Janet's struct? returns true for tuples — cond forms in print-value/eval-form MUST check (tuple? x) before (struct? x) or (get x :key). Otherwise Janet sees a tuple, says yes to struct?, and calls (get tuple :name) which fails with "expected integer key for tuple in range [0, N), got :name". This hit us in print-value rendering and eval-form struct handling.
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Protocol system: Type registry in context env (:type-registry) maps type-tag→proto-name→method-name→fn. Three dispatch special forms: protocol-dispatch (resolves method via registry or reified methods), register-method (stores impl in registry), make-reified (creates anonymous object with :jolt/protocol-methods). fn* forms emitted by extend-type/extend-protocol MUST be @[...] (array) for eval-list dispatch. Protocols are maps with :jolt/type :jolt/protocol and :methods map.
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Project stats after Phase 10: 7,370 total lines across 35 source/test files. Key sources: compiler.janet (869 lines), evaluator.janet (869 lines), core.janet (1373 lines), types.janet (441 lines), reader.janet (463 lines), main.janet (125 lines), api.janet (93 lines), loader.janet (79 lines), phm.janet (199 lines). Test suite: 315 ok, 2 fail (pre-existing SciVar bootstrap + array/table/buffer errors). 9 .clj standard library modules under src/jolt/clojure/ and src/jolt/jolt/. All tests run via `jpm test`.
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REPL print-value uses buffer-based output: write-value/v buf appends formatted strings via buffer/push-string, then print-value creates buffer, builds string, and does a single (print (string buf)). This prevents Janet C runtime from interleaving native <tuple 0x...> output between prin statements in jpm build executables. Cond catch-all must use true clause: Janet's cond treats plain expressions as tests, so (push-str buf (string v)) at end of cond would be evaluated as a test — need true before it.