diff --git a/backend/app/schemas/ai_session.py b/backend/app/schemas/ai_session.py
index 973de98c..983eb113 100644
--- a/backend/app/schemas/ai_session.py
+++ b/backend/app/schemas/ai_session.py
@@ -228,6 +228,8 @@ class AISessionDetail(AISessionSummary):
     ticket_data: dict[str, Any] | None = None
     steps: list[AISessionStepResponse] = []
     conversation_messages: list[dict[str, Any]] = []  # Chat sessions store messages here
+    is_branching: bool = False
+    active_branch_id: str | None = None
 
     model_config = {"from_attributes": True}
 
diff --git a/backend/app/schemas/session_branch.py b/backend/app/schemas/session_branch.py
new file mode 100644
index 00000000..deebaca2
--- /dev/null
+++ b/backend/app/schemas/session_branch.py
@@ -0,0 +1,83 @@
+"""Pydantic schemas for session branches and fork points."""
+from __future__ import annotations
+from typing import Any
+from uuid import UUID
+from datetime import datetime
+from pydantic import BaseModel, Field
+
+
+class BranchCreate(BaseModel):
+    label: str = Field(..., max_length=200)
+    status: str = "untried"
+
+
+class BranchUpdate(BaseModel):
+    status: str = Field(..., pattern="^(active|dead_end|solved|untried|revived)$")
+    status_reason: str | None = None
+
+
+class BranchResponse(BaseModel):
+    id: UUID
+    session_id: UUID
+    parent_branch_id: UUID | None
+    fork_point_step_id: UUID | None
+    branch_order: int
+    label: str
+    status: str
+    status_reason: str | None
+    status_changed_at: datetime | None
+    context_summary: dict[str, Any] | None
+    evidence_from_branch_id: UUID | None
+    evidence_description: str | None
+    step_count: int = 0
+    created_at: datetime
+    updated_at: datetime
+    model_config = {"from_attributes": True}
+
+
+class BranchTreeResponse(BaseModel):
+    branches: list[BranchResponse]
+    active_branch_id: UUID | None
+
+
+class ForkOption(BaseModel):
+    label: str = Field(..., max_length=200)
+    description: str = Field(..., max_length=500)
+
+
+class ForkCreateRequest(BaseModel):
+    fork_reason: str = Field(..., min_length=5, max_length=2000)
+    options: list[ForkOption] = Field(..., min_length=2, max_length=10)
+
+
+class ForkPointResponse(BaseModel):
+    id: UUID
+    session_id: UUID
+    parent_branch_id: UUID
+    trigger_step_id: UUID | None
+    fork_reason: str
+    options: list[dict[str, Any]]
+    created_at: datetime
+    model_config = {"from_attributes": True}
+
+
+class BranchSwitchResponse(BaseModel):
+    active_branch_id: UUID
+    branch: BranchResponse
+    conversation_messages: list[dict[str, Any]]
+
+
+class ReviveRequest(BaseModel):
+    evidence_from_branch_id: UUID
+    evidence_description: str = Field(..., min_length=5, max_length=2000)
+
+
+class BranchMessageRequest(BaseModel):
+    message: str = Field(..., min_length=1, max_length=8000)
+    upload_ids: list[UUID] = Field(default_factory=list, max_length=10)
+
+
+class BranchMessageResponse(BaseModel):
+    content: str
+    branch_id: UUID
+    step_id: UUID | None = None
diff --git a/backend/app/schemas/session_handoff.py b/backend/app/schemas/session_handoff.py
new file mode 100644
index 00000000..da1a52cb
--- /dev/null
+++ b/backend/app/schemas/session_handoff.py
@@ -0,0 +1,57 @@
+"""Pydantic schemas for session handoffs."""
+from __future__ import annotations
+from typing import Any
+from uuid import UUID
+from datetime import datetime
+from pydantic import BaseModel, Field
+
+
+class HandoffCreateRequest(BaseModel):
+    intent: str = Field(..., pattern="^(park|escalate)$")
+    engineer_notes: str | None = None
+    priority: str = Field("normal", pattern="^(normal|elevated)$")
+
+
+class HandoffResponse(BaseModel):
+    id: UUID
+    session_id: UUID
+    handed_off_by: UUID
+    intent: str
+    source_branch_id: UUID | None
+    snapshot: dict[str, Any]
+    ai_assessment: str | None
+    ai_assessment_data: dict[str, Any] | None
+    artifacts: list[dict[str, Any]] | None
+    engineer_notes: str | None
+    priority: str
+    claimed_by: UUID | None
+    claimed_at: datetime | None
+    psa_note_pushed: bool
+    notification_sent: bool
+    created_at: datetime
+    model_config = {"from_attributes": True}
+
+
+class HandoffClaimRequest(BaseModel):
+    pass
+
+
+class HandoffBriefingResponse(BaseModel):
+    briefing: str
+    handoff: HandoffResponse
+
+
+class QueueItemResponse(BaseModel):
+    handoff_id: UUID
+    session_id: UUID
+    intent: str
+    problem_summary: str | None
+    problem_domain: str | None
+    priority: str
+    handed_off_by_name: str | None
+    engineer_notes: str | None
+    branch_count: int = 0
+    created_at: datetime
+    claimed_by: UUID | None
+    claimed_at: datetime | None
+    model_config = {"from_attributes": True}
diff --git a/backend/app/schemas/session_resolution.py b/backend/app/schemas/session_resolution.py
new file mode 100644
index 00000000..126c93fb
--- /dev/null
+++ b/backend/app/schemas/session_resolution.py
@@ -0,0 +1,42 @@
+"""Pydantic schemas for session resolution outputs."""
+from __future__ import annotations
+from typing import Any
+from uuid import UUID
+from datetime import datetime
+from pydantic import BaseModel, Field
+
+
+class ResolutionOutputResponse(BaseModel):
+    id: UUID
+    session_id: UUID
+    output_type: str
+    generated_content: str
+    structured_data: dict[str, Any] | None
+    edited_content: str | None
+    status: str
+    pushed_to: str | None
+    pushed_at: datetime | None
+    pushed_reference: str | None
+    generated_by_model: str
+    created_at: datetime
+    updated_at: datetime
+    model_config = {"from_attributes": True}
+
+
+class ResolutionOutputEditRequest(BaseModel):
+    edited_content: str = Field(..., min_length=1)
+
+
+class ResolutionOutputPushRequest(BaseModel):
+    destination: str = Field(..., pattern="^(psa|kb_library|clipboard|email)$")
+
+
+class ResolutionOutputPushResponse(BaseModel):
+    output_id: UUID
+    status: str
+    pushed_to: str
+    pushed_reference: str | None = None
+
+
+class AllResolutionOutputsResponse(BaseModel):
+    outputs: list[ResolutionOutputResponse]