9:20128", "re-run updates baseURL in place");
+    assert.equal(
+      omniEntries[0][1].baseURL,
+      "http://10.0.0.9:20128",
+      "re-run updates baseURL in place"
+    );
   });
 
   it("removes the legacy opencode-omniroute-auth entry (#3711) and preserves unrelated plugins", async () => {