diff --git a/.changeset/readonly-flow-write-json-warning.md b/.changeset/readonly-flow-write-json-warning.md
new file mode 100644
index 000000000..da016cade
--- /dev/null
+++ b/.changeset/readonly-flow-write-json-warning.md
@@ -0,0 +1,11 @@
+---
+"@objectstack/cli": patch
+---
+
+fix(cli): include readonly flow-write warnings in `os validate --json` output
+
+The `readonlyWhen` flow-write advisory (`validateReadonlyFlowWrites`, #3465) was
+printed in human mode but omitted from the `--json` summary's `warnings` array,
+where every other advisory category is aggregated. `os validate --json`
+consumers (CI, editors) therefore never saw those warnings. Added
+`...readonlyWriteWarnings` to the summary array so JSON and human output agree.
diff --git a/packages/cli/src/commands/validate.ts b/packages/cli/src/commands/validate.ts
index 75a5a608b..bead03cf1 100644
--- a/packages/cli/src/commands/validate.ts
+++ b/packages/cli/src/commands/validate.ts
@@ -562,7 +562,7 @@ export default class Validate extends Command {
           valid: true,
           manifest: config.manifest,
           stats,
-          warnings: [...exprWarnings, ...widgetWarnings, ...actionRefWarnings, ...styleWarnings, ...jsxWarnings, ...capWarnings, ...flowReadinessWarnings, ...flowTemplateWarnings, ...securityAdvisories, ...capProviderWarnings],
+          warnings: [...exprWarnings, ...widgetWarnings, ...actionRefWarnings, ...styleWarnings, ...jsxWarnings, ...capWarnings, ...flowReadinessWarnings, ...flowTemplateWarnings, ...readonlyWriteWarnings, ...securityAdvisories, ...capProviderWarnings],
           conversions: conversionNotices,
           specVersionGap: specGap,
           duration: timer.elapsed(),