diff --git a/.github/workflows/codelens-benchmark.yml b/.github/workflows/codelens-benchmark.yml
index 3b1c3a4..40f9a17 100644
--- a/.github/workflows/codelens-benchmark.yml
+++ b/.github/workflows/codelens-benchmark.yml
@@ -15,7 +15,7 @@ jobs:
         with:
           python-version: '3.12'
       - name: Install dependencies
-        run: pip install pyyaml tree-sitter pytest
+        run: pip install pyyaml "tree-sitter>=0.21.0,<0.26" pytest
       - name: Run full benchmarks
         run: python3 benchmarks/run_benchmarks.py
       - name: Check regression
diff --git a/.github/workflows/codelens-ci.yml b/.github/workflows/codelens-ci.yml
index 81ea5e7..5cffd26 100644
--- a/.github/workflows/codelens-ci.yml
+++ b/.github/workflows/codelens-ci.yml
@@ -33,16 +33,17 @@ jobs:
       - name: Install dependencies
         run: |
           python -m pip install --upgrade pip
-          pip install tree-sitter pyyaml pytest pytest-cov pygls lsprotocol
+          # tree-sitter pinned <0.26: core 0.26.0 changed Node lifetime handling
+          # and causes a native use-after-free SIGSEGV in tree_sitter_python._binding
+          # even on shallow files (issue #235). python_parser.py's keep_alive
+          # mitigation is insufficient for 0.26; 0.25.x is known-safe.
+          pip install "tree-sitter>=0.21.0,<0.26" pyyaml pytest pytest-cov pygls lsprotocol
           # Install optional grammar packages for full parser coverage
           pip install tree-sitter-python tree-sitter-javascript tree-sitter-html tree-sitter-css || true
           pip install tree-sitter-typescript tree-sitter-rust || true
 
       - name: Run test suite
         run: |
-          # ulimit -s unlimited prevents SIGSEGV from tree-sitter's internal C
-          # recursion on deeply-nested ASTs (issue #235, test_large_file_parsing.py)
-          ulimit -s unlimited
           cd scripts && python -m pytest ../tests/ -v --tb=short \
             --ignore=../tests/test_integration.py
 
@@ -68,7 +69,7 @@ jobs:
       - name: Install dependencies
         run: |
           python -m pip install --upgrade pip
-          pip install tree-sitter pyyaml
+          pip install "tree-sitter>=0.21.0,<0.26" pyyaml
           pip install tree-sitter-python tree-sitter-javascript tree-sitter-html tree-sitter-css || true
           pip install tree-sitter-typescript tree-sitter-rust || true
 
@@ -98,7 +99,7 @@ jobs:
       - name: Install dependencies
         run: |
           python -m pip install --upgrade pip
-          pip install tree-sitter pyyaml
+          pip install "tree-sitter>=0.21.0,<0.26" pyyaml
           pip install tree-sitter-python tree-sitter-javascript tree-sitter-html tree-sitter-css || true
           pip install tree-sitter-typescript tree-sitter-rust || true
 
diff --git a/.github/workflows/codelens-sarif.yml b/.github/workflows/codelens-sarif.yml
index 9eba6c0..cb6103c 100644
--- a/.github/workflows/codelens-sarif.yml
+++ b/.github/workflows/codelens-sarif.yml
@@ -33,7 +33,7 @@ jobs:
       - name: Install dependencies
         run: |
           python -m pip install --upgrade pip
-          pip install tree-sitter pyyaml
+          pip install "tree-sitter>=0.21.0,<0.26" pyyaml
           pip install tree-sitter-python tree-sitter-javascript tree-sitter-html tree-sitter-css || true
           pip install tree-sitter-typescript tree-sitter-rust || true
 
diff --git a/pyproject.toml b/pyproject.toml
index 5805a2b..75021ae 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -39,7 +39,11 @@ classifiers = [
 ]
 
 dependencies = [
-    "tree-sitter>=0.21.0",
+    # Upper-bound <0.26: tree-sitter core 0.26.0 changed Node lifetime handling,
+    # causing a native use-after-free SIGSEGV in the grammar bindings even on
+    # shallow files (issue #235). Remove the cap once python_parser.py's
+    # keep_alive strategy is made 0.26-safe.
+    "tree-sitter>=0.21.0,<0.26",
 ]
 
 [project.optional-dependencies]