diff --git a/.github/workflows/ci-cd.yml b/.github/workflows/ci-cd.yml
index b1bde397283..9a366681b87 100644
--- a/.github/workflows/ci-cd.yml
+++ b/.github/workflows/ci-cd.yml
@@ -182,6 +182,7 @@ jobs:
       fail-fast: true
     runs-on: ${{ matrix.os }}-latest
     continue-on-error: ${{ matrix.experimental }}
+    timeout-minutes: 15
     steps:
     - name: Checkout
       uses: actions/checkout@v6
@@ -294,6 +295,7 @@ jobs:
         os: [ubuntu]
       fail-fast: true
     runs-on: ${{ matrix.os }}-latest
+    timeout-minutes: 15
     steps:
     - name: Checkout
       uses: actions/checkout@v6
@@ -346,7 +348,7 @@ jobs:
         PIP_USER: 1
       run: >-
         PATH="${HOME}/Library/Python/3.11/bin:${HOME}/.local/bin:${PATH}"
-        pytest --junitxml=junit.xml --cov=aiohttp/ --cov=tests/ -m autobahn
+        pytest --junitxml=junit.xml --cov=aiohttp/ --cov=tests/ --timeout=0 -m autobahn
       shell: bash
     - name: Turn coverage into xml
       env:
@@ -409,7 +411,7 @@ jobs:
       uses: CodSpeedHQ/action@v4
       with:
         mode: instrumentation
-        run: python -Im pytest --no-cov -vvvvv --codspeed --durations=30
+        run: python -Im pytest --no-cov -vvvvv --codspeed --durations=30 --timeout=0
 
 
   cython-coverage:
@@ -422,6 +424,7 @@ jobs:
       matrix:
         os: [ubuntu, windows]
     runs-on: ${{ matrix.os }}-latest
+    timeout-minutes: 15
     steps:
     - name: Checkout
       uses: actions/checkout@v6
diff --git a/.gitignore b/.gitignore
index 0081b62ae7f..ee06baff610 100644
--- a/.gitignore
+++ b/.gitignore
@@ -65,3 +65,6 @@ sources
 var/*
 venv
 virtualenv.py
+
+# Claude Code per-checkout overrides
+CLAUDE.local.md
diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index 12f2c8678e9..ce55819c793 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -64,7 +64,7 @@ repos:
   hooks:
   - id: isort
 - repo: https://github.com/psf/black-pre-commit-mirror
-  rev: '26.3.1'
+  rev: '26.5.0'
   hooks:
     - id: black
       language_version: python3 # Should be a command that runs python
diff --git a/CHANGES/12606.contrib.rst b/CHANGES/12606.contrib.rst
new file mode 100644
index 00000000000..72925114e8c
--- /dev/null
+++ b/CHANGES/12606.contrib.rst
@@ -0,0 +1,6 @@
+Reduced runtime of several of the slowest unit tests
+(decompress size-limit payloads from 64 MiB to 2 MiB,
+``test_chunk_splits_after_pause`` chunk count from 50000
+to 20000, and ``test_set_cookies_max_age`` sleep from 2
+seconds to 1.1 seconds) without changing what they
+exercise -- by :user:`bdraco`.
diff --git a/CHANGES/12617.contrib.rst b/CHANGES/12617.contrib.rst
new file mode 100644
index 00000000000..fab91aea8e0
--- /dev/null
+++ b/CHANGES/12617.contrib.rst
@@ -0,0 +1,9 @@
+Restructured the root :file:`CLAUDE.md` to import contributor
+context from a shared ``aio-libs`` layer
+(``~/.claude/aio-libs/context.md``), a project-specific layer
+(``~/.claude/aio-libs/aiohttp/context.md``), the in-tree
+:file:`AGENTS.md`, and an optional per-checkout
+:file:`CLAUDE.local.md` override (added to :file:`.gitignore`),
+so shared ``aio-libs`` guidance can live outside the repository
+while project rules continue to load automatically in Claude
+Code -- by :user:`aiolibsbot`.
diff --git a/CHANGES/12618.contrib.rst b/CHANGES/12618.contrib.rst
new file mode 120000
index 00000000000..7efbc0b7ed6
--- /dev/null
+++ b/CHANGES/12618.contrib.rst
@@ -0,0 +1 @@
+12617.contrib.rst
\ No newline at end of file
diff --git a/CHANGES/12624.contrib.rst b/CHANGES/12624.contrib.rst
new file mode 100644
index 00000000000..0c7e2a0a548
--- /dev/null
+++ b/CHANGES/12624.contrib.rst
@@ -0,0 +1,4 @@
+Added a default 120-second per-test timeout via ``pytest-timeout`` so a
+hung test surfaces by name in CI output instead of getting hidden behind
+the job-level timeout added in :pr:`12619`. The ``autobahn`` and
+benchmark jobs opt out with ``--timeout=0`` -- by :user:`bdraco`.
diff --git a/CLAUDE.md b/CLAUDE.md
index 43c994c2d36..30ceb187918 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -1 +1,4 @@
+@~/.claude/aio-libs/context.md
+@~/.claude/aio-libs/aiohttp/context.md
 @AGENTS.md
+@CLAUDE.local.md
diff --git a/requirements/test-common.in b/requirements/test-common.in
index b50aed3be7f..9b3c5839b1f 100644
--- a/requirements/test-common.in
+++ b/requirements/test-common.in
@@ -9,6 +9,7 @@ pytest
 pytest-aiohttp
 pytest-cov
 pytest-mock
+pytest-timeout
 pytest-xdist
 pytest_codspeed
 python-on-whales
diff --git a/requirements/test-common.txt b/requirements/test-common.txt
index 94aa95d62be..1faa93e7c1f 100644
--- a/requirements/test-common.txt
+++ b/requirements/test-common.txt
@@ -111,6 +111,8 @@ pytest-cov==7.1.0
     # via -r requirements/test-common.in
 pytest-mock==3.15.1
     # via -r requirements/test-common.in
+pytest-timeout==2.4.0
+    # via -r requirements/test-common.in
 pytest-xdist==3.8.0
     # via -r requirements/test-common.in
 python-dateutil==2.9.0.post0
diff --git a/requirements/test-ft.txt b/requirements/test-ft.txt
index fcad3f25513..073a4360a15 100644
--- a/requirements/test-ft.txt
+++ b/requirements/test-ft.txt
@@ -134,6 +134,8 @@ pytest-cov==7.1.0
     # via -r requirements/test-common.in
 pytest-mock==3.15.1
     # via -r requirements/test-common.in
+pytest-timeout==2.4.0
+    # via -r requirements/test-common.in
 pytest-xdist==3.8.0
     # via -r requirements/test-common.in
 python-dateutil==2.9.0.post0
diff --git a/requirements/test.txt b/requirements/test.txt
index 16cb56e094f..3c84d9304c1 100644
--- a/requirements/test.txt
+++ b/requirements/test.txt
@@ -134,6 +134,8 @@ pytest-cov==7.1.0
     # via -r requirements/test-common.in
 pytest-mock==3.15.1
     # via -r requirements/test-common.in
+pytest-timeout==2.4.0
+    # via -r requirements/test-common.in
 pytest-xdist==3.8.0
     # via -r requirements/test-common.in
 python-dateutil==2.9.0.post0
diff --git a/setup.cfg b/setup.cfg
index 8a721800cf3..e78606ecd57 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -58,6 +58,9 @@ addopts =
     # Disable entry-point auto-load, otherwise we miss coverage.
     -p no:aiohttp
 asyncio_mode = auto
+# 2-minute per-test timeout so a hung test surfaces by name instead of taking
+# down the whole job. Autobahn and benchmark jobs override with `--timeout=0`.
+timeout = 120
 filterwarnings =
     error
     ignore:module 'ssl' has no attribute 'OP_NO_COMPRESSION'. The Python interpreter is compiled against OpenSSL < 1.0.0. Ref. https.//docs.python.org/3/library/ssl.html#ssl.OP_NO_COMPRESSION:UserWarning
diff --git a/tests/test_client_functional.py b/tests/test_client_functional.py
index cfc2d4529c5..10953516a0a 100644
--- a/tests/test_client_functional.py
+++ b/tests/test_client_functional.py
@@ -2416,7 +2416,7 @@ async def test_payload_decompress_size_limit(aiohttp_client: AiohttpClient) -> N
     we raise DecompressSizeError.
     """
     # Create a highly compressible payload.
-    payload_size = 64 * 2**20
+    payload_size = 2 * 2**20
     original = b"A" * payload_size
     compressed = zlib.compress(original)
     assert len(original) > DEFAULT_CHUNK_SIZE
@@ -2448,7 +2448,7 @@ async def test_payload_decompress_size_limit_brotli(
     """Test that brotli decompression size limit triggers DecompressSizeError."""
     assert brotli is not None
     # Create a highly compressible payload
-    payload_size = 64 * 2**20
+    payload_size = 2 * 2**20
     original = b"A" * payload_size
     compressed = brotli.compress(original)
     assert len(original) > DEFAULT_CHUNK_SIZE
@@ -2479,7 +2479,7 @@ async def test_payload_decompress_size_limit_zstd(
     """Test that zstd decompression size limit triggers DecompressSizeError."""
     assert ZstdCompressor is not None
     # Create a highly compressible payload.
-    payload_size = 64 * 2**20
+    payload_size = 2 * 2**20
     original = b"A" * payload_size
     compressor = ZstdCompressor()
     compressed = compressor.compress(original) + compressor.flush()
@@ -2904,7 +2904,7 @@ async def handler(request: web.Request) -> web.Response:
         assert 200 == resp.status
         cookie_names = {c.key for c in client.session.cookie_jar}
         assert cookie_names == {"c1", "c2", "c3"}
-        await asyncio.sleep(2)
+        await asyncio.sleep(1.1)
         cookie_names = {c.key for c in client.session.cookie_jar}
         assert cookie_names == {"c1", "c2"}
 
diff --git a/tests/test_http_parser.py b/tests/test_http_parser.py
index fa71d9aa2ed..147785def1c 100644
--- a/tests/test_http_parser.py
+++ b/tests/test_http_parser.py
@@ -1155,9 +1155,10 @@ def test_max_header_value_size_under_limit(parser: HttpRequestParser) -> None:
 
 
 async def test_chunk_splits_after_pause(parser: HttpRequestParser) -> None:
+    num_chunks = 20000  # comfortably above the 16385 pause threshold
     text = (
         b"GET /test HTTP/1.1\r\nHost: a\r\nTransfer-Encoding: chunked\r\n\r\n"
-        + b"1\r\nb\r\n" * 50000
+        + b"1\r\nb\r\n" * num_chunks
         + b"0\r\n\r\n"
     )
 
@@ -1168,8 +1169,9 @@ async def test_chunk_splits_after_pause(parser: HttpRequestParser) -> None:
     assert len(payload._http_chunk_splits) == 16385
     # We should still get the full result after read(), as it will continue processing.
     result = await payload.read()
-    assert len(result) == 50000  # Compare len first, as it's easier to debug in diff.
-    assert result == b"b" * 50000
+    # Compare len first, as it's easier to debug in diff.
+    assert len(result) == num_chunks
+    assert result == b"b" * num_chunks
 
 
 async def test_compressed_with_tail(response: HttpResponseParser) -> None: