diff --git a/README.md b/README.md
index 1b423b2..8328845 100644
--- a/README.md
+++ b/README.md
@@ -533,6 +533,9 @@ Lane discovery uses the gate's sanitized Git command and rejects malformed or
 unterminated ls-tree rows; shared subprocess timeout/output bounds remain open.
 `workflow::workflow_job` selects exact generated-workflow text and transitive
 job dependencies; it follows the legacy layout contract, not general YAML.
+`selection_json::select_json` preserves legacy integer JSON selections. Selected
+floats, JSON extensions and nesting above 127 containers refuse with named
+`input-selection-*` reasons; extension diagnostics identify the token and byte offset.
 
 ### Main-push tree-equality evidence
 
diff --git a/crates/mergemaster-evidence/src/evidence/legacy_verify.rs b/crates/mergemaster-evidence/src/evidence/legacy_verify.rs
index a8c0a92..77acd33 100644
--- a/crates/mergemaster-evidence/src/evidence/legacy_verify.rs
+++ b/crates/mergemaster-evidence/src/evidence/legacy_verify.rs
@@ -7,6 +7,7 @@ pub mod lane_entry;
 pub mod lane_git;
 pub mod lanes;
 pub mod routing;
+pub mod selection_json;
 pub mod workflow;
 use super::legacy_policy::kind_rules::KindRule;
 use serde::Serialize;
diff --git a/crates/mergemaster-evidence/src/evidence/legacy_verify/selection_json.rs b/crates/mergemaster-evidence/src/evidence/legacy_verify/selection_json.rs
new file mode 100644
index 0000000..244dd72
--- /dev/null
+++ b/crates/mergemaster-evidence/src/evidence/legacy_verify/selection_json.rs
@@ -0,0 +1,98 @@
+//! Exact supported JSON selections; approved refusals never become missing entries.
+use crate::evidence::{
+    legacy_json::{self, Value, encode_integer, extension_syntax, has_float, limits},
+    legacy_policy::PolicyError,
+};
+fn error(reason: &'static str, detail: impl Into<String>) -> PolicyError {
+    PolicyError {
+        reason,
+        detail: detail.into(),
+    }
+}
+fn unit(bytes: Option<&[u8]>) -> Option<u16> {
+    u16::from_str_radix(std::str::from_utf8(bytes?).ok()?, 16).ok()
+}
+/// The first extension token and its byte offset, excluding escaped backslashes and paired surrogates.
+fn extension(text: &str) -> Option<(&str, usize)> {
+    let b = text.as_bytes();
+    let (mut i, mut quoted) = (0, false);
+    while i < b.len() {
+        if b[i] == b'"' {
+            quoted = !quoted;
+            i += 1;
+            continue;
+        }
+        if quoted && b[i] == b'\\' {
+            if b.get(i + 1) == Some(&b'u') {
+                let value = unit(b.get(i + 2..i + 6))?;
+                if (0xd800..=0xdfff).contains(&value) {
+                    if value <= 0xdbff
+                        && b.get(i + 6..i + 8) == Some(b"\\u")
+                        && unit(b.get(i + 8..i + 12))
+                            .is_some_and(|v| (0xdc00..=0xdfff).contains(&v))
+                    {
+                        i += 12;
+                        continue;
+                    }
+                    return Some((&text[i..i + 6], i));
+                }
+                i += 6;
+            } else {
+                i += 2;
+            }
+            continue;
+        }
+        if !quoted
+            && let Some(token) = ["-Infinity", "Infinity", "NaN"]
+                .into_iter()
+                .find(|t| b[i..].starts_with(t.as_bytes()))
+        {
+            return Some((token, i));
+        }
+        i += 1;
+    }
+    None
+}
+pub fn select_json(text: &str, selector: &str) -> Result<Option<Vec<u8>>, PolicyError> {
+    let (depth, long) = limits(text);
+    if long {
+        return Err(error("error", "JSON integer exceeds 4300 digits"));
+    }
+    if depth > 127 {
+        return Err(error(
+            "input-selection-nesting-depth",
+            "JSON exceeds 127 open containers",
+        ));
+    }
+    let mut value = legacy_json::parse(text.as_bytes()).map_err(|_| {
+        if let Some((token, at)) = extension(text).filter(|_| extension_syntax(text)) {
+            error(
+                "input-selection-json-extensions",
+                format!("unsupported JSON token {token} at byte offset {at}"),
+            )
+        } else {
+            error("error", "selected input is not supported JSON")
+        }
+    })?;
+    for key in selector.split('.') {
+        let Value::Object(mut object) = value else {
+            return Ok(None);
+        };
+        let Some(next) = object.remove(key) else {
+            return Ok(None);
+        };
+        value = next;
+    }
+    if has_float(&value) {
+        return Err(error(
+            "input-selection-float-text",
+            "selected value contains a floating number",
+        ));
+    }
+    let mut output = String::new();
+    encode_integer(&value, &mut output);
+    Ok(Some(output.into_bytes()))
+}
+#[cfg(test)]
+#[path = "selection_json_tests.rs"]
+mod tests;
diff --git a/crates/mergemaster-evidence/src/evidence/legacy_verify/selection_json_tests.rs b/crates/mergemaster-evidence/src/evidence/legacy_verify/selection_json_tests.rs
new file mode 100644
index 0000000..d461414
--- /dev/null
+++ b/crates/mergemaster-evidence/src/evidence/legacy_verify/selection_json_tests.rs
@@ -0,0 +1,164 @@
+use super::select_json;
+use serde_json::{Value, json};
+#[test]
+fn selected_json_matches_oracle_or_explicit_rejected_reason() {
+    type Case = (
+        String,
+        &'static str,
+        Option<&'static str>,
+        Option<(&'static str, usize)>,
+    );
+    let mut cases: Vec<Case> = [
+        r#"{"selected":{"z":1,"a":[null,true,"é😀"]}}"#,
+        r#"{"selected":18446744073709551616}"#,
+        r#"{"selected":-0}"#,
+        r#"{"selected":0,"selected":1}"#,
+        r#"{"selected":{"z":0,"z":1}}"#,
+        r#"{"selected":1.0,"selected":1}"#,
+        r#"{"selected":"\\ud800"}"#,
+        r#"{"selected":"\ud83d\ude00"}"#,
+        r#"{"selected":1,"other":1e400}"#,
+        "{}",
+        "[]",
+        "null",
+        "not JSON",
+        r#"{"selected":01}"#,
+    ]
+    .map(|text| (text.into(), "selected", None, None))
+    .into();
+    cases.push((
+        r#"{"selected":{"inner":1}}"#.into(),
+        "selected.inner",
+        None,
+        None,
+    ));
+    for number in [
+        "1.0",
+        "-0.0",
+        "1e16",
+        "1e-5",
+        "0.1",
+        "5e-324",
+        "1.7976931348623157e308",
+        "1e400",
+        "{\"n\":1.0}",
+    ] {
+        cases.push((
+            format!("{{\"selected\":{number}}}"),
+            "selected",
+            Some("input-selection-float-text"),
+            None,
+        ));
+    }
+    for (value, token) in [
+        ("NaN", "NaN"),
+        ("Infinity", "Infinity"),
+        ("-Infinity", "-Infinity"),
+        (r#""\ud800""#, r#"\ud800"#),
+        (r#""\udcff""#, r#"\udcff"#),
+    ] {
+        for text in [
+            format!("{{\"selected\":{value}}}"),
+            format!("{{\"é\":0,\"selected\":{{\"ok\":1}},\"other\":{value}}}"),
+        ] {
+            let at = text.find(token).unwrap();
+            cases.push((
+                text,
+                "selected",
+                Some("input-selection-json-extensions"),
+                Some((token, at)),
+            ));
+        }
+    }
+    for digits in [4300, 4301] {
+        cases.push((
+            format!("{{\"selected\":{}}}", "9".repeat(digits)),
+            "selected",
+            None,
+            None,
+        ));
+    }
+    for depth in [127, 128, 200, 1200] {
+        for member in ["selected", "other"] {
+            let text = format!(
+                "{{\"{member}\":{}null{},\"ok\":1}}",
+                "[".repeat(depth - 1),
+                "]".repeat(depth - 1)
+            );
+            cases.push((
+                text,
+                if member == "selected" {
+                    "selected"
+                } else {
+                    "ok"
+                },
+                (depth > 127).then_some("input-selection-nesting-depth"),
+                None,
+            ));
+        }
+    }
+    let results: Vec<_> = cases
+        .iter()
+        .map(|(text, key, _, _)| select_json(text, key))
+        .collect();
+    let actual: Vec<_> = results
+        .iter()
+        .map(|result| match result {
+            Ok(bytes) => json!({"hex":bytes.as_ref().map(hex::encode)}),
+            Err(e) => json!({"reason":e.reason}),
+        })
+        .collect();
+    let root = std::env::var("MERGEMASTER_PYTHON_ORACLE")
+        .expect("MERGEMASTER_PYTHON_ORACLE must point to the pinned Python oracle");
+    let fractal = std::env::var("MERGEMASTER_FRACTAL_FIXTURE")
+        .expect("MERGEMASTER_FRACTAL_FIXTURE must point to the pinned Fractal consumer");
+    let script = r#"
+import json, runpy, sys
+o = runpy.run_path(sys.argv[1] + '/scripts/evidence-verify')
+gate = runpy.run_path(sys.argv[2] + '/scripts/ci-evidence-gate')
+results = []
+for (text, key, _, _), actual in zip(json.loads(sys.argv[3]),json.loads(sys.argv[4])):
+    try:
+        value = o['select_part'](text,'fixture.json',key)
+        result = dict(hex=value.hex() if value is not None else None)
+    except o['Failure'] as e:
+        result = dict(reason=e.reason)
+    category = gate['classify'](1,dict(satisfied=False,reason=actual['reason'])) if 'reason' in actual else None
+    results.append(dict(oracle=result,category=category))
+print(json.dumps(results))
+"#;
+    let output = std::process::Command::new("python3")
+        .args([
+            "-c",
+            script,
+            &root,
+            &fractal,
+            &json!(cases).to_string(),
+            &json!(actual).to_string(),
+        ])
+        .output()
+        .unwrap();
+    assert!(
+        output.status.success(),
+        "{}",
+        String::from_utf8_lossy(&output.stderr)
+    );
+    let expected: Vec<Value> = serde_json::from_slice(&output.stdout).unwrap();
+    assert_eq!(actual.len(), expected.len());
+    for (i, (_, _, reason, token)) in cases.iter().enumerate() {
+        println!("{}", json!({"rust":actual[i],"oracle":expected[i]}));
+        if let Some(reason) = reason {
+            assert_eq!(actual[i]["reason"], *reason);
+            assert_eq!(expected[i]["category"], "rejected");
+            assert!(expected[i]["oracle"]["hex"].is_string());
+        } else {
+            assert_eq!(actual[i], expected[i]["oracle"], "{}", cases[i].0);
+        }
+        if let Some((token, at)) = token {
+            assert_eq!(
+                results[i].as_ref().unwrap_err().detail,
+                format!("unsupported JSON token {token} at byte offset {at}")
+            );
+        }
+    }
+}
diff --git a/scripts/PROVENANCE b/scripts/PROVENANCE
index 9cfe7ee..d8aeebe 100644
--- a/scripts/PROVENANCE
+++ b/scripts/PROVENANCE
@@ -16,6 +16,14 @@
 # dependency closure match; workflow layout is not interpreted as general YAML.
 # Shared legacy JSON guards/encoding preserve lane behavior; native and push
 # parsing and all JSON dependency features remain unchanged.
+# Rust parity: JSON input selection (543-563), including large integers, -0,
+# duplicate keys and the 4300-digit cap; unrelated floats remain supported.
+# Conservative divergences: input-selection-float-text (selected floats),
+# input-selection-json-extensions (whole-document NaN/Infinity/lone surrogates;
+# diagnostic names the token and byte offset), input-selection-nesting-depth
+# (more than 127 open containers). Oracle accepts the 1200-container fixtures;
+# Rust refuses; pinned classify() reports rejected. Approved after a zero-hit
+# selected-input history scan (243 blob-selector pairs, maximum depth 8).
 # Hardening divergence: discovery-input-hardening rejects invalid ref prefixes,
 # non-OID commits, LF/CR/NUL note paths and malformed batch frames. Python callers
 # never supply these; its suffix-only test counts ambiguous replies as present (impossible with full OIDs).