Add nom parsers for go and python

src/data_value.rs

@@ -67,6 +67,40 @@ pub fn extract_json_field(text: &str, field_path: &str) -> Option<String> {
     }
 }
 
+/// Flattens a JSON object into dot-separated field paths mapped to each leaf scalar's raw text form
+/// (string/number/bool), for [`crate::engine::auto_declare_params`] when a line is JSON
+/// (`crate::logfmt::detect_format`) rather than logfmt — the JSON equivalent of
+/// `crate::logfmt::extract_pairs`'s `key=value` scan. Nested objects recurse, dot-joining the path
+/// (`"foo": {"bar": 1}` yields `"foo.bar"`); arrays and null are skipped since there's no single leaf
+/// scalar to declare a param against, matching `extract_json_field`'s own restriction to scalars.
+/// Returns an empty vec for anything that isn't a JSON object, same as `extract_pairs` returns empty
+/// for a line with no `key=value` pairs.
+pub fn flatten_json_object(text: &str) -> Vec<(String, String)> {
+    let Ok(serde_json::Value::Object(root)) = serde_json::from_str::<serde_json::Value>(text) else {
+        return Vec::new();
+    };
+    let mut results = Vec::new();
+    flatten_json_object_into(&root, "", &mut results);
+    results
+}
+
+fn flatten_json_object_into(
+    object: &serde_json::Map<String, serde_json::Value>,
+    prefix: &str,
+    results: &mut Vec<(String, String)>,
+) {
+    for (key, value) in object {
+        let path = if prefix.is_empty() { key.clone() } else { format!("{prefix}.{key}") };
+        match value {
+            serde_json::Value::String(s) => results.push((path, s.clone())),
+            serde_json::Value::Number(n) => results.push((path, n.to_string())),
+            serde_json::Value::Bool(b) => results.push((path, b.to_string())),
+            serde_json::Value::Object(nested) => flatten_json_object_into(nested, &path, results),
+            serde_json::Value::Null | serde_json::Value::Array(_) => {}
+        }
+    }
+}
+
 /// `rename_all = "lowercase"` matches other `kind`-style enums, so JSON bodies use "string"/"number"/"timestamp".
 #[allow(dead_code)]
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]

src/engine.rs

@@ -356,37 +356,79 @@ fn auto_derived_param_count(index: &BTreeMap<IndexKey, DataValue>) -> usize {
     param_declarations_range(index).filter(|declaration| declaration.6).count()
 }
 
-/// Scans `text` for `key=value`/`key="value"` pairs (`crate::logfmt::extract_pairs`) and declares a
-/// standalone param for any key not already declared — auto or manual. A manual declaration for a
-/// name always wins and is never touched here; this only fills in names nobody has declared yet.
-/// Run on every ingested line (`EngineMessage::Ingest`), same as `apply_all_metrics`, but note param
-/// *values* are still recomputed from raw text at read time (`derive_log_params`), not stored here —
-/// so a key discovered on line N also back-fills the column for lines before N on the next read.
-/// Bounded by `MAX_AUTO_DECLARED_PARAMS`/`MAX_NEW_AUTO_PARAMS_PER_LINE` (see their doc comments) so a
-/// single burst of unusual lines can't permanently inflate the declared-param set (ticket 050).
+/// One param worth auto-declaring, found on an ingested line by either extraction path
+/// `auto_declare_params` supports: a logfmt `key=value` pair (name, and a regex/capture-group built
+/// from it) or a JSON leaf field (name being its dot-separated path, extracted via `json_field_path`
+/// instead of a regex). Lets `auto_declare_params` share one insert-and-budget loop across both.
+struct AutoParamCandidate {
+    name: String,
+    value: String,
+    message_match_regex: String,
+    capture_group: String,
+    json_field_path: Option<String>,
+}
+
+/// Scans `text` for auto-derivable params and declares a standalone param for any name not already
+/// declared — auto or manual. A manual declaration for a name always wins and is never touched here;
+/// this only fills in names nobody has declared yet. JSON lines (`crate::logfmt::detect_format`) are
+/// scanned via `crate::data_value::flatten_json_object` (dot-path leaf fields, extracted by
+/// `json_field_path` rather than regex, since a `key=value` scan finds nothing useful in JSON's
+/// `"key":value` shape); anything else falls back to the original `key=value` pair scan
+/// (`crate::logfmt::extract_pairs`). Run on every ingested line (`EngineMessage::Ingest`), same as
+/// `apply_all_metrics`, but note param *values* are still recomputed from raw text at read time
+/// (`derive_log_params`), not stored here — so a key discovered on line N also back-fills the column
+/// for lines before N on the next read. Bounded by `MAX_AUTO_DECLARED_PARAMS`/
+/// `MAX_NEW_AUTO_PARAMS_PER_LINE` (see their doc comments) so a single burst of unusual lines can't
+/// permanently inflate the declared-param set (ticket 050).
 fn auto_declare_params(index: &mut BTreeMap<IndexKey, DataValue>, text: &str) {
     let mut total = auto_derived_param_count(index);
     if total >= MAX_AUTO_DECLARED_PARAMS {
         return;
     }
-    let mut new_this_line = 0;
-    for (key, value, quoted) in crate::logfmt::extract_pairs(text) {
-        if new_this_line >= MAX_NEW_AUTO_PARAMS_PER_LINE || total >= MAX_AUTO_DECLARED_PARAMS {
-            break;
-        }
-        let index_key = IndexKey::ParamDeclaration { name: key.to_string() };
-        if index.contains_key(&index_key) {
-            continue;
-        }
+    let candidates: Vec<AutoParamCandidate> = if crate::logfmt::detect_format(text) == "json" {
+        crate::data_value::flatten_json_object(text)
+            .into_iter()
+            .map(|(path, value)| AutoParamCandidate {
+                name: path.clone(),
+                value,
+                message_match_regex: String::new(),
+                capture_group: String::new(),
+                json_field_path: Some(path),
+            })
+            .collect()
+    } else {
+        crate::logfmt::extract_pairs(text)
+            .into_iter()
+            .map(|(key, value, quoted)| {
                 let group = sanitize_group_name(key);
-        index.insert(
-            index_key,
-            DataValue::ParamDeclaration(ParamDeclaration {
+                AutoParamCandidate {
                     name: key.to_string(),
+                    value: value.to_string(),
                     message_match_regex: build_auto_param_pattern(key, &group, quoted),
                     capture_group: group,
                     json_field_path: None,
-                kind: infer_kind(value),
+                }
+            })
+            .collect()
+    };
+
+    let mut new_this_line = 0;
+    for candidate in candidates {
+        if new_this_line >= MAX_NEW_AUTO_PARAMS_PER_LINE || total >= MAX_AUTO_DECLARED_PARAMS {
+            break;
+        }
+        let index_key = IndexKey::ParamDeclaration { name: candidate.name.clone() };
+        if index.contains_key(&index_key) {
+            continue;
+        }
+        index.insert(
+            index_key,
+            DataValue::ParamDeclaration(ParamDeclaration {
+                name: candidate.name,
+                message_match_regex: candidate.message_match_regex,
+                capture_group: candidate.capture_group,
+                json_field_path: candidate.json_field_path,
+                kind: infer_kind(&candidate.value),
                 elapsed_since_last: false,
                 auto_derived: true,
             }),
@@ -2012,6 +2054,27 @@ mod tests {
         assert_eq!(params.get("msg"), Some(&MetricPrimitive::String("entity_moved".to_string())));
     }
 
+    #[test]
+    fn auto_declare_params_discovers_json_leaf_fields_via_json_field_path() {
+        let mut index = BTreeMap::new();
+        auto_declare_params(&mut index, r#"{"level":"error","code":500,"request":{"path":"/x"}}"#);
+
+        let declarations: HashMap<&str, _> =
+            param_declarations_range(&index).map(|d| (d.0, d)).collect();
+        assert_eq!(declarations.len(), 3);
+        assert_eq!(declarations["code"].4, MetricPrimitiveKind::Number);
+        assert_eq!(declarations["code"].3, Some("code"));
+        assert!(declarations["level"].6, "expected level to be flagged auto_derived");
+        assert_eq!(declarations["request.path"].3, Some("request.path"));
+
+        let compiled = compiled_param_declarations(&index);
+        let params =
+            derive_log_params(r#"{"level":"error","code":500,"request":{"path":"/x"}}"#, &compiled);
+        assert_eq!(params.get("level"), Some(&MetricPrimitive::String("error".to_string())));
+        assert_eq!(params.get("code"), Some(&MetricPrimitive::Number(Number::Int(500))));
+        assert_eq!(params.get("request.path"), Some(&MetricPrimitive::String("/x".to_string())));
+    }
+
     #[test]
     fn auto_declare_params_never_overwrites_an_existing_declaration() {
         let mut index = BTreeMap::new();

src/fixtures/go_log_sample.txt

@@ -0,0 +1,3 @@
+{"time":"2026-09-06T10:35:34.499921+01:00","level":"WARN","msg":"eventC","labelC":1}
+{"time":"2026-09-06T10:35:35.000837+01:00","level":"ERROR","msg":"eventB","labelC":2,"labelA":3}
+{"time":"2026-09-06T10:35:36.504236+01:00","level":"INFO","msg":"eventB","labelB":"three"}

src/fixtures/py_log_sample.txt

@@ -0,0 +1,3 @@
+2026-09-06 10:35:55,217 INFO delete-py-log event=eventC labelC=1
+2026-09-06 10:35:55,627 INFO delete-py-log event=eventB labelB=one
+2026-09-06 10:35:56,442 INFO delete-py-log event=eventB labelA=1

src/logfmt.rs

@@ -4,7 +4,7 @@
 //! with an arbitrary non-logfmt prefix/suffix (e.g. `ts=... msg="..." x1=-4 y1=34`).
 
 use nom::branch::alt;
-use nom::bytes::complete::{escaped, take_while1};
+use nom::bytes::complete::{escaped, tag, take_until, take_while1};
 use nom::character::complete::{char, none_of, one_of};
 use nom::error::{Error, ErrorKind};
 use nom::sequence::delimited;
@@ -112,16 +112,77 @@ pub const LOG_STREAM_PROCESS_PATTERN: &str =
 pub const LOG_STREAM_PID_PATTERN: &str =
     r"^\d{4}-\d{2}-\d{2}\s+\S+\s+0x[0-9a-fA-F]+\s+\S+\s+0x[0-9a-fA-F]+\s+(?P<pid>\d+)\s+\d+\s+[^\s:]+:\s";
 
+/// Go `log/slog` `NewJSONHandler` output (the `go-log` label): a single-line JSON object whose first
+/// three fields are always `time`, `level`, `msg` in that fixed order (slog's `JSONHandler` writes the
+/// built-in attrs before any caller-supplied ones), followed by zero or more arbitrary attrs and a
+/// closing `}`. Parsed with nom rather than a full JSON decode since only that fixed prefix shape
+/// needs verifying; the variable tail is deliberately not parsed field-by-field the way
+/// `crate::engine::auto_declare_params` will separately pick up JSON leaf fields from the line.
+/// Checked ahead of the generic JSON object check in `detect_format` since it's the more specific of
+/// the two (see that function's doc comment for the general ordering rationale).
+fn go_log_prefix(input: &str) -> IResult<&str, (&str, &str, &str)> {
+    let (input, _) = tag("{\"time\":\"")(input)?;
+    let (input, time) = take_until("\"")(input)?;
+    let (input, _) = tag("\",\"level\":\"")(input)?;
+    let (input, level) = take_until("\"")(input)?;
+    let (input, _) = tag("\",\"msg\":\"")(input)?;
+    let (input, msg) = take_until("\"")(input)?;
+    let (input, _) = char('"')(input)?;
+    Ok((input, (time, level, msg)))
+}
+
+pub fn is_go_log_line(text: &str) -> bool {
+    match go_log_prefix(text) {
+        Ok((rest, _)) => rest.trim_end().ends_with('}'),
+        Err(_) => false,
+    }
+}
+
+/// Python `logging` module output in the shape `"%(asctime)s %(levelname)s %(name)s %(message)s"`
+/// (the `py-log` label): a `YYYY-MM-DD HH:MM:SS,mmm` timestamp, an uppercase level word, a logger
+/// name, then a message tail that (for `delete-py-log`, and any caller using `logger.info("event=%s
+/// %s=%s", ...)`-style calls) is itself logfmt `key=value` pairs. Only the fixed prefix is parsed with
+/// nom; the tail is handed to `extract_pairs` both to confirm the shape (a py-log line with no pairs
+/// at all wouldn't be distinguishable from plain prose after this prefix) and because that's the same
+/// extraction `crate::engine::auto_declare_params` needs anyway. Checked ahead of the generic logfmt
+/// check in `detect_format` since it's the more specific of the two.
+fn py_log_prefix(input: &str) -> IResult<&str, (&str, &str, &str, &str)> {
+    let (input, date) = take_while1(|c: char| c.is_ascii_digit() || c == '-')(input)?;
+    let (input, _) = char(' ')(input)?;
+    let (input, time) = take_while1(|c: char| c.is_ascii_digit() || c == ':' || c == ',')(input)?;
+    let (input, _) = char(' ')(input)?;
+    let (input, level) = take_while1(|c: char| c.is_ascii_uppercase())(input)?;
+    let (input, _) = char(' ')(input)?;
+    let (input, logger) =
+        take_while1(|c: char| c.is_ascii_alphanumeric() || c == '_' || c == '-' || c == '.')(input)?;
+    let (input, _) = char(' ')(input)?;
+    Ok((input, (date, time, level, logger)))
+}
+
+pub fn is_py_log_line(text: &str) -> bool {
+    match py_log_prefix(text) {
+        Ok((rest, _)) => !extract_pairs(rest).is_empty(),
+        Err(_) => false,
+    }
+}
+
 /// The value of the `ottyl_fmt` reserved param (`crate::engine::compile_filter`/`eval_alert_expr`):
-/// which format a line was recognized as when parsed. `log stream`'s fixed-column shape is checked
-/// first (see `LOG_STREAM_RE`'s doc comment for why it's the most specific of the four). JSON is
-/// checked next since a JSON object can incidentally contain `key=value`-shaped substrings that
-/// `extract_pairs` would otherwise pick up; only a top-level object counts (arrays/scalars aren't what
-/// `crate::engine::eval_json_comparison` treats as JSON either). Anything else falls back to
-/// logfmt-style pair extraction, and a line with none of the above is `"none"`.
+/// which format a line was recognized as when parsed. Checked most-specific-first: `log stream`'s
+/// fixed-column shape (see `LOG_STREAM_RE`'s doc comment for why it's the most specific), then the two
+/// named-tool shapes `go-log` (a `time`/`level`/`msg`-prefixed JSON object) and `py-log` (a
+/// timestamp/level/logger prefix over logfmt pairs) — each is a strict subset of the generic JSON/logfmt
+/// case checked right after it, so they'd otherwise never be reached. JSON is checked next since a JSON
+/// object can incidentally contain `key=value`-shaped substrings that `extract_pairs` would otherwise
+/// pick up; only a top-level object counts (arrays/scalars aren't what `crate::engine::eval_json_comparison`
+/// treats as JSON either). Anything else falls back to logfmt-style pair extraction, and a line with
+/// none of the above is `"none"`.
 pub fn detect_format(text: &str) -> &'static str {
     if is_log_stream_line(text) {
         "log_stream"
+    } else if is_go_log_line(text) {
+        "go-log"
+    } else if is_py_log_line(text) {
+        "py-log"
     } else if serde_json::from_str::<serde_json::Value>(text).is_ok_and(|value| value.is_object()) {
         "json"
     } else if !extract_pairs(text).is_empty() {
@@ -250,4 +311,59 @@ mod tests {
         // The embedded key=value pairs are still there for auto_declare_params to see.
         assert!(!extract_pairs(line).is_empty());
     }
+
+    const GO_LOG_FIXTURE: &str = include_str!("fixtures/go_log_sample.txt");
+    const PY_LOG_FIXTURE: &str = include_str!("fixtures/py_log_sample.txt");
+
+    #[test]
+    fn detects_go_log_shaped_lines() {
+        for line in GO_LOG_FIXTURE.lines() {
+            assert!(is_go_log_line(line), "expected go-log line to match: {line}");
+            assert_eq!(detect_format(line), "go-log");
+        }
+    }
+
+    #[test]
+    fn detects_py_log_shaped_lines() {
+        for line in PY_LOG_FIXTURE.lines() {
+            assert!(is_py_log_line(line), "expected py-log line to match: {line}");
+            assert_eq!(detect_format(line), "py-log");
+        }
+    }
+
+    #[test]
+    fn a_generic_json_object_is_not_detected_as_go_log() {
+        let line = r#"{"level":"error","code":500}"#;
+        assert!(!is_go_log_line(line));
+        assert_eq!(detect_format(line), "json");
+    }
+
+    #[test]
+    fn a_generic_logfmt_line_is_not_detected_as_py_log() {
+        let line = r#"ts=1788648105773 msg="entity_moved" x1=-4"#;
+        assert!(!is_py_log_line(line));
+        assert_eq!(detect_format(line), "logfmt");
+    }
+
+    #[test]
+    fn go_log_prefix_extracts_time_level_and_msg() {
+        let (rest, (time, level, msg)) =
+            go_log_prefix(r#"{"time":"2026-09-06T10:35:34.499921+01:00","level":"WARN","msg":"eventC","labelC":1}"#)
+                .unwrap();
+        assert_eq!(time, "2026-09-06T10:35:34.499921+01:00");
+        assert_eq!(level, "WARN");
+        assert_eq!(msg, "eventC");
+        assert_eq!(rest, r#","labelC":1}"#);
+    }
+
+    #[test]
+    fn py_log_prefix_extracts_date_time_level_and_logger() {
+        let (rest, (date, time, level, logger)) =
+            py_log_prefix("2026-09-06 10:35:55,217 INFO delete-py-log event=eventC labelC=1").unwrap();
+        assert_eq!(date, "2026-09-06");
+        assert_eq!(time, "10:35:55,217");
+        assert_eq!(level, "INFO");
+        assert_eq!(logger, "delete-py-log");
+        assert_eq!(rest, "event=eventC labelC=1");
+    }
 }

webapp/src/assets/ottyl-icon.svg

@@ -0,0 +1,26 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<svg id="Layer_1" data-name="Layer 1" xmlns="http://www.w3.org/2000/svg" viewBox="0 0 100 100">
+  <defs>
+    <style>
+      .cls-1 {
+        fill: #fff;
+        stroke-width: 9px;
+      }
+
+      .cls-1, .cls-2 {
+        stroke: #000;
+        stroke-miterlimit: 10;
+      }
+
+      .cls-2 {
+        fill: none;
+        stroke-width: 8px;
+        stroke-linecap: round;
+        stroke-linejoin: round;
+      }
+    </style>
+  </defs>
+  <rect class="cls-1" x="10" y="10" width="80" height="80" rx="18.79" ry="18.79"/>
+  <polyline class="cls-2" points="25,33 42,50 25,67"/>
+  <line class="cls-2" x1="46" y1="66" x2="75" y2="37"/>
+</svg>

webapp/src/components/Docs.tsx

@@ -150,6 +150,65 @@ const SECTIONS: DocSection[] = [
       </div>
     ),
   },
+  {
+    id: 'auto-formats',
+    title: 'Auto-detected formats',
+    body: (
+      <div className="flex flex-col gap-2">
+        <p>
+          Every ingested line is classified into one of four formats, exposed as the reserved{' '}
+          <Code>ottyl_fmt</Code> param (see <em>Filtering</em> above). The format also decides what — if anything —
+          gets auto-declared as a param without you doing anything:
+        </p>
+        <ul className="list-disc pl-5">
+          <li>
+            <span className="font-semibold text-text">
+              <Code>log_stream</Code>
+            </span>{' '}
+            — macOS <Code>{'log stream'}</Code> output's fixed-column shape (timestamp, thread, type, activity id,
+            pid, ttl, then <Code>process: message</Code>). The first such line seen auto-declares{' '}
+            <Code>log_type</Code>, <Code>process</Code>, and <Code>pid</Code> as params, parsed straight out of those
+            columns.
+          </li>
+          <li>
+            <span className="font-semibold text-text">
+              <Code>json</Code>
+            </span>{' '}
+            — the line parses as a JSON object (a bare array or scalar doesn't count). Every leaf scalar field
+            (string/number/bool) auto-declares a param named after its dot-separated path, extracted by JSON field
+            path rather than regex — a nested field like <Code>{'{"request":{"path":"/x"}}'}</Code> becomes a param
+            named <Code>request.path</Code>. Nested objects are walked into automatically; arrays and <Code>null</Code>{' '}
+            fields are skipped since there's no single scalar value to declare a param against.
+          </li>
+          <li>
+            <span className="font-semibold text-text">
+              <Code>logfmt</Code>
+            </span>{' '}
+            — the line contains at least one <Code>key=value</Code>/<Code>{'key="value"'}</Code> pair anywhere in its
+            text (it doesn't need to be logfmt end-to-end — a free-text prefix or suffix around the pairs is fine).
+            Every distinct key auto-declares a param of the same name, type-inferred as <Code>number</Code> if its
+            first-seen value parses as one, else <Code>string</Code>.
+          </li>
+          <li>
+            <span className="font-semibold text-text">
+              <Code>none</Code>
+            </span>{' '}
+            — none of the above; plain prose with no structure ottyl can key off of. Nothing is auto-declared, though
+            the line is still fully searchable via <Code>regex(...)</Code> in the filter bar.
+          </li>
+        </ul>
+        <p>
+          Auto-declared params are flagged <Code>auto_derived</Code> in <Code>GET /api/params</Code> and show up as
+          log-table columns immediately, same as a manually declared param — but they can't be edited or removed
+          individually, and they're never persisted to a profile (so they're rediscovered fresh each run rather than
+          traveling with a profile like manual declarations do). A manual param declaration for a name always takes
+          precedence and is never overwritten by auto-detection. To keep one unusual line from flooding the params
+          list, auto-detection is capped at 64 auto-derived params total and 8 new ones per line — once either cap is
+          hit, further would-be auto-declarations from new keys/fields are simply skipped.
+        </p>
+      </div>
+    ),
+  },
   {
     id: 'parameters',
     title: 'Parameters',

webapp/src/components/NavMenu.tsx

@@ -6,6 +6,7 @@ import { useDocsNav, type DocsTarget } from '../lib/docsNav'
 import { DocsPanel } from './Docs'
 import { HelpIcon } from './HelpIcon'
 import { BUILTIN_THEMES, downloadThemeFile, generateThemeCss, parseThemeCss } from '../lib/themes'
+import ottylIcon from '../assets/ottyl-icon.svg'
 
 type PanelName = 'settings' | 'docs' | null
 
@@ -67,7 +68,10 @@ export function NavMenu({ stats }: { stats: Stats | null }) {
     <div className="flex h-full">
       <div className="flex h-full w-48 shrink-0 flex-col justify-between border-r border-border p-3">
         <div>
-          <div className="mb-4 text-lg font-semibold text-text">ottyl</div>
+          <div className="mb-4 flex items-center gap-2 text-lg font-semibold text-text">
+            <img src={ottylIcon} alt="" className="h-5 w-5" />
+            ottyl
+          </div>
           <PresetsDropdown panel={panel} />
           <nav className="mt-2 flex flex-col gap-1 text-sm text-text-muted">
             <button