diff --git a/pyproject.toml b/pyproject.toml
index 3c2d2232..c6254db8 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -42,15 +42,23 @@ cloudpickle = ">=2.0"
 # Agent framework integrations — optional, activated via [tool.poetry.extras] below.
 # Floors raised to the versions ConductorAgent's own uv.lock proved mutually compatible
 # (langchain's 0.3.x-floor collided with today's published 1.x line during resolution).
-langchain = { version = ">=1.2.13", optional = true }
-langchain-core = { version = ">=1.2.20", optional = true }
-langchain-openai = { version = ">=1.1.11", optional = true }
-langgraph = { version = ">=1.1.3", optional = true }
-google-adk = { version = ">=1.27.1", optional = true }
-openai = { version = ">=2.28.0", optional = true }
-openai-agents = { version = ">=0.12.2", optional = true }
-anthropic = { version = ">=0.91.0", optional = true }
-claude-code-sdk = { version = ">=0.0.25", optional = true }
+#
+# CEILINGS: every one of these was previously unbounded (">=X" only), so
+# `conductor-python[agents]` accepted any future major of langgraph/openai/anthropic/etc.
+# A breaking upstream release therefore reached users — and the downstream e2e bundle's
+# CI lanes — with no change here, presenting as an SDK or server regression. These are
+# integration surfaces we call directly, so a major bump is exactly where they break.
+# Caps are next-major (next-minor for the 0.x projects, whose minors are breaking by
+# convention). Raise a cap deliberately, with a run of the agent suites behind it.
+langchain = { version = ">=1.2.13,<2", optional = true }
+langchain-core = { version = ">=1.2.20,<2", optional = true }
+langchain-openai = { version = ">=1.1.11,<2", optional = true }
+langgraph = { version = ">=1.1.3,<2", optional = true }
+google-adk = { version = ">=1.27.1,<3", optional = true }
+openai = { version = ">=2.28.0,<3", optional = true }
+openai-agents = { version = ">=0.12.2,<0.13", optional = true }
+anthropic = { version = ">=0.91.0,<0.121", optional = true }
+claude-code-sdk = { version = ">=0.0.25,<0.1", optional = true }
 
 [tool.poetry.extras]
 langchain = ["langchain", "langchain-core", "langchain-openai"]
diff --git a/scripts/package-e2e-bundle.sh b/scripts/package-e2e-bundle.sh
index 43fab234..56db1d24 100755
--- a/scripts/package-e2e-bundle.sh
+++ b/scripts/package-e2e-bundle.sh
@@ -56,13 +56,18 @@ cat > "$STAGE/requirements.txt" <<'EOF'
 conductor-python[agents]==@VERSION@
 
 # Test runner + e2e support deps (mirrors .github/workflows/agent-e2e.yml).
-pytest
-pytest-asyncio
-pytest-xdist
-pytest-rerunfailures
+# Bounded, not bare: these were unpinned, so `pip install -r requirements.txt` inside
+# run.sh resolved to whatever was newest on the day a downstream lane happened to run.
+# A pytest or plugin major could then redden a consumer's gating CI with no change to
+# this bundle — and look like a server regression to whoever triaged it. Floors are the
+# versions this bundle was cut against; ceilings are next-major.
+pytest>=8,<10
+pytest-asyncio>=1,<2
+pytest-xdist>=3,<4
+pytest-rerunfailures>=16,<17
 
 # Live MCP server used by the MCP tool suites.
-mcp-testkit
+mcp-testkit>=1,<2
 EOF
 
 cat > "$STAGE/run.sh" <<'EOF'