diff --git a/bun.lock b/bun.lock
index 12e53065df2..ada1a57699e 100644
--- a/bun.lock
+++ b/bun.lock
@@ -366,6 +366,7 @@
         "hono-openapi": "catalog:",
         "ignore": "7.0.5",
         "jsonc-parser": "3.3.1",
+        "langfuse": "3.38.6",
         "mime-types": "3.0.2",
         "minimatch": "10.0.3",
         "open": "10.1.2",
@@ -3407,6 +3408,10 @@
 
     "lang-map": ["lang-map@0.4.0", "", { "dependencies": { "language-map": "^1.1.0" } }, "sha512-oiSqZIEUnWdFeDNsp4HId4tAxdFbx5iMBOwA3666Fn2L8Khj8NiD9xRvMsGmKXopPVkaDFtSv3CJOmXFUB0Hcg=="],
 
+    "langfuse": ["langfuse@3.38.6", "", { "dependencies": { "langfuse-core": "^3.38.6" } }, "sha512-mtwfsNGIYvObRh+NYNGlJQJDiBN+Wr3Hnr++wN25mxuOpSTdXX+JQqVCyAqGL5GD2TAXRZ7COsN42Vmp9krYmg=="],
+
+    "langfuse-core": ["langfuse-core@3.38.6", "", { "dependencies": { "mustache": "^4.2.0" } }, "sha512-EcZXa+DK9FJdi1I30+u19eKjuBJ04du6j2Nybk19KKCuraLczg/ppkTQcGvc4QOk//OAi3qUHrajUuV74RXsBQ=="],
+
     "language-map": ["language-map@1.5.0", "", {}, "sha512-n7gFZpe+DwEAX9cXVTw43i3wiudWDDtSn28RmdnS/HCPr284dQI/SztsamWanRr75oSlKSaGbV2nmWCTzGCoVg=="],
 
     "lazy-val": ["lazy-val@1.0.5", "", {}, "sha512-0/BnGCCfyUMkBpeDgWihanIAF9JmZhHBgUhEqzvf+adhNGLoP6TaiI5oF8oyb3I45P+PcnrqihSf01M0l0G5+Q=="],
diff --git a/packages/opencode/package.json b/packages/opencode/package.json
index 47948acb228..5521f2881a8 100644
--- a/packages/opencode/package.json
+++ b/packages/opencode/package.json
@@ -130,6 +130,7 @@
     "hono-openapi": "catalog:",
     "ignore": "7.0.5",
     "jsonc-parser": "3.3.1",
+    "langfuse": "3.38.6",
     "mime-types": "3.0.2",
     "minimatch": "10.0.3",
     "open": "10.1.2",
diff --git a/packages/opencode/src/provider/transform.ts b/packages/opencode/src/provider/transform.ts
index f651a5b91aa..ad608629c58 100644
--- a/packages/opencode/src/provider/transform.ts
+++ b/packages/opencode/src/provider/transform.ts
@@ -329,7 +329,7 @@ export namespace ProviderTransform {
     if (id.includes("glm-4.7")) return 1.0
     if (id.includes("minimax-m2")) return 1.0
     if (id.includes("kimi-k2")) {
-      // kimi-k2-thinking & kimi-k2.5 && kimi-k2p5 && kimi-k2-5
+      // kimi-k2-thinking, kimi-k2.5, kimi-k2p5, kimi-k2-5
       if (["thinking", "k2.", "k2p", "k2-5"].some((s) => id.includes(s))) {
         return 1.0
       }
@@ -373,9 +373,7 @@ export namespace ProviderTransform {
       id.includes("minimax") ||
       id.includes("glm") ||
       id.includes("mistral") ||
-      id.includes("kimi") ||
-      // TODO: Remove this after models.dev data is fixed to use "kimi-k2.5" instead of "k2p5"
-      id.includes("k2p5")
+      id.includes("kimi")
     )
       return {}
 
diff --git a/packages/opencode/src/session/langfuse.ts b/packages/opencode/src/session/langfuse.ts
new file mode 100644
index 00000000000..c7bd6d11c6a
--- /dev/null
+++ b/packages/opencode/src/session/langfuse.ts
@@ -0,0 +1,42 @@
+import Langfuse from "langfuse"
+import { Log } from "../util/log"
+
+const log = Log.create({ service: "langfuse" })
+
+let client: Langfuse | undefined
+let initFailed = false
+
+export function getLangfuse(): Langfuse | undefined {
+  if (client) return client
+  if (initFailed) return undefined
+
+  const secretKey = process.env.LANGFUSE_SECRET_KEY
+  const publicKey = process.env.LANGFUSE_PUBLIC_KEY
+  const baseUrl = process.env.LANGFUSE_BASE_URL
+
+  if (!secretKey || !publicKey) {
+    log.info("langfuse disabled: missing LANGFUSE_SECRET_KEY or LANGFUSE_PUBLIC_KEY")
+    initFailed = true
+    return undefined
+  }
+
+  try {
+    client = new Langfuse({
+      secretKey,
+      publicKey,
+      baseUrl: baseUrl ?? "https://cloud.langfuse.com",
+    })
+    log.info("langfuse initialized", { baseUrl })
+    return client
+  } catch (e) {
+    log.error("langfuse init failed", { error: e })
+    initFailed = true
+    return undefined
+  }
+}
+
+export async function flushLangfuse() {
+  if (client) {
+    await client.flushAsync()
+  }
+}
diff --git a/packages/opencode/src/session/prompt.ts b/packages/opencode/src/session/prompt.ts
index a9edf838ca8..3e66b1f8990 100644
--- a/packages/opencode/src/session/prompt.ts
+++ b/packages/opencode/src/session/prompt.ts
@@ -49,6 +49,7 @@ import { Shell } from "@/shell/shell"
 import { Truncate } from "@/tool/truncate"
 import { decodeDataUrl } from "@/util/data-url"
 import { Process } from "@/util/process"
+import { getLangfuse, flushLangfuse } from "./langfuse"
 
 // @ts-ignore
 globalThis.AI_SDK_LOG_WARNINGS = false
@@ -293,6 +294,14 @@ export namespace SessionPrompt {
     // on the user message and will be retrieved from lastUser below
     let structuredOutput: unknown | undefined
 
+    // Langfuse tracing: one trace per loop invocation (coding session turn)
+    const langfuse = getLangfuse()
+    const trace = langfuse?.trace({
+      name: "opencode.loop",
+      sessionId: sessionID,
+      metadata: { resume_existing },
+    })
+
     let step = 0
     const session = await Session.get(sessionID)
     while (true) {
@@ -335,13 +344,29 @@ export namespace SessionPrompt {
       }
 
       step++
-      if (step === 1)
+      if (step === 1) {
+        // Langfuse: capture user input on first step
+        if (trace) {
+          const userMsg = msgs.findLast((m) => m.info.role === "user")
+          const userText = userMsg?.parts
+            .filter((p): p is MessageV2.TextPart => p.type === "text")
+            .map((p) => p.text)
+            .join("\n")
+          trace.update({
+            input: userText,
+            metadata: {
+              agent: lastUser.agent,
+              model: `${lastUser.model.providerID}/${lastUser.model.modelID}`,
+            },
+          })
+        }
         ensureTitle({
           session,
           modelID: lastUser.model.modelID,
           providerID: lastUser.model.providerID,
           history: msgs,
         })
+      }
 
       const model = await Provider.getModel(lastUser.model.providerID, lastUser.model.modelID).catch((e) => {
         if (Provider.ModelNotFoundError.isInstance(e)) {
@@ -690,6 +715,16 @@ export namespace SessionPrompt {
         system.push(STRUCTURED_OUTPUT_SYSTEM_PROMPT)
       }
 
+      // Langfuse: create a span for this loop iteration
+      const iterationSpan = trace?.span({
+        name: `loop.step-${step}`,
+        input: {
+          agent: agent.name,
+          model: `${model.providerID}/${model.id}`,
+          toolCount: Object.keys(tools).length,
+        },
+      })
+
       const result = await processor.process({
         user: lastUser,
         agent,
@@ -713,6 +748,151 @@ export namespace SessionPrompt {
         toolChoice: format.type === "json_schema" ? "required" : undefined,
       })
 
+      // Langfuse: record the LLM generation and tool calls from this iteration
+      // The parts array for an assistant message flows in order:
+      //   step-start → reasoning → text → tool (calls+results) → step-finish
+      //   → step-start (next internal step) → reasoning → text → ... → step-finish
+      // We reconstruct each LLM call as a generation with its full context.
+      if (iterationSpan) {
+        const parts = await MessageV2.parts(processor.message.id)
+
+        let stepIndex = 0
+        // Accumulate parts for the current LLM step
+        let currentReasoning: string[] = []
+        let currentText: string[] = []
+        let currentToolCalls: { tool: string; input: any; output?: string; error?: string }[] = []
+        // Track tool results from the PREVIOUS step (they become input to the next LLM call)
+        let prevToolResults: { tool: string; input: any; output?: string; error?: string }[] = []
+
+        const flushStep = (stepPart: MessageV2.StepFinishPart) => {
+          const reasoning = currentReasoning.join("")
+          const text = currentText.join("")
+          const toolCalls = currentToolCalls.map((tc) => ({
+            tool: tc.tool,
+            input: tc.input,
+            ...(tc.output ? { output: tc.output.slice(0, 500) } : {}),
+            ...(tc.error ? { error: tc.error } : {}),
+          }))
+
+          // Input: first step gets the user message; subsequent steps get tool results
+          const input = stepIndex === 0
+            ? msgs
+                .filter((m) => m.info.role === "user")
+                .slice(-1)
+                .map((m) =>
+                  m.parts
+                    .filter((p): p is MessageV2.TextPart => p.type === "text")
+                    .map((p) => p.text)
+                    .join("\n"),
+                )
+                .join("\n")
+            : prevToolResults
+
+          // Output: structured to show reasoning + text + tool calls (mirrors the TUI)
+          const outputParts: Record<string, unknown> = {}
+          if (reasoning) outputParts.thinking = reasoning
+          if (text) outputParts.text = text
+          if (toolCalls.length > 0) outputParts.toolCalls = toolCalls
+          const output = Object.keys(outputParts).length > 0 ? outputParts : undefined
+
+          iterationSpan.generation({
+            name: `llm-call-${stepIndex}`,
+            model: `${model.providerID}/${model.id}`,
+            modelParameters: {
+              ...(agent.temperature != null ? { temperature: String(agent.temperature) } : {}),
+            },
+            input,
+            output,
+            usage: {
+              input: stepPart.tokens.input,
+              output: stepPart.tokens.output,
+              total: stepPart.tokens.total ?? stepPart.tokens.input + stepPart.tokens.output,
+            },
+            metadata: {
+              finishReason: stepPart.reason,
+              cost: stepPart.cost,
+              reasoning_tokens: stepPart.tokens.reasoning,
+              cache_read: stepPart.tokens.cache.read,
+              cache_write: stepPart.tokens.cache.write,
+            },
+          })
+
+          // Carry tool calls forward as input context for the next step
+          prevToolResults = currentToolCalls.map((tc) => ({
+            tool: tc.tool,
+            input: tc.input,
+            ...(tc.output ? { output: tc.output.slice(0, 500) } : {}),
+            ...(tc.error ? { error: tc.error } : {}),
+          }))
+
+          stepIndex++
+          currentReasoning = []
+          currentText = []
+          currentToolCalls = []
+        }
+
+        for (const part of parts) {
+          // Accumulate reasoning (thinking) for the current step
+          if (part.type === "reasoning") {
+            currentReasoning.push(part.text)
+          }
+
+          // Accumulate text output for the current step
+          if (part.type === "text") {
+            currentText.push(part.text)
+          }
+
+          // Record each tool call as a span and accumulate for generation context
+          if (part.type === "tool" && part.state.status === "completed") {
+            currentToolCalls.push({
+              tool: part.tool,
+              input: part.state.input,
+              output: part.state.output,
+            })
+            iterationSpan.span({
+              name: `tool.${part.tool}`,
+              input: part.state.input,
+              output: part.state.output,
+              startTime: new Date(part.state.time.start),
+              endTime: new Date(part.state.time.end),
+              metadata: {
+                title: part.state.title,
+                ...part.state.metadata,
+              },
+            })
+          }
+          if (part.type === "tool" && part.state.status === "error") {
+            currentToolCalls.push({
+              tool: part.tool,
+              input: part.state.input,
+              error: part.state.error,
+            })
+            iterationSpan.span({
+              name: `tool.${part.tool}`,
+              input: part.state.input,
+              output: part.state.error,
+              startTime: new Date(part.state.time.start),
+              endTime: new Date(part.state.time.end),
+              level: "ERROR",
+            })
+          }
+
+          // Flush accumulated content when a step finishes
+          if (part.type === "step-finish") {
+            flushStep(part)
+          }
+        }
+
+        iterationSpan.end({
+          output: {
+            finish: processor.message.finish,
+            result,
+            tokens: processor.message.tokens,
+            cost: processor.message.cost,
+          },
+        })
+      }
+
       // If structured output was captured, save it and exit immediately
       // This takes priority because the StructuredOutput tool was called successfully
       if (structuredOutput !== undefined) {
@@ -749,6 +929,14 @@ export namespace SessionPrompt {
       }
       continue
     }
+    // Langfuse: finalize trace
+    if (trace) {
+      trace.update({
+        output: { steps: step },
+      })
+      flushLangfuse().catch(() => {})
+    }
+
     SessionCompaction.prune({ sessionID })
     for await (const item of MessageV2.stream(sessionID)) {
       if (item.info.role === "user") continue
diff --git a/packages/opencode/src/sync/index.ts b/packages/opencode/src/sync/index.ts
index 270950fd4b8..b40e8d2acd4 100644
--- a/packages/opencode/src/sync/index.ts
+++ b/packages/opencode/src/sync/index.ts
@@ -159,8 +159,6 @@ export namespace SyncEvent {
     })
   }
 
-  // TODO:
-  //
   // * Support applying multiple events at one time. One transaction,
   //   and it validets all the sequence ids
   // * when loading events from db, apply zod validation to ensure shape