Cosmos: Implement binary round trip fuzzer

Cargo.toml

@@ -87,6 +87,8 @@ version = "1.0.0"
 version = "1.0.0"
 
 [workspace.dependencies]
+arbitrary = { version = "1.4", features = ["derive"] }
+arbitrary-json = "0.1"
 async-lock = "3.4"
 async-stream = { version = "0.3.6" }
 async-trait = "0.1"
@@ -115,6 +117,7 @@ hdrhistogram = "7.5"
 hostname = "0.4"
 hmac = { version = "0.12" }
 include-file = { version = "1.0.0", default-features = false }
+json-canon = "0.1"
 openssl = { version = "0.10.79" }
 opentelemetry = { version = "0.32", features = ["trace"] }
 opentelemetry-appender-tracing = { version = "0.32" }

sdk/cosmos/.cspell.json

@@ -8,6 +8,7 @@
     "ALPN",
     "apacsoutheast",
     "Appleby's",
+    "AQID",
     "argtypes",
     "asyncio",
     "australiacentral",
@@ -19,6 +20,7 @@
     "azurecosmos",
     "azurecosmosdriver",
     "backoff",
+    "backoffs",
     "backpressure",
     "BADFUNC",
     "bindgen",
@@ -30,6 +32,7 @@
     "cabi",
     "canadacentral",
     "canadaeast",
+    "CBOR",
     "cbindgen",
     "CDLL",
     "cdriver",
@@ -49,6 +52,7 @@
     "chinaeast",
     "chinanorth",
     "chokepoint",
+    "canonicalizer",
     "cloneable",
     "codepoint",
     "codepoints",
@@ -61,6 +65,7 @@
     "consumingly",
     "Conv",
     "cooldown",
+    "cosmosbinary",
     "cosmosclient",
     "cosmosdriver",
     "correlator",
@@ -78,6 +83,7 @@
     "dcount",
     "dedicatedgateway",
     "deprioritized",
+    "dkunda",
     "deprioritizes",
     "derefs",
     "dhat",
@@ -125,6 +131,7 @@
     "Geospatial",
     "fshort",
     "funct",
+    "fuzzable",
     "gatewayversion",
     "germanycentral",
     "germanynorth",
@@ -148,10 +155,12 @@
     "inclusivity",
     "inlines",
     "inmemory",
+    "ints",
     "INVALIDARG",
     "isquery",
     "japaneast",
     "japanwest",
+    "jsontext",
     "keepalive",
     "keyspace",
     "koreacentral",
@@ -163,6 +172,7 @@
     "libazurecosmosdriver",
     "libclang",
     "LIBCLANG",
+    "libfuzzer",
     "libqueryplaninterop",
     "QUERYPLANINTEROP",
     "linearizability",
@@ -198,6 +208,7 @@
     "nocoll",
     "noretry",
     "normalises",
+    "notneg",
     "northcentralus",
     "northeurope",
     "norwayeast",
@@ -233,6 +244,7 @@
     "precomputation",
     "preimage",
     "Prereqs",
+    "PRNG",
     "ptrs",
     "pushback",
     "pushdown",
@@ -242,10 +254,15 @@
     "RAII",
     "readfeed",
     "recompiles",
+    "redecoded",
+    "reencode",
+    "reencoded",
     "refetch",
     "refetched",
     "refetches",
     "refcounted",
+    "reparses",
+    "reparsed",
     "Replicaset",
     "reqs",
     "restype",
@@ -262,9 +279,11 @@
     "RUPM",
     "rwcache",
     "sbyte",
+    "seqs",
     "serviceunavailable",
     "serviceversion",
     "sess",
+    "Signedness",
     "southafricanorth",
     "southafricawest",
     "southcentralus",
@@ -275,6 +294,7 @@
     "sprocs",
     "staticlib",
     "stdlib",
+    "streamable",
     "subrange",
     "submitret",
     "subsec",
@@ -293,10 +313,13 @@
     "testdb",
     "thinclient",
     "threadsafe",
+    "tmin",
     "TOCTOU",
     "Tokio",
     "TOPCOUNT",
     "TPIO",
+    "transcoders",
+    "trippable",
     "uaecentral",
     "uaenorth",
     "udfs",
@@ -307,6 +330,7 @@
     "unavail",
     "uncollapsed",
     "uncontended",
+    "undecoded",
     "undrained",
     "unfaulted",
     "ungoverned",
@@ -356,7 +380,8 @@
     "**/query_plan_native/QueryPlanInterop.h",
     "**/query_plan_native/bindgen_wrapper.h",
     "**/query_plan_native/generated/native_bindings.rs",
-    "vnext-emulator-matrix.json"
+    "vnext-emulator-matrix.json",
+    "**/azure_data_cosmos_perf/testdata/**"
   ],
   "overrides": [
     {

sdk/cosmos/azure_data_cosmos/CHANGELOG.md

@@ -4,11 +4,7 @@
 
 ### Features Added
 
-### Breaking Changes
-
-### Bugs Fixed
-
-### Other Changes
+- Added opt-in Cosmos binary JSON encoding for item operations (`create`/`read`/`replace`/`upsert`). Enable it via `CosmosClientBuilder::with_binary_encoding_options` (or the `AZURE_COSMOS_BINARY_ENCODING_ENABLED` environment-variable fallback). Off by default; when disabled, requests and responses are byte-for-byte unchanged. ([#4671](https://github.com/Azure/azure-sdk-for-rust/pull/4671))
 
 ## 0.37.1 (2026-07-23)
 

sdk/cosmos/azure_data_cosmos/Cargo.toml

@@ -122,6 +122,11 @@ name = "split"
 path = "tests/split.rs"
 required-features = ["key_auth", "fault_injection"]
 
+[[test]]
+name = "binary_encoding"
+path = "tests/binary_encoding.rs"
+required-features = ["key_auth", "fault_injection"]
+
 [[test]]
 name = "gateway_v2"
 path = "tests/gateway_v2.rs"

sdk/cosmos/azure_data_cosmos/build.rs

@@ -7,6 +7,6 @@
 fn main() {
     // Allow `#[cfg_attr(not(test_category = "..."), ignore)]` in `tests/*.rs`.
     println!(
-        "cargo:rustc-check-cfg=cfg(test_category, values(\"emulator\", \"emulator_vnext\", \"multi_write\", \"split\", \"gateway_v2\", \"gateway_v2_multi_region\"))"
+        "cargo:rustc-check-cfg=cfg(test_category, values(\"emulator\", \"emulator_vnext\", \"multi_write\", \"split\", \"binary_encoding\", \"gateway_v2\", \"gateway_v2_multi_region\"))"
     );
 }