oharboe · Oct 16, 2026 · Oct 20, 2026
diff --git a/docs/contrib/EndpointSlackTracking.md b/docs/contrib/EndpointSlackTracking.md
@@ -27,19 +27,21 @@ cells) re-time the design if it is loaded, or else copy the previous step's
 snapshot. Intermediate `.odb` files written through `orfs_write_db` (e.g. CTS
 `save_progress`) also get a snapshot; `*-failed` ones don't.
 
-So that all steps are timed the same way, parasitics are estimated before
-reporting as in `open.tcl`, based on the step number:
+A placed step is timed with the parasitics OpenROAD has for it: a bare
+`estimate_parasitics` estimates from the global routes when there are any,
+else from placement, and does nothing once `read_spef` has read the
+extracted parasitics:
 
 | Steps | Parasitics |
 | --- | --- |
-| 1, 2 | none (cells are not placed) |
-| 3, 4 | `estimate_parasitics -placement` |
-| 5, `6_1_fill` | `estimate_parasitics -global_routing` if global routes exist |
-| `6_final` | `rcx`: the extracted `6_final.spef`, as in `6_finish.rpt` (`global_routing` on platforms without `RCX_RULES`) |
+| before placement, and `3_1_place_gp_skip_io` while the pins are unplaced | `none` |
+| placed, before global route | `placement` |
+| global route and later | `global_routing` |
+| `6_final` | `spef`: the extracted `6_final.spef`, as in `6_finish.rpt` (`global_routing` on platforms without `RCX_RULES`) |
 
 The parasitics model is recorded in each snapshot and shown by
 `endpointSlack.py`. Slack changes between steps with different models (e.g.
-`2_4_floorplan_pdn` to `3_1_place_gp_skip_io`, `4_1_cts` to `5_1_grt`, or
+`2_4_floorplan_pdn` to the first placed step, `4_1_cts` to `5_1_grt`, or
 `6_1_fill` to `6_final`) include the change of model. Detailed routing is
 only extracted in `6_final`, so `5_2_route` to `6_1_fill` show global routing
 estimates.

diff --git a/docs/user/FlowVariables.md b/docs/user/FlowVariables.md
@@ -641,6 +641,7 @@ configuration file.
 ## generate_abstract variables
 
 - [ABSTRACT_SOURCE](#ABSTRACT_SOURCE)
+- [SKIP_DETAILED_ROUTE](#SKIP_DETAILED_ROUTE)
 
 ## Uncategorized variables
 

diff --git a/flow/scripts/cts.tcl b/flow/scripts/cts.tcl
@@ -36,7 +36,7 @@ set_dont_use $::env(DONT_USE_CELLS)
 log_cmd clock_tree_synthesis {*}$cts_args
 
 utl::push_metrics_stage "cts__{}__pre_repair_timing"
-log_cmd estimate_parasitics -placement
+log_cmd estimate_parasitics
 if { $::env(DETAILED_METRICS) } {
   report_metrics 4 "cts pre-repair-timing"
 }
@@ -52,7 +52,7 @@ if { $result != 0 } {
   error "Detailed placement failed in CTS: $msg"
 }
 
-log_cmd estimate_parasitics -placement
+log_cmd estimate_parasitics
 
 if { $::env(CTS_SNAPSHOTS) } {
   save_progress 4_1_pre_repair_setup_hold
@@ -79,7 +79,7 @@ if { !$::env(SKIP_CTS_REPAIR_TIMING) } {
 
   check_placement -verbose
 
-  log_cmd estimate_parasitics -placement
+  log_cmd estimate_parasitics
 }
 
 report_metrics 4 "cts final"

diff --git a/flow/scripts/detail_place.tcl b/flow/scripts/detail_place.tcl
@@ -26,7 +26,7 @@ proc do_dpl { } {
 
   utl::info FLW 12 "Placement violations [check_placement -verbose]."
 
-  log_cmd estimate_parasitics -placement
+  log_cmd estimate_parasitics
 }
 
 set result [catch { do_dpl } errMsg]

diff --git a/flow/scripts/final_outputs.tcl b/flow/scripts/final_outputs.tcl
@@ -20,10 +20,7 @@ if { $::env(SEC_CHECK) } {
 }
 
 # Run extraction and STA
-if {
-  [env_var_exists_and_non_empty RCX_RULES]
-  && !$::env(SKIP_DETAILED_ROUTE)
-} {
+if { [final_extracts_parasitics] } {
   # RCX section
   define_process_corner -ext_model_index 0 X
   set_extraction_rules_file $::env(RCX_RULES)
@@ -35,7 +32,6 @@ if {
 
   # Read Spef for OpenSTA
   read_spef $::env(RESULTS_DIR)/6_final.spef
-  set final_parasitics rcx
 
   # Static IR drop analysis
   if { [env_var_exists_and_non_empty PWR_NETS_VOLTAGES] } {
@@ -57,12 +53,10 @@ if {
     puts "IR drop analysis for ground nets is skipped because GND_NETS_VOLTAGES is undefined"
   }
 } else {
-  puts "OpenRCX is not enabled for this platform."
-  puts "Falling back to global route-based estimates."
-  log_cmd estimate_parasitics -global_routing
-  set final_parasitics global_routing
+  puts "OpenRCX is not enabled for this platform or detailed route was skipped."
+  log_cmd estimate_parasitics
 }
-write_endpoint_slack 6_final $final_parasitics
+write_endpoint_slack 6_final
 
 report_cell_usage
 

diff --git a/flow/scripts/generate_abstract.tcl b/flow/scripts/generate_abstract.tcl
@@ -13,12 +13,11 @@ set sdc_file [lindex $result 1]
 
 log_cmd load_design $stem.odb [file tail $sdc_file]
 
-if { $design_stage >= 6 && [file exists $::env(RESULTS_DIR)/$stem.spef] } {
-  log_cmd read_spef $::env(RESULTS_DIR)/$stem.spef
-} elseif { $design_stage >= 5 } {
-  log_cmd estimate_parasitics -global_routing
-} elseif { $design_stage >= 3 } {
-  log_cmd estimate_parasitics -placement
+if { $stem == "6_final" && [final_extracts_parasitics] } {
+  log_cmd read_spef $::env(RESULTS_DIR)/6_final.spef
+}
+if { [grt::design_is_placed] } {
+  log_cmd estimate_parasitics
 }
 
 if { $design_stage >= 4 } {

diff --git a/flow/scripts/global_place.tcl b/flow/scripts/global_place.tcl
@@ -77,11 +77,11 @@ if { $result != 0 } {
   error $errMsg
 }
 
-log_cmd estimate_parasitics -placement
+log_cmd estimate_parasitics
 
 if { $::env(CLUSTER_FLOPS) } {
   log_cmd cluster_flops {*}[env_var_or_empty CLUSTER_FLOPS_ARGS]
-  log_cmd estimate_parasitics -placement
+  log_cmd estimate_parasitics
 }
 
 report_metrics 3 "global place" false false

diff --git a/flow/scripts/global_route.tcl b/flow/scripts/global_route.tcl
@@ -39,7 +39,8 @@ proc global_route_helper { } {
         error $errMsg
       }
       orfs_write_sdc $::env(RESULTS_DIR)/5_1_grt.sdc
-      orfs_write_db $::env(RESULTS_DIR)/5_1_grt.odb
+      # A route that failed has no parasitics to time the endpoints with.
+      orfs_write_db $::env(RESULTS_DIR)/5_1_grt.odb 0
       return 0
     }
     return 1
@@ -74,7 +75,7 @@ proc global_route_helper { } {
     -right $::env(CELL_PAD_IN_SITES_DETAIL_PLACEMENT)
 
   set_propagated_clock [all_clocks]
-  log_cmd estimate_parasitics -global_routing
+  log_cmd estimate_parasitics
 
   if { [env_var_exists_and_non_empty DONT_USE_CELLS] } {
     set_dont_use $::env(DONT_USE_CELLS)
@@ -106,7 +107,7 @@ proc global_route_helper { } {
 
     # Repair timing using global route parasitics
     puts "Repair setup and hold violations..."
-    log_cmd estimate_parasitics -global_routing
+    log_cmd estimate_parasitics
 
     repair_timing_helper
 
@@ -126,7 +127,7 @@ proc global_route_helper { } {
       return
     }
 
-    log_cmd estimate_parasitics -global_routing
+    log_cmd estimate_parasitics
 
     if { $::env(OPT_POST_GRT_WNS) } {
       set repair_timing_args \
@@ -171,7 +172,7 @@ proc global_route_helper { } {
   }
 
   puts "Estimate parasitics..."
-  log_cmd estimate_parasitics -global_routing
+  log_cmd estimate_parasitics
 
   report_metrics 5 "global route"
 

diff --git a/flow/scripts/open.tcl b/flow/scripts/open.tcl
@@ -59,16 +59,14 @@ proc read_timing { input_file } {
     set_propagated_clock [all_clocks]
   }
 
-  if { $design_stage >= 6 && [file exist $::env(RESULTS_DIR)/6_final.spef] } {
+  if {
+    [file rootname [file tail $input_file]] == "6_final"
+    && [final_extracts_parasitics]
+  } {
     log_cmd read_spef $::env(RESULTS_DIR)/6_final.spef
-  } elseif { $design_stage >= 5 } {
-    if { [log_cmd grt::have_routes] } {
-      log_cmd estimate_parasitics -global_routing
-    } else {
-      puts "No global routing results available, skipping estimate_parasitics"
-    }
-  } elseif { $design_stage >= 3 } {
-    log_cmd estimate_parasitics -placement
+  }
+  if { [grt::design_is_placed] } {
+    log_cmd estimate_parasitics
   }
 
   # Warm up OpenSTA, so clicking on timing related buttons reacts faster

diff --git a/flow/scripts/resize.tcl b/flow/scripts/resize.tcl
@@ -4,7 +4,7 @@ erase_non_stage_variables place
 load_design 3_3_place_gp.odb 2_floorplan.sdc
 source_step_tcl PRE RESIZE
 
-log_cmd estimate_parasitics -placement
+log_cmd estimate_parasitics
 
 set instance_count_before [sta::network_leaf_instance_count]
 set pin_count_before [sta::network_leaf_pin_count]
@@ -28,7 +28,7 @@ repair_design_helper
 if { $::env(ENABLE_PLACE_REPAIR_TIMING) } {
   # Repair timing using placement parasitics.
   puts "Repair setup and hold violations..."
-  log_cmd estimate_parasitics -placement
+  log_cmd estimate_parasitics
 
   repair_timing_helper
 }

diff --git a/flow/scripts/util.tcl b/flow/scripts/util.tcl
@@ -343,32 +343,29 @@ proc endpoint_slack_file { step } {
   return $::env(REPORTS_DIR)/${step}_endpoint_slack.json
 }
 
+# The final stage extracts parasitics into 6_final.spef when the platform
+# has OpenRCX rules and the design is detail routed. 6_final.odb is timed
+# with that SPEF; whether a .spef file exists says nothing.
+proc final_extracts_parasitics { } {
+  return [expr {
+    [env_var_exists_and_non_empty RCX_RULES]
+    && !$::env(SKIP_DETAILED_ROUTE)
+  }]
+}
+
 # Write the setup and hold slack of every endpoint at the end of a flow
 # step so they can be compared across steps with
-# flow/util/endpointSlack.py. Parasitics are estimated the same way as
-# open.tcl so that every step is timed consistently, unless the caller
-# has already loaded parasitics (e.g. extracted ones) and passes their
-# name as parasitics.
-proc write_endpoint_slack { step { parasitics "" } } {
+# flow/util/endpointSlack.py. A placed design is timed with the parasitics
+# OpenROAD has for it, a design before placement without any.
+proc write_endpoint_slack { step } {
   if { !$::env(REPORT_ENDPOINT_SLACK) || [string match "*-failed" $step] } {
     return
   }
   set filename [endpoint_slack_file $step]
   puts "Writing endpoint slack to $filename"
 
-  if { $parasitics == "" } {
-    set design_stage [lindex [split $step _] 0]
-    set parasitics none
-    if { $design_stage >= 5 } {
-      if { [grt::have_routes] } {
-        set parasitics global_routing
-      }
-    } elseif { $design_stage >= 3 } {
-      set parasitics placement
-    }
-    if { $parasitics != "none" } {
-      estimate_parasitics -$parasitics
-    }
+  if { [grt::design_is_placed] } {
+    log_cmd estimate_parasitics
   }
   # Update timing before sta::endpoints: the endpoint set is cached the
   # first time it is requested and misses gated clock enable checks if the
@@ -379,7 +376,7 @@ proc write_endpoint_slack { step { parasitics "" } } {
   puts $fileId "{"
   puts $fileId "\"design\": \"$::env(DESIGN_NAME)\","
   puts $fileId "\"step\": \"$step\","
-  puts $fileId "\"parasitics\": \"$parasitics\","
+  puts $fileId "\"parasitics\": \"[est::parasitics_source]\","
   # Seconds per reported time unit
   puts $fileId "\"time_unit\": [sta::time_ui_sta 1],"
   # endpoint: [setup slack, hold slack], null if unconstrained

diff --git a/flow/scripts/variables.json b/flow/scripts/variables.json
diff --git a/flow/scripts/variables.yaml b/flow/scripts/variables.yaml
@@ -1588,6 +1588,7 @@ SKIP_DETAILED_ROUTE:
   stages:
     - route
     - final
+    - generate_abstract
 MAX_REPAIR_ANTENNAS_ITER_DRT:
   default: 5
   description: >