2026.9.30.1: a build names each package when it does work, one status row with a screen of dots, --play-game, and one lock entry per identity

[speak-agent]

Build output design revision 3 (.agents/docs/2026-09-30-build-output-refinement-design.md), from a report on mcpp build in the xlings repository with 2026.9.29.5, and two defects found while measuring it. Version 2026.9.30.1.

What was measured

A pseudo-terminal recording of a first build of xlings under strace --trace-fds=1,2, replayed write by write:

• 184 of 202 frames left in two writes (stdout is line-buffered), and every line above the region in three (erase, text, redraw);
• the status line was drawn 0.6 ms into the command and pushed down by each early line;
• the cache pass ran unread, so a cache-served dependency never completed and the folded dependency line waited 27 s for ninja to exit;
• the phase stayed on the build programs for 13 s of planning;
• a planned build rewrote the committed mcpp.lock with a second entry per [dependencies.mcpplibs] key (since 2026.9.29.1).

Changes

• Package lines. A package is named once, when it does work: Compiling at its first step that is not a dependency scan (or its first check or prepare action), Cached … (N units) when the cache places its units. Nothing is folded; a package with nothing to do has no line (--verbose: Fresh, and Compiled with steps and span). A package inside the project is named by its short name, version and directory; any other by its identity, with (index …), (git …) or its relative directory; the name's colour states the source.
• The live display. One status row, aligned with the verbs, drawn half a second in, each frame one write that overwrites in place with autowrap off for the row. last N running once ninja's %u reaches 0. A screen of 24 braille cells (mcpp.ui.dots_screen, one partition per animation) plays the chomper, the snake, the stack or the ions; MCPP_PROGRESS names one, or plain, or off.
• --play-game[=snake|stack|runner] on build, run and test: a game on the screen, steered from the keyboard; the terminal's mode is restored on exit and, through the signal guard, on Ctrl-C.
• Finished. The breakdown and longest from one minute (was ten seconds); a compile is named by its source file relative to its package (longest slow: src/main.cpp 1m08s); the fast path states the profile's descriptor, carried by the step record's header. One function, profile_descriptor, spells it for both paths.
• Programs and failures. A build program has a line when it runs or fails; error: build failed in <package>; the phase returns to Planning after the programs.
• W-b. A bare key of a path or git dependency states only the short name; its adoption of the declared namespace is not reported. A contradicting namespace is reported once per consumer manifest (package-identity §4.2).
• The lock. One entry per identity, spelled as 2026.9.28.3 spelled it; a lock holding two is reduced to one (e2e 844; verified on the xlings repository: its committed lock stays byte-identical, and the 15 entries 2026.9.29.5 wrote return to 13).
• Keys. The game reads keys only when mcpp is in the terminal's foreground (a background job that changed the mode would be stopped by SIGTTOU); a control sequence with parameters is decoded whole, so Ctrl-Up is Up and F5 is no key.
• Repository layout. The Windows resource script of mcpp.exe moves from res/ to docs/res/, the packaging and release scripts from scripts/ to tools/; the empty cdb.json committed by 2026.9.29.1 is removed.
• The bundled xlings is 2026.9.30.1.

Tests

• Unit: test_build_progress (21), test_dots_screen (11), test_platform_terminal (3).
• e2e: 842, 843 revised; 844, 845 new; the tests that read revision 2's lines follow them.
• 842, 843, 844 and 845 fail with the released 2026.9.29.5 and pass with this branch.