feat: IMCore bridge via dylib injection for typing indicators#59
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alexrudloffBot wants to merge 7 commits intosteipete:mainfrom
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feat: IMCore bridge via dylib injection for typing indicators#59alexrudloffBot wants to merge 7 commits intosteipete:mainfrom
alexrudloffBot wants to merge 7 commits intosteipete:mainfrom
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Objective-C dylib that gets injected into Messages.app via DYLD_INSERT_LIBRARIES. Provides file-based IPC (JSON command/response files in the Messages.app container) with a 100ms polling timer on the main run loop. Supports commands: typing, read, status, list_chats, ping. Chat resolution tries multiple methods: - existingChatWithGUID: with all known prefixes (iMessage, SMS, any) - existingChatWithChatIdentifier: - Participant matching with phone number normalization Requires SIP disabled for DYLD_INSERT_LIBRARIES to work on system apps.
MessagesLauncher manages the Messages.app lifecycle: - Kills running instance, relaunches with DYLD_INSERT_LIBRARIES - Waits for lock file confirming dylib initialization - Sends commands via file-based IPC (JSON files in container) - Provides async sendCommand() API IMCoreBridge wraps the launcher with a high-level Swift API: - setTyping(for:typing:) - typing indicators - markAsRead(handle:) - read receipts - listChats() / getStatus() - debugging - checkAvailability() - diagnostic messages Both are @unchecked Sendable singletons following imsg's patterns.
- launch: Kills Messages.app, relaunches with dylib injection. Supports --dylib for custom path, --kill-only to just terminate. - status: Shows diagnostic report of feature availability. Reports basic vs advanced feature status with setup instructions. - Both support --json output. - Registered in CommandRouter between typing and rpc.
TypingIndicator.setTyping() now tries the IMCoreBridge first (dylib injected into Messages.app via DYLD_INSERT_LIBRARIES). If the bridge is unavailable or fails, falls back to the existing direct IMCore access via dlopen. This fixes the core issue: standalone CLI processes can't connect to imagent via XPC due to Apple's entitlement wall. The bridge runs inside Messages.app which already has the required entitlements. Uses a thread-safe BridgeResultBox to bridge async/sync boundary in a Swift 6 strict concurrency compatible way.
- build-dylib: Compiles IMsgInjected.m as arm64e dynamic library - imsg target now depends on build-dylib - install target copies both binary and dylib to /usr/local/ - clean removes the built dylib - Suppresses expected performSelector ARC warnings
- IMCoreBridgeTests: Verify shared instance, availability check, error descriptions, and launcher properties - LaunchStatusCommandTests: Verify commands are registered in router, status produces both JSON and text output
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Heads up, I'm pretty sure this won't work on macOS 26 (Sequoia/Tahoe) due to library-validation enforcement, even with SIP disabled. The IssuemacOS 26 introduced a new code signature flag on Messages.app that blocks dylib injection: $ codesign -dv /System/Applications/Messages.app 2>&1 | grep flags
CodeDirectory v=20400 size=2764 flags=0x2000(library-validation)
^^^^^^^^^^^^^^^^^^^^^^^^^^This flag prevents DYLD_INSERT_LIBRARIES from loading third-party/unsigned dylibs into Messages.app, even with SIP disabled. The injection silently fails at the kernel level. What I've Tested
Why This Happens The library-validation flag requires all loaded libraries to:
Since the injected dylib is ad-hoc signed and Messages.app is Apple-signed, the kernel blocks loading. Potential Solutions?
Has anyone tested this on macOS 26? Or have ideas for alternative approaches that don't require dylib injection? |
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Problem
imsg typingdoes not work becauseIMChatRegistryis empty when called from a standalone CLI process. Apple's entitlement wall blocks XPC connections toimagent. Documented in #58.Solution
Inject a helper dylib into Messages.app via
DYLD_INSERT_LIBRARIES. Messages.app already has the required entitlements, so IMCore works fully inside its process. The CLI communicates with the injected dylib through file-based IPC (JSON files in the Messages container).Same approach as BlueBubbles and imsg-plus.
Architecture
New files:
Sources/IMsgHelper/IMsgInjected.m— Obj-C injectable dylib (__attribute__((constructor))). Connects to IMDaemon, polls commands via NSTimer.Sources/IMsgCore/MessagesLauncher.swift— Kill/relaunch Messages.app withDYLD_INSERT_LIBRARIES.Sources/IMsgCore/IMCoreBridge.swift— Swift API wrapping file IPC.Modified:
TypingIndicator.swift— Prefers bridge, falls back to direct IMCore.Makefile—build-dylibtarget.New commands:
imsg launch,imsg statusAlso fixes
GUID prefix mismatch (#58): modern macOS uses
any;-;prefix. The dylib tries all prefixes plus participant matching with phone normalization.Requirements
Tested
make build-dylib+swift build— cleanCloses #58