diff --git a/Cargo.toml b/Cargo.toml
index cc5f12b..370e08f 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -5,6 +5,7 @@ members = ["contracts/round"]
 [workspace.package]
 version = "0.1.0"
 edition = "2021"
+rust-version = "1.85.0"
 license = "MIT"
 authors = ["Sub Rosa"]
 
diff --git a/docs/CI.md b/docs/CI.md
index 4a3af75..8f5918a 100644
--- a/docs/CI.md
+++ b/docs/CI.md
@@ -83,3 +83,18 @@ print order are asserted by:
 ```bash
 node --test scripts/check-bindings-cli.test.mjs
 ```
+
+## Pinned Rust toolchain
+
+The workspace pins Rust **1.85.0** with target `wasm32v1-none` in
+`rust-toolchain.toml` and `Cargo.toml` (`[workspace.package] rust-version = "1.85.0"`),
+replacing a moving `stable` channel reference so contract builds and
+`stellar-cli` bindings checks stay reproducible across local runs and both
+contract workflows (`.github/workflows/contract.yml` and
+`.github/workflows/bindings-check.yml`). Validate the pin and alignment locally
+with:
+
+```bash
+pnpm rust:toolchain:test
+pnpm rust:toolchain:check
+```
diff --git a/package.json b/package.json
index 66e5b7c..7fca775 100644
--- a/package.json
+++ b/package.json
@@ -76,7 +76,9 @@
     "snapshot:check": "node scripts/check-snapshots.mjs",
     "docs:check": "node scripts/check-deploy-docs.mjs",
     "docs:check-links": "node scripts/check-links.js",
-    "coverage:test": "node --test scripts/run-ts-coverage.test.mjs && node scripts/run-ts-coverage.mjs",
+    "coverage:test": "node --test scripts/check-rust-toolchain.test.mjs && node scripts/check-rust-toolchain.mjs && node --test scripts/run-ts-coverage.test.mjs && node scripts/run-ts-coverage.mjs",
+    "rust:toolchain:check": "node scripts/check-rust-toolchain.mjs",
+    "rust:toolchain:test": "node --test scripts/check-rust-toolchain.test.mjs",
     "drand:test": "pnpm --filter @sub-rosa/drand-tools test",
     "drand:typecheck": "pnpm --filter @sub-rosa/drand-tools typecheck",
     "receipt:test": "pnpm --filter @sub-rosa/receipt-cli test",
diff --git a/rust-toolchain.toml b/rust-toolchain.toml
index e25fb76..25b3f02 100644
--- a/rust-toolchain.toml
+++ b/rust-toolchain.toml
@@ -1,3 +1,3 @@
 [toolchain]
-channel = "stable"
+channel = "1.85.0"
 targets = ["wasm32v1-none"]
diff --git a/scripts/check-rust-toolchain.mjs b/scripts/check-rust-toolchain.mjs
new file mode 100644
index 0000000..8c6d96f
--- /dev/null
+++ b/scripts/check-rust-toolchain.mjs
@@ -0,0 +1,137 @@
+#!/usr/bin/env node
+// Copyright (c) 2026 Sub Rosa contributors
+import { existsSync, readFileSync } from "node:fs";
+import { resolve } from "node:path";
+import { fileURLToPath, pathToFileURL } from "node:url";
+import { createLogger } from "../packages/logging/src/index.cjs";
+
+const diagnostics = createLogger("scripts.check-rust-toolchain");
+
+export const PINNED_RUST_VERSION = "1.85.0";
+export const REQUIRED_TARGET = "wasm32v1-none";
+
+const DEFAULT_ROOT = fileURLToPath(new URL("..", import.meta.url));
+
+/**
+ * Validate `rust-toolchain.toml` content.
+ * @param {string} tomlText
+ */
+export function inspectRustToolchainToml(tomlText) {
+  const errors = [];
+  const channelMatch = tomlText.match(/^\s*channel\s*=\s*"([^"]+)"/m);
+  if (!channelMatch) {
+    errors.push('rust-toolchain.toml is missing a channel = "..." entry');
+  } else {
+    const channel = channelMatch[1];
+    if (/^(stable|beta|nightly)$/i.test(channel)) {
+      errors.push(
+        `rust-toolchain.toml uses moving channel "${channel}"; pin to an exactMAJOR.MINOR.PATCH version`,
+      );
+    } else if (!/^\d+\.\d+\.\d+$/.test(channel)) {
+      errors.push(
+        `rust-toolchain.toml channel "${channel}" must be an exact MAJOR.MINOR.PATCH version`,
+      );
+    } else if (channel !== PINNED_RUST_VERSION) {
+      errors.push(
+        `rust-toolchain.toml channel "${channel}" does not match reviewed version ${PINNED_RUST_VERSION}`,
+      );
+    }
+  }
+
+  if (!tomlText.includes(`"${REQUIRED_TARGET}"`)) {
+    errors.push(
+      `rust-toolchain.toml must include "${REQUIRED_TARGET}" in targets`,
+    );
+  }
+
+  return { channel: channelMatch?.[1] ?? null, errors };
+}
+
+/**
+ * Validate workspace Rust toolchain alignment across `rust-toolchain.toml`,
+ * `Cargo.toml`, contract workflows, and `docs/CI.md`.
+ * @param {string} [rootDir]
+ */
+export function validateRustToolchain(rootDir = DEFAULT_ROOT) {
+  const errors = [];
+
+  const toolchainPath = resolve(rootDir, "rust-toolchain.toml");
+  const cargoTomlPath = resolve(rootDir, "Cargo.toml");
+  const contractWfPath = resolve(rootDir, ".github/workflows/contract.yml");
+  const bindingsWfPath = resolve(rootDir, ".github/workflows/bindings-check.yml");
+  const ciDocsPath = resolve(rootDir, "docs/CI.md");
+
+  let pinnedChannel = null;
+  if (!existsSync(toolchainPath)) {
+    errors.push("Missing rust-toolchain.toml at repository root");
+  } else {
+    const res = inspectRustToolchainToml(readFileSync(toolchainPath, "utf8"));
+    pinnedChannel = res.channel;
+    errors.push(...res.errors);
+  }
+
+  if (!existsSync(cargoTomlPath)) {
+    errors.push("Missing Cargo.toml at repository root");
+  } else {
+    const cargoText = readFileSync(cargoTomlPath, "utf8");
+    const rvMatch = cargoText.match(/^\s*rust-version\s*=\s*"([^"]+)"/m);
+    if (!rvMatch) {
+      errors.push('Cargo.toml [workspace.package] must declare rust-version = "1.85.0"');
+    } else if (pinnedChannel && rvMatch[1] !== pinnedChannel) {
+      errors.push(
+        `Cargo.toml rust-version "${rvMatch[1]}" does not match rust-toolchain.toml "${pinnedChannel}"`,
+      );
+    }
+  }
+
+  if (existsSync(contractWfPath) && existsSync(bindingsWfPath)) {
+    const contractWf = readFileSync(contractWfPath, "utf8");
+    const bindingsWf = readFileSync(bindingsWfPath, "utf8");
+    const contractRef =
+      contractWf.match(/uses:\s*(dtolnay\/rust-toolchain@\S+)/)?.[1] ?? null;
+    const bindingsRef =
+      bindingsWf.match(/uses:\s*(dtolnay\/rust-toolchain@\S+)/)?.[1] ?? null;
+
+    if (!contractRef || !bindingsRef) {
+      errors.push(
+        "Both contract.yml and bindings-check.yml must use dtolnay/rust-toolchain",
+      );
+    } else if (contractRef !== bindingsRef) {
+      errors.push(
+        `Rust toolchain action mismatch between contract.yml (${contractRef}) and bindings-check.yml (${bindingsRef})`,
+      );
+    }
+  }
+
+  if (!existsSync(ciDocsPath)) {
+    errors.push("Missing docs/CI.md");
+  } else {
+    const docs = readFileSync(ciDocsPath, "utf8");
+    if (!docs.includes(PINNED_RUST_VERSION)) {
+      errors.push(
+        `docs/CI.md must document the pinned Rust toolchain version ${PINNED_RUST_VERSION}`,
+      );
+    }
+  }
+
+  return { ok: errors.length === 0, errors };
+}
+
+function main() {
+  const res = validateRustToolchain();
+  if (!res.ok) {
+    for (const err of res.errors) {
+      diagnostics.error("rust-toolchain-check-failed", `FAIL: ${err}`);
+    }
+    process.exit(1);
+  }
+
+  diagnostics.info(
+    "rust-toolchain-check-passed",
+    `PASS: Rust toolchain is pinned to ${PINNED_RUST_VERSION} (${REQUIRED_TARGET}) and aligned across Cargo.toml, workflows, and docs/CI.md.`,
+  );
+}
+
+if (import.meta.url === pathToFileURL(process.argv[1] ?? "").href) {
+  main();
+}
diff --git a/scripts/check-rust-toolchain.test.mjs b/scripts/check-rust-toolchain.test.mjs
new file mode 100644
index 0000000..7f09c2a
--- /dev/null
+++ b/scripts/check-rust-toolchain.test.mjs
@@ -0,0 +1,70 @@
+// Copyright (c) 2026 Sub Rosa contributors
+import { describe, it } from "node:test";
+import assert from "node:assert/strict";
+import { mkdtempSync, mkdirSync, copyFileSync, writeFileSync, rmSync } from "node:fs";
+import { tmpdir } from "node:os";
+import { join } from "node:path";
+import { fileURLToPath } from "node:url";
+
+import {
+  PINNED_RUST_VERSION,
+  inspectRustToolchainToml,
+  validateRustToolchain,
+} from "./check-rust-toolchain.mjs";
+
+const REPO_ROOT = fileURLToPath(new URL("..", import.meta.url));
+
+describe("check-rust-toolchain", () => {
+  it("passes on the repository configuration", () => {
+    const res = validateRustToolchain(REPO_ROOT);
+    assert.equal(res.ok, true, `Expected pass, got errors: ${res.errors.join("; ")}`);
+  });
+
+  it("rejects moving stable/nightly channels in rust-toolchain.toml", () => {
+    const stableRes = inspectRustToolchainToml(
+      '[toolchain]\nchannel = "stable"\ntargets = ["wasm32v1-none"]\n',
+    );
+    assert.ok(stableRes.errors.some((e) => e.includes('moving channel "stable"')));
+
+    const partialRes = inspectRustToolchainToml(
+      '[toolchain]\nchannel = "1.85"\ntargets = ["wasm32v1-none"]\n',
+    );
+    assert.ok(partialRes.errors.some((e) => e.includes("MAJOR.MINOR.PATCH")));
+  });
+
+  it("rejects missing wasm32v1-none target", () => {
+    const res = inspectRustToolchainToml(
+      `[toolchain]\nchannel = "${PINNED_RUST_VERSION}"\ntargets = []\n`,
+    );
+    assert.ok(res.errors.some((e) => e.includes("wasm32v1-none")));
+  });
+
+  it("rejects drift between rust-toolchain.toml, Cargo.toml, and contract workflows", () => {
+    const tmp = mkdtempSync(join(tmpdir(), "rust-toolchain-test-"));
+    try {
+      mkdirSync(join(tmp, ".github/workflows"), { recursive: true });
+      mkdirSync(join(tmp, "docs"), { recursive: true });
+      copyFileSync(join(REPO_ROOT, "rust-toolchain.toml"), join(tmp, "rust-toolchain.toml"));
+      copyFileSync(join(REPO_ROOT, "docs/CI.md"), join(tmp, "docs/CI.md"));
+      writeFileSync(
+        join(tmp, "Cargo.toml"),
+        '[workspace]\n[workspace.package]\nrust-version = "1.80.0"\n',
+      );
+      writeFileSync(
+        join(tmp, ".github/workflows/contract.yml"),
+        "steps:\n  - uses: dtolnay/rust-toolchain@stable\n",
+      );
+      writeFileSync(
+        join(tmp, ".github/workflows/bindings-check.yml"),
+        "steps:\n  - uses: dtolnay/rust-toolchain@nightly\n",
+      );
+
+      const res = validateRustToolchain(tmp);
+      assert.equal(res.ok, false);
+      assert.ok(res.errors.some((e) => e.includes("Cargo.toml rust-version")));
+      assert.ok(res.errors.some((e) => e.includes("Rust toolchain action mismatch")));
+    } finally {
+      rmSync(tmp, { recursive: true, force: true });
+    }
+  });
+});