diff --git a/vidyut-prakriya/src/angasya.rs b/vidyut-prakriya/src/angasya.rs
index bdab646..542bae1 100644
--- a/vidyut-prakriya/src/angasya.rs
+++ b/vidyut-prakriya/src/angasya.rs
@@ -55,8 +55,11 @@ fn add_num(t: &mut Term) {
 
 /// Runs rules that lengthen a vowel in the anga.
 fn try_do_dirgha(p: &mut Prakriya, i_anga: usize) -> Option<()> {
+    p.debug(format!("TRY DO HALAH {i_anga}"));
     let anga = p.get_if(i_anga, |t| t.is_anga())?;
-    let n = p.get_if(i_anga + 1, |t| t.is_pratyaya())?;
+    // Also include yAsut-Agama for ji + yAs + t --> jIyAt.
+    // TODO: extend?
+    let n = p.get_if(i_anga + 1, |t| t.is_pratyaya() || t.has_u("yAsu~w"))?;
 
     // Exclude tin -- otherwise, we get "daDAntaH" instead of "daDantaH".
     // "kvisāhacaryeṇa tiṅbhinnasyaiva jhalādestatra grahaṇāt" -- Balamanorama on 6.4.48.
diff --git a/vidyut-prakriya/src/samprasarana.rs b/vidyut-prakriya/src/samprasarana.rs
index 174ae4d..a8db8b0 100644
--- a/vidyut-prakriya/src/samprasarana.rs
+++ b/vidyut-prakriya/src/samprasarana.rs
@@ -7,6 +7,7 @@ use crate::core::{Code, Prakriya};
 /// - Must follow atidesha so that suffixes have the kit/Nit annotations necessary to cause
 ///   samprasanara.
 use crate::dhatu_gana as gana;
+use crate::sounds;
 
 fn is_vaci_svapi(t: &Term) -> bool {
     t.is_dhatu()
@@ -64,11 +65,11 @@ fn find_samprasarana_match(p: &Prakriya, i: usize) -> Option<&'static str> {
     ];
     const AFTER: &[&str] = &[
         // vaci-svapi
-        "uc", "uc", "sup", "ij", "up", "uh", "us", "u", "vI", "hU", "ud", "SU",
+        "uac", "uac", "suap", "iaj", "uap", "uah", "uas", "ue", "vie", "hue", "uad", "Sui",
         // grahi-jyA
-        "gfh", "ji", "uy", "uy", "viD", "uS", "vic", "vfsc", "pfC", "Bfsj",
+        "gfah", "jiA", "uay", "uay", "viaD", "uaS", "viac", "vfasc", "pfaC", "Bfasj",
         // other rules
-        "sim", "sim",
+        "siam", "siam",
     ];
     debug_assert!(BEFORE.len() == AFTER.len());
 
@@ -80,15 +81,32 @@ fn find_samprasarana_match(p: &Prakriya, i: usize) -> Option<&'static str> {
     }
 }
 
+// Deletes the vowel that follows the samprasarana vowel.
+//
+// Example: "uac" --> "uc"
+fn run_samprasaranac_ca(p: &mut Prakriya, i_dhatu: usize) -> Option<()> {
+    // The code here is inelegant, but it works.
+    let dhatu = p.get(i_dhatu)?;
+    for i in 0..dhatu.len() - 1 {
+        if let (Some(x), Some(y)) = (dhatu.get_at(i), dhatu.get_at(i + 1)) {
+            if sounds::is_ac(x) && sounds::is_ac(y) {
+                p.run_at("6.1.108", i_dhatu, |t| t.set_at(i + 1, ""));
+                return Some(());
+            }
+        }
+    }
+
+    Some(())
+}
+
 /// Runs a hacky version of samprasarana that runs 6.1.108 (samprasAraNAcca) immediately.
-///
-/// TODO: properly annotate 6.1.108 and related rules here.
-fn do_samprasarana(rule: Code, p: &mut Prakriya, i_dhatu: usize) -> Option<()> {
-    let after = find_samprasarana_match(p, i_dhatu)?;
+fn do_samprasarana_for_dhatu(rule: Code, p: &mut Prakriya, i_dhatu: usize) -> Option<()> {
+    let new_text = find_samprasarana_match(p, i_dhatu)?;
     p.run_at(rule, i_dhatu, |t| {
-        t.set_text(after);
+        t.set_text(new_text);
         t.add_tag(T::FlagSamprasarana);
     });
+    run_samprasaranac_ca(p, i_dhatu);
     Some(())
 }
 
@@ -99,6 +117,7 @@ fn do_samprasarana_for_abhyasa(rule: Code, p: &mut Prakriya, i_abhyasa: usize) -
         t.set_text(after);
         t.add_tag(T::FlagSamprasarana);
     });
+    run_samprasaranac_ca(p, i_dhatu);
     Some(())
 }
 
@@ -156,10 +175,10 @@ pub fn run_for_dhatu_after_atidesha(p: &mut Prakriya) -> Option<()> {
     let is_ve = dhatu.has_u("ve\\Y");
     if dhatu.has_u("Yizva\\pa~") && n.has_u("Ric") && p.has(i_n + 1, |t| t.has_u("caN")) {
         // asUzupat
-        do_samprasarana("6.1.18", p, i);
+        do_samprasarana_for_dhatu("6.1.18", p, i);
     } else if dhatu.has_u_in(&["Yizva\\pa~", "syamu~", "vye\\Y"]) && n_is_yan {
         // sozupyate, sesimyate, vevIyate
-        do_samprasarana("6.1.19", p, i);
+        do_samprasarana_for_dhatu("6.1.19", p, i);
     } else if dhatu.has_u("vaSa~") && n_is_yan {
         // vAvaSyate (exception to grahi-jyA-...)
         p.step("6.1.20");
@@ -203,12 +222,12 @@ pub fn run_for_dhatu_after_atidesha(p: &mut Prakriya) -> Option<()> {
     } else {
         // General rules
         if is_vaci_svapi(dhatu) && n.has_tag(T::kit) {
-            do_samprasarana("6.1.15", p, i);
+            do_samprasarana_for_dhatu("6.1.15", p, i);
         } else if is_grahi_jya(dhatu) && n.is_knit() {
             if dhatu.has_u("pra\\Ca~") && n.has_u("naN") {
                 // Per ashtadhyayi.com, skip samprasarana for praC + naN.
             } else {
-                do_samprasarana("6.1.16", p, i);
+                do_samprasarana_for_dhatu("6.1.16", p, i);
                 if p.has(i, |t| t.has_text("uy") && t.has_u("vayi~")) {
                     optional_set_text("6.1.39", p, "uv");
                 }
diff --git a/vidyut-prakriya/test_utils/src/lib.rs b/vidyut-prakriya/test_utils/src/lib.rs
index 94afd01..122e8a5 100644
--- a/vidyut-prakriya/test_utils/src/lib.rs
+++ b/vidyut-prakriya/test_utils/src/lib.rs
@@ -996,23 +996,27 @@ fn debug_text(rule: Rule) -> String {
 /// Nicely prints out the given prakriyas.
 pub fn print_all_prakriyas(prakriyas: &[Prakriya]) {
     for p in prakriyas {
-        for step in p.history() {
-            let mut result = String::new();
-            for (i, t) in step.result().iter().enumerate() {
-                if i != 0 {
-                    result += " + ";
-                }
-                if t.was_changed() {
-                    result += &format!("[{}]", t.text());
-                } else {
-                    result += t.text();
-                }
+        print_prakriya(p);
+    }
+}
+
+pub fn print_prakriya(p: &Prakriya) {
+    for step in p.history() {
+        let mut result = String::new();
+        for (i, t) in step.result().iter().enumerate() {
+            if i != 0 {
+                result += " + ";
+            }
+            if t.was_changed() {
+                result += &format!("[{}]", t.text());
+            } else {
+                result += t.text();
             }
-            println!("{} --> {}", debug_text(step.rule()), result);
         }
-        println!("{:?}", p.rule_choices());
-        println!();
+        println!("{} --> {}", debug_text(step.rule()), result);
     }
+    println!("{:?}", p.rule_choices());
+    println!();
 }
 
 // Heavy assert helpers
@@ -1038,3 +1042,36 @@ pub fn assert_has_results(prakriyas: Vec<Prakriya>, expected: &[&str]) {
 
     assert_eq!(expected, actuals);
 }
+
+pub fn assert_matches_prakriya(p: &Prakriya, expected: &[(Rule, Vec<&str>)]) {
+    let mut i_start = 0;
+    for (e_rule, e_result) in expected {
+        let i = p.history()[i_start..]
+            .iter()
+            .enumerate()
+            .find(|(_, x)| x.rule() == *e_rule)
+            .map(|x| x.0);
+
+        if i.is_none() {
+            print_prakriya(p);
+            assert!(
+                false,
+                "Could not find expected rule {:?} in prakriya.",
+                e_rule
+            );
+        }
+
+        i_start += i.unwrap();
+
+        let step = &p.history()[i_start];
+        let items: Vec<_> = step.result().iter().map(|x| x.text()).collect();
+        if &items != e_result {
+            print_prakriya(p);
+            assert!(
+                false,
+                "Mismatch for prakriya on code {:?}, {}.",
+                e_rule, i_start
+            );
+        }
+    }
+}
diff --git a/vidyut-prakriya/tests/prakriyas.rs b/vidyut-prakriya/tests/prakriyas.rs
new file mode 100644
index 0000000..94ca2e7
--- /dev/null
+++ b/vidyut-prakriya/tests/prakriyas.rs
@@ -0,0 +1,37 @@
+//! Tests that verify that a prakriya has a specific format.
+//!
+//! TODO: add tests from the पाणिनीयव्याकरणोदाहरणकोषः
+extern crate test_utils;
+use test_utils::*;
+use vidyut_prakriya::args::Gana::*;
+use vidyut_prakriya::args::*;
+use vidyut_prakriya::Rule;
+
+#[test]
+fn bhavadi() {
+    let bhu = d("BU", Bhvadi);
+    let args = Tinanta::builder()
+        .dhatu(bhu)
+        .prayoga(Prayoga::Kartari)
+        .purusha(Purusha::Prathama)
+        .vacana(Vacana::Eka)
+        .lakara(Lakara::Lat)
+        .build()
+        .unwrap();
+    let t = Tester::default();
+    let ps = t.derive_tinantas(&args);
+    let p = ps.iter().find(|p| p.text() == "Bavati").unwrap();
+
+    use Rule::Ashtadhyayi as A;
+
+    assert_matches_prakriya(
+        p,
+        &[
+            (A("1.3.1"), vec!["BU"]),
+            (A("3.4.78"), vec!["BU", "tip"]),
+            (A("3.1.68"), vec!["BU", "Sap", "ti"]),
+            (A("7.3.84"), vec!["Bo", "a", "ti"]),
+            (A("6.1.78"), vec!["Bav", "a", "ti"]),
+        ],
+    );
+}
diff --git a/vidyut-prakriya/tests/regressions.rs b/vidyut-prakriya/tests/regressions.rs
index 3564b71..0a5cc87 100644
--- a/vidyut-prakriya/tests/regressions.rs
+++ b/vidyut-prakriya/tests/regressions.rs
@@ -3,6 +3,8 @@ extern crate test_utils;
 use test_utils::*;
 use vidyut_prakriya::args::Gana::*;
 use vidyut_prakriya::args::Lakara::*;
+use vidyut_prakriya::args::*;
+use vidyut_prakriya::Rule;
 
 #[test]
 fn ambibat() {
@@ -41,3 +43,38 @@ fn irshy_san_lan() {
         &["Erzyiyizat", "Erzyizizat"],
     );
 }
+
+/// Fixes https://github.com/ambuda-org/vidyut/issues/118
+///
+/// This test verifies the following:
+/// - We correctly apply 6.4.108.
+/// - We lengthen the dhatu's vowel with 6.4.2.
+#[test]
+fn jiyat_prakriya() {
+    let jya = d("jyA\\", Kryadi);
+    let args = Tinanta::builder()
+        .dhatu(jya)
+        .prayoga(Prayoga::Kartari)
+        .purusha(Purusha::Prathama)
+        .vacana(Vacana::Eka)
+        .lakara(Lakara::AshirLin)
+        .build()
+        .unwrap();
+    let t = Tester::default();
+    let ps = t.derive_tinantas(&args);
+    let p = ps.iter().find(|p| p.text() == "jIyAt").unwrap();
+
+    use Rule::Ashtadhyayi as A;
+
+    assert_matches_prakriya(
+        p,
+        &[
+            (A("1.3.1"), vec!["jyA\\"]),
+            (A("3.4.116"), vec!["jyA", "ti"]),
+            (A("6.1.16"), vec!["jiA", "yAs", "st"]),
+            (A("6.1.108"), vec!["ji", "yAs", "st"]),
+            (A("6.4.2"), vec!["jI", "yAs", "st"]),
+            (A("8.4.56"), vec!["jI", "yA", "t"]),
+        ],
+    );
+}