1. Most turns and time: finding where the fault was. The brief pointed at views.nika (rsrc_*) and text_tiers.nika. The cause was in buffers.nika (made_here), with a second part in views.nika. I spent about 15 turns reading rsrc_method, rsrc_callee, the tier code and tether.nika before a --tethers probe showed the free-call case (make) already uses the caller’s keep and the method case does not. On time, the tests/compiler runs cost most: three full runs of about 10 minutes each. One was spent only to find the new test’s line, because nikaia test has no name filter. Another was a rerun after four other-session tests landed mid-run and one failed against my stale binary.
2. What the brief could have handed me:
   • The diagnostic flags: nikaia check --tethers and the nikaia.contracts file written beside a lowered probe. These localised the bug in two calls.
   • That ADR-353 D10 already lowers “a view of a local owned String returned” through __keep. The brief’s expected -> String conflicts with that, and I had to decide alone (I reported it under Deviation:).
   • buffers.nika/tether.nika (made_here, makes_a_buffer, a_call_buffer) as the place to look.
3. Checks run:
   • The probe on the old binary, which reproduced the bug.
   • A small probe matrix: free call, method with/without args, local receiver, a parameter view, a view-of-self method.
   • Two cycles, plus one manual extra lower-std to check the fixpoint.
   • The it filters and guard set (209 passed), clippy, pre-push-check, and tests/compiler at both settings, three times.
   • Wasted: the second tests/compiler run, only to grep the new test’s name, because the first output had been cut by tail. Also --lib contracts::keep (0 tests).
   • Gap: I did not rerun the it gate on the final rebased tree.
4. One change: give builder.md a line on diagnosis: “for a wrong lowering, run nikaia check --tethers F.nika and read the nikaia.contracts beside the probe first”. Also have briefs state the expected lowering only after checking the ADR that governs it, or say “any lowering rustc accepts”. Smaller: nikaia test needs a name filter, or builder.md should say to grep the full output rather than tail it.

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