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diff --git a/jstests/noPassthroughWithMongod/command_let_variables.js b/jstests/noPassthroughWithMongod/command_let_variables.js
new file mode 100644
index 00000000000..75f34d24d08
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+++ b/jstests/noPassthroughWithMongod/command_let_variables.js
@@ -0,0 +1,131 @@
+// Tests that commands like find, aggregate and update accepts a 'let' parameter which defines
+// variables for use in expressions within the command.
+// TODO SERVER-46707: move this back to core after let params work in sharded aggreggate.
+// @tags: [assumes_against_mongod_not_mongos, requires_fcv46]
+
+(function() {
+"use strict";
+
+const coll = db.update_let_variables;
+coll.drop();
+
+assert.commandWorked(coll.insert([
+    {
+        Species: "Blackbird (Turdus merula)",
+        population_trends: [
+            {term: {start: 1970, end: 2014}, pct_change: -16, annual: -0.38, trend: "no change"},
+            {term: {start: 2009, end: 2014}, pct_change: -2, annual: -0.36, trend: "no change"}
+        ]
+    },
+    {
+        Species: "Bullfinch (Pyrrhula pyrrhula)",
+        population_trends: [
+            {term: {start: 1970, end: 2014}, pct_change: -39, annual: -1.13, trend: "no change"},
+            {term: {start: 2009, end: 2014}, pct_change: 12, annual: 2.38, trend: "weak increase"}
+        ]
+    },
+    {
+        Species: "Chaffinch (Fringilla coelebs)",
+        population_trends: [
+            {term: {start: 1970, end: 2014}, pct_change: 27, annual: 0.55, trend: "no change"},
+            {term: {start: 2009, end: 2014}, pct_change: -7, annual: -1.49, trend: "weak decline"}
+        ]
+    },
+    {
+        Species: "Song Thrush (Turdus philomelos)",
+        population_trends: [
+            {term: {start: 1970, end: 2014}, pct_change: -53, annual: -1.7, trend: "weak decline"},
+            {term: {start: 2009, end: 2014}, pct_change: -4, annual: -0.88, trend: "no change"}
+        ]
+    }
+]));
+
+// Aggregate tests
+const pipeline = [
+    {$project: {_id: 0}},
+    {$unwind: "$population_trends"},
+    {$match: {$expr: {$eq: ["$population_trends.trend", "$$target_trend"]}}},
+    {$sort: {Species: 1}}
+];
+let expectedResults = [{
+    Species: "Bullfinch (Pyrrhula pyrrhula)",
+    population_trends:
+        {term: {start: 2009, end: 2014}, pct_change: 12, annual: 2.38, trend: "weak increase"}
+}];
+assert.eq(coll.aggregate(pipeline, {let : {target_trend: "weak increase"}}).toArray(),
+          expectedResults);
+
+expectedResults = [
+    {
+        Species: "Chaffinch (Fringilla coelebs)",
+        population_trends:
+            {term: {start: 2009, end: 2014}, pct_change: -7, annual: -1.49, trend: "weak decline"}
+    },
+    {
+        Species: "Song Thrush (Turdus philomelos)",
+        population_trends:
+            {term: {start: 1970, end: 2014}, pct_change: -53, annual: -1.7, trend: "weak decline"}
+    }
+];
+assert.eq(coll.aggregate(pipeline, {let : {target_trend: "weak decline"}}).toArray(),
+          expectedResults);
+
+// Test that if runtimeConstants and let are both specified, both will coexist.
+let constants = {
+    localNow: new Date(),
+    clusterTime: new Timestamp(0, 0),
+};
+
+assert.eq(
+    coll.aggregate(pipeline, {runtimeConstants: constants, let : {target_trend: "weak decline"}})
+        .toArray(),
+    expectedResults);
+
+// Test that undefined let params in the pipeline fail gracefully.
+assert.commandFailedWithCode(db.runCommand({
+    aggregate: coll.getName(),
+    pipeline: pipeline,
+    runtimeConstants: constants,
+    cursor: {},
+    let : {cat: "not_a_bird"}
+}),
+                             17276);
+
+// Test null and empty let parameters
+const pipeline_no_lets = [
+    {$project: {_id: 0}},
+    {$unwind: "$population_trends"},
+    {$match: {$expr: {$eq: ["$population_trends.trend", "weak decline"]}}},
+    {$sort: {Species: 1}}
+];
+assert.eq(coll.aggregate(pipeline_no_lets, {runtimeConstants: constants, let : {}}).toArray(),
+          expectedResults);
+
+assert.commandFailedWithCode(db.runCommand({
+    aggregate: coll.getName(),
+    pipeline: pipeline_no_lets,
+    runtimeConstants: constants,
+    cursor: {},
+    let : null
+}),
+                             ErrorCodes.TypeMismatch);
+
+// Update
+assert.commandWorked(db.runCommand({
+    update: coll.getName(),
+    let : {target_species: "Song Thrush (Turdus philomelos)", new_name: "Song Thrush"},
+    updates: [
+        {q: {$expr: {$eq: ["$Species", "$$target_species"]}}, u: [{$set: {Species: "$$new_name"}}]}
+    ]
+}));
+
+assert.commandWorked(db.runCommand({
+    update: coll.getName(),
+    let : {target_species: "Song Thrush (Turdus philomelos)"},
+    updates: [{
+        q: {$expr: {$eq: ["$Species", "$$target_species"]}},
+        u: [{$set: {Location: "$$place"}}],
+        c: {place: "North America"}
+    }]
+}));
+}());