diff --git a/migrations/0006_acp.up.sql b/migrations/0006_acp.up.sql
new file mode 100644
index 0000000..4e86835
--- /dev/null
+++ b/migrations/0006_acp.up.sql
@@ -0,0 +1,75 @@
+-- ============ AgentKind ============
+CREATE TABLE acp_agent_kinds (
+  id              UUID PRIMARY KEY,
+  name            TEXT NOT NULL UNIQUE,
+  display_name    TEXT NOT NULL,
+  description     TEXT NOT NULL DEFAULT '',
+  binary_path     TEXT NOT NULL,
+  args            TEXT[] NOT NULL DEFAULT '{}',
+  encrypted_env   BYTEA,
+  enabled         BOOLEAN NOT NULL DEFAULT TRUE,
+  created_by      UUID NOT NULL REFERENCES users(id) ON DELETE RESTRICT,
+  created_at      TIMESTAMPTZ NOT NULL DEFAULT now(),
+  updated_at      TIMESTAMPTZ NOT NULL DEFAULT now()
+);
+CREATE INDEX idx_acp_agent_kinds_enabled ON acp_agent_kinds(enabled) WHERE enabled = TRUE;
+
+-- ============ Prerequisites for composite FK ============
+ALTER TABLE issues       ADD CONSTRAINT issues_project_id_unique       UNIQUE (project_id, id);
+ALTER TABLE requirements ADD CONSTRAINT requirements_project_id_unique UNIQUE (project_id, id);
+
+-- ============ Sessions ============
+CREATE TABLE acp_sessions (
+  id                 UUID PRIMARY KEY,
+  workspace_id       UUID NOT NULL REFERENCES workspaces(id) ON DELETE CASCADE,
+  project_id         UUID NOT NULL REFERENCES projects(id) ON DELETE CASCADE,
+  agent_kind_id      UUID NOT NULL REFERENCES acp_agent_kinds(id) ON DELETE RESTRICT,
+  user_id            UUID NOT NULL REFERENCES users(id) ON DELETE RESTRICT,
+  issue_id           UUID,
+  requirement_id     UUID,
+  agent_session_id   TEXT,
+  branch             TEXT NOT NULL,
+  cwd_path           TEXT NOT NULL,
+  is_main_worktree   BOOLEAN NOT NULL DEFAULT FALSE,
+  status             TEXT NOT NULL,
+  pid                INT,
+  exit_code          INT,
+  last_error         TEXT,
+  started_at         TIMESTAMPTZ NOT NULL DEFAULT now(),
+  ended_at           TIMESTAMPTZ,
+  CONSTRAINT acp_sessions_status_check CHECK (status IN ('starting','running','crashed','exited')),
+  CONSTRAINT acp_sessions_issue_project_fk
+    FOREIGN KEY (project_id, issue_id)
+    REFERENCES issues (project_id, id) MATCH SIMPLE ON DELETE SET NULL,
+  CONSTRAINT acp_sessions_req_project_fk
+    FOREIGN KEY (project_id, requirement_id)
+    REFERENCES requirements (project_id, id) MATCH SIMPLE ON DELETE SET NULL
+);
+CREATE INDEX idx_acp_sessions_workspace_status ON acp_sessions(workspace_id, status);
+CREATE INDEX idx_acp_sessions_user_status      ON acp_sessions(user_id, status);
+CREATE INDEX idx_acp_sessions_issue            ON acp_sessions(issue_id)       WHERE issue_id IS NOT NULL;
+CREATE INDEX idx_acp_sessions_requirement      ON acp_sessions(requirement_id) WHERE requirement_id IS NOT NULL;
+
+-- ============ Workspaces main worktree mutex ============
+ALTER TABLE workspaces ADD COLUMN active_main_session_id UUID;
+ALTER TABLE workspaces
+  ADD CONSTRAINT workspaces_active_main_session_fk
+  FOREIGN KEY (active_main_session_id)
+  REFERENCES acp_sessions(id) ON DELETE SET NULL DEFERRABLE INITIALLY DEFERRED;
+
+-- ============ Events ============
+CREATE TABLE acp_events (
+  id                BIGSERIAL PRIMARY KEY,
+  session_id        UUID NOT NULL REFERENCES acp_sessions(id) ON DELETE CASCADE,
+  direction         TEXT NOT NULL,
+  rpc_kind          TEXT NOT NULL,
+  method            TEXT,
+  payload           JSONB NOT NULL,
+  payload_size      INT NOT NULL,
+  truncated         BOOLEAN NOT NULL DEFAULT FALSE,
+  created_at        TIMESTAMPTZ NOT NULL DEFAULT now(),
+  CONSTRAINT acp_events_direction_check CHECK (direction IN ('in','out')),
+  CONSTRAINT acp_events_kind_check      CHECK (rpc_kind IN ('request','response','notification','error'))
+);
+CREATE INDEX idx_acp_events_session_id ON acp_events(session_id, id);
+CREATE INDEX idx_acp_events_created_at ON acp_events(created_at);