Merge main into fix/union-declarations-not-indexed

Resolves the CHANGELOG conflict — main and this branch each prepended a
bullet to [Unreleased] > Fixes; both are kept. Everything else auto-merged,
including src/mcp/tools.ts, which main reworked heavily for the explore
allocation/displacement work (CG-28/31/36/38) while this branch added the
`union` kind to its container sets.

Verified on the merged tree with the native kernel built: 3070 passed,
9 skipped, 0 failed.

CHANGELOG.md

@@ -15,20 +15,34 @@ and adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 - `codegraph_explore` no longer re-sends source it already returned earlier in the same conversation. A file it has already shown you comes back as a short pointer — the path, the symbols and the exact line range, with confirmation that the file hasn't changed since — and the space that frees is spent on code you haven't seen yet, so a follow-up call covers new ground instead of repeating the last one. If a file was edited in between, its source is always shown again in full. Set `CODEGRAPH_EXPLORE_DEDUP=0` to turn this off.
 
+- When an agent connects over MCP, CodeGraph now states up front that it indexes 30+ languages — TypeScript/JavaScript, Python, Go, Rust, Java, C#, C/C++, PHP, Ruby, Swift, Kotlin, and more — so agents no longer assume a language isn't supported and skip the graph. (#671)
+
+- GitHub Copilot is now a supported agent: `codegraph install` can configure Copilot Chat in VS Code (`copilot-vscode`), the GitHub Copilot CLI (`copilot-cli`), and the Copilot plugin in JetBrains IDEs (`copilot-jetbrains`). Installed Copilot surfaces are auto-detected like every other agent, existing MCP server entries in their config files are preserved, and `codegraph uninstall` reverses the setup cleanly. Restart VS Code or your JetBrains IDE after installing so Copilot picks up the server.
+
 ### Fixes
 
 - C, C++, Objective-C and Rust unions are now indexed as first-class `union` nodes. A `union` declaration previously produced no symbol at all, so it never appeared in search or `codegraph_explore`, and anything attached to it disappeared with it — in Rust, every `impl SomeTrait for MyUnion` lost its edge, the methods from that impl were left pointing at a type the graph did not contain, and asking which types implement a trait quietly skipped the union ones. A union-shaped dispatch table in C now resolves its function pointers like a struct-shaped one. A `typedef union { … } Name;` in C keeps the typedef's name and is no longer mistaken for a plain type alias. Thanks @ctype-lab. Re-index after upgrading to pick up unions in existing projects. (#1515)
 
+- A long-lived index no longer drifts away from what a fresh `codegraph index` would produce. When a file gained or lost a symbol, references to that name in files the sync never touched kept pointing at the definition that was correct before the change, and — because nothing distinguished two same-named definitions — the winner could come down to the order files happened to be written, which differs between a full index and a sync. On this project's own repository, replaying 80 commits through `sync` left 5.7% of connections wrong; it is now 1.3%, and the wrong-answers-still-being-asserted half drops by 99.7%. Since call edges are what flow questions follow and what `codegraph_explore` ranks files by, this quietly degraded answers as an index aged, with nothing to indicate it. Syncing is unchanged in speed, and an edit that only changes a function's body does no extra work at all. Set `CODEGRAPH_NO_REBIND=1` to opt out.
 - `codegraph_explore` now concentrates its answer on the code that actually answers your question instead of spreading it across files that merely share a word with it, so more of the answer arrives in a single call. Thanks @LeDuyViet for the detailed measurements and reproduction. (#1500)
 - Files only weakly related to your question now come back as a name, symbol and line number instead of spending the answer on their source — name one of them in a follow-up `codegraph_explore` to get it back in full. (#1500)
 - A generated CRUD or protobuf layer no longer crowds out the hand-written code sitting beside it: generated files are now recognized by the `// Code generated by … DO NOT EDIT.` style banner written at the top of the file, not just by a filename that looks generated. Re-index after upgrading to pick up the new detection. (#1500)
 - Test and spec files in a repository's top-level `test/` or `spec/` directory are now recognized as such, so they no longer take room from the code you asked about. (#1500)
+- Generated type-declaration files that announce themselves with a "Generated by … by running …" banner — Cloudflare Wrangler's `worker-configuration.d.ts` is the common one — are now recognized as generated. Previously a file like that could take most of a `codegraph_explore` answer on nothing more than a few common words, pushing the hand-written code you asked about out of the response entirely. Re-index after upgrading to pick up the new detection.
+- A hand-written type-declaration file — an ambient `.d.ts` of global shims, vendored typings, module augmentation — no longer takes over a `codegraph_explore` answer about how something works. Files like these declare common names (`Body`, `Message`, `ImageMetadata`) and nothing else, so a plainly-worded question could match one strongly enough that it ranked first and crowded the actual handler out of the answer. They are now ranked lower for questions about behaviour, and are still listed by name so one follow-up call fetches them. Asking about a type by name still returns its declaration first, and a shared types module the rest of your code imports is unaffected.
 - A CodeGraph process that gets force-killed — by the stuck-process watchdog, a crash, or the OS — no longer leaves the database's write-ahead log behind to grow without bound. Previously each killed session stacked more data onto the same log file and nothing ever shrank it, which on machines where sessions were killed regularly could quietly eat tens of gigabytes of disk. The log is now capped, and any oversized leftover is reclaimed automatically the next time the project is opened. Thanks @tiendungdev for the exceptional Windows report that pinned this down. (#1431)
 - The background server's watchdog no longer kills a healthy server that is just waiting on a slow disk: like indexing already does, it now checks whether the database files are still making progress before concluding the process is stuck. Fewer spurious kills also means fewer leftover write-ahead logs. (#1431)
 - `codegraph status` now shows the write-ahead log's size next to the database size and warns when killed sessions have left it oversized, and every line in the background server's log now carries a timestamp so kills and restarts can be placed in time. (#1431)
 - On Windows, the Claude Code prompt hook written by `codegraph install` failed with "command not found" when hooks run through Git Bash, which needs the `.cmd` extension to find the launcher. The installer now writes the platform-correct command, and re-running `codegraph install` (or `codegraph upgrade`) repairs an existing install in place. (#1466)
 - Python classes used as values — `return SomeSerializer` from a factory method, `handler = SomeClass` aliases, registry dicts and lists, and classes passed as arguments — now produce reference edges in the graph. Previously these idioms were invisible, so on Django and Django REST Framework projects, asking for a serializer's callers or the impact of editing it missed the views that actually use it. Re-index after upgrading to pick up the new edges. (#1478)
 - When a file changed on disk after its last index sync, `codegraph_node` and `codegraph_explore` could return a different symbol's code under the requested name — current file bytes cut at outdated line positions — while presenting it as verbatim, trustworthy source. This hit hardest on projects queried through `projectPath` (for example, sub-projects of a monorepo), which have no live file watcher to flag pending edits. Both tools now verify each file against the index before showing sliced code: an out-of-date file is either shown whole with its full current source, or its code is withheld with a clear "changed on disk" notice — never served as a wrong slice. A fresh re-index restores normal output automatically. Thanks @inth3shadows for the thorough report and verification passes. (#1474)
+- A file built around one very long function no longer takes the whole `codegraph_explore` answer for itself — or disappears from it. Previously such a file was shown in full however big it was, which used up the room every file after it needed, and when the function was larger than the entire response the file was dropped without a word. These files now come back as a bounded window on whole lines — the signature and the top of the body, plus the call site when the call path runs through it — with the rest one follow-up `codegraph_explore` away.
+- `codegraph_explore` no longer lets the first file in an answer spend the room set aside for the files below it, so the rest of the answer still arrives. Previously a large file near the top could quietly use up everything left, and the files ranked under it — each already judged relevant enough to include — were dropped with no source at all; on one question only one of six made it into the answer. Every file now keeps what it was given, and a question that really is about one file still concentrates on that file.
+- When a `codegraph_explore` answer runs right up against its size limit, it now drops the trailing notes rather than a whole file's source. Previously the last file was cut even though trimming the notes alone would have fit, so a file that had already been read, ranked and rendered was thrown away at the last moment. Across a range of real projects this returns one more file and up to 20% more source per call.
+- Every file `codegraph_explore` decides to include now actually arrives. A file shown in full could still spend room set aside for files below it — the fix above covered files shown as excerpts but not files shown whole — and the answer's own size bookkeeping under-counted each file's heading, so the answer ran past its limit and a fully prepared file was discarded at the end. A file that no longer fits whole is now shown as excerpts instead of vanishing, and one that overshoots by a little is trimmed to fit rather than dropped.
+- The list of files an answer could not cover — the "explore these names for their source" pointers — is no longer thrown away when the answer is full. It is now budgeted for and trimmed to fit, so a full answer still tells you what it left out and which names to ask for next, instead of ending with no pointers at all.
+- When a `codegraph_explore` answer shows a file as excerpts, a large excerpt that no longer fit was dropped entirely instead of being shortened. If the file's first excerpt happened to be a trivial one — an import block, a one-line helper next to the code you asked about — the excerpt carrying the actual answer was the one thrown away, and the file came back with a quarter of the room it had been given. On real projects that meant the top-ranked file delivered a fraction of its share while a far less relevant file took the rest. Excerpts are now shortened to fit, whole method by whole method, and only dropped when what is left is too small to hold anything readable.
+- When you name a symbol in a `codegraph_explore` query, its definition now actually comes back. Two cases previously lost it. If the symbols you named don't call one another — sibling functions inside the same factory or module are the everyday example — CodeGraph stopped treating them as symbols you had asked for, and answered with whatever sat at the top of their file instead; on one 1,400-line file that meant a same-stem `QueuedMessage` interface on line 70 came back while the `queueMessage` function on line 1087 did not. And when an answer had to be trimmed to fit, it was trimmed from the bottom of the file down, so a symbol near the end of a long file was always the first thing cut. Trimming now protects the definitions you named wherever they sit in the file.
 - The blast-radius section of `codegraph_explore` flagged "no covering tests found" whenever no test called a symbol directly — falsely branding helpers that tests exercise through their callers as untested (about 40% of flagged symbols in a measured sample). The check now follows caller chains up to 3 hops and reports indirect coverage as "tested via callers"; when nothing is found it states exactly what was checked instead of an unconditional warning. Thanks @inth3shadows for measuring the false-positive rate. (#1475)
 
 ## [1.5.0] - 2026-07-21