Highlight Elixir and Erlang files in the file editor

[camilohollanda]

Summary

The file editor shows .ex, .erl and .hrl files as plain text, and opens .exs files in the video player. The bundled highlight.js 11.11.1 registers both elixir and erlang, so two things were missing:

• LanguageCatalog had no entry for these extensions, so they never reached highlighting. This PR maps ex/exs to elixir and erl/hrl to erlang.
• macOS resolves .exs to com.apple.logic.exs (Logic's sampler instrument format), which conforms to audiovisualContent, so FilePreviewKindResolver routed Elixir scripts to media before the editor. This PR adds ex, exs, erl and hrl to textExtensions, which sends them through the same media-collision sniff .ts already uses. A text .exs opens in the editor; a binary Logic .exs keeps the media route.

.heex/.eex stay unmapped: highlight.js has no grammar for them, and forcing elixir or xml would mis-color the other half of every template.

Testing

• Commits 1 and 3 add the tests on their own; commits 2 and 4 add the fixes.
• LanguageCatalogTests.mapsBeamExtensions: swift test in Packages/Shared/CmuxSyntaxHighlighting passes 25 tests in 5 suites.
• FilePreviewKindResolverTests.beamSourceFilesRouteDirectlyToTextPreview: xcodebuild test -scheme cmux-unit -only-testing:cmuxTests/FilePreviewKindResolverTests passes 5 tests, including the existing .ts/.mts and movie cases.
• In a tagged Debug build, .ex, .exs and .erl files open highlighted in the editor. Before the routing fix, .exs opened in the video player.
• I left out an engine-level highlighting test on purpose: Highlightr retries with highlightAuto when a language id is unknown, so a test that looks for colored output passes even when the id is wrong (checked by swapping in elixirx).

Checklist

• I added or updated tests for behavior changes
• I tested the change locally (tagged Debug build; .ex/.exs/.erl checked in the editor)

🤖 Generated with Claude Code

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Summary by cubic

Highlights Elixir and Erlang source files in the file editor instead of showing them as plain text or opening them as media.

• Maps ex/exs to elixir and erl/hrl to erlang in the LanguageCatalog.
• Routes those extensions to the text preview; macOS resolves .exs to Logic's com.apple.logic.exs UTI, which conforms to audiovisualContent and previously opened Elixir scripts as media, so a text .exs opens in the editor while a binary Logic .exs keeps the media route.
• Leaves .heex and .eex unmapped because highlight.js has no grammar for them and forcing a language would mis-color templates.

Tests cover both the new mappings and the preview routing.

^{Written for commit 70a22d5. Summary will update on new commits.}

Summary by CodeRabbit

• New Features
  • Added syntax highlighting support for Elixir files (.ex, .exs) and Erlang files (.erl, .hrl).
  • Elixir and Erlang files now open in text preview mode.

Changelog

Added: The file editor highlights Elixir (.ex, .exs) and Erlang (.erl, .hrl) files

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[github-actions]

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Reviewing files that changed from the base of the PR and between aabbc49 and dc015a0.

📒 Files selected for processing (2)

• Sources/Panels/FilePreviewPanel.swift
• cmuxTests/FilePreviewKindResolverTests.swift

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📝 Walkthrough

Walkthrough

The language catalog maps four BEAM-related extensions to Elixir and Erlang. The file preview resolver classifies .erl, .ex, and .exs files as text. Tests cover the language mappings and text preview behavior.

Changes

BEAM File Extension Support

Layer / File(s)	Summary
Language mappings and tests Packages/Shared/CmuxSyntaxHighlighting/Sources/CmuxSyntaxHighlighting/LanguageCatalog.swift, Packages/Shared/CmuxSyntaxHighlighting/Tests/CmuxSyntaxHighlightingTests/LanguageCatalogTests.swift	The catalog maps ex and exs to Elixir, and erl and hrl to Erlang. Tests verify the highlight.js identifiers.
Text preview classification and tests Sources/Panels/FilePreviewPanel.swift, cmuxTests/FilePreviewKindResolverTests.swift	The preview resolver adds erl, ex, and exs to its text extension set. Tests check text preview before and after asynchronous resolution.

Estimated code review effort: 2 (Simple) | ~10 minutes

Suggested reviewers: austinywang

Merge Risk: ⚪ Minimal · up to dc015

The PR adds Elixir and Erlang syntax mappings and text previews for their source files, including .hrl. The reviewed routing behavior is supported, with no unresolved merge-blocking issue evident.

🚥 Pre-merge checks | ✅ 24 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 6 functions across 4 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (24 passed)

Check name	Status	Explanation
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Cmux Cloud Persistent Session And Early Input	✅ Passed	PASS: The pull request changes only syntax-language mappings and file-preview routing for Elixir and Erlang extensions, plus tests. The authoritative diff contains no Cloud terminal creation, transpor…
Cmux Swift Actor Isolation	✅ Passed	The production diff only adds four string-to-string entries in LanguageCatalog and four string literals in FilePreviewKindResolver.textExtensions. It does not introduce or modify a model, service …
Cmux Swift Blocking Runtime	✅ Passed	The production diff only adds four language-catalog mappings and four text extensions. The added Swift tests create temporary files and use synchronous expectations; they add no blocking or timing pri…
Cmux Browser Automation Off-Main	✅ Passed	PASS: The pull request changes only language mappings, file-preview extension routing, and related tests. It does not modify browser socket commands, processV2Command, socketWorkerMethods, WebKit/…
Cmux Expensive Synchronous Load	✅ Passed	PASS. The authoritative diff changes only four files. The production changes add four extension mappings and four text-extension set entries. They do not add or move agent-history loads, session store…
Cmux Cache Substitution Correctness	✅ Passed	The diff only adds static extension mappings and text-preview classification. LanguageCatalog reads a built-in dictionary, and FilePreviewKindResolver classifies URLs from their extensions and UTT…
Cmux No Hacky Sleeps	✅ Passed	PASS: The pull request changes only Swift source and Swift tests. The authoritative diff adds language mappings, text extensions, and assertions; it introduces no sleeps, timers, polling, delayed disp…
Cmux Algorithmic Complexity	✅ Passed	The PR adds four entries to a fixed language dictionary and four entries to a fixed Set<String>. The resolver uses constant-time membership checks for these extensions. The diff adds no nested scala…
Cmux Swift Concurrency	✅ Passed	PASS. The PR adds extension mappings, text-extension entries, and synchronous tests only. The added Swift lines introduce no Dispatch queues, Combine state, completion-handler API, or fire-and-forget …
Cmux Swift @Concurrent	✅ Passed	The PR adds extension mappings, text-preview routing, and tests. It does not add or change any async, nonisolated, @concurrent, or actor-isolation declaration. The existing file-I/O and mode-res…
Cmux Swift Package Boundaries	✅ Passed	PASS. The core extension-to-language mapping is implemented in the existing CmuxSyntaxHighlighting SwiftPM target and covered by its package tests. The only app-target production change adds four en…
Cmux Swiftpm Lockfiles	✅ Passed	The pull request changes only Swift source and test files. It does not change any Package.swift dependency declaration, Package.resolved file, Xcode project package reference, .gitignore, or workflow.…
Cmux Swift Logging	✅ Passed	The PR adds only language mappings, text-extension entries, and tests. The diff adds no print, debugPrint, dump, NSLog, file/stdout logging, Logger declaration, or sensitive-data log. The logg…
Cmux User-Facing Error Privacy	✅ Passed	The pull request does not add or materially change a user-facing error, alert, command output, API error body, or recovery message. The production changes only add Elixir/Erlang language mappings and …
Cmux Full Internationalization	✅ Passed	PASS. The diff only adds Elixir/Erlang file-extension and highlight.js identifier mappings, text-preview extension tokens, and tests. It introduces no production user-facing text, localization keys, s…
Cmux Swiftui State Layout	✅ Passed	PASS: The pull request does not introduce a SwiftUI state or layout change. Its only application-code change in FilePreviewPanel.swift adds erl, ex, exs, and hrl to the existing `textExtensi…
Cmux Architecture Rethink	✅ Passed	The pull request makes a small, local correctness change. It adds four static extension mappings and four text-extension entries, with focused tests. The diff introduces no sleeps, delayed dispatch, p…
Cmux Swift Auxiliary Window Close Shortcuts	✅ Passed	The PR does not add or materially change a standalone cmux-owned window. Its Swift changes only add Elixir/Erlang language mappings, text extensions, and tests. No changed line introduces or modifies …
Cmux Source Artifacts	✅ Passed	The pull request changes only four intentional Swift source and test files. The diff adds Elixir/Erlang language mappings, text-preview routing, and tests for that behavior. No logs, screenshots, reco…
Cmux No Test Or Debug Seam In Production Source	✅ Passed	PASS. The production diff adds only four language-catalog mappings and four text extensions. It adds no test/debug-only extension or member, test-seam name, wrapper accessor, or visibility widening. E…
Title check	✅ Passed	The title clearly summarizes the main change: adding Elixir and Erlang highlighting in the file editor.
Description check	✅ Passed	The description is complete and relevant. It explains the problem, implementation, supported extensions, testing commands and results, screenshots, limitations, and changelog entry. Screenshots provid…

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[camilohollanda]

I have read the CLA Document v2.2 and I hereby sign the CLA

[teamleaderleo]

dw bout the red ci imma rebase

[camilohollanda]

dw bout the red ci imma rebase

@teamleaderleo done

[teamleaderleo]

Merged, thanks @camilohollanda :)

[github-actions]

Merge receipt for 70a22d5f39, merged 2026-09-27 14:18:27 UTC

• Not verified at merge: Web complexity (in progress), ios-simulator (ipad) (failure), ios-simulator (iphone) (failure), ios-tests (failure)
• Verified: app-host unit tests, ci-status, macOS compile admission, web-validation, CI fast guards, CI timing, detect-ios-changes, Fast static checks, GhosttyKit release check, guards (17), ios-simulator-build, linux-preflight, and 8 more
• Skipped by policy: admission-placement, browser, Claude wrapper regressions, CLI product tests, late-placement, release-admission, release-build, remote-daemon, suite-coverage, tests-build-and-lag, web, web-build, and 2 more
• Full suite: runs on main after merge.

Labeled merged-unverified: if main breaks near this merge, look here first.