diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index c4fe747..81f4a6c 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -63,6 +63,38 @@ jobs:
             --locked \
             -- -D warnings
 
+      - name: Run clippy without default features
+        run: |
+          cargo clippy \
+            --workspace \
+            --all-targets \
+            --no-default-features \
+            --locked \
+            -- -D warnings
+
+  check:
+    name: cargo check
+    runs-on: ubuntu-latest
+    timeout-minutes: 20
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6
+        with:
+          persist-credentials: false
+
+      - name: Install Rust toolchain
+        uses: actions-rust-lang/setup-rust-toolchain@46268bd060767258de96ed93c1251119784f2ab6 # v1
+        with:
+          cache-key: check
+
+      - name: Run check without default features
+        run: |
+          cargo check \
+            --workspace \
+            --no-default-features \
+            --locked
+
   test:
     name: cargo test
     runs-on: ubuntu-latest
@@ -87,6 +119,13 @@ jobs:
             --all-features \
             --locked
 
+      - name: Run tests without default features
+        run: |
+          cargo test \
+            --workspace \
+            --no-default-features \
+            --locked
+
   docs:
     name: cargo doc
     runs-on: ubuntu-latest
diff --git a/README.md b/README.md
index 443b6d2..3878e87 100644
--- a/README.md
+++ b/README.md
@@ -84,10 +84,16 @@ irtt-cli <server> --duration 0 --interval 250ms --output machine
 Each line represents one client event and starts with an `event` field, for example:
 
 ```text
-event=echo_reply seq=4 logical_seq=4 remote=203.0.113.10:2112 raw_rtt_us=12400 effective_rtt_us=12100 adjusted_rtt_us=12100 server_processing_us=300 dscp=0 ecn=0 kernel_rx_ns=none
+event=echo_reply seq=4 remote=203.0.113.10:2112 client_send_wall_ns=1760000000000000000 client_receive_wall_ns=1760000000012400000 raw_rtt_us=12400 effective_rtt_us=12100 adjusted_rtt_us=12100 server_receive_wall_ns=1760000000006100000 server_receive_mono_ns=5000006100000 server_send_wall_ns=1760000000006400000 server_send_mono_ns=5000006400000 server_processing_us=300 client_to_server_us=6100 server_to_client_us=6000 server_received_count=5 server_received_window=0x1f dscp=0 ecn=0 kernel_rx_ns=none
 ```
 
 Consumers should match on `event=...` and read the fields they need. Unknown fields should be ignored.
+RTT fields are reported in microseconds. `raw_rtt_us` is the measured client
+send-to-receive RTT. `effective_rtt_us` and `adjusted_rtt_us` are signed and may
+be negative when server processing exceeds the raw RTT or timing correction
+produces a negative adjusted value. When one-way delay fields are present,
+`client_to_server_us` and `server_to_client_us` are also signed microseconds and
+may be negative due to wall-clock skew.
 
 For consumers that only need RTT values, use:
 
diff --git a/crates/irtt-cli/src/lib.rs b/crates/irtt-cli/src/lib.rs
index 4ee268b..953f05e 100644
--- a/crates/irtt-cli/src/lib.rs
+++ b/crates/irtt-cli/src/lib.rs
@@ -894,7 +894,6 @@ mod tests {
         }
     }
 
-    #[cfg(feature = "stats")]
     fn negative_adjusted_reply_event() -> ClientEvent {
         ClientEvent::EchoReply {
             seq: 8,
@@ -1233,6 +1232,22 @@ mod tests {
         );
     }
 
+    #[test]
+    fn human_and_simple_print_negative_effective_rtt() {
+        let event = negative_adjusted_reply_event();
+
+        assert!(format_event(&event, OutputMode::Human)
+            .unwrap()
+            .contains("rtt=-1.5ms"));
+        assert_eq!(
+            format_event(&event, OutputMode::Simple),
+            Some(
+                "reply seq=8 remote=127.0.0.1:2112 rtt_us=-1500 raw_rtt_us=500 server_processing_us=2000"
+                    .to_owned()
+            )
+        );
+    }
+
     #[test]
     #[cfg(feature = "stats")]
     fn streamed_and_summary_rtt_use_signed_effective_policy() {