diff --git a/Cargo.lock b/Cargo.lock
index d936bc3..3596402 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -84,6 +84,7 @@ dependencies = [
  "serde_json",
  "tempfile",
  "tree-sitter",
+ "tree-sitter-c",
  "tree-sitter-cpp",
  "tree-sitter-dart",
  "tree-sitter-javascript",
@@ -423,6 +424,16 @@ dependencies = [
  "tree-sitter-language",
 ]
 
+[[package]]
+name = "tree-sitter-c"
+version = "0.24.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a9b2eb57a55fed6b00812912e730b7a275cf4fe98bfd6a5d76263d4438371728"
+dependencies = [
+ "cc",
+ "tree-sitter-language",
+]
+
 [[package]]
 name = "tree-sitter-cpp"
 version = "0.23.4"
diff --git a/Cargo.toml b/Cargo.toml
index d492c7d..b2a1318 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -16,6 +16,7 @@ regex = "1.12"
 serde = { version = "1.0", features = ["derive"] }
 serde_json = "1.0"
 tree-sitter = "=0.26.13"
+tree-sitter-c = "=0.24.2"
 tree-sitter-cpp = "=0.23.4"
 tree-sitter-javascript = "=0.25.0"
 tree-sitter-typescript = "=0.23.2"
diff --git a/README.md b/README.md
index c4cd919..ee9367b 100644
--- a/README.md
+++ b/README.md
@@ -6,8 +6,8 @@ elements, and dependency edges show calls, imports, and inheritance. The same
 model is emitted as versioned JSON for other tools, including a future Fold
 integration.
 
-The default extractor uses pinned Tree-sitter grammars for Rust, Dart, C/C++,
-JavaScript/JSX, and TypeScript/TSX. Python and Swift retain the lexical preview;
+The default extractor uses pinned Tree-sitter grammars for Rust, Dart, C
+(`.c`), C++ (including headers), JavaScript/JSX, and TypeScript/TSX. Python and Swift retain the lexical preview;
 P4_16 retains its separate lexical and optional pilot paths. Declarations are
 Syntactic evidence. Calls, imports, and inheritance retain Heuristic target
 resolution with backend, confidence, and source location, independently of
@@ -32,8 +32,16 @@ Layer Fold findings onto the building:
       --json fold.brick.json \
       --html fold.brick.html
 
+A report must be a SARIF log or a Fold findings report; anything else is an
+error. Findings keep Fold's symbolic lane only when the report names Fold as its
+producer (`tool.name` / `tool.driver.name`); other producers' findings are
+imported, never symbolic. Findings without a file location are diagnosed, and
+SARIF `file://` URIs are decoded before matching.
+
 Fold artifact paths are normalized lexically across `/`, `\\`, `.`, and `..`
-components before exact repository-relative matching. Absolute paths are
+components before exact repository-relative matching; a path with `..` that
+exists in this checkout follows the filesystem instead, so `link/..` resolves
+through the symlink. Absolute paths are
 accepted only beneath the model's scan root (including existing filesystem
 aliases whose canonical targets are beneath that root); leading traversal and unrelated
 suffix paths remain diagnostics. Findings for excluded, generated, or genuinely
@@ -152,26 +160,43 @@ Brick extracts syntax, without compiler type checking or build configuration.
 Macro expansion, overload resolution, dynamic dispatch, generated code, and
 full package/build-system resolution remain outside the default frontend.
 Malformed syntax produces diagnostics; recoverable sibling facts remain visible.
+A file with invalid UTF-8 is decoded lossily with a diagnostic; files with NUL
+bytes are skipped as binary. `build` prints diagnostic counts, and a scan that
+finds no supported source says so. `check` recomputes metrics from the graph
+(stored metrics are never trusted) and fails a model with no scanned source.
 Its score is not proof of correctness, maintainability,
 or security. Use the component metrics and evidence records; do not rank teams
 or repositories by the composite alone.
 
-Resolution respects language, file, declaration ownership, and lexical namespace.
-Relative JS/TS and Dart imports resolve against the importing directory; missing
-paths never fall back to unrelated basenames. Explicit JS/TS named/default import
-bindings, module-scoped Rust grouped/aliased imports, and module-qualified Rust
-public calls can resolve across files.
+Grammar-based resolution respects language, file, declaration ownership, and
+lexical namespace. Relative JS/TS and Dart imports resolve against the importing
+directory (Dart `package:<own package>/` against `lib/`); missing paths never
+fall back to unrelated basenames. Explicit JS/TS named/default import bindings,
+module-scoped Rust grouped/aliased imports, module-qualified Rust public calls,
+and public top-level Dart names from imported libraries can resolve across files
+(Dart `show`/`hide` combinators are not modelled). The lexical preview resolves
+Python names in the calling file, then in files it imports; Swift names in the
+calling file, then by a module-wide unique name (Swift files of one module see
+each other without imports).
 C++ calls resolve through the include closure: a header prototype pairs with
 its definition in another translation unit, lookup walks class (including
 in-repository bases) and namespace scopes outward, and `static`/anonymous
-definitions stay file-local. C++ and Rust member calls resolve only through an
-explicitly declared receiver type (parameter, local, field, `this`/`self`,
-smart pointer, or `Self`-returning constructor) and carry
-`source.resolution`. Calls inside Rust expression macros (`assert!`, `format!`,
+definitions stay file-local. Declarations in `#elif`/`#else` branches stay in
+the graph (`source.preprocessor-branch: alternative`) but are never call
+targets, because Brick does not evaluate conditions; several `using`
+directives that nominate different declarations make a call ambiguous. C++ and
+Rust member calls resolve only through an explicitly declared receiver type
+(parameter, local, field, `this`/`self`, smart pointer, or `Self`-returning
+constructor) and carry `source.resolution`. Rust types are identified by their
+declaring file, so same-named types in different modules resolve through the
+caller's `use` binding or stay ambiguous. Calls inside Rust expression macros (`assert!`, `format!`,
 `vec!`, ...) are recovered by re-parsing and carry `source.extraction`.
 Every unresolved call edge records `source.unresolved-reason`, and
-`metrics.resolution` reports per-language call-site coverage. Ambiguous
-targets stay external. Bare package specifiers, tsconfig aliases, Rust
+`metrics.resolution` reports per-language call-site coverage; read the graph
+with that coverage in mind (on a large C++ repository only a minority of call
+sites resolve). Ambiguous targets stay external. Virtual calls resolve to the
+declared type's method only (overrides are not fanned out), and Catch2
+`TEST_CASE` bodies are not yet recognized as functions. Bare package specifiers, tsconfig aliases, Rust
 wildcard/block-local binding expansion, Cargo workspace module paths,
 `compile_commands.json` include paths, and compiler-grade dispatch need further
 adapters. File fan-out remains an observation rather
diff --git a/docs/research/language-correctness.md b/docs/research/language-correctness.md
index dc1dbaf..b2b343a 100644
--- a/docs/research/language-correctness.md
+++ b/docs/research/language-correctness.md
@@ -42,7 +42,8 @@ change cycle, isolation, and fan metrics; no health weights are changed.
 | Rust const/impl | Const function, distinct type-owned methods, stable IDs after unrelated insertions; unresolved impl cannot create cyclic ownership |
 | Fold absolute alias | `src/fold.rs` tests existing root aliases while rejecting outside and excluded files; original default-tempdir test passes |
 
-The grammar versions are pinned in Cargo.toml and Cargo.lock: C++ 0.23.4,
+The grammar versions are pinned in Cargo.toml and Cargo.lock: C 0.24.2 (`.c`
+files), C++ 0.23.4,
 JavaScript 0.25.0, TypeScript/TSX 0.23.2, Dart 0.2.0, Rust 0.24.2, with the
 Tree-sitter Rust runtime at 0.26.13. Upstream API/grammar references:
 [C++](https://docs.rs/tree-sitter-cpp/0.23.4/tree_sitter_cpp/),
diff --git a/src/fold.rs b/src/fold.rs
index 56613fa..77390a9 100644
--- a/src/fold.rs
+++ b/src/fold.rs
@@ -2,7 +2,7 @@ use crate::metrics;
 use crate::model::{
     Building, Confidence, Edge, EdgeKind, Evidence, EvidenceLane, Node, NodeKind, stable_id,
 };
-use anyhow::{Context, Result};
+use anyhow::{Context, Result, bail};
 use serde_json::Value;
 use std::collections::BTreeMap;
 use std::fs;
@@ -13,11 +13,67 @@ pub fn import_findings(building: &mut Building, report: &Path) -> Result<usize>
         .with_context(|| format!("cannot read Fold report {}", report.display()))?;
     let value: Value = serde_json::from_str(&raw)
         .with_context(|| format!("invalid JSON in Fold report {}", report.display()))?;
-    let findings = if value.get("runs").is_some() {
+    let sarif_runs = value.get("runs").and_then(Value::as_array);
+    let is_native = value.get("findings").and_then(Value::as_array).is_some();
+    if sarif_runs.is_none() && !is_native {
+        // Anything else imported zero findings silently, like a clean run.
+        bail!(
+            "{} is not a Fold report: expected a SARIF log (`runs`) or a Fold findings report (`findings`)",
+            report.display()
+        );
+    }
+    // Fold's proved/latent tiers mean something only when Fold produced them:
+    // a report from another tool never earns the Symbolic lane by labelling itself.
+    let producers: Vec<Option<&str>> = match sarif_runs {
+        Some(runs) => runs
+            .iter()
+            .map(|run| run.pointer("/tool/driver/name").and_then(Value::as_str))
+            .collect(),
+        None => vec![value.pointer("/tool/name").and_then(Value::as_str)],
+    };
+    let from_fold = !producers.is_empty() && producers.iter().all(|name| *name == Some("fold"));
+    if !from_fold {
+        let named: Vec<&str> = producers
+            .iter()
+            .map(|name| name.unwrap_or("unnamed"))
+            .collect();
+        building.diagnostics.push(crate::model::Diagnostic {
+            level: "warning".into(),
+            message: format!(
+                "report {} was not produced by Fold (producer: {}); its findings are imported, never symbolic",
+                report.display(),
+                named.join(", ")
+            ),
+            path: None,
+        });
+    }
+    if let Some(version) = value.get("output_version")
+        && version.as_u64() != Some(1)
+    {
+        building.diagnostics.push(crate::model::Diagnostic {
+            level: "warning".into(),
+            message: format!(
+                "Fold report {} has unsupported output_version {version}; read as version 1",
+                report.display()
+            ),
+            path: None,
+        });
+    }
+    let (findings, unlocated) = if sarif_runs.is_some() {
         sarif_findings(&value)
     } else {
         native_findings(&value)
     };
+    if unlocated > 0 {
+        building.diagnostics.push(crate::model::Diagnostic {
+            level: "warning".into(),
+            message: format!(
+                "{unlocated} Fold finding(s) in {} had no file location and were not imported",
+                report.display()
+            ),
+            path: None,
+        });
+    }
 
     let mut imported = 0;
     for finding in findings {
@@ -83,7 +139,7 @@ pub fn import_findings(building: &mut Building, report: &Path) -> Result<usize>
             .unwrap_or_else(|| format!("{}:{}:{}", finding.rule, relative_path, finding.line));
         let node_id = stable_id("finding", &identity);
         let evidence = Evidence {
-            lane: fold_lane(&backend, finding.confidence.as_deref()),
+            lane: fold_lane(&backend, finding.confidence.as_deref(), from_fold),
             backend: format!("fold:discover:{backend}"),
             confidence: finding.confidence.clone().map(Confidence::Label),
             provenance: format!("{}:{}", report.display(), finding.line),
@@ -141,12 +197,17 @@ struct Finding {
     backend: Option<String>,
 }
 
-fn native_findings(value: &Value) -> Vec<Finding> {
-    value
+/// Findings plus the number dropped for lack of a file location.
+fn native_findings(value: &Value) -> (Vec<Finding>, usize) {
+    let items: Vec<&Value> = value
         .get("findings")
         .and_then(Value::as_array)
         .into_iter()
         .flatten()
+        .collect();
+    let total = items.len();
+    let findings: Vec<Finding> = items
+        .into_iter()
         .filter_map(|item| {
             Some(Finding {
                 stable_id: string(item, ["id", "finding_id"]),
@@ -159,11 +220,14 @@ fn native_findings(value: &Value) -> Vec<Finding> {
                 backend: native_backend(item),
             })
         })
-        .collect()
+        .collect();
+    let dropped = total - findings.len();
+    (findings, dropped)
 }
 
-fn sarif_findings(value: &Value) -> Vec<Finding> {
-    value
+/// Findings plus the number dropped for lack of a file location.
+fn sarif_findings(value: &Value) -> (Vec<Finding>, usize) {
+    let items: Vec<&Value> = value
         .get("runs")
         .and_then(Value::as_array)
         .into_iter()
@@ -174,6 +238,10 @@ fn sarif_findings(value: &Value) -> Vec<Finding> {
                 .into_iter()
                 .flatten()
         })
+        .collect();
+    let total = items.len();
+    let findings: Vec<Finding> = items
+        .into_iter()
         .filter_map(|item| {
             let location = item.pointer("/locations/0/physicalLocation")?;
             Some(Finding {
@@ -194,7 +262,7 @@ fn sarif_findings(value: &Value) -> Vec<Finding> {
                     .and_then(Value::as_str)
                     .unwrap_or_default()
                     .into(),
-                path: location.pointer("/artifactLocation/uri")?.as_str()?.into(),
+                path: sarif_uri_path(location.pointer("/artifactLocation/uri")?.as_str()?),
                 line: location
                     .pointer("/region/startLine")
                     .and_then(Value::as_u64)
@@ -209,7 +277,34 @@ fn sarif_findings(value: &Value) -> Vec<Finding> {
                     .map(str::to_owned),
             })
         })
-        .collect()
+        .collect();
+    let dropped = total - findings.len();
+    (findings, dropped)
+}
+
+/// SARIF `artifactLocation.uri` as a path: `file://[localhost]/p` loses its scheme and
+/// percent-escapes (`%20`) are decoded; relative URIs pass through unchanged.
+fn sarif_uri_path(uri: &str) -> String {
+    let Some(rest) = uri.strip_prefix("file://") else {
+        return uri.to_owned();
+    };
+    let rest = rest.strip_prefix("localhost").unwrap_or(rest);
+    let bytes = rest.as_bytes();
+    let mut decoded = Vec::with_capacity(bytes.len());
+    let mut i = 0;
+    while i < bytes.len() {
+        if bytes[i] == b'%'
+            && i + 2 < bytes.len()
+            && let Ok(byte) = u8::from_str_radix(&rest[i + 1..i + 3], 16)
+        {
+            decoded.push(byte);
+            i += 3;
+            continue;
+        }
+        decoded.push(bytes[i]);
+        i += 1;
+    }
+    String::from_utf8(decoded).unwrap_or_else(|_| rest.to_owned())
 }
 
 fn string<const N: usize>(value: &Value, keys: [&str; N]) -> Option<String> {
@@ -277,7 +372,24 @@ fn find_file(building: &Building, path: &str) -> Option<String> {
         {
             return None;
         }
-        normalized
+        // When the path exists here, follow the filesystem: `link/../x` names what
+        // the OS resolves through `link`, not the lexical `x`. Paths absent from this
+        // checkout (a report from another machine) keep lexical matching.
+        let on_disk = Path::new(&building.root).join(path.replace('\\', "/"));
+        if path.contains("..")
+            && let (Ok(canonical), Ok(root)) = (
+                on_disk.canonicalize(),
+                Path::new(&building.root).canonicalize(),
+            )
+        {
+            canonical
+                .strip_prefix(&root)
+                .ok()?
+                .to_str()?
+                .replace('\\', "/")
+        } else {
+            normalized
+        }
     };
     building
         .nodes
@@ -327,9 +439,10 @@ fn normalize_lexical_path(path: &str) -> String {
     }
 }
 
-fn fold_lane(backend: &str, confidence: Option<&str>) -> EvidenceLane {
+fn fold_lane(backend: &str, confidence: Option<&str>, from_fold: bool) -> EvidenceLane {
     const SYMBOLIC_CONFIDENCE: [&str; 3] = ["concrete-witness", "proved", "latent"];
-    if backend == "source"
+    if from_fold
+        && backend == "source"
         && confidence.is_some_and(|confidence| SYMBOLIC_CONFIDENCE.contains(&confidence))
     {
         EvidenceLane::Symbolic
@@ -362,6 +475,8 @@ mod tests {
         fs::write(dir.path().join("main.cpp"), "int main() { return 0; }\n").unwrap();
         let report = dir.path().join("fold.json");
         let value = serde_json::json!({
+            "output_version": 1,
+            "tool": {"name": "fold", "version": "0.1.0"},
             "findings": [{
                 "id": "f1",
                 "kind": "null-deref",
@@ -414,7 +529,10 @@ mod tests {
         })).collect();
         fs::write(
             &report,
-            serde_json::to_vec(&serde_json::json!({"findings": findings})).unwrap(),
+            serde_json::to_vec(
+                &serde_json::json!({"tool": {"name": "fold"}, "findings": findings}),
+            )
+            .unwrap(),
         )
         .unwrap();
         let mut model = scan(&root).unwrap();
@@ -439,6 +557,7 @@ mod tests {
             &report,
             r#"{
               "runs": [{
+                "tool": {"driver": {"name": "fold"}},
                 "results": [
                   {
                     "ruleId": "fold.valid",
@@ -485,6 +604,7 @@ mod tests {
         let outside = dir.path().parent().unwrap().join("other/main.cpp");
         let report = dir.path().join("fold.json");
         let value = serde_json::json!({
+            "tool": {"name": "fold"},
             "findings": [
                 {
                     "id": "absolute-outside",
@@ -634,4 +754,131 @@ mod tests {
                 .any(|evidence| evidence.provenance.contains("second.json"))
         );
     }
+
+    #[test]
+    fn rejects_a_file_that_is_not_a_fold_report() {
+        // `{"hello":1}` imported 0 findings with no diagnostic, indistinguishable
+        // from a clean Fold run.
+        let dir = tempfile::tempdir().unwrap();
+        fs::write(dir.path().join("main.rs"), "fn main() {}\n").unwrap();
+        let report = dir.path().join("fold.json");
+        fs::write(&report, r#"{"hello": 1}"#).unwrap();
+        let mut building = scan(dir.path()).unwrap();
+        let error = import_findings(&mut building, &report).unwrap_err();
+        assert!(
+            format!("{error:#}").contains("not a Fold report"),
+            "{error:#}"
+        );
+    }
+
+    #[test]
+    fn symbolic_lane_requires_a_fold_producer_not_a_self_declared_label() {
+        // Any JSON claiming backend "source" and confidence "proved" got the Symbolic
+        // lane. Only a report produced by Fold may carry Fold's proved tier.
+        let dir = tempfile::tempdir().unwrap();
+        fs::write(dir.path().join("main.cpp"), "int main() { return 0; }\n").unwrap();
+        let report = dir.path().join("other.json");
+        let value = serde_json::json!({
+            "tool": {"name": "someone-else"},
+            "findings": [{
+                "id": "x", "kind": "null-deref",
+                "locations": [{"file": "main.cpp", "line": 1}],
+                "confidence": "proved", "evidence": {"backend": "source"}
+            }]
+        });
+        fs::write(&report, serde_json::to_vec(&value).unwrap()).unwrap();
+        let mut building = scan(dir.path()).unwrap();
+        assert_eq!(import_findings(&mut building, &report).unwrap(), 1);
+        let flags = building
+            .edges
+            .iter()
+            .find(|edge| edge.kind == EdgeKind::Flags)
+            .unwrap();
+        assert_eq!(flags.evidence[0].lane, crate::model::EvidenceLane::Imported);
+        assert!(
+            building
+                .diagnostics
+                .iter()
+                .any(|d| d.message.contains("not produced by Fold"))
+        );
+    }
+
+    #[test]
+    fn sarif_file_uris_match_and_unlocated_findings_are_diagnosed() {
+        let dir = tempfile::tempdir().unwrap();
+        fs::write(dir.path().join("my file.cpp"), "int main() { return 0; }\n").unwrap();
+        let mut building = scan(dir.path()).unwrap();
+        let uri = format!(
+            "file://{}",
+            dir.path()
+                .join("my file.cpp")
+                .to_str()
+                .unwrap()
+                .replace(' ', "%20")
+        );
+        let report = dir.path().join("fold.sarif");
+        let value = serde_json::json!({
+            "version": "2.1.0",
+            "runs": [{
+                "tool": {"driver": {"name": "fold"}},
+                "results": [
+                    {"ruleId": "div-by-zero", "message": {"text": "x"},
+                     "locations": [{"physicalLocation": {"artifactLocation": {"uri": uri},
+                                    "region": {"startLine": 1}}}],
+                     "properties": {"confidence": "proved", "backend": "source"}},
+                    {"ruleId": "no-location", "message": {"text": "y"},
+                     "properties": {"confidence": "heuristic", "backend": "source"}}
+                ]
+            }]
+        });
+        fs::write(&report, serde_json::to_vec(&value).unwrap()).unwrap();
+        assert_eq!(import_findings(&mut building, &report).unwrap(), 1);
+        assert!(
+            building
+                .diagnostics
+                .iter()
+                .any(|d| d.message.contains("no file location")),
+            "{:?}",
+            building.diagnostics
+        );
+    }
+
+    #[cfg(unix)]
+    #[test]
+    fn parent_steps_after_a_symlinked_directory_follow_the_filesystem() {
+        // `linkout/../src/main.rs` with `linkout` pointing outside the root was
+        // normalized lexically to `src/main.rs`, a file the OS path does not name.
+        use std::os::unix::fs::symlink;
+        let workspace = tempfile::tempdir().unwrap();
+        let root = workspace.path().join("repo");
+        fs::create_dir_all(root.join("src")).unwrap();
+        fs::write(root.join("src/main.rs"), "fn main() {}\n").unwrap();
+        let outside = workspace.path().join("elsewhere/deeper");
+        fs::create_dir_all(&outside).unwrap();
+        fs::create_dir_all(workspace.path().join("elsewhere/src")).unwrap();
+        fs::write(
+            workspace.path().join("elsewhere/src/main.rs"),
+            "fn other() {}\n",
+        )
+        .unwrap();
+        symlink(&outside, root.join("linkout")).unwrap();
+        let report = workspace.path().join("fold.json");
+        let value = serde_json::json!({
+            "tool": {"name": "fold"},
+            "findings": [{
+                "id": "through-link", "kind": "test",
+                "locations": [{"file": "linkout/../src/main.rs", "line": 1}],
+                "confidence": "heuristic", "evidence": {"backend": "source"}
+            }]
+        });
+        fs::write(&report, serde_json::to_vec(&value).unwrap()).unwrap();
+        let mut model = scan(&root).unwrap();
+        assert_eq!(import_findings(&mut model, &report).unwrap(), 0);
+        assert!(
+            model
+                .diagnostics
+                .iter()
+                .any(|d| d.message.contains("did not match a scanned file"))
+        );
+    }
 }
diff --git a/src/main.rs b/src/main.rs
index 94b6eac..37efe92 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -182,16 +182,28 @@ fn run(cli: Cli) -> Result<()> {
                 .count();
             write_json(&building, &json)?;
             render::render(&building, &html, &cytoscape_url)?;
+            let warnings = building
+                .diagnostics
+                .iter()
+                .filter(|diagnostic| diagnostic.level == "warning")
+                .count();
             println!(
-                "built {} nodes / {} edges; score {:.1}; imported {} Fold findings / {} p4c diagnostics\nJSON: {}\nHTML: {}",
+                "built {} nodes / {} edges; score {:.1}; imported {} Fold findings / {} p4c diagnostics; {} diagnostics ({} warnings)\nJSON: {}\nHTML: {}",
                 building.metrics.node_count,
                 building.metrics.edge_count,
                 building.metrics.structural_health.score,
                 imported_fold,
                 imported_p4c,
+                building.diagnostics.len(),
+                warnings,
                 json.display(),
                 html.display()
             );
+            if !has_source_files(&building) {
+                eprintln!(
+                    "brick: warning: no supported source files were found; the model is empty and its score describes nothing"
+                );
+            }
         }
         Command::Mcp { input } => {
             let building = read_json(&input)?;
@@ -227,8 +239,24 @@ fn run(cli: Cli) -> Result<()> {
                 bail!("--min-score must be a finite number");
             }
             let building = read_json(&input)?;
-            let metrics = &building.metrics;
+            // Gate on metrics recomputed from the graph, never on the stored copy:
+            // editing `metrics` in the JSON must not be able to pass a gate.
+            let mut recomputed = building.clone();
+            brick::metrics::calculate(&mut recomputed);
             let mut failures = Vec::new();
+            if serde_json::to_value(&recomputed.metrics)?
+                != serde_json::to_value(&building.metrics)?
+            {
+                failures.push(
+                    "stored metrics do not match the graph; gating on recomputed metrics".into(),
+                );
+            }
+            let metrics = &recomputed.metrics;
+            if !has_source_files(&building) {
+                failures.push(
+                    "the model contains no scanned source files; nothing was analysed".into(),
+                );
+            }
             if metrics.structural_health.score < min_score {
                 failures.push(format!(
                     "score {:.1} is below {:.1}",
@@ -402,6 +430,14 @@ fn write_json(building: &Building, path: &PathBuf) -> Result<()> {
         .with_context(|| format!("cannot write graph {}", path.display()))
 }
 
+/// At least one source file was scanned into the model.
+fn has_source_files(building: &Building) -> bool {
+    building
+        .nodes
+        .iter()
+        .any(|node| node.kind == brick::model::NodeKind::File)
+}
+
 fn read_json(path: &PathBuf) -> Result<Building> {
     let raw = fs::read_to_string(path)
         .with_context(|| format!("cannot read graph {}", path.display()))?;
diff --git a/src/scan.rs b/src/scan.rs
index 244eca9..c32e56a 100644
--- a/src/scan.rs
+++ b/src/scan.rs
@@ -100,6 +100,14 @@ pub fn scan_with_options(root: &Path, options: &ScanOptions) -> Result<Building>
     state.walk(&root)?;
     state.resolve_relationships();
     state.annotate_indirect_uses();
+    // An analysis of nothing must not read as a healthy repository.
+    if !state.nodes.iter().any(|node| node.kind == NodeKind::File) {
+        state.diagnostics.push(Diagnostic {
+            level: "warning".into(),
+            message: "no supported source files were found; the model is empty".into(),
+            path: None,
+        });
+    }
 
     let mut building = Building {
         schema_version: SCHEMA_VERSION,
@@ -140,16 +148,21 @@ struct RustCall {
     receiver: Option<crate::source::Receiver>,
 }
 
-/// A method node id and the trait it implements, if any.
-type RustMethod = (String, Option<String>);
+/// A method node id, the trait it implements (if any), and the file of its `impl`.
+type RustMethod = (String, Option<String>, String);
 
-/// Crate-wide Rust impl/trait facts keyed by leaf type names.
+/// Crate-wide Rust impl/trait facts keyed by leaf type names. Leaf names are not
+/// identities: when several files declare the same name, `rust_type_file` settles
+/// which one a use site means (declaring file, then `use` binding) or reports it
+/// as ambiguous.
 #[derive(Default)]
 struct RustIndex {
     /// (type or trait, method) -> candidate methods.
     methods: HashMap<(String, String), Vec<RustMethod>>,
     /// Struct, enum, and trait names declared in the repository.
     types: HashSet<String>,
+    /// Leaf type/trait name -> files declaring it.
+    type_files: HashMap<String, Vec<String>>,
     /// (struct, field) -> declared type.
     fields: HashMap<(String, String), crate::source::CppType>,
     /// Method node id -> declared return type.
@@ -233,11 +246,25 @@ struct ScanState {
     rust: RustIndex,
     /// Language -> identifiers used outside call/declaration-name positions.
     references: HashMap<String, HashSet<String>>,
+    /// Lexical-language file -> repository files it imports (resolved edges).
+    imported_paths: HashMap<String, Rc<HashSet<String>>>,
+    /// `name:` of the root pubspec.yaml, so `package:<name>/x.dart` maps to lib/x.dart.
+    dart_package: Option<String>,
 }
 
 impl ScanState {
     fn new(root: PathBuf, root_id: String, options: &ScanOptions) -> Self {
+        let dart_package = fs::read_to_string(root.join("pubspec.yaml"))
+            .ok()
+            .and_then(|pubspec| {
+                pubspec.lines().find_map(|line| {
+                    line.strip_prefix("name:")
+                        .map(|name| name.trim().trim_matches(['\'', '"']).to_owned())
+                        .filter(|name| !name.is_empty())
+                })
+            });
         Self {
+            dart_package,
             root,
             root_id,
             nodes: Vec::new(),
@@ -255,6 +282,7 @@ impl ScanState {
             cpp: CppIndex::default(),
             rust: RustIndex::default(),
             references: HashMap::new(),
+            imported_paths: HashMap::new(),
         }
     }
 
@@ -340,17 +368,39 @@ impl ScanState {
                 return;
             }
         };
-        let content = match fs::read_to_string(path) {
+        let bytes = match fs::read(path) {
             Ok(value) => value,
             Err(error) => {
                 self.diagnostics.push(Diagnostic {
                     level: "warning".into(),
-                    message: format!("skipped non-UTF-8 or unreadable source: {error}"),
+                    message: format!("skipped unreadable source: {error}"),
                     path: Some(relative),
                 });
                 return;
             }
         };
+        // NUL bytes mean a binary file, not source. Any other invalid UTF-8 (a
+        // Latin-1 byte in a comment) is decoded lossily: dropping the whole file hid
+        // every symbol in it.
+        if bytes.contains(&0) {
+            self.diagnostics.push(Diagnostic {
+                level: "warning".into(),
+                message: "skipped binary file with a source extension".into(),
+                path: Some(relative),
+            });
+            return;
+        }
+        let content = match String::from_utf8(bytes) {
+            Ok(value) => value,
+            Err(error) => {
+                self.diagnostics.push(Diagnostic {
+                    level: "warning".into(),
+                    message: "decoded non-UTF-8 bytes lossily (U+FFFD)".into(),
+                    path: Some(relative.clone()),
+                });
+                String::from_utf8_lossy(error.as_bytes()).into_owned()
+            }
+        };
         let file_id = stable_id("file", &relative);
         let parent = path
             .parent()
@@ -408,9 +458,14 @@ impl ScanState {
             let line = strip_line_comment(raw_line, language);
             let call_line = mask_quoted_strings(line);
             let indent = raw_line.len() - raw_line.trim_start().len();
-            if language == "python" && !line.trim().is_empty() {
-                while scopes.last().is_some_and(|scope| scope.indent >= indent) {
-                    scopes.pop();
+            if language == "python" {
+                // Blank and comment-only lines say nothing about Python scope. They
+                // used to fall through to the brace-depth rule below, which popped
+                // every open scope: calls after a blank line left their function.
+                if !line.trim().is_empty() {
+                    while scopes.last().is_some_and(|scope| scope.indent >= indent) {
+                        scopes.pop();
+                    }
                 }
             } else {
                 while scopes
@@ -421,9 +476,11 @@ impl ScanState {
                 }
             }
 
+            let mut class_name = None;
             if let Some(captures) = patterns.class.captures(line)
                 && let Some(name) = captures.name("name")
             {
+                class_name = Some(name.as_str().to_owned());
                 let owner_id = scopes
                     .last()
                     .map(|scope| scope.id.clone())
@@ -525,7 +582,11 @@ impl ScanState {
                 let target = target_match.as_str();
                 let prefix = call_line[..target_match.start()].trim_end();
                 let member_call = prefix.ends_with('.') || prefix.ends_with("->");
-                if definition_name.as_deref() != Some(target) && !is_keyword(target) {
+                // `class Child(Base):` names the class being declared, not a call.
+                if definition_name.as_deref() != Some(target)
+                    && class_name.as_deref() != Some(target)
+                    && !is_keyword(target)
+                {
                     self.pending.push(PendingRelationship {
                         source: source.clone(),
                         target_name: clean_target(target),
@@ -611,6 +672,12 @@ impl ScanState {
                 if declaration.is_virtual {
                     attributes.insert("source.virtual".into(), serde_json::json!(true));
                 }
+                if declaration.preprocessor_alternative {
+                    attributes.insert(
+                        "source.preprocessor-branch".into(),
+                        serde_json::json!("alternative"),
+                    );
+                }
                 if document.parse_incomplete && declaration.kind == NodeKind::Function {
                     attributes.insert("source.parse-incomplete".into(), serde_json::json!(true));
                 }
@@ -657,6 +724,14 @@ impl ScanState {
                 let Some(id) = id else { continue };
                 if declaration.kind == NodeKind::Class {
                     self.rust.types.insert(declaration.name.clone());
+                    let files = self
+                        .rust
+                        .type_files
+                        .entry(declaration.name.clone())
+                        .or_default();
+                    if !files.iter().any(|file| file == path) {
+                        files.push(path.to_owned());
+                    }
                     continue;
                 }
                 let Some(owner) = declaration
@@ -676,7 +751,7 @@ impl ScanState {
                     .methods
                     .entry((owner, declaration.name.clone()))
                     .or_default()
-                    .push((id.clone(), implemented));
+                    .push((id.clone(), implemented, path.to_owned()));
                 if let Some(returns) = &declaration.return_type {
                     self.rust.returns.insert(id.clone(), returns.clone());
                 }
@@ -699,6 +774,9 @@ impl ScanState {
             }
         }
         for (declaration, id) in document.declarations.iter().zip(&ids) {
+            if declaration.preprocessor_alternative {
+                continue;
+            }
             if declaration.kind == NodeKind::Class
                 && let Some(name) = &declaration.qualified_name
             {
@@ -1226,6 +1304,32 @@ impl ScanState {
         }
     }
 
+    /// Repository files that `path` imports through already-resolved edges.
+    /// Imports resolve before calls, so the cached set is complete once built.
+    fn imported_paths(&mut self, path: &str) -> Rc<HashSet<String>> {
+        if let Some(found) = self.imported_paths.get(path) {
+            return Rc::clone(found);
+        }
+        let paths: HashSet<String> = self
+            .nodes
+            .iter()
+            .find(|n| n.kind == NodeKind::File && n.path.as_deref() == Some(path))
+            .map(|file| {
+                self.edges
+                    .iter()
+                    .filter(|e| e.kind == EdgeKind::Imports && e.source == file.id)
+                    .filter_map(|e| self.node(&e.target))
+                    .filter(|n| n.kind == NodeKind::File)
+                    .filter_map(|n| n.path.clone())
+                    .collect()
+            })
+            .unwrap_or_default();
+        let paths = Rc::new(paths);
+        self.imported_paths
+            .insert(path.to_owned(), Rc::clone(&paths));
+        paths
+    }
+
     /// Mark functions that may be used without a resolvable call: named outside
     /// a call position anywhere in the language, or C++ virtual via a prototype.
     fn annotate_indirect_uses(&mut self) {
@@ -1304,6 +1408,11 @@ impl ScanState {
             if let Some(id) = self.resolve_qualified_symbol(relationship) {
                 return (id, None, None);
             }
+            let imported = if language == "python" || language == "dart" {
+                self.imported_paths(&relationship.path)
+            } else {
+                Rc::default()
+            };
             let candidates: Vec<_> = self
                 .symbols_by_name
                 .get(name)
@@ -1339,10 +1448,49 @@ impl ScanState {
                 if let Some(id) = self.resolve_imported_symbol(relationship) {
                     return (id, None, None);
                 }
-            } else if candidates.len() == 1 {
-                return (candidates[0].id.clone(), None, None);
-            } else if candidates.len() > 1 {
-                reason = "ambiguous";
+                // A Dart import exposes the library's public top-level names with no
+                // per-name binding: resolve through the libraries this file imports.
+                if language == "dart" && reason != "ambiguous" {
+                    let exposed: Vec<_> = candidates
+                        .iter()
+                        .filter(|n| {
+                            !n.name.starts_with('_')
+                                && n.path.as_ref().is_some_and(|p| imported.contains(p))
+                                && n.parent
+                                    .as_deref()
+                                    .and_then(|parent| self.node(parent))
+                                    .is_some_and(|parent| parent.kind == NodeKind::File)
+                        })
+                        .collect();
+                    match exposed.as_slice() {
+                        [only] => return (only.id.clone(), None, None),
+                        [] => {}
+                        _ => reason = "ambiguous",
+                    }
+                }
+            } else {
+                // Lexical languages: the caller's own file first, then (Python)
+                // only files it imports. Swift files in one module see each other
+                // without imports, so Swift keeps a module-wide unique name.
+                let same_file: Vec<_> = candidates
+                    .iter()
+                    .filter(|n| n.path.as_deref() == Some(&relationship.path))
+                    .collect();
+                let visible: Vec<_> = if !same_file.is_empty() {
+                    same_file
+                } else if language == "python" {
+                    candidates
+                        .iter()
+                        .filter(|n| n.path.as_ref().is_some_and(|p| imported.contains(p)))
+                        .collect()
+                } else {
+                    candidates.iter().collect()
+                };
+                match visible.as_slice() {
+                    [only] => return (only.id.clone(), None, None),
+                    [] => {}
+                    _ => reason = "ambiguous",
+                }
             }
         }
         if !relationship.member_call
@@ -1467,11 +1615,24 @@ impl ScanState {
             }
         }
         if !absolute {
-            for qualified in self.cpp_using_candidates(name, &call.lookup_scope, &closure) {
-                if let Some(result) = self.cpp_lookup(&qualified, &closure) {
-                    return result.map(|id| (id, Some("using-directive")));
+            // Every directive is consulted: two that nominate different
+            // declarations make the call ambiguous rather than first-come.
+            let mut nominated: Vec<(String, Result<String, &'static str>)> = Vec::new();
+            for group in self.cpp_using_candidate_groups(name, &call.lookup_scope, &closure) {
+                for qualified in group {
+                    if let Some(result) = self.cpp_lookup(&qualified, &closure) {
+                        if !nominated.iter().any(|(seen, _)| seen == &qualified) {
+                            nominated.push((qualified, result));
+                        }
+                        break;
+                    }
                 }
             }
+            match nominated.as_slice() {
+                [] => {}
+                [(_, result)] => return result.clone().map(|id| (id, Some("using-directive"))),
+                _ => return Err("ambiguous"),
+            }
         }
         Err("not-visible")
     }
@@ -1588,7 +1749,27 @@ impl ScanState {
         scope: &str,
         closure: &HashSet<String>,
     ) -> Vec<String> {
-        let mut candidates = Vec::new();
+        let mut candidates: Vec<String> = self
+            .cpp_using_candidate_groups(name, scope, closure)
+            .into_iter()
+            .flatten()
+            .collect();
+        let mut seen = HashSet::new();
+        candidates.retain(|candidate| seen.insert(candidate.clone()));
+        candidates
+    }
+
+    /// `cpp_using_candidates` grouped by directive: one group per `using N::x;`
+    /// and per `using namespace N;`, whose members are the scope levels that
+    /// directive may name (innermost first). Separate groups are rival
+    /// nominations, so more than one resolving group is ambiguous.
+    fn cpp_using_candidate_groups(
+        &self,
+        name: &str,
+        scope: &str,
+        closure: &HashSet<String>,
+    ) -> Vec<Vec<String>> {
+        let mut groups = Vec::new();
         let (head, rest) = match name.split_once("::") {
             Some((head, rest)) => (head, Some(rest)),
             None => (name, None),
@@ -1598,21 +1779,24 @@ impl ScanState {
         for file in files {
             for (leaf, target) in self.cpp.using_names.get(file).into_iter().flatten() {
                 if leaf == head {
-                    candidates.push(match rest {
+                    groups.push(vec![match rest {
                         Some(rest) => qualify(target, rest),
                         None => target.clone(),
-                    });
+                    }]);
                 }
             }
             for namespace in self.cpp.using_namespaces.get(file).into_iter().flatten() {
-                for level in scope_levels(scope) {
-                    candidates.push(qualify(&qualify(&level, namespace), name));
-                }
+                groups.push(
+                    scope_levels(scope)
+                        .into_iter()
+                        .map(|level| qualify(&qualify(&level, namespace), name))
+                        .collect(),
+                );
             }
         }
         let mut seen = HashSet::new();
-        candidates.retain(|candidate| seen.insert(candidate.clone()));
-        candidates
+        groups.retain(|group| seen.insert(group.clone()));
+        groups
     }
 
     /// Method lookup in a class, then breadth-first through in-repository bases.
@@ -1690,7 +1874,7 @@ impl ScanState {
                 (field.accessed(true), "declared-receiver-type")
             }
             Some(Receiver::Returned { ty, func, fallible }) => (
-                self.rust_constructed_type(ty, func, *fallible, call)
+                self.rust_constructed_type(ty, func, *fallible, call, path)
                     .ok_or("receiver-type-unknown")?,
                 "declared-receiver-type",
             ),
@@ -1699,7 +1883,7 @@ impl ScanState {
         if self.rust_type_is_foreign(&ty, path) {
             return Err("receiver-type-external");
         }
-        self.rust_method(&ty, method).map(|id| (id, label))
+        self.rust_method(&ty, method, path).map(|id| (id, label))
     }
 
     /// A type name the caller's file imports from outside the crate.
@@ -1746,30 +1930,86 @@ impl ScanState {
         if !self.rust.types.contains(&ty) {
             return Err("qualifier-unknown");
         }
-        self.rust_method(&ty, method)
+        self.rust_method(&ty, method, path)
     }
 
-    fn rust_method(&self, ty: &str, method: &str) -> Result<String, &'static str> {
+    fn rust_method(&self, ty: &str, method: &str, path: &str) -> Result<String, &'static str> {
         let candidates = self
             .rust
             .methods
             .get(&(ty.to_owned(), method.to_owned()))
             .map(Vec::as_slice)
             .unwrap_or_default();
-        let inherent: Vec<_> = candidates.iter().filter(|(_, t)| t.is_none()).collect();
-        let chosen: Vec<_> = if inherent.is_empty() {
+        // Several repository types share this leaf name: keep only the impls of the
+        // one this use site means, or refuse to guess.
+        let candidates: Vec<&RustMethod> = if self
+            .rust
+            .type_files
+            .get(ty)
+            .is_some_and(|files| files.len() > 1)
+        {
+            let Some(meant) = self.rust_type_file(ty, path) else {
+                return Err("ambiguous");
+            };
+            candidates
+                .iter()
+                .filter(|(_, _, impl_path)| {
+                    self.rust_type_file(ty, impl_path).as_deref() == Some(meant.as_str())
+                })
+                .collect()
+        } else {
             candidates.iter().collect()
+        };
+        let inherent: Vec<_> = candidates
+            .iter()
+            .copied()
+            .filter(|(_, t, _)| t.is_none())
+            .collect();
+        let chosen: Vec<_> = if inherent.is_empty() {
+            candidates
         } else {
             inherent
         };
         match chosen.as_slice() {
-            [(id, _)] => Ok(id.clone()),
+            [(id, _, _)] => Ok(id.clone()),
             [] if self.rust.types.contains(ty) => Err("member-not-found"),
             [] => Err("receiver-type-external"),
             _ => Err("ambiguous"),
         }
     }
 
+    /// The file declaring the repository type `leaf` as seen from `path`: the file
+    /// itself, then a `use` binding that names it, then the only declaration. `None`
+    /// when several files declare `leaf` and nothing in `path` says which.
+    fn rust_type_file(&self, leaf: &str, path: &str) -> Option<String> {
+        let files = self.rust.type_files.get(leaf)?;
+        if files.iter().any(|file| file == path) {
+            return Some(path.to_owned());
+        }
+        for binding in self
+            .source_bindings
+            .get(path)
+            .into_iter()
+            .flatten()
+            .filter(|binding| binding.local == leaf)
+        {
+            let Some(file) = self
+                .resolve_import(&binding.module, "rust", path)
+                .and_then(|id| self.node(&id))
+                .and_then(|node| node.path.clone())
+            else {
+                continue;
+            };
+            if files.contains(&file) {
+                return Some(file);
+            }
+        }
+        match files.as_slice() {
+            [only] => Some(only.clone()),
+            _ => None,
+        }
+    }
+
     /// `Type::func(..)` yields `Type` when `func` is declared to return `Self`
     /// or `Type` (behind `?`, also `Result<..>`/`Option<..>` of either).
     fn rust_constructed_type(
@@ -1778,13 +2018,14 @@ impl ScanState {
         func: &str,
         fallible: bool,
         call: &RustCall,
+        path: &str,
     ) -> Option<String> {
         let ty = if ty == "Self" {
             call.self_type.clone()?
         } else {
             ty.to_owned()
         };
-        let id = self.rust_method(&ty, func).ok()?;
+        let id = self.rust_method(&ty, func, path).ok()?;
         let returns = self.rust.returns.get(&id)?;
         let returns_type = |value: &str| value == "Self" || value == ty;
         let direct = returns_type(returns);
@@ -1986,10 +2227,18 @@ impl ScanState {
                 }
             }
             "dart" => {
-                if name.contains(':') {
+                if let Some(rest) = name.strip_prefix("package:") {
+                    // Only this repository's own package maps into it: `lib/<rest>`.
+                    let (package, rest) = rest.split_once('/')?;
+                    if self.dart_package.as_deref() != Some(package) {
+                        return None;
+                    }
+                    paths.push(normalize_import_path(&format!("lib/{rest}"))?);
+                } else if name.contains(':') {
                     return None;
+                } else {
+                    paths.push(local()?);
                 }
-                paths.push(local()?);
             }
             "cpp" | "p4" => {
                 if language == "cpp" && !name.contains('/') && Path::new(name).extension().is_none()
diff --git a/src/source.rs b/src/source.rs
index 8228191..31726aa 100644
--- a/src/source.rs
+++ b/src/source.rs
@@ -30,6 +30,9 @@ pub(crate) struct Declaration {
     /// Rust outer attributes that may register the item with a framework
     /// (`test`, `tokio::main`, `tool`, ...), excluding lint/doc/cfg attributes.
     pub attributes: Vec<String>,
+    /// C/C++: inside an `#elif`/`#else` branch. Which branch is compiled is
+    /// unknown, so such declarations are structure, never resolution targets.
+    pub preprocessor_alternative: bool,
 }
 
 pub(crate) struct ImportBinding {
@@ -129,8 +132,61 @@ pub(crate) fn supports(language: &str) -> bool {
     )
 }
 
+/// Inside an `#elif`/`#else` branch of a conditional. Brick does not evaluate
+/// preprocessor conditions, so only the first branch is treated as live. The
+/// directive lines are tracked textually: conditions such as
+/// `#if __has_include(<x>)` leave tree-sitter with an error-recovered tree
+/// that has no `preproc_else` node to find.
+fn in_preprocessor_alternative(node: Node<'_>, alternative_lines: &[bool]) -> bool {
+    alternative_lines
+        .get(node.start_position().row)
+        .copied()
+        .unwrap_or(false)
+}
+
+/// Per 0-based line: inside a non-first branch of some enclosing conditional.
+fn preprocessor_alternative_lines(source: &str) -> Vec<bool> {
+    // One entry per open conditional: the index of the branch being read.
+    let mut branches: Vec<usize> = Vec::new();
+    source
+        .lines()
+        .map(|line| {
+            let directive = line.trim_start();
+            let directive = directive
+                .strip_prefix('#')
+                .map(|rest| rest.trim_start())
+                .unwrap_or("");
+            let word = directive
+                .split(|c: char| !c.is_ascii_alphanumeric() && c != '_')
+                .next()
+                .unwrap_or("");
+            match word {
+                "if" | "ifdef" | "ifndef" => {
+                    let alternative = branches.iter().any(|&branch| branch > 0);
+                    branches.push(0);
+                    alternative
+                }
+                "elif" | "elifdef" | "elifndef" | "else" => {
+                    if let Some(branch) = branches.last_mut() {
+                        *branch += 1;
+                    }
+                    true
+                }
+                "endif" => {
+                    branches.pop();
+                    branches.iter().any(|&branch| branch > 0)
+                }
+                _ => branches.iter().any(|&branch| branch > 0),
+            }
+        })
+        .collect()
+}
+
 pub(crate) fn extract(language: &str, path: &str, source: &str) -> Result<Document> {
     let (grammar, version) = match language {
+        // `.c` shares the C/C++ extraction path (and header index) but must parse
+        // as C: identifiers such as `new`, `delete` or `class` are valid C.
+        "cpp" if path.ends_with(".c") => (tree_sitter_c::LANGUAGE, "c:0.24.2"),
         "cpp" => (tree_sitter_cpp::LANGUAGE, "cpp:0.23.4"),
         "rust" => (tree_sitter_rust::LANGUAGE, "rust:0.24.2"),
         "javascript" => (tree_sitter_javascript::LANGUAGE, "javascript:0.25.0"),
@@ -144,6 +200,11 @@ pub(crate) fn extract(language: &str, path: &str, source: &str) -> Result<Docume
         "dart" => (tree_sitter_dart::LANGUAGE, "dart:0.2.0"),
         _ => anyhow::bail!("unsupported grammar: {language}"),
     };
+    let alternative_lines = if language == "cpp" {
+        preprocessor_alternative_lines(source)
+    } else {
+        Vec::new()
+    };
     let mut parser = Parser::new();
     parser
         .set_language(&grammar.into())
@@ -181,6 +242,9 @@ pub(crate) fn extract(language: &str, path: &str, source: &str) -> Result<Docume
     // Iterative traversal avoids a Rust stack overflow on deeply nested source.
     // Error subtrees are omitted; complete sibling declarations remain usable.
     let mut nodes = Vec::new();
+    // Parent of every traversed node. tree-sitter's `Node::parent` re-descends from
+    // the root (O(depth)), so ancestor walks through it were quadratic in nesting.
+    let mut parents: HashMap<usize, Node<'_>> = HashMap::new();
     let mut errors: Vec<(usize, usize)> = Vec::new();
     let mut stack = vec![tree.root_node()];
     while let Some(node) = stack.pop() {
@@ -251,6 +315,9 @@ pub(crate) fn extract(language: &str, path: &str, source: &str) -> Result<Docume
         }
         let mut cursor = node.walk();
         let children: Vec<_> = node.named_children(&mut cursor).collect();
+        for child in &children {
+            parents.insert(child.id(), node);
+        }
         stack.extend(children.into_iter().rev());
     }
     // Anonymous MISSING tokens (`#endif`, `;`, `}`) are not named children; find
@@ -304,7 +371,11 @@ pub(crate) fn extract(language: &str, path: &str, source: &str) -> Result<Docume
                 ),
                 None => (name.clone(), String::new(), None, false),
             };
-            if let Some(qualified) = &qualified_name {
+            let preprocessor_alternative =
+                language == "cpp" && in_preprocessor_alternative(node, &alternative_lines);
+            if let Some(qualified) = &qualified_name
+                && !preprocessor_alternative
+            {
                 doc.declared.push(qualified.clone());
             }
             let (impl_type, impl_trait) = if language == "rust" {
@@ -323,13 +394,14 @@ pub(crate) fn extract(language: &str, path: &str, source: &str) -> Result<Docume
                 Vec::new()
             };
             doc.declarations.push(Declaration {
+                preprocessor_alternative,
                 is_virtual,
                 attributes,
                 exports: exported_names(node, &name),
                 name,
                 kind,
                 owner: None,
-                scope: lexical_scope(node, source),
+                scope: lexical_scope(node, source, &parents),
                 line: node.start_position().row + 1,
                 identity,
                 qualifier,
@@ -352,7 +424,7 @@ pub(crate) fn extract(language: &str, path: &str, source: &str) -> Result<Docume
                 let ty = ancestor
                     .child_by_field_name("type")
                     .map(|n| base_type(n, source));
-                let scope = lexical_scope(ancestor, source);
+                let scope = lexical_scope(ancestor, source, &parents);
                 let candidates: Vec<_> = doc
                     .declarations
                     .iter()
@@ -365,7 +437,13 @@ pub(crate) fn extract(language: &str, path: &str, source: &str) -> Result<Docume
                                 declaration_nodes[*i],
                                 &declarations,
                                 &doc.declarations,
-                            ) == enclosing_function(ancestor, &declarations, &doc.declarations)
+                                &parents,
+                            ) == enclosing_function(
+                                ancestor,
+                                &declarations,
+                                &doc.declarations,
+                                &parents,
+                            )
                     })
                     .map(|(i, _)| i)
                     .collect();
@@ -408,8 +486,8 @@ pub(crate) fn extract(language: &str, path: &str, source: &str) -> Result<Docume
         {
             continue;
         }
-        let owner = enclosing_function(node, &declarations, &doc.declarations);
-        let scope = lexical_scope(node, source);
+        let owner = enclosing_function(node, &declarations, &doc.declarations, &parents);
+        let scope = lexical_scope(node, source, &parents);
         if language == "rust" && node.kind() == "use_declaration" && !has_error(node) {
             for (target, binding) in rust_imports(node, source) {
                 if owner.is_none() {
@@ -440,6 +518,7 @@ pub(crate) fn extract(language: &str, path: &str, source: &str) -> Result<Docume
         }
         if language == "cpp" {
             if !has_error(node)
+                && !in_preprocessor_alternative(node, &alternative_lines)
                 && let Some(prototype) = cpp_prototype(node, source)
             {
                 if cpp_is_virtual(node) {
@@ -472,7 +551,7 @@ pub(crate) fn extract(language: &str, path: &str, source: &str) -> Result<Docume
             for (target, line) in cpp_vexing_calls(node, source) {
                 doc.relationships.push(Relationship {
                     owner,
-                    shadowed: parameter_shadows(node, &target, source),
+                    shadowed: parameter_shadows(node, &target, source, &parents),
                     target,
                     kind: EdgeKind::Calls,
                     member: false,
@@ -513,6 +592,7 @@ pub(crate) fn extract(language: &str, path: &str, source: &str) -> Result<Docume
             if node.kind() == "macro_invocation" {
                 let context = MacroContext {
                     position: node,
+                    parents: &parents,
                     owner,
                     scope: &scope,
                     self_type: &self_type,
@@ -565,7 +645,7 @@ pub(crate) fn extract(language: &str, path: &str, source: &str) -> Result<Docume
                     None
                 };
                 doc.relationships.push(Relationship {
-                    shadowed: !member && parameter_shadows(node, &target, source),
+                    shadowed: !member && parameter_shadows(node, &target, source, &parents),
                     owner,
                     target,
                     member,
@@ -765,8 +845,20 @@ fn cpp_leaf_name(name: Node<'_>, source: &str) -> Option<String> {
     Some(text(name, source).to_owned())
 }
 
-fn lexical_scope(node: Node<'_>, source: &str) -> String {
-    let mut parent = node.parent();
+/// The parent recorded during traversal, else tree-sitter's (O(depth)) lookup.
+fn parent_of<'tree>(
+    node: Node<'tree>,
+    parents: &HashMap<usize, Node<'tree>>,
+) -> Option<Node<'tree>> {
+    parents.get(&node.id()).copied().or_else(|| node.parent())
+}
+
+fn lexical_scope<'tree>(
+    node: Node<'tree>,
+    source: &str,
+    parents: &HashMap<usize, Node<'tree>>,
+) -> String {
+    let mut parent = parent_of(node, parents);
     let mut names = Vec::new();
     while let Some(n) = parent {
         if matches!(
@@ -779,25 +871,26 @@ fn lexical_scope(node: Node<'_>, source: &str) -> String {
                     .unwrap_or("<anonymous>"),
             );
         }
-        parent = n.parent();
+        parent = parent_of(n, parents);
     }
     names.reverse();
     names.join("::")
 }
 
-fn enclosing_function(
-    node: Node<'_>,
+fn enclosing_function<'tree>(
+    node: Node<'tree>,
     ids: &HashMap<usize, usize>,
     declarations: &[Declaration],
+    parents: &HashMap<usize, Node<'tree>>,
 ) -> Option<usize> {
-    let mut parent = node.parent();
+    let mut parent = parent_of(node, parents);
     while let Some(n) = parent {
         if let Some(&index) = ids.get(&n.id())
             && declarations[index].kind == NodeKind::Function
         {
             return Some(index);
         }
-        parent = n.parent();
+        parent = parent_of(n, parents);
     }
     None
 }
@@ -869,7 +962,24 @@ fn bases(node: Node<'_>, source: &str) -> Vec<String> {
             child.kind(),
             "base_class_clause" | "class_heritage" | "superclass" | "extends_type_clause"
         ) {
-            let mut stack = vec![child];
+            let mut stack = Vec::new();
+            if child.kind() == "superclass" {
+                // tree-sitter-dart gives `extends Bloc<Ev, St>` as sibling `type`
+                // fields: the first is the base, later ones are its type arguments.
+                let mut first_type = true;
+                let mut c = child.walk();
+                for part in child.named_children(&mut c) {
+                    if part.kind() == "type" {
+                        if !first_type {
+                            continue;
+                        }
+                        first_type = false;
+                    }
+                    stack.push(part);
+                }
+            } else {
+                stack.push(child);
+            }
             while let Some(base) = stack.pop() {
                 if matches!(
                     base.kind(),
@@ -882,8 +992,20 @@ fn bases(node: Node<'_>, source: &str) -> Vec<String> {
                     result.push(base_type(base, source));
                     continue;
                 }
+                // Type arguments name parameters of the base, not further bases:
+                // `extends Bloc<Ev, St>` / `: public Base<Arg>` inherit only Bloc/Base.
+                if matches!(
+                    base.kind(),
+                    "type_arguments" | "template_argument_list" | "type_parameters"
+                ) {
+                    continue;
+                }
                 let mut c = base.walk();
-                stack.extend(base.named_children(&mut c));
+                let nested_type_arguments = base.kind() == "type";
+                stack.extend(
+                    base.named_children(&mut c)
+                        .filter(|part| !(nested_type_arguments && part.kind() == "type")),
+                );
             }
         }
     }
@@ -927,8 +1049,13 @@ fn exported_names(node: Node<'_>, name: &str) -> Vec<String> {
     Vec::new()
 }
 
-fn parameter_shadows(node: Node<'_>, name: &str, source: &str) -> bool {
-    let mut parent = node.parent();
+fn parameter_shadows<'tree>(
+    node: Node<'tree>,
+    name: &str,
+    source: &str,
+    parents: &HashMap<usize, Node<'tree>>,
+) -> bool {
+    let mut parent = parent_of(node, parents);
     while let Some(n) = parent {
         let signature = n
             .child_by_field_name("signature")
@@ -962,7 +1089,7 @@ fn parameter_shadows(node: Node<'_>, name: &str, source: &str) -> bool {
                 );
             }
         }
-        parent = n.parent();
+        parent = parent_of(n, parents);
     }
     false
 }
@@ -994,7 +1121,7 @@ fn import_bindings(node: Node<'_>, module: &str, source: &str) -> Vec<ImportBind
                 local: local.into(),
                 exported: exported.into(),
                 module: module.into(),
-                scope: lexical_scope(node, source),
+                scope: lexical_scope(node, source, &HashMap::new()),
             });
         }
         let mut cursor = n.walk();
@@ -1064,7 +1191,7 @@ fn rust_imports(node: Node<'_>, source: &str) -> Vec<(String, Option<ImportBindi
                         local,
                         exported: exported.into(),
                         module: module.into(),
-                        scope: lexical_scope(node, source),
+                        scope: lexical_scope(node, source, &HashMap::new()),
                     })
                 };
                 output.push((target, binding));
@@ -1751,6 +1878,7 @@ fn rust_fields(node: Node<'_>, source: &str) -> Vec<(String, String, CppType)> {
 
 struct MacroContext<'a, 'tree> {
     position: Node<'tree>,
+    parents: &'a HashMap<usize, Node<'tree>>,
     owner: Option<usize>,
     scope: &'a str,
     self_type: &'a Option<String>,
@@ -1847,7 +1975,12 @@ fn rust_macro_calls(
                 });
                 relationships.push(Relationship {
                     shadowed: !member
-                        && parameter_shadows(context.position, &target, context.source),
+                        && parameter_shadows(
+                            context.position,
+                            &target,
+                            context.source,
+                            context.parents,
+                        ),
                     owner: context.owner,
                     target,
                     member,
diff --git a/tests/cpp_xtu.rs b/tests/cpp_xtu.rs
index f2e2ebe..1ecdb0b 100644
--- a/tests/cpp_xtu.rs
+++ b/tests/cpp_xtu.rs
@@ -326,3 +326,110 @@ fn brace_default_arguments_do_not_hide_prototypes_or_report_errors() {
     assert_eq!(reason, None);
     assert!(model.diagnostics.is_empty(), "{:?}", model.diagnostics);
 }
+
+#[test]
+fn two_using_directives_naming_the_same_function_are_ambiguous() {
+    // With `using namespace a; using namespace b;` and both `a::run` and `b::run`
+    // defined, the call resolved to whichever directive came first. C++ makes that
+    // ambiguous (or an overload choice Brick cannot make), so it must stay external.
+    let model = scan_files(&[
+        ("src/a.h", "namespace a { int run(int x); }\n"),
+        ("src/b.h", "namespace b { int run(int x); }\n"),
+        (
+            "src/defs.cpp",
+            "#include \"a.h\"\n#include \"b.h\"\nnamespace a { int run(int x) { return x; } }\nnamespace b { int run(int x) { return -x; } }\n",
+        ),
+        (
+            "src/main.cpp",
+            "#include \"a.h\"\n#include \"b.h\"\nusing namespace a;\nusing namespace b;\nint main() { return run(1); }\n",
+        ),
+        // Clean negative: one directive still resolves with its label.
+        (
+            "src/only_a.cpp",
+            "#include \"a.h\"\nusing namespace a;\nint only() { return run(1); }\n",
+        ),
+    ]);
+    let (target, reason) = single_call(&model, function(&model, "src/main.cpp", "main"));
+    assert_eq!(target.kind, NodeKind::External);
+    assert_eq!(reason.as_deref(), Some("ambiguous"));
+    let (target, reason) = single_call(&model, function(&model, "src/only_a.cpp", "only"));
+    assert_eq!(target.path.as_deref(), Some("src/defs.cpp"));
+    assert_eq!(reason, None);
+}
+
+#[test]
+fn preprocessor_alternative_branches_are_not_call_targets() {
+    // An `#else` fallback (yams' spdlog stubs in InternalEventBus.h) was indexed as
+    // live, so every spdlog::warn call site in the repository resolved to the stub and
+    // the stubs became false hubs. Brick cannot know which branch is active, so only
+    // the first branch may be a resolution target.
+    let model = scan_files(&[
+        (
+            "include/log.h",
+            "#if __has_include(<spdlog/spdlog.h>)\n#include <spdlog/spdlog.h>\n#elif defined(ALT)\nnamespace spdlog { inline void info(const char*) {} }\n#else\nnamespace spdlog { inline void warn(const char*) {} }\n#endif\n#ifndef LOG_H\n#define LOG_H\nnamespace app { inline int level() { return 1; } }\n#endif\n",
+        ),
+        (
+            "src/main.cpp",
+            "#include \"log.h\"\nint main() { spdlog::warn(\"x\"); spdlog::info(\"y\"); return app::level(); }\n",
+        ),
+    ]);
+    let found = calls(&model, function(&model, "src/main.cpp", "main"));
+    let mut by_name: Vec<(String, NodeKind, Option<String>)> = found
+        .iter()
+        .map(|(node, reason)| (node.name.clone(), node.kind, reason.clone()))
+        .collect();
+    by_name.sort_by(|a, b| a.0.cmp(&b.0));
+    // First-branch (include-guard) code still resolves; the alternatives do not.
+    assert!(
+        by_name
+            .iter()
+            .any(|(name, kind, _)| name == "level" && *kind == NodeKind::Function)
+    );
+    for (name, kind, _) in &by_name {
+        if name.ends_with("warn") || name.ends_with("info") {
+            assert_eq!(
+                *kind,
+                NodeKind::External,
+                "{name} resolved into an #else/#elif branch"
+            );
+        }
+    }
+    let stub = model
+        .nodes
+        .iter()
+        .find(|n| n.kind == NodeKind::Function && n.name == "warn")
+        .expect("alternative branches stay visible as structure");
+    assert_eq!(
+        stub.attributes
+            .get("source.preprocessor-branch")
+            .and_then(|v| v.as_str()),
+        Some("alternative")
+    );
+}
+
+#[test]
+fn c_sources_parse_with_the_c_grammar() {
+    // `.c` files went through the C++ grammar, so valid C using C++ keywords as
+    // identifiers produced grammar-error diagnostics and damaged extraction.
+    let model = scan_files(&[
+        ("src/util.h", "int twice(int new);\n"),
+        (
+            "src/util.c",
+            "#include \"util.h\"\nint twice(int new) { int delete = new; return delete * 2; }\n",
+        ),
+        (
+            "src/main.c",
+            "#include \"util.h\"\nint main(void) { int class = 1; return twice(class); }\n",
+        ),
+    ]);
+    let grammar_errors: Vec<_> = model
+        .diagnostics
+        .iter()
+        .filter(|d| d.path.as_deref().is_some_and(|p| p.ends_with(".c")))
+        .map(|d| d.message.clone())
+        .collect();
+    assert!(grammar_errors.is_empty(), "{grammar_errors:?}");
+    let (target, reason) = single_call(&model, function(&model, "src/main.c", "main"));
+    assert_eq!(target.path.as_deref(), Some("src/util.c"));
+    assert_eq!(reason, None);
+}
diff --git a/tests/diff_cli.rs b/tests/diff_cli.rs
index e732ebb..19c09cb 100644
--- a/tests/diff_cli.rs
+++ b/tests/diff_cli.rs
@@ -259,3 +259,97 @@ fn relocated_artifacts_compare_after_checkouts_are_deleted() {
         );
     }
 }
+
+#[test]
+fn check_recomputes_metrics_instead_of_trusting_the_file() {
+    // `check` gated on the metrics stored in the JSON, so editing `cycle_count` and
+    // `score` turned a failing gate into a pass without changing the graph.
+    let directory = tempfile::tempdir().unwrap();
+    let project = directory.path().join("project");
+    fs::create_dir(&project).unwrap();
+    fs::write(
+        project.join("lib.rs"),
+        "pub fn alpha() { beta(); }\nfn beta() { alpha(); }\n",
+    )
+    .unwrap();
+    let model = scan::scan(&project).unwrap();
+    assert!(model.metrics.cycle_count > 0);
+    let honest = directory.path().join("honest.json");
+    write_model(&honest, &model);
+    let gate = |path: &Path| {
+        Command::new(env!("CARGO_BIN_EXE_brick"))
+            .args([
+                "check",
+                path.to_str().unwrap(),
+                "--max-cycles",
+                "0",
+                "--min-score",
+                "0",
+            ])
+            .output()
+            .unwrap()
+    };
+    assert!(!gate(&honest).status.success());
+
+    let mut value: Value = serde_json::to_value(&model).unwrap();
+    value["metrics"]["cycle_count"] = 0.into();
+    value["metrics"]["structural_health"]["score"] = 100.0.into();
+    let tampered = directory.path().join("tampered.json");
+    fs::write(&tampered, serde_json::to_vec_pretty(&value).unwrap()).unwrap();
+    let output = gate(&tampered);
+    assert!(!output.status.success(), "tampered metrics passed the gate");
+    let text = format!(
+        "{}{}",
+        String::from_utf8_lossy(&output.stdout),
+        String::from_utf8_lossy(&output.stderr)
+    );
+    assert!(text.contains("stored metrics"), "{text}");
+}
+
+#[test]
+fn a_scan_with_no_supported_source_is_reported_and_fails_check() {
+    // A Go/Java-only directory built "1 nodes / 0 edges; score 100.0" with no
+    // diagnostic, and `check --min-score 90 --max-cycles 0` passed: an analysis of
+    // nothing looked like a perfectly healthy repository.
+    let directory = tempfile::tempdir().unwrap();
+    let project = directory.path().join("project");
+    fs::create_dir(&project).unwrap();
+    fs::write(project.join("main.go"), "package main\nfunc main() {}\n").unwrap();
+    fs::write(project.join("App.java"), "class App {}\n").unwrap();
+    let json = directory.path().join("model.json");
+    let html = directory.path().join("model.html");
+    let build = Command::new(env!("CARGO_BIN_EXE_brick"))
+        .args([
+            "build",
+            project.to_str().unwrap(),
+            "--json",
+            json.to_str().unwrap(),
+            "--html",
+            html.to_str().unwrap(),
+        ])
+        .output()
+        .unwrap();
+    assert!(build.status.success());
+    let stderr = String::from_utf8_lossy(&build.stderr);
+    assert!(stderr.contains("no supported source files"), "{stderr}");
+    let model: Value = serde_json::from_slice(&fs::read(&json).unwrap()).unwrap();
+    assert!(
+        model["diagnostics"]
+            .as_array()
+            .is_some_and(|d| d.iter().any(|d| d["message"]
+                .as_str()
+                .is_some_and(|m| m.contains("no supported source files"))))
+    );
+    let check = Command::new(env!("CARGO_BIN_EXE_brick"))
+        .args([
+            "check",
+            json.to_str().unwrap(),
+            "--min-score",
+            "90",
+            "--max-cycles",
+            "0",
+        ])
+        .output()
+        .unwrap();
+    assert!(!check.status.success(), "an empty model passed check");
+}
diff --git a/tests/languages.rs b/tests/languages.rs
index 8c174c6..c26f721 100644
--- a/tests/languages.rs
+++ b/tests/languages.rs
@@ -539,3 +539,193 @@ fn cpp_parent_relative_includes_resolve_without_basename_fallback() {
             .any(|n| n.kind == NodeKind::External && n.name == "../missing/base.h")
     );
 }
+
+#[test]
+fn generic_type_arguments_are_not_base_classes() {
+    // `extends Bloc<Ev, St>` produced inherits edges to Ev and St: the base walker
+    // descended into the type-argument list. On pipe 39 of 145 Dart inherits edges
+    // (27%) pointed at type arguments. C++ `: public Base<Arg>` shared the walker.
+    let (_, model) = project(&[
+        (
+            "lib/bloc.dart",
+            "class Ev {}\nclass St {}\nclass Bloc<E, S> {}\nclass MyBloc extends Bloc<Ev, St> {}\n",
+        ),
+        (
+            "src/base.cpp",
+            "template <class T> class Base {};\nclass Arg {};\nclass Derived : public Base<Arg> {};\n",
+        ),
+    ]);
+    let inherits = |source: &Node| {
+        let mut names: Vec<String> = model
+            .edges
+            .iter()
+            .filter(|e| e.kind == EdgeKind::Inherits && e.source == source.id)
+            .map(|e| {
+                model
+                    .nodes
+                    .iter()
+                    .find(|n| n.id == e.target)
+                    .unwrap()
+                    .name
+                    .clone()
+            })
+            .collect();
+        names.sort();
+        names
+    };
+    assert_eq!(
+        inherits(symbol(&model, "lib/bloc.dart", "MyBloc")),
+        ["Bloc"]
+    );
+    assert_eq!(
+        inherits(symbol(&model, "src/base.cpp", "Derived")),
+        ["Base"]
+    );
+}
+
+#[test]
+fn python_calls_keep_their_function_and_resolve_only_what_is_visible() {
+    let (_, model) = project(&[
+        (
+            "pkg/a.py",
+            "def process(x):\n    return x\n\ndef unrelated():\n    pass\n",
+        ),
+        (
+            "pkg/b.py",
+            "class Base:\n    pass\n\ndef helper():\n    pass\n",
+        ),
+        (
+            "pkg/c.py",
+            // A blank line and a comment inside the body used to pop the function
+            // scope, attributing the later calls to the file.
+            "from pkg.b import Base\n\nclass Child(Base):\n    def go(self):\n        x = 1\n\n        # comment\n        helper()\n        process(1)\n        unrelated()\n",
+        ),
+        (
+            "pkg/d.py",
+            "from pkg.a import process\n\ndef use():\n    return process(2)\n",
+        ),
+    ]);
+    let go = symbol(&model, "pkg/c.py", "go");
+    let outgoing = |source: &Node| {
+        let mut found: Vec<(String, String)> = model
+            .edges
+            .iter()
+            .filter(|e| e.kind == EdgeKind::Calls && e.source == source.id)
+            .map(|e| {
+                let target = model.nodes.iter().find(|n| n.id == e.target).unwrap();
+                (target.name.clone(), target.path.clone().unwrap_or_default())
+            })
+            .collect();
+        found.sort();
+        found
+    };
+    // helper comes from the imported pkg/b.py; process and unrelated are never
+    // imported by c.py, so they stay external instead of resolving by unique name.
+    assert_eq!(
+        outgoing(go),
+        [
+            ("helper".to_owned(), "pkg/b.py".to_owned()),
+            ("process".to_owned(), String::new()),
+            ("unrelated".to_owned(), String::new()),
+        ]
+    );
+    // An imported name still resolves across files.
+    assert_eq!(
+        outgoing(symbol(&model, "pkg/d.py", "use")),
+        [("process".to_owned(), "pkg/a.py".to_owned())]
+    );
+    // A class header is not a call.
+    let file_c = model
+        .nodes
+        .iter()
+        .find(|n| n.kind == NodeKind::File && n.path.as_deref() == Some("pkg/c.py"))
+        .unwrap();
+    assert!(
+        !model
+            .edges
+            .iter()
+            .any(|e| e.kind == EdgeKind::Calls && e.source == file_c.id),
+        "file-level call edges in pkg/c.py"
+    );
+}
+
+#[test]
+fn dart_calls_resolve_through_imported_libraries() {
+    // Dart imports expose a library's public top-level names without a binding per
+    // name, so no cross-file Dart call ever resolved even when its import did.
+    let (_, model) = project(&[
+        ("pubspec.yaml", "name: demo\n"),
+        (
+            "lib/util.dart",
+            "int helper() => 1;\nint _secret() => 2;\nclass Tool { int use() => 3; }\n",
+        ),
+        ("lib/other.dart", "int shared() => 4;\n"),
+        ("lib/twin.dart", "int shared() => 5;\n"),
+        (
+            "lib/main.dart",
+            "import 'util.dart';\nimport 'package:demo/other.dart';\nimport 'twin.dart';\nvoid run() {\n  helper();\n  _secret();\n  shared();\n}\n",
+        ),
+        // Clean negative: no import, no edge.
+        ("lib/stranger.dart", "void stray() {\n  helper();\n}\n"),
+    ]);
+    let targets = |source: &Node| {
+        let mut found: Vec<(String, String, String)> = model
+            .edges
+            .iter()
+            .filter(|e| e.kind == EdgeKind::Calls && e.source == source.id)
+            .map(|e| {
+                let target = model.nodes.iter().find(|n| n.id == e.target).unwrap();
+                (
+                    target.name.clone(),
+                    target.path.clone().unwrap_or_default(),
+                    e.attributes
+                        .get("source.unresolved-reason")
+                        .and_then(|v| v.as_str())
+                        .unwrap_or("")
+                        .to_owned(),
+                )
+            })
+            .collect();
+        found.sort();
+        found
+    };
+    assert_eq!(
+        targets(symbol(&model, "lib/main.dart", "run")),
+        [
+            ("_secret".into(), String::new(), "not-visible".into()),
+            ("helper".into(), "lib/util.dart".into(), String::new()),
+            ("shared".into(), String::new(), "ambiguous".into()),
+        ]
+    );
+    assert_eq!(
+        targets(symbol(&model, "lib/stranger.dart", "stray")),
+        [("helper".into(), String::new(), "not-visible".into())]
+    );
+}
+
+#[test]
+fn a_non_utf8_byte_does_not_drop_the_whole_file() {
+    // One Latin-1 `é` in a comment made the whole file (and its functions) vanish.
+    let dir = tempfile::tempdir().unwrap();
+    let mut source = b"// caf".to_vec();
+    source.push(0xE9);
+    source.extend_from_slice(b"\nfn kept() {}\nfn caller() { kept(); }\n");
+    fs::write(dir.path().join("latin1.rs"), source).unwrap();
+    fs::write(dir.path().join("blob.rs"), [0u8, 159, 146, 150]).unwrap();
+    let model = scan::scan(dir.path()).unwrap();
+    let caller = symbol(&model, "latin1.rs", "caller");
+    assert!(calls(&model, caller, symbol(&model, "latin1.rs", "kept")));
+    assert!(
+        model
+            .diagnostics
+            .iter()
+            .any(|d| d.path.as_deref() == Some("latin1.rs") && d.message.contains("non-UTF-8"))
+    );
+    // A file with NUL bytes is binary, not source: still skipped with a diagnostic.
+    assert!(
+        !model
+            .nodes
+            .iter()
+            .any(|n| n.path.as_deref() == Some("blob.rs"))
+    );
+}
diff --git a/tests/rust_methods.rs b/tests/rust_methods.rs
index fdd79a3..72849b2 100644
--- a/tests/rust_methods.rs
+++ b/tests/rust_methods.rs
@@ -153,3 +153,52 @@ fn foreign_imports_generics_and_competing_trait_impls_never_guess() {
         );
     }
 }
+
+#[test]
+fn same_named_types_in_different_modules_resolve_through_use_bindings() {
+    // Types were keyed by leaf name, so `b::Config` (method from a trait impl) and
+    // `a::Config` (inherent method) shared one key and the inherent one won: a call on
+    // `b::Config` was attributed to `a::Config::load`.
+    let model = scan_files(&[
+        ("src/lib.rs", "pub mod a;\npub mod b;\npub mod user;\n"),
+        (
+            "src/a.rs",
+            "pub struct Config;\nimpl Config {\n    pub fn load(&self) -> u32 { 1 }\n}\n",
+        ),
+        (
+            "src/b.rs",
+            "pub struct Config;\npub trait Loader { fn load(&self) -> u32; }\nimpl Loader for Config {\n    fn load(&self) -> u32 { 2 }\n}\n",
+        ),
+        (
+            "src/user.rs",
+            "use crate::b::Config;\nuse crate::b::Loader;\npub fn run(c: &Config) -> u32 { c.load() }\n",
+        ),
+        (
+            "src/other.rs",
+            "pub fn guess(c: &Config) -> u32 { c.load() }\n",
+        ),
+    ]);
+    let targets = |source: &Node| {
+        model
+            .edges
+            .iter()
+            .filter(|e| e.kind == EdgeKind::Calls && e.source == source.id)
+            .map(|e| {
+                let target = model.nodes.iter().find(|n| n.id == e.target).unwrap();
+                (
+                    target.path.clone().unwrap_or_default(),
+                    e.attributes
+                        .get("source.unresolved-reason")
+                        .and_then(|v| v.as_str())
+                        .unwrap_or("")
+                        .to_owned(),
+                )
+            })
+            .collect::<Vec<_>>()
+    };
+    let run = function(&model, "src/user.rs", "run");
+    assert_eq!(targets(run), [("src/b.rs".to_owned(), String::new())]);
+    // Without a binding, two same-named types leave the call ambiguous, not guessed.
+    let guess = function(&model, "src/other.rs", "guess");
+    assert_eq!(targets(guess), [(String::new(), "ambiguous".to_owned())]);
+}