[teamleaderleo]

Summary

cmux NEXT's main executable exports all 110,746 of its symbols. The export trie (2.9 MiB), symbol table (1.8 MiB) and string table (6.8 MiB) take about 11.5 MiB of the installed app, and nothing looks them up at runtime. An audit found:

• no -bundle_loader plug-ins or test hosts in the app;
• dlsym calls only into system libraries, CEF and the shim;
• Rust FFI linked statically;
• Objective-C and Swift runtime lookups that go through metadata sections, not exports.

Leo approved hiding them, on one condition: nobody reads raw offsets.

• Link: the cmux-next Release executable links with -Xlinker -no_exported_symbols. Debug (DEV) is unchanged. The Linux builder mirrors the flag from the pbxproj (cmuxterm-hq#2100).
• Landing order: the nightly picks up the flag only after hq#2100 lands and nightly-next's builder copy is redeployed (nightly-next-linux/deploy.sh). Until then nothing changes: the exports stay, and the map is written alongside them.
• Symbol map: before the release strip removes the names, scripts/strip-release-bundle.sh runs scripts/write-app-symbol-map.py. It writes Contents/Resources/cmux-symbols.bin: for each slice, the LC_UUID and the __TEXT,__text functions as offsets, compressed with raw DEFLATE. A second strip pass over the stripped executable keeps the map.
• In-app symbolication: StackSymbolicator names frames in the app executable through the map (AppSymbolMap, only the running slice is loaded), and frames in other images through dladdr as before.
  • Hang records (debug.hangs) and uncaught exception traces (now read from callStackReturnAddresses, which feed the next launch's crash notice and issue report) both use it.
  • A frame with no name keeps its offset from the image header, for symbolication from the dSYM. The dSYM is still built from the unstripped link and uploaded as before.

arm64 cmux executable	nightly (exports kept)	this PR, Release after strip
export trie	2.88 MiB	8 B
symbol table	1.76 MiB	0.07 MiB (4,856 entries)
string table	6.82 MiB	0.19 MiB
names total	11.46 MiB	0.27 MiB
cmux-symbols.bin (arm64 slice)	none	2.6 MiB

Net: about −8.6 MiB installed for the arm64 nightly. The universal Release executable from this head strips to 189,379,088 bytes (arm64 slice 91,812,368), and its universal map is 5.1 MiB (447,385 functions over two slices).

Sample trace. Below is a sample of the stripped Release app from this head, on a capture Mac. sample printed ??? (in cmux) for every app frame. The same offsets, resolved through the shipped map by AppSymbolMap, give these frames, and the per-function offsets match atos against the dSYM:

main + 16
CmuxNextApp.main() + 1884
thunk for @escaping @callee_guaranteed () -> () + 28
partial apply for closure #2 in LineTransport.start(onEvent:onClose:) + 36
LineTransport.readLoop(fd:onEvent:onClose:) + 216
partial apply for closure #5 in MainThreadWatchdog.start() + 24
MainThreadWatchdog.watch(sampler:) + 488
ProviderConnection.readLoop() + 292

Ghostty's internal (Zig) functions have no symbols even today, so they still resolve to the nearest Ghostty export (for example ghostty_surface_new + 255408), the same as before this change. Their image offset is kept for dSYM lookup.

Verification

• Red, CI: at 1c49b8b (test only), the checks job failed in Script tests (job 116145395398): cmux-symbols.bin missing.
• Green: at 635d7bd, the same checks job ran Script tests green (job 116175372658), including the second-strip-pass case (red locally before its fix). Crash safety is green as well. Its remaining reds are base reds fixed by Fix base red: chief_brains state root asks the build identity (cx-8oudl) #20767.
• Release compile (fleet): check-release-compile.sh passed on the merged head 9b10dd2 (fleet step 0c4e8ad3b304, xcodebuild exit 0).
• Release app build at the exact head: a Release app built and stripped from 3735e93 (the same link settings and map writer) gave the sizes and trace above. The commits since then change the decoder's checked reads, the second-pass fix, and the base merge.

Review

A correctness review subagent covered this PR and cmuxterm-hq#2100.

• Fixed: the nightly's second strip pass rewrote the map with the one name that survives the first strip (__mh_execute_header). The map now stays when it already covers the executable's UUIDs. The test failed before the fix and passes after it.
• Follow-ups, none blocking:
  • a Swift test that decodes a map the script wrote;
  • returning nil past the end of __text, so stubs are not named after the last function;
  • looking up address - 1 for frames after the first;
  • decoding names lazily, so the first exception trace does not inflate the whole map.

Changelog

Changed: cmux NEXT takes about 11 MB less disk space (the app executable no longer carries its symbol names; hang and crash traces still name app functions).

🤖 Generated with Claude Code

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[github-actions]

all web/size checks green

[github-actions]

Not verified: macOS jobs did not run: compile and app tests were skipped on 9b10dd2ed8; ci-status is green without them.

CI passes on 9b10dd2ed8 (run 38662185733 attempt 1).
macOS jobs did not run: compile and app tests were skipped: Fast static checks skipped (the macos job needs both to succeed). Re-run CI once they pass, before merging.

Written by scripts/ci/classify_failures.py (ci-failure-attribution.yml); signatures are its SIGNATURES table. A machine verdict is the runner's fault, not this PR's; yours means the failing file is one this PR changes, also red on main that main's latest full suite fails the same way, seen on other PRs that it failed on another pull request's run lately.

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[github-actions]

cmux-next tour of 9b10dd2ed80ca44825d74e6e019f4e43b86b3818 (run)

Path-selected interactions

Interaction

Changed paths

core

Packages/macOS/CmuxNext/Sources/CmuxNextApp/Crash/UncaughtExceptionRecorder.swift Packages/macOS/CmuxNext/Sources/CmuxNextControl/Diagnostics/AppSymbolMap.swift Packages/macOS/CmuxNext/Sources/CmuxNextControl/Diagnostics/HangLog.swift Packages/macOS/CmuxNext/Sources/CmuxNextControl/Diagnostics/StackSymbolicator.swift Packages/macOS/CmuxNext/Sources/CmuxNextControl/Diagnostics/ThreadStackSampler.swift

Core UI (before): 12 ok

Video (mp4)

#	Step	Result	Command
1	Launch	ok
2	New workspace	ok	cmux workspace new --name Tour
3	Type in the terminal	ok	cmux workspace name:Tour screen current pane current tab current terminal current write --text "echo hello from the cmux-next tour\r"
4	Split right	ok	cmux action run splitRight
5	Split down	ok	cmux action run splitDown
6	New terminal tab	ok	cmux action run newSurface
7	Browser tab	ok	cmux tab new-browser --url https://example.com
8	Hide the sidebar	ok	cmux action run toggleSidebar
9	Show the sidebar	ok	cmux action run toggleSidebar
10	Notification	ok	cmux notify --title Tour --body "Hello from CI"
11	Notifications panel	ok	cmux action run showNotifications
12	Agent chat	ok	cmux agent new-chat

Screenshots (11)

1. Launch


2. New workspace


3. Type in the terminal


4. Split right


5. Split down


6. New terminal tab


7. Browser tab


8. Hide the sidebar


10. Notification


11. Notifications panel


12. Agent chat

### Core UI \(after\): 12 ok

Video (mp4)

#	Step	Result	Command
1	Launch	ok
2	New workspace	ok	cmux workspace new --name Tour
3	Type in the terminal	ok	cmux workspace name:Tour screen current pane current tab current terminal current write --text "echo hello from the cmux-next tour\r"
4	Split right	ok	cmux action run splitRight
5	Split down	ok	cmux action run splitDown
6	New terminal tab	ok	cmux action run newSurface
7	Browser tab	ok	cmux tab new-browser --url https://example.com
8	Hide the sidebar	ok	cmux action run toggleSidebar
9	Show the sidebar	ok	cmux action run toggleSidebar
10	Notification	ok	cmux notify --title Tour --body "Hello from CI"
11	Notifications panel	ok	cmux action run showNotifications
12	Agent chat	ok	cmux agent new-chat

Screenshots (11)

1. Launch


2. New workspace


3. Type in the terminal


4. Split right


5. Split down


6. New terminal tab


7. Browser tab


8. Hide the sidebar


10. Notification


11. Notifications panel


12. Agent chat

_{Tours are data in scripts/cmux-next/media/tours: add a step or a tour file to show your feature.}