snapshot: /session/:id/diff returns 500 "bad object" for turns captured before a project ID change #60857

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1. opencodejr commented on Oct 31, 2026

   

   opencodejrBot

   on Oct 31, 2026

   Contributor

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   Thanks for the detailed report, I could reproduce this.

   Steps (opencode 2.1.2, isolated data dirs, a local OpenAI-compatible mock as the model):

   1. git init and a root commit.
   2. opencode run --standalone --auto ...: one turn that writes one.txt.
   3. opencode api session.diff --standalone --param sessionID=$SID returns 200 with the one.txt patch.
   4. git remote add origin [email protected]:example/repro.git.
   5. The same call now returns HTTP 500, and the server log has failed to diff session turn with Snapshot.Error: fatal: bad object <tree>.

   As you described, snapshot/ now has a directory for the old project ID and one for the new ID. git cat-file finds the tree in the old store but not in the new one, so the data is still there; it just isn't read any more.

   It still happens on the latest dev (6c24ec9), run from source. The script below reproduces it end to end, including the mock model.

   Related: #57985 (same project ID change hides sessions), #59371 / #59946 (duplicate project rows and the session-list fix, which doesn't cover snapshot stores), #36093 (snapshot retention).

   Reproduction script (repro.sh)

   #!/usr/bin/env bash
   # Repro for #60857: /session/:id/diff returns 500 "bad object" after `git remote add` changes the project ID.
   # Needs bun and git. Starts an inline OpenAI-compatible mock that makes the model call `write` once.
   # Usage: ./repro.sh                       (uses `opencode` from PATH)
   #   from source: BUN_OPTIONS="--conditions=browser --preload=<repo>/packages/tui/node_modules/@opentui/solid/scripts/preload.js" OC="bun <repo>/packages/cli/src/index.ts" ./repro.sh
   OC=${OC:-opencode}
   HERE=$(cd "$(dirname "$0")" && pwd)
   R=$(mktemp -d)
   cat > "$R/mock.ts" <<'MOCK'
   // Minimal OpenAI-compatible chat completions mock.
   // First request of a turn: call the `write` tool to create one.txt. After a tool result: reply "done".
   Bun.serve({
     port: Number(process.env.PORT ?? 4555),
     async fetch(req) {
       const url = new URL(req.url)
       if (url.pathname.endsWith("/models")) return Response.json({ object: "list", data: [{ id: "mock", object: "model" }] })
       const body: any = await req.json().catch(() => ({}))
       const last = body.messages?.[body.messages.length - 1]
       const tools = (body.tools ?? []).map((t: any) => t.function?.name)
       if (process.env.MOCK_DEBUG) console.error("tools:", tools.join(","), "last role:", last?.role)
       const chunk = (o: unknown) => `data: ${JSON.stringify(o)}\n\n`
       const base = { id: "c1", object: "chat.completion.chunk", created: 0, model: "mock" }
       const usage = { prompt_tokens: 1, completion_tokens: 1, total_tokens: 2 }
       let out: string
       if (last?.role !== "tool" && tools.includes("write")) {
         out =
           chunk({ ...base, choices: [{ index: 0, delta: { role: "assistant", tool_calls: [{ index: 0, id: "call_1", type: "function", function: { name: "write", arguments: JSON.stringify({ path: "one.txt", content: "one\n" }) } }] }, finish_reason: null }] }) +
           chunk({ ...base, choices: [{ index: 0, delta: {}, finish_reason: "tool_calls" }], usage })
       } else {
         out =
           chunk({ ...base, choices: [{ index: 0, delta: { role: "assistant", content: "done" }, finish_reason: null }] }) +
           chunk({ ...base, choices: [{ index: 0, delta: {}, finish_reason: "stop" }], usage })
       }
       return new Response(out + "data: [DONE]\n\n", { headers: { "content-type": "text/event-stream" } })
     },
   })
   MOCK
   export XDG_DATA_HOME=$R/data XDG_STATE_HOME=$R/state XDG_CACHE_HOME=$R/cache XDG_CONFIG_HOME=$R/config
   PORT=4555 bun "$R/mock.ts" & MOCK=$!; trap 'kill $MOCK' EXIT; sleep 1
   export OPENCODE_CONFIG_CONTENT='{"providers":{"mock":{"name":"Mock","package":"@opencode/ai/providers/openai-compatible","settings":{"baseURL":"http://127.0.0.1:4555/v1","apiKey":"x"},"models":{"mock":{"name":"mock"}}}},"model":"mock/mock"}'
   DIR=$R/repro; mkdir -p "$DIR"; cd "$DIR"
   git init -q && printf 'seed\n' > seed.txt && git add . && git -c user.email=a@b -c user.name=a commit -qm root
   $OC run --standalone --auto -m mock/mock "Create one.txt containing exactly: one" ; echo "run exit=$?"
   SID=$($OC session list --standalone | head -1 | cut -f1); echo "SID=$SID"
   echo "--- diff before remote add"; $OC api session.diff --standalone --param sessionID=$SID; echo " exit=$?"
   git remote add origin [email protected]:example/repro.git
   echo "--- diff after remote add"; $OC api session.diff --standalone --param sessionID=$SID; echo " exit=$?"
   echo "--- snapshot stores"; ls "$XDG_DATA_HOME"/opencode/snapshot/
   grep -rh "bad object" "$XDG_DATA_HOME"/opencode/log "$XDG_STATE_HOME" 2>/dev/null | tail -2
   echo "--- the missing tree is still in the old store"
   TREE=$(grep -rhoE "bad object [0-9a-f]+" "$XDG_DATA_HOME"/opencode/log "$XDG_STATE_HOME" 2>/dev/null | tail -1 | awk '{print $3}')
   for s in "$XDG_DATA_HOME"/opencode/snapshot/*/*; do echo -n "$s: "; git --git-dir="$s" cat-file -t "$TREE" 2>&1; done

   Run it: bash repro.sh
2. opencodejr

   added

   reproduced

   on Oct 31, 2026