Enforce the file-length rule and delete its empty baseline

changelog_entry.yaml

@@ -16,6 +16,7 @@
       - Ran Stage 12 US national simulations as 20 region-group calls each, and built an independent, immutable Stage 12 cache of three annual US datasets and 60 current-law baselines before each deployment, publishing it only after a recorded determinism check and recording its release in the v2 version manifest under a new key, while the existing key keeps a copy that earlier readers accept
       - Made the budget refuse a household count outside its country's plausible range (above 200 million in the US or 60 million in the UK, negative or not finite), raising ImplausibleEntityCountError instead of publishing a count like #767's
     changed:
+      - Enforced the file-length rule sim.quality.python-file-length, now that every tracked Python file is within its limit: its empty baseline and its downgrade section are gone, and its tier is metric rather than mechanical, because it measures a number against a threshold, with the at-the-limit and one-over fixtures as its below and above proof
       - Moved the entrypoint's backend calls, response telemetry and comparison dispatch out of app.py (925 lines, now 583) into entry_runtime.py, which app.py re-exports and which still logs under the policyengine_simulation_entry.app logger; the routes stay in app.py, so FastAPI and ruff read their annotations as before; the 2,251-line deployment asset test file is split into seven test files and a support module named test_deployment_assets_support.py, the rules registry names each moved test by its new file, and its guard-test discovery now covers tests/test_deployment_assets*.py
       - Moved the worker's credential setup, request year and policy parsing, and region resolution out of simulation_runtime.py (1,111 lines, now 651) into gcp_credentials.py, request_policy.py and region_resolution.py; simulation_runtime.py keeps dataset selection and loading, simulation building, local-area breakdowns and the run itself, which tests replace by name there, and re-exports the moved names, so every caller still imports them from simulation_runtime; the shared helpers _parse_year, _normalise_policy, _compile_interval_policy, _runtime_policy (now wrapper_policy), _resolve_region, _resolve_dataset_reference and _require_local_area_breakdown are now public, and the credential messages still log under the simulation_runtime logger; the 3,048-line output builder test file is split into seven test files and a module of shared fakes, all named test_simulation_output_*.py so the weighted-frame rule still checks them
       - Split the artifact precompute (precompute.py, 931 lines) and the Stage 12 cache precompute (stage12_cache/precompute.py, 844 lines) each into planning, dataset-building and baseline modules, with the manifest and run_precompute left in the original module, which re-exports every public name, so the Modal precompute apps and their tests import from the same paths; the cache precompute's _scoped_planned_simulation and _baseline_identity are now public, and the worker validation imports scoped_planned_simulation from its new module; the 1,835-line precompute test file is split into four, and the cache precompute tests patch each name in the module whose code reads it

docs/engineering/skills/file-length.md

@@ -17,17 +17,14 @@ complexity, branch, statement and argument rules each measure one function, so
 a module can keep growing while every function in it passes. A long module
 usually holds several responsibilities, and is hard to review.
 
-## The baseline
+## No exceptions
 
-While the rule is ratcheted, `rules/baselines/python-file-length.txt` lists the
-files that were already over their limit when the rule was added. The guard
-fails on a file over its limit that the baseline doesn't list, and on a listed
-file that is now within its limit or no longer tracked. The pull request that
-splits a listed file therefore removes its entry and lowers the rule's baseline
-`count`.
+The rule is enforced: every tracked Python file is within its limit, and there
+is no baseline of tolerated files. A file that grows past its limit fails the
+`quality-guards` job, so split it in the same pull request.
 
-Never add an entry, or move a file out of the rule's scope: that weakens the
-rule, which only a person may decide (see
+Never add a baseline or an exception, or move a file out of the rule's scope:
+that weakens the rule, which only a person may decide (see
 [the registry's baselines](rules-registry.md#baselines)). Split the file
 instead.
 

docs/generated/rules.md

@@ -8,8 +8,8 @@ Every rule that governs `policyengine-sim-api` is listed here with how it is enf
 
 | Tier | enforced | ratcheted | advisory | doc-only | Total |
 | --- | ---: | ---: | ---: | ---: | ---: |
-| mechanical | 53 | 3 | 0 | 14 | 70 |
-| metric | 0 | 0 | 0 | 0 | 0 |
+| mechanical | 53 | 2 | 0 | 14 | 69 |
+| metric | 1 | 0 | 0 | 0 | 1 |
 | judgment | 0 | 0 | 0 | 0 | 0 |
 
 **Blocking:** 56 of 70 rules.
@@ -66,7 +66,6 @@ Every rule that governs `policyengine-sim-api` is listed here with how it is enf
 
 - `sim.ci.multiline-run-is-script`: 13 remaining in `rules/baselines/ci-multiline-run.txt`
 - `sim.microdata.weight-stripping-confined`: 0 remaining in `rules/baselines/sim-microdata-weight-stripping.txt`
-- `sim.quality.python-file-length`: 0 remaining in `rules/baselines/python-file-length.txt`
 
 ### Exceptions and review dates
 
@@ -312,7 +311,7 @@ flowchart LR
 | `sim.quality.pyright-executor` | The simulation executor has no Pyright errors, checked with the pinned Pyright version in the executor's own locked environment. | mechanical | enforced | yes | pyright in `projects/policyengine-simulation-executor` | `pr.yml:pyright` | yes |
 | `sim.quality.pyright-gateway` | The simulation gateway has no Pyright errors, checked with the pinned Pyright version in the gateway's own locked environment. | mechanical | enforced | yes | pyright in `projects/policyengine-simulation-gateway` | `pr.yml:pyright` | yes |
 | `sim.quality.pyright-libraries-and-entry` | The contract, observability, Stage 12 persistence and fastapi libraries and the simulation entry have no Pyright errors, checked with the pinned Pyright version in each package's own locked environment. | mechanical | enforced | yes | pyright in `libs/policyengine-simulation-contract`, `libs/policyengine-simulation-observability`, `libs/policyengine-stage12-persistence`, `libs/policyengine-fastapi`, `projects/policyengine-simulation-entry` | `pr.yml:pyright` | yes |
-| `sim.quality.python-file-length` | No tracked Python file has more than 800 lines, or more than 1,500 lines if it is test code: a file under a tests or fixtures directory, or a conftest.py. | mechanical | ratcheted | yes | quality guard `file-length` | `pr.yml:quality-guards` | yes |
+| `sim.quality.python-file-length` | No tracked Python file has more than 800 lines, or more than 1,500 lines if it is test code: a file under a tests or fixtures directory, or a conftest.py. | metric | enforced | yes | quality guard `file-length` | `pr.yml:quality-guards` | yes |
 | `sim.quality.ruff-format-src` | Source code under projects/*/src and libs/*/src is formatted with ruff format. | mechanical | enforced | yes | ruff format | `pr.yml:lint` | — |
 | `sim.quality.ruff-format-tests` | Test code is formatted with ruff format too; CI currently checks only src directories. | mechanical | doc-only | no | nothing | — | — |
 | `sim.quality.ruff-lint` | All Python code passes ruff check with every ruff rule selected (ALL), with no ratchet, except the ignores in ruff.toml: COM812 and ISC001, which conflict with ruff format, and D203 and D213, which conflict with the kept D211 and D212. | mechanical | enforced | yes | ruff check (ALL) | `pr.yml:lint` | — |
@@ -345,7 +344,7 @@ flowchart LR
   e_pyright_in_projects_policyengine_simulation_gateway["pyright in projects/policyengine-simulation-gateway"]
   r_sim_quality_pyright_libraries_and_entry("sim.quality.pyright-libraries-and-entry (enforced)")
   e_pyright_in_libs_policyengine_simulation_contract__libs_policyengine_simulation_observability__libs_policyengine_stage12_persistence__libs_policyengine_fastapi__projects_policyengine_simulation_entry["pyright in libs/policyengine-simulation-contract, libs/policyengine-simulation-observability, libs/policyengine-stage12-persistence, libs/policyengine-fastapi, projects/policyengine-simulation-entry"]
-  r_sim_quality_python_file_length("sim.quality.python-file-length (ratcheted)")
+  r_sim_quality_python_file_length("sim.quality.python-file-length (enforced)")
   e_quality_guard_file_length["quality guard file-length"]
   r_sim_quality_ruff_format_src("sim.quality.ruff-format-src (enforced)")
   e_ruff_format["ruff format"]

rules/registry.toml

@@ -1178,8 +1178,8 @@ category = "quality"
 statement = "No tracked Python file has more than 800 lines, or more than 1,500 lines if it is test code: a file under a tests or fixtures directory, or a conftest.py."
 rationale = "docs/engineering/skills/file-length.md#the-rule"
 scope = ["**/*.py"]
-tier = "mechanical"
-status = "ratcheted"
+tier = "metric"
+status = "enforced"
 autofix = false
 [rule.enforcer]
 kind = "quality-guard"
@@ -1188,19 +1188,16 @@ name = "file-length"
 workflow = ".github/workflows/pr.yml"
 job = "quality-guards"
 invocation = "run_quality_guards.py"
-[rule.baseline]
-file = "rules/baselines/python-file-length.txt"
-count = 0
 [rule.proof]
-bad_fixture = "rules/fixtures/sim.quality.python-file-length/bad_files.toml"
-good_fixture = "rules/fixtures/sim.quality.python-file-length/good_files.toml"
+# Files at their limit (below) pass, and files one line over it (above) fail.
+below_fixture = "rules/fixtures/sim.quality.python-file-length/good_files.toml"
+above_fixture = "rules/fixtures/sim.quality.python-file-length/bad_files.toml"
+# The source limit; both fixtures also cover the 1,500-line limit for test code.
+threshold = 800
 test = "scripts/rules/tests/test_file_length.py::TestFileLengthProof::test_rule_proof_python_file_length"
 workflow = ".github/workflows/pr.yml"
 job = "quality-guards"
 invocation = "unittest discover -s scripts/rules/tests"
-[rule.downgrade]
-reason = "Authorized by Anthony (anth-volk) on 2026-10-27: the rule starts ratcheted with the 14 files that were over their limit on main when it was added, and the pull requests stacked on #920 split them and shrink the baseline to empty."
-issue = 921
 
 # --- Dependency locking -----------------------------------------------------