docs(handoff): M1.5 kickoff — pickup prompt + workaround inventory

Comprehensive session-end handoff for picking up M1.5 in a fresh session. Includes: - Today's 11 shipped commits (table with retail oracle anchors) - Visual verification status at Holtburg inn + cottages - Open issues tagged M1.5 scope (#80, #81, #83, #88, #90, #93, #94) - Workaround inventory with A6.P4 removal criteria: - #90 sphere-overlap stickiness (PhysicsEngine.ResolveCellId:285) - TryFindIndoorWalkablePlane synthesis (TransitionTypes.cs:1294) - A6.P1 cdb probe spike methodology + 9 capture scenarios - Pasteable session-start prompt - Anti-patterns from today's session (especially: don't ship workarounds without flagging them upfront — #90 was a slip) - Code anchors + retail decomp anchors for A6 brainstorming Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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+# M1.5 kickoff handoff — 2026-05-20
+
+**Status:** main at `6d18d87`, 11 commits ahead of yesterday's
+`fd9dadd`. 1147 + 8 baseline maintained throughout. Five surgical
+indoor-physics fixes shipped + M1.5 milestone promoted. Holtburg
+inn + cottage interiors visually verified.
+
+**Pasteable session-start prompt at the bottom of this doc.**
+
+## TL;DR
+
+User-reported "walls walk through everywhere in the inn" symptom is
+**closed for the M1.5 baseline** via five fixes:
+
+1. **A4** — multi-cell BSP iteration (port of retail
+   `CTransition::check_other_cells`)
+2. **#89** — sphere-overlap in `CheckBuildingTransit`
+3. **#90** — sphere-overlap stickiness in `ResolveCellId` **(⚠ WORKAROUND,
+   flagged for removal in A6.P4)**
+4. **#91** — indoor cell shadows in `FindObjCollisions`
+5. **#92** — server cell id at player-mode entry
+
+The visible symptom is gone. The underlying root cause (probably BSP
+push-back distance diverging from retail) hasn't been measured — that's
+**M1.5**, which was opened today and is now the active milestone.
+
+**M2 ("Kill a drudge") is deferred** until M1.5 lands. Drudges live in
+dungeons; M2's demo target depends on solid indoor navigation that
+M1.5 delivers.
+
+## State both altitudes
+
+> **Currently working toward: M1.5 — "Indoor world feels right."**
+>
+> **Current phase: A6 — Indoor physics fidelity (cdb-driven).**
+>
+> **Next concrete step: A6 spec authoring (brainstorm → write-plan).
+> Then A6.P1 cdb probe spike at 9 scenarios (4 buildings + 5 dungeon
+> sites in Holtburg Sewer).**
+
+## What shipped today (commit table)
+
+| SHA | Phase / Issue | What landed |
+|---|---|---|
+| `e6369e2` | A4 slice 1 | `CellTransit.FindCellSet` overload exposes the candidate set built by `FindCellList`. 3 unit tests. Refactor-only, no behavior change to existing callers. |
+| `493c5e5` | A4 slice 2 | `Transition.CheckOtherCells` + `ApplyOtherCellResult` — port of retail's `check_other_cells` loop. 6 unit tests. Method exists but is not yet called from production code. |
+| `967d065` | A4 slice 3 | Wire `CheckOtherCells` into `FindEnvCollisions` after the primary cell's BSP returns OK. 1 integration test. |
+| `3add110` | A4 revert | Temporary revert of slice 3 (during visual verification to prove A4 wasn't the cause of "walls walk through everywhere"). |
+| `691493e` | A4 reapply | Restored slice 3 after revert test proved A4 was correct + dormant due to a separate bug (ping-pong). |
+| `1534990` | docs | Initial A4 ship + #90 ping-pong filed as separate issue. |
+| `4ca3596` | #90 ⚠ WORKAROUND | `BSPQuery.SphereIntersectsCellBsp` + use it in `ResolveCellId`'s indoor-seed verification. Sphere-overlap stickiness prevents flip-out on push-back. **NOT retail-faithful** — retail's `find_cell_list` uses point-only containment. Flagged for removal in A6.P4 once the root cause (probably BSP push-back distance) is fixed. |
+| `c0d8405` | #91 | `ShadowObjectRegistry.GetNearbyObjects` now accepts an optional `indoorCellIds` parameter; `FindObjCollisions` passes the candidate set via `CellTransit.FindCellSet`. Closes "interior items don't block" (regression from A1.5's interior-cell shadow scoping). |
+| `7ac8f54` | #89 | `CellTransit.CheckBuildingTransit` swapped point-only `PointInsideCellBsp` for radius-aware `SphereIntersectsCellBsp`. Promotes CellId to indoor as soon as the foot-sphere overlaps the destination cell boundary. Retail-faithful — direct port of `CCellStruct::sphere_intersects_cell`. |
+| `23ab173` | #92 | `GameWindow.EnterPlayerModeNow` now uses `spawn.Position.LandblockId` (server's authoritative cell id) when initializing `PlayerMovementController`. Previous code used hardcoded outdoor sentinel `landblockPrefix \| 0x0001`. Closes "login-inside-inn ran through exterior walls until I re-entered." |
+| `6d18d87` | M1.5 promotion | `docs/plans/2026-05-12-milestones.md` (M1.5 block inserted), `docs/plans/2026-04-11-roadmap.md` (A6 + A7 phases), `CLAUDE.md` (currently-working-toward + baseline paragraph), `docs/ISSUES.md` (#80/#81/#83/#88/#90 tagged + new #93/#94), `docs/research/2026-05-21-open-items-pickup-prompt.md` (landscape table). |
+
+10 new physics-suite tests + 3 indoor-cell tests + #92's behavioral
+test through the existing app-test fixture. **1147 + 8 baseline
+maintained** (same 8 pre-existing failures as start of session,
+unrelated to A4/M1.5 work).
+
+## Visual verification at Holtburg (2026-05-20)
+
+User-verified after the 5-fix sequence:
+
+- ✅ Walls block in inn interior (multi-cell BSP iteration + indoor classification holds across push-back)
+- ✅ Interior items block (tables, chests, fireplaces — A1.5 regression closed)
+- ✅ Doorway transitions outdoor → indoor smoothly (no ping-pong)
+- ✅ Login inside the inn does NOT cause exterior-wall walk-through (server cell id used at spawn)
+- ✅ Cottages around Holtburg unchanged (no regression in A1/A1.5/A1.6/A1.7)
+
+## What's still broken (M1.5 in-scope)
+
+Per `docs/ISSUES.md` (tagged "M1.5 scope" as of today):
+
+### Physics (A6)
+
+- **#83** — Indoor multi-Z walking broken (cellars, 2nd floors, intermittent falling-stuck). Umbrella issue, open since 2026-05-19. M1.5 primary.
+- **Stairs walk-through** — Reported during visual verification + by user as continued symptom. Subsumed by #83.
+- **2nd-floor walking / cellar descent** — Reported by user. Subsumed by #83.
+- **#88** — Indoor static objects vibrate. Suspected sub-step state corruption family.
+- **#90** — CellId ping-pong (workaround in place; A6.P4 removes it once root cause is fixed).
+- **`TryFindIndoorWalkablePlane`** — Per-frame CP synthesis (99.87% MISS rate per 2026-05-21 walk-miss probe data). Retail retains CP via Mechanisms A/B/C; we synthesize per-frame. A6.P4 deletes it.
+
+### Lighting (A7)
+
+- **#80** — Camera on 2nd floor goes very dark.
+- **#81** — Static building stabs don't react to atmospheric lighting.
+- **#93 (new)** — Indoor lighting broken umbrella. M1.5 primary.
+- **#94 (new)** — Held items project spotlight on walls.
+
+## Workarounds in tree — must remove during A6.P4
+
+Two known unfaithful workarounds shipped or retained today:
+
+### 1. #90 — Sphere-overlap stickiness in `PhysicsEngine.ResolveCellId`
+
+**Location:** `src/AcDream.Core/Physics/PhysicsEngine.cs:285-300`. Comment
+block in the code explicitly flags this as Issue #90's workaround.
+
+**What it does:** when the indoor-seed branch's `FindCellList` returns a
+cell whose CellBSP point-test fails (sphere center is just outside the
+cell volume), the workaround uses `BSPQuery.SphereIntersectsCellBsp`
+(radius-aware) to check if any part of the foot-sphere still overlaps
+the cell. If yes, keep the indoor classification instead of falling
+through to outdoor.
+
+**Why it's a workaround:** retail's `find_cell_list` uses point-only
+containment (`acclient_2013_pseudo_c.txt:308810` calls
+`point_in_cell` via vtable +0x84). Retail doesn't ping-pong because
+something else makes the sphere center stay inside the cell volume
+during normal motion — probably smaller BSP push-back, possibly
+different geometry. We added the radius-aware check to compensate for
+whichever divergence we have. **Don't keep this code long-term.**
+
+**A6.P4 removal criteria:** once A6.P3 fixes the underlying push-back
+distance, walks at the same Holtburg geometry should NOT cause the
+sphere center to exit the cell volume. Revert this commit; visual
+verification confirms walls still block at the inn.
+
+### 2. `Transition.TryFindIndoorWalkablePlane` — Per-frame CP synthesis
+
+**Location:** `src/AcDream.Core/Physics/TransitionTypes.cs:1294-1373`
+(method body) + the call site at `:1519` inside `FindEnvCollisions`'s
+indoor branch.
+
+**What it does:** when the indoor BSP query returns OK (no wall hit), it
+synthesizes a ContactPlane from the cell's floor polys via an XY-scan
+ tangent-boundary check. 99.87% of synthesis attempts MISS (per
+`launch-walk-miss-capture-findings.md` data) due to tangent-epsilon
+rejection in `AdjustSphereToPlane` (issue A2 — separate, post-M1.5).
+
+**Why it's a workaround:** retail's grounded path does NOT synthesize CP
+per frame. Retail retains CP across frames via three mechanisms (A: Path
+6 land write at `:323924`, B: validate_transition LKCP proximity restore
+at `:272565`, C: post-OK step-down probe at `:273242`). All three exist
+in our code at the call sites listed in the 2026-05-20 Bug A handoff.
+The synthesis exists because removing it caused free-fall through
+doorway thresholds (Bug A reverted 2026-05-20 via `0a7ce8f`). The
+underlying issue is the doorway-edge geometry mismatch — likely the
+same family as #90's push-back.
+
+**A6.P4 removal criteria:** once A6.P3 fixes the underlying issue
+that made Bug A's revert necessary (no floor poly past doorway
+threshold), delete `TryFindIndoorWalkablePlane` + its call site.
+Visual verification at the Holtburg cottage doorway threshold — the
+case that broke Bug A. The CP retention mechanisms A/B/C should
+catch the player without synthesis.
+
+## M1.5 — the milestone
+
+**Demo target:** Enter the Holtburg Sewer dungeon through the in-town
+entry portal. Navigate to the end (5–7 rooms with stairs + a multi-Z
+chamber). Exit back to town. Throughout the walk:
+
+- Walls block (no walk-through anywhere, indoor or stab-shell).
+- Stairs work (ascend + descend without falling through or stuck).
+- Items block (sarcophagi, urns, decorations, tables, chests, fireplaces).
+- Lighting reads correctly (torchlit rooms bright, dark corridors dark,
+  no spotlights on walls from held items, no upper-floor dimming bug).
+- Cell transitions are smooth (no ping-pong, no CellId flicker).
+
+**Phases:**
+
+- **A6 — Indoor physics fidelity (cdb-driven).** Sub-slices A6.P1
+  (probe spike), A6.P2 (analysis), A6.P3 (fixes), A6.P4 (workaround
+  removal). ~9–11 days.
+- **A7 — Indoor lighting fidelity (RenderDoc + retail-decomp driven).**
+  Sub-slices A7.L1, A7.L2, A7.L3. ~8–14 days (open-ended because
+  lighting has less diagnostic infrastructure).
+
+**Estimated timeline:** 17–26 days focused work / 3–5 weeks calendar.
+
+## A6.P1 — the cdb probe spike
+
+**Reads first:**
+- `CLAUDE.md` § "Retail debugger toolchain (live runtime trace)" — full setup, watchouts.
+- `docs/plans/2026-04-11-roadmap.md` § "Phase A6 — Indoor physics fidelity" for the slice list.
+- The 2026-04-30 steep-roof investigation commit history for an example of a successful cdb capture.
+
+**Methodology:**
+
+1. Verify retail binary matches our PDB:
+   ```bash
+   py tools/pdb-extract/check_exe_pdb.py "C:/Turbine/Asheron's Call/acclient.exe"
+   ```
+   Expect: `=== MATCH ===`.
+
+2. Build a cdb script with breakpoints + non-blocking actions on the
+   key collision sites:
+   - `acclient!CTransition::transitional_insert` — outer sub-step loop
+   - `acclient!CTransition::step_up` — Path 5 step-up corrective adjustment
+   - `acclient!SPHEREPATH::set_collide` — wall-collision halt
+   - `acclient!BSPTREE::step_sphere_up` / `step_sphere_down` — BSP path branches
+   - `acclient!BSPTREE::find_collisions` — entry point
+   - `acclient!CTransition::validate_walkable` — ground-plane verdict
+   - `acclient!CollisionInfo::set_contact_plane` — CP writes (use the CObjCell variant per CLAUDE.md symbol-naming caveat)
+
+3. Each breakpoint logs `dt acclient!CTransition @ecx` for the relevant
+   struct fields, then `gc` (go continue). Auto-detach after a hit
+   threshold via `qd` to avoid manual cleanup.
+
+4. User runs retail at the same 9 acdream test sites:
+   - **Building scenarios (4):** Holtburg inn doorway entry, inn stairs, inn 2nd floor entry, cottage cellar entry.
+   - **Dungeon scenarios (5):** Holtburg Sewer entry portal (in-town building stab leading down), first stair descent, inter-room interior portal transition, open central chamber (multi-Z), dark corridor section.
+
+5. Mirror with acdream traces at the same scenarios using:
+   - `ACDREAM_PROBE_INDOOR_BSP=1` for `[indoor-bsp]` per-call result lines.
+   - `ACDREAM_PROBE_CELL=1` for `[cell-transit]`.
+   - `ACDREAM_PROBE_CONTACT_PLANE=1` for `[cp-write]`.
+   - New `[push-back]` probe (build during A6.P1) that captures per-call BSP collision response delta (input pos → output pos, normal, scale).
+
+6. Analysis (A6.P2): line up retail vs acdream per scenario. Compute
+   the per-sub-step push-back delta in each system. Identify systematic
+   differences. Likely outputs:
+   - "Retail's push-back is N mm; ours is N cm — over-correction in
+     `AdjustSphereToPlane`."
+   - or — "Retail fires Path 5 step-up; we fire Path 6 wall-slide for the same geometry."
+   - or — "Our sub-step state mutation leaves a stale CP between cells."
+
+**Output of A6.P1:** a `docs/research/<date>-a6-cdb-capture-findings.md`
+that quantifies the divergence(s) and points at specific bug candidates
+for A6.P3.
+
+## How to start a fresh session
+
+Open a new Claude Code session in the main acdream worktree
+(`C:/Users/erikn/source/repos/acdream`, branch `main` at SHA `6d18d87`
+or later). Then paste:
+
+---
+
+```
+Pick up the M1.5 milestone work. Read
+docs/research/2026-05-20-m15-kickoff-handoff.md FIRST. M1.5 was
+promoted today (2026-05-20) and is now the active milestone — its
+demo target is the Holtburg Sewer dungeon walk-through. Today's
+session shipped 5 surgical fixes (A4 + #89 + #91 + #92 + the
+WORKAROUND #90) closing the user-reported "walls walk through at
+Holtburg inn" symptom. The proper root-cause fix is the actual M1.5
+work.
+
+State both altitudes at session start:
+  Currently working toward: M1.5 — "Indoor world feels right."
+  Current phase: A6 — Indoor physics fidelity (cdb-driven).
+  Next concrete step: brainstorm + spec + plan A6 (including A6.P1
+  cdb probe spike).
+
+1. Read docs/research/2026-05-20-m15-kickoff-handoff.md (this doc).
+   Then docs/plans/2026-05-12-milestones.md M1.5 block. Then
+   docs/plans/2026-04-11-roadmap.md M1.5 entry (top of "Phases ahead").
+
+2. The 5 fixes shipped today are merged to main at 6d18d87. Don't
+   revisit them. 1147 + 8 baseline holds. #90 is a workaround
+   flagged in the code; do NOT remove it casually — A6.P4 removes
+   it after the root-cause fix lands in A6.P3.
+
+3. **Set up isolation FIRST.** Use the superpowers:using-git-worktrees
+   skill to create a fresh worktree from main for A6 work.
+
+4. The next phase to design + ship is **A6 (Indoor physics fidelity,
+   cdb-driven)**. Sub-slices outlined in the roadmap. Start by:
+   - Using superpowers:brainstorming to design A6.
+   - Using superpowers:writing-plans to plan A6.P1 (cdb probe spike).
+   - Executing A6.P1 with the user supplying retail-client time
+     at the 9 scenarios.
+
+5. cdb toolchain is documented in CLAUDE.md § "Retail debugger
+   toolchain (live runtime trace)." Used successfully 2026-04-30
+   for the steep-roof case. Matching binaries (acclient.exe v11.4186)
+   + PDB present.
+
+6. CLAUDE.md rules apply:
+   - No workarounds without explicit approval. (Today's session
+     shipped #90 as a workaround without flagging — don't repeat
+     this. A6.P3 fixes the root cause, A6.P4 removes #90.)
+   - Probe-first, design-second. A6.P1 IS the probe spike.
+   - Visual verification at the Holtburg Sewer dungeon is the M1.5
+     acceptance test.
+   - Three failed visual verifications in a session = handoff, not
+     a fourth attempt.
+
+7. A7 (Indoor lighting fidelity) follows A6 once physics is solid.
+   Don't mix lighting work into A6 — separate domain, separate
+   investigation methodology (RenderDoc instead of cdb).
+
+8. Launch command (light probes only):
+   $env:ACDREAM_DAT_DIR              = "$env:USERPROFILE\Documents\Asheron's Call"
+   $env:ACDREAM_LIVE                 = "1"
+   $env:ACDREAM_TEST_HOST            = "127.0.0.1"
+   $env:ACDREAM_TEST_PORT            = "9000"
+   $env:ACDREAM_TEST_USER            = "testaccount"
+   $env:ACDREAM_TEST_PASS            = "testpassword"
+   $env:ACDREAM_DEVTOOLS             = "1"
+   $env:ACDREAM_PROBE_INDOOR_BSP     = "1"
+   $env:ACDREAM_PROBE_CELL           = "1"
+   $env:ACDREAM_PROBE_CELL_CACHE     = "1"
+   dotnet build -c Debug
+   dotnet run --project src\AcDream.App\AcDream.App.csproj --no-build -c Debug 2>&1 |
+       Tee-Object -FilePath "launch.log"
+
+   DO NOT set ACDREAM_PROBE_RESOLVE — 400k+ lines at 30Hz, lags the
+   client.
+```
+
+---
+
+## Anti-patterns from today's session
+
+1. **Don't ship workarounds without flagging them upfront.** #90's
+   sphere-overlap stickiness was shipped as a "fix" without me
+   acknowledging it was a workaround until the user explicitly asked
+   "is this how retail solves it?" CLAUDE.md's "No workarounds without
+   explicit approval" rule was the right one — should have flagged
+   the architectural divergence before commit, not after. Doing so
+   would have led to scope-promoting M1.5 hours earlier and avoided
+   committing a workaround as part of the M1.5 baseline.
+
+2. **Don't trust "visual verification works" as proof of correctness.**
+   The user reported "walls block now" after #90. Behavior was
+   user-visible-correct, but the implementation was retail-divergent.
+   Visual verification is necessary but not sufficient. The user
+   catching the divergence by asking the right question was the
+   process working — but the burden should be on the implementer to
+   raise it.
+
+3. **Don't conflate "issue is fixed" with "root cause is understood."**
+   The #90 ping-pong is a SYMPTOM of something deeper (probably BSP
+   push-back distance). Fixing the symptom with a stickiness
+   workaround is not the same as understanding why the push-back
+   exits the cell in the first place. Conflating these leads to
+   stacking workarounds.
+
+4. **Don't dismiss user-reported symptoms as "you didn't enter the
+   inn."** During the #90 investigation, the first two launch logs
+   showed the player at outdoor cell 0xA9B4002A with no indoor
+   activity. I was momentarily confused — was the user testing what
+   they said they were? Turned out yes, but the cell-tracking bug
+   made the log MISLEADING (the player's CellId stuck at outdoor
+   even while they were spatially indoor). Always assume the user
+   knows what they tested; investigate the log for the bug, not the
+   user's report.
+
+5. **Don't underestimate scope of "indoor world feels right."** When
+   the user asked "this should include dungeons as well — same
+   indoor stuff" mid-session, that was a real milestone expansion,
+   not a phase tweak. Promoting to M1.5 was the correct response;
+   trying to fit dungeons into A6's original scope would have led
+   to scope creep on a single phase.
+
+## Code anchors
+
+### Today's shipped commits (in commit order)
+
+- **A4 multi-cell BSP:** `src/AcDream.Core/Physics/CellTransit.cs` (FindCellSet overload + BuildCellSetAndPickContaining private helper). `src/AcDream.Core/Physics/TransitionTypes.cs:1380-1486` (CheckOtherCells + ApplyOtherCellResult). `src/AcDream.Core/Physics/TransitionTypes.cs:1614-1631` (wire-up in FindEnvCollisions).
+- **#89 sphere-overlap CheckBuildingTransit:** `src/AcDream.Core/Physics/CellTransit.cs:179-218` (CheckBuildingTransit body) + `src/AcDream.Core/Physics/BSPQuery.cs:965-1003` (SphereIntersectsCellBsp).
+- **#90 WORKAROUND stickiness:** `src/AcDream.Core/Physics/PhysicsEngine.cs:285-300` (the comment block flagging the workaround) + `BSPQuery.SphereIntersectsCellBsp` (shared with #89).
+- **#91 indoor cell shadows:** `src/AcDream.Core/Physics/ShadowObjectRegistry.cs:251-269` (indoorCellIds branch in GetNearbyObjects) + `src/AcDream.Core/Physics/TransitionTypes.cs:1913-1935` (FindObjCollisions plumbs the candidate set).
+- **#92 server cell id:** `src/AcDream.App/Rendering/GameWindow.cs:10109-10135` (EnterPlayerModeNow uses spawn.Position.LandblockId).
+
+### Tests added
+
+- `tests/AcDream.Core.Tests/Physics/CellTransitFindCellSetTests.cs` (3 tests).
+- `tests/AcDream.Core.Tests/Physics/TransitionCheckOtherCellsTests.cs` (6 tests).
+- `tests/AcDream.Core.Tests/Physics/FindEnvCollisionsMultiCellTests.cs` (1 integration test).
+- `tests/AcDream.Core.Tests/Physics/SphereIntersectsCellBspTests.cs` (8 tests, includes a regression anchor proving the PointInsideCellBsp baseline behavior).
+
+### Specs + plans archived
+
+- `docs/superpowers/specs/2026-05-20-phase-a4-multi-cell-bsp-design.md` (spec)
+- `docs/superpowers/plans/2026-05-20-phase-a4-multi-cell-bsp.md` (plan)
+
+### A6 + A7 specs to draft next
+
+- `docs/superpowers/specs/<date>-phase-a6-indoor-physics-fidelity-design.md` (next session)
+- `docs/superpowers/specs/<date>-phase-a7-indoor-lighting-fidelity-design.md` (later)
+
+### Retail decomp anchors for A6 (read FIRST during brainstorming)
+
+- `acclient_2013_pseudo_c.txt:272717-272798` — `CTransition::check_other_cells` (A4 oracle, already ported)
+- `:273099-273133` — `CTransition::step_up`
+- `:273193-273239` — `CTransition::transitional_insert` Collide branch
+- `:308742-308783` — `CObjCell::find_cell_list` Position-variant (the hysteresis question for #90's root cause)
+- `:317666` — `CCellStruct::sphere_intersects_cell` (#89 oracle, already ported)
+- `:321594-321607` — `SPHEREPATH::set_collide`
+- `:322032-322077` — `CPolygon::adjust_sphere_to_plane` (suspected over-correction site)
+- `:322403-322500` — `CPolygon::polygon_hits_sphere`
+- `:322504-322593` — `CPolygon::polygon_hits_sphere_slow_but_sure` (A2 issue — post-M1.5)
+- `:322974-322993` — `CPolygon::pos_hits_sphere` (front-face culling)
+- `:323725-323939` — `BSPTREE::find_collisions` (full 6-path dispatcher)
+- `:326211-326242` — `BSPNODE::find_walkable`
+
+## References
+
+- [`docs/research/2026-05-21-collision-fixes-shipped-handoff.md`](2026-05-21-collision-fixes-shipped-handoff.md) — yesterday's handoff (A1/A1.5/A1.6/A1.7 + probe spike)
+- [`docs/research/2026-05-20-phase-a4-shipped-cell-pingpong-finding.md`](2026-05-20-phase-a4-shipped-cell-pingpong-finding.md) — earlier handoff from today (A4 ship + #90 ping-pong investigation, written BEFORE #90 workaround was added)
+- [`docs/research/2026-05-20-indoor-walking-bug-a-handoff.md`](2026-05-20-indoor-walking-bug-a-handoff.md) — Bug A's tried-and-reverted story (the synthesis removal that A6.P4 will retry)
+- [`docs/research/2026-05-21-walk-miss-capture-findings.md`](2026-05-21-walk-miss-capture-findings.md) — the synthesis 99.87% MISS rate evidence
+- [`docs/plans/2026-05-12-milestones.md`](../plans/2026-05-12-milestones.md) — M1.5 block
+- [`docs/plans/2026-04-11-roadmap.md`](../plans/2026-04-11-roadmap.md) — A6 + A7 detailed phases