[simen-strand]

Description

External models inherit the pre_statements, post_statements and on_virtual_update from model_defaults, but they never run them, and they're built without the project's macros. If a default statement calls a project macro and you edit it, the plan tries to render the external models' copies and fails:

ConfigError: Failed to resolve macros for
@tag_query('v2')
Macro 'tag_query' does not exist.
 at '.../external_models.yaml'

This PR stops external models from inheriting those three defaults, the same way they already skip the default gateway. Statements set explicitly on an external model are kept. The docs now say the defaults don't apply to external models.

Upgrade impact

Projects whose model_defaults define statements will see a one-off change on their first plan after upgrading:

• Every external model shows as changed (non-breaking), and the models downstream of it as indirectly changed. No backfill is needed.
• Exception: if SQLMesh can't determine the columns of the external model or of any model downstream of it (e.g. SELECT * from an undeclared source), the default external: full auto-categorization makes the change breaking, and that external model's downstream models are backfilled. A forward-only plan, or external: semi, avoids that.

Projects without default statements are unaffected.

Alternatives considered

• If rendering fails, compare the unrendered statements of external models: fingerprints stay the same, so there's no upgrade impact. But external models keep statements that never run, and the fix relies on catching render errors.
• Pass the project's macros to external models: rendering works. But fingerprints still change, so the upgrade impact is the same, and external models still carry statements that never run.

Test Plan

• New unit test: external models no longer inherit the default statements, explicit ones are kept, and SQL models still inherit them.
• New context test, for pre- and post-statements: plan with @tag_query('v1'), change it to v2, plan again. It fails on main with the error above and passes here.
• Upgrade checked by applying state with main and planning with this branch. The results match the impact described above, and a forward-only plan needs no backfill.

Checklist

• I have run make style and fixed any issues
• I have added tests for my changes (if applicable)
• All existing tests pass (make fast-test)
• My commits are signed off (git commit -s) per the DCO

Summary by CodeRabbit

• Bug Fixes

  • External models no longer inherit project-level default pre-statements, post-statements, or virtual-update statements. Statements specified directly on an external model are preserved, and other models continue to receive the defaults.
  • Changes to project-level default statements no longer cause external models to be marked as modified; affected SQL models continue to be evaluated.

• Documentation

  • Clarified which models receive project-level statement defaults and how defaults combine with model-specific statements.

[coderabbitai]

No actionable comments were generated in the recent review.

Walkthrough

External models no longer inherit project-level pre_statements, post_statements, or on_virtual_update defaults. Explicitly supplied statements remain. Documentation and tests cover default inheritance and model modification tracking.

Changes: External model default statements

Layer / File(s)	Summary
Exclude inherited statement defaults sqlmesh/core/model/definition.py, docs/reference/model_configuration.md, tests/core/test_model.py	External models exclude inherited pre-statements, post-statements, and virtual-update defaults. Tests verify that explicit external-model statements remain and SQL models inherit the defaults.
Cover model modification tracking sqlmesh/migrations/v0103_exclude_default_statements_from_external_models.py, tests/core/test_context.py	The migration module adds no-op schema and row migration functions. Context tests check that changing statement defaults marks the SQL model as directly modified and that the external model has no inherited pre- or post-statements.

Estimated code review effort: 2 (Simple) | ~10 minutes

Change: Bug fix

Suggested reviewers: mday-io

Merge Risk: Low · up to 000c7

The first upgrade plan can trigger downstream backfills when columns are unknown. The change is mergeable with this upgrade impact noted for release guidance.

Security architecture risk: Low · up to 000c7

The change narrowly excludes inherited statements from external models while preserving explicit statements and ordinary model defaults. The main design risk is upgrade-time replanning: projects with unknown downstream schemas can receive breaking classifications and backfills. No introduced security finding was established.

Retained concerns
No architecture-level concerns identified.

Security review details

Security Blast Radius

• inferred — The supported propagation scope is an affected project's external-model dependency graph: inherited statement removal can cause downstream replanning and execution through existing backfill mechanisms. The inspected change does not add credentials, select a new gateway, or introduce a new execution authority.

Trust Boundaries and Controls

• observed — The external-model loader supplies project defaults separately from explicit YAML model fields. Filtering the defaults therefore preserves explicit model values rather than treating inherited statements as model-specific input. The public-entrypoint routing subjects are test-only code, including a nested writer operating in a temporary project.

Resilience and Maintainability Implications

• observed — Snapshot persistence and environment promotion retain existing transactional updates, environment locking, and plan-identity conflict checks. Apply is not globally atomic across physical execution and promotion, but the inspected PR does not introduce that limitation or change its control flow.

Pre-merge checks: 5

Check name	Status	Explanation
Title check		The title clearly and concisely describes the main change: preventing model_defaults statements from applying to external models.
Description check		The description includes the required Description, Test Plan, and Checklist sections. It explains the issue, implementation, upgrade impact, alternatives, tests, and completed checklist items.
Docstring Coverage		Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff with cyclomatic complexity of at least 2. Documentat…
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.

Full details: Docstring Coverage

Explanation

Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff with cyclomatic complexity of at least 2. Documentation-only edits and deletions within surviving functions are included; unchanged diff context and fully deleted functions are excluded. Analyzed 3 functions across 4 files.

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• Run ID: 0a4ef7e7-b6f3-4c2f-b061-2a5fb7a8c21b

Commits

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Files selected for processing: 1

• tests/core/test_context.py

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