A session mode is a named, logged, per-agent policy state: mode/set as a
log-only SessionEventMap member (todo/write shape), a foldMode over the log,
soft enforcement at system-prompt/assemble (filtered schemas + mode section,
auto-logged as request/header-delta), hard enforcement at tools/pre-execute
(deny-by-default against the mode allowlist), and a thin ctx.modes service
with turn-boundary pending-intent flush for user flips. One new product
package dsh-mode (packages/mode/mode, the approval-group shape); plan is the
only shipped definition.
Lands as ONE feature — a plan mode without a model-driven, approvable exit is
not a smaller version of the feature. The roadmap's two stages are build-and-
review order for a single stacked landing: the mode core, then exit_plan_mode
(ask-gated through the approval seam; the plan text rides the tool args as
the reviewable log artifact), the stdio readline answerer, and the ACP
session-mode surface (session/set_mode, current_mode_update, available
modes). Hard prerequisite: the approval seam lands first; the stack bases on
feat/sandbox-support meanwhile.
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