Closes the SSOT gap for chat-history hydration: today every consumer
(canvas TS) re-implements an A2A-envelope walk to map activity_logs
rows into rendered ChatMessage objects. This PR moves that walk into
the server.
## What's added
GET /workspaces/:id/chat-history?limit=N&before_ts=T
Returns:
{
"messages": [
{"id": "<uuid>", "role": "user"|"agent"|"system",
"content": "...", "attachments": [...], "timestamp": "<RFC3339>"}
],
"reached_end": false
}
Auth chain: same wsAuth as /workspaces/:id/activity (tenant ADMIN_TOKEN
+ X-Molecule-Org-Id). No new trust boundary.
Filter: a2a_receive rows with source_id IS NULL — same canvas-source
filter the canvas applies via /activity?type=a2a_receive&source=canvas,
centralized so future API consumers don't need to know it.
## What's mirrored from canvas TS
Direct port of canvas/src/components/tabs/chat/historyHydration.ts
+ message-parser.ts:
- extractRequestText / extractFilesFromUserMessage — user-side parts
walk through request_body.params.message.parts[]
- extractChatResponseText — agent-side response_body collector across
the four shapes (string, A2A JSON-RPC parts, older nested
parts.root.text, task artifacts) joined with "\n" (matches canvas
multi-source collector — claude-code emits multiple text parts;
hermes emits summary+artifacts)
- extractFilesFromResponse / extractFilesFromTask — file walk across
parts[] + artifacts[].parts[] + status.message.parts[] +
message.parts[]
- v0 hot path ({kind:"file", file:{...}}) AND v1 protobuf flat shape
({url, filename, mediaType}) both supported
- Role decision: status='error' OR text starts with "agent error"
(case-insensitive) → "system", else "agent"
- isInternalSelfMessage prefix filter (Delegation results are
ready...)
- Timestamp pinned to row.created_at (regression cover for
2026-04-25 bubble-collapse bug)
## Tests
22 unit tests in chat_history_test.go, every TS test case in
historyHydration.test.ts has a Go counterpart:
Timestamp preservation (3): user/agent pin to created_at, two-rows
produce two distinct timestamps.
User-message extraction (5): text-only, internal-self skip,
null body, attachments hydrated, attachments-only-when-text-empty,
internal-self suppresses even with attachments.
Agent-message extraction (4): result-string, status=error→system,
agent-error-prefix→system, response_body.parts attachments,
null body, no-text-no-files-no-bubble.
End-to-end (1): paired user+agent same timestamp.
Go-specific (5): malformed JSON returns empty (no panic), v1
protobuf flat shape extraction, task-artifacts extraction, older
nested root.text shape, basename helper edge cases.
isInternalSelfMessage predicate (1): prefix match, non-prefix non-
match, empty-text non-match.
Mutation-tested. Removed the role-promotion branch (status=error +
agent-error prefix → system); confirmed both
TestChatHistory_RoleSystemWhenStatusError and
TestChatHistory_RoleSystemWhenAgentErrorPrefix fire red. Restored.
Both green.
Full handlers test suite (4.3s) green; full repo `go test ./...` green.
## SSOT decision
Parsing logic lives in workspace-server/internal/handlers/chat_history.go
ONLY. Canvas keeps historyHydration.ts + message-parser.ts during the
transition because:
- PR-C-2 (follow-up): canvas loadMessagesFromDB swaps to new
endpoint. Today's canvas still calls /activity for backward
compatibility.
- The TS parsers are still load-bearing for LIVE message handling
(WebSocket A2A_RESPONSE events) until RFC #2945 PR-B-2 mirrors
the typed event payloads to canvas consumers.
Canvas's TS path will be deleted in a separate PR after a one-week
observation window confirms no live-message consumers depend on it.
## Security review
- Untrusted input? YES — request_body and response_body come from
agents (potentially OSS / third-party). Defensive: any malformed
JSON returns empty content + no attachments, no panic. Tested
via TestChatHistory_MalformedJSONInRequestBodyReturnsEmpty.
- Trust boundary? Same as today: agent → workspace-server.
No new boundary; reuses existing wsAuth middleware.
- Auth/authz? Inherits wsAuth chain. Cross-workspace access blocked
by existing TenantGuard middleware.
- PII / secrets in logs? None. The handler logs nothing on the
happy path; errors log 502 without body content.
- Output sanitization? ChatMessage.content is plain text returned
as-is; canvas already sanitizes via ReactMarkdown. Attachment
URIs are agent-provided (workspace: / platform-pending: /
https:); canvas's existing scheme allow-list still applies.
## Versioning / backwards compatibility
- New endpoint /chat-history. /activity unchanged.
- Canvas historyHydration.ts + message-parser.ts intact during
transition (will be removed in PR-C-2 follow-up).
- No public API consumer of /activity is broken — added route is
additive.
- No semver bump (server is internal versioning).
## Three weakest spots (hostile-reviewer self-pass)
1. extractRequestText returns ONLY parts[0].text. If a user message
contains multiple text parts (uncommon — canvas only ever emits
one), we lose later parts. Matches canvas exactly today, but a
future change that emits multi-text user messages needs both
parsers updated. Documented in code; covered by test if/when
added.
2. activityRowToChatMessages rebuilds ChatMessage IDs every call (no
caching). Each chat reload mints fresh UUIDs. This is fine because
canvas dedupes by (role, content, timestamp window) not id, but a
future API consumer that DID rely on id stability would break.
Documented in the ChatMessage struct comment.
3. The handler scopes to source_id IS NULL only (canvas-source rows).
A future "show all messages, including agent-to-agent" mode would
need a new endpoint or a parameter. Out of scope for PR-C; canvas's
/activity?source=canvas already enforces the same filter.
Closes#3017. Unblocks RFC #2945 PR-D (MessageStore interface) which
returns []ChatMessage typed values.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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