Retire next-work item 1: the gap question is answered from the chain

The button latch is SET by lid-open or the SoC lock and RESET by the
button only; the charge-pump watchdog feeds HV_ENABLE, not the latch.
A kernel-run gap inside an armed job drops HV_ENABLE and leaves the
latch alone, and the next run has HV_ENABLE back before its first step.
No keepalive.

laser.emission-witness carries a G4 P2 between the second and third
sides of its square and checks cnc/button_latch clear in every armed
sample, HV_ENABLE dropped across the dwell and back with emission after
it; the operator confirms all four sides.

BRINGUP: item 1 removed, items 2 to 21 are now 1 to 20, the five
cross-references follow, the flow-band sentence is in the facts bank.
CAMPAIGN-LOG: the answer, the retired item, and the unattended set run
green on the hot-deployed board (campaign c-20260831151846).

docs/BRINGUP.md

@@ -355,7 +355,7 @@ factory 2.6.0-2228 session; measured numbers in the facts bank).
   alike: the retrace is sized to `cnc/max_backtrack` and the lead follows it,
   so a pause with little history behind it shortens both rather than failing.
   GRBL mode uses feed hold / cycle start, so a resumed GRBL cut picks up where
-  the deceleration ended (item 16). A pause is not a cancel: the latch
+  the deceleration ended (item 15). A pause is not a cancel: the latch
   stays unlocked and the window open across it. There is no resume dwell: the
   safing chain re-arms ~216 ms before the first step (facts bank).
 - **`lid_policy = hold`** selects stock grblHAL door behavior instead (park in
@@ -958,7 +958,10 @@ is committed.
   coolant thermistor conversion is the factory B-equation recovered from the
   v2.6.0 binary — derivation in `kernel-module-glowforge/UAPI.md`; the old
   UAPI "best guess" linear formula was 3–5 °C high and everything derived from
-  it had to be re-derived.
+  it had to be re-derived. The flow check's bands hold from 19 to 27 C, the
+  loop heater's ceiling in a 20 C room, with the margin widening warm; above
+  that only a running tube warms the loop, and the check takes the tube's
+  share off.
 - **The four `pic/lid_ir_*` channels are first of all a photometer for the lid
   lamp.** Measured against `lid_led` (sysfs brightness, 0 to 1023): all four
   channels follow it as a straight line, 2 counts dark, 32 to 35 at 128, 54 to
@@ -1096,13 +1099,7 @@ is committed.
 
 Open items only. Anything closed is in `CAMPAIGN-LOG.md`.
 
-1. **Laser commissioning leftovers.** Verify the hardware button latch persists
+1. **Low-temperature gates and warm-up (planned).** Two keys in the Cooling
-   across kernel-run gaps mid-job (if OK_2_FIRE drops between motion bursts, the
-   fix is a stream keepalive across armed gaps). The flow check's bands
-   hold from 19 to 27 C, the loop heater's ceiling in a 20 C room, with the
-   margin widening warm; above that only a running tube warms the loop,
-   and the check takes the tube's share off.
-2. **Low-temperature gates and warm-up (planned).** Two keys in the Cooling
    card: `cool_temp_min` (hard floor, default ~5 °C, a fire gate) and
    `cool_temp_start` (warm-up gate, default ~16 °C) — a job starting below the
    gate holds in a factory-style warm-up phase with the loop heater on and
@@ -1111,7 +1108,7 @@ Open items only. Anything closed is in `CAMPAIGN-LOG.md`.
    coolant. Sequencing: warm-up first, flow check after. Measured physics on
    this bench: 50 % duty warms the bulk ~0.5–0.8 °C/min and plateaus ~8–9 °C
    above ambient — the same unaided limit the factory has.
-3. **TEC handling (planned).** `thermal/tec_on` is a bare on/off output with no
+2. **TEC handling (planned).** `thermal/tec_on` is a bare on/off output with no
    readback, so presence cannot be detected: it becomes a `tec_present` user
    setting (Machine tab, default off; ForgeFIRM never drives `tec_on` unless
    set), which also covers retrofits. Operation when present: simple hysteresis
@@ -1123,7 +1120,7 @@ Open items only. Anything closed is in `CAMPAIGN-LOG.md`.
    all is a spec-level claim (Glowforge ships it on the Pro; Basic/Plus use the
    same passive closed-loop cooling), not teardown-verified per unit — another
    reason it is a setting.
-4. **Fire watch (lid IR) redesign.** The gate stays disabled
+3. **Fire watch (lid IR) redesign.** The gate stays disabled
    (`cool_fire_ir_delta = 0`) until it is lamp-aware: the engine must own or
    observe the lamp level (suspend the watch and re-baseline for a few ticks
    after any `lid_led` change) and the threshold must be relative to the
@@ -1146,11 +1143,11 @@ Open items only. Anything closed is in `CAMPAIGN-LOG.md`.
    cloud job carries. By decision those header thresholds (`IR??`) are the
    prior for this redesign and nothing else: the cloud client declares them
    ignored, and the watch stays disabled until it is lamp-aware.
-5. **Limit-switch homing.** The planned second homing method (`$22` stays 0
+4. **Limit-switch homing.** The planned second homing method (`$22` stays 0
    until it lands); printable brackets are in `3d-models/`. Also: calibrate
    `gfcloud_home_x/y` against a jog to a known reference if the factory corner
    offset matters.
-6. **Cameras.** **First light on an 8 MP (OV8856) machine**: the
+5. **Cameras.** **First light on an 8 MP (OV8856) machine**: the
    whole path is written but nothing has run on one, and only that hardware can
    answer whether the 2-lane RAW8 full-resolution mode locks the D-PHY at
    720 Mbps/lane and what exposure/gain the sensor wants; the details, the
@@ -1165,7 +1162,7 @@ Open items only. Anything closed is in `CAMPAIGN-LOG.md`.
    no register file. No shipped machine applies a per-unit shading table,
    so ForgeFIRM owes none. Finally the deferred emulator
    homing-image smoke, now that the emulator can be pointed at live snapshots.
-7. **Cloud mode.** A print is no longer capped by the ring: the client holds
+6. **Cloud mode.** A print is no longer capped by the ring: the client holds
    the compressed body, fills the ring before the button, and tops it up as it
    plays, with the body bounded by `pulse_reject_threshold_bytes` because
    memory is what that costs. A feed that wedges is caught by progress rather
@@ -1207,7 +1204,7 @@ Open items only. Anything closed is in `CAMPAIGN-LOG.md`.
    the cancel-with-a-rejected-`settings`-action case, a malformed frame
    (needs a MITM), a body past the memory guard (the service has no such job
    to send), and a wedged feed (a healthy machine will not stall on request).
-8. **Shared machine services — remaining polish.** None of it blocking:
+7. **Shared machine services — remaining polish.** None of it blocking:
    - **Diagnostics as engine modes.** The flow tools still drive the thermal
      hardware themselves while the engine suspends its writes; the check
      parameters are already shared (`cool.h`), so what remains is folding the
@@ -1223,26 +1220,26 @@ Open items only. Anything closed is in `CAMPAIGN-LOG.md`.
      `ensure_engine` `popen()`s should move out of the HTTP callback so a slow
      media-ctl cannot stall the request thread. Changing the MHD start flags
      touches the streaming model, so this wants a bench slot of its own.
-9. **Physical-evidence negatives still open.** A present head answering I²C
+8. **Physical-evidence negatives still open.** A present head answering I²C
    badly (the K-11 runtime case) and a failed head capture leaving the measure
    laser off — both need the head connected and a fault injected. Opportunistic:
    `STATE_FAULT` recovery via `enable` the next time a DRV8825 fault line
    actually trips.
-10. **Debug-kernel checks.** Module load/unload under `CONFIG_DEBUG_MUTEXES`
+9. **Debug-kernel checks.** Module load/unload under `CONFIG_DEBUG_MUTEXES`
     and a forced `-EPROBE_DEFER` unwind still need a debug kernel build. Both
     drills cycle what the rail policy avoids: a module unload powers the 40 V
     rail off (a stepper driver can come out of the power-up unserviceable),
     and a forced defer needs the 40 V regulator or the SDMA device unbound
     under the module's probe. This is a bench slot with the rail-cycle gamble
     accepted, not a quick check.
-11. **Wi-Fi SDIO CRC watch.** The uSDHC pads now carry the factory-exact values
+10. **Wi-Fi SDIO CRC watch.** The uSDHC pads now carry the factory-exact values
     and ship in every image. Watch `dmesg | grep -c "sdio .* failed"` across
     sessions (baseline: 1 event in 49 min of uptime). Effect if one lands
     mid-job: a 1–2 s sender stall — a cut-quality nuisance, never a safety
     matter. Only if it still recurs, cap the bus with
     `max-frequency = <25000000>` on `&usdhc1` (halves Wi-Fi throughput — last
     resort; the factory ran 50 MHz on these pads).
-12. **Release acceptance follow-through.** The campaign is the release gate
+11. **Release acceptance follow-through.** The campaign is the release gate
     and runs as designed: dev image `20260824230512`, 45 of 45 from nothing,
     36 of them unattended with the bench actuator in the loop, release
     authorized (the export is on the board at `/data/forgetest/export/`).
@@ -1256,16 +1253,16 @@ Open items only. Anything closed is in `CAMPAIGN-LOG.md`.
     changes off the offline tests (a gfutilities refactor, not a map).
     Tools that genuinely need a second host (LAN flood, remote auth probes)
     stay host-side by design, and the registry marks them so. The first
-    release is item 13.
+    release is item 12.
-13. **Publish.** The first release: `releases/v<version>/acceptance.json`
+12. **Publish.** The first release: `releases/v<version>/acceptance.json`
     from the authorized export, `scripts/release.sh`, the kas flip and the
     first GitHub release, per the site (Developers, "Release flow"), once
     ready to publish. Repoint the core submodule to
     upstream if the `step_us_min` sizing fix merges.
-14. **Update system Phase 5 — recovery refresh.** The remaining phase of
+13. **Update system Phase 5 — recovery refresh.** The remaining phase of
     `docs/UPDATE-SYSTEM.md` (a refreshed recovery image in boot0); Phases 0–4
     are done.
-15. **Head-IRQ source validation — beam-emission hypothesis (exploratory, not
+14. **Head-IRQ source validation — beam-emission hypothesis (exploratory, not
     gating).** The EV_SW `head` bit (GPIO3_22, factory pad HEAD_IRQ) is the head
     MCU's attention line — idle LOW with a healthy head, pulsing on head reboot,
     floating to the SoC pull-up with no head — so the raw level is not a
@@ -1281,7 +1278,7 @@ Open items only. Anything closed is in `CAMPAIGN-LOG.md`.
     log EV_SW head-bit edges plus `head/beam_detect_digital|_analog` while
     firing.
 
-16. **Gapless pause and resume in GRBL mode (planned).** A pause leaves a mark
+15. **Gapless pause and resume in GRBL mode (planned).** A pause leaves a mark
     in the cut. With laser mode on, the core stops the beam at the start of the
     hold (`disable_laser_during_hold`, on by default), so the head travels the
     whole deceleration dark, and the resume re-accelerates from a standstill at
@@ -1315,7 +1312,7 @@ Open items only. Anything closed is in `CAMPAIGN-LOG.md`.
     line does to it, and how it composes with the armed window's disarm grace
     across a long hold.
 
-17. **Head crash and rail-contact detector (planned).** The head
+16. **Head crash and rail-contact detector (planned).** The head
     accelerometer is the motion-liveness probe and nothing more; the
     factory runs two tiers off the same sensor (a per-axis alert that
     pauses, a per-axis abort), and its thresholds arrive in every pulse
@@ -1327,7 +1324,7 @@ Open items only. Anything closed is in `CAMPAIGN-LOG.md`.
     are established. A pause on contact, on the factory's shape, would be
     the first use.
 
-18. **A sender change while a job runs: discussion.** Today a sender that
+17. **A sender change while a job runs: discussion.** Today a sender that
     disconnects mid-job leaves the motion running to the end of what the
     controller holds, with the window closed and fire suppressed (the
     consent belonged to the displaced session), so the job finishes dark
@@ -1344,9 +1341,9 @@ Open items only. Anything closed is in `CAMPAIGN-LOG.md`.
     a hold parks the head over hot material with the assist air on the run
     profile, and the grace then closes the window in Hold as it does today;
     running on leaves a clean stop position but wastes the piece. Decide
-    with the gapless pause and resume item (16), which owns the resume
+    with the gapless pause and resume item (15), which owns the resume
     mechanics.
-19. **The flow check while the tube is lit.** The arm-time heater check
+18. **The flow check while the tube is lit.** The arm-time heater check
     starts at the session open, so with a prompt press the tube is lit
     for most of its window, and a lit CW window adds about 1.5 C to the
     rise (0.5 C at 45 % density) against a 1.6 C margin; on top of that the
@@ -1379,7 +1376,7 @@ Open items only. Anything closed is in `CAMPAIGN-LOG.md`.
     remains; a scope on the two sensor lines during a cut is the next
     instrument. It sits inside the ceiling's 2 C hysteresis and the flow
     check reads means, so it is a measurement item, not a gate item.
-20. **Laser power-good: what the line means.** `cnc/laser_pgood` and its
+19. **Laser power-good: what the line means.** `cnc/laser_pgood` and its
     sampled count are defined in the UAPI (active low, one sample every
     ~3.9 ms), the facts bank records that the sampled count reads 0 through
     real cutting, and the cooling engine warns
@@ -1391,7 +1388,7 @@ Open items only. Anything closed is in `CAMPAIGN-LOG.md`.
     scope against `hv_current` through an armed cut, its meaning written
     into the facts bank and the UAPI, and then either a warning that means
     something or no warning.
-21. **Initial commissioning: measure and set the machine's own numbers
+20. **Initial commissioning: measure and set the machine's own numbers
     methodically.** Every tunable that was measured on the bench machine
     and shipped as a default varies from machine to machine: the flow
     check's bands and `cool_flow_rise`, the tube's heat coefficients
@@ -1427,7 +1424,7 @@ covers the warm-up hold), the supply temperature window (the service sends
 the whole ADC range and the factory binds it to nothing; the supply is
 watched per job instead), the head, lid, interconnect and fused temperature
 ceilings (no sensor at those locations; the chassis is watched per job), the
-head accelerometer thresholds (item 17), the lid IR thresholds (item 4), the
+head accelerometer thresholds (item 16), the lid IR thresholds (item 3), the
 HV current caps (the sampled emission witness covers the idle case, and HV
 current is ranged per job), the thermal report upload conditions and the
-pump flag. Beam detect stays with item 15.
+pump flag. Beam detect stays with item 14.

docs/CAMPAIGN-LOG.md

@@ -4726,6 +4726,55 @@ does not carry, and the 5 MP driver has no way to take one. BRINGUP
 item 6 now says so, and the factory-slot session it asked for is not
 needed.
 
+## 2026-08-31: the mid-job gap question, answered from the chain
+
+Item 1 asked whether the hardware button latch persists across a
+kernel-run gap inside an armed job, with a stream keepalive as the fix if
+it did not. The safing chain answers it (`docs/SAFETY.md` section 2): the
+button latch is U23 latch 1, SET by lid-open OR the SoC lock (U32) and
+RESET by the physical button only. The charge-pump watchdog feeds
+HV_ENABLE, not the latch. A gap (a `G4` dwell, a hold, the end of a cycle
+before the next) drops HV_ENABLE 454 ms after the last pump pulse and
+leaves the latch as it was, while the driver keeps the SoC lock released
+through the armed window; on the next run HV_ENABLE is back within ~3 ms,
+~216 ms before the first step (the pads measurement of 2026-08-15). A
+planner starve is not a gap: the stream pads the ring dark and the run
+keeps playing. A keepalive would hold HV_ENABLE up while nothing is cut,
+the one state the watchdog exists to prevent, so none is built.
+
+The one thing never watched on the bench, the latch readback through a
+lit-dwell-lit sequence, rides `laser.emission-witness` from now on: the
+square carries a `G4 P2` between its second and third sides, the sampler
+reads `cnc/button_latch` and `switches.hv_enable`, and the test checks
+the latch clear in every armed sample, HV_ENABLE dropped across the
+dwell and back with emission after it, and the operator confirms all
+four sides. It runs with the attended set. Item 1 is retired; its
+flow-band sentence is a fact and moved to the facts bank ("Cooling
+operating point").
+
+## 2026-08-31: the unattended set on the hot-deployed board
+
+The first unattended run of the day (campaign c-20260831143855) stopped
+on `cooling.aa-offset-calibrate`, the test's first campaign run ever,
+queued right after `cooling.flow-verify`: the loop was still mixing
+after the no-flow trial (19.6 C rise, the sensors 13.5 C apart), the
+tool's fixed 6 s settle let the trend into its first edge (+44.7 and
++20.6 counts against 13 to 18 on the settled edges), and its spread
+check refused the result (35.5 counts against a limit of 8). Fix: the
+tool waits at the flow tools' stationary gate before its first edge
+(forgectrl 7dbb5e1) and the test gives it 540 s (forgefirm eb8935c).
+
+By operator decision the fix went onto the board without an image:
+the pinned forgectrl built by bitbake (md5 7e1f28cc) and the suite
+file installed over ssh on dev 20260831141210, forgectrl and forgetest
+restarted. The test then passed alone (offset 15.0 counts, spread 6.0,
+edges 12.2 to 18.2), and the unattended queue of 20 ran green behind it
+in campaign c-20260831151846 (21 PASS, the 17 other unattended tests
+inherited from the morning run, one ABORTED record from a page start
+before the fix was in). The attended set is deferred by decision. The
+campaign that authorizes a release runs on the image that carries every
+fix, burned once.
+
 ## Superseded status notes
 
 ### Shared machine services — remaining polish, as listed 2026-08-13
@@ -6247,6 +6296,19 @@ stay as decided there.
     `MAGIC_SYSRQ`: no runtime cost unused, root-only exposure, and root can
     load modules anyway).
 
+### Laser commissioning leftovers (item 1), retired 2026-08-31
+
+Closed: the gap question is answered from the safing chain (the entry
+above); the confirmation rides `laser.emission-witness`; the flow-band
+sentence is in the facts bank. Items 2 to 21 are now 1 to 20.
+
+1. **Laser commissioning leftovers.** Verify the hardware button latch persists
+   across kernel-run gaps mid-job (if OK_2_FIRE drops between motion bursts, the
+   fix is a stream keepalive across armed gaps). The flow check's bands
+   hold from 19 to 27 C, the loop heater's ceiling in a 20 C room, with the
+   margin widening warm; above that only a running tube warms the loop,
+   and the check takes the tube's share off.
+
 ## Reference notes
 
 ### Head-IRQ source validation — the beam-emission hypothesis

forgetest/forgetest/suite/laser.py

@@ -95,6 +95,8 @@ def sample(ctx):
         "beam": hw.sysfs_int("head/beam_detect_analog"),
         "beam_d": hw.sysfs_int("head/beam_detect_digital"),
         "button_lit": hw.button_lit(),
+        "hv_enable": (st.get("switches") or {}).get("hv_enable"),
+        "button_latch": hw.sysfs_int("cnc/button_latch"),
     }
 
 
@@ -347,14 +349,19 @@ def power_floor(ctx):
       actions=["button"],
       steps=["Scrap under the head with 20 mm of free +X and +Y travel; lid closed; exhaust on.",
              "Press the physical button when it lights white (the arm).",
-             "At the end, confirm the square the laser marked: the one judgment by eye in the "
+             "At the end, confirm the square the laser marked, all four sides: the one judgment "
-             "campaign, the calibration of the sensor witnesses."],
+             "by eye in the campaign, the calibration of the sensor witnesses."],
-      description="A 20 mm square outline at S400/F600 in dynamic laser mode: emission_samples "
+      description="A 20 mm square outline at S400/F600 in dynamic laser mode with a 2 s dwell "
-                  "(the kernel's LASER_ON sample count) goes nonzero during the fire window and "
+                  "(G4) between its second and third sides: emission_samples (the kernel's "
-                  "returns to 0 at Idle, HV current rises during the burn, the head's beam "
+                  "LASER_ON sample count) goes nonzero during the fire window and returns to 0 "
-                  "detector sees the beam, the armed window is observed, the M2 program end "
+                  "at Idle, HV current rises during the burn, the head's beam detector sees the "
-                  "disarms promptly at Idle (job-based, not the 60 s idle grace) and the button "
+                  "beam, the armed window is observed, the M2 program end disarms promptly at "
-                  "goes dark. The operator confirms the mark.")
+                  "Idle (job-based, not the 60 s idle grace) and the button goes dark. Across "
+                  "the dwell the kernel run ends and restarts: HV_ENABLE drops with the "
+                  "charge-pump watchdog and is back for the third side, while the hardware "
+                  "button latch stays clear (cnc/button_latch 0 in every armed sample), so the "
+                  "second half of the square marks without a second press. The operator "
+                  "confirms all four sides.")
 def emission_witness(ctx):
     ev = ctx.evidence
     with ctx.grbl() as g, LiveJob(ctx, g):
@@ -367,7 +374,7 @@ def emission_witness(ctx):
         ctx.check(not base["emission"], "emission_samples nonzero before the job (%s)", base["emission"])
         ctx.ready(ARM_CUE % "20 mm +X and +Y")
         job = ["G91", "G21", "M4", "S400",
-               "G1 X20 F600", "G1 Y20 F600", "G1 X-20 F600", "G1 Y-20 F600",
+               "G1 X20 F600", "G1 Y20 F600", "G4 P2", "G1 X-20 F600", "G1 Y-20 F600",
                "M5", "G90", "M2"]
         ctx.arm_press()
         try:
@@ -391,6 +398,21 @@ def emission_witness(ctx):
                    "pgood_peak": max((s["pgood"] for s in samples if s["pgood"] is not None), default=None)})
         ctx.log("emission_samples peak=%s end=%s; hv %s..%s; lid_ir peak %s; armed seen %s",
                 peak, end, ev["hv_min"], ev["hv_max"], ir_peak, armed_seen)
+        # The dwell: a kernel-run gap inside the armed window. The button
+        # latch has no input from the charge-pump watchdog (its SET inputs
+        # are the lid and the SoC lock), so it must read clear through the
+        # gap, while HV_ENABLE drops with the watchdog and returns for the
+        # third side.
+        latch_armed = [s["button_latch"] for s in samples if s["armed"] and s["button_latch"] is not None]
+        first_fire = next((i for i, s in enumerate(samples) if s["emission"]), None)
+        hv_en = [s["hv_enable"] for s in samples[first_fire:]] if first_fire is not None else []
+        dip = next((i for i, v in enumerate(hv_en) if v is False), None)
+        back_lit = dip is not None and any(
+            s["hv_enable"] and s["emission"] for s in samples[first_fire + dip:])
+        ev.update({"button_latch_armed_max": max(latch_armed) if latch_armed else None,
+                   "hv_enable_dipped": dip is not None, "hv_enable_back_lit": back_lit})
+        ctx.log("dwell gap: button latch through the armed window max=%s; HV_ENABLE dipped=%s, "
+                "back with emission after it=%s", ev["button_latch_armed_max"], dip is not None, back_lit)
         # X-3: job-based disarm at Idle after M2
         dt = wait_disarm(ctx, 75)
         ev["disarm_after_idle_s"] = round(dt, 1) if dt is not None else None
@@ -403,9 +425,14 @@ def emission_witness(ctx):
     ctx.check(dt is not None and dt < 10.0,
               "the M2 job did not disarm promptly at Idle (%s s; the idle grace is ~60 s)",
               ev["disarm_after_idle_s"])
+    ctx.check(latch_armed and max(latch_armed) == 0,
+              "the hardware button latch read SET inside the armed window (max %s over %d samples)",
+              ev["button_latch_armed_max"], len(latch_armed))
+    ctx.check(ev["hv_enable_dipped"], "HV_ENABLE never dropped across the 2 s dwell (the kernel run did not end)")
+    ctx.check(back_lit, "HV_ENABLE did not return with emission after the dwell (the third side ran dark)")
     judge_beam(ctx, beam)
     check_button_dark(ctx, ev)
-    ctx.confirm("Did the laser mark a 20 mm square outline on the scrap?")
+    ctx.confirm("Did the laser mark a 20 mm square outline on the scrap, all four sides?")
     ctx.log("PASS: emission peak %s -> 0, HV %s..%s, beam +%s, disarmed %.1f s after Idle, button "
             "dark, mark confirmed", peak, ev["hv_min"], ev["hv_max"], beam["delta"], dt)