fix(agent-chat): show ACP paths and diffs for tool calls

[teamleaderleo]

ACP tool-call transcript blocks now show the files an ACP tool touched and useful output for edits and terminals. The existing tool block and rendering path remain unchanged.

Summary

• tool-start uses ACP location paths when present and keeps the raw-input JSON fallback when they are absent.
• tool-end renders diff paths with added and removed line counts, includes the new text, and names terminal IDs. The existing 400-character truncation remains in place.
• Added a stdio fake ACP process and regression coverage for location paths, raw-input fallback, added-file diffs, line counts, and mixed content.

Verification

The focused regression was committed before the fix and run with the same command.

Test commit 6e87bf05564 (bun test test/acp-tool-detail.test.ts):

FAIL 1 · Tests
error: expect(received).toEqual(expected)
0 pass
1 fail
Ran 1 test across 1 file.

Fix commit d3108259e98 (bun test test/acp-tool-detail.test.ts):

1 pass
0 fail
9 expect() calls
Ran 1 test across 1 file.

Full package verification with cd agent-chat && bun install && bun run check passed: 22 script checks and 43 tests across 13 Bun test files, with 0 failures.

The pull request CI job that executes the agent-chat suite is workflow-guard-tests / preflight, in the guards run.

Scope notes

files-changed is not affected and already works for ACP sessions. The block is produced from git in server.ts by filesChangedEvents, and adapters/acp.ts already threads generation into its done event, so the end-of-turn edited-files list is not the broken path here.

A clickable inline diff card for a single tool call is a separate feature and is deliberately not included in this pull request.

Changelog

Fixed ACP tool-call transcript details for file paths, diffs, and terminals.

🤖 Generated with Claude Code

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📥 Commits

Reviewing files that changed from the base of the PR and between 547340a and d310825.

📒 Files selected for processing (3)

• agent-chat/adapters/acp.ts
• agent-chat/test/acp-tool-detail.test.ts
• agent-chat/test/fake-acp-tool-detail.ts

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[github-actions]

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[teamleaderleo]

Review: Checked the ACP adapter diff, focused regression, TypeScript compile, and full agent-chat suite. Found no correctness issues.
Fixed: Added location-path details and diff and terminal content formatting with the existing truncation limits.
Left: Did not add a new block kind, UI component, colour, inline diff card, or change files-changed handling because those are outside this fix.

[github-actions]

Merge receipt for d3108259e9: every check was green at merge (12 verified; 17 skipped by policy). Full suite runs on main after merge.

[teamleaderleo]

Post-merge review of this change, since it landed on green before I got to it.

Review: the two exported helpers do what the PR says. acpToolCallDetail prefers locations and falls back to the rawInput JSON, including when locations is present but empty, so a tool call with no paths still shows its command. diffText handles oldText: null by counting zero removed lines, which is the shape an ACP agent sends for a file it creates, and the added/removed counts in the test match by hand. The fake agent covers the three ToolCallContent variants and a mixed array, which is the part that was previously collapsing to an empty string.

Left: one cosmetic defect in contentText. The map still joins with the empty string, which was correct when every element was a text chunk of a streamed message, but is wrong now that elements can be whole blocks. A mixed array renders as text outputdiff src/mixed.ts (+1/-1) newterminal term-42: the words run together at each boundary. The test does not catch it because it asserts with toContain on each piece separately. The fix is to keep concatenating adjacent text chunks and put a separator only around the diff and terminal blocks.

Also worth knowing for the next change in this area: truncate in adapters/lines.ts collapses every run of whitespace to a single space before cutting, so the \n that diffText puts in front of newText never survives. The detail is always one line. That is fine for a transcript detail string, but it means a clickable inline diff card cannot be built by formatting more text into this field; it needs its own block kind, which is still the separate feature described on cmuxterm-hq#852.

I am folding the separator fix into a follow-up PR that also fixes the stop path noted on #15781, since both touch adapters/acp.ts and two open PRs on that file would conflict.