diff --git a/.github/actionlint.yaml b/.github/actionlint.yaml
index 6c85e2cb4124a..8b9e24ce59700 100644
--- a/.github/actionlint.yaml
+++ b/.github/actionlint.yaml
@@ -13,8 +13,3 @@ self-hosted-runner:
     - github-windows-2025-x86_64-8
     - github-windows-2025-x86_64-16
     - codspeed-macro
-
-paths:
-  ".github/workflows/mypy_primer.yaml":
-    ignore:
-      - 'constant expression "false" in condition. remove the if: section'
diff --git a/.github/mypy-primer-ty.toml b/.github/ty-ecosystem.toml
similarity index 81%
rename from .github/mypy-primer-ty.toml
rename to .github/ty-ecosystem.toml
index 578712348647c..69c2b83665c43 100644
--- a/.github/mypy-primer-ty.toml
+++ b/.github/ty-ecosystem.toml
@@ -1,5 +1,5 @@
 #:schema ../ty.schema.json
-# Configuration overrides for the mypy primer run
+# Configuration overrides for ty ecosystem analysis
 
 # Enable off-by-default rules.
 [rules]
diff --git a/.github/workflows/memory_report.yaml b/.github/workflows/memory_report.yaml
index 438a28e8677b8..a63a5e2552e50 100644
--- a/.github/workflows/memory_report.yaml
+++ b/.github/workflows/memory_report.yaml
@@ -20,7 +20,7 @@ on:
       - "!**.md"
       - "!**.snap"
       # It's tempting to skip all Python files in every directory,
-      # but changes to Python files in `ty_vendored` can affect the output of mypy_primer,
+      # but changes to Python files in `ty_vendored` can affect the output of ecosystem runs,
       # so we apply a narrow exemption for all files in the corpus directory instead.
       - "!crates/ty_python_semantic/resources/corpus/**"
 
diff --git a/.github/workflows/mypy_primer.yaml b/.github/workflows/mypy_primer.yaml
deleted file mode 100644
index 96e4266789109..0000000000000
--- a/.github/workflows/mypy_primer.yaml
+++ /dev/null
@@ -1,124 +0,0 @@
-name: Run mypy_primer
-
-permissions: {}
-
-on:
-  pull_request:
-    # The default for `pull_request` is to trigger on `synchronize`, `opened` and `reopened`.
-    # We also add `labeled` here so that the workflow triggers when a label is initially added.
-    types:
-      - labeled
-      - synchronize
-      - opened
-      - reopened
-
-concurrency:
-  group: mypy-primer-${{ github.ref_name }}-${{ github.event.pull_request.number || github.sha }}
-  cancel-in-progress: ${{ github.event_name == 'pull_request' && contains(github.event.pull_request.labels.*.name, 'mypy_primer') }}
-
-defaults:
-  run:
-    shell: bash
-
-env:
-  CARGO_INCREMENTAL: 0
-  CARGO_NET_RETRY: 10
-  CARGO_TERM_COLOR: always
-  RUSTUP_MAX_RETRIES: 10
-  RUST_BACKTRACE: 1
-
-jobs:
-  mypy_primer:
-    name: Run mypy_primer
-    runs-on: ${{ github.repository == 'astral-sh/ruff' && 'depot-ubuntu-22.04-32' || 'ubuntu-latest' }}
-    timeout-minutes: 20
-    if: contains(github.event.pull_request.labels.*.name, 'mypy_primer')
-    steps:
-      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
-        with:
-          path: ruff
-          fetch-depth: 0
-          persist-credentials: false
-
-      - name: Install the latest version of uv
-        uses: astral-sh/setup-uv@37802adc94f370d6bfd71619e3f0bf239e1f3b78 # v7.6.0
-        with:
-          version: "0.10.10"
-
-      - uses: Swatinem/rust-cache@779680da715d629ac1d338a641029a2f4372abb5 # v2.8.2
-        with:
-          shared-key: "mypy-primer"
-          workspaces: "ruff"
-
-      - name: Install Rust toolchain
-        run: rustup show
-
-      - name: Run mypy_primer
-        env:
-          PRIMER_SELECTOR: crates/ty_python_semantic/resources/primer/good.txt
-          CLICOLOR_FORCE: "1"
-          DIFF_FILE: mypy_primer.diff
-        run: |
-          cd ruff
-          scripts/mypy_primer.sh
-
-      # NOTE: astral-sh-bot uses this artifact to post comments on PRs.
-      # Make sure to update the bot if you rename the artifact.
-      - name: Upload diff
-        uses: actions/upload-artifact@bbbca2ddaa5d8feaa63e36b76fdaad77386f024f # v7.0.0
-        with:
-          name: mypy_primer_diff
-          path: mypy_primer.diff
-
-  # Runs mypy twice against the same ty version to catch any non-deterministic behavior (ideally).
-  # The job is disabled for now because there are some non-deterministic diagnostics.
-  mypy_primer_same_revision:
-    name: Run mypy_primer on same revision
-    runs-on: ${{ github.repository == 'astral-sh/ruff' && 'depot-ubuntu-22.04-32' || 'ubuntu-latest' }}
-    timeout-minutes: 20
-    # TODO: Enable once we fixed the non-deterministic diagnostics
-    if: false && contains(github.event.pull_request.labels.*.name, 'mypy_primer')
-    steps:
-      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
-        with:
-          path: ruff
-          fetch-depth: 0
-          persist-credentials: false
-
-      - name: Install the latest version of uv
-        uses: astral-sh/setup-uv@37802adc94f370d6bfd71619e3f0bf239e1f3b78 # v7.6.0
-        with:
-          version: "0.10.10"
-
-      - uses: Swatinem/rust-cache@779680da715d629ac1d338a641029a2f4372abb5 # v2.8.2
-        with:
-          workspaces: "ruff"
-          shared-key: "mypy-primer"
-
-      - name: Install Rust toolchain
-        run: rustup show
-
-      - name: Run determinism check
-        env:
-          BASE_REVISION: ${{ github.event.pull_request.head.sha }}
-          PRIMER_SELECTOR: crates/ty_python_semantic/resources/primer/good.txt
-          CLICOLOR_FORCE: "1"
-          DIFF_FILE: mypy_primer_determinism.diff
-        run: |
-          cd ruff
-          scripts/mypy_primer.sh
-
-      - name: Check for non-determinism
-        run: |
-          # Remove ANSI color codes for checking
-          sed -e 's/\x1b\[[0-9;]*m//g' mypy_primer_determinism.diff > mypy_primer_determinism_clean.diff
-
-          # Check if there are any differences (non-determinism)
-          if [ -s mypy_primer_determinism_clean.diff ]; then
-            echo "ERROR: Non-deterministic output detected!"
-            echo "The following differences were found when running ty twice on the same commit:"
-            cat mypy_primer_determinism_clean.diff
-            exit 1
-          else
-            echo "✓ Output is deterministic"
-          fi
diff --git a/.github/workflows/ty-ecosystem-analyzer.yaml b/.github/workflows/ty-ecosystem-analyzer.yaml
index ba21c95446447..c82284d417974 100644
--- a/.github/workflows/ty-ecosystem-analyzer.yaml
+++ b/.github/workflows/ty-ecosystem-analyzer.yaml
@@ -15,9 +15,8 @@ on:
       - "crates/ruff_python_ast"
       - "crates/ruff_python_parser"
       - ".github/workflows/ty-ecosystem-analyzer.yaml"
-      - ".github/workflows/mypy_primer.yaml"
-      - "scripts/mypy_primer.sh"
-      - "scripts/mypy_primer_selector.py"
+      - ".github/ty-ecosystem.toml"
+      - "crates/ty_python_semantic/resources/primer/**"
       - "Cargo.lock"
       - "!**.md"
       - "!**.snap"
@@ -69,9 +68,9 @@ jobs:
         run: |
           cd ruff
 
-          echo "Enabling configuration overloads (see .github/mypy-primer-ty.toml)"
+          echo "Enabling configuration overloads (see .github/ty-ecosystem.toml)"
           mkdir -p ~/.config/ty
-          cp .github/mypy-primer-ty.toml ~/.config/ty/ty.toml
+          cp .github/ty-ecosystem.toml ~/.config/ty/ty.toml
 
           echo "new commit"
           git checkout -b new_commit "$GITHUB_SHA"
diff --git a/.github/workflows/ty-ecosystem-report.yaml b/.github/workflows/ty-ecosystem-report.yaml
index bf4705a4e374c..081514b242721 100644
--- a/.github/workflows/ty-ecosystem-report.yaml
+++ b/.github/workflows/ty-ecosystem-report.yaml
@@ -50,9 +50,9 @@ jobs:
         run: |
           cd ruff
 
-          echo "Enabling configuration overloads (see .github/mypy-primer-ty.toml)"
+          echo "Enabling configuration overloads (see .github/ty-ecosystem.toml)"
           mkdir -p ~/.config/ty
-          cp .github/mypy-primer-ty.toml ~/.config/ty/ty.toml
+          cp .github/ty-ecosystem.toml ~/.config/ty/ty.toml
 
           cd ..
 
diff --git a/.github/workflows/typing_conformance.yaml b/.github/workflows/typing_conformance.yaml
index d362edb514e8f..00938f1046eef 100644
--- a/.github/workflows/typing_conformance.yaml
+++ b/.github/workflows/typing_conformance.yaml
@@ -19,8 +19,8 @@ on:
       - "Cargo.lock"
       - "!**.md"
       - "!**.snap"
-      # It's tempting to skip all Python files in every directory,
-      # but changes to Python files in `ty_vendored` can affect the output of mypy_primer,
+      # It's tempting to skip all Python files in every directory, but changes to
+      # Python files in `ty_vendored` can affect the output of the ecosystem analysis,
       # so we apply a narrow exemption for all files in the corpus directory instead.
       - "!crates/ty_python_semantic/resources/corpus/**"
 
diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 08ca5a502a2c8..9441658a198da 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -52,14 +52,6 @@ repos:
         language: system
         types: [rust]
         priority: 0
-      - id: check-mypy-primer-sha
-        name: Check mypy-primer SHA is in sync
-        entry: python3 scripts/check_mypy_primer_sha.py
-        language: system
-        pass_filenames: false
-        files: ^scripts/(mypy_primer\.sh|setup_primer_project\.py)$
-        priority: 0
-
   # Prettier
   - repo: https://github.com/rbubley/mirrors-prettier
     rev: v3.8.1
diff --git a/crates/ruff_benchmark/benches/ty_walltime.rs b/crates/ruff_benchmark/benches/ty_walltime.rs
index d2f14129c816c..67d40295ab9a5 100644
--- a/crates/ruff_benchmark/benches/ty_walltime.rs
+++ b/crates/ruff_benchmark/benches/ty_walltime.rs
@@ -224,8 +224,8 @@ static STATIC_FRAME: Benchmark = Benchmark::new(
         repository: "https://github.com/static-frame/static-frame",
         commit: "34962b41baca5e7f98f5a758d530bff02748a421",
         paths: &["static_frame"],
-        // N.B. `arraykit` is installed as a dependency during mypy_primer runs,
-        // but it takes much longer to be installed in a Codspeed run than it does in a mypy_primer run
+        // N.B. `arraykit` is installed as a dependency during ecosystem runs,
+        // but it takes much longer to be installed in a Codspeed run
         // (seems to be built from source on the Codspeed CI runners for some reason).
         dependencies: &["numpy"],
         max_dep_date: "2025-08-09",
diff --git a/crates/ty/CONTRIBUTING.md b/crates/ty/CONTRIBUTING.md
index 6633a7a7cf1e5..305c7f2da8c55 100644
--- a/crates/ty/CONTRIBUTING.md
+++ b/crates/ty/CONTRIBUTING.md
@@ -142,11 +142,11 @@ The property tests do not run in CI on every PR, just once daily. It is advisabl
 locally after modifying core type relation methods (`is_subtype_of`, `is_equivalent_to`, etc.) to
 ensure that the changes do not break any of the properties.
 
-## Ecosystem CI (mypy-primer)
+## Ecosystem CI (`ecosystem-analyzer`)
 
-GitHub Actions will run your changes against a number of real-world projects from GitHub and
-report on any linter or formatter differences. See [`crates/ty/docs/mypy_primer.md`](./docs/mypy_primer.md)
-for instructions on running these checks locally.
+GitHub Actions will run your changes against a number of real-world projects from GitHub and report
+any differences in ty's diagnostic output. You can use [`setup_primer_project.py`](./scripts/setup_primer_project.py)
+to reproduce the same testing conditions locally.
 
 ## Coding guidelines
 
diff --git a/crates/ty/docs/mypy_primer.md b/crates/ty/docs/mypy_primer.md
deleted file mode 100644
index bd14bfaa96f20..0000000000000
--- a/crates/ty/docs/mypy_primer.md
+++ /dev/null
@@ -1,69 +0,0 @@
-# Running `mypy_primer`
-
-## Basics
-
-`mypy_primer` can be run using `uvx --from "…" mypy_primer`. For example, to see the help message, run:
-
-```sh
-uvx --from "git+https://github.com/hauntsaninja/mypy_primer" mypy_primer -h
-```
-
-Alternatively, you can install the forked version of `mypy_primer` using:
-
-```sh
-uv tool install "git+https://github.com/hauntsaninja/mypy_primer"
-```
-
-and then run it using `uvx mypy_primer` or just `mypy_primer`, if your `PATH` is set up accordingly (see: [Tool executables]).
-
-## Showing the diagnostics diff between two Git revisions
-
-To show the diagnostics diff between two Git revisions (e.g. your feature branch and `main`), run:
-
-```sh
-mypy_primer \
-    --type-checker ty \
-    --old origin/main \
-    --new my/feature \
-    --debug \
-    --output concise \
-    --project-selector '/black$'
-```
-
-This will show the diagnostics diff for the `black` project between the `main` branch and your `my/feature` branch. To run the
-diff for all projects we currently enable in CI, use `--project-selector "$(uv run scripts/mypy_primer_selector.py crates/ty_python_semantic/resources/primer/good.txt)"`.
-
-You can also take a look at the [full list of ecosystem projects]. Note that some of them might still need a `ty_paths` configuration
-option to work correctly.
-
-## Avoiding recompilation
-
-If you want to run `mypy_primer` repeatedly, e.g. for different projects, but for the same combination of `--old` and `--new`, you
-can use set the `MYPY_PRIMER_NO_REBUILD` environment variable to avoid recompilation of ty:
-
-```sh
-MYPY_PRIMER_NO_REBUILD=1 mypy_primer …
-```
-
-## Running from a local copy of the repository
-
-If you are working on a local branch, you can use `mypy_primer`'s `--repo` option to specify the path to your local copy of the `ruff` repository.
-This allows `mypy_primer` to check out local branches:
-
-```sh
-mypy_primer --type-checker ty \
-  --repo ./ruff \
-  --old main \
-  --new my/local-branch \
-  --project-selector '/beartype$' \
-  --debug \
-  --output concise
-```
-
-Notes:
-
-- You might need to clean up `/tmp/mypy_primer` in order for this to work correctly.
-- This must be run from _outside_ the `ruff` repo.
-
-[full list of ecosystem projects]: https://github.com/hauntsaninja/mypy_primer/blob/master/mypy_primer/projects.py
-[tool executables]: https://docs.astral.sh/uv/concepts/tools/#tool-executables
diff --git a/crates/ty_python_semantic/src/types/tuple.rs b/crates/ty_python_semantic/src/types/tuple.rs
index e197814f3989c..99f8a28c148a4 100644
--- a/crates/ty_python_semantic/src/types/tuple.rs
+++ b/crates/ty_python_semantic/src/types/tuple.rs
@@ -198,7 +198,7 @@ impl<'db> TupleType<'db> {
     }
 
     // N.B. If this method is not Salsa-tracked, we take 10 minutes to check
-    // `static-frame` as part of a mypy_primer run! This is because it's called
+    // `static-frame` as part of the ecosystem analysis. This is because it's called
     // from `NominalInstanceType::class()`, which is a very hot method.
     #[salsa::tracked(cycle_initial=to_class_type_cycle_initial, heap_size=ruff_memory_usage::heap_size)]
     pub(crate) fn to_class_type(self, db: &'db dyn Db) -> ClassType<'db> {
diff --git a/scripts/check_mypy_primer_sha.py b/scripts/check_mypy_primer_sha.py
deleted file mode 100644
index 06b5287969ba8..0000000000000
--- a/scripts/check_mypy_primer_sha.py
+++ /dev/null
@@ -1,40 +0,0 @@
-#!/usr/bin/env python3
-"""Check that the mypy-primer SHA in setup_primer_project.py matches mypy_primer.sh."""
-
-from __future__ import annotations
-
-import re
-import sys
-from pathlib import Path
-
-ROOT = Path(__file__).parent.parent
-
-SH_FILE = ROOT / "scripts" / "mypy_primer.sh"
-PY_FILE = ROOT / "scripts" / "setup_primer_project.py"
-
-SHA_RE = re.compile(r"mypy_primer@([0-9a-f]{40})")
-REV_RE = re.compile(r'rev\s*=\s*"([0-9a-f]{40})"')
-
-
-def extract(pattern: re.Pattern[str], path: Path, label: str) -> str:
-    m = pattern.search(path.read_text())
-    if m is None:
-        print(f"error: could not find {label} in {path}", file=sys.stderr)
-        sys.exit(1)
-    return m.group(1)
-
-
-sh_sha = extract(SHA_RE, SH_FILE, "mypy_primer SHA")
-py_sha = extract(REV_RE, PY_FILE, "mypy-primer rev")
-
-if sh_sha != py_sha:
-    print(
-        f"error: mypy-primer SHA mismatch\n"
-        f"  {SH_FILE.relative_to(ROOT)}: {sh_sha}\n"
-        f"  {PY_FILE.relative_to(ROOT)}: {py_sha}\n"
-        f"Update the rev in {PY_FILE.relative_to(ROOT)} to match {SH_FILE.relative_to(ROOT)}.",
-        file=sys.stderr,
-    )
-    sys.exit(1)
-
-print(f"ok: mypy-primer SHA is in sync ({sh_sha[:12]}...)")
diff --git a/scripts/mypy_primer.sh b/scripts/mypy_primer.sh
deleted file mode 100755
index c86b94b230497..0000000000000
--- a/scripts/mypy_primer.sh
+++ /dev/null
@@ -1,40 +0,0 @@
-#!/usr/bin/env bash
-set -eu
-
-echo "Enabling mypy primer specific configuration overloads (see .github/mypy-primer-ty.toml)"
-mkdir -p ~/.config/ty
-cp .github/mypy-primer-ty.toml ~/.config/ty/ty.toml
-
-PRIMER_SELECTOR="$(uv run scripts/mypy_primer_selector.py "${PRIMER_SELECTOR}")"
-
-echo "new commit"
-git rev-list --format=%s --max-count=1 "${GITHUB_SHA}"
-
-if [ -z "${BASE_REVISION:-}" ]; then
-  BASE_REVISION="$(git merge-base "${GITHUB_SHA}" "origin/${GITHUB_BASE_REF}")"
-fi
-git checkout -b base_commit "${BASE_REVISION}"
-echo "base commit"
-git rev-list --format=%s --max-count=1 base_commit
-
-cd ..
-
-echo "Project selector: ${PRIMER_SELECTOR}"
-# Allow the exit code to be 0 or 1, only fail for actual mypy_primer crashes/bugs
-uvx \
-  --from="git+https://github.com/hauntsaninja/mypy_primer@850d65d9da947ef9e02498b6f07598e7c8401641" \
-  mypy_primer \
-  --repo ruff \
-  --type-checker ty \
-  --cargo-profile profiling \
-  --old base_commit \
-  --new "${GITHUB_SHA}" \
-  --project-selector "${PRIMER_SELECTOR}" \
-  --output concise \
-  --debug > "${DIFF_FILE}" || [ $? -eq 1 ]
-
-# Output diff with ANSI color codes
-cat "${DIFF_FILE}"
-
-# Remove ANSI color codes before uploading
-sed -ie 's/\x1b\[[0-9;]*m//g' "${DIFF_FILE}"
diff --git a/scripts/mypy_primer_selector.py b/scripts/mypy_primer_selector.py
deleted file mode 100644
index 38c0c6650b80b..0000000000000
--- a/scripts/mypy_primer_selector.py
+++ /dev/null
@@ -1,40 +0,0 @@
-#!/usr/bin/env python3
-
-from __future__ import annotations
-
-import argparse
-import re
-from pathlib import Path
-
-CPYTHON_PROJECTS = {
-    "CPython (Argument Clinic)": "cpython",
-    "CPython (cases_generator)": "cpython",
-    "CPython (peg_generator)": "cpython",
-}
-
-
-def main() -> None:
-    parser = argparse.ArgumentParser(
-        description="Build a mypy_primer project-selector regex from a project list."
-    )
-    parser.add_argument("project_list", type=Path)
-    args = parser.parse_args()
-
-    projects: list[str] = []
-    seen: set[str] = set()
-
-    for line in args.project_list.read_text().splitlines():
-        project = line.strip()
-        if not project:
-            continue
-
-        selector = CPYTHON_PROJECTS.get(project, project)
-        if selector not in seen:
-            projects.append(re.escape(selector))
-            seen.add(selector)
-
-    print(f"/({'|'.join(projects)})$")
-
-
-if __name__ == "__main__":
-    main()
diff --git a/scripts/setup_primer_project.py b/scripts/setup_primer_project.py
old mode 100755
new mode 100644
index c1530f76b96e1..deb9ce21d4b6b
--- a/scripts/setup_primer_project.py
+++ b/scripts/setup_primer_project.py
@@ -5,7 +5,7 @@
 # dependencies = ["mypy-primer"]
 #
 # [tool.uv.sources]
-# mypy-primer = { git = "https://github.com/hauntsaninja/mypy_primer", rev = "850d65d9da947ef9e02498b6f07598e7c8401641" }
+# mypy-primer = { git = "https://github.com/hauntsaninja/mypy_primer" }
 # ///
 
 """Clone a mypy-primer project and set up a virtualenv with its dependencies installed.