BUG: fix Monte Carlo release blockers

CHANGELOG.md

@@ -32,6 +32,7 @@ Attention: The newest changes should be on top -->
 
 ### Added
 
+- ENH: Accept `random_seed` in `MonteCarlo.simulate_convergence`, including across batches. [#1198](https://github.com/RocketPy-Team/RocketPy/pull/1198) [#1209](https://github.com/RocketPy-Team/RocketPy/issues/1209)
 - ENH: Reproducible Monte Carlo seeding, and an append that continues the same study [#1187](https://github.com/RocketPy-Team/RocketPy/pull/1187) [#1053](https://github.com/RocketPy-Team/RocketPy/issues/1053) [#1075](https://github.com/RocketPy-Team/RocketPy/issues/1075)
 - ENH: 3-DOF single rail button flight phase (tip-off analysis), enabled with the opt-in `Flight(use_udot_rail2=True)`. Between the upper rail button leaving the rail and the lower one following it, the rocket pivots about the lower button under a solved constraint wrench instead of jumping straight to free 6-DOF flight. The window is reported as `between_rails_time`, `between_rails_velocity` and `tip_off_duration`, printed by `Flight.info()` and shaded in the attitude plots. Requires `simulation_mode="6 DOF"` and `equations_of_motion="standard"`. [#920](https://github.com/RocketPy-Team/RocketPy/pull/920)
 - ENH: Support fixed-time parachute deployment triggers [#1133](https://github.com/RocketPy-Team/RocketPy/pull/1133) [#437](https://github.com/RocketPy-Team/RocketPy/issues/437)
@@ -50,7 +51,7 @@ Attention: The newest changes should be on top -->
 
 ### Changed
 
-- ENH: Number the simulations of a serial Monte Carlo run from zero, as the parallel path already did — the two used to name the same simulation `1, 2, 3` and `0, 1, 2`. The `index` field written into the inputs and outputs rows shifts by one for serial runs, so code reading indices off those files has to expect a run of `n` simulations to be numbered `0` to `n - 1`. An append onto a study written before this release is refused rather than continued, since its rows do not record which root drew them. [#1187](https://github.com/RocketPy-Team/RocketPy/pull/1187)
+- ENH: Number new Monte Carlo runs from zero in both execution modes, as the parallel path already did; serial runs used `1..n`, so their `index` shifts by one. Every simulation is now reseeded from one study `random_seed` (a non-negative integer), so individual object seeds are ignored and fixed-seed results from v1.13 change. New input rows record that `seed`; metadata is kept out of results, statistics and plots. Legacy checkpoints keep their numbering when extended, with a warning that their original draws cannot be reproduced. [#1187](https://github.com/RocketPy-Team/RocketPy/pull/1187) [#1209](https://github.com/RocketPy-Team/RocketPy/issues/1209)
 - ENH: Compute the rocket static margin lazily [#1135](https://github.com/RocketPy-Team/RocketPy/pull/1135) [#780](https://github.com/RocketPy-Team/RocketPy/issues/780)
 - DOC: Tighten the comments that came with the sampler seed groups [#1154](https://github.com/RocketPy-Team/RocketPy/pull/1154)
 - CI: make the Gemini PR reviewer actually review [#1140](https://github.com/RocketPy-Team/RocketPy/pull/1140)
@@ -61,6 +62,7 @@ Attention: The newest changes should be on top -->
 
 ### Fixed
 
+- BUG: Keep checkpoint metadata out of Monte Carlo plots and statistics, recover missing simulation indices without repeating completed flights, and warn when appending v1.13 logs. Preserve explicit initial flight states, `terminate_on_apogee`, `use_udot_rail2` and solid-motor grain bonding in stochastic models. [#1209](https://github.com/RocketPy-Team/RocketPy/issues/1209)
 - BUG: A `Flight` continued from another `Flight` object now records `t_initial`, so a rocket carrying sensors or controllers no longer raises `AttributeError` on that path. [#920](https://github.com/RocketPy-Team/RocketPy/pull/920)
 - BUG: Correct the gravity sign an `Accelerometer` applies when `consider_gravity=True`. The gravitational field was added to the inertial acceleration instead of subtracted from it, so the sensor reported the negative of the proper acceleration along the vertical: one at rest read -g rather than +g. Recorded accelerometer data taken with `consider_gravity=True` changes sign in that term. [#1175](https://github.com/RocketPy-Team/RocketPy/pull/1175)
 - BUG: Report a Monte Carlo worker that fails instead of hanging or passing for a finished run [#1182](https://github.com/RocketPy-Team/RocketPy/pull/1182)
@@ -84,7 +86,7 @@ Attention: The newest changes should be on top -->
 - BUG: Restore the UTC fallback without timezonefinder [#1143](https://github.com/RocketPy-Team/RocketPy/pull/1143)
 - BUG: Pick between the candidate values of a list input with the stochastic model's own seeded generator. `random.choice` was used, which draws from the interpreter-wide stream that `_set_stochastic` does not reseed, so a fixed seed did not reproduce the values chosen from a list, and Monte Carlo workers forked from one process walked a single shared stream instead of sampling independently. Fixed-seed baselines that vary a list input change. [#953](https://github.com/RocketPy-Team/RocketPy/issues/953)
 - BUG: Report the atmospheric model time period and ensemble member count for lower-case model types. `set_atmospheric_model` documents `type` as case-insensitive, but `Environment.info()` and `all_info()` compared against capitalised literals, so `type="ensemble"` printed no time period and no member count, and skipped the ensemble comparison plot. [#520](https://github.com/RocketPy-Team/RocketPy/issues/520)
-- BUG: Give each `CustomSampler` input its own deterministic stream, and seed samplers sharing one generator once as a group. Existing fixed-seed `CustomSampler` baselines change, and samplers built on the legacy `RandomState` must move to `default_rng` because seeds now carry the full 128 bits. [#1102](https://github.com/RocketPy-Team/RocketPy/pull/1102)
+- BUG: Give each `CustomSampler` input its own deterministic stream, and seed samplers sharing one generator once as a group. Reset callbacks receive a 32-bit integer compatible with both `RandomState` and `default_rng`; existing fixed-seed baselines change. [#1102](https://github.com/RocketPy-Team/RocketPy/pull/1102) [#1209](https://github.com/RocketPy-Team/RocketPy/issues/1209)
 - BUG: Accept the callable parachute triggers `StochasticParachute` documents, and reject the ones it cannot mean. An invalid string, an empty list or a boolean now fails during validation instead of reaching `Parachute` or becoming a one-metre height trigger. [#1103](https://github.com/RocketPy-Team/RocketPy/pull/1103)
 - BUG: Accept a deterministic aerodynamic surface in `StochasticRocket.add_nose`, `add_trapezoidal_fins`, `add_elliptical_fins` and `add_tail`. Each wrapped the surface with a `component=` keyword none of the stochastic classes accept, so passing anything other than an already-stochastic surface raised a `TypeError`. [#953](https://github.com/RocketPy-Team/RocketPy/issues/953)
 - BUG: rocket with a late-starting thrust curve never leaves the rail [#1085](https://github.com/RocketPy-Team/RocketPy/pull/1085)

docs/user/stochastic.rst

@@ -316,11 +316,9 @@ on equal values, and a specification with no spread always will.
 The reset is what builds the tree, not ``add_parachute`` or ``add_nose``. A
 rocket resets itself once while being constructed, when it has no components
 yet, so anything attached afterwards keeps the generator it was built with until
-something resets it again. A serial ``MonteCarlo`` run does not reset it at
-all. A parallel one tries to, once per worker, but hands the model a
-``SeedSequence`` where an integer is wanted, so that path does not get as far
-as building the tree either. Resetting per simulation, from an integer seed the
-caller chooses, is what the Monte Carlo seeding work adds.
+something resets it again. ``MonteCarlo`` resets the tree before every
+simulation in both serial and parallel runs, using the study seed and the
+simulation index to derive independent streams.
 
 Each collection is spawned separately, so adding an aerodynamic surface does not
 move what the parachutes draw. Within a collection the stream follows insertion
@@ -348,10 +346,12 @@ draws under a fixed seed. The rocket's own inputs, such as ``mass`` and
     split over any number of workers, and whether it was reached first or last.
     A run of ``n`` simulations numbers them 0 to ``n - 1`` either way, which is
     what makes one index name one simulation.
-    Every input row records the root it came from, so appending carries that
+    Every input row records one integer ``seed``, so appending carries that
     study on whether or not the seed is given again, and a different one is
-    refused rather than mixed in. Without a seed a run draws fresh entropy and
-    reproduces nothing.
+    refused rather than mixed in. Without a seed, a new run generates and prints
+    one. Pass that integer as ``random_seed`` to reproduce the study. Seeds on
+    individual stochastic models are overridden; a new study without
+    ``random_seed`` warns when these models have already been seeded.
 
     An index fixes the draw, not the object it is drawn around. Where the note
     above says a value follows its deterministic object, moving that object
@@ -360,6 +360,25 @@ draws under a fixed seed. The rocket's own inputs, such as ``mass`` and
     rather than from the generator it is handed sits outside all of this, as
     :ref:`custom_sampler` warns.
 
+    ``simulate_convergence(random_seed=...)`` uses the same study seed for every
+    batch. Changing the batch size does not change the inputs of a given index.
+
+Resuming a study
+----------------
+
+Use ``simulate(number_of_simulations=100, append=True)`` to reach a total of
+100 simulations. A completed index is kept; missing indices below the target
+are simulated, including gaps left by interrupted parallel workers. Keep the
+input and output logs together: they are checked for matching indices and
+duplicate records before any new rows are written. The study's models must
+still describe the same rocket, flight and environment.
+
+Logs from v1.13 have no study seed. Appending preserves their rows and emits a
+warning: the old random stream cannot be recovered. New rows record the reported
+seed. Existing one-based serial numbering is preserved; new studies start at
+zero. Checkpoint fields (``index``, ``seed`` and the earlier ``run_root`` field)
+are excluded from ``results``, summary statistics and plots.
+
 Conclusion
 ----------