ANW-42 Telemetry: take export config from OTEL_ environment variables only

Delete the uptrace DSN parser and the {endpoint}/v1/* concatenation that
produced the dead export, and build the OTLP exporters with no endpoint,
headers, or protocol so the SDK reads OTEL_EXPORTER_OTLP_* itself.

The SDK concatenates as naively as we did: measured against a local sink,
a ?query base sends POST /?query/v1/metrics and a #fragment base sends
POST /. So one check stays -- a query or fragment on
OTEL_EXPORTER_OTLP_ENDPOINT fails at startup. Per-signal variables are
used verbatim and need none.

A protocol variable is the second startup check. The exporter picks its
transport at build time and this binary ships OTLP/HTTP alone, so
OTEL_EXPORTER_OTLP_PROTOCOL=grpc kept exporting over HTTP with nothing in
the log -- the same silence this change removes.

service.name stays a default rather than policy: an attribute set on the
resource builder wins over the SDK detectors that read OTEL_SERVICE_NAME
and OTEL_RESOURCE_ATTRIBUTES, so anwesen supplies its own only for keys
the environment leaves alone.

Telemetry-off is our own check on the endpoint variables: with none set
the exporter would still build and aim at the SDK default localhost:4318.

--uptrace-dsn, --otlp-endpoint, and --otlp-header stay parsed but hidden,
so a deployment upgrading with them set fails naming the OTEL_
replacement instead of going quiet.

Assumed hidden clap stubs are the right migration shape; clap rejecting
the flags as unknown would say nothing about the replacement. Flag if a
plain unknown-argument error is wanted instead.

Assumed rejecting http/json alongside grpc is right: neither has a
transport in this build. Flag if a build with both features is wanted
instead.

README.md

@@ -56,8 +56,7 @@ anwesen merge --vault /path/to/vault --query 'tags=adr&__anw-order=title' > ADRs
 
 ```
 anwesen serve  --vault <path> [--bind <addr:port>] [--log-level <level>]
-               [--uptrace-dsn <dsn> | --otlp-endpoint <url>]
+               [--otlp-slow-request-ms <n>]
-               [--otlp-header <key=value>]... [--otlp-slow-request-ms <n>]
 anwesen doctor --vault <path>
 anwesen merge  --vault <path> --query <query-string>
 anwesen version
@@ -69,24 +68,62 @@ anwesen version
 | `--bind <addr:port>`        | `ANWESEN_BIND`                 | `127.0.0.1:8080`       | Listen address for `serve`.                                                   |
 | `--log-level <level>`       | `ANWESEN_LOG_LEVEL`            | `info`                 | `error`, `warn`, `info`, `debug`, or `trace`.                                  |
 | `--query <query-string>`    | --                             | _required for `merge`_ | A `/query` query string: frontmatter predicates plus `__anw-` controls.       |
-| `--uptrace-dsn <dsn>`       | `ANWESEN_UPTRACE_DSN`          | unset                  | uptrace DSN (`https://<token>@api.uptrace.dev`). Excludes `--otlp-endpoint`.  |
-| `--otlp-endpoint <url>`     | `ANWESEN_OTLP_ENDPOINT`        | unset                  | OTLP/HTTP base URL. Excludes `--uptrace-dsn`.                                 |
-| `--otlp-header <key=value>` | `ANWESEN_OTLP_HEADERS`         | none                   | Extra export header, repeatable. The env var takes a comma-separated list.    |
 | `--otlp-slow-request-ms`    | `ANWESEN_OTLP_SLOW_REQUEST_MS` | `500`                  | Requests at or over this duration, or answering 5xx, also export a span.      |
 
-Every flag has a matching `ANWESEN_<UPPER>` environment variable, except
+Every flag has a matching `ANWESEN_<UPPER>` environment variable. CLI flags win
-`--otlp-header`, whose env var is the plural `ANWESEN_OTLP_HEADERS` because it
+over env vars.
-takes a list. CLI flags win over env vars.
 
-Telemetry is off unless `--uptrace-dsn` or `--otlp-endpoint` is set. With
+`--bind` and `--otlp-slow-request-ms` apply to `serve` only. Where telemetry is
-neither, nothing is exported and no exporter is built. The four telemetry
+exported is configured entirely through the standard `OTEL_` variables below.
-flags apply to `serve` only.
 
 - **`serve`** -- run the daemon: walk the vault, build the index, watch for changes, serve the API.
 - **`doctor`** -- walk the vault once and report what would stop clean ingestion: unreadable files, unparseable YAML, path collisions on the HTTP surface, and frontmatter type drift (the same key carrying incompatible types across notes). Read-only; non-zero exit if any issue is found.
 - **`merge`** -- one-shot local generation: walk the vault, evaluate `--query`, and write the merged markdown document to stdout. No server, no HTTP. See [Local generation](#local-generation).
 - **`version`** -- print version and exit.
 
+## Telemetry
+
+anwesen exports OTLP metrics for every request, and a span for requests at or
+over `--otlp-slow-request-ms` or answering a 5xx. Export is configured through
+the standard OpenTelemetry environment variables, which the SDK reads directly:
+
+| Variable                               | Meaning                                                          |
+| -------------------------------------- | ---------------------------------------------------------------- |
+| `OTEL_EXPORTER_OTLP_ENDPOINT`          | Base URL. The SDK appends `/v1/metrics` and `/v1/traces`.        |
+| `OTEL_EXPORTER_OTLP_METRICS_ENDPOINT`  | Full metrics URL, used as given. Overrides the base for metrics. |
+| `OTEL_EXPORTER_OTLP_TRACES_ENDPOINT`   | Full traces URL, used as given. Overrides the base for traces.   |
+| `OTEL_EXPORTER_OTLP_HEADERS`           | Export headers, `key=value` comma-separated.                     |
+| `OTEL_EXPORTER_OTLP_PROTOCOL`          | `http/protobuf`, the default and the only value this build speaks. |
+| `OTEL_SERVICE_NAME`, `OTEL_RESOURCE_ATTRIBUTES` | Override the `anwesen` service identity.                |
+
+The per-signal `OTEL_EXPORTER_OTLP_METRICS_PROTOCOL` and
+`OTEL_EXPORTER_OTLP_TRACES_PROTOCOL` are read the same way.
+
+With none of the three endpoint variables set, telemetry is off: no exporter is
+built and the request middleware is not installed.
+
+Two settings fail at startup rather than export nowhere in silence:
+
+- A query or a fragment on `OTEL_EXPORTER_OTLP_ENDPOINT`. The base URL must be
+  a base URL; the SDK appends the signal path after whatever it is given.
+- A protocol other than `http/protobuf`. The binary ships the OTLP/HTTP
+  transport alone, so `grpc` would keep exporting over HTTP with nothing in the
+  log. Point the endpoint at the collector's HTTP port, not its gRPC one.
+
+uptrace:
+
+```
+OTEL_EXPORTER_OTLP_ENDPOINT=https://api.uptrace.dev
+OTEL_EXPORTER_OTLP_HEADERS=uptrace-dsn=https://TOKEN@api.uptrace.dev?grpc=4317
+```
+
+Paste the DSN from Project Settings into the header verbatim, tail and all --
+it is a credential there, not an address. The endpoint is the host alone.
+
+Removed in 0.3.0: `--uptrace-dsn`, `--otlp-endpoint`, `--otlp-header` and their
+`ANWESEN_` variables. Passing any of them fails at startup with the `OTEL_`
+replacement to use.
+
 ## HTTP API
 
 All endpoints are `GET` and return JSON unless noted.

src/cli.rs

@@ -4,18 +4,22 @@
 //!
 //! ```text
 //! anwesen serve  --vault <path> [--bind <addr:port>] [--log-level <level>]
-//!                [--uptrace-dsn <dsn> | --otlp-endpoint <url>]
+//!                [--otlp-slow-request-ms <n>]
-//!                [--otlp-header <key=value>]... [--otlp-slow-request-ms <n>]
 //! anwesen doctor --vault <path> [--log-level <level>]
 //! anwesen merge  --vault <path> [--query <string>] [--log-level <level>]
 //! anwesen version
 //! ```
 //!
-//! `--bind` and the OTLP telemetry flags are `serve`-only ([ANW-37]);
+//! `--bind` and `--otlp-slow-request-ms` are `serve`-only ([ANW-37]);
 //! `doctor` and `merge` do not bind a port; `version` takes no flags. Each
 //! flag has a matching `ANWESEN_<UPPER>` environment variable and CLI wins
-//! over env per the manual. With no `--otlp-endpoint`/`--uptrace-dsn`,
+//! over env per the manual.
-//! telemetry is off and the server behaves exactly as without these flags.
+//!
+//! Telemetry export is configured through the standard `OTEL_EXPORTER_OTLP_*`
+//! environment variables ([ANW-42](https://crvrs.youtrack.cloud/issue/ANW-42)).
+//! With none of them set, telemetry is off and the server behaves as it did
+//! before telemetry existed. The removed flags below are still parsed so an
+//! upgrade fails loudly instead of dropping export config in silence.
 
 use std::net::SocketAddr;
 use std::path::PathBuf;
@@ -56,25 +60,22 @@ pub struct ServeArgs {
     #[arg(long, env = "ANWESEN_LOG_LEVEL", default_value = "info")]
     pub log_level: LogLevel,
 
-    /// uptrace DSN shorthand (`https://<token>@api.uptrace.dev`), parsed
+    /// Removed (ANW-42): use `OTEL_EXPORTER_OTLP_ENDPOINT` plus
-    /// into the OTLP endpoint plus an `uptrace-dsn` header. Mutually
+    /// `OTEL_EXPORTER_OTLP_HEADERS=uptrace-dsn=<dsn>`. Still accepted so
-    /// exclusive with --otlp-endpoint. When this and --otlp-endpoint are
+    /// startup fails with that message rather than exporting nowhere.
-    /// both unset, telemetry is fully off (ANW-37).
+    #[arg(long, env = "ANWESEN_UPTRACE_DSN", hide = true)]
-    #[arg(long, env = "ANWESEN_UPTRACE_DSN")]
     pub uptrace_dsn: Option<String>,
 
-    /// Generic OTLP/HTTP endpoint base URL for telemetry export. The
+    /// Removed (ANW-42): use `OTEL_EXPORTER_OTLP_ENDPOINT`.
-    /// per-signal path (`/v1/metrics`, `/v1/traces`) is appended by the
+    #[arg(long, env = "ANWESEN_OTLP_ENDPOINT", hide = true)]
-    /// exporter. Mutually exclusive with --uptrace-dsn.
-    #[arg(long, env = "ANWESEN_OTLP_ENDPOINT")]
     pub otlp_endpoint: Option<String>,
 
-    /// Extra OTLP export header as `key=value`, repeatable. On the env var
+    /// Removed (ANW-42): use `OTEL_EXPORTER_OTLP_HEADERS`.
-    /// (`ANWESEN_OTLP_HEADERS`) pass a comma-separated `key=value` list.
     #[arg(
         long = "otlp-header",
         env = "ANWESEN_OTLP_HEADERS",
-        value_delimiter = ','
+        value_delimiter = ',',
+        hide = true
     )]
     pub otlp_headers: Vec<String>,
 
@@ -172,6 +173,34 @@ mod tests {
         }
     }
 
+    /// The removed telemetry flags still parse, hidden from `--help`. Clap
+    /// rejecting them as unknown would say nothing about the `OTEL_`
+    /// replacement; the migration error in `telemetry::TelemetryConfig`
+    /// needs the values to reach it (ANW-42).
+    #[test]
+    fn serve_still_parses_the_removed_telemetry_flags() {
+        let cli = parse(&[
+            "serve",
+            "--vault",
+            "/tmp/v",
+            "--uptrace-dsn",
+            "https://tok@api.uptrace.dev",
+            "--otlp-endpoint",
+            "https://collector.example.com",
+            "--otlp-header",
+            "authorization=Bearer xyz",
+        ])
+        .expect("parse");
+        match cli.command {
+            Command::Serve(a) => {
+                assert!(a.uptrace_dsn.is_some());
+                assert!(a.otlp_endpoint.is_some());
+                assert_eq!(a.otlp_headers, vec!["authorization=Bearer xyz".to_string()]);
+            }
+            _ => panic!("expected serve"),
+        }
+    }
+
     #[test]
     fn serve_rejects_malformed_bind_at_parse_time() {
         let err = parse(&["serve", "--vault", "/tmp/v", "--bind", "not-an-addr"]).unwrap_err();

src/http.rs

@@ -819,18 +819,23 @@ mod tests {
     }
 
     /// With telemetry installed, a normal request is answered byte-for-byte
-    /// as without it. The exporter points at an unreachable local port, so
+    /// as without it. The test process sets no `OTEL_EXPORTER_OTLP_*`
-    /// export fails instantly in the background and never touches the
+    /// variables, so the exporter aims at the SDK default and fails in the
-    /// response path.
+    /// background without ever touching the response path.
     #[tokio::test]
     async fn telemetry_layer_does_not_alter_responses() {
-        use crate::telemetry::{self, RawTelemetryArgs, TelemetryConfig};
+        use crate::telemetry::{self, OtelEnv, RawTelemetryArgs, TelemetryConfig};
 
-        let cfg = TelemetryConfig::resolve(RawTelemetryArgs {
+        let cfg = TelemetryConfig::resolve(
-            otlp_endpoint: Some("http://127.0.0.1:9".into()),
+            &RawTelemetryArgs {
-            slow_request_ms: 500,
+                slow_request_ms: 500,
-            ..Default::default()
+                ..Default::default()
-        })
+            },
+            OtelEnv {
+                endpoint: Some("http://127.0.0.1:9".into()),
+                ..OtelEnv::default()
+            },
+        )
         .unwrap()
         .expect("telemetry on");
         let tel = Arc::new(telemetry::init(cfg).expect("telemetry init"));

src/main.rs

@@ -10,7 +10,7 @@ use std::sync::Arc;
 use anwesen::app::Anwesen;
 use anwesen::doctor;
 use anwesen::merge;
-use anwesen::telemetry::{self, RawTelemetryArgs, TelemetryConfig};
+use anwesen::telemetry::{self, OtelEnv, RawTelemetryArgs, TelemetryConfig};
 use anyhow::Result;
 use clap::Parser;
 use hydra::Application;
@@ -25,14 +25,18 @@ fn main() -> Result<()> {
     match cli.command {
         Command::Serve(args) => {
             init_logging(args.log_level);
-            // Resolve telemetry config before the supervisor starts; an
+            // Resolve telemetry config before the supervisor starts; no
-            // unset endpoint leaves it `None` (export off, behaves as today).
+            // OTEL_EXPORTER_OTLP_* endpoint leaves it `None` (export off,
-            let telemetry = match TelemetryConfig::resolve(RawTelemetryArgs {
+            // no middleware). A removed flag is a startup error (ANW-42).
-                uptrace_dsn: args.uptrace_dsn,
+            let telemetry = match TelemetryConfig::resolve(
-                otlp_endpoint: args.otlp_endpoint,
+                &RawTelemetryArgs {
-                otlp_headers: args.otlp_headers,
+                    uptrace_dsn: args.uptrace_dsn,
-                slow_request_ms: args.otlp_slow_request_ms,
+                    otlp_endpoint: args.otlp_endpoint,
-            })? {
+                    otlp_headers: args.otlp_headers,
+                    slow_request_ms: args.otlp_slow_request_ms,
+                },
+                OtelEnv::from_env(),
+            )? {
                 Some(cfg) => Some(Arc::new(telemetry::init(cfg)?)),
                 None => None,
             };

src/telemetry.rs

@@ -12,140 +12,288 @@
 //!   the propagated context. Every other request stays metrics-only, so the
 //!   ~3.6k requests/min steady state does not drown the trace backend.
 //!
-//! When no OTLP endpoint (or uptrace DSN) is configured, [`init`] returns
+//! Transport configuration comes from the standard `OTEL_EXPORTER_OTLP_*`
+//! environment variables only, read by the `OpenTelemetry` SDK itself
+//! ([ANW-42](https://crvrs.youtrack.cloud/issue/ANW-42)). anwesen parses no
+//! addresses and appends no per-signal paths. It checks two things at
+//! startup, both cases the SDK would otherwise export nowhere in silence:
+//!
+//! - `OTEL_EXPORTER_OTLP_ENDPOINT` carries no query or fragment, because the
+//!   SDK's own concatenation mangles those (measured against a sink: a
+//!   `?tail` base sends `POST /?tail/v1/metrics`, a `#frag` base sends
+//!   `POST /`).
+//! - No protocol variable asks for anything but `http/protobuf`, the only
+//!   transport this binary is built with.
+//!
+//! When no endpoint variable is set, [`TelemetryConfig::resolve`] returns
 //! `None`, the request middleware is not installed, and the server behaves
 //! exactly as it did before this module existed. External installs run
 //! unchanged.
-//!
-//! Config mirrors the gestell uptrace surface (see the gestell PDR-GES-136
-//! `[otel]` section): a `uptrace_dsn` shorthand, or a generic endpoint plus
-//! headers.
 
-use std::collections::HashMap;
 use std::time::{Duration, SystemTime};
 
-use anyhow::{Context as _, anyhow, bail};
+use anyhow::{Context as _, bail};
 use axum::http::HeaderMap;
 use opentelemetry::KeyValue;
 use opentelemetry::metrics::{Counter, Histogram, MeterProvider as _};
 use opentelemetry::propagation::{Extractor, TextMapPropagator};
 use opentelemetry::trace::{Span, SpanKind, Tracer, TracerProvider as _};
-use opentelemetry_otlp::{
+use opentelemetry_otlp::{MetricExporter, SpanExporter};
-    MetricExporter, Protocol, SpanExporter, WithExportConfig, WithHttpConfig,
-};
 use opentelemetry_sdk::Resource;
 use opentelemetry_sdk::metrics::{PeriodicReader, SdkMeterProvider};
 use opentelemetry_sdk::propagation::TraceContextPropagator;
 use opentelemetry_sdk::trace::Sampler;
 use opentelemetry_sdk::trace::{SdkTracer, SdkTracerProvider};
-use opentelemetry_semantic_conventions::resource::SERVICE_VERSION;
+use opentelemetry_semantic_conventions::resource::{SERVICE_NAME, SERVICE_VERSION};
 
-/// Raw telemetry options as parsed by clap on the `serve` command. Resolved
+/// The removed telemetry options, still parsed so their presence is an error
-/// into an [`Option<TelemetryConfig>`] by [`TelemetryConfig::resolve`].
+/// rather than a silent config drop on upgrade
+/// ([ANW-42](https://crvrs.youtrack.cloud/issue/ANW-42)), plus the one
+/// surviving option. Resolved into an [`Option<TelemetryConfig>`] by
+/// [`TelemetryConfig::resolve`].
 #[derive(Debug, Default)]
 pub struct RawTelemetryArgs {
-    /// `--uptrace-dsn` / `ANWESEN_UPTRACE_DSN`.
+    /// Removed `--uptrace-dsn` / `ANWESEN_UPTRACE_DSN`.
     pub uptrace_dsn: Option<String>,
-    /// `--otlp-endpoint` / `ANWESEN_OTLP_ENDPOINT`.
+    /// Removed `--otlp-endpoint` / `ANWESEN_OTLP_ENDPOINT`.
     pub otlp_endpoint: Option<String>,
-    /// `--otlp-header` / `ANWESEN_OTLP_HEADERS`, each `key=value`.
+    /// Removed `--otlp-header` / `ANWESEN_OTLP_HEADERS`.
     pub otlp_headers: Vec<String>,
-    /// `--otlp-slow-request-ms` / `ANWESEN_OTLP_SLOW_REQUEST_MS`.
+    /// `--otlp-slow-request-ms` / `ANWESEN_OTLP_SLOW_REQUEST_MS`. Kept: it
+    /// decides when anwesen emits a span, not where the export goes, and no
+    /// standard variable covers it.
     pub slow_request_ms: u64,
 }
 
-/// A resolved, telemetry-on configuration. Built only when an endpoint or a
+/// The OTLP transport variables the SDK reads, captured once at startup so
-/// DSN is present; absence is represented by `Ok(None)` from [`resolve`].
+/// the telemetry-on decision and the startup checks stay pure functions of
+/// them. Values are the raw strings; anwesen does not parse them beyond the
+/// checks in [`check_generic_endpoint`] and [`check_protocols`].
+#[derive(Debug, Default, Clone, PartialEq, Eq)]
+pub struct OtelEnv {
+    /// `OTEL_EXPORTER_OTLP_ENDPOINT`: base URL, per-signal path appended by
+    /// the SDK.
+    pub endpoint: Option<String>,
+    /// `OTEL_EXPORTER_OTLP_METRICS_ENDPOINT`: full URL, used verbatim.
+    pub metrics_endpoint: Option<String>,
+    /// `OTEL_EXPORTER_OTLP_TRACES_ENDPOINT`: full URL, used verbatim.
+    pub traces_endpoint: Option<String>,
+    /// `OTEL_EXPORTER_OTLP_PROTOCOL`.
+    pub protocol: Option<String>,
+    /// `OTEL_EXPORTER_OTLP_METRICS_PROTOCOL`.
+    pub metrics_protocol: Option<String>,
+    /// `OTEL_EXPORTER_OTLP_TRACES_PROTOCOL`.
+    pub traces_protocol: Option<String>,
+}
+
+impl OtelEnv {
+    /// Read the transport variables from the process environment. An empty or
+    /// whitespace-only value counts as unset: an empty endpoint would
+    /// otherwise turn telemetry on and export to the SDK's `localhost:4318`
+    /// default.
+    #[must_use]
+    pub fn from_env() -> Self {
+        let var = |name: &str| {
+            std::env::var(name)
+                .ok()
+                .map(|v| v.trim().to_string())
+                .filter(|v| !v.is_empty())
+        };
+        Self {
+            endpoint: var("OTEL_EXPORTER_OTLP_ENDPOINT"),
+            metrics_endpoint: var("OTEL_EXPORTER_OTLP_METRICS_ENDPOINT"),
+            traces_endpoint: var("OTEL_EXPORTER_OTLP_TRACES_ENDPOINT"),
+            protocol: var("OTEL_EXPORTER_OTLP_PROTOCOL"),
+            metrics_protocol: var("OTEL_EXPORTER_OTLP_METRICS_PROTOCOL"),
+            traces_protocol: var("OTEL_EXPORTER_OTLP_TRACES_PROTOCOL"),
+        }
+    }
+
+    /// Whether any endpoint variable is set. No endpoint means telemetry off.
+    fn any_endpoint(&self) -> bool {
+        self.endpoint.is_some() || self.metrics_endpoint.is_some() || self.traces_endpoint.is_some()
+    }
+
+    /// The endpoint to name in the startup log: the generic base when set,
+    /// otherwise whichever per-signal URL is.
+    fn describe(&self) -> &str {
+        self.endpoint
+            .as_deref()
+            .or(self.metrics_endpoint.as_deref())
+            .or(self.traces_endpoint.as_deref())
+            .unwrap_or("")
+    }
+}
+
+/// A resolved, telemetry-on configuration. Built only when an endpoint
+/// variable is set; absence is represented by `Ok(None)` from [`resolve`].
+/// It carries no transport settings: the exporters read those from the
+/// environment themselves.
 ///
 /// [`resolve`]: TelemetryConfig::resolve
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub struct TelemetryConfig {
-    /// OTLP/HTTP base URL. The exporter appends the per-signal path
-    /// (`/v1/metrics`, `/v1/traces`).
-    pub endpoint: String,
-    /// Export headers (for uptrace, the `uptrace-dsn` entry) as ordered
-    /// `(name, value)` pairs.
-    pub headers: Vec<(String, String)>,
     /// A request at or over this duration, or answering a 5xx, is recorded
     /// as a server span.
     pub slow_request: Duration,
+    /// The transport variables, kept for the startup log line only.
+    env: OtelEnv,
 }
 
 impl TelemetryConfig {
-    /// Resolve raw clap options into an optional config.
+    /// Resolve the surviving option plus the OTLP transport variables into an
+    /// optional config.
     ///
-    /// - Both `uptrace_dsn` and `otlp_endpoint` set is an error (they are
+    /// - A removed flag or `ANWESEN_` variable is an error naming its `OTEL_`
-    ///   two ways to name the same endpoint).
+    ///   replacement: a deployment exporting today must fail one restart
-    /// - Neither set means telemetry is off: `Ok(None)`.
+    ///   rather than go quiet.
-    /// - A malformed `key=value` header or an unparseable DSN is an error,
+    /// - No endpoint variable set means telemetry is off: `Ok(None)`.
-    ///   surfaced at startup rather than silently dropping export.
+    /// - A query or fragment on `OTEL_EXPORTER_OTLP_ENDPOINT` is an error.
+    /// - A protocol this binary cannot speak is an error.
     ///
     /// # Errors
-    /// Returns an error when the two endpoint sources conflict, a header is
+    /// Returns an error when a removed option is present, when the generic
-    /// not `key=value`, or the uptrace DSN cannot be parsed.
+    /// endpoint carries a query or a fragment, or when a protocol variable
-    pub fn resolve(raw: RawTelemetryArgs) -> anyhow::Result<Option<Self>> {
+    /// asks for anything but `http/protobuf`.
-        let slow_request = Duration::from_millis(raw.slow_request_ms);
+    pub fn resolve(raw: &RawTelemetryArgs, env: OtelEnv) -> anyhow::Result<Option<Self>> {
-        let mut headers = parse_headers(&raw.otlp_headers)?;
+        check_removed(raw)?;
-
+        if !env.any_endpoint() {
-        match (raw.uptrace_dsn, raw.otlp_endpoint) {
+            return Ok(None);
-            (Some(_), Some(_)) => {
-                bail!("--uptrace-dsn and --otlp-endpoint are mutually exclusive");
-            }
-            (Some(dsn), None) => {
-                let (endpoint, dsn_header) = parse_uptrace_dsn(&dsn)?;
-                // The DSN header leads; any explicit --otlp-header follows.
-                headers.insert(0, dsn_header);
-                Ok(Some(Self {
-                    endpoint,
-                    headers,
-                    slow_request,
-                }))
-            }
-            (None, Some(endpoint)) => Ok(Some(Self {
-                endpoint,
-                headers,
-                slow_request,
-            })),
-            (None, None) => Ok(None),
         }
+        if let Some(endpoint) = &env.endpoint {
+            check_generic_endpoint(endpoint)?;
+        }
+        check_protocols(&env)?;
+        Ok(Some(Self {
+            slow_request: Duration::from_millis(raw.slow_request_ms),
+            env,
+        }))
     }
 }
 
-/// Parse `key=value` header specs. Whitespace around key and value is
+/// Fail on any removed telemetry option, naming the `OTEL_` variable that
-/// trimmed; an empty key or a spec with no `=` is an error.
+/// replaces it. Silence is the expensive failure here: an upgrade that drops
-fn parse_headers(specs: &[String]) -> anyhow::Result<Vec<(String, String)>> {
+/// the export config would stop telemetry with nothing in the log.
-    let mut out = Vec::with_capacity(specs.len());
+fn check_removed(raw: &RawTelemetryArgs) -> anyhow::Result<()> {
-    for spec in specs {
+    let removed: [(&str, &str, bool); 3] = [
-        let (k, v) = spec
+        (
-            .split_once('=')
+            "--uptrace-dsn / ANWESEN_UPTRACE_DSN",
-            .ok_or_else(|| anyhow!("OTLP header {spec:?} is not key=value"))?;
+            "OTEL_EXPORTER_OTLP_ENDPOINT=https://api.uptrace.dev plus \
-        let k = k.trim();
+             OTEL_EXPORTER_OTLP_HEADERS=uptrace-dsn=<the DSN, verbatim>",
-        if k.is_empty() {
+            raw.uptrace_dsn.is_some(),
-            bail!("OTLP header {spec:?} has an empty key");
+        ),
+        (
+            "--otlp-endpoint / ANWESEN_OTLP_ENDPOINT",
+            "OTEL_EXPORTER_OTLP_ENDPOINT",
+            raw.otlp_endpoint.is_some(),
+        ),
+        (
+            "--otlp-header / ANWESEN_OTLP_HEADERS",
+            "OTEL_EXPORTER_OTLP_HEADERS",
+            !raw.otlp_headers.is_empty(),
+        ),
+    ];
+    for (option, replacement, present) in removed {
+        if present {
+            bail!("{option} was removed in anwesen 0.3.0; use {replacement} instead");
         }
-        out.push((k.to_string(), v.trim().to_string()));
     }
-    Ok(out)
+    Ok(())
 }
 
-/// Parse an uptrace DSN (`https://<token>@host[:port]`) into the OTLP
+/// Reject a query or fragment on `OTEL_EXPORTER_OTLP_ENDPOINT`. The SDK
-/// endpoint base URL and the `uptrace-dsn` header uptrace expects. The full
+/// appends the per-signal path to this value textually, so a `?grpc=4317`
-/// DSN is echoed as the header value per uptrace's ingest contract.
+/// tail sends `POST /?grpc=4317/v1/metrics` and a `#frag` tail sends
-fn parse_uptrace_dsn(dsn: &str) -> anyhow::Result<(String, (String, String))> {
+/// `POST /` -- both dead exports, neither logged. Measured against a sink on
-    let dsn = dsn.trim();
+/// opentelemetry-otlp 0.32 ([ANW-42]). A path prefix composes correctly and
-    let (scheme, rest) = dsn
+/// is left alone.
-        .split_once("://")
+///
-        .context("uptrace DSN has no scheme (expected https://<token>@host)")?;
+/// [ANW-42]: https://crvrs.youtrack.cloud/issue/ANW-42
-    // Host is whatever follows the credentials `@`; a DSN with no `@` is
+fn check_generic_endpoint(endpoint: &str) -> anyhow::Result<()> {
-    // treated as endpoint-only (lenient, though real uptrace DSNs carry a
+    if let Some(bad) = endpoint.find(['?', '#']) {
-    // token).
+        let tail = &endpoint[bad..];
-    let host = rest.rsplit_once('@').map_or(rest, |(_, h)| h);
+        bail!(
-    let host = host.trim_end_matches('/');
+            "OTEL_EXPORTER_OTLP_ENDPOINT {endpoint:?} has a trailing {tail:?}; \
-    if host.is_empty() {
+             the exporter would append the signal path after it and export nowhere. \
-        bail!("uptrace DSN has no host");
+             Pass the base URL alone, and put an uptrace DSN in \
+             OTEL_EXPORTER_OTLP_HEADERS=uptrace-dsn=<the DSN, verbatim>"
+        );
     }
-    let endpoint = format!("{scheme}://{host}");
+    Ok(())
-    Ok((endpoint, ("uptrace-dsn".to_string(), dsn.to_string())))
+}
+
+/// The one OTLP protocol this binary speaks. `opentelemetry-otlp` is built
+/// with the `http-proto` feature alone (Cargo.toml), so neither `grpc` nor
+/// `http/json` has a transport behind it.
+const SUPPORTED_PROTOCOL: &str = "http/protobuf";
+
+/// Reject a protocol variable this binary cannot honor. The exporter builder
+/// picks its transport at compile time, so `OTEL_EXPORTER_OTLP_PROTOCOL=grpc`
+/// does not switch anything: the export keeps going out as HTTP protobuf,
+/// with nothing in the log (measured, [ANW-42]). An operator who follows
+/// uptrace's console to the gRPC port would get exactly the dead-silent
+/// export this issue exists to remove, so it fails at startup instead.
+///
+/// [ANW-42]: https://crvrs.youtrack.cloud/issue/ANW-42
+fn check_protocols(env: &OtelEnv) -> anyhow::Result<()> {
+    let vars = [
+        ("OTEL_EXPORTER_OTLP_PROTOCOL", env.protocol.as_deref()),
+        (
+            "OTEL_EXPORTER_OTLP_METRICS_PROTOCOL",
+            env.metrics_protocol.as_deref(),
+        ),
+        (
+            "OTEL_EXPORTER_OTLP_TRACES_PROTOCOL",
+            env.traces_protocol.as_deref(),
+        ),
+    ];
+    for (name, value) in vars {
+        let Some(value) = value else { continue };
+        if value != SUPPORTED_PROTOCOL {
+            bail!(
+                "{name}={value:?} is not supported; this build speaks \
+                 {SUPPORTED_PROTOCOL} only. Unset the variable, and point the \
+                 endpoint at the collector's HTTP port rather than its gRPC one"
+            );
+        }
+    }
+    Ok(())
+}
+
+/// The resource attributes anwesen supplies as defaults, minus every key the
+/// environment already sets.
+///
+/// `service.name=anwesen` and the crate version are defaults, not policy:
+/// contract point 6 of [ANW-42] keeps `OTEL_SERVICE_NAME` and
+/// `OTEL_RESOURCE_ATTRIBUTES` working. Attaching them unconditionally blocks
+/// the override, because an attribute set on the builder wins over the one
+/// the SDK's own detectors read from those variables (measured by sie).
+///
+/// Only key presence matters here; the values stay the SDK's to parse.
+///
+/// [ANW-42]: https://crvrs.youtrack.cloud/issue/ANW-42
+fn default_resource_attrs(
+    service_name: Option<&str>,
+    resource_attributes: Option<&str>,
+) -> Vec<KeyValue> {
+    let from_attrs: Vec<&str> = resource_attributes
+        .unwrap_or_default()
+        .split(',')
+        .filter_map(|entry| entry.split_once('='))
+        .map(|(key, _)| key.trim())
+        .collect();
+    let set_by_env = |key: &str| {
+        (key == SERVICE_NAME && service_name.is_some_and(|v| !v.trim().is_empty()))
+            || from_attrs.contains(&key)
+    };
+    [
+        (SERVICE_NAME, "anwesen"),
+        (SERVICE_VERSION, env!("CARGO_PKG_VERSION")),
+    ]
+    .into_iter()
+    .filter(|(key, _)| !set_by_env(key))
+    .map(|(key, value)| KeyValue::new(key, value))
+    .collect()
 }
 
 /// Semantic route bucket for the `http.route` label. Coarser than the axum
@@ -332,28 +480,29 @@ struct TelemetryInner {
 
 impl TelemetryInner {
     fn new(config: TelemetryConfig) -> anyhow::Result<Self> {
-        let TelemetryConfig {
+        let TelemetryConfig { slow_request, env } = config;
-            endpoint,
-            headers,
-            slow_request,
-        } = config;
-        // `.with_endpoint()` is used verbatim by the exporter (the `/v1/*`
-        // suffix is only auto-appended for the generic OTEL env var), so we
-        // append the per-signal path ourselves.
-        let endpoint = endpoint.trim_end_matches('/').to_string();
-        let header_map: HashMap<String, String> = headers.into_iter().collect();
 
-        let resource = Resource::builder()
+        // Service identity is a default only: a key OTEL_SERVICE_NAME or
-            .with_service_name("anwesen")
+        // OTEL_RESOURCE_ATTRIBUTES already carries is left to the SDK's own
-            .with_attribute(KeyValue::new(SERVICE_VERSION, env!("CARGO_PKG_VERSION")))
+        // detectors, because a builder attribute would win over them.
-            .build();
+        let mut resource = Resource::builder();
+        for attr in default_resource_attrs(
+            std::env::var("OTEL_SERVICE_NAME").ok().as_deref(),
+            std::env::var("OTEL_RESOURCE_ATTRIBUTES").ok().as_deref(),
+        ) {
+            resource = resource.with_attribute(attr);
+        }
+        let resource = resource.build();
 
         // -- metrics: thread-based periodic reader over an OTLP/HTTP exporter.
+        // No endpoint, headers, or protocol here: the SDK reads
+        // OTEL_EXPORTER_OTLP_* itself and composes the per-signal URL
+        // (ANW-42). `.with_http()` picks the only transport this binary is
+        // built with, http/protobuf -- the default, and what anwesen sent
+        // before. Any other OTEL_EXPORTER_OTLP_PROTOCOL value would be
+        // ignored here, so `check_protocols` rejects it at startup.
         let metric_exporter = MetricExporter::builder()
             .with_http()
-            .with_protocol(Protocol::HttpBinary)
-            .with_endpoint(format!("{endpoint}/v1/metrics"))
-            .with_headers(header_map.clone())
             .build()
             .context("build OTLP metric exporter")?;
         let reader = PeriodicReader::builder(metric_exporter)
@@ -386,9 +535,6 @@ impl TelemetryInner {
         // -- traces: thread-based batch processor over an OTLP/HTTP exporter.
         let span_exporter = SpanExporter::builder()
             .with_http()
-            .with_protocol(Protocol::HttpBinary)
-            .with_endpoint(format!("{endpoint}/v1/traces"))
-            .with_headers(header_map)
             .build()
             .context("build OTLP span exporter")?;
         let tracer_provider = SdkTracerProvider::builder()
@@ -401,7 +547,7 @@ impl TelemetryInner {
         let tracer = tracer_provider.tracer("anwesen");
 
         tracing::info!(
-            endpoint = %endpoint,
+            endpoint = %env.describe(),
             slow_request_ms = slow_request.as_millis(),
             "telemetry: OTLP export enabled"
         );
@@ -489,93 +635,208 @@ mod tests {
         RawTelemetryArgs::default()
     }
 
-    #[test]
+    fn generic(endpoint: &str) -> OtelEnv {
-    fn resolve_off_when_nothing_set() {
+        OtelEnv {
-        let cfg = TelemetryConfig::resolve(raw()).unwrap();
+            endpoint: Some(endpoint.into()),
-        assert!(cfg.is_none(), "no endpoint/DSN means telemetry off");
+            ..OtelEnv::default()
+        }
     }
 
     #[test]
-    fn resolve_generic_endpoint() {
+    fn resolve_off_when_no_endpoint_variable_is_set() {
-        let cfg = TelemetryConfig::resolve(RawTelemetryArgs {
+        let cfg = TelemetryConfig::resolve(&raw(), OtelEnv::default()).unwrap();
-            otlp_endpoint: Some("https://collector.example.com".into()),
+        assert!(cfg.is_none(), "no OTEL_ endpoint means telemetry off");
-            otlp_headers: vec!["authorization=Bearer xyz".into()],
+    }
-            slow_request_ms: 500,
+
-            ..raw()
+    #[test]
-        })
+    fn resolve_on_for_each_endpoint_variable() {
-        .unwrap()
+        let per_signal = |field: fn(&mut OtelEnv)| {
-        .expect("telemetry on");
+            let mut env = OtelEnv::default();
-        assert_eq!(cfg.endpoint, "https://collector.example.com");
+            field(&mut env);
-        assert_eq!(
+            env
-            cfg.headers,
+        };
-            vec![("authorization".to_string(), "Bearer xyz".to_string())]
+        for env in [
+            generic("https://collector.example.com"),
+            per_signal(|e| {
+                e.metrics_endpoint = Some("https://collector.example.com/v1/metrics".into());
+            }),
+            per_signal(|e| {
+                e.traces_endpoint = Some("https://collector.example.com/v1/traces".into());
+            }),
+        ] {
+            let cfg = TelemetryConfig::resolve(
+                &RawTelemetryArgs {
+                    slow_request_ms: 250,
+                    ..raw()
+                },
+                env.clone(),
+            )
+            .unwrap_or_else(|e| panic!("{env:?}: {e}"))
+            .expect("telemetry on");
+            assert_eq!(cfg.slow_request, Duration::from_millis(250));
+        }
+    }
+
+    /// The tails the SDK mangles: a query lands in the query string with the
+    /// signal path behind it, a fragment drops the signal path entirely.
+    #[test]
+    fn resolve_rejects_a_query_or_fragment_on_the_generic_endpoint() {
+        for endpoint in [
+            "https://api.uptrace.dev?grpc=4317",
+            "https://api.uptrace.dev/?grpc=4317",
+            "https://api.uptrace.dev:4318?grpc=4317",
+            "https://api.uptrace.dev#frag",
+        ] {
+            let err = TelemetryConfig::resolve(&raw(), generic(endpoint)).unwrap_err();
+            assert!(err.to_string().contains("trailing"), "{endpoint}: {err}");
+        }
+    }
+
+    /// A path prefix composes correctly (`/otlp` -> `POST /otlp/v1/metrics`),
+    /// and the per-signal variables are used verbatim, tail and all.
+    #[test]
+    fn resolve_accepts_a_path_prefix_and_per_signal_tails() {
+        for env in [
+            generic("https://collector.example.com/otlp"),
+            generic("https://collector.example.com/"),
+            OtelEnv {
+                metrics_endpoint: Some("https://api.uptrace.dev/v1/metrics?grpc=4317".into()),
+                ..OtelEnv::default()
+            },
+        ] {
+            TelemetryConfig::resolve(&raw(), env.clone())
+                .unwrap_or_else(|e| panic!("{env:?}: {e}"))
+                .expect("telemetry on");
+        }
+    }
+
+    /// `.with_http()` fixes the transport at compile time, so a protocol this
+    /// build cannot speak is a dead export with nothing in the log.
+    #[test]
+    fn resolve_rejects_a_protocol_this_build_cannot_speak() {
+        let with_protocol = |field: fn(&mut OtelEnv)| {
+            let mut env = generic("https://collector.example.com");
+            field(&mut env);
+            env
+        };
+        for env in [
+            with_protocol(|e| e.protocol = Some("grpc".into())),
+            with_protocol(|e| e.protocol = Some("http/json".into())),
+            with_protocol(|e| e.metrics_protocol = Some("grpc".into())),
+            with_protocol(|e| e.traces_protocol = Some("grpc".into())),
+        ] {
+            let err = TelemetryConfig::resolve(&raw(), env.clone())
+                .unwrap_err()
+                .to_string();
+            assert!(err.contains("http/protobuf"), "{env:?}: {err}");
+        }
+    }
+
+    /// The default protocol is the one this build speaks, so naming it
+    /// explicitly is not an error.
+    #[test]
+    fn resolve_accepts_the_supported_protocol_spelled_out() {
+        let env = OtelEnv {
+            protocol: Some("http/protobuf".into()),
+            metrics_protocol: Some("http/protobuf".into()),
+            ..generic("https://collector.example.com")
+        };
+        TelemetryConfig::resolve(&raw(), env)
+            .unwrap()
+            .expect("telemetry on");
+    }
+
+    /// Contract point 6: `service.name` stays anwesen's default only while
+    /// the environment supplies none. A builder attribute wins over the SDK's
+    /// detectors, so the default has to step aside for the override to work.
+    #[test]
+    fn service_identity_defaults_step_aside_for_the_environment() {
+        let keys = |attrs: &[KeyValue]| {
+            attrs
+                .iter()
+                .map(|kv| kv.key.as_str().to_string())
+                .collect::<Vec<_>>()
+        };
+
+        let plain = default_resource_attrs(None, None);
+        assert_eq!(keys(&plain), [SERVICE_NAME, SERVICE_VERSION]);
+
+        let named = default_resource_attrs(Some("svcname-override"), None);
+        assert_eq!(keys(&named), [SERVICE_VERSION]);
+
+        let attrs = default_resource_attrs(
+            None,
+            Some("deployment.environment=prod,service.name=attrs-override"),
         );
-        assert_eq!(cfg.slow_request, Duration::from_millis(500));
+        assert_eq!(keys(&attrs), [SERVICE_VERSION]);
+
+        let versioned = default_resource_attrs(None, Some("service.version=9.9.9"));
+        assert_eq!(keys(&versioned), [SERVICE_NAME]);
+
+        // An empty OTEL_SERVICE_NAME supplies nothing; the SDK ignores it too.
+        let empty = default_resource_attrs(Some("  "), None);
+        assert_eq!(keys(&empty), [SERVICE_NAME, SERVICE_VERSION]);
     }
 
     #[test]
-    fn resolve_uptrace_dsn_splits_endpoint_and_header() {
+    fn resolve_rejects_the_removed_uptrace_dsn() {
-        let cfg = TelemetryConfig::resolve(RawTelemetryArgs {
+        let err = TelemetryConfig::resolve(
-            uptrace_dsn: Some("https://SECRET_TOKEN@api.uptrace.dev".into()),
+            &RawTelemetryArgs {
-            slow_request_ms: 250,
+                uptrace_dsn: Some("https://tok@api.uptrace.dev".into()),
-            ..raw()
+                ..raw()
-        })
+            },
-        .unwrap()
+            OtelEnv::default(),
-        .expect("telemetry on");
+        )
-        assert_eq!(cfg.endpoint, "https://api.uptrace.dev");
+        .unwrap_err()
-        assert_eq!(
+        .to_string();
-            cfg.headers,
+        assert!(err.contains("--uptrace-dsn"), "{err}");
-            vec![(
+        assert!(err.contains("OTEL_EXPORTER_OTLP_HEADERS"), "{err}");
-                "uptrace-dsn".to_string(),
-                "https://SECRET_TOKEN@api.uptrace.dev".to_string()
-            )]
-        );
-        assert_eq!(cfg.slow_request, Duration::from_millis(250));
     }
 
     #[test]
-    fn resolve_dsn_header_leads_explicit_headers() {
+    fn resolve_rejects_the_removed_otlp_endpoint() {
-        let cfg = TelemetryConfig::resolve(RawTelemetryArgs {
+        let err = TelemetryConfig::resolve(
-            uptrace_dsn: Some("https://tok@api.uptrace.dev".into()),
+            &RawTelemetryArgs {
-            otlp_headers: vec!["x-extra=1".into()],
+                otlp_endpoint: Some("https://collector.example.com".into()),
-            ..raw()
+                ..raw()
-        })
+            },
-        .unwrap()
+            OtelEnv::default(),
-        .expect("telemetry on");
+        )
-        assert_eq!(cfg.headers[0].0, "uptrace-dsn");
+        .unwrap_err()
-        assert_eq!(cfg.headers[1], ("x-extra".to_string(), "1".to_string()));
+        .to_string();
+        assert!(err.contains("--otlp-endpoint"), "{err}");
+        assert!(err.contains("OTEL_EXPORTER_OTLP_ENDPOINT"), "{err}");
     }
 
     #[test]
-    fn resolve_rejects_both_endpoint_sources() {
+    fn resolve_rejects_the_removed_otlp_header() {
-        let err = TelemetryConfig::resolve(RawTelemetryArgs {
+        let err = TelemetryConfig::resolve(
-            uptrace_dsn: Some("https://tok@api.uptrace.dev".into()),
+            &RawTelemetryArgs {
-            otlp_endpoint: Some("https://collector.example.com".into()),
+                otlp_headers: vec!["authorization=Bearer xyz".into()],
-            ..raw()
+                ..raw()
-        })
+            },
+            OtelEnv::default(),
+        )
+        .unwrap_err()
+        .to_string();
+        assert!(err.contains("--otlp-header"), "{err}");
+        assert!(err.contains("OTEL_EXPORTER_OTLP_HEADERS"), "{err}");
+    }
+
+    /// A removed option fails even with a correct `OTEL_` endpoint alongside
+    /// it: the operator's intent is in the flag, and half-applied config is
+    /// the silent failure this issue removes.
+    #[test]
+    fn resolve_rejects_a_removed_option_alongside_a_good_endpoint() {
+        let err = TelemetryConfig::resolve(
+            &RawTelemetryArgs {
+                uptrace_dsn: Some("https://tok@api.uptrace.dev".into()),
+                ..raw()
+            },
+            generic("https://api.uptrace.dev"),
+        )
         .unwrap_err();
-        assert!(err.to_string().contains("mutually exclusive"));
+        assert!(err.to_string().contains("removed"), "{err}");
-    }
-
-    #[test]
-    fn resolve_rejects_malformed_header() {
-        let err = TelemetryConfig::resolve(RawTelemetryArgs {
-            otlp_endpoint: Some("https://collector.example.com".into()),
-            otlp_headers: vec!["no-equals-sign".into()],
-            ..raw()
-        })
-        .unwrap_err();
-        assert!(err.to_string().contains("key=value"));
-    }
-
-    #[test]
-    fn resolve_rejects_dsn_without_scheme() {
-        let err = TelemetryConfig::resolve(RawTelemetryArgs {
-            uptrace_dsn: Some("tok@api.uptrace.dev".into()),
-            ..raw()
-        })
-        .unwrap_err();
-        assert!(err.to_string().contains("scheme"));
     }
 
     #[test]