Diagnosing and Fixing IntelliJ IDEA Indexing Stalls (2023.1+)

Recognizable condition

Indexing stalls appear as a persistent "Indexing…" badge in the status bar for more than five minutes, grayed‑out nodes in the Project tool window, broken code completion, empty Find Usages results, or a Java process (often named Shared Indexes or JPS Build) consuming 100 % CPU. The .idea/index folder may exceed 2 GB.

Cause / diagnostic table

Ordered checks

1. Indexing status – In the IDE: Help → Diagnostic Tools → Show Indexing Status. Note the counts for Indexing files, Queued, Paused.
2. Log inspection – Open ~/.cache/JetBrains/IntelliJIdea<version>/log/idea.log (Linux/macOS) or %APPDATA%\JetBrains\IntelliJIdea<version>\log\idea.log (Windows). Search for Indexing, FileBasedIndex, Corrupted, AccessDenied.

   grep -E "Indexing|FileBasedIndex|Corrupted|AccessDenied" ~/.cache/JetBrains/IntelliJIdea2024.2/log/idea.log

3. Invalidate caches – File → Invalidate Caches…, check Clear file system cache and Local History, then restart. Observe whether indexing finishes in <3 minutes.
4. Build‑tool auto‑reload – Settings → Build, Execution, Deployment → Build Tools → Maven/Gradle. Disable Reload projects after changes in build scripts if a sync loop is suspected.
5. Antivirus exclusions – Add folder exclusions for the project root, ~/.cache/JetBrains, and ~/.local/share/JetBrains (Linux) or %APPDATA%\JetBrains (Windows). Requires admin rights on managed machines.
6. Case‑sensitivity alignment – On WSL2/Docker run:

   git config core.ignorecase false

   Verify with git ls-files | sort -f | uniq -iD (should return nothing). Re‑clone if mismatched.

Fixes tied to findings

1. Corrupted indexes – Run Invalidate Caches (step 3). If the problem persists, shut down IDE and delete .idea/index manually.
2. Shared indexes stuck – Settings → Appearance & Behavior → System Settings → Shared Indexes. Turn off Download pre‑built shared indexes, then remove ~/.cache/JetBrains/SharedIndexes.
3. Sync loop – Disable auto‑reload (step 4) and use Reload All Gradle Projects manually.
4. FBI migration – After Invalidate Caches, delete .idea/index (IDE closed) and restart; a fresh FBI index will be built (2023.1+).
5. Antivirus lock – Apply exclusions (step 5) and restart IDE.
6. Case‑sensitivity – Align core.ignorecase and filesystem semantics (step 6), then re‑clone the repository.

Concrete example

A 50 k‑file Kotlin/Spring project is switched to a feature branch that changes 10 k files. The status bar shows Indexing… for 12 minutes, CPU stays at 95 % on the Shared Indexes process. Running the log grep (step 2) reveals repeated FileBasedIndex corruption entries. Invalidate Caches (step 3) reduces the next indexing run to 2 minutes and the log now contains FileBasedIndex: indexing completed in 112345 ms.

Escalation criteria

• Indexing does not complete after two full Invalidate Caches cycles.
• idea.log shows repeated FileBasedIndex corruption or AccessDenied after antivirus exclusions are in place.
• Shared indexes download fails with HTTP 403 or timeout on a clean network.
• CPU > 80 % for > 30 minutes post‑restart on a project with <50 k files.
• Issue reproduces in a clean configuration (Help → Collect Logs and Diagnostic Data → Create reproducible test case).

Limitations & verification

Invalidate Caches deletes Local History – any uncommitted changes not in VCS are lost. Disabling shared indexes increases first‑index time for large frameworks (Spring, Android) by 2–5×. Deleting .idea/index while the IDE runs causes undefined behavior; always shut down first. Antivirus exclusions may need IT approval; record the ticket number. The WSL2 case‑sensitivity fix requires a re‑clone, so stash or push uncommitted work first. IntelliJ 2024.2+ changed the FBI storage format – indexes from 2023.x are incompatible and auto‑purged on first launch.

To verify a fix: after Invalidate Caches, indexing should finish <3 minutes for a 50 k‑file project on SSD with 16 GB RAM; the log must contain a line like FileBasedIndex: indexing completed in XX ms. In Settings → Shared Indexes → Show downloaded indexes you should see entries for used libraries (e.g., kotlin-stdlib, spring-boot). On Windows, Process Monitor (Procmon) should show no Access Denied on .idea/index/* during indexing. The command git ls-files | sort -f | uniq -iD must return empty in the repo root.