chore: remove mypy from CI

[ogabrielluiz]

Summary

• Removed mypy from CI -- it hasn't caught any issues in a long time, likely because the config was extremely lenient (follow_imports = "skip", ignore_missing_imports = true)
• Removed mypy, all types-* stub packages, and [tool.mypy] config sections
• We evaluated ty as a replacement but it's not mature enough yet -- Pydantic (astral-sh/ty#2403) and SQLModel (astral-sh/ty#2888) support are still missing, which produces too many false positives in our codebase
• make lint is a no-op for now until we have a viable type checker

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Walkthrough

This pull request removes the lint-backend CI job from GitHub Actions and replaces all mypy type-checking tooling with ty across the project configuration files, including updating cache directories, build targets, and dependency specifications.

Changes

Cohort / File(s)	Summary
CI/Workflow .github/workflows/ci.yml	Removed standalone lint-backend job and its conditional execution logic; updated ci_success job dependencies to exclude lint-backend; removed corresponding failure-description branch for the job.
Build Tooling Makefile	Updated clean_python_cache target to clear .ty_cache instead of .mypy_cache; replaced mypy --namespace-packages -p "langflow" with ty check src/backend/base/langflow in lint target; updated help text from "mypy" to "ty".
Root Development Configuration pyproject.toml	Removed entire [tool.mypy] section with Pydantic plugin and mypy settings; added [tool.ty] configuration with Python 3.10 version and rule overrides; removed types-* stub packages and mypy from dev dependencies; added ty to dev dependencies.
Backend Development Configuration src/backend/base/pyproject.toml	Removed types-* stub packages and mypy from dev dependencies; added ty to dev dependencies; replaced [tool.mypy] configuration with [tool.ty.environment] and [tool.ty.rules] sections with Python version and diagnostic suppression rules.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~15 minutes

🚥 Pre-merge checks | ✅ 7

✅ Passed checks (7 passed)

Check name	Status	Explanation
Title check	✅ Passed	The PR title 'chore: remove mypy from CI' accurately reflects the main change in the changeset (removing the lint-backend job from CI), though the broader scope includes replacing mypy with ty for local type checking.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Test Coverage For New Implementations	✅ Passed	This PR is a tooling migration replacing mypy with ty for type checking, modifying only configuration files with no changes to application code.
Test Quality And Coverage	✅ Passed	This PR is a tooling and configuration change replacing mypy with ty for type checking, with no new code implementations introduced.
Test File Naming And Structure	✅ Passed	The PR modifies only configuration/workflow files and no test files are added, modified, or removed. Test file structure guidelines are not applicable to this infrastructure-focused change.
Excessive Mock Usage Warning	✅ Passed	This PR modifies only configuration and workflow files, with no changes to test files that would be subject to the Excessive Mock Usage Warning check.
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch chore/replace-mypy-with-ty

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[github-actions]

Frontend Unit Test Coverage Report

Coverage Summary

Lines	Statements	Branches	Functions
	28.01% (29184/104184)	64.76% (3717/5739)	30.03% (689/2294)

Unit Test Results

Tests	Skipped	Failures	Errors	Time
3014	0 💤	0 ❌	0 🔥	4m 37s ⏱️

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 48.86%. Comparing base (389f702) to head (7baa125).
⚠️ Report is 3 commits behind head on release-1.9.0.

❌ Your project status has failed because the head coverage (45.87%) is below the target coverage (60.00%). You can increase the head coverage or adjust the target coverage.

Additional details and impacted files

@@               Coverage Diff                @@
##           release-1.9.0   #12448     +/-   ##
================================================
  Coverage          48.86%   48.86%             
================================================
  Files               1897     1896      -1     
  Lines             167656   168352    +696     
  Branches           23193    24429   +1236     
================================================
+ Hits               81928    82271    +343     
- Misses             84817    85158    +341     
- Partials             911      923     +12     

Flag	Coverage Δ
backend	54.84% <ø> (-0.05%)	⬇️
frontend	48.15% <ø> (-0.06%)	⬇️
lfx	45.87% <ø> (+0.33%)	⬆️

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see 218 files with indirect coverage changes

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[coderabbitai]

🧹 Nitpick comments (1)

Makefile (1)

100-100: Optional: keep transitional cleanup for legacy mypy cache.

Line 100 removes ty cache correctly; consider also cleaning .mypy_cache for a couple of releases to avoid stale local artifacts on upgraded dev machines.

Suggested diff

-	$(call CLEAR_DIRS,.ty_cache )
+	$(call CLEAR_DIRS,.ty_cache .mypy_cache)

🤖 Prompt for AI Agents

Verify each finding against the current code and only fix it if needed.

In `@Makefile` at line 100, The Makefile currently calls $(call
CLEAR_DIRS,.ty_cache) to remove legacy ty cache; extend this transitional
cleanup to also remove .mypy_cache by updating the CLEAR_DIRS invocation to
include both caches (e.g., pass ".ty_cache .mypy_cache") so that both .ty_cache
and .mypy_cache are cleaned for a couple of releases; locate the CLEAR_DIRS call
in the Makefile (symbol: CLEAR_DIRS, argument ".ty_cache") and add ".mypy_cache"
to the arguments.

🤖 Prompt for all review comments with AI agents

Verify each finding against the current code and only fix it if needed.

Nitpick comments:
In `@Makefile`:
- Line 100: The Makefile currently calls $(call CLEAR_DIRS,.ty_cache) to remove
legacy ty cache; extend this transitional cleanup to also remove .mypy_cache by
updating the CLEAR_DIRS invocation to include both caches (e.g., pass ".ty_cache
.mypy_cache") so that both .ty_cache and .mypy_cache are cleaned for a couple of
releases; locate the CLEAR_DIRS call in the Makefile (symbol: CLEAR_DIRS,
argument ".ty_cache") and add ".mypy_cache" to the arguments.

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ℹ️ Review info

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Configuration used: Path: .coderabbit.yaml

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📥 Commits

Reviewing files that changed from the base of the PR and between 08bf984 and dab1b12.

⛔ Files ignored due to path filters (1)

• uv.lock is excluded by !**/*.lock

📒 Files selected for processing (4)

• .github/workflows/ci.yml
• Makefile
• pyproject.toml
• src/backend/base/pyproject.toml

💤 Files with no reviewable changes (1)

• .github/workflows/ci.yml