fix(client): harden nested Tool call projection

.agents/notes/implemented/feature/2026-07-26-code-mode-chat-subcall-rows.md

@@ -12,12 +12,12 @@ With Code Mode enabled, the chat view showed one opaque `run_code` row: raw prog
 
 ## Decision
 
-**Sub-calls are `ToolResultNode`s indexed off the surface flow, rendered through the same keyed slot as native rows, nested always-visible under their parent.**
+**Sub-calls are standard Tool call blocks attached recursively to their parent outside the surface flow, rendered through the same keyed slot as native rows, and always visible under their parent.**
 
-- **Data layer**: `Session.applyEventSideEffects` folds each in-window `tool/code-dispatch` into `ConversationSnapshot.codeDispatches: ReadonlyMap<parentCallId, readonly CodeSubCall[]>`, where `CodeSubCall` IS `ToolResultNode` (the sub-call id as `callId`, the logged args JSON-stringified into `call.argsRaw`, the full logged `content`/`isError`). Live mux frames and history replay build the identical index (`rebuildDerivedFromWindow` clears and re-derives; copy-on-write per-parent arrays keep snapshot references memo-stable). Sub-calls never join `nodes` — the surface flow remains exactly the model-visible turn structure. The event is narrowed structurally at the wire-consumer boundary (dsh-tools' host types cannot enter the client program — the host/client `Context` merges collide), the same posture as every cross-wire payload.
-- **Render layer**: `ChatView` passes each parent and its indexed children through the whole-Tool `'conversation.chat.tool'` seat. ui-tool's `ToolCallTree` renders the parent followed by a `[data-subcalls]` nest, and every atomic call dispatches through the same `'tool.call.toolview'` keyed slot with `entryKey = Tool name` and the same `GenericToolCard` fallback. A keyed registration therefore takes over child and top-level calls without registration changes. Running parents (`runningCalls`) receive their accumulated dispatches through the same owner payload, so child rows stream in during the run.
+- **Data layer**: Runtime's `ToolCallTree` folds in-window `tool/code-dispatch-start` and `tool/code-dispatch` events into a private per-parent index, then projects running and settled children onto recursive `ToolCallBlock.subCalls`. Live Session projection and `projectConversationHistory` share that fold; copy-on-write parent arrays and path-copy projection keep unrelated roots and siblings reference-stable. Sub-calls never join `nodes` — the surface flow remains exactly the model-visible turn structure. The events are narrowed structurally at the wire-consumer boundary, which also rejects cyclic parent relationships (dsh-tools' host types cannot enter the client program because the host/client `Context` merges collide).
+- **Render layer**: `ChatView` passes each parent with its recursive children through the whole-Tool `'conversation.chat.tool'` seat. ui-tool's `ToolCallTree` renders the parent followed by `[data-subcalls]` nests, and every atomic call dispatches through the same `'tool.call.toolview'` keyed slot with `entryKey = Tool name` and the same `GenericToolCard` fallback. A keyed registration therefore takes over descendant and top-level calls without registration changes. Running parents (`runningCalls`) receive accumulated dispatches in the same recursive block, so child rows stream in during the run.
 - **`run_code` presentation**: a new `code` row variant (classifier `run_code → code`, `Code` title, `IconCodeOutline16`) summarizes with the model-authored `description` and expands to the program itself (monospace on the markdown code-block fill) rather than the args JSON envelope.
-- **Details panel**: `materialFor` falls through nodes → runningCalls → the dispatch index, so a selected sub-callId resolves to full args and complete output through the identical rendering path as a native settled call.
+- **Details panel**: `materialFor` recursively searches `nodes` and `runningCalls`, so a selected descendant callId resolves to full args and complete output through the identical rendering path as a native settled call.
 
 ## Alternatives considered
 
@@ -29,4 +29,4 @@ With Code Mode enabled, the chat view showed one opaque `run_code` row: raw prog
 
 ## Consequences
 
-Custom toolview registrations apply to sub-calls for free — and deliberately: there is no per-registration opt-out short of the component reading its own context, which no current consumer needs. Selection highlighting reaches nested rows through the same `selectedCallId` channel (group membership tests both levels). Trajectory/waterfall still render `run_code` as a single row — their sub-call spans are deferred to the PR that adds dispatch timing (start/end events), without which a waterfall span would be a lie. Fixture turn 64 (`?fixture`) plus the `code-mode-round` browser e2e (recorded real round, keyless replay) pin the full surface; the jsdom suites pin the slot dispatch, error states, details resolution, and index reference stability.
+Custom toolview registrations apply to sub-calls for free — and deliberately: there is no per-registration opt-out short of the component reading its own context, which no current consumer needs. Selection highlighting reaches nested rows through the same `selectedCallId` channel (group membership searches the whole tree). Trajectory/waterfall still render `run_code` as a single row — their sub-call spans are deferred to the PR that adds dispatch timing (start/end events), without which a waterfall span would be a lie. Fixture turn 64 (`?fixture`) plus the `code-mode-round` browser e2e (recorded real round, keyless replay) pin the full surface; the jsdom and Runtime suites pin slot dispatch, error states, recursive details resolution, history projection, and reference-stable path copying.