t27f: deps view answers why A imports B -- one shortest use chain (Closes #10705)

.claude/skills/t27f/SKILL.md

@@ -81,7 +81,7 @@ the diagram core in detail, then the other surfaces and the topic-map applicatio
 | Spec -> graph IR schema (the core) | `specs/t27f/spec_graph.t27` (t27#10020) | spec with tests: node / edge kinds, labels, spans, `validate_graph`, line -> node mapping, node -> ui_plan widget, one hand-read fixture (`specs/tutorial/08_modules_and_arrays.t27`) |
 | Graph view: layout of a spec graph | `specs/t27f/spec_graph_view.t27` (t27#10034) | spec with tests: one column per node kind, size / colour / dash / row order from the inference label, UNKNOWN nodes alone in a band, every edge with a source line, node -> widget through `node_widget`; numbers only, laid out on the hand-read fixture; drawn by the MCP tool `t27f_graph` (gHashTag/t27-mcp#9) |
 | Graph view for big specs: wrap, fold, expand, hit | `specs/t27f/spec_graph_fold.t27` (t27#10218) | spec with tests: a kind column taller than N = 12 rows wraps into sub-columns so the canvas aspect is near phi (identical to the view when nothing wraps); a fold to one box per kind with the exact count and one arc per pair of kinds with the exact edge count, each labelled by its weakest member; `expand_graph` = one kind plus its direct neighbours, copied verbatim with an origin map; `wrap_hit` / `wrap_hit_line_start` / `wrap_hit_line_end` take a click to a node and its lines; numbers only, the view's colours are not touched |
-| Dependencies view: the specs around one spec | `specs/t27f/spec_deps.t27` (t27#10680) | spec with tests: reads `t27c use-edges --specs-dir specs`; layer 0 is the focus, +k the specs k imports away (right), -k the specs k importers away (left), each spec once in its shortest-path layer; every edge-list line between two drawn specs is one `exact` edge, a repeated line drawn once; `cycle=1` when the focus imports itself or is imported by a spec in its own import closure; a walk past the caller's room or depth is refused whole (`refused\tfull` / `refused\tdeep`), never cut. A `use` line t27c does not resolve is not in the edge list, so `deps_unknown` (t27#10702) reads the focus source and writes each such line as `unknown\tpath`, mirroring `use_resolve.rs` (whole path, then one fallback level) without looking for a file; on master f33f269d5 that was 23 lines in 13 specs, byte for byte the `t27c gen` warnings. Limits: the view flags only the focus, and `deps_cycles` (t27#10693) lists every spec on a cycle, each once, refused whole (`cap + 1`) if anything does not fit; a spec on a cycle through the focus is drawn on both sides; no host draws it yet. Corpus on master e607228f7: 806 specs, 2461 edge lines, nothing refused at depth 32, deepest walks 6, one real cycle (igla race `backend` <-> `rtl`), which `deps_cycles` lists exactly on master f7efbc232 and lists as empty with #10689 |
+| Dependencies view: the specs around one spec | `specs/t27f/spec_deps.t27` (t27#10680) | spec with tests: reads `t27c use-edges --specs-dir specs`; layer 0 is the focus, +k the specs k imports away (right), -k the specs k importers away (left), each spec once in its shortest-path layer; every edge-list line between two drawn specs is one `exact` edge, a repeated line drawn once; `cycle=1` when the focus imports itself or is imported by a spec in its own import closure; a walk past the caller's room or depth is refused whole (`refused\tfull` / `refused\tdeep`), never cut. A `use` line t27c does not resolve is not in the edge list, so `deps_unknown` (t27#10702) reads the focus source and writes each such line as `unknown\tpath`, mirroring `use_resolve.rs` (whole path, then one fallback level) without looking for a file; on master f33f269d5 that was 23 lines in 13 specs, byte for byte the `t27c gen` warnings. `deps_why a b` (t27#10705) writes one shortest chain of edge-list lines from a to b, each `exact`, a tie taken in edge-list order, `none` when a does not reach b, refused whole when it does not fit. Limits: the view flags only the focus, and `deps_cycles` (t27#10693) lists every spec on a cycle, each once, refused whole (`cap + 1`) if anything does not fit; a spec on a cycle through the focus is drawn on both sides; no host draws it yet. Corpus on master e607228f7: 806 specs, 2461 edge lines, nothing refused at depth 32, deepest walks 6, one real cycle (igla race `backend` <-> `rtl`), which `deps_cycles` lists exactly on master f7efbc232 and lists as empty with #10689 |
 | Spec -> graph IR exporter | `specs/t27f/spec_graph_export.t27` (t27#10162) | spec with tests: `export_graph(path, src)` is a deterministic byte scanner over the source, `export_verdict` is `validate_graph` of the result. One node per top-level declaration (a leading `pub ` is allowed), spans to the matching closing brace, every node and edge EXACT or (unclassifiable) OPAQUE + UNKNOWN, CALLS / USES / CONSTRAINS edges with the line of the use, refusal past 1024 nodes or 4096 edges. On the tutorial 08 snapshot it equals the hand-read fixture on all 14 declaration nodes and all 9 EXACT edges; it does not emit the fixture's `std.testing` UNKNOWN node, nor its 7 DERIVED edges (4 data flow, 3 tested_by), because a scanner never derives; the derive pass below adds them. Limits: textual matching without scope or type resolution, no block comments, no struct/enum bodies, no cross-spec `use` resolution, capacity 1024 nodes and 4096 edges, u16 indices (all 2225 specs in specs/ fit, largest 775 nodes and 3194 edges after derive; anything past the cap is refused, never truncated), takes a `[]const u8` slice rather than `[65536]u8` plus a length. AST/IR audit is trinity#1650, pilot choice #1651 |
 | Graph IR derive pass | `specs/t27f/spec_graph_derive.t27` (t27#10191) | spec with tests: `derive_graph(g, src)` appends what the exporter must not claim and changes nothing it holds. R1 DERIVED `tested_by` = every EXACT CALLS edge from a test, invariant or bench to a fn read backwards (no line). R2 DERIVED `data_flow` = a const or `use` that an EXACT USES edge ties to a fn and that is named inside one of the fn's return statements (from `return` to the next `;`), on the line of the first such name. R3 UNKNOWN opaque node = an undeclared qualified call target of three or more segments (`std.testing.expectEqual(` names `std.testing`), spanning the lines that call through it. Exporter plus derive equal the tutorial 08 fixture as sets: 15 of 15 nodes, 16 of 16 edges, no special case. Limits: names matched as text; call results and flow through locals are not derived; R3 needs 3 or more segments (two cannot be told from a method call); a graph that does not validate, or a source of another line count, comes back unchanged; past 1024 nodes or 4096 edges the result is refused with the too-many verdict. Not wired to a host: the MCP tool does not call it |
 | UI plan IR + trusted widget catalog | `specs/t27f/ui_plan.t27` (t27#9962) | spec with tests; no renderer draws a plan yet |
@@ -166,6 +166,7 @@ Traps from this tick (ffmpeg on the lab):
 - The lab cgroup has `pids.max` 1000, and a graph with many `drawtext` filters starts 400 to 700 threads. Cap them with `-threads 2 -filter_threads 2 -filter_complex_threads 2` and `-threads 1` on the output. Never run two renders at once. "ff_frame_thread_encoder_init failed" means the cap was hit. Look for a stuck ffmpeg and kill it by pid.
 - lavfi rejects `d=.900`. Print the duration as `$((m/1000)).$(printf %03d $((m%1000)))`.
 - `pkill -f` on the loop script leaves its child renders running. Find them with `ps -eo pid,args | grep '[s]h xf'` and kill them by pid.
+- Through `fs-lab.sh`, `pkill -f 'why_seal'` also matches the ssh command line that carries it and kills your own session; the output comes back empty. Bracket the first letter (`pkill -f '[w]hy_seal'`) so the pattern does not match itself. A killed session leaves the detached ratchets it started running, so several end up writing one log; list them with `ps -eo pid,etimes,args | grep '[c]orpus-only'` before you read a verdict.
 
 **Holding the address when the voice runs long (t27#10629).** If an overlay must stay on screen for a minimum time and must also stay off a crossfade, then the crossfade has to move; the overlay cannot. Work out in frames the latest cut that still leaves the last scene its minimum: cut 1 is capped at `BEAT_CUT1_LAST_MS` = 13249. Prove it is the latest with a one-ms-later control. Only the voices the reel speeds up are affected, so the `cmp` diff is limited to those voices and to crossfade 1's offset. The cost is real: the crossfade starts up to 184 ms under the task's last word, and lesson 1's measured voice (1300/4200/6800) is one of the affected voices. Write a test that bounds that overlap.
 
@@ -383,6 +384,27 @@ for byte.
    `spec<TAB>unknown<TAB>X` in `git ls-files` order, which is the order gen ran in.
 3. Controls: the same list minus one line must FAIL, and so must `w == 0`. On master f33f269d5
    it was 23 lines in 13 specs (#7176 had counted 119 in 70), and both controls failed.
+4. All 13 of those specs fail `t27c test-report` for other reasons before the dropped `use`
+   matters (`std::*` imports, an undeclared `gf32_from_f64`, `Float`, Rust syntax). Repairing a
+   dropped import alone therefore fixes none of them. Classify a spec before you promise a fix.
+
+### Check one chain per reached spec (t27#10705)
+
+`deps_why a b` answers the question that `cargo tree -i`, `npm explain` and `pnpm why` answer:
+why does a import b. It writes one shortest chain of edge-list lines. The corpus check holds it
+to three properties:
+
+1. Over the `use-edges` list, call `deps_why focus x` for every spec x the focus reaches. The
+   chain must have exactly `layer(x)` hops, every hop must be an edge-list line, and each hop
+   must start where the last one ended: at the focus first, at x last. Count the specs checked
+   and compare with `deps_count` of the walk, so no spec is skipped.
+2. Control: expect one hop more (`zz_check(1)`). It must FAIL.
+3. Mutation: drop the last edge from the chain. Two unit tests must FAIL.
+
+Build the scratch spec by concatenation (head of the template, the escaped edges, then the
+tail). A `sed s#@EDGES@#...#` with 2466 lines fails with "Argument list too long". A focus with
+no outgoing edge, such as `verified/reuse`, checks only itself, so `> 1` fails for it; that is
+the probe, not the function.
 
 ## What this skill does not claim
 

.trinity/seals/t27f_t27f_spec_deps.json

@@ -15,23 +15,23 @@
     }
   ],
   "config": "gen=c,rust,verilog,zig;tests=zig",
-  "gen_hash_c": "sha256:a827ac501c5bc3a6cb34fb9eed1a765efaf6c65dcaef25c64ff4ab34e053f47f",
-  "gen_hash_rust": "sha256:ecd73ef257fce64599a99a522559ac91b0fe6a1a364863f163584bdd253e0673",
-  "gen_hash_verilog": "sha256:47a568b333eb16e44c62b907f678ab98e42ea629611d36a2d52edd91a95e4023",
-  "gen_hash_zig": "sha256:8082c63e31383157aaa1771ec8d4feaf6b1090da42127267c41b8a8afad06251",
+  "gen_hash_c": "sha256:cf159312ea60356819669f1af08181d3fa7698777fc89621d64814413c9335f6",
+  "gen_hash_rust": "sha256:912f179d20bcb6f7af05cb7688e3b095fb2ced9c9b1449edb6322d2d3c413e61",
+  "gen_hash_verilog": "sha256:4950c28e69b7b88e812544714f55a9814f40eb4e94296ec5dc981759630b2750",
+  "gen_hash_zig": "sha256:963538cd84850fba1814350998a496856a3ba35709ab952b5f9b2965602fdcda",
   "module": "t27f_spec_deps",
   "ring": 12,
   "seal_schema": 2,
-  "sealed_at": "2026-10-18T22:58:06Z",
+  "sealed_at": "2026-10-18T23:14:31Z",
   "sealed_by": "t27c-bootstrap@0.5.2",
-  "spec_hash": "sha256:c7b44f43776b8a7b0d21aee8a73502e996ec9fb35cd56935bd300b4358f8d4be",
+  "spec_hash": "sha256:c6e6c03537dd7238ce7cceb937dfe307294ab59d4946de95f7d96e40333cb070",
   "spec_path": "specs/t27f/spec_deps.t27",
   "tests": {
     "failed": 0,
     "failing": [],
     "forced": false,
-    "passed": 25,
-    "total": 25,
+    "passed": 31,
+    "total": 31,
     "vacuous": 0
   },
   "toolchain": {