diff --git a/docs/agent-environments.md b/docs/agent-environments.md
index fad7eee9de..04925f1649 100644
--- a/docs/agent-environments.md
+++ b/docs/agent-environments.md
@@ -488,8 +488,10 @@ within 30 seconds, including reading the body; `mimeType`, when given, is
 `application/json`. A `file://` URL naming another host, or a UNC path such as
 `file:////server/share/state.json`, is refused before anything is opened, so a
 load never reaches a network share. A loaded document is at most 32
-MiB; an inline part also stays within the 4 MiB request body bound, so larger
-states arrive by `uri`. Anything else, including `{"parts": []}`, is `-32602
+MiB, and so is the state as `data/get` writes it back with the members a
+document may omit (`types`, `state_evidence_id`, record citations), so a
+reported state always loads again; an inline part also stays within the 4 MiB
+request body bound, so larger states arrive by `uri`. Anything else, including `{"parts": []}`, is `-32602
 invalid params`; a download that fails or answers a non-2xx status is
 `-32000`. Errors never echo the uri or the content; a file or download failure
 names its category in `error.data.reason`: `not-found`, `permission`,
diff --git a/docs/specs/agent-environments/state-serve/spec.md b/docs/specs/agent-environments/state-serve/spec.md
index ae08ecd656..49837d5bd8 100644
--- a/docs/specs/agent-environments/state-serve/spec.md
+++ b/docs/specs/agent-environments/state-serve/spec.md
@@ -77,7 +77,9 @@ this increment: write tools are not served from the state.
   `mimeType` when given is `application/json`) and `data/get` (`{parts:
   [{kind: "data", data: rea_state}]}`). A `file://` uri whose host is neither
   empty nor `localhost`, or whose path is a UNC path, is `-32602` before
-  anything is opened. Anything else is `-32602`, including empty `parts`; a
+  anything is opened. A document that `data/get` would write back past 32 MiB,
+  once it adds the members a document may omit, is `-32602`, so a reported
+  state always loads again. Anything else is `-32602`, including empty `parts`; a
   failed download is `-32000`; errors never echo a uri or content and name a
   coarse failure category in `error.data.reason`. Calls run one at a time in
   arrival order across requests; every message of a batch is queued when the
diff --git a/src/application/environment/environmentState.test.ts b/src/application/environment/environmentState.test.ts
index 7402f3dbbe..bced6224af 100644
--- a/src/application/environment/environmentState.test.ts
+++ b/src/application/environment/environmentState.test.ts
@@ -28,6 +28,7 @@ import {
   loadEnvironmentState,
   prepareServedState,
 } from "./environmentState.js";
+import { STATE_INTAKE_LIMIT_BYTES } from "./environmentStateDocument.js";
 import { EnvironmentStateStore } from "./environmentStateStore.js";
 
 const fixture = environmentStateServeFixture();
@@ -373,6 +374,48 @@ describe("EnvironmentStateStore", () => {
     expect(refused.ok).toBe(false);
     expect(store.snapshot()).toEqual(before);
   });
+
+  it("refuses a document that data/get would write back past what data/add loads", () => {
+    const store = new EnvironmentStateStore(state);
+    const { rea_state: held } = store.snapshot();
+    // Without the members data/get adds back, the document fits only until they return.
+    const document = {
+      rea_state: {
+        version: held.version,
+        entities: held.entities.map(({ type, collection, id, fields }) => ({
+          type,
+          collection,
+          id,
+          fields: { ...fields },
+        })),
+        documents: held.documents,
+      },
+    };
+    const entity = document.rea_state.entities[0]!;
+    const { fields } = entity;
+    const idField = state.types.find(
+      (type) => type.collection_template === entity.type,
+    )?.id_field;
+    const text = Object.keys(fields).find(
+      (field) => field !== idField && typeof fields[field] === "string",
+    )!;
+    fields[text] = `${String(fields[text])}${"a".repeat(
+      STATE_INTAKE_LIMIT_BYTES -
+        Buffer.byteLength(JSON.stringify(document), "utf8"),
+    )}`;
+    expect(Buffer.byteLength(JSON.stringify(document), "utf8")).toBe(
+      STATE_INTAKE_LIMIT_BYTES,
+    );
+    const before = store.snapshot();
+    const replaced = store.replace(document);
+    expect(!replaced.ok && replaced.error.issues).toEqual([
+      expect.objectContaining({
+        reason: "out_of_range",
+        maximum: STATE_INTAKE_LIMIT_BYTES,
+      }),
+    ]);
+    expect(store.snapshot()).toEqual(before);
+  });
 });
 
 describe("rea-state/v1 validation", () => {