diff --git a/AGENTS.md b/AGENTS.md
index 008feb4..f17b645 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -30,6 +30,7 @@ Runtime: Node.js (ESM, `.mjs` throughout). No build step. No bundler. `server.mj
 
 - `server.mjs` — the proxy itself; every request path lives here. Governed by `ALIGNMENT.md`.
 - `models.json` — single source of truth for model IDs, aliases, and context windows. See ADR 0003.
+- `models.schema.json` — the schema `models.json` declares in its `$schema`. CI validates the SPOT against it (`test-features.mjs`) using the repo's own `validateJsonSchema`, so a malformed entry fails the build instead of surfacing downstream in OpenClaw.
 - `setup.mjs` — first-time installer; reads `models.json` to derive bootstrap config.
 - `scripts/sync-openclaw.mjs` — idempotent OpenClaw registry sync invoked by `ocp update`. See ADR 0004.
 - `ocp` — user-facing CLI (install, update, start, stop, status, logs, etc.).
diff --git a/README.md b/README.md
index 3cc3d38..b79d648 100644
--- a/README.md
+++ b/README.md
@@ -177,7 +177,7 @@ Any tool use happens server-side, under the `--allowedTools` set configured on t
 | `claude-sonnet-4-6` | Previous Sonnet, retained for pinning |
 | `claude-haiku-4-5-20251001` | Fastest, lightweight (default for `haiku` alias) |
 
-The canonical list lives in [`models.json`](./models.json) — the single source of truth as of v3.11.0. Both `server.mjs` (the `/v1/models` endpoint) and `setup.mjs` (the OpenClaw registration) derive from it. Adding a new model is now a one-file edit:
+The canonical list lives in [`models.json`](./models.json) — the single source of truth as of v3.11.0, validated in CI against [`models.schema.json`](./models.schema.json). Both `server.mjs` (the `/v1/models` endpoint) and `setup.mjs` (the OpenClaw registration) derive from it. Adding a new model is now a one-file edit:
 
 ```bash
 # 1. Edit models.json — add an entry
diff --git a/models.schema.json b/models.schema.json
new file mode 100644
index 0000000..3db19e6
--- /dev/null
+++ b/models.schema.json
@@ -0,0 +1,65 @@
+{
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "$id": "https://github.com/dtzp555-max/ocp/blob/main/models.schema.json",
+  "title": "OCP models.json",
+  "description": "Schema for models.json, the single source of truth for model metadata (ADR 0003). Enforced in CI by test-features.mjs, which validates models.json against this file using the repo's own validateJsonSchema (lib/structured-output.mjs) — no new dependency. NOTE: referential integrity (every aliases/legacyAliases target must exist as a models[].id) is NOT expressible here and is covered by separate tests.",
+  "type": "object",
+  "required": ["version", "models", "aliases", "legacyAliases"],
+  "additionalProperties": false,
+  "properties": {
+    "$schema": {
+      "type": "string",
+      "description": "Relative path to this file. Editors use it for completion; CI does not read it."
+    },
+    "version": {
+      "const": 1,
+      "description": "Schema version of this document. Bump only alongside a shape change and an ADR."
+    },
+    "models": {
+      "type": "array",
+      "minItems": 1,
+      "description": "Every model OCP advertises on /v1/models, newest first. Order is load-bearing: ocp-connect uses model_ids[0] as a primary fallback.",
+      "items": {
+        "type": "object",
+        "required": ["id", "displayName", "openclawName", "reasoning", "contextWindow", "maxTokens"],
+        "additionalProperties": false,
+        "properties": {
+          "id": {
+            "type": "string",
+            "description": "Canonical CLI model id, passed verbatim to `claude --model`. Must match the id in the compiled CLI registry."
+          },
+          "displayName": {
+            "type": "string",
+            "description": "Human label. Also used as the OpenClaw agent alias by scripts/sync-openclaw.mjs."
+          },
+          "openclawName": {
+            "type": "string",
+            "description": "Label written into OpenClaw's model registry."
+          },
+          "reasoning": {
+            "type": "boolean",
+            "description": "Whether OpenClaw should treat the model as reasoning-capable."
+          },
+          "contextWindow": {
+            "type": "integer",
+            "description": "Advertised context window. GLOBAL side effect: MAX_PROMPT_CHARS derives from max(contextWindow) x 3 across ALL entries (lib/prompt.mjs derivePromptCharBudget), so raising this on ONE model raises the truncation ceiling for EVERY model. See ADR 0009. Also feeds OpenClaw's compaction budget."
+          },
+          "maxTokens": {
+            "type": "integer",
+            "description": "Advertised output cap. OCP does not enforce it; it is propagated to OpenClaw (via setup.mjs / scripts/sync-openclaw.mjs) where it bounds request and compaction budgets."
+          }
+        }
+      }
+    },
+    "aliases": {
+      "type": "object",
+      "description": "Short name -> canonical models[].id. Client-addressable, so a repoint changes routing for every request using the alias. Cache keys resolve these before hashing (server.mjs cacheModel).",
+      "additionalProperties": { "type": "string" }
+    },
+    "legacyAliases": {
+      "type": "object",
+      "description": "Retired ids kept resolvable for backward compatibility -> canonical models[].id. Also client-addressable and also resolved in cache keys.",
+      "additionalProperties": { "type": "string" }
+    }
+  }
+}
diff --git a/test-features.mjs b/test-features.mjs
index c157ffd..e4b0797 100644
--- a/test-features.mjs
+++ b/test-features.mjs
@@ -4305,6 +4305,52 @@ test("models.json: every legacyAliases value resolves to a real models[].id (ref
   }
 });
 
+// ── models.json validates against models.schema.json (#196) ─────────────────
+// models.json carried `"$schema": "./models.schema.json"` while that file had never been
+// committed, so the SPOT that ADR 0003 makes canonical had no structural validation at all —
+// a missing contextWindow or a typo'd openclawName would only surface downstream, in OpenClaw
+// or in a truncation budget. Validated with the repo's OWN validator (lib/structured-output.mjs,
+// shipped for #153) rather than a new dependency: zero deps added, and it exercises that
+// validator on a second real input.
+//
+// The schema deliberately does NOT try to express referential integrity (alias -> models[].id);
+// that is not a JSON Schema concept and is covered by the two tests directly above.
+import { validateJsonSchema as _spotValidate } from "./lib/structured-output.mjs";
+
+const _spotSchema = JSON.parse(spotReadFileSync(spotJoin(_spotDir, "models.schema.json"), "utf8"));
+
+test("models.json: the $schema reference resolves to a committed file", () => {
+  assert.equal(_spotModels.$schema, "./models.schema.json", "models.json must point at the schema");
+  assert.ok(_ltExists(spotJoin(_spotDir, "models.schema.json")),
+    "models.schema.json must exist — a dangling $schema is what #196 was filed for");
+});
+
+test("models.json validates against models.schema.json (strict)", () => {
+  const errors = _spotValidate(_spotModels, _spotSchema, "$", true);
+  assert.deepEqual(errors, [], `models.json violates its own schema:\n  ${errors.join("\n  ")}`);
+});
+
+// Guards the guard: if the schema were vacuous (e.g. `{}` or a typo'd `properties`), the test
+// above would pass on anything. Each corruption below must be caught.
+test("models.schema.json actually rejects malformed entries (guard is not vacuous)", () => {
+  const clone = () => JSON.parse(JSON.stringify(_spotModels));
+  const cases = [
+    ["missing required field", m => { delete m.models[0].contextWindow; }],
+    ["wrong scalar type", m => { m.models[0].reasoning = "yes"; }],
+    ["non-integer window", m => { m.models[0].contextWindow = 200000.5; }],
+    ["unknown extra field", m => { m.models[0].tokensPerSecond = 42; }],
+    ["alias mapped to non-string", m => { m.aliases.opus = { id: "x" }; }],
+    ["empty models array", m => { m.models = []; }],
+    ["wrong document version", m => { m.version = 2; }],
+    ["unknown top-level key", m => { m.providers = {}; }],
+  ];
+  for (const [label, corrupt] of cases) {
+    const bad = clone(); corrupt(bad);
+    const errs = _spotValidate(bad, _spotSchema, "$", true);
+    assert.ok(errs.length > 0, `schema failed to reject: ${label}`);
+  }
+});
+
 // ── escapeHtml + key-name validator (issue #114) ────────────────────────────
 // Replicated verbatim from dashboard.html so tests run without a browser.
 function escapeHtml(s) {