[priyam0k]

Summary of Changes

• Initialize origin and development on Triangle via TriangleAxis descriptors (axis 2 and 3), centralizing axis storage into Triangle._axes alongside index and columns (incorporates [FEAT] Centralize axis descriptors #1454).
• Move _set_origin, _get_origin, _set_development, and _get_development helpers to chainladder.core.axis.
• Deprecate odims (Deprecate odims #1012) and ddims (Deprecate ddims #1013) on Triangle with FutureWarning shims pointing to origin and development.
• Update internal usage across core modules, estimators, adjustments, and tails to prevent internal deprecation warnings.
• Preserve legacy pickle compatibility in Triangle.__setstate__ to migrate legacy pickled instances cleanly.
• Add test coverage for 4-axis descriptor validation, edge cases, deprecation warnings, and pickle round-trips.

Related GitHub Issue(s)

Closes #1012, closes #1013, closes #1053 , #1454, refs #601, refs #1216, refs #1466

Additional Context for Reviewers

• Existing code reading or setting odims and ddims continues to work with deprecation warnings for backward compatibility.
• Incorporates the centralized axis descriptor work previously staged in [FEAT] Centralize axis descriptors #1454 so all four dimensions (0..3) follow the TriangleAxis pattern established in feat(core): deprecate vdims (#1011) and kdims (#1010) #1303.

Checklist

• I passed tests locally for both code (uv run pytest) and documentation changes (uv run --directory docs jb build . --builder=custom --custom-builder=doctest)

---

Note

Medium Risk
Wide refactor of how all four Triangle axes are stored and accessed touches core slicing, I/O, and every estimator; public origin/development should be compatible but direct odims/ddims use will warn and pickle migration paths add regression surface.

Overview
Refactors Triangle origin/development to match the existing index/columns axis pattern: raw timestamps/lags live in _axes as _odims/_ddims, while origin and development are public TriangleAxis descriptors with get/set logic moved to chainladder.core.axis.

odims and ddims are deprecated (FutureWarning) but remain as thin shims; library code now uses _odims/_ddims internally so estimators and core paths do not warn. Slicing, concat, arithmetic broadcasting, and _get_axis_value were updated accordingly; axis number resolution is centralized via utility_functions / typing re-exports.

Legacy pickle __setstate__ migrates odims/ddims (and redundant _axes keys) into the unified _axes store. DevelopmentConstant pattern detection is tightened so DataFrames with origin/development columns are not mistaken for Triangles.

Tests cover descriptor behavior, deprecation, pickle round-trips, valuation-triangle errors for bootstrap/incremental additive, and assorted estimator edge cases.

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[codecov]

Codecov Report

❌ Patch coverage is 97.77778% with 6 lines in your changes missing coverage. Please review.
✅ Project coverage is 94.74%. Comparing base (67dea50) to head (a9066cf).

Files with missing lines	Patch %	Lines
chainladder/core/triangle.py	95.45%	2 Missing and 2 partials ⚠️
chainladder/core/axis.py	94.73%	0 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1304      +/-   ##
==========================================
+ Coverage   94.35%   94.74%   +0.38%     
==========================================
  Files          97       97              
  Lines        6183     6274      +91     
  Branches      796      811      +15     
==========================================
+ Hits         5834     5944     +110     
+ Misses        225      208      -17     
+ Partials      124      122       -2     

Flag	Coverage Δ
unittests	94.74% <97.77%> (+0.38%)	⬆️

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[github-actions]

Pyright Type Completeness

View the full pyright --verifytypes output for this commit

Project (full chainladder package, at this PR's head): 15.7% of exported symbols fully typed (241 / 1532)

	Known	Ambiguous	Unknown	Total
Project (head)	241	106	1185	1532

Other symbols referenced but not exported by chainladder: 13

	Known	Ambiguous	Unknown	Total
Other (head)	3	1	9	13

Symbols without documentation:

• Functions without docstring: 348
• Functions without default param: 0
• Classes without docstring: 8

Patch (exported symbols added or changed by this PR): 12.5% fully typed (2 / 16)

	Known	Ambiguous	Unknown	Total
Patch	2	0	14	16

Patch symbol details

Symbol	Status	Change
chainladder.adjustments.tests.test_bootstrap.test_bootstrap_odp_val_triangle_error	❌ unknown	new
chainladder.core.tests.test_triangle.test_centralized_axis_edge_cases	❌ unknown	new
chainladder.core.tests.test_triangle.test_ddims_deprecation_warning	❌ unknown	new
chainladder.core.tests.test_triangle.test_odims_deprecation_warning	❌ unknown	new
chainladder.core.tests.test_triangle.test_set_axis	❌ unknown	new
chainladder.core.triangle.Triangle.ddims	❌ unknown	changed (was ✅ known)
chainladder.core.triangle.Triangle.development	✅ known	changed (was ❌ unknown)
chainladder.core.triangle.Triangle.odims	❌ unknown	changed (was ✅ known)
chainladder.core.triangle.Triangle.origin	✅ known	changed (was ❌ unknown)
chainladder.development.tests.test_constant.test_constant_dataframe_with_origin_development_columns	❌ unknown	new
chainladder.development.tests.test_constant.test_constant_incr_cumulative_none	❌ unknown	new
chainladder.development.tests.test_incremental.test_incremental_additive_val_triangle_error	❌ unknown	new
chainladder.development.tests.test_munich.test_munich_properties	❌ unknown	new
chainladder.methods.tests.test_predict.test_predict_age_exceeds_model	❌ unknown	new
chainladder.tails.tests.test_constant.test_constant_attachment_age	❌ unknown	new
chainladder.tails.tests.test_exponential.test_tail_curve_attachment_age	❌ unknown	new

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[genedan]

I wasn't sure if this was ready for review, so I figure I'd chime in just in case. Let's follow the general strategy we took in #1303:

• _ddims will become develoment and be initialized via TriangleAxis
• _odims will become origin and be initialized via TriangleAxis

[priyam0k]

I wasn't sure if this was ready for review, so I figure I'd chime in just in case. Let's follow the general strategy we took in #1303:

• _ddims will become develoment and be initialized via TriangleAxis
• _odims will become origin and be initialized via TriangleAxis

Folded the descriptor commits into this branch per your note. origin and development are now wired through TriangleAxis (axis 2 and 3) with _set_origin and _set_development in axis.py, and _axes stores all four dimensions (0..3).

Since bringing the descriptors and call-site updates together touches around 40 files, we can either review it in one go to get the full dimension stack in, or split it up if you'd rather review in smaller chunks.

[genedan]

I can review it one go, let's get the ddims and odims replaced with development and origin, respectively.

[priyam0k]

I can review it one go, let's get the ddims and odims replaced with development and origin, respectively.

Works for me. The swap to origin and development is in place, so all set for review.