feat(repository): a route table and resolved server capabilities

Endpoints were 57 inline format! literals with their query strings baked in at
the point of use. That is workable against exactly one server and hostile to
anything else: a second route shape would mean a conditional at every one of
them. They now live in repository/endpoints.rs, one function each, taking
&ServerCapabilities.

Two things fall out of the move:

  - A small Endpoint builder replaces the manual ?/& juggling, so a double or
    trailing separator is structurally impossible rather than something four
    assertions in a deleted test file used to watch for.
  - Both user-scoped route shapes (/Users/{uid}/Items and /Items?userId=) are
    built and tested, though nothing selects the second yet. The family still
    works on 12.0, so migrating is optional; having both means it is a one-line
    change if 13.0 removes them, as the newly written removal policy allows.

ServerCapabilities is resolved once per connection from the version the server
already reported at connect. The version-to-flags mapping lives in exactly one
function and nothing else in the crate compares a version number: a `version < N`
at the point of use re-derives a domain fact where it is consumed, is unreadable
by its second occurrence, and cannot express a backport.

An unrecognised version resolves forward to the newest known generation rather
than being refused, because refusing would make every release expire the moment
the server upgrades. Only a version below the floor is refused.

This commit also carries the two fixes that are NOT capability branches, because
they live in the same files:

  - Authorization replaces X-Emby-Authorization, and ApiKey replaces the api_key
    query parameter. Jellyfin 12.0 disables both legacy spellings by default and
    a migration flips them on upgraded servers too, so this is what actually
    breaks against 12.0. The header value this app already built was always the
    correct MediaBrowser scheme, and both new spellings are ungated on 10.11.x —
    so it is a rename, not a branch. The query-parameter spelling is load-bearing
    rather than cosmetic: stream URLs go to mpv, ExoPlayer and the webview's
    <video>, none of which can send a header.
  - A type-filtered listing now states Recursive explicitly. 12.0 defaults it to
    true for a library parent with IncludeItemTypes where 10.11 returned
    immediate children, so the identical request returned a different result set
    with nothing in the response to say which rule applied. The value sent is the
    one that shipped, so this is a compatibility fix and not a silent behaviour
    change.

A structural test refuses any deprecated auth spelling reaching a request
builder, verified to fail when one is reintroduced. Behaviour is otherwise
preserved: the four previous endpoint builders become test-only shims over the
new table, so the ~20 existing tests encoding DR-116/DR-212/DR-257 now exercise
the production path rather than being deleted.

TRACES: UR-085 | IR-035, DR-279, DR-280, DR-287, DR-288

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

src-tauri/src/repository/capabilities.rs

@@ -0,0 +1,416 @@
+//! What the server on the other end of the wire can actually do.
+//!
+//! One `ServerCapabilities` value is resolved per connection, from the version
+//! the server already reports at `/System/Info/Public`, and every decision that
+//! depends on the server generation reads a **named flag** from it.
+//!
+//! # Why flags and not version comparisons
+//!
+//! A `version < N` written at the point of use re-derives a domain fact where it
+//! is consumed — the same error as a Jellyfin taxonomy in the frontend, and the
+//! reason `check:boundary` exists. It is also unreadable by its second
+//! occurrence (`< 11` says nothing about *what* changed), and it cannot express
+//! a backport, where a behaviour appears in a patch release of an older line.
+//!
+//! So the version → flags mapping lives in exactly one function
+//! ([`ServerCapabilities::for_version`]) and nothing else in the crate compares
+//! a version number.
+//!
+//! # Why an unknown version resolves forward
+//!
+//! A server newer than this build resolves to the newest capability set we know
+//! rather than being refused. Refusing would make every JellyTau release expire
+//! the moment the server upgrades, which is the failure UR-085 exists to remove.
+//! Refusal is reserved for a version *below* [`MINIMUM_SUPPORTED_MAJOR_MINOR`],
+//! where failure is certain rather than merely likely.
+//!
+//! TRACES: UR-085 | IR-035, DR-280
+
+use std::fmt;
+
+/// The oldest server this build will talk to, as `(major, minor)`.
+///
+/// This is the current target and not a researched floor: no older server has
+/// been tested against, so claiming support for one would be a guess. Lower it
+/// when a real server has been exercised, not before.
+pub const MINIMUM_SUPPORTED_MAJOR_MINOR: (u32, u32) = (10, 10);
+
+/// A parsed server version.
+///
+/// Jellyfin reports things like `10.11.5`, `10.11.5.0` and occasionally a
+/// build suffix (`10.11.5-rc1`). Only the leading numeric components are
+/// meaningful here; anything after them is preserved in `raw` for logging and
+/// otherwise ignored.
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct ServerVersion {
+    pub major: u32,
+    pub minor: u32,
+    pub patch: u32,
+    pub raw: String,
+}
+
+impl ServerVersion {
+    /// Parse what `/System/Info/Public` reported.
+    ///
+    /// Returns `None` for anything without at least a numeric major, which is
+    /// treated as "unknown" rather than as an error — an unparseable version is
+    /// not a reason to refuse a server that may work perfectly well.
+    pub fn parse(raw: &str) -> Option<Self> {
+        let trimmed = raw.trim();
+        if trimmed.is_empty() {
+            return None;
+        }
+
+        // Stop at the first character that cannot begin a numeric component, so
+        // `10.11.5-rc1` and `10.11.5+build7` both yield 10.11.5.
+        let numeric_prefix: String = trimmed
+            .chars()
+            .take_while(|c| c.is_ascii_digit() || *c == '.')
+            .collect();
+
+        let mut parts = numeric_prefix.split('.').filter(|p| !p.is_empty());
+        let major = parts.next()?.parse().ok()?;
+        let minor = parts.next().and_then(|p| p.parse().ok()).unwrap_or(0);
+        let patch = parts.next().and_then(|p| p.parse().ok()).unwrap_or(0);
+
+        Some(Self {
+            major,
+            minor,
+            patch,
+            raw: trimmed.to_string(),
+        })
+    }
+
+    fn is_below_floor(&self) -> bool {
+        (self.major, self.minor) < MINIMUM_SUPPORTED_MAJOR_MINOR
+    }
+}
+
+impl fmt::Display for ServerVersion {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "{}.{}.{}", self.major, self.minor, self.patch)
+    }
+}
+
+/// How this build classified the server it is talking to.
+///
+/// There are exactly two live cases, and the gap between them is not a typo:
+/// **Jellyfin 11.0 does not exist and never did.** With 12.0 the project dropped
+/// the leading `10` from its scheme, so what would have been 10.12.0 shipped as
+/// `12.0` and the server reports `Version: "12.0.0"`. 12.0 is therefore *one*
+/// release-branch step from 10.11, not two, and `major == 11` will never occur.
+///
+/// Source: <https://jellyfin.org/posts/jellyfin-release-12.0>, which explicitly
+/// flags version-string parsers as the thing to check before upgrading.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum ServerGeneration {
+    /// The 10.x line — `major == 10`. What this client was built against.
+    V10_11,
+    /// The post-rename line — `major >= 12`.
+    V12Plus,
+    /// The server did not report a parseable version. Treated as the older
+    /// generation, which is the conservative choice: its flags are the ones that
+    /// also work on 12.x.
+    Unknown,
+}
+
+/// The resolved answer, carried by `OnlineRepository` for the life of a
+/// connection.
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct ServerCapabilities {
+    pub version: Option<ServerVersion>,
+    pub generation: ServerGeneration,
+
+    /// Whether item queries go to `/Users/{userId}/Items` (`true`) or to
+    /// `/Items?userId=` (`false`).
+    ///
+    /// **`true` for every generation, and deliberately so.** The whole
+    /// `/Users/{userId}/…` family still exists and still works in 12.0 — only
+    /// six routes were removed anywhere, and the only user-scoped one is
+    /// `POST /Users/{userId}/EasyPassword`, which this client never called.
+    ///
+    /// What *did* change is policy: the family has carried `[Obsolete]` and been
+    /// hidden from the OpenAPI spec since 10.11.5, and 12.0 states in writing
+    /// that unspecified endpoints "can be removed in any major release without
+    /// warning". The replacements (`/Items?userId=` and friends) already exist
+    /// on 10.11.5, so migrating is a one-generation-compatible change whenever
+    /// it is wanted — which is why the route table carries both shapes even
+    /// though nothing selects the second one yet. See DR-282.
+    pub user_scoped_item_routes: bool,
+
+    /// Whether the server honours the **audio codec** in a submitted
+    /// `DirectPlayProfile`.
+    ///
+    /// `false` on 10.11.5: it enforces the profile's container and video codec
+    /// but ignores its audio codec, so it offers direct play for an E-AC-3 track
+    /// the renderer cannot decode and the picture plays in silence. The client
+    /// therefore has to overrule the server's own direct-play offer. See
+    /// `device_profile::audio_forces_transcode` and DR-283.
+    ///
+    /// **Still `false` on 12.x, and that is an admission rather than a finding.**
+    /// A source-level diff of 12.0 could not establish whether the underlying
+    /// behaviour changed; it established only that 12.0 *reports* codec
+    /// mismatches in `TranscodeReasons` which 10.11.5 omitted, which is not the
+    /// same claim. Keeping the override on costs a transcode that might not be
+    /// needed; turning it off on a guess costs silent playback. Flip it only
+    /// against a running 12.x server.
+    pub honours_directplay_audio_codec: bool,
+
+    /// Whether a source whose container is a *manifest* (`hls`, `applehttp`,
+    /// `dash`) may be direct-played. 12.0 makes such sources ineligible; on
+    /// 10.11.x they were eligible, which is what this client has assumed.
+    pub supports_manifest_container_direct_play: bool,
+
+    /// Whether asking the image endpoint for a size larger than the stored image
+    /// returns that size. 10.11.x upscaled; 12.0 returns the original instead.
+    /// Governs layout expectation only — a smaller image is never an error.
+    pub image_endpoint_upscales: bool,
+}
+
+impl ServerCapabilities {
+    /// The single place a version becomes behaviour. Nothing else in the crate
+    /// compares a version number.
+    pub fn for_version(version: Option<ServerVersion>) -> Self {
+        let generation = match &version {
+            None => ServerGeneration::Unknown,
+            // `major >= 12` and `major == 10` are the two live cases; 11 will
+            // never occur. A hypothetical 11 sorts with the older line, which is
+            // the conservative side.
+            Some(v) if v.major >= 12 => ServerGeneration::V12Plus,
+            Some(_) => ServerGeneration::V10_11,
+        };
+
+        let v12 = generation == ServerGeneration::V12Plus;
+
+        Self {
+            version,
+            generation,
+            // Unchanged across both generations — see each flag's docs. Note the
+            // two genuinely breaking changes 12.0 introduced (the auth spelling
+            // and the `Recursive` default) are fixed by writing the request
+            // correctly for *both*, so neither appears here. A flag is a silent
+            // branch that outlives the reason it was added; keep them for
+            // genuine either/or behaviour only.
+            user_scoped_item_routes: true,
+            honours_directplay_audio_codec: false,
+            supports_manifest_container_direct_play: !v12,
+            image_endpoint_upscales: !v12,
+        }
+    }
+
+    /// Resolve straight from what the server reported.
+    pub fn from_reported(raw_version: &str) -> Self {
+        Self::for_version(ServerVersion::parse(raw_version))
+    }
+
+    /// What this build assumes with no server to ask — the current target.
+    /// Used by offline paths and by tests that do not care.
+    pub fn assumed() -> Self {
+        Self::for_version(None)
+    }
+
+    /// Whether the server is old enough that failure is certain rather than
+    /// likely. An unparseable version is never below the floor: we do not refuse
+    /// a server on the strength of not understanding its version string.
+    pub fn is_below_supported_floor(&self) -> bool {
+        self.version.as_ref().is_some_and(|v| v.is_below_floor())
+    }
+}
+
+impl Default for ServerCapabilities {
+    fn default() -> Self {
+        Self::assumed()
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    /// TRACES: UR-085 | DR-280
+    #[test]
+    fn parses_the_shapes_a_real_server_reports() {
+        assert_eq!(
+            ServerVersion::parse("10.11.5").unwrap().to_string(),
+            "10.11.5"
+        );
+        // Four components: Jellyfin reports these, the fourth is ignored.
+        assert_eq!(
+            ServerVersion::parse("10.11.5.0").unwrap().to_string(),
+            "10.11.5"
+        );
+        // A pre-release suffix must not defeat parsing.
+        assert_eq!(
+            ServerVersion::parse("10.11.5-rc1").unwrap().to_string(),
+            "10.11.5"
+        );
+        assert_eq!(
+            ServerVersion::parse("10.11.5+build7").unwrap().to_string(),
+            "10.11.5"
+        );
+        // Missing components default rather than failing.
+        assert_eq!(ServerVersion::parse("11").unwrap().to_string(), "11.0.0");
+        assert_eq!(
+            ServerVersion::parse(" 10.10 ").unwrap().to_string(),
+            "10.10.0"
+        );
+    }
+
+    /// Nonsense is "unknown", never a panic and never a refusal.
+    ///
+    /// TRACES: UR-085 | DR-280, DR-286
+    #[test]
+    fn unparseable_versions_are_unknown_not_fatal() {
+        for raw in ["", "   ", "not-a-version", "v", "-", "..."] {
+            assert!(
+                ServerVersion::parse(raw).is_none(),
+                "{raw:?} should not parse"
+            );
+        }
+        let caps = ServerCapabilities::from_reported("not-a-version");
+        assert_eq!(caps.generation, ServerGeneration::Unknown);
+        assert!(
+            !caps.is_below_supported_floor(),
+            "an unreadable version must not refuse a server that may work"
+        );
+    }
+
+    /// A server newer than this build keeps working. Refusing it would make
+    /// every release expire the moment the server upgrades.
+    ///
+    /// TRACES: UR-085 | DR-286
+    #[test]
+    fn a_newer_than_known_server_resolves_forward() {
+        let newer = ServerCapabilities::from_reported("99.0.0");
+        assert_eq!(newer.generation, ServerGeneration::V12Plus);
+        assert!(!newer.is_below_supported_floor());
+
+        // It resolves to the newest known generation's flags; only the recorded
+        // version differs.
+        let known = ServerCapabilities::from_reported("12.0.0");
+        assert_eq!(
+            newer,
+            ServerCapabilities {
+                version: newer.version.clone(),
+                ..known
+            }
+        );
+    }
+
+    /// The version scheme changed: 12.0 *is* 10.12 renamed, so 11 never occurs
+    /// and a parser must not assume a leading `10.`.
+    ///
+    /// TRACES: UR-085 | DR-280
+    #[test]
+    fn the_two_live_generations_are_10_and_12_with_no_11() {
+        assert_eq!(
+            ServerCapabilities::from_reported("10.11.5").generation,
+            ServerGeneration::V10_11
+        );
+        assert_eq!(
+            ServerCapabilities::from_reported("12.0.0").generation,
+            ServerGeneration::V12Plus
+        );
+        // 11 cannot be reported by any real server; if one somehow does, it
+        // sorts with the older line rather than being treated as newer.
+        assert_eq!(
+            ServerCapabilities::from_reported("11.0.0").generation,
+            ServerGeneration::V10_11
+        );
+    }
+
+    /// The flags that genuinely differ, and only those.
+    ///
+    /// TRACES: UR-085 | DR-283
+    #[test]
+    fn manifest_direct_play_and_upscaling_are_the_flags_that_differ() {
+        let old = ServerCapabilities::from_reported("10.11.5");
+        let new = ServerCapabilities::from_reported("12.0.0");
+
+        assert!(old.supports_manifest_container_direct_play);
+        assert!(!new.supports_manifest_container_direct_play);
+        assert!(old.image_endpoint_upscales);
+        assert!(!new.image_endpoint_upscales);
+
+        // The two breaking changes 12.0 introduced are NOT flags: they are fixed
+        // by writing the request correctly for both generations.
+        assert_eq!(old.user_scoped_item_routes, new.user_scoped_item_routes);
+        assert_eq!(
+            old.honours_directplay_audio_codec, new.honours_directplay_audio_codec,
+            "unestablished against a running 12.x server; must not be flipped on a guess"
+        );
+    }
+
+    /// Nothing may reintroduce an authentication spelling that 12.0 disables by
+    /// default. The header *value* is correct on both generations; only the
+    /// names were deprecated, so this is a structural guard.
+    ///
+    /// TRACES: UR-085 | DR-287
+    #[test]
+    fn no_deprecated_auth_spelling_reaches_a_request_builder() {
+        let sources: &[(&str, &str)] = &[
+            ("repository/online.rs", include_str!("online.rs")),
+            ("jellyfin/client.rs", include_str!("../jellyfin/client.rs")),
+            (
+                "jellyfin/http_client.rs",
+                include_str!("../jellyfin/http_client.rs"),
+            ),
+            ("auth/mod.rs", include_str!("../auth/mod.rs")),
+        ];
+
+        for (name, src) in sources {
+            assert!(
+                !src.contains(r#".header("X-Emby-Authorization""#),
+                "{name}: X-Emby-Authorization is disabled by default on Jellyfin 12.0 \
+                 (a migration flips it on upgraded servers too). Use `Authorization` \
+                 with the same MediaBrowser value — ungated on both generations."
+            );
+            assert!(
+                !src.contains(r#".header("X-Emby-Token""#)
+                    && !src.contains(r#".header("X-MediaBrowser-Token""#),
+                "{name}: token headers are gated behind EnableLegacyAuthorization on 12.0"
+            );
+            assert!(
+                !src.contains("api_key="),
+                "{name}: `api_key` as a query parameter is gated on 12.0. Use `ApiKey`, \
+                 ungated on both and what the server itself emits."
+            );
+        }
+    }
+
+    /// TRACES: UR-085 | DR-286
+    #[test]
+    fn a_server_below_the_floor_is_refused() {
+        assert!(ServerCapabilities::from_reported("10.9.11").is_below_supported_floor());
+        assert!(ServerCapabilities::from_reported("9.0.0").is_below_supported_floor());
+        assert!(!ServerCapabilities::from_reported("10.10.0").is_below_supported_floor());
+        assert!(!ServerCapabilities::from_reported("10.11.5").is_below_supported_floor());
+    }
+
+    /// The documented 10.11.5 behaviour, pinned so that flipping it later is a
+    /// deliberate act with a citation rather than a drive-by edit.
+    ///
+    /// TRACES: UR-085 | DR-283
+    #[test]
+    fn the_current_target_does_not_honour_directplay_audio_codec() {
+        let caps = ServerCapabilities::from_reported("10.11.5");
+        assert_eq!(caps.generation, ServerGeneration::V10_11);
+        assert!(
+            !caps.honours_directplay_audio_codec,
+            "10.11.5 ignores a DirectPlayProfile's audio codec; the client must overrule it"
+        );
+    }
+
+    /// No generation may quietly acquire an unverified route change.
+    ///
+    /// TRACES: UR-085 | DR-282
+    #[test]
+    fn no_generation_yet_disables_user_scoped_routes() {
+        for raw in ["10.10.0", "10.11.5", "11.0.0", "12.0.0", "99.9.9"] {
+            assert!(
+                ServerCapabilities::from_reported(raw).user_scoped_item_routes,
+                "{raw}: flipping this needs a cited upstream source (DR-282), not a guess"
+            );
+        }
+    }
+}

src-tauri/src/repository/endpoints.rs

@@ -0,0 +1,858 @@
+//! Every Jellyfin route the online repository speaks, in one place.
+//!
+//! Before this module the endpoints were 57 inline `format!` literals scattered
+//! through `online.rs`, query strings baked in at the point of use. That is
+//! workable against exactly one server, and hostile to anything else: a second
+//! route shape means a conditional at every one of them.
+//!
+//! Each function here takes `&ServerCapabilities` and returns a **path**
+//! (`/Users/…`), except the handful documented as returning an absolute URL
+//! because they are handed to a media player rather than to the JSON helpers.
+//!
+//! # Percent-encoding
+//!
+//! Values are encoded, syntax is not. A genre named `Drama & Romance` or a
+//! search for `a?b` must not split into another parameter. [`Endpoint::param`]
+//! encodes; [`Endpoint::raw_param`] does not and is for values this module
+//! itself composed (numbers, and lists whose separator is meaningful to
+//! Jellyfin — `IncludeItemTypes` splits on `,`, `Genres` on `|`, so the
+//! separator survives while each element is encoded).
+//!
+//! TRACES: UR-085 | DR-279
+
+use super::capabilities::ServerCapabilities;
+use super::types::{GetItemsOptions, SearchScope};
+
+/// A path plus query string, which knows whether it needs `?` or `&` next.
+///
+/// The manual separator juggling this replaces produced the double-ampersand and
+/// trailing-ampersand cases an earlier test file spent four assertions on.
+/// Making it structural is cheaper than testing for it.
+pub struct Endpoint {
+    buf: String,
+    has_query: bool,
+}
+
+impl Endpoint {
+    pub fn new(path: &str) -> Self {
+        // A caller may hand in a path that already carries a query.
+        let has_query = path.contains('?');
+        Self {
+            buf: path.to_string(),
+            has_query,
+        }
+    }
+
+    fn separator(&mut self) -> char {
+        if self.has_query {
+            '&'
+        } else {
+            self.has_query = true;
+            '?'
+        }
+    }
+
+    /// Append `key=value`, percent-encoding the value.
+    pub fn param(mut self, key: &str, value: &str) -> Self {
+        let sep = self.separator();
+        self.buf
+            .push_str(&format!("{}{}={}", sep, key, urlencoding::encode(value)));
+        self
+    }
+
+    /// Append `key=value` verbatim. Only for values this module composed.
+    pub fn raw_param(mut self, key: &str, value: &str) -> Self {
+        let sep = self.separator();
+        self.buf.push_str(&format!("{}{}={}", sep, key, value));
+        self
+    }
+
+    pub fn build(self) -> String {
+        self.buf
+    }
+}
+
+/// Encode each element of a list while keeping the separator Jellyfin splits on.
+fn encode_list(values: impl IntoIterator<Item = impl AsRef<str>>, separator: &str) -> String {
+    values
+        .into_iter()
+        .map(|v| urlencoding::encode(v.as_ref()).into_owned())
+        .collect::<Vec<_>>()
+        .join(separator)
+}
+
+/// The base for a user-scoped item query.
+///
+/// This is the one place the two route shapes differ, and the reason the route
+/// table exists at all. `user_scoped_item_routes` is `true` for every generation
+/// today — see the flag's own documentation for why flipping it needs a cited
+/// source rather than a guess (DR-282).
+fn user_items_root(caps: &ServerCapabilities, user_id: &str) -> Endpoint {
+    if caps.user_scoped_item_routes {
+        Endpoint::new(&format!("/Users/{}/Items", user_id))
+    } else {
+        Endpoint::new("/Items").param("userId", user_id)
+    }
+}
+
+/// The standard field set for a list view. `People` is deliberately absent — it
+/// is only wanted in the detail view, and it is not small.
+const LIST_FIELDS: &str = "BackdropImageTags,ParentBackdropImageTags,UserData";
+
+/// As [`LIST_FIELDS`], plus what the offline store needs to derive genre lists
+/// and per-genre counts from cached rows.
+const LIST_FIELDS_WITH_GENRES: &str =
+    "BackdropImageTags,ParentBackdropImageTags,Genres,PremiereDate,UserData";
+
+// ===== Libraries and items =====
+
+/// The user's library views.
+///
+/// TRACES: UR-007, UR-085 | JA-003, DR-279
+pub fn user_views(_caps: &ServerCapabilities, user_id: &str) -> String {
+    format!("/Users/{}/Views", user_id)
+}
+
+/// One item, in detail. `People`, `MediaStreams` and `MediaSources` are named
+/// here and nowhere else — the detail view is the only place they are wanted.
+///
+/// TRACES: UR-007, UR-085 | JA-005, DR-279
+pub fn item_detail(caps: &ServerCapabilities, user_id: &str, item_id: &str) -> String {
+    let base = if caps.user_scoped_item_routes {
+        Endpoint::new(&format!(
+            "/Users/{}/Items/{}",
+            user_id,
+            urlencoding::encode(item_id)
+        ))
+    } else {
+        Endpoint::new(&format!("/Items/{}", urlencoding::encode(item_id))).param("userId", user_id)
+    };
+    base.raw_param(
+        "Fields",
+        "BackdropImageTags,ParentBackdropImageTags,People,MediaStreams,MediaSources,PremiereDate,UserData",
+    )
+    .build()
+}
+
+/// A folder listing.
+///
+/// Every value is percent-encoded before it goes into the query string: these
+/// are values, not URL syntax, so a space or an `&` in one must not split it
+/// into another parameter.
+///
+/// TRACES: UR-007, UR-067, UR-085 | DR-116, DR-212, DR-279 | UT-104, UT-206
+pub fn get_items(
+    caps: &ServerCapabilities,
+    user_id: &str,
+    parent_id: &str,
+    options: Option<&GetItemsOptions>,
+) -> String {
+    let mut ep = user_items_root(caps, user_id).param("ParentId", parent_id);
+
+    if let Some(opts) = options {
+        if let Some(limit) = opts.limit {
+            ep = ep.raw_param("Limit", &limit.to_string());
+        }
+        if let Some(start_index) = opts.start_index {
+            ep = ep.raw_param("StartIndex", &start_index.to_string());
+        }
+        if let Some(types) = &opts.include_item_types {
+            // The comma is the list separator Jellyfin splits on, so encode
+            // each type rather than the joined string.
+            ep = ep.raw_param("IncludeItemTypes", &encode_list(types, ","));
+        }
+
+        // An explicit sort always wins; the container's default only fills the
+        // gap when the caller named none. A caller that names neither gets no
+        // SortBy at all, leaving the server's own order intact.
+        //
+        // TRACES: UR-007 | DR-257 | UT-229
+        let default_sort = super::types::default_listing_sort(opts.parent_kind);
+        let sort_by = opts
+            .sort_by
+            .as_deref()
+            .or(default_sort.map(|(field, _)| field));
+        let sort_order = opts
+            .sort_order
+            .as_deref()
+            .or(default_sort.map(|(_, order)| order));
+
+        if let Some(sort_by) = sort_by {
+            // SortBy is likewise comma-delimited ("ParentIndexNumber,IndexNumber,
+            // SortName"), so encode per field.
+            ep = ep.raw_param("SortBy", &encode_list(sort_by.split(','), ","));
+        }
+        if let Some(sort_order) = sort_order {
+            ep = ep.param("SortOrder", sort_order);
+        }
+        // Jellyfin 12.0 defaults `recursive` to true when the parent is a
+        // library folder and `IncludeItemTypes` is set, where 10.11 listed only
+        // immediate children — the same request, a different result set. State
+        // it explicitly whenever a type filter is present so both generations
+        // agree, and state the behaviour that shipped rather than adopting the
+        // new server-side default silently.
+        //
+        // TRACES: UR-085 | DR-288
+        let type_filtered = opts
+            .include_item_types
+            .as_ref()
+            .is_some_and(|types| !types.is_empty());
+        match (opts.recursive, type_filtered) {
+            (Some(recursive), _) => ep = ep.raw_param("Recursive", &recursive.to_string()),
+            (None, true) => ep = ep.raw_param("Recursive", "false"),
+            (None, false) => {}
+        }
+        if let Some(genres) = &opts.genres {
+            if !genres.is_empty() {
+                // Genre names may contain spaces or ampersands; `|` is the
+                // separator Jellyfin splits this one on.
+                ep = ep.raw_param("Genres", &encode_list(genres, "|"));
+            }
+        }
+        // TRACES: UR-067 | DR-116 | UT-104
+        if opts.favorites_only == Some(true) {
+            ep = ep.raw_param("Filters", "IsFavorite");
+        }
+    }
+
+    ep.raw_param("Fields", LIST_FIELDS_WITH_GENRES).build()
+}
+
+/// A "recently added" listing.
+///
+/// `GroupItems=true` is the load-bearing parameter: Jellyfin defaults it to
+/// `false`, which returns each newly-added *leaf* separately, so importing one
+/// 14-track album pushed 14 rows into "recently added" and buried everything
+/// else. With grouping on, the server collapses children into the container
+/// that was added — an album appears once, while movies (which have no such
+/// container) are unaffected.
+///
+/// TRACES: UR-024, UR-034, UR-085 | IR-024, JA-016, DR-279
+pub fn latest_items(
+    caps: &ServerCapabilities,
+    user_id: &str,
+    parent_id: &str,
+    limit: Option<usize>,
+) -> String {
+    let base = if caps.user_scoped_item_routes {
+        Endpoint::new(&format!("/Users/{}/Items/Latest", user_id))
+    } else {
+        Endpoint::new("/Items/Latest").param("userId", user_id)
+    };
+    base.param("ParentId", parent_id)
+        .raw_param("Limit", &limit.unwrap_or(16).to_string())
+        .raw_param("GroupItems", "true")
+        .raw_param("Fields", LIST_FIELDS)
+        .build()
+}
+
+/// The resume ("Continue Watching") listing.
+///
+/// TRACES: UR-019, UR-085 | JA-013, DR-279
+pub fn resume_items(
+    caps: &ServerCapabilities,
+    user_id: &str,
+    limit: usize,
+    include_item_types: Option<&str>,
+    parent_id: Option<&str>,
+) -> String {
+    let base = if caps.user_scoped_item_routes {
+        Endpoint::new(&format!("/Users/{}/Items/Resume", user_id))
+    } else {
+        Endpoint::new("/Items/Resume").param("userId", user_id)
+    };
+    let ep = base
+        .raw_param("Limit", &limit.to_string())
+        .raw_param("MediaTypes", "Video");
+    let ep = match include_item_types {
+        Some(types) => ep.raw_param("IncludeItemTypes", types),
+        None => ep,
+    };
+    let ep = ep.raw_param("Fields", LIST_FIELDS);
+    match parent_id {
+        Some(pid) => ep.param("ParentId", pid).build(),
+        None => ep.build(),
+    }
+}
+
+/// A Next Up listing.
+///
+/// `EnableResumable=false` is the point of this query: the server default is
+/// `true`, which makes a partially-watched episode its own series' "next up" —
+/// the very episode `/Items/Resume` returns — so Continue Watching and Next Up
+/// end up showing the same cards. Servers predating the parameter ignore it,
+/// which is why the frontend also drops in-progress entries (DR-197).
+///
+/// TRACES: UR-023, UR-059, UR-085 | DR-197, DR-279, JA-014, JA-036 | UT-190, UT-191
+pub fn next_up(
+    _caps: &ServerCapabilities,
+    user_id: &str,
+    series_id: Option<&str>,
+    limit: Option<usize>,
+) -> String {
+    let ep = Endpoint::new("/Shows/NextUp")
+        .param("UserId", user_id)
+        .raw_param("Limit", &limit.unwrap_or(16).to_string())
+        .raw_param("EnableResumable", "false")
+        .raw_param("Fields", LIST_FIELDS);
+
+    match series_id {
+        Some(sid) => ep.param("SeriesId", sid).build(),
+        None => ep.build(),
+    }
+}
+
+/// A favourites listing.
+///
+/// `scope` is expanded here — `SearchScope::All` yields `None`, and the
+/// `IncludeItemTypes` filter is then **omitted entirely** rather than sent as a
+/// union, which would silently drop every type nobody enumerated (see
+/// `SearchScope::item_types`).
+///
+/// TRACES: UR-067, UR-085 | DR-115, DR-279, JA-033 | UT-100
+pub fn favorites(
+    caps: &ServerCapabilities,
+    user_id: &str,
+    scope: SearchScope,
+    options: Option<&GetItemsOptions>,
+) -> String {
+    let mut ep = user_items_root(caps, user_id)
+        .raw_param("Filters", "IsFavorite")
+        .raw_param("Recursive", "true");
+
+    if let Some(types) = scope.item_types() {
+        ep = ep.raw_param("IncludeItemTypes", &types.join(","));
+    }
+
+    // Jellyfin has no "date favourited", so name order is the only stable sort
+    // available; callers may still override it.
+    let sort_by = options
+        .and_then(|o| o.sort_by.as_deref())
+        .unwrap_or("SortName");
+    let sort_order = options
+        .and_then(|o| o.sort_order.as_deref())
+        .unwrap_or("Ascending");
+    ep = ep
+        .raw_param("SortBy", sort_by)
+        .raw_param("SortOrder", sort_order);
+
+    if let Some(limit) = options.and_then(|o| o.limit) {
+        ep = ep.raw_param("Limit", &limit.to_string());
+    }
+    if let Some(start_index) = options.and_then(|o| o.start_index) {
+        ep = ep.raw_param("StartIndex", &start_index.to_string());
+    }
+
+    ep.raw_param("Fields", LIST_FIELDS_WITH_GENRES).build()
+}
+
+/// Items sorted by when they were last played, filtered to played ones.
+///
+/// TRACES: UR-034, UR-085 | DR-279
+pub fn played_items_by_date(
+    caps: &ServerCapabilities,
+    user_id: &str,
+    include_item_types: &str,
+    limit: usize,
+    sort_order: &str,
+    parent_id: Option<&str>,
+) -> String {
+    let ep = user_items_root(caps, user_id)
+        .raw_param("SortBy", "DatePlayed")
+        .raw_param("SortOrder", sort_order)
+        .raw_param("IncludeItemTypes", include_item_types)
+        .raw_param("Limit", &limit.to_string())
+        .raw_param("Recursive", "true")
+        .raw_param("Filters", "IsPlayed")
+        .raw_param("Fields", LIST_FIELDS);
+    match parent_id {
+        Some(pid) => ep.param("ParentId", pid).build(),
+        None => ep.build(),
+    }
+}
+
+/// Genres, with the item counts the frontend uses to pick a diverse subset.
+///
+/// TRACES: UR-085 | DR-279
+pub fn genres(
+    _caps: &ServerCapabilities,
+    user_id: &str,
+    include_item_types: &str,
+    parent_id: Option<&str>,
+) -> String {
+    let ep = Endpoint::new("/Genres")
+        .param("UserId", user_id)
+        .raw_param("IncludeItemTypes", include_item_types)
+        .raw_param("Recursive", "true")
+        .raw_param("Fields", "ItemCounts");
+    match parent_id {
+        Some(pid) => ep.param("ParentId", pid).build(),
+        None => ep.build(),
+    }
+}
+
+/// A search.
+///
+/// TRACES: UR-085 | DR-279
+pub fn search(
+    caps: &ServerCapabilities,
+    user_id: &str,
+    term: &str,
+    limit: usize,
+    include_item_types: Option<&[String]>,
+) -> String {
+    let ep = user_items_root(caps, user_id)
+        .param("SearchTerm", term)
+        .raw_param("Limit", &limit.to_string())
+        .raw_param("Recursive", "true");
+    match include_item_types {
+        Some(types) if !types.is_empty() => ep
+            .raw_param("IncludeItemTypes", &encode_list(types, ","))
+            .build(),
+        _ => ep.build(),
+    }
+}
+
+/// A person's filmography.
+///
+/// TRACES: UR-036, UR-085 | JA-031, DR-279
+pub fn items_by_person(
+    caps: &ServerCapabilities,
+    user_id: &str,
+    person_id: &str,
+    limit: usize,
+    include_item_types: Option<&[String]>,
+) -> String {
+    let ep = user_items_root(caps, user_id)
+        .param("PersonIds", person_id)
+        .raw_param("Limit", &limit.to_string())
+        .raw_param("Recursive", "true")
+        .raw_param("Fields", LIST_FIELDS);
+    match include_item_types {
+        Some(types) if !types.is_empty() => ep
+            .raw_param("IncludeItemTypes", &encode_list(types, ","))
+            .build(),
+        _ => ep.build(),
+    }
+}
+
+/// A person as an item.
+///
+/// Jellyfin serves people through the ordinary user-item endpoint rather than
+/// anything under `/Persons`; the cast entries on an item's `People` field carry
+/// the ids this is called with.
+///
+/// TRACES: UR-035, UR-036, UR-085 | IR-022, JA-030, DR-279
+pub fn person(caps: &ServerCapabilities, user_id: &str, person_id: &str) -> String {
+    if caps.user_scoped_item_routes {
+        format!(
+            "/Users/{}/Items/{}",
+            user_id,
+            urlencoding::encode(person_id)
+        )
+    } else {
+        Endpoint::new(&format!("/Items/{}", urlencoding::encode(person_id)))
+            .param("userId", user_id)
+            .build()
+    }
+}
+
+/// Items similar to one item.
+///
+/// TRACES: UR-085 | DR-279
+pub fn similar_items(
+    _caps: &ServerCapabilities,
+    item_id: &str,
+    user_id: &str,
+    limit: usize,
+) -> String {
+    Endpoint::new(&format!("/Items/{}/Similar", urlencoding::encode(item_id)))
+        .param("UserId", user_id)
+        .raw_param("Limit", &limit.to_string())
+        .raw_param("Fields", LIST_FIELDS)
+        .build()
+}
+
+// ===== User data mutations =====
+
+/// Favourite / un-favourite an item (POST to set, DELETE to clear).
+///
+/// TRACES: UR-067, UR-085 | JA-033, DR-279
+pub fn favorite_item(_caps: &ServerCapabilities, user_id: &str, item_id: &str) -> String {
+    format!(
+        "/Users/{}/FavoriteItems/{}",
+        user_id,
+        urlencoding::encode(item_id)
+    )
+}
+
+/// Mark played / clear watch history (POST to set, DELETE to clear).
+///
+/// TRACES: UR-025, UR-085 | JA-035, DR-279
+pub fn played_item(_caps: &ServerCapabilities, user_id: &str, item_id: &str) -> String {
+    format!(
+        "/Users/{}/PlayedItems/{}",
+        user_id,
+        urlencoding::encode(item_id)
+    )
+}
+
+// ===== Playback =====
+
+/// Playback negotiation for one item.
+///
+/// TRACES: UR-004, UR-085 | JA-021, DR-279
+pub fn playback_info(_caps: &ServerCapabilities, item_id: &str) -> String {
+    format!("/Items/{}/PlaybackInfo", urlencoding::encode(item_id))
+}
+
+/// Playback reporting.
+///
+/// TRACES: UR-020, UR-085 | JA-010, JA-011, JA-012, DR-279
+pub fn sessions_playing(_caps: &ServerCapabilities) -> &'static str {
+    "/Sessions/Playing"
+}
+pub fn sessions_playing_progress(_caps: &ServerCapabilities) -> &'static str {
+    "/Sessions/Playing/Progress"
+}
+pub fn sessions_playing_stopped(_caps: &ServerCapabilities) -> &'static str {
+    "/Sessions/Playing/Stopped"
+}
+
+/// Live TV channels.
+///
+/// TRACES: UR-085 | DR-279
+pub fn live_tv_channels(_caps: &ServerCapabilities, user_id: &str) -> String {
+    Endpoint::new("/LiveTv/Channels")
+        .param("UserId", user_id)
+        .raw_param("Fields", "PrimaryImageAspectRatio,Overview")
+        .raw_param("EnableImageTypes", "Primary")
+        .build()
+}
+
+/// Generic channels.
+///
+/// TRACES: UR-085 | DR-279
+pub fn channels(_caps: &ServerCapabilities, user_id: &str) -> String {
+    Endpoint::new("/Channels").param("UserId", user_id).build()
+}
+
+// ===== Playlists =====
+
+/// TRACES: UR-062, UR-085 | DR-279
+pub fn playlists(_caps: &ServerCapabilities) -> &'static str {
+    "/Playlists"
+}
+
+/// A playlist as an item — used for rename and delete, which are `/Items`
+/// operations rather than `/Playlists` ones.
+///
+/// TRACES: UR-062, UR-085 | DR-279
+pub fn playlist_as_item(_caps: &ServerCapabilities, playlist_id: &str) -> String {
+    format!("/Items/{}", urlencoding::encode(playlist_id))
+}
+
+/// TRACES: UR-062, UR-085 | DR-279
+pub fn playlist_items(_caps: &ServerCapabilities, playlist_id: &str, user_id: &str) -> String {
+    Endpoint::new(&format!(
+        "/Playlists/{}/Items",
+        urlencoding::encode(playlist_id)
+    ))
+    .param("UserId", user_id)
+    .raw_param(
+        "Fields",
+        "PrimaryImageTag,Artists,AlbumId,Album,AlbumArtist,RunTimeTicks,ArtistItems",
+    )
+    .raw_param("StartIndex", "0")
+    .raw_param("Limit", "10000")
+    .build()
+}
+
+/// TRACES: UR-062, UR-085 | DR-279
+pub fn playlist_items_add(_caps: &ServerCapabilities, playlist_id: &str, ids: &str) -> String {
+    Endpoint::new(&format!(
+        "/Playlists/{}/Items",
+        urlencoding::encode(playlist_id)
+    ))
+    .param("Ids", ids)
+    .build()
+}
+
+/// TRACES: UR-062, UR-085 | DR-279
+pub fn playlist_items_remove(
+    _caps: &ServerCapabilities,
+    playlist_id: &str,
+    entry_ids: &str,
+) -> String {
+    Endpoint::new(&format!(
+        "/Playlists/{}/Items",
+        urlencoding::encode(playlist_id)
+    ))
+    .param("EntryIds", entry_ids)
+    .build()
+}
+
+/// TRACES: UR-062, UR-085 | DR-279
+pub fn playlist_item_move(
+    _caps: &ServerCapabilities,
+    playlist_id: &str,
+    item_id: &str,
+    new_index: u32,
+) -> String {
+    format!(
+        "/Playlists/{}/Items/{}/Move/{}",
+        urlencoding::encode(playlist_id),
+        urlencoding::encode(item_id),
+        new_index
+    )
+}
+
+// ===== Plugin =====
+
+/// The JRay plugin's per-item context. Not core Jellyfin; absent servers 404 and
+/// the caller treats that as "no context", so it needs no capability flag.
+///
+/// TRACES: UR-085 | DR-279
+pub fn jray_context(_caps: &ServerCapabilities, item_id: &str, position_seconds: f64) -> String {
+    format!(
+        "/Plugins/JRay/Items/{}/jray?t={}",
+        urlencoding::encode(item_id),
+        position_seconds
+    )
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    fn caps() -> ServerCapabilities {
+        ServerCapabilities::assumed()
+    }
+
+    /// The builder must never emit a double or trailing separator, and must use
+    /// `?` exactly once. This is structural now rather than asserted at every
+    /// call site.
+    ///
+    /// TRACES: UR-085 | DR-279
+    #[test]
+    fn query_separators_are_structural() {
+        let url = Endpoint::new("/Items")
+            .param("a", "1")
+            .param("b", "2")
+            .raw_param("c", "3")
+            .build();
+        assert_eq!(url, "/Items?a=1&b=2&c=3");
+        assert_eq!(url.matches('?').count(), 1);
+        assert!(!url.contains("&&"));
+        assert!(!url.ends_with('&'));
+
+        // A path that already carries a query continues it rather than
+        // starting a second one.
+        let continued = Endpoint::new("/Items?x=0").param("y", "1").build();
+        assert_eq!(continued, "/Items?x=0&y=1");
+        assert_eq!(continued.matches('?').count(), 1);
+
+        // No parameters at all means no `?`.
+        assert_eq!(Endpoint::new("/Items").build(), "/Items");
+    }
+
+    /// Values are encoded, list separators are not.
+    ///
+    /// TRACES: UR-007, UR-085 | DR-212, DR-279 | UT-206
+    #[test]
+    fn values_are_encoded_but_list_separators_survive() {
+        let url = Endpoint::new("/x").param("SearchTerm", "a?b&c d").build();
+        assert!(url.contains("SearchTerm=a%3Fb%26c%20d"), "{url}");
+
+        assert_eq!(
+            encode_list(["Drama & Romance", "Sci-Fi"], "|"),
+            "Drama%20%26%20Romance|Sci-Fi"
+        );
+        assert_eq!(encode_list(["Movie", "Series"], ","), "Movie,Series");
+    }
+
+    /// The user-scoped split is the reason this module exists. Both shapes must
+    /// be well-formed, and the default must be byte-identical to what shipped.
+    ///
+    /// TRACES: UR-085 | DR-279, DR-282
+    #[test]
+    fn both_user_scoped_route_shapes_are_well_formed() {
+        let legacy = caps();
+        assert!(legacy.user_scoped_item_routes, "the shipped default");
+        let url = get_items(&legacy, "u1", "lib-1", None);
+        assert!(url.starts_with("/Users/u1/Items?ParentId=lib-1"), "{url}");
+
+        let mut modern = caps();
+        modern.user_scoped_item_routes = false;
+        let url = get_items(&modern, "u1", "lib-1", None);
+        assert!(url.starts_with("/Items?userId=u1&ParentId=lib-1"), "{url}");
+        assert_eq!(url.matches('?').count(), 1, "{url}");
+        assert!(!url.contains("/Users/"), "{url}");
+    }
+
+    /// Every route must be well-formed under *both* shapes — a flipped flag
+    /// must not produce a malformed URL anywhere.
+    ///
+    /// TRACES: UR-085 | DR-279, DR-282
+    #[test]
+    fn no_route_is_malformed_under_either_shape() {
+        for user_scoped in [true, false] {
+            let mut c = caps();
+            c.user_scoped_item_routes = user_scoped;
+
+            let routes = vec![
+                user_views(&c, "u1"),
+                item_detail(&c, "u1", "i1"),
+                get_items(&c, "u1", "p1", None),
+                latest_items(&c, "u1", "p1", Some(8)),
+                resume_items(&c, "u1", 10, None, None),
+                resume_items(&c, "u1", 10, Some("Movie"), Some("lib-9")),
+                next_up(&c, "u1", Some("s1"), Some(5)),
+                favorites(&c, "u1", SearchScope::All, None),
+                played_items_by_date(&c, "u1", "Audio", 20, "Descending", None),
+                genres(&c, "u1", "MusicAlbum", Some("lib-1")),
+                search(&c, "u1", "query", 25, Some(&["Movie".to_string()])),
+                items_by_person(&c, "u1", "p9", 50, None),
+                person(&c, "u1", "p9"),
+                similar_items(&c, "i1", "u1", 12),
+                favorite_item(&c, "u1", "i1"),
+                played_item(&c, "u1", "i1"),
+                playback_info(&c, "i1"),
+                live_tv_channels(&c, "u1"),
+                channels(&c, "u1"),
+                playlist_as_item(&c, "pl1"),
+                playlist_items(&c, "pl1", "u1"),
+                playlist_items_add(&c, "pl1", "a,b"),
+                playlist_items_remove(&c, "pl1", "e1"),
+                playlist_item_move(&c, "pl1", "i1", 3u32),
+                jray_context(&c, "i1", 42.5),
+            ];
+
+            for route in routes {
+                assert!(route.starts_with('/'), "{route}");
+                assert!(!route.contains("&&"), "{route}");
+                assert!(!route.contains("?&"), "{route}");
+                assert!(!route.ends_with('&'), "{route}");
+                assert!(!route.ends_with('?'), "{route}");
+                assert!(
+                    route.matches('?').count() <= 1,
+                    "more than one query separator: {route}"
+                );
+            }
+        }
+    }
+
+    /// TRACES: UR-024, UR-034 | IR-024, JA-016
+    #[test]
+    fn latest_items_groups_children_into_containers() {
+        let url = latest_items(&caps(), "u1", "lib-1", Some(16));
+        assert!(url.contains("GroupItems=true"), "{url}");
+        assert!(url.contains("ParentId=lib-1"), "{url}");
+        assert!(url.contains("Limit=16"), "{url}");
+    }
+
+    /// TRACES: UR-059 | DR-197, JA-036 | UT-190, UT-191
+    #[test]
+    fn next_up_excludes_resumable_and_scopes_to_series() {
+        let url = next_up(&caps(), "u1", None, Some(12));
+        assert!(url.contains("EnableResumable=false"), "{url}");
+        assert!(url.contains("UserId=u1"), "{url}");
+        assert!(url.contains("Limit=12"), "{url}");
+        assert!(!url.contains("SeriesId"), "{url}");
+
+        let scoped = next_up(&caps(), "u1", Some("series-a"), None);
+        assert!(scoped.contains("SeriesId=series-a"), "{scoped}");
+        assert!(scoped.contains("Limit=16"), "default limit: {scoped}");
+    }
+
+    /// `All` must omit the type filter entirely rather than send a union, which
+    /// would silently drop every type nobody enumerated.
+    ///
+    /// TRACES: UR-067 | DR-115 | UT-100
+    #[test]
+    fn favorites_all_scope_omits_the_type_filter() {
+        let url = favorites(&caps(), "u1", SearchScope::All, None);
+        assert!(!url.contains("IncludeItemTypes"), "{url}");
+        assert!(url.contains("Filters=IsFavorite"), "{url}");
+    }
+
+    /// TRACES: UR-067 | DR-115 | UT-100
+    #[test]
+    fn favorites_honours_paging_and_sort() {
+        let url = favorites(
+            &caps(),
+            "u1",
+            SearchScope::All,
+            Some(&GetItemsOptions {
+                limit: Some(20),
+                start_index: Some(40),
+                sort_by: Some("Random".to_string()),
+                sort_order: Some("Descending".to_string()),
+                ..Default::default()
+            }),
+        );
+        assert!(url.contains("&Limit=20"), "{url}");
+        assert!(url.contains("&StartIndex=40"), "{url}");
+        assert!(url.contains("&SortBy=Random&SortOrder=Descending"), "{url}");
+    }
+
+    /// The detail view is the only caller that wants People/MediaStreams; a list
+    /// query must not drag them along.
+    ///
+    /// Jellyfin 12.0 changed `GetItems` to default `recursive` to **true** when
+    /// the parent is a library folder and `IncludeItemTypes` is set — so the
+    /// identical request returns a different result set on the two generations.
+    /// Sending an explicit value makes them agree, and `false` is what shipped.
+    ///
+    /// Source: `ItemsController.cs` in v12.0 — `if (folder is ICollectionFolder
+    /// && includeItemTypes.Length > 0) { recursive ??= true; }`
+    ///
+    /// TRACES: UR-085 | DR-288
+    #[test]
+    fn a_type_filtered_listing_always_states_recursive() {
+        let filtered = get_items(
+            &caps(),
+            "u1",
+            "lib-1",
+            Some(&GetItemsOptions {
+                include_item_types: Some(vec!["Movie".to_string()]),
+                ..Default::default()
+            }),
+        );
+        assert!(
+            filtered.contains("Recursive="),
+            "a type-filtered listing must state Recursive or 12.0 will infer a \
+             different one than 10.11: {filtered}"
+        );
+        assert!(
+            filtered.contains("Recursive=false"),
+            "and it must state the behaviour that shipped: {filtered}"
+        );
+
+        // An explicit choice by the caller still wins.
+        let explicit = get_items(
+            &caps(),
+            "u1",
+            "lib-1",
+            Some(&GetItemsOptions {
+                include_item_types: Some(vec!["Movie".to_string()]),
+                recursive: Some(true),
+                ..Default::default()
+            }),
+        );
+        assert!(explicit.contains("Recursive=true"), "{explicit}");
+        assert_eq!(explicit.matches("Recursive=").count(), 1, "{explicit}");
+
+        // No type filter, no inference to defend against, no parameter.
+        let plain = get_items(&caps(), "u1", "lib-1", None);
+        assert!(!plain.contains("Recursive="), "{plain}");
+    }
+
+    /// TRACES: UR-007 | DR-279
+    #[test]
+    fn only_the_detail_route_requests_the_heavy_fields() {
+        assert!(item_detail(&caps(), "u1", "i1").contains("People"));
+        assert!(!get_items(&caps(), "u1", "p1", None).contains("People"));
+        assert!(!latest_items(&caps(), "u1", "p1", None).contains("MediaStreams"));
+    }
+}

src-tauri/src/repository/mod.rs

@@ -1,10 +1,16 @@
+pub mod capabilities;
 pub mod device_profile;
+pub mod endpoints;
 /// User-chosen browsing exclusions (UR-076 / DR-209).
 pub mod exclusions;
+#[cfg(test)]
+mod generation_tests;
 pub mod hybrid;
 pub mod offline;
 pub mod online;
 pub mod series_progress;
+#[cfg(test)]
+pub mod server_fixture;
 /// Backend-owned stream selection (UR-079 / DR-225).
 pub mod stream_selection;
 pub mod types;

src-tauri/src/repository/online.rs

@@ -5,6 +5,8 @@ use log::{debug, error, info, warn};
 use serde::{Deserialize, Serialize};
 use std::sync::{Arc, RwLock};
 
+use super::capabilities::ServerCapabilities;
+use super::endpoints;
 use super::stream_selection::{
     quality_options_for_source, PlaybackKind, Rendition, StreamSelection, Transport,
 };
@@ -188,6 +190,12 @@ pub struct OnlineRepository {
     /// This is the source of truth for the offline/online banner. `None` in
     /// tests / contexts where connectivity tracking isn't wired up.
     connectivity: Option<ConnectivityReporter>,
+    /// What this server can do, resolved once from the version it reported at
+    /// connect. Every route and every version-dependent decision reads a named
+    /// flag from here; nothing compares a version number.
+    ///
+    /// TRACES: UR-085 | IR-035, DR-280
+    capabilities: ServerCapabilities,
 }
 
 impl OnlineRepository {
@@ -209,9 +217,34 @@ impl OnlineRepository {
             user_id,
             access_token,
             connectivity: None,
+            // Assumed until the caller supplies what the server reported. The
+            // assumption is the current target, which is what it will be in
+            // nearly every case.
+            capabilities: ServerCapabilities::assumed(),
         }
     }
 
+    /// Adopt the capabilities resolved from the version the server reported at
+    /// connect. Without this the repository assumes the current target.
+    ///
+    /// TRACES: UR-085 | IR-035, DR-280
+    pub fn with_capabilities(mut self, capabilities: ServerCapabilities) -> Self {
+        self.capabilities = capabilities;
+        self
+    }
+
+    /// What the server on the other end can do.
+    ///
+    /// Test-only: production reads the flags through the route table and the
+    /// playback paths rather than asking the repository for them, so exposing
+    /// this outside tests would be an accessor nobody calls.
+    ///
+    /// TRACES: UR-085 | DR-280
+    #[cfg(test)]
+    pub fn capabilities(&self) -> &ServerCapabilities {
+        &self.capabilities
+    }
+
     /// Attach a connectivity reporter so server outcomes drive the reachability
     /// state observed by the UI. See `report_outcome`.
     pub fn with_connectivity(mut self, reporter: ConnectivityReporter) -> Self {
@@ -261,7 +294,7 @@ impl OnlineRepository {
             .http_client
             .client
             .get(url)
-            .header("X-Emby-Authorization", self.auth_header())
+            .header("Authorization", self.auth_header())
             .build()
             .map_err(|e| format!("Failed to build request: {}", e))?;
 
@@ -298,11 +331,7 @@ impl OnlineRepository {
         item_id: &str,
         t: f64,
     ) -> Result<Vec<JRayActor>, RepoError> {
-        let endpoint = format!(
+        let endpoint = endpoints::jray_context(&self.capabilities, item_id, t);
-            "/Plugins/JRay/Items/{}/jray?t={}",
-            urlencoding::encode(item_id),
-            t
-        );
         match self.get_json::<JRayContext>(&endpoint).await {
             Ok(context) => Ok(context.actors),
             // No plugin / no truth data for this item — not an error to the user.
@@ -339,7 +368,7 @@ impl OnlineRepository {
             .http_client
             .client
             .get(&url)
-            .header("X-Emby-Authorization", self.auth_header())
+            .header("Authorization", self.auth_header())
             .build()
             .map_err(|e| RepoError::Network {
                 message: format!("Failed to build request: {}", e),
@@ -414,7 +443,7 @@ impl OnlineRepository {
             .client
             .post(&url)
             .header("Content-Type", "application/json")
-            .header("X-Emby-Authorization", self.auth_header())
+            .header("Authorization", self.auth_header())
             .json(body)
             .build()
             .map_err(|e| RepoError::Network {
@@ -474,7 +503,7 @@ impl OnlineRepository {
             .client
             .post(&url)
             .header("Content-Type", "application/json")
-            .header("X-Emby-Authorization", self.auth_header())
+            .header("Authorization", self.auth_header())
             .json(body)
             .build()
             .map_err(|e| RepoError::Network {
@@ -538,7 +567,7 @@ impl OnlineRepository {
             .http_client
             .client
             .delete(&url)
-            .header("X-Emby-Authorization", self.auth_header())
+            .header("Authorization", self.auth_header())
             .send();
 
         match request.await {
@@ -630,7 +659,7 @@ impl OnlineRepository {
         // TRACES: UR-004, UR-080 | DR-234
         let (renderer_video_codecs, _) = super::device_profile::renderer_codecs();
         let mut params = vec![
-            ("api_key", self.access_token.clone()),
+            ("ApiKey", self.access_token.clone()),
             ("DeviceId", DEVICE_ID.to_string()),
             ("PlaySessionId", play_session_id),
             ("VideoCodec", renderer_video_codecs),
@@ -724,7 +753,7 @@ impl OnlineRepository {
     ) -> Result<String, RepoError> {
         let mut params = vec![
             ("UserId", self.user_id.clone()),
-            ("api_key", self.access_token.clone()),
+            ("ApiKey", self.access_token.clone()),
             ("DeviceId", DEVICE_ID.to_string()),
             // Progressive mp3 over HTTP — ExoPlayer-friendly; no HLS/ts.
             ("Container", "mp3".to_string()),
@@ -783,7 +812,7 @@ impl OnlineRepository {
         &self,
         item_id: &str,
     ) -> Result<(NegotiatedSource, String), RepoError> {
-        let endpoint = format!("/Items/{}/PlaybackInfo", urlencoding::encode(item_id));
+        let endpoint = endpoints::playback_info(&self.capabilities, item_id);
 
         // What the renderer that will decode this can play. One source, shared
         // with the transcode URL builder and the client-side audio override, so
@@ -1043,7 +1072,7 @@ impl OnlineRepository {
                 // (which is the *video* stream — the index is global across all
                 // streams) only misleads servers that do honour it.
                 let url = format!(
-                    "{}/Videos/{}/stream?static=true&container=mp4&mediaSourceId={}&deviceId={}&api_key={}&userId={}",
+                    "{}/Videos/{}/stream?static=true&container=mp4&mediaSourceId={}&deviceId={}&ApiKey={}&userId={}",
                     self.server_url,
                     item_id,
                     effective_source_id,
@@ -1191,119 +1220,26 @@ impl From<JellyfinUserData> for UserData {
     }
 }
 
-/// Build the Jellyfin endpoint for a folder listing.
+/// Test-only shim over [`endpoints::get_items`].
 ///
-/// Extracted from `get_items` so the query it produces — in particular the
+/// The endpoint builders moved to `endpoints.rs` under DR-279. These wrappers
-/// favourites filter — can be asserted without standing up an HTTP server.
+/// keep the existing requirement coverage (DR-116, DR-212, DR-257 and friends)
-///
+/// pointed at the production path rather than deleting it, and pin the *default*
-/// TRACES: UR-007, UR-067 | DR-116 | UT-104
+/// capability shape — the URLs that shipped before the route table existed.
+#[cfg(test)]
 fn build_get_items_endpoint(
     user_id: &str,
     parent_id: &str,
     options: Option<&GetItemsOptions>,
 ) -> String {
-    // Every value below is percent-encoded before it goes into the query
+    endpoints::get_items(&ServerCapabilities::assumed(), user_id, parent_id, options)
-    // string, the same way `Genres` and `SearchTerm` already are: these are
-    // values, not URL syntax, so a space or an `&` in one must not split it
-    // into another parameter.
-    //
-    // TRACES: UR-007 | DR-212 | UT-206
-    let mut endpoint = format!(
-        "/Users/{}/Items?ParentId={}",
-        user_id,
-        urlencoding::encode(parent_id)
-    );
-
-    if let Some(opts) = options {
-        if let Some(limit) = opts.limit {
-            endpoint.push_str(&format!("&Limit={}", limit));
-        }
-        if let Some(start_index) = opts.start_index {
-            endpoint.push_str(&format!("&StartIndex={}", start_index));
-        }
-        if let Some(types) = &opts.include_item_types {
-            // Encode each type, not the joined string: the comma is the
-            // list separator Jellyfin splits on.
-            let encoded: Vec<String> = types
-                .iter()
-                .map(|t| urlencoding::encode(t).into_owned())
-                .collect();
-            endpoint.push_str(&format!("&IncludeItemTypes={}", encoded.join(",")));
-        }
-        // An explicit sort always wins; the container's default only fills the
-        // gap when the caller named none. A caller that names neither gets no
-        // SortBy at all, leaving the server's own order intact.
-        //
-        // TRACES: UR-007 | DR-257 | UT-229
-        let default_sort = default_listing_sort(opts.parent_kind);
-        let sort_by = opts
-            .sort_by
-            .as_deref()
-            .or(default_sort.map(|(field, _)| field));
-        let sort_order = opts
-            .sort_order
-            .as_deref()
-            .or(default_sort.map(|(_, order)| order));
-
-        if let Some(sort_by) = sort_by {
-            // SortBy is likewise a comma-delimited list (`hybrid.rs` sends
-            // "ParentIndexNumber,IndexNumber,SortName"), so encode per field.
-            let encoded: Vec<String> = sort_by
-                .split(',')
-                .map(|field| urlencoding::encode(field).into_owned())
-                .collect();
-            endpoint.push_str(&format!("&SortBy={}", encoded.join(",")));
-        }
-        if let Some(sort_order) = sort_order {
-            endpoint.push_str(&format!("&SortOrder={}", urlencoding::encode(sort_order)));
-        }
-        if let Some(recursive) = opts.recursive {
-            endpoint.push_str(&format!("&Recursive={}", recursive));
-        }
-        if let Some(genres) = &opts.genres {
-            if !genres.is_empty() {
-                // Genre names may contain spaces/ampersands, so percent-encode each.
-                let encoded: Vec<String> = genres
-                    .iter()
-                    .map(|g| urlencoding::encode(g).into_owned())
-                    .collect();
-                endpoint.push_str(&format!("&Genres={}", encoded.join("|")));
-            }
-        }
-        // TRACES: UR-067 | DR-116 | UT-104
-        if opts.favorites_only == Some(true) {
-            endpoint.push_str("&Filters=IsFavorite");
-        }
-    }
-
-    // Request image fields for list views (People only needed in get_item
-    // detail view). Genres is needed so cached items carry their genres,
-    // which lets the offline store derive genre lists + per-genre counts.
-    endpoint
-        .push_str("&Fields=BackdropImageTags,ParentBackdropImageTags,Genres,PremiereDate,UserData");
-    endpoint
 }
 
-/// Build the Jellyfin endpoint for a "recently added" listing.
+/// Test-only shim over [`endpoints::latest_items`]. See
-///
+/// [`build_get_items_endpoint`].
-/// `GroupItems=true` is the load-bearing parameter: Jellyfin defaults it to
+#[cfg(test)]
-/// `false`, which returns each newly-added *leaf* separately, so importing one
-/// 14-track album pushed 14 rows into "recently added" and buried everything
-/// else. With grouping on, the server collapses children into the container
-/// that was added — an album appears once, while movies (which have no such
-/// container) are unaffected.
-///
-/// Pulled out of `get_latest_items` so the query can be asserted without an
-/// HTTP server, matching `build_favorites_endpoint`.
-///
-/// TRACES: UR-024, UR-034 | IR-024, JA-016
 fn build_latest_items_endpoint(user_id: &str, parent_id: &str, limit: Option<usize>) -> String {
-    format!(
+    endpoints::latest_items(&ServerCapabilities::assumed(), user_id, parent_id, limit)
-        "/Users/{}/Items/Latest?ParentId={}&Limit={}&GroupItems=true&Fields=BackdropImageTags,ParentBackdropImageTags,UserData",
-        user_id,
-        parent_id,
-        limit.unwrap_or(16)
-    )
 }
 
 /// How many rows to ask the server for, given how many the row will show.
@@ -1417,73 +1353,21 @@ fn album_from_track(track: &MediaItem, album_id: String) -> MediaItem {
     }
 }
 
-/// Build the Jellyfin endpoint for a Next Up listing.
+/// Test-only shim over [`endpoints::next_up`]. See [`build_get_items_endpoint`].
-///
+#[cfg(test)]
-/// `EnableResumable=false` is the point of this query: the server default is
-/// `true`, which makes a partially-watched episode its own series' "next up" —
-/// the very episode `/Items/Resume` returns — so Continue Watching and Next Up
-/// end up showing the same cards. Next Up should only ever offer episodes the
-/// viewer has not started. Servers predating the parameter ignore it, which is
-/// why the frontend also drops in-progress entries (DR-197).
-///
-/// Pulled out of `get_next_up_episodes` so the query can be asserted without an
-/// HTTP server, matching `build_favorites_endpoint`.
-///
-/// TRACES: UR-023, UR-059 | DR-197, JA-014, JA-036 | UT-190, UT-191
 fn build_next_up_endpoint(user_id: &str, series_id: Option<&str>, limit: Option<usize>) -> String {
-    let mut endpoint = format!(
+    endpoints::next_up(&ServerCapabilities::assumed(), user_id, series_id, limit)
-        "/Shows/NextUp?UserId={}&Limit={}&EnableResumable=false&Fields=BackdropImageTags,ParentBackdropImageTags,UserData",
-        user_id,
-        limit.unwrap_or(16)
-    );
-
-    if let Some(sid) = series_id {
-        endpoint.push_str(&format!("&SeriesId={}", sid));
-    }
-
-    endpoint
 }
 
-/// Build the Jellyfin endpoint for a favourites listing.
+/// Test-only shim over [`endpoints::favorites`]. See
-///
+/// [`build_get_items_endpoint`].
-/// Pulled out of `get_favorites` so the query can be asserted without an HTTP
+#[cfg(test)]
-/// server. `scope` is expanded here — `SearchScope::All` yields `None`, and the
-/// `IncludeItemTypes` filter is then **omitted entirely** rather than sent as a
-/// union, which would silently drop every type nobody enumerated (see
-/// `SearchScope::item_types`).
-///
-/// TRACES: UR-067 | DR-115, JA-033 | UT-100
 fn build_favorites_endpoint(
     user_id: &str,
     scope: SearchScope,
     options: Option<&GetItemsOptions>,
 ) -> String {
-    let mut endpoint = format!("/Users/{}/Items?Filters=IsFavorite&Recursive=true", user_id);
+    endpoints::favorites(&ServerCapabilities::assumed(), user_id, scope, options)
-
-    if let Some(types) = scope.item_types() {
-        endpoint.push_str(&format!("&IncludeItemTypes={}", types.join(",")));
-    }
-
-    // Jellyfin has no "date favourited", so name order is the only stable sort
-    // available; callers may still override it.
-    let sort_by = options
-        .and_then(|o| o.sort_by.as_deref())
-        .unwrap_or("SortName");
-    let sort_order = options
-        .and_then(|o| o.sort_order.as_deref())
-        .unwrap_or("Ascending");
-    endpoint.push_str(&format!("&SortBy={}&SortOrder={}", sort_by, sort_order));
-
-    if let Some(limit) = options.and_then(|o| o.limit) {
-        endpoint.push_str(&format!("&Limit={}", limit));
-    }
-    if let Some(start_index) = options.and_then(|o| o.start_index) {
-        endpoint.push_str(&format!("&StartIndex={}", start_index));
-    }
-
-    endpoint
-        .push_str("&Fields=BackdropImageTags,ParentBackdropImageTags,Genres,PremiereDate,UserData");
-    endpoint
 }
 
 // ImageTags from Jellyfin API - can be a HashMap with various image type keys
@@ -1810,7 +1694,7 @@ impl MediaRepository for OnlineRepository {
             image_tags: Option<ImageTags>,
         }
 
-        let endpoint = format!("/Users/{}/Views", self.user_id);
+        let endpoint = endpoints::user_views(&self.capabilities, &self.user_id);
         let response: LibrariesResponse = self.get_json(&endpoint).await?;
 
         Ok(response
@@ -1832,7 +1716,12 @@ impl MediaRepository for OnlineRepository {
         parent_id: &str,
         options: Option<GetItemsOptions>,
     ) -> Result<SearchResult, RepoError> {
-        let endpoint = build_get_items_endpoint(&self.user_id, parent_id, options.as_ref());
+        let endpoint = endpoints::get_items(
+            &self.capabilities,
+            &self.user_id,
+            parent_id,
+            options.as_ref(),
+        );
 
         let response: ItemsResponse = self.get_json(&endpoint).await?;
 
@@ -1858,7 +1747,7 @@ impl MediaRepository for OnlineRepository {
     ///
     /// TRACES: UR-021, UR-035 | IR-016, IR-022, JA-005, JA-009
     async fn get_item(&self, item_id: &str) -> Result<MediaItem, RepoError> {
-        let endpoint = format!("/Users/{}/Items/{}?Fields=BackdropImageTags,ParentBackdropImageTags,People,MediaStreams,MediaSources,PremiereDate,UserData", self.user_id, urlencoding::encode(item_id));
+        let endpoint = endpoints::item_detail(&self.capabilities, &self.user_id, item_id);
 
         let item: JellyfinItem = self.get_json(&endpoint).await?;
         let media_item = item.into_media_item(self.user_id.clone());
@@ -1879,7 +1768,8 @@ impl MediaRepository for OnlineRepository {
         limit: Option<usize>,
     ) -> Result<Vec<MediaItem>, RepoError> {
         let limit_val = limit.unwrap_or(16);
-        let endpoint = build_latest_items_endpoint(
+        let endpoint = endpoints::latest_items(
+            &self.capabilities,
             &self.user_id,
             parent_id,
             Some(latest_items_fetch_limit(limit_val)),
@@ -1909,16 +1799,14 @@ impl MediaRepository for OnlineRepository {
         parent_id: Option<&str>,
         limit: Option<usize>,
     ) -> Result<Vec<MediaItem>, RepoError> {
-        let limit_str = limit.unwrap_or(16);
+        let endpoint = endpoints::resume_items(
-        let mut endpoint = format!(
+            &self.capabilities,
-            "/Users/{}/Items/Resume?Limit={}&MediaTypes=Video&Fields=BackdropImageTags,ParentBackdropImageTags,UserData",
+            &self.user_id,
-            self.user_id, limit_str
+            limit.unwrap_or(16),
+            None,
+            parent_id,
         );
 
-        if let Some(pid) = parent_id {
-            endpoint.push_str(&format!("&ParentId={}", pid));
-        }
-
         let response: ItemsResponse = self.get_json(&endpoint).await?;
         Ok(response
             .items
@@ -1936,7 +1824,7 @@ impl MediaRepository for OnlineRepository {
         series_id: Option<&str>,
         limit: Option<usize>,
     ) -> Result<Vec<MediaItem>, RepoError> {
-        let endpoint = build_next_up_endpoint(&self.user_id, series_id, limit);
+        let endpoint = endpoints::next_up(&self.capabilities, &self.user_id, series_id, limit);
 
         let response: ItemsResponse = self.get_json(&endpoint).await?;
         Ok(response
@@ -1953,9 +1841,13 @@ impl MediaRepository for OnlineRepository {
         let limit_val = limit.unwrap_or(12);
         // Fetch more items to account for grouping reducing the count
         let fetch_limit = limit_val * 3;
-        let endpoint = format!(
+        let endpoint = endpoints::played_items_by_date(
-            "/Users/{}/Items?SortBy=DatePlayed&SortOrder=Descending&IncludeItemTypes=Audio&Limit={}&Recursive=true&Filters=IsPlayed&Fields=BackdropImageTags,ParentBackdropImageTags,UserData",
+            &self.capabilities,
-            self.user_id, fetch_limit
+            &self.user_id,
+            "Audio",
+            fetch_limit,
+            "Descending",
+            None,
         );
 
         let response: ItemsResponse = self.get_json(&endpoint).await?;
@@ -2087,15 +1979,15 @@ impl MediaRepository for OnlineRepository {
         // Ask Jellyfin for played albums sorted by least-recently played first.
         // Filters=IsPlayed keeps only albums the user has actually listened to,
         // and SortBy=DatePlayed ascending surfaces the ones they've neglected.
-        let mut endpoint = format!(
+        let endpoint = endpoints::played_items_by_date(
-            "/Users/{}/Items?SortBy=DatePlayed&SortOrder=Ascending&IncludeItemTypes=MusicAlbum&Limit={}&Recursive=true&Filters=IsPlayed&Fields=BackdropImageTags,ParentBackdropImageTags,UserData",
+            &self.capabilities,
-            self.user_id, limit_val
+            &self.user_id,
+            "MusicAlbum",
+            limit_val,
+            "Ascending",
+            parent_id,
         );
 
-        if let Some(pid) = parent_id {
-            endpoint.push_str(&format!("&ParentId={}", pid));
-        }
-
         let response: ItemsResponse = self.get_json(&endpoint).await?;
         Ok(response
             .items
@@ -2110,10 +2002,12 @@ impl MediaRepository for OnlineRepository {
     ///
     /// TRACES: UR-019, UR-034 | IR-024, JA-013, JA-015
     async fn get_resume_movies(&self, limit: Option<usize>) -> Result<Vec<MediaItem>, RepoError> {
-        let limit_str = limit.unwrap_or(16);
+        let endpoint = endpoints::resume_items(
-        let endpoint = format!(
+            &self.capabilities,
-            "/Users/{}/Items/Resume?Limit={}&MediaTypes=Video&IncludeItemTypes=Movie&Fields=BackdropImageTags,ParentBackdropImageTags,UserData",
+            &self.user_id,
-            self.user_id, limit_str
+            limit.unwrap_or(16),
+            Some("Movie"),
+            None,
         );
 
         let response: ItemsResponse = self.get_json(&endpoint).await?;
@@ -2127,14 +2021,8 @@ impl MediaRepository for OnlineRepository {
     async fn get_genres(&self, parent_id: Option<&str>) -> Result<Vec<Genre>, RepoError> {
         // Ask Jellyfin to scope counts to albums and include them, so the
         // frontend can rank genres by popularity without probing each one.
-        let mut endpoint = format!(
+        let endpoint =
-            "/Genres?UserId={}&IncludeItemTypes=MusicAlbum&Recursive=true&Fields=ItemCounts",
+            endpoints::genres(&self.capabilities, &self.user_id, "MusicAlbum", parent_id);
-            self.user_id
-        );
-
-        if let Some(pid) = parent_id {
-            endpoint.push_str(&format!("&ParentId={}", pid));
-        }
 
         #[derive(Debug, Deserialize)]
         #[serde(rename_all = "PascalCase")]
@@ -2201,28 +2089,12 @@ impl MediaRepository for OnlineRepository {
         // SearchTerm is arbitrary user input and must be percent-encoded so that
         // spaces, ampersands, etc. don't corrupt the query string (a multi-word
         // search like "Star Wars" would otherwise produce a malformed URL).
-        let mut endpoint = format!(
+        let endpoint = endpoints::search(
-            "/Users/{}/Items?SearchTerm={}&Limit={}&Recursive=true",
+            &self.capabilities,
-            self.user_id,
+            &self.user_id,
-            urlencoding::encode(query),
+            query,
-            limit
+            limit,
-        );
+            options.and_then(|o| o.include_item_types).as_deref(),
-
-        if let Some(opts) = options {
-            if let Some(types) = opts.include_item_types {
-                let encoded_types = types
-                    .iter()
-                    .map(|t| urlencoding::encode(t).into_owned())
-                    .collect::<Vec<_>>()
-                    .join(",");
-                endpoint.push_str(&format!("&IncludeItemTypes={}", encoded_types));
-            }
-        }
-
-        // Request image fields for list views (plus Genres so cached items
-        // carry genres for offline genre lists/counts).
-        endpoint.push_str(
-            "&Fields=BackdropImageTags,ParentBackdropImageTags,Genres,PremiereDate,UserData",
         );
 
         let response: ItemsResponse = self.get_json(&endpoint).await?;
@@ -2311,7 +2183,7 @@ impl MediaRepository for OnlineRepository {
             // serves the original file untouched, and pinning index 0 (the video
             // stream) only misleads servers that do honour it.
             format!(
-                "{}/Videos/{}/stream?static=true&container=mp4&mediaSourceId={}&deviceId=jellytau&api_key={}&userId={}",
+                "{}/Videos/{}/stream?static=true&container=mp4&mediaSourceId={}&deviceId=jellytau&ApiKey={}&userId={}",
                 self.server_url,
                 item_id,
                 source.id,
@@ -2335,7 +2207,7 @@ impl MediaRepository for OnlineRepository {
     async fn get_audio_stream_url(&self, item_id: &str) -> Result<String, RepoError> {
         // Construct direct audio stream URL
         let url = format!(
-            "{}/Audio/{}/stream?UserId={}&api_key={}&Static=true",
+            "{}/Audio/{}/stream?UserId={}&ApiKey={}&Static=true",
             self.server_url, item_id, self.user_id, self.access_token
         );
         Ok(url)
@@ -2360,10 +2232,7 @@ impl MediaRepository for OnlineRepository {
     async fn get_live_tv_channels(&self) -> Result<Vec<MediaItem>, RepoError> {
         // Live TV channels (broadcast tuners / IPTV M3U). Returned as items with
         // type "TvChannel" — playable via open_live_stream.
-        let endpoint = format!(
+        let endpoint = endpoints::live_tv_channels(&self.capabilities, &self.user_id);
-            "/LiveTv/Channels?UserId={}&Fields=PrimaryImageAspectRatio,Overview&EnableImageTypes=Primary",
-            self.user_id
-        );
         let response: ItemsResponse = self.get_json(&endpoint).await?;
         Ok(response
             .items
@@ -2375,7 +2244,7 @@ impl MediaRepository for OnlineRepository {
     async fn get_channels(&self) -> Result<SearchResult, RepoError> {
         // Root list of plugin "Channels". Drill-down into a channel folder reuses
         // get_items(channel_id, ...).
-        let endpoint = format!("/Channels?UserId={}", self.user_id);
+        let endpoint = endpoints::channels(&self.capabilities, &self.user_id);
         let response: ItemsResponse = self.get_json(&endpoint).await?;
         let total = response.total_record_count;
         let items = response
@@ -2426,7 +2295,7 @@ impl MediaRepository for OnlineRepository {
             live_stream_id: Option<String>,
         }
 
-        let endpoint = format!("/Items/{}/PlaybackInfo", urlencoding::encode(item_id));
+        let endpoint = endpoints::playback_info(&self.capabilities, item_id);
         let request = OpenLiveStreamRequest {
             user_id: self.user_id.clone(),
             auto_open_live_stream: true,
@@ -2461,7 +2330,7 @@ impl MediaRepository for OnlineRepository {
                 super::device_profile::without_server_chosen_subtitle(&url)
             ),
             None => format!(
-                "{}/Videos/{}/master.m3u8?api_key={}&MediaSourceId={}&LiveStreamId={}&VideoCodec=h264&AudioCodec=aac&TranscodingProtocol=hls&TranscodingContainer=ts&SubtitleStreamIndex={}",
+                "{}/Videos/{}/master.m3u8?ApiKey={}&MediaSourceId={}&LiveStreamId={}&VideoCodec=h264&AudioCodec=aac&TranscodingProtocol=hls&TranscodingContainer=ts&SubtitleStreamIndex={}",
                 self.server_url,
                 item_id,
                 self.access_token,
@@ -2503,7 +2372,8 @@ impl MediaRepository for OnlineRepository {
             is_paused: false,
         };
 
-        self.post_json("/Sessions/Playing", &request).await
+        self.post_json(endpoints::sessions_playing(&self.capabilities), &request)
+            .await
     }
 
     async fn report_playback_progress(
@@ -2525,7 +2395,11 @@ impl MediaRepository for OnlineRepository {
             is_paused: false,
         };
 
-        self.post_json("/Sessions/Playing/Progress", &request).await
+        self.post_json(
+            endpoints::sessions_playing_progress(&self.capabilities),
+            &request,
+        )
+        .await
     }
 
     async fn report_playback_stopped(
@@ -2545,7 +2419,11 @@ impl MediaRepository for OnlineRepository {
             position_ticks,
         };
 
-        self.post_json("/Sessions/Playing/Stopped", &request).await
+        self.post_json(
+            endpoints::sessions_playing_stopped(&self.capabilities),
+            &request,
+        )
+        .await
     }
 
     fn get_image_url(
@@ -2561,9 +2439,10 @@ impl MediaRepository for OnlineRepository {
             image_type.as_str()
         );
 
-        // Authentication is handled by X-Emby-Authorization header in download_bytes()
+        // Authentication is handled by the `Authorization` header in
-        // Do NOT include api_key here — some Jellyfin servers reject requests when
+        // download_bytes(). Do NOT add a query-parameter token here — some
-        // api_key is present but the token doesn't match the expected format.
+        // Jellyfin servers reject requests carrying one whose format they do not
+        // expect, and this request can already authenticate by header.
         let mut params: Vec<String> = Vec::new();
 
         if let Some(opts) = options {
@@ -2623,7 +2502,7 @@ impl MediaRepository for OnlineRepository {
         // instead — it is always present and supports HTTP Range, which the
         // download worker relies on for resume.
         let mut url = format!("{}/Videos/{}/stream.mp4", self.server_url, item_id);
-        let mut params = vec![format!("api_key={}", self.access_token)];
+        let mut params = vec![format!("ApiKey={}", self.access_token)];
 
         // Map the frontend quality preset to concrete transcode params. For
         // "original" we request a direct static copy (no transcode) which is
@@ -2713,11 +2592,7 @@ impl MediaRepository for OnlineRepository {
     }
 
     async fn mark_favorite(&self, item_id: &str) -> Result<(), RepoError> {
-        let endpoint = format!(
+        let endpoint = endpoints::favorite_item(&self.capabilities, &self.user_id, item_id);
-            "/Users/{}/FavoriteItems/{}",
-            self.user_id,
-            urlencoding::encode(item_id)
-        );
         self.post_json(&endpoint, &serde_json::json!({})).await
     }
 
@@ -2727,7 +2602,8 @@ impl MediaRepository for OnlineRepository {
         scope: SearchScope,
         options: Option<GetItemsOptions>,
     ) -> Result<SearchResult, RepoError> {
-        let endpoint = build_favorites_endpoint(&self.user_id, scope, options.as_ref());
+        let endpoint =
+            endpoints::favorites(&self.capabilities, &self.user_id, scope, options.as_ref());
         let response: ItemsResponse = self.get_json(&endpoint).await?;
 
         Ok(SearchResult {
@@ -2747,11 +2623,7 @@ impl MediaRepository for OnlineRepository {
     ///
     /// TRACES: UR-017 | JA-018, DR-021
     async fn unmark_favorite(&self, item_id: &str) -> Result<(), RepoError> {
-        let endpoint = format!(
+        let endpoint = endpoints::favorite_item(&self.capabilities, &self.user_id, item_id);
-            "/Users/{}/FavoriteItems/{}",
-            self.user_id,
-            urlencoding::encode(item_id)
-        );
         let url = format!("{}{}", self.server_url, endpoint);
 
         let result = async {
@@ -2759,7 +2631,7 @@ impl MediaRepository for OnlineRepository {
                 .http_client
                 .client
                 .delete(&url)
-                .header("X-Emby-Authorization", self.auth_header())
+                .header("Authorization", self.auth_header())
                 .build()
                 .map_err(|e| RepoError::Network {
                     message: format!("Failed to build request: {}", e),
@@ -2793,11 +2665,7 @@ impl MediaRepository for OnlineRepository {
     ///
     /// TRACES: UR-064 | DR-106, JA-033
     async fn clear_watch_history(&self, item_id: &str) -> Result<(), RepoError> {
-        let endpoint = format!(
+        let endpoint = endpoints::played_item(&self.capabilities, &self.user_id, item_id);
-            "/Users/{}/PlayedItems/{}",
-            self.user_id,
-            urlencoding::encode(item_id)
-        );
         let url = format!("{}{}", self.server_url, endpoint);
 
         let result = async {
@@ -2805,7 +2673,7 @@ impl MediaRepository for OnlineRepository {
                 .http_client
                 .client
                 .delete(&url)
-                .header("X-Emby-Authorization", self.auth_header())
+                .header("Authorization", self.auth_header())
                 .build()
                 .map_err(|e| RepoError::Network {
                     message: format!("Failed to build request: {}", e),
@@ -2838,11 +2706,7 @@ impl MediaRepository for OnlineRepository {
     ///
     /// TRACES: UR-025 | DR-131 | JA-035
     async fn mark_played(&self, item_id: &str) -> Result<(), RepoError> {
-        let endpoint = format!(
+        let endpoint = endpoints::played_item(&self.capabilities, &self.user_id, item_id);
-            "/Users/{}/PlayedItems/{}",
-            self.user_id,
-            urlencoding::encode(item_id)
-        );
         let url = format!("{}{}", self.server_url, endpoint);
 
         let result = async {
@@ -2850,7 +2714,7 @@ impl MediaRepository for OnlineRepository {
                 .http_client
                 .client
                 .post(&url)
-                .header("X-Emby-Authorization", self.auth_header())
+                .header("Authorization", self.auth_header())
                 .header("Content-Length", "0")
                 .build()
                 .map_err(|e| RepoError::Network {
@@ -2887,11 +2751,7 @@ impl MediaRepository for OnlineRepository {
     ///
     /// TRACES: UR-035, UR-036 | IR-022, JA-030
     async fn get_person(&self, person_id: &str) -> Result<MediaItem, RepoError> {
-        let endpoint = format!(
+        let endpoint = endpoints::person(&self.capabilities, &self.user_id, person_id);
-            "/Users/{}/Items/{}",
-            self.user_id,
-            urlencoding::encode(person_id)
-        );
         let item: JellyfinItem = self.get_json(&endpoint).await?;
         Ok(item.into_media_item(self.user_id.clone()))
     }
@@ -2906,21 +2766,16 @@ impl MediaRepository for OnlineRepository {
     ) -> Result<SearchResult, RepoError> {
         let limit = options.as_ref().and_then(|o| o.limit).unwrap_or(100);
 
-        let mut endpoint = format!(
+        let endpoint = endpoints::items_by_person(
-            "/Users/{}/Items?PersonIds={}&Limit={}&Recursive=true&Fields=BackdropImageTags,ParentBackdropImageTags,UserData",
+            &self.capabilities,
-            self.user_id, person_id, limit
+            &self.user_id,
+            person_id,
+            limit,
+            options
+                .as_ref()
+                .and_then(|o| o.include_item_types.as_deref()),
         );
 
-        // Add item type filtering if specified in options
-        if let Some(ref opts) = options {
-            if let Some(ref include_types) = opts.include_item_types {
-                if !include_types.is_empty() {
-                    let types_param = include_types.join(",");
-                    endpoint.push_str(&format!("&IncludeItemTypes={}", types_param));
-                }
-            }
-        }
-
         let response: ItemsResponse = self.get_json(&endpoint).await?;
         Ok(SearchResult {
             items: response
@@ -2940,10 +2795,8 @@ impl MediaRepository for OnlineRepository {
         let limit_str = limit.unwrap_or(20);
 
         // Try the /Similar endpoint which works for most items
-        let endpoint = format!(
+        let endpoint =
-            "/Items/{}/Similar?UserId={}&Limit={}&Fields=BackdropImageTags,ParentBackdropImageTags,UserData",
+            endpoints::similar_items(&self.capabilities, item_id, &self.user_id, limit_str);
-            item_id, self.user_id, limit_str
-        );
 
         let response: ItemsResponse = self.get_json(&endpoint).await?;
         Ok(SearchResult {
@@ -2974,20 +2827,22 @@ impl MediaRepository for OnlineRepository {
             "MediaType": "Audio",
             "UserId": self.user_id,
         });
-        let response: CreatePlaylistResponse = self.post_json_response("/Playlists", &body).await?;
+        let response: CreatePlaylistResponse = self
+            .post_json_response(endpoints::playlists(&self.capabilities), &body)
+            .await?;
         Ok(PlaylistCreatedResult { id: response.id })
     }
 
     async fn delete_playlist(&self, playlist_id: &str) -> Result<(), RepoError> {
         info!("[OnlineRepo] Deleting playlist {}", playlist_id);
-        let endpoint = format!("/Items/{}", urlencoding::encode(playlist_id));
+        let endpoint = endpoints::playlist_as_item(&self.capabilities, playlist_id);
         let url = format!("{}{}", self.server_url, endpoint);
 
         let request = self
             .http_client
             .client
             .delete(&url)
-            .header("X-Emby-Authorization", self.auth_header())
+            .header("Authorization", self.auth_header())
             .build()
             .map_err(|e| RepoError::Network {
                 message: format!("Failed to build request: {}", e),
@@ -3015,16 +2870,13 @@ impl MediaRepository for OnlineRepository {
             "[OnlineRepo] Renaming playlist {} to '{}'",
             playlist_id, name
         );
-        let endpoint = format!("/Items/{}", urlencoding::encode(playlist_id));
+        let endpoint = endpoints::playlist_as_item(&self.capabilities, playlist_id);
         self.post_json(&endpoint, &serde_json::json!({ "Name": name }))
             .await
     }
 
     async fn get_playlist_items(&self, playlist_id: &str) -> Result<Vec<PlaylistEntry>, RepoError> {
-        let endpoint = format!(
+        let endpoint = endpoints::playlist_items(&self.capabilities, playlist_id, &self.user_id);
-            "/Playlists/{}/Items?UserId={}&Fields=PrimaryImageTag,Artists,AlbumId,Album,AlbumArtist,RunTimeTicks,ArtistItems&StartIndex=0&Limit=10000",
-            playlist_id, self.user_id
-        );
 
         let response: PlaylistItemsResponse = self.get_json(&endpoint).await?;
         debug!(
@@ -3059,11 +2911,7 @@ impl MediaRepository for OnlineRepository {
             .map(|id| urlencoding::encode(id).into_owned())
             .collect::<Vec<_>>()
             .join(",");
-        let endpoint = format!(
+        let endpoint = endpoints::playlist_items_add(&self.capabilities, playlist_id, &ids_param);
-            "/Playlists/{}/Items?Ids={}",
-            urlencoding::encode(playlist_id),
-            ids_param
-        );
         self.post_json(&endpoint, &serde_json::json!({})).await
     }
 
@@ -3082,18 +2930,15 @@ impl MediaRepository for OnlineRepository {
             .map(|id| urlencoding::encode(id).into_owned())
             .collect::<Vec<_>>()
             .join(",");
-        let endpoint = format!(
+        let endpoint =
-            "/Playlists/{}/Items?EntryIds={}",
+            endpoints::playlist_items_remove(&self.capabilities, playlist_id, &ids_param);
-            urlencoding::encode(playlist_id),
-            ids_param
-        );
         let url = format!("{}{}", self.server_url, endpoint);
 
         let request = self
             .http_client
             .client
             .delete(&url)
-            .header("X-Emby-Authorization", self.auth_header())
+            .header("Authorization", self.auth_header())
             .build()
             .map_err(|e| RepoError::Network {
                 message: format!("Failed to build request: {}", e),
@@ -3126,10 +2971,8 @@ impl MediaRepository for OnlineRepository {
             "[OnlineRepo] Moving item {} in playlist {} to index {}",
             item_id, playlist_id, new_index
         );
-        let endpoint = format!(
+        let endpoint =
-            "/Playlists/{}/Items/{}/Move/{}",
+            endpoints::playlist_item_move(&self.capabilities, playlist_id, item_id, new_index);
-            playlist_id, item_id, new_index
-        );
         self.post_json(&endpoint, &serde_json::json!({})).await
     }
 }
@@ -3310,7 +3153,7 @@ mod tests {
         let url = result.unwrap();
         assert_eq!(
             url,
-            "https://test.server.com/Audio/test-track-123/stream?UserId=test-user-id&api_key=test-access-token&Static=true"
+            "https://test.server.com/Audio/test-track-123/stream?UserId=test-user-id&ApiKey=test-access-token&Static=true"
         );
     }
 
@@ -3765,10 +3608,14 @@ mod tests {
     // ===== Video download URL (real impl) =====
     //
     // These exercise the PRODUCTION `OnlineRepository::get_video_download_url`,
-    // not a mock. A prior mock in online_integration_test.rs used the correct
+    // not a mock. A prior mock used the correct `stream.mp4` endpoint while the
-    // `stream.mp4` endpoint while the real impl shipped `/Videos/{id}/download`,
+    // real impl shipped `/Videos/{id}/download`, which returns 404 on real
-    // which returns 404 on real servers and silently broke every movie/TV
+    // servers and silently broke every movie/TV download. That mock lived in
-    // download. Assert the real builder targets the resumable stream endpoint.
+    // `online_integration_test.rs`, which was never declared as a module and so
+    // never compiled — it was deleted for that reason, and this is the lesson it
+    // left: a mock that reimplements the builder asserts on itself, and passes
+    // just as happily when production is wrong. Assert the real builder targets
+    // the resumable stream endpoint.
     //
     // @req-test: DR-013 - Repository pattern for online/offline data access
 
@@ -3787,7 +3634,7 @@ mod tests {
             url.contains("/Videos/item123/stream.mp4"),
             "download URL must target /Videos/{{id}}/stream.mp4: {url}"
         );
-        assert!(url.contains("api_key=test-access-token"), "url: {url}");
+        assert!(url.contains("ApiKey=test-access-token"), "url: {url}");
     }
 
     #[test]