diff --git a/cli/tri/src/main.rs b/cli/tri/src/main.rs
index e1469dcf51..8b459ce448 100644
--- a/cli/tri/src/main.rs
+++ b/cli/tri/src/main.rs
@@ -10,6 +10,7 @@ use std::process::Command;
 mod depin;
 mod discard;
 mod abandoned;
+mod orphaned;
 mod cibase;
 mod fleet;
 mod fpga;
@@ -147,6 +148,11 @@ enum Commands {
         #[command(subcommand)]
         action: quant::QuantCmd,
     },
+    /// Checks whose input is not in the tree.
+    Orphaned {
+        #[command(subcommand)]
+        action: orphaned::OrphanedCmd,
+    },
     /// What the parser reads and throws away, ranked against its pinned bound.
     Discard {
         #[command(subcommand)]
@@ -784,6 +790,7 @@ fn main() -> Result<()> {
         Commands::Abandoned { action } => abandoned::run(action)?,
         Commands::Types { action } => types_dup::run(action)?,
         Commands::Quantifiers { action } => quant::run(action)?,
+        Commands::Orphaned { action } => orphaned::run(action)?,
         Commands::Discard { action } => discard::run(action)?,
         Commands::Seals { action } => seals::run(action)?,
         Commands::Hooks { action } => hooks::run(action)?,
diff --git a/cli/tri/src/orphaned.rs b/cli/tri/src/orphaned.rs
new file mode 100644
index 0000000000..957ef23c32
--- /dev/null
+++ b/cli/tri/src/orphaned.rs
@@ -0,0 +1,352 @@
+//! Checks whose input is not there.
+//!
+//! WHY THIS EXISTS
+//! ---------------
+//! The catalog gate's field-by-field comparison had never run. `gen/` is
+//! gitignored and a cleanup commit untracked the artifacts it read, so the check
+//! was left with nothing -- and it reported that into a variable the master gate
+//! does not print. Zero occurrences of the word in the output of the command
+//! that gates master (W702).
+//!
+//! **Removing a check's input does not make it fail. It makes it quiet.** That
+//! is a shape, not an incident, and this looks for it.
+//!
+//! WHAT IT LOOKS FOR
+//! -----------------
+//! Path-shaped string literals in gate and tool sources whose path does not
+//! exist in the tree, EXCLUDING the ones that are supposed to be absent:
+//!
+//!   * fixtures inside a self-check or a test module -- `specs/a.t27`,
+//!     `docs/planted.md` and friends are planted into temp directories on
+//!     purpose, and a first version that did not exclude them reported 126 hits
+//!     of which almost none were real
+//!   * outputs the code WRITES rather than reads
+//!   * anything under `target/`, `/tmp`, or carrying a format placeholder
+//!
+//! THE CONTROL FAILED, AND THAT IS IN THE DOCUMENTATION RATHER THAN FIXED AWAY
+//! ---------------------------------------------------------------------------
+//! Run against the commit before W702's fix, this command does **not** find the
+//! case it was written for. The pre-fix code built the path as
+//!
+//!     let json = emitted.join("formats_catalog.json");   // no slash
+//!     ... .unwrap_or_else(|| Path::new("gen/numeric"))   // no extension
+//!
+//! Neither literal is a path by this command's test, and the assembled one never
+//! appears as a literal at all. **Zero of one on its founding case.**
+//!
+//! The window is not being widened until it says one. Following `join` chains
+//! through variables is a dataflow problem, and a heuristic stretched until it
+//! hits its own motivating example has stopped being evidence (skill 177).
+//!
+//! What it does find is a different and real class: an input named outright in
+//! production code that is not in the tree. That is how `public/index.html` was
+//! found -- the Railway HTTP server's static fallback and its 404 page both point
+//! at a directory that has never existed in any commit.
+//!
+//! WHAT IT CANNOT DO
+//! -----------------
+//! It cannot tell a check that is silent about a missing input from one that
+//! reports it properly -- that needs the control flow, not the literal. It marks
+//! a line `quiet?` when the nearest handling looks like a bare early return with
+//! no report, and that mark is a HINT for a human, never a verdict.
+//!
+//! It also cannot see a path built by concatenation. Everything here is a lower
+//! bound.
+use anyhow::{Context, Result};
+use clap::Subcommand;
+use std::path::{Path, PathBuf};
+
+#[derive(Subcommand)]
+pub enum OrphanedCmd {
+    /// List gate and tool sources that name an input which is not in the tree.
+    List {
+        /// Also print the fixture paths that were filtered out, to check the filter.
+        #[arg(long)]
+        show_filtered: bool,
+    },
+}
+
+/// Directories whose sources are gates, tools or the CLI itself.
+const ROOTS: [&str; 3] = ["tools", "bootstrap/src", "cli/tri/src"];
+
+/// A line is fixture context when it sits inside a self-check or a test module.
+/// Tracked by a simple depth counter rather than a parser: these files put
+/// `mod tests` and `def self_check` at column 0, and a counter that is wrong
+/// would show up as fixtures leaking back into the report.
+fn fixture_regions(text: &str) -> Vec<bool> {
+    let mut out = Vec::with_capacity(text.lines().count());
+    // Rust: a test module is a brace-delimited region. An indent rule cannot do
+    // this -- a first version set the region's indent from `#[test]` and then let
+    // the `fn` on the next line close it, so 41 fixture paths leaked back in.
+    let mut rust_depth: Option<i32> = None;
+    let mut depth: i32 = 0;
+    // Python: indentation is the structure, and a `def` at or shallower than the
+    // one that opened the region ends it.
+    let mut py_indent: Option<usize> = None;
+
+    for line in text.lines() {
+        let trimmed = line.trim_start();
+        let indent = line.len() - trimmed.len();
+
+        let opens_rust = trimmed.starts_with("#[cfg(test)]")
+            || trimmed.starts_with("mod tests")
+            || trimmed.starts_with("pub mod tests");
+        let opens_py = trimmed.starts_with("def self_check")
+            || trimmed.starts_with("def _self_check")
+            || trimmed.starts_with("def test_");
+
+        if opens_rust && rust_depth.is_none() {
+            rust_depth = Some(depth);
+        }
+        if opens_py && py_indent.is_none() {
+            py_indent = Some(indent);
+        }
+        if let Some(pi) = py_indent {
+            if !trimmed.is_empty() && indent <= pi && !opens_py && trimmed.starts_with("def ") {
+                py_indent = None;
+            }
+        }
+
+        let inside = rust_depth.is_some() || py_indent.is_some();
+        out.push(inside);
+
+        // Count braces AFTER recording, so the line that opens the module is
+        // itself inside it.
+        for c in line.chars() {
+            match c {
+                '{' => depth += 1,
+                '}' => depth -= 1,
+                _ => {}
+            }
+        }
+        if let Some(entry) = rust_depth {
+            // Back to the depth we entered at, and past the module body.
+            if depth <= entry && !opens_rust && trimmed.contains('}') {
+                rust_depth = None;
+            }
+        }
+    }
+    out
+}
+
+/// Extensions a repository file actually has. Without this, `v0.1` in a schema
+/// identifier and `github.io` in a repository name both read as paths -- they
+/// contain a slash and a dot, which is all the shape test asks for.
+const FILE_EXT: [&str; 22] = [
+    "py", "rs", "json", "md", "t27", "txt", "yml", "yaml", "toml", "sh", "html", "inc", "bin", "v",
+    "sv", "lean", "tex", "csv", "tsv", "log", "zig", "c",
+];
+
+fn looks_like_path(s: &str) -> bool {
+    let Some(file) = s.rsplit('/').next() else {
+        return false;
+    };
+    let Some((_, ext)) = file.rsplit_once('.') else {
+        return false;
+    };
+    s.contains('/')
+        && FILE_EXT.contains(&ext)
+        && !s.starts_with('/')
+        && !s.starts_with("target/")
+        && !s.starts_with("http")
+        && !s.contains('{')
+        && !s.contains('*')
+        && !s.contains(' ')
+        // Regex source is full of slashes and dots and is not a path.
+        && !s.contains('^')
+        && !s.contains('$')
+        && !s.contains('|')
+        && !s.contains('\\')
+        && !s.contains('(')
+        && !s.contains('?')
+        && !s.contains('+')
+        && s.len() > 4
+}
+
+/// Extract double-quoted literals from one line.
+fn literals(line: &str) -> Vec<String> {
+    let mut out = Vec::new();
+    let mut cur = String::new();
+    let mut inside = false;
+    let mut prev = '\0';
+    for c in line.chars() {
+        if c == '"' && prev != '\\' {
+            if inside {
+                out.push(std::mem::take(&mut cur));
+            }
+            inside = !inside;
+        } else if inside {
+            cur.push(c);
+        }
+        prev = c;
+    }
+    out
+}
+
+fn repo_root() -> Result<PathBuf> {
+    let out = std::process::Command::new("git")
+        .args(["rev-parse", "--show-toplevel"])
+        .output()
+        .context("running `git rev-parse --show-toplevel`")?;
+    if !out.status.success() {
+        anyhow::bail!("not inside a git repository");
+    }
+    Ok(PathBuf::from(String::from_utf8(out.stdout)?.trim()))
+}
+
+fn sources(root: &Path) -> Vec<PathBuf> {
+    let mut v = Vec::new();
+    for r in ROOTS {
+        let dir = root.join(r);
+        let Ok(rd) = std::fs::read_dir(&dir) else {
+            continue;
+        };
+        for e in rd.flatten() {
+            let p = e.path();
+            match p.extension().and_then(|x| x.to_str()) {
+                Some("py") | Some("rs") => v.push(p),
+                _ => {}
+            }
+        }
+    }
+    v.sort();
+    v
+}
+
+/// A hint, not a verdict: does the handling nearby look like a bare exit?
+fn looks_quiet(lines: &[&str], at: usize) -> bool {
+    let lo = at.saturating_sub(2);
+    let hi = (at + 6).min(lines.len());
+    let window = lines[lo..hi].join(" ");
+    let exits = window.contains("return")
+        || window.contains("continue")
+        || window.contains("Ok(())")
+        || window.contains("=> {}");
+    let reports = window.contains("bail")
+        || window.contains("findings.push")
+        || window.contains("FAIL")
+        || window.contains("eprintln")
+        || window.contains("panic")
+        || window.contains("exit(1")
+        || window.contains("exit(2");
+    exits && !reports
+}
+
+pub fn run(cmd: &OrphanedCmd) -> Result<()> {
+    let OrphanedCmd::List { show_filtered } = cmd;
+    let root = repo_root()?;
+    let mut hits = 0usize;
+    let mut filtered = 0usize;
+    let mut scanned = 0usize;
+
+    for src in sources(&root) {
+        let Ok(text) = std::fs::read_to_string(&src) else {
+            continue;
+        };
+        let fixture = fixture_regions(&text);
+        let lines: Vec<&str> = text.lines().collect();
+        let rel = src
+            .strip_prefix(&root)
+            .unwrap_or(&src)
+            .display()
+            .to_string();
+        for (i, line) in lines.iter().enumerate() {
+            let t = line.trim_start();
+            if t.starts_with("//") || t.starts_with('#') || t.starts_with('*') {
+                continue;
+            }
+            for lit in literals(line) {
+                if !looks_like_path(&lit) {
+                    continue;
+                }
+                scanned += 1;
+                if root.join(&lit).exists() {
+                    continue;
+                }
+                if fixture.get(i).copied().unwrap_or(false) {
+                    filtered += 1;
+                    if *show_filtered {
+                        println!("  filtered (fixture)  {}:{}  {}", rel, i + 1, lit);
+                    }
+                    continue;
+                }
+                hits += 1;
+                let quiet = if looks_quiet(&lines, i) {
+                    "  quiet?"
+                } else {
+                    ""
+                };
+                println!("  {}:{}{}", rel, i + 1, quiet);
+                println!("      names {} -- not in the tree", lit);
+                println!("      {}", t.trim_end());
+            }
+        }
+    }
+
+    println!();
+    println!(
+        "  {hits} absent input(s) named in production code; {filtered} fixture(s) filtered out of \
+         {scanned} path literal(s)"
+    );
+    println!();
+    println!("  `quiet?` marks a line whose nearby handling looks like a bare exit with no");
+    println!("  report. It is a HINT for a reader, never a verdict -- the control flow decides,");
+    println!("  and this reads literals. Paths built by concatenation are invisible here, so");
+    println!("  every number above is a lower bound.");
+    Ok(())
+}
+
+#[cfg(test)]
+mod tests {
+    use super::{fixture_regions, literals, looks_like_path};
+
+    /// The leak that mattered: after `#[test]`, the `fn` on the next line used
+    /// to close the region, and 41 fixture paths came back into the report.
+    #[test]
+    fn a_test_module_stays_a_fixture_region_past_its_first_fn() {
+        let src = "fn real() {\n    read(\"specs/live.t27\");\n}\n#[cfg(test)]\nmod tests {\n    #[test]\n    fn one() { read(\"specs/a.t27\"); }\n    #[test]\n    fn two() { read(\"specs/b.t27\"); }\n}\n";
+        let f = fixture_regions(src);
+        assert!(!f[1], "production line");
+        assert!(f[6], "first test fn");
+        assert!(f[8], "SECOND test fn -- the one that used to leak");
+    }
+
+    #[test]
+    fn a_fixture_inside_a_test_module_is_marked() {
+        let src = "fn real() {\n    read(\"specs/live.t27\");\n}\n#[cfg(test)]\nmod tests {\n    fn t() { read(\"specs/a.t27\"); }\n}\n";
+        let f = fixture_regions(src);
+        assert!(!f[1], "the production line must not be a fixture");
+        assert!(f[5], "the line inside mod tests must be");
+    }
+
+    /// The filter that mattered: without it a first run reported 126 hits, of
+    /// which almost none were real.
+    #[test]
+    fn a_python_self_check_is_a_fixture_region() {
+        let src = "def main():\n    open(\"gen/real.json\")\n\ndef self_check():\n    plant(\"docs/planted.md\")\n";
+        let f = fixture_regions(src);
+        assert!(!f[1]);
+        assert!(f[4]);
+    }
+
+    #[test]
+    fn path_shapes_are_recognised_and_noise_is_not() {
+        assert!(looks_like_path("gen/numeric/formats_catalog.json"));
+        assert!(looks_like_path("tools/gen_formats_catalog.py"));
+        assert!(!looks_like_path("target/release/t27c"));
+        assert!(!looks_like_path("https://example.com/x.json"));
+        assert!(!looks_like_path("{}/out.json"));
+        assert!(!looks_like_path("plain text here"));
+        assert!(!looks_like_path("noslash.json"));
+        // The two shapes that got through the first version.
+        assert!(!looks_like_path("t27-conformance-index/v0.1"));
+        assert!(!looks_like_path("gHashTag/ghashtag.github.io"));
+        assert!(!looks_like_path(r"^(tbd|todo|wip|n/?a)$"));
+    }
+
+    #[test]
+    fn escaped_quotes_do_not_split_a_literal() {
+        let v = literals(r#"let s = "a\"b/c.json";"#);
+        assert_eq!(v.len(), 1, "{v:?}");
+    }
+}
diff --git a/docs/now/2026-08-29-a-detector-that-fails-its-own-founding-case-and-says-so.md b/docs/now/2026-08-29-a-detector-that-fails-its-own-founding-case-and-says-so.md
new file mode 100644
index 0000000000..1005287618
--- /dev/null
+++ b/docs/now/2026-08-29-a-detector-that-fails-its-own-founding-case-and-says-so.md
@@ -0,0 +1,8 @@
+# NOW -- A detector that fails its own founding case, and says so (2026-08-29)
+
+## A detector that fails its own founding case, and says so (Refs #2762)
+
+- tri orphaned list: inputs named outright in production code that are not in the tree -- 21 findings, 110 fixtures filtered out of 241 literals
+- historical control FAILED: at the commit before W702 it finds ZERO of one, because that path was assembled from a variable and a bare filename and never appears as a literal
+- the window stays where it is; the miss is in the module docs, not tuned away
+- it earned its place on a different case: the Railway server's static fallback and 404 page point at public/, which has never existed in any commit