phase 8: navigation — definition, refs, hover, completion, ws/symbol

P8 resolved (SPEC §11): lazy + background indexing with progress.
Initial scan runs in a tokio task spawned from `initialized`; the
server stays responsive immediately and nav features answer with
partial data until the index is complete.

WorkspaceIndex (`index.rs`):
- Per-URI `IndexedPage` keeps name, title, headings, outgoing links.
- Reverse maps: `pages_by_name`, `backlinks: HashMap<page, …>`.
- `upsert` scrubs stale entries first so re-parses don't leak.
- `resolve` handles Wiki + AnchorOnly link kinds against the index;
  other kinds (Interwiki/Diary/File/Local/Raw) fall through.
- `slugify` for anchors (lowercases, collapses runs, drops trailing
  dashes, preserves Unicode), `page_name_from_uri` for workspace-
  rooted names, `walk_wiki_files` for the background scanner.

Backend wiring (`lib.rs`):
- `initialize` captures workspace root from `workspaceFolders` or the
  deprecated `root_uri`; advertises definition/references/hover/
  completion (trigger `[`)/workspace_symbol providers.
- `initialized` spawns the indexer, wrapped in
  `window/workDoneProgress` begin/end notifications.
- `did_open`/`did_change` synchronously update the index alongside
  publishing diagnostics; `did_close` keeps the indexed projection
  (file may still exist on disk and other pages link to it) and
  only clears diagnostics + drops the live document state.

Position lookup (`nav.rs`):
- `lsp_to_byte_pos` translates between LSP encoding (UTF-8 or
  UTF-16) and our byte columns.
- `find_inline_at` descends blocks → inlines → inline containers,
  returning the most specific inline whose span covers the cursor.

Handlers:
- definition: wikilinks resolve to a target URI; anchored links
  return the range at the matching heading.
- references: backlinks of the cursor's link target, or of the
  current page when the cursor isn't on a link. Ranges fall back
  to byte-column LSP positions when the source doc isn't open.
- hover: markdown preview with page title + outline (first 8
  headings), or a "not in index" fallback.
- completion: fires only inside an unterminated `[[ … ` on the
  current line; suggests every indexed page name.
- workspace/symbol: case-insensitive substring over every indexed
  heading.

Tests (20 new): slugify (basic / punctuation / Unicode / trailing
dash), page-name derivation under various roots, upsert / replace /
remove, resolve for Wiki + AnchorOnly, sorted `page_names`, UTF-8
passthrough + UTF-16 conversion, position lookup hits and misses.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

README.md

@@ -3,10 +3,10 @@
 A Vim/Neovim plugin providing full vimwiki syntax support, implemented as a
 Rust-based language server (LSP).
 
-> **Status:** Phase 7 (semantic tokens) complete. The server now serves
-> `semanticTokens/full` + `/range` with custom `vimwiki*` token types and
-> `level1`..`level6` + `centered` modifiers. Navigation features and
-> editor glue still pending.
+> **Status:** Phase 8 (navigation) complete. The server now serves
+> definition, references, hover, completion, `workspace/symbol`, plus a
+> background-indexed workspace per P8. Only editor glue and the release
+> pipeline are still pending.
 
 See [`SPEC.md`](./SPEC.md) for the full project specification.
 
@@ -22,8 +22,8 @@ See [`SPEC.md`](./SPEC.md) for the full project specification.
 | 5 | Renderer | ✅ done |
 | 6 | LSP Foundation | ✅ done |
 | 7 | Semantic Tokens | ✅ done |
-| 8 | Navigation | ⏳ next |
-| 9 | Editor Glue | ⏳ |
+| 8 | Navigation | ✅ done |
+| 9 | Editor Glue | ⏳ next |
 | 10 | CI/CD release pipeline | ⏳ |
 
 ## Repository layout

SPEC.md

@@ -1,7 +1,7 @@
 # nuwiki — Project Specification
 
 > Last updated: 2026-05-10
-> Status: Phase 7 (Semantic Tokens) complete — moving to Phase 8 (Navigation)
+> Status: Phase 8 (Navigation) complete — moving to Phase 9 (Editor Glue)
 
 ---
 
@@ -591,6 +591,6 @@ These decisions are required before or during the phase indicated.
 | P5 | **Minimum Neovim version** | Phase 9 | 0.8 (`vim.lsp.start`) · 0.11 (`vim.lsp.config`) | 0.8 = broader compat; 0.11 = cleaner Lua API |
 | P6 | **Minimum Vim version** | Phase 9 | Vim 8.2 · Vim 9.0 · Vim 9.1 | LSP client plugins work best on 9.0+; recommend documenting 9.1 as minimum |
 | ~~P7~~ | ~~**Semantic token type mapping**~~ | ~~Phase 7~~ | ✅ **Custom vimwiki-specific token types** | ~20 types (`vimwikiHeading`, `vimwikiBold`, …) + `level1`..`level6` + `centered` modifiers. Phase 9 ships default highlight groups in `syntax/nuwiki.vim` and the Lua glue. |
-| P8 | **Workspace indexing strategy** | Phase 8 | Eager on startup · Lazy + background | Eager blocks startup on large wikis; recommend lazy with progress notification |
+| ~~P8~~ | ~~**Workspace indexing strategy**~~ | ~~Phase 8~~ | ✅ **Lazy + background with progress** | Initial scan runs as a background tokio task; nav features answer with partial data until complete; progress reported via `window/workDoneProgress`. |
 | P9 | **macOS runner** | Phase 10 | Stay manual · Register macOS runner
 | Revisit if a Mac is available; no action needed now |

crates/nuwiki-lsp/src/index.rs

@@ -0,0 +1,365 @@
+//! Workspace index — the in-memory model of every `.wiki` page nuwiki
+//! has seen, used to power Phase 8 nav features.
+//!
+//! Per P8 (SPEC §11), the initial scan runs as a background tokio task so
+//! the server stays responsive on startup. Per-document updates land here
+//! synchronously via `upsert` whenever the LSP backend re-parses on
+//! `didOpen` / `didChange`.
+//!
+//! The index keeps only the projections nav needs (headings + outgoing
+//! links) — the full AST already lives in the backend's `documents`
+//! `DashMap`.
+
+use std::collections::HashMap;
+use std::path::{Path, PathBuf};
+
+use nuwiki_core::ast::{
+    BlockNode, BlockquoteNode, DocumentNode, InlineNode, LinkKind, LinkTarget, ListNode, Span,
+    TableNode,
+};
+use tower_lsp::lsp_types::Url;
+
+#[derive(Debug, Clone)]
+pub struct IndexedPage {
+    pub uri: Url,
+    /// Page name relative to the workspace root, without the `.wiki`
+    /// extension. Falls back to the URL's last path segment if no root.
+    pub name: String,
+    pub title: Option<String>,
+    pub headings: Vec<HeadingInfo>,
+    pub outgoing: Vec<OutgoingLink>,
+}
+
+#[derive(Debug, Clone)]
+pub struct HeadingInfo {
+    pub title: String,
+    pub level: u8,
+    pub anchor: String,
+    pub span: Span,
+}
+
+#[derive(Debug, Clone)]
+pub struct OutgoingLink {
+    /// Resolved target page name (for `LinkKind::Wiki`) or `None` for kinds
+    /// that don't address another page in the workspace (`AnchorOnly`,
+    /// `Raw`, `File`, `Local`, `Diary`, …).
+    pub target_page: Option<String>,
+    pub anchor: Option<String>,
+    pub kind: LinkKind,
+    pub span: Span,
+}
+
+#[derive(Debug, Clone)]
+pub struct Backlink {
+    pub source_uri: Url,
+    pub source_span: Span,
+    pub target_anchor: Option<String>,
+}
+
+#[derive(Debug, Default)]
+pub struct WorkspaceIndex {
+    pub root: Option<PathBuf>,
+    pub pages_by_uri: HashMap<Url, IndexedPage>,
+    pub pages_by_name: HashMap<String, Url>,
+    pub backlinks: HashMap<String, Vec<Backlink>>,
+}
+
+impl WorkspaceIndex {
+    pub fn new(root: Option<PathBuf>) -> Self {
+        Self {
+            root,
+            ..Default::default()
+        }
+    }
+
+    /// Insert or update an indexed page. Removes any prior indexing for
+    /// the same URI first (handles renames and re-parses without leaking
+    /// stale backlinks).
+    pub fn upsert(&mut self, uri: Url, ast: &DocumentNode) {
+        self.remove(&uri);
+        let name = page_name_from_uri(&uri, self.root.as_deref());
+        let mut page = IndexedPage {
+            uri: uri.clone(),
+            name: name.clone(),
+            title: ast.metadata.title.clone(),
+            headings: Vec::new(),
+            outgoing: Vec::new(),
+        };
+        index_blocks(&ast.children, &mut page);
+
+        for link in &page.outgoing {
+            if let Some(tgt) = &link.target_page {
+                self.backlinks
+                    .entry(tgt.clone())
+                    .or_default()
+                    .push(Backlink {
+                        source_uri: uri.clone(),
+                        source_span: link.span,
+                        target_anchor: link.anchor.clone(),
+                    });
+            }
+        }
+
+        self.pages_by_name.insert(name, uri.clone());
+        self.pages_by_uri.insert(uri, page);
+    }
+
+    pub fn remove(&mut self, uri: &Url) {
+        if let Some(page) = self.pages_by_uri.remove(uri) {
+            self.pages_by_name.remove(&page.name);
+        }
+        for entries in self.backlinks.values_mut() {
+            entries.retain(|b| &b.source_uri != uri);
+        }
+        self.backlinks.retain(|_, v| !v.is_empty());
+    }
+
+    /// Resolve a `LinkTarget` to a page URI in this workspace.
+    /// `source_page` is the name of the page the link originates from —
+    /// needed for `AnchorOnly` resolution.
+    pub fn resolve(&self, target: &LinkTarget, source_page: &str) -> Option<&Url> {
+        match target.kind {
+            LinkKind::Wiki => target
+                .path
+                .as_deref()
+                .and_then(|p| self.pages_by_name.get(p)),
+            LinkKind::AnchorOnly => self.pages_by_name.get(source_page),
+            // Interwiki / Diary / File / Local / Raw aren't resolved
+            // against the workspace index here. The handlers fall back to
+            // best-effort resolution (e.g. building file:// URLs).
+            _ => None,
+        }
+    }
+
+    pub fn page(&self, uri: &Url) -> Option<&IndexedPage> {
+        self.pages_by_uri.get(uri)
+    }
+
+    pub fn page_by_name(&self, name: &str) -> Option<&IndexedPage> {
+        self.pages_by_name
+            .get(name)
+            .and_then(|u| self.pages_by_uri.get(u))
+    }
+
+    pub fn page_names(&self) -> Vec<String> {
+        let mut v: Vec<String> = self.pages_by_name.keys().cloned().collect();
+        v.sort();
+        v
+    }
+
+    pub fn backlinks_for(&self, page_name: &str) -> &[Backlink] {
+        self.backlinks
+            .get(page_name)
+            .map(Vec::as_slice)
+            .unwrap_or(&[])
+    }
+}
+
+/// Derive a page name from a `file://` URL. With a workspace root the name
+/// is the URL's path relative to root, sans `.wiki`. Without a root it's
+/// just the filename stem.
+pub fn page_name_from_uri(uri: &Url, root: Option<&Path>) -> String {
+    if let (Some(root), Ok(p)) = (root, uri.to_file_path()) {
+        if let Ok(rel) = p.strip_prefix(root) {
+            let stripped = rel.with_extension("");
+            return stripped
+                .to_string_lossy()
+                .replace(std::path::MAIN_SEPARATOR, "/");
+        }
+    }
+    // Fallback: last path segment, strip .wiki if present.
+    if let Ok(p) = uri.to_file_path() {
+        return p
+            .file_stem()
+            .map(|s| s.to_string_lossy().into_owned())
+            .unwrap_or_default();
+    }
+    uri.path_segments()
+        .and_then(|mut s| s.next_back())
+        .map(|s| {
+            s.strip_suffix(".wiki")
+                .unwrap_or(s)
+                .trim_start_matches('/')
+                .to_string()
+        })
+        .unwrap_or_default()
+}
+
+/// Normalise heading text into a URL-safe anchor slug.
+pub fn slugify(s: &str) -> String {
+    let mut out = String::with_capacity(s.len());
+    let mut prev_dash = false;
+    for ch in s.chars() {
+        if ch.is_alphanumeric() {
+            for c in ch.to_lowercase() {
+                out.push(c);
+            }
+            prev_dash = false;
+        } else if (ch.is_whitespace() || ch == '-' || ch == '_') && !prev_dash && !out.is_empty() {
+            out.push('-');
+            prev_dash = true;
+        }
+        // other punctuation: drop
+    }
+    while out.ends_with('-') {
+        out.pop();
+    }
+    out
+}
+
+// ===== Indexing helpers =====
+
+fn index_blocks(blocks: &[BlockNode], page: &mut IndexedPage) {
+    for block in blocks {
+        index_block(block, page);
+    }
+}
+
+fn index_block(block: &BlockNode, page: &mut IndexedPage) {
+    match block {
+        BlockNode::Heading(h) => {
+            let title = inline_to_text(&h.children);
+            page.headings.push(HeadingInfo {
+                title: title.clone(),
+                level: h.level,
+                anchor: slugify(&title),
+                span: h.span,
+            });
+            index_inlines(&h.children, page);
+        }
+        BlockNode::Paragraph(p) => index_inlines(&p.children, page),
+        BlockNode::Blockquote(BlockquoteNode { children, .. }) => {
+            for c in children {
+                index_block(c, page);
+            }
+        }
+        BlockNode::List(ListNode { items, .. }) => {
+            for item in items {
+                index_inlines(&item.children, page);
+                if let Some(sub) = &item.sublist {
+                    index_block(&BlockNode::List(sub.clone()), page);
+                }
+            }
+        }
+        BlockNode::DefinitionList(dl) => {
+            for item in &dl.items {
+                if let Some(term) = &item.term {
+                    index_inlines(term, page);
+                }
+                for def in &item.definitions {
+                    index_inlines(def, page);
+                }
+            }
+        }
+        BlockNode::Table(TableNode { rows, .. }) => {
+            for row in rows {
+                for cell in &row.cells {
+                    index_inlines(&cell.children, page);
+                }
+            }
+        }
+        _ => {}
+    }
+}
+
+fn index_inlines(inlines: &[InlineNode], page: &mut IndexedPage) {
+    for n in inlines {
+        match n {
+            InlineNode::WikiLink(w) => {
+                page.outgoing.push(OutgoingLink {
+                    target_page: w.target.path.clone(),
+                    anchor: w.target.anchor.clone(),
+                    kind: w.target.kind,
+                    span: w.span,
+                });
+                if let Some(desc) = &w.description {
+                    index_inlines(desc, page);
+                }
+            }
+            InlineNode::ExternalLink(e) => {
+                if let Some(desc) = &e.description {
+                    index_inlines(desc, page);
+                }
+            }
+            InlineNode::Bold(b) => index_inlines(&b.children, page),
+            InlineNode::Italic(i) => index_inlines(&i.children, page),
+            InlineNode::BoldItalic(bi) => index_inlines(&bi.children, page),
+            InlineNode::Strikethrough(s) => index_inlines(&s.children, page),
+            InlineNode::Superscript(s) => index_inlines(&s.children, page),
+            InlineNode::Subscript(s) => index_inlines(&s.children, page),
+            InlineNode::Color(c) => index_inlines(&c.children, page),
+            _ => {}
+        }
+    }
+}
+
+fn inline_to_text(inlines: &[InlineNode]) -> String {
+    let mut out = String::new();
+    inline_to_text_into(inlines, &mut out);
+    out.trim().to_string()
+}
+
+fn inline_to_text_into(inlines: &[InlineNode], out: &mut String) {
+    for n in inlines {
+        match n {
+            InlineNode::Text(t) => out.push_str(&t.content),
+            InlineNode::Bold(b) => inline_to_text_into(&b.children, out),
+            InlineNode::Italic(i) => inline_to_text_into(&i.children, out),
+            InlineNode::BoldItalic(bi) => inline_to_text_into(&bi.children, out),
+            InlineNode::Strikethrough(s) => inline_to_text_into(&s.children, out),
+            InlineNode::Code(c) => out.push_str(&c.content),
+            InlineNode::Superscript(s) => inline_to_text_into(&s.children, out),
+            InlineNode::Subscript(s) => inline_to_text_into(&s.children, out),
+            InlineNode::MathInline(m) => out.push_str(&m.content),
+            InlineNode::Color(c) => inline_to_text_into(&c.children, out),
+            InlineNode::WikiLink(w) => {
+                if let Some(d) = &w.description {
+                    inline_to_text_into(d, out);
+                } else if let Some(p) = &w.target.path {
+                    out.push_str(p);
+                }
+            }
+            InlineNode::ExternalLink(e) => match &e.description {
+                Some(d) => inline_to_text_into(d, out),
+                None => out.push_str(&e.url),
+            },
+            InlineNode::Keyword(_) => {}
+            InlineNode::Transclusion(t) => out.push_str(t.alt.as_deref().unwrap_or(&t.url)),
+            InlineNode::RawUrl(r) => out.push_str(&r.url),
+        }
+    }
+}
+
+// ===== Filesystem walking =====
+
+/// Recursively collect every `.wiki` file under `root`, skipping dotfiles
+/// and dot-directories.
+pub fn walk_wiki_files(root: &Path) -> Vec<PathBuf> {
+    let mut out = Vec::new();
+    let mut stack = vec![root.to_path_buf()];
+    while let Some(dir) = stack.pop() {
+        let entries = match std::fs::read_dir(&dir) {
+            Ok(e) => e,
+            Err(_) => continue,
+        };
+        for entry in entries.flatten() {
+            let path = entry.path();
+            let Some(name) = path.file_name() else {
+                continue;
+            };
+            if name.to_string_lossy().starts_with('.') {
+                continue;
+            }
+            let Ok(meta) = entry.metadata() else {
+                continue;
+            };
+            if meta.is_dir() {
+                stack.push(path);
+            } else if meta.is_file() && path.extension().and_then(|e| e.to_str()) == Some("wiki") {
+                out.push(path);
+            }
+        }
+    }
+    out.sort();
+    out
+}

crates/nuwiki-lsp/src/lib.rs

@@ -1,36 +1,52 @@
 //! LSP protocol bridge for nuwiki.
 //!
-//! `tower-lsp` server that maintains a `DocumentStore` (SPEC §6.10) and
-//! exposes the Phase 6 feature set:
+//! `tower-lsp` server that maintains a `DocumentStore` (SPEC §6.10) plus a
+//! workspace-wide index (SPEC §6.10 + P8) and exposes every LSP method
+//! through Phase 8:
 //!
 //!   - `initialize` / `initialized` / `shutdown`
 //!   - `textDocument/didOpen`, `didChange` (full sync), `didClose`
 //!   - `textDocument/publishDiagnostics` from `BlockNode::Error` nodes
 //!   - `textDocument/documentSymbol` — nested outline from headings
+//!   - `textDocument/semanticTokens/full` + `/range`
+//!   - `textDocument/definition`, `references`, `hover`
+//!   - `textDocument/completion` (trigger: `[`)
+//!   - `workspace/symbol` — search across indexed headings
 //!
 //! Position encoding is negotiated as UTF-8 when the client supports LSP
 //! 3.17+ encodings (SPEC §6.11). When the client only supports the legacy
 //! UTF-16 default, positions get translated through a per-line lookup.
 //!
 //! Re-parses are full per change (incremental parsing deferred post-v1).
+//! The workspace scan runs in a background tokio task spawned from
+//! `initialize` (P8) with `window/workDoneProgress` begin/end events.
 
+pub mod index;
+pub mod nav;
 pub mod semantic_tokens;
 
 use std::io;
+use std::path::PathBuf;
 use std::sync::atomic::{AtomicBool, Ordering};
-use std::sync::Arc;
+use std::sync::{Arc, RwLock};
 
 use dashmap::DashMap;
 use tokio::io::{AsyncRead, AsyncWrite};
 use tower_lsp::jsonrpc::Result as LspResult;
 use tower_lsp::lsp_types::{
+    CompletionItem, CompletionItemKind, CompletionOptions, CompletionParams, CompletionResponse,
     Diagnostic, DiagnosticSeverity, DidChangeTextDocumentParams, DidCloseTextDocumentParams,
     DidOpenTextDocumentParams, DocumentSymbol, DocumentSymbolParams, DocumentSymbolResponse,
-    InitializeParams, InitializeResult, InitializedParams, MessageType, OneOf,
-    PositionEncodingKind, SemanticTokens, SemanticTokensFullOptions, SemanticTokensOptions,
-    SemanticTokensParams, SemanticTokensRangeParams, SemanticTokensRangeResult,
-    SemanticTokensResult, SemanticTokensServerCapabilities, ServerCapabilities, ServerInfo,
-    SymbolKind, TextDocumentSyncCapability, TextDocumentSyncKind, Url, WorkDoneProgressOptions,
+    GotoDefinitionParams, GotoDefinitionResponse, Hover, HoverContents, HoverParams,
+    HoverProviderCapability, InitializeParams, InitializeResult, InitializedParams, Location,
+    MarkupContent, MarkupKind, MessageType, OneOf, PositionEncodingKind, ProgressParams,
+    ProgressParamsValue, ProgressToken, Range, ReferenceParams, SemanticTokens,
+    SemanticTokensFullOptions, SemanticTokensOptions, SemanticTokensParams,
+    SemanticTokensRangeParams, SemanticTokensRangeResult, SemanticTokensResult,
+    SemanticTokensServerCapabilities, ServerCapabilities, ServerInfo,
+    SymbolInformation as LspSymbolInformation, SymbolKind, TextDocumentSyncCapability,
+    TextDocumentSyncKind, Url, WorkDoneProgress, WorkDoneProgressBegin, WorkDoneProgressEnd,
+    WorkDoneProgressOptions, WorkspaceSymbolParams,
 };
 use tower_lsp::{Client, LanguageServer, LspService, Server};
 
@@ -41,6 +57,8 @@ use nuwiki_core::ast::{
 use nuwiki_core::syntax::vimwiki::VimwikiSyntax;
 use nuwiki_core::syntax::SyntaxRegistry;
 
+use crate::index::{IndexedPage, WorkspaceIndex};
+
 /// Run the LSP server over the given async reader/writer pair. The binary
 /// (`nuwiki-ls`) just calls this with stdin/stdout.
 pub async fn run<I, O>(reader: I, writer: O)
@@ -78,6 +96,8 @@ struct Backend {
     /// True after `initialize` if the client opted into UTF-8 encoding.
     /// Otherwise we keep the LSP 3.16 default of UTF-16.
     use_utf8: Arc<AtomicBool>,
+    /// Workspace index — populated lazily in the background per P8.
+    index: Arc<RwLock<WorkspaceIndex>>,
 }
 
 impl Backend {
@@ -89,6 +109,7 @@ impl Backend {
             documents: Arc::new(DashMap::new()),
             registry: Arc::new(registry),
             use_utf8: Arc::new(AtomicBool::new(false)),
+            index: Arc::new(RwLock::new(WorkspaceIndex::default())),
         }
     }
 
@@ -106,6 +127,13 @@ impl Backend {
         };
         let ast = plugin.parse(&text);
         let diagnostics = ast_diagnostics(&ast, &text, self.use_utf8.load(Ordering::Relaxed));
+
+        // Keep the workspace index in sync with what the editor is showing.
+        {
+            let mut idx = self.index.write().expect("index lock poisoned");
+            idx.upsert(uri.clone(), &ast);
+        }
+
         self.documents
             .insert(uri.clone(), DocumentState { text, ast, version });
         self.client
@@ -133,6 +161,12 @@ impl LanguageServer for Backend {
             None // server defaults to UTF-16 per LSP 3.16.
         };
 
+        // Capture the workspace root for the background indexer.
+        let root = workspace_root_from_params(&params);
+        if let Some(p) = &root {
+            self.index.write().expect("index lock poisoned").root = Some(p.clone());
+        }
+
         Ok(InitializeResult {
             capabilities: ServerCapabilities {
                 position_encoding,
@@ -140,6 +174,14 @@ impl LanguageServer for Backend {
                     TextDocumentSyncKind::FULL,
                 )),
                 document_symbol_provider: Some(OneOf::Left(true)),
+                workspace_symbol_provider: Some(OneOf::Left(true)),
+                definition_provider: Some(OneOf::Left(true)),
+                references_provider: Some(OneOf::Left(true)),
+                hover_provider: Some(HoverProviderCapability::Simple(true)),
+                completion_provider: Some(CompletionOptions {
+                    trigger_characters: Some(vec!["[".into()]),
+                    ..CompletionOptions::default()
+                }),
                 semantic_tokens_provider: Some(
                     SemanticTokensServerCapabilities::SemanticTokensOptions(
                         SemanticTokensOptions {
@@ -171,6 +213,17 @@ impl LanguageServer for Backend {
                 format!("nuwiki-lsp initialized (positionEncoding={enc})"),
             )
             .await;
+
+        // Kick off the background workspace scan (P8). Skips if no root.
+        let root = self.index.read().expect("index lock poisoned").root.clone();
+        if let Some(root) = root {
+            let index = Arc::clone(&self.index);
+            let client = self.client.clone();
+            let registry = Arc::clone(&self.registry);
+            tokio::spawn(async move {
+                index_workspace(root, index, client, registry).await;
+            });
+        }
     }
 
     async fn shutdown(&self) -> LspResult<()> {
@@ -194,10 +247,13 @@ impl LanguageServer for Backend {
     }
 
     async fn did_close(&self, params: DidCloseTextDocumentParams) {
-        self.documents.remove(&params.text_document.uri);
+        let uri = &params.text_document.uri;
+        self.documents.remove(uri);
+        // Keep the index entry — the file may still exist on disk and other
+        // pages can still link to it. We only drop the live document state.
         // Clear lingering diagnostics so closed buffers don't keep red squiggles.
         self.client
-            .publish_diagnostics(params.text_document.uri, Vec::new(), None)
+            .publish_diagnostics(params.text_document.uri.clone(), Vec::new(), None)
             .await;
     }
 
@@ -245,6 +301,211 @@ impl LanguageServer for Backend {
             data: pack_data(&data),
         })))
     }
+
+    async fn goto_definition(
+        &self,
+        params: GotoDefinitionParams,
+    ) -> LspResult<Option<GotoDefinitionResponse>> {
+        let pos = params.text_document_position_params.position;
+        let uri = &params.text_document_position_params.text_document.uri;
+        let Some(doc) = self.documents.get(uri) else {
+            return Ok(None);
+        };
+        let utf8 = self.use_utf8.load(Ordering::Relaxed);
+        let (line, col) = nav::lsp_to_byte_pos(pos, &doc.text, utf8);
+        let Some(node) = nav::find_inline_at(&doc.ast, line, col) else {
+            return Ok(None);
+        };
+        let location = match node {
+            InlineNode::WikiLink(w) => {
+                let source_page = index::page_name_from_uri(
+                    uri,
+                    self.index
+                        .read()
+                        .expect("index lock poisoned")
+                        .root
+                        .as_deref(),
+                );
+                let idx = self.index.read().expect("index lock poisoned");
+                let target_uri = idx.resolve(&w.target, &source_page).cloned();
+                target_uri.map(|target| {
+                    let target_range = w
+                        .target
+                        .anchor
+                        .as_deref()
+                        .and_then(|a| heading_range_in(&idx, &target, a, utf8))
+                        .unwrap_or_else(zero_range);
+                    Location {
+                        uri: target,
+                        range: target_range,
+                    }
+                })
+            }
+            InlineNode::ExternalLink(_) | InlineNode::RawUrl(_) => None,
+            _ => None,
+        };
+        Ok(location.map(GotoDefinitionResponse::Scalar))
+    }
+
+    async fn references(&self, params: ReferenceParams) -> LspResult<Option<Vec<Location>>> {
+        let pos = params.text_document_position.position;
+        let uri = &params.text_document_position.text_document.uri;
+        let Some(doc) = self.documents.get(uri) else {
+            return Ok(None);
+        };
+        let utf8 = self.use_utf8.load(Ordering::Relaxed);
+        let (line, col) = nav::lsp_to_byte_pos(pos, &doc.text, utf8);
+
+        // Identify the page (and optional anchor) the cursor is "asking
+        // about". Two cases:
+        //   - cursor is on a wikilink → references to the linked page
+        //   - cursor isn't on a link → references to the *current* page
+        let source_page = index::page_name_from_uri(
+            uri,
+            self.index
+                .read()
+                .expect("index lock poisoned")
+                .root
+                .as_deref(),
+        );
+        let target_page = match nav::find_inline_at(&doc.ast, line, col) {
+            Some(InlineNode::WikiLink(w)) => match w.target.kind {
+                nuwiki_core::ast::LinkKind::Wiki => w.target.path.clone(),
+                nuwiki_core::ast::LinkKind::AnchorOnly => Some(source_page.clone()),
+                _ => None,
+            },
+            _ => Some(source_page),
+        };
+        let Some(page) = target_page else {
+            return Ok(None);
+        };
+        let idx = self.index.read().expect("index lock poisoned");
+        let locations: Vec<Location> = idx
+            .backlinks_for(&page)
+            .iter()
+            .filter_map(|b| {
+                self.documents.get(&b.source_uri).map(|src| Location {
+                    uri: b.source_uri.clone(),
+                    range: span_to_lsp_range(&b.source_span, &src.text, utf8),
+                })
+            })
+            .collect();
+        if locations.is_empty() {
+            // Even without open docs we can still produce LSP ranges from
+            // the stored span; the editor opens the file to display it.
+            let locations: Vec<Location> = idx
+                .backlinks_for(&page)
+                .iter()
+                .map(|b| Location {
+                    uri: b.source_uri.clone(),
+                    range: span_to_lsp_range_no_text(&b.source_span),
+                })
+                .collect();
+            return Ok(Some(locations));
+        }
+        Ok(Some(locations))
+    }
+
+    async fn hover(&self, params: HoverParams) -> LspResult<Option<Hover>> {
+        let pos = params.text_document_position_params.position;
+        let uri = &params.text_document_position_params.text_document.uri;
+        let Some(doc) = self.documents.get(uri) else {
+            return Ok(None);
+        };
+        let utf8 = self.use_utf8.load(Ordering::Relaxed);
+        let (line, col) = nav::lsp_to_byte_pos(pos, &doc.text, utf8);
+        let Some(node) = nav::find_inline_at(&doc.ast, line, col) else {
+            return Ok(None);
+        };
+
+        let (markdown, hover_span) = match node {
+            InlineNode::WikiLink(w) => {
+                let source_page = index::page_name_from_uri(
+                    uri,
+                    self.index
+                        .read()
+                        .expect("index lock poisoned")
+                        .root
+                        .as_deref(),
+                );
+                let idx = self.index.read().expect("index lock poisoned");
+                let target_uri = idx.resolve(&w.target, &source_page).cloned();
+                let body = match target_uri.as_ref().and_then(|u| idx.page(u)) {
+                    Some(page) => preview_for(page, w.target.anchor.as_deref()),
+                    None => match &w.target.path {
+                        Some(p) => format!("**{p}** — page not in index"),
+                        None => "(unresolved link)".into(),
+                    },
+                };
+                (body, w.span)
+            }
+            InlineNode::ExternalLink(e) => (format!("[{0}]({0})", e.url), e.span),
+            InlineNode::RawUrl(u) => (format!("<{0}>", u.url), u.span),
+            _ => return Ok(None),
+        };
+
+        Ok(Some(Hover {
+            contents: HoverContents::Markup(MarkupContent {
+                kind: MarkupKind::Markdown,
+                value: markdown,
+            }),
+            range: Some(span_to_lsp_range(&hover_span, &doc.text, utf8)),
+        }))
+    }
+
+    async fn completion(&self, params: CompletionParams) -> LspResult<Option<CompletionResponse>> {
+        let uri = &params.text_document_position.text_document.uri;
+        let Some(doc) = self.documents.get(uri) else {
+            return Ok(None);
+        };
+        let utf8 = self.use_utf8.load(Ordering::Relaxed);
+        let (line, col) =
+            nav::lsp_to_byte_pos(params.text_document_position.position, &doc.text, utf8);
+        // Only fire completion inside an unterminated `[[ ... ` run.
+        if !is_inside_wikilink(&doc.text, line, col) {
+            return Ok(None);
+        }
+        let idx = self.index.read().expect("index lock poisoned");
+        let items: Vec<CompletionItem> = idx
+            .page_names()
+            .into_iter()
+            .map(|name| CompletionItem {
+                label: name.clone(),
+                kind: Some(CompletionItemKind::FILE),
+                insert_text: Some(name),
+                ..CompletionItem::default()
+            })
+            .collect();
+        Ok(Some(CompletionResponse::Array(items)))
+    }
+
+    async fn symbol(
+        &self,
+        params: WorkspaceSymbolParams,
+    ) -> LspResult<Option<Vec<LspSymbolInformation>>> {
+        let q = params.query.to_lowercase();
+        let idx = self.index.read().expect("index lock poisoned");
+        let mut out = Vec::new();
+        for page in idx.pages_by_uri.values() {
+            for h in &page.headings {
+                if q.is_empty() || h.title.to_lowercase().contains(&q) {
+                    #[allow(deprecated)]
+                    out.push(LspSymbolInformation {
+                        name: h.title.clone(),
+                        kind: SymbolKind::STRING,
+                        tags: None,
+                        deprecated: None,
+                        location: Location {
+                            uri: page.uri.clone(),
+                            range: span_to_lsp_range_no_text(&h.span),
+                        },
+                        container_name: Some(page.name.clone()),
+                    });
+                }
+            }
+        }
+        Ok(Some(out))
+    }
 }
 
 fn pack_data(flat: &[u32]) -> Vec<tower_lsp::lsp_types::SemanticToken> {
@@ -469,3 +730,165 @@ fn keyword_str(k: nuwiki_core::ast::Keyword) -> &'static str {
         nuwiki_core::ast::Keyword::Xxx => "XXX",
     }
 }
+
+// ===== Workspace + navigation helpers =====
+
+fn workspace_root_from_params(params: &InitializeParams) -> Option<PathBuf> {
+    if let Some(folders) = &params.workspace_folders {
+        if let Some(first) = folders.first() {
+            if let Ok(p) = first.uri.to_file_path() {
+                return Some(p);
+            }
+        }
+    }
+    #[allow(deprecated)]
+    if let Some(uri) = &params.root_uri {
+        if let Ok(p) = uri.to_file_path() {
+            return Some(p);
+        }
+    }
+    None
+}
+
+/// Background workspace scan (P8). Walks every `.wiki` file under `root`,
+/// parses it, and feeds it into the shared index. Wraps the work in a
+/// `window/workDoneProgress` begin/end pair so editors can show progress.
+async fn index_workspace(
+    root: PathBuf,
+    index: Arc<RwLock<WorkspaceIndex>>,
+    client: Client,
+    registry: Arc<SyntaxRegistry>,
+) {
+    let token = ProgressToken::String("nuwiki-index".into());
+    // Best-effort: if the client doesn't pre-create progress tokens we just
+    // send the begin/end directly. tower-lsp permits this.
+    let _ = client
+        .send_notification::<tower_lsp::lsp_types::notification::Progress>(ProgressParams {
+            token: token.clone(),
+            value: ProgressParamsValue::WorkDone(WorkDoneProgress::Begin(WorkDoneProgressBegin {
+                title: "Indexing wiki".into(),
+                cancellable: Some(false),
+                message: None,
+                percentage: None,
+            })),
+        })
+        .await;
+
+    let plugin = registry.get("vimwiki");
+    let files = index::walk_wiki_files(&root);
+    for path in files {
+        let Ok(text) = std::fs::read_to_string(&path) else {
+            continue;
+        };
+        let Some(plugin) = plugin else { continue };
+        let ast = plugin.parse(&text);
+        let Ok(uri) = Url::from_file_path(&path) else {
+            continue;
+        };
+        if let Ok(mut idx) = index.write() {
+            idx.upsert(uri, &ast);
+        }
+    }
+
+    let _ = client
+        .send_notification::<tower_lsp::lsp_types::notification::Progress>(ProgressParams {
+            token,
+            value: ProgressParamsValue::WorkDone(WorkDoneProgress::End(WorkDoneProgressEnd {
+                message: Some("done".into()),
+            })),
+        })
+        .await;
+}
+
+fn span_to_lsp_range(span: &Span, text: &str, utf8: bool) -> Range {
+    to_lsp_range(span, text, utf8)
+}
+
+fn span_to_lsp_range_no_text(span: &Span) -> Range {
+    Range {
+        start: tower_lsp::lsp_types::Position {
+            line: span.start.line,
+            character: span.start.column,
+        },
+        end: tower_lsp::lsp_types::Position {
+            line: span.end.line,
+            character: span.end.column,
+        },
+    }
+}
+
+fn zero_range() -> Range {
+    Range {
+        start: tower_lsp::lsp_types::Position {
+            line: 0,
+            character: 0,
+        },
+        end: tower_lsp::lsp_types::Position {
+            line: 0,
+            character: 0,
+        },
+    }
+}
+
+fn heading_range_in(idx: &WorkspaceIndex, uri: &Url, anchor: &str, _utf8: bool) -> Option<Range> {
+    let page = idx.page(uri)?;
+    let h = page.headings.iter().find(|h| h.anchor == anchor)?;
+    Some(span_to_lsp_range_no_text(&h.span))
+}
+
+fn is_inside_wikilink(text: &str, line: u32, byte_col: u32) -> bool {
+    // Scan the current line for the most recent unclosed `[[` before the
+    // cursor.
+    let mut cur = 0u32;
+    let mut current_line = 0u32;
+    let bytes = text.as_bytes();
+    while current_line < line && cur < bytes.len() as u32 {
+        if bytes[cur as usize] == b'\n' {
+            current_line += 1;
+        }
+        cur += 1;
+    }
+    let line_start = cur as usize;
+    let limit = (line_start + byte_col as usize).min(bytes.len());
+    let segment = &bytes[line_start..limit];
+    // Find last "[[" and check no "]]" closes it before cursor.
+    let mut open_at: Option<usize> = None;
+    let mut i = 0;
+    while i + 1 < segment.len() {
+        if segment[i] == b'[' && segment[i + 1] == b'[' {
+            open_at = Some(i);
+            i += 2;
+        } else if segment[i] == b']' && segment[i + 1] == b']' {
+            open_at = None;
+            i += 2;
+        } else {
+            i += 1;
+        }
+    }
+    open_at.is_some()
+}
+
+fn preview_for(page: &IndexedPage, anchor: Option<&str>) -> String {
+    let mut buf = String::new();
+    let title = page.title.as_deref().unwrap_or(&page.name);
+    buf.push_str("**");
+    buf.push_str(title);
+    buf.push_str("**\n\n");
+    if let Some(anchor) = anchor {
+        if let Some(h) = page.headings.iter().find(|h| h.anchor == anchor) {
+            buf.push_str(&format!("§ {}\n", h.title));
+        } else {
+            buf.push_str(&format!("(anchor `{anchor}` not found)\n"));
+        }
+    } else if let Some(h) = page.headings.first() {
+        buf.push_str(&format!("§ {}\n", h.title));
+    }
+    if !page.headings.is_empty() {
+        buf.push_str("\nOutline:\n");
+        for h in page.headings.iter().take(8) {
+            let indent = "  ".repeat((h.level.saturating_sub(1)) as usize);
+            buf.push_str(&format!("{indent}- {}\n", h.title));
+        }
+    }
+    buf
+}

crates/nuwiki-lsp/src/nav.rs

@@ -0,0 +1,149 @@
+//! Helpers shared by the Phase 8 navigation handlers (definition,
+//! references, hover, completion).
+//!
+//! Two responsibilities:
+//!
+//! 1. **Position conversion** — clients send LSP `Position`s in either
+//!    UTF-8 or UTF-16 encoding; nuwiki AST spans are byte offsets.
+//!    `lsp_to_byte_pos` translates the LSP position into the same shape
+//!    so it can be compared against AST spans.
+//! 2. **Position lookup** — given a byte position, find the most specific
+//!    `InlineNode` whose span covers it. Used to identify the link under
+//!    the cursor.
+
+use nuwiki_core::ast::{BlockNode, DocumentNode, InlineNode, ListItemNode, Span};
+use tower_lsp::lsp_types::Position as LspPosition;
+
+use crate::semantic_tokens::LineIndex;
+
+/// Translate an LSP `Position` (whose `character` is a UTF-16 code-unit
+/// offset by default, or a UTF-8 byte offset when negotiated) into our
+/// internal `(line, byte_col)` shape.
+pub fn lsp_to_byte_pos(p: LspPosition, text: &str, utf8: bool) -> (u32, u32) {
+    if utf8 {
+        return (p.line, p.character);
+    }
+    let idx = LineIndex::new(text);
+    let line_str = idx.line_str(p.line, text);
+    let byte_col = utf16_to_byte_col(line_str, p.character);
+    (p.line, byte_col)
+}
+
+fn utf16_to_byte_col(line: &str, target_utf16: u32) -> u32 {
+    let mut byte = 0u32;
+    let mut units = 0u32;
+    for ch in line.chars() {
+        if units >= target_utf16 {
+            break;
+        }
+        units += ch.len_utf16() as u32;
+        byte += ch.len_utf8() as u32;
+    }
+    byte
+}
+
+/// Find the most specific inline node whose span covers the given byte
+/// position. Walks block structure first, then descends into inline
+/// containers (bold, italic, …) until no child claims the position.
+pub fn find_inline_at(doc: &DocumentNode, line: u32, byte_col: u32) -> Option<&InlineNode> {
+    for block in &doc.children {
+        if let Some(node) = find_in_block(block, line, byte_col) {
+            return Some(node);
+        }
+    }
+    None
+}
+
+fn find_in_block(block: &BlockNode, line: u32, col: u32) -> Option<&InlineNode> {
+    match block {
+        BlockNode::Heading(h) => find_in_inlines(&h.children, line, col),
+        BlockNode::Paragraph(p) => find_in_inlines(&p.children, line, col),
+        BlockNode::Blockquote(b) => b.children.iter().find_map(|c| find_in_block(c, line, col)),
+        BlockNode::List(l) => l
+            .items
+            .iter()
+            .find_map(|it| find_in_list_item(it, line, col)),
+        BlockNode::DefinitionList(dl) => dl.items.iter().find_map(|it| {
+            it.term
+                .as_ref()
+                .and_then(|t| find_in_inlines(t, line, col))
+                .or_else(|| {
+                    it.definitions
+                        .iter()
+                        .find_map(|d| find_in_inlines(d, line, col))
+                })
+        }),
+        BlockNode::Table(t) => t.rows.iter().find_map(|r| {
+            r.cells
+                .iter()
+                .find_map(|c| find_in_inlines(&c.children, line, col))
+        }),
+        _ => None,
+    }
+}
+
+fn find_in_list_item(item: &ListItemNode, line: u32, col: u32) -> Option<&InlineNode> {
+    find_in_inlines(&item.children, line, col).or_else(|| {
+        item.sublist.as_ref().and_then(|sub| {
+            sub.items
+                .iter()
+                .find_map(|i| find_in_list_item(i, line, col))
+        })
+    })
+}
+
+fn find_in_inlines(inlines: &[InlineNode], line: u32, col: u32) -> Option<&InlineNode> {
+    for n in inlines {
+        if !span_contains(span_of_inline(n), line, col) {
+            continue;
+        }
+        // Descend into inline containers so we return the *innermost* hit.
+        let deeper = match n {
+            InlineNode::Bold(b) => find_in_inlines(&b.children, line, col),
+            InlineNode::Italic(i) => find_in_inlines(&i.children, line, col),
+            InlineNode::BoldItalic(bi) => find_in_inlines(&bi.children, line, col),
+            InlineNode::Strikethrough(s) => find_in_inlines(&s.children, line, col),
+            InlineNode::Superscript(s) => find_in_inlines(&s.children, line, col),
+            InlineNode::Subscript(s) => find_in_inlines(&s.children, line, col),
+            InlineNode::Color(c) => find_in_inlines(&c.children, line, col),
+            InlineNode::WikiLink(w) => w
+                .description
+                .as_ref()
+                .and_then(|d| find_in_inlines(d, line, col)),
+            InlineNode::ExternalLink(e) => e
+                .description
+                .as_ref()
+                .and_then(|d| find_in_inlines(d, line, col)),
+            _ => None,
+        };
+        return Some(deeper.unwrap_or(n));
+    }
+    None
+}
+
+fn span_contains(s: Span, line: u32, col: u32) -> bool {
+    let start = (s.start.line, s.start.column);
+    let end = (s.end.line, s.end.column);
+    let p = (line, col);
+    p >= start && p < end
+}
+
+pub fn span_of_inline(node: &InlineNode) -> Span {
+    match node {
+        InlineNode::Text(n) => n.span,
+        InlineNode::Bold(n) => n.span,
+        InlineNode::Italic(n) => n.span,
+        InlineNode::BoldItalic(n) => n.span,
+        InlineNode::Strikethrough(n) => n.span,
+        InlineNode::Code(n) => n.span,
+        InlineNode::Superscript(n) => n.span,
+        InlineNode::Subscript(n) => n.span,
+        InlineNode::MathInline(n) => n.span,
+        InlineNode::Keyword(n) => n.span,
+        InlineNode::Color(n) => n.span,
+        InlineNode::WikiLink(n) => n.span,
+        InlineNode::ExternalLink(n) => n.span,
+        InlineNode::Transclusion(n) => n.span,
+        InlineNode::RawUrl(n) => n.span,
+    }
+}

crates/nuwiki-lsp/tests/nav.rs

@@ -0,0 +1,228 @@
+//! Tests for the Phase 8 navigation pieces: WorkspaceIndex queries,
+//! page-name derivation, anchor slugify, position lookup, and link
+//! resolution. The async LSP handlers are exercised through these
+//! helpers; end-to-end JSON-RPC drive lives in a follow-up phase.
+
+use std::path::PathBuf;
+
+use nuwiki_core::ast::{InlineNode, LinkKind};
+use nuwiki_core::syntax::vimwiki::VimwikiSyntax;
+use nuwiki_core::syntax::SyntaxPlugin;
+use nuwiki_lsp::index::{page_name_from_uri, slugify, WorkspaceIndex};
+use nuwiki_lsp::nav::{find_inline_at, lsp_to_byte_pos};
+use tower_lsp::lsp_types::{Position as LspPosition, Url};
+
+fn parse(src: &str) -> nuwiki_core::ast::DocumentNode {
+    VimwikiSyntax::new().parse(src)
+}
+
+// ===== Slugify =====
+
+#[test]
+fn slugify_basic_title() {
+    assert_eq!(slugify("Hello World"), "hello-world");
+}
+
+#[test]
+fn slugify_strips_punctuation_and_collapses_dashes() {
+    assert_eq!(slugify("Hello, World!  Again"), "hello-world-again");
+}
+
+#[test]
+fn slugify_unicode_lowercase() {
+    assert_eq!(slugify("Crème Brûlée"), "crème-brûlée");
+}
+
+#[test]
+fn slugify_no_trailing_dash() {
+    assert_eq!(slugify("Title — "), "title");
+}
+
+// ===== Page name from URI =====
+
+#[test]
+fn page_name_relative_to_root() {
+    let root = PathBuf::from("/wiki");
+    let uri = Url::from_file_path("/wiki/dir/Page.wiki").unwrap();
+    assert_eq!(page_name_from_uri(&uri, Some(&root)), "dir/Page");
+}
+
+#[test]
+fn page_name_at_root() {
+    let root = PathBuf::from("/wiki");
+    let uri = Url::from_file_path("/wiki/Index.wiki").unwrap();
+    assert_eq!(page_name_from_uri(&uri, Some(&root)), "Index");
+}
+
+#[test]
+fn page_name_without_root_falls_back_to_stem() {
+    let uri = Url::from_file_path("/tmp/foo.wiki").unwrap();
+    assert_eq!(page_name_from_uri(&uri, None), "foo");
+}
+
+// ===== Workspace index =====
+
+#[test]
+fn upsert_indexes_headings_and_outgoing_links() {
+    let mut idx = WorkspaceIndex::new(Some(PathBuf::from("/wiki")));
+    let uri = Url::from_file_path("/wiki/Home.wiki").unwrap();
+    let ast = parse("= Home =\n[[Other]] and [[#Section]]\n");
+    idx.upsert(uri.clone(), &ast);
+
+    let page = idx.page(&uri).expect("page indexed");
+    assert_eq!(page.name, "Home");
+    assert_eq!(page.headings.len(), 1);
+    assert_eq!(page.headings[0].title, "Home");
+    assert_eq!(page.headings[0].anchor, "home");
+    assert_eq!(page.outgoing.len(), 2);
+    assert_eq!(page.outgoing[0].target_page.as_deref(), Some("Other"));
+    assert_eq!(page.outgoing[0].kind, LinkKind::Wiki);
+    assert_eq!(page.outgoing[1].kind, LinkKind::AnchorOnly);
+}
+
+#[test]
+fn upsert_registers_page_by_name_and_records_backlinks() {
+    let mut idx = WorkspaceIndex::new(Some(PathBuf::from("/wiki")));
+    let home = Url::from_file_path("/wiki/Home.wiki").unwrap();
+    let about = Url::from_file_path("/wiki/About.wiki").unwrap();
+
+    idx.upsert(home.clone(), &parse("[[About]]\n"));
+    idx.upsert(about.clone(), &parse("= About =\n"));
+
+    assert_eq!(idx.page_by_name("About").unwrap().uri, about);
+
+    let backlinks = idx.backlinks_for("About");
+    assert_eq!(backlinks.len(), 1);
+    assert_eq!(backlinks[0].source_uri, home);
+}
+
+#[test]
+fn upsert_replaces_prior_indexing_for_same_uri() {
+    let mut idx = WorkspaceIndex::new(Some(PathBuf::from("/wiki")));
+    let uri = Url::from_file_path("/wiki/Home.wiki").unwrap();
+    idx.upsert(uri.clone(), &parse("[[A]]\n"));
+    assert_eq!(idx.backlinks_for("A").len(), 1);
+
+    // Re-upsert with different content: old backlinks must drop.
+    idx.upsert(uri.clone(), &parse("[[B]]\n"));
+    assert_eq!(idx.backlinks_for("A").len(), 0);
+    assert_eq!(idx.backlinks_for("B").len(), 1);
+}
+
+#[test]
+fn remove_drops_page_and_backlinks() {
+    let mut idx = WorkspaceIndex::new(Some(PathBuf::from("/wiki")));
+    let home = Url::from_file_path("/wiki/Home.wiki").unwrap();
+    let about = Url::from_file_path("/wiki/About.wiki").unwrap();
+    idx.upsert(home.clone(), &parse("[[About]]\n"));
+    idx.upsert(about.clone(), &parse("= About =\n"));
+
+    idx.remove(&home);
+    assert!(idx.page(&home).is_none());
+    assert!(idx.backlinks_for("About").is_empty());
+    // The target page is untouched.
+    assert!(idx.page(&about).is_some());
+}
+
+#[test]
+fn resolve_wiki_link_to_uri() {
+    let mut idx = WorkspaceIndex::new(Some(PathBuf::from("/wiki")));
+    let about = Url::from_file_path("/wiki/About.wiki").unwrap();
+    idx.upsert(about.clone(), &parse("= About =\n"));
+
+    let target = nuwiki_core::ast::LinkTarget {
+        kind: LinkKind::Wiki,
+        path: Some("About".into()),
+        ..Default::default()
+    };
+    assert_eq!(idx.resolve(&target, "Home"), Some(&about));
+}
+
+#[test]
+fn resolve_anchor_only_link_returns_source_page() {
+    let mut idx = WorkspaceIndex::new(Some(PathBuf::from("/wiki")));
+    let home = Url::from_file_path("/wiki/Home.wiki").unwrap();
+    idx.upsert(home.clone(), &parse("= H =\n[[#Section]]\n"));
+
+    let target = nuwiki_core::ast::LinkTarget {
+        kind: LinkKind::AnchorOnly,
+        anchor: Some("section".into()),
+        ..Default::default()
+    };
+    assert_eq!(idx.resolve(&target, "Home"), Some(&home));
+}
+
+#[test]
+fn page_names_lists_indexed_pages_sorted() {
+    let mut idx = WorkspaceIndex::new(Some(PathBuf::from("/wiki")));
+    for name in ["Charlie", "Alpha", "Bravo"] {
+        let uri = Url::from_file_path(format!("/wiki/{name}.wiki")).unwrap();
+        idx.upsert(uri, &parse(&format!("= {name} =\n")));
+    }
+    let names = idx.page_names();
+    assert_eq!(names, vec!["Alpha", "Bravo", "Charlie"]);
+}
+
+// ===== Position conversion =====
+
+#[test]
+fn lsp_to_byte_pos_passthrough_in_utf8() {
+    let p = LspPosition {
+        line: 2,
+        character: 5,
+    };
+    let (line, col) = lsp_to_byte_pos(p, "ignored", true);
+    assert_eq!((line, col), (2, 5));
+}
+
+#[test]
+fn lsp_to_byte_pos_converts_from_utf16() {
+    // 'é' is one UTF-16 code unit, two UTF-8 bytes. Char "2" after 'é':
+    // UTF-16 col 2 → byte col 3.
+    let text = "héllo\n";
+    let p = LspPosition {
+        line: 0,
+        character: 2,
+    };
+    let (line, col) = lsp_to_byte_pos(p, text, false);
+    assert_eq!(line, 0);
+    assert_eq!(col, 3);
+}
+
+// ===== Position lookup =====
+
+#[test]
+fn find_inline_at_returns_wikilink_under_cursor() {
+    let src = "see [[Other]] now\n";
+    let doc = parse(src);
+    // Cursor inside "Other" — byte col 6 falls inside "[[Other]]" (which
+    // starts at byte 4 and ends at byte 13).
+    let node = find_inline_at(&doc, 0, 6).expect("wikilink at cursor");
+    assert!(matches!(node, InlineNode::WikiLink(_)));
+}
+
+#[test]
+fn find_inline_at_returns_none_for_plain_text() {
+    let src = "just text\n";
+    let doc = parse(src);
+    let node = find_inline_at(&doc, 0, 3);
+    // "just text" → Text node, which is what we get back from the inner
+    // walk (not None). Verify it's a Text.
+    assert!(matches!(node, Some(InlineNode::Text(_))));
+}
+
+#[test]
+fn find_inline_at_descends_into_inline_containers() {
+    let src = "*bold text*\n";
+    let doc = parse(src);
+    // Inside "bold" — should return the inner Text, not the wrapping Bold.
+    let node = find_inline_at(&doc, 0, 3).expect("hit");
+    assert!(matches!(node, InlineNode::Text(_)));
+}
+
+#[test]
+fn find_inline_at_returns_none_past_eol() {
+    let src = "short\n";
+    let doc = parse(src);
+    assert!(find_inline_at(&doc, 0, 999).is_none());
+}