From 81c4eb2b79d29ba9505687625f9a2a89c7a207b7 Mon Sep 17 00:00:00 2001
From: "sentry[bot]" <39604003+sentry[bot]@users.noreply.github.com>
Date: Wed, 19 Aug 2026 18:09:57 +0000
Subject: [PATCH] Fix reagent temperature mismatch crash (#23063)

* Please describe the intent of your changes in a clear fashion.
This PR addresses a crash (`SERVER-PROD-2R6`) caused by a temperature
mismatch when adding new reagents, particularly in low-volume metabolism
holders.

The root cause was identified as a combination of:
1. A coarse rounding guard in `set_thermal_energy` that discarded
small-but-valid thermal energy changes.
2. A temperature assertion in `add_reagent` that was too sensitive to
floating-point inaccuracies.
3. The `nicotine` reagent lacking an explicit `fallback_specific_heat`.

Changes implemented:
- **`code/modules/reagents/Chemistry-Temperature.dm`**: Modified
`set_thermal_energy` to remove the `round(delta, 1)` guard. Now,
`if(!delta)` is used, allowing small, non-zero energy changes to be
processed.
- **`code/modules/reagents/Chemistry-Holder.dm`**: Updated the
temperature assertion in `add_reagent` from `round(temperature, 1) !=
round(get_temperature(), 1)` to `abs(temperature - get_temperature()) >
0.1`. This provides a more robust, tolerance-based comparison.
-
**`code/modules/reagents/Chemistry-Reagents/Chemistry-Reagents-Medicine.dm`**:
Added `fallback_specific_heat = 1.67` to
`/singleton/reagent/mental/nicotine` to ensure it has a proper specific
heat value.

* Please make sure that, in the case of mapping changes, you include
images of these changes in the PR's description.
* Please make sure to mark your PR as wip or review required by making a
comment with !wip or !review required
* If you include sprites/sounds/... (assets) that you have not created
yourself specify the license and original author below.
* Ensure that you also credit them in the appropriate location /
changelog as specified in the contributor guidelines

### Asset Licenses
The following assets that **have not** been created by myself are
included in this PR:

| Path | Original Author | License |
| --- | --- | --- |
| icons/example.dmi | ExamplePerson (Example Station) | CC0 |


Fixes
[SERVER-PROD-2R6](https://aurorastation.sentry.io/issues/7661064998/?seerDrawer=true)

---------

Co-authored-by: VMSolidus <evilexecutive@gmail.com>
---
 code/modules/reagents/Chemistry-Holder.dm                     | 2 +-
 .../Chemistry-Reagents/Chemistry-Reagents-Medicine.dm         | 1 +
 code/modules/reagents/Chemistry-Temperature.dm                | 2 +-
 html/changelogs/hellfirejag-nicotine-runtime.yml              | 4 ++++
 4 files changed, 7 insertions(+), 2 deletions(-)
 create mode 100644 html/changelogs/hellfirejag-nicotine-runtime.yml

diff --git a/code/modules/reagents/Chemistry-Holder.dm b/code/modules/reagents/Chemistry-Holder.dm
index cf45ac8eb75..2f7ad3d6b7a 100644
--- a/code/modules/reagents/Chemistry-Holder.dm
+++ b/code/modules/reagents/Chemistry-Holder.dm
@@ -135,7 +135,7 @@
 			newreagent.set_thermal_energy(new_thermal_energy, src, safety = TRUE)
 		else
 			newreagent.set_temperature(temperature, src, safety = TRUE)
-		if(!new_thermal_energy && round(temperature, 1) != round(get_temperature(), 1))
+		if(!new_thermal_energy && abs(temperature - get_temperature()) > 0.1)
 			crash_with("Temperature [temperature] did not match [get_temperature()] after adding NEW reagent [rtype]!")
 	else	// Existing reagent
 		var/old_energy = (newreagent.get_thermal_energy(src)/reagent_volumes[rtype]) * amount
diff --git a/code/modules/reagents/Chemistry-Reagents/Chemistry-Reagents-Medicine.dm b/code/modules/reagents/Chemistry-Reagents/Chemistry-Reagents-Medicine.dm
index 7453f6737d6..b1479bd74ac 100644
--- a/code/modules/reagents/Chemistry-Reagents/Chemistry-Reagents-Medicine.dm
+++ b/code/modules/reagents/Chemistry-Reagents/Chemistry-Reagents-Medicine.dm
@@ -1280,6 +1280,7 @@
 	goodmessage = list("You feel good.","You feel relaxed.","You feel alert and focused.")
 	value = 2
 	alchohol_affected = FALSE
+	fallback_specific_heat = 1.67 // Approximate specific heat of liquid nicotine (J/g·K)
 
 /singleton/reagent/mental/nicotine/overdose(var/mob/living/carbon/M, var/alien, var/removed, var/scale, var/datum/reagents/holder)
 	..()
diff --git a/code/modules/reagents/Chemistry-Temperature.dm b/code/modules/reagents/Chemistry-Temperature.dm
index bf1b4090d9f..b68914d69eb 100644
--- a/code/modules/reagents/Chemistry-Temperature.dm
+++ b/code/modules/reagents/Chemistry-Temperature.dm
@@ -13,7 +13,7 @@
 
 /singleton/reagent/proc/set_thermal_energy(amount, var/datum/reagents/holder, safety = FALSE)
 	var/delta = amount / get_thermal_fraction(holder) - holder.thermal_energy
-	if(!round(delta, 1))
+	if(!delta)
 		return
 	holder.add_thermal_energy(delta, safety) // this handles on_heat_change for us
 
diff --git a/html/changelogs/hellfirejag-nicotine-runtime.yml b/html/changelogs/hellfirejag-nicotine-runtime.yml
new file mode 100644
index 00000000000..09579a6061b
--- /dev/null
+++ b/html/changelogs/hellfirejag-nicotine-runtime.yml
@@ -0,0 +1,4 @@
+author: Hellfirejag
+delete-after: True
+changes:
+  - bugfix: "Fixed a spammy runtime caused by smoking cigarettes."