diff --git a/.github/workflows/check-diff.yml b/.github/workflows/check-diff.yml
deleted file mode 100644
index ecb22827d..000000000
--- a/.github/workflows/check-diff.yml
+++ /dev/null
@@ -1,46 +0,0 @@
-name: Check diff from main
-
-on:
-  workflow_call:
-    outputs:
-      run_arduino:
-        description: 'Return true if Arduino tests should be run'
-        value: ${{ jobs.check.outputs.run_arduino == 'true' }}
-      run_macos:
-        description: 'Return true if macOS tests should be run'
-        value: ${{ jobs.check.outputs.run_macos == 'true' }}
-      run_python:
-        description: 'Return true if Python tests should be run'
-        value: ${{ jobs.check.outputs.run_python == 'true' }}
-      run_windows:
-        description: 'Return true if Windows tests should be run'
-        value: ${{ jobs.check.outputs.run_windows == 'true' }}
-      run_zephyr:
-        description: 'Return true if Zephyr tests should be run'
-        value: ${{ jobs.check.outputs.run_zephyr == 'true' }}
-
-jobs:
-  check:
-    runs-on: ubuntu-latest
-    outputs:
-      run_arduino: ${{ steps.do.outputs.changed_arduino == 1 || github.ref == 'refs/heads/main' }}
-      run_macos: ${{ steps.do.outputs.changed_macos == 1 || github.ref == 'refs/heads/main' }}
-      run_python: ${{ steps.do.outputs.changed_python == 1 || github.ref == 'refs/heads/main' }}
-      run_windows: ${{ steps.do.outputs.changed_windows == 1 || github.ref == 'refs/heads/main' }}
-      run_zephyr: ${{ steps.do.outputs.changed_zephyr == 1 || github.ref == 'refs/heads/main' }}
-      
-    steps:
-      - name: Check out reactor-c repository
-        uses: actions/checkout@v3
-        with:
-          fetch-depth: 0
-      - id: do
-        name: Check which targets have changes
-        run: |
-          ./check-diff.sh "arduino" arduino
-          ./check-diff.sh "macos|unix" macos
-          ./check-diff.sh "python" python
-          ./check-diff.sh "windows" windows
-          ./check-diff.sh "zephyr" zephyr
-        shell: bash
-        working-directory: .github/scripts
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 26795c446..fa8a5f752 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -7,6 +7,11 @@ on:
   pull_request:
   # Also allow running this workflow manually from the Actions tab.
   workflow_dispatch:
+  merge_group:
+
+concurrency:
+  group: ci-${{ github.ref }}-${{ github.event_path }}
+  cancel-in-progress: ${{ github.ref != 'refs/heads/master' }}
 
 jobs:
   unit-tests-single:
@@ -25,60 +30,57 @@ jobs:
   build-trace-tools:
     uses: ./.github/workflows/build-trace-tools.yml
 
-  check-diff:
-    uses: ./.github/workflows/check-diff.yml
-
   fetch-lf:
     uses: lf-lang/lingua-franca/.github/workflows/extract-ref.yml@master
     with:
       file: 'lingua-franca-ref.txt'
 
   lf-default-arduino:
-    needs: [fetch-lf, check-diff]
+    needs: [fetch-lf]
     uses: lf-lang/lingua-franca/.github/workflows/c-arduino-tests.yml@master
     with:
       runtime-ref: ${{ github.ref }}
       compiler-ref: ${{ needs.fetch-lf.outputs.ref }}
-    if: ${{ needs.check-diff.outputs.run_arduino == 'true' }}
+    if: ${{ github.event_name == 'merge_group' || github.ref == 'refs/heads/main' || contains( github.event.pull_request.labels.*.name, 'arduino') }}
 
   lf-default-zephyr:
-    needs: [fetch-lf, check-diff]
+    needs: [fetch-lf]
     uses: lf-lang/lingua-franca/.github/workflows/c-zephyr-tests.yml@master
     with:
       runtime-ref: ${{ github.ref }}
       compiler-ref: ${{ needs.fetch-lf.outputs.ref }}
-    if: ${{ needs.check-diff.outputs.run_zephyr == 'true' }}
+    if: ${{ github.event_name == 'merge_group' || github.ref == 'refs/heads/main' ||contains( github.event.pull_request.labels.*.name, 'zephyr') }}
 
   lf-default:
-    needs: [fetch-lf, check-diff]
+    needs: [fetch-lf]
     uses: lf-lang/lingua-franca/.github/workflows/c-tests.yml@master
     with:
       runtime-ref: ${{ github.ref }}
       compiler-ref: ${{ needs.fetch-lf.outputs.ref }}
-      all-platforms: ${{ needs.check-diff.outputs.run_macos == 'true' || needs.check-diff.outputs.run_windows == 'true' }}
+      all-platforms: ${{ github.event_name == 'merge_group' || github.ref == 'refs/heads/main' || contains( github.event.pull_request.labels.*.name, 'mac') || contains( github.event.pull_request.labels.*.name, 'windows') }}
 
   lf-python:
-    needs: [fetch-lf, check-diff]
+    needs: [fetch-lf]
     uses: lf-lang/lingua-franca/.github/workflows/py-tests.yml@master
     with:
       reactor-c-ref: ${{ github.ref }}
       compiler-ref: ${{ needs.fetch-lf.outputs.ref }}
-    if: ${{ needs.check-diff.outputs.run_python == 'true' }}
+    if: ${{ github.event_name == 'merge_group' || github.ref == 'refs/heads/main' ||contains( github.event.pull_request.labels.*.name, 'python') }}
 
   lf-gedf-np:
-    needs: [fetch-lf, check-diff]
+    needs: [fetch-lf]
     uses: lf-lang/lingua-franca/.github/workflows/c-tests.yml@master
     with:
       runtime-ref: ${{ github.ref }}
       compiler-ref: ${{ needs.fetch-lf.outputs.ref }}
       scheduler: GEDF_NP
-      all-platforms: ${{ needs.check-diff.outputs.run_macos == 'true' || needs.check-diff.outputs.run_windows == 'true' }}
+      all-platforms: ${{ github.event_name == 'merge_group' || github.ref == 'refs/heads/main' || contains( github.event.pull_request.labels.*.name, 'mac') || contains( github.event.pull_request.labels.*.name, 'windows') }}
 
   lf-adaptive:
-    needs: [fetch-lf, check-diff]
+    needs: [fetch-lf]
     uses: lf-lang/lingua-franca/.github/workflows/c-tests.yml@master
     with:
       runtime-ref: ${{ github.ref }}
       compiler-ref: ${{ needs.fetch-lf.outputs.ref }}
       scheduler: ADAPTIVE
-      all-platforms: ${{ needs.check-diff.outputs.run_macos == 'true' || needs.check-diff.outputs.run_windows == 'true' }}
+      all-platforms: ${{ github.event_name == 'merge_group' || github.ref == 'refs/heads/main' || contains( github.event.pull_request.labels.*.name, 'mac') || contains( github.event.pull_request.labels.*.name, 'windows') }}
diff --git a/core/federated/RTI/rti_common.h b/core/federated/RTI/rti_common.h
index a97c211b2..b55273e6e 100644
--- a/core/federated/RTI/rti_common.h
+++ b/core/federated/RTI/rti_common.h
@@ -182,9 +182,10 @@ void notify_advance_grant_if_safe(scheduling_node_t* e);
 void notify_provisional_tag_advance_grant(scheduling_node_t* e, tag_t tag);
 
 /**
- * Determine whether the specified scheduling node is eligible for a tag advance grant,
- * (TAG) and, if so, return the details. This is called upon receiving a LTC, NET
- * or resign from an upstream node.
+ * @brief Determine whether the specified scheduling node is eligible for a tag advance grant,
+ * (TAG) and, if so, return the details.
+ * 
+ * This is called upon receiving a LTC, NET or resign from an upstream node.
  *
  * This function calculates the minimum M over
  * all upstream scheduling nodes of the "after" delay plus the most recently
diff --git a/core/federated/federate.c b/core/federated/federate.c
index 17544aeb4..a5424c51f 100644
--- a/core/federated/federate.c
+++ b/core/federated/federate.c
@@ -2730,8 +2730,8 @@ int lf_send_tagged_message(environment_t* env,
         if (message_type == MSG_TYPE_P2P_TAGGED_MESSAGE) {
             lf_print_warning("Failed to send message to %s. Dropping the message.", next_destination_str);
         } else {
-            lf_print_error_system_failure("Failed to send message to %s. Connection lost to the RTI.",
-                    next_destination_str);
+            lf_print_error_system_failure("Failed to send message to %s with error code %d (%s). Connection lost to the RTI.",
+                    next_destination_str, errno, strerror(errno));
         }
     }
     LF_MUTEX_UNLOCK(&lf_outbound_socket_mutex);
diff --git a/core/reactor_common.c b/core/reactor_common.c
index 8492ef48a..bd9cc1210 100644
--- a/core/reactor_common.c
+++ b/core/reactor_common.c
@@ -1325,3 +1325,8 @@ void termination(void) {
     }
     lf_tracing_global_shutdown();
 }
+
+index_t lf_combine_deadline_and_level(interval_t deadline, int level) {
+    if (deadline > ULLONG_MAX >> 16) return ((ULLONG_MAX >> 16) << 16) | level;
+    else return (deadline << 16) | level;
+}
diff --git a/core/tag.c b/core/tag.c
index 55937259c..3dbffec16 100644
--- a/core/tag.c
+++ b/core/tag.c
@@ -128,6 +128,10 @@ instant_t lf_time_start(void) {
 }
 
 size_t lf_readable_time(char* buffer, instant_t time) {
+    if (time <= (instant_t)0) {
+        snprintf(buffer, 2, "0");
+        return 1;
+    }
     char* original_buffer = buffer;
     bool lead = false; // Set to true when first clause has been printed.
     if (time > WEEKS(1)) {
@@ -147,8 +151,8 @@ size_t lf_readable_time(char* buffer, instant_t time) {
         size_t printed = lf_comma_separated_time(buffer, time / DAYS(1));
         time = time % DAYS(1);
         buffer += printed;
-        snprintf(buffer, 6, " days");
-        buffer += 5;
+        snprintf(buffer, 3, " d");
+        buffer += 2;
     }
     if (time > HOURS(1)) {
         if (lead == true) {
@@ -159,8 +163,8 @@ size_t lf_readable_time(char* buffer, instant_t time) {
         size_t printed = lf_comma_separated_time(buffer, time / HOURS(1));
         time = time % HOURS(1);
         buffer += printed;
-        snprintf(buffer, 7, " hours");
-        buffer += 6;
+        snprintf(buffer, 3, " h");
+        buffer += 2;
     }
     if (time > MINUTES(1)) {
         if (lead == true) {
@@ -171,8 +175,8 @@ size_t lf_readable_time(char* buffer, instant_t time) {
         size_t printed = lf_comma_separated_time(buffer, time / MINUTES(1));
         time = time % MINUTES(1);
         buffer += printed;
-        snprintf(buffer, 9, " minutes");
-        buffer += 8;
+        snprintf(buffer, 5, " min");
+        buffer += 4;
     }
     if (time > SECONDS(1)) {
         if (lead == true) {
@@ -183,28 +187,26 @@ size_t lf_readable_time(char* buffer, instant_t time) {
         size_t printed = lf_comma_separated_time(buffer, time / SECONDS(1));
         time = time % SECONDS(1);
         buffer += printed;
-        snprintf(buffer, 9, " seconds");
-        buffer += 8;
+        snprintf(buffer, 3, " s");
+        buffer += 2;
     }
     if (time > (instant_t)0) {
         if (lead == true) {
             snprintf(buffer, 3, ", ");
             buffer += 2;
         }
-        const char* units = "nanoseconds";
+        const char* units = "ns";
         if (time % MSEC(1) == (instant_t) 0) {
-            units = "milliseconds";
+            units = "ms";
             time = time / MSEC(1);
         } else if (time % USEC(1) == (instant_t) 0) {
-            units = "microseconds";
+            units = "us";
             time = time / USEC(1);
         }
         size_t printed = lf_comma_separated_time(buffer, time);
         buffer += printed;
-        snprintf(buffer, 14, " %s", units);
+        snprintf(buffer, 3, " %s", units);
         buffer += strlen(units) + 1;
-    } else {
-        snprintf(buffer, 2, "0");
     }
     return (buffer - original_buffer);
 }
diff --git a/core/threaded/reactor_threaded.c b/core/threaded/reactor_threaded.c
index 19ffee43c..f85baef33 100644
--- a/core/threaded/reactor_threaded.c
+++ b/core/threaded/reactor_threaded.c
@@ -632,6 +632,8 @@ void _lf_initialize_start_tag(environment_t *env) {
     LF_PRINT_LOG("Waiting for start time " PRINTF_TIME " plus STA " PRINTF_TIME ".",
             start_time, lf_fed_STA_offset);
 #else
+    // For other than federated decentralized execution, there is no lf_fed_STA_offset variable defined.
+    // To use uniform code below, we define it here as a local variable.
     instant_t lf_fed_STA_offset = 0;
     LF_PRINT_LOG("Waiting for start time " PRINTF_TIME ".",
             start_time);
diff --git a/include/core/reactor_common.h b/include/core/reactor_common.h
index 97ec976b8..92630be1e 100644
--- a/include/core/reactor_common.h
+++ b/include/core/reactor_common.h
@@ -65,6 +65,16 @@ extern struct allocation_record_t* _lf_reactors_to_free;
 
 //////////////////////  Functions  //////////////////////
 
+/**
+ * @brief Combine a deadline and a level into a single index for sorting in the reaction queue.
+ * 
+ * This shifts the deadline right by 16 bits and inserts the level in the low-order 16 bits.
+ * If the deadline is larger than `ULLONG_MAX >> 16`, then it is treated as the largest possible deadline.
+ * @oaran deadline THe deadline.
+ * @param level The level in the reaction graph.
+*/
+index_t lf_combine_deadline_and_level(interval_t deadline, int level);
+
 /**
  * @brief Create and initialize the required number of environments for the program.
  * @note This function will be code generated by the compiler.
diff --git a/logging/api/logging_macros.h b/logging/api/logging_macros.h
index 6ecc7e7ce..0864cdea7 100644
--- a/logging/api/logging_macros.h
+++ b/logging/api/logging_macros.h
@@ -78,19 +78,22 @@
 #define LF_ASSERT(condition, format, ...) \
 	do { \
 		if (!(condition)) { \
-				lf_print_error_and_exit(format, ##__VA_ARGS__); \
+            lf_print_error_and_exit("`" format "`. Failed assertion in %s:%d(%s):(" #condition \
+            ") != true`", ##__VA_ARGS__, __FILE__, __LINE__, __func__); \
 		} \
 	} while(0)
 #define LF_ASSERTN(condition, format, ...) \
 	do { \
 		if (condition) { \
-				lf_print_error_and_exit(format, ##__VA_ARGS__); \
+            lf_print_error_and_exit("`" format "`. Failed assertion in %s:%d(%s):(" #condition \
+            ") != false`", ##__VA_ARGS__, __FILE__, __LINE__, __func__); \
 		} \
 	} while(0)
 #define LF_ASSERT_NON_NULL(pointer) \
     do { \
         if (!(pointer)) { \
-            lf_print_error_and_exit("Assertion failed: pointer is NULL Out of memory?."); \
+            lf_print_error_and_exit("`Out of memory?` Assertion failed in %s:%d(%s):`" #pointer " == NULL`",\
+            __FILE__, __LINE__, __func__); \
         } \
     } while(0)
 #endif // NDEBUG
diff --git a/tag/api/tag.h b/tag/api/tag.h
index 55d83c35d..4f2dbd031 100644
--- a/tag/api/tag.h
+++ b/tag/api/tag.h
@@ -199,21 +199,22 @@ instant_t lf_time_start(void);
  * Maximum number of nanoseconds is 999,999,999
  * Maximum number of microsteps is 4,294,967,295
  * Total number of characters for the above is 24.
- * Text descriptions and spaces add an additional 55,
- * for a total of 79. One more allows for a null terminator.
+ * Text descriptions and spaces add an additional 30,
+ * for a total of 54. One more allows for a null terminator.
+ * Round up to a power of two.
  */
-#define LF_TIME_BUFFER_LENGTH 80
+#define LF_TIME_BUFFER_LENGTH 64
 
 /**
  * Store into the specified buffer a string giving a human-readable
  * rendition of the specified time. The buffer must have length at least
  * equal to LF_TIME_BUFFER_LENGTH. The format is:
  * ```
- *    x weeks, x days, x hours, x minutes, x seconds, x unit
+ *    x weeks, x d, x hr, x min, x s, x unit
  * ```
  * where each `x` is a string of numbers with commas inserted if needed
- * every three numbers and `unit` is nanoseconds, microseconds, or
- * milliseconds.
+ * every three numbers and `unit` is ns, us, or
+ * ms.
  * @param buffer The buffer into which to write the string.
  * @param time The time to write.
  * @return The number of characters written (not counting the null terminator).
diff --git a/util/tracing/visualization/fedsd.py b/util/tracing/visualization/fedsd.py
index 253218684..0d7f57246 100644
--- a/util/tracing/visualization/fedsd.py
+++ b/util/tracing/visualization/fedsd.py
@@ -113,7 +113,7 @@
 # Events matching at the sender and receiver ends depend on whether they are tagged
 # (the elapsed logical time and microstep have to be the same) or not. 
 # Set of tagged events (messages)
-non_tagged_messages = {'FED_ID', 'ACK', 'RESIGN', 'FAILED', 'REJECT', 'ADR_RQ', 'ADR_AD', 'MSG', 'P2P_MSG', 'STOP'}
+non_tagged_messages = {'FED_ID', 'ACK', 'RESIGN', 'FAILED', 'REJECT', 'ADR_QR', 'ADR_AD', 'MSG', 'P2P_MSG', 'STOP'}
 
 
 ################################################################################
@@ -680,7 +680,7 @@ def get_and_convert_lft_files(rti_lft_file, federates_lft_files, start_time, end
             # FIXME: Using microseconds is hardwired here.
             physical_time = f'{int(row["physical_time"]/1000):,}'
 
-            if (row['event'] in {'FED_ID', 'ACK', 'FAILED', 'REJECT', 'ADR_RQ', 'ADR_AD', 'MSG', 'P2P_MSG', 'STOP'}):
+            if (row['event'] in {'FED_ID', 'ACK', 'FAILED', 'REJECT', 'ADR_QR', 'ADR_AD', 'MSG', 'P2P_MSG', 'STOP'}):
                 label = row['event']
             else:
                 label = row['event'] + '(' + f'{int(row["logical_time"]):,}' + ', ' + str(row['microstep']) + ')'