Merge remote-tracking branch 'origin/master' into codex/fs-directory-listing

# Conflicts:
#	docs/rfc/README.md
#	packages/fs/fs-local/src/index.ts

docs/rfc/implemented/architecture/2026-07-02-result-time-applied-hunk-diffs.md

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+# RFC: Result-time applied-hunk diffs for file mutations
+
+Status: implemented
+
+## Problem
+
+The [tagged render-intent union](2026-07-02-tool-render-intent-union.md) gave `dsh-tool-fs` write/edit a `card:'diff'` at CALL time, derived purely from the tool's args: write ⇒ `{oldText:null, newText:content}` (the whole new file), edit ⇒ `{oldText:old_string, newText:new_string}` (the bare replaced snippet). An editor renders that as an inline diff, but it is a **context-free** diff — the bare `old_string`→`new_string` with no surrounding lines, and a `replace_all` that touched five scattered sites still renders as one snippet pair.
+
+Driving `claude-agent-acp`'s own ACP bridge shows what a full editor diff looks like: after the mutation applies, it emits a SECOND `tool_call_update` whose diff is the **applied hunk with ±3 context lines** (and one hunk per changed site for `replace_all`), reconstructed from the tool's `structuredPatch`. That result-time hunk is what makes Zed show the change *in place* in the file rather than as a floating snippet. Our tools stopped at the call-time snippet; the completed result carried only the plain "updated successfully" text, no diff.
+
+The obstacle is a seam boundary: `presentResult(args, result)` is a **pure function of `args` + the model-facing `result` (`{content, isError}`)** — it runs on live streaming AND on session-log replay, so it must be replay-deterministic and cannot do I/O. It never sees the file's before/after content, and `FsEditOutcome`/`FsWriteOutcome` carried only a replacement count + version, not the text. So there was no way to compute — or even carry — an applied hunk to the presenter.
+
+## Decision
+
+Add a **persisted, tool-private presentation channel** so a tool's `execute` can attach a result-time render payload that survives replay, and use it to carry the applied-hunk diff.
+
+### 1. A `meta` channel on the tool result (core)
+
+`ToolDefinition.execute` may now return either its model-facing `ContentBlock[]` (unchanged, the common case) OR `{ content: ContentBlock[]; meta?: unknown }`:
+
+```ts ignore-check
+type ToolExecuteReturn = ContentBlock[] | { content: ContentBlock[]; meta?: unknown }
+```
+
+`meta` is an opaque payload the core never interprets — typed `unknown` at every seam (the tool that produced it owns and narrows its shape). It MUST be JSON-serializable: the registry threads it onto the `tool/result` **session event**, and `Session.append` runtime-validates all event data with the existing `isJsonValue` predicate, so a non-serializable `meta` is rejected at the source. On replay the same `meta` is read back and handed to `presentResult` via a widened `ToolResult` (`{ content, isError, meta? }`). Because the payload lives in the event log, the diff reproduces on session reload / snapshot replay **for free** — the event-sourcing guarantee, not a re-computation. Typing `meta` as `unknown` (rather than a shared serializable-value type) keeps the tools core free of a dependency it would otherwise take just to name the type, and the runtime `isJsonValue` gate — not the static type — is what actually enforces serializability.
+
+This is the general shape ("a tool attaches durable result presentation"), not an fs-specific one — any tool can use it.
+
+### 2. The tool computes the hunk; the backend returns before/after (fs)
+
+Per the [capability-seam split](2026-06-13-capability-seams.md), the storage backend returns only **storage facts** and the model-facing tool owns **presentation**:
+
+- `dsh-fs` widens `FsEditOutcome` with `{ before: string; after: string }` and `FsWriteOutcome` with `{ before: string | null; after: string }` (`before: null` ⇒ a create, or an existing-but-undiffable binary/non-UTF-8 file). The local backend already holds both texts at write time; it returns them as raw LF-normalized text, with **no diff/UI concept** entering the seam.
+- `dsh-tool-fs` computes the contextual hunk from before/after and attaches it as `meta: { diffs: FileDiff[] }`. A contextual hunk is computed only when a before-version exists — edit always; write on overwrite; a create has no before, matching `claude-agent-acp`'s empty `structuredPatch` on create. But the completed `tool_call_update` is ALWAYS a `diff` card for a successful mutation: an ACP `tool_call_update.content` REPLACES the call's content, so rendering the model-facing result text would clobber the pending diff. So `write`'s result falls back to an args-derived whole-file diff (`oldText: null`) when it has no contextual hunk (a create, or an overwrite whose content is unchanged), and `edit` — which always changes content — always has a hunk. A failed/aborted/policy-rejected mutation applied nothing, so it carries no `meta` and falls through to the generic error rendering (its message must show).
+
+### 3. The bridge renders a `diff` result card
+
+`ToolResultView` gains a `DiffResultView { card:'diff'; title?; diffs: FileDiff[] }`; the bridge's result-side `switch (view.card)` gets a `diff` arm emitting the `{type:'diff'}` `ToolCallContent` blocks (mirroring the call-side arm). An ACP `tool_call_update.content` REPLACES the call's content in an editor, so the result diff **supersedes** the call-time snippet (and keeps the model-facing result text from clobbering it) — the two-update sequence (call snippet, then result diff) matches `claude-agent-acp` exactly.
+
+### The diff algorithm — a third-party runtime dependency over vendoring
+
+Computing hunks-with-context is a solved problem with sharp edge cases (grouping, context coalescing, the trailing-newline marker). Rather than hand-roll it, `dsh-tool-fs` takes a runtime dependency on the npm [`diff`](https://www.npmjs.com/package/diff) package (a `^9.0.0` range, exact-pinned by the lockfile; it ships its own types) and uses its `structuredPatch`. The repo's default is to vendor Cordis-framework source, but that policy is about the *framework*; a leaf tool package taking a small, well-known, self-typed utility dependency is the same shape as `dsh-acp` depending on `@agentclientprotocol/sdk`. Vendoring a diff algorithm would be re-implementing a battle-tested one for no benefit — the [pre-release "foundation over blast radius"](../../../../AGENTS.md) reasoning does not argue for re-deriving standard algorithms. The dependency's output is normalized in one small module (`packages/fs/tool-fs/src/diff.ts`).
+
+## Non-goals
+
+- **Live incremental diff streaming.** The hunk is computed once, after the mutation completes; there is no per-keystroke diff.
+- **Diffing a binary/non-UTF-8 overwrite.** `before` is `null` for such a file (it has no text diff basis); the write still succeeds and the result renders a whole-file diff (`oldText: null`) rather than a contextual hunk.
+- **Rename/move diffs.** Only content diffs of a single resolved path.
+- **Bounding the overwrite diff basis.** An overwrite reads the whole prior file into memory to compute the contextual hunk (on top of the new content already held), so a very large text overwrite allocates both texts for a UI-only diff. A future refinement can bound the pre-read and fall back to a whole-file / no contextual diff above a size threshold; tracked as `TODO(overwrite-diff-bound)` at the read site.
+
+## Related
+
+- Completes the one remaining representation difference named as a non-goal in [Tagged render-intent union](2026-07-02-tool-render-intent-union.md) — that RFC's Non-goals section is updated to record that applied-hunk diffs shipped here.
+- Builds on the [filesystem capability seam](2026-06-17-filesystem-capability-seam.md) (the before/after are storage facts the backend returns) and [event-sourced sessions](2026-06-11-event-sourced-sessions.md) (the `meta` payload persists on the `tool/result` event, so replay reproduces the card).
+- The `meta` channel is deliberately generic: a future tool (a structured search, a data-table result) can attach its own durable result presentation without another core change.

docs/rfc/implemented/architecture/2026-07-02-tool-render-intent-union.md

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+# RFC: Tagged render-intent union for tool-call presentation
+
+Status: implemented
+
+## Problem
+
+A tool declares how its calls render in a UI (an editor's tool-call card) through two callbacks, `presentCall`/`presentResult` on `ToolDefinition`, returning `ToolCallPresentation` / `ToolResultPresentation` with an optional `ToolTerminal` sub-shape. These grew incrementally into a **bag of optional fields**: `title`, `kind`, `rawInput`, `content`, `locations`, `terminal` on the call; `title`, `content`, `terminal` on the result; `cwd`/`output`/`exitCode`/`signal` on `ToolTerminal`. The split of responsibility is muddy:
+
+- The call-side and result-side `terminal` fields overlap, and the bridge reconciles a `content` block AND a `terminal` block AND `rawInput` per call, stitching them together with ad-hoc conditionals.
+- Which combinations are *valid* is unwritten: a `terminal` call that also sets `content` means "description above the card"; a generic call that sets `terminal` is meaningless but representable. The type permits nonsense.
+- There is no way to express the one file-tool affordance an editor most wants — a **diff card** (`{path, oldText, newText}`, which Zed renders as an inline diff / new-file preview). `ToolCallPresentation.content` is the *LLM* `ContentBlock[]` vocabulary (text/image), so a tool literally cannot ask for a diff.
+
+The existing `FIXME(tool-presentation)` in `packages/core/tools/src/index.ts` named the fix: "redesign the type so a tool declares its render INTENT once (e.g. a tagged union over card kinds) rather than a bag of optional fields the bridge stitches together." The rejected RFC [Collapse tool-owned UI presentation](../../rejected/simplification/2026-06-20-generic-tool-rendering.md) deferred it explicitly: rich rendering "should return later as a tagged render-intent union after there are at least two real tools and two real consumers to validate the vocabulary." That bar is now met — two producer families (`dsh-tool-bash`, `dsh-tool-fs`) and two consumers (the ACP bridge live path + the snapshot-golden replay path).
+
+## Decision
+
+Replace the optional-field bag with a **`card`-tagged discriminated union**. A tool declares one render intent per call/result; the bridge switches on the tag.
+
+```ts ignore-check
+type FileLocation = { path: string; line?: number }
+type FileDiff = { path: string; oldText: string | null; newText: string } // oldText null ⇒ new file
+
+// presentCall → ToolCallView
+type ToolCallView = GenericCallView | TerminalCallView | DiffCallView
+interface GenericCallView { card: 'generic'; title: string; kind?: ToolCallKind; rawInput?: unknown; content?: ContentBlock[]; locations?: FileLocation[] }
+interface TerminalCallView { card: 'terminal'; title: string; description?: string; cwd?: string }
+interface DiffCallView { card: 'diff'; title: string; diffs: FileDiff[]; locations?: FileLocation[] }
+
+// presentResult → ToolResultView
+type ToolResultView = GenericResultView | TerminalResultView
+interface GenericResultView { card: 'generic'; title?: string; content?: ContentBlock[] }
+interface TerminalResultView { card: 'terminal'; title?: string; output?: string; exitCode?: number; signal?: string }
+```
+
+`card` is **required** on every variant — a real discriminant, not an optional default. The bridge does `switch (view.card) { case 'generic': … case 'terminal': … case 'diff': … default: assertNever(view) }`. The union is **closed** (per the [switch-exhaustiveness convention](../../../../AGENTS.md)): a fourth render intent (a table, a chart) needs new bridge code to render it anyway, so a plugin-added variant that the bridge silently drops would be worse than a compile error. Adding a variant breaks compilation at the bridge switch — exactly the signal we want.
+
+### Why a tagged union beats the field-bag
+
+- **Invalid states become unrepresentable.** A generic card cannot carry terminal output; a terminal card cannot carry a diff. The old bag permitted all of these.
+- **The bridge switches instead of stitching.** One arm per card kind, each producing exactly the wire shape that card needs, rather than reconciling five optional fields whose interactions are undocumented.
+- **`diff` is a first-class intent.** `dsh-tool-fs` write/edit declare `card:'diff'`; the bridge emits an ACP `{type:'diff', path, oldText, newText}` `ToolCallContent` (already in the SDK's `ToolCallContent` union, previously unused by the bridge). This is the affordance the redesign unlocks.
+
+### Producer mapping
+
+- `dsh-tool-fs` read → `generic` (`kind:'read'`, a follow-along `location`); write → `diff` (`oldText:null`); edit → `diff` (`oldText:old_string || null`, `newText:new_string ?? ''`). This mirrors `claude-agent-acp`'s `toolInfoFromToolUse` Read/Write/Edit arms field-for-field.
+- `dsh-tool-bash` foreground → `terminal` call + `terminal` result; `run_in_background` and `bash_output`/`bash_kill` → `generic`.
+- `dsh-tool-todo` → `generic`.
+
+### Terminal fallback ownership
+
+`TerminalResultView` carries only `output`/`exitCode`/`signal`. A UI without the terminal capability needs a fenced ` ```console ` text fallback; that derivation moves to the **bridge** (it wraps `output` in a fenced block on the no-capability path), rather than the tool double-encoding it. This keeps the bash tool's result a single structured shape and preserves the existing capability-gated behavior byte-for-byte.
+
+### Purity preserved
+
+`presentCall`/`presentResult` remain pure functions of `args` (+ the result for `presentResult`) — they run on live streaming AND session-log replay, so they must be replay-deterministic. Every view is derived from args alone: write's diff is new-file style (`oldText:null`) because the tool has no old content at call time; edit's diff is `old_string`→`new_string`.
+
+## Relative-path display titles
+
+`claude-agent-acp` relativizes a file card's title path against the session cwd (`toDisplayPath`) — `Read src/foo.ts`, not `/abs/proj/src/foo.ts` — while keeping `locations[]`/`diff.path` **raw** (the editor opens the real path). Our `presentCall` is pure/args-only and cannot see the session cwd, so this relativization happens at the **bridge**, which already threads the session cwd into tool-call rendering (the same cwd it uses to resolve a terminal card's header). The bridge relativizes the title only, by an exact structured replace of the known `locations[0].path`/`diffs[0].path` substring — generic over the file-card kinds, never special-casing tool names.
+
+## Non-goals
+
+- **Live incremental `terminal_output_delta` streaming** and **command classification** — the terminal-rendering RFC's own deferred follow-ups, untouched here.
+
+## Related
+
+- Supersedes the deferral in [Collapse tool-owned UI presentation](../../rejected/simplification/2026-06-20-generic-tool-rendering.md) (rejected — "wait for two real tools and two real consumers, then a tagged render-intent union"). That bar is now met; this is that union.
+- Extended by [Result-time applied-hunk diffs](2026-07-02-result-time-applied-hunk-diffs.md), which adds a persisted `meta` channel so write/edit emit a result-time `DiffResultView` — the applied change (a contextual hunk with context lines / one per `replace_all` site, or a whole-file diff for a create) — on top of this union's call-time diff card.
+- Folds `ToolTerminal` into the `terminal` views described by [ACP terminal and tool-call rendering](../feature/2026-06-18-acp-terminal-and-tool-rendering.md) (the `_meta` terminal-card convention and capability gate are unchanged; only the harness-side presentation type changes).
+- The ACP SDK's `Diff` / `ToolCallContent` types back the new `diff` card.