From 61b6387269233bd89e0db076fc7e58aa7b2f8599 Mon Sep 17 00:00:00 2001
From: Jean-Pierre Martineau <johnputer@meshterm.net>
Date: Sun, 6 Sep 2026 20:12:07 -0400
Subject: [PATCH] Every zip says whether its sides are the same length
MIME-Version: 1.0
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`B905` over 56 sites, and the answer differs by idiom rather than by file.

21 were the sliding window `zip(xs, xs[1:])` — ragged by exactly one, on
purpose, so `strict=` is the wrong question entirely. Those become
`itertools.pairwise`, which is what they always meant and needs no flag: the
walk's SNR stops, the heat ladder, the route chains in `topology`/`records`,
every polyline in `mapcanvas`, and the graph's edge sets in `pathgraph`.

The other 35 pair sequences that must line up, so they now say `strict=True`
and a mismatch raises instead of silently truncating the longer side. Running
them under that assertion is what sorted the two groups: the first pass put
`strict=True` everywhere and 208 tests failed, all of them a sliding window.

One goes the other way. `mvt._decode_feature` reads tags off a network tile,
where an odd-length list means the tile is malformed — and this decoder answers
that with a shrug everywhere else (`if not geom_ints: return None`, bounds-
checked key and value indices). It keeps `strict=False`, now with a comment
saying why, so a bad basemap tile still can't crash the map.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
---
 .claude/skills/add-narrow-emoji/classify.py    |  2 +-
 .../profile-picocalc/scripts/bench_ablate.py   |  4 ++--
 meshterm/core/contact_score.py                 |  2 +-
 meshterm/core/mvt.py                           |  4 +++-
 meshterm/services/records.py                   |  5 +++--
 meshterm/services/topology.py                  |  6 +++---
 meshterm/ui/braillechart.py                    |  4 ++--
 meshterm/ui/map_screen.py                      |  2 +-
 meshterm/ui/mapcanvas.py                       |  5 +++--
 meshterm/ui/menu.py                            |  2 +-
 meshterm/ui/menus.py                           |  2 +-
 meshterm/ui/node_detail_screen.py              |  3 ++-
 meshterm/ui/pathgraph.py                       | 18 +++++++++---------
 meshterm/ui/purge_screen.py                    |  2 +-
 meshterm/ui/records_screen.py                  |  4 ++--
 meshterm/ui/timemachine_screen.py              |  8 ++++----
 meshterm/ui/trace_screen.py                    |  2 +-
 meshterm/ui/tui/frame.py                       |  2 +-
 meshterm/ui/tui/session.py                     |  6 +++---
 meshterm/ui/walk_screen.py                     |  7 ++++---
 meshterm/ui/widgets.py                         |  5 +++--
 tests/test_chat.py                             |  3 ++-
 tests/test_contact_score.py                    |  2 +-
 tests/test_map.py                              |  6 +++---
 tests/test_menus.py                            |  8 ++++----
 tests/test_pathgraph.py                        | 13 +++++++------
 tests/test_pathline.py                         |  2 +-
 tests/test_timemachine.py                      |  3 ++-
 tests/test_tui.py                              |  4 ++--
 tests/test_walk.py                             |  2 +-
 tests/test_watchtower.py                       |  9 ++++++---
 31 files changed, 80 insertions(+), 67 deletions(-)

diff --git a/.claude/skills/add-narrow-emoji/classify.py b/.claude/skills/add-narrow-emoji/classify.py
index 632be1a..ccbeccf 100644
--- a/.claude/skills/add-narrow-emoji/classify.py
+++ b/.claude/skills/add-narrow-emoji/classify.py
@@ -1,4 +1,4 @@
-"""Diagnose one emoji for the MeshTerm terminal-aligned width machinery.
+r"""Diagnose one emoji for the MeshTerm terminal-aligned width machinery.
 
 Given an emoji on the command line, report its codepoints and how the three width
 authorities measure it (wcwidth, Rich, prompt_toolkit), then classify it and print the
diff --git a/.claude/skills/profile-picocalc/scripts/bench_ablate.py b/.claude/skills/profile-picocalc/scripts/bench_ablate.py
index 252f060..179fd25 100644
--- a/.claude/skills/profile-picocalc/scripts/bench_ablate.py
+++ b/.claude/skills/profile-picocalc/scripts/bench_ablate.py
@@ -131,9 +131,9 @@ def measure(name, cols, rows, reps):
 
             # How different are the two frames, in rows?
             rows_a, rows_b = f_a.split("\n"), f_b.split("\n")
-            changed = sum(1 for x, y in zip(rows_a, rows_b) if x != y)
+            changed = sum(1 for x, y in zip(rows_a, rows_b, strict=True) if x != y)
             rows_far = f_far.split("\n")
-            changed_far = sum(1 for x, y in zip(rows_a, rows_far) if x != y)
+            changed_far = sum(1 for x, y in zip(rows_a, rows_far, strict=True) if x != y)
     return {
         "compose": compose_ms,
         "parse": parse_ms,
diff --git a/meshterm/core/contact_score.py b/meshterm/core/contact_score.py
index 9dbe277..cc2c173 100644
--- a/meshterm/core/contact_score.py
+++ b/meshterm/core/contact_score.py
@@ -576,7 +576,7 @@ def rank_contacts(
             reasons=_reasons(sig, terms, weights),
         )
         for contact, sig, score, terms in zip(
-            contacts, gathered, scores, per_contact_terms
+            contacts, gathered, scores, per_contact_terms, strict=True
         )
     ]
     ranked.sort(key=lambda scored: (-scored.score, scored.contact.name.casefold()))
diff --git a/meshterm/core/mvt.py b/meshterm/core/mvt.py
index c549df6..1cde365 100644
--- a/meshterm/core/mvt.py
+++ b/meshterm/core/mvt.py
@@ -234,7 +234,9 @@ def _decode_feature(buf: bytes, keys: list[str], values: list[Any]) -> Feature |
     if not geom_ints:
         return None
     tags: dict[str, Any] = {}
-    for k, v in zip(tag_ints[0::2], tag_ints[1::2]):
+    # A malformed tile may carry an odd tag list; drop the dangling key rather than
+    # raise — the rest of this decoder is deliberately lenient about bad tiles.
+    for k, v in zip(tag_ints[0::2], tag_ints[1::2], strict=False):
         if 0 <= k < len(keys) and 0 <= v < len(values):
             tags[keys[k]] = values[v]
     return Feature(geom_type=geom_type, rings=_decode_geometry(geom_ints), tags=tags)
diff --git a/meshterm/services/records.py b/meshterm/services/records.py
index b4c4381..f0934e6 100644
--- a/meshterm/services/records.py
+++ b/meshterm/services/records.py
@@ -34,6 +34,7 @@ from __future__ import annotations
 import math
 from collections.abc import Callable, Sequence
 from dataclasses import dataclass
+from itertools import pairwise
 
 from ..core.geo import haversine_km
 from ..core.models import Hop, TraceResult
@@ -69,7 +70,7 @@ def first_repeated_edge(nodes: Sequence[str]) -> tuple[str, str] | None:
     """
     walked = [n.strip().lower() for n in nodes if n and n.strip()]
     seen: set[tuple[str, str]] = set()
-    for pair in zip(walked, walked[1:]):
+    for pair in pairwise(walked):
         if pair in seen:
             return pair
         seen.add(pair)
@@ -306,7 +307,7 @@ def compute_walk_stats(
     complete = True
     leg_km: float | None = None
     leg_link: tuple[str | None, str | None] | None = None
-    for i, (a, b) in enumerate(zip(points, points[1:])):
+    for i, (a, b) in enumerate(pairwise(points)):
         if a is None or b is None:
             complete = False
             continue
diff --git a/meshterm/services/topology.py b/meshterm/services/topology.py
index dd35c12..aecb49f 100644
--- a/meshterm/services/topology.py
+++ b/meshterm/services/topology.py
@@ -35,7 +35,7 @@ import math
 import statistics
 from dataclasses import dataclass, field
 from datetime import datetime
-from itertools import chain
+from itertools import chain, pairwise
 
 from ..core.models import Contact, utcnow
 from ..persistence.repository import NeighbourLink, PacketPath, TracedPath
@@ -823,7 +823,7 @@ class MeshTopology:
         weakest_strength: float | None = None
         weakest_snr: float | None = None
         samples = 0
-        for a, b in zip(chain, chain[1:]):
+        for a, b in pairwise(chain):
             link = self.link(a, b)
             if link is None:
                 return 0.0, None, samples
@@ -912,7 +912,7 @@ class MeshTopology:
 
         def path_cost(path: list[str]) -> float:
             total = 0.0
-            for a, b in zip(path, path[1:]):
+            for a, b in pairwise(path):
                 total += min((c for v, c in neighbors.get(a, ()) if v == b), default=math.inf)
             return total
 
diff --git a/meshterm/ui/braillechart.py b/meshterm/ui/braillechart.py
index a03178a..e5fdaeb 100644
--- a/meshterm/ui/braillechart.py
+++ b/meshterm/ui/braillechart.py
@@ -431,7 +431,7 @@ def axis_caption(
         taken: list[tuple[int, int]] = []  # placed [start, end) spans, in order
         ticks: list[int] = []  # the chart column each label points at
         ok = True
-        for frac, label in zip(fractions, labels):
+        for frac, label in zip(fractions, labels, strict=True):
             if frac == 0.0:
                 start = 0
                 ref = 0
@@ -626,7 +626,7 @@ def axis_chart(
     marks = y_axis_labels(peak, len(chart_rows), lo=floor)
     label_w = label_w or max([1, *(len(mark) for mark in marks)])
     out: list[Text] = []
-    for mark, row in zip(marks, chart_rows):
+    for mark, row in zip(marks, chart_rows, strict=True):
         line = Text(f"{mark:>{label_w}} " + ("┤" if mark else "│"), style=style)
         line.append_text(row)
         line.append("├" if mark else "│", style=style)
diff --git a/meshterm/ui/map_screen.py b/meshterm/ui/map_screen.py
index 16ce28d..a10907e 100644
--- a/meshterm/ui/map_screen.py
+++ b/meshterm/ui/map_screen.py
@@ -141,7 +141,7 @@ class MapScreen(Screen):
 
     @property
     def fkey_lane(self):
-        """The PicoCalc lane: three ways to frame the view, then the zoom rocker.
+        r"""The PicoCalc lane: three ways to frame the view, then the zoom rocker.
 
         The map is the one screen that repurposes the nav actions wholesale: PgUp/PgDn
         zoom, Home reframes, and ``end`` is bound to nothing at all — so the shared lane's
diff --git a/meshterm/ui/mapcanvas.py b/meshterm/ui/mapcanvas.py
index a610328..99b6258 100644
--- a/meshterm/ui/mapcanvas.py
+++ b/meshterm/ui/mapcanvas.py
@@ -16,6 +16,7 @@ from __future__ import annotations
 
 import unicodedata
 from dataclasses import dataclass
+from itertools import pairwise
 
 from ..platforms import Platform, on_platform
 from .marks import RGB, parse_hex  # noqa: F401 - canonical home; re-exported for importers
@@ -177,7 +178,7 @@ class MapCanvas:
         self, points: list[tuple[float, float]], color: RGB, priority: int
     ) -> None:
         """Rasterize a polyline through ``points`` (dot coordinates) as braille dots."""
-        for (x0, y0), (x1, y1) in zip(points, points[1:]):
+        for (x0, y0), (x1, y1) in pairwise(points):
             self._segment(x0, y0, x1, y1, color, priority)
 
     def _segment(
@@ -232,7 +233,7 @@ class MapCanvas:
         edges: list[tuple[float, float, float, float]] = []
         ys: list[float] = []
         for ring in rings:
-            for (x0, y0), (x1, y1) in zip(ring, ring[1:]):
+            for (x0, y0), (x1, y1) in pairwise(ring):
                 if y0 != y1:
                     edges.append((x0, y0, x1, y1))
                     ys.extend((y0, y1))
diff --git a/meshterm/ui/menu.py b/meshterm/ui/menu.py
index 8974ccb..a361c93 100644
--- a/meshterm/ui/menu.py
+++ b/meshterm/ui/menu.py
@@ -522,7 +522,7 @@ async def _menu_loop(ctx: AppContext, session: TuiSession) -> None:
     name_w = max((label.cell_len for label in labels), default=0)
     items: list = []
     current_category: str | None = None
-    for tool, row in zip(tools, labels):
+    for tool, row in zip(tools, labels, strict=True):
         if tool.category != current_category:
             current_category = tool.category
             items.append(section_heading(current_category))
diff --git a/meshterm/ui/menus.py b/meshterm/ui/menus.py
index b09df94..8c41a91 100644
--- a/meshterm/ui/menus.py
+++ b/meshterm/ui/menus.py
@@ -333,7 +333,7 @@ def column_header(lanes: Sequence[Lane], width: int, *, indent: int = 2) -> str:
 
     def line() -> str:
         out = " " * indent
-        for lane, form in zip(lanes, picked):
+        for lane, form in zip(lanes, picked, strict=True):
             label = lane.forms[form]
             out += label + " " * max(0, lane.width - cell_len(label))
         return out
diff --git a/meshterm/ui/node_detail_screen.py b/meshterm/ui/node_detail_screen.py
index 1f4bbe7..a108017 100644
--- a/meshterm/ui/node_detail_screen.py
+++ b/meshterm/ui/node_detail_screen.py
@@ -78,6 +78,7 @@ import re
 import time
 from dataclasses import dataclass, field, replace
 from datetime import datetime
+from itertools import pairwise
 from typing import TYPE_CHECKING
 
 from rich.cells import cell_len
@@ -2013,7 +2014,7 @@ def _route_is_fresh(topo, hops: tuple[str, ...], target: str, now: datetime) ->
     is treated as fresh — we have no age to hold against it.
     """
     chain = [topo.self_id, *hops, target]
-    for a, b in zip(chain, chain[1:]):
+    for a, b in pairwise(chain):
         link = topo.link(a, b)
         if link is None:
             return False
diff --git a/meshterm/ui/pathgraph.py b/meshterm/ui/pathgraph.py
index 2b92dd5..4ac9321 100644
--- a/meshterm/ui/pathgraph.py
+++ b/meshterm/ui/pathgraph.py
@@ -104,7 +104,7 @@ from __future__ import annotations
 
 from collections.abc import Callable, Sequence
 from dataclasses import dataclass
-from itertools import permutations, product
+from itertools import pairwise, permutations, product
 from math import ceil
 
 from .mapcanvas import MapCanvas
@@ -375,7 +375,7 @@ def revisited_hops(hops: Sequence[str]) -> tuple[str, ...]:
 
 
 def _split_revisits(layers: Sequence[PathLayer]) -> list[PathLayer]:
-    """Give every revisit *within* a path its own node id, so no walk folds into a cycle.
+    r"""Give every revisit *within* a path its own node id, so no walk folds into a cycle.
 
     The k-th occurrence of a hop in one layer becomes ``hop\\x00#k`` (the first keeps the bare
     id), which leaves the flow acyclic and lets the balanced rank spread the walk evenly again.
@@ -555,7 +555,7 @@ def render_path_graph(
             if node not in seen:
                 seen.add(node)
                 ordered_nodes.append(node)
-        edges.update(zip(seq, seq[1:]))
+        edges.update(pairwise(seq))
 
     xfrac = _balanced_x(ordered_nodes, edges)
 
@@ -667,9 +667,9 @@ def render_path_graph(
     # dropping out where it overlaps another. A two-way pair (``bidir``, above) draws as the
     # one honest vertical rather than a lane change.
     edge_style: dict[frozenset[str], tuple[int, RGB]] = {}
-    for layer, seq in sorted(zip(drawn, seqs), key=lambda ls: _draw_rank(ls[0])):
+    for layer, seq in sorted(zip(drawn, seqs, strict=True), key=lambda ls: _draw_rank(ls[0])):
         rank = _draw_rank(layer)
-        for u, v in zip(seq, seq[1:]):
+        for u, v in pairwise(seq):
             key = frozenset((u, v))
             prev = edge_style.get(key)
             if prev is None or rank > prev[0]:
@@ -731,7 +731,7 @@ def _route(
         (xu, yu), (xv, yv) = (xv, yv), (xu, yu)
     anchors: list[tuple[float, float]] = [(xu, yu), *sorted(vias), (xv, yv)]
     pts: list[tuple[float, float]] = [anchors[0]]
-    for (xa, ya), (xb, yb) in zip(anchors, anchors[1:]):
+    for (xa, ya), (xb, yb) in pairwise(anchors):
         if ya == yb:
             pts.append((xb, yb))
             continue
@@ -845,7 +845,7 @@ def bidir_clusters(sequences: Sequence[tuple[str, ...]]) -> list[tuple[str, ...]
     Returns each cluster's member ids in first-appearance order (endpoints excluded); a lone
     node or the tidy two-node pair is not a cluster and is not returned.
     """
-    edges = {pair for seq in sequences for pair in zip(seq, seq[1:])}
+    edges = {pair for seq in sequences for pair in pairwise(seq)}
     ordered = list(dict.fromkeys(node for seq in sequences for node in seq))
     rep = _merge_bidir_pairs(ordered, edges)
     groups: dict[str, list[str]] = {}
@@ -1047,7 +1047,7 @@ def _bypass_vias(
     level: list[tuple[frozenset[str], float, int, int]] = []
     seen: set[frozenset[str]] = set()
     for seq in seqs:
-        for u, v in zip(seq, seq[1:]):
+        for u, v in pairwise(seq):
             key = frozenset((u, v))
             if key in seen or key in bidir:
                 continue
@@ -1328,7 +1328,7 @@ def _balance_sides(
     best_assign: dict[int, int] | None = None
     best_key: tuple[int, int, int] | None = None
     for combo in product((-1, 1), repeat=len(routes)):
-        assign = dict(zip(routes, combo))
+        assign = dict(zip(routes, combo, strict=True))
         if any(assign[d] != assign[s] for d, s in tie.items()):  # a nest split off its sibling
             continue
         deep_above, deep_below = flanks(assign)
diff --git a/meshterm/ui/purge_screen.py b/meshterm/ui/purge_screen.py
index 277c890..01a875f 100644
--- a/meshterm/ui/purge_screen.py
+++ b/meshterm/ui/purge_screen.py
@@ -211,7 +211,7 @@ async def _rank(ctx: AppContext, contacts: list[Contact]) -> list[ScoredContact]
 
     watch = getattr(ctx, "watch_store", None)
     admin = getattr(ctx, "admin_store", None)
-    for contact, node in zip(contacts, nodes):
+    for contact, node in zip(contacts, nodes, strict=True):
         found = signals.get(node)
         if found is None:
             continue
diff --git a/meshterm/ui/records_screen.py b/meshterm/ui/records_screen.py
index f66fa1c..e05a216 100644
--- a/meshterm/ui/records_screen.py
+++ b/meshterm/ui/records_screen.py
@@ -446,10 +446,10 @@ class RecordDialog(Screen):
         canvas.draw_line(closed, _AREA_TONE, priority=0)
         # Hops first, then our own node last, so the star always wins its cell — a hop that
         # projects onto the same cell can never hide us.
-        for v, (dx, dy) in zip(verts, ring):
+        for v, (dx, dy) in zip(verts, ring, strict=True):
             if not v.is_self:
                 canvas.marker(int(round(dx)), int(round(dy)), v.glyph, v.color)
-        for v, (dx, dy) in zip(verts, ring):
+        for v, (dx, dy) in zip(verts, ring, strict=True):
             if v.is_self:
                 canvas.marker(int(round(dx)), int(round(dy)), v.glyph, v.color)
         return canvas.to_ansi_lines()
diff --git a/meshterm/ui/timemachine_screen.py b/meshterm/ui/timemachine_screen.py
index 935e5ea..ccecc31 100644
--- a/meshterm/ui/timemachine_screen.py
+++ b/meshterm/ui/timemachine_screen.py
@@ -668,7 +668,7 @@ def _ticks_fit(picks: list[int], labels: list[str], centers: list[int], chars: i
     label would drop ticks a variable-width axis has ample room for.
     """
     last_end = -_TICK_GAP
-    for i, label in zip(picks, labels):
+    for i, label in zip(picks, labels, strict=True):
         cell = max(0, min(chars - 1, centers[i]))
         start = max(0, min(chars - len(label), cell - len(label) // 2))
         if start < last_end + _TICK_GAP:
@@ -707,9 +707,9 @@ def _fit_ticks(
             continue  # rounding fused two picks — this many will not fit cleanly
         labels = label_of(picks)
         if _ticks_fit(picks, labels, centers, chars):
-            return list(zip((centers[i] for i in picks), labels))
+            return list(zip((centers[i] for i in picks), labels, strict=True))
     picks = [0] if n == 1 else [0, n - 1]
-    return list(zip((centers[i] for i in picks), label_of(picks)))
+    return list(zip((centers[i] for i in picks), label_of(picks), strict=True))
 
 
 def _day_ticks(shown: list, chars: int) -> list[tuple[int, str]]:
@@ -912,7 +912,7 @@ def _day_columns(values: list[int], chars: int) -> list:
         :data:`~meshterm.ui.braillechart.GAP` marks a day-boundary notch).
     """
     out: list = [GAP] * (chars * 2)
-    for value, (start, width) in zip(values, _day_spans(len(values), chars)):
+    for value, (start, width) in zip(values, _day_spans(len(values), chars), strict=True):
         out[start : start + width] = [value] * width
     return out
 
diff --git a/meshterm/ui/trace_screen.py b/meshterm/ui/trace_screen.py
index 04fe516..5add13c 100644
--- a/meshterm/ui/trace_screen.py
+++ b/meshterm/ui/trace_screen.py
@@ -1177,7 +1177,7 @@ class TraceScreen(Screen):
             rows.append(spin)
         elif self._status:
             rows.append(Text(self._status, style="err"))
-        for number, trace in zip(range(len(self._traces), 0, -1), reversed(self._traces)):
+        for number, trace in zip(range(len(self._traces), 0, -1), reversed(self._traces), strict=True):
             rows.append(self._trace_row(number, trace))
         return Group(*rows)
 
diff --git a/meshterm/ui/tui/frame.py b/meshterm/ui/tui/frame.py
index ec1ddb8..b24b107 100644
--- a/meshterm/ui/tui/frame.py
+++ b/meshterm/ui/tui/frame.py
@@ -372,7 +372,7 @@ def _banner_lines(banner: Sequence[str], cols: int) -> list[str]:
         return []
     widths = [cell_len(Text.from_ansi(row).plain) for row in banner]
     width = max(widths)
-    padded = [fold_text(row) + " " * (width - w) for row, w in zip(banner, widths)]
+    padded = [fold_text(row) + " " * (width - w) for row, w in zip(banner, widths, strict=True)]
     return _center(padded, cols)
 
 
diff --git a/meshterm/ui/tui/session.py b/meshterm/ui/tui/session.py
index 9d4dd20..3e38957 100644
--- a/meshterm/ui/tui/session.py
+++ b/meshterm/ui/tui/session.py
@@ -267,7 +267,7 @@ def _changed_rows(before: str, after: str) -> list[int] | None:
     old, new = before.split("\n"), after.split("\n")
     if len(old) != len(new):
         return None
-    return [i for i, (a, b) in enumerate(zip(old, new)) if a != b]
+    return [i for i, (a, b) in enumerate(zip(old, new, strict=True)) if a != b]
 
 
 def _has_wide_glyph(text: str) -> bool:
@@ -680,7 +680,7 @@ class TuiSession:
         self._scrub_columns(cols - count, cols)
 
     def _scrub_rows(self, rows: Sequence[int]) -> bool:
-        """Force prompt_toolkit to rewrite these whole terminal rows on the next diff.
+        r"""Force prompt_toolkit to rewrite these whole terminal rows on the next diff.
 
         The row-wise twin of :meth:`_scrub_columns`, and the cheap form of the wide-glyph
         repaint (:meth:`_emit`): every column of each listed row is sentinelled, so pt finds
@@ -1539,7 +1539,7 @@ class TuiSession:
         return bool(self._float_layers())
 
     def _emit(self, text: str, layer: str = "base") -> ANSI:
-        """Wrap a composed frame as prompt_toolkit :class:`ANSI`, repainting whole *rows*
+        r"""Wrap a composed frame as prompt_toolkit :class:`ANSI`, repainting whole *rows*
         when it holds a glyph the terminal may draw narrower than pt reserves for it.
 
         prompt_toolkit paints differentially: it rewrites only the cells that changed since
diff --git a/meshterm/ui/walk_screen.py b/meshterm/ui/walk_screen.py
index 4569026..c65dfae 100644
--- a/meshterm/ui/walk_screen.py
+++ b/meshterm/ui/walk_screen.py
@@ -57,6 +57,7 @@ from __future__ import annotations
 import math
 from collections import deque
 from datetime import datetime
+from itertools import pairwise
 from typing import TYPE_CHECKING
 
 from rich.cells import cell_len
@@ -201,10 +202,10 @@ def _snr_rgb(snr: float | None) -> RGB:
     if snr >= _SNR_STOPS[-1][0]:
         return _SNR_STOPS[-1][1]
     (x0, c0), (x1, c1) = next(
-        (lo, hi) for lo, hi in zip(_SNR_STOPS, _SNR_STOPS[1:]) if lo[0] <= snr <= hi[0]
+        (lo, hi) for lo, hi in pairwise(_SNR_STOPS) if lo[0] <= snr <= hi[0]
     )
     f = (snr - x0) / (x1 - x0)
-    return tuple(round(a + (b - a) * f) for a, b in zip(c0, c1))  # type: ignore[return-value]
+    return tuple(round(a + (b - a) * f) for a, b in zip(c0, c1, strict=True))  # type: ignore[return-value]
 
 
 def _scaled(rgb: RGB, factor: float) -> RGB:
@@ -1039,7 +1040,7 @@ class WalkScreen(Screen):
         # marker, in cells, doubled into dot space.
         rx = max(floor, 2 * (width - 2 - _FAN_BASE_LABEL_W)) - ax
         phi = _FAN_HALF_ANGLE * min(1.0, (len(keys) - 1) / 5.0)
-        for i, (node, row, label) in enumerate(zip(keys, rows, labels)):
+        for i, (node, row, label) in enumerate(zip(keys, rows, labels, strict=True)):
             angle = 0.0 if len(keys) == 1 else -phi + (2 * phi) * i / (len(keys) - 1)
             x = ax + rx * math.cos(angle * _FAN_X_FLATTEN)
             room = 2 * (width - 2 - min(cell_len(label), _FAN_LABEL_W))
diff --git a/meshterm/ui/widgets.py b/meshterm/ui/widgets.py
index 48e2c09..13e8bfa 100644
--- a/meshterm/ui/widgets.py
+++ b/meshterm/ui/widgets.py
@@ -6,6 +6,7 @@ import math
 from collections.abc import Callable, Sequence
 from dataclasses import dataclass, field
 from datetime import datetime
+from itertools import pairwise
 from typing import TYPE_CHECKING
 
 from rich import box
@@ -935,10 +936,10 @@ def _recency_gradient(secs: float | None) -> str:
         r, g, b = _HEAT_STOPS[-1][1]
     else:
         (x0, c0), (x1, c1) = next(
-            (lo, hi) for lo, hi in zip(_HEAT_STOPS, _HEAT_STOPS[1:]) if lo[0] <= x <= hi[0]
+            (lo, hi) for lo, hi in pairwise(_HEAT_STOPS) if lo[0] <= x <= hi[0]
         )
         f = (x - x0) / (x1 - x0)
-        r, g, b = (round(a + (bb - a) * f) for a, bb in zip(c0, c1))
+        r, g, b = (round(a + (bb - a) * f) for a, bb in zip(c0, c1, strict=True))
     return f"#{r:02x}{g:02x}{b:02x}"
 
 
diff --git a/tests/test_chat.py b/tests/test_chat.py
index e8f1a12..c724cd6 100644
--- a/tests/test_chat.py
+++ b/tests/test_chat.py
@@ -495,7 +495,8 @@ def test_title_preview_column_aligns_regardless_of_label_length(repo: Repository
 def test_title_leads_with_openness_glyph(repo: Repository) -> None:
     """Channel rows lead with an openness glyph: ＃ name-derived, 🌐 fixed-key public, 🔒 private."""
     ctx = _RowCtx(repo)
-    head = lambda conv: _title(ctx, conv, {}, _NO_KEYS).plain.split(" ", 1)[0]
+    def head(conv):
+        return _title(ctx, conv, {}, _NO_KEYS).plain.split(" ", 1)[0]
     named = Conversation(
         label="#general", is_channel=True, channel_id="c0", secret=derive_secret("#general")
     )
diff --git a/tests/test_contact_score.py b/tests/test_contact_score.py
index 1c232e2..7524420 100644
--- a/tests/test_contact_score.py
+++ b/tests/test_contact_score.py
@@ -41,7 +41,7 @@ def _rank(*specs) -> list:  # noqa: ANN001
     """Rank ``(name, signal-overrides)`` pairs, returning the scored contacts strongest first."""
     contacts = [_contact(name) for name, _ in specs]
     signals = {}
-    for contact, (_, overrides) in zip(contacts, specs):
+    for contact, (_, overrides) in zip(contacts, specs, strict=True):
         node = contact.public_key[:12]
         signals[node] = ContactSignals(node=node, **{**_BASE, **overrides})
     return rank_contacts(contacts, signals)
diff --git a/tests/test_map.py b/tests/test_map.py
index d00d9fc..97ec21e 100644
--- a/tests/test_map.py
+++ b/tests/test_map.py
@@ -615,7 +615,7 @@ def test_render_map_brightens_piled_markers() -> None:
     crowd = [MapMarker(f"n{i}", 45.50, -73.57) for i in range(8)]
     piled = _glyph_color(render_map(vp, {}, crowd), "●")
     # Washed toward white: every channel is brighter than the base cyan.
-    assert all(p > b for p, b in zip(piled, base))
+    assert all(p > b for p, b in zip(piled, base, strict=True))
     assert piled != base
 
 
@@ -684,7 +684,7 @@ def test_the_ghost_ground_lands_where_the_pan_put_it() -> None:
     assert len(before) == len(after)
     matched = sum(
         1
-        for old, new in zip(before, after)
+        for old, new in zip(before, after, strict=True)
         if old[shift:].rstrip() and new.rstrip() == old[shift:].rstrip()
     )
     assert matched > len(before) // 2, "the ground did not slide with the view"
@@ -906,7 +906,7 @@ def test_decoded_layers_survive_a_round_trip() -> None:
 
     assert restored is not None
     assert [(l.name, l.extent) for l in restored] == [(l.name, l.extent) for l in original]
-    for before, after in zip(original, restored):
+    for before, after in zip(original, restored, strict=True):
         assert after.features == before.features
 
 
diff --git a/tests/test_menus.py b/tests/test_menus.py
index ebdbcd8..bc61128 100644
--- a/tests/test_menus.py
+++ b/tests/test_menus.py
@@ -56,7 +56,7 @@ def test_menu_rows_align_descriptions_in_display_cells() -> None:
     from rich.cells import cell_len
 
     starts = {cell_len(r.title.plain[: r.title.plain.index(d)]) for r, d in
-              zip(rows, ["Restart it", "Second"])}
+              zip(rows, ["Restart it", "Second"], strict=True)}
     assert len(starts) == 1  # one shared description column
 
 
@@ -219,14 +219,14 @@ def test_marked_label_lines_up_a_mixed_list_when_told_its_lane() -> None:
         marked_label(_WIDE, "View archived contacts", "", lane=lane),
     ]
     starts = {cell_len(row.plain[: row.plain.index(word)])
-              for row, word in zip(rows, ("Purge", "View"))}
+              for row, word in zip(rows, ("Purge", "View"), strict=True)}
     assert starts == {lane + 1}
 
     # Without the lane each mark measures itself, which is right for a list whose rows all
     # lead with the same icon — and is exactly what misaligns a mixed one.
     solo = [marked_label(_NARROW, "A", "err"), marked_label(_WIDE, "B", "")]
     assert len({cell_len(row.plain[: row.plain.index(letter)])
-                for row, letter in zip(solo, ("A", "B"))}) == 2
+                for row, letter in zip(solo, ("A", "B"), strict=True)}) == 2
 
 
 def test_the_main_menu_starts_every_title_in_the_same_cell() -> None:
@@ -252,7 +252,7 @@ def test_the_main_menu_starts_every_title_in_the_same_cell() -> None:
     assert widths == {1, 2}, "a menu of one icon width would prove nothing"
     starts = {
         label.cell_len - cell_len(tool.title or tool.name)
-        for tool, label in zip(tools, labels)
+        for tool, label in zip(tools, labels, strict=True)
     }
     assert len(starts) == 1, "a title starts a column early"
 
diff --git a/tests/test_pathgraph.py b/tests/test_pathgraph.py
index 63d83b2..e4f3654 100644
--- a/tests/test_pathgraph.py
+++ b/tests/test_pathgraph.py
@@ -3,6 +3,7 @@
 from __future__ import annotations
 
 import re
+from itertools import pairwise
 
 import pytest
 
@@ -197,7 +198,7 @@ def test_revisited_path_folds_into_a_cycle_that_piles_its_relays() -> None:
     hops = ("7f", "c1", "8e", "da", "ee", "c1", "27")
     seq = (SRC_NODE, *hops, DST_NODE)
     ordered = list(dict.fromkeys(seq))
-    x = _balanced_x(ordered, set(zip(seq, seq[1:])))
+    x = _balanced_x(ordered, set(pairwise(seq)))
     # Evenly spread, these eight nodes would sit 1/7 apart and the four loop members would
     # span three of those gaps; folded, the whole loop fits inside a single one.
     loop = [x[node] for node in ("c1", "8e", "da", "ee")]
@@ -217,12 +218,12 @@ def test_allow_duplicate_nodes_keeps_x_strictly_rising_along_the_walk() -> None:
     [layer] = _split_revisits([PathLayer(hops, WHITE, 3)])
     seq = (SRC_NODE, *layer.hops, DST_NODE)
     ordered = list(dict.fromkeys(seq))
-    x = _balanced_x(ordered, set(zip(seq, seq[1:])))
+    x = _balanced_x(ordered, set(pairwise(seq)))
     walked = [x[node] for node in seq]
     assert walked == sorted(walked) and len(set(walked)) == len(walked)
     assert x[SRC_NODE] == 0.0 and x[DST_NODE] == 1.0
     # A single walk with nothing else to balance against spreads dead evenly end to end.
-    gaps = [b - a for a, b in zip(walked, walked[1:])]
+    gaps = [b - a for a, b in pairwise(walked)]
     assert max(gaps) - min(gaps) < 1e-9
 
 
@@ -390,7 +391,7 @@ def _packed_lanes(layers, width=60, max_rows=15):  # noqa: ANN001
             if node not in seen:
                 seen.add(node)
                 ordered.append(node)
-        edges.update(zip(seq, seq[1:]))
+        edges.update(pairwise(seq))
     xfrac = _balanced_x(ordered, edges)
     best = max(range(len(drawn)), key=lambda j: drawn[j].priority)
     owner: dict[str, int] = {}
@@ -632,7 +633,7 @@ def _vias_for(layers, width=60, max_rows=15):  # noqa: ANN001
             if node not in seen:
                 seen.add(node)
                 ordered.append(node)
-        edges.update(zip(seq, seq[1:]))
+        edges.update(pairwise(seq))
     xfrac = _balanced_x(ordered, edges)
     best = max(range(len(drawn)), key=lambda j: drawn[j].priority)
     owner: dict[str, int] = {}
@@ -774,7 +775,7 @@ def test_bidir_pair_does_not_jam_a_sibling_relay_against_the_origin() -> None:
     ]
     seqs = [(SRC_NODE, *layer.hops, DST_NODE) for layer in layers]
     ordered = list(dict.fromkeys(n for seq in seqs for n in seq))
-    edges = {pair for seq in seqs for pair in zip(seq, seq[1:])}
+    edges = {pair for seq in seqs for pair in pairwise(seq)}
     x = _balanced_x(ordered, edges)
     assert x[SRC_NODE] == 0.0 and x[DST_NODE] == 1.0
     assert x["cc"] == pytest.approx(1 / 3)  # its natural spot, not jammed toward 0
diff --git a/tests/test_pathline.py b/tests/test_pathline.py
index 814cc64..a3020df 100644
--- a/tests/test_pathline.py
+++ b/tests/test_pathline.py
@@ -57,7 +57,7 @@ def _char_styles(text) -> list[tuple[str, str]]:  # noqa: ANN001
     for span in text.spans:
         for i in range(span.start, span.end):
             styles[i] = str(span.style)
-    return list(zip(text.plain, styles))
+    return list(zip(text.plain, styles, strict=True))
 
 
 def test_plain_mode_matches_the_app_wide_arrow_presentation() -> None:
diff --git a/tests/test_timemachine.py b/tests/test_timemachine.py
index 44f3caa..7288d62 100644
--- a/tests/test_timemachine.py
+++ b/tests/test_timemachine.py
@@ -8,6 +8,7 @@ from __future__ import annotations
 
 import re
 from datetime import timedelta
+from itertools import pairwise
 from pathlib import Path
 from types import SimpleNamespace
 
@@ -344,7 +345,7 @@ def test_day_columns_widths_differ_by_at_most_one_dot_and_interleave() -> None:
     notches = [i for i, c in enumerate(cols) if c is GAP]  # one per day boundary
     assert len(notches) == 12
     edges = [-1, *notches, len(cols)]  # each bar runs between two notches
-    widths = [b - a - 1 for a, b in zip(edges, edges[1:])]
+    widths = [b - a - 1 for a, b in pairwise(edges)]
     assert len(widths) == 13 and set(widths) == {3, 4}
     first_wide = widths.index(4)
     last_wide = len(widths) - 1 - widths[::-1].index(4)
diff --git a/tests/test_tui.py b/tests/test_tui.py
index acba2a2..68570ad 100644
--- a/tests/test_tui.py
+++ b/tests/test_tui.py
@@ -1241,7 +1241,7 @@ def test_device_picker_builds_aligned_columns(tmp_path) -> None:
     assert rows[-2].strip().endswith("Add a network device…")  # no caveat tag trailing it
     assert rows[-1].strip().endswith("Quit")
     device_rows = rows[:2]
-    assert all(port in row for port, row in zip(("COM5", "/dev/ttyUSB0"), device_rows))
+    assert all(port in row for port, row in zip(("COM5", "/dev/ttyUSB0"), device_rows, strict=True))
     assert device_rows[0].index("COM5") == device_rows[1].index("/dev/ttyUSB0")
 
 
@@ -2765,7 +2765,7 @@ def test_the_rows_a_dialog_does_not_reach_come_back_unchanged() -> None:
     session.push(ButtonDialog("Sure?", [("Cancel", 0), ("Yes", 1)]))
     second = session._plain_frame().split("\n")
 
-    unchanged = sum(1 for a, b in zip(first, second) if a == b)
+    unchanged = sum(1 for a, b in zip(first, second, strict=True) if a == b)
     assert unchanged >= 10, "the box should only rewrite the rows it covers"
 
 
diff --git a/tests/test_walk.py b/tests/test_walk.py
index 9f8bfac..7cc0269 100644
--- a/tests/test_walk.py
+++ b/tests/test_walk.py
@@ -135,7 +135,7 @@ def test_walk_graph_labels_names_in_full_when_the_canvas_has_room() -> None:
     ]
     topo = MeshTopology(US, contacts=long_names)
     when = utcnow()
-    for c, snr in zip(long_names, (8.0, 1.0)):
+    for c, snr in zip(long_names, (8.0, 1.0), strict=True):
         topo.add_walk([topo.self_id, topo.canonical(c.public_key)], snrs=[snr], when=when,
                       source="trace")
     screen = WalkScreen(
diff --git a/tests/test_watchtower.py b/tests/test_watchtower.py
index 879a9e4..28c6f06 100644
--- a/tests/test_watchtower.py
+++ b/tests/test_watchtower.py
@@ -238,7 +238,8 @@ def test_alert_row_hues_the_label_by_resolved_key(tmp_path: Path) -> None:
     from meshterm.ui.theme import name_style
     from meshterm.ui.watchtower_screen import _alert_lanes
 
-    key_of = lambda label: "d4" * 6 if label == "Roof" else None
+    def key_of(label):
+        return "d4" * 6 if label == "Roof" else None
     alert = Alert(ident=1, when=utcnow(), kind="silence", label="Roof", message="quiet")
     row = _alert_lanes(alert, key_of)
     at = row.plain.index("Roof")
@@ -261,8 +262,10 @@ def test_alert_row_leads_node_name_with_type_glyph(tmp_path: Path) -> None:
     from meshterm.ui.watchtower_screen import _alert_lanes
     from meshterm.ui.widgets import _DEFAULT_GLYPH, _NODE_GLYPHS
 
-    key_of = lambda label: None
-    type_of = lambda label: 2 if label == "Roof" else None  # Roof advertises as a repeater
+    def key_of(label):
+        return None
+    def type_of(label):
+        return 2 if label == "Roof" else None  # Roof advertises as a repeater
     glyph, glyph_style = _NODE_GLYPHS[2]
 
     alert = Alert(ident=1, when=utcnow(), kind="silence", label="Roof", message="quiet")