[lawrencecchen]

Summary

This is the follow-up to #21980. #21980 is merged into feat-cmux-next. This branch is rebased on feat-cmux-next, so the diff has only the change of this PR (3 commits).

When the Linux build pool builds a new stamp, cmux-remote and acpmux no longer recompile.

• cmux-remote: ssh_bootstrap.rs read CMUX_TUI_DISTRIBUTION_VERSION and CMUX_TUI_NPM_BOOTSTRAP_VERSION with option_env!. The pool sets the first to 0.0.0-r2.sha-<stamp>. The two constants move to the binary (cmux-tui/src/distribution.rs) with the same values and the same fallback (CARGO_PKG_VERSION). SshBootstrapConfig::defaults now takes them as arguments, as it already takes build_identity. The cmux-remote tests pass the same values.
• acpmux: Its build script reran on every new CMUX_GIT_SHORT_SHA and SOURCE_DATE_EPOCH (the pool sets both for each stamp) and on every commit. A rerun recompiles every target of the package (17 s).
  • The script moves to a new leaf crate, acpmux-build-id. The logic does not change. The git calls still run in the acpmux crate directory, and the dirty check and the rerun-if-changed paths are still acpmux's.
  • acpmux reads the id through hub::build(). With its default build-id feature (the standalone acpmux binary and the acpmux tests), the stamped value is the default.
  • cmux-tui uses default-features = false, depends on acpmux-build-id itself, and installs the same value in main(), next to install_build_stamp.
  • acpmux --version uses hub::version_line(), which gives the same text.
• cmux-build-identity: No change.
  • In the pool, its build script takes less than 0.05 s for each stamp, because the pool sets CMUX_TUI_BUILD_TIME. When CMUX_TUI_BUILD_COMMIT is set, the script already skips the git source walk.
  • The 8.8 s in the cmux-tui: a new build stamp no longer recompiles cmux-tui-core #21980 measurement came from the proof setup and not from the pool. My fake stamp aaaa… is not in the Testbox repository, and that repository is a partial clone (blob:none). So git log -1 --format=%ct <stamp> in build_time() started a lazy fetch from GitHub. With a real local commit, or with CMUX_TUI_BUILD_TIME set, the script ran in 0.00 s.

Proof (Blacksmith Testbox, 32 vCPU)

Command: cargo build -v --timings -p cmux-tui --bin cmux-tui --locked. The settings are the pool Linux twin settings (CARGO_INCREMENTAL=0, CARGO_PROFILE_DEV_DEBUG=0). Every stamp variable follows the stamp, as in build-cmux-tui-source.sh: CMUX_TUI_BUILD_COMMIT, CMUX_TUI_GHOSTTY_COMMIT, CMUX_TUI_DISTRIBUTION_VERSION=0.0.0-r2.sha-<stamp>, CMUX_GIT_SHORT_SHA, SOURCE_DATE_EPOCH, CMUX_TUI_BUILD_TIME. The stamps are A=aaaa… and B=bbbb….

tree	stamp change	wall	recompiled
before (#21980 head dc61324)	A to B	35.1 s	acpmux 17.2 s, cmux-remote 9.9 s, cmux-tui 20.4 s
before	B to A	35.2 s	acpmux 17.3 s, cmux-remote 10.3 s, cmux-tui 20.5 s
after (a501c02)	A to B	21.0 s	cmux-tui 20.1 s (acpmux-build-id and cmux-build-identity less than 0.05 s each)
after	B to A	20.6 s	cmux-tui 19.6 s

Together with #21980, a new stamp went from about 52 s to about 21 s on the twin. The feat-cmux-next base before #21980 took 51.5 s and 52.5 s.

Readers, before and after, with the same stamp. All values are identical:

--version:          cmux 0.1.0 (aaaa…; ghostty cccc…)
acpmux --version:   acpmux 0.1.0 (aaaaaaaaa 2026-10-14)
remote-probe --json: distribution_version=0.0.0-r2.sha-aaaa…, npm_bootstrap_version=None, build_identity=aaaa…, build_time=1792000000
identify / ping:    build_commit=aaaa…, ghostty_commit=cccc…, build_id=aaaa…

For B, every reader reports bbbb…, bbbbbbbbb 2026-10-15 and 1792100000.

Binary differences between A and B (equal sizes). The sections with differences are the same before and after this PR, so this PR adds no new kind of difference:

• before: .rodata 7407, .text 3897, .rela.dyn 839, .symtab 116, .note.gnu.build-id 20 bytes
• after: .rodata 7337, .text 3910, .rela.dyn 845, .symtab 114, .note.gnu.build-id 20 bytes

These numbers are larger than the 380 bytes in #21980. Here the pool stamps change string lengths (distribution version, short SHA, date), so code and relocations that refer to .rodata move.

Tests (Testbox)

• cargo fmt --check for acpmux, acpmux-build-id, cmux-remote and cmux-tui: ok
• cargo test -p cmux-remote --test ssh_cross_platform_bootstrap: 17 passed (bootstrap with the passed distribution version)
• cargo test -p cmux-tui --test cli remote_update_need: 5 passed
• cargo clippy --all-targets -D warnings for acpmux, acpmux-build-id, cmux-remote and cmux-tui: ok. Also -p acpmux --no-default-features: ok.

I ran the timing proof at a501c02. The 2 later commits are a rustfmt change and one path qualification.

No new tests. Cargo.lock gains the acpmux-build-id package (path crate, no new external dependency).

🤖 Generated with Claude Code

---

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---

Summary by cubic

A new build stamp from the Linux pool now recompiles only cmux-tui; cmux-remote, acpmux, and cmux-tui-core no longer do. This cuts the per-stamp rebuild from about 52 s to about 21 s.

• Stamped distribution versions move to the binary (distribution.rs) and pass into SshBootstrapConfig::defaults; the build and Ghostty commits install into cmux-tui-core at the top of main via install_build_stamp.
• acpmux's build script moves to the leaf crate acpmux-build-id; cmux-tui depends on acpmux without its default build-id feature and installs the same value through hub::install_build, so a new stamp recompiles only the tiny leaf crate.
• Every entry point that serves identify or ping must call install_build_stamp; a process that doesn't reports build_commit: null as before. --version, acpmux --version, and remote-probe --json output are unchanged.

^{Written for commit 8795cbe. Summary will update on new commits.}

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[github-actions]

cmux status _{(one comment, edited in place; each line is updated by the job that owns it)}

Review 8795cbe: HQ feed card · gallery before/after runs · checks

App of this head (app.zip, kept 1 day)

gh workflow run reload-build.yml -R manaflow-ai/cmux --ref feat-cmux-next -f tag=pr22030 -f ref=feat-cmux-next-tui-stamp-runtime2 -f platform=macos -f backend_mode=local

red: cmux-next checks (god files, concurrency, crash safety, l10n); no finished base run on ad45b0b to compare; do not merge until green; see lane-rules

[teamleaderleo]

Visual preview of 8795cbe: in the maintainers' private review feed.

[teamleaderleo]

Bead cx-rcunq created for this PR by the cmux coordinator.

[blacksmith-sh]

Found 8 test failures on Blacksmith runners:

Failures

Test	View Logs
/tmp/tmpn5qyf8yp/summary-missing.json (live):/summary-missing.json (live):	View Logs
/tmp/tmpwhncgjkv/summary-fail.json (live):/summary-fail.json (live):	View Logs
bundle-map.json does not require CEF's LICENSE.txt/ bundle-map.json does not require CEF's LICENSE.txt	View Logs
bundle-map.json does not require CEF's LICENSE.txt/ bundle-map.json does not require CEF's LICENSE.txt	View Logs
convention violations found (ERROR lines above)./ convention violations found (ERROR lines above).	View Logs
test_a_file_a_test_reads_selects_that_test (main.PullRequestTiers.test_a_file_a_tes t_reads_selects_that_test)/ test_a_file_a_test_reads_selects_that_test (main.PullRequestTiers.test_a_file_a_tes t_reads_selects_that_test)	View Logs
test_batch_dispatch_runs_every_dispatch_gated_job (main.PathRoutingStructure.test_b atch_dispatch_runs_every_dispatch_gated_job) (job='request-cmux-next-dev-publish')/ test_batch_dispatch_runs_every_dispatch_gated_job (main.PathRoutingStructure.test_b atch_dispatch_runs_every_dispatch_gated_job) (job='request-cmux-next-dev-publish')	View Logs
test_every_submodule_free_checkout_on_an_owned_runner_resets_submodules (main.Reuse dWorkspaceSubmodules.test_every_submodule_free_checkout_on_an_owned_runner_resets_submo dules)/ test_every_submodule_free_checkout_on_an_owned_runner_resets_submodules (main.Reuse dWorkspaceSubmodules.test_every_submodule_free_checkout_on_an_owned_runner_resets_submo dules)	View Logs

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[lawrencecchen]

Correctness review (subagent, head 9fa2ee5)

Blocker: none. Behavior is the same where the real binaries run: the distribution constants in cmux-tui/src/distribution.rs copy the old ssh_bootstrap.rs values and fallback (raw stamp, CARGO_PKG_VERSION); the only callers of SshBootstrapConfig::defaults are remote_runtime.rs and 4 test calls; every acpmux child process starts through cmux_tui::main, which calls install_build before the acpmux argv check; acpmux-build-id/build.rs still runs every git call in ../acpmux (same short hash, dirty scope, fingerprint, SOURCE_DATE_EPOCH, rerun paths). The red checks (Swift process-scan, menu-actions, phone-lane schema, same-tree artifact) come from the base branch, not this diff.

Should-fix

1. acpmux/src/hub/mod.rs:305-308: cmux-tui integration tests that run an in-process Hub without install_build now see "unstamped" instead of the real id. Call acpmux::hub::install_build(acpmux_build_id::BUILD) there, or document the rule.
2. hub/mod.rs grows to 1095 lines (god-file warning, not in baseline): move build, install_build, version_line to hub/build.rs.

Nits: build-id sources outside acpmux no longer add +dirty; mod distribution placement under the hook-helper comment; acpmux-build-id version not workspace = true; the test copies the option_env! logic.

Resolution: should-fix 1 and 2 go to the rebase owner before merge; resolution follows in a later comment.

[lawrencecchen]

Resolution (review at 9fa2ee5), new head a144005:

• In-process acpmux hubs in cmux-tui tests (agent_cli_job_journey.rs, inventory_refresh_journey.rs, agent_message_launch_credential.rs) now call acpmux::hub::install_build(acpmux_build_id::BUILD) before Hub::new, as main() does. They report the real build id, not unstamped.
• build, install_build and version_line moved to acpmux/src/hub/build.rs. hub/mod.rs re-exports them, so callers do not change. hub/mod.rs is 1069 lines (1095 before; feat-cmux-next has 1070).
• acpmux-build-id uses version.workspace = true. The Cargo.lock entry is 1.0.0.
• Doc fix in acpmux-build-id/src/lib.rs: the path is acpmux::hub::install_build.
• Not done: moving #[cfg(unix)] mod distribution; next to remote_cli. rustfmt sorts it into the feature_flags group (this is why the rustfmt commit moved it there).

[teamleaderleo]

cmux-next guards / defaults-snapshot is red on 19 of 19 fresh feat-cmux-next PR heads in the last 2:00:00, so it is most likely a base red, not this PR's. The base-reds lane has it; a base merge picks up the fix once it lands.

[teamleaderleo]

cmux-next / cmux-next checks (god files, concurrency, crash safety, l10n) › Browser chrome icons is red on 16 of 16 fresh feat-cmux-next PR heads in the last 2:00:00, so it is most likely a base red, not this PR's. The base-reds lane has it; a base merge picks up the fix once it lands.

[teamleaderleo]

cmux-next / cmux-next checks (god files, concurrency, crash safety, l10n) › Capability texts never say update the app is red on 16 of 16 fresh feat-cmux-next PR heads in the last 2:00:00, so it is most likely a base red, not this PR's. The base-reds lane has it; a base merge picks up the fix once it lands.

[teamleaderleo]

cmux-next / cmux-next checks (god files, concurrency, crash safety, l10n) › Checks job structure is red on 16 of 16 fresh feat-cmux-next PR heads in the last 2:00:00, so it is most likely a base red, not this PR's. The base-reds lane has it; a base merge picks up the fix once it lands.

[teamleaderleo]

cmux-tui spec inventory / inventory is red on 8 of 8 fresh feat-cmux-next PR heads in the last 2:00:00, so it is most likely a base red, not this PR's. The base-reds lane has it; a base merge picks up the fix once it lands.

[teamleaderleo]

cmux-next / cmux-next checks (god files, concurrency, crash safety, l10n) › Main-thread concurrency is red on 11 of 11 fresh feat-cmux-next PR heads in the last 2:00:00, so it is most likely a base red, not this PR's. The base-reds lane has it; a base merge picks up the fix once it lands.

[teamleaderleo]

cmux-next / cmux-next checks (god files, concurrency, crash safety, l10n) › No process scanning (holders register themselves, plans/cmux-next/pty-holder.md 4) is red on 10 of 10 fresh feat-cmux-next PR heads in the last 2:00:00, so it is most likely a base red, not this PR's. The base-reds lane has it; a base merge picks up the fix once it lands.

[teamleaderleo]

cmux-next / cmux-next checks (god files, concurrency, crash safety, l10n) › Package conventions lint is red on 10 of 10 fresh feat-cmux-next PR heads in the last 2:00:00, so it is most likely a base red, not this PR's. The base-reds lane has it; a base merge picks up the fix once it lands.

[teamleaderleo]

cmux-next / cmux-next checks (god files, concurrency, crash safety, l10n) › Phone lane field allowlist is red on 10 of 10 fresh feat-cmux-next PR heads in the last 2:00:00, so it is most likely a base red, not this PR's. The base-reds lane has it; a base merge picks up the fix once it lands.

[lawrencecchen]

Closed by the perf lead (agent, cmux-ad order 2026-10-31): stale, with no owner. This is an agent PR (lawrencecchen account). It was opened on 2026-10-19, its last commit is from 2026-10-20, no person pushed or commented in the last 3 days (automated review and sweep notes do not count), no live session names it in the lead status of the last 24 h, and it conflicts with feat-cmux-next (DIRTY).

The branch feat-cmux-next-tui-stamp-runtime2 stays. To reopen: click Reopen (or gh pr reopen 22030 -R manaflow-ai/cmux), merge origin/feat-cmux-next into the branch, get a review receipt on the new head, then add ready-to-land.