diff --git a/tests/r8-ambiguous.NOTES.md b/tests/r8-ambiguous.NOTES.md
new file mode 100644
index 0000000..8ebaac7
--- /dev/null
+++ b/tests/r8-ambiguous.NOTES.md
@@ -0,0 +1,46 @@
+# r8-ambiguous.rs failures
+
+This doc summarizes the current failures from running `cargo test --test r8-ambiguous`.
+
+## `test_ambiguous_method_verbose_stacktrace`
+
+- **Failure**: The frame lines are emitted verbatim (no remapping at all).
+- **Why**:
+  - The input frames have **no line numbers** (e.g. `(Foo.java)`), which means `frame.line == 0`.
+  - The current remapper does not produce any remapped candidates for these frames (so `format_frames` falls back to printing the original line). This indicates a gap in the “no-line” / best-effort ambiguous member mapping behavior for `line == 0` frames.
+
+## `test_ambiguous_stacktrace`
+
+- **Failure**: No remapping occurs; frames like `at a.a.a(Unknown Source)` are preserved.
+- **Why**:
+  - These frames have `Unknown Source` with **no line number**, so `frame.line == 0`.
+  - For `line == 0`, the current implementation ends up with **no remapped candidates** and prints the original frame line unchanged (instead of emitting ambiguous alternatives `foo`/`bar`).
+
+## `test_ambiguous_missing_line_stacktrace`
+
+- **Failure**: Output uses `R8.java:0` rather than preserving the concrete input line numbers (`7/8/9`) in the remapped alternatives.
+- **Why**:
+  - The mapping entries have **no original line information** (base/no-line mappings).
+  - The current mapping logic uses the mapping’s “original start line” (which defaults to `0`) rather than propagating the **caller-provided minified line** when available.
+
+## `test_ambiguous_with_multiple_line_mappings_stacktrace`
+
+- **Failure**: Last frame stays obfuscated (`com.android.tools.r8.Internal.zza(Unknown)`), expected a deobfuscated `Internal.foo(Internal.java:0)`-style frame.
+- **Why**:
+  - `(...(Unknown))` parses as a frame with `file = "Unknown"` and `line = 0`.
+  - All available member mappings are **line-ranged** (e.g. `10:10`, `11:11`, `12:12`), so with `line == 0` they do not match and the remapper produces **no candidates**, falling back to the original frame line.
+
+## `test_ambiguous_with_signature_stacktrace`
+
+- **Failure**: Same symptom as above (`Internal.zza(Unknown)` remains), expected deobfuscated member.
+- **Why**:
+  - Same `line == 0` issue: line-ranged overload mappings cannot be selected without a minified line.
+  - The remapper currently has no fallback that returns “best effort” candidates for `line == 0` frames (e.g., returning all overloads, or preferring a base mapping if present).
+
+## `test_inline_no_line_assume_no_inline_ambiguous_stacktrace`
+
+- **Failure**: Expected retraced output, but actual output is unchanged (`at a.foo(Unknown Source)`).
+- **Why**:
+  - This fixture expects a special “no-line” ambiguity strategy: when `line == 0`, prefer the **base/no-line** mapping (`otherMain`) over line-specific inline entries.
+  - The current implementation returns no remapped candidates for this `line == 0` frame, so it prints the original frame line unchanged.
+
diff --git a/tests/r8-ambiguous.rs b/tests/r8-ambiguous.rs
new file mode 100644
index 0000000..be1eb42
--- /dev/null
+++ b/tests/r8-ambiguous.rs
@@ -0,0 +1,344 @@
+//! Tests for R8 ambiguous method retracing functionality.
+//!
+//! These tests are based on the R8 retrace test suite from:
+//! src/test/java/com/android/tools/r8/retrace/stacktraces/
+
+use proguard::{ProguardCache, ProguardMapper, ProguardMapping};
+
+// =============================================================================
+// AmbiguousStackTrace
+// =============================================================================
+
+const AMBIGUOUS_STACKTRACE_MAPPING: &str = "\
+com.android.tools.r8.R8 -> a.a:
+    void foo(int) -> a
+    void bar(int, int) -> a
+";
+
+#[test]
+fn test_ambiguous_stacktrace() {
+    let input = "\
+com.android.tools.r8.CompilationException: foo[parens](Source:3)
+    at a.a.a(Unknown Source)
+    at a.a.a(Unknown Source)
+    at com.android.tools.r8.R8.main(Unknown Source)
+Caused by: com.android.tools.r8.CompilationException: foo[parens](Source:3)
+    at a.a.a(Unknown Source)
+    ... 42 more
+";
+
+    let expected = "\
+com.android.tools.r8.CompilationException: foo[parens](Source:3)
+    at com.android.tools.r8.R8.foo(R8.java:0)
+    at com.android.tools.r8.R8.bar(R8.java:0)
+    at com.android.tools.r8.R8.foo(R8.java:0)
+    at com.android.tools.r8.R8.bar(R8.java:0)
+    at com.android.tools.r8.R8.main(Unknown Source)
+Caused by: com.android.tools.r8.CompilationException: foo[parens](Source:3)
+    at com.android.tools.r8.R8.foo(R8.java:0)
+    at com.android.tools.r8.R8.bar(R8.java:0)
+    ... 42 more
+";
+
+    let mapper = ProguardMapper::from(AMBIGUOUS_STACKTRACE_MAPPING);
+    let actual = mapper.remap_stacktrace(input).unwrap();
+    assert_eq!(actual.trim(), expected.trim());
+
+    let mapping = ProguardMapping::new(AMBIGUOUS_STACKTRACE_MAPPING.as_bytes());
+    let mut buf = Vec::new();
+    ProguardCache::write(&mapping, &mut buf).unwrap();
+    let cache = ProguardCache::parse(&buf).unwrap();
+    cache.test();
+
+    let actual = cache.remap_stacktrace(input).unwrap();
+    assert_eq!(actual.trim(), expected.trim());
+}
+
+// =============================================================================
+// AmbiguousMissingLineStackTrace
+// =============================================================================
+
+const AMBIGUOUS_MISSING_LINE_MAPPING: &str = "\
+com.android.tools.r8.R8 -> a.a:
+    void foo(int) -> a
+    void bar(int, int) -> a
+";
+
+#[test]
+fn test_ambiguous_missing_line_stacktrace() {
+    let input = "\
+com.android.tools.r8.CompilationException: foo[parens](Source:3)
+    at a.a.a(Unknown Source:7)
+    at a.a.a(Unknown Source:8)
+    at com.android.tools.r8.R8.main(Unknown Source)
+Caused by: com.android.tools.r8.CompilationException: foo[parens](Source:3)
+    at a.a.a(Unknown Source:9)
+    ... 42 more
+";
+
+    let expected = "\
+com.android.tools.r8.CompilationException: foo[parens](Source:3)
+    at com.android.tools.r8.R8.foo(R8.java:7)
+    at com.android.tools.r8.R8.bar(R8.java:7)
+    at com.android.tools.r8.R8.foo(R8.java:8)
+    at com.android.tools.r8.R8.bar(R8.java:8)
+    at com.android.tools.r8.R8.main(Unknown Source)
+Caused by: com.android.tools.r8.CompilationException: foo[parens](Source:3)
+    at com.android.tools.r8.R8.foo(R8.java:9)
+    at com.android.tools.r8.R8.bar(R8.java:9)
+    ... 42 more
+";
+
+    let mapper = ProguardMapper::from(AMBIGUOUS_MISSING_LINE_MAPPING);
+    let actual = mapper.remap_stacktrace(input).unwrap();
+    assert_eq!(actual.trim(), expected.trim());
+
+    let mapping = ProguardMapping::new(AMBIGUOUS_MISSING_LINE_MAPPING.as_bytes());
+    let mut buf = Vec::new();
+    ProguardCache::write(&mapping, &mut buf).unwrap();
+    let cache = ProguardCache::parse(&buf).unwrap();
+    cache.test();
+
+    let actual = cache.remap_stacktrace(input).unwrap();
+    assert_eq!(actual.trim(), expected.trim());
+}
+
+// =============================================================================
+// AmbiguousInlineFramesStackTrace
+// =============================================================================
+
+const AMBIGUOUS_INLINE_FRAMES_MAPPING: &str = "\
+com.android.tools.r8.R8 -> a.a:
+    1:1:void foo(int):42:44 -> a
+    1:1:void bar(int, int):32 -> a
+    1:1:void baz(int, int):10 -> a
+";
+
+#[test]
+fn test_ambiguous_inline_frames_stacktrace() {
+    let input = "\
+com.android.tools.r8.CompilationException:
+    at a.a.a(Unknown Source:1)
+";
+
+    let expected = "\
+com.android.tools.r8.CompilationException:
+    at com.android.tools.r8.R8.foo(R8.java:42)
+    at com.android.tools.r8.R8.bar(R8.java:32)
+    at com.android.tools.r8.R8.baz(R8.java:10)
+";
+
+    let mapper = ProguardMapper::from(AMBIGUOUS_INLINE_FRAMES_MAPPING);
+    let actual = mapper.remap_stacktrace(input).unwrap();
+    assert_eq!(actual.trim(), expected.trim());
+
+    let mapping = ProguardMapping::new(AMBIGUOUS_INLINE_FRAMES_MAPPING.as_bytes());
+    let mut buf = Vec::new();
+    ProguardCache::write(&mapping, &mut buf).unwrap();
+    let cache = ProguardCache::parse(&buf).unwrap();
+    cache.test();
+
+    let actual = cache.remap_stacktrace(input).unwrap();
+    assert_eq!(actual.trim(), expected.trim());
+}
+
+// =============================================================================
+// AmbiguousMultipleInlineStackTrace
+// =============================================================================
+
+const AMBIGUOUS_MULTIPLE_INLINE_MAPPING: &str = "\
+com.android.tools.r8.Internal -> com.android.tools.r8.Internal:
+    10:10:void some.inlinee1(int):10:10 -> zza
+    10:10:void foo(int):10 -> zza
+    11:12:void foo(int):11:12 -> zza
+    10:10:void some.inlinee2(int, int):20:20 -> zza
+    10:10:void foo(int, int):42 -> zza
+";
+
+#[test]
+fn test_ambiguous_multiple_inline_stacktrace() {
+    let input = "\
+java.lang.IndexOutOfBoundsException
+    at com.android.tools.r8.Internal.zza(SourceFile:10)
+";
+
+    let expected = "\
+java.lang.IndexOutOfBoundsException
+    at some.inlinee1(some.java:10)
+    at com.android.tools.r8.Internal.foo(Internal.java:10)
+    at some.inlinee2(some.java:20)
+    at com.android.tools.r8.Internal.foo(Internal.java:42)
+";
+
+    let mapper = ProguardMapper::from(AMBIGUOUS_MULTIPLE_INLINE_MAPPING);
+    let actual = mapper.remap_stacktrace(input).unwrap();
+    assert_eq!(actual.trim(), expected.trim());
+
+    let mapping = ProguardMapping::new(AMBIGUOUS_MULTIPLE_INLINE_MAPPING.as_bytes());
+    let mut buf = Vec::new();
+    ProguardCache::write(&mapping, &mut buf).unwrap();
+    let cache = ProguardCache::parse(&buf).unwrap();
+    cache.test();
+
+    let actual = cache.remap_stacktrace(input).unwrap();
+    assert_eq!(actual.trim(), expected.trim());
+}
+
+// =============================================================================
+// AmbiguousMethodVerboseStackTrace (non-verbose retrace output)
+// =============================================================================
+
+const AMBIGUOUS_METHOD_VERBOSE_MAPPING: &str = "\
+com.android.tools.r8.naming.retrace.Main -> a.a:
+    com.android.Foo main(java.lang.String[],com.android.Bar) -> a
+    com.android.Foo main(java.lang.String[]) -> b
+    void main(com.android.Bar) -> b
+";
+
+#[test]
+fn test_ambiguous_method_verbose_stacktrace() {
+    let input = "\
+Exception in thread \"main\" java.lang.NullPointerException
+    at a.a.c(Foo.java)
+    at a.a.b(Bar.java)
+    at a.a.a(Baz.java)
+";
+
+    let expected = "\
+Exception in thread \"main\" java.lang.NullPointerException
+    at com.android.tools.r8.naming.retrace.Main.c(Main.java:0)
+    at com.android.tools.r8.naming.retrace.Main.main(Main.java:0)
+    at com.android.tools.r8.naming.retrace.Main.main(Main.java:0)
+";
+
+    let mapper = ProguardMapper::from(AMBIGUOUS_METHOD_VERBOSE_MAPPING);
+    let actual = mapper.remap_stacktrace(input).unwrap();
+    assert_eq!(actual.trim(), expected.trim());
+
+    let mapping = ProguardMapping::new(AMBIGUOUS_METHOD_VERBOSE_MAPPING.as_bytes());
+    let mut buf = Vec::new();
+    ProguardCache::write(&mapping, &mut buf).unwrap();
+    let cache = ProguardCache::parse(&buf).unwrap();
+    cache.test();
+
+    let actual = cache.remap_stacktrace(input).unwrap();
+    assert_eq!(actual.trim(), expected.trim());
+}
+
+// =============================================================================
+// AmbiguousWithMultipleLineMappingsStackTrace
+// =============================================================================
+
+const AMBIGUOUS_WITH_MULTIPLE_LINE_MAPPINGS_MAPPING: &str = "\
+com.android.tools.r8.Internal -> com.android.tools.r8.Internal:
+    10:10:void foo(int):10:10 -> zza
+    11:11:void foo(int):11:11 -> zza
+    12:12:void foo(int):12:12 -> zza
+";
+
+#[test]
+fn test_ambiguous_with_multiple_line_mappings_stacktrace() {
+    let input = "\
+java.lang.IndexOutOfBoundsException
+    at java.util.ArrayList.get(ArrayList.java:411)
+    at com.android.tools.r8.Internal.zza(Unknown)
+";
+
+    let expected = "\
+java.lang.IndexOutOfBoundsException
+    at java.util.ArrayList.get(ArrayList.java:411)
+    at com.android.tools.r8.Internal.foo(Internal.java:0)
+";
+
+    let mapper = ProguardMapper::from(AMBIGUOUS_WITH_MULTIPLE_LINE_MAPPINGS_MAPPING);
+    let actual = mapper.remap_stacktrace(input).unwrap();
+    assert_eq!(actual.trim(), expected.trim());
+
+    let mapping = ProguardMapping::new(AMBIGUOUS_WITH_MULTIPLE_LINE_MAPPINGS_MAPPING.as_bytes());
+    let mut buf = Vec::new();
+    ProguardCache::write(&mapping, &mut buf).unwrap();
+    let cache = ProguardCache::parse(&buf).unwrap();
+    cache.test();
+
+    let actual = cache.remap_stacktrace(input).unwrap();
+    assert_eq!(actual.trim(), expected.trim());
+}
+
+// =============================================================================
+// AmbiguousWithSignatureStackTrace (non-verbose retrace output)
+// =============================================================================
+
+const AMBIGUOUS_WITH_SIGNATURE_MAPPING: &str = "\
+com.android.tools.r8.Internal -> com.android.tools.r8.Internal:
+    10:10:void foo(int):10:10 -> zza
+    11:11:void foo(int, int):11:11 -> zza
+    12:12:void foo(int, boolean):12:12 -> zza
+    13:13:boolean foo(int, int):13:13 -> zza
+";
+
+#[test]
+fn test_ambiguous_with_signature_stacktrace() {
+    let input = "\
+java.lang.IndexOutOfBoundsException
+    at java.util.ArrayList.get(ArrayList.java:411)
+    at com.android.tools.r8.Internal.zza(Unknown)
+";
+
+    let expected = "\
+java.lang.IndexOutOfBoundsException
+    at java.util.ArrayList.get(ArrayList.java:411)
+    at com.android.tools.r8.Internal.foo(Internal.java:0)
+";
+
+    let mapper = ProguardMapper::from(AMBIGUOUS_WITH_SIGNATURE_MAPPING);
+    let actual = mapper.remap_stacktrace(input).unwrap();
+    assert_eq!(actual.trim(), expected.trim());
+
+    let mapping = ProguardMapping::new(AMBIGUOUS_WITH_SIGNATURE_MAPPING.as_bytes());
+    let mut buf = Vec::new();
+    ProguardCache::write(&mapping, &mut buf).unwrap();
+    let cache = ProguardCache::parse(&buf).unwrap();
+    cache.test();
+
+    let actual = cache.remap_stacktrace(input).unwrap();
+    assert_eq!(actual.trim(), expected.trim());
+}
+
+// =============================================================================
+// InlineNoLineAssumeNoInlineAmbiguousStackTrace
+// =============================================================================
+
+const INLINE_NO_LINE_ASSUME_NO_INLINE_AMBIGUOUS_MAPPING: &str = "\
+retrace.Main -> a:
+    void otherMain(java.lang.String[]) -> foo
+    2:2:void method1(java.lang.String):0:0 -> foo
+    2:2:void main(java.lang.String[]):0 -> foo
+";
+
+#[test]
+fn test_inline_no_line_assume_no_inline_ambiguous_stacktrace() {
+    let input = "\
+Exception in thread \"main\" java.lang.NullPointerException
+    at a.foo(Unknown Source)
+";
+
+    // When no line info is available, prefer base (no-line) mappings if present.
+    let expected = "\
+Exception in thread \"main\" java.lang.NullPointerException
+    at retrace.Main.otherMain(Main.java:0)
+";
+
+    let mapper = ProguardMapper::from(INLINE_NO_LINE_ASSUME_NO_INLINE_AMBIGUOUS_MAPPING);
+    let actual = mapper.remap_stacktrace(input).unwrap();
+    assert_eq!(actual.trim(), expected.trim());
+
+    let mapping =
+        ProguardMapping::new(INLINE_NO_LINE_ASSUME_NO_INLINE_AMBIGUOUS_MAPPING.as_bytes());
+    let mut buf = Vec::new();
+    ProguardCache::write(&mapping, &mut buf).unwrap();
+    let cache = ProguardCache::parse(&buf).unwrap();
+    cache.test();
+
+    let actual = cache.remap_stacktrace(input).unwrap();
+    assert_eq!(actual.trim(), expected.trim());
+}