APP-2527 Phase 3: MCP JSON tree rendering

[cephalonaut]

What

Replace the flat pretty-printed JSON text in the MCP tool call detail view with an interactive, collapsible JSON tree rendered by the JsonTreeView component built in Phases 1 and 2.

json_tree.rs: Updated render_json_tree, render_value, render_container_node, and render_scalar_row callback signatures to accept &mut EventContext as first argument, allowing callers to dispatch typed actions from Hoverable click handlers.

requested_command.rs:

• Added CopyJsonToClipboard { text: String } to RequestedCommandViewAction to bridge EventContext right-click handlers (which lack clipboard access) to ViewContext::clipboard() in handle_action
• Added mcp_scroll_state: ClippedScrollStateHandle field to preserve scroll position across renders
• Replaced should_render_mcp_content body: request section renders render_json_tree with mcp_request_tree_state (or a "(no arguments)" placeholder), response section renders tree/error/cancelled once a finished result is available, all wrapped in a NewScrollable + ConstrainedBox::with_max_height(MAX_EDITOR_HEIGHT) + SelectableArea

Why

Replaces an unformatted flat JSON blob with an interactive tree that lets users collapse uninteresting subtrees and expand long strings on demand.

Agent Mode

• This PR was created by Warp Agent Mode

Manual Validation Checklist (from TECH.md Phase 3)

• Configure a local MCP server (e.g. filesystem) and expand a tool call: root expanded, nested collapsed, chevrons toggle independently, indentation per level
• Large/nested response: Request/Response labels visible, typed colors for all value types, light↔dark theme switch recolors without restart
• Long string (file contents): elision preview + chevron, expands/collapses in place without disturbing siblings
• Very tall expanded tree: tree scrolls, does not push subsequent blocks off-screen
• Response arrives while header is collapsed: expand header to confirm both request and response trees are shown
• Error and cancelled tool calls show labeled messages
• Right-click → Copy JSON on a collapsed container copies complete JSON
• Right-click → Copy JSON on the Request label copies the full request JSON
• Copy with no selection is a no-op
• Text selection and copy across key/value rows works
• Collapsed header, accept/reject, and a non-MCP action (shell command) are visually unchanged

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Conversation: https://staging.warp.dev/conversation/3a48e515-b541-4d6d-bc95-0bd50f8b9124
Run: https://oz.staging.warp.dev/runs/019edff8-41ce-7cf2-891d-3e1c4bcd4608
This PR was generated with Oz.

[cephalonaut]

Phase 3 Code Review — APP-2527 MCP JSON Tree Rendering

Verdict: MINOR — core implementation is correct; four items need resolution before merge.

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✅ Passing criteria

• should_render_mcp_content block fully replaced by Request + Response sections calling render_json_tree ✓
• Request section renders the tree when args are known, or "(no arguments)" placeholder when mcp_request is None (Behavior 29) ✓
• Response section gated on finished_result() only; mcp_result_to_renderable correctly dispatches to Tree/Error/Cancelled (Behavior 28) ✓
• Tree body wrapped in NewScrollable::vertical (Clipped) + ConstrainedBox::with_max_height(MAX_EDITOR_HEIGHT) (Behavior 17) ✓
• mcp_scroll_state: ClippedScrollStateHandle added to struct and initialized via Default::default() ✓
• ToggleJsonNode callbacks dispatch McpTree::Request / McpTree::Response correctly ✓
• on_copy_json serializes with serde_json::to_string_pretty and dispatches CopyJsonToClipboard; handler calls ctx.clipboard().write(...) (Behavior 27) ✓
• SelectableArea + mcp_content_selection_handle wraps the constrained scrollable (Behavior 25) ✓
• Outer Container retains background + bottom CornerRadius; with_border and margin structure unchanged (Behavior 33) ✓
• No hard-coded colors — all resolved through JsonTreeColors::from_theme(theme) and theme.ui_error_color() (Behavior 18–20) ✓
• CopyJsonToClipboard uses ClipboardContent::plain_text via ctx.clipboard().write(...) — consistent with other copy surfaces ✓
• ToggleJsonString handler wired in handle_action but not yet dispatched from UI — acceptable follow-up ✓
• No spec/process references in comments ✓
• PR body includes full manual validation checklist from TECH.md Phase 3 ✓

Spec deviation — &mut EventContext in callbacks (evaluated as required): Adding EventContext as the first argument to on_toggle and on_copy_json is the minimal necessary change. Without it, closures captured inside Hoverable::on_click/on_right_click cannot call ctx.dispatch_typed_action(...). Alternatives (returning a Box<dyn Action>, using a channel) would be more complex and less idiomatic. No existing callers outside this PR are affected (the component was new in Phase 1). The change is correct and appropriate.

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⚠️ Minor issues (must be resolved before merge)

1. No right-click context menu — Behavior 26 and PR checklist item 9 unmet

render_container_node and render_scalar_row invoke on_copy_clone directly on right-click rather than showing a Menu with "Copy" and "Copy JSON" items. PRODUCT.md Behavior 26 explicitly requires a context menu; TECH.md Design §E1 (recommended) specifies a warpui Menu. The PR's own checklist item — "Copy menu item is greyed out" — cannot be verified because there is no menu to inspect.

Text selection + Cmd+C still works via SelectableArea, so Behavior 25 is met for the keyboard path, but the right-click surface deviates from spec. This was not implemented in Phase 1 and Phase 3 inherits the gap.

2. Padding moved from outer Container to scroll child

The criterion is "Outer Container (padding, background, bottom corner radius) unchanged." INLINE_ACTION_HORIZONTAL_PADDING and REQUESTED_COMMAND_BODY_VERTICAL_PADDING were removed from the outer Container and applied to the inner Container that is the SingleAxisConfig::Clipped child. The background and corner radius correctly remain on the outer container.

Moving padding inside the scroll viewport is the correct UX approach (so the tree content is padded from the viewport edges, not the clip boundary), but it is a visual change: the scrollbar thumb now appears flush with the container edge rather than inset by INLINE_ACTION_HORIZONTAL_PADDING. Verify against the existing shell-command body rendering to ensure the visual treatment is consistent with the rest of the action container.

3. tree_font_size local duplicates private constant

// requested_command.rs (new)
let tree_font_size = 12.0_f32;

json_tree.rs already defines const TREE_FONT_SIZE: f32 = 12.; but it is private. The local literal is used only for the "no arguments" / error / cancelled label text in requested_command.rs. Either make TREE_FONT_SIZE pub and import it, or document the value with a comment so the coupling is explicit and a future change to TREE_FONT_SIZE isn't silently missed here.

4. depth proxy in ToggleJsonNode handler is implicit

RequestedCommandViewAction::ToggleJsonNode { path, tree } => {
    let depth = path.len();   // depth == path length by tree construction
    ...
}

Using path.len() as depth is correct — the render tree is built such that depth always equals path length (root: [] / depth 0, first child: [Key] / depth 1, etc.). This invariant is implicit; a one-line comment (as shown) would prevent a future maintainer from wondering if the proxy is exact or approximate.

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Reviewed against TECH.md Phase 3 criteria and PRODUCT.md.

[cephalonaut]

Phase 3 Static Verification — APP-2527 MCP JSON Tree Rendering

Static Checks

Check	Result
serde_json::to_string_pretty removed from flat render path	✅ PASS — two remaining calls are correct (inside on_copy_req/on_copy_resp for Copy JSON)
render_json_tree called twice (request + response)	✅ PASS — lines 1562, 1621
NewScrollable + ConstrainedBox::with_max_height(MAX_EDITOR_HEIGHT) present	✅ PASS
Icon::ChevronDown/Icon::ChevronRight in json_tree.rs; no render_expansion_icon import	✅ PASS
No hard-coded color literals in json_tree.rs	✅ PASS
mcp_scroll_state: ClippedScrollStateHandle added and initialized	✅ PASS
on_toggle dispatches ToggleJsonNode { path, tree: McpTree::Request/Response }	✅ PASS
CopyJsonToClipboard uses ctx.clipboard().write(ClipboardContent::plain_text(...))	✅ PASS
SelectableArea + mcp_content_selection_handle still wraps content	✅ PASS
Outer Container retains background and bottom corner radius (Behavior 33)	✅ PASS
No hard-coded colors in new render path	✅ PASS
Code comments: no spec/process references	✅ PASS
PR body contains manual validation checklist	✅ PASS
cargo fmt clean	✅ PASS
ToggleJsonString defined + handler present but not wired in render	✅ Acceptable follow-up

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Spec Deviation: &mut EventContext in callbacks

The change from Fn(Vec<PathSegment>, usize) to Fn(&mut EventContext, Vec<PathSegment>, usize) is the minimal necessary change: Hoverable click callbacks receive &mut EventContext, and callers need it to dispatch typed actions via ctx.dispatch_typed_action(...). Without it, a channel or side-channel workaround would be needed. There is only one caller (requested_command.rs), so no existing callers are broken. The design rationale is documented in the CopyJsonToClipboard doc comment. Acceptable.

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Minor Items

M1 — No context menu on right-click (pre-existing from Phase 1, not a Phase 3 regression)

Right-click on a tree row directly dispatches CopyJsonToClipboard (copying JSON immediately) rather than showing a context menu with "Copy / Copy JSON" items as specified in PRODUCT.md Behavior 26 and Design §E1. The "Copy" item (greyed out when no selection) is absent from the right-click path. Confirmed that Phase 1 shipped the same behavior — this is a carry-forward from Phase 1, not introduced here. The text-selection Copy path still works via SelectableArea. Should be tracked as a follow-up for the full menu, not a blocker on this PR.

M2 — PR checklist missing screenshot item

The TECH.md Phase 3 checklist includes: "Screenshots of expanded tree in dark and light themes attached to the PR." This item is absent from the PR body checklist and no screenshots are attached.

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Manual Testing Checklist

The following items cannot be verified statically and require a running Warp instance with a local MCP server configured:

• Chevrons expand/collapse nodes correctly; clicking anywhere on the row toggles (Behavior 9)
• Theme colors apply correctly in dark and light themes; switching theme recolors without restart (Behavior 18-19)
• Long-string elision shows truncated preview with expander — note: ToggleJsonString not yet wired in render_json_tree; long strings render but expander click is a no-op (known gap)
• Right-click copies correct subtree JSON to clipboard (Behavior 27)
• Tree scrolls when taller than MAX_EDITOR_HEIGHT; outer block list scroll unaffected (Behavior 17)
• SelectableArea + Hoverable right-click interaction does not conflict (TECH.md risk item)
• Non-MCP actions (commands, file edits) are visually unchanged (Behavior 35)
• Error and cancelled tool calls show "Error: …" / "Cancelled" labels (Behavior 28)
• "(no arguments)" placeholder renders when mcp_request is absent (Behavior 29)
• Scroll position preserved when re-entering MCP content (via mcp_scroll_state)
• Screenshots of expanded tree in dark and light themes

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Verdict: MINOR — Core implementation correct; two minor items to address before merge: acknowledge the menu gap as a tracked follow-up, and add the screenshot checklist item to the PR body.

[cephalonaut]

Re-review: M1–M4 status + one new blocker

All four requested fixes are correctly implemented. However, the rewrite of the MCP render block accidentally dropped a call that existed outside that block and is now dead code.

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✅ M1 — Right-click context menu

ShowMcpContextMenu, CopyMcpSelection, and CloseMcpContextMenu action variants are present and fully handled. The menu is constructed with MenuVariant::Fixed, "Copy" is greyed out when there is no selection (with_disabled(!has_selection)), and "Copy JSON" always fires CopyJsonToClipboard. The menu is overlaid via root_stack.add_positioned_child anchored to the SavePosition ID of the MCP section. PASS.

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✅ M2 — Padding on outer Container

INLINE_ACTION_HORIZONTAL_PADDING and REQUESTED_COMMAND_BODY_VERTICAL_PADDING are now on the outer Container that wraps selectable_content, not on the inner scroll child. Confirmed against the pre-fix commit (d97a2568e). PASS.

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✅ M3 — TREE_FONT_SIZE made pub const

pub const TREE_FONT_SIZE: f32 = 12. in json_tree.rs, imported via use crate::ui_components::json_tree::{..., TREE_FONT_SIZE}; in requested_command.rs. No local duplicate. PASS.

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✅ M4 — Depth comment

A node's depth in the tree always equals its path length: the root has an empty path (depth 0) and each level down adds one segment.

Present immediately above let depth = path.len();. PASS.

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🚫 NEW BLOCKER — maybe_render_footer call was dropped

In the previous commit (d97a2568e), maybe_render_footer(app) was called after the if should_render_mcp_content { … } block, not inside it — rendering citations footers and autonomy speedbumps for all command types (MCP and shell commands alike). The PR removed that call entirely; maybe_render_footer is now dead code.

The impact: citations ("Copied from" / "Derived from" chips) and autonomy setting speedbumps (ShouldShowForAutoexecutingReadonlyCommands, ShouldShowForProfileCommandAutoexecution) will no longer appear on any requested-command block. The has_citations_footer variable still suppresses the header's rounded bottom corner even though there is no footer, causing a visual glitch on top of the functional regression.

The fix is straightforward — restore the call after the MCP content block:

        } // end if should_render_mcp_content

        if let Some(footer) = self.maybe_render_footer(app) {
            content.add_child(Clipped::new(footer).finish());
        }

        let border_color = …

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Minor — action variant doc comments describe callers

The new doc comments on CopyJsonToClipboard, ShowMcpContextMenu, and CopyMcpSelection each contain a sentence describing which UI element triggers them ("Triggered from …", "Used by …"). Per the project comment policy, comments should take a local view and not describe the behavior of callers. These lines should be dropped from the doc comments. Not blocking by itself, but should be cleaned up alongside the footer fix.

[cephalonaut]

Final re-review — PASS

Commit 3b54a1cf4 cleanly addresses both outstanding items. Only requested_command.rs was touched.

✅ Blocker resolved — maybe_render_footer restored

The call is back in exactly the right position: after the if should_render_mcp_content { … } closing brace and before let border_color. Citations footers and autonomy speedbumps will render correctly for all requested-command block types again.

✅ Minor resolved — doc comments no longer describe callers

• CopyJsonToClipboard: caller-describing sentence removed; only the local "write to clipboard" description remains.
• ShowMcpContextMenu: revised to explain why the json_text field is carried, without referencing caller behavior.
• CopyMcpSelection: simplified to "Copy the currently selected MCP tree text to the clipboard."
• CloseMcpContextMenu: already clean.

No other code was changed. PR is ready to merge.